Analysis On The Associations Between The Single Nucleotide Polymorphisms(SNPs) Of PPARα/δ/γ And Mean Arterial Pressure And Pulse Pressure

Peroxisome proliferator activated receptors(PPARs), the transcription factors of ligand activation type, are acted as the important roles in anti-inflammatory, lipid metabolism, sugar steady state, cell proliferation and differentiation. There are three subtypes of PPARs: α,δ and γ, which genes were located on the human chromosome 22, 6 and 3, respectively. According to the results from the previous studies, single nucleotide polymorphisms(SNPs) of PPARs gene were significantly related with the high blood pressure, diabetes, dyslipidemia and obesity. Mean arterial pressure(MAP) and pulse pressure(PP), the important phenotypic markers of artery elasticity, are the independent risk factors for cardiovascular disease. Previously, the results from SNPs analysis, GWAS analysis and Meta analysis showed that the SNPs of some genes related metabolism, such as rs17249754 and rs2681492 of ATP2B1 gene, were significantly associated with MAP and PP.Until now, the relationships between SNPs of PPARα/δ/γ genes and MAP and PP remain unclear, and lack of the reliable evidence from population. Ryan et al. reported that PPARγ ligands could decrease MAP level in transgenic mice. In addition, the results from 94 cases with metabolic syndromes suggested that the patients with genotype CC of PPARγ(C-161T) had higher levels of PP compared to those with CT+TT genotype. Based on the cohort study of “the Prevention of Metabolic syndrome and Multi-metabolic Disorders in Jiangsu province of China Study(PMMJS)”, we performed the present study to analyze the associations between SNPs and haplotype of PPARα/δ/γ genes with MAP and PP. Moreover, the effects of gene-gene interactions of PPARs gene, the PPARs haplotype-environment interactions on MAP and PP were also investigated. The results of the present study would provide a new insight into the etiology and prevention research on the cardiovascular disease. The main thesis consists of the following four parts.Part I: Association study on the SNPs of PPARα/δ/γgenes and MAP and PPObjective: To investigate the relationships between ten SNPs of PPARα/δ/γ genes and MAP and PP.Methods: 820 subjects were from the cohort study of “the Prevention of Metabolic syndrome and Multi-metabolic Disorders in Jiangsu province of China Study(PMMJS)”. Study population is composed of 550 females and 270 males. Ten SNPs of PPARα/δ/γ genes were selected with the following criteria:(i) MAF(minor allele frequency) of ≥0.05,(ii) reported the association with Metabolic Syndrome, and(iii) locus at functional region or possible occurrence of mutation lying in the area. The association of single SNP with the traits was analyzed by SNP Assoc program from R packages.Results:(1) Hardy-Weinberg equilibrium analysis: Ten SNPs of PPARα/δ/γ genes were analyzed by the Hardy-Weinberg equilibrium. The results showed that all of selected SNPs satisfied Hardy-Weinberg equilibrium(P>0.05). It means each SNPs were evenly distributed among study population.(2) Association between SNPs of PPARs gene and MAP: Compared to the persons with wild genotype of PPARs genes, the MAP levels in people with mutant genotype of rs135539 in PPARα(AC+CC) and rs9794 in PPARδ(CG+GG) decreased-2.200 mm Hg(95% CI:-3.677--0.722 mm Hg) and-1.579 mm Hg(95% CI:-3.069--0.089 mm Hg), respectively. However, the mean levels of MAP in the subjects with mutant genotype of rs10865710 in PPARγ genes(CG+GG) increased 1.565 mm Hg(95% CI :0.096-3.033 mm Hg).(3) Association between SNPs of PPARs gene and PP: The mean levels of PP in people with mutant genotype of rs1805192 in PPARγ genes(PA+AA) significantly increased 1.341 mm Hg(95% CI:0.431-2.252 mm Hg) compared to the persons with wild genotype(PP).Conclusions: rs135539 of PPARα gene, rs9794 of PPARδ gene and rs10865710 of PPARγ gene were significantly associated with MAP levels. Meanwhile, there was a significant relationship between rs1805192 of PPARγ gene and PP levels.Part II: Association study on the gene-gene interaction amongPPARα/δ/γ genes and MAP and PPObjective: To investigate the relationships between gene-gene interaction among PPARα/δ/γ genes and MAP and PP based on the results from single SNPs analysis.Methods: To analyze linkage disequilibrium(LD) for the pair of polymorphisms of ten SNPs selected presently, the value of D’ was estimated by Haploview program from Hapmap Website. GMDR software(version 1.0.1) was used to evaluate the gene-gene interactions among PPARs SNPs associated with MAP and PP. The testing balanced accuracy is the measure of the degree to which the interaction accurately predicts the value of MAP and PP with scores between 0.50(indicating that the model predicts no better than chance) and 1.00(indicating perfect prediction).Finally, a sign test or a permutation test(providing empirical P values) for prediction accuracy can be used to measure the significance of an identified model.Results:(1) Linkage disequilibrium analysis: As the results shown, the strong linage disequilibriums were not observed among selected 10 SNPs. Therefore, on the basis of relatively independent of each SNPs of PPARs gene, the gene-gene interactions among different SNPs could be analyzed.