Plasma leptin level is associated with myocardial wall thickness in hypertensive insulin-resistant men

Abstract

Leptin, the product of the ob gene, has been shown to increase heart rate and blood pressure through a stimulation of cardiac sympathetic nervous system activity, a phenomenon also involved in the pathogenesis of left ventricular hypertrophy in hypertensives. Thus, we hypothesize that plasma leptin concentration is associated with left ventricular hypertrophy. Forty hypertensive males and 15 healthy male subjects underwent anthropometric and echocardiographic evaluations, assessment of insulin sensitivity through euglycemic glucose clamp combined with indirect calorimetry, and determination of fasting plasma leptin concentration. Fasting plasma leptin levels were higher in hypertensives than in controls (6.48±2.9 versus 4.62±1.5 ng/mL, P<0.05); these results were unchanged after adjustment for body mass index (P<0.05). In the whole group of patients (n=55), fasting plasma leptin concentration was correlated with body mass index (r=0.46, P<0.001) and waist/hip ratio (r=0.50, P<0.001); independent of body mass index and waist/hip ratio, fasting plasma leptin concentration was correlated (n=55) with whole-body glucose disposal (r=-0.27, P<0.04), interventricular septum thickness (r=0.34, P<0.001), posterior wall thickness (r=0.38, P<0.003), and the sum of wall thicknesses (r=0.68, P<0.001). In a multivariate analysis (n=55), age, body mass index, fasting plasma leptin concentration, plasma Na+ concentration, whole-body glucose disposal, and diastolic blood pressure explained 68% of the variability of the sum of wall thicknesses with fasting plasma leptin concentration (P<0.03), whole body glucose disposal (P<0.002), and diastolic blood pressure (P<0.001), which were significantly and independently associated with the sum of wall thicknesses. In conclusion, our study demonstrates that fasting plasma leptin levels are associated with increased myocardial wall thickness independent of body composition and blood pressure levels in hypertensives.