Clostridioides difficile is a major nosocomial pathogen, causing significant morbidity and mortality worldwide. Antibiotic usage, a major risk factor for Clostridioides difficile infection (CDI), disrupts the gut microbiota, allowing C. difficile to proliferate and cause infection, and can often lead to recurrent CDI (rCDI). Fecal microbiota transplantation (FMT) and live biotherapeutic products (LBPs) have emerged as effective treatments for rCDI and aim to restore colonization resistance provided by a healthy gut microbiota. However, much is still unknown about the mechanisms mediating their success. Bile acids, extensively modified by gut microbes, affect C. difficile\'s germination, growth, and toxin production while also shaping the gut microbiota and influencing host immune responses. Additionally, microbial interactions, such as nutrient competition and cross-feeding, contribute to colonization resistance against C. difficile and may contribute to the success of microbiota-focused therapeutics. Bile acids as well as other microbial mediated interactions could have implications for other diseases being treated with microbiota-focused therapeutics. This review focuses on the intricate interplay between bile acid modifications, microbial ecology, and host responses with a focus on C. difficile, hoping to shed light on how to move forward with the development of new microbiota mediated therapeutic strategies to combat rCDI and other intestinal diseases.

During pregnancy, the maternal body undergoes a series of adaptative physiological changes, leading to a slight increase in serum bile acid (BA) levels. Although the fetal liver can synthesize BAs since the first trimester through the alternative pathway, the BA metabolic system is immature in the fetus. Compared to adults, the fetus has a distinct composition of BA pool and limited expression of BA synthesis enzymes and transporters. Besides, the \"enterohepatic circulation\" of BAs is absent in fetus. Thus, fetal BAs need to be transported to the mother through the placenta for further metabolism and excretion, and maternal BAs can also be transported to the fetus. That is what we call the \"fetal-placental-maternal BA circulation\". Various BA transporters and nuclear receptors are essential for maintaining the balance of this BA circulation to ensure normal fetal development. However, prenatal adverse environments can alter fetal BA metabolism, resulting in intrauterine developmental abnormalities and susceptibility to a variety of adult chronic diseases. This review summarizes the current understanding of the fetal-placental-maternal BA circulation and discusses the effects of prenatal adverse environments on this particular BA circulation, aiming to provide a theoretical basis for exploring early prevention and treatment strategies for BA metabolism-associated adverse pregnancy outcomes and long-term impairments.

The ISS rodent habitat has provided crucial insights into the impact of spaceflight on mammals, inducing symptoms characteristic of liver disease, insulin resistance, osteopenia, and myopathy. Although these physiological responses can involve the microbiome on Earth, host-microbiota interactions during spaceflight are still being elucidated. We explore murine gut microbiota and host gene expression in the colon and liver after 29 and 56 days of spaceflight using multiomics. Metagenomics revealed significant changes in 44 microbiome species, including relative reductions in bile acid and butyrate metabolising bacteria like Extibacter muris and Dysosmobacter welbionis. Functional prediction indicate over-representation of fatty acid and bile acid metabolism, extracellular matrix interactions, and antibiotic resistance genes. Host gene expression described corresponding changes to bile acid and energy metabolism, and immune suppression. These changes imply that interactions at the host-gut microbiome interface contribute to spaceflight pathology and that these interactions might critically influence human health and long-duration spaceflight feasibility.

