Detection of Gut Dysbiosis due to Reduced Clostridium Subcluster XIVa Using the Fecal or Serum Bile Acid Profile

Distinctive duodenal microbiomes and bile acid profiles in duodenal tumor patients revealed by prospective observational study

The incidence of duodenal tumors (DTs) is increasing. However, the mechanisms underlying its development remain unclear. Environmental factors, including the microbiome and bile acids (BAs), are believed to influence tumor development. Therefore, we conducted a single-center, prospective, observational study to investigate the potential differences between patients with DTs and healthy controls (HCs) based on these factors. In addition, the BAs in the duodenal fluid were measured using liquid chromatography-tandem mass spectrometry. We recruited 41 patients and performed 16S rRNA-seq. There was no difference in the observed ASVs or PCoA plot of Bray-Curtis dissimilarity between the DTs and HCs. The lithocholic acid concentration was significantly lower in the DT group than in the control group. The ratio of CDCA to LCA was significantly higher in patients with DTs. No significant differences in microbiota were observed between DTs and HCs. In patients with DTs, the lithocholic acid concentration in duodenal was significantly lower than in HCs.

Galacto-Oligosaccharides and the Elderly Gut: Implications for Immune Restoration and Health

The increasing prevalence of noncommunicable diseases in the aging population has been correlated with a decline in innate and adaptive immune responses; hence, it is imperative to identify approaches to improve immune function, prevent related disorders, and reduce or treat age-associated health complications. Prebiotic supplementation is a promising approach to modulate the gut microbiome and immune system, offering a potential strategy to maintain the integrity of immune function in older individuals. This review summarizes the current research on prebiotic galacto-oligosaccharide (GOS) immunomodulatory mechanisms mediated by bacterial-derived metabolites, including short-chain fatty acids and secondary bile acids, to maintain immune homeostasis. The potential applications of GOS as immunotherapy for age-related disease prevention in older individuals are also highlighted. This aligns with the global shift toward proactive healthcare and emphasizes the significance of early intervention in directing an individual's health trajectory.

Hyperbaric oxygen therapy ameliorates intestinal and systematic inflammation by modulating dysbiosis of the gut microbiota in Crohn's disease

BACKGROUND

Dysbiosis of the gut microbiota is pivotal in Crohn's disease (CD) and modulated by host physiological conditions. Hyperbaric oxygen therapy (HBOT) is a promising treatment for CD that can regulate gut microbiota. The relationship between HBOT and the gut microbiota in CD remains unknown.

METHODS

CD patients were divided into an HBOT group (n = 10) and a control group (n = 10) in this open-label prospective interventional study. The fecal samples before and after HBOT were used for 16 S rRNA gene sequencing and fecal microbiota transplantation (FMT). A colitis mouse model was constructed using dextran sulfate sodium, and intestinal and systematic inflammation was evaluated. The safety and long-term effect of HBOT were observed.

RESULTS

HBOT significantly reduced the level of C-reactive protein (CRP) (80.79 ± 42.05 mg/L vs. 33.32 ± 18.31 mg/L, P = 0.004) and the Crohn's Disease Activity Index (CDAI) (274.87 ± 65.54 vs. 221.54 ± 41.89, P = 0.044). HBOT elevated the declined microbial diversity and ameliorated the altered composition of gut microbiota in patients with CD. The relative abundance of Escherichia decreased, and that of Bifidobacterium and Clostridium XIVa increased after HBOT. Mice receiving FMT from donors after HBOT had significantly less intestinal inflammation and serum CRP than the group before HBOT. HBOT was safe and well-tolerated by patients with CD. Combined with ustekinumab, more patients treated with HBOT achieved clinical response (30%vs.70%, P = 0.089) and remission (20%vs.50%, P = 0.160) at week 4.

CONCLUSIONS

HBOT modulates the dysbiosis of gut microbiota in CD and ameliorates intestinal and systematic inflammation. HBOT is a safe option for CD and exhibits a promising auxiliary effect to ustekinumab.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2200061193. Registered 15 June 2022, https://www.chictr.org.cn/showproj.html?proj=171605 .

Bile Acids and Risk of Adverse Cardiovascular Events and All-Cause Mortality in Patients with Acute Coronary Syndrome

The relationship between bile acids (BAs) and adverse cardiovascular events following acute coronary syndrome (ACS) have been little investigated. We aimed to examine the associations of BAs with the risk of cardiovascular events and all-cause mortality in ACS. We conducted a prospective study on 309 ACS patients who were followed for 10 years. Plasma BAs were quantified by liquid chromatography coupled to tandem mass spectrometry. Cox regression analyses with elastic net penalties were performed to associate BAs with MACE and all-cause mortality. Weighted scores were computed using the 100 iterated coefficients corresponding to each selected BA, and the associations of these scores with these adverse outcomes were assessed using multivariable Cox regression models. A panel of 10 BAs was significantly associated with the increased risk of MACE. The hazard ratio of MACE per SD increase in the estimated BA score was 1.35 (95% CI 1.12-1.63). Furthermore, four BAs were selected from the elastic net model for all-cause mortality, although their weighted score was not independently associated with mortality. Our findings indicate that primary and secondary BAs may play a significant role in the development of MACE. This insight holds potential for developing strategies to manage ACS and prevent adverse outcomes.

Novel approaches in IBD therapy: targeting the gut microbiota-bile acid axis

Inflammatory bowel disease (IBD) is a chronic and recurrent condition affecting the gastrointestinal tract. Disturbed gut microbiota and abnormal bile acid (BA) metabolism are notable in IBD, suggesting a bidirectional relationship. Specifically, the diversity of the gut microbiota influences BA composition, whereas altered BA profiles can disrupt the microbiota. IBD patients often exhibit increased primary bile acid and reduced secondary bile acid concentrations due to a diminished bacteria population essential for BA metabolism. This imbalance activates BA receptors, undermining intestinal integrity and immune function. Consequently, targeting the microbiota-BA axis may rectify these disturbances, offering symptomatic relief in IBD. Here, the interplay between gut microbiota and bile acids (BAs) is reviewed, with a particular focus on the role of gut microbiota in mediating bile acid biotransformation, and contributions of the gut microbiota-BA axis to IBD pathology to unveil potential novel therapeutic avenues for IBD.

High-Throughput Sequencing Technology Assisted Investigation of the Correlation Between Intestinal Flora, Serum Biochemistry, Blood Lipids, and Tumour Markers in Patients with Gastric Cancer and Healthy Plateau Residents

AIM

The goal is to use high-throughput sequencing technology to compare and study the structure and variety of intestinal flora in people with gastric cancer and healthy people in the Qinghai-Tibet Plateau.

