Metabolic outcome due to melatonin action in the hypothalamus

Abstract

Melatonin is the main endocrine secretion of the pineal gland and plays a role in the physiology of vertebrates generally related to the synchronization of circadian rhythms liked to cyclically variations in ambient light. Recent studies have shown that melatonin also plays an important role in the control of energy metabolism. Pinealectomized rats have impaired glucose tolerance and insulin resistance at different times of light /dark cycle. Besides, it was recently demonstrated that animals with the pineal gland exhibit a higher level of gluconeogenesis, which may contribute to impaired glucose tolerance. The precise mechanism by which melatonin modulates energy metabolism, however, is not described yet. Previous studies from our group showed that melatonin displays the ability to activate the insulin signaling in specific regions of the hypothalamus. The metabolic impact of this molecular events are also not yet known. This project aims to assess whether the action of melatonin on proteins of the signaling pathway of insulin in hypothalamus of rats results in some kind of control of hepatic gluconeogenesis. To this end, mice will receive injections of melatonin intracerebroventricular and will be then subjected to pyruvate tolerance test. The animals are also used for western blot. Alternative treatments include melatonin receptor antagonists, blocking of insulin signaling and cholinergic blockers. (AU)