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

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.