Stigmasterol Protects Against Steatohepatitis Induced by High-Fat and High-Cholesterol Diet in Mice by Enhancing the Alternative Bile Acid Synthesis Pathway.

BACKGROUND: Hepatic cholesterol accumulation is a significant risk factor in the progression of nonalcoholic fatty liver disease (NAFLD) to steatohepatitis. However, the precise mechanism by which stigmasterol (STG) mitigates this process remains unclear. OBJECTIVES: This study aimed to investigate the potential mechanism underlying the protective effect of STG in mice with NAFLD progressing to steatohepatitis while being fed a high-fat and high-cholesterol (HFHC) diet. METHODS: Male C57BL/6 mice were fed an HFHC diet for 16 wk to establish the NAFLD model. Subsequently, the mice received STG or a vehicle via oral gavage while continuing the HFHC diet for an additional 10 wk. The study evaluated hepatic lipid deposition and inflammation as well as the expression of key rate-limiting enzymes involved in the bile acid (BA) synthesis pathways. BAs in the colonic contents were quantified using ultra-performance liquid chromatography-tandem mass spectrometry. RESULTS: Compared with the vehicle control group, STG significantly reduced hepatic cholesterol accumulation (P < 0.01) and suppressed the gene expression of NLRP3 inflammasome and interleukin-18 (P < 0.05) in the livers of HFHC diet-fed mice. The total fecal BA content in the STG group was nearly double that of the vehicle control group. Additionally, the administration of STG increased the concentrations of representative hydrophilic BAs in the colonic contents (P < 0.05) along with the upregulation of gene and protein expression of CYP7B1 (P < 0.01). Furthermore, STG enhanced the α-diversity of the gut microbiota and partially reversed the alterations in the relative abundance of the gut microbiota induced by the HFHC diet. CONCLUSIONS: STG mitigates steatohepatitis by enhancing the alternative pathway for BA synthesis.

Dietary cholesterol drives the development of nonalcoholic steatohepatitis by altering gut microbiota mediated bile acid metabolism in high-fat diet fed mice.

Nonalcoholic fatty liver disease (NAFLD) is the most widespread chronic liver disorder globally. Unraveling the pathogenesis of simple fatty liver to nonalcoholic steatohepatitis (NASH) has important clinical significance for improving the prognosis of NAFLD. Here, we explored the role of a high-fat diet alone or combined with high cholesterol in causing NASH progression. Our results demonstrated that high dietary cholesterol intakes accelerate the progression of spontaneous NAFLD and induces liver inflammation in mice. An elevation of hydrophobic unconjugated bile acids cholic acid (CA), deoxycholic acid (DCA), muricholic acid and chenodeoxycholic acid, was observed in high-fat and high-cholesterol diet fed mice. Full-length sequencing of the 16S rDNA gene of gut microbiota revealed a significant increase in the abundance of Bacteroides, Clostridium, and Lactobacillus that possess bile salt hydrolase activity. Furthermore, the relative abundance of these bacterial species was positively correlated with content of unconjugated bile acids in liver. Moreover, the expression of genes related to bile acid reabsorption (organic anion-transporting polypeptides, Na+-taurocholic acid cotransporting polypeptide, apical sodium dependent bile acid transporter and organic solute transporter ß) was found to be increased in mice with a high-cholesterol diet. Lastly, we observed that hydrophobic bile acids CA and DCA induce an inflammatory response in free fatty acids-induced steatotic HepG2 cells. In conclusion, high dietary cholesterol promotes the development of NASH by altering gut microbiota composition and abundance and thereby influencing with bile acid metabolism.

Intermittent Fasting Alleviates Non-Alcoholic Steatohepatitis by Regulating Bile Acid Metabolism and Promoting Fecal Bile Acid Excretion in High-Fat and High-Cholesterol Diet Fed Mice.

SCOPE: Intermittent fasting (IF) has a protective role across a wide range of chronic disorders, including obesity, diabetes, and cardiovascular disease, but its protection against non-alcoholic steatohepatitis (NASH) is still lacking. This study seeks to investigate how IF alleviates NASH by regulating gut microbiota and bile acids (BAs) composition. METHODS AND RESULTS: Male C57BL/6 mice are fed a high-fat and high-cholesterol (HFHC) diet for 16 weeks to establish a NASH model. Mice then continued HFHC feeding and are treated with or without every other day fasting for 10 weeks. Hepatic pathology is assessed using hematoxylin-eosin staining. Gut microbiota of the cecum are profiled using 16S rDNA gene sequencing and the levels of BAs in serum, colon contents, and feces are measured using ultra-performance liquid chromatography-tandem mass spectrometry. Results indicate that IF significantly decreases murine body weight, insulin resistance, hepatic steatosis, ballooning, and lobular inflammation. IF reshapes the gut microbiota, reduces the accumulation of serum BAs, and increases total colonic and fecal BAs. Moreover, IF increases the expression of cholesterol 7α-hydroxylase 1 in liver, but decreases the expressions of both farnesoid-X-receptor and fibroblast growth factor 15 in the ileum. CONCLUSION: IF alleviates NASH by regulating bile acid metabolism and promoting fecal bile acid excretion.

