Review

Ursodeoxycholic acid ‘mechanisms of action and clinical use in hepatobiliary disorders’☆

Peach gum polysaccharides have multiple biological functions, such as anti-oxidation, blood lipids reduction, and immune protection. However, their impact on the gut microbiota was still unclear. Here, high throughput sequencing was used to study the regulatory effects of peach gum polysaccharide on gut microbiota using an in vitro fermentation model of human gut microbiota. The results showed that gut microbiota species increased significantly and α-diversity index (Sobs, Ace, Chao1, Shannon) decreased significantly after polysaccharide fermentation compared with control group (distilled water). At phylum level, the relative abundance of Firmicutes and Actinomyces increased (61.76% vs. 56.64%, 28.24% vs. 23.11%). In contrast, relative abundance of Bacteroides decreased significantly (8.10% vs. 19.21%). At genus level, the relative abundance of Bifidobacteria, Colinella and Parazobacteria increased significantly (21.43% vs. 19.08%, 6.32% vs. 3.73%, 6.37% vs. 0.00%), while the relative abundance of Bacteroides and Prevotella decreased significantly (3.83% vs. 5.52%, 3.49% vs. 12.15%). Precisely, peach gum polysaccharide can effectively regulate the structure of gut microbiota and has potential probiotic effects including anti-obesity, anti-inflammatory, maintenance of gut epithelial barrier and so on.

Based on our experiences in bile acid profiling, this work developed and validated a liquid chromatography electrospray ionization tandem mass spectrometry method to separate endogenous bile acid isomers and quantitatively determine ursodeoxycholic acid (UDCA), glycoursodeoxycholic acid (GUDCA) and tauroursodeoxycholic acid (TUDCA) in human plasma. The separation was performed on a CORTECS C18 column with the mobile phase consisting of 1.0 mM ammonium acetate and acetonitrile-methanol (80:20, v/v). UDCA, GUDCA and TUDCA were detected in the negative mode on a triple-quadrupole mass spectrometer at the ion transitions of m/z 391 > 391, m/z 448 > 74, m/z 498 > 80, respectively. Phosphate buffer was employed as the surrogate matrix to establish the isotope internal standard corrected calibration curves of analytes. The background-method with a linearity range of 10–200 ng/mL was partially validated to determine the endogenous levels of analytes in blank human plasma, which was incorporated into the validation of bioequivalence-method with a linearity range of 50–10000 ng/mL. The bioequivalence (BE)-method was fully validated with special focus on matrix effects, which have been critically evaluated using the precision and accuracy of quality control samples prepared from the blank human plasma of 12 individuals. It is disclosed for the first time that the BE results of UDCA formulation may yield false results when the method is insufficient to separate UDCA from isoursodeoxycholic acid, a microbial metabolite of both endogenous and exogenous UDCA. The present method has established a milestone for the evaluation of UDCA formulations and is expected to provide a valuable reference for the bioanalytical development of endogenous medicinal products.

In cancer therapy, a drug delivery system (DDS) has been widely studied to achieve selective drug accumulation at the tumor site. However, DDS still has a major drawback in that it requires multistep processes for intracellular delivery, resulting in low efficiency of drug delivery. To overcome this problem, we recently reported a molecular block (MB) that disrupts cancer cell membranes in the cancer microenvironment using deoxycholic acid (DCA). However, the MB showed considerable cytotoxicity even at neutral pH, possibly due to the structural hydrophobic property of DCA. Herein, we focused on selecting the most suitable bile acid for an MB that possessed high responsiveness to the cancer microenvironment without cytotoxicity at neutral pH. Cell viabilities of the free bile acids such as DCA, chenodeoxycholic acid (CDCA), cholic acid (CA), and ursodeoxycholic acid (UDCA) were evaluated at neutral pH (pH = 7.4) and a cancer acidic environment (pH = 6.3–6.5). The half-maximal inhibition concentration (IC₅₀) value of UDCA at pH = 7.4 showed an approximately 7.5-fold higher IC₅₀ value than that at pH = 6.3, whereas the other bile acids yielded less than a 4-fold IC₅₀ value difference between the same pHs. Biocompatible poly­(vinyl alcohol) (PVA) was functionalized with UDCA (PVA-UDCA) for the synthesis of higher responsiveness to the cancer microenvironment without cytotoxicity at neutral pH. Importantly, 56% pancreatic cancer cell death was observed at pH = 6.5, whereas only 10% was detected at neutral pH by the PVA-UDCA treatment. However, PVA-DCA indicated almost the same cancer cell death property, independent of pH conditions. These results suggest PVA-UDCA shows great potential for a new class of MB.

Dysregulation of lipid metabolism and diabetes are risk factors for nonalcoholic fatty liver disease (NAFLD), and the gut–liver axis and intestinal microbiome are known to be highly associated with the pathogenesis of this disease. In Japan, the traditional medicine daisaikoto (DST) is prescribed for individuals affected by hepatic dysfunction. Herein, we evaluated the therapeutic potential of DST for treating NAFLD through modification of the liver and stool metabolome and microbiome by using STAM mice as a model of NAFLD. STAM mice were fed a high-fat diet with or without 3 % DST for 3 weeks. Plasma and liver of STAM, STAM with DST, and C57BL/6J (“Normal”) mice were collected at 9 weeks, and stools at 4, 6, and 9 weeks of age. The liver pathology, metabolome and stool microbiome were analyzed. DST ameliorated the NAFLD activity score of STAM mice and decreased the levels of several liver lipid mediators such as arachidonic acid and its derivatives. In normal mice, nine kinds of family accounted for 94.1 % of microbiome composition; the total percentage of these family was significantly decreased in STAM mice (45.6 %), and DST administration improved this imbalance in microbiome composition (65.2 %). In stool samples, DST increased ursodeoxycholic acid content and altered several amino acids, which were correlated with changes in the gut microbiome and liver metabolites. In summary, DST ameliorates NAFLD by decreasing arachidonic acid metabolism in the liver; this amelioration seems to be associated with crosstalk among components of the liver, intestinal environment, and microbiome.

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) affecting the liver is a rare, possibly life-threatening complication of hematopoietic stem cell transplantation (HSCT). Sinusoidal endothelial cell (SEC) damage triggered by various factors (especially conditioning regimen) results in post sinusoidal portal hypertension due to obstruction of the hepatic vein. Diagnosis is guided by traditional clinical diagnostic criteria; the modified Seattle criteria, the Baltimore and revised European Group for Blood and Marrow Transplantation (EBMT), specifically. While there are promising results of imaging techniques studies in the diagnosis of VOD/SOS, none of those imaging techniques are routinely utilized in diagnosis yet. However, risk stratification is essential; conflicting results have been shown in studies aiming to define risk factors for development of VOD/SOS conducted to date. The only approved drug for the treatment of VOD/SOS yet is defibrotide, with early treatment offering higher chances of survival. In this review, we will focus on pathogenesis, clinical presentation and diagnostic criteria, risk factors, prophylaxis, and treatment of the VOD/SOS occurring post-HSCT.