Vitamin D receptor (BsmI) genotypes influence inflammatory and oxidative stress responses to altered vitamin D intake in subjects with Type 2 diabetes: A randomized controlled trial

The purpose of our study was to investigate the possible effect of BsmI vitamin D receptor (VDR’s) polymorphism on changes of the inflammatory and oxidative stress (OS) biomarkers in response to daily intake of vitamin D- fortified yogurt drink (doogh) in subjects with type 2 diabetes (T2D). In a randomized controlled trial, 100 T2D subjects were allocated to two groups to receive either plain doogh (PD; n = 50, containing 170 mg calcium and no vitamin D/250 ml) or vitamin D3-fortified doogh (FD; n = 50, containing 170 mg calcium and 500 IU/250 ml) twice a day for 12 weeks. 25(OH)D, glycemic status, inflammatory as well as OS biomarkers were evaluated before and after the intervention. VDR-BsmI genotypes in an extended number of T2D subjects in the FD group (n = 140) were determined as BB, Bb, and bb. After 12 weeks, in FD compared to PD, serum 25(OH)D increased (+30.0 nmol/l vs. −4.8 nmol/l, p < 0.001). The 25(OH)D, parathyroid hormone, highly sensitive C-reactive protein (hs-CRP), malondialdehyde (MDA), and glutathione (GSH) in patients with the BB genotype were more responsive to vitamin D intake in which the maximum increment in 25(OH)D was in BB (31.8 nmol/l) compared with Bb (24.4 nmol/l) and bb (20.8 nmol/l) (p for trend < 0.001), and the difference in BB, compared to Bb and bb was significant [Bb (p = 0.024) and bb (p = 0.037)]. This difference was accompanied by a significant difference for other biomarkers including fasting serum glucose (p trend = 0.039), fat mass % (p trend < 0.001), interleukin 6 (p trend = 0.033), hs-CRP (p trend < 0.001), and MDA (p trend = 0.028) which significantly all decreased in BB genotype except for GSH which significantly increased (p trend = 0.035). Daily intake of vitamin D-FD for 12 weeks improved the inflammatory and OS biomarkers in T2D subjects, and the improvement was more pronounced in the carriers of BB genotype of VDR-Bsm.