PRELIMINARY EVALUATION OF PHARMACOLOGICAL LOWERING OF AGEs
Condition: DIABETES; DIABETIC RETINOPATHY; DIABETIC NEUROPATHY
MeSH terms: Diabetic Neuropathies; Diabetic Retinopathy
Study type: Interventional
Phase: Phase 4

Summary: 
      There is evidence of the association between diabetic microangiopathy and elevated serum
      concentrations of advanced glycation end-products (AGEs). AGEs levels are associated with
      ingestion of specific foods (baked meats and milk powder); reducing their dietary intake
      lowers AGEs concentrations, with beneficial metabolic effects; however threre is still no
      evidence of whether this has an impact on microvascular complications of DM. We recently
      applied for funding to compare in a RCT the effects of Cholestyramine versus placebo, on
      visual electrophysiology. This drug is similar to Sevelamer in structure, both act as
      chelators of bile salts, and reduce absorption of dietary AGE, lowering serum levels. However
      it is essential to carry out preliminary tests to assess aspects that may imply adjustments
      to the proposed protocol, such as: 1) tolerance to the drug 2) short term effect of the drug
      versus placebo on serum levels of AGEs 3) effects of the drug versus placebo in levels of fat
      soluble vitamins (D and K specifically) 4) intra and interindividual variability of
      electrophysiological measurements of vision (ERGMF and optic nerve conduction velocity) 5)
      drug versus placebo in electrophysiological measurements of vision (neuroconduction ERGMF and
      optic nerve). Objective: The present project is planned as a pilot study, which will clarify
      points 1 to 5. Methodology: patients (6 DM2, 25 -50 y) will be assessed through
      anthropometry, clinical laboratory tests (creatinine, chemistry profile, lipid profile,
      microalbuminuria glycosylated hemoglobin, vitamin B12, 25OH vitamin D and prothrombin),
      dietary recalls specifically designed to analyze the regular consumption of AGEs, serum CML
      and neuro-ophthalmological study (fundus, ERGMF and optic nerve conduction). Subsequently
      each patient will be assigned to treatment with placebo for 3 months and then Cholestyramine
      6 g / day for 12 weeks and at the end of each period will be reassessed using the same
      methodology. If patients cannot tolerate the drug, they will be assigned to a reduced AGE
      diet.

      Expected results: Cholestyramine will have side effect similar to placebo (mainly digestive).
      The active drug and not placebo will reduce serum levels of AGEs and electrophysiological
      parameters of vision at 12 weeks. It is expected that a low AGEs diet in patients who do not
      tolerate the drug will also reduce serum CML although to a lesser degree and will also induce
      electrophysiologic changes.
    

Detailed description: 
      Patients: 6 adults with type 2diabetes will be selected, ages between 25 and 50 years, with
      more than 5 and less than 10 years of disease, adherent to treatment with oral hypoglycemic
      agents or insulin, who agree to participate in the study through a written informed consent.
      Only those with a high habitual intake of AGEs according the food recall will be included.
      Patients with the following characteristics will be excluded: -Severe Obesity (BMI> 35 kg /
      m2), glycosylated hemoglobin> 9%, anemia, renal failure (creatinine> 1.5 mg / dL or
      calculated creatinine clearance <60 ml / min), fasting plasma glucose> 250 mg / dL or a
      history of acute hyperglycemic complications requiring hospitalization in the past 2 years,
      severe diabetic dyslipidemia (LDL> 130, TG> 350 mg / dL) or vitamin B12 deficiency, a history
      of heart, liver, lung cancer or chronic diseases, clinical diagnosis of diabetic neuropathy
      and eye conditions that could hinder electroretinogram, such as uncorrected refractive
      defects, cataracts and severe diabetic retinopathy or macular edema. Other exclusion criteria
      will be poorly controlled hypertension or acute vascular event in the past 2 years and
      pregnancy.

