The acidic pathway of bile acid synthesis: Not just an alternative pathway☆

Organobromine compounds in aquatic environments: Embryotoxicity linked to lipophilicity and molecular structure

Organobromine compounds, prevalent in marine environments due to both anthropogenic activities and natural processes, have been shown to exhibit significant toxicity toward aquatic organisms. This study investigates the embryotoxicity and teratogenic effects of six bromophenol compounds using zebrafish (Danio rerio) embryos as a model. The compounds exhibited varying degrees of toxicity, with BP-6 and BP-5 showing the lowest LC50 values. The study identified distinct embryonic malformations, including venous sinus edema, pericardial cysts, and craniofacial malformations. A correlation was observed between the toxicity of the bromophenols and their lipophilicity, with higher lipophilicity compounds demonstrating greater toxicity. Mechanistic insights into the toxicity of bromophenols were further explored through transcriptomic analysis, which identified significant effects on retinol metabolism, modulation of myocardial contraction via Ca²⁺/Na⁺ ion flux, stimulation of nonspecific immune responses, and suppression of primary bile acid synthesis. BP-2 exposure significantly altered calcium signaling and bile acid biosynthesis, indicating a potential mechanism for its enhanced toxicity. These findings underscore the need for further investigation into the environmental and health impacts of bromophenols, particularly as they accumulate in marine ecosystems and the food chain.

Metabolome-wide association identifies ferredoxin-1 (FDX1) as a determinant of cholesterol metabolism and cardiovascular risk in Asian populations

The burden of cardiovascular disease is rising in the Asia-Pacific region, in contrast to falling cardiovascular disease mortality rates in Europe and North America. Here we perform quantification of 883 metabolites by untargeted mass spectroscopy in 8,124 Asian adults and investigate their relationships with carotid intima media thickness, a marker of atherosclerosis. Plasma concentrations of 3beta-hydroxy-5-cholestenoate (3BH5C), a cholesterol metabolite, were inversely associated with carotid intima media thickness, and Mendelian randomization studies supported a causal relationship between 3BH5C and coronary artery disease. The observed effect size was 5- to 6-fold higher in Asians than Europeans. Colocalization analyses indicated the presence of a shared causal variant between 3BH5C plasma levels and messenger RNA and protein expression of ferredoxin-1 (FDX1), a protein that is essential for sterol and bile acid synthesis. We validated FDX1 as a regulator of 3BH5C synthesis in hepatocytes and macrophages and demonstrated its role in cholesterol efflux in macrophages and aortic smooth muscle cells, using knockout and overexpression models.

AKR1D1 suppresses liver cancer progression by promoting bile acid metabolism-mediated NK cell cytotoxicity

Bile acid metabolism and antitumor immunity are both disrupted during liver cancer progression. However, the complex regulatory relationship between them remains largely unclear. Here, we find that loss of aldo-keto reductase 1D1 (AKR1D1) promotes the accumulation of isolithocholic acid (iso-LCA) through gut microbiome dysregulation, thereby impairing the cytotoxic function of natural killer (NK) cells and leading to the accelerated development of hepatocellular carcinoma (HCC). Mechanistically, AKR1D1 deficiency leads to an increased proportion of Bacteroidetes ovatus (B. ovatus), which breaks down chenodeoxycholic acid (CDCA) into iso-LCA. Moreover, accumulated iso-LCA impairs the antitumor activity of hepatic NK cells in a phosphorylated-CREB1 (p-CREB1)-dependent manner. The potassium-sparing diuretic spironolactone treatment significantly enhances the inhibitory effect of anti-PD1 antibody on HCC progression by targeting iso-LCA-mediated tumor immune escape. Taken together, our results uncover a previously unappreciated link between AKR1D1 and HCC and suggest that targeting iso-LCA produced by B. ovatus might be a promising strategy to activate NK cell cytotoxicity to treat HCC.

Longitudinal characterization of plasma and fecal bile acids in dairy heifers from birth to first calving in response to transition milk feeding

This study aimed to characterize plasma bile acid changes from birth to first calving and evaluate the effects of early transition milk (TM) feeding versus milk replacer (MR) during key stages. Fecal bile acids in TM-fed calves were also analyzed, offering insights into bile acid metabolism. Thirty female Holstein calves were fed TM or MR for the first 5 d, followed by 12 L/d MR. From d 14, calves were fed MR and starter with gradual weaning between wk 8 and 14. Blood samples were collected at 7 time points: 30 min and 12 h after birth, preweaning (wk 2, 6), weaning (wk 14), 8 mo, 13 mo, 3 wk before calving, at calving, and 3 wk after calving. Fecal samples were collected from a subset of TM-fed calves (n = 10) at birth, wk 6, wk 14, 8 mo, and calving. Samples were analyzed for bile acids using the Biocrates MxP Quant 500 kit. Cholic acid (CA) in plasma showed significant time-treatment interactions, with higher levels in TM-fed calves at weaning. Taurine- and glycine-conjugated bile acids had no treatment or time-treatment interactions, but all plasma bile acids showed significant time effects. Principal component analysis revealed that bile acid profiles at birth and after colostrum intake were tightly clustered. Plasma bile acid profiles showed greater dispersion during milk feeding and weaning, with tighter clustering observed postweaning, particularly at 13 mo, and in the transition period. Significant effects were observed for CA, deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA), with CA showing a notable interaction and being higher in TM-fed calves at weaning than in MR-fed calves. Bile acid levels increased toward weaning, peaked at wk 14, and decreased after weaning. Glycine-conjugated bile acids changed over time, with glycocholic acid (GCA) and glycodeoxycholic acid (GDCA) peaking at weaning, and glycochenodeoxycholic acid (GCDCA) being elevated before weaning, decreasing thereafter, and increasing again at calving. Taurine-conjugated bile acids also showed temporal changes, peaking at wk 6. The shifts in bile acid composition from birth to postcalving, with taurolithocholic acid (TLCA), GDCA, and taurocholic acid (TCA) initially dominating, CA increasing at weaning, and GDCA and DCA dominating at calving, with CA increasing again postcalving. During the transition to calving, CA decreased whereas glycine-conjugated bile acids increased relative to taurine-conjugated bile acids in plasma, irrespective of treatment. Fecal bile acid profiles in TM-fed calves clustered distinctly at birth, evolving through pre- to postweaning and calving, with increasing profile overlap over time. Most fecal bile acids, except DCA and CA, were abundant at birth but declined over time. Both DCA and CA increased postweaning, mirroring plasma trends. From wk 6 to calving, DCA was the dominant bile acid, accounting for the highest percentage of total bile acids excreted in feces. Spearman's correlation analysis was performed to assess the relationship between plasma and fecal bile acids in TN-fed calves. A significant positive correlation was observed only for GCDCA (Spearman's rank correlation coefficient [rho] = 0.35), whereas all other bile acids were not correlated. These results illustrate the complex dynamics of bile acid profiles during calf development.

Natural bioactive compounds reprogram bile acid metabolism in MAFLD: Multi-target mechanisms and therapeutic implications

Metabolic-associated fatty liver disease (MAFLD) has become an increasingly prevalent liver disorder worldwide, being closely associated with obesity, metabolic syndrome, and insulin resistance. Bile acids (BAs), beyond their traditional role in lipid digestion, play a pivotal part in regulating lipid and glucose metabolism as well as inflammatory responses. Recent investigations have recognized BAs as key factors in the onset and progression of MAFLD, mainly via their interactions with nuclear receptors such as the farnesoid X receptor (FXR) and the G protein-coupled bile acid receptor (TGR5). Additionally, active compounds derived from traditional Chinese medicine (TCM) have shown promising potential in the treatment of MAFLD. This study systematically reviews and analyzes the molecular mechanisms and recent progress in the application of TCM active ingredients for MAFLD treatment, with a focus on their regulation of BAs. These active ingredients, including saponins, flavonoids, polysaccharides, and sterols, exert therapeutic effects through diverse mechanisms, such as modulating BA synthesis and mediating receptor-signaling pathways, and are expected to restore metabolic homeostasis.

Acalabrutinib alleviates metabolic dysfunction-associated steatotic liver disease by regulating bile acid metabolism

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a global epidemic of chronic liver disease currently lacking effective treatment. Evaluating the therapeutic effects of existing drugs on MASLD is a time and cost-effective strategy. Bruton's tyrosine kinase (BTK) is an inflammatory signaling molecule playing an important role in the progression of MASLD. Aclabrutinib, a BTK inhibitor approved for treating mantle-cell lymphoma and chronic lymphocytic leukemia, has not been investigated for its potential to treat MASLD. This study examined the therapeutic effects and mechanisms of aclabrutinib on MASLD using a high-fat diet-induced mouse model. Results demonstrated significant alleviation of pathological parameters associated with MASLD upon administration of aclabrutinib. TSE PhenoMaster results revealed that aclabrutinib increased energy expenditure in mice. Furthermore, aclabrutinib upregulated the expression of genes associated with thermogenesis and lipolysis in adipose tissues. Additionally, it inhibited the transcription of genes related to lipid absorption in the small intestine and liver, while increasing the expression of hormone-sensitive lipase, hepatic nuclear factor 4 alpha and fibroblast growth factor 21 in the liver. Further analysis indicated that aclabrutinib promoted the alternative pathway of bile acid synthesis while restoring gut microbiota homeostasis. The altered bile acid profiles upregulated G protein-coupled bile acid receptor 1 expression in adipose tissues as well as vitamin D receptor expression in liver and small intestine. Our findings suggest that by regulating bile acid metabolism and gut microbiota, aclabrutinib may promote thermogenesis and lipolysis, thereby alleviating MASLD. This study provides novel insights into clinical applications targeting BTK for treating MASLD.

