Experimental investigation of the effects of Apelin on nutrition behavior

Experimental Investigation of the Effects of Apelin on Nutrition BehaviorApelin is the endogenous ligand for the G-protein coupled APJ receptor. The apelinergic system (apelin, APJ) have been found to have a widespread distribution in both the central nervous system such as arcuate, supraoptic and paraventricular nuclei of the hypothalamus and the peripheral tissues such as adipose tissue, stomach and gastrointestinal tract. This distribution suggests apelin may play a important role in feeding behavior and energy homeostasis, but previous studies in this area have shown conflicting results. This study aims to investigate the relationship between apelin-13 and leptin, ghrelin, Neuropeptide Y and Peptide YY levels effect on body weight, food intake and water consumption which are involved in nutrition behaviour regulation. In this study, 32 male Sprague Dawley rats were selected randomly and divided into 4 groups, each consisting of 8 rats. At dark phase transition, rats were injected intraperitoneally % 0.9 saline to control group, respectively 30, 100 and 300 µg/kg Apelin-13 to the other study group for 10 days. The rats' body weight, food intake and water consumption were recorded in 12-hour intervals during the experiment. At the end of the study, the rats were decapitated and blood samples were collected. Biochemical analyzes were performed to determine the levels of peptide in the blood samples. Metabolic results show that the groups which were implemented apelin-13, compared with the control group, increase body weight (p<0.05). In addition to, food and water intake values of the apelin-13 administered groups did not change at the light phase; however, an increase was observed according to the dark phase and the evaluation of the the average of a one-day period. It was found in biochemical analyses that serum leptin levels had an increase on the groups administered 100 and 300 µg/kg apelin-13. Ghrelin levels were found higher in all of the groups administered apelin-13. While serum neuropeptide Y levels were gradually decreasing, there occured a significant decrease just in group administered 300 µg/kg apelin-13. Serum Peptide YY levels did not change. As a result, it was found that chronic peripheral administration of apelin-13 increased body weight, food intake and water intake per day in rats. These results suggest that apelin-13 is able to regulate food intake through the peripheral peptides such as ghrelin and leptin. Keywords: Apelin-13, Feeding, Ghrelin, Leptin, Neuropeptide Y, Peptide YY