Hyperinsulinemia: possible role in obesity-induced hypertension.

Data in support of the hypothesis that insulin-mediated sympathetic stimulation contributes to the hypertension that occurs in association with obesity are presented. The relation between insulin and the sympathetic nervous system derives from the effect of diet on sympathetic activity. Fasting suppresses but overfeeding stimulates the sympathetic nervous system. Insulin-mediated glucose metabolism within central neurons sensitive to insulin and glucose appears to be one important signal in this relation between diet and sympathetic activity. In the obese, hyperinsulinemia and hypertension track together in epidemiological studies. Evidence from a human population-based study (the Normative Aging Study) indicates that the abdominal form of obesity is associated with both hyperinsulinemia and increased urinary norepinephrine excretion. Elevations in urinary norepinephrine excretion, moreover, were highest in those with the highest fasting levels of insulin and glucose. These observations are consistent with the hypothesis that insulin-mediated sympathetic stimulation is a mechanism recruited in the obese to increase metabolic rate and restore energy balance; concomitant increases in sympathetic stimulation of the heart, vasculature, and kidney result in hypertension, which, according to this formulation, is an unfortunate by-product of the cardiovascular response to a metabolic adaptation.