Chronic Leptin Infusion Increases Arterial Pressure

Plasma leptin concentration is increased in hypertensive obese humans, but whether leptin contributes to the increased arterial pressure in obesity is not known. In this study, we tested whether chronic increases in leptin, to levels comparable to those in obesity, could cause a sustained increase in arterial pressure and also the importance of central nervous system (CNS) versus systemic mechanisms. Five male Sprague-Dawley rats were implanted with chronic nonoccluding catheters in the abdominal aorta and both carotid arteries for CNS infusion, and five other rats were implanted with an abdominal aorta catheter and femoral vein catheter for intravenous (I.V.) infusion. After 7 days of control, leptin was infused into the carotid arteries or femoral vein at 0.1 microg/kg/min for 5 days and 1.0 microg/kg/min for 7 days, followed by a 7-day recovery period. The carotid artery and i.v. infusions of leptin at 1 microg/kg/min significantly increased plasma leptin levels, from 1.2+/-0.4 ng/mL to 91+/-5 ng/mL and from 0.9+/-0.1 ng/mL to 94+/-9 ng/mL, respectively, but there was no significant increase in either group at the low dose. Food intake also did not change at the low dose but decreased by approximately 65% in the carotid group and 69% in the i.v. group after 7 days of the 1 microg/kg/min infusion. Mean arterial pressure (MAP) increased slightly at the low dose only in the carotid group, but this was not statistically significant. At the higher dose, however, MAP increased significantly from 86+/-1 mm Hg to 94+/-1 mm Hg in the carotid group and from 87+/-1 mm Hg to 93+/-1 mm Hg in the i.v. group. Heart rate also increased significantly in both groups at 1 microg/kg/min leptin infusion. Fasting blood glucose and insulin levels decreased significantly at 1 microg/kg/min in both the carotid artery group (-10.5% and -82.5%, respectively) and the i.v. group (-13.6% and -80.4%, respectively). All variables returned to control levels after leptin infusion was stopped. These results indicate that chronic increases in circulating leptin cause sustained increases in arterial pressure and heart rate and are consistent with a possible role for leptin in obesity hypertension.