Exercise Makes Stronger Insulin Signals

Science's STKE  18 Jan 2000:
Vol. 2000, Issue 15, pp. tw2
DOI: 10.1126/stke.2000.15.tw2

Exercise is known to improve glucose homeostasis and sensitivity of insulin target cells, but the molecular basis of these effects is not well understood. Two early effects of exercise are increased expression of glucose transporters and increased translocation of such transporters to the cell surface. Chibalin et al. wanted to explore whether longer-term effects of exercise might be influenced by changes in signaling pathways coupled to the insulin receptor. In rats that exercised by swimming 6 hours a day for 1 or 5 days (please, don't try this at home!), they found that insulin signaling was indeed enhanced. Expression of the insulin receptor and insulin-induced receptor phosphorylation were increased in response to exercise. Although the amount of insulin receptor substrate (IRS) 1 protein was decreased, insulin-stimulated phosphorylation of IRS1 and associated phosphatidylinositol 3-kinase (PI3K) activity were both increased. The IRS2 protein was regulated differently, increasing in amount and associated insulin-stimulated PI3K activity after 1 day of exercise but returning to basal expression and activity after 5 days of exercise. Insulin-stimulated phosphorylation of the protein kinase Akt was also increased in response to exercise. The authors conclude that the abundance and signaling activity of a number of components of insulin-activated signaling pathways is altered in response to exercise. They also point out that the distinct regulation of IRS1 and IRS2 suggests that these similar members of the IRS protein family may have distinct functions.

Chibalin, A.V., Yu, M., Ryder, J.W., Song, X.M., Galuska, D., Krook, A., Wallberg-Henriksson, H., and Zierath, J.R. (2000) Exercise-induced changes in expression and activity of proteins involved ininsulin signal transduction in skeletal muscle: differential effects on insulin-receptor substrates 1 and 2. Proc. Natl. Acad. Sci. U.S.A. 97: 38-43. [Abstract] [Full Text]