Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

The bile acid receptor TGR5 inhibits platelet activation and thrombus formation

Liver failure and cirrhosis are characterized by abnormal hemostasis with aberrant platelet activation. In particular, the consequences of cholestatic liver disease and molecular mechanisms, including the role of bile acids leading to impaired platelet responses, are not well understood. Here, we demonstrate that bile acids inhibit human and murine platelet activation, adhesion and spreading, leading to reduced thrombus formation under flow conditions. We identified the G-protein coupled receptor TGR5 in platelets and provide support for its role as mediator of bile acid-induced impairment of platelet activation. In the liver, TGR5 couples to Gαs proteins, activates the adenylate cyclase to induce a transient cAMP rise and stimulates the MAPK signaling pathway to regulate cholangiocyte proliferation, hepatocyte survival and inflammation. In this report, we demonstrate that the genetic deficiency of TGR5 in mice led to enhanced platelet activation and thrombus formation, suggesting that TGR5 plays an important role in hemostasis. Mechanistically, platelet inhibition is achieved by TGR5 mediated PKA activation and modulation of AKT and ERK1/2 phosphorylation. Thus, this report provides evidence for the ability of TGR5 ligands to reduce platelet activation and identifies TGR5 agonism as a new target for the prevention of cardiovascular diseases.

Isotschimgine promotes lifespan, healthspan and neuroprotection of Caenorhabditis elegans via the activation of nuclear hormone receptors

Isotschimgine (ITG) is a bornane-type monoterpenoid derivative naturally occurring in genus Ferula plants and propolis. Its effects on aging and the underlying mechanisms are not yet well understood. This study employed Caenorhabditis elegans (C. elegans) as a model organism to evaluate the potential of ITG in extending lifespan, enhancing healthspan, and promoting neuroprotection, while exploring the underlying mechanisms involved. The results showed that ITG extended the lifespan and healthspan of C. elegans, significantly enhanced stress resistance and detoxification functions. Studies on mutants and qPCR data indicated that ITG-mediated lifespan extension was modulated by the insulin/IGF-1 signaling pathway and nuclear hormone receptors. Furthermore, ITG markedly increased stress-responsive genes, including daf-16 and its downstream genes sod-3 and hsp-16.2, as well as NHR downstream detoxification-related genes cyp35a1, cyp35b3, cyp35c1, gst-4, pgp-3 and pgp-13. Additionally, ITG alleviated β-amyloid-induced paralysis and behavioral dysfunction in transgenic C. elegans strains. The neuroprotective efficacy of ITG was weakened by RNAi knockdown of nuclear hormone receptors daf-12 and nhr-8. Overall, our study identifies ITG as a potential compound for promoting longevity and neuroprotection, mediated through nuclear hormone receptors.

Activation of TGR5 in the injured nerve site according to a prevention protocol mitigates partial sciatic nerve ligation-induced neuropathic pain by alleviating neuroinflammation

ABSTRACT

Neuropathic pain is a pervasive medical challenge currently lacking effective treatment options. Molecular changes at the site of peripheral nerve injury contribute to both peripheral and central sensitization, critical components of neuropathic pain. This study explores the role of the G-protein-coupled bile acid receptor (GPBAR1 or TGR5) in the peripheral mechanisms underlying neuropathic pain induced by partial sciatic nerve ligation in male mice. TGR5 was upregulated in the injured nerve site and predominantly colocalized with macrophages. Perisciatic nerve administration of the TGR5 agonist, INT-777 according to a prevention protocol (50 μg/μL daily from postoperative day [POD] 0 to POD6) provided sustained relief from mechanical allodynia and spontaneous pain, whereas the TGR5 antagonist, SBI-115 worsened neuropathic pain. Transcriptome sequencing linked the pain relief induced by TGR5 activation to reduced neuroinflammation, which was further evidenced by a decrease in myeloid cells and pro-inflammatory mediators (eg, CCL3, CXCL9, interleukin [IL]-6, and tumor necrosis factor [TNF] α) and an increase in CD86-CD206+ anti-inflammatory macrophages at POD7. Besides, myeloid-cell-specific TGR5 knockdown in the injured nerve site exacerbated both neuropathic pain and neuroinflammation, which was substantiated by bulk RNA-sequencing and upregulated expression levels of inflammatory mediators (including CCL3, CCL2, IL-6, TNF α, and IL-1β) and the increased number of monocytes/macrophages at POD7. Furthermore, the activation of microglia in the spinal cord on POD7 and POD14 was altered when TGR5 in the sciatic nerve was manipulated. Collectively, TGR5 activation in the injured nerve site mitigates neuropathic pain by reducing neuroinflammation, while TGR5 knockdown in myeloid cells worsens pain by enhancing neuroinflammation.

Effects of bile acids on the growth, composition and metabolism of gut bacteria

Bile acids (BAs) exert a profound influence on the body's pathophysiology by intricately shaping the composition of gut bacteria. However, the complex interplay between BAs and gut microbiota has impeded a systematic exploration of their impact on intestinal bacteria. Initially, we investigated the effects of 21 BAs on the growth of 65 gut bacterial strains in vitro. Subsequently, we examined the impact of BAs on the overall composition of intestinal bacteria, both in vivo and in vitro. The results unveiled distinct effects of various BAs on different intestinal strains and their diverse impacts on the composition of gut bacteria. Mechanistically, the inhibition of intestinal strains by BAs occurs through the accumulation of these acids within the strains. The intracellular accumulation of deoxycholic acid (DCA) significantly influenced the growth of intestinal bacteria by impacting ribosome transcription and amino-acid metabolism. The metabolomic analysis underscores the pronounced impact of DCA on amino-acid profiles in both in vivo and in vitro settings. This study not only elucidates the effects of BAs on a diverse range of bacterial strains and their role in shaping the gut microbiota but also reveals underlying mechanisms essential for understanding and maintaining a healthy gut microbiota.

Zhi-Kang-Yin formula attenuates high-fat diet-induced metabolic disorders through modulating gut microbiota-bile acids axis in mice

BACKGROUND

Metabolic disorders have become one of the global medical problems. Due to the complexity of its pathogenesis, there is still no effective treatment. Bile acids (BAs) and gut microbiota (GM) have been proved to be closely related to host metabolism, which could be important targets for metabolic disorders. Zhi-Kang-Yin (ZKY) is a traditional Chinese medicine (TCM) formula developed by the research team according to theory of TCM and has been shown to improve metabolism in clinic. However, the underlying mechanisms are unclear.

AIM OF THE STUDY

This study aimed to investigate the potential mechanisms of the beneficial effect of ZKY on metabolism.

METHODS

High-fat diet (HFD)-fed mice were treated with and without ZKY. The glucose and lipid metabolism-related indexes were measured. BA profile, GM composition and hepatic transcriptome were then investigated to analyze the changes of BAs, GM, and hepatic gene expression. Moreover, the relationship between GM and BAs was identified with functional gene quantification and ex vivo fermentation experiment.

RESULTS

ZKY reduced weight gain and lipid levels in both liver and serum, attenuated hepatic steatosis and improved glucose tolerance in HFD-fed mice. BA profile detection showed that ZKY changed the composition of BAs and increased the proportion of unconjugated BAs and non-12-OH BAs. Hepatic transcriptomic analysis revealed fatty acid metabolism and BA biosynthesis related pathways were regulated. In addition, ZKY significantly changed the structure of GM and upregulated the gene copy number of bacterial bile salt hydrolase. Meanwhile, ZKY directly promoted the growth of Bifidobacterium, which is a well-known bile salt hydrolase-producing genus. The ex vivo co-culture experiment with gut microbiota and BAs demonstrated that the changes of BAs profile in ZKY group were mediated by ZKY-shifted GM, which led to increased expression of genes associated with fatty acid degradation in the liver.

CONCLUSION

Our study indicated that the effect of ZKY on improving metabolism is associated with the modulation of GM-BAs axis, especially, by upregulating the abundance of bile salt hydrolase-expression bacteria and increasing the levels of unconjugated BAs. This study indicates that GM-BAs axis might be an important pathway for improving metabolic disorders by ZKY.

The bile acid profile

As a large and structurally diverse family of small molecules, bile acids play a crucial role in regulating lipid, glucose, and energy metabolism. In the human body, bile acids share a similar chemical structure with many isomers, exhibit little difference in polarity, and possess various physiological activities. The types and contents of bile acids present in different diseases vary significantly. Therefore, comprehensive and accurate detection of the content of various types of bile acids in different biological samples can not only provide new insights into the pathogenesis of diseases but also facilitate the exploration of novel strategies for disease diagnosis, treatment, and prognosis. The detection of disease-induced changes in bile acid profiles has emerged as a prominent research focus in recent years. Concurrently, targeted metabolomics methods utilizing high-performance liquid chromatography-mass spectrometry (HPLC-MS) have progressively established themselves as the predominant technology for the separation and detection of bile acids. Bile acid profiles will increasingly play an important role in diagnosis and guidance in the future as the relationship between disease and changes in bile acid profiles becomes clearer. This highlights the growing diagnostic value of bile acid profiles and their potential to guide clinical decision-making. This review aims to explore the significance of bile acid profiles in clinical diagnosis from four perspectives: the synthesis and metabolism of bile acids, techniques for detecting bile acid profiles, changes in bile acid profiles associated with diseases, and the challenges and future prospects of applying bile acid profiles in clinical settings.

