Gene analysis of Δ^4-3-oxosteroid 5β-reductase in neonatal hepatitis patients with predominant urinary Δ^4-3-oxo bile acids

点击翻译按钮获取中文摘要

Background - Numbers of neonatal hepatitis patients exhibiting predominant urinary excretion of Δ^4-3-oxo bile acids have been reported since 1988. There has been some controversy whether this phenomenon is due to primary genetic deficiency or secondary impairment of Δ^4-3-oxosteroid 5β-reductase (5β-reductase) in bile acids' biosynthetic pathway.Aim - To study such patients genetically using the techniques of molecular biology.Patients and Methods - Liver specimens obtained from four neonatal hepatitis patients exhibiting predominant amounts of urinary Δ^4-3-oxo bile acids (48.8 to 88.9 %) were examined. All had chronic cholestasis with hepatic failure of unclear etiologies. Immunoblot analysis, RNA blot hybridization analysis, and analysis of the cDNA sequences amplified by the reverse transcriptase-polymerase chain reaction method were employed for 5β-reductase. Bile acids profiles of serum as well as urine were also analyzed by gas chromatography-mass spectrometry.Results - In all patients immunoblot analysis showed a weak band of the enzyme though the amounts were smaller than those in the control group. In one patient, RNA blot hybridization analysis also revealed an indistinct band of the enzyme. The full length of cDNA of the enzyme was amplified in all patients, and none exhibited a mutation in the DNA sequence. Despite Δ^4-3-oxo bile acids' predominancy in urine, the amounts of these acids in serum were extremely small compared to normal bile acids.Conclusions - Predominant excretion of urinary Δ^4-3-oxo bile acids in our patients was not caused by genetic defect of 5β-reductase. Even predominancy of urinary Δ^4-3-oxo bile acids does not lead to the diagnosis of 5β-reductase deficiency, for which combined evaltuations of the steroid metabolism in biological fluids including urine, serum, and bile are necessary.