Insulin Resistance and Exercise

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This is a discussion of research article listed at end of paper

When muscle is damaged, there is a general resistance to insulin. The physiological stress that is associated with damaged muscle impairs how insulin stimulates IRS-1, PI 3-kinase, and Akt-kinase. This presumably leads to less glucose absorption. Previous studies have shown that there has been temporary insulin resistance due to the physiological stress associated with muscle damage. However, the molecular mechanisms by which physiological stress induces insulin resistance is not known.

The many effects that insulin has on metabolism and cellular growth begin when insulin binds to its receptor at the cell membrane. The insulin signals from the insulin receptor is transmitted through the insulin receptor substrate (IRS)-1. The phosphorylation (creation of a phosphate derivative of an organic molecule) of IRS-1 has been linked to signal transduction from the insulin receptor to PI 3-kinase. This leads to GLUT-4 translocation and subsequent glucose uptake. Preliminary studies have shown that the enzyme PI 3-kinase is correlated with glucose being absorbed by the entire body. This suggests that the enzyme is important in regulating insulin-mediated glucose uptake in skeletal muscle. PKB (AKT)has been proposed as a key step linking the activation of PI 3-kinase to glucose uptake.

Also, type 2 diabetes is accompanied by impaired insulin signal transduction. Thus, the insulin signaling pathway plays a critical role in the regulation of insulin action in health, and abnormailities in insulin signal transduction likely underlie important disease processes. The study explored what changes in the insulin signaling pathway are associated with muscle damage-induced whole ...

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...which also occurs after musculoskeletal injury and surgery.

What About You??

If you lead a normally sedentary lifestyle and exercise rigorously one day, you will likely experience insulin resistance. Don't worry, it is only temporary and causes no long term damage. Your muscles will be sore! Skiing, running downhill, and horseback riding are a few examples of ecentric exercise. It also occurs in weight lifting. To build your muscles, concentrate on lengthening exercises, not just the contracting ones. For example: when performing a bicep curl, take twice as long to bring the weight down (ecentric movement) as you did lifting it up (contraction).

References

Del Aguila, L.F. et al. "Muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase in human skeletal muscle". Am. J. Physiol. Endocrinol Metab. 279, E206 (2000).

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