Discovery of a novel regulator, 3β-sulfate-5-cholestenoic acid, of lipid metabolism and inflammation

Mitochondrial oxysterols, cholestenoic acid (CA), 25-hydroxycholesterol (25HC), and 27-hydroxycholesterol (27HC), are potent regulators involved in many important biological events. This study aimed to investigate the metabolic pathways of these oxysterols and their roles between hepatocytes and macrophages. LC-MS/MS analysis showed a novel regulatory molecule, 3β-sulfate-5-cholestenoic acid (3SCA), following the addition of CA in media culturing hepatocytes. Further study showed that 3SCA could also be derived from 27HC. In comparison, 25HC was converted to 25HC3S, which mostly remained in the cells and nuclei. The functional study showed that 3SCA significantly downregulated the expression of genes involved in lipid metabolism in hepatocytes and suppressed gene expression of proinflammatory cytokines induced by lipopolysaccharide in human macrophages. Based on the results, we conclude that 3SCA acts as a secretory regulator for the regulation of lipid metabolism and inflammatory responses in hepatocytes and macrophages. These findings shed light on understanding the unique metabolic pathways of these oxysterols and their possible roles in liver tissues.NEW & NOTEWORTHY This study identifies a novel oxysterol metabolite, 3β-sulfate-5-cholestenoic acid (3SCA), secreted by hepatocytes, which regulates lipid metabolism and inflammatory responses in hepatocytes and macrophages. These findings reveal previously unknown metabolic pathways of mitochondrial oxysterols and their roles in the progression and recovery of metabolic dysfunction-associated steatotic liver disease (MASLD), offering novel insights into potential therapeutic targets.

Liver specific transgenic expression of CYP7B1 attenuates early western diet-induced MASLD progression

Effect of liver specific oxysterol 7α-hydroxylase (CYP7B1) overexpression on the Western diet (WD)-induced metabolic dysfunction-associated steatotic liver disease (MASLD) progression was studied in mice. Among various hepatic genes impacted during MASLD development, CYP7B1 is consistently suppressed in multiple MASLD mouse models and in human MASLD cohorts. CYP7B1 enzyme suppression leads to accumulations of bioactive oxysterols such as (25R)26-hydroxycholesterol (26HC) and 25-hydroxycholesterol (25HC). We challenged liver specific CYP7B1 transgenic (CYP7B1hep.tg) overexpressing mice with ad libitum WD feeding. Unlike their WT counterparts, WD-fed CYP7B1hep.tg mice developed no significant hepatotoxicity as evidenced by liver histology, lipid quantifications, and serum biomarker analyses. Hepatic 26HC and 25HC levels were maintained at the basal levels. The comparative gene expression/lipidomic analyses between WT and CYP7B1hep.tg mice revealed that chronically accumulated 26HC initiates LXR/PPAR-mediated hepatic fatty acid uptake and lipogenesis which surpasses fatty acid metabolism and export; compromising metabolic functions. In addition, major pathways related to oxidative stress, inflammation, and immune system including retinol metabolism, arachidonic acid metabolism, and linoleic acid metabolism were significantly impacted in the WD-fed WT mice. All pathways were unaltered in CYP7B1hep.tg mice liver. Furthermore, the nucleus of WT mouse liver but not of CYP7B1hep.tg mouse liver accumulated 26HC and 25HC in response to WD. These data strongly suggested that these two oxysterols are specifically important in nuclear transcriptional regulation for the described cytotoxic pathways. In conclusion, this study represents a "proof-of-concept" that maintaining normal mitochondrial cholesterol metabolism with hepatic CYP7B1 expression prevents oxysterol-driven liver toxicity; thus attenuating MASLD progression.

Liver-specific actions of GH and IGF1 that protect against MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD; also known as nonalcoholic fatty liver disease) is a chronic condition associated with metabolic syndrome, a group of conditions that includes obesity, insulin resistance, hyperlipidaemia and cardiovascular disease. Primary growth hormone (GH) deficiency is associated with MASLD, and the decline in circulating levels of GH with weight gain might contribute to the development of MASLD. Raising endogenous GH secretion or administering GH replacement therapy in the context of MASLD enhances insulin-like growth factor 1 (IGF1) production and reduces steatosis and the severity of liver injury. GH and IGF1 indirectly control MASLD progression by regulating systemic metabolic function. Evidence supports the proposal that GH and IGF1 also have a direct role in regulating liver metabolism and health. This Review focuses on how GH acts on the hepatocyte in a sex-dependent manner to limit lipid accumulation, reduce stress, and promote survival and regeneration. In addition, we discuss how GH and IGF1 might regulate non-parenchymal cells of the liver to control inflammation and fibrosis, which have a major effect on hepatocyte survival and regeneration. Development of a better understanding of how GH and IGF1 coordinate the functions of specific, individual liver cell types might provide insight into the aetiology of MASLD initiation and progression and suggest novel approaches for the treatment of MASLD.

Host metabolism balances microbial regulation of bile acid signalling

Metabolites derived from the intestinal microbiota, including bile acids (BA), extensively modulate vertebrate physiology, including development1, metabolism2-4, immune responses5-7 and cognitive function8. However, to what extent host responses balance the physiological effects of microbiota-derived metabolites remains unclear9,10. Here, using untargeted metabolomics of mouse tissues, we identified a family of BA-methylcysteamine (BA-MCY) conjugates that are abundant in the intestine and dependent on vanin 1 (VNN1), a pantetheinase highly expressed in intestinal tissues. This host-dependent MCY conjugation inverts BA function in the hepatobiliary system. Whereas microbiota-derived free BAs function as agonists of the farnesoid X receptor (FXR) and negatively regulate BA production, BA-MCYs act as potent antagonists of FXR and promote expression of BA biosynthesis genes in vivo. Supplementation with stable-isotope-labelled BA-MCY increased BA production in an FXR-dependent manner, and BA-MCY supplementation in a mouse model of hypercholesteraemia decreased lipid accumulation in the liver, consistent with BA-MCYs acting as intestinal FXR antagonists. The levels of BA-MCY were reduced in microbiota-deficient mice and restored by transplantation of human faecal microbiota. Dietary intervention with inulin fibre further increased levels of both free BAs and BA-MCY levels, indicating that BA-MCY production by the host is regulated by levels of microbiota-derived free BAs. We further show that diverse BA-MCYs are also present in human serum. Together, our results indicate that BA-MCY conjugation by the host balances host-dependent and microbiota-dependent metabolic pathways that regulate FXR-dependent physiology.

Effect of Vitamin D Supplementation on Lipid Profile in Overweight or Obese Women: A Meta-analysis and Systematic Review of Randomized Controlled Trials

CONTEXT

Previous studies have explored the relationship between vitamin D and lipid profile in individuals with obesity or overweight women, but the results have been inconsistent.

OBJECTIVE

This meta-analysis and systematic review of randomized controlled trials (RCTs) was conducted to assess the effect of vitamin D on lipid profile in women who are overweight or obese.

DATA SOURCES

A meticulous search strategy was used across the Scopus, PubMed/Medline, Web of Science, and Embase databases up to June 2024.

DATA EXTRACTION

RCT studies administering vitamin D to overweight or obese women were extracted. A random-effects model was applied to compute the weighted mean difference (WMD) and 95% CIs of the intervention on each variable.

DATA ANALYSES

Thirteen eligible publications with 16 arms focused on low-density-lipoprotein cholesterol (LDL-C), 16 arms on high-density-lipoprotein cholesterol (HDL-C), 18 arms on total cholesterol (TC), and 18 arms on triglycerides (TG) were included in the final quantitative analysis. Vitamin D supplementation resulted in significant reductions in TG (WMD: -6.13 mg/dL; 95% CI: -8.99 to -3.28; P = .000) and TC (WMD: -4.45 mg/dL; 95% CI: -7.06 to -1.83; P = .001), as well as a significant increase in HDL-C concentrations (WMD: 1.54 mg/dL; 95% CI: 0.57 to 2.52; P = .002). Stratified analysis indicated a greater reduction in TG levels in studies with a mean baseline TG concentration ≥150 mg/dL (WMD: -23.58 mg/dL) and when vitamin D was administered for ≤26 weeks (WMD: -11.44 mg/dL).

CONCLUSION

According to our findings, vitamin D has a significant effect on hypertriglyceridemia in individuals who are overweight or obese. However, vitamin D has no significant effect on LDL-C concentrations in this population.

Exploring bile acid transporters as key players in cancer development and treatment: Evidence from preclinical and clinical studies

Bile acid transporters (BATs) are integral membrane proteins belonging to various families, such as solute carriers, organic anion transporters, and ATP-binding cassette families. These transporters play a crucial role in bile acid transportation within the portal and systemic circulations, with expression observed in tissues, including the liver, kidney, and small intestine. Bile acids serve as signaling molecules facilitating the absorption and reabsorption of fats and lipids. Dysregulation of bile acid concentration has been implicated in tumorigenesis, yet the role of BATs in this process remains underexplored. Emerging evidence suggests that BATs may modulate various stages of cancer progression, including initiation, development, proliferation, metastasis, and tumor microenvironment regulation. Targeting BATs using siRNAs, miRNAs, and small compound inhibitors in preclinical models and their polymorphisms are well-studied for transporters like BSEP, MDR1, MRP2, OATP1A2, etc., and have shed light on their involvement in tumorigenesis, particularly in cancers such as those affecting the liver and gastrointestinal tract. While BATs' role in diseases like Alagille syndrome, biliary atresia, and cirrhosis have been extensively studied, their implications in cancer warrant further investigation. This review highlights the expression and function of BATs in cancer development and emphasizes the potential of targeting these transporters as a novel therapeutic strategy for various malignancies.

Si-Ni-San alleviates intestinal and liver damage in ulcerative colitis mice by regulating cholesterol metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Si-Ni-San (SNS), a traditional Chinese medicinal formula derived from Treatise on Febrile Diseases, is considered effective in the treatment of inflammatory bowel diseases based upon thousands of years of clinical practice. However, the bioactive ingredients and underlying mechanisms are still unclear and need further investigation.

