Abstract
INTRODUCTION: We previously reported lower serum 25-hydroxyvitamin D concentrations in patients with Alzheimer's disease (AD), Parkinson's disease (PD) and Multiple system atrophy (MSA) compared to healthy controls (HC), whereas 1,25-di-hydroxyvitamin D levels were solely lower in MSA patients. We investigate serum concentrations of P450 involved in Vitamin D(VD) hydroxylation to clarify the responsible hydroxylase for the low serum concentrations of VD metabolites. METHODS: A total of 79 individuals were enrolled including 20 HC, 20 AD, 19 PD and 20 MSA patients. The serum concentrations of P450 involved in VD hydroxylation were assayed by ELISA. The data were analyzed by the nonparametric Kruskal-Wallis test between groups. RESULTS: Though CYP2R1 and CYP27A1 mediate 25-hydroxylation for VD, CYP2R1 is the main hydroxylase, and CYP27A1 is also involved in VD synthesis. CYP2R1 concentrations showed no differences among groups, while lower CYP27A1 concentrations were found in PD (p < 0.05) and MSA (p < 0.005) compared to HC and differences between AD and MSA (p < 0.05), however no differences between PD and MSA. CYP27B1 is the main 1α-hydroxylase for 25-hydroxyvitamin D and showed differences between HC and PD (p < 0.05), between HC and MSA (p < 0.005) and between PD and MSA (p = 0.055). CYP24A1, which inactivate 1,25-di-hydroxyvitamin D, showed no differences among groups. CONCLUSIONS: CYP27A1 might affect VD synthesis and cause low 25-hydroxyvitamin D levels in AD, PD and MSA patients. Low 1,25-di-hydroxyvitamin D levels in MSA patients might be caused by impaired feedback mediated by CYP27B1.