Gut microbiota dysbiosis is involved in cholestatic liver diseases. However, the mechanisms remain to be elucidated. The purpose of this study was to examine the effects and mechanisms of Lactobacillus acidophilus (L. acidophilus) on cholestatic liver injury in both animals and humans. Bile duct ligation (BDL) was performed to mimic cholestatic liver injury in mice and serum liver function was tested. Gut microbiota were analyzed by 16S rRNA sequencing. Fecal bacteria transplantation (FMT) was used to evaluate the role of gut microbiota in cholestasis. Bile acids (BAs) profiles were analyzed by targeted metabolomics. Effects of L. acidophilus in cholestatic patients were evaluated by a randomized controlled clinical trial (NO: ChiCTR2200063330). BDL induced different severity of liver injury, which was associated with gut microbiota. 16S rRNA sequencing of feces confirmed the gut flora differences between groups, of which L. acidophilus was the most distinguished genus. Administration of L. acidophilus after BDL significantly attenuated hepatic injury in mice, decreased liver total BAs and increased fecal total BAs. Furthermore, after L. acidophilus treatment, inhibition of hepatic Cholesterol 7α-hydroxylase (CYP7α1), restored ileum Fibroblast growth factor 15 (FGF15) and Small heterodimer partner (SHP) accounted for BAs synthesis decrease, whereas enhanced BAs excretion was attributed to the increase of unconjugated BAs by enriched bile salt hydrolase (BSH) enzymes in feces. Similarly, in cholestasis patients, supplementation of L. acidophilus promoted the recovery of liver function and negatively correlated with liver function indicators, possibly in relationship with the changes in BAs profiles and gut microbiota composition. L. acidophilus treatment ameliorates cholestatic liver injury through inhibited hepatic BAs synthesis and enhances fecal BAs excretion.

5β-Dihydrosteroids are produced by the reduction of Δ4-3-ketosteroids catalyzed by steroid 5β-reductase (AKR1D1). By analogy with steroid 5α-reductase, genetic deficiency exists in AKR1D1 which leads to errors in newborn metabolism and in this case to bile acid deficiency. Also, like the 5α-dihydrosteroids (e.g., 5α-dihydrotestosterone), the 5β-dihydrosteroids produced by AKR1D1 are not inactive but regulate ligand access to nuclear receptors, can act as ligands for nuclear and membrane-bound receptors, and regulate ion-channel opening. For example, 5β-reduction of cortisol and cortisone yields the corresponding 5β-dihydroglucocorticoids which are inactive on the glucocorticoid receptor (GR) and provides an additional mechanism of pre-receptor regulation of ligands for the GR in liver cells. By contrast, 5β-pregnanes can act as neuroactive steroids at the GABAA and NMDA receptors and at low-voltage-activated calcium channels, act as tocolytic agents, have analgesic activity and act as ligands for PXR, while bile acids act as ligands for FXR and thereby control cholesterol homeostasis. The 5β-androstanes also have potent vasodilatory properties and work through blockade of Ca2+ channels. Thus, a preference for 5β-dihydrosteroids to work at the membrane level exists via a variety of mechanisms. This article reviews the field and identifies gaps in knowledge to be addressed in future research.

