Clinical trial NCT03733132
Conditions: Insulin Resistance Obesity Obesity, Abdominal
Keywords: Insulin Resistance Cognition Cognitive Impairment Brain Function
Sponsor: Mayo Clinic
Start date: 2019-03-15; Completion date: 2023-04-05
Enrollment: 40 participants; Allocation: RANDOMIZED; Intervention model: PARALLEL

Brief summary:
Alzheimer's disease (AD) and other forms of dementia are rapidly increasing with the aging of the population, and show a clear preponderance among people with insulin resistance. Metformin, an insulin sensitizer, is being examined in clinical trials as an anti-aging drug. However, very little objective data is available regarding metformin's effect on the brain, a major organ affected by aging.

Detailed description:
Insulin resistance is highly prevalent with advancing age. Metformin is an insulin sensitizer and is currently being extensively investigated for its potential anti-aging effect. However, only very limited information is available on metformin effect on brain, which is a major organ affected by aging. With appropriate experimental design, the investigators are attempting to understand the mechanism of metformin treatment on the physiology of the brain as well as cognitive effects. These studies may uncover relationships that could be favorably manipulated to decrease health risks associated with insulin sensitivity and the effect on the brain.

The study results may lead to a breakthrough in providing either definitive data or sufficiently strong preliminary data regarding metformin's effect on elderly people with insulin resistance, on whether the drug enhances brain mitochondrial function in conjunction with improvement of brain functional network and cognitive function.

The overall hypothesis is that metformin administration to elderly people with insulin resistance enhances brain mitochondrial function in conjunction with improvement of brain function. To test this hypothesis, the investigators will address the following Specific Aims:

1. Determine whether 40 weeks of metformin administration in elderly people (\> 65 years) with insulin resistance enhances brain mitochondrial ATP production. The investigators will measure brain ATP production by 31P-MRS.
2. Determine the effect of 40 weeks of metformin administration in elderly people (\> 65 years) with insulin resistance on blood flow and functional network in different areas of brain. As a secondary outcome, the investigators will measure structural changes in white and grey matter areas of brain to determine whether metformin has any effect on brain structure.
3. Determine the effect of 40 weeks of metformin administration in elderly people (\> 65 years) with insulin resistance on cognitive function. The investigators will utilize the computerized NIH Toolbox to measure cognitive outcomes.

The investigators will also associate outcomes from our specific aims with improvements in whole-body insulin sensitivity and skeletal muscle mitochondrial function.

The investigators propose to complete 40 weeks of study in 40 elderly (\> 65 years) participants with fasting glucose between 100 to 140 mg/dl and abdominal girth of \>102 cm in men and \> 88 cm in women. All participants will be those who are not oral hypoglycemic agents including metformin. In this double-blind placebo trial, the investigators will randomly assign the participants to placebo or metformin in an escalated dose to reach a maximum of 2500 mg per day.

Arms: arm 1: Participants in placebo group will receive Placebo Oral Tablets identical to the metformin tablets for 10 months. arm 2: Participants in placebo group will receive an escalating dose of Metformin hydrochloride tablets up to a dose of 2500mg for 10 months.
Interventions: intervention 1: Metformin Hydrochloride intervention 2: Placebo Oral Tablet
Intervention descriptions: intervention 1: Metformin treatment of 2500mg for 10 months in the Metformin group intervention 2: Placebo treatment of identical tablets to metformin group

Protocol documents:
Prot_SAP_ICF_001.pdf: 
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Metformin Effect on Brain Function in Insulin Resistant Elderly People 
NCT03733132 
June 22, 2021 
 
 
 
 


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Institutional Review Board Protocol 
 
Title of study: Metformin Effect on Brain Function in Insulin Resistant Elderly People 
June 22, 2021 
Version 17 
 
 
Research Design and Methods 
Participants: We will recruit equal numbers of pre-diabetic, elderly men and women using the 
following criteria: age ≥ 60 yrs. BMI > 25fasting glucose ≥ 100-140 mg/dL. These selection 
criteria will allow us to recruit participants with reduced insulin sensitivity, but the variations in 
insulin sensitivity among participants will be evident from hyperinsulinemia glucose clamp that 
we will perform. People on medications that interfere with primary outcome measurements will 
be excluded (See under Subject Details). Importantly, people on hypoglycemic drugs including 
metformin will be excluded. We will exclude T2D/pre-diabetic people on oral hypoglycemic 
agents due to their variability in insulin secretion and also because most people in Olmsted 
County with fasting glucose >140 mg/dl are on metformin and it would be unethical to withhold 
treatment from these individuals. People who engage in structured aerobic exercise ≥ 3 d/wk or 
have active cardiovascular disease, renal failure, or liver function abnormalities will also be 
excluded (see Subject Details). In the current study, we will screen medical records for any 
diagnosis of cognitive impairment/dementia. We do not intend to target people with clinical 
dementia in the current study.  We will also administer the Montreal Cognitive Assessment 
(MoCA) at the screening visit and exclude any individual with a score < 22. English language 
proficiency will also be included as a criterion for enrollment, as strong English proficiency will 
be necessary for proper administration of the NIH Toolbox cognitive testing.  We will recruit 
equal numbers of men and women and strive to recruit all ethnic groups represented in the 
community. 
 
Overall Study Design: We will conduct a placebo-controlled, double-blind randomized trial 
with longitudinal (pre- & post-intervention) measurements. 40 participants will be randomized to 
placebo or metformin (2000 mg/d) groups. The initial study visit will include a screen, including 
testing for the criteria mentioned above.  Participants will be asked to report to the CRTU fasting 
for a blood test, including a CBC, liver function, fasting glucose, lipid panel, and TSH.  They 
will also have height and weight measurements taken and the MoCA test administered.  While 
this is being done, the blood test results will be made available to the study team.   If the 
participant passes the screening criteria, an outpatient visit will include a DEXA scan to assess 
body composition, a VO2max test on a cycle ergometer to test aerobic capacity.The first inpatient 
day will examine baseline brain structure and function using fMRI analysis.  For fMRI 
measurements, a minimum 20 participants are recommended for sufficient reliability for fMRI 
neuroimaging studies (4). Additionally, cognition will be assessed by the NIH Toolbox-
Cognition Battery (NIHTB-CB). Participants will be asked to report to the Charlton CRTU 
fasting on the day of their fMRI study.  They will have a fasting blood draw, followed by the 
MRI test at Neuroradiology.  Imaging will be performed on a 3 Tesla Siemens Skyra equipped 
with a 32-channel head coil and the multi-nuclear option (MNO) running VE11C software. 
Imaging sequences include the following: To measure structural information:  A sagittal 3D 


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MPRAGE sequence with 0.7mm isotropic voxels (TR=2400, TE=2.57, TI=1100, FA=8) will be 
used to acquire high-resolution structural data for volumetric analysis of brain region changes 
related to metformin.  The higher resolution allows for less variable segmentation and 
parcellation resulting in more accurate volumetric measurements. To measure white matter 
information: An axial 2D symmetric multi-slice (SMS) diffusion tensor imaging (DTI) sequence 
with 60 diffusion directions, 5 B0 acquisitions and 2mm isotropic voxels (TR=3000, TE=73, 
FA=90, ETL 43, both A-P and P-A phase encoding for B0 images) will be used to acquire white 
matter integrity data related to metformin.  To measure global brain blood flow information: An 
axial 3D pseudo-continuous arterial spin labelling (pCASL) sequence (WIP 818) with 4mm 
isotropic voxels (TI1=1800, TI2=3600, iPat ≤ 2) will be used to acquire quantitative blood flow 
measurements (flow in ml/100g/min) throughout the brain.  A post-label delay of 1800 ms will 
be used as we are imaging otherwise healthy subjects. To measure global brain functional 
network information: An axial 2D echo-planar imaging sequence with 3mm isotropic voxels 
(FA=90, TE=30, TR=2000, # slices=50) will be used to acquire resting state functional MRI data 
throughout the brain. To measure brain lactate: A single voxel point-resolved MR spectroscopy 
sequence (PRESS, 2 cm isotropic voxel, TE=30, TR=2000, 5000 Hz, 2048 points, 128 
acquisitions with water suppression and 16 acquisitions without water suppression) will be used 
to acquire metabolite information from the right dorsolateral prefrontal cortex. To measure brain 
ATP levels: Multivoxel chemical shift imaging (dual-tuned proton (Helmholtz pair)/phosphorus 
(loop) flex coil applied such that the phosphorus loop overlies the right DLPFC, WIP 1071, axial 
1.5 cm slice prescribed to encompass the right dorsolateral prefrontal cortex, 12x12 matrix 
reconstructed to 16x16 matrix, 1.5 cm nominal isotropic voxels, TR=1500) will be used to 
acquire phosphorus metabolite information from the right DLPFC.  
Following the MRI measurement, the subject will remain at Charlton 6 for a brain PET scan.  
Brain glucose uptake will be evaluated using 18F-Fludeoxyglucose injection and positron 
emission tomography (PET) scans at baseline and following 40-weeks of placebo or metformin 
treatment.  The results will provide insight into how brain metabolism changes with metformin 
treatment.   
 
Imaging:  Each patient will be injected with approximately 8 mCi (440 MBq) (range 7-10mCi) 
of F-18 FDG.  The F-18 FDG scan will be performed 30 minutes after injection is performed 
with an 8-10-minute acquisition. The PET sinograms will be reconstructed using iterative 
reconstruction into a 256 mm field of view; the pixel size is 1.0 mm and the slice thickness is 3.3 
mm. A helical CT image, obtained prior to injection of FDG, will be used for attenuation 
correction and a model-based scatter correction applied. Random coincidences will be corrected 
for using single event count rates and corrections for dead-time and decay will be applied. An 
absolute calibration correction, which converts the image intensity into activity concentration, 
will be used. 
 
