Changes of chicken liver-enriched antimicrobial peptide 2 across feeding states and body weight and its regulatory role in feed intake

1. Liver-enriched antimicrobial peptide 2 (LEAP2), ghrelin and growth hormone secretagogue receptor (GHSR) are critical components of the appetite regulation system. This study analysed changes in LEAP2-ghrelin-GHSR expression across diverse feeding conditions and body weights in adult broilers and investigated the effects of intraperitoneally injected LEAP2 and ghrelin peptides on the feed intake of chicks.2. In adult broilers, the expression of LEAP2 in the liver and intestine exhibited significant variations under different feeding conditions (fed, fasting and refeeding), with a notable reduction observed during fasting. Compared to the fed group, proventriculus ghrelin and hypothalamus GHSR gene expression doubled, but was not statistically significant. Serum analyses revealed that fasting significantly decreased LEAP2 levels relative to the fed state and a significant negative correlation was identified between LEAP2 levels and body weight in fasting chickens. Conversely, ghrelin levels remained stable irrespective of feeding states and showed no correlation with body weight.3. Intraperitoneal injection of LEAP2 mature peptide, comprising the N-terminal 14 amino acids significantly reduced feed intake of chicks within the initial 4 h. In contrast, ghrelin injection resulted in a decrease in feed intake during the first 30 min. However, prior administration of ghrelin followed by LEAP2 mitigated the suppressive effect of ghrelin on feed intake within this timeframe.4. This study demonstrated that chicken LEAP2 gives a more sensitive feedback factor than ghrelin under different feeding conditions in adult broilers. It revealed that LEAP2 in a chick model modulated feed intake. These findings provide a theoretical basis for exploring the underlying mechanisms of LEAP2-mediated feed intake regulation in poultry.