Vol.:(0123456789) 1 3 Molecular Biology Reports https://doi.org/10.1007/s11033-019-04796-6 ORIGINAL ARTICLE Strong association between VDR FokI (rs2228570) gene variant and serum vitamin D levels in Turkish Cypriots Gulten Tuncel 1,2  · Sehime Gulsun Temel 3,4  · Mahmut Cerkez Ergoren 1,2 Received: 29 January 2019 / Accepted: 3 April 2019 © Springer Nature B.V. 2019 Abstract Vitamin D is an important molecule to keep teeth, bones and muscles healthy. It is obtained from diet, supplements and primarily from exposure to sunlight. In recent years, vitamin D defciency is recognised as a worldwide health problem, which results in disturbances in mineral metabolism and skeletal problems. Defciency might be caused due to sedentary lifestyle, insufcient diet, age as well as some polymorphisms in the VDR gene. In this study the four most common VDR polymorphisms (rs1544410 (BsmI), rs731236 (TaqI), rs7975232 (ApaI) and rs2228570 (FokI)) are investigated in a cohort of Turkish Cypriots and aimed to detect any possible links between low serum vitamin D levels and these variants. The rs2228570 (FokI) variant but not others were shown to have a signifcant association with decreased serum vitamin D levels in the Turkish Cypriot population. Keywords VDR · Polymorphism · Vitamin D defciency · Cyprus Introduction Vitamin D is a fat-soluble prohormone, which is well known to be a major player in bone metabolism and calcium homeo- stasis in animals [1, 2]. Chemically, vitamin D molecules are classifed as secosteroids as their molecular structure is very similar to that of steroid hormones, but they have one broken carbon–carbon bond [3]. There are two major forms of vitamin D. First one is vitamin D 2 or ergocalciferol, which is synthesized by some plants and fungi, and the second form is vitamin D 3 or cholecalciferol, which is produced by animals [4]. The major sources of vitamin D for humans are diet, sup- plementations and sun exposure. Vitamin D from the diet is absorbed via the lymphatic system and transported to the liver by the vitamin D-binding proteins [4, 5]. However, the primary source in humans is the conversion of 7-dehydro- cholesterol, which is present in the skin, to vitamin D 3 by solar ultraviolet (UV) B rays (290–320 nm) [2, 4, 6]. It was shown in a study that vitamin D produced in the skin can last almost twice as long in the circulation compared to ingested vitamin D [4, 6]. Biologically inactive vitamin D obtained from the diet or skin is hydroxylated to prohormone 25-hydroxyvitamin D (25(OH)D) in the liver [1, 5, 6]. Serum 25-hydroxyvi- tamin D concentrations are measured when assessing the vitamin D status, as it refects total body vitamin D reserves [7]. Circulating 25-hydroxyvitamin D is then converted into 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D), which is the bio- logically active form, by a second hydroxylation event in the renal tissues [1, 5]. Gulten Tuncel and Sehime Gulsun Temel are co-authors. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11033-019-04796-6) contains supplementary material, which is available to authorized users. * Mahmut Cerkez Ergoren mahmutcerkez.ergoren@neu.edu.tr Gulten Tuncel 20173423@std.neu.edu.tr Sehime Gulsun Temel sehime@uludag.edu.tr 1 Department of Medical Biology, Faculty of Medicine, Near East University, 99138 Nicosia, Cyprus 2 Research Center of Experimental Health Sciences (DESAM), Near East University, 99138 Nicosia, Cyprus 3 Department of Medical Genetics, Faculty of Medicine, Uludag University, Bursa, Turkey 4 Department of Histology and Embryology, Faculty of Medicine, Uludag University, Bursa, Turkey