Indicators of marginal biotin deficiency and repletion in humans: validation of 3-hydroxyisovaleric acid excretion and a leucine challenge.
BACKGROUND
The results of clinical studies have provided evidence that marginal biotin deficiency is more common than was previously thought. A previous study of 10 subjects showed that the urinary excretion of biotin and 3-hydroxyisovaleric acid (3HIA) are early and sensitive indicators of marginal biotin deficiency.


OBJECTIVE
Marginal biotin deficiency was experimentally induced and corrected to assess the utility of 3 indicators of biotin status: urinary excretion of biotin and 3HIA and the increase in 3HIA excretion after leucine loading.


METHODS
Eleven healthy adults consumed an egg white diet for 28 d. Blood and 24-h urine samples were collected before the start of the diet and twice weekly thereafter. In 5 subjects, an oral leucine challenge was performed weekly for 4 wk. After depletion, biotin status was restored with a general diet with or without a supplement containing 80 micro g biotin. Urinary excretion of biotin, bisnorbiotin, and biotin sulfoxides was determined by avidin-binding assay after HPLC. Excretion of 3HIA, an indicator of reduced activity of the biotin-dependent enzyme methylcrotonyl-CoA carboxylase (EC 6.4.1.4), was measured by gas chromatography-mass spectrometry.


RESULTS
3HIA excretion increased significantly with time on the egg white diet (P < 0.0001), as did 3HIA excretion in response to the leucine challenge (P < 0.002); the excretion of both biotin and bisnorbiotin decreased significantly with time (P < 0.0001). In most subjects, biotin status returned to normal after 1 wk of a general diet.


CONCLUSIONS
Excretion of 3HIA and of biotin are early and sensitive indicators of biotin deficiency. 3HIA excretion after a leucine challenge is at least as sensitive.
Mock
Donald M
DM
Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock 72205, USA. mockdonaldm@uams.edu
Henrich
Cindy L
CL
Carnell
Nadine
N
Mock
Nell I
NI
D000328:Adult; D001710:Biotin / Q000031:analogs & derivatives* / Q000172:deficiency* / Q000378:metabolism* / Q000652:urine; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004529:Egg White; D005260:Female; D006801:Humans; D007930:Leucine / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D013997:Time Factors; D014631:Valerates / Q000652:urine*
D014631:Valerates; C002143:bisnorbiotin; C004961:beta-hydroxyisovaleric acid; D001710:Biotin; D007930:Leucine; C017072:D-biotin-d-sulfoxide