Chenodeoxycholic acid sulfate

Serum transaminases tend to double or triple in the early weeks of treatment with chenodeoxycholic acid in about one-third of patients (10). There is a hypothesis that this is due to impaired lithocholate sulfation. Lithochohc acid is... 

As a consequence of the 7a-dehydroxylation process, the bile acid composition of bile in healthy subjects usually comprises around 30 to 40% conjugated cholic acid, 30 to 40% conjugated chenodeoxycholic acid, 10 to 30% conjugated deoxycholic acid, and less than 5% conjugated lithocholic acid, of which the majority is sulfated (H18). 

The low concentrations of bile acids in urine have also been measured by radioimmunoassay. In one study, total cholic and chenodeoxycholic acid conjugates were measured after extraction and solvolysis to remove sulfate groups, giving a mean urinary excretion of 0.6 p.mol/24 hours for cholic acid and 1.2 p.mol/24 hours for chenodeoxycholic acid in normal subjects (S7). These estimates can be compared with values of 2.1 xmol/24 hours for conjugated cholic acid and 8.4 xmol/24 hours for sulfoglycolithocholic acid obtained for the urinary excretion of bile acids using commercially available radioimmunoassays (WIO). 

Palmer [56-58] first reported the presence in human bile of a sulfate ester of lithocholate in as much as 40-80% of the small amounts of available glyco- and taurolithocholate. Following intragastric or intraduodenal intubation of glyco-[24- C]lithocholic acid 3-sulfate to rats with bile fistulas, 70-89% of the radioactivity was recovered in bile [59] allolithocholate 3-sulfate was also reported in rat bile [60]. The radioactive conjugate was absorbed intact without loss of the sulfate, and was not metabolized in the liver (e.g., to the muricholates or chenodeoxycholate) [58,59]. Similarly, chenodeoxycholate 3-sulfate was not metabolized after intravenous infusion into rats or hamsters with or without obstruction of the biliary tract [58,59,61]. Lithocholate 3-sulfate is efficiently removed from the body [62]. 

The intestinal microflora of man and animals can biotransform bile acids into a number of different metabolites. Normal human feces may contain more than 20 different bile acids which have been formed from the primary bile acids, cholic acid and chenodeoxycholic acid [1-5], Known microbial biotransformations of these bile acids include the hydrolysis of bile acid conjugates yielding free bile acids, oxidation of hydroxyl groups at C-3, C-6, C-7 and C-12 and reduction of oxo groups to give epimeric hydroxy bile acids. In addition, certain members of the intestinal microflora la- and 7j8-dehydroxylate primary bile acids yielding deoxycholic acid and lithocholic acid (Fig. 1). Moreover, 3-sulfated bile acids are converted into a variety of different metabolites by the intestinal microflora [6,7]. 

Huijghebaert et al. [23] isolated a bile salt sulfatase-producing strain designated, Clostridium S, from rat feces. This bacterium hydrolyzed the 3-sulfates of lithocholic acid, chenodeoxycholic acid, deoxycholic acid and cholic acid but not the 7-or 12-monosulfates. Sulfatase activity required the 3-sulfate group to be in the equatorial position. A free C-24 or C-26 carboxyl group was also required for sulfatase activity in whole cells of this bacterium. The 3-sulfate of cholesterol, Cj,-and Cji-steroids were not hydrolyzed by Clostridium S, [24]. Nevertheless, C,9- and C2]-steroid sulfates are hydrolyzed in the gut by microbial activity suggesting that the intestinal microflora may contain bacteria with steroid sulfatases possessing different substrate specificities. However, it should be noted that enzyme substrate specificity studies carried out in whole cells may reflect both cell wall permeability and enzyme specificity. 

FIGURE 14.7 Derivatization for ESI-MS/MS. (A) Preparation of the dimethylaminoethylester of dihydroxycholestanoic acid bis acetate. (B) Preparation of aminoethanesulfonate derivative of chenodeoxycholic acid. (C) Formation of sulfate ester of cholesterol. (D) Preparation of oxime of testosterone. 

The liver, and also bacteria in the small and large intestine, can cause other structural modifications to bile acids as they undergo their entero-hepatic cycle. The formation of sulfate esters, already mentioned with respect to lithocholate in Section 4.2.1, is carried out primarily in the liver in man by a sulfotransferase (Lll). Other bile acids can also be sulfoconjugated to a small extent, mainly at the 3a-hydroxyl position. Bacteria, which have been isolated anaerobically from human feces, are known to possess bile acid sulfatase activity, which removes the 3a-sul te group of chenodeoxycholic and cholic acids (H24). The action of this bacterial enzyme probably explains why only trace amounts of sul ted bile acids, which are poorly absorbed in the intestine, are detected in the feces (12). Another type of bile acid conjugate, which has been identified in the urine of healthy subjects and patients with hepatobiliary disease, is the glucuronide (A7, S41). Both the liver and extrahepatic tissues, such as the kidney and small intestinal mucosa, are capable of glucuronidation of bile acids in man (M14). 

Bile acids in meconium also reflect atypical synthesis. Back and Walter [209] reported on the presence of 14 bile acids obtained from meconium of 6 healthy infants (Table 2B). On the average 21% of chenodeoxycholate and of hyocholate and 8% of cholate were sulfated. Deoxycholate was the major bile acid of the sulfate fraction lithocholate, 3/8-hydroxy-5-cholenate [175] and 3, 12a-dihydroxy-5-cholenate were found only in the sulfate fraction, but quantities of lithocholate (range 0.3-1.4%) and 3i8,12a-dihydroxy-5-cholenate were small. The amount of l, 3tt,7a,12a-tetrahydroxy acid (79% as the taurine conjugate and 21% unconjugated) ranged from 3.6 to 11.1% of the total bile acids [209]. The feta bile adds of a number of animals, normal, adrenalectomized, thyroidectomized, or diabetic, are reviewed by Subbiah and Hassan ]210]. 

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