Quantitative PET ROI Analysis: Anatomic standardization and statistical quantification of FDG 
PET image sets will be performed using a program (Cortex ID, GE Healthcare, WI) that 
generates standardized three-dimensional stereotactic surface projection datasets for individual 
subjects. In this algorithm, an individual brain image set will be first realigned to the midsagittal 
plane. The AC-PC line (a line passing through the anterior and posterior commissures) will be 
estimated by iterative matching between the individual image set and a standard atlas template. 
This standard atlas template was produced as an average of FDG images from 66 healthy 


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volunteers. The individual image sets will be realigned to the standard stereotactic coordinate 
system based on the estimated AC-PC line. Differences in size between the individual brain and 
the standard template will be removed by linear scaling. For this process, nine affine 
transformation parameters will be estimated. To adjust the individual brain shape to the 
stereotactic atlas coordinate system proposed by Talairach and Tournoux, nonlinear warping 
along the directions of major neuronal fiber bundles within the brain will be performed. The 
directions will be predefined in the stereotactic coordinate space on the basis of the fiber origins 
and their cortical projections. Individual landmarks for cortical projections will be searched 
iteratively between centers and cortical landmarks predetermined on the template brain using a 
profile curve analysis. Detected individual landmarks will then be warped to predefined 
landmarks, resulting in a standardized image set with a uniform voxel size of 2.25 mm, 
interpolation to 60 slices, and a matrix size of 128 x128. This enables reliable pixel-by-pixel 
comparisons of these anatomically standardized brain images. To determine projection map 
values, the program will use a predetermined vector that is 6 pixels (13.5mm) long and oriented 
perpendicular to the outer and medial surfaces of the right and left-brain hemispheres for each 
surface pixel. The surface pixel will be assigned the highest pixel value found along this vector. 
We will normalize surface pixel values to the pons although cerebellar or whole brain 
normalization measures will be calculated also for comparison. The normalized cortical pixel 
values will be used to calculate a statistical map, which will show surface pixel-by-pixel z-scores 
derived from comparing an individual’s scan with results in normal controls. These Z-score maps 
and values will be used for comparison of baseline and post-test scans to detect changes in brain 
metabolism. 
 
Approximately 1 week after completion of the outpatient study visits, we will assess insulin 
sensitivity by performing a 6 hour two-stage hyperinsulinemic-euglycemic clamp at Mayo 
Clinical Research Trial Unit (CRTU) as an inpatient study following an overnight fast. On the 
evening prior to the clamp, participants will receive a standardized diet from the CRTU research 
kitchen (10kcal/kg body weight; composition 20% protein, 30% fat and 50% carbohydrate). 
Following the meal, we will use the computerized NIH toolbox to measure cognitive outcomes. 
The NIH encourages the use of these tools to enhance collection of data in large studies and for 
clinical trials (7). The cognitive and behavioral tests were normed across a national sample of 
persons aged 3-85 years. We will utilize the iPad version of the NIH Toolbox because we have 
shown that residents within Olmsted County, MN prefer the iPad over a personal computer (8). 
The NIH Toolbox-Cognition Battery is composed of 7 core tests and 2 supplemental tests (~30-
45 minutes) including the Dimensional Change Card Sort (DCCS) Test (executive function), the 
Flanker Inhibitory Control Test (executive function), the Picture Sequence Memory Test 
(episodic memory), the Picture Vocabulary Test (vocabulary), the Oral Reading Recognition 
Test (reading), the List Sorting Working Memory Test (working memory), the Pattern 
Comparison Processing Speed Test (processing speed), the Rey Auditory Verbal Learning Test 
Trials 1-3 (episodic memory), and the Oral Symbol Digit Test (processing speed).  For each test, 
the raw scores will be converted to normally distributed standard scores. The NIH Toolbox-
Cognition is an in-person test that requires specialized knowledge for administration (use is 
limited to individuals supervised by a psychologist), as well as back and forth interactions with 
the patient and a provider throughout its administration. Several measures use computer adaptive 
testing, which bases subsequent items on a subject’s previous response, essentially shortening the 
time to administer the measure while improving the psychometric properties of the measure (e.g., 


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reliability, validity). Because it is administered directly on the iPad, scoring is instantaneous 
which greatly improves clinical efficiency and reduces costs. Also, iPad administration will help 
to reduce administration and scoring errors and further increase standardization across sites. Due 
to this iPad administration and the use of computer adaptive testing, there is no single form for 
this test than can be reviewed. However, detailed training videos are available online that 
illustrate test content and administration: http://www.healthmeasures.net/NIH_Toolbox_iPad_e-
learning/story_html5.html  
 
Participants will be offered the opportunity at their screening visit to meet with the dietary staff 
of the CRTU to discuss dietary preferences and address any concerns or questions. Three hours 
prior to start of hormone (somatostatin) infusion, priming [6,6’2H2 ]glucose bolus 
(approximately 6 mg/kg FFM) will be administered followed by continuous infusion of 
[6,6’2H2]glucose (approximately 4 mg/kg FFM/h). [6,6’2H2] glucose infusion rate will be 
titrated downward by 10-30% at 1-2-hour intervals after start of the hormone infusions. For the 
first 3 hours regular insulin will be infused at a rate of 0.6 mU/kgFFM/minute then 2.4 
mU/kgFFM/minute for 3 hours. Euglycemic blood glucose will be maintained with titrated 
infusion of [6,6’2H2] glucose labeled 40% dextrose solution.  Blood will be collected from a 
catheter inserted in their dorsal hand vein that is kept in a hot box to collect arterialized venous 
blood.  Urine will be collected prior to starting the insulin clamp until the end of the clamp. A 
stool sample will also be collected during this visit to assess changes to the microbiome based on 
the study intervention.  If participants are unable to provide a stool sample at this time, a kit will 
be provided with instructions on how to perform the collection at home and how to return the kit 
to the study team. The stool samples will be sent to the Cell Signaling Clinical Core Lab in the 
Guggenheim for storage. When the samples are pulled for testing, they will be sent to the 
University of MN – Genomics Center to have the test performed.  After the clamp participants 
will be able to resume their usual diet and will be discharged from the CRU. We will perform 
indirect calorimetry of 20 min each at the baseline and during the second phase of 
hyperinsulinemic-euglycemic clamp.  


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Approximately 1 week after the inpatient study visit, we will have a second outpatient visit to  
assess skeletal muscle changes.  Participants will be asked to report to the St. Mary’s CRTU 
fasting at 6am.  Percutaneous vastus lateralis muscle biopsies will be performed prior to and 1-h 
post a 25 kcal/kg FFM mixed meal (50% Fat, 30% Carbohydrate HO, 20% Protein) as we have 
previously described (9). Briefly, muscle biopsies will be performed with a percutaneous biopsy 
needle (modified Bergstrom needle).  Local subcutaneous injection of 2% lidocaine buffered 
with 8.4% sodium bicarbonate will be used for analgesia.  A small incision will be made through 
the skin and fascia. After the biopsy, pressure will be held over the incision until hemostasis is 
achieved.  The incision is closed with sterile strips, gauze, and an Ace wrap.  Risks of this 
procedure include hematoma, infection, and pain.  Hematoma likelihood is minimized by 
holding pressure after the biopsy to ensure hemostasis, followed by a pressure dressing.  The risk 
of infection is minimized by using sterile surgical techniques. Pain is managed by local analgesia 
during the procedure and Tylenol following the procedure. Muscle mitochondrial studies will be 
performed in muscle samples as we have previously reported (9). We will also be examining 
muscle samples for changes in protein expression, metabolite concentrations, and gene 
expression.  This visit should last approximately 5 hours.   
The plan for various measurements and study days is outlined in Figure 1.  
Following the baseline study visits, participants will be randomly assigned to placebo or 
metformin. A pharmacist will administer identical placebo or metformin tablets and study 
coordinator will call subjects twice a month for the first 2 months to ensure compliance. 
Participants will return every 4 weeks to refill their prescription where a tablet tally will be 
performed to determine the adherence to the drug. We will measure plasma metformin levels at 
each monthly return visit.  
At the conclusion of the 40-week intervention period, subjects will return to repeat the4 study 
visits outlined above (DEXA scan/VO2max test, MRI/cognitive study/PET scan, inpatient clamp 
study, and muscle biopsy study).  A study flow diagram is shown in Figure 2 for clarity.   
Figure 1. An outline of the study day plan includes an initial study day to examine the primary outcome of brain measures, followed by subsequent 
hyperinsulinemic euglycemic clamp and muscle biopsy with mixed meal challenge.  
 


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Figure 2.  Diagram of the overall study design with visits marked with blue arrows.  Study consists of both pre- and post-intervention 
study visits. 
 
We will escalate the dose of metformin (500 mg metformin  and blinded placebo) (week 1, 1 tablet 
each with breakfast and dinner twice daily; week 2, 2 tablets  with breakfast and 1 with dinner, 
and week 3,  2 tablets with breakfast and 2 tablets with dinner). Administration of tablets with 
meal reduces the gastro-intestinal (GI) adverse effects which are the most common adverse effects 
especially when taking metformin on an empty stomach. If the participant develops any adverse 
GI symptoms on escalating the dose, we will revert back to the previous dose. The maximal dose 
that is FDA approved is 2500 mg, and the optimum dose clinically used is 2000 mg. We opted to 
target the maximum dose since some aging literature suggests that for anti-aging effect the higher 
dose is preferred. The time scale for escalation of metformin dose will be standardized for all 
participants. Those who develop gastrointestinal symptoms as we escalate the dose to the optimum 
dose will be analyzed separately from the participants that are able to adhere to the escalation 
protocol. To account for the anticipated 10% that will experience GI symptoms, we have increased 
our accrual by 3 participants and will monitor the study to determine if additional participants are 
needed to complete the per protocol analysis.  The PI is a consultant endocrinologist treating 
exclusively patients with diabetes and lipid disorders at Mayo Clinic and he has extensive 
experience in using metformin in patients as well as in research (5). 
The randomization order will be determined by the statistician and the tablets will be administered 
by the pharmacy staff in our CRTU pharmacy department.  Since vitamin B12 deficiency has been 
reported (6) (4.3 VS:2.3% Metformin VS Placebo on 5 year) we will check vitamin B12 and more 
sensitive methyl malonic acid at pre-intervention MRI outpatient visit, 4, 12, 24 weeks, and post 
intervention MRI outpatient visit. All participants will be given vitamin B12 replacement per 
DSMB recommendation. 
To ensure participant safety we will monitor glucose (fasting) when the participants present for 
scheduled visits to collect medication / placebo. If fasting glucose is > 140 mg/dl we will measure 
HbA1c. If the HbA1c is >7% we will refer to our safety officer (Dr. Adrian Vella who is consultant 
diabetologist) who will determine whether the participants need to be placed on “open label” 


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metformin. Since the HbA1c target in that age group is 7% we consider up to 7% as a level that 
does not need intervention. While this management could break study blinding, the cognitive 
assessments and imaging will be conducted by individuals that remain blind to the treatment.  
Participants who do not show a reaction to the high dose insulin during the post-intervention 
hyperinsulinemic-euglycemic clamp will be asked to repeat this visit to rule out vein infiltration 
during the previous post-intervention insulin clamp.  
Sample size justification. This is a developmental grant, so the sample size is not justified based 
on power for any of the particular aims. Rather, the estimate is based on precision and reliable 
estimates of the imaging studies. In particular, for the fMRI study Thirion et al (4) found that 20 
to 25 subjects were necessary to achieve reliable results. Given we want to study 20 within-group 
metformin subjects with fMRI, balancing the randomization 1:1 will yield a total sample size of 
40. The effect sizes for between group differences are unknown; however, we will have 80% power 
to detect an effect size of at least 0.9 SD difference between the groups at alpha=0.05 (two-sided). 
Statistical Considerations 
Statistical plan: The analysis of the aims will be focused on estimation – standard deviations of 
MRS estimates and initial examinations of the changes in measures over time. With 20/group and 
repeated measures, we will be able to fit repeated measures models (e.g., mixed effects 
“trajectories”). For MRS with only a pre-post assessment, the mixed model framework is 
essentially a two-sample t-test on the changes over time, but importantly, the modeling framework 
will allow inclusion of all available data. This is to provide the most degrees of freedom to estimate 
the residual error, which will be used to plan a definitive study should these results appear 
promising (biological engagement as quantified by MRS and fMRI, change in insulin sensitivity, 
etc.) Supporting these analyses will be standard descriptive and graphical summaries of the data.   
Interpretation: In this double-blind placebo-controlled study all data interpretation will be 
performed at the end of the study and the un-blinding will be done by the statistician. Statistical 
plan is as outlined above. We will make conclusions on whether our hypotheses are proved or 
disproved based on statistical significance (P<0.05) of the outcomes that are outlined under MR 
data analysis and cognitive functions. If the observed data reaches statistical significance for one 
or more outcomes our outlined hypotheses will be proven. However, if the significance level does 
not reach statistical significance but shows promising results, that will offer opportunities for a 
larger study with more participants and perhaps longer duration. 
 
