Bile Acid Diarrhea and NAFLD: Shared Pathways for Distinct Phenotypes

Crosstalk Between Bile Acids and Intestinal Epithelium: Multidimensional Roles of Farnesoid X Receptor and Takeda G Protein Receptor 5

Bile acids and their corresponding intestinal epithelial receptors, the farnesoid X receptor (FXR), the G protein-coupled bile acid receptor (TGR5), play crucial roles in the physiological and pathological processes of intestinal epithelial cells. These acids and receptors are involved in the regulation of intestinal absorption, signal transduction, cellular proliferation and repair, cellular senescence, energy metabolism, and the modulation of gut microbiota. A comprehensive literature search was conducted using PubMed, employing keywords such as bile acid, bile acid receptor, FXR (nr1h4), TGR5 (gpbar1), intestinal epithelial cells, proliferation, differentiation, senescence, energy metabolism, gut microbiota, inflammatory bowel disease (IBD), colorectal cancer (CRC), and irritable bowel syndrome (IBS), with a focus on publications available in English. This review examines the diverse effects of bile acid signaling and bile receptor pathways on the proliferation, differentiation, senescence, and energy metabolism of intestinal epithelial cells. Additionally, it explores the interactions between bile acids, their receptors, and the microbiota, as well as the implications of these interactions for host health, particularly in relation to prevalent intestinal diseases. Finally, the review highlights the importance of developing highly specific ligands for FXR and TGR5 receptors in the context of metabolic and intestinal disorders.

High throughput bioanalysis of serum 7a-hydroxy-4-cholesten-3-one (C4) using LC-MS/MS: Devising an end-to-end single vial solution for a sample limited application

Crohn's disease (CD) is characterized by chronic ileal/ileocolonic inflammation, and in some cases, can result in bile acid malabsorption (BAM) and subsequent bile acid diarrhea (BAD). Although BAD is common in CD, diagnosis is difficult. In patients with CD who had ileal resection (IR), elevated serum 7a-hydroxy-4-cholesten-3-one (C4), a cholesterol-derived stable intermediate in bile acid synthesis, is associated with diarrhea attributable to BAM and therefore, may have diagnostic utility. The previously existing validated methodology to measure C4 in human serum required 100 μL with an analytical range of 0.5-100 ng/mL, making it incompatible with the clinical trial sample set we had available for analysis due to limited serum volume and an extended assay range requirement (up-to 1 μg/mL). We present here a simplified, end-to-end single vial approach performed in a 96-well format for clinical sample C4 analysis for application in sample limited settings.

Analyzing MASLD interventional clinical trial registration based on the ClinicalTrials.gov database

OBJECTIVE

With the rising incidence of MASLD, extensive drug research has been conducted in clinical trials. The study examined the design principles and research objectives of MASLD therapeutics, in order to offer guidance to clinical trial participants and decision makers.

METHODS

By searching the clinical research trial data registered on clinicaltrials.gov platform, 1209 interventional clinical trials were screened. These trials were subsequently evaluated based on clinical stage, trial design, intervention modalities, outcome metrics, and other pertinent factors.

RESULTS

A total of 1,209 trials were included, of which 199 were registered from 2000 to 2012 (16.46%) and 1010 were registered from 2013 to 2024 (83.54%), reflecting the growing body of research on MASLD. Regarding the intervention model type, single-group designs were employed in 232 (19.19%) trials, and parallel designs were employed in 873(72.21%). A total of 13 trials were early phase 1 (1.08%), 152 (12.57%) were phase 1, 34 (2.81%) were phase 1/phase 2, 301 were phase 2 (24.90%), 19 (1.57%) were phase 2/phase 3, 72 (5.96%) were phase 3, and 84 (6.95%) were phase 4. Within these trials, the three primary clinical outcomes for drug interventions were hepatic histological improvement, hepatic fat content and adverse events. Furthermore, 140 drug interventional trials with results for therapeutic purposes (This accounted for 88.61% of the 158 drug interventional trials with results) primarily aimed to improve MASLD through mechanisms such as metabolic and energy balance, inflammatory and immunomodulatory, and lipid reduction, targeting primarily PPAR, FXR, ACC and GLP-1.

