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Objective: The present study aimed to investigate the relationship between environmental factors, C-344T polymorphism of CYP11B2 and essential hypertension (EH), and gene-environment interaction on EH in Chinese Mongolian population.Methods: A cross-sectional study was conducted between 2003-2004 in Tongliao City of Inner Mongolia, China. Demographic data, lifestyle factors, blood pressure (BP) measurements, physical examination and blood samples were obtained and analyzed for all individuals. Linear regression models were used to estimate the associations between environmental factors, the C-344T polymorphism of CYP11B2 gene and BP; Logistic regression models were used to estimate the associations between environmental factors, the C-344T polymorphism of CYP11B2 gene and EH. The gene-environment interactions were analyzed with the multifactor dimensionality reduction (MDR) model, linear and logistic regression models.Results:1.The relationship between environmental factors and EHThe results of the multiple factors analysis shows, body mass index (BMI) (≥24kg/m2) was associated with systolic blood pressure(SBP) (β=7.5; 95%CI=3.4～11.6), diastolic blood pressure (DBP) (β=5.2;95%CI=3.0～7.4) and EH (OR=2.0; 95%CI=1.3～3.0). Drinking index (DI) (≥90 liang?year), waist circumference (WC) (≥85cm), WHR, TC, TG were associated with EH (DI: OR=1.8, 95%CI=1.3～2.7; WC: OR=1.6, 95%CI=1.0～2.4; WHR: OR=1.9, 95%CI=1.4～2.5; TC: OR=2.2, 95%CI= 1.3～3.7; TG: OR=2.0, 95%CI=1.4～2.7); The association between Smoking index (SI) (≥14.3 pack?years), LDL_C, fast plasma glucose (FPG) and EH were not significant.2. The relationship between the CYP11B2 C-344T genotype and EH The results of the univariate-analysis shows the CYP11B2 C-344T genotypes were associated with DBP (TT/CC:β=2.2, 95%CI=0.1～4.3; TC/CC:β=2.8, 95%CI=0.7～4.8); The association between TT, TC genotype and EH was not significant (P≥0.065). After adjustment for age gender, DI, SI, BMI, WC, TC, TG, and LDL_C, the CYP11B2 genotype was associated with DBP (TC/CC:β=2.2, 95%CI=0.3～4.1; TT/CC:β=2.6, 95%CI=0.7～4.4). The association between the CYP11B2 genotype and EH was not significant (P>0.10).3. Interaction between the CYP11B2 C-344T genotype and environmental factors.3.1 Results from stratified analysis3.1.1 The association between the CYP11B2 genotype and DBP was significant among non-smokers (P≤0.033), but it was not significant among smokers, after adjustment for age, gender, drink, BMI and WC. A test of interaction between the CYP11B2 genotype and smoke was not statistically significant (P=0.802).3.1.2 The association between the CYP11B2 TC genotype and EH was significant in DI(≥90) (P=0.009), but it was not significant in DI(<90), after adjustment for age, gender, smoke, BMI and WC. A test of interaction between the CYP11B2 genotype and DI was statistically significant (P=0.002).3.1.3 The association between the CYP11B2 genotype and DBP was significant in BMI (≥24 kg/m2) and WC (≥85cm), but it was not significant in BMI (<24 kg/m2) and WC (< 85cm), after controlling confounders such as age, gender, smoke and drink. A test of interaction of the CYP11B2 genotype with BMI (P=0.020) and WC (P=0.037) was statistically significant.3.2 Results from MDR modelThe optimal model containing CYP11B2 , Age, WC and TG obtained with MDR was found to be statistically significant (χ~2 =162.7,P<0.001). The model Training Balance Accuracy was 0.68 and the model Testing Balance Accuracy was 0.64. The Cross-Validation consistency was 10/10.3.3 Results from combined effects on EHBased on the result of the best MDR model, the final multiple logistic regression models showed the combined effects as following. 3.3.1 The combined association between the CYP11B2 genotype and age (52～83 years) was significant (TT/CC: OR=3.8, 95%CI=1.9～7.6; TC/CC: OR=3.2, 95%CI= 1.5～6.6) after adjustment for gender, BMI, WC, SI, DI, TG, TC and LDL_C.3.3.2 The combined association between the CYP11B2 genotype and WC (≥85cm) was significant (TT/CC: OR=2.6, 95%CI=1.3～5.2; TC/CC: OR=2.7, 95%CI=1.4～5.3) after adjustment for age, gender, BMI, SI, DI, TG, TC and LDL_C.3.3.3 The combined association between the CYP11B2 genotype and TG (≥1.70mmol/L) was significant (TT/CC: OR=2.6, 95%CI=1.5～4.7; TC/CC: OR=2.3, 95%CI=1.3～4.1) after adjustment for age, gender, BMI, WC, SI, DI, TC and LDL_C.Conclusion:1.Age, BMI, waist circumference, WHR, drink and TG were associated with EH, and no associations between smoke, fasting plasma glucose and EH were found in Chinese Mongolian population.2.There were association between the CYP11B2 gene and DBP, and the association was modified by BMI and waist circumference, suggesting the interaction of the CYP11B2 genotype with BMI and waist circumference in Chinese Mongolian population.3.Interaction of the CYP11B2 genotype with age, drinking index, waist circumference and TG on EH was significant in Chinese Mongolian population.?Further investigation in other population might be necessary to corroborate these findings.
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