Feeding habit affects gut microbiota and intestinal SCFAs in zebrafish. Adult zebrafish (2-month-old) were fed with CD, OD and HD for 2 weeks. (a) Principal coordinate analysis (PCoA) of all samples by weighted UniFrac distance. The relative bacterial abundance at the phylum (b), genus (c) and species (d) levels of the gut microbiota of adult zebrafish. (e) Heatmap shows the relative abundance of relevant species. (f) Intestinal acetate levels, propionate levels and butyrate levels in zebrafish which was performed with GC-MS. Data were expressed as the mean ± SEM (n = 3 or 4 biological replicates). *p < .05; **p < .01

Feeding habit affects gut microbiota and intestinal SCFAs in zebrafish. Adult zebrafish (2-month-old) were fed with CD, OD and HD for 2 weeks. (a) Principal coordinate analysis (PCoA) of all samples by weighted UniFrac distance. The relative bacterial abundance at the phylum (b), genus (c) and species (d) levels of the gut microbiota of adult zebrafish. (e) Heatmap shows the relative abundance of relevant species. (f) Intestinal acetate levels, propionate levels and butyrate levels in zebrafish which was performed with GC-MS. Data were expressed as the mean ± SEM (n = 3 or 4 biological replicates). *p < .05; **p < .01

Feeding habit affects glucose homeostasis in zebrafish. Postprandial blood glucose (a) and insulin levels (b) in zebrafish. Adult zebrafish (2-month-old) were fed CD, OD and HD with antibiotic mixture (Polymyxin B 2.5 g/kg diet and Neomycin 3.3 g/kg diet) for 1 week. Postprandial blood glucose (c) and insulin (d) in zebrafish after antibiotic treatment. The intestinal microbiota of CD, OD and HD-treated zebrafish were transferred to GF zebrafish. Free glucose (e) and the relative expression of insulin (f) of GF zebrafish inoculated with intestinal bacteria of CD, OD and HD treated zebrafish. Data were expressed as the mean ± SEM (n = 3 biological replicates). *p < .05; **p < .01; ***p < .001; ****p < .0001

Effect of C. somerae on glucose homeostasis in adult zebrafish. Adult zebrafish (2-month-old) were fed basal diet with antibiotic mixture or without for 1 week. Then, the zebrafish fed with antibiotics were treated with C. somerae or A. veronii B565 for 2 weeks. Total number of bacteria (a), the number of Fusobacteria (b) and Cetobacterium (c) in the intestinal microbiota of zebrafish. Intestinal acetate (d), postprandial blood glucose (e) and insulin (f) in zebrafish. Data were expressed as the mean ± SEM (n = 3 biological replicates). *p < .05; **p < .01; ***p < .001

Effect of C. somerae on glucose homeostasis in larval zebrafish. 4 dpf GF zebrafish were inoculated with A. veronii B565 + P. shigelloides, and A. veronii B565 + P. shigelloides+C. somerae for 2 weeks. Total number of bacteria (a), the number of Fusobacteria (b) and Cetobacterium (c) of the microbiota of zebrafish larvae at 6 dpf. Free glucose (d), acetate (e) and the relative expression of insulin (f) of zebrafish larvae at 6 dpf. Data were expressed as the mean ± SEM (n = 3 biological replicates). *p < .05; **p < .01; ***p < .001; ****p < .0001

Dietary sodium acetate promotes glucose homeostasis in zebrafish. Postprandial blood glucose (a) and insulin (b) of zebrafish fed with control and 0.15% NaAc diets for 4 weeks. Data were expressed as the mean ± SEM (n = 3 biological replicates). *p < .05; **p < .01

Sodium acetate drives insulin secretion via parasympathetic activation. Postprandial blood glucose (a) and insulin (b) of zebrafish after ICV injection of saline or 75 mg/kg NaAc at 4 h and 6 h. Postprandial blood glucose (c) and insulin (d) of zebrafish after ICV injection of saline, 75 mg/kg NaAc, 0.1 mg/kg atropine, or 75 mg/kg NaAc + 0.1 mg/kg atropine at 4 h and 6 h. Data were expressed as the mean ± SEM (n = 3 biological replicates). *p < .05; **p < .01; ***p < .001

Mannose promotes the enrichment of gut Cetobacterium in zebrafish. Adult zebrafish (2-month-old) were fed with control diet, 10% xylose diet or 1.0% mannose diet for 2 weeks. Total number of bacteria (a), the number of Fusobacteria (b), Cetobacterium (c), Proteobacteria (d), Plesiomonas (e) and Aeromonas (f) in the intestinal microbiota of zebrafish. Intestinal acetate (g), postprandial blood glucose (h) and insulin (i) in zebrafish. Data were expressed as the mean ± SEM (n = 3 or 4 biological replicates). *p < .05; **p < .01; ***p < .001