SUBJECT DETAILS 
 
1. Overview 
We will recruit 40 subjects with equal 
numbers of men and women age ≥ 60 
yrs.,  BMI > 25, fasting glucose ≥ 100-
140 mg/dL (1). Subjects will be 
randomized to one of 2 intervention 
groups as described below.  
 
Protocols: A common protocol will be 
followed for baseline studies and post 
intervention-studies. Our sample size assumes 25% drop-out (see Statistical Analysis section of 
Research Plan for more details. We will exclude anybody taking anti-hyperglycemic drugs 
including metformin. We excluded T2D people because of the variability of their insulin secretion 
Metformin (n=20) 
Placebo (n=20) 
Pre 
Post 
Pre 
Post 


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and because in Olmsted County, most people with a fasting glucose >140 mg/dl are on metformin. 
We will also exclude people who engage in aerobic training ≥ 3 d/wk and anybody with association 
active cardiovascular disease, renal failure, or liver function abnormalities. Subjects meeting the 
inclusion criteria will undergo a DEXA scan to determine body composition, which will be 
repeated following 40 weeks. 
 
Approach to recruitment:   
Volunteers will be recruited from advertisements in the Mayo bulletin boards, electronic bulletin 
boards and local and regional newspapers and magazines.  Regional radio advertising will also 
be used. The Mayo Clinic biobank and Rochester Epidemiology Project will be utilized to 
identify potential volunteers.  Each volunteer will meet one of the investigators who will explain 
the scientific rationale of the study, the procedures, potential risks involved and rights of the 
participant in the study.  The consent form will be approved by the Mayo Clinic. 
 
2. Risks to subjects 
 
2.1.1. Human Subjects Involvement, Characteristics, Design and Procedures: 
We anticipate recruiting a total of 54 adults ages ≥ 60 yrs. All racial/ethnic groups will be eligible 
for participation. Based on our experience, we expect that approximately 75% in each arm will 
complete the study (N=20 for each group).  
 
Human Subjects Involvement and Characteristics:  All protocols and all techniques to be 
used will be approved by the Mayo Clinic Institutional Review Board prior to initiation of any 
studies. Subject characteristics have been briefly mentioned above.   
 
Inclusion criteria:  To be eligible for the study, a subject must be willing to be randomized and be 
retained in the study for its duration and meet the following criteria: 
 
Age ≥ 60 yrs. 
BMI ≥ 25 kg/m2 
Fasting glucose ≥ 100-140 mg/dL  
Non-smoker 
English language proficiency 
 
Exclusion Criteria: The presence of any of the following is an exclusion for the study: 
• Active coronary artery disease or heart failure.   
• A known medical condition that in the judgment of the investigator might interfere with the 
completion of the protocol such as the following examples: 
o Inpatient psychiatric treatment in the past 6 months  
o Presence of a known and active adrenal disorder 
o Abnormal liver function test results (Transaminase >2 times the upper limit of normal); 
testing required for subjects taking medications known to affect liver function or with 
diseases known to affect liver function 
o Abnormal renal function test results (calculated GFR <60 mL/min/1.73m2); testing 
required for subjects with diabetes duration of greater than 5 years post onset of puberty  
o Active gastroparesis 
o If on antihypertensive, thyroid, anti-depressant or lipid lowering medication, lack of 
stability on the medication for the past 2 months prior to enrollment in the study 
o Uncontrolled thyroid disease (TSH undetectable or >10 mlU/L); testing required within 
three months prior to admission for subjects with a goiter, positive antibodies, or who are 
on thyroid hormone replacement, and within one year otherwise 
o Abuse of alcohol or recreational drugs 
o Infectious process not anticipated to resolve prior to study procedures (e.g. meningitis, 
pneumonia, osteomyelitis).  


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o Uncontrolled arterial hypertension (Resting diastolic blood pressure >90 mmHg and/or 
systolic blood pressure >160 mmHg) at the time of screening. 
o Oral steroids 
o A recent injury to body or limb, muscular disorder, use of any medication, any carcinogenic 
disease, or other significant medical disorder if that injury, medication, or disease in the 
judgment of the investigator will affect the completion of the protocol  
o Any metal in the body that could interfere with magnetic resonance imaging (MRI) 
including pacemaker or implanted defibrillator, neurostimulators, ear implants, metal 
fragments within the body, metal joints, rods, pins, plates, or screws. 
o Subjects without English proficiency 
Restrictions on Use of Other Drugs or Treatments: 
1. 
Medications that may impact study end points such as mitochondrial biology e.g. beta 
blockers 
2. 
Anti-hyperglycemic drugs including metformin 
3. 
Any other medication that the investigator believes is a contraindication to the subject’s 
participation. 
 
Procedures: MRI scanning of the brain: We will be performing pre- and post-intervention MRI 
scanning to measure brain ATP production by NMR spectroscopy. We will measure brain structure 
(grey and white matter content) and functions by MRI, fMRI. Participants will be explained all 
testing procedures and how the test can be terminated if the participant wishes to be removed from 
scanner. Injury within the MRI will be minimized by having each participant complete a magnetic 
materials safety questionnaire to ensure that it is safe for them to be exposed to strong magnetic 
fields.   Burns due to touching the sides of the magnet will be avoided by instruction participants 
of proper positioning. 
 
Interventions:  Metformin: We will use Metformin in half of the participants.  We will enquire 
about the prior use of this agent during a detailed history and physical examination as part of the 
screening visit.  We will also ensure that the likelihood of subjects developing gastrointestinal side 
effects is low by taking tablets in the middle of meals. Subjects will start metformin at 500 mg 
twice daily and titrate upwards by 500 mg every 1-2 weeks to reach a maximum dose of 2000 mg 
(week 1, 1 tablet each with breakfast and dinner. Week 2, two tablets with breakfast and 1 with 
dinner and week 3 two tablets with breakfast and two tablets with dinner).   
 
2.1.2. Sources of Materials: 
Samples of blood obtained during the course of the experiments will be used exclusively for 
research purposes. No use will be made of pre-existing specimens. 
 
Screening visit:  All subjects will be consented by one of the study personnel after giving them 
appropriate time to understand the procedures and commitment needed to complete the study. The 
study physician will perform a detailed history and physical with special emphasis on history of 
glucose tolerance. Clinical Research Unit (CRU) personnel will obtain routine vital signs and draw 
blood for screening labs, including hematocrit, comprehensive chemistry panel (including 
hematocrit, fasting plasma glucose, serum creatinine, liver function tests and TSH). If these tests 
are available close to recruitment, the same results will be used, and unnecessary testing avoided.  
This study is not meant to find out if the participant has any other disease or problem. The study 
leaders will alert the participant if any of the research results are important to his/her health during 
the study. The participant may have a copy of the screening tests to discuss with his/her personal 
physician. When the blood tests are completed, any blood left over will be thrown away. It will 
not be stored for any future testing. 
 
Metabolic Measures: We will record participants’ body weight, height, body mass index (BMI). 
All subjects will be studied after fasting with a hyperinsulinemic, hyperglycemic clamp.  After an 
overnight fast, participants will have catheter inserted in their dorsal hand vein that is kept in a hot 


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box to collect arterialized venous blood at Mayo Clinical Research Trial Unit (CRTU) where 
baseline blood samples and then following an insulin infusion at two different doses at 3 hours 
interval. We will collect blood samples every 10 min to adjust dextrose infusion to maintain blood 
glucose between 85 to 90 mg/dl. Another day they will be given a mixed meal and pre and post 
meal (1 hour) needle biopsy of muscle will be performed.  
We will perform muscle biopsy of the vastus lateralis muscle under sterile precautions under local 
anesthesia. We have performed over 4000 muscle biopsies without any major adverse effects. The 
potential side effects are local hematoma that is mostly prevented by pressure applied for 10-15 
min following biopsy. Infection is extremely rarely occurred as we perform the biopsies under 
strict sterile precautions and follow up carefully.  
There is an institutional electronic tracking system to ensure that a patient is not in more than one 
study at a time.  Intravenous risks will be minimized by having experienced CRU staff place the 
lines and infusing normal saline to decrease the risk of phlebitis or occlusion.   
 
Randomization: A participant who meets all the inclusion and exclusion criteria will be enrolled 
in the study. After completion of baseline studies, the participant will be randomized to one of the 
study groups as described above.  
Medical/Technical support: Study personnel will be available at all times during the length of the 
trial to answer any question or troubleshoot any problem. 
Access to individually identifiable private information about human subjects: Permission to gather, 
use and share information about the participant will be obtained in the consent forms. If the 
participant decides not to give permission, he/she cannot be in the study. This collected 
information may include personal information such as name, address, date of birth, social security 
number, medical records and test results from before, during and after the study from any of the 
participant’s doctors or health care providers (including mental health, substance abuse, and 
HIV/AIDS records) and information needed to bill others for participants care. These records may 
be accessed by the study team, people or committees that oversee the study, people who pay for 
the study, including insurance companies, tax reporting offices, people who evaluate study results, 
and government agencies that provide oversight such as the Office for Research Subject protection. 
The information collected might be published in a medical journal in a way that protects participant 
privacy. The participant may change his/her mind at any time; however, permission does not end 
unless the participant cancels it by sending a letter or email to the researcher. The researchers will 
still use information about the participant that was collected before his/her participation ended. All 
researchers will do everything possible to protect participant privacy.  
 
