Dietary macronutrient composition affects hypothalamic appetite regulation in chicks.

Objective: The objective was to determine the effects of high-protein and high-fat diets, and fasting and refeeding, on appetite regulation in chicks.

Methods: Day of hatch chicks were fed one of four diets: basal, high protein (25% crude protein), and 15 and 30% high fat (15 and 30% metabolizable energy derived from soybean oil, respectively), and assigned to one of three treatments at 4 days: (1) access to feed, (2) 3 hours of fasting, or (3) fasting followed by 1 hour of refeeding. The hypothalamus was collected, total RNA isolated, and mRNA abundance measured.

Results: Food intake was reduced in chicks fed the high-protein and high-fat diets. Agouti-related peptide, neuropeptide Y (NPY), NPY receptors 1, 2, and 5, melanocortin receptors 3 and 4 (MC3R and 4R, respectively), mesotocin, corticotropin-releasing factor (CRF), and CRF receptor sub-type 2 (CRFR2) mRNAs were greatest in chicks that consumed the basal diet. Refeeding was associated with increased MC3R mRNA in the high-protein diet group. CRFR2 mRNA was increased by fasting and refeeding in chicks that consumed the high-protein diet.

Discussion: Food intake and hypothalamic gene expression of some important appetite-associated factors were reduced in chicks fed the high-protein or high-fat diets. Fasting and refeeding accentuated several differences and results suggest that the CRF and melanocortin pathways are involved.