Peripheral ghrelin reduces food intake and respiratory quotient in chicken

Ghrelin injection, either centrally or peripherally strongly stimulates feeding in human and rodents. In contrast, centrally injected ghrelin inhibits food intake in neonatal chickens. No information is available about the mechanism and its relationship with energy homeostasis in chicken. Since ghrelin is predominantly produced in the stomach, we investigated the effect of peripherally injected ghrelin (1 nmol/100g body weight) on food intake and energy expenditure as measured in respiratory cells by indirect calorimetry for 24h in one-week-old chickens. Plasma glucose, triglycerides, free fatty acids, total protein and T(3) were measured in a separate experiment until 60 min after injection. Food intake decreased until at least 1h after intravenous ghrelin administration. The respiratory quotient (RQ) in ghrelin-injected chickens was reduced until 14 h after administration whereas plasma glucose and triglycerides concentrations were not altered. Free fatty acids and total protein levels also remained unchanged. Ghrelin did not influence heat production and this was supported by the absence of changes in plasma T(3) levels when compared to the control values. In conclusion, peripheral ghrelin reduces food intake as well as RQ and might influence the type of substrate (macronutrient) that is used as metabolic fuel.