Genetic defects in bile acid conjugation cause fat-soluble vitamin deficiency

Gastroenterology. 2013 May;144(5):945-955.e6; quiz e14-5. doi: 10.1053/j.gastro.2013.02.004. Epub 2013 Feb 13.


Background & aims: The final step in bile acid synthesis involves conjugation with glycine and taurine, which promotes a high intraluminal micellar concentration to facilitate lipid absorption. We investigated the clinical, biochemical, molecular, and morphologic features of a genetic defect in bile acid conjugation in 10 pediatric patients with fat-soluble vitamin deficiency, some with growth failure or transient neonatal cholestatic hepatitis.

Methods: We identified the genetic defect that causes this disorder using mass spectrometry analysis of urine, bile, and serum samples and sequence analysis of the genes encoding bile acid-CoA:amino acid N-acyltransferase (BAAT) and bile acid-CoA ligase (SLC27A5).

Results: Levels of urinary bile acids were increased (432 ± 248 μmol/L) and predominantly excreted in unconjugated forms (79.4% ± 3.9%) and as sulfates and glucuronides. Glycine or taurine conjugates were absent in the urine, bile, and serum. Unconjugated bile acids accounted for 95.7% ± 5.8% of the bile acids in duodenal bile, with cholic acid accounting for 82.4% ± 5.5% of the total. Duodenal bile acid concentrations were 12.1 ± 5.9 mmol/L, which is too low for efficient lipid absorption. The biochemical profile was consistent with defective bile acid amidation. Molecular analysis of BAAT confirmed 4 different homozygous mutations in 8 patients tested.

Conclusions: Based on a study of 10 pediatric patients, genetic defects that disrupt bile acid amidation cause fat-soluble vitamin deficiency and growth failure, indicating the importance of bile acid conjugation in lipid absorption. Some patients developed liver disease with features of a cholangiopathy. These findings indicate that patients with idiopathic neonatal cholestasis or later onset of unexplained fat-soluble vitamin deficiency should be screened for defects in bile acid conjugation.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Acyltransferases / genetics
  • Acyltransferases / metabolism
  • Avitaminosis / genetics*
  • Avitaminosis / metabolism
  • Avitaminosis / pathology
  • Bile Acids and Salts / metabolism*
  • Biopsy
  • Child
  • Child, Preschool
  • Coenzyme A Ligases / genetics*
  • Coenzyme A Ligases / metabolism
  • DNA / genetics*
  • DNA Mutational Analysis
  • Fatty Acid Transport Proteins / genetics
  • Fatty Acid Transport Proteins / metabolism
  • Female
  • Genetic Predisposition to Disease*
  • Homozygote
  • Humans
  • Infant
  • Liver / pathology
  • Male
  • Mass Spectrometry
  • Mutation, Missense*


  • Bile Acids and Salts
  • Fatty Acid Transport Proteins
  • SLC27A5 protein, human
  • DNA
  • Acyltransferases
  • bile acid-CoA amino acid N-acyltransferase
  • Coenzyme A Ligases
  • bile acid-CoA ligase