Liraglutide Attenuates Nonalcoholic Fatty Liver Disease by Modulating Gut Microbiota in Rats Administered a High-Fat Diet

Abstract

This study aimed to determine whether modulation of the gut microbiota structure by liraglutide helps improve nonalcoholic fatty liver disease (NAFLD) in rats on a high-fat diet (HFD). Rats were administered an HFD for 12 weeks to induce NAFLD and then administered liraglutide for 4 additional weeks. Next-generation sequencing and multivariate analysis were performed to assess structural changes in the gut microbiota. Liraglutide attenuated excessive hepatic ectopic fat deposition, maintained intestinal barrier integrity, and alleviated metabolic endotoxemia in HFD rats. Liraglutide significantly altered the overall structure of the HFD-disrupted gut microbiota and gut microbial composition in HFD rats in comparison to those on a normal diet. An abundance of 100 operational taxonomic units (OTUs) were altered upon liraglutide administration, with 78 OTUs associated with weight gain or inflammation. Twenty-three OTUs positively correlated with hepatic steatosis-related parameters were decreased upon liraglutide intervention, while 5 OTUs negatively correlated with hepatic steatosis-related parameters were increased. These results suggest that liraglutide-mediated attenuation of NAFLD partly results from structural changes in gut microbiota associated with hepatic steatosis.

Figure 1

Liraglutide attenuates nonalcoholic fatty liver disease, retains intestinal barrier function, and decreases inflammation levels in rats on a high-fat diet. (a) Oil Red O staining of liver sections; (b) body weight of rats; (c) relative levels of triglycerides (TG) in the liver; (d) levels of serum alanine transaminase (ALT), (e) aspartate transaminase (AST), (f) tumor necrosis factor-α (TNF-α), (g) lipopolysaccharide (LPS), and (h) diamine oxidase (DAO); (i) ultrastructure of tight junctions in the ileal mucosa (transmission electron microscopy, 20,000x). Data are expressed as mean ± standard deviation values. ^∗P < 0.05 vs NC group; ^∗∗P < 0.01 vs NC group; ^#P < 0.05 vs HFD group; ^##P < 0.01 vs HFD group.

Figure 2

α-Diversity analysis and structural changes in the gut microbiota upon liraglutide administration. (a) Rarefaction curves of multiple samples; (b) Chao index curve; (c) Ace index curve; (d) Shannon curve; (e) Simpson index curve; principal coordinate analysis (PCoA) score plot based on unweighted (f) and weighted (g) PCoA scores. UniFrac tree based on unweighted (h) and weighted (i) PCoA scores.

Figure 3

An abundance of 100 operational taxonomic units (OTUs) was altered upon liraglutide administration. Indicated are the OTUs that were more (red) and less abundant (blue) in the high-fat diet (HFD) + liraglutide group and the control group relative to the HFD group, respectively. (a) Heatmap of 100 OTUs. (b) Altered direction of the 100 OTUs upon liraglutide administration. Taxa of the OTUs (genus, family, and phylum) are shown on the right side. The asterisk (^∗) represents OTUs wherein abundance was altered via the HFD and reversed upon liraglutide administration.

Figure 4

Seventy-eight operational taxonomic units (OTUs) altered upon liraglutide administration were significantly correlated with host metabolic parameters in accordance with Spearman's correlation analysis. (a) Correlation between 76 OTUs and host metabolic parameters. Rows correspond to OTUs with identities shown on the left and columns correspond to metabolic parameters. Red and blue colors indicate positive and negative associations, respectively. Color intensity represents the degree of association between the OTU abundances and host parameters, as assessed via Spearman's correlation analysis. Asterisks indicate significant associations. Taxonomic classification of the OTUs is shown on the right side. (b) Altered direction of 76 OTUs. Red and blue colors indicate the OTUs that were more and less abundant, respectively, in the H + L and control groups in comparison with the high-fat diet (HFD) group. The asterisk (^∗) represents OTUs whose level was altered via an HFD and then reversed significantly upon liraglutide administration.