2.1.3. Potential Risks and minimization: 
 
Feasibility, Recruitment, and Informed Consent: These have been described earlier in this 
section.   
Each willing participant will meet one of the investigators who will explain the scientific rationale 
of the study, the procedures and potential risks involved in the study.  The consent forms will be 
approved by the Mayo Foundation IRB prior to use.  Informed written consent from the participant 
will be obtained by one of the investigators prior to participation. An electronic note will be entered 
in each participant’s medical record regarding the consent and a copy of the consent will be 
electronically kept with the participant’s medical record.  A copy of the consent will be given to 
the subject and the original kept in the study records.  
 
The principal investigators or their co-investigators meet with each participant, review the consent 
form in detail and confirm the subjects understanding of the study. They answer all questions posed 
by the participants and when convinced that the subject verbally demonstrates understanding of 
the protocol obtain a signed consent. Only designated study staff is authorized to obtain informed 
consent. 
 


13 
 
All experimental protocols will be conducted at Mayo Clinic Rochester CRU of the Mayo Clinic 
Center for Clinical and Translational studies (CCaTS).  
Protection during in-patient studies:  All protocols and all techniques to be used will be 
approved by the Mayo Clinic Institutional Review Board prior to initiation of any studies.  All 
participants will have the Mayo Clinic paging operator available to them 24 hours a day to contact 
the investigators for any problems.  The following protection will be taken for the risks identified 
above: 
 
1. Intravenous risks will be minimized by having experienced CRU and study staff place the lines 
and infusing 0.9% normal saline throughout the study to decrease the risk of phlebitis or 
occlusion.   
2. The amount of blood drawn is within the amounts acceptable by the institution. There is a 
Center for Clinical and Translational Studies (CCaTS) electronic tracking system that monitors 
if a subject is in more than one research study at a time.   
 
The following are the potential risks for this study with minimization strategies. 
 
a) Blood will be withdrawn. The total blood withdrawn during each study protocol will not exceed 
550 ml. Hemoglobin measured before starting the study will be greater than 12.0 g/dl in males and 
11.0 g/dl in females. All subjects will refrain from giving blood or being in any other research 
study eight weeks prior to the study and until eight weeks after the completion of the study. 
 
b) Metformin will be administered. We will enquire about the prior use of this agent during a 
detailed history and physical examination as part of the screening visit.  Subjects will start 
metformin at 500 mg twice daily and titrate upwards by 500 mg every 1-2 weeks to reach a 
maximum dose of 2000mg (week 1, 1 tablet each with breakfast and dinner twice daily; week 2, 
two tablets each with breakfast and one with dinner and week 3,  two tablets with breakfast and 
two tablets with dinner).  Administration of tablets with meal reduces the gastro-intestinal (GI) 
adverse effects which are the most common adverse effects, particularly when taking metformin 
on an empty stomach. If the participant develops any adverse GI symptoms on escalating the dose 
we will revert back to the previous dose. The maximal dose FDA approved is 2500 mg and the 
optimum dose clinically used is 2000 mg. Since vitamin B12 deficiency has been reported (4) (4.3 
VS:2.3% Metformin VS Placebo on 5 year) we will check vitamin B12 and more sensitive methyl 
malonic acid at pre-intervention outpatient MRI visit, 4, 12, 24 weeks, and post-intervention 
outpatient MRI visit. All participants will be given Vitamin B12 replacement per DSMB 
recommendation 
 
c)  Vascular catheters will be placed.  Catheter insertion and blood withdrawal are associated with 
a small risk of phlebitis.  This will be minimized by careful attention to sterile technique.  If 
phlebitis occurs, it will be treated conservatively with heat and when appropriate, with antibiotics. 
In all experiments, “arterialized – venous” blood will be obtained by placing a hand in which a 
catheter has been inserted, in a heated box during the study.  The temperature inside the box is 
maintained at ~55°C.  With prolonged exposure to continuous heat, there is a potential risk of local 
skin irritation or a minor burn.  If this occurs, it will be treated appropriately. However, we have 
used this technique for the past 25 years and have had no instances of hot box related burns or 
injuries. The potential risks of catheters and hot box use will be discussed with the volunteers prior 
to obtaining consent for the study. 
 
D)  We will be performing pre- and post-intervention MRI scanning to measure brain ATP 
production by NMR spectroscopy. We will measure brain structure (grey and white matter content) 
and functions by MRI, fMRI. The main risk of MRI procedures is claustrophobia.  Participants 
will be explained all testing procedures and how the test can be terminated if the participant wishes 
to be removed from scanner. Injury within the MRI will be minimized by having each participant 
complete a magnetic materials safety questionnaire to ensure that it is safe for them to be exposed 


14 
 
to strong magnetic fields. Burns due to touching the sides of the magnet will be avoided by 
instruction participants of proper positioning. 
 
2.2.  Potential Benefits of the Proposed Research to the Subjects and Others 
The risks to the subjects, including the risk of blood drawing, metformin administration, 
vascular catheters, muscle biopsies, and MRI scanning are minimal. In our opinion, the risks are 
justified by the expected knowledge gained from the studies proposed in this application. 
 
2.3.  Importance of the Knowledge to be Gained 
Our work seeks to build on more than 25 years of clinical investigative experience and more 
than 20 years of technology development.  Both age and insulin resistance are associated with a 
high prevalence of dementia. Insulin resistance is highly prevalent with advancing age. Metformin 
is an insulin sensitizer and is currently being extensively investigated for its potential anti-aging 
effect. However, only very limited information is available on metformin effect on brain, which is 
a major organ affected by aging. With appropriate experimental design, we are attempting to 
understand the mechanism of metformin treatment on the physiology of the brain as well as 
cognitive effects. Our studies may uncover relationships that could be favorably manipulated to 
decrease health risks associated with insulin sensitivity and the effect on the brain.  
 
VI. Gender/Minority Mix 
 
There are no exclusions based on gender or minority.   
 
VII. References 
 
1. 
Araki A. [Dementia and insulin resistance in patients with diabetes mellitus]. Nihon 
rinsho Japanese journal of clinical medicine. 2010;68(3):569-74. 
2. 
Gupta A, Bisht B, and Dey CS. Peripheral insulin-sensitizer drug metformin ameliorates 
neuronal insulin resistance and Alzheimer's-like changes. Neuropharmacology. 
2011;60(6):910-20. 
3. 
Konopka AR, Asante A, Lanza IR, Robinson MM, Johnson ML, Dalla Man C, et al. 
Defects in mitochondrial efficiency and H2O2 emissions in obese women are restored to 
a lean phenotype with aerobic exercise training. Diabetes. 2015;64(6):2104-15. 
4. 
Thirion B, Pinel P, Meriaux S, Roche A, Dehaene S, and Poline JB. Analysis of a large 
fMRI cohort: Statistical and methodological issues for group analyses. NeuroImage. 
2007;35(1):105-20. 
5. 
Konopka AR, Esponda RR, Robinson MM, Johnson ML, Carter RE, Schiavon M, et al. 
Hyperglucagonemia Mitigates the Effect of Metformin on Glucose Production in 
Prediabetes. Cell reports. 2016;15(7):1394-400. 
6. 
Aroda VR, Edelstein SL, Goldberg RB, Knowler WC, Marcovina SM, Orchard TJ, et al. 
Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention 
Program Outcomes Study. The Journal of clinical endocrinology and metabolism. 
2016;101(4):1754-61. 
7. 
Gershon RC, Wagster MV, Hendrie HC, Fox NA, Cook KF, and Nowinski CJ. NIH 
toolbox for assessment of neurological and behavioral function. Neurology. 2013;80(11 
Suppl 3):S2-6. 
8. 
Mielke MM, Machulda MM, Hagen CE, Edwards KK, Roberts RO, Pankratz VS, et al. 
Performance of the CogState computerized battery in the Mayo Clinic Study on Aging. 


15 
 
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2015;11(11):1367-
76. 
9. 
Robinson MM, Dasari S, Konopka AR, Johnson ML, Manjunatha S, Esponda RR, et al. 
Enhanced Protein Translation Underlies Improved Metabolic and Physical Adaptations to 
Different Exercise Training Modes in Young and Old Humans. Cell metabolism. 
2017;25(3):581-92. 
 


Statistical Analysis Plan 
 
Statistical plan: The analysis of the aims will be focused on estimation – standard deviations of 
MRS estimates and initial examinations of the changes in measures over time. With 20/group and 
repeated measures, we will be able to fit repeated measures models (e.g., mixed effects 
“trajectories”). For MRS with only a pre-post assessment, the mixed model framework is 
essentially a two-sample t-test on the changes over time, but importantly, the modeling framework 
will allow inclusion of all available data. This is to provide the most degrees of freedom to estimate 
the residual error, which will be used to plan a definitive study should these results appear 
promising (biological engagement as quantified by MRS and fMRI, change in insulin sensitivity, 
etc.) Supporting these analyses will be standard descriptive and graphical summaries of the data.   
 
Sample size justification. This is a developmental grant, so the sample size is not justified based 
on power for any of the particular aims. Rather, the estimate is based on precision and reliable 
estimates of the imaging studies. In particular, for the fMRI study Thirion et al (1) found that 20 to 
25 subjects were necessary to achieve reliable results. Given we want to study 20 within-group 
metformin subjects with fMRI, balancing the randomization 1:1 will yield a total sample size of 40. 
The effect sizes for between group differences are unknown; however, we will have 80% power 
to detect an effect size of at least 0.9 SD difference between the groups at alpha=0.05 (two-
sided). 
 
MR Data Acquisition: As the effects of metformin on the human brain are not known, a multi-
parametric imaging approach will be used to probe different aspects of the CNS.  Imaging will be 
performed on a 3 Tesla Siemens Skyra equipped with a 32-channel head coil and the multi-
nuclear option (MNO) running VE11C software. Imaging sequences include the following: To 
measure structural information:  A sagittal 3D MPRAGE sequence with 0.7mm isotropic voxels 
(TR=2400, TE=2.57, TI=1100, FA=8) will be used to acquire high-resolution structural data for 
volumetric analysis of brain region changes related to metformin.  The higher resolution allows 
for less variable segmentation and parcellation resulting in more accurate volumetric 
measurements. To measure white matter information: An axial 2D symmetric multi-slice (SMS) 
diffusion tensor imaging (DTI) sequence with 60 diffusion directions, 5 B0 acquisitions and 2mm 
isotropic voxels (TR=3000, TE=73, FA=90, ETL 43, both A-P and P-A phase encoding for B0 
images) will be used to acquire white matter integrity data related to metformin.  To measure 
global brain blood flow information: An axial 3D pseudo-continuous arterial spin labelling (pCASL) 
sequence (WIP 818) with 4mm isotropic voxels (TI1=1800, TI2=3600, iPat ≤ 2) will be used to 
acquire quantitative blood flow measurements (flow in ml/100g/min) throughout the brain.  A post-
label delay of 1800 ms will be used (2) as we are imaging otherwise healthy subjects. To measure 
global brain functional network information: An axial 2D echo-planar imaging sequence with 3mm 
isotropic voxels (FA=90, TE=30, TR=2000, # slices=50) will be used to acquire resting state 
functional MRI data throughout the brain. To measure brain lactate: A single voxel point-resolved 
MR spectroscopy sequence (PRESS, 2 cm isotropic voxel, TE=30, TR=2000, 5000 Hz, 2048 
points, 128 acquisitions with water suppression and 16 acquisitions without water suppression) 
will be used to acquire metabolite information from the right dorsolateral prefrontal cortex (DLPFC, 
chosen due to the high number of insulin receptors in this region (3).  As metformin has been 
shown to alter mitochondrial function in other organs, we will measure lactate in study participants 
to determine if they have significant anaerobic metabolism. To measure brain ATP levels: 
Multivoxel chemical shift imaging (dual-tuned proton (Helmholtz pair)/phosphorus (loop) flex coil 
applied such that the phosphorus loop overlies the right DLPFC, WIP 1071, axial 1.5 cm slice 
prescribed to encompass the right dorsolateral prefrontal cortex, 12x12 matrix reconstructed to 
16x16 matrix, 1.5 cm nominal isotropic voxels, TR=1500) will be used to acquire phosphorus 
metabolite information from the right DLPFC.  B1 in homogeneities will be corrected using a 
second high-speed acquisition (4). We may be able to detect changes in ATP levels in metformin 
subjects due to less efficient ATP production. 