Objective: To summarize the clinical features and genetic characteristics of Congenital bile acid synthetic disorder type 3 (BASD3) disorder caused by CYP7B1 gene variation. Methods: This was a case series study. Clinical data and genetic results of 2 cases of congenital bile acid synthetic disorder type 3 caused by CYP7B1 gene variations in the Department of Infectious Diseases, Children\'s Hospital of Fudan University at Xiamen and Department of Pediatrics, Women and Children\'s Hospital, School of Medicine, Xiamen University from January 2021 to December 2023 were retrospectively collected and analyzed. Literature up to December 2023 was searched from electronic databases of China National Knowledge Infrastructure (CNKI), Wanfang Data and PubMed with the combined keywords of \" Congenital bile acid synthetic disorder type 3\"\"Oxysterol 7-alpha-hydroxylase\"\"Oxysterol 7α-Hydroxylase Deficiency\"\"BASD3\" and \"CYP7B1 liver\" both in Chinese and English. The main clinical features and genetic characteristics of BASD3 disorder caused by CYP7B1 gene variations were summarized. Results: Two BASD3 patients, 1 male and 1 female, were admitted at the ages of 3 months and 18 days, and 2 months and 7 days, respectively. Both patients presented with neonatal cholestasis and hepatomegaly. Biochemical evidence indicated direct hyper-bilirubinemia with elevated aminotransferase levels, while gamma-glutamyltransferase (GGT) and total bile acid levels were normal or nearly normal. Patient 1 was a compound heterozygotes of the CYP7B1 gene variants c.525-526insCAAGTTGG(p.Asp176GInfs*15) and c.334C>T(p.Arg112Ter). Patient 1 jaundice resolved and liver function tests normalized after oral administration of chenodeoxycholic acid (CDCA). Patient 2 was homozygous for variant c.334C>T(p.Arg112Ter) in CYP7B1 gene. Patient 2 was in liver failure status already and not reactive to oral CDCA administration. Patient 2 received living-related liver transplantation for enhanced abdominal CT revealed a liver tumor likely vascular origin. Literature review revealed no cases of BASD3 reported in Chinese literature, including 2 patients in this study, while 12 patients (9 males and 3 females) were reported in 9 English literatures. All of the 12 manifested jaundice and hepatosplenomegaly in infancy, with cirrhosis, liver failure, kidney enlargement, hypoglycemia, and spontaneous bleeding in some cases, polycystic kidney disease was demonstrated in 5 cases of them. The c.334C>T (p.Arg112Ter) of the CYP7B1 gene was homozygous in 4 cases and compound heterozygous in 2 cases. Among the 12 children, 6 cases received CDCA treatment, while 6 cases not. Four survived with their native liver in the 6 cases who received CDCA therapy, while none in the 6 cases not received CDCA therapy. Conclusions: BASD3 is a rare hereditary cholestatic disorder. Markedly elevated levels of conjugated bilirubin and aminotransferases, with normal or nearly normal GGT and total bile acid levels can serve as diagnostic clue. c.334C>T is the most common pathogenic variant of the CYP7B1 gene. Timely administration of CDCA may save the liver.
目的： 总结 CYP7B1基因变异致先天性胆汁酸合成障碍3型患儿的临床表型和遗传学特点。 方法： 病例系列研究，回顾性分析2021年1月至2023年12月复旦大学附属儿科医院厦门医院感染科和厦门大学附属妇女儿童医院儿内科诊治的2例因CYP7B1基因变异致BASD3的临床资料和遗传学检测结果。并分别以“先天性胆汁酸合成障碍3型”“氧固醇7α-羟化酶”“BASD3”“Oxysterol 7α-Hydroxylase Deficiency”“Oxysterol 7α-Hydroxylase Gene”“CYP7B1 liver”为关键词检索中国知网、万方数据库和PubMed数据库自建库至2023年12月的中英文文献。对CYP7B1基因变异致BASD3患儿的主要临床表现和基因型特点进行描述和总结。 结果： 2例BASD3患儿中男女各1例，就诊年龄分别为3月龄18日龄和2月龄7日龄，均以新生儿胆汁淤积症伴肝大就诊。生化提示高直接胆红素血症，转氨酶升高，但γ-谷氨酰转移酶（GGT）和总胆汁酸正常或基本正常。例1为CYP7B1基因c.525-526insCAAGTTGG（p.Asp176GInfs*15）和c.334C>T（p.Arg112Ter）复合杂合变异，经口服鹅脱氧胆酸治疗黄疸消退，肝功能恢复正常；例2为CYP7B1基因c.334C>T（p.Arg112Ter）纯合，确诊时已发生肝衰竭，口服鹅脱氧胆酸无效，因腹部增强CT提示血管源性肿瘤行亲体肝移植。文献复习符合检索条件英文文献9篇、无中文文献报道。包括本研究2例共报道12例患儿，男9例、女3例。所有BASD3患儿均在婴幼儿期起病，主要表现为黄疸、肝大和（或）脾大，部分伴有肝硬化、肝衰竭、肾肿大、低血糖、自发性出血。伴多囊肾5例。CYP7B1基因c.334C>T（p.Arg112Ter）为最常见变异，纯合4例，复合杂合2例。12例患儿中，口服鹅去氧胆酸治疗6例，自体肝存活4例；6例未用鹅去氧胆酸治疗，均肝移植或死亡。 结论： BASD3是一种罕见的遗传性胆汁淤积症，结合胆红素和转氨酶明显升高，而GGT和总胆汁酸正常可作为诊断线索。c.334C>T是CYP7B1基因常见致病变异。口服鹅去氧胆酸治疗可望避免患儿死亡或肝移植。.