Perinatal exposure to perfluorooctane sulfonate and the risk of hepatic inflammation in rat offspring: Perturbation of gut-liver crosstalk

Perfluorooctane sulfonate (PFOS) exposure is associated with harmful hepatic outcomes. Growing evidence indicates that crosstalk between the gut microbiome, immune system, and liver plays a vital role in the pathogenesis of liver diseases. However, the underlying mechanism is not fully understood. In the present study, we aimed to investigate the effects of PFOS exposure during pregnancy and lactation on hepatic inflammation in rat offspring. Features of hepatic inflammation and increased levels of aspartate-amino transferase (AST) were found in pups on postnatal day 28 (PND28) in PFOS-exposed groups. Gut microbiota analysis identified Chitinophaga, Ralstonia, and Alloprevotella as the key genera in distinguishing the PFOS-exposed group from the control group. Metabolic and transcriptomic analyses found that PFOS exposure resulted in 48 differentially expressed metabolites (DEMs) in the serum, 62 DEMs in the liver, and 289 differentially expressed genes (DEGs) in the liver of PND28 pups. The immune response is significantly enriched in PFOS-exposed liver on PND28; multi-omics analysis indicated that PFOS might lead to immune response perturbation by disturbing the metabolic profiling in the liver. The changed gut microbiota was significantly related to the serum level of the liver function index. Specifically, Alloprevotella, Chitinophage, Ruminococcus, and Allobaculum were significantly associated with the metabolic abundance changes of 4-Hydroxydebrisoquine, L-Norvaline, and Eremopetasinorol, and the gene expression changes of Acat211, Msmol, Idi1, Sqle, and Gadd45b in the liver. These findings suggest that early-life PFOS exposure may be associated with adverse hepatic inflammation in young offspring via disruption of the gut-liver crosstalk, which may provide mechanistic clues for clarifying the hepatotoxicity in offspring associated with perinatal PFOS exposure.

The gut microbiome and dietary fibres: implications in obesity, cardiometabolic diseases and cancer

Dietary fibres constitute a heterogeneous class of nutrients that are key in the prevention of various chronic diseases. Most dietary fibres are fermented by the gut microbiome and may, thereby, modulate the gut microbial ecology and metabolism, impacting human health. Dietary fibres may influence the occurrence of specific bacterial taxa, with this effect varying between individuals. The effect of dietary fibres on microbial diversity is a matter of debate. Most intervention studies with dietary fibres in the context of obesity and related metabolic disorders reveal the need for an accurate assessment of the microbiome to better understand the variable response to dietary fibres. Epidemiological studies confirm that a high dietary fibre intake is strongly associated with a reduced occurrence of many types of cancer. However, there is a need to determine the impact of intervention with specific dietary fibres on cancer risk, therapy efficacy and toxicity, as well as in cancer cachexia. In this Review, we summarize the mechanisms by which the gut microbiome can mediate the physiological benefits of dietary fibres in the contexts of obesity, cardiometabolic diseases and cancer, their incidence being clearly linked to low dietary fibre intake.

Triclosan exposure causes abnormal bile acid metabolism through IL-1β-NF-κB-Fxr signaling pathway

Triclosan (TCS) is an eminent antibacterial agent. However, extensive usage causes potential health risks like hepatotoxicity, intestinal damage, kidney injury, etc. Existing studies suggested that TCS would disrupt bile acid (BA) enterohepatic circulation, but its toxic mechanism remains unclear. Hence, the current study established an 8-week TCS exposure model to explore its potential toxic mechanism. The results discovered 8 weeks consecutive administration of TCS induced distinct programmed cell death, inflammatory cell activation and recruitment, and excessive BA accumulation in liver. Furthermore, the expression of BA synthesis and transport associated genes were significantly dysregulated upon TCS treatment. Additional mechanism exploration revealed that Fxr inhibition induced by TCS would be the leading cause for unusual BA biosynthesis and transport. Subsequent Fxr up-stream investigation uncovered TCS exposure caused pyroptosis and its associated IL-1β would be the reason for Fxr reduction mediated by NF-κB. NF-κB blocking by dimethylaminoparthenolide ameliorated TCS induced BA disorder which confirmed the contribution of NF-κB in Fxr repression. To sum up, our findings conclud TCS-caused BA disorder is attributed to Fxr inhibition, which is regulated by the IL-1β-NF-κB signaling pathway. Hence, we suggest Fxr would be a potential target for abnormal BA stimulated by TCS and its analogs.

A prognostic model established using bile acid genes to predict the immunity and survival of patients with gastrointestinal cancer

BACKGROUND

The metabolism of abnormal bile acids (BAs) is implicated in the initiation and development of gastrointestinal (GI) cancer. However, there was a lack of research on the molecular mechanisms of BAs metabolism in GI.

METHODS

Genes involved in BAs metabolism were excavated from public databases of The Cancer Genome Atlas (TCGA) database, Gene Expression Omnibus (GEO) database, and Molecular Signatures Database (MSigDB). ConsensusClusterPlus was used to classify molecular subtypes for GI. To develop a RiskScore model for predicting GI prognosis, univariate Cox analysis was performed on the genes in protein-protein interaction (PPI) network, followed by using Lasso regression and stepwise regression to refine the model and to determine the key prognostic genes. Tumor immune microenvironment in GI patients from different risk groups was assessed using the ESTIMATE algorithm and enrichment analysis. Reverse transcription-quantitative real-time PCR (RT-qPCR), Transwell assay, and wound healing assay were carried out to validate the expression and functions of the model genes.

RESULTS

This study defined three molecular subtypes (C1, C2, and C3). Specifically, C1 had the best prognosis, while C3 had the worst prognosis with high immune checkpoint gene expression levels and TIDE scores. We selected nine key genes (AXIN2, ATOH1, CHST13, PNMA2, GYG2, MAGEA3, SNCG, HEYL, and RASSF10) that significantly affected the prognosis of GI and used them to develop a RiskScore model accordingly. Combining the verification results from a nomogram, the prediction of the model was proven to be accurate. The high RiskScore group was significantly enriched in tumor and immune-related pathways. Compared with normal gastric mucosal epithelial cells, the mRNA levels of the nine genes were differential in the gastric cancer cells. Inhibition of PNMA2 suppressed migration and invasion of the cancer cells.

CONCLUSION

We distinguished three GI molecular subtypes with different prognosis based on the genes related to BAs metabolism and developed a RiskScore model, contributing to the diagnosis and treatment of patients with GI.

The impact of artificial liver support system on intestinal microbiota and serum bile acid profiles in patients with acute-on-chronic liver failure: a prospective cohort study

BACKGROUND

Acute-on-chronic liver failure (ACLF) patients exhibit an imbalance in intestinal microbiota, and bile acids (BAs) can affect the composition of intestinal microbiota. Although Artificial liver support system (ALSS) is a treatment for ACLF, the impact of ALSS on intestinal microbiota and serum BA profiles of ACLF patients remains unclear.

METHODS

A prospective study was conducted, which included 51 patients diagnosed with ACLF. These patients were stratified into two groups based on the utilization of an ALSS during their treatment period: a standard medical treatment group (SMT group), comprising 19 patients, and an ALSS combined with SMT group (ALSS group), comprising 32 patients. Blood and stool samples were collected from the patients on the day of admission and 14 days after treatment. Additionally, eight healthy controls were recruited, and their stool samples were also collected. The intestinal microbiota was sequenced using the 16S rRNA sequencing technique, while the serum BA profiles were determined using ultra-performance liquid chromatography/mass spectrometry.

RESULTS

ACLF patients exhibited imbalances in intestinal microbiota and abnormalities in BA profiles. Compared to SMT alone, the combined ALSS and SMT was more effective in regulating intestinal microbiota imbalance and increasing the concentrations of ursodeoxycholic acid and glycoursodeoxycholic acid. Correlation analysis revealed a significant correlation between intestinal microbiota and Bas. Furthermore, the preliminary correlation heatmap indicated that the Faecalibaculum, Gemmiger, and taurochenodeoxycholic acid were associated with clinical improvement.

CONCLUSIONS

Our study identified the compositional characteristics of the intestinal microbiota and serum BA in ACLF patients, emphasizing the impact of ALSS on both intestinal microbiota and serum BA profiles.

Aging-associated atrial fibrillation: A comprehensive review focusing on the potential mechanisms

Atrial fibrillation (AF) has been receiving a lot of attention from scientists and clinicians because it is an extremely common clinical condition. Due to its special hemodynamic changes, AF has a high rate of disability and mortality. So far, although AF has some therapeutic means, it is still an incurable disease because of its complex risk factors and pathophysiologic mechanisms, which is a difficult problem for global public health. Age is an important independent risk factor for AF, and the incidence of AF increases with age. To date, there is no comprehensive review on aging-associated AF. In this review, we systematically discuss the pathophysiologic evidence for aging-associated AF, and in particular explore the pathophysiologic mechanisms of mitochondrial dysfunction, telomere attrition, cellular senescence, disabled macroautophagy, and gut dysbiosis involved in recent studies with aging-associated AF. We hope that by exploring the various dimensions of aging-associated AF, we can better understand the specific relationship between age and AF, which may be crucial for innovative treatments of aging-associated AF.

