Project description:Lipid accumulation associated with immune cell infiltration leading to hepatocellular ballooning and lobular inflammation are the cardinal features of NASH. With onset and development of multi-omics approaches in the last decade, we have been able to comprehend the existence and functionality of gut microbial ecology. Apart from the compositional variation (dysbiosis), functional alteration of the microbial population i.e., the impact of the crosstalk between gut microbiota-derived metabolites with host cells also remains elusive in terms of regulation of immunometabolic homeostasis and overall human health and disease. Sodium butyrate (NaBu), a short chain fatty acid derived metabolite is known to modulate the inflammatory status of NASH pathogenesis; however, its mechanism of action is not clearly deciphered. To unveil the immunomodulatory activity of NaBu, we found robust anti-inflammatory effect of NaBu in diet induced NASH model with reduced macrophage infiltration. Mechanistically, independent of p65 nuclear translocation, by maintaining the enhanced acetylation status of p65 along with differential p65 recruitment to the proinflammatory gene promoter, NaBu suppressed the inflammatory milieu and resulted in better prognosis. Along with transcriptional rewiring, NaBu also altered the metabolic status, modified the functional outcome and exhibited differential secretome which ultimately resulted skewing of macrophages towards a prohealing phenotype and induced autocrine as well as paracrine death of proinflammatory macrophages to abrogate inflammation in both isolated LMs and in vivo model.
Project description:Background & Aims: In obesity-associated non-alcoholic steatohepatitis (NASH), persistent hepatocellular damage and inflammation are key drivers of fibrosis, the main determinant of NASH-associated mortality. The short chain fatty acid butyrate can exert metabolic improvements and anti-inflammatory activities in NASH. However, its effects on NASH-associated liver fibrosis remains unclear. Methods: Putative antifibrotic effects of butyrate were studied in Ldlr-/-.Leiden mice fed an obesogenic NASH-inducing diet (HFD) containing 2.5% (w/w) butyrate for 38 weeks and compared to an HFD control group. Antifibrotic mechanisms of butyrate were further investigated in TGF-β-stimulated primary human hepatic stellate cells (HSC). Results: HFD-fed mice developed obesity, insulin resistance, increased levels of plasma leptin, adipose tissue inflammation, gut permeability, dysbiosis and NASH-associated fibrosis. Butyrate corrected hyperinsulinemia, lowered plasma leptin levels and attenuated adipose tissue inflammation, without affecting gut permeability or microbiota composition. Butyrate lowered plasma ALT and CK-18M30 and attenuated hepatic steatosis and inflammation. Butyrate inhibited fibrosis development as demonstrated by decreased hepatic collagen content and Sirius-red-positive area. In TGF-β-stimulated HSC, butyrate dose-dependently reduced collagen deposition and decreased procollagen1α1 and PAI-1 protein expression. Transcriptomic analysis and subsequent pathway and upstream regulator analysis revealed deactivation of specific non-canonical TGF-β signaling pathways RhoA/Rock and PI3K/AKT and other important pro-fibrotic regulators (e.g. YAP/TAZ and MYC) by butyrate, providing a potential rationale for its antifibrotic effects. Conclusions: Butyrate protects against the development of obesity and insulin resistance-associated NASH and liver fibrosis. These antifibrotic effects are at least in part attributable to a direct effect on collagen production in hepatic stellate cells, as a result of inhibiting non-canonical TGF-β signaling.
Project description:Tissue resident macrophages and recruited monocyte-derived macrophages contribute to host defense but also play pathological roles in a diverse range of human diseases. Multiple macrophage phenotypes are often represented in a diseased tissue, but we lack a deep understanding of the mechanisms that control diversification. Here we use a combination of genetic, genomic, and imaging approaches to investigate the origins and epigenetic trajectories of hepatic myeloid cells during a diet-induced model of nonalcoholic steatohepatitis (NASH). We provide evidence that distinct microenvironments within the NASH liver induce strikingly divergent transcriptomes of resident and infiltrating cells. Myeloid cell diversification results from both remodeling open chromatin landscapes of recruited monocytes and altering activities of preexisting enhancers of resident Kupffer cells. These findings provide evidence that niche-specific combinations of disease-associated environmental signals instruct resident and recruited macrophages to acquire distinct programs of gene expression and corresponding phenotypes.