Vitamin D metabolism in living kidney donors before and after organ donation

Abstract

Abstract Objectives Living kidney donors provide a unique setting to study functional and metabolic consequences after organ donation. Since the lack of data of the homoeostasis of numerous vitamin D metabolites in these healthy subjects, the aim of this study was to assess the vitamin D metabolism before and after kidney donation. Methods We investigated the 25-dihydroxyvitamin D2 (25[OH]D2), 25-dihydroxyvitamin D3 (25[OH]D3), 1,25-dihydroxyvitamin D3 (1,25[OH]2D3), 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), 25,26-dihydroxyvitamin D3 (25,26[OH]2D3), and the native vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) in a well characterized study cohort of 32 healthy living kidney donors before and after organ donation. Results Thirty-two healthy subjects after kidney donation had significantly lower median (interquartile range) 1,25(OH)2D3 serum concentrations (88.6 [62.6–118.8] vs. 138.0 [102.6–152.4] pmol/L, p<0.001) and significantly higher median 25(OH)D2 serum levels (1.80 [1.19–2.19] vs. 1.11 [0.74–1.59] nmol/L, p=0.019) than before donation. Similar serum concentrations of 25(OH)D3 and 25,26(OH)2D3 were observed before and after donation. The 24,25(OH)2D3 blood levels distinctly decreased after organ donation (4.1 [2.3–5.3] vs. 5.3 [2.2–6.9] nmol/L, p=0.153). Native vitamin D2 (0.10 [0.08–0.14] vs. 0.08 [0.06–0.12] nmol/L, p=0.275) was slightly increased and vitamin D3 (1.6 [0.6–7.2] vs. 2.5 [0.9–8.6] nmol/L, p=0.957) decreased after kidney donation. Conclusions Living kidney donors were found with decreased 1,25(OH)2D3 and 24,25(OH)2D3, increased 25(OH)D2 and consistent 25(OH)D3 and 25,26(OH)2D3 serum concentrations after organ donation. The current study advances the understanding on vitamin D metabolism suggesting that altered hydroxylase-activities after donation is accompanied by compensatory elevated dietary-related 25(OH)D2 blood concentrations.