Neuropeptidergic Regulation of Pancreatic Hormones, a Therapeutic Approach for Type 2 Diabetes Mellitus
Amna Rashid Tariq*, Zia ur Rahman
Institute of Molecular Biology and Biotechnology, University of Lahore, Defence Road, Bhupatian Chowk, Off Raiwind Road, Lahore, Pakistan
A number of factors are considered responsible for type 2 diabetes, which has become epidemic. Apart from regular modulators (insulin and glucagon) of glucose metabolism, brain has also been observed to be involved in regulating pancreatic hormone release. Hypothalamic neuronal interactions are involved in insulin and leptin regulation as these neurons are very sensitive to insulin levels. Many neuropeptides have also been studied in the recent years to play a role in the maintenance of pancreatic hormone secretions. In this review, roles of some neuropeptides in the regulation of pancreatic hormones are reviewed. Substantial data signifies the involvement of neuropeptides in regulating food intake, glucose metabolism and energy expenditure. Studies indicate that acetylcholine and other neuropeptides are diffused to the endocrine islet cells and stimulate insulin and glucagon release upon activation of their specific receptors. Studies in dogs, mice and pigs showed that gastrin releasing peptides (GRP) stimulate insulin secretion via ganglionic GRP receptor activation. A positive correlation was found between plasma insulin and plasma 26RFa in healthy, obese and type 2 diabetic patients. An in vitro direct action of neuropeptide Y (NPY) on insulin release from pancreatic islets is inhibitory, but in vivo effect of NPY increases plasma insulin. A thorough knowledge of these neuropeptides in glucose signaling points out towards the major therapeutic role of neuropeptides in diabetes.