INSULIN-RESISTANCE IS AN IMPORTANT DETERMINANT OF LEFT-VENTRICULAR MASS IN THE OBESE

Background. Obesity in adults is associated with increased left ventricular (LV) mass. The mechanism for this is unclear, however. We tested the hypothesis that insulin resistance is an important independent contributing factor to LV mass in the healthy obese population. Methods and Results. The study population consisted of 40 normotensive, nondiabetic, otherwise healthy obese subjects with body mass index (BMI) >25 kg/m2. LV mass was echocardiographically determined according to the Penn convention, using the formula of Devereux and Reichek. Insulin resistance was assessed using indices derived from Intravenous Glucose Tolerance Test (IVGTT): insulin level at baseline, insulin level at 90 minutes of IVGTT (insulin-90), insulin integration over 90 minutes of IVGTT, and rate of glucose disposal (k value). Insulin-90 (r=.61, P=.0001), k value (r=.55, P=.003), insulin integration over 90 minutes (r=.46, P=.003), basal insulin (r=.44, P=.005), and BMI (r=.59, P=.0001) were all strongly correlated with LV mass by univariate analysis. No significant correlation was found with blood pressure or age. In multivariate regression analysis, only insulin-90 and k value correlated significantly with LV mass (P=.03, P=.02, respectively), accounting for 50% of the variance of LV mass, whereas the association with BMI became insignificant (P=.2). Conclusions. LV mass in the normotensive nondiabetic obese population is strongly associated with, and may be mediated by, the degree of insulin resistance and its associated hyperinsulinemia, independent of BMI and blood pressure.