Changes in body weight and BMI in zebrafish on the different diets. (A, B) Changes in body weight during 5 weeks. (C) BMI in adult zebrafish after 5 weeks.

Boxplots of alpha diversity indices of gut microbiota community based on 16S rRNA sequencing. (A–D) Gut microbial alpha diversity of C, P, H and HP groups based on (A) Chao1, (B) Shannon, (C) Simpson, and (D) Observed species. All data are normalized to C group (100%) (*p < 0.05). (E, F) Gut microbial alpha diversity of C and H groups based on (E) Shannon, and (F) Simpson. All data are normalized to C group (100%) (*p < 0.05). (G, H) Gut microbial alpha diversity of H and HP groups based on (G) Shannon and (H) Simpson. All data are normalized to H group (100%) (*p < 0.05).

Principal coordinate analysis (Bray-Curtis dissimilarity) score plot of gut microbiota of the zebrafish fed on four different groups (A), on C and H group (B), and on H and HP group (C).

The gut microbiota of zebrafish in C, P, H, and HP groups. Relative abundance at phylum (A) and genus (B) level of the gut microbiota.

LEfSe analysis explored the discriminative microbiota in group C, P, H, and HP, respectively. (A) The LDA score histogram; (B) the cladogram. p < 0.05 was used as a threshold for LEfSe analysis.

Sample functional abundances predicted by PICRUSt2 based on the abundance of labeled gene sequences in the samples. (A) KEGG databases. (B) Metacyc databases. (C) Significant pathway analysis between H and HP groups based on KEGG databases. (D) Significant pathway analysis between C and H groups based on Metacyc databases. (E) Significant pathway analysis between H and HP groups based on Metacyc databases.

Effect of P. pentosaceus PR-1 on intestinal inflammation, gut permeability, and lipid metabolism in HFD-fed zebrafish. (A–C) The total RNA was extracted from the intestine, and the relative mRNA expression levels of TNF-α (A), IL-1ß (B), and IL-6 (C) were determined by qRT-PCR. (D–F) The total RNA was extracted from the intestine, and the relative mRNA expression levels of Occludin (D), Claudin-1 (E), and ZO-1 (F) were determined by qRT-PCR. (G, H) The total RNA was extracted from the liver, and the relative mRNA expression levels of SREBP1 (G), FAS (H), and LEPTIN (I) were determined by qRT-PCR. Values were represented as the mean ± S.D. (n = 6). Values with different superscript letters are significantly different (p < 0.05).

Effect of P. pentosaceus PR-1 on liver pro-inflammatory cytokines (A–C) and biochemical parameters (D–F) in HFD-fed zebrafish. (A) Hepatic concentration of tumor necrosis factor α (TNF-α). (B) Hepatic concentration of interleukin-1ß (IL-1ß). (C) Hepatic concentration of interleukin-6 (IL-6). (D) Hepatic level of triglyceride. (E) Hepatic level of total cholesterol. (F) Hepatic level of low-density lipoprotein (LDL). Values were represented as the mean ± S.D. (n = 3). Values with different superscript letters are significantly different (p < 0.05).

Histological changes of liver sections measured by H&E staining (scale bar is 50 μm). The black arrows indicate extensive hydropic degeneration of hepatocytes characterized by swollen, pale, vacuolated cytoplasm.