Limosilactobacillus reuteri in Promoting Growth Performance and  Regulating Lipid Metabolism in Zuili Black Pigs
BackgroundThe gut microbiota is a key regulator of host lipid metabolism. In indigenous pigs, variation in growth performance and intramuscular fat (IMF) deposition has been linked to microbiota-host interactions, yet the specific taxa and metabolites that govern host lipid handling remain incompletely defined. We compared the gut microbiome, metabolome and transcriptome of high-body-weight (HBW) versus low-body-weight (LBW) Zuili Black Pigs to identify differentially abundant taxa and evaluate their roles and mechanisms in lipid regulation and growth promotion.ResultsComparative profiling of the gut microbiome, metabolome, and transcriptome clearly distinguished HBW and LBW Zuili Black Pigs. The two groups differed in gut microbial composition; notably, Limosilactobacillus reuteri was enriched in HBW pigs and correlated positively with growth performance and IMF. Lipid-related metabolites dominated the differential features, and growth-associated gene co-expression modules were enriched for lipid-metabolic pathways. Concordantly, HBW pigs showed elevated hepatic expression of lipid uptake/transport genes (Mtp, Fatp4, Cd36, Abca1) and increased intestinal expression of Fatp4, Abca1, and Npc1, consistent with enhanced lipid handling and higher IMF. In vivo, L. reuteri supplementation in mice increased body weight gain and average daily gain, improved small-intestinal morphology (greater villus height and villus-to-crypt ratio), and raised colonic phenylacetic acid (PAA). Mechanistically, L. reuteri produced PAA when provided phenylalanine, and HBW pigs exhibited higher colonic PAA levels. Taken together, these findings support an L. reuteri-phenylalanine-PAA axis that engages host lipid-metabolic programs to promote lipid absorption, deposition, and growth.ConclusionsOur findings demonstrate that L. reuteri converts phenylalanine to PAA, thereby activating host lipid-metabolic pathways to promote lipid absorption and deposition, ultimately contributing to improved growth performance. These results nominate the L. reuteri-PAA axis as a tractable microbiome target for enhancing growth traits in indigenous pig populations, with potential to inform probiotic and breeding strategies aimed at sustainable production and meat-quality improvement.