CONCLUSION

This study suggests the basic characteristics of global MASLD clinical trial design, and the current global interventional clinical trials are mainly focused on drug-related treatments, and drugs to improve inflammation and metabolism are still the first choice for MASLD drug intervention studies.

NAFLD Is Associated With Quiescent Rather Than Active Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease (CD) confers an increased risk of nonalcoholic fatty liver disease (NAFLD), but the pathogenesis remains poorly understood. We determined if active intestinal inflammation increases the risk of NAFLD in patients with CD.

METHODS

Two cohorts (2017/2018 and 2020) with CD and no known liver disease were enrolled consecutively during staging magnetic resonance enterography. We quantified proton density fat fraction, MaRIA (Magnetic Resonance Index of Activity), and visceral adipose tissue. NAFLD was diagnosed when proton density fat fraction ≥5.5%. Synchronous endoscopy was graded by the Simple Endoscopic Score for CD and Rutgeerts score, while clinical activity was graded by the Harvey-Bradshaw index. Cytokine profiling was performed for the 2020 cohort. Transient elastography and liver biopsy were requested by standard of care.

RESULTS

NAFLD was diagnosed in 40% (n = 144 of 363), with higher prevalence during radiographically quiescent disease (odds ratio, 1.7; P = .01), independent of body mass index/visceral adipose tissue (adjusted odds ratio, 7.8; P = .03). These findings were corroborated by endoscopic disease activity, but not by aggregate clinical symptoms. Circulating interleukin-8 was independent of body mass index to predict NAFLD, but traditional proinflammatory cytokines were not. NAFLD subjects had similar liver stiffness estimates regardless of CD activity. Definitive or borderline steatohepatitis was present in most patients that underwent liver biopsy.

CONCLUSIONS

Quiescent CD is associated with risk of NAFLD. These findings suggest potentially distinct pathogenic mechanisms of NAFLD in patients with CD compared with the prevailing leaky gut hypothesis proposed for individuals without inflammatory bowel disease. Future validation and mechanistic studies are needed to dissect these distinct disease modifying factors.

Pharmacological modulation of cholesterol 7α-hydroxylase (CYP7A1) as a therapeutic strategy for hypercholesterolemia

Despite the availability of many therapeutic options, the prevalence of hypercholesterolemia remains high. There exists a significant unmet medical need for novel drugs and/or treatment combinations to effectively combat hypercholesterolemia while minimizing adverse reactions. The modulation of cholesterol 7α-hydroxylase (CYP7A1) expression via perturbation of the farnesoid X receptor (FXR) - dependent pathways, primarily FXR/small heterodimer partner (SHP) and FXR/ fibroblast growth factor (FGF)-19/ fibroblast growth factor receptor (FGFR)-4 pathways, presents as a potential option to lower cholesterol levels. This paper provides a comprehensive review of the important role that CYP7A1 plays in cholesterol homeostasis and how its expression can be exploited to assert differential control of bile acid synthesis and cholesterol metabolism. Additionally, the paper also summarizes the current therapeutic options for hypercholesterolemia, and positions modulators of CYP7A1 expression, namely FGFR4 inhibitors and FXR antagonists, as emerging and distinct pharmacological agents to complement and diversify the treatment regime. Their mechanistic and clinical considerations are also extensively described to interrogate the benefits and risks associated with using FXR-mediating agents, either singularly or in combination with recognised agents such as statins to target hypercholesterolemia.

Roles for Bile Acid Signaling and Nonsense-Mediated Ribonucleic Acid Decay in Small Bowel Resection-Associated Liver Injury

INTRODUCTION

Massive intestinal loss resulting in short bowel syndrome has been linked to intestinal failure associated liver disease. Efforts to elucidate the driving force behind the observed hepatic injury have identified inflammatory mediators, alterations in the microbiome, extent of structural and functional intestinal adaptation, and toxic shifts in the bile acid pool. In the present study, we posit that ileocecal resection interrupts the delivery of these hepatotoxic substances to the liver by physically disrupting the enterohepatic circulation, thereby shielding the liver from exposure to the aforementioned noxious stimuli.

