24,25-Dihydroxyvitamin D3 and Vitamin D Status of Community-Dwelling Black and White Americans

Abstract

BACKGROUND 24,25-dihydroxyvitamin D (24,25(OH)2D) is a metabolite of 25-hydroxyvitamin D (25D). Blacks frequently have low total 25D without manifestations of vitamin D deficiency, suggesting that total serum 25D may incorrectly reflect vitamin D status in different racial groups. The ratio of serum 24,25(OH)2D to 25D (Vitamin D Metabolite Ratio [VMR]) represents a new candidate biomarker for vitamin D status. METHODS We measured 24,25(OH)2D3 and 25D3 by mass spectrometry in a random community cohort of black (n=212) and white (n=164) Americans to evaluate VMR as a marker for vitamin D status. We measured parathyroid hormone concentrations by immunoassay to compare VMR and 25D3 against a physiological indicator of vitamin D deficiency. RESULTS Serum 24,25(OH)2D3 strongly correlated with 25D3 in both black and white subjects (r = 0.90, p<0.001 and r = 0.86, p<0.001 respectively). Blacks had lower mean 25D3 than whites (17.0±7.8 vs. 27.5±11.3 ng/mL (42.4±19.5 vs. 68.6±28.2 nmol/L), p<0.001) and lower mean 24,25(OH)2D3 (2.1±1.3 vs. 3.6±2.0 ng/mL (5.1±3.1 vs. 8.7±4.8 nmol/L)), p<0.001). In contrast to total 25D3 concentrations, mean VMR values were similar in blacks and whites (11.9±4.0 vs. 12.5±3.4, p=0.16, respectively) and were negatively correlated with parathyroid hormone concentrations in both races (rs= −0.26, p<0.001 and rs= −0.25, p<0.001, respectively). CONCLUSIONS Our results provide further evidence that measurement of total 25D for assessment of vitamin D status in patients of African descent deserves reevaluation, and suggests that alternative measures such as VMR should be considered.

Assessment of vitamin D status – a changing landscape

“…Studies have also shown differences in the relationship between 25-OHD and PTH in Black compared to White subjects. While Blacks have serum concentrations of 25-OHD approximately 30% lower than Whites [106][107][108], this is not associated with a proportional increase in PTH. When considering individuals with comparable PTH concentrations, serum 25-OHD is again significantly lower in Blacks than in Whites.…”

“…Considering there is direct enzymatic conversion of 25-OHD into 24,25-OH 2 D it is not surprising that the concentrations of both compounds are strongly correlated [113]. In contrast to DBP, this correlation is comparable across different races (Blacks: r = 0.86, p < 0.001; Whites: r = 0.90, p < 0.001) [107]. 24,25-OH 2 D possesses some conceptual advantages over DBP, BAVD and 25-OHD.…”

LC–MS/MS based 25(OH)D status in a large Southern European outpatient cohort: gender- and age-specific differences

“…Consequently, the recommended 25(OH)D cut-offs vary between different scientific bodies [7][8][9][10]. Age or gender specific cut-offs are not suggested by any guideline although several studies suggest that physiologic 25(OH)D requirements may vary with age, gender and ethnicity [11][12][13][14][15]. Interpretation of 25(OH) D results is further complicated by a variable accuracy of 25(OH)D assays and a strong seasonal variability of up to 20% [16][17][18][19].…”

Impact of a single oral dose of 100,000 IU vitamin D3 on profiles of serum 25(OH)D3 and its metabolites 24,25(OH)2D3, 3-epi-25(OH)D3, and 1,25(OH)2D3 in adults with vitamin D insufficiency

“…Furthermore, the relationship between circulating 25(OH)D3 concentrations and clinical outcomes such as osteoporosis and fracture risk may differ between racial groups, raising the question of whether 25(OH)D3 provides a reliable estimate of vitamin D status in all populations [18,19]. For these reasons, increasing attention is being paid to the measurement of 24,25(OH) 2 D3 (the major circulating catabolite of vitamin D), and the ratio of 24,25(OH) 2 D3 to 25(OH)D3, as potential markers of vitamin D catabolism and predictors of the serum 25(OH)D response to vitamin D supplementation [5,6,12,18,20].…”