Dietary fat alters the response of hypothalamic neuropeptide Y to subsequent energy intake in broiler chickens

Abstract

Dietary fat affects appetite and appetite-related peptides in birds and mammals; however, the effect of dietary fat on appetite is still unclear in chickens faced with differential energy statuses. Two experiments were conducted to investigate the effects of dietary fat on feed intake and hypothalamic neuropeptides in chickens subjected to two feeding states or two diets. In Experiment 1, chickens were fed a high-fat diet (HF) or low-fat diet (LF) for 35d, and then subjected to fed (HF-fed, LF-fed) or fasted (HF-fasted, LF-fasted) statuses for 24h. In Experiment 2, chickens that were fed with HF or LF for 35d were fasted for 24h and then re-fed with HF (HF-RHF, LF-RHF) or LF (HF-RLF, LF-RLF) for 3h. The results showed that 35d-HF chickens had increased body fat deposition despite decreasing feed intake even when the diet was altered during the re-feeding period (P<0.05). 35d-LF promoted agouti-related peptide (AgRP) expression compared with HF (P<0.05) under both fed and fasted conditions. LF chickens with RHF had lower neuropeptide Y (NPY) expression compared to RLF chickens, while HF chickens showed the opposite result in which RHF chickens had higher NPY expression than RLF chickens (P<0.05). These results demonstrate (1) that high-fat diet decreases feed intake even when the subsequent diet is altered; (2) the orexigenic effect of hypothalamic AgRP; and (3) that dietary fat alters the response of hypothalamic NPY to subsequent energy intake. These findings provide a novel view of the metabolic perturbations associated with long-term dietary fat over-ingestion in chickens.