In ovo betaine injection improves breast muscle growth in newly hatched goslings through FXR/IGF-2 pathway

Betaine has been shown to enhance growth performance and increase breast muscle yield in ducks and broilers through various mechanisms, including the modification of DNA methylation. However, the impact of in ovo betaine injection on muscle growth in newly hatched goslings remains unclear. In this study, fifty eggs were injected with saline or betaine at 7.5 mg/egg prior to incubation, and the subsequent effects on breast muscle growth in the newly hatched goslings were investigated. Betaine significantly increased (P < 0.05) the hatch weight, breast muscle weight, and breast muscle index, accompanied by an augmentation in muscle bundle cross-sectional area. Concurrently, betaine significantly upregulated (P < 0.05) the expression levels of myogenic regulatory factors, including myogenin (MyoG) and paired box 7 (Pax7) both mRNA and protein, while downregulating (P < 0.05) the mRNA and protein levels of myostatin (MSTN). Histological analysis revealed a higher abundance of proliferating cell nuclear antigen (PCNA) and Pax7 immune-positive cells in the breast muscle of the betaine group, consistent with elevated PCNA and Pax7 mRNA and protein levels. Additionally, significantly increased (P < 0.05) contents of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor 2 (IGF-2) were observed in the breast muscle of the betaine group, so was mRNA expression of IGF-1, IGF-2, and insulin-like growth factor 1 receptor (IGF-1R). Betaine also significantly in8creased (P < 0.05) global DNA methylation of the breast muscle, accompanied by enhanced mRNA and protein levels of methionine cycle and DNA methylation-related enzymes, Interestingly, the promoter regions of IGF-1, IGF-2, and IGF-1R genes were significantly hypomethylated (P < 0.05). Moreover, in ovo betaine injection significantly upregulated (P < 0.05) the protein level of farnesoid X receptor (FXR) in breast muscle and FXR binding to the promoter of IGF-2 gene. These findings suggest that in ovo betaine injection promotes breast muscle growth during embryonic development in goslings through the FXR-mediated IGF-2 pathway, ultimately improving hatch weight and breast muscle weight.

Bile acid metabolism and signaling in liver disease

Bile acids (BAs) have signaling functions efficiently regulating their own metabolism and transport as well as key aspects of lipid and glucose homeostasis. BAs shape the gut microbial flora and conversely are metabolized by microbiota. Disruption of BA transport, metabolism and physiological signaling function contribute to the pathogenesis and progression of a wide range of liver diseases including cholestatic disorders and metabolic dysfunction-associated steatotic liver disease (MASLD) as well as hepatocellular and cholangiocellular carcinoma. Additionally, impaired BA signaling may also affect the intestine and kidney, thereby contributing to failure of gut integrity driving the progression and complications of portal hypertension, cholemic nephropathy and the development of extrahepatic malignancies such as colorectal cancer. This review will summarize recent advances in the understanding of BA signaling, metabolism and transport focusing on transcriptional regulation and novel BA-focused therapeutic strategies for cholestatic and metabolic liver diseases.

Correlation of bilirubin and toxic bile acids in critically ill patients with cholestatic liver dysfunction and adsorber application

Bilirubin is one of the most frequently used laboratory values to monitor critically ill patients with cholestatic liver dysfunction. Besides bilirubin, toxic bile acids (TBAs), which may cause severe organ damage, are typically elevated. A correlation between both parameters seems plausible, but data are lacking. The aim was to investigate whether there is a correlation between bilirubin and TBAs in patients' blood and whether a compareable reduction can be observed during the use of the adsorber CytoSorb (CS). As part of the Cyto-SOLVE study (NCT04913298), 16 critically ill patients with cholestatic liver dysfunction, bilirubin concentration > 10 mg/dl, continuous kidney replacement therapy and CS-application were investigated. Bilirubin and TBA concentrations were measured from arterial blood at defined time points (before start, after 6 and 12 h). Relative reduction (RR) was calculated using the formula[Formula: see text]. A moderate to high correlation between bilirubin and TBA concentration at all defined timepoints (rstart=0.64, p = 0.008; r6h = 0.85, p < 0.001, r12h = 0.72, p = 0.002) was observed. In the first six hours of CS-application, a significant elimination of TBA (median TBA: 30.8→20.1µmol/l, p < 0.001) and bilirubin (median bilirubin: 17.1→11.9 mg/dl, p < 0.001) was observed. The median RR after 6 h was 26.1% and 39.8% for bilirubin and TBA, respectively. No further reduction was observed after 12 h (RRbilirubin: - 0.6%, RRTBA: 1.8%). There was an at least moderate correlation between bilirubin and TBA in patients with cholestatic liver dysfunction. Therefore, bilirubin seems to be a suitable surrogate parameter for TBA elimination during CytoSorb application.

VSV infection and LPS treatment alter serum bile acid profiles, bile acid biosynthesis, and bile acid receptors in mice

Pathogen infections remain a significant public health problem worldwide. Accumulating evidence regarding the crosstalk between bile acid (BA) metabolism and immune response reveals that BA metabolism regulates host immunity and microbial pathogenesis, making it an attractive target for disease prevention and infection control. However, the effect of infection on circulating BA profiles, the biosynthesis-related enzymes, and their receptors remains to be depicted. Here, we investigated the effect of viral (vesicular stomatitis virus, VSV) and bacterial (lipopolysaccharide, LPS) infections on BA metabolism and signaling. Infection models were successfully established by intraperitoneally injecting VSV and LPS, respectively. VSV and LPS injection significantly changed the circulating BA profiles, with highly increased levels of taurine-conjugated BAs and significant decreases in unconjugated BAs. Consistent with the decreased levels of circulating cholic acid (CA) and chenodeoxycholic acid (CDCA), the expression of BA biosynthesis-related rate-limiting enzymes (Cyp7a1, Cyp27a1, Cyp8b1, and Hsd3b7) were significantly reduced. Furthermore, hepatic and pulmonary BA receptors (BARs) expression varied in different infection models. LPS treatment had an extensive impact on tested hepatic and pulmonary BARs, resulting in the upregulation of TGR5, S1PR2, and VDR, while VSV infection only promoted VDR expression. Our study provides insights into the involvement of BA metabolism in the pathophysiology of infection, which may provide potential clues for targeting BA metabolism and BAR signaling to boost innate immunity and control infection.

IMPORTANCE

This study focuses on the crosstalk between bile acid (BA) metabolism and immune response in VSV infection and LPS treatment models and depicts the effect of infection on circulating BA profiles, the biosynthesis-related enzymes, and their receptors. These findings provide insights into the effect of infection on BA metabolism and signaling, adding a more comprehensive understanding to the relationship between infection, BA metabolism and immune responses.

Hypothalamic SLC7A14 accounts for aging-reduced lipolysis in white adipose tissue of male mice

The central nervous system has been implicated in the age-induced reduction in adipose tissue lipolysis. However, the underlying mechanisms remain unclear. Here, we show the expression of SLC7A14 is reduced in proopiomelanocortin (POMC) neurons of aged mice. Overexpression of SLC7A14 in POMC neurons alleviates the aging-reduced lipolysis, whereas SLC7A14 deletion mimics the age-induced lipolysis impairment. Metabolomics analysis reveals that POMC SLC7A14 increased taurochenodeoxycholic acid (TCDCA) content, which mediates the SLC7A14 knockout- or age-induced WAT lipolysis impairment. Furthermore, SLC7A14-increased TCDCA content is dependent on intestinal apical sodium-dependent bile acid transporter (ASBT), which is regulated by intestinal sympathetic afferent nerves. Finally, SLC7A14 regulates the intestinal sympathetic afferent nerves by inhibiting mTORC1 signaling through inhibiting TSC1 phosphorylation. Collectively, our study suggests the function for central SLC7A14 and an upstream mechanism for the mTORC1 signaling pathway. Moreover, our data provides insights into the brain-gut-adipose tissue crosstalk in age-induced lipolysis impairment.

Bile acids promote lipopolysaccharide clearance via the hepato-biliary pathway in broiler chickens

Lipopolysaccharide (LPS) acts as a trigger that disrupts metabolic functions and the immune system. While bile acids (BA) have detoxification and anti-inflammatory effects, their role in promoting LPS excretion in broiler chickens remains unclear. This study aimed to investigate the potential of exogenous BA to enhance hepatic clearance of LPS and thereby potentially alleviate LPS-induced liver injury in broiler chickens. Forty-five 21-day-old male broiler chickens were randomly assigned to three groups: the control group, which received daily intraperitoneal injections of a solvent for LPS treatment and a gavage solvent for BA treatment; the LPS group, which received daily intraperitoneal injections of 0.5 mg/kg body weight LPS and a gavage solvent for BA treatment; the LPS + BA group, which received daily intraperitoneal injections of 0.5 mg/kg body weight LPS and 60 mg/kg body weight BA by gavage. BA administered by gavage protected the broiler chickens from increases in liver and spleen indices, systemic inflammatory response, and hepatic damage induced by LPS. Hepatic clearance of LPS was enhanced, as evidenced by decreased serum LPS levels and accelerated excretion into the gallbladder. Additionally, the LPS-induced downregulation of detoxification genes, including those for the lipoprotein receptor and bile acids export pump, was reversed by BA administered by gavage. Furthermore, nuclear transcription factors such as the Farnesoid X receptor (FXR) and Liver X receptor α (LXRα) were enhanced in BA-treated broiler chickens. These findings suggest that BA administration via gavage enhances hepatic LPS clearance through the upregulation of hepatic uptake and efflux proteins, likely mediated by the activation of nuclear transcription factors FXR and LXRα.

