Engineered butyrate-producing bacteria prevents high fat diet-induced obesity in mice

Abstract

Background: Obesity is a major problem worldwide and severely affects public safety. As a metabolite of gut microbiota, endogenous butyric acid participates in energy and material metabolism. Considering the serious side effects and weight regain associated with existing weight loss interventions, novel strategies are urgently needed for prevention and treatment of obesity.

Results: In the present study, we engineered Bacillus subtilis SCK6 to exhibited enhanced butyric acid production. Compared to the original Bacillus subtilis SCK6 strain, the genetically modified BsS-RS06550 strain had higher butyric acid production. The mice were randomly divided into four groups: a normal diet (C) group, a high-fat diet (HFD) group, an HFD + Bacillus subtilis SCK6 (HS) group and an HFD + BsS-RS06550 (HE) group. The results showed BsS-RS06550 decreased the body weight, body weight gain, and food intake of HFD mice. BsS-RS06550 had beneficial effects on blood glucose, insulin resistance and hepatic biochemistry. After the 14-week of experiment, fecal samples were collected for nontargeted liquid chromatography-mass spectrometry analysis to identify and quantify significant changes in metabolites. Sixteen potentially significant metabolites were screened, and BsS-RS06550 was shown to potentially regulate disorders in glutathione, methionine, tyrosine, phenylalanine, and purine metabolism and secondary bile acid biosynthesis.

Conclusions: In this study, we successfully engineered Bacillus subtilis SCK6 to have enhanced butyric acid production. The results of this work revealed that the genetically modified live bacterium BsS-RS06550 showed potential anti-obesity effects, which may have been related to regulating the levels of metabolites associated with obesity. These results indicate that the use of BsS-RS06550 may be a promising strategy to attenuate obesity.

Keywords: Butyric acid; Engineered bacteria; Fecal metabolomics; High-fat diet; Obesity.

Fig. 1

In vitro culture of B. subtilis SCK6 and BsS-RS06550. a BA production of SCK6 and BsS-RS06550. b Growth curves of B. subtilis SCK6 and BsS-RS06550 at OD₆₀₀. Growth curve parameters, k is the maximum possible population size in particular environment or the carrying capacity; r is the intrinsic growth rate of the population and t-gen is doubling time or generation time of a population. c SCFAs production in microbial community co-culture with SCK6 and BsS-RS06550, respectively, including acetic acid (AA), propanoic acid (PA), and butyric acid (BA). Data are represented as mean ± SD, n = 5 repeats for (a, c). *p value < 0.05, **p < 0.01 and ***p < 0.001

Fig. 2

Effects of BsS-RS06550 on physiology and lipid metabolism in blood. a Weekly body weight, b glucose tolerance test following intervention. c Insulin tests following intervention, d weekly food intake, lipid metabolism in blood, TC (e), TG (f), HDL-C (g) and LDL-C (h). Data represented as mean ± SD, n = 8 mice/group for (a–h). *p value < 0.05, **p < 0.01 and ***p < 0.001

Fig. 3

Effects of BsS-RS06550 on HFD-induced hepatic steatosis. a Serum TBA level, b serum ALT level, c serum AST level, d hematoxylin and eosin (H&E) staining and oil red O staining of and livers (×200). Data represented as mean ± SD, and n = 8 mice/group for (a–c). *p value < 0.05, **p < 0.01 and ***p < 0.001

Fig. 4

Untargeted fecal metabolomics analysis. a Hierarchical clustering of differentially metabolites in all groups. b Tree analysis of samples. c PCA score plots of fecal metabolic profiles, normal diet group (C), a high-fat diet group (HFD), HFD + Bacillus subtilis SCK6 group (HS) and HFD + BsS-RE06550 (HE). d OPLS-DA score plots of fecal metabolic profiling of C, HFD, HS and HE

Fig. 5

Box plots of relative abundance of significance metabolites in glutathione, methionine, tyrosine, phenylalanine metabolism, and C (control), HFD (high-fat diet), HFD + Bacillus subtilis SCK6 group (HS) and HFD + BsS-RS06550 (HE) groups (n = 8 for each group). Normalizing the intensity data with log function conversion (based on 10)

Fig. 6

Box plots of relative abundance of significance metabolites in purine metabolism and secondary bile acid biosynthesis, and C (control), HFD (high-fat diet), HFD + Bacillus subtilis SCK6 group (HS) and HFD + BsS-RS06550 (HE) groups (n = 8 for each group). Normalizing the intensity data with log function conversion (based on 10)

Fig. 7

Schematic diagram of proposed metabolic pathways in all fecal samples. Red and green represent up- and downregulated metabolites, respectively