Altered fecal bile acid composition in active ulcerative colitis

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

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

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.

Unique sterol metabolite shifts in inflammatory bowel disease and primary sclerosing cholangitis

Inflammatory bowel disease (IBD) triggers chronic intestinal inflammation and is linked to primary sclerosing cholangitis (PSC). Cholesterol homeostasis, tightly regulated under normal conditions, becomes disrupted in both inflammation and chronic liver disease. We analyzed fecal and serum levels of cholesterol synthesis precursors, oxysterols, and phytosterols in 87 patients with IBD (81 for serum analysis) including patients with Crohn's disease (CD) and ulcerative colitis (UC), 11 patients with PSC, 21 patients with PSC-IBD (18 for serum analysis), and 16 healthy controls (17 for serum analysis). Cholesterol was analysed by flow injection analysis on a high-resolution hybrid quadrupole-Orbitrap mass spectrometer and further serum sterols and all fecal sterols were analysed by a gas chromatograph mass spectrometer. Serum levels of lanosterol, 7-dehydrocholesterol, 7-beta-hydroxycholesterol, 27-hydroxycholesterol, and the plant sterols campesterol, stigmasterol, and sitosterol were similar across control and patient groups. Notably, serum lathosterol was elevated in CD patients compared to those with UC, PSC, PSC-IBD, and healthy controls. All other serum and fecal sterols showed no differences between CD and UC. Cholesterol synthesis precursors in serum, serum cholesterol levels, and both serum and fecal plant sterol levels decreased with increasing IBD severity. Consequently, serum cholesterol, campesterol, sitosterol, and fecal 5-beta sitostanol and 5-alpha sitostanol were negatively correlated with C-reactive protein and fecal calprotectin. The conversion of cholesterol to coprostanol in feces was impaired in IBD, PSC, and PSC-IBD, independent of bowel inflammation severity or liver disease extent. Patients with PSC, and to a lesser extent PSC-IBD, had elevated serum plant sterol levels, positively correlating with liver disease markers. In conclusion, in patients with IBD, cholesterol biosynthetic precursors, serum cholesterol levels, and fecal plant sterols decrease with intestinal inflammation. An inverse association of serum plant sterols with intestinal inflammation was observed in patients with IBD and a direct association of serum phytosterols with liver injury in patients with PSC. The conversion of fecal cholesterol to coprostanol was impaired in all patient cohorts. IBD and PSC alter serum sterol levels differently, whereas changes in fecal sterols are not disease specific and are moderate.

Pharmacological Mechanisms of Bile Acids Targeting the Farnesoid X Receptor

Bile acids (BAs), a category of amphiphilic metabolites synthesized by liver cells and released into the intestine via the bile duct, serve a vital role in the emulsification of ingested fats during the digestive process. Beyond their conventional emulsifying function, BAs, with their diverse structures, also act as significant hormones within the body. They are pivotal in facilitating nutrient absorption by interacting with the farnesoid X receptor (FXR), and they serve as key regulators of lipid and glucose metabolism, as well as immune system balance. Consequently, BAs contribute to the metabolism of glucose and lipids, enhance the digestion and absorption of lipids, and maintain the equilibrium of the bile pool. Their actions are instrumental in addressing obesity, managing cholestasis, and treating diabetes, and are involved in the onset and progression of cancer. This paper presents an updated systematic review of the pharmacological mechanisms by which BAs target the FXR, incorporating recent findings and discussing their signaling pathways in the context of novel research, including their distinct roles in various disease states and populations. The aim is to provide a theoretical foundation for the continued research and clinical application of BAs.

Bile Acids in Inflammatory Bowel Disease: From Pathophysiology to Treatment

Inflammatory bowel disease (IBD) is a chronic condition that affects about 7 million people worldwide, and new therapies are needed. Understanding the complex roles that bile acids (BAs) play in IBD may lead to the development of novel IBD treatments independent of direct immunosuppression. This review discusses the latest discoveries in the roles BAs play in IBD pathogenesis and explores how these discoveries offer promising new therapeutic targets to treat IBD and improve patient outcomes. Several therapies discussed include specific BA receptor (BAR) agonists, dietary therapies, supplements, probiotics, and mesenchymal stem cell therapies that have all been shown to decrease IBD disease activity.

