| Type 2 diabetes mellitus(T2DM) is a metabolic disorder disease characterized by chronic hyperglycemia caused by insulin inadequate or insulin resistance which involves multiple metabolic disorders in carbohydrate, lipids and protein metabolism. Dysfunction and/or even failures of some organs, e.g. heart, eye, brain, and kidney are the common complications of T2 DM. Along with the fast development of socioeconomy, the living condition and food supply have been changed significantly in China during the past decades. Dietary pattern and life style tend to be high energy intake and less physical activity, which contribute to the increasing incidence of T2 DM worldwide. T2 DM has been become the third chronic non-communicable diseases(NCDs) after malignant tumor and cardiovascular and cerebrovascular diseases in the world。 It is also the important causal factor of disability and death. The development of T2 DM is the consequence of the interaction between genetic and environmental factors. After the finishing of human genome sequencing, some of the candidate genes associated with T2 DM have been verified. However, these genes could explain only 10% ~ 20% of genetic variation, up to date, there is no one single gene could explain most of the genetic variation of T2 DM. It is possible that gene–gene(environment) interactions in the body lead to T2 DM. This study would mainly explore the relationships between gene–gene interaction on TCF7L2 gene, LRP5 gene, the downstream GCG gene in the WNT signaling pathway and gene-environment interaction with T2 DM, to better understand the influence of genetic factor on T2 DM development and to provide scientific base in exploring the genetic pathogenesis of T2 DM.ObjectivesThe purposes of this study were to investigate the correlation between T2 DM and TCF7L2, LRP5 and GCG genes in WNT signaling pathway, to screen out the environmental risk factors for T2 DM, and to explore the effect of gene–gene and gene-environment interaction on T2 DM in the WNT pathway.Materials and methods1 SubjectTotal of 9619 individuals were recruited in the study, including 1842 T2 DM cases, of which 810 came from local community, 1032 were outpatients of three hospitals in Henan Province and 7777 controls selected from two villages of Luoyang by random cluster sampling method in Henan. The villagers aged 20 and above in the two villages were screened for blood glucose, only those with normal glucose level were selected as control subjects.2 Method2.1 A case –control study design was performed in this study.2.2 All subjects were interviewed through face to face, the information collected including: general demographic characteristics(gender, age, nationality, family income per capita and education level), living behavior risk factors(smoking, alcohol consumption, physical activity), family genetic history(stroke, hypertension, myocardial infarction, hyperlipidemia, and diabetes), and history of present illness(ever suffered from diabetes, hypertension, myocardial infarction, stroke, hyperlipidemia, end-stage renal disease, and tumor).2.3 Height, weight, waist circumference, and blood pressure were measured for all the subjects.2.4 A volume of 5 ml fasting venous blood was drawn from all of the subjects, for the purpose of blood glucose and lipid profiles, which were carried out by using automatic biochemical analyzer; low-density lipoprotein cholesterol(LDL-C) concentration was calculated by the Friedewald formula.2.5 Genome DNA were extracted from whole blood, all the single nucleotide polymorphisms(SNPs) were genotyped by polymerase chain reaction-restriction fragment length polymorphism(PCR-LFLP) and polymerase chain reaction-ligase detection reaction(PCR-LDR).2.6 Gene-gene interaction of WNT pathway was analyzed by multifactor dimensionality reduction(MDR) method.2.7 Gene-environment interaction of WNT pathway was analyzed by logistic multiplication and Additive model.3 Statistical analysis3.1 Data were analyzed using SPSS21.0 software. Numerical variables were expressed as median(range) for statistical description since they were not in normal distribution pattern, nonparametric test was used to compare the difference between groups; All classification variables were expressed with frequency(percentile), comparison