BACKGROUND

Recent research has connected gut flora structure to numerous disorders. Metabolites, endotoxins, and immunomodulatory modulation might cause gastrointestinal or other systemic diseases and affect gastric cancer treatment and prognosis. We used the correlation study to uncover biomarkers associated with good intestinal flora and gastric cancer groups on the plateau to investigate their involvement in gastric cancer development.

OBJECTIVES

To investigate the possible links between intestinal flora and gastric cancer in the Qinghai Plateau region using a variety of clinical phenotypic data and to investigate the flora that may be linked to gastric cancer.

METHODS

The 22 Qinghai Province tertiary hospital gastric cancer patients and 30 healthy people had their fresh faeces collected. To examine intestinal flora diversity and composition, 52 patients underwent 16S rDNA high-throughput gene sequencing of intestinal bacteria. The correlation between clinical phenotypes and the top 15 dominant intestinal flora at the phylum level was analyzed.

RESULTS

The difference in total protein TP between the healthy group and the gastric cancer group was statistically significant (P<0.001). Globulin was significantly different (P<0.05), TC of total cholesterol was significantly different (P<0.05). High-density lipoprotein showed statistical significance (P<0.05).The difference in low-density lipoprotein was statistically significant (P<0.001). Alphafetoprotein was significantly different (P<0.05). CA72-4 carbohydrate antigen (P<0.05).

CONCLUSION

There were significant differences in total protein, globulin, total cholesterol, high density lipoprotein, low-density lipoprotein, alpha-fetoprotein and carbohydrate antigen CA72-4 in patients with gastric cancer in the plateau area compared with the healthy group, and the different clinical variables were correlated with intestinal flora at some phylum and genus levels.

Current insights on the roles of gut microbiota in inflammatory bowel disease-associated extra-intestinal manifestations: pathophysiology and therapeutic targets

Inflammatory bowel disease (IBD) is a chronic, recurrent inflammatory disease of the gastrointestinal tract. In addition to digestive symptoms, patients with IBD may also develop extra-intestinal manifestations (EIMs), the etiology of which remains undefined. The gut microbiota has been reported to exert a critical role in the pathogenesis of IBD, with a similar pattern of gut dysbiosis observed between patients with IBD and those with EIMs. Therefore, it is hypothesized that the gut microbiota is also involved in the pathogenesis of EIMs. The potential mechanisms are presented in this review, including: 1) impaired gut barrier: dysbiosis induces pore formation in the intestinal epithelium, and activates pattern recognition receptors to promote local inflammation; 2) microbial translocation: intestinal pathogens, antigens, and toxins translocate via the impaired gut barrier into extra-intestinal sites; 3) molecular mimicry: certain microbial antigens share similar epitopes with self-antigens, inducing inflammatory responses targeting extra-intestinal tissues; 4) microbiota-related metabolites: dysbiosis results in the dysregulation of microbiota-related metabolites, which could modulate the differentiation of lymphocytes and cytokine production; 5) immunocytes and cytokines: immunocytes are over-activated and pro-inflammatory cytokines are excessively released. Additionally, we summarize microbiota-related therapies, including probiotics, prebiotics, postbiotics, antibiotics, and fecal microbiota transplantation, to promote better clinical management of IBD-associated EIMs.

Berberine improves DSS-induced colitis in mice by modulating the fecal-bacteria-related bile acid metabolism

Ulcerative colitis (UC) has been confirmed as a disease with a high incidence and low cure rate worldwide. In severe cases, UC can develop into colon cancer. Modern research has confirmed that berberine (BBR) can treat UC by inhibiting the expressions of inflammatory factors. However, the contribution of gut microbiota and flora metabolites in treating UC with BBR remains unclear. In this study, the ameliorative effects of BBR on gut microbiota dysbiosis and flora metabolites were investigated in a dextran sodium sulfate (DSS)-induced UC rodent model. We found that BBR significantly improved the pathological phenotype, attenuated intestinal barrier disruption, and mitigated colonic inflammation in DSS mice. By 16 S rDNA sequencing, BBR alleviated gut microbiota dysbiosis in UC mice. Moreover, the gut microbiota depletion experiment confirmed that the therapeutic effect of BBR was inextricably correlated with the gut microbiota. Besides, the flora metabolites (e.g., short-chain fatty acids, bile acids, and 5-hydroxytryptamine) were studied using HPLC-MS. The results suggested that BBR ameliorated the bile acid imbalance induced by DSS in the liver and gut. Furthermore, BBR treatment repaired gut barrier damage. The above results revealed that BBR alleviated DSS-induced UC in mice by restoring the disturbed gut microbiota, elevating unconjugated and secondary bile acids in the gastrointestinal tract, and activating the FXR and TGR5 signal pathway. This study provides novel insights into the mechanism of BBR in treating UC.

Perinatal Morphine Exposure Induces Long-Term Changes in the Intestinal Microbiota of Male and Female Rats

The increased use of opioids by women of reproductive age has resulted in a dramatic rise in number of infants exposed to opioids in utero. Although perinatal opioid exposure (POE) has been associated with an elevated risk of infection and hospitalization later in life, the mechanism(s) by which opioids influence immune development and maturation is not fully elucidated. Alterations in the intestinal microbiota composition, which leads to changes in immune training and maturation, could be at play. Chronic opioid use in adults is associated with a proinflammatory and pathogenic microbiota composition; therefore, we hypothesized here that in utero morphine exposure could negatively affect intestinal microbiota composition, leading to alterations in immune system function. We report that a clinically-relevant model of perinatal opioid exposure, in rats, induces profound intestinal microbiota dysbiosis that is maintained into adulthood. Furthermore, microbial maturity was reduced in morphine-exposed offspring. This suggests that increased risk of infection observed in children exposed to opioids during gestation may be a consequence of microbiota alterations with downstream impact on immune system development. Further investigation of how perinatal morphine induces dysbiosis will be critical to the development of early life interventions designed to ameliorate the increased risk of infection observed in these children.