Depletion of key gut bacteria predicts disrupted bile acid metabolism in inflammatory bowel disease

The gut microbiome plays a key role in bile acid (BA) metabolism, where a diversity of metabolic products contribute to human health and disease. In particular, Inflammatory Bowel Disease (IBD) is characterized by a low concentration of secondary bile acids (SBAs), whose transformation from primary bile acids (PBAs) is an essential function performed solely by gut bacteria. BA-transformation activity mediated by the bile acid inducible (bai) operon has been functionally characterized in the genus Clostridium, and homologous bai gene sequences have been found in metagenome-assembled genomes (MAGs) belonging to other taxa in the human gut, but it is unclear which species of bai-carrying bacteria perform physiologically significant amounts of bile acid transformation in healthy and sick individuals. Here, we analyzed hundreds of stool samples with paired metagenomic and metabolomic data from IBD patients and controls and found that the abundance of the bai operon in metagenomic samples was highly predictive of that sample's high- or low-SBA metabolic state. We further found that bai genes from the Clostridium species best characterized as BA transformers were more prevalent in IBD patients than in non-IBD controls, while bai genes from uncharacterized taxa known only from MAGs were much more physiologically relevant in non-IBD samples. These un-isolated clades of BA-transforming bacteria merit further research; as beyond their prevalence in the human population, we found some cases in which they engrafted in IBD patients who had undergone fecal microbiota transplantation and experienced a clinical response.IMPORTANCEIn this paper, we identify specific bacteria that perform an important metabolic function in the human gut and demonstrate that in the guts of a large subset of patients with IBD, these bacteria are missing and the function is defective. This is a rare example where the correlation between the absence of specific bacteria and the dysfunction of metabolism is directly observed, not in mice nor in the lab, but in physiologic microbial communities in the human gut. Our results point to a path for studying how a small but important set of bacteria is affected by conditions in the IBD gut and perhaps to the development of interventions to mitigate the loss of these bacteria in IBD.

Fecal Nervonic Acid as a Biomarker for Diagnosing and Monitoring Inflammatory Bowel Disease

BACKGROUND/OBJECTIVES

Inflammatory bowel disease (IBD) is a chronic immune-mediated pathology associated with the dysregulation of lipid metabolism. The administration of nervonic acid, a very long-chain fatty acid, has been shown to improve colonic inflammation in a mouse model of colitis. Our study aimed to quantify fecal levels of nervonic acid, as well as the very long-chain fatty acids, lignoceric acid, and pentacosanoic acid, to identify associations with IBD activity.

METHODS

Stool samples were collected from 62 patients with IBD and 17 healthy controls. Nervonic acid, lignoceric acid, and pentacosanoic acid were quantified by gas chromatography coupled with mass spectrometry (GC-MS). Lipid levels, normalized to the dry weight of fecal homogenates, were used for calculations.

RESULTS

Patients with IBD exhibited elevated fecal nervonic acid levels compared to healthy controls, with no significant differences observed between ulcerative colitis and Crohn's disease. A fecal nervonic acid concentration of 0.49 µmol/g distinguished IBD patients from controls, achieving a sensitivity of 71% and a specificity of 82%. Fecal nervonic acid levels showed a positive correlation with both C-reactive protein and fecal calprotectin and increased proportionally with rising fecal calprotectin levels. IBD patients treated with corticosteroids or interleukin-12/23 antibodies had higher levels of fecal nervonic acid than those in other therapies, with no difference in serum C-reactive protein and calprotectin levels between these groups.

CONCLUSIONS

In summary, this analysis indicates that fecal nervonic acid may emerge as a novel specific biomarker for IBD diagnosis and disease monitoring.

Gut Microbiota Features in Relation to Fecal Microbiota Transplantation Outcome in Ulcerative Colitis: A Systematic Review and Meta-Analysis

BACKGROUND & AIMS

Fecal microbiota transplantation (FMT) can induce remission in patients with ulcerative colitis, yet its efficacy needs improvement. We conducted a comprehensive evaluation of the current literature on microbial factors affecting outcome, as well as a meta-analysis on some of the largest datasets regarding composition.