MR Data Analysis: Brain volumetrics: MPRAGE data will be analyzed using Freesurfer 6.0 
(http://surfer.nmr.mgh.harvard/edu). Briefly, MPRAGE images are converted to a NIFTI volume 
using mri_convert, then processed using recon_all with manual inspection of data between each 
recon step.  Cortical and subcortical parcellation (5;6) is then performed using the freesurfer 
DKT40 classifier atlas (reportedly more accurate than the Desikan-Killiany atlas) (7) using 
mris_ca_label. Volumetric data from each brain region will be compared by group (metformin vs. 
control) and across time (timepoint A and B).  As an exploratory analysis, we may also perform 
hippocampal subfield parcellation (8), and see how the longitudinal processing stream compares 
to conventional two-timepoint analysis (Reuter et al 2012). DTI analysis: DTI data will be 
processed using dt recon with eddy current and motion correction. MPRAGE structural data will 
then be resampled into DTI space mri_vol2vol, and various DTI metrics (fractional anisotropy 
(FA), apparent diffusion coefficient (ADC), trace, radial diffusivity (RD) and axial diffusivity (AD) 
tabulated for each cortical, subcortical and white matter region using mri_segstats. ASL analysis: 
CBF maps will be calculated per the method of Wang et al (9).  CBF data will then be converted 
into a volume, then co-registered to the MPRAGE data using bbregister.  Parcellation masks will 
then be used to calculate the average CBF in each region. rsFMR analysis: rsFMRI data will be 
denoised by a well-established preprocessing pipeline (10;11), and registered to the MPRAGE 
structural data to get functional connectivity matrices across cortical and subcortical parcellations 
from FreeSurfer. Individual connectivity matrices for whole subjects will be used for the group 
comparison between placebo and drug-dose groups, and also for canonical correlation analysis 
between connectivity strength and clinical outcomes (behavioral scores)(12). Proton MRS 
analysis: single voxel proton MRS data will be processed using LCModel 6.3-1L (13). Phosphorus 
MRSI analysis: multivoxel phosphorus MRSI data will be reconstructed and quantified using 
jMRUI 6.0 (http://www.jmrui.eu). For the primary and calibration acquisitions, a simulated 7 
metabolite basis set (PME, Pi, PDE, PCr, γ-ATP, α-ATP, β-ATP) will be fit to data following zero- 
and first-order phasing, and 8 Hz spectral apodization. Data will then be corrected for B1 
inhomogeneity per the method of Chmelik (14). Metabolite data from the voxels incorporating the 
right DLPFC will be averaged and used in the statistical analysis. 
 
Cognitive function: We will use the computerized NIH toolbox to measure cognitive outcomes. 
The NIH encourages the use of these tools to enhance collection of data in large studies and for 
clinical trials (15). The cognitive and behavioral tests were normed across a national sample of 
persons aged 3-85 years. We will utilize the iPad version of the NIH Toolbox because we have 
shown that residents within Olmsted County, MN prefer the iPad over a personal computer (16).  
Dr. Mielke will oversee this aspect of the proposal.  She is an expert in cognitive function and was 
a member of the NIH task force on computerized cognitive batteries.   
Cognitive Outcomes. The NIH Toolbox-Cognition Battery is composed of 7 tests (~30 minutes) 
including the Dimensional Change Card Sort (DCCS) Test (executive function), the Flanker 
Inhibitory Control Test (executive function), the Picture Sequence Memory Test (episodic 
memory), the Picture Vocabulary Test (vocabulary), the Oral Reading Recognition Test (reading), 
the List Sorting Working Memory Test (working memory), and the Pattern Comparison Processing 
Speed Test (processing speed).  For each test, the raw scores will be converted to normally 
distributed standard scores (scaled scores) having a mean of 10 and a standard deviation of 3.  
To reduce the number of outcomes, our primary outcomes will focus on the following three 
composite scores: Crystalized Cognition Composite (Picture Volabulator Test and Oral 
Completion Test), Fluid Cognition Composite (DCCS, Flanker test, Picture Sequence Memory 
Test, List Sorting Working Memory, and Pattern Comparison Processing Speed), and the Total 
Cognition Composite score. Both the individual tests and composite outcomes have been found 
to have good convergent and discriminant validity and test-retest reliability (17-19).  
 
Interpretation: In this double-blind placebo-controlled study all data interpretation will be 
performed at the end of the study and the un-blinding will be done by the statistician. Statistical 
plan is as outlined above. We will make conclusions on whether our hypotheses are proved or 
disproved based on statistical significance (P<0.05) of the outcomes that are outlined under MR 


data analysis and cognitive functions. If the observed data reaches statistical significance for one 
or more outcomes our outlined hypotheses will be proven. However, if the significance level does 
not reach statistical significance but shows promising results, that will offer opportunities for a 
larger study with more participants and perhaps longer duration. 
 
Limitations: We appreciate that this exploratory (R21) study plan is without having sufficient 
preliminary data to determine the optimum study duration and the number of participants required 
to prove or disprove our hypotheses definitively. The primary objective of this type of grant is to 
obtain robust preliminary data for larger more definitive clinical trials. However, the robust study 
design, reasonable studies duration (e.g. a preliminary report of 8 weeks administration of 
metformin reported cognitive improvements (20) may help to overcome the limitation. The 
objective of acquiring robust preliminary data to determine whether metformin has any definitive 
or potential benefit is likely accomplished from the current study proposal. Although it has been 
shown that brain protein synthesis is low at 0.6%/h and half-life is 10 days (21), and may vary in 
different regions,  a 40 week study duration to determine if metformin has any effect on brain 
structure has a very reasonable chance of detecting changes with our MR approach, especially 
as suggested by our preliminary studies in diabetic mice. Assuming that human brain tissue 
turnover is slower than in rodents we are still likely to observe changes in brain structure and 
functions in 40 weeks. 31P-MRS based ATP production changes are likely to occur relatively 
rapidly because the enzymes involved rapidly are responsive to stimuli. Here we target our study 
in a susceptible population without a clinical diagnosis of dementia. Other interventions such as 
aerobic exercise in our experience enhances brain metabolism even in healthy people with no 
known cognitive issues with normal fasting glucose up on enhancing insulin sensitivity. Moreover, 
our main interest is whether metformin reported to have anti-aging effects has any effect on brain 
in an elderly population who is relatively sedentary and have insulin resistance. Eventually the 
goal is to combine metformin with other lifestyle measures such as exercise program.  
 
References 
 
1. Thirion B, Pinel P, Meriaux S, Roche A, Dehaene S, Poline JB. Analysis of a large fMRI 
cohort: Statistical and methodological issues for group analyses. Neuroimage. 2007 
Mar;35(1):105-20 
2. Alsop DC, Detre JA, Golay X, Gunther M, Hendrikse J, Hernandez-Garcia L, Lu H, 
MacIntosh BJ, Parkes LM, Smits M, et al. Recommended implementation of arterial spin-
labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study 
group and the European consortium 
3. Kleinridders A, Ferris HA, Cai W, Kahn CR. Insulin action in brain regulates systemic 
metabolism and brain function. Diabetes 2014 Jul;63(7):2232-43. PMCID:PMC4066341 
4. Chmelik M, Povazan M, Jiru F, Just K, I, Dezortova M, Krssak M, Bogner W, Hajek M, 
Trattnig S, Valkovic L. Flip-angle mapping of 31P coils by steady-state MR spectroscopic 
imaging. J Magn Reson.Imaging 2014 Aug;40(2):391-7 
5. Fischl B, Salat DH, Busa E, Albert M, Dieterich M, Haselgrove C, Van der Kouwe A, 
Killiany R, Kennedy D, Klaveness S, et al. Whole brain segmentation: automated labeling 
of neuroanatomical structures in the human brain. Neuron 2002 Jan 31;33(3):341-55 
6. Fischl B, Van der Kouwe A, Destrieux C, Halgren E, Segonne F, Salat DH, Busa E, 
Seidman LJ, Goldstein J, Kennedy D, et al. Automatically parcellating the human cerebral 
cortex. Cereb Cortex 2004 Jan;14(1):11-22 
7. Klein A, Tourville J. 101 labeled brain images and a consistent human cortical labeling 
protocol. Front Neurosci 2012;6:171. PMCID:PMC3514540 
8. Van Leemput K., Bakkour A, Benner T, Wiggins G, Wald LL, Augustinack J, Dickerson 
BC, Golland P, Fischl B. Automated segmentation of hippocampal subfields from ultra-
high resolution in vivo MRI. Hippocampus 2009 Jun;19(6):549-57. PMCID:PMC2739884 


