Effects of central injection of liver-expressed antimicrobial peptide-2 (LEAP2) on feed intake in broiler chickens: interactions with opioidergic and serotonergic systems.

The liver-expressed antimicrobial peptide-2 (LEAP2) is recognized for its role in regulating meal consumption in mammals, but its function in avian species, especially broiler chickens, is not well understood. This study investigates the impact of central LEAP2 injection on food intake in broiler chickens, and explores its interactions with the opioidergic and serotonergic systems. Across eight trials, we examined the relationships between these systems and LEAP2 concerning meal intake in meat-type chickens. In Experiment 1, broilers received an intracerebroventricular (ICV) infusion of LEAP2 (0.75, 1.5, and 3 nmol) alongside a control solution. Subsequent experiments involved injecting birds with β-FNA (mu opioid receptor antagonist), LEAP2 (3 nmol), and β-FNA + LEAP2 (Experiment 2), with Experiments 3-8 following a similar design, substituting β-FNA with nor-BNI (kappa opioid receptor antagonist), NTI (delta opioid receptor antagonist), PCPA (serotonin synthesis inhibitor), fluoxetine (serotonin reuptake inhibitor), 8-OH-DPAT (5-HT1A receptor agonist), and SB242084 (5-HT2C receptor antagonist). Cumulative meal consumption was measured for 120 min post-infusion. Results indicated that LEAP2 injection (1.5 and 3 nmol) significantly reduced feed intake in broilers compared to the control treatment (P < 0.05). Co-infusion of β-FNA, PCPA, and SB242084 + LEAP2 attenuated LEAP2-induced hypophagia (P < 0.05), while co-infusion of fluoxetine + LEAP2 amplified LEAP2-induced hypophagia compared to the control treatment (P < 0.05). These findings suggest that LEAP2 induces hypophagic effects in broiler chickens, potentially mediated through the mu opioid and 5-HT2C receptors.