AIM OF THE STUDY

This study aimed to evaluate the effect, explore the bioactive ingredients and the underlying mechanisms of SNS in ameliorating ulcerative colitis (UC) and associated liver injury in dextran sodium sulphate (DSS)-induced mouse colitis models.

MATERIALS AND METHODS

The effect of SNS (1.5, 3, 6 g/kg) on 3% DSS-induced acute murine colitis was evaluated by disease activity index (DAI), colon length, inflammatory cytokines, hematoxylin-eosin (H&E) staining, tight junction proteins expression, ALT, AST, and oxidative stress indicators. HPLC-ESI-IT/TOF MS was used to analyze the chemical components of SNS and the main xenobiotics in the colon of UC mice after oral administration of SNS. Network pharmacological study was then conducted based on the main xenobiotics. Flow cytometry and immunohistochemistry techniques were used to demonstrate the inhibitory effect of SNS on Th17 cells differentiation and the amelioration of Th17/Treg cell imbalance. LC-MS/MS, Real-time quantitative polymerase chain reaction (RT-qPCR), and western blotting techniques were performed to investigate the oxysterol-Liver X receptor (LXRs) signaling activity in colon. Targeted bile acids metabolomics was conducted to reveal the change of the two major pathways of bile acid synthesis in the liver, and the expression of key metabolic enzymes of bile acids synthesis was characterized by RT-qPCR and western blotting techniques.

RESULTS

SNS (1.5, 3, 6 g/kg) decreased the DAI scores, protected intestinal mucosa barrier, suppressed the production of pro-inflammatory cytokines, improved hepatic and splenic enlargement and alleviated liver injury in a dose-dependent manner. A total of 22 components were identified in the colon of SNS (6 g/kg) treated colitis mice, and the top 10 components ranked by relative content were regarded as the potential effective chemical components of SNS, and used to conduct network pharmacology research. The efficacy of SNS was mediated by a reduction of Th17 cell differentiation, restoration of Th17/Treg cell homeostasis in the colon and spleen, and the experimental results were consistent with our hypothesis and the biological mechanism predicted by network pharmacology. Mechanistically, SNS regulated the concentration of 25-OHC and 27-OHC by up-regulated CH25H, CYP27A1 protein expression in colon, thus affected the expression and activity of LXR, ultimately impacted Th17 differentiation and Th17/Treg balance. It was also found that SNS repressed the increase of hepatic cholesterol and reversed the shift of BA synthesis to the acidic pathway in UC mice, which decreased the proportion of non-12-OH BAs in total bile acids (TBAs) and further ameliorated colitis and concomitant liver injury.

CONCLUSIONS

This study set the stage for considering SNS as a multi-organ benefited anti-colitis prescription based on the significant effect of ameliorating intestinal and liver damage, and revealed that derivatives of cholesterol, namely oxysterols and bile acids, were closely involved in the mechanism of SNS anti-colitis effect.

Polystyrene microplastic exposure modulates gut microbiota and gut-liver axis in gilthead seabream (Sparus aurata)

Microplastics (MPs) are a threat of growing concern for living organisms as they exist in all ecosystems. The bidirectional communication between the gut, its microbiota, and the liver, has been conceptualized as gut-liver axis and may be influenced by environmental factors. MPs can cause intestinal and hepatic injuries, but there is still limited research exploring their impact on gut-liver axis. The aim of this study was to assess the effects of MP ingestion on gut-liver axis balance in gilthead seabream (Sparus aurata) fed with a diet enriched with polystyrene (PS)-MPs (0, 25, or 250 mg/kg b.w./day) for 21 days. PS-MPs affected the composition of gut microbiota, enhancing the evenness of gut microbial species. We also observed the impoverishment of core microbiota, suggesting reduced stability and permanence of microbiota members. Furthermore, PS-MPs reduced predominant bacteria in the gut of gilthead seabreams, increasing low-abundance species, including potential harmful taxa. On the other hand, PS-MPs increased the gene expression of immune and inflammatory mediators (i.e., TLR2, TLR5, and COX-2) in the liver. PS-MP exposure also increased serum triglycerides and bile acids (BAs) without modifying cholesterol. Moreover, the hepatic BA metabolism was impacted by PS-MPs which increased the expression of genes involved in primary BA kinetic (i.e., CYP27A1 and LXRa), which in turn can modulate intestinal microbial community. Indeed, PICRUSt2 mapping of BA-related functions predicted the increase of factors involved in BA metabolism. Specifically, K01442 (choloylglycine hydrolase) and K00076 (7α-hydroxysteroid dehydrogenase) were augmented by PS-MPs, suggesting a possible adaptation or co-evolution of gut microbiota to the modified hepatic BA metabolism. Thus, the obtained results showed that ingested PS-MPs impact the gut microbiota architecture and functions, the hepatic innate immunity, and the BA metabolism, suggesting the involvement of the gut-liver axis in MP-induced toxicity.

Sphingosine kinase 2 (SphK2) depletion alters redox metabolism and enhances inflammation in a diet-induced MASH mouse model

BACKGROUND

Sphingosine-1 phosphate (S1P) is a bioactive lipid molecule that modulates inflammation and hepatic lipid metabolism in MASLD, which affects 1 in 3 people and increases the risk of liver fibrosis and hepatic cancer. S1P can be generated by 2 isoforms of sphingosine kinase (SphK). SphK1 is well-studied in metabolic diseases. In contrast, SphK2 function is not well characterized. Both sphingolipid and redox metabolism dysregulation contribute to MASLD pathologic progression. While SphK2 localizes to both the nucleus and mitochondria, its specific role in early MASH is not well defined.

METHODS

This study examined SphK2 depletion effects on hepatic redox metabolism, mitochondrial function, and inflammation in a 16-week western diet plus sugar water (WDSW)-induced mouse model of early MASH.

RESULTS

WDSW-SphK2-/- mice exhibit increased hepatic lipid accumulation and hepatic redox dysregulation. In addition, mitochondria-localized cholesterol and S1P precursors were increased. We traced SphK2-/--mediated mitochondrial electron transport chain impairment to respiratory complex-IV and found that decreased mitochondrial redox metabolism coincided with increased oxidase gene expression and oxylipin production. Consistent with this relationship, we observed pronounced increases in hepatic inflammatory gene expression, prostaglandin accumulation, and innate immune homing in WDSW-SphK2-/- mice compared to WDSW-wild-type mice.

CONCLUSIONS

These studies suggest SphK2-derived S1P maintains hepatic redox metabolism and describe the potential consequences of SphK2 depletion on proinflammatory gene expression, lipid mediator production, and immune infiltration in MASH progression.

Efficacy and safety of switching therapy from chenodeoxycholic acid to cholic acid in Japanese patients with bile acid synthesis disorders

Objectives

This study aimed to assess the safety and efficacy of cholic acid (CA) treatment over 74 weeks in Japanese patients with inherited enzymatic bile acid synthesis disorders (BASD).

Methods

This phase 3, open-label, single-arm study enrolled four Japanese patients diagnosed with BASD, including two with 3β-hydroxy-Δ 5-C27-steroid dehydrogenase/isomerase (HSD3B7) deficiency and two with Δ 4-3-oxosteroid 5β-reductase (SRD5B1) deficiency. The patients had received chenodeoxycholic acid (CDCA) treatment but were switched to CA treatment. Treatment efficacy was evaluated by measuring serum and urinary bile acid levels and liver-related biomarkers, and adverse events were evaluated to monitor safety.

Results

The daily CA doses ranged from 3.8 to 13.7 mg/kg/day. Laboratory values of liver-related biomarkers were maintained within normal ranges or improved. Bile acid analysis revealed CDCA replacement with CA in serum within the initial few weeks of CA treatment. Urinary concentrations of toxic bile acid metabolites associated with liver damage were higher than serum. Adverse effects from CA treatment were mild to moderate, and no treatment discontinuations were due to adverse events.

Conclusions

CA treatment over 74 weeks resulted in favorable efficacy and safety outcomes in Japanese patients with BASD, consistent with previous studies. These results support the utility of CA as a therapeutic option for Japanese patients with BASD.

Integrative analysis of non12-hydroxylated bile acid revealed the suppressed molecular map of alternative pathway in nonalcoholic steatohepatitis mice

Bile acids (BAs) are significantly altered in the liver and serum of patients with nonalcoholic steatohepatitis (NASH). However, the underlying mechanisms of these changes, particularly BA alternative pathways (BAP) responsible for non12-OH BAs, remain unclear. RNA-seq data were initially analyzed to reveal the changes of gene expression in NASH patients. Targeted metabolomics were conducted on plasma from NASH mice induced by high-fat or western diet with CCl4 for 10-24 weeks. Liver tissues were examined using proteomics, RT-qPCR, and western blotting. An integrated approach was then employed to analyze protein interactions and network correlations. Analysis of RNA-seq data revealed the inhibition of CYP7B1 in NASH patients, indicating the dysregulation of BAP. In NASH mouse models, dysregulation of BA circulation was observed by increased plasma total BA (TBA) levels and decreased liver TBA, with liver swelling and histopathological changes. Targeted metabolomics revealed suppressed levels of non12-OH BAs, which inversely correlated with increased liver injury markers. The reduced mRNA and protein expression of Fxr and upregulation of Lxr signaling in livers suggested the suppressed BAP was modulated by Fxr-Lxr signaling. Moreover, BAP interactions predominantly implicated multiple metabolism disruptions, involving 7 hub proteins (Hk1, Acadsb, Pklr, Insr, Ldlr, Cyp27a1, and Cyp7b1), offering promising therapeutic targets for NASH. We presented the metabolic and proteomic map of BAP and its regulatory network in NASH progression. Therapeutic targeting of BAP or its co-regulatory proteins holds promise for NASH treatment and metabolic syndrome management.