Inflammatory bowel disease is defined by inflammation and immune dysregulation. This study investigated the effects of Gα13 liver-specific knockout (LKO) on proximal and distal colons of dextran sodium sulfate (DSS)-induced mice in conjunction with a high-fat diet (HFD). HFD improved body weight gain and disease activity index scores. Gα13LKO exerted no improvement. In the proximal colon, HFD augmented the DSS effect on Il6, which was not observed in Gα13LKO mice. In the distal colon, HFD plus DSS oppositely fortified an increase in Tnfa and Cxcl10 mRNA in Gα13LKO but not WT. Il6 levels remained unchanged. Bioinformatic approaches using Gα13LKO livers displayed bile acid and cholesterol metabolism-related gene sets. Cholic acid and chenodeoxycholic acid levels were increased in the liver of mice treated with DSS, which was reversed by Gα13LKO. Notably, mice treated with DSS showed a reduction in hepatic ABCB11, CYP7B1, CYP7A1, and CYP8B1, which was reversed by Gα13LKO. Overall, feeding HFD augments the effect of DSS on Il6 in the proximal colon of WT, but not Gα13LKO mice, and enhances DSS effect on Tnfa and Cxcl10 in the distal colon of Gα13LKO mice, suggesting site-specific changes in the inflammatory cytokines, potentially resulting from changes in BA synthesis and excretion.

BACKGROUND: Silymarin is recognized for its excellent hepato-protective properties. Recent clinical studies have examined the effects of silymarin on metabolic dysfunction-associated steatotic liver disease (MASLD), highlighting the necessity of further exploration into optimal dosages, active components, and mechanisms of action.
RESULTS: This study assessed the anti-inflammatory activity of the principal constituents of silymarin at the cellular level. The therapeutic effects of varying silymarin doses and components on MASLD in mouse models induced by a high-fat diet (HFD) were also examined. These findings indicate the superior efficacy of 80 mg kg-1 silymarin in mitigating liver steatosis and reducing lipid accumulation compared to 30 mg kg-1 silymarin or a combination of silybin and isosilybin A. The mechanism of silymarin involves regulating gut microbiota homeostasis and influencing the TLR4/NF-κB signalling pathway through LPS. Bile acid-targeted metabolomics analysis revealed that silymarin significantly decreases the HFD-induced increase in 7-keto-deoxycholic acid (7-KDCA). Further investigations suggested that 7-KDCA as an antagonist targeted farnesoid X receptor (FXR) and that both silybin and isosilybin A could directly interact with FXR.
CONCLUSIONS: These findings elucidate that 80 mg kg-1 of silymarin can exert therapeutic effects on MASLD mice and offer novel insights into the mechanism of silymarin in treating MASLD. Especially, it was found that silymarin could regulate bile acid metabolism, reduce the concentration of 7-KDCA, and thus perform negative feedback regulation on FXR.

