Metabolic syndrome (MS) includes a variety of metabolic components in abnormal pathological state, which contains abnormal plasma glucose, dyslipidemia, high blood pressure, and high cholesterol . Patients with MS have a greater risk of developing cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) [2–4]. For the past few years, the prevalence of MS has been on the rise in adults globally, increasing from about 20% to 40% [5–8] in multiple groups of people, and is becoming a serious global health burden. Although insulin resistance  and central obesity  are considered to be its primary etiological factors, genetics undoubtedly plays an important role as well. In particular, genetic influence may be different among various ethnic groups .
The Vitamin D receptor (VDR) is a member of the steroid hormone receptor family that acts as a transcriptional activator of many genes. The DNA polymorphisms that have been often reported for the VDR gene are (described in both restriction sites and dbSNP info): BsmI (rs1544410 A > G), FokI (rs 2228570 C > T), TaqI (rs731236 T > C), and ApaI (rs 7975232 C > T). In past years, many studies have found that these polymorphisms are related to bone mineral density(BMD) , calcium metabolism , tuberculosis, hepatitis  and cancer [15, 16]. Additionally, some of these polymorphisms have been recently identified to be associated with type 1 diabetes , T2DM , and insulin secretion .
Although the molecular mechanisms of VDR in components of MS remain unclear, a relationship between 25(OH)D3 and the disorders of MS has been previously demonstrated [20–23]. Studies have also discussed VDR gene polymorphisms for associations with the components of MS, which suggest that two major VDR gene polymorphisms (BsmI and FokI) seemed to influence BMI, insulin resistance, and serum HDL cholesterol [24, 25]. However, little is known about the role of VDR gene polymorphisms in MS for Chinese population.
Therefore, we suppose the two single-nucleotide polymorphisms (SNPs), BsmI (rs1544410 A > G) and FokI (rs 2228570 C > T), of the VDR gene intricately affect the development of MS. This study was designed to determine the contribution of VDR polymorphisms to MS in a population from North China.