Aerobic capacity and exercise mediate protection against hepatic steatosis via enhanced bile acid metabolism

High cardiorespiratory fitness and exercise show evidence of altering bile acid (BA) metabolism and are known to protect or treat diet-induced hepatic steatosis, respectively. Here, we tested the hypothesis that high intrinsic aerobic capacity and exercise both increase hepatic BA synthesis measured by the incorporation of 2H2O. We also leveraged mice with inducible liver-specific deletion of Cyp7a1 (LCyp7a1KO), which encodes the rate-limiting enzyme for BA synthesis, to test if exercise-induced BA synthesis is critical for exercise to reduce hepatic steatosis. The synthesis of hepatic BA, cholesterol, and de novo lipogenesis was measured in rats bred for either high (HCR) vs. low (LCR) aerobic capacity consuming acute and chronic high-fat diets. HCR rats had increased synthesis of cholesterol and certain BA species in the liver compared to LCR rats. We also found that chronic exercise with voluntary wheel running (VWR) (4 weeks) increased newly synthesized BAs of specific species in male C57BL/6J mice compared to sedentary mice. Loss of Cyp7a1 resulted in fewer new BAs and increased liver triglycerides compared to controls after a 10-week high-fat diet. Additionally, exercise via VWR for 4 weeks effectively reduced hepatic triglycerides in the high-fat diet-fed control male and female mice as expected; however, exercise in LCyp7a1KO mice did not lower liver triglycerides in either sex. These results show that aerobic capacity and exercise increase hepatic BA metabolism, which may be critical for combatting hepatic steatosis.

Bile Acid Signaling in Metabolic and Inflammatory Diseases and Drug Development

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites, and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, type-2 diabetes, and inflammatory bowel diseases. Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. SIGNIFICANCE STATEMENT: Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling holds promise for treating metabolic and inflammatory diseases.

CYP8B1 Catalyzes 12alpha-Hydroxylation of C27 Bile Acid: In Vitro Conversion of Dihydroxycoprostanic Acid into Trihydroxycoprostanic Acid

Sterol 12α-hydroxylase (CYP8B1) is the unique P450 enzyme with sterol 12-oxidation activity, playing an exclusive role in 12α-hydroxylating intermediates along the bile acid (BA) synthesis pathway. Despite the long history of BA metabolism studies, it is unclear whether CYP8B1 catalyzes 12α-hydroxylation of C27 BAs, the key intermediates shuttling between mitochondria and peroxisomes. This work provides robust in vitro evidence that both microsomal and recombinant CYP8B1 enzymes catalyze the 12α-hydroxylation of dihydroxycoprostanic acid (DHCA) into trihydroxycoprostanic acid (THCA). On the one hand, DHCA 12α-hydroxylation reactivity is conservatively detected in liver microsomes of both human and preclinical animals. The reactivity of human tissue fractions conforms well with the selectivity of CYP8B1 mRNA expression, while the contribution of P450 enzymes other than CYP8B1 is excluded by reaction phenotyping in commercial recombinant enzymes. On the other hand, we prepared functional recombinant human CYP8B1 proteins according to a recently published protocol. Titration of the purified CYP8B1 proteins with either C4 (7α-hydroxy-4-cholesten-3-one) or DHCA yields expected blue shifts of the heme Soret peak (type I binding). The recombinant CYP8B1 proteins efficiently catalyze 12α-hydroxylation of both DHCA and C4, with substrate concentration occupying half of the binding sites of 3.0 and 1.9 μM and kcat of 3.2 and 2.6 minutes-1, respectively. In summary, the confirmed role of CYP8B1 in 12α-hydroxylation of C27 BAs has furnished the forgotten passageway in the BA synthesis pathway. The present finding might have opened a new window to consider the biology of CYP8B1 in glucolipid metabolism and to evaluate CYP8B1 inhibition as a therapeutic approach of crucial interest for metabolic diseases. SIGNIFICANCE STATEMENT: The academic community has spent approximately 90 years interpreting the synthesis of bile acids. However, the 12α-hydroxylation of intermediates catalyzed by CYP8B1 is not completely mapped on the classic pathway, particularly for the C27 bile acids, the pivotal intermediates shuttling between mitochondria and peroxisomes. This work discloses the forgotten 12α-hydroxylation pathway from dihydroxycoprostanic acid into trihydroxycoprostanic acid. The present finding may facilitate evaluating CYP8B1 inhibition as a therapeutic approach of crucial interest for metabolic diseases.

Comparative analysis of bile acid composition and metabolism in the liver of Bufo gargarizans aquatic larvae and terrestrial adults

Bile acids are crucial for lipid metabolism and their composition and metabolism differ among species. However, there have been no data on the differences in the composition and metabolism of bile acids between aquatic larvae and terrestrial adults of amphibians. This study explored the differences in composition and metabolism of bile acid between Bufo gargarizans larvae and adults. The results demonstrated that adult liver had a lower total bile acid level and a higher conjugated/total bile acid ratio than larval liver. Meanwhile, histological analysis revealed that the larvae showed a larger cross-sectional area of bile canaliculi lumen compared with the adults. The transcriptomic analysis showed that B. gargarizans larvae synthesized bile acids through both the alternative and the 24-hydroxylase pathway, while adults only synthesized bile acids through the 24-hydroxylase pathway. Moreover, bile acid regulator-related genes FXR and RXRα were highly expressed in adult, whereas genes involved in bile acid synthesis (CYP27A1 and CYP46A1) were highly expressed in larvae. The present study will provide valuable insights into understanding metabolic disorders and exploring novel bile acid-based therapeutics.

The mitochondrial translocator protein (TSPO, 18 kDa): A key multifunctional molecule in liver diseases

Translocator protein (TSPO, 18 kDa), previously known as peripheral-type benzodiazepine receptor, is an evolutionarily conserved and tryptophan-rich 169-amino-acid protein located on the outer mitochondrial membrane. TSPO plays a crucial role in various fundamental physiological functions and cellular processes. Its expression is altered in pathological conditions, thus rendering TSPO a potential tool for diagnostic imaging and an appealing therapeutic target. The investigation of synthetic TSPO ligands as both agonists and antagonists has provided valuable insights into the regulatory mechanisms and functional properties of TSPO. Recently, accumulating evidence has highlighted the significance of TSPO in liver diseases. However, a comprehensive summary of TSPO function in the normal liver and diverse liver diseases is lacking. This review aims to provide an overview of recent advances in understanding TSPO function in both normal liver cells and various liver diseases, with a particular emphasis on its involvement in liver fibrosis and inflammation and addresses the existing knowledge gaps in the field that require further investigation.

Emerging Roles of Bile Acids and TGR5 in the Central Nervous System: Molecular Functions and Therapeutic Implications

Bile acids (BAs) are cholesterol derivatives synthesized in the liver and released into the digestive tract to facilitate lipid uptake during the digestion process. Most of these BAs are reabsorbed and recycled back to the liver. Some of these BAs progress to other tissues through the bloodstream. The presence of BAs in the central nervous system (CNS) has been related to their capacity to cross the blood-brain barrier (BBB) from the systemic circulation. However, the expression of enzymes and receptors involved in their synthesis and signaling, respectively, support the hypothesis that there is an endogenous source of BAs with a specific function in the CNS. Over the last decades, BAs have been tested as treatments for many CNS pathologies, with beneficial effects. Although they were initially reported as neuroprotective substances, they are also known to reduce inflammatory processes. Most of these effects have been related to the activation of the Takeda G protein-coupled receptor 5 (TGR5). This review addresses the new challenges that face BA research for neuroscience, focusing on their molecular functions. We discuss their endogenous and exogenous sources in the CNS, their signaling through the TGR5 receptor, and their mechanisms of action as potential therapeutics for neuropathologies.

The role of botanical triterpenoids and steroids in bile acid metabolism, transport, and signaling: Pharmacological and toxicological implications

Bile acids (BAs) are synthesized by the host liver from cholesterol and are delivered to the intestine, where they undergo further metabolism by gut microbes and circulate between the liver and intestines through various transporters. They serve to emulsify dietary lipids and act as signaling molecules, regulating the host's metabolism and immune homeostasis through specific receptors. Therefore, disruptions in BA metabolism, transport, and signaling are closely associated with cholestasis, metabolic disorders, autoimmune diseases, and others. Botanical triterpenoids and steroids share structural similarities with BAs, and they have been found to modulate BA metabolism, transport, and signaling, potentially exerting pharmacological or toxicological effects. Here, we have updated the research progress on BA, with a particular emphasis on new-found microbial BAs. Additionally, the latest advancements in targeting BA metabolism and signaling for disease treatment are highlighted. Subsequently, the roles of botanical triterpenoids in BA metabolism, transport, and signaling are examined, analyzing their potential pharmacological, toxicological, or drug interaction effects through these mechanisms. Finally, a research paradigm is proposed that utilizes the gut microbiota as a link to interpret the role of these important natural products in BA signaling.

