Glycogen Synthase: Key Effect of Exercise on Insulin Action

In Brief CHRIST-ROBERTS, C. Y., and MANDARINO, L. J. Glycogen synthase: key effect of exercise on insulin action. Exerc. Sport Sci. Rev., Vol. 32, No. 3, pp. 90–94, 2004. Exercise improves insulin action in muscle, but the mechanisms are poorly characterized. Despite the notion that increased insulin signaling would accompany improved insulin sensitivity, this is not universally true. Increased activity or expression of other proteins seems to be more important. An increase in activity and expression of glycogen synthase and GLUT4 may be key to the effects of exercise. Exercise improves muscle insulin action primarily by increasing expression and activity of effectors of insulin action rather than insulin signaling.