Integrative Analysis of the Gut Microbiota and Metabolome for In Vitro Human Gut Fermentation Modeling

Bifidobacterium breve Protects the Intestinal Epithelium and Mitigates Inflammation in Colitis via Regulating the Gut Microbiota-Cholic Acid Pathway

In this study, we aimed to explore the protective effects of Bifidobacterium in colitis mice and the potential mechanisms. Results showed that Bifidobacterium breve (B. breve) effectively colonized the intestinal tract and alleviated colitis symptoms by reducing the disease activity index. Moreover, B. breve mitigated intestinal epithelial cell damage, inhibited the pro-inflammatory factors, and upregulated tight junction (TJ)-proteins. Gut microbiota and metabolome analysis found that B. breve boosted bile acid-regulating genera (such as Bifidobacterium and Clostridium sensu stricto 1), which promoted bile acid deconjugation in the intestine. Notably, cholic acid (CA) was closely associated with the expression levels of inflammatory factors and TJ-proteins (p < 0.05). Our in vitro cell experiments further confirmed that CA (20.24 ± 4.53 pg/mL) contributed to the inhibition of lipopolysaccharide-induced tumor necrosis factor-α expression (49.32 ± 5.27 pg/mL) and enhanced the expression of TJ-proteins (Occludin and Claudin-1) and MUC2. This study suggested that B. breve could be a probiotic candidate for use in infant foods.

Bergamot polysaccharides relieve DSS-induced ulcerative colitis via regulating the gut microbiota and metabolites

This study aimed to explore the efficacy of polysaccharides from bergamot (BP) in alleviating DSS-induced colitis. Results showed that BP was primarily composed of two components, BP-1 and BP-2, with similar monosaccharide compositions to BP (mainly glucose and xylose) and molecular weights (Mw) of 4.50 × 105 and 2.35 × 105 Da. This study found BP relieved disease symptoms such as weight loss and colon shortening in mice with colitis. Gut microbiota and metabolomics analysis revealed that the BP could also promote the proliferation of beneficial bacteria such as Bifidobacteria, Butyrivibrio, and Blautia, resulting in increased levels of SCFAs and L-phenylalanine, which were associated with phenylalanine, tyrosine, and tryptophan metabolism pathways. Further analysis validated the inflammatory activity of L-phenylalanine. Hence, BP may relieve colitis symptoms by regulating the gut microbiota and metabolism, which reduced inflammation and enhanced the expression of tight junctional proteins (TJ proteins) and mucin in the intestine.

Gut microbiota-bile acid crosstalk regulates murine lipid metabolism via the intestinal FXR-FGF19 axis in diet-induced humanized dyslipidemia

BACKGROUND

Diet-induced dyslipidemia is linked to the gut microbiota, but the causality of microbiota-host interaction affecting lipid metabolism remains controversial. Here, the humanized dyslipidemia mice model was successfully built by using fecal microbiota transplantation from dyslipidemic donors (FMT-dd) to study the causal role of gut microbiota in diet-induced dyslipidemia.

RESULTS

We demonstrated that FMT-dd reshaped the gut microbiota of mice by increasing Faecalibaculum and Ruminococcaceae UCG-010, which then elevated serum cholicacid (CA), chenodeoxycholic acid (CDCA), and deoxycholic acid (DCA), reduced bile acid synthesis and increased cholesterol accumulation via the hepatic farnesoid X receptor-small heterodimer partner (FXR-SHP) axis. Nevertheless, high-fat diet led to decreased Muribaculum in the humanized dyslipidemia mice induced by FMT-dd, which resulted in reduced intestinal hyodeoxycholic acid (HDCA), raised bile acid synthesis and increased lipid absorption via the intestinal farnesoid X receptor-fibroblast growth factor 19 (FXR-FGF19) axis.

CONCLUSIONS

Our studies implicated that intestinal FXR is responsible for the regulation of lipid metabolism in diet-induced dyslipidemia mediated by gut microbiota-bile acid crosstalk. Video Abstract.