9. Wang J, Zhang Y, Wolf RL, Roc AC, Alsop DC, Detre JA. Amplitude-modulated 
continuous arterial spin-labeling 3.0-T perfusion MR imaging with a single coil: feasibility 
study. Radiology 2005 Apr;235(1):218-28 
10. Jo HJ, Saad ZS, Simmons WK, Milbury LA, Cox RW. Mapping sources of correlation in 
resting state FMRI, with artifact detection and removal. Neuroimage 2010 Aug 
15;52(2):571-82. PMCID:PMC2897154 
11. Jo HJ, Gotts SJ, Reynolds RC, Bandettini PA, Martin A, Cox RW, Saad ZS. Effective 
Preprocessing Procedures Virtually Eliminate Distance-Dependent Motion Artifacts in 
Resting State FMRI. J Appl Math 2013 May 21;2013:10.1155/2013/935154. 
PMCID:PMC3886863 
12. Drysdale AT, Grosenick L, Downar J, Dunlop K, Mansouri F, Meng Y, Fetcho RN, Zebley 
B, Oathes D, Etkin A, et al. Resting-state connectivity biomarkers define 
neurophysiological subtypes of depression. Nature Medicine 2017;23:28-38 
13. Provencher SW. Estimation of metabolite concentrations from localized in vivo proton 
NMR spectra. Magn Reson Med 1993 Dec;30(6):672-9 
14. Chmelik M, Povazan M, Jiru F, Just K, I, Dezortova M, Krssak M, Bogner W, Hajek M, 
Trattnig S, Valkovic L. Flip-angle mapping of 31P coils by steady-state MR spectroscopic 
imaging. J Magn Reson.Imaging 2014 Aug;40(2):391-7 
15. Gershon RC, Wagster MV, Hendrie HC, Fox NA, Cook KF, Nowinski CJ. NIH toolbox for 
assessment of neurological and behavioral function. Neurology 2013 Mar 12;80(11 Suppl 
3):S2-S6. PMCID:PMC3662335 
16. Mielke MM, Machulda MM, Hagen CE, Edwards KK, Roberts RO, Pankratz VS, Knopman 
DS, Jack CR, Jr., Petersen RC. Performance of the CogState computerized battery in the 
Mayo Clinic Study on Aging. Alzheimers.Dement. 2015 Nov;11(11):1367-76. 
PMCID:PMC4595161 
17. Mungas D, Heaton R, Tulsky D, Zelazo PD, Slotkin J, Blitz D, Lai JS, Gershon R. Factor 
structure, convergent validity, and discriminant validity of the NIH Toolbox Cognitive 
Health Battery (NIHTB-CHB) in adults. J Int.Neuropsychol.Soc 2014 Jul;20(6):579-87. 
PMCID:PMC4103956 
18. Heaton RK, Akshoomoff N, Tulsky D, Mungas D, Weintraub S, Dikmen S, Beaumont J, 
Casaletto KB, Conway K, Slotkin J, et al. Reliability and validity of composite scores from 
the NIH Toolbox Cognition Battery in adults. J Int.Neuropsychol.Soc 2014 Jul;20(6):588-
98. PMCID:PMC4103963 
19. Carlozzi NE, Tulsky DS, Chiaravalloti ND, Beaumont JL, Weintraub S, Conway K, 
Gershon RC. NIH Toolbox Cognitive Battery (NIHTB-CB): the NIHTB Pattern Comparison 
Processing 
Speed 
Test. 
J 
Int.Neuropsychol.Soc 
2014 
Jul;20(6):630-41. 
PMCID:PMC4424947 
20. Luchsinger JA, Perez T, Chang H, Mehta P, Steffener J, Pradabhan G, Ichise M, Manly J, 
Devanand DP, Bagiella E. Metformin in Amnestic Mild Cognitive Impairment: Results of a 
Pilot Randomized Placebo Controlled Clinical Trial. J Alzheimers.Dis. 2016;51(2):501-14. 
PMCID:PMC5079271 
21. Lajtha A, Latzkovits L, Toth J. Comparison of turnover rates of proteins of the brain, liver 
and kidney in mouse in vivo following long term labeling. Biochim.Biophys.Acta 1976 Apr 
2;425(4):511-20 
 
 
 
 


 
 
Approval Date: 
August 5, 2022 
 
Not to be used after: August 26, 2022 
 
IRB#: 18-004012 00                e-sign 
Page 1 of 17 
IRB Doc. Ctrl # 10013.30 
 
 
 
 
 
 
 
Name and Clinic Number 
 
RESEARCH PARTICIPANT CONSENT AND PRIVACY 
AUTHORIZATION FORM 
 
Study Title: Metformin Effect on Brain Function in Insulin Resistant Elderly People  
 
IRB#:  
18-004012  
 
Principal Investigator: K. Sreekumaran Nair, M.D., Ph.D., and Colleagues 
 
Please read this information carefully. It tells you important things about this research study. A 
member of our research team will talk to you about taking part in this research study. If you have 
questions at any time, please ask us. 
 
Take your time to decide. Feel free to discuss the study with your family, friends, and healthcare 
provider before you make your decision.  
 
To help you decide if you want to take part in this study, you should know: 
• Taking part in this study is completely voluntary.  
• You can choose not to participate.  
• You are free to change your mind at any time if you choose to participate.  
• Your decision will not cause any penalties or loss of benefits to which you are otherwise 
entitled. 
• Your decision will not change the access to medical care you get at Mayo Clinic now or 
in the future if you choose not to participate or discontinue your participation.  
 
For purposes of this form, Mayo Clinic refers to Mayo Clinic in Arizona, Florida and Rochester, 
Minnesota; Mayo Clinic Health System; and all owned and affiliated clinics, hospitals, and 
entities. 
 
If you decide to take part in this research study, you will sign this consent form to show that you 
want to take part. We will give you a copy of this form to keep. A copy of this form will be put 
in your medical record. 
 
 


 
 
Approval Date: 
August 5, 2022 
 
Not to be used after: August 26, 2022 
 
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Name and Clinic Number 
 
CONTACT INFORMATION 
 
 
You can contact … 
At … 
If you have questions about … 
Principal Investigator: 
K. Sreekumaran Nair, 
M.D., Ph.D. 
 
Study Team Contact: 
Fred de Ruiter 
 
 
Phone: 
(507) 255-2415 
 
Phone: 
(507) 255-8932 
 
Institution Name and Address: 
Mayo Clinic 
200 First Street SW 
Rochester, MN 55905 
 
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emergencies 
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complaints 
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Toll-Free: 
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 Rights of a research participant 
 
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Name and Clinic Number 
Other Information:   
A description of this clinical trial will be available on http://www.ClinicalTrials.gov, as required 
by U.S. Law. This Web site will not include information that can identify you. At most, the Web 
site will include a summary of the results. You can search this Web site at any time. 
 
1. 
Why are you being asked to take part in this research study? 
 
 
You are being asked to take part in this research study because you are insulin resistant, a non-
smoker and 60 years or older and otherwise healthy.  
 
 
2. 
Why is this research study being done? 
 
 
This study is being done to understand metformin’s mechanisms of action regarding glucose 
production, insulin sensitivity, and brain function. 
 
The plan is to have 40 people complete this study at Mayo Clinic. 
 
 
3. 
Information you should know 
 
 
Who is Funding the Study? 
The National Institutes of Health is funding the study. The National Institutes of Health will pay 
your study doctor or the institution to cover costs related to running the study. 
 
Information Regarding Conflict of Interest: 
Your healthcare provider may be referring you to this research study. If your healthcare provider 
is also an investigator on this study, there is the chance that his or her responsibilities for the 
study could influence his or her recommendation for your participation. If you prefer, your 
healthcare provider will be happy to refer you to another investigator on the research study team 
for you to decide if you want to participate in the study and to see you for the research study 
activities while you are in the study. 
 
 


 
 
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4. 
How long will you be in this research study? 
 
 
You will be in the study for approximately 48 weeks. 
 
 
5. 
What will happen to you while you are in this research study? 
 
 
If you agree to be in the study, you will be asked to participate in the following:  
 
The initial study visit will be a Screening Visit. You will be asked to report to the Clinical 
Research and Trials Unit (CRTU) fasting (nothing to eat or drink after 7 pm the evening before 
except water) for a blood test, including a CBC, liver function, fasting glucose, lipid panel, and 
TSH. You will also have height and weight measurements taken and the MoCA test 
administered. While this is being done, the blood test results will be made available to the study 
team, and if you will be told if you pass the screening criteria. You will also be offered the 
opportunity to meet with the dietary staff of the CRTU to discuss dietary preferences and address 
any questions or concerns. This visit will take approximately 2 hours. 
 
Within 60 days after the Screening Visit, you will have your first outpatient visit: 
• You will have a Dual-energy X-ray absorptiometry (DEXA) scan to assess body 
composition 
• You will perform a VO2max test on a cycle ergometer to assess aerobic capacity. This 
test involves running on a treadmill while you are hooked up to a breathing mask. The 
test aims to measure your rate of oxygen consumption while your heart rate is elevated. It 
will be a progressively difficult test.  
• This visit will take approximately 3 hours 
 
Approximately 7 days after your first outpatient visit you will have your second outpatient visit: 
• You will be asked to start fasting, take nothing by mouth except water after 7 pm. 
• You will then go to the MRI unit in the Charlton building for your MRI testing in the 
a.m. 
• A small blood sample will be taken.  
• You will then undergo a special brain MRI that will not use contrast. We will not need to 
give you any medications for the MRI. The MRI testing will take approximately 1 hour.  


 
 
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• Lastly, you will have a PET scan done on your brain. Before beginning, we will check 
your blood glucose levels by doing a finger stick. The PET scan is done with a very small 
amount of a radioactive form of sugar, called 18F-fluorodeoxyglucose, or FDG. A small 
catheter will be placed in your arm to inject this compound. Once this is injected you will 
sit for 30 minutes before the pictures begin.  
You will be placed on a scanner bed for 10 minutes while the scans are completed. 
Afterwards you will be asked to drink fluids and go to the bathroom. This will take about 
1 hour. 
• Arrive at the CRTU on Charlton 07. 
• A small blood sample will be taken.  
• Vitamin B12 levels will be assessed. 
• You will then be given a meal and allowed to leave after the visit is completed  
• This visit will take approximately 3-4 hours.  
 
Approximately 1 week after completion of the MRI study visit, you will be admitted to the 
CRTU to stay overnight. The following will happen during your first overnight stay:  
• You will be given a standardized meal at 6:00 pm.  
• We will then ask you to perform approximately 1 hour of cognitive testing. These tests 
check your memory, thinking speed and other aspects of your thinking.  
• You will be asked to fast and take nothing by mouth except water after 7 pm. On the day 
after admission, we will ask that you have nothing at all by mouth except water for the 6 
1/2 hours of this study day.  
• Your resting energy expenditure (REE) will also be measured by performing indirect 
calorimetry during this visit. We will measure how much energy your body uses at rest 
by placing a special plastic dome over your head and having you rest quietly for 20 
minutes. We will be measuring how much oxygen you breathe in and how much carbon 
dioxide you breathe out. One indirect calorimetry (REE) will be done at the beginning of 
the clamp and a second indirect calorimetry (REE) will be done during the second phase 
of the clamp. 
• We will be placing a special kind of “backward” intravenous catheter into your hand and 
then placing that hand into a “hot box.”  This special kind of IV is the easiest way for us 
to get samples of blood during the study. The “hot box” is a transparent plastic box that is 
heated with a small motor to  50 degrees Celsius (122 degrees Fahrenheit). We will be 
taking frequent samples of blood throughout the study. The total amount of blood taken 
during study (including blood taken during the medical evaluation and all stays on the 
CRTU) will be about one pint (about as much as a standard blood donation).  
• At approximately 4 a.m. we will be placing intravenous (IV) needles to give you insulin 
and somatostatin. When these IV fluids are prepared, a small amount of albumin, a 
protein common in our bodies, is used. Both insulin and somatostatin are hormones that 
are normally present in your body. The somatostatin used in this study is considered 


 
 
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investigational. It has not been approved by the Food and Drug Administration (FDA) for 
routine clinical use. However, the FDA has allowed the use of somatostatin in this 
research study. Giving you insulin and somatostatin into your veins is called an “insulin 
clamp.”  
• Urine will be collected prior to starting the insulin clamp until the end of the clamp. A 
stool sample will be collected at this visit. If you are unable to provide a stool sample at 
this time, a kit will be provided with instructions on how to perform the collection at 
home, and how to return the kit to the study team. 
• You will also receive IV glucose. Glucose is produced in your body mainly by the liver. 
By giving you glucose that is slightly different than the glucose produced by your body, 
we will be able to measure how much glucose you produce. 
• When the intravenous lines are started, you will also receive a small amount of IV fluid 
that contains sodium chloride. 
• All infusions will be stopped by 1:30pm and a meal will be provided for you by the 
metabolic kitchen to consume.  
• Once deemed stable by the investigative team you will be allowed to leave. 
 