METHODS

Mice underwent sham, 50% proximal, or 50% distal small bowel resection (SBR), with or without tauroursodeoxycolic acid supplementation. Enterohepatic signaling and nonsense-mediated ribonucleic acid (RNA) decay were evaluated and correlated with hepatic injury.

RESULTS

When compared to 50% proximal SBR, mice that underwent ileocecal resection exhibited reduced hepatic oxidative stress and exhibited a more physiological bile acid profile with increased de novo bile acid synthesis, enhanced colonic bile acid signaling, and reduced hepatic proliferation. Distal intestinal resection promoted an adaptive response including via the nonsense-mediated RNA decay pathway to satisfactorily process injurious messenger RNA and successfully maintain homeostasis. By contrast, this adaptive response was not observed in the proximal SBR group and hepatic injury persisted.

CONCLUSIONS

In summary, interruption of enterohepatic circulation via ileocecal resection abrogates the liver's exposure to toxic and inflammatory mediators while promoting physiological adaptations in bile acid metabolism and maintaining existing homeostatic pathways.

The use of bicarbonate-sulphate-calcium-magnesium and sodium-low drinkable water improves functional gastrointestinal symptoms in patients with non-alcoholic fatty liver disease: A prospective study

BACKGROUND & AIMS

Non-alcoholic fatty liver disease is increasingly gaining epidemiological ground in liver diseases. Among the proposed non-pharmacologic interventions, dietary interventions have been widely used. Several patients suffering from it complain of gastrointestinal symptoms unrelated to organic gastrointestinal tract disease. However, the role of drinking water quality modifications in this regard has not been investigated in depth.

METHODS

Patients with upper or lower functional gastrointestinal symptoms were enrolled and divided into groups based on bright liver ultrasound relief's presence (SP) or absence (NSP). These patients were asked to drink bicarbonate-sulphate-calcium-magnesium and sodium-low drinkable water (Fonte Essenziale ®) for six months. Participants were assessed at baseline (T0), at the end of six months of drinking water intake (T6), and after an additional six months of washout (T12) by questionnaires designed to evaluate lower and upper gastrointestinal symptoms (Leeds dyspepsia score, short form) severity and frequency.

RESULTS

A total of 61 patients were enrolled. In the SP population, the severity of lower gastrointestinal symptoms improved between T0-T6 (Z: -2.437; ES: 0.312) and worsened after the water washout (Z: -2.492; ES: 0.319). The same was for the Leeds score severity sub score in T0-T6 (Z: -2.850; ES: 0.364) and T6-T12 (Z: -2.921; ES: 0.374). These improvements seem unrelated to the severity of liver steatosis at baseline. Furthermore, no safety issues were recorded while taking the water nor during the six-month follow-up afterwards.

CONCLUSION

Regular six-month intake of 400 mL of Fonte Essenziale® water was associated, in the absence of dietary regimen modifications, with an improvement in some qualitative and quantitative features of upper and lower functional gastrointestinal symptoms in both an SP and NSP sample.

Associations between irritable bowel syndrome and non-alcoholic fatty liver disease: A systematic review

BACKGROUND

Irritable bowel syndrome (IBS) is associated with obesity and metabolic syndrome. IBS and non-alcoholic fatty liver disease (NAFLD) are highly prevalent entities worldwide and may share similar mechanisms including gut dysbiosis, impaired intestinal mucosal barrier and immune system activation.

AIM

To systematically review their association according to the Preferred Reporting Items for Systemic Review and Meta-analyses guidelines.

METHODS

PubMed, EMBASE and Cochrane Database of Systematic Reviews were searched for relevant papers. Manual searches were also performed.

RESULTS

Six studies were included. Both IBS and NAFLD subjects had significantly more metabolic risk factors like hypertension, obesity, dyslipidaemia and diabetes. Our review showed that 23.2% to 29.4% of NAFLD patients had IBS. IBS was significantly higher in NAFLD patients compared with patients without NAFLD (23.2% vs 12.5%, P < 0.01). A higher proportion of IBS patients had NAFLD (65.8% to 74.0%). IBS patients were three times more likely to have NAFLD compared with non-IBS patients (P < 0.001). Two studies showed a significant correlation between the severity of IBS and NAFLD. The proportion of NAFLD subjects with IBS increased with NAFLD severity.

