Background: Increase in obesity and metabolic syndrome are associated with increases in insulin resistance (IR) and type 2 diabetes mellitus. Results from animal intervention studies and human epidemiological studies suggest that n-3 polyunsaturated fatty acids can prevent and reverse IR, but results from human intervention studies have varied. Results from some human and animal studies suggest that docosahexaenoic acid (22:6n-3; DHA) may be more effective than eicosapentaenoic acid (20:5n-3; EPA) in the prevention of IR.
Methods: By using a placebo-controlled, parallel study design, we examined the effects of DHA supplementation (3 grams/day, 90 days) in the absence of EPA on glucocentric and lipocentric markers of IR in hypertriglyceridemic men (n=14-17/group).
Results: DHA supplementation increased fasting plasma glucose concentration by 4.7% (P<0.05), but did not alter other indices of IR based on fasting (insulin and homeostasis model assessment of insulin resistance [HOMA-IR]) or postprandial insulin and glucose concentrations (areas under curves for insulin and glucose, Matsuda index). Glucose increased by 2.7% in the placebo group and was not significant; increases in glucose in the two groups did not differ from each other. DHA decreased circulating concentrations of several lipocentric markers of IR, including plasma concentrations of nonesterified fatty acids (13.0%), small, dense low-density lipoprotein (LDL) particles (21.7%), and ratio of tryglycerides to high-density lipoprotein cholesterol (TG/HDL-C) (34.0%) (P<0.05). None of the variables changed in the placebo group.
Conclusions: Our results suggest that lipocentric markers of IR are more responsive to DHA supplementation than the glucocentric markers. Future studies with DHA in prediabetic subjects and direct measures of insulin sensitivity are needed.
Trial registration: ClinicalTrials.gov NCT00728338.