Bile acid profiles and mRNA abundance of bile acid-related genes in adipose tissue of dairy cows with high versus normal body condition

Besides their lipid-digestive role, bile acids (BA) influence overall energy homeostasis, such as glucose and lipid metabolism. We hypothesized that BA along with their receptors, regulatory enzymes, and transporters are present in subcutaneous adipose tissue (scAT). In addition, we hypothesized that their mRNA abundance varies with the body condition of dairy cows around calving. Therefore, we analyzed BA in serum and scAT as well as the mRNA abundance of BA-related enzymes, transporters, and receptors in scAT during the transition period in cows with different body conditions around calving. In a previously established animal model, 38 German Holstein cows were divided into either a high (HBCS; n = 19) or normal BCS (NBCS; n = 19) group based on their BCS and back-fat thickness (BFT). Cows were fed different diets to achieve the targeted differences in BCS and BFT (NBCS: BCS <3.5, BFT <1.2 cm; HBCS: BCS >3.75, BFT >1.4 cm) until dry-off at 7 wk antepartum. During the dry period and subsequent lactation, both groups were fed the same diets according to their energy demands. Using a targeted metabolomics approach via liquid chromatography-electrospray ionization-MS /MS, BA were analyzed in serum and scAT at wk -7, 1, 3, and 12 relative to parturition. In serum, 15 BA were observed: cholic acid (CA), chenodeoxycholic acid (CDCA), glycocholic acid (GCA), taurocholic acid (TCA), glycochenodeoxycholic acid (GCDCA), taurochenodeoxycholic acid, deoxycholic acid (DCA), lithocholic acid, glycodeoxycholic acid (GDCA), glycolithocholic acid, taurodeoxycholic acid, taurolithocholic acid, β-muricholic acid, tauromuricholic acid (sum of α and β), and glycoursodeoxycholic acid, whereas in scAT 7 BA were detected: CA, GCA, TCA, GCDCA, taurochenodeoxycholic acid, GDCA, and taurodeoxycholic acid. In serum and scAT samples, the primary BA CA and its conjugate GCA were predominantly detected. Increasing serum concentrations of CA, CDCA, TCA, GCA, GCDCA, DCA, and β-muricholic acid with the onset of lactation might be related to the increasing DMI after parturition. Furthermore, serum concentrations of CA, CDCA, GCA, DCA, GCDCA, TCA, lithocholic acid, and GDCA were lower in HBCS cows compared with NBCS cows, concomitant with increased lipolysis in HBCS cows. The correlation between CA in serum and scAT may point to the transport of CA across cell membranes. Overall, the findings of the present study suggest a potential role of BA in lipid metabolism depending on the body condition of periparturient dairy cows.

Cholesterol-Lowering Effect of Polysaccharides from Cyclocarya paliurus In Vitro and in Hypercholesterolemia Mice

In this study, a new component of Cyclocarya paliurus polysaccharides (CPP20) was precipitated by the gradient ethanol method, and the protective effect of CPP20 on hypercholesterolemia mice was investigated. In vitro, CPP20 had the ability to bind bile salts and inhibit cholesterol micelle solubility, and it could effectively clear free radicals (DPPH•, •OH, and ABTS+). In vivo, CPP20 effectively alleviated hypercholesterolemia and liver damage in mice. After CPP20 intervention, the activity of antioxidant enzymes (SOD, CAT, and GSH-Px) and the level of HDL-C in liver and serum were increased, and the activity of aminotransferase (ALT and AST) and the level of MDA, TC, TG, LDL-C, and TBA were decreased. Molecular experiments showed that CPP20 reduced cholesterol by regulating the mRNA expression of antioxidation-related genes (SOD, GSH-Px, and CAT) and genes related to the cholesterol metabolism (CYP7A1, CYP27A1, SREBP-2, HMGCR, and FXR) in liver. In addition, CPP20 alleviated intestinal microbiota disturbances in mice with hypercholesterolemia and increased levels of SCFAs. Therefore, CPP20 alleviates hypercholesterolemia by alleviating oxidative damage, maintaining cholesterol homeostasis, and regulating gut microbiota.

Taurine-conjugated bile acids and their link to hepatic S1PR2 play a significant role in hepatitis C-related liver disease

BACKGROUND

Bile acids mediate gut-liver cross-talk through bile acid receptors. Serum, hepatic, and microbial bile acid metabolism was evaluated in HCV-compensated chronic liver disease.

METHODS

Patients underwent liver biopsy; portal and peripheral blood were obtained before (HCVi), and 6 months after sustained virologic response (SVR), splenic blood was obtained only after SVR. The fecal microbiome and liver transcriptome were evaluated using RNA-Seq. Twenty-four bile acids were measured in serum, summed as free, taurine-conjugated bile acids (Tau-BAs), and glycine-conjugated bile acids.

RESULTS

Compared to SVR, HCVi showed elevated conjugated bile acids, predominantly Tau-BA, compounded in HCVi cirrhosis. In the liver, transcription of bile acids uptake, synthesis, and conjugation was decreased with increased hepatic spillover into systemic circulation in HCVi. There was no difference in the transcription of microbial bile acid metabolizing genes in HCVi. Despite an overall decrease, Tau-BA remained elevated in SVR cirrhosis, mainly in splenic circulation. Only conjugated bile acids, predominantly Tau-BA, correlated with serum proinflammatory markers and hepatic proinflammatory pathways, including NLRP3 and NFKB. Among hepatic bile acid receptors, disease-associated conjugated bile acids showed the strongest association with hepatic spingosine-1-phosphate receptor 2 (S1PR2).

CONCLUSIONS

Enhanced expression of hepatic S1PR2 in HCVi and HCVi-cirrhosis and strong associations of S1PR2 with Tau-BAs suggest pathological relevance of Tau-BA-hepatic S1PR2 signaling in chronic liver disease. These findings have therapeutic implications in chronic liver diseases.

Bile acid profiles and mRNA expression of bile acid-related genes in the liver of dairy cows with high versus normal body condition

Bile acids (BA) play a crucial role not only in lipid digestion but also in the regulation of overall energy homeostasis, including glucose and lipid metabolism. The aim of this study was to investigate BA profiles and mRNA expression of BA-related genes in the liver of high versus normal body condition in dairy cows. We hypothesized that body condition and the transition from gestation to lactation affect hepatic BA concentrations as well as the mRNA abundance of BA-related receptors, regulatory enzymes, and transporters. Therefore, we analyzed BA in the liver as well as the mRNA abundance of BA-related synthesizing enzymes, transporters, and receptors in the liver during the transition period in cows with different body conditions around calving. In a previously established animal model, 38 German Holstein cows were divided into groups with high body condition score (BCS) (HBCS; n = 19) or normal BCS (NBCS; n = 19) based on BCS and backfat thickness (BFT). Cows were fed diets aimed at achieving the targeted differences in BCS and BFT (NBCS: BCS <3.5, BFT <1.2 cm; HBCS: BCS >3.75, BFT >1.4 cm) until they were dried off at wk 7 before parturition. Both groups were fed identical diets during the dry period and subsequent lactation. Liver biopsies were taken at wk -7, 1, 3, and 12 relative to parturition. For BA measurement, a targeted metabolomics approach with LC-ESI-MS/MS was used to analyze BA in the liver. The mRNA abundance of targeted genes related to BA-synthesizing enzymes, transporters, and receptors in the liver was analyzed using microfluidic quantitative PCR. In total, we could detect 14 BA in the liver: 6 primary and 8 secondary BA, with glycocholic acid (GCA) being the most abundant one. The increase of glycine-conjugated BA after parturition, in parallel to increasing serum glycine concentrations may originate from an enhanced mobilization of muscle protein to meet the high nutritional requirements in early lactating cows. Higher DMI in NBCS cows compared with HBCS cows was associated with higher liver BA concentrations such as GCA, deoxycholic acid (DCA), and cholic acid (CA). The mRNA abundance of BA-related enzymes measured herein suggests the dominance of the alternative signaling pathway in the liver of HBCS cows. Overall, BA profiles and BA metabolism in the liver depend on both, the body condition and lactation-induced effects in periparturient dairy cows.

LC-MS/MS profiling of colon oxysterols and cholesterol precursors in mouse model of ulcerative colitis

Oxysterols and cholesterol precursors are being increasingly investigated in humans and laboratory animals as markers for various diseases in addition to their important functions. However, the quantitative analysis of these bioactive molecules is obstructed by high structural similarity, poor ionization efficiency and low abundance. The current assay methods are still cumbersome to be of practical use, and their applicability in different bio-samples needs to be evaluated and optimized as necessary. In the present work, chromatographic separation conditions were carefully studied to achieve baseline separation of difficult-to-isolate compound pairs. On the other hand, an efficient sample purification method was established for colon tissue samples with good recoveries of sterols, demonstrating negligible autoxidation of cholesterol into oxysterols. The developed UPLC-APCI-MS/MS method was thoroughly validated and applied to measure oxysterols and cholesterol precursors in colon tissue of dextran sulfate sodium (DSS)-induced mouse colitis models, and it is expected to be successfully applied to the quantitative determination of such components in other tissue samples.

Bile acid signaling in the regulation of whole body metabolic and immunological homeostasis

Bile acids (BAs) play a crucial role in nutrient absorption and act as key regulators of lipid and glucose metabolism and immune homeostasis. Through the enterohepatic circulation, BAs are synthesized, metabolized, and reabsorbed, with a portion entering the vascular circulation and distributing systemically. This allows BAs to interact with receptors in all major organs, leading to organ-organ interactions that regulate both local and global metabolic processes, as well as the immune system. This review focuses on the whole-body effects of BA-mediated metabolic and immunological regulation, including in the brain, heart, liver, intestine, eyes, skin, adipose tissue, and muscle. Targeting BA synthesis and receptor signaling is a promising strategy for the development of novel therapies for various diseases throughout the body.

Larsucosterol: endogenous epigenetic regulator for treating chronic and acute liver diseases

Larsucosterol, a potent endogenous epigenetic regulator, has been reported to play a significant role in lipid metabolism, inflammatory responses, and cell survival. The administration of larsucosterol has demonstrated a reduction in lipid accumulation within hepatocytes and the attenuation of inflammatory responses induced by lipopolysaccharide (LPS) and TNFα in macrophages, alleviating LPS- and acetaminophen (ATMP)-induced multiple organ injury, and decreasing mortalities in animal models. Results from phase 1 and 2 clinical trials have shown that larsucosterol has potential as a biomedicine for the treatment of acute and chronic liver diseases. Recent evidence suggests that larsucosterol is a promising candidate for treating alcohol-associated hepatitis with positive results from a phase 2a clinical trial, and for metabolic dysfunction-associated steatohepatitis (MASH) from a phase 1b clinical trial. In this review, we present a culmination of our recent research efforts spanning two decades. We summarize the discovery, physiological and pharmacological mechanisms, and clinical applications of larsucosterol. Furthermore, we elucidate the pathophysiological pathways of metabolic dysfunction-associated steatotic liver diseases (MASLD), metabolic dysfunction-associated steatohepatitis (MASH), and acute liver injuries. A central focus of the review is the exploration of the therapeutic potential of larsucosterol in treating life-threatening conditions, including acetaminophen overdose, endotoxin shock, MASLD, MASH, hepatectomy, and alcoholic hepatitis.

