Improvement of insulin sensitivity contributes to blood pressure reduction after weight loss in hypertensive subjects with obesity

To assess the role of insulin resistance in obesity hypertension, we examined the change of insulin sensitivity after weight loss in 24 obese hypertensive subjects by the euglycemic hyperinsulinemic glucose clamp method. The results of the 4-week calorie-restricted diet were a weight loss of 10.2% (from 74+/-12 to 67+/-11 kg, P<.01) and a decrease in mean blood pressure of 13.1% (from 124+/-7 to 107+/-9 mm Hg, P<.01). A decrease in plasma norepinephrine (from 208+/-74 to 142+/-52 pg/mL, P<.01) was associated with decreases in plasma renin activity (from 1.06+/-0.98 to 0.62+/-0.63 ng/mL per hour, P<.01) and serum aldosterone (from 70+/-28 to 57+/-24 pg/mL, P<.05). Glucose infusion rate increased significantly (42.9%), from 809+/-194 to 1155+/-251 mu mol/m(2) per minute. The insulin sensitivity index, which is a measure of the glucose infusion rate divided by plasma insulin, increased significantly (42.6%), from 10.8+/-3.5 to 15.4+/-4.4 (mu mol/m(2) per minute)/(mu U/mL). Stepwise multiple linear regression analysis showed that changes of plasma norepinephrine, insulin sensitivity index, plasma renin activity, and age were significant predictive factors for the change of mean blood pressure after weight loss. These results indicate a distinct relation between an improvement of insulin sensitivity and a decrease in blood pressure after weight loss in obese hypertensive subjects. The decrease in blood pressure after weight loss is probably related to the suppression of sympathetic nervous activity.