Association Of OPN Gene Polymorphisms With Type 2 Diabetic Nephropathy

Background: Diabetic nephropathy(DN)is the leading cause of end-stage kidney disease all over the world and associated with adverse cardiovascular events and death.Its pathogenesis is quite complicated and has not been fully elucidated.Many studies have shown that genetic factors and abnormal carbohydrate metabolism are the main causes of DN.Epidemiologic and familial aggregation studies have indicated that genetic susceptibility also influences the development of DN.Recently osteopontin(OPN)gene has been confirmed as a new candidate gene for Indian patients with DN in type 2 diabetes(T2DM).Chinese are susceptible to DN.However,the relevance of the single-nucleotide polymorphism(SNP)of OPN gene to DN is still unclear.Objectives: 1.To explore the distribution of allelic frequencies and genotypic frequencies of OPN promoter SNP loci rs11730582(C-443T),rs11439060(del G-156G),and rs28357094(G-66T)in Han patients with T2 DM in Hubei Province.2.To explore the relation between three OPN promoter SNP loci rs11730582(C-443T),rs11439060(del G-156G),and rs28357094(G-66T)and the susceptibility of Han people in Hubei Province to DN in T2 DM,thus providing a powerful evidence for early prevention of DN.Methods: 600 patients with T2 DM hospitalized in Department of Endocrinology,the Affiliated First Hospital of Yangtze University from July 2015 to March 2016 were studied and divided into 2 groups according to their urinary albumin excretion rate(UAER)and urinary albumin-creatinine ratio(ACR).The case group(T2DM with DN group,UAER ? 30 mg/24 h twice out of three times or urinary ACR ? 30 ? g/mg)included 334 patients in total,179 male and 155 female,with the average age of 60.61±12.16.The control group(T2DM and no DN,UAER<30mg/24 h for three times or urinary ACR<30?g/mg)included 266 patients in total,136 male and 130 female,with the average age of 59.36±10.43.Three OPN promoter SNP loci rs11730582(C-443T),rs11439060(del G-156G),and rs28357094(G-66T)in Indian study were chosen as candidate gene loci.Single-base extension(SBE)or its modified form was used in combination with Matrix assisted laser desorption ionization time of flight(MALDI-TOF)mass spectrometry for genotyping of these SNP loci.Clinical characteristics,allelic and genotypic frequencies was compared between two groups.Statistical analysis for each clinical characteristic was carried out using SPSS version20.0 for Windows software package.Linkage disequilibrium,haplotype construction,Hardy-Weinberg equilibrium testing and allelic and genotypic frequency analysis were performed with SHEsis software by means of expection-maximization algorithms.Results: 1.Two groups showed similar age,gender,family history of diabetes,fasting blood glucose,fasting insulin,glycosylated hemoglobin,total cholesterol,body mass index,and usage rate of ACEI/ARB and insulin(P>0.05).Compared with the control group,the case group showed longer course of diabetes and higher creatinine,triglyceride,systolic blood pressure,and diastolic blood pressure,and higher incidence of DR and hypertension.The difference was statistically significant(P<0.05).2.The minor allele frequencies(MAF)of locus rs11730582(C-443T)in the control group and the case group were respectively C=0.33 and C=0.31.The MAF of locus rs11439060(del G-156G)in the control group and the case group were respectively G=0.42 and G=0.39.Locus rs28357094(G-66T)in the control group and the case group both showed homozygote with genotype TT instead of polymorphism.Genotypic frequencies of loci rs11730582(C-443T)and rs11439060(del G-156G)in the control group and the case group were consistent with the Hardy–Weinberg equilibrium(P>0.05)and can be considered to have population representativeness.The difference between the control group and the case group in both allelic frequencies and genotypic frequencies of loci rs11730582(C-443T)and rs11439060(del G-156G)was not statistically significant(P>0.05).3.Software SHEsis was used to analyze linkage disequilibrium at loci rs11730582 and rs11439060 which showed consistency with the Hardy–Weinberg equilibrium and strong linkage disequilibrium was found.SHEsis was used for haplotype analysis,with frequencies >0.03,and three haplotypes were found,with T-G the most,C-del G the next,and T-del G the fewest.The difference between the control group and the case group in three haplotypes was not statistically significant(P>0.05).Conclusion: Genetic polymorphism existed in OPN promoter SNP loci rs11730582(C-443T),rs11439060(del G-156G),and rs28357094(G-66T)in Han people in Hubei province.2.OPN promoter SNP locus rs28357094(G-66T)had only homozygote with genotype TT and no polymorphism.3.The difference between the control group and the case group in both allelic frequencies and genotypic frequencies of loci rs11730582(C-443T)and rs11439060(del G-156G)was not statistically significant.Loci rs11730582(C-443T)and rs11439060(del G-156G)had three haplotypes,with T-G the most,C-del G the next,and T-del G the fewest.The difference between the control group and the case group in three haplotypes was not statistically significant.Such result indicates that OPN promoter SNP is not related to the susceptibility of Han people in Hubei Province to DN in T2DM.