Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRR) with a crucial function in innate immune responses. Activation of TLR4 signaling at the plasma membrane by lipopolysaccharide (LPS) stimulates proinflammatory signaling pathways dependent on the E3 ubiquitin ligase TRAF6. Here we show the LPS-induced long non-coding RNA (lncRNA) Mirt2 functions as a checkpoint to prevent aberrant activation of inflammation, and is a potential regulator of macrophage polarization. Mirt2 associates with, and attenuates Lys63 (K63)-linked ubiquitination of, TRAF6, thus inhibiting activation of NF-κB and MAPK pathways and limiting production of proinflammatory cytokines. Adenovirus mediated gene transfer of Mirt2 protects mice from endotoxemia induced fatality and multi-organ dysfunction. These findings identify lncRNA Mirt2 as a negative feedback regulator of excessive inflammation.

The gut-liver axis is associated with the progression of non-alcoholic fatty liver disease (NAFLD). Targeting the gut-liver axis and bile acid-based pharmaceuticals are potential therapies for NAFLD. The effect of tauroursodeoxycholic acid (TUDCA), a candidate drug for NAFLD, on intestinal barrier function, intestinal inflammation, gut lipid transport and microbiota composition was analysed in a murine model of NAFLD. EXPERIMENTAL APPROACHThe NAFLD mouse model was established by feeding mice a high-fat diet (HFD) for 16 weeks. TUDCA was administered p.o. during the last 4 weeks. The expression levels of intestinal tight junction genes, lipid metabolic and inflammatory genes were determined by quantitative PCR. Tissue inflammation was evaluated by haematoxylin and eosin staining. The gut microbiota was analysed by 16S rRNA gene sequencing. KEY RESULTSTUDCA administration attenuated HFD-induced hepatic steatosis, inflammatory responses, obesity and insulin resistance in mice. Moreover, TUDCA attenuated gut inflammatory responses as manifested by decreased intestinal histopathology scores and inflammatory cytokine levels. In addition, TUDCA improved intestinal barrier function by increasing levels of tight junction molecules and the solid chemical barrier. The components involved in ileum lipid transport were also reduced by TUDCA administration in HFD-fed mice. Finally, the TUDCA-treated mice showed a different gut microbiota composition compared with that in HFD-fed mice but similar to that in normal chow diet-fed mice. CONCLUSIONS AND IMPLICATIONSTUDCA attenuates the progression of HFD-induced NAFLD in mice by ameliorating gut inflammation, improving intestinal barrier function, decreasing intestinal fat transport and modulating intestinal microbiota composition. Abbreviations ACOX1, peroxisomal acyl-CoA oxidase 1; ANOSIM, analysis of similarities; C3GNT, core 3β1,3-N-acetyl glucosaminyltransferase; CYP7a, cholesterol 7α-hydroxylase; ER, endoplasmic reticulum; FABP, fatty acid-binding protein; FATP4, fatty acid transport protein 4; FAR3, fatty acid receptor 3; H&E, haematoxylin and eosin; HFD, high-fat diet; HOMA-IR, homeostasis model assessment of the insulin resistance index; Iap, intestinal alkaline phosphatase; ICAM1, intercellular cell adhesion molecule-1; IPGTT, i.p. glucose tolerance test; IPITT, i.p. insulin tolerance test; Irak4, IL-1 receptor-associated kinase 4; JAM, junctional adhesion molecule; Lcad, long-chain acyl-CoA dehydrogenase; NAFLD, non-alcoholic fatty liver disease; NAS, non-alcoholic fatty liver disease activity score; NASH, non-alcoholic steatohepatitis; NCD, normal chow diet; OTU, operational taxonomic unit; PCoA, principal coordinates analysis; Tab1, TGF-β activated kinase 1 mitogen-activated protein kinase kinase kinase 7-binding protein 1; TC, total cholesterol; TEERs, transepithelial electrical resistances; TGs, triglycerides; TLR, toll-like receptor; Tram, toll or IL-1 receptor domain-containing adaptor inducing IFN-β-related adaptor molecule; TUDCA, tauroursodeoxycholic acid; UDCA...

A high-fat diet (HFD) causes hyperlipidemia, which worsens disturbances in bile acid (BA) metabolism and gut microbiota. This study aimed to investigate the regulation of flavonoids from whole-grain oat (FO) on BA metabolism and gut microbiota in HFD-induced hyperlipidemic mice. The experiment results showed that FO improved serum lipid profiles and decreased body weight and lipid deposition in HFD-fed mice. Through real-time qualitative polymerase chain reaction (RT-qPCR) and Western blot assays, by up-regulating the expression of PPARα, CPT-1, CYP7A1, FXR, TGR5, NTCP, and BSTP, and downregulating those of SREBP-1c, FAS, and ASBT, FO suppressed lipogenesis, promoted lipolysis and BA synthesis, and efflux to faeces via the FXR pathway. 16s rRNA sequencing revealed that FO significantly increased Akkermansia and significantly decreased Lachnoclostridium, Blautia, Colidextribacter, and Desulfovibrio. Spearman's correlation analysis showed that these bacteria were strongly correlated with hyperlipidemia-related parameters. Therefore, our results indicated that FO possessed an antihyperlipidemic effect via regulating the gut−liver axis, i.e., BA metabolism and gut microbiota.