CONCLUSION

Further prospective studies are warranted to evaluate the relationship and shared pathways between IBS and NAFLD, potentially leading to the development of future therapeutics.

Gut-liver axis in the progression of nonalcoholic fatty liver disease: From the microbial derivatives-centered perspective

Nonalcoholic fatty liver disease (NAFLD) is one of the world's most common chronic liver diseases. However, its pathogenesis remains unclear. With the deepening of research, NAFLD is considered a metabolic syndrome associated with the environment, heredity, and metabolic disorders. Recently, the close relationship between the intestinal microbiome and NAFLD has been discovered, and the theory of the "gut-liver axis" has been proposed. In short, the gut bacteria directly reach the liver via the portal vein through the damaged intestinal wall or indirectly participate in the development of NAFLD through signaling pathways mediated by their components and metabolites. This review focuses on the roles of microbiota-derived lipopolysaccharide, DNA, peptidoglycan, bile acids, short-chain fatty acids, endogenous ethanol, choline and its metabolites, indole and its derivatives, and bilirubin and its metabolites in the progression of NAFLD, which may provide significative insights into the pathogenesis, diagnosis, and treatment for this highly prevalent liver disease.

Association of Serum and Fecal Bile Acid Patterns With Liver Fibrosis in Biopsy-Proven Nonalcoholic Fatty Liver Disease: An Observational Study

INTRODUCTION

No reports on both blood and fecal bile acids (BAs) in patients with nonalcoholic fatty liver disease (NAFLD) exist. We simultaneously assessed the serum and fecal BA patterns in healthy participants and those with NAFLD.

METHODS

We collected stool samples from 287 participants from 5 hospitals in Japan (healthy control [HC]: n = 88; mild fibrosis: n = 104; and advanced fibrosis group: n = 95). Blood samples were collected and analyzed for serum BAs and 7α-hydroxy-4-cholesten-3-one (C4)-a surrogate marker for BA synthesis ability-from 141 patients. Concentrations of BAs, including cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid, ursodeoxycholic acid, and lithocholic acid (LCA), were measured using liquid chromatography-mass spectrometry.

RESULTS

The total fecal BA concentration was significantly higher in the NAFLD group with worsening of fibrosis than in the HC group. Most of the fecal BAs were secondary and unconjugated. In the fecal BA fraction, CA, DCA, chenodeoxycholic acid, ursodeoxycholic acid, and LCA were significantly higher in the NAFLD than in the HC group. The total serum BA concentration was higher in the NAFLD group with worsening of fibrosis than in the HC group. In the serum BA fraction, CA, LCA, and C4 concentrations were significantly higher in the NAFLD than in the HC group.

DISCUSSION

Fecal and serum BA and C4 concentrations were high in patients with NAFLD with worsening of fibrosis, suggesting involvement of abnormal BA metabolism in NAFLD with fibrosis progression. Abnormalities in BA metabolism may be a therapeutic target in NAFLD with fibrosis.

Intestinal secretory mechanisms and diarrhea

One of the primary functions of the intestinal epithelium is to transport fluid and electrolytes to and from the luminal contents. Under normal circumstances, absorptive and secretory processes are tightly regulated such that absorption predominates, thereby enabling conservation of the large volumes of water that pass through the intestine each day. However, in conditions of secretory diarrhea, this balance becomes dysregulated, so that fluid secretion, driven primarily by Cl- secretion, overwhelms absorptive capacity, leading to increased loss of water in the stool. Secretory diarrheas are common and include those induced by pathogenic bacteria and viruses, allergens, and disruptions to bile acid homeostasis, or as a side effect of many drugs. Here, we review the cellular and molecular mechanisms by which Cl- and fluid secretion in the intestine are regulated, how these mechanisms become dysregulated in conditions of secretory diarrhea, currently available and emerging therapeutic approaches, and how new strategies to exploit intestinal secretory mechanisms are successfully being used in the treatment of constipation.