UNASSIGNED: Previous epidemiological studies have repeatedly found per- and polyfluoroalkyl substances (PFAS) exposure associated with higher circulating cholesterol, one of the greatest risk factors for development of coronary artery disease. The main route of cholesterol catabolism is through its conversion to bile acids, which circulate between the liver and ileum via enterohepatic circulation. Patients with coronary artery disease have decreased bile acid excretion, indicating that PFAS-induced impacts on enterohepatic circulation may play a critical role in cardiovascular risk.
UNASSIGNED: Using a mouse model with high levels of low-density and very low-density lipoprotein (LDL and VLDL, respectively) cholesterol and aortic lesion development similar to humans, the present study investigated mechanisms linking exposure to a PFAS mixture with increased cholesterol.
UNASSIGNED: Male and female Ldlr-/- mice were fed an atherogenic diet (Clinton/Cybulsky low fat, 0.15% cholesterol) and exposed to a mixture of 5 PFAS representing legacy, replacement, and emerging subtypes (i.e., PFOA, PFOS, PFHxS, PFNA, GenX), each at a concentration of 2mg/L, for 7 wk. Blood was collected longitudinally for cholesterol measurements, and mass spectrometry was used to measure circulating and fecal bile acids. Transcriptomic analysis of ileal samples was performed via RNA sequencing.
UNASSIGNED: After 7 wk of PFAS exposure, average circulating PFAS levels were measured at 21.6, 20.1, 31.2, 23.5, and 1.5μg/mL in PFAS-exposed females and 12.9, 9.7, 23, 14.3, and 1.7μg/mL in PFAS-exposed males for PFOA, PFOS, PFHxS, PFNA, and GenX, respectively. Total circulating cholesterol levels were higher in PFAS-exposed mice after 7 wk (352mg/dL vs. 415mg/dL in female mice and 392mg/dL vs. 488mg/dL in male mice exposed to vehicle or PFAS, respectively). Total circulating bile acid levels were higher in PFAS-exposed mice (2,978 pg/μL vs. 8,496 pg/μL in female mice and 1,960 pg/μL vs. 4,452 pg/μL in male mice exposed to vehicle or PFAS, respectively). In addition, total fecal bile acid levels were lower in PFAS-exposed mice (1,797 ng/mg vs. 682 ng/mg in females and 1,622 ng/mg vs. 670 ng/mg in males exposed to vehicle or PFAS, respectively). In the ileum, expression levels of the apical sodium-dependent bile acid transporter (ASBT) were higher in PFAS-exposed mice.
UNASSIGNED: Mice exposed to a PFAS mixture displayed higher circulating cholesterol and bile acids perhaps due to impacts on enterohepatic circulation. This study implicates PFAS-mediated effects at the site of the ileum as a possible critical mediator of increased cardiovascular risk following PFAS exposure. https://doi.org/10.1289/EHP14339.

BACKGROUND: Bile acid diarrhoea (BAD) can occur due to disruption to the enterohepatic circulation such as following cholecystectomy. However, the mechanism behind this is as yet unknown. The aim of this study was to determine the rate of post-cholecystectomy diarrhoea and to assess whether FGF19 within the gallbladder was associated with the development of BAD.
METHODS: This was a prospective case-control study in which patients were assessed pre- and post- cholecystectomy (study group) and compared with patients also having laparoscopic surgery but not cholecystectomy (control group). Their bowel habits and a GIQLI questionnaire was performed to compare the pre- and post-operative condition of the two groups. Gallbladder tissue sample was tested for FGF19 and PPARα in the study group patients. A subset had serum lipid levels, FGF19 and C4 measurements.
RESULTS: Gallbladder PPAR α was found to have a significant correlation with stool consistency, with the lower the PPARα concentration the higher the Bristol stool chart number (i.e. looser stool). There were no significant correlation when assessing the effect of gallbladder FGF19 concentration on bowel habit, stool consistency, lipid levels, BMI or smoking. The study group showed a significant increase in triglycerides post-operatively, however there were no changes in cholesterol, HDL and LDL levels. Correlation of the increased triglyceride levels with stool consistency and frequency showed no significant results DISCUSSION AND CONCLUSION: We did not find any direct evidence that FGF19 levels within the gallbladder impact the development of post-cholecystectomy diarrhoea. There was however a significant increase in triglycerides postoperatively. There was also no correlation of bowel habits with PPARα suggesting the observed rise is independent of this pathway. Further work is required particularly relating to the gut microbiome to further investigate this condition.