Decoding the microbiota metabolome in hepatobiliary and pancreatic cancers: Pathways to precision diagnostics and targeted therapeutics

We delve into the critical role of the gut microbiota and its metabolites in the pathogenesis and progression of hepatobiliary and pancreatic (HBP) cancers, illuminating an urgent need for breakthroughs in diagnostic and therapeutic strategies. Given the high mortality rates associated with HBP cancers, which are attributed to aggressive recurrence, metastasis, and poor responses to chemotherapy, exploring microbiome research presents a promising frontier. This research highlights how microbial metabolites, including secondary bile acids, short-chain fatty acids, and lipopolysaccharides, crucially influence cancer cell behaviors such as proliferation, apoptosis, and immune evasion, significantly contributing to the oncogenesis and progression of HBP cancers. By integrating the latest findings, we discuss the association of microbial alterations with HBP cancers, key metabolites, and their implications, and how metabolomics and microbiomics can enhance diagnostic precision. Furthermore, the paper explores strategies for targeted therapies through microbiome metabolomics, including the direct therapeutic effects of microbiome metabolites and potential synergistic effects on conventional therapies. We also recognize that the field of microbial metabolites for the diagnosis and treatment of tumors still has a lot of problems to be solved. The aim of this study is to pioneer microbial metabolite research and provide a reference for HBP cancer diagnosis, treatment, and prognosis.

Core biomarkers analysis benefit for diagnosis on human intrahepatic cholestasis of pregnancy

BACKGROUND

The pregnant women with intrahepatic cholestasis were at high risk of fetal distress, preterm birth and unexpected stillbirth. Intrahepatic cholestasis of pregnancy (ICP) was mainly caused by disorder of bile acid metabolism, whereas the specific mechanism was obscure.

METHODS

We performed proteomics analysis of 10 ICP specimens and 10 placenta specimens from patients without ICP through data-independent acquisition (DIA) technique to disclose differentially expressed proteins. We executed metabolomic analysis of 30 ICP specimens and 30 placenta specimens from patients without ICP through UPLC-MS/MS to identify differentially expressed metabolites. Enrichment and correlation analysis was used to obtain the direct molecular insights of ICP development. The ICP rat models were constructed to validate pathological features.

RESULTS

The heatmap of proteomics analysis showed the top 30 up-regulated and 30 down-regulated proteins. The metabolomic analysis revealed 20 richer and 4 less abundant metabolites in ICP samples compared with placenta specimens from patients without ICP, and enrichment pathways by these metabolites included primary bile acid biosynthesis, cholesterol metabolism, bile secretion, nicotinate and nicotinamide metabolism, purine metabolism and metabolic pathways. Combined analysis of multiple omics results demonstrated that bile acids such as Glycohyocholic acid, Glycine deoxycholic acid, beta-Muricholic acid, Noncholic acid, cholic acid, Gamma-Mercholic Acid, alpha-Muricholic acid and Glycochenodeoxycholic Aicd were significantly associated with the expression of GLRX3, MYL1, MYH7, PGGT1B, ACTG1, SP3, LACTB2, C2CD5, APBB2, IPO9, MYH2, PPP3CC, PIN1, BLOC1S1, DNAJC7, RASAL2 and ATCN3 etc. The core protein ACAT2 was involved in lipid metabolic process and animal model showed that ACAT2 was up-regulated in placenta and liver of pregnant rats and fetal rats. The neonates had low birth weight and Safranin O-Fast green FCF staining of animal models showed that poor osteogenic and chondrogenic differentiation of fetal rats.

CONCLUSION

Multiple metabolites-alpha-Muricholic acid, beta-Muricholic acid, Glycine deoxycholic acid and Glycochenodeoxycholic Acid etc. were perfect biomarkers to predict occurrence of ICP. Bile acids were significantly associated with varieties of protein expression and these proteins were differentially expressed in ICP samples. Our study provided several biomarkers for ICP detection and potential therapeutic targets for ICP development.

Large-scale genomic investigation of pediatric cholestasis reveals a novel hepatorenal ciliopathy caused by PSKH1 mutations

PURPOSE

Pediatric cholestasis is the phenotypic expression of clinically and genetically heterogeneous disorders of bile acid synthesis and flow. Although a growing number of monogenic causes of pediatric cholestasis have been identified, the majority of cases remain undiagnosed molecularly.

METHODS

In a cohort of 299 pediatric participants (279 families) with intrahepatic cholestasis, we performed exome sequencing as a first-tier diagnostic test.

RESULTS

A likely causal variant was identified in 135 families (48.56%). These comprise 135 families that harbor variants spanning 37 genes with established or tentative links to cholestasis. In addition, we propose a novel candidate gene (PSKH1) (HGNC:9529) in 4 families. PSKH1 was particularly compelling because of strong linkage in 3 consanguineous families who shared a novel hepatorenal ciliopathy phenotype. Two of the 4 families shared a founder homozygous variant, whereas the third and fourth had different homozygous variants in PSKH1. PSKH1 encodes a putative protein serine kinase of unknown function. Patient fibroblasts displayed abnormal cilia that are long and show abnormal transport. A homozygous Pskh1 mutant mouse faithfully recapitulated the human phenotype and displayed abnormally long cilia. The phenotype could be rationalized by the loss of catalytic activity observed for each recombinant PSKH1 variant using in vitro kinase assays.

CONCLUSION

Our results support the use of genomics in the workup of pediatric cholestasis and reveal PSKH1-related hepatorenal ciliopathy as a novel candidate monogenic form.

Mechanism of Bile Acid in Regulating Platelet Function and Thrombotic Diseases

Platelets play a key role in physiological hemostasis and pathological thrombosis. Based on the limitations of current antiplatelet drugs, it's important to elucidate the mechanisms of regulating platelet activation. In addition to dissolving lipid nutrients, bile acids (BAs) can regulate platelet function. However, the specific mechanisms underlying BAs-mediated effects on platelet activation and thrombotic diseases remain unknown. Therefore, the effects of BAs on platelets and intracellular regulatory mechanisms are explored. It is showed that the inhibitory effect of secondary BAs is more significant than that of primary BAs; lithocholic acid (LCA) shows the highest inhibitory effect. In the process of platelet activation, BAs suppress platelet activation via the spleen tyrosine kinase (SYK), protein kinase B (Akt), and extracellular signal-regulated kinase1/2 (Erk1/2) pathways. Nck adaptor proteins (NCK1) deficiency significantly suppress the activity of platelets and arterial thrombosis. Phosphorylated proteomics reveal that LCA inhibited phosphorylation of syntaxin-11 at S80/81 in platelets. Additional LCA supplementation attenuated atherosclerotic plaque development and reduced the inflammation in mice. In conclusion, BAs play key roles in platelet activation via Syk, Akt, ERK1/2, and syntaxin-11 pathways, which are associated with NCK1. The anti-platelet effects of BAs provide a theoretical basis for the prevention and therapy of thrombotic diseases.

Yin-Yang control of energy balance by lipids in the hypothalamus: The endocannabinoids vs bile acids case

Obesity is a chronic and debilitating disorder that originates from alterations in energy-sensing brain circuits controlling body weight gain and food intake. The dysregulated syntheses and actions of lipid mediators in the hypothalamus induce weight gain and overfeeding, but the molecular and cellular underpinnings of these alterations remain elusive. In response to changes in the nutritional status, different lipid sensing pathways in the hypothalamus direct body energy needs in a Yin-Yang model. Endocannabinoids orchestrate the crosstalk between hypothalamic circuits and the sympathetic nervous system to promote food intake and energy accumulation during fasting, whereas bile acids act on the same top-down axis to reduce energy intake and possibly storage after the meal. In obesity, the bioavailability and downstream cellular actions of endocannabinoids and bile acids are altered in hypothalamic neurons involved in body weight and metabolic control. Thus, the onset and progression of this disease might result from an imbalance in hypothalamic sensing of multiple lipid signals, which are possibly integrated by common molecular nodes. In this viewpoint, we discuss a possible model that explains how bile acids and endocannabinoids may exert their effects on energy balance regulation via interconnected mechanisms at the level of the hypothalamic neuronal circuits. Therefore, we propose a new conceptual framework for understanding and treating central mechanisms of maladaptive lipid action in obesity.

Crohn's Disease-Associated Pathogenic Mutation in the Manganese Transporter ZIP8 Shifts the Ileal and Rectal Mucosal Microbiota Implicating Aberrant Bile Acid Metabolism

BACKGROUND

A pathogenic mutation in the manganese transporter ZIP8 (A391T; rs13107325) increases the risk of Crohn's disease. ZIP8 regulates manganese homeostasis and given the shared need for metals between the host and resident microbes, there has been significant interest in alterations of the microbiome in carriers of ZIP8 A391T. Prior studies have not examined the ileal microbiome despite associations between ileal disease and ZIP8 A391T.

