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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #207024
Title: Skeletal Muscle Lipid Deposition and Insulin Resistance: Impact of Dietary Fatty Acids and Exercise

Author
item CORCORAN, MICHAEL - HNRCA AT TUFTS UNIVERSITY
item LAMON-FAVA, STEFANIA - HNRCA AT TUFTS UNIVERSITY
item Fielding, Roger

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2006
Publication Date: 3/1/2007
Citation: Corcoran, M.P., Lamon-Fava, S., Fielding, R. 2007. Skeletal Muscle Lipid Deposition and Insulin Resistance: Impact of Dietary Fatty Acids and Exercise. American Journal of Clinical Nutrition. 85(3):662-677.

Interpretive Summary: Type 2 diabetes mellitus, or late onset diabetes, is characterized by the body’s inability to respond to the hormone insulin, resulting in reduced uptake of glucose by tissues such as skeletal muscle. Diabetes frequently leads to cardiovascular disease, kidney disease, blindness, and neuropathy. Obesity has been shown to increase the risk of developing diabetes. Thus, the increase in the prevalence of obesity both in the Western world and in Asia is possibly responsible for the doubling of the prevalence of diabetes during the past 40 years. Due to the economic burden from type 2 diabetes associated with obesity, it is imperative to identify environmental factors that may contribute to the development of diabetes. This review analyses the role of dietary fatty acids and of exercise on insulin's ability to activate the intracellular pathways that result in skeletal muscle uptake of glucose from the bloodstream.

Technical Abstract: Evidence has mounted indicating that elevated intramuscular triacylglycerol levels are associated with diminished insulin sensitivity in skeletal muscle. This lipid accumulation is most likely due to enhanced fatty acid uptake into the muscle coupled with diminished mitochondrial lipid oxidation. The excess fatty acids are esterified and either stored or metabolized to various molecules that may participate or interfere with normal cellular signaling, particularly insulin-mediated signal transduction, thus altering cellular and subsequently whole-body glucose and lipid metabolism. Impaired insulin responsiveness, if not managed, can further progress to type two diabetes mellitus, an all too common condition. For the majority of the human population, this is avoidable given that the causes of intramuscular lipid deposition are predominantly lifestyle mediated. Chronic overconsumption of calories coupled with deleterious intakes of saturated or trans-unsaturated fatty acids inconsistent with the recommendations outlined in the dietary guidelines for Americans has been shown to increase the risk of insulin resistance. Furthermore, lack of exercise, which has a profound effect on lipid turnover in skeletal muscle, is implicated in the development of insulin resistance. This review summarizes the current understanding on the lipotoxic effects of elevated intramuscular lipids on insulin signaling and how these effects are altered by varying dietary fat composition and exercise.