Submitted on November 13, 2003
Accepted on March 31, 2004
Plasma Hyperosmolality Stimulates Leptin Secretion Acutely by a Vasopressin - Adrenal Mechanism
James R. Levy1* and Wayne Stevens1
1 Section of Endocrinology and Metabolism, McGuire Veterans Administration Medical Center, Richmond, VA, USA; Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
* To whom correspondence should be addressed. E-mail: James.Levy{at}med.va.gov.
Glucose administration to rodents acutely stimulates leptin secretion. To investigate the mechanism, rats were infused intravenously with various concentrations of glucose and plasma leptin concentrations were measured with time. The osmolality of the infusates were equalized with various concentrations of carbohydrates that are not metabolized. Hyperosmolar glucose stimulates leptin secretion in a dose-dependent manner with peak plasma leptin concentrations occurring approximately 3 hours after the end of the glucose infusion. Hypertonic infusions of galactose, mannitol, and sodium chloride independently stimulate leptin secretion with approximately half the strength as equivalent osmolar concentrations of glucose. Peak plasma leptin concentrations occur approximately 4 hours after the end of the hypertonic solution infusion. Hypertonic solutions of mannitol do not stimulate leptin secretion in vasopressin-deficient or in adrenalectomized animals. In conclusion, intravenous infusions of hypertonic glucose and hypertonic mannitol independently stimulate leptin secretion. Hyperosmolality stimulates leptin secretion by a vasopressin - adrenal mechanism.
