ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 S22.3

Why does physical exercise improve insulin sensitivity, the role of adipose tissue?

Jan Polak

Charles Univeristy, Prague, Czech Republic.

Modern lifestyle diminished significantly the need of everyday exercise, which is probably one of the major factors leading to the development of several metabolic diseases including type 2 diabetes, hypertension and atherosclerosis with its deadly consequences. Epidemiological studies proved that higher levels of cardio-respiratory fitness are associated with lower mortality irrespective of fat stores. Physical activity reduces all-cause, cardiovascular as well as cancer associated mortality. Beneficial effects of exercise on insulin sensitivity have been demonstrated in a short term as well as following a longer periods of physical activity. Short-term effects are detectable even after a single bout of exercise and are mediated mostly by the metabolic changes in insulin signalling and substrate fluxes inside the muscle tissue. Especially modifications in fatty acid metabolism related to decreased intracellular accumulation of intermediary metabolites interfering with insulin signalling have strong impact on improved muscle insulin sensitivity. In a longer perspective, physical activity modifies gene expression of key proteins involved in a regulation of insulin signalling, glucose transport and substrate metabolism in muscle (GLUT4, glycogen synthesis) leading to an improved glucose tolerance. Moreover, regular physical activity has been shown to change the metabolism of adipose tissue. Adipose tissue is potent endocrine organ producing several proteins collectively called ‘adipokines’, several of which regulate insulin sensitivity in a negative while others in a positive way. Modification of gene expression and production of adipokines represents another possibility, how exercise improves insulin sensitivity, decrease pro-inflammatory state and mediate its wide spread beneficial effects. Other factors, like changes in sympathetic nervous activity or endothelial dysfunction might also be involved.

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