Upregulation of Taurine Biosynthesis and Bile Acid Conjugation with Taurine through FXR in a Mouse Model with Human-like Bile Acid Composition

Taurine, the end product in the sulfur-containing amino acid pathway, is conjugated with bile acids (BAs) in the liver. The rate-limiting enzymes in both taurine synthesis and BA conjugation may be regulated by a nucleus receptor, FXR, that promotes BA homeostasis. However, it is controversial because BAs act as natural FXR agonists or antagonists in humans and mice, respectively, due to the species differences in BA synthesis. The present study evaluated the influences of different BA compositions on both pathways in the liver by comparing Cyp2a12^-/-/Cyp2c70^-/- mice with a human-like BA composition (DKO) and wild-type (WT) mice. The DKO liver contains abundant natural FXR agonistic BAs, and the taurine-conjugated BA proportion and the taurine concentration were significantly increased, while the total BA concentration was significantly decreased compared to those in the WT liver with natural FXR antagonistic BAs. The mRNA expression levels of the enzymes Bacs and Baat in BA aminations and Cdo and Fmo1 in the taurine synthesis, as well as Fxr and its target gene, Shp, were significantly higher in the DKO liver than in the WT liver. The present study, using a model with a human-like BA composition in the liver, confirmed, for the first time in mice, that both the taurine synthesis and BA amidation pathways are upregulated by FXR activation.

Bile acid alterations associated with indolent course of inflammatory bowel disease

BACKGROUND

The indolent course of treatment-naive patients with inflammatory bowel disease (IBD) is confirmed predictable based on clinical characteristics. Current evidences supported that bile acids (BAs) alteration might be promising biomarkers in the field of IBD. We aimed to analyze the alterations of BAs as the disease progresses and explore their predictive value for indolent course of IBD.

METHODS

The indolent course of IBD was defined as a disease course without need for strict interventions throughout the entire follow-up. A targeted metabolomics method was used to detect the concentration of 27 BAs from serum sample in treatment-naive patients with IBD (Crohn's disease [CD], n = 27; ulcerative colitis [UC], n = 50). Patients with CD and UC were individually divided into two groups for further study according to the median time of indolent course. The overall BAs profile and the clinical value of BAs in predicting indolent course of IBD were identified between different groups.

RESULTS

For CD, the levels of deoxycholic acid, glycodeoxycholic acid, taurodeoxycholic acid, glycolithocholic acid-3-sulfate disodium salt and iso-lithocholic acid were significantly increased in patients with indolent course > 18 M (p < 0.05). These five BAs owned 83.5% accuracy for predicting indolent course over 18 months in CD. For UC, the concentration of deoxycholic acid and glycodeoxycholic acid were significantly higher, while dehydrocholic acid were lower in patients with indolent course > 48 M (p < 0.05). These three BAs predicted indolent course over 48 months of 69.8% accuracy in UC.

CONCLUSION

The specific BAs alterations might be potential biomarkers in predicting disease course of IBD patients.

Myeloid TLR4 signaling promotes post-injury withdrawal resolution of murine liver fibrosis

The fate of resolution of liver fibrosis after withdrawal of liver injury is still incompletely elucidated. Toll-like receptor 4 (TLR4) in tissue fibroblasts is pro-fibrogenic. After withdrawal of liver injury, we unexpectedly observed a significant delay of fibrosis resolution as TLR4 signaling was pharmacologically inhibited in vivo in two murine models. Single-cell transcriptome analysis of hepatic CD11b⁺ cells, main producers of matrix metalloproteinases (MMPs), revealed a prominent cluster of restorative Tlr4-expressing Ly6c2-low myeloid cells. Delayed resolution after gut sterilization suggested its microbiome-dependent nature. Enrichment of a metabolic pathway linking to a significant increase of bile salt hydrolase-possessing family Erysipelotrichaceae during resolution. Farnesoid X receptor-stimulating secondary bile acids including 7-oxo-lithocholic acids upregulated MMP12 and TLR4 in myeloid cells in vitro. Fecal material transplant in germ-free mice confirmed phenotypical correlations in vivo. These findings highlight a pro-fibrolytic role of myeloid TLR4 signaling after injury withdrawal and may provide targets for anti-fibrotic therapy.

Defecation status, intestinal microbiota, and habitual diet are associated with the fecal bile acid composition: a cross-sectional study in community-dwelling young participants

PURPOSE

Bile acid (BA) metabolism by intestinal bacteria is associated with the risk of gastrointestinal diseases; additionally, its control has become a modern strategy for treating metabolic diseases. This cross-sectional study investigated the influence of defecation status, intestinal microbiota, and habitual diet on fecal BA composition in 67 community-dwelling young participants.

METHODS

Feces were collected for intestinal microbiota and BA analyses; data about defecation status and dietary habits were collected using the Bristol stool form scales and a brief-type self-administered diet history questionnaire, respectively. The participants were categorized into four clusters based on their fecal BA composition, according to cluster analysis, and tertiles based on deoxycholic acid (DCA) and lithocholic acid (LCA) levels.

RESULTS

The high primary BA (priBA) cluster with high fecal cholic acid (CA) and chenodeoxycholic acid (CDCA) levels had the highest frequency of normal feces, whereas the second BA (secBA) cluster with high levels of fecal DCA and LCA had the lowest. Alternately, the high-priBA cluster had a distinct intestinal microbiota, with higher Clostridium subcluster XIVa and lower Clostridium cluster IV and Bacteroides. The low-secBA cluster with low fecal DCA and LCA levels had the lowest animal fat intake. Nevertheless, the insoluble fiber intake of the high-priBA cluster was significantly higher than that of the high-secBA cluster.

CONCLUSION

High fecal CA and CDCA levels were associated with distinct intestinal microbiota. Conversely, high levels of cytotoxic DCA and LCA were associated with increased animal fat intake and decreased frequency of normal feces and insoluble fiber intake.

CLINICAL TRIAL REGISTRY

University Hospital Medical Information Network (UMIN) Center system (UMIN000045639); date of registration: 15/11/2019.

Microbiome and metabolome in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease of unknown etiology, involving complex interactions between the gut microbiome and host immune response. The microbial dysbiosis is well documented in IBD and significantly influences the host metabolic pathways. Thus, a metabolomic fingerprint resulting from the influence of gut dysbiosis in IBD could aid in assessing the disease activity. PubMed, Medline, Science Direct, and Web of Science were searched for studies exploring the association between microbiome and metabolome in IBD patients in the last 5 years. Additionally, references of cited original articles and reviews were further assessed for relevant work. We provide a literature overview of the recent metabolomic studies performed on patients with IBD. The findings report alterations in the metabolite levels of these patients. We also discuss the gut dysbiosis observed in IBD and its influence on host metabolic pathways such as lipids, amino acids, short-chain fatty acids, and others. IBD, being a chronic idiopathic disease, requires routine monitoring. The available non-invasive markers have their limitations. The metabolite changes account for both dysbiosis and its influence on the host's immune response and metabolism. A metabolome approach would thus facilitate the identification of surrogate metabolite markers reflecting the disease activity.

