Clinical and metabolic phenotypes of Oxford Biobank subjects with variations in human flavin-containing monooxygenase 5 (FMO5).

INTRODUCTION

Knockout of the Fmo5 gene in mice led to a lean, slow-ageing phenotype characterised by the presence of 2,3-butanediol isomers in their urine and plasma. Oral treatment of wildtype mice with 2,3-butanediol led to a low cholesterol, low epididymal fat phenotype.

OBJECTIVES

Determine if significant, heterozygous coding variations in human FMO5 would give rise to similar clinical and metabolic phenotypes in humans, as in C57BL/6J mice with knockout of the Fmo5 gene and in particular, increased excretion of 2,3-butanediol.

METHODS

Recruitment of 12 female, Oxford Biobank volunteers with heterozygous coding variations in FMO5, associated with changed clinical traits, and 12 age- and gender-matched controls. Analysis of the key NMR-based, urine and plasma, metabolic phenotypes of these volunteers to determine if there were any statistically significant differences.

RESULTS

Some clinical parameters of the female volunteers with heterozygous coding variations in FMO5 were altered in a direction consistent with our hypothesis viz; lower insulin levels and lower waist circumference, but no consistent elevation of urinary 2,3-butanediol was found in the subjects with heterozygous coding variations in FMO5.

CONCLUSION

Heterozygous coding variations in human FMO5 appeared to have some impact on the clinical phenotype of the females in this study but the natural variation in the levels of 2,3-butanediol was higher than any inter-group differences between women with heterozygous coding variations in human FMO5 and the women in the control group with wildtype FMO5.