METHODS

MEDLINE, Embase, and Cochrane were systematically searched through August 2024 for relevant studies. The quality of studies was analyzed with JBI tools and a composite critical appraisal score. Additionally, species-level data from 2 landmark FMT trials (the Transplantation of Feces in Ulcerative Colitis; Returning Nature's Homeostasis [TURN] and Fecal Microbiota Transplantation for Chronic Active Ulcerative Colitis [FOCUS] trials) were reanalyzed from a compositional perspective.

RESULTS

Out of 3755 citations identified, 56 met the inclusion criteria, of which 29 fulfilled quality standards. Higher microbial α-diversity, either in donors or recipients (at baseline or following FMT treatment), was associated with better clinical response rates. Engraftment of the donors' microbiota could not be clearly linked with clinical response, possibly because not every donor has an ideal microbiome. Butyrate-producing species from the Lachnospiraceae and Oscillospiraceae families were often related with response, whereas the reverse was true for Fusobacteria, many Proteobacteria, and Ruminococcus gnavus. Compositional analyses showed that clinical response is associated with a shift from a low-diversity, often Bacteroides-dominant composition to one with higher diversity, either dominated by various butyrate producers, the Christensenellaceae-Methanobrevibacter trophic network, or a moderate/high-diversity composition with abundant but not excessive levels of Prevotella copri.

CONCLUSIONS

This systematic review/meta-analysis yielded a coherent picture from a compositional perspective, which may help identify beneficial donor profiles and guide personalized FMT approaches.

Disturbance of bile acids profile aggravates the diarrhea induced by capecitabine through inhibiting the Wnt/β-catenin pathway

INTRODUCTION

Diarrhea is the primary dose-limiting side effect of capecitabine(Cap) hindering its clinical application, but the mechanism is unclear. Clarifying this mechanism may enhance the patient compliance and improve the treatment outcome.

OBJECTIVES

To assess if the endogenous metabolic profile could prodict the diarrhea induced by Cap and explore and validate underlying mechanisms.

METHODS

Untargeted and targeted bile acids(BAs) metabolomics were performed to analyzed the metabolic profile of baseline samples from colorectal cancer(CRC) patients and the association with the diarrhea induced by Cap was assessed. The toxicity of BAs and Cap and its metabolites alone or their combinations to the human normal intestinal epithelial cell(HIEC) was assessed, and the key genes that mediated the BAs-enhanced toxicity of Cap were discovered by RNA-seq and then validated. A mouse model with high exposure levels of BAs was constructed and then treated with Cap to verify the Cap-induced diarrhea enhanced by BAs.

RESULTS

The baseline endogenous metabolic profile showed obviously difference between diarrhea and non-diarrhea CRC patients, and the differential metabolites mainly enriched in BAs metabolism; the deoxycholic acid(DCA) and lithocholic acid(LCA) were selected to be the key BAs that enhanced the toxicity of Cap metabolite 5-FU to the HIEC cell; the DCA and LCA could inhibit the Wnt/β-catenin signaling pathway, which then suppressed the P-glycoprotein and increased the exposure level of 5-FU in the HIEC cell. The results of animal experiment verified that the excessive DCA and LCA could aggravate the Cap-induced diarrhea through inhibiting Wnt/β-catenin-P-glycoprotein pathway.

CONCLUSIONS

The disordered BAs metabolic profile showed close relationship with diarrhea induced by Cap, and excessive DCA and LCA were proved to be the key BAs, which could aggravate the Cap-induced diarrhea through inhibiting Wnt/β-catenin-P-glycoprotein pathway.