A Potential Role for Bile Acid Signaling in Celiac Disease-Associated Fatty Liver

Celiac disease (CeD) is a chronic autoimmune disorder characterized by an intolerance to storage proteins of many grains. CeD is frequently associated with liver damage and steatosis. Bile acid (BA) signaling has been identified as an important mediator in gut-liver interaction and the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Here, we aimed to analyze BA signaling and liver injury in CeD patients. Therefore, we analyzed data of 20 CeD patients on a gluten-free diet compared to 20 healthy controls (HC). We furthermore analyzed transaminase levels, markers of cell death, BA, and fatty acid metabolism. Hepatic steatosis was determined via transient elastography, by MRI and non-invasive scores. In CeD, we observed an increase of the apoptosis marker M30 and more hepatic steatosis as compared to HC. Fibroblast growth factor 19 (FGF19) was repressed in CeD, while low levels were associated with steatosis, especially in patients with high levels of anti-tissue transglutaminase antibodies (anti-tTG). When comparing anti-tTG-positive CeD patients to individuals without detectable anti-tTG levels, hepatic steatosis was accentuated. CeD patients with significant sonographic steatosis (defined by CAP ≥ 283 db/m) were exclusively anti-tTG-positive. In summary, our results suggest that even in CeD patients in clinical remission under gluten-free diet, alterations in gut-liver axis, especially BA signaling, might contribute to steatotic liver injury and should be further addressed in future studies and clinical practice.

Nonalcoholic fatty liver disease is associated with worse intestinal complications in patients hospitalized for Clostridioides difficile infection

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become the leading cause of chronic liver disease with increasing prevalence worldwide. Clostridioides difficile infection (CDI) remains the most common cause of nosocomial diarrhea in developed countries.

AIM

To assess the impact of NAFLD on the outcomes of hospitalized patients with CDI.

METHODS

This study was a retrospective cohort study. The Nationwide Inpatient Sample database was used to identify a total of 7239 adults admitted as inpatients with a primary diagnosis of CDI and coexisting NAFLD diagnosis from 2010 to 2014 using ICD-9 codes. Patients with CDI and coexisting NAFLD were compared to those with CDI and coexisting alcoholic liver disease (ALD) and viral liver disease (VLD), individually. Primary outcomes included mortality, length of stay, and total hospitalization charges. Secondary outcomes were in-hospital complications. Multivariate regression was used for outcome analysis after adjusting for possible confounders.

RESULTS

CDI with NAFLD was independently associated with lower rates of acute respiratory failure (2.7% vs 4.2%, P < 0.01; 2.7% vs 4.2%, P < 0.05), shorter length of stay (days) (5.75 ± 0.16 vs 6.77 ± 0.15, P < 0.001; 5.75 ± 0.16 vs 6.84 ± 0.23, P <0.001), and lower hospitalization charges (dollars) (38150.34 ± 1757.01 vs 46326.72 ± 1809.82, P < 0.001; 38150.34 ± 1757.01 vs 44641.74 ± 1660.66, P < 0.001) when compared to CDI with VLD and CDI with ALD, respectively. CDI with NAFLD was associated with a lower rate of acute kidney injury (13.0% vs 17.2%, P < 0.01), but a higher rate of intestinal perforation (P < 0.01) when compared to VLD. A lower rate of mortality (0.8% vs 2.7%, P < 0.05) but a higher rate of intestinal obstruction (4.6% vs 2.2%, P = 0.001) was also observed when comparing CDI with NAFLD to ALD.

CONCLUSION

Hospitalized CDI patients with NAFLD had more intestinal complications compared to CDI patients with VLD and ALD. Gut microbiota dysbiosis may contribute to the pathogenesis of intestinal complications.

