Hyperbaric oxygen augments susceptibility to C. difficile infection by impairing gut microbiota ability to stimulate the HIF-1α-IL-22 axis in ILC3

Hyperbaric oxygen (HBO) therapy is a well-established method for improving tissue oxygenation and is typically used for the treatment of various inflammatory conditions, including infectious diseases. However, its effect on the intestinal mucosa, a microenvironment known to be physiologically hypoxic, remains unclear. Here, we demonstrated that daily treatment with hyperbaric oxygen affects gut microbiome composition, worsening antibiotic-induced dysbiosis. Accordingly, HBO-treated mice were more susceptible to Clostridioides difficile infection (CDI), an enteric pathogen highly associated with antibiotic-induced colitis. These observations were closely linked with a decline in the level of microbiota-derived short-chain fatty acids (SCFAs). Butyrate, a SCFA produced primarily by anaerobic microbial species, mitigated HBO-induced susceptibility to CDI and increased epithelial barrier integrity by improving group 3 innate lymphoid cell (ILC3) responses. Mice displaying tissue-specific deletion of HIF-1 in RORγt-positive cells exhibited no protective effect of butyrate during CDI. In contrast, the reinforcement of HIF-1 signaling in RORγt-positive cells through the conditional deletion of VHL mitigated disease outcome, even after HBO therapy. Taken together, we conclude that HBO induces intestinal dysbiosis and impairs the production of SCFAs affecting the HIF-1α-IL-22 axis in ILC3 and worsening the response of mice to subsequent C. difficile infection.

Butyrate reduces high-fat diet-induced metabolic alterations, hepatic steatosis and pancreatic beta cell and intestinal barrier dysfunctions in prediabetic mice

In this study, we investigated the effect of diet supplementation with sodium butyrate (5% w/w), a short-chain fatty acid produced by the intestinal microbiota, on metabolic parameters, body adiposity, hepatic and pancreatic lipid accumulation, beta cell function/mass as well as on the structure and function of the tight junction-mediated intestinal epithelial barrier in both normal and obese/prediabetic C57 mice fed a regular (control) or high-fat diet for 60 days, respectively. Butyrate treatment significantly inhibited all the high-fat-induced metabolic dysfunctions evaluated, i.e. significantly reduced the weight gain and body adiposity as well as the insulin resistant state, hyperglycemia and hyperinsulinemia, without changing food intake. In addition, high-fat-fed mice treated with this short-chain fatty acid displayed no compensatory hyperplasia of pancreatic beta cells nor marked hepatic steatosis as seen in prediabetic mice after high-fat diet only. Isolated pancreatic islets from high-fat-fed mice treated with butyrate showed improvement of the insulin secretion, which was associated with a significant decrease in lipid accumulation within the pancreas. Butyrate enhanced the intestinal epithelial barrier, as revealed by the FITC-Dextran permeability assay, which was accompanied by a significant increase in the junctional content of the tight junction-associated claudin-1 in intestinal epithelia of jejunum, ileum, and colon of both control and high-fat mice. In conclusion, our results showed that diet supplementation with butyrate inhibits the deleterious effects of high-fat diet intake on metabolic parameters and structure/function of several tissues/organs associated with type 2 diabetes mellitus in a mouse model, suggesting a potential use of this short-chain fatty acid in the treatment of this endocrine-metabolic disorder. Impact statement Butyrate is a short-chain fatty acid produced by the intestinal microbiota through the fermentation of non-absorbable carbohydrates and proteins (e.g. fibers). Sodium butyrate incorporated into the diet displayed a protective action on metabolic, hepatic, pancreatic and intestinal alterations induced by high-fat diet in mice, resulting in significant inhibition of the development of a prediabetic state. Thus, our data suggest that butyrate may have a potential therapeutic use in the treatment of type 2 diabetes and related disorders.