between groups were using chi-square test. Environment risk factors were analyzed by logistic regression and expressed the odds ratio by the OR(95% CI). The significant level was set as α = 0.05.3.2 The SHEsis software was employed to analyze the linkage disequilibrium at different sites and Hardy Weinberg equilibrium test. The correlation between different SNPs genotype and T2 DM was studied using multivariable logistic regression analysis after adjusting the confounding factors such as gender, age, and BMI. The degree of association between different genotype and T2 DM was expressed with odds ratio(OR) and 95% confidence interval(95%CI). Gene-gene interaction was analyzed by the MDR 3.0.2 software.3.3 The multiplication interaction between WNT pathway genes and each environment factor was analyzed by non-conditioned logistic regression model. The interaction between genes and the environment additive model was analyzed by the Toms Anderson compiled software. The quantitative evaluation was conducted using the formula of quantitative analysis by introducing the OR values calculated from the interactions.Results1 Total of 9619 individuals were investigated in this study, including 1842 patients with T2 DM and 7777 controls, aged 20 ~ 85, the ratio of male to female was 1:1. 3. BMI, waist circumference, systolic blood pressure and diastolic blood pressure in case group was higher than that in control group(P < 0.001); the fasting blood glucose, triglyceride(TG), total cholesterol(TC), high-density lipoprotein cholesterol(HDL-C) and LDL-C in case group also were higher than that in control group(P < 0.001).2 Risk factors of T2 DM were: general obesity: OR(95% CI) = 3.987(3.078 5.164), family history of diabetes: OR(95% CI) = 2.818(2.241-3.544), abdominal obesity: OR(95% CI) = 1.846(1.459- 2.335), smoking: OR(95% CI) = 1.548(1.290-1.858), TG: OR(95% CI) = 1.499(1.275-1.763), overweight: OR(95% CI) = 1.490(1.181-1.879), TC: OR(95% CI) = 1.416(1.115-1.799), LDL-C: OR(95% CI) = 1.347(1.037-1.750) and hypertension: OR(95% CI) = 1.290(1.083-1.536); The protective factors of T2 DM were moderate physical activity: OR(95% CI) = 0.413(0.328- 0.518) and high levels of physical activity: OR(95% CI) = 0.452(0.381-0.536).3 The study on SNP loci associated with T2 DM in WNT pathways found that only rs11196218 loci and rs290487 loci of TCF7L2 gene were associated with T2 DM. Taking the wild genotype AA of rs11196218 loci as reference, heterozygote AG could increase the risk of T2 DM, OR= 1.322, 95% CI: 1.025-1.704; The mutation genotype CC’s risk of rs290487 locus for T2 DM was 1.377 times that of wild genotype TT, 95% CI: 1.159- 1.636.4 The gene-gene interaction in WNT pathways showed that three loci(rs290487, rs7903146, and rs11196218 loci) of TCF7L2 gene had positive collaborative interaction. There was a gene-gene interaction of positive synergy among TCF7L2, LRP5, and the GCG gene, which had synergistically enhance the risk of T2 DM development..5 The interaction of gene to environment factors in the WNT pathways indicated that there was a positive additive model interaction(S=1.822, 1.675) between rs290487 loci of TCF7L2 gene and BMI, WC. A multiplication model of interaction and negative additive model of interaction(S=-0.762) were found between rs 12104705 loci of GCG gene and physical activity.Conclusions1 Family history of diabetes, smoking, overweight, obesity, high blood pressure, higher TG, TC, and HDL- C could increase the risk of T2 DM. Strengthen physical exercise can reduce the risk of T2 DM.2 There was a locus-locus interaction between rs7903146, rs290487, rs11196218 luci of TCF7L2 gene; versus the role of a single locus, the interaction between the three luci could enhance the risk of T2DM3 There was a gene-gene interaction between TCF7L2, LRP5 and GCG gene and the interaction increases the risk of T2 DM compared with the role of a single gene.4 A positive additive model interaction between the rs290487 locus of TCF7L2 gene and BMI, WC, which has coordination enhancement effect for T2 DM.5 There are a multiplication model of interaction and negative additive model interaction between GCG gene and regular physical activity, the interaction could decrease the risk of T2 DM development. |
PDF Full Text Request