Endothelin-1 response to glucose and insulin among African Americans.

Endothelin-1 (ET-1) is implicated in the pathogenesis of hypertension. In vitro studies demonstrate that ET-1 is upregulated by insulin and glucose. The purpose of this study was to determine the effects of insulin and glucose on ET-1 levels in young adult African Americans, a population with a high burden of hypertension and diabetes. Plasma and urine ET-1 levels were measured before and after an oral glucose tolerance test (OGTT) and insulin clamp procedure in 288 participants. Subjects were classified according to glucose tolerance and blood pressure (BP) status. Plasma and urine ET-1 were not significantly different among the glucose tolerance groups. There was a trend toward increased plasma ET-1 among those with diabetes compared with impaired glucose tolerance and normal glucose tolerance; however, this was not statistically significant (P = .085). According to BP status, plasma ET-1 was highest among the high BP group compared with the normal BP group (P = .01). After glucose challenge, plasma ET-1 levels decreased and urine ET-1 increased in all three BP groups (P = .037). Our data show that plasma ET-1 is higher among young adult African Americans with hypertension compared with normotension. Urine ET-1 levels increased in response to glucose challenge, possibly indicating early renal injury.