Association between PPARα Gene Polymorphism and Metabolic Syndrome

• Main Authors: Sir-Chen Lin, 林斯晨
• Other Authors: 江福田
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/02513932262038170157

碩士 === 臺灣大學 === 臨床醫學研究所 === 96 === Introduction Characteristics of the metabolic syndrome are abdominal obesity, atherogenic dyslipidemia, raised blood pressure, insulin resistance, prothrombotic and proinflammatory states. Patients with metabolic syndrome are at increased risk for developing diabetes mellitus (DM) and cardiovascular diseases. Peroxisome proliferator-activated receptors (PPARs) are nuclear proteins that belong to the superfamily of nuclear hormone receptors. PPARs are found in liver, heart, liver and skeletal muscle. PPARs are ligand-induced transcription factors that regulate the transcription of target genes in response to specific ligands, both synthetic and endogenous. PPARα regulates many genes involved in the uptake, transport, and oxidation of fatty acids. Therefore, PPARα is a potential candidate gene that may influence the risk of developing the metabolic syndrome. This study is aimed to find out the association between PPARα gene polymorphism and metabolic syndrome, its components or associated diseases. Methods A total of 300 patients with diagnosis of metabolic syndrome were enrolled in this study. The diagnosis of every patient is based on the criteria of Department of Health, Executive Yuan (1994). 300 controls were recruited who do not have metabolic syndrome. DNA was extracted from 10cc venous blood. Three single nucleotide polymorphisms (SNP) in intron 3: C/A (IMS-JST019819), T/C (IMS-JST019815), A/G (rs4253730) were selected from the JSNP and NCBI database. PCR-RFLP was performed to identify genotypes. We calculated the genotypes distribution and allele frequency among control groups. Chi-square was done and odds ratio was calculated concerning the association between gene polymorphism and metabolic syndrome, associated diseases such as hypertension or DM or coronary artery disease. In different genotypes, ANOVA was used to test the difference of the continuous variables, such as triglyceride, total cholesterol, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), and body mass index (BMI). Statistical significance is confirmed if p value<0.05. In addition, multilocus haplotype analysis was also done. We also select another polymorphism Leu162Val (rs1800206) over exon 5 for the second part of study. A total of 40 subjects without metabolic syndrome were genotyped by the means of PCR-RFLP. Allele frequency was calculated, too. Furthermore, in the third part of study, we focused on promoter region of this gene. There were totally 20 samples from subjects without metabolic syndrome were collected. In order to find possible SNPs in promoter region, PCR and sequencing was performed. Sequences were compared with each other to observe nucleotide variants. Results Single locus analysis revealed significant association between these three SNP and metabolic syndrome-associated diseases. SNP C/A (IMS-JST019819): For AA genotype, there was higher risk to have coronary artery disease than CC+CA group (odds ratio=1.531, p=0.038). P value was still significant after adjusting for sex, age, hypertension and DM. However, p value was not significant if we adjust sex, age, hypertension, DM, LDL and HDL; SNP T/C (IMS-JST019815): Subjects with C allele (CC+TC group) had lower probability value of DM than TT group (odds ratio=0.63, p=0.014). P value was still significant after adjusting for sex and age; SNP A/G (rs4253730): Subjects with G allele (GG+AG group) were at higher risk of developing coronary artery disease than AA group (odds ratio=1.954, p=0.0003). P value was still significant even after adjustment for sex, age, hypertension, DM, LDL and HDL. Subjects having more G alleles were also prone to have higher LDL (p=0.017); nonetheless, there was no strong correlation between these three polymorphisms and following items: metabolic syndrome, hypertension, triglyceride, total cholesterol, HDL or BMI. In multilocus haplotype analysis, concerning following 4 situations including metabolic syndrome, hypertension, DM and coronary artery disease, all the p values of omnibus likelihood ratio test were not significant, which indicated the overall haplotype frequency profile difference between cases and controls were not significant. Besides, using individual haplotype analysis, we were not able to identify any haplotype with significant p value either. In the second part of study, all the 40 samples were Leu162 homozygote. So we could predict that the actual allele frequency of 162Val is less than 1.25% among Taiwanese. In the third part of study, totally 20 sets of DNA samples were successfully sequenced. There was no identified SNP in the promoter region between nucleotide -1664 and -712 among Taiwanese. Conclusion This study demonstrated that polymorphisms of PPARα gene intron 3 might be associated with coronary artery disease, DM and LDL level.