CYP8B1 Catalyzes 12alpha-Hydroxylation of C Bile Acid: In Vitro Conversion of Dihydroxycoprostanic Acid into Trihydroxycoprostanic Acid.

Sterol 12α-hydroxylase (CYP8B1) is the unique P450 enzyme with sterol 12-oxidation activity, playing an exclusive role in 12-hydroxylating intermediates along the bile acid (BA) synthesis pathway. Despite the long history of BA metabolism studies, it is unclear whether CYP8B1 catalyzes 12-hydroxylation of C BAs, the key intermediates shuttling between mitochondria and peroxisomes. This work provides robust in vitro evidence that both microsomal and recombinant CYP8B1 enzymes catalyze the 12-hydroxylation of dihydroxycoprostanic acid (DHCA) into trihydroxycoprostanic acid (THCA).

Comparison of 1Beta- and 5Beta-hydroxylation of Deoxycholate and Glycodeoxycholate as In Vitro Index Reactions for Cytochrome P450 3A Activities.

Cytochrome P450 3A (CYP3A) participates in the metabolism of more than 30% of clinical drugs. The vast intra- and inter-individual variations in CYP3A activity pose great challenges to drug development and personalized medicine. It has been disclosed that human CYP3A4 and CYP3A7 are exclusively responsible for the tertiary oxidations of deoxycholic acid (DCA) and glycodeoxycholic acid (GDCA) regioselectivity at C-1 and C-5 This work aimed to compare the 1- and 5-hydroxylation of DCA and GDCA as potential in vitro CYP3A index reactions in both human liver microsomes and recombinant P450 enzymes.

The prognostic value of adding systemic inflammation response index to Epstein-Barr virus DNA in childhood nasopharyngeal carcinoma: A real-world study.

Background: To assess the prognostic value of the systemic inflammation response index (SIRI) combined with plasma load of Epstein-Barr virus (EBV) DNA in children and adolescents with locoregionally advanced nasopharyngeal carcinoma (CALANPC).

Methods: A total of 205 consecutive patients with CALANPC were enrolled. We used recursive partitioning analysis (RPA) to classify patients into various risk groups, with a primary endpoint of overall survival (OS).

Reevaluate In Vitro CYP3A Index Reactions of Benzodiazepines and Steroids between Humans and Dogs.

Cytochrome P450 3A (CYP3A), the most important class of drug-metabolizing enzymes, participates in the metabolism of half of clinically used drugs. The CYP3A index reactions of dogs, one of the most widely used preclinical nonrodent species, are still poorly understood. This work evaluated the activity and selectivity of 10 CYP3A index reactions, including midazolam (MDZ) 1'- and 4-hydroxylation, alprazolam (APZ) and triazolam (TRZ) - and 4-hydroxylation, testosterone (T) 6-hydroxylation, lithocholate (LCA) 6-hydroxylation, deoxycholate (DCA) 1- and 5-hydroxylation, with quantitative reaction phenotyping and kinetic analysis in human and canine recombinant CYP enzymes (rCYPs).

Compensatory Transition of Bile Acid Metabolism from Fecal Disposition of Secondary Bile Acids to Urinary Excretion of Primary Bile Acids Underlies Rifampicin-Induced Cholestasis in Beagle Dogs.

Drug induced cholestasis (DIC) is complexly associated with dysbiosis of the host-gut microbial cometabolism of bile acids (BAs). Murine animals are not suitable for transitional studies because the murine BA metabolism is quite different from human metabolism. In this work, the rifampicin (RFP) induced cholestasis was established in beagle dogs that have a humanlike BA profile to disclose how RFP affects the host-gut microbial cometabolism of BAs.

Tertiary Oxidation of Deoxycholate Is Predictive of CYP3A Activity in Dogs.

Deoxycholic acid (DCA, 3, 12-dihydroxy-5-cholan-24-oic acid) is the major circulating secondary bile acid, which is synthesized by gut flora in the lower gut and selectively oxidized by CYP3A into tertiary metabolites, including 1,3,12-trihydroxy-5-cholan-24-oic acid (DCA-1-ol) and 3,5,12-trihydroxy-5-cholan-24-oic acid (DCA-5-ol) in humans. Since DCA has the similar exogenous nature and disposition mechanisms as xenobiotics, this work aimed to investigate whether the tertiary oxidations of DCA are predictive of in vivo CYP3A activities in beagle dogs. In vitro metabolism of midazolam (MDZ) and DCA in recombinant canine CYP1A1, 1A2, 2B11, 2C21, 2C41, 2D15, 3A12, and 3A26 enzymes clarified that CYP3A12 was primarily responsible for either the oxidation elimination of MDZ or the regioselective oxidation metabolism of DCA into DCA-1-ol and DCA-5-ol in dog liver microsomes.

Species Differences of Bile Acid Redox Metabolism: Tertiary Oxidation of Deoxycholate is Conserved in Preclinical Animals.

It was recently disclosed that CYP3A is responsible for the tertiary stereoselective oxidations of deoxycholic acid (DCA), which becomes a continuum mechanism of the host-gut microbial cometabolism of bile acids (BAs) in humans. This work aims to investigate the species differences of BA redox metabolism and clarify whether the tertiary metabolism of DCA is a conserved pathway in preclinical animals. With quantitative determination of the total unconjugated BAs in urine and fecal samples of humans, dogs, rats, and mice, it was confirmed that the tertiary oxidized metabolites of DCA were found in all tested animals, whereas DCA and its oxidized metabolites disappeared in germ-free mice.