Evaluation of gut dysbiosis using serum and fecal bile acid profiles

Dysbiosis in the intestinal microflora can affect the gut production of microbial metabolites, and toxic substances can disrupt the barrier function of the intestinal wall, leading to the development of various diseases. Decreased levels of Clostridium subcluster XIVa (XIVa) are associated with the intestinal dysbiosis found in inflammatory bowel disease (IBD) and Clostridium difficile infection (CDI). Since XIVa is a bacterial group responsible for the conversion of primary bile acids (BAs) to secondary BAs, the proportion of intestinal XIVa can be predicted by determining the ratio of deoxycholic acid (DCA)/[DCA + cholic acid (CA)] in feces orserum. For example, serum DCA/(DCA+CA) was significantly lower in IBD patients than in healthy controls, even in the remission period. These results suggest that a low proportion of intestinal XIVa in IBD patients might be a precondition for IBD onset but not a consequence of intestinal inflammation. Another report showed that a reduced serum DCA/(DCA + CA) ratio could predict susceptibility to CDI. Thus, the BA profile, particularly the ratio of secondary to primary BAs, can serve as a surrogate marker of the intestinal dysbiosis caused by decreased XIVa.

New insights into the interplay between intestinal flora and bile acids in inflammatory bowel disease

Intestinal flora plays a key role in nutrient absorption, metabolism and immune defense, and is considered to be the cornerstone of maintaining the health of human hosts. Bile acids synthesized in the liver can not only promote the absorption of fat-soluble substances in the intestine, but also directly or indirectly affect the structure and function of intestinal flora. Under the action of intestinal flora, bile acids can be converted into secondary bile acids, which can be reabsorbed back to the liver through the enterohepatic circulation. The complex dialogue mechanism between intestinal flora and bile acids is involved in the development of intestinal inflammation such as inflammatory bowel disease (IBD). In this review, the effects of intestinal flora, bile acids and their interactions on IBD and the progress of treatment were reviewed.

Association of lithocholic acid with skeletal muscle hypertrophy through TGR5-IGF-1 and skeletal muscle mass in cultured mouse myotubes, chronic liver disease rats and humans

Background:

Hepatic sarcopenia is one of many complications associated with chronic liver disease (CLD) and has a high mortality rate; however, the liver-muscle axis is not fully understood. Therefore, few effective treatments exist for hepatic sarcopenia, the best of which being branched-chain amino acid (BCAA) supplementation to help increase muscle mass. Our aim was to investigate the molecular mechanism(s) of hepatic sarcopenia focused on bile acid (BA) composition.

Methods:

The correlation between serum BA levels and psoas muscle mass index (PMI) was examined in 73 CLD patients. Gastrocnemius muscle phenotype and serum BA levels were assessed in CLD rats treated with BCAA. Mouse skeletal muscle cells (C2C12) were incubated with lithocholic acid (LCA), G-protein-coupled receptor 5 (TGR5) agonist or TGR5 antagonist to assess skeletal muscle hypertrophy.

Results:

In human CLD, serum LCA levels were the sole factor positively correlated with PMI and were significantly decreased in both the low muscle mass group and the deceased group. Serum LCA levels were also shown to predict patient survival. Gastrocnemius muscle weight significantly increased in CLD rats treated with BCAA via suppression of protein degradation pathways, coupled with a significant increase in serum LCA levels. LCA treated C2C12 hypertrophy occurred in a concentration-dependent manner linked with TGR5-Akt pathways based upon inhibition results via a TGR5 antagonist.

Conclusions:

Our results indicate LCA-mediated skeletal muscle hypertrophy via activation of TGR5-IGF1-Akt signaling pathways. In addition, serum LCA levels were associated with skeletal muscle mass in cirrhotic rats, as well as CLD patients, and predicted overall patient survival.

Funding:

This research was supported by JSPS KAKENHI Grant Number 22K08011 and 21H02892, and AMED under Grant Number JP21fk0210090 and JP22fk0210115. Maintaining cirrhotic rats were partially supported by Otsuka Pharmaceutical Company.

Alterations of Serum Bile Acid Profile in Patients with Crohn’s Disease

Background

Bile acid (BA) metabolism may be influenced by gut dysbiosis and alterations of intestinal epithelium in patients with Crohn's disease (CD). Here, we aimed at investigating the alterations of serum BA profile in CD patients and analyzing the correlation between BAs and CD disease activity.

Methods

A total of 62 CD patients (29 active and 33 remission) and 33 healthy volunteers (HVs) were enrolled in this retrospective study. Serum BA profiles were measured by liquid chromatography-tandem mass spectrometry.

Results

Levels of primary BAs components, including cholic acid (CA) and chenodeoxycholic acid (CDCA), showed no significant difference when compared with HVs. Secondary BAs (SBA) were significantly decreased in CD patients compared with HVs. Importantly, the deoxycholic acid (DCA) and glycodeoxycholic acid (GDCA) levels were significantly lower in CD active than in CD remission patients. The DCA/(DCA + CA) ratio was also decreased in CD active patients than in CD remission patients while the LCA/(LCA + CDCA) ratio showed no difference between them. Principal component analysis also indicated a clear separation among the three groups, with a total variance of 93.43%. The correlation analysis showed that the SBA, DCA, GDCA levels, and DCA/(DCA + CA) ratio had an inverse relationship with Crohn's Disease Activity Index.

Conclusion

The BA profile exhibits significant alterations in CD patients. The SBA, DCA, GDCA levels, and DCA/(DCA + CA) ratio were significantly decreased in CD active patients. The DCA/(DCA + CA) ratio had an inverse correlation with CD disease activity.

Characterization of long-chain fatty acid-linked bile acids: a major conjugation form of 3β-hydroxy bile acids in feces

Although most bile acids (BAs) in feces are present in noncovalent forms that can be extracted with ethanol, non-negligible amounts of saponifiable BAs are also present. It is a major concern that such saponifiable BAs are routinely omitted from fecal BA measurements. We compared the BA profiles of healthy stools that were obtained with/without alkaline hydrolysis and found that as much as 29.7% (2.1–67.7%) of total BAs were saponifiable. Specifically, alkaline treatment led to significant elevations of isodeoxycholic acid (isoDCA) and isolithocholic acid (isoLCA) concentrations, suggesting that considerable proportions of isoDCA and isoLCA were esterified. Precursor ion scan data from LC/MS suggested the presence of long-chain FA-linked BAs. We chemically synthesized a series of fatty acid 3β-acyl conjugates of isoDCA and isoLCA as analytical standards and analyzed their fecal profiles from newborns to adults (n = 64) by LC/MS. FA-conjugated isobile acids (FA-isoBAs) were constantly present from 2 years of age to adulthood. C16- and C18-chain FA-isoBA esters were predominantly found regardless of age, but small amounts of acetic acid esters were also found. FA-isoBA concentrations were not correlated to fecal FA concentrations. Interestingly, there were some adults who did not have FA-isoBAs. Gut bacteria involved in the production of FA-isoBAs have not been identified yet. The present study provides insight into the establishment of early gut microbiota and the interactive development of esterified BAs.The contribution of FA-isoBAs to gut physiology and their role in pathophysiologic conditions such as inflammatory bowel disease are currently under investigation.

