High plasma leptin concentrations in hypertensive men but not in hypertensive women

Previous studies on humans have reported higher leptin levels in women than in men, independent of body fat, and leptin has been correlated with insulin resistance in men but not in women. Since insulin resistance is thought to play a role in raising blood pressure, we investigated sex differences in leptin concentrations between hypertensive and normotensive individuals.

Ninety-two nondiabetic hypertensive patients (48 men and 44 women) and 92 age, body mass index (BMI)-matched normotensive control individuals were studied. Fasting plasma glucose, insulin, leptin and lipoprotein concentrations, glucose and insulin responses to 75 g oral glucose tolerance test (OGTT) and insulin suppression tests were determined.

Fasting plasma leptin concentrations were higher in hypertensive men than in normotensive men (5.1 +/- 0.5 versus 3.9 +/- 0.4 ng/ml, P = 0.015). However, fasting plasma leptin concentrations were not significantly different between hypertensive and normotensive women (11.8 +/- 1.0 versus 10.9 +/- 1.0 ng/ml, P = 0.440). Fasting plasma leptin concentrations showed good correlation with BMI, body fat, fasting plasma insulin concentrations, and insulin area to OGTT in both men and women (all P < 0.001). However, fasting plasma leptin concentrations were related to steady-state plasma glucose (SSPG) concentrations, a measure of insulin sensitivity by insulin suppression test, in men only (P < 0.001). After adjustment for body fat amount, age and duration of hypertension, fasting plasma leptin levels still correlated significantly with SSPG concentrations in men. These four variables together accounted for a 67.9% variation in fasting plasma leptin levels in men. In women, body fat amount was the only significant determinant for plasma leptin levels. These four variables accounted for a 78.2% variation in plasma leptin levels in women.

Our study confirmed a sex difference in leptin levels both in hypertensive and normotensive subjects. Higher plasma leptin concentrations in hypertensive men but not in hypertensive women when compared with normotensive control individuals was also demonstrated. These observations are consistent with the findings that plasma leptin is correlated with insulin sensitivity in men but not in women. Further studies are needed to understand the causes and consequences of sex effects on leptin in blood pressure regulation.