      After signing an informed consent, patients will undergo the following assessments: 1)
      History and drug registration. 2) dietary survey including methods of food preparation,
      consumption of dietary products containing fructose or corn starches and specific foods rich
      in AGEs according to measurements made in Chilean foods (milk and concentrated powder,
      biscuits, cheeses was also specifically recorded, roasted meats and grilled sausages etc.).
      3) anthropometry (weight, height, waist circumference) 4) fasting basic laboratory tests
      fasting (hemoglobin, TSH, glucose, glycosylated hemoglobin, creatinine, prothrombin, lipid
      profile and serum levels of vitamin B12 and vitamin D), using automated clinical laboratory
      techniques. 5) morning urine for determination of microalbuminuria (MAU / creatinine) 6)
      Inflammatory markers (ultrasensitive PCR) using a commercial ELISA kit. 7) Concentration of
      serum AGEs (CML through Abcam ELISA Antibody) 8) Visual evoked potentials as indicator of
      electrophysiological conduction after visual stimulation through the optic nerve (ON)
      exploring the visual pathway (myelin) to the occipital cortex. 9) ophtalmologic examination
      with biomicroscopy for evaluation of refractive defects and fundus (to diagnose the presence
      or absence of retinopathy) and evoked potentials by multifocal electroretinography.

      This series of evaluations will be repeated after each each treatment period of 12 weeks
      each, ie on 3 occasions. Indications and reinforcement of traditional dietary measures to
      improve glycemic control (restriction of caloric intake according to body composition,
      decrease of intake of simple carbohydrates and increase of soluble and insoluble fiber to
      reduce glycemic load), according to the standards for diabetes management from the Ministry
      of Health. Also if necessary the hypoglycemic or insulin therapy will be adjusted in order to
      achieve adequate metabolic control (HbA1c <7%).

      For the specific drug treatment, initially inert placebo (talc) capsuleswill be prescribed
      during 12 weeks then switching to Cholestyramine during 12 weeks, with equal physical
      characteristics of capsules, after which all initial evaluations be repeated. Cholestyramine
      treatment will be prescribed using a 6 g daily dose (4 tablets daily of 500 mg each of
      cholestyramine with each main meal). Patients that manifest adverse effects with the use of
      the active drug and cannot maintain the treatment, will be assigned to a dietary treatment
      with a reduced AGE diet according to the recommendations of Uribarri et. al. (32) for 12
      weeks, at the end of which the initial evaluation will be repeated. In both periods
      supplementation with vitamin D in doses adjusted to pre-intervention, vitamin A and E in
      adequate doses to meet the DRI level and vitamin K if needed will be prescribed. Patients
      will be monitored monthly by their treating diabetologist, verifying compliance, registering
      adverse events, anthropometric measurements and fasting blood glucose. If elevated blood
      glucose levels are detected infectious causes or failure to adhere dietary indications will
      be discarded and corrective measures will be initiated. In patients who do not meet the
      inclusion criteria due to vitamin B12 deficiency, intramuscular supplementation will be
      indicated and will be referred to their respective centers. If vitamin D deficiency is
      detected, proper supplementation before entering the study will be indicated. At the end of
      the control period (placebo for 12 weeks), the same initial assessments will be repeated and
      then a second treatment (cholestyramine 6 g / day) will be assigned, repeating the same
      assessments at the end of these 3 months.

      Blood samples for determination of CML and ultrasensitive PCR will remain frozen at -70
      degrees to be processed all at the end of the study, avoiding to make any technical changes
      on 2 times. Instead determinations to be made in clinical laboratory (TSH, prothrombin,
      glycemia, lipid profile, creatinine, glycated hemoglobin, microalbuminuria and levels of
      vitamins B12 and D), will be processed immediately, delivering a copy of the results to each
      patient to facilitate corrective measures necessary.

      Primary endpoint and sample size: For this pilot study sample size was not estimated because
      one of the objectives is to assess variability and detect whether the short period of
      treatment does induce changes in electrophysiological variables that are clearly detectable,
      in addition to assessing drug tolerance. With this information you can better estimate the
      sample size for a randomized controlled larger. In addition it was felt necessary to begin
      the study using the placebo and no treatment assigned randomly because washout period would
      be necessary for a randomized crossover study of random type is unknown. The proposed (6
      patients) sample size was calculated based on the available budget. It is important to note
      that analysis of evoked potentials and electroretinography considers each eye separately, so
      that there will be 12 eyes in 6 patients.
    

Intervention name(s): CHOLESTYRAMINE
Intervention type(s): Drug
Intervention description(s): CHOLESTYRAMINE CAPSULES, 6 G/DAY P.O. DURING 12 WEEKS
Other intervention name(s): QUESTRAN
Intervention MeSH terms: Cholestyramine Resin
Allocation: Non-Randomized
Intervention model: Sequential Assignment
Intervention model description: Prescription of 6 g oral cholestiramine in 7 patients with type 2 DM, to study changes in neuroophtalmologic variables (electroretinogram and optic nerve conduction)
Masking: None (Open Label)
Primary purpose: Prevention