25(OH)D2 half-life is shorter than 25(OH)D3 half-life and is influenced by DBP concentration and genotype
Jones, K S × Assar, S Harnpanich, D Bouillon, Roger Lambrechts, D Prentice, A Schoenmakers, I #
The Journal of clinical endocrinology and metabolism vol:99 issue:9 pages:3373-81
Context: There is uncertainty over the equivalence of vitamins D2 and D3 to maintain plasma 25-hydroxyvitamin D (25(OH)D). Objective: To compare the plasma half-lives of 25(OH)D2 and 25(OH)D3 in two distinct populations with different dietary calcium intake and 25(OH)D status. Participants: Healthy men (aged 24 and 39 years), resident in The Gambia (n=18) or UK (n=18). Interventions: Oral tracer dose of deuterated-25(OH)D2 and deuterated-25(OH)D3 (both 40 nmol). Blood samples were collected over 33 days. Main outcome measures: 25(OH)D2 and 25(OH)D3 plasma half-lives, concentrations of 25(OH)D and DBP and DBP genotypes. Results: 25(OH)D2 half-life (mean (SD)) (13.9 (2.6) d) was shorter than 25(OH)D3 half-life (15.1 (3.1) d; P=0.001) for countries combined, and in Gambians (12.8 (2.3) d vs. 14.7 (3.5) d; P<0.001), but not in the UK (15.1 (2.4) d vs. 15.6 (2.5) d; P=0.3). 25(OH)D concentration was 69 (13) and 29 (11) nmol/L (P<0.0001) and DBP concentration was 259 (33) and 269 (23) mg/l (P=0.4) in The Gambia and UK, respectively. Half-lives were positively associated with plasma DBP concentration for countries combined: (25(OH)D2 half-life: regression coefficient (SE) 0.03 (0.01) d per 1 mg/l DBP; P=0.03; 25(OH)D3 half-life: 0.04 (0.02) d; P=0.02) and in Gambians (25(OH)D2 half-life: 0.04 (0.01) d; P=0.02; 25(OH)D3 half-life: 0.06 (0.02) d; P=0.01), but not in UK participants. DBP concentration*country interactions were not significant. DBP Gc1f/1f homozygotes had shorter 25(OH)D2 half-lives compared to other combined genotypes (P=0.007), after correction for country. Conclusions: 25(OH)D2 half-life was shorter than 25(OH)D3 half-life, and half-lives were affected by DBP concentration and genotype. Stable isotope 25(OH)D half-life measurements provide a novel tool to investigate vitamin D metabolism and vitamin D expenditure, and aid in the assessment of vitamin D requirements.