INSULIN-RESISTANT LIPOLYSIS IN ABDOMINALLY OBESE HYPERTENSIVE INDIVIDUALS - ROLE OF THE RENIN-ANGIOTENSIN SYSTEM

Resistance to the capacity of insulin to suppress lipolysis may be an important link in the association between abdominal obesity and hypert ension, Furthermore, a more active renin-angiotensin system in adipose tissue may contribute to insulin-resistant lipolysis in abdominally o bese hypertensive subjects. We determined nonesterified fatty acid con centrations and turnover as well as lipid oxidation under basal condit ions and during steady-state euglycemia with two levels of insulinemia (72 and 287 pmol/L) in lean normotensive, abdominally obese normotens ive, and abdominally obese hypertensive subjects. To assess the role o f the renin-angiotensin system in determining nonesterified fatty acid turnover, we repeated studies in the abdominally obese hypertensive s ubjects after double-blind random assignment to placebo or enalapril f or 1 month each. The main findings were the following: (1) Nonesterifi ed fatty acid flux was significantly higher in abdominally obese hyper tensive subjects at both levels of insulinemia than in either abdomina lly obese normotensive or lean normotensive subjects and correlated si gnificantly with both mean blood pressure and total systemic resistanc e during the higher level of insulinemia. (2) Enalapril significantly improved insulin-resistant lipolysis in the abdominally obese hyperten sive subjects. The improvement in insulin suppressibility of nonesteri fied fatty acid flux at the high hormonal concentrations correlated po sitively with the magnitude of reduction in blood pressure. (3) Basal lipid oxidation and suppression in response to insulin were similarly impaired in both obese groups, Resistance to the antilipolytic actions of insulin is thus a characteristic feature in abdominally obese hype rtensive subjects and may be linked to the elevated blood pressure in these individuals. A more active renin-angiotensin system may partly e xplain the insulin-resistant lipolysis in this form of hypertension.