The Association Of Vitamin D Pathway Genes VDR And CYP2R1 Polymorphisms With Type 2 Diabetes Mellitus

Type 2 diabetes mellitus(T2DM) is a chronic disease with rapidly increased incidence rate in the recent year, and its pathogenesis is complicated. Many studies suppose that vitamin D plays an important role in the process of type 2 diabetes mellitus because it can promote the secretion of insulin and improve insulin resistance. VDR and CYP2R1 genes are the key genes on the metabolic pathways of vitamin D and may involve in the pathogenesis of T2 DM. ObjectiveThe purpose of this study was to explore the level of serum 25(OH)D3 and its influence factors in the rural population of Henan province, and to identify the relationship between the T2 DM susceptibility and the polymorphisms in VDR and CYP2R1 gene. Subject and Method1 SubjectA total of 2215 subjects were collected based on the family unit in Zhengzhou Houzhai town, Jiaozuo Wuzhi county and Luoyang Xin’an county. All the subjects were recruited in studying the vitamin D status in these areas. 397 T2 DM patients and 794 controls were screened for the case-control study. 142 T2 DM families and 142 control families were selected for the case-control family study.2 MethodFace-to-face survey was used to collect the basic information including the demographic characteristics, dietary and living behavior habits, family history of T2 DM, history of present illness and other medical issues.Anthropometry was conducted in the entire study population. 10 m L fasting venous blood was drawn from every participant. The biochemical indexes were tested including fasting plasma glucose(FPG), lipid profile, fasting insulin(FIN), and 25(OH)D3. After isolating the genomic DNA, the selected SNPs markers were genotyped automatically by Taqman fluorescence probe method. Epidata 3.1 software was used for data double entry and conformity test was also conducted. The categorical data were analyzed using the chi-square test. The continuous variables were compared using the student’s test, one-way analysis of variance(ANOVA), and multiple factorial analysis of variance or non-parameters tests. The OR(odds ratios) and 95% CI(confidence intervals) were examined between SNPs in gene or risk environmental factors and the risk of T2 DM or the level of 25(OH)D3 using unconditional logistic regression adjusting for covariates. All analyses were performed using SPSS software(Version21.0). Hardy–Weinberg equilibrium was tested using SHEsis online software. Haplotypes were estimated by program of Haplo.em, Haplo.score and Haplo.glm from Haplo.stats in R. Gene-gene interaction and gene-environment interaction were evaluated by Multifactor dimensionality reduction software(MDR). Results1. Serum vitamin D level of rural residents in HenanThe research results showed that the average serum 25(OH)D3 level was 27.51±22.33 ng/m L. The percentage of vitamin D deficiency and insufficiency was 77.9% and the sufficiency percentage was only 22.1%.The 25(OH)D3levelin the male was more than female;The 25(OH)D3 level of the participants aged above 55 years was higher than those aged below 55. More education received go together with higher 25(OH)D3 level. The 25(OH)D3 concentration in workers and officers was higher than in farmers. We found a positive association between serum levels of 25(OH)D3 and smoking and alcohol consumption,a negative association between serum level of 25OHD3 and salt vegetable intake. Low vitamin D levels were associated with obesity. Those with abnormal WHR, WHt R, serum TG and HDL-C have lower 25(OHD)3 level. The 25(OH)D3 level in T2 DM or hypertensive patients were significantly lower than those in control. The logistic regression analysis showed that ten factors was related to the serum level of25(OH)D3, the education and smoking were positively associated with the serum 25(OH)D3 level, while older age, working in farm, more salt intake, abnormal WHR, WHt R, TG and HDL-C were negatively associated with the serum 25(OH)D3 level.2. Case-control studyUnivariate and multivariate analysis indicated that the obesity index such as BMI, WC, WHR, WHt R were significantly positively associated with T2 DM. Abnormity of of blood lipid metabolic(high level TG and LDL-C, low level HDL-C), hypertension and salt vegetables intake were significantly positively associated with T2 DM, too. Alcohol drinking, physical activity and fresh vegetables and fruits intake were negatively associated with the development of T2 DM.For rs739837, the adjusted logistic regression analysis indicated that G allele and GG genotype were negatively associated with the development of T2 DM in the whole subject, females and those aged above 55. In addition, the TT genotype of rs739837 carriers had higher triacylglycerol than GG and TG genotype carriers, and had higher total cholesterol level than GG genotype carriers. For rs2239179, the adjusted logistic regression analysis indicated that G allele and GG genotype were negatively associated with the development of T2 DM in the whole subject, males, and those aged above 55.The haplotype GCGG of VDR was negatively associated with the development of T2 DM. The result of w-GRS showed that the individuals with higher level of GRS were more susceptible to T2 DM.For CYP2R1 gene, the results of subgroup analysis by gender and age showed that the heterozygotes AG may have a higher susceptibility to T2 DM than homozygote.The result of gene-gene interaction analysis showed that rs2228570, rs739837, rs2239179, rs10766197 and rs10741657 may have a significant interaction in the process of T2 DM. The result of gene-environment interaction analysis showed that rs2239179 and fresh vegetables intake as well as rs739837, fresh vegetables intake andphysical activity may have significant interaction in the T2 DM.3. Case-control family studyThe case families had higher prevalence of diabetes in parents, children and all first-degree relatives than the control families. T2 DM patients had some familial aggregation and a high degree of genetic tendency.The subjects in case families had higher levels of BMI, WC, arm circumference, skin fold, body fat, FIN, TG and LDL-C, but lower level of HDL-C than those in control families. The subjects in T2 DM families consumed more salty vegetable, less fresh vegetables and fruits than those in controls. The case families had stronger family history and more obese people than the control families.The results of association analysis of gene and the T2 DM in different family showed that the CC genotype of rs2189480 in VDR had lower risk of developing T2 DM than other genotypes in the whole families and case families and its recessive model CA+CC is the protective factors for T2 DM. The variants at rs3847987 and rs739837 in VDR were related to the risk of T2 DM in control families. There were no significant differences between case and control families at each site in CYP2R1 gene. Conclusion(1) The serum 25(OH)D3 level is negatively associated with age, obesity and lipid metabolic index. The 25(OH)D3 concentration is high in the male, drinkers,smokers and high education receivers. The serum 25(OH)D3 levels are significantlylow in T2 DM or hypertensive patients.(2) The prevalence of vitamin D deficiency and insufficiency in the investigationareas is high(77.9%), only 22.1% participants have sufficient vitamin D. Therefore,the rational measures should be established to improve the vitamin D status inthese areas.(3) The variants at rs739837 and rs2239179 in VDR are significantly associatedwith T2 DM, the G allele and GG genotypes of rs739837 and rs2239179 are theprotective factors for T2 DM. The variants at rs739837 are associated with theabnormity of blood lipid metabolic.(4) VDR and CYP2R1 may have a significant interaction in the process of T2 DM. The rs2239179 and fresh vegetables intake as well as rs739837, fresh vegetables intake andphysical activity may have significant interaction in the T2 DM. The rs10766197 in CYP2R1, fresh vegetables intake and alcohol drinking may have significant interaction in the T2 DM.(5) The case families have higher prevalence of diabetes in parents, children and all first-degree relatives than the control families. T2 DM patients have some familial aggregation and a high degree of genetic tendency.(6) Alcohol consumption and more vegetables or fruits intake are the protective factors for T2 DM patients, while obesity and abnormal of blood lipid metabolic are the risk factors for T2 DM.