Hyperinsulinemia and hypertension: Do intestinal hormones play a role?

Gastric inhibitory polypeptide (GIP) is one of the strongest insulinotropic gut factors. Its secretion is induced by oral (but not intravenous) glucose and it has been implicated in the pathogenesis of hyperinsulinemic states (NIDDM, obesity). To determine its relevance to hypertension, 54 subjects were studied: 26 normotensives (12 with and 14 without family history of essential hypertension), and 28 essential hypertensive subjects. Plasma glucose, serum insulin (IRI), and GIP were evaluated after a mixed meal containing a total of 82 g of carbohydrates, and 2 g sodium chloride. Venous blood was collected at baseline and every 15 min during a 3-h period. Baseline levels of glucose, IRI, and GIP were comparable in the three groups. At 30 min, however, IRI and GIP were higher in normotensives with a family history of hypertension and in established hypertensive versus control subjects. Both in normotensive and in hypertensive groups, glucose, IRI, and GIP responses to the meal were significantly correlated. Our data suggest the contribution of altered GIP secretion in the pathogenesis of hyperinsulinemia in essential hypertension.