Antibiotic Therapy as a Risk Factor of Obesity Development in Children

Настоящий обзор научной литературы посвящен вопросам, связанным с механизмами антибактериально-индуцированного адипогенеза. Антибиотиками, наиболее высоко ассоциированными с развитием ожирения у детей, считают: амоксициллин, цефотаксим, макролиды, тетрациклины, ванкомицин. На основании результатов филогенетических, метагеномных исследований эффектов антибиотиков установлено, что их применение в антенатальном, раннем постнатальном периоде приводит к пролонгированным изменениям как состава, так и функционирования микробиома, которые ассоциированы с повышенным риском последующего увеличения массы тела ребенка. Механизмы непосредственного влияния антибиотиков на адипогенез связаны с их способностью повышать аппетит за счет стимуляции высвобождения орексина и меланин-концентрирующего гормона; увеличивать абсорбцию пищевых ингредиентов; активировать липогенез; индуцировать митохондриальную дисфункцию и тем самым способствовать накоплению жирных кислот. Применение антибиотиков существенно изменяет структуру микробиома кишечника, а именно: развитие ожирения связано с высоким уровнем представительства бактерий филюмов Actinobacteria и Firmicutes в сочетании со снижением численности бактерий Bacteroidetes, Verrucomicrobia и Faecalibacterium prausnitzii. Антибиотик-индуцированные изменения микробиома могут существенно влиять на аппетит, так как уровень грелина, вызывающего аппетит, положительно коррелирует с представительством бактерий Bacteroides и Prevotella, и отрицательно – с численностью бактерий Bifidobacterium, Lactobacillus, Blautia coccoides и Eubacterium rectale. Доказано, что применение некоторых антибиотиков сопровождается не только накоплением висцерального жира, но и приводит к развитию как неалкогольной болезни печени, так и инсулинорезистентности. Рецепторы FXR и TGR5 являются сенсорами изменений микробиоты кишечника, которые участвуют в регуляции метаболических процессов макроорганизма. Развитие ожирения характеризуется наличием низкоуровневого системного воспаления. При развитии ожирения по мере увеличения размеров адипоцитов фенотип макрофагов меняется на провоспалительный фенотип М1. Накопление провоспалительных клеток в висцеральной жировой ткани является важной причиной развития инсулинорезистентности. В настоящее время необходимость применения антибиотиков при лечении инфекционных заболеваний, вызванных бактериальными агентами, не вызывает никаких клинических сомнений. Однако появление научных сведений о метаболических эффектах, возникновение которых ассоциировано с антибиотикотерапией, ставит клинические новые задачи, решение которых, вероятно, лежит в оптимизации режимов применения антибиотиков и выборе сопровождающих лекарственных средств.

This review of scientific literature is devoted to issues related to the mechanisms of antibacterial- induced adipogenesis. The antibiotics most highly associated with the development of obesity in children are the following: amoxicillin, cefotaxime, macrolides, tetracyclines, vancomycin. On the base of the results of phylogenetic, metagenomic studies of the effects of antibiotics, it was found that their use in the antenatal, early postnatal period leads to prolonged changes in both the composition and functioning of the microbiome, which is associated with the increased risk of subsequent increase of body weight of the child. The mechanisms of direct effect of antibiotics on adipogenesis are associated with their ability to increase appetite, by stimulating the release of orexin and melanin-concentrating hormone; increase the absorption of food ingredients; activate lipogenesis; induce mitochondrial dysfunction and thereby contribute to accumulation of fatty acids. The use of antibiotics significantly changes the structure of the intestinal microbiome, namely, the development of obesity is associated with a high representation of phylum bacteria Actinobacteria and Firmicutes in combination with the decrease of the number of bacteria Bacteroidetes, Verrucomicrobia and Faecalibacterium prausnitzii. Antibiotic-induced changes in the microbiome can significantly affect appetite, because the level of ghrelin that causes appetite positively correlates with the presence of bacteria Bacteroides and Prevotella, and negatively with the number of bacteria Bifidobacterium, Lactobacillus, Blautia coccoides and Eubacterium rectale. It was proved that the use of certain antibiotics is accompanied not only by the accumulation of visceral fat, but also leads to the development of both non-alcoholic liver disease and insulin resistance. The FXR and TGR5 receptors are the sensors of changes in the intestinal microbiota, which is involved in the regulation of the metabolic processes of the macroorganism. The development of obesity is characterized by the presence of low-level systemic inflammation. With the development of obesity, as the size of adipocytes increases, the macrophage phenotype changes to the pro- inflammatory M1 phenotype. The accumulation of pro-inflammatory cells in visceral adipose tissue is an important reason for development of insulin resistance. Currently, the need for antibiotics in the treatment of infectious diseases caused by bacterial agents does not raise any clinical doubts. However, the emergence of scientific information about metabolic effects, the occurrence of which is associated with antibiotic therapy, presents new clinical challenges, the solution of which probably lies in optimizing antibiotic regimens and choosing the accompanying drugs.