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Unformatted text preview: Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Prevention of insulin resistance by n-3 polyunsaturated fatty acids Dawn Fedor and Darshan S. Kelley Introduction Insulin resistance is a condition in which normal amounts of insulin fail to maintain normal blood glucose because of decreased responsiveness of muscle (glucose uptake), liver (inhibition of gluconeogenesis) and fat cells (inhi- bition of lipolysis) [1,2]. About 35% of the adult US population has insulin resistance, whereas only about 10% have type 2 diabetes . Insulin resistance is often associated with nonalcoholic fatty liver disease (NAFLD), which is the most common liver disease in the Western world. There are many factors including genetic predisposition, diet, inactivity, antibodies against insulin or its receptor, stress and inflammation that may contribute to the development of insulin resistance. Results from human epidemiological studies indicate that n-3 polyunsaturated fatty acids (PUFA) reduce the development of insulin resistance and diabetes, whereas those from intervention studies in animal models showed that high-fat (particularly saturated and trans fatty acids) and high-sucrose diets induced insulin resistance. There are only a limited number of human intervention studies regarding the effects of n-3 PUFA on insulin resistance and the results have been variable. Here we will review the results from recent human and animal studies that examined the effects of n-3 PUFA on insulin resistance, and will attempt to explain the inconsistencies. Results from earlier studies can be found in other reviews [1,2]. Animal studies We found three reports in rats and five in mice published within the last 2 years that examined the effects of n-3 PUFA on insulin resistance (Table 1). Rat studies In a study with male rats fed control and high-fat diets, intubating eicosapentaenoic acid (20 : 5, n-3; EPA) reduced fasting insulin and insulin resistance in both groups as determined by the homeostasis model assess- ment of insulin resistance (HOMA-IR); however, it did Western Human Nutrition Research Center, ARS, USDA Department of Nutrition, University of California, Davis, California, USA Correspondence to Darshan S. Kelley, PhD, USDA/ ARS/WHNRC, Department of Nutrition, University of California-Davis, 430 West Health Sciences Drive, Davis, CA 95616, USA Tel: +1 530 752 5138; fax: +1 530 752 5271; e-mail: Darshan.Kelley@ARS.USDA.GOV Current Opinion in Clinical Nutrition and Metabolic Care 2009, 12:138146 Purpose of review Review results from recent human and animal studies regarding the effects of n-3 polyunsaturated fatty acid (PUFA) in the prevention of insulin resistance....
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