METHODS

Here, we used the Pediatric Risk Stratification Study (RISK) cohort to perform a secondary analysis of 16S ribosomal RNA gene sequencing data obtained from ileal and rectal mucosa to study associations between ZIP8 A391T carrier status and microbiota composition.

RESULTS

We found sequence variants mapping to Veillonella were decreased in the ileal mucosa of ZIP8 A391T carriers. Prior human studies have demonstrated the sensitivity of Veillonella to bile acid abundance. We therefore hypothesized that bile acid homeostasis is differentially regulated in carriers of ZIP8 A391T. Using a mouse model of ZIP8 A391T, we demonstrate an increase in total bile acids in the liver and stool and decreased fibroblast growth factor 15 (Fgf15) signaling, consistent with our hypothesis. We confirmed dysregulation of FGF19 in the 1000IBD cohort, finding that plasma FGF19 levels are lower in ZIP8 A391T carriers with ileocolonic Crohn's disease.

CONCLUSIONS

In the search for genotype-specific therapeutic paradigms for patients with Crohn's disease, these data suggest targeting the FGF19 pathway in ZIP8 A391T carriers. Aberrant bile acid metabolism may precede development of Crohn's disease and prioritize study of the interactions between manganese homeostasis, bile acid metabolism and signaling, and complicated ileal Crohn's disease.

Repairing gut barrier by traditional Chinese medicine: roles of gut microbiota

Gut barrier is not only part of the digestive organ but also an important immunological organ for the hosts. The disruption of gut barrier can lead to various diseases such as obesity and colitis. In recent years, traditional Chinese medicine (TCM) has gained much attention for its rich clinical experiences enriched in thousands of years. After orally taken, TCM can interplay with gut microbiota. On one hand, TCM can modulate the composition and function of gut microbiota. On the other hand, gut microbiota can transform TCM compounds. The gut microbiota metabolites produced during the actions of these interplays exert noticeable pharmacological effects on the host especially gut barrier. Recently, a large number of studies have investigated the repairing and fortifying effects of TCM on gut barriers from the perspective of gut microbiota and its metabolites. However, no review has summarized the mechanism behand this beneficiary effects of TCM. In this review, we first briefly introduce the unique structure and specific function of gut barrier. Then, we summarize the interactions and relationship amidst gut microbiota, gut microbiota metabolites and TCM. Further, we summarize the regulative effects and mechanisms of TCM on gut barrier including physical barrier, chemical barrier, immunological barrier, and microbial barrier. At last, we discuss the effects of TCM on diseases that are associated gut barrier destruction such as ulcerative colitis and type 2 diabetes. Our review can provide insights into TCM, gut barrier and gut microbiota.

Microbial bile acid metabolite ameliorates mycophenolate mofetil-induced gastrointestinal toxicity through vitamin D3 receptor

Mycophenolate mofetil (MMF) is one of the most used immunosuppressive drugs in organ transplantation, but frequent gastrointestinal (GI) side effects through unknown mechanisms limit its clinical use. Gut microbiota and its metabolites were recently reported to play a vital role in MMF-induced GI toxicity, but the specific mechanism of how they interact with the human body is still unclear. Here, we found that secondary bile acids (BAs), as bacterial metabolites, were significantly reduced by MMF administration in the gut of mice. Microbiome data and fecal microbiota transfer model supported a microbiota-dependent effect on the reduction of secondary BAs. Supplementation of the secondary BA lithocholic acid alleviated MMF-induced weight loss, colonic inflammation, and oxidative phosphorylation damage. Genetic deletion of the vitamin D3 receptor (VDR), which serves as a primary colonic BA receptor, in colonic epithelial cells (VDRΔIEC) abolished the therapeutic effect of lithocholic acid on MMF-induced GI toxicity. Impressively, we discovered that paricalcitol, a Food and Drug Administration-approved VDR agonist that has been used in clinics for years, could effectively alleviate MMF-induced GI toxicity. Our study reveals a previously unrecognized mechanism of gut microbiota, BAs, and VDR signaling in MMF-induced GI side effects, offering potential therapeutic strategies for clinics.

Dietary iron intake has long-term effects on the fecal metabolome and microbiome

Iron is essential for life, but its imbalances can lead to severe health implications. Iron deficiency is the most common nutrient disorder worldwide, and iron dysregulation in early life has been found to cause long-lasting behavioral, cognitive, and neural effects. However, little is known about the effects of dietary iron on gut microbiome function and metabolism. In this study, we sought to investigate the impact of dietary iron on the fecal metabolome and microbiome by using mice fed with three diets with different iron content: an iron deficient, an iron sufficient (standard), and an iron overload diet for 7 weeks. Additionally, we sought to understand whether any observed changes would persist past the 7-week period of diet intervention. To assess this, all feeding groups were switched to a standard diet, and this feeding continued for an additional 7 weeks. Analysis of the fecal metabolome revealed that iron overload and deficiency significantly alter levels of peptides, nucleic acids, and lipids, including di- and tri-peptides containing branched-chain amino acids, inosine and guanosine, and several microbial conjugated bile acids. The observed changes in the fecal metabolome persist long after the switch back to a standard diet, with the cecal gut microbiota composition and function of each group distinct after the 7-week standard diet wash-out. Our results highlight the enduring metabolic consequences of nutritional imbalances, mediated by both the host and gut microbiome, which persist after returning to the original standard diets.

The changing metabolic landscape of bile acids - keys to metabolism and immune regulation

Bile acids regulate nutrient absorption and mitochondrial function, they establish and maintain gut microbial community composition and mediate inflammation, and they serve as signalling molecules that regulate appetite and energy homeostasis. The observation that there are hundreds of bile acids, especially many amidated bile acids, necessitates a revision of many of the classical descriptions of bile acids and bile acid enzyme functions. For example, bile salt hydrolases also have transferase activity. There are now hundreds of known modifications to bile acids and thousands of bile acid-associated genes, especially when including the microbiome, distributed throughout the human body (for example, there are >2,400 bile salt hydrolases alone). The fact that so much of our genetic and small-molecule repertoire, in both amount and diversity, is dedicated to bile acid function highlights the centrality of bile acids as key regulators of metabolism and immune homeostasis, which is, in large part, communicated via the gut microbiome.

Postbiotics Prepared Using Lactobacillus reuteri Ameliorates Ethanol-Induced Liver Injury by Regulating the FXR/SHP/SREBP-1c Axis

SCOPE

While probiotics-based therapies have exhibited potential in alleviating alcohol-associated liver disease (ALD), the specific role of postbiotics derived from Lactobacillus reuteri (L. reuteri) in ALD remains elusive. This study aims to investigate the impact of postbiotics on ameliorating alcohol-induced hepatic steatosis and the underlying mechanisms.

METHODS AND RESULTS

Using network pharmacology, the study elucidates the targets and pathways impacted by postbiotics from L. reuteri, identifying the farnesoid X receptor (FXR) as a promising target for postbiotics against ALD, and lipid metabolism and alcoholism act as crucial pathways associated with postbiotics-targeting ALD. Furthermore, the study conducts histological and biochemical analyses coupled with LC/MS to evaluate the protective effects and mechanisms of postbiotics against ALD. Postbiotics may modulate bile acid metabolism in vivo by regulating FXR signaling, activating the FXR/FGF15 pathway, and influencing the enterohepatic circulation of bile acids (BAs). Subsequently, postbiotics regulate hepatic FXR activated by BAs and modulate the expression of FXR-mediated protein, including short regulatory partner (SHP) and sterol regulatory element binding protein-1c (SREBP-1c), thereby ameliorating hepatic steatosis in mice with ALD.

CONCLUSION

Postbiotics effectively alleviate ethanol-induced hepatic steatosis by regulating the FXR/SHP/SREBP-1c axis, as rigorously validated in both in vivo and in vitro.

Saponin monomers: Potential candidates for the treatment of type 2 diabetes mellitus and its complications

Type 2 diabetes mellitus (T2DM), a metabolic disease with persistent hyperglycemia primarily caused by insulin resistance (IR), has become one of the most serious health challenges of the 21st century, with considerable economic and societal implications worldwide. Considering the inevitable side effects of conventional antidiabetic drugs, natural ingredients exhibit promising therapeutic efficacy and can serve as safer and more cost-effective alternatives for the management of T2DM. Saponins are a structurally diverse class of amphiphilic compounds widely distributed in many popular herbal medicinal plants, some animals, and marine organisms. There are many saponin monomers, such as ginsenoside compound K, ginsenoside Rb1, ginsenoside Rg1, astragaloside IV, glycyrrhizin, and diosgenin, showing great efficacy in the treatment of T2DM and its complications in vivo and in vitro. However, although the mechanisms of action of saponin monomers at the animal and cell levels have been gradually elucidated, there is a lack of clinical data, which hinders the development of saponin-based antidiabetic drugs. Herein, the main factors/pathways associated with T2DM and the comprehensive underlying mechanisms and potential applications of these saponin monomers in the management of T2DM and its complications are reviewed and discussed, aiming to provide fundamental data for future high-quality clinical studies and trials.

