Vitamin D Metabolism in Peripheral Blood Mononuclear Cells Is Influenced by Chewing “Betel Nut” (Areca catechu) and Vitamin D Status

Context: Vitamin D deficiency, common in South Asians, is a risk factor for metabolic syndrome, type 2 diabetes, and ischemic heart disease. Vitamin D receptor (VDR) activation depends on activated vitamin D [1,25-dihydroxyvitamin D (1,25(OH)2D)] concentration, reflecting opposing actions of 25-hydroxyvitamin D-1α-hydroxylase [1-α(OH)ase] for formation and 25(OH)D-24-hydroxylase [24(OH)ase] for catabolism. We previously reported that circulating 1,25(OH)2D contributed to determination of VDR-protein levels and VDR genotype was a determinant of both VDR mRNA and VDR-protein in South Asians. Objective: We hypothesized that chewing betel nut, an addictive habit common throughout South Asian communities, contributes to hypovitaminosis-D by modulating the enzymes regulating circulating 1,25(OH)2D concentration. Design: Peripheral blood mononuclear cell (PBMC) 1-α(OH)ase and 24(OH)ase mRNA concentrations were measured and examined in relation to cross-sectional data on the vitamin-D axis, diet, smoking, and bet...