3-7-dihydroxycholestan-26-oic-acid and Zellweger-Syndrome

We identified a new peroxisomal disorder caused by a deficiency of the enzyme alpha-methylacyl-coenzyme A (CoA) racemase. Patients with this disorder show elevated plasma levels of pristanic acid and the bile acid intermediates di- and trihydroxycholestanoic acid (DHCA and THCA), which are all substrates for the peroxisomal beta-oxidation system. alpha-Methylacyl-CoA racemase plays an important role in the beta-oxidation of branched-chain fatty acids and fatty acid derivatives because it catalyzes the conversion of several (2R)-methyl-branched-chain fatty acyl-CoAs to their (2S)-isomers. Only stereoisomers with the 2-methyl group in the (S)-configuration can be degraded via beta-oxidation. In this study we used liquid chromatography/tandem mass spectrometry (LC-MS/MS) to analyze the bile acid intermediates that accumulate in plasma from patients with a deficiency of alpha-methylacyl-CoA racemase and, for comparison, in plasma from patients with Zellweger syndrome and patients with cholestatic liver disease.We found that racemase-deficient patients accumulate exclusively the (R)-isomer of free and taurine-conjugated DHCA and THCA, whereas in plasma of patients with Zellweger syndrome and patients with cholestatic liver disease both isomers were present. On the basis of these results we describe an easy and reliable method for the diagnosis of alpha-methylacyl-CoA racemase-deficient patients by plasma analysis. Our results also show that alpha-methylacyl-CoA racemase plays a unique role in bile acid formation. - Ferdinandusse, S., H. Overmars, S. Denis, H. R. Waterham, R. J. A. Wanders, and P. Vreken. Plasma analysis of di- and trihydroxycholestanoic acid diastereoisomers in peroxisomal alpha-methylacyl-CoA racemase deficiency. J. Lipid Res. 2001. 42: 137;-141.

Topics: Bile Acids and Salts; Child, Preschool; Cholestanols; Cholestasis, Intrahepatic; Diagnosis, Differential; Female; Humans; Infant; Male; Oxidation-Reduction; Peroxisomal Disorders; Peroxisomes; Racemases and Epimerases; Spectrometry, Mass, Electrospray Ionization; Stereoisomerism; Zellweger Syndrome

Two patients with a suspected peroxisomal disorder on the basis of neurological, craniofacial, hepatological and other abnormalities were studied. The phenotype of both girls was remarkably similar from birth until age 1.5 yr. Detailed studies in plasma revealed normal plasma very-long-chain fatty acids but the presence of di- and trihydroxycholestanoic acids and the C29-dicarboxylic bile acid, all known to occur in plasma from Zellweger patients. These results suggest an isolated defect in the peroxisomal beta-oxidation of the side chains of the cholestanoic acids. Activation of trihydroxycholestanoic acid and beta-oxidation of trihydroxycholestanoyl-CoA, measured in a liver biopsy, were normal, however, as was the peroxisomal beta-oxidation of palmitate. Although the molecular defect remains unknown, the results stress the importance of performing multiple analyses in any patient suspected to suffer from a peroxisomal disorder and indicate that screening for peroxisomal disorders based upon analysis of only plasma very long chain fatty acids with or without analysis of erythrocyte plasmalogen levels, may be inadequate.

Topics: Abnormalities, Multiple; Acyl Coenzyme A; Bile Acids and Salts; Cells, Cultured; Cholestanols; Coenzyme A Ligases; Dicarboxylic Acids; Diseases in Twins; Fatty Acids, Nonesterified; Female; Fibroblasts; Humans; Infant; Liver; Microbodies; Palmitoyl Coenzyme A; Phenotype; Repressor Proteins; Saccharomyces cerevisiae Proteins; Skin; Twins, Dizygotic; Zellweger Syndrome

Infantile Zellweger syndrome belongs to the group of peroxisomal disorders that lack peroxisomes. Both trihydroxycoprostanic acid (THCA), the precursor to cholic acid, and dihydroxycoprostanic acid (DHCA), the precursor to chenodeoxycholic acid, accumulate in this disease. In previous studies, we have shown that liver peroxisomes are required for the conversion of THCA into cholic acid both in vitro and in vivo by measuring a defective conversion in infants with Zellweger syndrome. In our present study, the conversion of DHCA into chenodeoxycholic acid has been measured in an infant with Zellweger syndrome to evaluate the importance of liver peroxisomes for the formation of chenodeoxycholic acid. Coprostanic acidemia was present from the second day of life with high levels of THCA and only trace amounts of DHCA. The conversion of i.v. administered [3H]DHCA into chenodeoxycholic acid was only 7% compared with the 80% conversion in an analogous study in an adult. There was, however, a rapid incorporation of 3H into biliary THCA and, after a lag phase, the 3H was incorporated into biliary cholic acid. After 72 h, 15% of [3H]DHCA was converted to cholic acid. The pool size of DHCA was 1.2 mg/m2 and the pool size of both cholic acid and chenodeoxycholic acid was markedly reduced. The renal excretion of cholic acid was more efficient than that of the less polar chenodeoxycholic acid. More polar metabolites of DHCA and THCA are formed in alternative metabolic pathways facilitating renal excretion of these toxic intermediates. We conclude that liver peroxisomes are essential for a normal conversion of DHCA into chenodeoxycholic acid.

Topics: Bile; Bile Acids and Salts; Chenodeoxycholic Acid; Cholestanols; Humans; Infant; Kidney; Liver; Male; Microbodies; Zellweger Syndrome