Approximately 1 week after the inpatient study visit, you will have a third outpatient visit to 
assess skeletal muscle changes. 
• You will be asked to fast and take nothing by mouth except water after 7 pm. The next 
day you will be asked to arrive at the CRTU at 6am for admission. On the day of 
admission, we will ask that you have nothing at all by mouth except water for the 6 1/2 
hours of this study day.  
• We will be placing a special kind of “backward” intravenous catheter into your hand and 
then placing that hand into a “hot box.”  This special kind of IV is the easiest way for us 
to get samples of blood during the study. The “hot box” is a transparent plastic box that is 
heated with a small motor to 55 degrees Celsius (131 degrees Fahrenheit). We will be 
taking frequent samples of blood throughout the study. The total amount of blood taken 
during study (including blood taken during the medical evaluation and all stays on the 
CRTU) will be about one pint (about as much as a standard blood donation).  
• When the intravenous lines are started, you will also receive a small amount of IV fluid 
that contains sodium chloride (i.e., saline). 
• We will perform two muscle biopsies to obtain a small piece of your muscle from the 
upper part of your leg. Muscle biopsies are obtained to measure markers of protein 
metabolism and function, including your DNA. The area of your leg will be numbed with 
Lidocaine that is mixed with a small amount of sodium bicarbonate. The Lidocaine can 
sting, and the sodium bicarbonate decreases the amount of stinging. A needle will then be 
used to remove the muscle. We will take a small sample at 7:00am and 9:00am.  


 
 
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• After the first muscle biopsy, we will give you a milk shake to drink, and we will take 
small blood samples for the next 2 hours to see how your body processes the protein, 
sugar, and fat. We will ask you to complete the entire milk shake within 15 minutes. 
• After the second biopsy, you will be given a standardized meal and allowed to leave by 
11:00am. This visit will take approximately 5 hours. 
• After completion of this visit you will pick up your first month’s study medication from 
the Research Pharmacy and begin taking the capsules as instructed. 
 
We will assign you by chance (like a coin toss) to the metformin group or the placebo group. 
You and the Principal Investigator cannot choose your study group. You will have an equal 
chance of being assigned to the metformin group.  
 
Placebo and Metformin 
This study uses a placebo. A placebo looks exactly like the study drug, but it contains no active 
ingredient. We use placebos in research studies to learn if the effects seen in research participants 
are truly from the study drug. You will be asked to swallow 2 capsules per day for the 1st week. 
One capsule will be taken with the morning meal and 1 capsule will be taken with the evening 
meal. For the 2nd week, you will be asked to swallow 3capsules per day. Two capsules will be 
taken with the morning meal and 1 capsule will be taken with the evening meal. From the 3rd 
week onward, you will be asked to increase to 4 capsules a day. Two capsules will be taken with 
the morning meal, and 2 capsules will be taken with the evening meal.  
 
The placebo capsule will contain lactulose and the Metformin capsule will contain 500 
milligrams of metformin. You will be given your first month’s supply of capsules upon 
discharge from the CRTU (Clinical Research and Trials Unit) at the end of your baseline studies. 
Once a month thereafter, you will be asked to report to the CRTU to pick up your new supply of 
capsules. At this time, you will be asked to return any capsules that you did not consume during 
the previous month. You will also have a brief appointment where a small amount of blood will 
be taken to measure markers of renal and liver function. These measurements are done to make 
sure it is safe for you to continue with the study.  
 
You will then report to the CRTU monthly for the 40 weeks that you will be taking metformin or 
the placebo. You must report to the CRTU fasting (nothing to eat or drink after 7 pm) for a 
weight check, blood test, and to pick up new capsules. You will be asked to return any unused 
capsules at this time as well. Your vitamin B12 levels will be checked pre-intervention, during 
the, 1, 3, 6 monthly visits, and post intervention. You will be given 1000mg vitamin B12 
replacement to be taken weekly. The study coordinator will also call you twice a month for the 
first 2 months to ensure compliance. After 40 weeks of taking metformin or placebo you will 
return to the CRTU to repeat the 1 inpatient and 3 outpatient visits as listed above. All 
procedures will be the same. 
 


 
 
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You will be asked to refrain from changing any lifestyle habits such as physical activity or diet 
for the entire duration of the study. You will also need to refrain from giving blood or being in 
any other research study eight weeks prior to the study and until eight weeks after the completion 
of the study. 
 
 
6. 
What are the possible risks or discomforts from being in this research 
study? 
 
 
Metformin may cause nausea or diarrhea. Metformin has been shown to cause lactic acidosis in 
patients with impaired liver, renal or heart function. Although these side-effects are rare, we will 
perform routine blood tests to make sure it is safe for you to be in the study. As with any 
medication, allergic reactions are a possibility.  
 
If you have recently had (<6 weeks) or are planning to have medical imaging performed on your 
body that requires contrast agents (i.e., dye) to be consumed please inform the investigators. 
 
You will receive the following drug and hormones during the study: Lidocaine, insulin, 
somatostatin, and labeled glucose. Infusion of insulin may decrease blood glucose (sugar) levels. 
Low blood sugar levels can cause you to feel sweaty, shaky, dizzy, or weak. Changes in blood 
glucose will be managed by checking blood glucose every 10 minutes and giving you a glucose 
solution. Somatostatin is an investigational drug.  
 
Giving somatostatin in the vein can cause nausea and rarely vomiting. If this occurs, we will 
promptly stop the study and respond appropriately. The special glucose we will be using has 
been changed very slightly from the glucose we eat every day. This change allows us to tell the 
difference between the glucose that is already in your system from the glucose we are giving you 
during the test. No side effects have been reported due to this change in the glucose molecule. A 
small amount of albumin, a protein found normally in our bodies, is used when the hormone 
solutions are prepared. No side effects have been reported from intravenous albumin. Lidocaine 
usually causes a mild burning sensation when it is first given into the skin. This stinging is 
lessened by our adding some sodium bicarbonate. As with any medication, allergic reactions are 
a possibility. In addition to the IV fluids containing medications, you will receive fluids that 
contain sodium chloride (salt). This fluid helps keep the veins open if the other fluids are not 
running and helps make the sugar water less irritating to your vein. 
 
You will have blood tests, body measurements, and blood pressure measurements that could 
uncover a condition you did not know you had. This can be stressful. We will fully explain any 
results that are not normal.  


 
 
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To measure your blood pressure, a cuff will be placed around your arm and this will be pumped 
up and become tight. This can cause temporary discomfort. You will talk with a dietician so that 
you will not receive food to which you may be allergic or dislike.  
 
The risks of drawing blood include pain, bruising, and rarely, infection at the site of the needle 
stick. 
 
The risks of placing the IV catheters include pain, bruising, or, rarely, infection at the site of 
catheter placement. There is also the possibility that you may have a reaction to the tape or other 
materials to hold the IV in place. 
 
The “hot box” may cause mild discomfort and reddening of your skin. This will go away when 
your hand is taken out of the “hot box.” 
 
We will be collecting urine and stool samples during your stay in the Clinical Research Unit. We 
will need to ask you to use a urinal or bedside commode. This may be embarrassing. We will 
provide privacy to minimize any embarrassment.  
 
A DEXA scan uses X-rays to measure body composition or bone density. You will be exposed to 
radiation during the DEXA scan. The amount of radiation you will receive has a low risk of 
harmful effects.  
 
The treadmill exercise test may be uncomfortable because of the mouthpiece and nose clip. 
Breathing through the mouthpiece during the exercise can cause your throat to feel dry. We will 
be asking you to exercise as long as possible. Your heart rate and blood pressure will be watched 
closely, and the test can be stopped at any time. 
 
Participating in unaccustomed resistance exercise may include risk of injury. To reduce this risk, 
the exercise will be performed under the supervision of qualified study team member, which will 
also decrease the likelihood of injury. 
 
There is a risk of claustrophobia (fear of closed space) while you are in the transparent plastic 
hood during the indirect calorimetry (REE). Fresh air does come through the hood. This risk will 
be decreased by allowing you to watch television or a movie while the hood is on. If you are 
unable to tolerate the hood, it will be removed. 
 
Side affects you may experience from the muscle biopsy include bleeding, collection of blood 
under the skin, bruising or infection. By applying proper pressure over the site, bleeding and 
bruising are usually avoided. Strict sterile precautions will be taken to avoid infection. Pain is 
unlikely since a local anesthetic is used. However, you may experience a deep pressure feeling at 


 
 
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the site of the biopsy. You will have temporary discomfort for 2 to 7 days following the 
procedure at the site where the incision was made. In rare instances, people have reported 
numbness around the biopsy site for up to one year or longer. You may have a scar from the 
incision. 
 
During tests of memory and thinking you may experience anxiety or fatigue like taking a test in 
school. 
 
There is no radiation associated with MRI, but people who have metal devices like pacemakers 
cannot have an MRI and will not be able to participate in the study.  People with claustrophobia 
may feel too closed in and may not tolerate MRI scanning. If you feel too confined in the MRI 
scanner you can inform the technologist and the MRI scan will be stopped. The MRI machine 
makes loud knocking sounds when it is scanning. Because of this you will be asked to wear 
earplugs while getting your MRI scan. The earplugs minimize discomfort from noise and keep 
the MRI noise within the safety range. 
 
There is a small amount of radiation exposure from the images used in the PET scan. There is 
also a minor risk of pain and bruising at the injection site.  
 
Risk summary  
Most side effects go away shortly after the intravenous infusions and muscle biopsies are 
stopped, but in rare cases side effects can be serious, long lasting, or may never go away. There 
is the potential for side effects may not be known. Side effects may range from mild to life-
threatening. Other drugs may be given to make side effects less serious and less uncomfortable. 
Talk to the researcher and/or your healthcare provider about side effects and ask any other 
questions. 
 
