The Putative Roles of Adenosine in Insulin- and Exercise-Mediated Regulation of Glucose Transport and Glycogen Metabolism in Skeletal Muscle

Abstract

Skeletal muscle is the primary site of whole-body glucose disposal and is vital in determining the overall insulin sensitivity and carbohydrate management. Insulin and physical exercise are important stimuli for muscle glucose transport and glycogen metabolism. While it is known that both insulin and contraction stimulate muscle glucose uptake and glycogen metabolism, the post-receptor mechanisms are not completely understood. Local metabolic factors, such as adenosine, have been suggested to play a role in insulin and contraction regulation of carbohydrate metabolism in skeletal muscle. While adenosine has clearly been shown to potentiate insulin-stimulated glucose transport in adipocytes and heart muscle, its role in carbohydrate metabolism in skeletal muscle is less clear, with numerous diverging findings published to date. This review article summarizes findings on the putative roles of adenosine in insulin and exercise-mediated regulation of carbohydrate metabolism and the signalling pathways proposed to be central to these metabolic stimuli in skeletal muscle. Key words: carbohydrate metabolism, adenosine receptor, signal transduction, insulin resistance, diabetes mellitus, obesity