Indole-3-Lactic Acid Modulates Feeding Behavior and Appetite-Related Signals in Weaned Piglets

Gut microbiota-derived metabolites act as important mediators linking the gut microbiome with host physiological functions and participate in the regulation of metabolic homeostasis and behavior. However, whether the tryptophan metabolite indole-3-lactic acid (ILA) regulates feeding behavior in piglets and its potential central regulatory mechanisms remain unclear. In this study, 12 weaned piglets were used as a model to investigate the effects of ILA on feeding behavior regulation. The results showed that ILA supplementation did not significantly affect growth performance (p > 0.05), although final body weight, average daily gain, and average daily feed intake were numerically higher in the ILA group than in the control group. ILA also altered feeding behavior patterns, characterized by reduced daily feeding frequency (p < 0.05) and increased feeding rate (p = 0.053). Furthermore, ILA significantly increased serum concentrations of several appetite-related gastrointestinal hormones, including glucagon-like peptide-1, peptide YY, ghrelin, and cholecystokinin, and modified serum lipid metabolism-related parameters (p < 0.05). Hypothalamic transcriptomic analysis identified 240 differentially expressed genes in the ILA group compared with the CON group, with enrichment of genes involved in neural signaling and appetite regulation. These findings suggest that ILA may influence feeding behavior in weaned piglets, accompanied by numerical increases in feed intake and growth-related parameters, as well as changes in peripheral appetite-related gastrointestinal hormones and hypothalamic transcriptional responses.