Hepatocellular Carcinoma: How the Gut Microbiota Contributes to Pathogenesis, Diagnosis, and Therapy

The gut microbiota is gaining increasing attention, and the concept of the "gut-liver axis" is gradually being recognized. Leaky gut resulting from injury and/or inflammation can cause the translocation of flora to the liver. Microbiota-associated metabolites and components mediate the activation of a series of signalling pathways, thereby playing an important role in the development of hepatocellular carcinoma (HCC). For this reason, targeting the gut microbiota in the diagnosis, prevention, and treatment of HCC holds great promise. In this review, we summarize the gut microbiota and the mechanisms by which it mediates HCC development, and the characteristic alterations in the gut microbiota during HCC pathogenesis. Furthermore, we propose several strategies to target the gut microbiota for the prevention and treatment of HCC, including antibiotics, probiotics, faecal microbiota transplantation, and immunotherapy.

Evaluation of the Risk of Clostridium difficile Infection Using a Serum Bile Acid Profile

Since intestinal secondary bile acids (BAs) prevent Clostridium difficile infection (CDI), the serum BA profile may be a convenient biomarker for CDI susceptibility in human subjects. To verify this hypothesis, we investigated blood samples from 71 patients of the Division of Gastroenterology and Hepatology at the time of admission (prior to antibiotic use and CDI onset). Twelve patients developed CDI during hospitalization, and the other 59 patients did not. The serum unconjugated deoxycholic acid (DCA)/[DCA + unconjugated cholic acid (CA)] ratio on admission was significantly lower in patients who developed CDI than in patients who did not develop CDI (p < 0.01) and in 46 healthy controls (p < 0.0001). Another unconjugated secondary BA ratio, 3β-hydroxy (3βOH)-BAs/(3βOH + 3αOH-BAs), was also significantly lower in patients who developed CDI than in healthy controls (p < 0.05) but was not significantly different between patients who developed and patients who did not develop CDI. A receiver operating characteristic (ROC) curve determined a cut-off point of DCA/(DCA + CA) < 0.349 that optimally discriminated on admission the high-risk patients who would develop CDI (sensitivity 91.7% and specificity 64.4%). In conclusion, a decreased serum DCA/(DCA + CA) ratio on admission strongly correlated with CDI onset during hospitalization in patients with gastrointestinal and hepatobiliary diseases. Serum BA composition could be a helpful biomarker for predicting susceptibility to CDI.

Prebiotic effects of goji berry in protection against inflammatory bowel disease

The prevalence of inflammatory bowel disease (IBD) is increasing, which is concerning because IBD is a known risk factor for the development of colorectal cancer. Emerging evidence highlights environmental factors, particularly dietary factors and gut microbiota dysbiosis, as pivotal inducers of IBD onset. Goji berry, an ancient tonic food and a nutraceutical supplement, contains a range of phytochemicals such as polysaccharides, carotenoids, and polyphenols. Among these phytochemicals, L. barbarum polysaccharides (LBPs) are the most important functional constituents, which have protective effects against oxidative stress, inflammation, and neurodegeneration. Recently, the beneficial effects of goji berry and associated LBPs consumption were linked to prebiotic effects, which can prevent dysbiosis associated with IBD. This review assessed pertinent literature on the protective effects of goji berry against IBD focusing on the gut microbiota and their metabolites in mediating the observed beneficial effects.

Bile Acid-Gut Microbiota Axis in Inflammatory Bowel Disease: From Bench to Bedside

Inflammatory bowel disease (IBD) is a chronic, relapsing inflammatory disorder of the gastrointestinal tract, with increasing prevalence, and its pathogenesis remains unclear. Accumulating evidence suggested that gut microbiota and bile acids play pivotal roles in intestinal homeostasis and inflammation. Patients with IBD exhibit decreased microbial diversity and abnormal microbial composition marked by the depletion of phylum Firmicutes (including bacteria involved in bile acid metabolism) and the enrichment of phylum Proteobacteria. Dysbiosis leads to blocked bile acid transformation. Thus, the concentration of primary and conjugated bile acids is elevated at the expense of secondary bile acids in IBD. In turn, bile acids could modulate the microbial community. Gut dysbiosis and disturbed bile acids impair the gut barrier and immunity. Several therapies, such as diets, probiotics, prebiotics, engineered bacteria, fecal microbiota transplantation and ursodeoxycholic acid, may alleviate IBD by restoring gut microbiota and bile acids. Thus, the bile acid–gut microbiota axis is closely connected with IBD pathogenesis. Regulation of this axis may be a novel option for treating IBD.

Alterations in Bile Acid Metabolism Associated With Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory disorder closely related to gut dysbiosis, which is associated with alterations in an important bacterial metabolite, bile acids (BAs). Although certain findings pertinent to BA changes in IBD vary among studies owing to the differences in sample type, quantitated BA species, study methodology, and patient characteristics, a specific trend concerning variations of BAs in IBD has been identified. In elaborating on this observation, it was noted that primary BAs and conjugated BAs are augmented in fecal samples but there is a reduction in secondary BAs in fecal samples. It is not entirely clear why patients with IBD manifest these changes and what role these changes play in the onset and development of IBD. Previous studies have shown that IBD-associated BA changes may be caused by alterations in BA absorption, synthesis, and bacterial modification. The complex relationship between bacteria and BAs may provide additional and deeper insight into host-gut microbiota interactions in the pathogenesis of IBD. The characteristic BA changes may generate profound effects in patients with IBD by shaping the gut microbiota community, affecting inflammatory processes, causing BA malabsorption associated with diarrhea, and even leading to intestinal dysplasia and cancer. Thus, therapeutic strategies correcting the alterations in the composition of BAs, including the elimination of excess BAs and the supplementation of deficient BAs, may prove promising in IBD.

Relationship between the gut microbiota and bile acid composition in the ileal mucosa of Crohn's disease

Background/Aims

Crosstalk between the gut microbiota and bile acid plays an important role in the pathogenesis of gastrointestinal disorders. We investigated the relationship between microbial structure and bile acid metabolism in the ileal mucosa of Crohn's disease (CD).

