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.

Background: Wild-type (WT) mice fed a conventional high-fat/high-sucrose diet (HFHSD) rarely develop metabolic dysfunction–associated steatohepatitis (MASH) with HCC. Because mouse bile acid (BA) is highly hydrophilic, we hypothesized that making it hydrophobic would lead to MASH with HCC. Methods: Eleven-week-old WT and Cyp2a12/Cyp2c70 double knockout (DKO) mice were divided into two groups, including one which was fed a normal chow diet, and one which was fed an HFHSD. Samples were collected after 15, 30, 47, and 58 weeks for histological, biochemical, and immunological analyses. Results: In the HFHSD group, body weight gain did not differ in WT versus DKO mice, although HFHSD-fed DKO mice exhibited markedly accelerated liver inflammation, fibrosis, and carcinogenesis. HFHSD upregulated lipogenesis and downregulated fatty acid oxidation in both WT and DKO mice, which increased liver lipid accumulation and lipotoxicity. However, the increase in reactive oxygen species production and carcinogenesis observed in DKO mice could not be explained by abnormal lipid metabolism alone. Regarding BA metabolism, DKO mice had a higher hydrophobicity index. They exhibited an age-associated increase in chenodeoxycholic acid (CDCA) levels because of CYP8B1 activity inhibition due to the farnesoid X receptor activation. HFHSD further downregulated CYP8B1, presumably by activating the Liver X receptor. Liver CDCA accumulation was associated with increased inflammation, reactive oxygen species production, and hepatocyte FGF15 induction. Moreover, in noncancerous liver tissues, HFHSD appeared to activate STAT3, an oncogenic transcription factor, which was enhanced by a CDCA-rich environment. Conclusions: Here, we developed a new model of MASH with HCC using mice with human-like BA composition and found that HFHSD and elevated hepatic CDCA synergistically increased the risk of MASH with HCC.

Background: Covert hepatic encephalopathy (CHE) leads to devastating outcomes in patients with cirrhosis. This study aims to elucidate the current management and future perspectives of CHE in Japan. Methods: A questionnaire-based cross-sectional study was conducted among physicians involved in managing cirrhosis in Japan. The primary aim was to elucidate the real-world management of CHE, including testing and treatment. Factors influencing the implementation of CHE testing were analyzed using a logistic regression model. Limitations and future perspectives for improving the management of CHE were also evaluated. Results: Of 511 physicians surveyed, 93.9% recognized CHE as a significant problem, and 86.9% agreed that it should be tested. Overall, 62.8% of physicians tested for CHE, whereas 37.2% did not. Multivariable analysis identified institutional factors and certifying board as significant determinants of CHE test implementation. The Stroop (68.2%) and neuropsychiatric tests (57.5%) were the most commonly used methods of identifying CHE. Among those who tested for CHE, 87.7% treated CHE; the most common treatments were lactulose (81.5%), rifaximin (76.3%), and branched-chain amino acids (70.4%). Among non-testers, the primary barrier was the time requirement for testing. Proposals to encourage CHE testing included the development of simple tests and integration of multidisciplinary teams. Conclusions: Most physicians involved in cirrhosis care in Japan recognize CHE as a significant problem that warrants testing. However, testing for CHE remains limited by institutional factors and physician specialties. Time requirements for CHE testing are the primary barrier, and simple tests and multidisciplinary teams are recommended to enhance CHE management.

Aim: Bile acid (BA) signaling plays an important role in the pathogenesis of hepatic encephalopathy (HE), including covert (CHE) and overt HE (OHE). However, few studies have examined its clinical impact in patients with cirrhosis. Methods: This retrospective study included patients with cirrhosis who underwent CHE assessment using a computer‐aided neuropsychiatric test. BAs were quantified using liquid chromatography‐tandem mass spectrometry. Patients were divided into high and low groups according to their BA levels. Independent factors, namely CHE, OHE development, and mortality, were assessed using logistic, Fine–Gray competing risk, and Cox proportional hazards regression models. Results: Among the 189 patients, the median age was 71 years, 74.1% were male, and 28.0% were diagnosed with CHE. During a median follow‐up period of 3.1 years, 15.9% ( n = 30) developed OHE, and 33.3% ( n = 63) died. Considering mortality as a competing risk, multivariable analysis identified a high conjugated primary BA level (subdistribution hazard ratio [HR] 3.44; 95% confidence interval [CI] 1.08–10.97) as an independent factor for OHE development. Additionally, a high non‐conjugated primary BA level (odds ratio 2.18; 95% CI 1.06–4.46) was an independent factor of CHE. Furthermore, a high conjugated primary BA level (HR 2.06; 95% CI 1.11–3.83) was an independent predictor of mortality. Conclusions: Elevated serum conjugated primary BA levels are an independent factor for OHE development and mortality in patients with cirrhosis. Additionally, elevated non‐conjugated primary BA levels were an independent factor for CHE in these patients.

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.