Fucogalactan Sulfate (FS) from Laminaria japonica Regulates Lipid Metabolism in Diet-Induced Humanized Dyslipidemia Mice via an Intestinal FXR-FGF19-CYP7A1/CYP8B1 Pathway

Our previous study found that fucogalactan sulfate (FS) from Laminaria japonica exhibited significant hypolipidemic effects. To further elucidate the mechanism, we first constructed a dyslipidemia mouse model with humanized gut microbiota and proved the main differential metabolic pathway involved bile acid metabolism. Then, we evaluated the beneficial effects of FS on dyslipidemia in this model mice, which revealed that oral FS administration reduced serum cholesterol levels and mitigated liver fat accumulation. Gut microbiota and microbiome analysis showed FS increased the abundance of Ruminococcaceae_NK4A214_group, GCA-900066755, and Eubacterium, which were positively associated with the fecal DCA, β-MCA, and HDCA. Further investigation demonstrated that FS inhibited the hepatic farnesoid X receptor (FXR), while activating the intestinal FXR-FGF19 pathway, leading to suppression of CYP7A1 and CYP8B1, as well as potentially reduced bile acid synthesis and lipid absorption. Overall, FS regulated lipid metabolism in diet-induced humanized dyslipidemia mice via the bile acid-mediated intestinal FXR-FGF19-CYP7A1/CYP8B1 pathway.

Comparative Study on In Vitro Fermentation Characteristics of the Polysaccharides Extracted from Bergamot and Fermented Bergamot

This study aimed to compare the in vitro fermentation characteristics of polysaccharides from Bergamot and Laoxianghuang (fermented 1, 3, and 5 years from bergamot) using the stable in vitro human gut fermentation model. Results showed that bergamot polysaccharide (BP) and Laoxianghuang polysaccharides (LPs) with different surface topographies were characterized as mannorhamnan (comprising Mannose and Rhamnose) and polygalacturonic acid (comprising Galacturonic acid and Galactose), respectively. The distinct effects on the gut microbiota and metabolome of BP and LPs may be due to their different monosaccharide compositions and surface morphologies. BP decreased harmful Fusobacterium and promoted beneficial Bifidobacterium, which was positively correlated with health-enhancing metabolites such as acetic acid, propionic acid, and pyridoxamine. Lactobacillus, increased by LPs, was positively correlated with 4-Hydroxybenzaldehyde, acetic acid, and butyric acid. Overall, this study elucidated gut microbiota and the metabolome regulatory discrepancies of BP and LPs, potentially contributing to their development as prebiotics in healthy foods.

In vitro effects of two polysaccharide fractions from Laminaria japonica on gut microbiota and metabolome

To investigate the prebiotic potential of two Laminaria japonica polysaccharide (LJP) fractions with different molecular weights and structures, we conducted in vitro simulated digestion and fermentation with hyperlipidemia-associated human gut microbiota. The results indicated that the LJP fraction with higher molecular weight (HLJP) appeared to have a more complex monosaccharide composition and microstructure than did the LJP fraction with lower molecular weight (LLJP), and both fractions could not be digested by in vitro simulated digestion. After in vitro fermentation, HLJP generated more short-chain fatty acids (SCFAs) and showed stronger ability to regulate core metabolites. Intriguingly, LLJP is better at promoting the proliferation of Akkermansiaceae, while HLJP is more effective in reducing the Firmicutes/Bacteroidetes ratio and increasing the content of Bacteroidaceae and Tannerellaceae. The present study indicates that LLJP and HLJP may have probiotic effects through different approaches and these differences may be related to the molecular weight and structure of the polysaccharides.

Effect of Bergamot and Laoxianghuang Polysaccharides on Gut Microbiota Derived from Patients with Hyperlipidemia: An Integrative Analysis of Microbiome and Metabolome during In Vitro Fermentation

The aim of this study was to investigate the effects of bergamot polysaccharide (BP) and Laoxianghuang polysaccharides (LPs, fermented bergamot) on the microbiome and metabolome during the in vitro fermentation of gut microbiota from patients with hyperlipidemia. Results indicated that both BP and LPs were able to increase the production of acetic acid, propionic acid, and butyric acid. However, only LPs could decrease the content of isobutyric acid and isovaleric acid, which are detrimental to gut health. A 16S rRNA analysis showed that both BP and LPs could reduce the proportion of Fusobacterium, whereas they increased the Bacteroides content in hyperlipidemia. Untargeted UPLC-MS/MS metabolomic profiling found six bio-markers that were significantly changed after BP and LPs intervention, and four of the down-regulated metabolites were long-chain fatty acids associated with vascular diseases. These findings provide new evidence that BP and LPs have the potential to regulate imbalances in the gut microbiota in patients with hyperlipidemia and ameliorate its metabolic abnormalities.