Another renaissance for bile acid gastrointestinal microbiology

The field of bile acid microbiology in the gastrointestinal tract is going through a current rebirth after a peak of activity in the late 1970s and early 1980s. This renewed activity is a result of many factors, including the discovery near the turn of the century that bile acids are potent signalling molecules and technological advances in next-generation sequencing, computation, culturomics, gnotobiology, and metabolomics. We describe the current state of the field with particular emphasis on questions that have remained unanswered for many decades in both bile acid synthesis by the host and metabolism by the gut microbiota. Current knowledge of established enzymatic pathways, including bile salt hydrolase, hydroxysteroid dehydrogenases involved in the oxidation and epimerization of bile acid hydroxy groups, the Hylemon-Bjӧrkhem pathway of bile acid C7-dehydroxylation, and the formation of secondary allo-bile acids, is described. We cover aspects of bile acid conjugation and esterification as well as evidence for bile acid C3-dehydroxylation and C12-dehydroxylation that are less well understood but potentially critical for our understanding of bile acid metabolism in the human gut. The physiological consequences of bile acid metabolism for human health, important caveats and cautionary notes on experimental design and interpretation of data reflecting bile acid metabolism are also explored.

CYP7B1 as a Biomarker for Prostate Cancer Risk and Progression: Metabolic and Oncogenic Signatures (Diagnostic Immunohistochemistry Analysis by Tissue Microarray in Prostate Cancer Patients-Diamond Study)

We aimed to analyze the association between CYP7B1 and prostate cancer, along with its association with proteins involved in cancer and metabolic processes. A retrospective analysis was performed on 390 patients with prostate cancer (PC) or benign prostatic hyperplasia (BPH). We investigated the interactions between CYP7B1 expression and proteins associated with PC and metabolic processes, followed by an analysis of the risk of biochemical recurrence based on CYP7B1 expression. Of the 139 patients with elevated CYP7B1 expression, 92.8% had prostate cancer. Overall, no increased risk of biochemical recurrence was associated with CYP7B1 expression. However, in a non-diabetic subgroup analysis, higher CYP7B1 expression indicated a higher risk of biochemical recurrence, with an HR of 1.78 (CI: 1.0-3.2, p = 0.05). PC is associated with elevated CYP7B1 expression. In a subgroup analysis of non-diabetic patients, elevated CYP7B1 expression was associated with an increased risk of biochemical recurrence, suggesting increased cancer aggressiveness.

Exposure to environmental toxicants is associated with gut microbiome dysbiosis, insulin resistance and obesity

Environmental toxicants (ETs) are associated with adverse health outcomes. Here we hypothesized that exposures to ETs are linked with obesity and insulin resistance partly through a dysbiotic gut microbiota and changes in the serum levels of secondary bile acids (BAs). Serum BAs, per- and polyfluoroalkyl substances (PFAS) and additional twenty-seven ETs were measured by mass spectrometry in 264 Danes (121 men and 143 women, aged 56.6 ± 7.3 years, BMI 29.7 ± 6.0 kg/m2) using a combination of targeted and suspect screening approaches. Bacterial species were identified based on whole-genome shotgun sequencing (WGS) of DNA extracted from stool samples. Personalized genome-scale metabolic models (GEMs) of gut microbial communities were developed to elucidate regulation of BA pathways. Subsequently, we compared findings from the human study with metabolic implications of exposure to perfluorooctanoic acid (PFOA) in PPARα-humanized mice. Serum levels of twelve ETs were associated with obesity and insulin resistance. High chemical exposure was associated with increased abundance of several bacterial species (spp.) of genus (Anaerotruncus, Alistipes, Bacteroides, Bifidobacterium, Clostridium, Dorea, Eubacterium, Escherichia, Prevotella, Ruminococcus, Roseburia, Subdoligranulum, and Veillonella), particularly in men. Conversely, females in the higher exposure group, showed a decrease abundance of Prevotella copri. High concentrations of ETs were correlated with increased levels of secondary BAs including lithocholic acid (LCA), and decreased levels of ursodeoxycholic acid (UDCA). In silico causal inference analyses suggested that microbiome-derived secondary BAs may act as mediators between ETs and obesity or insulin resistance. Furthermore, these findings were substantiated by the outcome of the murine exposure study. Our combined epidemiological and mechanistic studies suggest that multiple ETs may play a role in the etiology of obesity and insulin resistance. These effects may arise from disruptions in the microbial biosynthesis of secondary BAs.

Polymethoxyflavones in citrus extract has a beneficial effect on hypercholesterolemia rats by promoting liver cholesterol metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Hyperlipidemia is characterized by the disorder of lipid metabolism accompanied by oxidative stress damage, and low-grade inflammation, with the pathway of cholesterol and bile acid metabolic are an important triggering mechanism. Polymethoxyflavones (PMFs) are the active constituents of Aurantii Fructus Immaturus, which have many biological effects, including anti-inflammatory, antioxidant activities, anti-obesity, suppressing adipogenesis in adipocytes, and ameliorate type 2 diabetes, with potential roles for regulation of lipid metabolism. However, its associated mechanisms on hyperlipidemia remain unclear.

AIM OF THE STUDY

This study aims to identify the anti-hypercholesterolemia effects and mechanisms of PMFs in a hypercholesterolemia model triggered by high-fat compounds in an excessive alcohol diet (HFD).

MATERIALS AND METHODS

A hypercholesterolemia rat model was induced by HFD, and PMFs was intragastric administered at 125 and 250 mg/kg daily for 16 weeks. The effects of PMFs on hypercholesterolemia were assessed using serum lipids, inflammatory cytokines, and oxidative stress levels. Hematoxylin & eosin (H&E) and Oil Red O staining were performed to evaluate histopathological changes in the rat liver. The levels of total cholesterol (TC) and total bile acid (TBA) in the liver and feces were determined to evaluate lipid metabolism. RAW264.7 and BRL cells loaded with NBD-cholesterol were used to simulate the reverse cholesterol transport (RCT) process in vitro. The signaling pathway of cholesterol and bile acid metabolic was evaluated by Western Blotting (WB) and qRT-PCR.

RESULTS

Lipid metabolism disorders, oxidative stress injury, and low-grade inflammation in model rats were ameliorated by PMFs administration. Numerous vacuoles and lipid droplets in hepatocytes were markedly reduced. In vitro experiments results revealed decreased NBD-cholesterol levels in RAW264.7 cells and increased NBD-cholesterol levels in BRL cells following PMFs intervention. PMFs upregulated the expression of proteins associated with the RCT pathway, such as LXRα, ABCA1, LDLR, and SR-BI, thereby promoting TC entry into the liver. Meanwhile, the expression of proteins associated with cholesterol metabolism and efflux pathways such as CYP7A1, CYP27A1, CYP7B1, ABCG5/8, ABCB1, and BSEP were regulated, thereby promoting cholesterol metabolism. Moreover, PMFs treatment regulated the expression of proteins related to the pathway of enterohepatic circulation of bile acids, such as ASBT, OSTα, NTCP, FXR, FGF15, and FGFR4, thereby maintaining lipid metabolism.

CONCLUSIONS

PMFs might ameliorate hypercholesterolemia by promoting the entry of cholesterol into the liver through the RCT pathway, followed by excretion via metabolism pathways of cholesterol and bile acid. These findings provide a promising therapeutic potential for PMFs to treat hypercholesterolemia.

Astragalus polysaccharide attenuates nonalcoholic fatty liver disease through THDCA in high-fat diet-fed mice

ETHNOPHARMACOLOGICAL RELEVANCE

Astragalus polysaccharide (APS) extracted from Astragalus membranaceus (Fisch.) Bunge was proven to be effective in preventing high-fat diet (HFD) induced nonalcoholic fatty liver disease (NAFLD). However, the exact mechanisms were not completely elucidated.

AIM OF THE STUDY

The aim was to reveal the mechanisms of APS on preventing NAFLD from the aspects of regulating bile acids (BAs) homeostasis.

MATERIALS AND METHODS

Serum and liver BAs in HFD fed mice with or without APS intervention were quantified with an ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) system. The effect of APS on hepatic proteins involved in BAs synthesis were analyzed with Western blot. Finally, the effect of identified taurohyodeoxycholic acid (THDCA) that was significantly increased by APS on hepatic triglyceride (TG) accumulation was explored in vivo and in vitro.

RESULTS

APS regulated serum and liver BA profiles in HFD fed mice, especially increased serum THDCA. The levels of hepatic cholesterol 7a-hydroxylase (CYP7A1) and sterol 12a-hydroxylase (CYP8B1) which catalyzed the classical BAs synthesis pathway were significantly decreased by APS, while oxysterol 7a-hydroxylase (CYP7B1) which catalyzed the alternative BAs synthesis pathway was significantly increased by APS. THDCA reduced HFD-induced hepatic lipid accumulation and improved glucose homeostasis in mice, and decreased TG level in palmitic acid/oleic acid treated alpha mouse liver 12 (AML-12) cells. THDCA significantly downregulated the protein level of cluster of differentiation 36 (CD36) involved in fatty acid transport into the liver. Importantly, THDCA showed similar effect with APS in upregulating hepatic CYP7B1 and downregulating CYP7A1.

