Insulin Resistance and Hyperinsulinemia

Abstract

Background —Hyperinsulinemia and insulin resistance may contribute to the development of cardiac hypertrophy. In humans, however, the evidence is inconclusive. Methods and Results —We studied 50 nondiabetic subjects covering a wide range of age (20 to 65 years), body mass index (BMI, 19 to 40 kg · m − 2 ), and mean blood pressure (72 to 132 mm Hg). Plasma insulin concentrations and secretory rates were measured at baseline and during an oral glucose tolerance test; insulin sensitivity was measured by the insulin clamp technique. Left ventricular mass (LVM) (by 2D M-mode echocardiography) was distributed normally and was higher in obese (BMI ≥27 kg · m − 2 , n=16) or hypertensive patients (blood pressure >140/90 mm Hg, n=21) (50±8 and 55±10 g · m − 2.7 , respectively) than in 13 nonobese, normotensive subjects (40±8 g · m − 2.7 , P =0.0004). In a multivariate model adjusting for sex, age, BMI, and blood pressure, neither insulin concentrations (fasting or postglucose) nor insulin sensitivity or secretory rates were significant correlates of LVM. Systolic blood pressure ( P =0.003) and BMI ( P =0.01) were the only independent correlates of LVM. From the regression, the impact of hypertension (as a systolic pressure of 180 versus 140 mm Hg=+20%) was twice as large as that of obesity (as a BMI of 35 versus 25 kg · m − 2 =+11%), the two factors being additive. Conclusions —When adequate account is taken of body mass and blood pressure, insulin, as concentration, secretion, or action, is not an independent determinant of LVM in nondiabetic subjects.