Metabolism-associated fatty liver disease (MAFLD), a growing health problem worldwide, is one of the major risks for the development of cirrhosis and liver cancer. Oral administration of nobiletin (NOB), a natural citrus flavonoid, modulates the gut microbes and their metabolites in mice. In the present study, we established a mouse model of MAFLD by subjecting mice to a high-fat diet (HFD) for 12 weeks. Throughout this timeframe, NOB was administered to investigate its potential benefits on gut microbial balance and bile acid (BA) metabolism using various techniques, including 16S rRNA sequencing, targeted metabolomics of BA, and biological assays. NOB effectively slowed the progression of MAFLD by reducing serum lipid levels, blood glucose levels, LPS levels, and hepatic IL-1β and TNF-α levels. Furthermore, NOB reinstated diversity within the gut microbial community, increasing the population of bacteria that produce bile salt hydrolase (BSH) to enhance BA excretion. By exploring further, we found NOB downregulated hepatic expression of the farnesoid X receptor (FXR) and its associated small heterodimer partner (SHP), and it increased the expression of downstream enzymes, including cholesterol 7α-hydroxylase (CYP7A1) and cytochrome P450 27A1 (CYP27A1). This acceleration in cholesterol conversion within the liver contributes to mitigating MAFLD. The present findings underscore the significant role of NOB in regulating gut microbial balance and BA metabolism, revealing that long-term intake of NOB plays beneficial roles in the prevention or intervention of MAFLD.

Toll-like receptors (TLRs) can recognize molecular patterns associated with microorganisms and induce immune responses. TLR3 is responsible for recognizing viruses and making hosts resistant to Coxsackie B3 (CVB3) infection. In this study, we found that Tectorigenin Sodium Sulfonate (TSS) has a TLR3 inhibitory effect and exerts strong anti-CVB3 activity through the TLR3 pathway both in vivo and in vitro. Balb/c mice were infected by ip injection of CVB3 virus, and subcutaneously injected with TSS at 264mg·Kg ^-1 ·d ^-1 for 7 d. The life extension rate of CVB3-infected mice was up to 46.67%, and the mean time to death was prolonged from 6.00 ± 0.47 d to 8.80 ± 2.78 d ( P < 0.01 ). TSS was also able to reduce the level of weight loss in mice, significantly reduce the symptoms of myocarditis caused by CVB3, reduce the virus titer in the heart, improve the spleen and thymus index, and enhance immune function. We further explored the underlying mechanism of TSS in CVB3-infected HT-29 cells and mice: TSS reduced TLR3 expression and downregulated its downstream TRIF, TRAF6, IRF3, NF-κ B. MAPK, AP1 expression, reduced expression of IFN-β、IL-6、TNF-α. TSS has strong anti-CVB3 activity in vitro and in vivo and has the effect of inhibiting the activation of TLR3 pathway. IMPORTANCE: TSS is expected to be an antiviral drug for the treatment of CVB3 infection. Its regulatory effect on the immune system provides a new approach for antiviral research.