Leptin association with erythrocyte sodium content in obesity-related hypertension

Abstract

Insulin resistance is frequently associated with obesity-related hypertension. Leptin resistance and increased plasma leptin levels are frequent companions in this association. To examine whether in obesity hypertension with insulin resistance, plus hyperleptinemia, the sodium content of erythrocyte (Naie) reflects a positive sodium balance related to the physiological loss of leptin in sodium reabsorption, we studied a group of obese hypertensive patients, and a group of lean normotensive subjects. In obese hypertensives, fasting glucose, insulin and the insulin resistance index were higher as compared to the lean individuals (107.0 ± 4.1 mg/dl, 10.2 ± 1.4 pU/ml and 2.94 ± 0.52, respectively, vs 98.7 ± 4.1 mg/dl, 7.22 ± 1.33 U/ml, and 1.79 ± 0.16, respectively, p < 0.002). Both the leptin/BMI 2 index as well as the Naie were significantly higher in the obese hypertensive group as compared to control group (1.9± 0.21 vs 1.25 ± 0.27, respectively p < 0.01, and 12.5 ± 0.51 vs 10.7 ± 0.5 mEq/ml/cell, respectively p < 0.05). In obese hypertensives the leptin/BMI 2 index was significantly associated with DBP (r= = 0.41, p < 0.04), MBP (r= 0.44, p < 0.03), Naie (r = 0.41, p < 0.05) and age (r = 0.43, p = 0.03). We conclude that in obese hypertensive patients Naie is increased reflecting a state of positive sodium balance. In these patients, the elevated circulating leptin concentrations were one of the main regulators of the content of sodium in erythrocytes.