Urinary soluble CD163 is a putative non-invasive biomarker for primary sclerosing cholangitis

Soluble CD163 (sCD163) is a selective marker of macrophages whose circulating levels have been found to be induced in patients with active inflammatory bowel disease (IBD). Urinary proteins are emerging as non-invasive diagnostic biomarkers, and here, sCD163 levels were measured in the urine of 18 controls and 63 patients with IBD by enzyme-linked immunosorbent assay. Urinary sCD163 levels did, however, not differentiate IBD patients from controls. Analysis of sCD163 in the serum of 51 of these patients did not show higher levels in IBD. Primary sclerosing cholangitis (PSC) is often associated with IBD, and sCD163 was higher in the urine of the 21 patients and in the serum of the 13 patients with PSC compared to patients with IBD. Of clinical relevance, urinary sCD163 levels were higher in PSC patients compared to those with other chronic liver diseases (n = 16), while serum sCD163 levels were comparable between the two groups. Serum sCD163 of IBD and PSC patients positively correlated with serum C-reactive protein. Serum creatinine and glomerular filtration rate, surrogate markers for renal function, did not significantly correlate with urinary or serum sCD163 levels in IBD or PSC patients. Moreover, urinary sCD163 was not related to fecal calprotectin levels whereas serum sCD163 of IBD patients showed a positive trend. PSC associated with IBD and PSC without underlying IBD had similar levels of urinary sCD163 while serum sCD163 tended to be higher in the latter group. In PSC patients, urinary sCD163 did not correlate with serum aminotransferase levels, gamma glutamyl transferase, alkaline phosphatase, bilirubin or the Model for End Stage Liver Disease score. Ursodeoxycholic acid was prescribed to our PSC patients and fecal levels of ursodeoxycholic acid and its conjugated forms were increased in PSC compared to IBD patients. Otherwise, fecal bile acid levels of IBD and PSC patients were almost identical, and were not correlated with urinary and serum sCD163 in PSC. In summary, our study identified urinary sCD163 as a potential biomarker for PSC.

The role of the microbiome in liver disease

PURPOSE OF REVIEW

The intestinal microbiome and the gut-liver axis play a major role in health and disease. The human gut harbors trillions of microbes and a disruption of the gut homeostasis can contribute to liver disease. In this review, the progress in the field within the last 3 years is summarized, focusing on metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), autoimmune liver disease (AILD), and hepatocellular carcinoma (HCC).

RECENT FINDINGS

Changes in the fecal virome and fungal mycobiome have been described in patients with various liver diseases. Several microbial derived metabolites including endogenous ethanol produced by bacteria, have been mechanistically linked to liver disease such as MASLD. Virulence factors encoded by gut bacteria contribute to ALD, AILD and HCC. Novel therapeutic approaches focused on the microbiome including phages, pre- and postbiotics have been successfully used in preclinical models. Fecal microbiota transplantation has been effective in attenuating liver disease. Probiotics are safe in patients with alcohol-associated hepatitis and improve liver disease and alcohol addiction.

SUMMARY

The gut-liver axis plays a key role in the pathophysiology of liver diseases. Understanding the microbiota in liver disease can help to develop precise microbiota centered therapies.

Gut metabolic changes during pregnancy reveal the importance of gastrointestinal region in sample collection

INTRODUCTION

Studies of gastrointestinal physiology and the gut microbiome often consider the influence of intestinal region on experimental endpoints. However, this same consideration is not often applied to the gut metabolome. Understanding the contribution of gut regionality may be critically important to the rapidly changing metabolic environments, such as during pregnancy.

OBJECTIVES

We sought to characterize the difference in the gut metabolome in pregnant mice stratified by region-comparing the small intestine, cecum, and feces. Pre-pregnancy feces were collected to understand the influence of pregnancy on the fecal metabolome.

METHODS

Feces were collected from CD-1 female mice before breeding. On gestation day (GD) 18, gut contents were collected from the small intestine, cecum, and descending colon. Metabolites were analyzed with LC-MS/MS using the Biocrates MetaboINDICATOR™ MxP® Quant 500 kit.

RESULTS

Of the 104 small molecule metabolites meeting analysis criteria, we found that 84 (81%) were differentially abundant based on gut region. The most significant regional comparison observed was between the cecum and small intestines, with 52 (50%) differentially abundant metabolites. Pregnancy itself altered 41 (39.4%) fecal small molecule metabolites.

CONCLUSIONS

The regional variation observed in the gut metabolome are likely due to the microbial and physiological differences between the different parts of the intestines. Additionally, pregnancy impacts the fecal metabolome, which may be due to evolving needs of both the dam and fetus.