Omega-3 Fatty Acids and Insulin Sensitivity

Study Overview
=================
Brief Summary
-----------------
This study is being done to understand the effects of dietary omega-3 fats on insulin sensitivity in adult men and women.

Detailed Description
-----------------
Dietary omega-3 polyunsaturated fatty acids (n-3 PUFA), which include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, prevent insulin resistance in rodents, but data in humans is ambiguous. No existing studies have systematically evaluated the influence of n-3 PUFAs on insulin sensitivity and beta cell function in insulin resistant, non-diabetic humans. The Investigators hypothesize that 6 months of oral supplementation of purified EPA/DHA (3.9g/day) will significantly improve hepatic and peripheral insulin sensitivity and beta cell responsiveness in insulin-resistant, non-diabetic individuals. Based on recent work in mice, the investigators also hypothesize that EPA/DHA will increase the content and function of mitochondria in skeletal muscle, measured using a combination of in vivo and in vitro methods. Overall, the investigators hypothesize that EPA+DHA supplementation will improve hepatic and peripheral insulin sensitivity in insulin resistant humans, and this improvement will be associated with mitochondrial biogenesis and attenuated lipid accumulation in skeletal muscle and liver. A sub-study was added in which participants receiving dietary omega-3 fatty acids or placebo supplements underwent abdominal subcutaneous adipose tissue biopsies to measure the content of total, pro- (M1) and anti- (M2) inflammatory macrophages (immunohistochemistry), crown-like structures (immunohistochemistry), and senescent cells (β-galactosidase staining), as well as a two-step euglycemic, pancreatic clamp with a stable-isotope labeled precursor ((U-13C)palmitate) infusion to determine the insulin concentration needed to suppress palmitate flux by 50% (IC50(palmitate)f).

Official Title
-----------------
Dietary Omega-3 Fatty Acids as a Therapeutic Strategy in Insulin Resistant Humans

Conditions
-----------------
Insulin Resistance

Intervention / Treatment
-----------------
* Drug: Omega-3
* Drug: placebo


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion criteria: Age 18-65 years Insulin resistant (Homeostasis Model Assessment (HOMA) Insulin Resistance (IR) ≥2.6) Exclusion criteria: Current use of omega-3 nutritional supplements Fasting plasma glucose ≥126 mg/dL Active coronary artery disease Participation in structured exercise (>2 times per week for 30 minutes or longer) Smoking Medications known to affect muscle metabolism (e.g., beta blockers, corticosteroids, tricyclic-antidepressants, benzodiazepines, opiates, barbiturates, anticoagulants) Renal failure (serum creatinine > 1.5mg/dl) Chronic active liver disease (AST>144 IU/L and alanine transaminase (ALT)>165 IU/L) Anti-coagulant therapy (warfarin/heparin) International normalized ratio (INR) >3 Use of systemic glucocorticoids Chronic use of NSAIDS or aspirin Pregnancy or breastfeeding Alcohol consumption greater than 2 glasses/day Hypothyroidism Fish or shellfish allergy

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Omega-3<br>Patients in this group will receive oral supplementation with EPA+DHA (3.9grams/day) for 6 months. | Drug: Omega-3<br>* Patients in this group will receive oral supplementation with EPA+DHA (3.9grams/day) for 6 months.<br>* Other names: Lovaza;|
| Placebo Comparator: Placebo<br>Patients in this group will be supplemented with placebo capsules containing ethyl oleate. | Drug: placebo<br> <br> |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Insulin Sensitivity by Hyperinsulinemic-euglycemic Clamp at Baseline and 6 Month Follow up | A 2-stage insulin clamp will be performed with titration of dextrose to maintain euglycemia. D2 glucose will be infused to evaluate hepatic glucose production at baseline and in response to insulin. Hyperinsulinemic-euglycemic clamp technique: The plasma insulin concentration is acutely raised and maintained by a continuous infusion of insulin. Meanwhile, the plasma glucose concentration is held constant at basal levels by a variable glucose infusion. When the steady-state is achieved, the glucose infusion rate (GIR) equals glucose uptake by all the tissues in the body and is therefore a measure of tissue insulin sensitivity. | Baseline, after 6 months of treatment | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Beta Cell Function From Insulin Secretion Following Ingestion of a Mixed Meal at Baseline and 6 Month Follow up | Following consumption of a mixed meal, beta cell function will be evaluated from serial measurements of C-peptide. C-peptide was measured using a two-side immunometric assay using electrochemiluminescence detection. | baseline, after 6 months of treatment | 
| Mitochondrial Function Determined by Muscle Biopsy at Baseline and 6 Month Follow up | Measurements of oxygen consumption in isolated mitochondria will be performed using a polarographic oxygen electrode. | Baseline, after 6 months of treatment | 
| Insulin Concentration Needed to Suppress Palmitate Appearance Rates (IC50(Palmitate)f) | Sensitivity of adipose tissue lipolysis to insulin suppression, was calculated as the insulin concentration needed to suppress palmitate appearance rates (ie, flux) by 50% (IC50(palmitate)f). | approximately after 6 months of treatment | 
| Senescent Cells | Tissue burden of senescent cells, which was measured by staining for senescence-associated B-galactosidase activity and expressed as the number per 100 nucleated positive cells. | approximately after 6 months of treatment | 
| Immunohistochemistry Assessments of Macrophage Burden | One week after the pancreatic clamp study, participants were provided a standardized meal before an overnight fast. The next morning an abdominal adipose tissue biopsy was collected, and the samples were analyzed for adipocyte size. Immunohistochemistry was used to assess macrophage burden (total (CD68), M1 (CD14) and M2 (CD206) macrophages per 100 adipocytes). | approximately after 6 months of treatment | 
| Macrophage Crown-like Structures | Macrophages surrounding dying or dead adipocytes form crown-like structures (CLSs). One week after the pancreatic clamp study, participants were provided a standardized meal before an overnight fast. The next morning an abdominal adipose tissue biopsy was collected, and the samples were analyzed for adipocyte size. Immunohistochemistry was used to assess the number of crown-like structures per 10 images. | approximately after 6 months of treatment |