Effect of Corticosterone on Gene Expression of Feed Intake Regulatory Peptides in Laying Hens

The present study was conducted to explore the effects of corticosterone (CORT) on the regulation of appetite-associated genes in laying hens. Forty eight laying hens were randomly divided into two groups: one received subcutaneous injection of CORT (2 mg/kg body weight, CORT-exposed) and the other received sham-treatment (Control). Treatment of hens with CORT stimulated an increase (P < 0.05) in plasma CORT, glucose, uric acid (UA), insulin, cholesterol (Chol) and triiodothyronine (T3), but the concentrations of plasma non-esterified fatty acids (NEFA) and triacylglycerol (TG) were decreased (P < 0.05). CORT treatment had no significant effect (P > 0.05) on the mRNA levels of neuropeptide Y (NPY), corticotropin-releasing hormone (CRH), melanocortin receptor 4 and 5 (MCR-4 and MCR-5) and cholecystokinin (CCK) in the hypothalamus when compared with control hens. However, the expression of pro-opiomelanocortin (POMC), agouti-related protein (AgRP) and melanocortin recepter 1 (MCR-1) were significantly (P < 0.05) suppressed while the mRNA levels of ghrelin and cocaine-and amphetamine-regulated transcript (CART) were significantly upregulated (P < 0.05) in CORT-treated hens. Treatment of laying hens with CORT had no significant (P > 0.05) effect on the mRNA levels of CCK in the glandular stomach and the duodenum, and those of ghrelin in the glandular stomach, the duodenum and the jejunum. However, the mRNA levels of CCK in the jejunum and the ileum, and those of ghrelin in the ileum were significantly (P < 0.05) suppressed by CORT treatment. In conclusion, these results suggest that CORT plays a unique role in some special neuropeptides (e.g., ghrelin, CART, POMC, CCK and MCRs) and a dynamic balance between these appetite-associated peptides in the hypothalamus and the gastrointestinal tract defines the feeding status of CORT-exposed laying hens.