Influence of calcineurin inhibitors and genetic polymorphism of transporters on enterohepatic circulation and exposure of mycophenolic acid in Chinese adult renal allograft recipients

Aim: Study the influence of calcineurin inhibitors (CNI) and genetic polymorphisms of transporters on enterohepatic circulation (EHC) of mycophenolic acid (MPA) in Chinese adult renal allograft recipients and estimate the effect of various covariates on prediction performance of MPA AUC0-12h. Method: MPA concentrations of 125 Chinese patients were collected 0-12 hours after administration. Genotypes of transporters were determined in 64 patients. The influence of type of CNI and genetic polymorphisms on MPA exposure was studied. Shapley additive explanations method was used to study the impact of sampling times and covariates related to EHC on AUC0-12h. Extreme gradient boosting (XGboost) machine learning-based model was established to predict AUC0-12h. Results: Dn-AUC6-12h was significantly lower in patients co-administered with CsA (P<0.05). When co-administered with TAC, for SLCO1B1 T521C or ABCC C-24T, patients with wild-type genotype had significantly higher dn-AUC6-12h (P <0.05). Patients with SLCO1B3 334T/699G alleles had significantly lower dn-AUC6-12h than homozygotes (P=0.004). No significant difference was found in CsA subgroup. For estimating AUC0-12h, C0h, C2h, C8h, type of CNI, transporters genotypes and the difference between C0h and C2h were retained in the final model, which had good prediction performance (r2=0.9739). Conclusion: Patients co-administered with CsA had lower MPA EHC than those who received TAC. MPA EHC is affected by ABCC2 C-24T, SLCO1B3 T334G/G699A, and SLCO1B1 T521C genotypes in patients treated with TAC. Type of CNI and genetic polymorphisms of transporters can improve prediction performance of MPA AUC0-12h estimating model, developed using XGboost machine learning method.

Arbutin Alleviates the Liver Injury of α-Naphthylisothiocyanate-induced Cholestasis Through Farnesoid X Receptor Activation

Cholestasis is a kind of stressful syndrome along with liver toxicity, which has been demonstrated to be related to fibrosis, cirrhosis, even cholangiocellular or hepatocellular carcinomas. Cholestasis usually caused by the dysregulated metabolism of bile acids that possess high cellular toxicity and synthesized by cholesterol in the liver to undergo enterohepatic circulation. In cholestasis, the accumulation of bile acids in the liver causes biliary and hepatocyte injury, oxidative stress, and inflammation. The farnesoid X receptor (FXR) is regarded as a bile acid–activated receptor that regulates a network of genes involved in bile acid metabolism, providing a new therapeutic target to treat cholestatic diseases. Arbutin is a glycosylated hydroquinone isolated from medicinal plants in the genus Arctostaphylos, which has a variety of potentially pharmacological properties, such as anti-inflammatory, antihyperlipidemic, antiviral, antihyperglycemic, and antioxidant activity. However, the mechanistic contributions of arbutin to alleviate liver injury of cholestasis, especially its role on bile acid homeostasis via nuclear receptors, have not been fully elucidated. In this study, we demonstrate that arbutin has a protective effect on α-naphthylisothiocyanate–induced cholestasis via upregulation of the levels of FXR and downstream enzymes associated with bile acid homeostasis such as Bsep, Ntcp, and Sult2a1, as well as Ugt1a1. Furthermore, the regulation of these functional proteins related to bile acid homeostasis by arbutin could be alleviated by FXR silencing in L-02 cells. In conclusion, a protective effect could be supported by arbutin to alleviate ANIT-induced cholestatic liver toxicity, which was partly through the FXR pathway, suggesting arbutin may be a potential chemical molecule for the cholestatic disease.

Perfluoroalkyl Carboxylic Acids Interact with the Human Bile Acid Transporter NTCP

Na+/taurocholate cotransporting polypeptide (NTCP) is important for the enterohepatic circulation of bile acids, which has been suggested to contribute to the long serum elimination half-lives of perfluoroalkyl substances in humans. We demonstrated that some perfluoroalkyl sulfonates are transported by NTCP; however, little was known about carboxylates. The purpose of this study was to determine if perfluoroalkyl carboxylates would interact with NTCP and potentially act as substrates. Sodium-dependent transport of [3H]-taurocholate was measured in human embryonic kidney cells (HEK293) stably expressing NTCP in the absence or presence of perfluoroalkyl carboxylates with varying chain lengths. PFCAs with 8 (PFOA), 9 (PFNA), and 10 (PFDA) carbons were the strongest inhibitors. Inhibition kinetics demonstrated competitive inhibition and indicated that PFNA was the strongest inhibitor followed by PFDA and PFOA. All three compounds are transported by NTCP, and kinetics experiments revealed that PFOA had the highest affinity for NTCP with a Km value of 1.8 ± 0.4 mM. The Km value PFNA was estimated to be 5.3 ± 3.5 mM and the value for PFDA could not be determined due to limited solubility. In conclusion, our results suggest that, in addition to sulfonates, perfluorinated carboxylates are substrates of NTCP and have the potential to interact with NTCP-mediated transport.