CONCLUSION

This study revealed the protective effect of APS on NAFLD was associated with the regulation on BA profiles, and proved the potential anti-NAFLD effect of THDCA, highlighting the involvement of BA metabolism in efficacy of herb-derived polysaccharides on metabolism.

Cholestenoic acid as endogenous epigenetic regulator decreases hepatocyte lipid accumulation in vitro and in vivo

Cholestenoic acid (CA) has been reported as an important biomarker of many severe diseases, but its physiological and pathological roles remain unclear. This study aimed to investigate the potential role of CA in hepatic lipid homeostasis. Enzyme kinetic studies revealed that CA specifically activates DNA methyltransferases 1 (DNMT1) at low concentration with EC50 = 1.99 × 10-6 M and inhibits the activity at higher concentration with IC50 = 9.13 × 10-6 M, and specifically inhibits DNMT3a, and DNMT3b activities with IC50= 8.41 × 10-6 M and IC50= 4.89 × 10-6 M, respectively. In a human hepatocyte in vitro model of high glucose (HG)-induced lipid accumulation, CA significantly increased demethylation of 5mCpG in the promoter regions of over 7,000 genes, particularly those involved in master signaling pathways such as calcium-AMPK and 0.0027 at 6 h. RNA sequencing analysis showed that the downregulated genes are affected by CA encoding key enzymes, such as PCSK9, MVK, and HMGCR, which are involved in cholesterol metabolism and steroid biosynthesis pathways. In addition, untargeted lipidomic analysis showed that CA significantly reduced neutral lipid levels by 60% in the cells cultured in high-glucose media. Administration of CA in mouse metabolic dysfunction-associated steatotic liver disease (MASLD) models significantly decreases lipid accumulation, suppresses the gene expression involved in lipid biosynthesis in liver tissues, and alleviates liver function. This study shows that CA as an endogenous epigenetic regulator decreases lipid accumulation via epigenetic regulation. The results indicate that CA can be considered a potential therapeutic target for the treatment of metabolic disorders.NEW & NOTEWORTHY To our knowledge, this study is the first to identify the mitochondrial monohydroxy bile acid cholestenoic acid (CA) as an endogenous epigenetic regulator that regulates lipid metabolism through epigenome modification in human hepatocytes. The methods used in this study are all big data analysis, and the results of each part show the global regulation of CA on human hepatocytes rather than narrow point effects.

Gut microbiota-mediated ursodeoxycholic acids regulate the inflammation of microglia through TGR5 signaling after MCAO

Ischemic stroke has been demonstrated to cause an imbalance of gut microbiota. However, the change in gut microbiota-mediated bile acids (BAs) metabolites remains unclear. Here, we observed a decrease in gut microbiota-mediated BAs, especially ursodeoxycholic acid (UDCA), in the serum of stroke patients as well as in the intestine, serum and brain of stroke mice. Restoration of UDCA could decrease the area of infarction and improve the neurological function and cognitive function in mice in association with inhibition of NLRP3-related pro-inflammatory cytokines through TGR5/PKA pathway. Furthermore, knocking out TGR5 and inhibiting PKA activity reduce the protective effect of UDCA. Taken together, our results suggest that microbiota-mediated UDCA plays an important role in alleviating inflammatory responses and might be a promising therapeutic target in ischemic stroke.

Potential role of bile acids in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is one of the most common acute gastrointestinal diseases in preterm infants. Recent studies have found that NEC is not only caused by changes in the intestinal environment but also by the failure of multiple systems and organs, including the liver. The accumulation of bile acids (BAs) in the ileum and the disorder of ileal BA transporters are related to the ileum injury of NEC. Inflammatory factors such as tumor necrosis factor (TNF)-α and interleukin (IL)-18 secreted by NEC also play an important role in regulating intrahepatic BA transporters. As an important link connecting the liver and intestinal circulation, the bile acid metabolic pathway plays an important role in the regulation of intestinal microbiota, cell proliferation, and barrier protection. In this review, we focus on how bile acids explore the dynamic changes of bile acid metabolism in necrotizing enterocolitis and the potential therapeutic value of targeting the bile acid signaling pathways.

Physical exercise plays a role in rebalancing the bile acids of enterohepatic axis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is considered as one of the most common diseases of lipid metabolism disorders, which is closely related to bile acids disorders and gut microbiota disorders. Bile acids are synthesized from cholesterol in the liver, and processed by gut microbiota in intestinal tract, and participate in metabolic regulation through the enterohepatic circulation. Bile acids not only promote the consumption and absorption of intestinal fat but also play an important role in biological metabolic signaling network, affecting fat metabolism and glucose metabolism. Studies have demonstrated that exercise plays an important role in regulating the composition and function of bile acid pool in enterohepatic axis, which maintains the homeostasis of the enterohepatic circulation and the health of the host gut microbiota. Exercise has been recommended by several health guidelines as the first-line intervention for patients with NAFLD. Can exercise alter bile acids through the microbiota in the enterohepatic axis? If so, regulating bile acids through exercise may be a promising treatment strategy for NAFLD. However, the specific mechanisms underlying this potential connection are largely unknown. Therefore, in this review, we tried to review the relationship among NAFLD, physical exercise, bile acids, and gut microbiota through the existing data and literature, highlighting the role of physical exercise in rebalancing bile acid and microbial dysbiosis.

Research progress on the relationship between bile acid metabolism and type 2 diabetes mellitus

Bile acids, which are steroid molecules originating from cholesterol and synthesized in the liver, play a pivotal role in regulating glucose metabolism and maintaining energy balance. Upon release into the intestine alongside bile, they activate various nuclear and membrane receptors, influencing crucial processes. These bile acids have emerged as significant contributors to managing type 2 diabetes mellitus, a complex clinical syndrome primarily driven by insulin resistance. Bile acids substantially lower blood glucose levels through multiple pathways: BA-FXR-SHP, BA-FXR-FGFR15/19, BA-TGR5-GLP-1, and BA-TGR5-cAMP. They also impact blood glucose regulation by influencing intestinal flora, endoplasmic reticulum stress, and bitter taste receptors. Collectively, these regulatory mechanisms enhance insulin sensitivity, stimulate insulin secretion, and boost energy expenditure. This review aims to comprehensively explore the interplay between bile acid metabolism and T2DM, focusing on primary regulatory pathways. By examining the latest advancements in our understanding of these interactions, we aim to illuminate potential therapeutic strategies and identify areas for future research. Additionally, this review critically assesses current research limitations to contribute to the effective management of T2DM.

The Role of Gut Microbiota-Derived Lithocholic Acid, Deoxycholic Acid and Their Derivatives on the Function and Differentiation of Immune Cells

A wide variety and large number of bacterial species live in the gut, forming the gut microbiota. Gut microbiota not only coexist harmoniously with their hosts, but they also induce significant effects on each other. The composition of the gut microbiota can be changed due to environmental factors such as diet and antibiotic intake. In contrast, alterations in the composition of the gut microbiota have been reported in a variety of diseases, including intestinal, allergic, and autoimmune diseases and cancer. The gut microbiota metabolize exogenous dietary components ingested from outside the body to produce short-chain fatty acids (SCFAs) and amino acid metabolites. Unlike SCFAs and amino acid metabolites, the source of bile acids (BAs) produced by the gut microbiota is endogenous BAs from the liver. The gut microbiota metabolize BAs to generate secondary bile acids, such as lithocholic acid (LCA), deoxycholic acid (DCA), and their derivatives, which have recently been shown to play important roles in immune cells. This review focuses on current knowledge of the role of LCA, DCA, and their derivatives on immune cells.

Comparison of fresh and browning lotus roots (Nelumbo nucifera Gaertn.) on modulating cholesterol metabolism via decreasing hepatic cholesterol deposition and increasing fecal bile acid excretion

Lotus root (LR) is prone to browning after harvest due to the oxidation of phenolic compounds by polyphenol oxidase (PPO). This study compared the effects of LR extract and BLR extract on cholesterol metabolism in high-fat diet (HFD) mice. Our findings highlighted the innovative potentiality of BLR extract in effectively regulating cholesterol metabolism via inhibiting the intestinal FXR-FGF15 signaling pathway and boosting probiotics in gut microbiota, offering valuable insights for hypercholesterolemia and metabolic disorders. In detail, catechin was the main phenolic compound in LR, while after browning, theaflavin was the main oxidation product of phenolic compounds in BLR. Both the intake of LR extract and BLR extract regulated the disorder of cholesterol metabolism induced by HFD. In particular, BLR extract intake exhibited more robust effects on increasing the BAs contents synthesized in the liver and excreted in feces compared with LR extract intake. Furthermore, the consumption of BLR extract was more effective than that of LR extract in reducing the ileal protein expressions of FXR and FGF15 and shifting BAs biosynthesis from the classical pathway to the alternative pathway. Moreover, LR extract and BLR extract had distinct effects on the gut microbiota in HFD-fed mice: BLR extract significantly elevated probiotics Akkermansia abundance, while LR extract increased Lactobacillus abundance. Therefore, both LR extract and BLR extract improved the cholesterol deposition effectively and BLR extract even showed a stronger effect on regulating key gene and protein expressions of cholesterol metabolism.

Pregnane X receptor as a therapeutic target for cholestatic liver injury

Cholestatic liver injury (CLI) is caused by toxic bile acids (BAs) accumulation in the liver and can lead to inflammation and liver fibrosis. The mechanisms underlying CLI development remain unclear, and this disease has no effective cure. However, regulating BA synthesis and homeostasis represents a promising therapeutic strategy for CLI treatment. Pregnane X receptor (PXR) plays an essential role in the metabolism of endobiotics and xenobiotics via the transcription of metabolic enzymes and transporters, which can ultimately modulate BA homeostasis and exert anticholestatic effects. Furthermore, recent studies have demonstrated that PXR exhibits antifibrotic and anti-inflammatory properties, providing novel insights into treating CLI. Meanwhile, several drugs have been identified as PXR agonists that improve CLI. Nevertheless, the precise role of PXR in CLI still needs to be fully understood. This review summarizes how PXR improves CLI by ameliorating cholestasis, inhibiting inflammation, and reducing fibrosis and discusses the progress of promising PXR agonists for treating CLI.