Bile acid metabolism in health and ageing-related diseases

Bile acids (BAs) have surpassed their traditional roles as lipid solubilizers and regulators of BA homeostasis to emerge as important signalling molecules. Recent research has revealed a connection between microbial dysbiosis and metabolism disruption of BAs, which in turn impacts ageing-related diseases. The human BAs pool is primarily composed of primary BAs and their conjugates, with a smaller proportion consisting of secondary BAs. These different BAs exert complex effects on health and ageing-related diseases through several key nuclear receptors, such as farnesoid X receptor and Takeda G protein-coupled receptor 5. However, the underlying molecular mechanisms of these effects are still debated. Therefore, the modulation of signalling pathways by regulating synthesis and composition of BAs represents an interesting and novel direction for potential therapies of ageing-related diseases. This review provides an overview of synthesis and transportion of BAs in the healthy body, emphasizing its dependence on microbial community metabolic capacity. Additionally, the review also explores how ageing and ageing-related diseases affect metabolism and composition of BAs. Understanding BA metabolism network and the impact of their nuclear receptors, such as farnesoid X receptor and G protein-coupled receptor 5 agonists, paves the way for developing therapeutic agents for targeting BA metabolism in various ageing-related diseases, such as metabolic disorder, hepatic injury, cardiovascular disease, renal damage and neurodegenerative disease.

Progress in the Management of Patients with Cholestatic Liver Disease: Where Are We and Where Are We Going?

Cholestatic liver disease is a group of diseases in which bile acid accumulates in the liver for various reasons, resulting in abnormal liver biochemical indicators and histological damage. Cholestasis can be divided into intrahepatic cholestasis and extrahepatic cholestasis, which will contribute to liver damage and progress to liver fibrosis and cirrhosis. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis are the two most typical cholestatic liver diseases. Ursodeoxycholic acid is currently the first-line treatment for PBC, while obeticholic acid, budesonide and fibrates have also shown good potential in the treatment of PBC. There are currently no official drugs approved to treat primary sclerosing cholangitis, and the use of ursodeoxycholic acid may have certain clinical benefits. At present, progress has been made in new treatment directions for cholestatic liver disease, including fibroblast growth factor 19, cholestyramine, S-adenosyl-L-methionine, steroid drugs, farnesoid X receptor agonists, and more. Considerable progress has been made in the management of cholestatic liver disease but there are still many opportunities and challenges. In this review, we summarized the recommended guidelines for the management of cholestatic disease and the progress of new drug research and development, in order to provide an important reference for the clinical practice of cholestatic liver disease.

Sex differences in lipidomic and bile acid plasma profiles in patients with and without coronary artery disease

BACKGROUND

Lipids, including phospholipids and bile acids, exert various signaling effects and are thought to contribute to the development of coronary artery disease (CAD). Here, we aimed to compare lipidomic and bile acid profiles in the blood of patients with and without CAD stratified by sex.

METHODS

From 2015 to 2022, 3,012 patients who underwent coronary angiography were recruited in the INTERCATH cohort. From the overall cohort, subgroups were defined using patient characteristics such as CAD vs. no CAD, 1st vs. 3rd tertile of LDL-c, and female vs. male sex. Hereafter, a matching algorithm based on age, BMI, hypertension status, diabetes mellitus status, smoking status, the Mediterranean diet score, and the intake of statins, triglycerides, HDL-c and hs-CRP in a 1:1 ratio was implemented. Lipidomic analyses of stored blood samples using the Lipidyzer platform (SCIEX) and bile acid analysis using liquid chromatography with tandem mass spectrometry (LC‒MS/MS) were carried out.

RESULTS

A total of 177 matched individuals were analyzed; the median ages were 73.5 years (25th and 75th percentile: 64.1, 78.2) and 71.9 years (65.7, 77.2) for females and males with CAD, respectively, and 67.6 years (58.3, 75.3) and 69.2 years (59.8, 76.8) for females and males without CAD, respectively. Further baseline characteristics, including cardiovascular risk factors, were balanced between the groups. Women with CAD had decreased levels of phosphatidylcholine and diacylglycerol, while no differences in bile acid profiles were detected in comparison to those of female patients without CAD. In contrast, in male patients with CAD, decreased concentrations of the secondary bile acid species glycolithocholic and lithocholic acid, as well as altered levels of specific lipids, were detected compared to those in males without CAD. Notably, male patients with low LDL-c and CAD had significantly greater concentrations of various phospholipid species, particularly plasmalogens, compared to those in high LDL-c subgroup.

CONCLUSIONS

We present hypothesis-generating data on sex-specific lipidomic patterns and bile acid profiles in CAD patients. The data suggest that altered lipid and bile acid composition might contribute to CAD development and/or progression, helping to understand the different disease trajectories of CAD in women and men.

REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04936438 , Unique identifier: NCT04936438.

A Prebiotic Diet Containing Galactooligosaccharides and Polydextrose Produces Dynamic and Reproducible Changes in the Gut Microbial Ecosystem in Male Rats

Despite substantial evidence supporting the efficacy of prebiotics for promoting host health and stress resilience, few experiments present evidence documenting the dynamic changes in microbial ecology and fecal microbially modified metabolites over time. Furthermore, the literature reports a lack of reproducible effects of prebiotics on specific bacteria and bacterial-modified metabolites. The current experiments examined whether consumption of diets enriched in prebiotics (galactooligosaccharides (GOS) and polydextrose (PDX)), compared to a control diet, would consistently impact the gut microbiome and microbially modified bile acids over time and between two research sites. Male Sprague Dawley rats were fed control or prebiotic diets for several weeks, and their gut microbiomes and metabolomes were examined using 16S rRNA gene sequencing and untargeted LC-MS/MS analysis. Dietary prebiotics altered the beta diversity, relative abundance of bacterial genera, and microbially modified bile acids over time. PICRUSt2 analyses identified four inferred functional metabolic pathways modified by the prebiotic diet. Correlational network analyses between inferred metabolic pathways and microbially modified bile acids revealed deoxycholic acid as a potential network hub. All these reported effects were consistent between the two research sites, supporting the conclusion that dietary prebiotics robustly changed the gut microbial ecosystem. Consistent with our previous work demonstrating that GOS/PDX reduces the negative impacts of stressor exposure, we propose that ingesting a diet enriched in prebiotics facilitates the development of a health-promoting gut microbial ecosystem.

Bile acid metabolism is altered in learning and memory impairment induced by chronic lead exposure

Lead is a neurotoxic contaminant that exists widely in the environment. Although lead neurotoxicity has been found to be tightly linked to gut microbiota disturbance, the effect of host metabolic disorders caused by gut microbiota disturbance on lead neurotoxicity has not been investigated. In this work, the results of new object recognition tests and Morris water maze tests showed that chronic low-dose lead exposure caused learning and memory dysfunction in mice. The results of 16 S rRNA sequencing of cecal contents and fecal microbiota transplantation showed that the neurotoxicity of lead could be transmitted through gut microbiota. The results of untargeted metabolomics and bile acid targeted metabolism analysis showed that the serum bile acid metabolism profile of lead-exposed mice was significantly changed. In addition, supplementation with TUDCA or INT-777 significantly alleviated chronic lead exposure-induced learning and memory impairment, primarily through inhibition of the NLRP3 inflammasome in the hippocampus to relieve neuroinflammation. In conclusion, our findings suggested that dysregulation of host bile acid metabolism may be one of the mechanisms of lead-induced neurotoxicity, and supplementation of specific bile acids may be a possible therapeutic strategy for lead-induced neurotoxicity.

Mesenchymal stem cell-derived exosomes promote tissue repair injury in rats with liver trauma by regulating gut microbiota and metabolism

OBJECTIVE

The effects of mesenchymal stem cells (MSCs) and MSC-derived exosomes (MSC-exos) on serum metabolites and intestinal microbiota in rats after liver trauma were discussed.

METHODS

Adult Wistar Albino rats were assigned into control, model (liver trauma), MSCs, and MSC-exos groups (n = 6). The study examined changes in the inflammatory environment in liver tissues were analyzed by histological examination and analysis of macrophage phenotypes. Alterations in serum metabolites were determined by untargeted metabonomics, and gut microbiota composition was characterized by 16S rDNA sequencing. Correlations between specific gut microbiota, metabolites, and inflammatory response were calculated using Spearman correlation analysis.

RESULTS

Rats with liver trauma after MSCs and MSC-exos treatment exhibited attenuated inflammatory infiltration and necrosis in liver tissues. MSCs and MSC-exos treatment reduced the proportion of M1 macrophages, accompanied by a decrease in inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-α) levels. Furthermore, MSCs and MSC-exos treatment expanded the proportion of M2 macrophages, accompanied by an increase in arginase-1 (Arg-1) and interleukin-10 (IL-10) levels. The beneficial effects of MSC-exo treatment on rats with liver trauma were superior to those of MSC treatment. The composition and abundance of the gut microbiota and metabolites were altered in pathological rats, whereas MSC and MSC-exo intervention partially restored specific gut microbiota and metabolite alterations. At the phylum level, alterations in Bacteroidota, Proteobacteria, and Verrucomicrobiota were observed after MSC and MSC-exo intervention. At the genus level, Intestinimonas, Alistipes, Aerococcus, Faecalibaculum, and Lachnospiraceae_ND3007_group were the main differential microbiota. 6-Methylnicotinamide, N-Methylnicotinamide, Glutathione, oxidized, ISOBUTYRATE, ASCORBATE, EICOSAPENTAENOATE, GLYCEROL 3-PHOSPHATE, and Ascorbate radical were selected as important differential metabolites. There was a clear correlation between Ascorbate, Intestinimonas/Faecalibaculum and inflammatory cytokines.

