Short-term dietary antibiotics altered the intestinal microbiota and improved the lipid metabolism in hybrid grouper fed medium and high-lipid diets

Abstract The increasing aquaculture production brought about the extensive use of high-lipid diets and antibiotics as effective means to spare costly protein and treat diseases, respectively. However dietary antibiotics and high-lipid diets both influence the gut microbiome. We hypothesized that antibiotics could affect the lipid metabolism by altering the composition of intestinal microbiota in fish at medium- and high-lipid diets. We explored this hypothesis by a 6-day administration of antibiotics mixtures to the diet of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂). Four diet groups were designed: medium-lipid (control diet, CD, 8.27% lipids), CD supplemented with antibiotics (vancomycin, neomycin sulfate, metronidazole; ACD), high-lipid diet (HD, 15.32% lipids), and HD with antibiotics (AHD). The ACD and AHD groups exhibited significantly decreased crude lipids, lipid droplets, triglycerides, and total cholesterol contents of the liver (compared to CD and HD). The antibiotics treatment mainly upregulated the expressions of genes associated with lipolysis at the medium-lipid diet and downregulated the expression of lipogenesis-associated genes at the high-lipid diet. The antibiotics treatment mainly inhibited the expression of lipogenesis-associated proteins in the high-lipid diet, and mainly facilitated lipolysis in the medium-lipid diet. The antibiotics treatment significantly reduced the abundance and diversity of microbes, the abundance of Firmicutes, and Firmicutes/Bacteroidetes ratio. In addition, antibiotics homogenized the intestinal microbiota, which in turn caused analogous effects in medium- and high-lipid diets in grouper. In conclusion, short-term dietary antibiotics treatment improved the accumulation of lipids and lipid metabolism by inhibiting lipogenesis at the high-lipid level and facilitating lipolysis at the medium-lipid level via affecting the composition, diversity and functional pathways of gut microbiota.