 
7. 
Are there reasons you might leave this research study early? 
 
 
You may decide to stop at any time. You should tell the Principal Investigator if you decide to 
stop and you will be advised whether any other tests may need to be done for your safety in 
addition, the Principal Investigator or Mayo Clinic may stop you from taking part in this study at 
any time: 
• if it is in your best interest,  
• if you do not follow the study procedures,  
• if the study is stopped.  
 


 
 
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If you leave this research study early, or are withdrawn from the study, no more information 
about you will be collected; however, information already collected about you in the study may 
continue to be used. 
 
We will tell you about any new information that may affect your willingness to stay in the 
research study.  
 
 
8. 
What if you are injured from your participation in this research study? 
 
 
Where to get help: 
If you think you have suffered a research-related injury, you should promptly notify the Principal 
Investigator listed in the Contact Information at the beginning of this form. Mayo Clinic will 
offer care for research-related injuries, including first aid, emergency treatment and follow-up 
care as needed. 
 
Who will pay for the treatment of research related injuries: 
Care for such research-related injuries will be billed in the ordinary manner, to you or your 
insurance. Treatment costs for research-related injuries not covered by your insurance will be 
paid by Mayo Clinic. 
 
 
9. 
What are the possible benefits from being in this research study? 
 
 
You will not benefit from taking part in this research study. It is for the benefit of research. 
 
 
10. 
What alternative do you have if you choose not to participate in this 
research study? 
 
 
This study is only being done to gather information. You may choose not to take part in this 
study. Your care at the Mayo Clinic or Olmsted Medical Center will not be jeopardized if you 
choose not to participate.  
 
 


 
 
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11. 
What tests or procedures will you need to pay for if you take part in this 
research study?  
 
 
You will not need to pay for tests and procedures which are done for this research study.  
These tests and procedures are: 
• Blood tests 
• Urine collections 
• Stool collections 
• Muscle biopsies 
• Brain MRIs 
• Cognitive function testing 
• REE’s (resting energy expenditure) 
• Study meals 
• Medication (i.e., metformin or placebo) 
• DEXA scans 
• PET Scans 
• Vitamin B12 replacements (if applicable) 
• VO2max tests 
 
However, you and/or your insurance will need to pay for all other tests and procedures that you 
would have as part of your clinical care, including co-payments and deductibles. 
 
If you have billing or insurance questions call Patient Account Services at the telephone 
number provided in the Contact Information section of this form. 
 
 
12. 
Will you be paid for taking part in this research study? 
 
 
You will receive $100.00 for each visit (excluding the monthly medication dispensing visits) you 
complete. If you complete the entire study, you will receive up to $900.00. You will receive one 
payment at the end of the study. 
 
You will receive reimbursement for driving mileage during the study. Reimbursement will be 
equivalent to the number of miles traveled multiplied by the IRS standard mileage 
reimbursement rate. As of January 1, 2022, this reimbursement rate was $0.585 per mile. This 


 
 
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will be calculated from the distance between the address you have in your Electronic Health 
Record and the St. Marys Campus.  
 
Payment for participation in research is considered taxable income and reportable to the Internal 
Revenue Service (IRS). Accounts Payable at Mayo Clinic will be given your name, address, and 
Social Security number to issue a check for your study participation. If you receive research 
payments totaling $600 or more in a calendar year, a tax Form 1099 will be sent to you. For 
Mayo Clinic employees, research payments are included in your paycheck with applicable taxes 
withheld and reported on your Form W2 after calendar year-end. 
 
You will receive a 3D printed model of your brain. The model will be scaled to approximately 
1/3rd of the size of your brain.  
 
 
13. 
What will happen to your samples? 
 
 
Your stool samples will be stored at Mayo Clinic and then sent to University of MN for research 
purposes only as described in the research study and this consent form. Your sample will be sent 
in a coded format, which protects your identity. 
 
We would like to keep your sample for future research. You can still take part in this current 
study even if you do not want your sample used for future research. If you agree to give your 
sample, it will be the property of Mayo Clinic. 
 
Other researchers at Mayo Clinic who are not involved with this study may ask to use your 
sample for future research. Researchers at other institutions may also ask for a part of your 
sample for future studies. Your sample will be sent to researchers in a coded format, which 
protects your identity. 
 
Some future studies may examine your DNA, which is the genetic information you inherited 
from your parents (genetic testing). The Principal Investigator may contact you if there are 
findings which may be useful for your health care. You would be given general information on 
the potential risks, benefits, and costs of choosing to learn about the findings.   
 
There is an exceedingly small chance that commercial value may result from the use of your 
donated sample. If that happens, you will not be offered a share in any profits. 
 
 
 


 
 
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Please read the following statements and mark your choices: 
 
 
1.  I permit my sample to be stored and used in future research of diabetes mellitus at 
Mayo Clinic: 
 
  Yes 
  No  
Please initial here: ________Date: ________ 
 
2.  I permit my sample to be stored and used in future research at Mayo Clinic to learn 
about, prevent, or treat any other health problems: 
 
  Yes 
  No  
Please initial here: ________Date: ________ 
 
3.  I permit Mayo Clinic to give my sample to researchers at other institutions: 
 
  Yes 
  No  
Please initial here: ________Date: ________ 
 
You may request to have your sample destroyed by writing to the Principal Investigator. The 
address is found in the “Contact Information" section of this consent form. 
 
Because we cannot predict how your sample will be used in the future, we cannot promise that 
samples can be retrieved and destroyed. 
 
 
14. 
How will your privacy and the confidentiality of your records be protected? 
 
 
Mayo Clinic is committed to protecting the confidentiality of information obtained about you in 
connection with this research study. The safeguards include coding data, removing identifiers 
before data analyses, storing electronic data files behind the Mayo security system accessible 
only to study team members by password protection and by keeping hard copy of subject details 
in institutionally secure offices. If the results of the research are made public, information that 
identifies you will not be used. 
 
All materials collected will be used for research purposes only and confidentiality will be assured 
by use of identification codes. Electronic data will be kept in a secure database, which is only 
accessible to the study investigators. 
 
During this research, information about your health will be collected. Under Federal law called 
the Privacy Rule, health information is private. However, there are exceptions to this rule, and 
you should know who may be able to see, use and share your health information for research and 
why they may need to do so. Information about you and your health cannot be used in this 
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research study without your written permission. If you sign this form, it will provide that 
permission (or “authorization”) to Mayo Clinic.  
 
Your health information may be collected from: 
• Past, present, and future medical records. 
• Research procedures, including research office visits, tests, interviews, and 
questionnaires. 
 
Your health information will be used and/or given to others to: 
• Do the research. 
• Report the results. 
• See if the research was conducted following the approved study plan, and applicable rules 
and regulations. 
 
Who may use or share your health information? 
• Mayo Clinic research staff involved in this study.  
 
Your health information may be used and shared with: 
• Mayo Clinic research staff involved in this study.  
• Other Mayo Clinic staff involved in your clinical care.  
• Researchers involved in this study at other institutions.  
• University of MN 
• The sponsor(s) of this study and the people or groups hired by the sponsor(s) to help 
perform this research. 
• The Mayo Clinic Institutional Review Board that oversees the research.  
• Federal and State agencies (such as the Food and Drug Administration, the Department of 
Health and Human Services, the National Institutes of Health, and other United States 
agencies) or government agencies in other countries that oversee or review research. 
• A group that oversees the data (study information) and safety of this research. 
 
How your information may be shared with others: 
While taking part in this study, you will be assigned a code that is unique to you, unless 
otherwise specified in this consent form, but does not include information that directly identifies 
you unless otherwise specified in this consent form. This code will be used if your study 
information is sent outside of Mayo Clinic. The groups or individuals who receive your coded 
information will use it only for the purposes described in this consent form. 
If the results of this study are made public (for example, through scientific meetings, reports, or 
media) information that identifies you will not be used. 
 


 
 
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In addition, individuals involved in study oversight and not employed by Mayo Clinic may be 
allowed to review your health information included in past, present, and future medical and/or 
research records. This review may be done on-site at Mayo Clinic or remotely (from an off-site 
location). These records contain information that directly identifies you. However, the 
individuals will not be allowed to record, print, copy (using paper, digital, photographic, or other 
methods), or remove your identifying information from Mayo Clinic. 
 
Is your health information protected after it has been shared with others? 
Mayo Clinic asks anyone who receives your health information from us to protect your privacy; 
however, once your information is shared outside Mayo Clinic, we cannot promise that it will 
remain private, and it may no longer be protected by the Privacy Rule. 
 
Your Privacy Rights 
You do not have to sign this form, but if you do not, you cannot take part in this research study. 
 
If you cancel your permission to use or share your health information, your participation in this 
study will end and no more information about you will be collected; however, information 
already collected about you in the study may continue to be used. 
 
If you choose not to take part or if you withdraw from this study, it will not harm your 
relationship with your own doctors or with Mayo Clinic. 
 
You can cancel your permission to use or share your health information at any time by sending a 
letter to the address below: 
 
Mayo Clinic 
Office for Human Research Protection 
ATTN:  Notice of Revocation of Authorization 
201 Building 4-60 
200 1st Street SW 
Rochester, MN  55905 
 
Alternatively, you may cancel your permission by emailing the Mayo Clinic Research Subject 
Advocate at: researchsubjectadvocate@mayo.edu. 
 
Please be sure to include in your letter or email: 
• The name of the Principal Investigator, 
• The study IRB number and /or study name, and 
• Your contact information. 
 


 
 
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Name and Clinic Number 
Your permission for Mayo Clinic to use and share your health information lasts until the end of 
this study unless you cancel it. The study does not end until all data has been collected, checked 
(or audited), analyzed, and reported. Because research is an ongoing process, we cannot give you 
an exact date when the study will end. Sometimes this can be years after your study visits and/or 
activities have ended. 
 
There is no expiration or end date related to the Sponsor’s use of your health information 
received from Mayo Clinic as part of this study. 
 
 
ENROLLMENT AND PERMISSION SIGNATURES 
 
 
Your signature documents your permission to take part in this research.  
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
  
Printed Name  
 
 
Date (mm/dd/yyyy) 
 
 
Time (hh:mm am/pm)  
 
 
 
 
 
 
 
 
_______________________________ 
Signature 
 
Person Obtaining Consent  
• I have explained the research study to the participant. 
• I have answered all questions about this research study to the best of my ability. 
 
 
 
Printed Name  
 
 
Date (mm/dd/yyyy) 
 
 
Time (hh:mm am/pm) 
 
 
_______________________________ 
Signature 
chkEsi
dteParticipantSig
sigParticipant
prtParticipantName
prtPOCName
dtePOCSig
sigPOC
sigWitness