(2) Associations between the gene-gene interaction among PPARα/δ/γ genes and MAP: The GMDR analysis results showed that a two-locus and a eight-locus model were significantly related with MAP level more than 70 mm Hg. Moreover, the eight-locus model comprised of rs135539 of PPARα, rs2016520 and rs9794 of PPARδ, rs3856806, rs1805192, rs709158, rs4684847 and rs10865710 of PPARγ had the highest level of prediction accuracy(0.605) and displayed a better cross-validation consistency(10/10).(3) Associations between the gene-gene interaction among PPARα/δ/γ genes and PP: In the subgroup of subjects with more than 30 mm Hg levels of PP, a six-locus model comprised of rs135539 of PPARα, rs2016520 of PPARδ, rs709158, rs1805192, rs3856806, and rs10865710 of PPARγ had the highest level of prediction accuracy(0.577) and displayed a better cross-validation consistency(10/10). In the subgroup of subjects with less than 40 mm Hg levels of PP, a two-locus model was statistically associated with PP with 0.628 of prediction accuracy and 10/10 of cross-validation consistency.Conclusions: There was a significant association between the gene-gene interaction among PPARα/δ/γ genes and MAP. Meanwhile, gene-gene interaction among rs135539 of PPARα, rs2016520 of PPARδ, rs10865710, rs1805192, rs709158 and rs3856806 of PPARγ were significantly related with PP.Part III: Association study on the haplotypes of PPARδ/γ genesand MAP and PPObjective: To analyze the relationships between the haplotype of PPARδ/γ genes and MAP and PP.Methods: According to the results from GMDR analysis, there were two SNPs of PPARδ gene and six SNPs of PPARγ gene exhibited the effects of gene-gene interactions on MAP and PP, while only one SNP of PPARα was observed. Therefore, Haplo.stats program from R package was used to construct haplotypes with SNPs located on the same chromosome of PPARδ and γ genes. After adjust covariates, the association between the haplotypes of PPARδ and γ genes were analyzed, respectively.Results:(1) Association between haplotype of PPARδ gene and MAP: As the results shown, the subjects with T-C haplotype of PPARδ gene had higher MAP levels than those with other haplotypes of PPARδ gene. The score statistics was 2.209(P=0.027).(2) Association between haplotype of PPARγ gene and MAP: People with haplotypes of G-P-C-G-C、G-P-C-A-T、G-P-T-A-C、G-P-T-G-T were significantly associated with MAP more than 70 mm Hg. The score statistics were-2.283(P=0.022), 1.992(P=0.046), 2.038(P=0.042) and 2.713(P=0.007), respectively.(3) Association between haplotype of PPARγ gene and PP: The results showed that there was significant relationships between PP(>30 mm Hg) and the people with G-P-A-T haplotype of PPARγ, with 2.348 of score statistics(P=0.019).Conclusions: The haplotype T-C of PPARδ and the haplotypes G-P-C-A-T, G-P-T-A-C, G-P-T-G-T and G-P-C-G-C of PPARγ gene might be as genetic markers for MAP regulation. Meanwhile, the G-P-A-T haplotype of PPARγ was significantly associated with PP in Chinese population.Part IV: Association study on the PPARδ/γ gene haplotypes-environment interaction and MAP and PPObjective: To analyze the interactions between the haplotype of PPARδ/γ genes and BMI, WC and smoking habit, and then explore their influences on the MAP and PP.Methods: Based on the results from association study on the haplotypes of PPARδ/γ genes and MAP and PP, the Haplo.glm of Haplo.stats program from R package was used to construct the models of gene-environment interaction. After adjust covariates, the interaction between the haplotype of PPARδ/γ genes and BMI, WC and smoking and its effects on MAP and PP were discussed, respectively.Results:(1) Interaction between haplotype of PPARδ gene and BMI, WC and smoking and their effects on MAP: As the results shown, interaction between haplotype T-C of PPARδ gene and BMI, WC and smoking did not have any effects on MAP(P>0.05).(2) Interaction between haplotype of PPARγ gene and BMI, WC and smoking and their effects on MAP: Among the people with MAP more than 70 mm Hg, interaction between BMI and PPARγ gene haplotypes C-A-C-G-T, C-A-T-G-T, C-P-C-A-C, C-P-C-G-C, G-A-C-A-T, G-A-T-G-T, G-P-C-G-T, G-P-T-A-C and G-P-T-A-T significantly related with MAP. Interaction between WC and PPARγ gene haplotypes C-A-C-G-T, C-P-C-A-C, C-P-T-G-C, G-A-C-A-T, G-A-T-G-T, G-P-C-G-T and G-P-T-A-T significantly associated with MAP. In addition, interaction between smoking and PPARγ gene haplotypes C-A-C-G-T, C-P-T-G-T, G-A-T-A-C, G-A-T-A-T and G-P-C-G-T had significant influences on the MAP.(3) Interaction between haplotype of PPARγ gene and BMI, WC and smoking and their effects on PP: Among the people with PP more than 30 mm Hg, interaction between WC and PPARγ gene haplotype G-P-A-C significantly associated with PP, with 4.832 of interaction coefficient(P<0.05). However, interaction between other haplotypes of PPARγ gene and BMI and smoking did not have any effects on PP(P>0.05).Conclusions: Among the people with MAP more than 70 mm Hg, interaction between the PPARγ gene haplotypes and BMI, WC and smoking significantly related with MAP. Meanwhile, the interaction between the PPARγ gene haplotypes and WC significantly affected PP among the people with more than 30 mm Hg of PP level.