Orlistat-Induced Gut Microbiota Modification in Obese Mice

Abstract

Introduction: Accumulating evidence has indicated that alterations of gut microbiota have been involved in various metabolic diseases. Orlistat, a reversible inhibitor of pancreatic and gastric lipase, has beneficial effects on weight loss and metabolism. However, the effect of orlistat on the composition of gut microbiota remains unclear.

Objective: We aimed to explore the effect of orlistat on gut microbiota in high-fat diet (HFD) fed C57BL/6J obese mice.

Methods: C57BL/6J mice were randomly divided into three groups: control (NCD), HFD, and HFD + orlistat (ORL). Mice in the NCD group were fed chow diet, while the other groups were fed HFD for 6 months, and orlistat was added in the final 3 months in the HFD + ORL group. After sacrifice, body weight and metabolic parameters were assessed, and the gut microbial composition was analyzed by 16S rRNA gene sequencing.

Results: Orlistat treatment exerted beneficial effects on body weight, plasma cholesterol, and glucose tolerance. Meanwhile, orlistat treatment modified the gut microbiota, presenting as reduced total microbial abundance and obvious upregulated bacteria. Moreover, the upregulated bacteria correlated with several metabolic pathways.

Conclusions: Orlistat may exert beneficial effects on body weight and glucose tolerance through modifying the composition of gut microbiota.

Figure 1

Effects of orlistat on weight, cholesterol, and glucose tolerance in HFD-induced obese mice. (a) Weight, (b) serum cholesterol, (c) IPGTT, and (d) AUC analysis of the IPGTT plot in mice of three groups. All data are expressed as mean ± SEM. ^▲▲▲p < 0.001, ^▲▲p < 0.01, ^▲p < 0.05 compared to NCD mice and ^###p < 0.001, ^##p < 0.01, ^#p < 0.05 compared with the HFD group.

Figure 2

Effects of orlistat on gut microbial composition in HFD-induced obese mice. Pairwise comparisons of α diversity, including (a) Shannon index and (b) Richness index, were detected among the NCD, HFD, and HFD + ORL group (blue squares). (c) Analysis of β diversity by principal coordinates analysis (PCoA) of weighted Unifrac distances in NCD (dots in orange), HFD (green triangles), and obese mice with orlistat supplementation (blue squares). (d) Rarefaction curves according to species richness (observed OTUs) in three groups. As the curves tend to be flat, enough extracted sequences were detected.

Figure 3

Relative abundances of bacterial community at different levels among 3 groups. (a) The bacterium with the top 6 relative abundances among the three groups at phylum level. (b) The boxplot presents comparisons of the 6 highest bacteria at phylum level among the three groups using one-way ANOVA with Tukey HSD test. ^∗∗∗p < 0.001, ^∗∗p < 0.01, and ^∗p < 0.05.

Figure 4

Differentially abundant bacterial taxa among the groups. Enriched bacterial taxa at genus level were identified by linear discriminant analysis (LDA) with effect size measurements shown in a log scale among three mice groups: the NCD (red histograms), HFD (green histograms), and HFD+ORL group (blue histograms).

Figure 5

Bacterial co-occurrence network analysis associated with high-fat diet and orlistat treatment. Each node in the network represents one of the 9 highest bacteria and the size of each node represents its relative abundance. Edges indicate the bacterial connections expressed Spearman's correlation coefficients with values greater than cut-off of 0.7 and adjusted p value less than 0.05. Positive and negative correlations are shown in red and blue edges, respectively. (a) NCD co-occurrence network. (b) HFD co-occurrence network. (c) HFD + ORL co-occurrence network

Figure 6

Heatmap of Spearman's correlation between enriched bacterial taxa and third level of KEGG metabolic pathways according to clustering of three groups. Spearman's correlation coefficients were calculated and shown in the left, with red representing more positively and blue being more negatively correlation. The clustering of the NCD (light blue box), HFD (green box), and HFD + ORL (orange box) group was presented above the figure. ^∗Spearman's correlation is significant with p < 0.05.