Roux-en-Y gastric bypass induces hepatic transcriptomic signatures and plasma metabolite changes indicative of improved cholesterol homeostasis

BACKGROUND & AIMS

Roux-en-Y gastric bypass (RYGB), the most effective surgical procedure for weight loss, decreases obesity and ameliorates comorbidities, such as non-alcoholic fatty liver (NAFLD) and cardiovascular (CVD) diseases. Cholesterol is a major CVD risk factor and modulator of NAFLD development, and the liver tightly controls its metabolism. How RYGB surgery modulates systemic and hepatic cholesterol metabolism is still unclear.

METHODS

We studied the hepatic transcriptome of 26 patients with obesity but not diabetes before and 1 year after undergoing RYGB. In parallel, we measured quantitative changes in plasma cholesterol metabolites and bile acids (BAs).

RESULTS

RYGB surgery improved systemic cholesterol metabolism and increased plasma total and primary BA levels. Transcriptomic analysis revealed specific alterations in the liver after RYGB, with the downregulation of a module of genes implicated in inflammation and the upregulation of three modules, one associated with BA metabolism. A dedicated analysis of hepatic genes related to cholesterol homeostasis pointed towards increased biliary cholesterol elimination after RYGB, associated with enhancement of the alternate, but not the classical, BA synthesis pathway. In parallel, alterations in the expression of genes involved in cholesterol uptake and intracellular trafficking indicate improved hepatic free cholesterol handling. Finally, RYGB decreased plasma markers of cholesterol synthesis, which correlated with an improvement in liver disease status after surgery.

CONCLUSIONS

Our results identify specific regulatory effects of RYGB on inflammation and cholesterol metabolism. RYGB alters the hepatic transcriptome signature, likely improving liver cholesterol homeostasis. These gene regulatory effects are reflected by systemic post-surgery changes of cholesterol-related metabolites, corroborating the beneficial effects of RYGB on both hepatic and systemic cholesterol homeostasis.

IMPACT AND IMPLICATIONS

Roux-en-Y gastric bypass (RYGB) is a widely used bariatric surgery procedure with proven efficacy in body weight management, combatting cardiovascular disease (CVD) and non-alcoholic fatty liver disease (NAFLD). RYGB exerts many beneficial metabolic effects, by lowering plasma cholesterol and improving atherogenic dyslipidemia. Using a cohort of patients undergoing RYGB, studied before and 1 year after surgery, we analyzed how RYGB modulates hepatic and systemic cholesterol and bile acid metabolism. The results of our study provide important insights on the regulation of cholesterol homeostasis after RYGB and open avenues that could guide future monitoring and treatment strategies targeting CVD and NAFLD in obesity.

Dried blood spot-based newborn screening for bile acid synthesis disorders, Zellweger spectrum disorder, and Niemann-Pick type C1 by detection of bile acid metabolites

OBJECTIVE

To examine whether it is possible to screen for bile acid synthesis disorders (BASDs) including peroxisome biogenesis disorder 1a (PBD1A) and Niemann-Pick type C1 (NPC1) at the time of newborn mass screening by measuring the intermediary metabolites of bile acid (BA) synthesis.

METHODS

Patients with 3β-hydroxy-ΔSuchy et al. (2021)5-C27-steroid dehydrogenase/isomerase (HSD3B7) deficiency (n = 2), 3-oxo-ΔPandak and Kakiyama (n.d.)4-steroid 5β-reductase (SRD5B1) deficiency (n = 1), oxysterol 7α-hydroxylase (CYP7B1) deficiency (n = 1), PBD1A (n = 1), and NPC1 (n = 2) with available dried blood spot (DBS) samples collected in the neonatal period were included. DBSs from healthy neonates at 4 days of age (n = 1055) were also collected for the control. Disease specific BAs were measured by newly optimized liquid chromatography-tandem mass spectrometry with short run cycle (5-min/run). The results were validated by comparing with those obtained by the conventional condition with longer run cycle (76-min/run).

RESULTS

In healthy specimens, taurocholic acid and cholic acid were the two major BAs which constituted approximately 80% in the measured BAs. The disease marker BAs presented <10%. In BASDs, the following BAs were determined for the disease specific markers: Glyco/tauro 3β,7α,12α-trihydroxy-5-cholenoic acid 3-sulfate for HSD3B7 deficiency (>70%); glyco/tauro 7α,12α-dihydroxy-3-oxo-4-cholenoic acid for SRD5B1 deficiency (54%); tauro 3β-hydroxy-5-cholenoic acid 3-sulfate for CYP7B1 deficiency (94%); 3α,7α,12α-trihydroxy-5β-cholestanoic acid for PBD1A (78%); and tauro 3β,7β-dihydroxy-5-cholenoic acid 3-sulfate for NPC1 (26%). *The % in the parenthesis indicates the portion found in the patient's specimen.

CONCLUSIONS

Early postnatal screening for BASDs, PBD1A and NPC1 is feasible with the described DBS-based method by measuring disease specific BAs. The present method is a quick and affordable test for screening for these inherited diseases.

Mass spectrometry reveals that oxysterols are secreted from non-alcoholic fatty liver disease induced organoids

Oxysterols are potential biomarkers for liver metabolism that are altered under disease conditions such as non-alcoholic fatty liver disease (NAFLD). We here apply sterolomics to organoids used for disease modeling of NAFLD. Using liquid chromatography-mass spectrometry with on-line sample clean-up and enrichment, we establish that liver organoids produce and secrete oxysterols. We find elevated levels of 26-hydroxycholesterol, an LXR agonist and the first oxysterol in the acidic bile acid synthesis, in medium from steatotic liver organoids compared to untreated organoids. Other upregulated sterols in medium from steatotic liver organoids are dihydroxycholesterols, such as 7α,26-dihydroxycholesterol, and 7α,25-dihydroxycholesterol. Through 26-hydroxycholesterol exposure to human stem cell-derived hepatic stellate cells, we observe a trend of expressional downregulation of the pro-inflammatory cytokine CCL2, suggesting a protective role of 26-hydroxycholesterol during early-phased NAFLD disease development. Our findings support the possibility of oxysterols serving as NAFLD indicators, demonstrating the usefulness of combining organoids and mass spectrometry for disease modeling and biomarker studies.

Altered bile acid metabolism in skin tissues in response to ionizing radiation: deoxycholic acid (DCA) as a novel treatment for radiogenic skin injury

OBJECTIVE

Radiogenic skin injury (RSI) is a common complication during cancer radiotherapy or accidental exposure to radiation. The aim of this study is to investigate the metabolism of bile acids (BAs) and their derivatives during RSI.

METHODS

Rat skin tissues were irradiated by an X-ray linear accelerator. The quantification of BAs and their derivatives were performed by liquid chromatography-mass spectrometry (LC-MS)-based quantitative analysis. Key enzymes in BA biosynthesis were analyzed from single-cell RNA sequencing (scRNA-Seq) data of RSI in the human patient and animal models. The in vivo radioprotective effect of deoxycholic acid (DCA) was detected in irradiated SD rats.

RESULTS

Twelve BA metabolites showed significant differences during the progression of RSI. Among them, the levels of cholic acid (CA), DCA, muricholic acid (MCA), chenodeoxycholic acid (CDCA), glycocholic acid (GCA), glycohyodeoxycholic acid (GHCA), 12-ketolithocholic acid (12-ketoLCA) and ursodeoxycholic acid (UDCA) were significantly elevated in irradiated skin, whereas lithocholic acid (LCA), tauro-β-muricholic acid (Tβ-MCA) and taurocholic acid (TCA) were significantly decreased. Additionally, the results of scRNA-Seq indicated that genes involved in 7a-hydroxylation process, the first step in BA synthesis, showed pronounced alterations in skin fibroblasts or keratinocytes. The alternative pathway of BA synthesis is more actively altered than the classical pathway after ionizing radiation. In the model of rat radiogenic skin damage, DCA promoted wound healing and attenuated epidermal hyperplasia.

CONCLUSIONS

Ionizing radiation modulates the metabolism of BAs. DCA is a prospective therapeutic agent for the treatment of RSI.

Dimethyl Sulfoxide Inhibits Bile Acid Synthesis in Healthy Mice but Does Not Protect Mice from Bile-Acid-Induced Liver Damage

Bile acids serve a vital function in lipid digestion and absorption; however, their accumulation can precipitate liver damage. In our study, we probed the effects of dimethyl sulfoxide (DMSO) on bile acid synthesis and the ensuing liver damage in mice induced by bile acids. Our findings indicate that DMSO efficaciously curbs bile acid synthesis by inhibiting key enzymes involved in the biosynthetic pathway, both in cultured primary hepatocytes and in vivo. Contrarily, we observed that DMSO treatment did not confer protection against bile-acid-induced liver damage in two distinct mouse models: one induced by a 0.1% DDC diet, leading to bile duct obstruction, and another induced by a CDA-HFD, resulting in non-alcoholic steatohepatitis (NASH). Histopathological and biochemical analyses unveiled a comparable extent of liver injury and fibrosis levels in DMSO-treated mice, characterized by similar levels of increase in Col1a1 and Acta2 expression and equivalent total liver collagen levels. These results suggest that, while DMSO can promptly inhibit bile acid synthesis in healthy mice, compensatory mechanisms might rapidly override this effect, negating any protective impact against bile-acid-induced liver damage in mice. Through these findings, our study underscores the need to reconsider treating DMSO as a mere inert solvent and prompts further exploration to identify more effective therapeutic strategies for the prevention and treatment of bile-acid-associated liver diseases.