Urinary 3-hydroxyisovaleryl carnitine excretion, protein energy malnutrition and risk of all-cause mortality in kidney transplant recipients: Results from the TransplantLines cohort studies

Leucine is an essential amino acid and a potent stimulator of muscle protein synthesis. Since muscle wasting is a major risk factor for mortality in kidney transplant recipients (KTR), dietary leucine intake might be linked to long-term mortality. Urinary 3-hydroxyisovaleryl carnitine (3-HIC) excretion, a functional marker of marginal biotin deficiency, may also serve as a marker for dietary leucine intake. In this study we aimed to investigate the cross-sectional determinants of urinary 3-HIC excretion and to prospectively investigate the association of urinary 3-HIC excretion with all-cause mortality in KTR. Urinary 3-HIC excretion and plasma biotin were measured in a longitudinal cohort of 694 stable KTR. Cross-sectional and prospective analyses were performed using ordinary least squares linear regression analyses and Cox regression analyses, respectively. In KTR (57% male, 53 ± 13 years, estimated glomerular filtration rate 45 ± 19 mL/min/1.73 m2), urinary 3-HIC excretion (0.80 [0.57–1.16] μmol/24 h) was significantly associated with plasma biotin (std. β = −0.17; P