Patricia A. Szczepanik

Increased bacterial degradation of bile acids in cholecystectomized patients.

Bile acid metabolism was studied in 10 patients previously cholecystectomized for cholesterol cholelithiasis, in 12 healthy subjects, and in 13 patients with cholesterol cholelithiasis (disease control subjects). The rate of bacterial deconjugation and 7-dehydroxylation was measured by using [2, 4- 3 H ]cholyl- [1- 14 C]glycine; measurements of synthesis and pool size were made simultaneously. Total bile acid pool size and biliary bile acid composition were determined by gas-liquid chromatography. Compared with healthy subjects, patients with cholecystectomy showed significantly increased deconjugation and dehydroxylation of the labeled cholylglycine. However, the pool of cholylglycine was considerably smaller, so that the absolute rate of deconjugation was similar. The pool of deoxycholylglycine was twice as large as that in the healthy control and the disease control subjects. In addition, ketohydroxy bile acids (resulting from bacterial dehydrogenation) composed 7 to 15% of the bile acid pool. The 7-keto and 12-keto derivatives of cholic acid were identified by mass spectrometry. The total bile acid pool in cholecystectomized patients did not differ from that in healthy control subjects but was larger than that in the disease control subjects. The size of the total bile acid pool in cholecystectomized patients correlated highly with the size of the pool of secondary bile acids, suggesting that its apparent return to a normal size in these patients after cholecystectomy could be explained in part by the increased input of secondary bile acids from the intestine.

Isotope and solvent effects of deuterium on aconitase.

Abstract The activity of aconitase has been compared in H 2 O and in 99% D 2 O, with deuteriocitrate and deuterioisocitrate as well as the protiated substrates, citrate, isocitrate, and aconitate. The rates of all six interconversions were markedly inhibited by D 2 O; the conversion of aconitate to citrate was affected much more than the conversion of aconitate to isocitrate. The values obtained for Michaelis constants and maximum velocities satisfactorily predict equilibrium conditions in H 2 O and D 2 O. Negligible isotope effects were observed with deuteriocitrate or deuterioisocitrate; this observation is consistent with the hypothesis that the first (and rate-limiting) step in the dehydration of these compounds is the rupture of the CO rather than the CH bond.

Identification and characterization of fully deuterated fatty acids isolated fromScenedesmus obliquus cultured in deuterium oxide

The algaScenedesmus obliquus cultured in deuterated water, synthesized fully deuterated saturated and unsaturated long chain fatty acids. Their methyl esters were purified and their equivalent chain lengths were determined by gas liquid chromatography (GLC). They were characterized by mass spectroscopy, IR and near-IR spectroscopy, and NMR spectroscopy. Hexadeca-3,6-dienoic acid was identified. The fatty acid compositions of the total lipid and of individual lipid classes were measured. The melting point of methyl perdeuteriohexadecanoate was lower than that of its hydrogen counterpart. Methyl esters of perdeuterio fatty acids had shorter retention times in GLC chromatography on polar and nonpolar phases.

453 CHOLESTASIS IN THE CEREBRO-HEPATO-RENAL (CHR) SYNDROME: BILE ACID AND MITOCHONDRIAL ABNORMALITIES

Electron microscopic examination of liver and analysis of bile acids were performed in order to examine the mechanism of cholestasis in 2 unrelated infants with CHR syndrome (of Zellweger). They exhibited characteristic facies, camptodactyly, liver enlargement, hypotonia, elevated urinary pipecolic acid concentration in addition to cerebral dysgenesis and renal cortical cysts at necropsy. Liver biopsies performed during a period of jaundice and mild hepatic dysfunction revealed normal intrahepatic bile ducts, hepatocellular cholestasis and no fibrosis. Electron microscopy specifically revealed abnormal, irregularly shaped mitochondria containing a dense matrix; cristae were dilated, irregular and increased in number. Non-sulfated trihydroxy-coprostanic acid (THCA), was identified as the predominant bile acid in bile and urine by GLC-mass spectroscopy. THCA, not found in 10 controls with cholestasis, is an intermediate in bile acid synthesis thought to require mitochondrial oxidation. The coexistence in CHR of mitochondrial abnormalities, cholestasis and accumulation of bile acid intermediates without structural bile duct abnormalities appears to comprise an entity distinct from infants with THCA and bile duct lesions (Hanson et al. JCI 56: 577, 1975). This suggests that in CHR, bile acid feeding may serve to ameliorate hepatic dysfunction and/or elucidate the pathogenesis of disease.

Local solvent structure as a factor in secondary isotope fractionation phenomena of labeled amino acids on ion-exchange columns.

Abstract The separation or displacement of 3H-labeled amino acids from 14C-labeled varieties of the same species on ion-exchange columns is influenced by the presence of unlabeled amino acid, local solvent structure and buffer composition. These factors may enhance or reduce the degree of separation observed and act by affecting the diffusion of the labeled molecules. A significant inverse relationship between peak disengagement and hand-broadening processes was observed.

471 ISOLATED INTESTINAL BILE ACID (BA) MALABSORPTION, A CAUSE OF CHRONIC DIARRHEA

We studied a 5 year old girl from early infancy with severe chronic diarrhea, steatorrhea and growth failure. Intestinal structure, pancreatic function, liver function and structure and a laparotomy all were normal. During the first 2 years of life BA levels in duodenal juice were consistently below the critical micellar concentration. In recent studies fecal BA were 7 times normal, serum BA by radioimmunassay failed to rise significantly after meals or after oral taurocholate and in duodenal juice, dihydroxy predominated over trihydroxy BA. Pool sizes of cholate and chenodeoxycholate, by isotope dilution were reduced to 6 and 23%, serum cholate T½ was 12% and chenodeoxycholate 7% of normal. Vitamin B12 absorption (Schilling test) at age 4 years was normal. These data lead us to conclude that our patient, who now thrives, suffers from a specific congenital defect of ileal transport of bile acids causing a depleted BA pool and steatorrhea. This defect has not been reported previously.

BILE SALT METABOLISM IN THE PREMATURE INFANT: INFLUENCE OF PRENATAL DEXAMETHASONE AND PHENOBARBITAL

Bile salt synthesis and pool size were determined by stable isotope dilution in 9 healthy premature infants of 32-36 wk gestation. In one group (4 infants), the mothers had received dexamethasone (3) or phenobarbital (1) prior to delivery; the other mothers had received no drugs. For infants of the treated mothers, total bile salt pool was 79 ± 20 mg (avg ± SE) and synthesis was 27 ± 5 mg/da; whereas in infants of untreated mothers, total bile salt pool was 20 ± 2 mg and synthesis was 8 ± 1 mg/da. When normalized for surface area, the cholic acid pool in the treated group was 321 ± 117 mg/M2 and synthesis was 98 ± 35 mg/M2/da, values egual to those obtained in full-term infants and 4 times those in the group with untreated mothers. Intraduodenal bile salt concentrations during meals in the treated group were 5.3 mM vs 1.2 mM for the untreated group, an increase associated with improved dietary lipid absorption to >90% of intake in 3 of 4 infants. Conclusions: (1) Premature infants have immature bile salt metabolism as demonstrated by reduced pool size and synthesis rates with intraduodenal bile salt concentrations below levels required for the complete solubilization of lipid. (2) Prenatal administration of dexamethasone or phenobarbital produces precocious maturation of these parameters and thus may profoundly influence the postnatal nutrition of the premature infant.