Efficiency of ursodeoxycholic acid for the treatment of nonalcoholic steatohepatitis: A systematic review and meta-analysis.

BACKGROUND: Previous studies have demonstrated that ursodeoxycholic acid (UDCA) possesses anti-inflammatory, antioxidant, and anti-fibrotic properties, and it may reduce the degree of liver damage caused by nonalcoholic steatohepatitis (NASH). However, the effectiveness of UDCA in improving liver function and histology in cases of NASH remains unclear. Therefore, we performed a meta-analysis to assess the efficacy of UDCA in the treatment of NASH. METHODS: PubMed, Web of Science, Embase, Cochrane, and other databases were searched for randomized controlled trials (RCTs) published before 1 January 2022, in which UDCA was used to treat patients with NASH. RESULTS: A total of 8 studies with 655 participantsmet the criteria for inclusion in this meta-analysis. The forest plot displayed that UDCA treatment significantly reduced blood concentrations of alanine aminotransferase (ALT) and γ-glutamyl transferase (GGT). However, the pooled effect size results did not suggest any significant effect of UDCA on anthropometric characteristics or hepatic histology. CONCLUSION: UDCA therapy can effectively reduce serum levels of ALT and GGT in patients with NASH but has no significant effects on physical characteristics or liver histology. Further large-scale and dose-response clinical studies are needed to evaluate the clinical potential of UDCA in treating NASH.

Deoxycholic Acid Promotes Pyroptosis in Free Fatty Acid-Induced Steatotic Hepatocytes by Inhibiting PINK1-Mediated Mitophagy.

Nonalcoholic steatohepatitis (NASH) is the inflammatory subtype of nonalcoholic fatty liver disease (NAFLD), which can lead to liver fibrosis and cirrhosis. Bile acid levels are correlated with markers of hepatic injury in NASH, suggesting a possible role for bile acids in the progression of NAFLD. Here, we examined the role of deoxycholic acid (DCA) in driving steatotic hepatocytes to pyroptosis, a pro-inflammatory form of programmed cell death. HepG2 cells were stimulated with odium oleate and sodium palmitate for modeling steatotic hepatocytes and then treated with DCA alone or in combination with a specific mitophagy agonist, carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Our results showed that DCA dose-dependently induced a pro-inflammatory response in steatotic hepatocytes but had no significant effect on lipid accumulation. Moreover, activation of the NLRP3 inflammasome and pyroptosis were triggered by DCA. Expression levels of the mitophagy markers PTEN-induced kinase 1 (PINK1) and E3 ubiquitin ligase Parkin were significantly diminished by DCA, whereas induction of mitophagy by CCCP prevented DCA-induced inflammatory response and restored the pyroptosis. Collectively, our data showed that DCA-induced pyroptosis involves the inhibition of PINK1-mediated mitophagy and the activation of the NLRP3 inflammasome. These findings provide insight into the association of DCA with mitophagy, pyroptosis, and inflammation in NASH.

Upregulated NLRP3 inflammasome activation is attenuated by anthocyanins in patients with nonalcoholic fatty liver disease: A case-control and an intervention study.

OBJECTIVES: Despite the recent attention focused on the roles of the NLRP3 inflammasome in the pathogenesis of metabolic and inflammatory diseases, little is known about the activation status of NLRP3 inflammasome in patients with nonalcoholic fatty liver disease (NAFLD). The present study aimed to investigate whether inflammasomes activation is upregulated in patients with NAFLD and the upregulation can be attenuated by anthocyanins, which are polyphenols with known anti-inflammatory activities. METHODS: This study included a case-control study and a randomized controlled intervention trial. In the first part, NAFLD patients and healthy controls were recruited from a cohort of railroad workers. In the second part, NAFLD patients were randomly assigned to receive either capsules of anthocyanins (320 mg daily) or placebo for 12 weeks. A series of genes and factors associated with activation of NLRP3 inflammasome in subjects' plasma and peripheral blood mononuclear cells (PBMCs) were analyzed. RESULTS: Compared with healthy controls, the mRNA levels of NLRP3 inflammasome components (NLRP3, caspase-1, interleukin (IL)-1ß, and IL-18) were significantly upregulated in the PBMCs of NAFLD patients. Consistently, plasma levels of mature IL-1ß and IL-18 in NAFLD patients were significantly higher than in controls. After anthocyanin administration, both mRNA expression of NLRP3 inflammasome components (caspase-1, IL-1ß, and IL-18) in PBMCs and plasma levels of IL-1ß and IL-18 decreased dramatically in NAFLD patients compared with controls. CONCLUSIONS: This study has demonstrated that the activation of NLRP3 inflammasome is highly increased in NAFLD patients, but it can be markedly suppressed by anthocyanins, which provides a rationale for the development of anti-inflammatory therapies in NAFLD.