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The Role of Conjugating Enzymes in the Biliary Excretion of Bilirubin
Published in Karel P. M. Heirwegh, Stanley B. Brown, Bilirubin, 1982
It is possible that rat liver slices can serve as a useful tool for investigating factors controlling the synthesis of bilirubin diglucuronide. When incubated with bilirubin29 they resemble the situation in vivo more closely than microsomes in that BDG is formed in significant amounts and can be excreted into the medium.
Analytical Chemistry of Rubins
Published in Karel P. M. Heirwegh, Stanley B. Brown, Bilirubin, 1982
Karel P. M. Heirwegh, Stanley B. Brown
In optimization of a diazo procedure for the direct-reacting fraction the following points must be considered: (1) At the time of optical reading a maximal stable azo color should have been reached, since the conversion rate may strongly depend on the rubin composition (e.g., mono- vs. diconjugates) and on matrix components such as albumin and reaction-promoting substances (e.g., bile salts or urea). Blumenfeld et al.97 compared the 10 min-reaction procedure of Walters and Gerarde98 and a 2 minprocedure. Both methods assayed bilirubin diglucuronide correctly but in the latter method, the response of monoglucuronide was only 50º/o of the expected value. Unfortunately, the extent of direct reaction of unconjugated bilirubin was not reported for the 10-min procedure. Selective underestimation of bilirubin monoglucuronide in a 1-min procedure has been invoked previously to explain discordant results obtained in assays of bilirubin UDP-glucuronyltransferase activity.99 (2) To a certain extent unconjugated bilirubin reacts with diazo reagents in absence of a reaction accelerator. The reaction rate is expected to increase with the concentration of endogeneous accelerator substances, and possibly with reaction temperature, and concentration and reactivity of the diazo reagent. It critically depends on pH, with low reaction rates over a range of acidic pH values (Figure 1).73, 75 Therefore, construction of a curve delineating reaction of unconjugated pigment and conjugated bilirubins at various pigment concentrations is required to assess the significance of the direct-reacting fraction, particularly for samples that contain predominantly unconjugated bilirubin.75
Vancomycin prevents fermentable fiber-induced liver cancer in mice with dysbiotic gut microbiota
Published in Gut Microbes, 2020
Vishal Singh, Beng San Yeoh, Ahmed A. Abokor, Rachel M. Golonka, Yuan Tian, Andrew D. Patterson, Bina Joe, Mathias Heikenwalder, Matam Vijay-Kumar
The mammalian gastrointestinal (GI) tract corrals trillions of bacteria that are collectively referred to as gut microbiota. This assemblage of gut microbes persists in a symbiotic relationship with their host by performing diverse metabolic functions and producing key nutrients that benefit the holobiont. Bacteria residing densely in the distal colon, for instance, largely depends on host-derived metabolites and undigested foods. For example, bacteria that express glucuronidases are capable of utilizing host-derived waste metabolites, such as bilirubin diglucuronide, as their carbon source. Other bacteria expressing BSH could acquire taurine or glycine as carbon sources from host-derived primary bile acids and generate secondary bile acids. These secondary bile acids can enter enterohepatic circulation and further serve as ligands for farnesoid X receptor (FXR) and Takeda G protein coupled receptor 5 (TGR5), whose signaling modulates cholesterol and bile acid homeostasis.22 In addition, diverse bacteria ferment dietary fibers and generate large quantities of calorific short-chain fatty acids (SCFAs; e.g. acetate, butyrate and propionate). Since not all bacteria are capable of catalyzing similar reactions, the constituents of the gut microbiota actively participate in quorum-sensing and cross-feeding to meet their nutritional requirement.