INSULIN ACTION IN MAN

Insulin action is crucial for the regulation of glucose metabolism. In sulin plays a key role in suppressing endogenous glucose production by the liver, both in fasting and postprandial states. Insulin is also n ecessary for the maintenance of normal rates of glucose oxidation and storage in insulin-sensitive tissues and for the prevention of excessi ve gluconeogenic substrate production. Various methods have been devel oped to assess insulin action in vivo, essentially at liver and muscle sites. Such methods evaluate the effect of exogenous or endogenous in sulin, using respectively the open-loop approach (interruption of the feedback loop by inhibiting endogenous insulin secretion) or the close d-loop approach (mathematical modelling of the insulin-glucose feedbac k loop). Knowledge of the successive steps of cellular insulin action has markedly improved during the last ten years. Preceptor, receptor a nd postreceptor levels need to be considered since they may be affecte d in insulin-resistant states. This general progress in the understand ing of insulin action in man improves our approach to the complex path ophysiology of non-insulin-dependent diabetes mellitus and opens up ne w prospects for treatment of the insulin-resistant syndrome which is a ssociated with several atherosclerotic risk factors.