Inborn errors of bile acid metabolism

Area of Science:

• Biochemistry
• Metabolic Disorders
• Genetics

Background:

• Cholesterol is a precursor to cholic acid and chenodeoxycholic acid through complex enzymatic pathways.
• Inborn errors of metabolism can disrupt these pathways, resulting in the synthesis of abnormal bile acids and alcohols.

Purpose of the Study:

• To identify and characterize inborn errors of metabolism affecting bile acid synthesis.
• To correlate specific metabolic defects with clinical presentations and identify diagnostic markers.
• To explore therapeutic interventions for bile acid synthesis disorders.

Main Methods:

• Gas chromatography-mass spectrometry (GC-MS) and fast atom bombardment mass spectrometry (FAB-MS) for identifying unusual bile acids and alcohols.
• Analysis of urinary and plasma metabolite profiles.
• Clinical observation and response to treatment.

Main Results:

• Two defects in steroid nucleus modification identified, causing neonatal cholestatic liver disease.
• 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase deficiency leads to specific urinary bile acid excretion and improves with chenodeoxycholic acid.
• Deficient 3-oxo-delta 4-steroid 5 beta-reductase activity is suspected in some familial liver diseases, but diagnosis is challenging.
• Defective side chain oxidation in cerebrotendinous xanthomatosis (CTX) results in bile alcohol accumulation and neurological issues, improved by chenodeoxycholic acid.
• Peroxisomal disorders involving defective side chain oxidation lead to accumulation of specific C27 bile acids like trihydroxycoprostanic acid (THCA).

Conclusions:

• Inborn errors of bile acid synthesis present with diverse clinical phenotypes, from neonatal liver disease to neurological disorders.
• Advanced mass spectrometry techniques are crucial for diagnosing these rare metabolic conditions.
• Targeted therapies, such as chenodeoxycholic acid, can significantly improve clinical outcomes in specific bile acid synthesis defects.