Novel therapeutic targets for cholestatic and fatty liver disease

Cholestatic and non-alcoholic fatty liver disease (NAFLD) share several key pathophysiological mechanisms which can be targeted by novel therapeutic concepts that are currently developed for both areas. Nuclear receptors (NRs) are ligand-activated transcriptional regulators of key metabolic processes including hepatic lipid and glucose metabolism, energy expenditure and bile acid (BA) homoeostasis, as well as inflammation, fibrosis and cellular proliferation. Dysregulation of these processes contributes to the pathogenesis and progression of cholestatic as well as fatty liver disease, placing NRs at the forefront of novel therapeutic approaches. This includes BA and fatty acid activated NRs such as farnesoid-X receptor (FXR) and peroxisome proliferator-activated receptors, respectively, for which high affinity therapeutic ligands targeting specific or multiple isoforms have been developed. Moreover, novel liver-specific ligands for thyroid hormone receptor beta 1 complete the spectrum of currently available NR-targeted drugs. Apart from FXR ligands, BA signalling can be targeted by mimetics of FXR-activated fibroblast growth factor 19, modulation of their enterohepatic circulation through uptake inhibitors in hepatocytes and enterocytes, as well as novel BA derivatives undergoing cholehepatic shunting (instead of enterohepatic circulation). Other therapeutic approaches more directly target inflammation and/or fibrosis as critical events of disease progression. Combination strategies synergistically targeting metabolic disturbances, inflammation and fibrosis may be ultimately necessary for successful treatment of these complex and multifactorial disorders.

Gut Microbiota-Related Cellular and Molecular Mechanisms in the Progression of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common and increasing liver diseases worldwide. NAFLD is a term that involves a variety of conditions such as fatty liver, steatohepatitis, or fibrosis. Gut microbiota and its products have been extensively studied because of a close relation between NAFLD and microbiota in pathogenesis. In the progression of NAFLD, various microbiota-related molecular and cellular mechanisms, including dysbiosis, leaky bowel, endotoxin, bile acids enterohepatic circulation, metabolites, or alcohol-producing microbiota, are involved. Currently, diagnosis and treatment techniques using these mechanisms are being developed. In this review, we will introduce the microbiota-related mechanisms in the progression of NAFLD and future directions will be discussed.

SLC51 family of steroid-derived molecule transporters in GtoPdb v.2021.3

The SLC51 organic solute transporter family of transporters is a pair of heterodimeric proteins which regulate bile salt movements in the small intestine, bile duct, and liver, as part of the enterohepatic circulation [2, 5, 1]. OSTα/OSTβ is also expressed in steroidogenic cells of the brain and adrenal gland, where it may contribute to steroid movement [6]. Bile acid transport is suggested to be facilitative and independent of sodium, potassium, chloride ions or protons [5, 2]. OSTα/OSTβ heterodimers have been shown to transport [3H]taurocholic acid, [3H]dehydroepiandrosterone sulphate, [3H]estrone-3-sulphate, [3H]pregnenolone sulphate and [3H]dehydroepiandrosterone sulphate [2, 5, 6]. OSTα/OSTβ-mediated transport of bile salts is inhibited by clofazimine [10]. OSTα is suggested to be a seven TM protein, while OSTβ is a single TM 'ancillary' protein, both of which are thought to have intracellular C-termini [8]. Both proteins function in solute transport [8, 4]. Inherited mutations in OSTα and OSTβ are associated with liver disease and congenital diarrhea in children [9, 7].

1134 Incidence of Bile Acid Diarrhoea Post-Cholecystectomy - A Single Centre Cohort

Aim Bile acid diarrhoea (BAD) can occur as a result of enterohepatic circulation interruption following cholecystectomy. Although up to 57.2% of patients are reported to develop post-cholecystectomy diarrhoea, this is not always because of BAD. The aim of this study was to determine the incidence of post-cholecystectomy BAD diagnosis and evaluate the current practices. Method This study was conducted as part of BADCAP study. The electronic records of patients underwent cholecystectomy operation at Oxford University Hospitals between January 2013 and December 2017 were retrospectively analysed. Records were matched with patients who underwent 75SeHCAT testing during the same time period. A positive 75SeHCAT testing was defined as a seven-day retention time of &lt; 15%. Results A total of 4327 patients underwent cholecystectomy operation. 2.05% (N = 89) investigated for diarrhoea by 75SeHCAT. Alongside 75SeHCAT, 69.7% (N = 62) had colonoscopy, 37.1% (N = 33) had CT abdomen and pelvis and 3.4% (N = 3) had MRCP/MRE. Gender wise statistics revealed females were 74.5% (N = 73) and males were 19.1% (N = 17). Median time from cholecystectomy to 75SeHCAT test was 780 days (SD +/-510 days). 70.8% (N = 63) had a positive 75SeHCAT test for BAD. IBD was confirmed in 2.2% (N = 2). Conclusions A small number of patients were investigated and only 1.5% were diagnosed with post-cholecystectomy diarrhoea. There was a significant time delay from operation to diagnosis. The true prevalence of BAD after cholecystectomy may be much higher and clinicians need to have an increased awareness of this condition. 75SeHCAT is a useful tool for diagnosis of bile acid diarrhoea.

Bile Acids, Liver Cirrhosis, and Extrahepatic Vascular Dysfunction

The bile acid pool with its individual bile acids (BA) is modulated in the enterohepatic circulation by the liver as the primary site of synthesis, the motility of the gallbladder and of the intestinal tract, as well as by bacterial enzymes in the intestine. The nuclear receptor farnesoid X receptor (FXR) and Gpbar1 (TGR5) are important set screws in this process. Bile acids have a vasodilatory effect, at least according to in vitro studies. The present review examines the question of the extent to which the increase in bile acids in plasma could be responsible for the hyperdynamic circulatory disturbance of liver cirrhosis and whether modulation of the bile acid pool, for example, via administration of ursodeoxycholic acid (UDCA) or via modulation of the dysbiosis present in liver cirrhosis could influence the hemodynamic disorder of liver cirrhosis. According to our analysis, the evidence for this is limited. Long-term studies on this question are lacking.