Methods

Twelve non-CD controls and 38 CD patients in clinical remission were enrolled. Samples were collected from the distal ileum under balloon-assisted enteroscopy. Bile acid composition was analyzed by liquid chromatography-mass spectrometry. The gut microbiota was analyzed by 16S rRNA gene sequencing.

Results

The Shannon evenness index was significantly lower in endoscopically active lesions than in non-CD controls. β-Diversity, evaluated by the UniFrac metric, revealed a significant difference between the active lesions and non-CD controls (P=0.039). The relative abundance of Escherichia was significantly higher and that of Faecalibacterium and Roseburia was significantly lower in CD samples than in non-CD controls. The increased abundance of Escherichia was more prominent in active lesions than in inactive lesions. The proportion of conjugated bile acids was significantly higher in CD patients than in non-CD controls, but there was no difference in the proportion of primary or secondary bile acids. The genera Escherichia and Lactobacillus were positively correlated with the proportion of conjugated bile acids. On the other hand, Roseburia, Intestinibacter, and Faecalibacterium were negatively correlated with the proportion of conjugated bile acids.

Conclusions

Mucosa-associated dysbiosis and the alteration of bile acid composition were identified in the ileum of CD patients. These may play a role in the pathophysiology of ileal lesions in CD patients.

Metabolomic Analysis in Inflammatory Bowel Disease: A Systematic Review

BACKGROUND AND AIMS

The inflammatory bowel diseases [IBD], Crohn's disease and ulcerative colitis, are chronic, idiopathic gastrointestinal diseases. Although their precise aetiology is unknown, it is thought to involve a complex interaction between genetic predisposition and an abnormal host immune response to environmental exposures, probably microbial. Microbial dysbiosis has frequently been documented in IBD. Metabolomics [the study of small molecular intermediates and end products of metabolism in biological samples] provides a unique opportunity to characterize disease-associated metabolic changes and may be of particular use in quantifying gut microbial metabolism. Numerous metabolomic studies have been undertaken in IBD populations, identifying consistent alterations in a range of molecules across several biological matrices. This systematic review aims to summarize these findings.

METHODS

A comprehensive, systematic search was carried out using Medline and Embase. All studies were reviewed by two authors independently using predefined exclusion criteria. Sixty-four relevant papers were assessed for quality and included in the review.

RESULTS

Consistent metabolic perturbations were identified, including increases in levels of branched chain amino acids and lipid classes across stool, serum, plasma and tissue biopsy samples, and reduced levels of microbially modified metabolites in both urine [such as hippurate] and stool [such as secondary bile acids] samples.

CONCLUSIONS

This review provides a summary of metabolomic research in IBD to date, highlighting underlying themes of perturbed gut microbial metabolism and mammalian-microbial co-metabolism associated with disease status.

Identification of colorectal neoplasia by using serum bile acid profile

BACKGROUND

Colonoscopy is the gold standard for detecting earlier stages of CRC, although screening of patients is difficult because of invasiveness, low compliance and procedural health risks. Therefore, the need for new screening methods for CRC is rising. Previous studies have demonstrated the diagnostic ability of serum BAs; however, the results have been inconsistent. In this study, we conducted a comprehensive analysis of serum BAs from patients with CRC and verified their diagnostic ability to detect CRC.

METHODS

A total of 56 CRC patients (n = 14 each of stages I-IV), 59 patients with colonic adenoma and 60 healthy controls were included. Age and sex were matched for each group. Serum BA compositions were measured by LC-MS/MS and serum concentration of 30 types of BAs were analysed by discriminant analysis with multidimensional scaling method.

RESULTS

Free CA, 3epi-DCA&CDCA, 3-dehydro CA, GCA and TCA were extracted as principal component (PC) 1 and free 3-dehydroDCA as PC 2 by canonical discriminant function coefficients. The verification of discriminability using cross-validation method revealed that the correct classification rate was 66.3% for original data and 52.6% for cross-validation data.

CONCLUSIONS

A combined analysis using comprehensive serum BA concentration can be an efficient method for screening CRC.

Developmental Patterns of Fecal Bile Acids in Healthy Neonates and Children

Background

Normal profiles of FBAs in healthy neonates and children in Kunming city and surrounding areas in China have not been previously determined. The objective of this study was to determine a developmental pattern of fecal bile acids (FBAs) in healthy neonates and children.

Material/Methods

A cross-sectional study was performed on 238 healthy neonates and children recruited in the First Affiliated Hospital of Kunming Medical University, China from October 2015 to September 2016. Secreted primary and secondary FBAs in fresh feces were quantitated by liquid chromatography mass spectrometry (LC-MS). Amounts of FBAs in feces were compared among various age groups.

Results

Trace amounts of cholic acid and chenodiol acid of primary FBAs were detectable at day 3 after birth, with a significant increase from day 3 to day 7. The primary FBAs gradually decreased from day 25 to the age of 6 years old. In contrast, a significant amount of glycochenodeoxycholic acid was detected on day 3 but decreased to a trace amount by day 7 and onwards. Primary FBAs appeared to maintain a high level, accounting for 98% of total FBAs, with no significant changes from day 7 to day 25 after birth. They gradually decreased from 90% to 10% from age 6 months to 6 years old. While the secondary FBAs were barely detected in neonates, only accounting for 2% of total FBAs, they were gradually elevated to 90% of total FBAs from age 6 months to 6 years old.

Conclusions

The liver can effectively synthesize primary bile acids 7 days after birth, and fecal primary bile acids tend to be stable after the neonate stage. Secondary bile acids continuously increase along with the maturation of intestinal flora, which reaches a relatively stable level at around 3 years old.

Immunosecurity: immunomodulants enhance immune responses in chickens

The global population has increased with swift urbanization in developing countries, and it is likely to result in a high demand for animal-derived protein-rich foods. Animal farming has been constantly affected by various stressful conditions, which can be categorized into physical, environmental, nutritional, and biological factors. Such conditions could be exacerbated by banning on the use of antibiotics as a growth promoter together with a pandemic situation including, but not limited to, African swine fever, avian influenza, and foot-and-mouth disease. To alleviate these pervasive tension, various immunomodulants have been suggested as alternatives for antibiotics. Various studies have investigated how stressors (i.e., imbalanced nutrition, dysbiosis, and disease) could negatively affect nutritional physiology in chickens. Importantly, the immune system is critical for host protective activity against pathogens, but at the same time excessive immune responses negatively affect its productivity. Yet, comprehensive review articles addressing the impact of such stress factors on the immune system of chickens are scarce. In this review, we categorize these stressors and their effects on the immune system of chickens and attempt to provide immunomodulants which can be a solution to the aforementioned problems facing the chicken industry.

