Obestatin and Ghrelin May Have a Complementary Function During Acute and Chronic Period in Mice

Abstract

Obestatin is described as an anorexigenic peptide, and has adverse effects of ghrelin. It has no inhibitory effects on acute/chronic food intake, and it has been reported by several researchers. The role of obestatin in metabolism is still not clear. In the present study, the purpose is to determine the effects of chronically administrated obestatin. For this purpose, (1 µmol/kg; i.p.) or ghrelin (1 µmol/kg; i.p.) and food restriction (24h fast:24h fed) on plasma obestatin, ghrelin, leptin, insulin, cholecystokinin (CCK) and glucose levels, and body weight gain were investigated for 14 days in mice. Additionally, mice were treated with acute ip (100 nmol/kg) injections of obestatin or ghrelin to investigate the food consumptions, plasma obestatin and ghrelin levels to determine unknown acute effects of obestatin. Plasma ghrelin levels increased significantly in obestatin administered mice when compared with the control group for chronic treatment. This increase is consistent with immunohistochemical findings which claim that the number of ghrelin and obestatin immunopositive cells in fundus tissue of stomach are considerably high in obestatin treated animals. Plasma obestatin and ghrelin levels has shown an increase endogenously in food restricted mice, but plasma leptin and insulin levels have been found to be lower compared to the control group. Acute administration of obestatin caused a decrease in plasma obestatin level at 60 min after injection and had no effect on the reduction of food intake in each treatment time. These results imply that obestatin may not itself be involved in the metabolism regulation; however, obestatin accompanied by ghrelin may play a role in the long-term regulation of metabolism.

Effect of Obestatin on Gastric Acid Secretion and Mucin Expression in Normal and Streptozoocin Induced Diabetic Rats

“…Many suggestions could explain this finding include, increased local ghrelin secretion as proved in the current work by a significant increase in ghrelin level in gastric secretion in obestatin treated groups. This finding can be supported by Duygu et al [32] who stated that the number of ghrelin immunopositive cells in fundus tissue of stomach are considerably high in obestatin treated animals for 14 days. The increased ghrelin may be the mediator of obestatin to enhance gastric acid secretion, as ghrelin has a stimulatory role in regulating gastric acid secretion [33] .…”