Role of Medullary AKT and p38 MAPK in Regulating Feeding of Broiler Chicks

In layer chicks, central administration of insulin and refeeding promote the phosphorylation of AKT and extracellular signal-regulated kinase (ERK) in the medulla oblongata. Broiler chicks consume more feed than layer chicks, suggesting distinct feeding regulation. This study aimed to clarify the involvement of medullary AKT and mitogen-activated kinases (MAPKs: ERK, c-Jun N-terminal kinase (JNK), and p38 MAPK) in regulating feeding of broiler chickens. The phosphorylation of AKT and p38 MAPK, but not that of ERK and JNK, was significantly higher in the medulla oblongata of broilers refed for 1 h after a 24-h fasting. Intracerebroventricular (ICV) administration of insulin significantly enhanced AKT phosphorylation in the medulla oblongata, but had no significant effect on the phosphorylation of MAPKs. Oral administration of glucose increased plasma glucose and the phosphorylation of AKT and p38 MAPK, but not ERK and JNK, in the medulla oblongata. ICV administration of the p38 MAPK activator anisomycin strongly induced the phosphorylation of p38 MAPK, but not JNK, without affecting feed intake. These findings suggest that medullary AKT contributes to insulin-induced suppression of feed intake in broiler chicks, while medullary p38 MAPK is phosphorylated in response to postprandial elevation of blood glucose, but is not involved in feeding regulation.