Insulin and blood pressure regulation.

Epidemiological evidence suggests that there is a close association between obesity, non-insulin-dependent diabetes (NIDDM) and hypertension. Obesity and NIDDM are the classical insulin-resistant states. Even in the absence of these conditions, essential hypertension is associated with insulin resistance. In view of the acute effects of insulin on renal sodium reabsorption, the sympathetic nervous system, the renin-angiotensin-aldosterone system, the transmembranous cation transport, the cardiovascular reactivity, the atrial natriuretic peptide and the kallikrein-kinin system, hyperinsulinaemia may contribute to the development of hypertension in these diseases. Preliminary evidence suggests that sensitivity to these possible blood-pressure-elevating action(s) of insulin is still present despite the resistance to the glucose-lowering action of the hormone. However, extrapolation of the epidemiological data and results of acute experiments indicate that the impact on blood pressure is rather small. The pathophysiological mechanisms of hypertension in the above-mentioned conditions are also not always consistent with insulin action(s). Moreover, some data suggest that insulin resistance, and not hyperinsulinaemia per se, underlies the blood pressure elevation, while the possibility cannot be excluded that both hypertension and insulin resistance are co-inherited, but unrelated, abnormalities.