Insulin Resistance and Blood Pressure Regulation in Blacks

BACKGROUND: Epidemiologic studies have demonstrated a greater prevalence of essential hypertension in Blacks with a disproportionately greater hypertension related mortality in Blacks. Similar vascular consequences occur with diabetes and obesity. These three diseases not only share a common outcome, but also overlap in occurrence with Blacks having greater prevalence rates in the three disorders. Insulin resistance has been documented in all three disorders and may contribute significantly to the vascular disease. This project originated in response to a Request for Applications on Biobehavioral Factors Affecting Hypertension in Blacks issued in December 1982. The original project was supported by the RFA for three years. The first three years of the study focussed on the hypothesis that sodium loading would augment cardiovascular responses of psychogenic stress in Blacks at high risk for hypertension. The first phase of the study examined and compared 80 Blacks and whites, 18-22 years of age. The second phase involved an additional 40 Black borderline hypertensives who were exposed to the same set of studies designed to examine possible interactions between neurogenic and renal controlled volume mechanisms in essential hypertension. The project was renewed as a regular research grant in 1986 and was designed to investigated biobehavioral factors in blood pressure control. In 1988, the study on insulin resistance was funded and continued through 1990. DESIGN NARRATIVE: Subjects in this project consisted of Blacks who were enrolled in the Collaborative Perinatal Project (CPP) at birth and who had been studied longitudinally in adolescence and young adulthood. Each subject brought to the study data on blood pressure, growth, and maturation from birth through late adolescence. Peripheral vascular structure was studied using measures of forearm blood flow and forearm vascular resistance. Measurements of peripheral vascular structure were compared to data on sodium sensitivity and potassium sensitivity in the population. Insulin resistance was studied using the euglycemic hyperinsulinemic clamp technique. Variations in the activity of the sodium-potassium pump and sodium-hydrogen exchange in red cells were correlated with insulin resistance to determine if hyperinsulinemia alters cation transport rates. The study completion date listed in this record was obtained from the "End Date" entered in the Protocol Registration and Results System (PRS) record.