The Role of Neurohormonal Imbalances in Obesity

Submit Manuscript | http://medcraveonline.com Hunger and satiety are generally regulated by the central nervous system (CNS) via the gut-brain axis and a number of hormones play critical roles in body weight management [3,4]. Among these hormones, the three most important hormones are leptin, ghrelin and insulin [5]. Leptin is a hormone secreted by fat cells which sends negative feedback signals to the brain to stop eating (satiety hormone) [6]. Ghrelin is a hormone secreted by the stomach when it is empty and stimulates appetite by binding to the growth hormone secretagogue receptors (GHSRs) in the brain (hunger hormone) [7-10]. On the other hand, insulin is a hormone that signals the cells to take glucose from the bloodstream and store it as a glycogen or fat and just like leptin it signals brain to stop eating. The other action of insulin is to interfere with the signals sent to the brain by leptin (reduces leptin sensitivity) and this action can be considered as the major cause of obesity. [11] People with chronically elevated insulin levels (hyperinsulinemia) thus become leptin resistant and start eating more as the brain cannot sense the signals sent by leptin which makes the brain to think that the body is still starving. Another action of insulin is to send signals to fat cells and stimulate them to store fat and keep fat stored for longer period [12]. However, this action of insulin is debatable and many researchers do not agree with the existence of this action.