The Study Of Single Nucleotide Polymorphism Of Susceptibility Genes Of Type Two Diabetes In Chinese Han Population

Objective:Type 2 Diabetes (T2DM) is one of the most common metabolic disorders with evident genetic predisposition. Over the past decade, serious efforts have been put into the search for T2DM susceptibility genes, but progress has been slower than anticipated. Recently, significant progress of T2DM susceptibility gene studies was made by genome-wide association studies(GWAS) which have identified common variants in CDKAL1, CDKN2A/B, IGF2BP2, SLC30A8, HHEX, PPARG, KCNJ11, EXT2 and LOC387761 loci that significantly increase risk of T2DM in several studies of European descents. But the contributions of these genetic variants in other ethnic groups are less clear. We aimed to replicate these observations in a population-based cohort of Chinese Hans and examine the associations of these genetic variants with T2DM.Methods:1. 2968 subjects were enrolled in the case-control study, including 1529 patients with T2DM(case) and 1439 participants with normal glucose tolerance(control). A face to face questionnaire survey was conducted to collect datas. All the subjects'body height, body weight, blood pressure, fasting blood glucose(FPG), total cholesterol(TC), high density lipoprotein cholesterol(HDL), low density lipoprotein cholesterol(LDL) and triacylglycerol(TG) levels were deteced. All completed questionnaires were manually checked and coded. T2DM genetic resource database was established using SPSS Data Entry 2.0 software.2. Haploview 4.1 was used to choose single nucleotide polymorohisms(SNPs) of PPARG, KCNJ11, TCF7L2, HHEX, SLC30A8, CDKAL1, CDKN2A/CDKN2B, IGF2BP2, FTO, EXT2 and LOC387761 gene/loci and perform linkage disequilibrium(LD) and haplotype analysis. Genotyping was detected by minisequencing method. Part of subjects were randomly selected from the sample population, the results of genotyping through minisequencing method were replicated by genotyping again and direct sequence analysis.3. SPSS 13.0 package was used to perform case-control analysis. Logistic regression model was constructed to analysis gene-gene interactions. The effect of single SNP on T2DM was analyzed by likeihood ratio test. Cumulative effect of SNPs on the risk of T2DM was performed by logistic regression analysis.4. T2DM patients and non-diabetic control participants 100 cases each was sent to do whole genome-wide association study using Affymetrix 500K and/or Illumina 317K SNPs array technology.Results:1. There were significant difference between T2DM group and control group in age, body mass index(BMI), systolic blood pressure(SDP), diastolic blood pressure(DBP) and the levels of TG, P value<0.05.2. Finished genotying of 20 SNPs which were chosen from T2DM susceptibility genes of PPARG,KCNJ11,TCF7L2,HHEX,SLC30A8,CDKAL1,IGF2BP2,EXT2 and LOC387761.3. Trend analysis of genotypes distribution between T2DM group and control group revealed genetic variants of TCF7L2, HHEX, CDKAL1 and SLC30A8 gene were associated with T2DM, P value <0.05. Distribution of risk allele frequencies of these SNPs in T2DM group were much more higher than in control group. We confirmed SNPs of the TCF7L2, SLC30A8, HHEX and CDKAL1 gene associated with risk for T2DM, with odds ratios ranging from 1.17 to 1.53.4. No significant differences was found between the case and control groups of PPARG(rs1801282, rs12636454 and rs11128597), KCNJ11(rs5215), LOC387761(rs7480010), IGF2BP2(rs4402960) and EXT2(rs11037909, rs3740878) variants, P>0.05.5.The results of haplotypes analysis in the case-control study of TCF7L2(rs7903146-rs11196218-rs6585205), SLC30A8 (rs13266634-rs3802177-rs11558471), HHEX(rs1111875-rs5015480), and CDKAL1(rs10946398-rs4712527-rs736425) were in agreement with the results on the comparation of gentotype and alleles of these SNPs, supported these genes variants associatied with T2DM of Chinese Hans.6. The interaction was presented among CDKAL1, HHEX, SLC30A8 and TCF7L2 genes. Odd ratio analysis showed that the individuals with only one risk genotype of the representative SNPs at four genes had lower relative risk of T2DM(OR=1.48); Moreover, the risk of T2DM reached the highestfor the individuals who carried four risk alleles(OR=7.26) and the population attribulative risk(PAR) is 39.76%. Conclusion:Our findings support the important contribution of TCF7L2, SLC30A8, HHEX and CDKAL1 genetic variants to T2DM in Chineses Han population. PPARG(rs1801282, rs12636454 and rs11128597), KCNJ11(rs5215), IGF2BP2(rs4402960) and LOC387761(rs7480010) variants were excluded association with T2DM in Chinese han population directly. There is much more difference compared with GWAS. At the same time, our reasch considered potential interaction among TCF7L2,SLC30A8,HHEX and CDKAL1 genes.