Oxidative stress, nitric oxide production, and renal sodium handling in leptin-induced hypertension

Chronic hyperleptinemia induces arterial hypertension in experimental animals and may contribute to the development of hypertension in obese humans; however, the mechanism of hypertensive effect of leptin is not completely elucidated. We investigated the effect of leptin on whole-body oxidative stress, nitric oxide production, and renal sodium handling. The study was performed on male Wistar rats divided into 3 groups: 1) control, fed standard chow ad libitum, 2) leptin-treated group, receiving leptin injections (0.25 mg/kg twice daily s.c. for 7 days), 3) pair-fed group, in which food intake was adjusted to the leptin group. Leptin caused 30.5% increase in systolic blood pressure. Plasma concentration and urinary excretion of 8-isoprostanes in animals receiving leptin was 46.4% and 49.2% higher, respectively. The level of lipid peroxidation products, malonyldialdehyde + 4-hydroxyalkenals, increased by 52.5% in the renal cortex and by 48.4% in the renal medulla following leptin treatment, whereas aconitase activity decreased in these regions of the kidney by 45.3% and 39.2%, respectively. Urinary excretion of nitric oxide metabolites (NOx) was 55.0% lower, and fractional excretion of NOx was 55.8% lower in the leptin-treated group. Urinary excretion of cGMP decreased in leptin-treated rats by 26.3%. Following leptin treatment, absolute and fractional sodium excretion decreased by 35.0% and 41.2%, respectively. These results indicate that hyperleptinemia induces systemic and intrarenal oxidative stress, decreases the amount of bioactive NO possibly due to its degradation by reactive oxygen species, and causes renal sodium retention by stimulating tubular sodium reabsorption. NO deficiency and abnormal renal Na+ handling may contribute to leptin-induced hypertension.