Gut microbiota associations with metabolic syndrome and relevance of its study in pediatric subjects

Childhood obesity and T2DM have shown a recent alarming increase due to important changes in global lifestyle and dietary habits, highlighting the need for urgent and novel solutions to improve global public health. Gut microbiota has been shown to be relevant in human health and its dysbiosis has been associated with MetS, a health condition linked to the onset of relevant diseases including T2DM. Even though there have been recent improvements in the understanding of gut microbiota-host interactions, pediatric gut microbiota has been poorly studied compared to adults. This review provides an overview of MetS and its relevance in school-age children, discusses gut microbiota and its possible association with this metabolic condition including relevant emerging gut microbiome-based interventions for its prevention and treatment, and outlines future challenges and perspectives in preventing microbiota dysbiosis from the early stages of life.

Integrated analysis of microbiome and host transcriptome reveals correlations between gut microbiota and clinical outcomes in HBV-related hepatocellular carcinoma

Background

The gut-liver axis plays a pivotal role in the pathogenesis of hepatocellular carcinoma (HCC). However, the correlations between the gut microbiome and the liver tumor transcriptome in patients with HCC and the impact of the gut microbiota on clinical outcome are less well-understood.

Methods

Fecal samples collected from HBV-related HCC patients (n = 113) and healthy volunteers (n = 100) were subjected to 16S rRNA sequencing of the microbiome. After a rigorous selection process, 32 paired tumor and adjacent non-tumor liver tissues from the HCC group were subjected to next-generation sequencing (NGS) RNA-seq. The datasets were analyzed individually and integrated with clinical characteristics for combined analysis using bioinformatics approaches. We further verified the potential of the gut microbiota to predict clinical outcome by a random forest model and a support vector machine model.

Results

We found that Bacteroides, Lachnospiracea incertae sedis, and Clostridium XIVa were enriched in HCC patients with a high tumor burden. By integrating the microbiome and transcriptome, we identified 31 robust associations between the above three genera and well-characterized genes, indicating possible mechanistic relationships in tumor immune microenvironment. Clinical characteristics and database analysis suggested that serum bile acids may be important communication mediators between these three genera and the host transcriptome. Finally, among these three genera, six important microbial markers associated with tumor immune microenvironment or bile acid metabolism showed the potential to predict clinical outcome (AUC = 81%).

Conclusions

This study revealed that changes in tumor immune microenvironment caused by the gut microbiota via serum bile acids may be important factors associated with tumor burden and adverse clinical outcome. Gut microbes can be used as biomarkers of clinical features and outcomes, and the microbe-associated transcripts of host tumors can partly explain how gut microbiota promotes HCC pathogenesis.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13073-020-00796-5.

Ten Reasons to Think About Bile Acids in Managing Inflammatory Bowel Disease

There are ten good reasons why it is important to think about abnormalities in bile acid control in inflammatory bowel disease. Before reviewing these reasons, it is relevant to review essential elements in the enterohepatic circulation, synthesis and actions of bile acids.

Epigallocatechin-3-gallate (EGCG) attenuates non-alcoholic fatty liver disease via modulating the interaction between gut microbiota and bile acids

The spectrum of non-alcoholic fatty liver disease (NAFLD) ranges from simple hepatic steatosis commonly associated with obesity, to non-alcoholic steatohepatitis, which can progress to fibrosis, cirrhosis and hepatocellular carcinoma. Recent reports have indicated the crucial role of gut microbiota and their metabolites in the progression of NAFLD. In the present review, we demonstrated the influence of oral administration of (-)-epigallocatechin-3-gallate (EGCG) on the gut microbiota, serum bile acid profile, and gene expression in the liver in mice fed a high-fat diet (HFD). EGCG significantly inhibited the increase in histological fatty deposit and triglyceride accumulation in the liver induced by HFD, and improved intestinal dysbiosis. One of important findings is that the abundance of Proteobacteria and Defferibacteres phylums increased markedly in the HFD group, and this increase was significantly suppressed in the EGCG group. Interestingly, taurine-conjugated cholic acid (TCA) increased in the HFD group, like the mirror image against a marked decrease in the cholic acid (CA) value, and this increase was markedly inhibited in the EGCG group. TCA is not a simple serum biomarker for liver injury but TCA may be a causal factor to disturb lipid metabolism. The distribution of correlation coefficients by Heatmap analysis showed that the abundance of Akkermansia and Parabacteroides genus showed a positive correlation with CA and a negative correlation with TCA, and significantly increased in the EGCG group as compared with the HFD group. In addition, nutrigenomics approaches demonstrated that sirtuin signaling, EIF2 pathway and circadian clock are involved in the anti-steatotic effects of EGCG. In the present paper, we summarized recent update data of EGCG function focusing on intestinal microbiota and their interaction with host cells.

Age-related analysis of the gut microbiome in a purebred dog colony

Dogs are model animals that can be used to study the gut microbiome. Although the gut microbiome is assumed to be closely related to aging, information pertaining to this relationship in dogs is limited. Here, we examined the association between the canine gut microbiome and age via a bacterial 16S rRNA gene amplicon sequence analysis in a colony of 43 Japanese purebred Shiba Inu dogs. We found that microbial diversity tended to decrease with aging. A differential abundance analysis showed an association of a single specific microbe with aging. The age-related coabundance network analysis showed that two microbial network modules were positively and negatively associated with aging, respectively. These results suggest that the dog gut microbiome is likely to vary with aging.

Impaired bile acid metabolism with defectives of mitochondrial-tRNA taurine modification and bile acid taurine conjugation in the taurine depleted cats

Taurine that conjugates with bile acid (BA) and mitochondrial-tRNA (mt-tRNA) is a conditional essential amino acid in humans, similarly to cats. To better understand the influence of acquired depletion of taurine on BA metabolism, the profiling of BAs and its intermediates, BA metabolism-enzyme expression, and taurine modified mt-tRNAs were evaluated in the taurine deficient diet-supplemented cats. In the taurine depleted cats, taurine-conjugated bile acids in bile and taurine-modified mt-tRNA in liver were significantly decreased, whereas unconjugated BA in serum was markedly increased. Impaired bile acid metabolism in the liver was induced accompanied with the decreases of mitochondrial cholesterol 27-hydroxylase expression and mitochondrial activity. Consequently, total bile acid concentration in bile was significantly decreased by the low activity of mitochondrial bile acid synthesis. These results implied that the insufficient dietary taurine intake causes impaired bile acid metabolism, and in turn, a risk for the various diseases similar to the mitochondrial diseases would be enhanced.

