Metabolic endotoxemia originating from dysbiotic gut microbiota has been identified as a primary mediator for triggering the chronic low-grade inflammation (CLGI) responsible for the development of obesity. Capsaicin (CAP) is the major pungent bioactivator in chili peppers and has potent anti-obesity functions, yet the mechanisms linking this effect to gut microbiota remain obscure. Here we show that mice fed a high-fat diet (HFD) supplemented with CAP exhibit lower levels of metabolic endotoxemia and CLGI associated with lower body weight gain. High-resolution responses of the microbiota were examined by 16S rRNA sequencing, short-chain fatty acid (SCFA) measurements, and phylogenetic reconstruction of unobserved states (PICRUSt) analysis. The results showed, among others, that dietary CAP induced increased levels of butyrate-producing Ruminococcaceae and Lachnospiraceae, while it caused lower levels of members of the lipopolysaccharide (LPS)-producing family S24_7. Predicted function analysis (PICRUSt) showed depletion of genes involved in bacterial LPS synthesis in response to CAP. We further identified that inhibition of cannabinoid receptor type 1 (CB1) by CAP also contributes to prevention of HFD-induced gut barrier dysfunction. Importantly, fecal microbiota transplantation experiments conducted in germfree mice demonstrated that dietary CAP-induced protection against HFD-induced obesity is transferrable. Moreover, microbiota depletion by a cocktail of antibiotics was sufficient to block the CAP-induced protective phenotype against obesity, further suggesting the role of microbiota in this context. Together, our findings uncover an interaction between dietary CAP and gut microbiota as a novel mechanism for the anti-obesity effect of CAP acting through prevention of microbial dysbiosis, gut barrier dysfunction, and chronic low-grade inflammation.

Our study showed that gut enterotypes may influence the beneficial effects of dietary CAP, providing new evidence for the personalized nutrition guidance of CAP intervention on health promotion linking with gut microbiota patterns.

Scope Previous studies have linked dietary capsaicin (CAP) intake to improved glucose homeostasis and insulin sensitivity. However, the underlying mechanisms remain unclear. Methods and results Type 2 diabetic db/db mice are fed a chow diet with or without CAP treatment for 8 weeks. CAP administration markedly improves glucose tolerance and insulin sensitivity through decreasing gluconeogenesis and increasing glycogen synthesis in the liver. Furthermore, CAP inhibits the increase in abundance of the genus Lactobacillus and its bile salt hydrolase (BSH) activity compared with levels in chow‐fed mice, thereby leading to the accumulation of tauro‐β‐muricholic acid (TβMCA), a natural antagonist of the farnesoid X receptor (FXR) that is involved in the regulation of BA and glucose metabolism. CAP‐induced suppression of enterohepatic FXR‐fibroblast growth factor 15 (FGF15) signaling contributes to the increased BA pool size, followed by increases in the expression of cholesterol 7α‐hydroxylase (CYP7A1) and hepatic BA synthesis. Additionally, depleting gut microbiota by antibiotics administration abolishes the beneficial effects of CAP on BA metabolism and glucose homeostasis. Conclusions CAP‐induced improvements in BA and glucose metabolism are partially mediated by the gut microbiota‐BA‐enterohepatic FXR axis in db/db mice.

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Scope Sirtuin 3 (SIRT3) plays a protective role against nonalcoholic fatty liver disease (NAFLD) by improving hepatic mitochondrial dysfunction. Gut microbiota imbalance contributes to the pathogenesis of NAFLD, yet the underlying mechanism linking SIRT3 with gut microbiota in NAFLD progression remains obscure. Methods and results Wild‐type 129 mice and SIRT3 knockout (SIRT3KO) mice are placed under a chow diet or high‐fat diet (HFD) treatment for 18 weeks. HFD resulted in a significantly increased hepatic steatosis and inflammation, which are exacerbated in SIRT3KO mice. The gut microbiota by 16s rRNA gene sequencing and phylogenetic reconstruction of unobserved states analysis are characterized. Lack of SIRT3 facilitates gut microbial dysbiosis in mice following HFD, with increased Desulfovibrio, Oscillibacter, and decreased Alloprevotella. SIRT3 deficiency resulted in an impaired intestinal permeability and inflammation in HFD‐fed mice, which can be attenuated by sodium butyrate (NaB). SIRT3KO HFD‐fed mice is followed by an increased lipopolysaccharide into the circulation and dysregulated expressions of cannabinoid receptor 1 and 2 in colon and liver, which are significantly associated with the alterations of intestinal microbiota. Conclusions SIRT3 deficiency promotes NAFLD progression in correlation with impaired intestinal permeability through gut microbiota dysbiosis.