摘要Trimethylamine oxide(TMAO)is a microbiota-derived metabolite,and numerous studies have shown that it could regulate fat metabolism in humans and mice.However,few studies have focused on the effects of TMAO on fat deposition in growing-finishing pigs.This study aimed to investigate the effect of TMAO on fat deposition and intestinal microbiota in growing-finishing pigs.Sixteen growing pigs were randomly divided into 2 groups and fed with a basal diet with 0 or 1 g/kg TMAO for 149 d.The intestinal microbial profiles,fat deposition indexes,and fatty acid profiles were measured.These results showed that TMAO supplementation had a tendency to decrease lean body mass(P＜0.10)and significantly increased backfat thickness(P＜0.05),but it did not affect growth performance.TMAO significantly increased total protein(TP)concentration,and reduced alkaline phosphatase(ALP)concentration in serum(P＜0.05).TMAO increased the α diversity of the ileal microbiota community(P＜0.05),and it did not affect the colonic microbial community.TMAO supplementation significantly increased acetate content in the ileum,and Proteobacteria and Escherichia-Shigella were significantly enriched in the TMAO group(P＜0.05).In addition,TMAO decreased fat content,as well as the ratio of linoleic acid,n-6 polyunsaturated fatty acids(PUFA),and PUFA in the liver(P＜0.05).On the contrary,TMAO increased intramuscular fat content of the longissimus dorsi muscle,whereas the C18:2n6c ratio was increased,and the n-6 PUFA:PUFA ratio was decreased(P＜0.05).In vitro,1 mmol/LTMAO treatment significantly upregulated the expression of FASN and SREBP1 in C2C12 cells(P＜0.05).Nevertheless,TMAO also increased adipocyte area and decreased the CPT-1B expression in subcutaneous fat(P＜0.05).Taken together,TMAO supplementation regulated ileal microbial composition and acetate production,and regulated fat distribution and fatty acid composition in growing-finishing pigs.These results provide new insights for understanding the role of TMAO in humans and animals.