PubMed · 6057592
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M H Floch. 1967. Bacteria, absorption and malabsorption.. https://doi.org/10.1093/ajcn%2F20.11.1244
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Clostridium scindens is a keystone bacterial species in the mammalian gut that, while low in abundance, has a significant impact on bile acid and steroid metabolism. Numerous studies indicate that the two most studied strains of C. scindens (i.e. ATCC 35704 and VPI 12708) are important for a myriad of physiological processes in the host. We focus on both historical and current microbiological and molecular biology work on the Hylemon-Björkhem pathway and the steroid-17,20-desmolase pathway that were first discovered in C. scindens. Our most recent analysis now calls into question whether strains currently defined as C. scindens represent two separate taxonomic groups. Future directions include developing genetic tools to further explore the physiological role of bile acid and steroid metabolism by strains of C. scindens and the causal role of these pathways in host physiology and disease.
Bile acids and bilirubin are synthesized by the fetal liver very early on during intrauterine life. The main fate of these compounds is to be transferred to the mother. This excretory role of the placenta is primarily determined by the ability of the trophoblast to transport them, which is believed to occur mainly by carrier-mediated processes. The aim of this study was to investigate the role of the cholephilic organic anion exchanger located in the fetal-facing plasma membrane of the human trophoblast in placental "biliary-like" function. No relationship between the magnitude of transplacental gradients for total bile acids and bilirubin was found. However, transport studies, which were carried out by using purified plasma membrane vesicles derived from the fetal-facing pole of the human trophoblast, revealed that [14C]taurocholate transport was affected by both another bile acid (taurochenodeoxycholic acid) and a non-bile acid cholephilic organic anion (bromosulfophthalein). On plotting the ability of different major bile acid species to inhibit radiolabeled taurocholate uptake by these vesicles versus their concentrations in fetal serum or the magnitude of their transplacental gradients, inverse relationships were found. Lower fetal serum concentrations and transplacental gradients were found for bile acid species with higher abilities to affect this transport and presumably to interact with the carrier. By contrast, the magnitude of the transplacental gradient for bile acid species was not correlated with their hydrophobic/hydrophilic balance, as would be expected if diffusion across the lipidic structures of the placental barrier would be the major pathway for the flux of bile acid across this organ.(ABSTRACT TRUNCATED AT 250 WORDS)
Ursodeoxycholic acid (UDCA) has beneficial effects in cholestatic diseases such as primary biliary cirrhosis, primary sclerosing cholangitis and cholestasis of pregnancy. In chronic hepatitis and alcoholic hepatitis, an effect of UDCA is uncertain. After organ transplantation (liver, bone, heart), favorable effects of UDCA which await confirmation were observed. UDCA very likely has a beneficial effect in children with Byler's and Alagille's syndrome, extrahepatic biliary atresia after the Kasai procedure and in cholestasis of cystic fibrosis. Unclear is the effect of UDCA in benign intermittent cholestasis (Summerskill-Tygstrup syndrome). Children with cholestasis and inborn errors of bile acid synthesis need additional administration of a primary bile acid (cholic acid, chenodeoxycholic acid). UDCA treatment in general does not lead to definitive cure of the disease but to improvement of laboratory parameters and possibly of symptoms and liver histology, and liver transplantation may be postponed to a later time point.