Regulation of bile acid metabolism in mouse models with hydrophobic bile acid composition

The bile acid (BA) composition in mice is substantially different from that in humans. Chenodeoxycholic acid (CDCA) is an end product in the human liver; however, mouse Cyp2c70 metabolizes CDCA to hydrophilic muricholic acids (MCAs). Moreover, in humans, the gut microbiota converts the primary BAs, cholic acid and CDCA, into deoxycholic acid (DCA) and lithocholic acid (LCA), respectively. In contrast, the mouse Cyp2a12 reverts this action and converts these secondary BAs to primary BAs. Here, we generated Cyp2a12 KO, Cyp2c70 KO, and Cyp2a12/Cyp2c70 double KO (DKO) mice using the CRISPR-Cas9 system to study the regulation of BA metabolism under hydrophobic BA composition. Cyp2a12 KO mice showed the accumulation of DCAs, whereas Cyp2c70 KO mice lacked MCAs and exhibited markedly increased hepatobiliary proportions of CDCA. In DKO mice, not only DCAs or CDCAs but also DCAs, CDCAs, and LCAs were all elevated. In Cyp2c70 KO and DKO mice, chronic liver inflammation was observed depending on the hepatic unconjugated CDCA concentrations. The BA pool was markedly reduced in Cyp2c70 KO and DKO mice, but the FXR was not activated. It was suggested that the cytokine/c-Jun N-terminal kinase signaling pathway and the pregnane X receptor-mediated pathway are the predominant mechanisms, preferred over the FXR/small heterodimer partner and FXR/fibroblast growth factor 15 pathways, for controlling BA synthesis under hydrophobic BA composition. From our results, we hypothesize that these KO mice can be novel and useful models for investigating the roles of hydrophobic BAs in various human diseases.

Decrease in major secondary bile acid, hyodeoxycholic acid, was the main alteration in hepatic bile acid compositions in a hypertensive nonalcoholic fatty liver disease model

BACKGROUND

Previous findings on hepatic bile acid compositions in nonalcoholic fatty liver disease (NAFLD) have been inconsistent and complicated. The aim of this study was to investigate the effects of steatosis on hepatic bile acid composition in a hypertensive NAFLD model without obesity and diabetes mellitus and compare hepatic bile acid composition between hypertensive rats with and without steatosis.

METHODS

Two groups of hypertensive rats were studied: spontaneously hypertensive rats (SHR) fed with a normal diet (SHR-N) or a choline-deficient diet (SHR-CD). Two groups of normotensive rats were studied: Wistar Kyoto rats (WKY) fed a normal diet (WKY-N) or a choline-deficient diet (WKY-CD). Hepatic bile acid analysis was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry.

RESULTS

Regarding bile acid composition, the hyodeoxycholic acid (HDCA) species in the SHR-CD group showed the largest change in bile acid composition, significantly decreasing to 21.9% of that found in the SHR-N group. In the WKY-CD group, no reduction of HDCA species was observed.

CONCLUSIONS

We demonstrated that the decrease in HDCA species was the main alteration in a hypertensive NAFLD model. It was suggested that the decrease in HDCA species in the SHR-CD group was caused by dysbiosis.

Green tea polyphenol (epigallocatechin-3-gallate) improves gut dysbiosis and serum bile acids dysregulation in high-fat diet-fed mice

Gut microbiota have profound effects on bile acid metabolism by promoting deconjugation, dehydrogenation, and dehydroxylation of primary bile acids in the distal small intestine and colon. High-fat diet-induced dysbiosis of gut microbiota and bile acid dysregulation may be involved in the pathology of steatosis in patients with non-alcoholic fatty liver disease. Epigallocatechin-3-gallate (EGCG), the most abundant polyphenolic catechin in green tea, has been widely investigated for its inhibitory or preventive effects against fatty liver. The aim of the present study was to investigate the effects of EGCG on the abundance of gut microbiota and the composition of serum bile acids in high-fat diet-fed mice and determine the specific bacterial genera that can improve the serum bile acid dysregulation associated with EGCG anti-hepatic steatosis action. Male C57BL/6N mice were fed with the control diet, high-fat diet, or high-fat diet + EGCG at a concentration of 0.32% for 8 weeks. EGCG significantly inhibited the increases in weight, the area of fatty lesions, and the triglyceride content in the liver induced by the high-fat diet. Principal coordinate analysis revealed significant differences in microbial structure among the groups. At the genus level, EGCG induced changes in the microbiota composition in high-fat diet-fed mice, showing a significantly higher abundance of Adlercreutzia, Akkermansia, Allobaculum and a significantly lower abundance of Desulfovibrionaceae. EGCG significantly reversed the decreased population of serum primary cholic acid and β-muricholic acid as well as the increased population of taurine-conjugated cholic acid, β-muricholic acid and deoxycholic acid in high-fat diet-fed mice. Finally, the correlation analysis between bile acid profiles and gut microbiota demonstrated the contribution of Akkermansia and Desulfovibrionaceae in the improvement of bile acid dysregulation in high-fat diet-fed mice by treatment with EGCG. In conclusion, the present study suggests that EGCG could alter bile acid metabolism, especially taurine deconjugation, and suppress fatty liver disease by improving the intestinal luminal environment.

Influences of Taurine Deficiency on Bile Acids of the Bile in the Cat Model

Taurine content in the body is maintained by both biosynthesis from sulfur-contained amino acids in the liver and ingestion from usual foods, mainly seafoods and meat. Contrary to the rodents, the maintenance of taurine content in the body depends on the oral taurine ingestion in cats as well as humans because of the low ability of the biosynthesis. Therefore, insufficient of dietary taurine intake increases the risks of various diseases such as blind and expanded cardiomyopathy in the cats. One of the most established physiological roles of taurine is the conjugation with bile acid in the liver. In addition, taurine has effect to increase the expression and activity of bile acid synthesis rate-limiting enzyme CYP7A1. Present study purposed to evaluate the influence of taurine deficiency on bile acids in the cats fed taurine-lacking diet. Adult cats were fed the soybean protein-based diet with 0.15% taurine or without taurine for 30 weeks. Taurine concentration in serum and liver was undetectable, and bile acids in the bile were significantly decreased in the taurine-deficient cats. Taurine-conjugated bile acids in the bile were significantly decreased, and instead, unconjugated bile acids were significantly increased in the taurine-deficient cats. Present results suggested that the taurine may play an important role in the synthesis of bile acids in the liver.