CONCLUSION

MSC-exos promoted the repair of tissue damage in rats with liver trauma by regulating serum metabolites and intestinal microbiota, providing new insights into how MSC-exos reduced inflammation in rats with liver trauma.

Evolutionary analysis of SLC10 family members and insights into function and expression regulation of lamprey NTCP

The Na ( +)-taurocholate cotransporting polypeptide (NTCP) is a member of the solute carrier family 10 (SLC10), which consists of 7 members (SLC10a1-SLC10a7). NTCP is a transporter localized to the basolateral membrane of hepatocytes and is primarily responsible for the absorption of bile acids. Although mammalian NTCP has been extensively studied, little is known about the lamprey NTCP (L-NTCP). Here we show that L-NTCP follows the biological evolutionary history of vertebrates, with conserved domain, motif, and similar tertiary structure to higher vertebrates. L-NTCP is localized to the cell surface of lamprey primary hepatocytes by immunofluorescence analysis. HepG2 cells overexpressing L-NTCP also showed the distribution of L-NTCP on the cell surface. The expression profile of L-NTCP showed that the expression of NTCP is highest in lamprey liver tissue. L-NTCP also has the ability to transport bile acids, consistent with its higher vertebrate orthologs. Finally, using a farnesoid X receptor (FXR) antagonist, RT-qPCR and flow cytometry results showed that L-NTCP is negatively regulated by the nuclear receptor FXR. This study is important for understanding the adaptive mechanisms of bile acid metabolism after lamprey biliary atresia based on understanding the origin, evolution, expression profile, biological function, and expression regulation of L-NTCP.

Glycoursodeoxycholic Acid Alleviates Arterial Thrombosis via Suppressing Diacylglycerol Kinases Activity in Platelet

BACKGROUND

Glycoursodeoxycholic acid (GUDCA) has been acknowledged for its ability to regulate lipid homeostasis and provide benefits for various metabolic disorders. However, the impact of GUDCA on arterial thrombotic events remains unexplored. The objective of this study is to examine the effects of GUDCA on thrombogenesis and elucidate its underlying mechanisms.

METHODS

Plasma samples from patients with arterial thrombotic events and diet-induced obese mice were collected to determine the GUDCA concentrations using mass spectrometry. Multiple in vivo murine thrombosis models and in vitro platelet functional assays were conducted to comprehensively evaluate the antithrombotic effects of GUDCA. Moreover, lipidomic analysis was performed to identify the alterations of intraplatelet lipid components following GUDCA treatment.

RESULTS

Plasma GUDCA level was significantly decreased in patients with arterial thrombotic events and negatively correlated with thrombotic propensity in diet-induced obese mice. GUDCA exhibited prominent suppressing effects on platelet reactivity as evidenced by the attenuation of platelet activation, secretion, aggregation, spreading, and retraction (P<0.05). In vivo, GUDCA administration robustly alleviated thrombogenesis (P<0.05) without affecting hemostasis. Mechanistically, GUDCA inhibited DGK (diacylglycerol kinase) activity, leading to the downregulation of the phosphatidic acid-mediated signaling pathway. Conversely, phosphatidic acid supplementation was sufficient to abolish the antithrombotic effects of GUDCA. More importantly, long-term oral administration of GUDCA normalized the enhanced DGK activity, thereby remarkably alleviating the platelet hyperreactivity as well as the heightened thrombotic tendency in diet-induced obese mice (P<0.05).

CONCLUSIONS

Our study implicated that GUDCA reduces platelet hyperreactivity and improves thrombotic propensity by inhibiting DGKs activity, which is a potentially effective prophylactic approach and promising therapeutic agent for arterial thrombotic events.

Hepatic interoception in health and disease

The liver is a large organ with crucial functions in metabolism and immune defense, as well as blood homeostasis and detoxification, and it is clearly in bidirectional communication with the brain and rest of the body via both neural and humoral pathways. A host of neural sensory mechanisms have been proposed, but in contrast to the gut-brain axis, details for both the exact site and molecular signaling steps of their peripheral transduction mechanisms are generally lacking. Similarly, knowledge about function-specific sensory and motor components of both vagal and spinal access pathways to the hepatic parenchyma is missing. Lack of progress largely owes to controversies regarding selectivity of vagal access pathways and extent of hepatocyte innervation. In contrast, there is considerable evidence for glucose sensors in the wall of the hepatic portal vein and their importance for glucose handling by the liver and the brain and the systemic response to hypoglycemia. As liver diseases are on the rise globally, and there are intriguing associations between liver diseases and mental illnesses, it will be important to further dissect and identify both neural and humoral pathways that mediate hepatocyte-specific signals to relevant brain areas. The question of whether and how sensations from the liver contribute to interoceptive self-awareness has not yet been explored.

Fermented bile acids improved growth performance and intestinal health by altering metabolic profiles and intestinal microbiome in Micropterus salmoides

A type of fermented bile acids (FBAs) has been produced through a biological method, and its effects on growth performance, metabolism, and intestinal microbiota in largemouth bass were investigated. The results demonstrated that incorporating 0.03 %-0.05 % FBAs diet could improve the final weight, weight gain and specific growth rate, and decrease the feed conversion ratio. Dietary FBAs did not significantly affect the levels of high-density lipoprotein, low-density lipoprotein, and triglycerides, but decreased the activities of α-amylase in most groups. Adding FBAs to the diet significantly increased the integrity of the microscopic structure of the intestine, thickened the muscular layer of the intestine, and notably enhanced its intestinal barrier function. The addition of FBAs to the diet increased the diversity of the gut microbiota in largemouth bass. At the phylum level, there was an increase in the abundance of Proteobacteria, Firmicutes, Tenericutes and Cyanobacteria and a significant decrease in Actinobacteria and Bacteroidetes. At the genus level, the relative abundance of beneficial bacteria Mycoplasma in the GN6 group and Coprococcus in the GN4 group significantly increased, while the pathogenic Enhydrobacter was inhibited. Meanwhile, the highest levels of AKP and ACP were observed in the groups treated with 0.03 % FBAs, while the highest levels of TNF-α and IL-10 were detected in the group treated with 0.04 % FBAs. Additionally, the highest levels of IL-1β, IL-8T, GF-β, IGF-1, and IFN-γ were noted in the group treated with 0.06 % FBAs. These results suggested that dietary FBAs improved growth performance and intestinal wall health by altering lipid metabolic profiles and intestinal microbiota in largemouth bass.

Characterization of individual bile acids in vivo utilizing a novel low bile acid mouse model

Bile acids (BAs) are signaling molecules synthesized in the liver initially by CYP7A1 and CYP27A1 in the classical and alternative pathways, respectively. BAs are essential for cholesterol clearance, intestinal absorption of lipids, and endogenous modulators of farnesoid x receptor (FXR). FXR is critical in maintaining BA homeostasis and gut-liver crosstalk. Complex reactions in vivo and the lack of suitable animal models impede our understanding of the functions of individual BAs. In this study, we characterized the in vivo effects of three-day feeding of cholic acid (CA), deoxycholic acid (DCA), or ursodeoxycholic acid (UDCA) at physiological/non-hepatotoxic concentrations in a novel low-BA mouse model (Cyp7a1-/-/Cyp27a1-/-, DKO). Liver injury, BA levels and composition and BA signaling by the FXR-fibroblast growth factor 15 (FGF15) axis were determined. Overall, higher basal inflammation and altered lipid metabolism in DKO mice might be associated with low BAs. CA, DCA, and UDCA feeding activated FXR signals with tissue specificity. Dietary CA and DCA similarly altered tissue BA profiles to be less hydrophobic, while UDCA promoted a more hydrophobic tissue BA pool with the profiles shifted toward non-12α-OH BAs and secondary BAs. However, UDCA did not offer any overt protective effects as expected. These findings allow us to determine the precise effects of individual BAs in vivo on BA-FXR signaling and overall BA homeostasis in liver physiology and pathologies.

Surgery for Crohn's Disease Is Associated With a Dysbiotic Microbiome and Metabolome: Results From Two Prospective Cohorts

BACKGROUND & AIMS

Crohn's disease is associated with alterations in the gut microbiome and metabolome described as dysbiosis. We characterized the microbial and metabolic consequences of ileal resection, the most common Crohn's disease surgery.

METHODS

Patients with and without intestinal resection were identified from the Diet to Induce Remission in Crohn's Disease and Study of a Prospective Adult Research Cohort with Inflammatory Bowel Disease studies. Stool samples were analyzed with shotgun metagenomics sequencing. Fecal butyrate was measured with 1H nuclear magnetic resonance spectroscopy. Fecal bile acids and plasma 7α-hydroxy-4-cholesten-3-one (C4) was measured with mass spectrometry.

