Parabacteroides distasonis ameliorates insulin resistance via activation of intestinal GPR109a.

Gut microbiota plays a key role in insulin resistance (IR). Here we perform a case-control study of Chinese adults (ChiCTR2200065715) and identify that Parabacteroides distasonis is inversely correlated with IR. Treatment with P. distasonis improves IR, strengthens intestinal integrity, and reduces systemic inflammation in mice. We further demonstrate that P. distasonis-derived nicotinic acid (NA) is a vital bioactive molecule that fortifies intestinal barrier function via activating intestinal G-protein-coupled receptor 109a (GPR109a), leading to ameliorating IR. We also conduct a bioactive dietary fiber screening to induce P. distasonis growth. Dendrobium officinale polysaccharide (DOP) shows favorable growth-promoting effects on P. distasonis and protects against IR in mice simultaneously. Finally, the reduced P. distasonis and NA levels were also validated in another human type 2 diabetes mellitus cohort. These findings reveal the unique mechanisms of P. distasonis on IR and provide viable strategies for the treatment and prevention of IR by bioactive dietary fiber.

Comprehensive evaluation of the prebiotic properties of Dendrobium officinale polysaccharides, ß-glucan, and inulin during in vitro fermentation via multi-omics analysis.

Dietary fiber is crucial for human health mainly due to its impact on gut microbiota structure and metabolites. This study aimed to investigate the impact of Dendrobium officinale polysaccharides (DOP) and two common fibers (ß-glucan and inulin) on the gut microbiome structure and metabolic profile in vitro. Fecal samples were obtained from 30 healthy volunteers, which were then individually subjected to fermentation with each type of fiber. The results revealed that all fibers were efficiently degraded by gut microbiota, with DOP exhibiting a slower fermentation rate compared to ß-glucan and inulin. The fermentation of all fibers led to a significant increase in the production of short-chain fatty acids (SCFAs) and a reduction in branched-chain fatty acids (BCFAs), sulfides, phenols, and indole. Moreover, the abundance of unclassified Enterobacteriaceae, which was positively correlated with sulfide, phenols, and indole levels, was significantly reduced by all fibers. Additionally, DOP specifically promoted the growth of Parabacteroides, while ß-glucan and inulin promoted the growth of Bifidobacterium and Faecalibacterium. Taken together, these findings enhance our understanding of the role of DOP, ß-glucan, and inulin in modulating gut microbiota and metabolites, where the fermentation with fecal bacteria from different volunteers could provide valuable insights for personalized therapeutic approaches.

Preventive effects of pectin with various degrees of esterification on ulcerative colitis in mice.

This work investigated the physiochemical characteristics and preventive effects of purified pectin (H121, L13 and L102) with different esterification degrees on dextran sulfate sodium (DSS)-induced colitis in mice. Three doses of each type of pectin were administered to C57BL/6J mice for 7 days before the DSS treatment, with dextran and mesalazine as positive controls. Results showed that pathological factors including the body weight, the disease activity index (DAI), the colonic weight/length ratio and the organ index of the spleen were improved with pre-intervention of a high dose of L13 or L102. Further studies showed that administration of a low dose of L13, low dose and medium dose of L102 or dextran improved intestinal permeability and tight junction function in colitis mice. Treatments of L13 of all doses and L102 of a high dose downregulated the oxidative stress-associated factors, while L102 of a low dose and H121 ameliorated the inflammatory cytokine production in serum and the colon. The above results suggested that pectin could attenuate DSS-induced intestinal epithelial injury, inflammation and oxidative stress. Specifically, compared to high esterified pectin, low esterified pectin displayed better protective effects in acute colitis mice.