RESULTS

Intestinal resection was associated with reduced alpha diversity and altered beta diversity with increased Proteobacteria and reduced Bacteroidetes and Firmicutes. Surgery was associated with higher representation of genes in the KEGG pathway for ABC transporters and reduction in genes related to bacterial metabolism. Surgery was associated with reduced concentration of the But gene but this did not translate to reduced fecal butyrate concentration. Surgery was associated with decreased abundance of bai operon genes, with increased plasma C4 concentration, increased primary bile acids and reduced secondary bile acids, including isoLCA. Additionally, Egerthella lenta, Adlercreutzia equalofaciens, and Gordonibacter pamelaeae were lower in abundance among patients with prior surgery in both cohorts.

CONCLUSIONS

In 2 different populations, prior surgery in Crohn's disease is associated with altered fecal microbiome. Patients who had undergone ileal resection had reduction in the potentially beneficial bacteria E lenta and related actinobacteria and secondary bile acids, including isoLCA, suggesting that these could be biomarkers of patients at higher risk for disease progression.

Bile acids and coronavirus disease 2019

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been significantly alleviated. However, long-term health effects and prevention strategy remain unresolved. Thus, it is essential to explore the pathophysiological mechanisms and intervention for SARS-CoV-2 infection. Emerging research indicates a link between COVID-19 and bile acids, traditionally known for facilitating dietary fat absorption. The bile acid ursodeoxycholic acid potentially protects against SARS-CoV-2 infection by inhibiting the farnesoid X receptor, a bile acid nuclear receptor. The activation of G-protein-coupled bile acid receptor, another membrane receptor for bile acids, has also been found to regulate the expression of angiotensin-converting enzyme 2, the receptor through which the virus enters human cells. Here, we review the latest basic and clinical evidence linking bile acids to SARS-CoV-2, and reveal their complicated pathophysiological mechanisms.

Changes in bile acid subtypes and improvements in lipid metabolism and atherosclerotic cardiovascular disease risk: the Preventing Overweight Using Novel Dietary Strategies (POUNDS Lost) trial

BACKGROUND

Distinct circulating bile acid (BA) subtypes may play roles in regulating lipid homeostasis and atherosclerosis.

OBJECTIVES

We investigated whether changes in circulating BA subtypes induced by weight-loss dietary interventions were associated with improved lipid profiles and atherosclerotic cardiovascular disease (ASCVD) risk estimates.

METHODS

This study included adults with overweight or obesity (n = 536) who participated in a randomized weight-loss dietary intervention trial. Circulating primary and secondary unconjugated BAs and their taurine-/glycine-conjugates were measured at baseline and 6 mo after the weight-loss diet intervention. The ASCVD risk estimates were calculated using the validated equations.

RESULTS

At baseline, higher concentrations of specific BA subtypes were related to higher concentrations of atherogenic very low-density lipoprotein lipid subtypes and ASCVD risk estimates. Weight-loss diet-induced decreases in primary BAs were related to larger reductions in triglycerides and total cholesterol [every 1 standard deviation (SD) decrease of glycocholate, glycochenodeoxycholate, or taurochenodeoxycholate was related to β (standard error) -3.3 (1.3), -3.4 (1.3), or -3.8 (1.3) mg/dL, respectively; PFDR < 0.05 for all]. Greater decreases in specific secondary BA subtypes were also associated with improved lipid metabolism at 6 mo; there was β -4.0 (1.1) mg/dL per 1-SD decrease of glycoursodeoxycholate (PFDR =0.003) for changes in low-density lipoprotein cholesterol. We found significant interactions (P-interaction < 0.05) between dietary fat intake and changes in BA subtypes on changes in ASCVD risk estimates; decreases in primary and secondary BAs (such as conjugated cholate or deoxycholate) were significantly associated with improved ASCVD risk after consuming a high-fat diet, but not after consuming a low-fat diet.

CONCLUSIONS

Decreases in distinct BA subtypes were associated with improved lipid profiles and ASCVD risk estimates, highlighting the importance of changes in circulating BA subtypes as significant factors linked to improved lipid metabolism and ASCVD risk estimates in response to weight-loss dietary interventions. Habitual dietary fat intake may modify the associations of changes in BAs with ASCVD risk. This trial was registered at clinicaltrials.gov as NCT00072995.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Baicalein alleviates intrahepatic cholestasis by regulating bile acid metabolism via an FXR-dependent manner

Cholestasis is characterized by impaired bile secretion and flow, leading to the accumulation of toxic bile acids in the liver, further causing inflammatory reaction, fibrosis, and ultimately liver transplantation. Although first-line clinical agents such as Ursodeoxycholic acid (UDCA) and Obeticholic acid (OCA) are available, serious side effects still exist. Therefore, pharmacologic treatment of cholestatic liver disease remains challenging. Here, we used a murine model of cholestasis treated with or without intraperitoneal injection of baicalein and found that baicalein could attenuate 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced inflammatory response, ductular reaction, liver fibrosis, and bile acid metabolism disorders. Furthermore, the therapeutic effect of baicalein was hampered in the presence of Guggulsterone (GS), an Farnesoid X receptor (FXR) antagonist. These results indicated that baicalein alleviated DDC diet-induced cholestatic liver injury in an FXR-dependent manner.

Intestinal FGF15 regulates bile acid and cholesterol metabolism but not glucose and energy balance

Fibroblast growth factor 15/19 (FGF15/19, mouse/human ortholog) is expressed in the ileal enterocytes of the small intestine and released postprandially in response to bile acid absorption. Previous reports of FGF15-/- mice have limited our understanding of gut-specific FGF15's role in metabolism. Therefore, we studied the role of endogenous gut-derived FGF15 in bile acid, cholesterol, glucose, and energy balance. We found that circulating levels of FGF19 were reduced in individuals with obesity and comorbidities, such as type 2 diabetes and metabolic dysfunction-associated fatty liver disease. Gene expression analysis of ileal FGF15-positive cells revealed differential expression during the obesogenic state. We fed standard chow or a high-fat metabolic dysfunction-associated steatohepatitis-inducing diet to control and intestine-derived FGF15-knockout (FGF15INT-KO) mice. Control and FGF15INT-KO mice gained similar body weight and adiposity and did not show genotype-specific differences in glucose, mixed meal, pyruvate, and glycerol tolerance. FGF15INT-KO mice had increased systemic bile acid levels but decreased cholesterol levels, pointing to a primary role for gut-derived FGF15 in regulating bile acid and cholesterol metabolism when exposed to obesogenic diet. These studies show that intestinal FGF15 plays a specific role in bile acid and cholesterol metabolism regulation but is not essential for energy and glucose balance.

The gut microbiome as a modulator of arterial function and age-related arterial dysfunction

The arterial system is integral to the proper function of all other organs and tissues. Arterial function is impaired with aging, and arterial dysfunction contributes to the development of numerous age-related diseases, including cardiovascular diseases. The gut microbiome has emerged as an important regulator of both normal host physiological function and impairments in function with aging. The purpose of this review is to summarize more recently published literature demonstrating the role of the gut microbiome in supporting normal arterial development and function and in modulating arterial dysfunction with aging in the absence of overt disease. The gut microbiome can be altered due to a variety of exposures, including physiological aging processes. We explore mechanisms by which the gut microbiome may contribute to age-related arterial dysfunction, with a focus on changes in various gut microbiome-related compounds in circulation. In addition, we discuss how modulating circulating levels of these compounds may be a viable therapeutic approach for improving artery function with aging. Finally, we identify and discuss various experimental considerations and research gaps/areas of future research.

Integrated gut metabolome and microbiome fingerprinting reveals that dysbiosis precedes allergic inflammation in IgE-mediated pediatric cow's milk allergy

BACKGROUND

IgE-mediated cow's milk allergy (IgE-CMA) is one of the first allergies to arise in early childhood and may result from exposure to various milk allergens, of which β-lactoglobulin (BLG) and casein are the most important. Understanding the underlying mechanisms behind IgE-CMA is imperative for the discovery of novel biomarkers and the design of innovative treatment and prevention strategies.

METHODS

We report a longitudinal in vivo murine model, in which two mice strains (BALB/c and C57Bl/6) were sensitized to BLG using either cholera toxin or an oil emulsion (n = 6 per group). After sensitization, mice were challenged orally, their clinical signs monitored, antibody (IgE and IgG1) and cytokine levels (IL-4 and IFN-γ) measured, and fecal samples subjected to metabolomics. The results of the murine models were further extrapolated to fecal microbiome-metabolome data from our population of IgE-CMA (n = 22) and healthy (n = 23) children (Trial: NCT04249973), on which polar metabolomics, lipidomics and 16S rRNA metasequencing were performed. In vitro gastrointestinal digestions and multi-omics corroborated the microbial origin of proposed metabolic changes.

RESULTS

During mice sensitization, we observed multiple microbially derived metabolic alterations, most importantly bile acid, energy and tryptophan metabolites, that preceded allergic inflammation. We confirmed microbial dysbiosis, and its associated effect on metabolic alterations in our patient cohort, through in vitro digestions and multi-omics, which was accompanied by metabolic signatures of low-grade inflammation.

CONCLUSION

Our results indicate that gut dysbiosis precedes allergic inflammation and nurtures a chronic low-grade inflammation in children on elimination diets, opening important new opportunities for future prevention and treatment strategies.