A Molecular Epidemiology Study On The Association Of Polymorphisms In Lipid Metabolism Related MiRNA Binding Sites With Metabolic Syndrome And Its Components

Metabolic syndrome (MetS) is a common, multicomponent condition characterizedby abdominal obesity, insulin resistance, dyslipidemia (elevated plasma triglyceridesand low high-density cholesterol) and hypertension that seriously impact to humanhealth. In2005, the International Diabetes Federation (IDF) estimated that there wereabout a quarter of people in the world with MetS. MetS is an important modifiablerisk factor for type2diabetes mellitus (T2DM) and cardiovscular disease. As a resultof economic growth, changes in lifestyle and diet have led to an increased burden ofMetS, which become a major public health concern. Therefore, the pathogenesis andpreventive measure of MetS are concerned widely.MetS is a complex, multifactorial disease, and its development is determined bya combination of genetic susceptibility and environmental factors. Severalmechanisms have been implicated in the pathogenesis of MetS: excess calories leadto the fat accumulated unduly in adipose tissue or non-fatty tissues and correlativeinsulin resistance. Mi(cro)RNAs play important regulatory roles in a variety ofbiological processes including adipocyte differentiation, metabolic integration, insulinresistance and appetite regulation. A multitude of studies have demonstratedassociations between MetS and specific miRNAs as microRNAs play a key role in thepathological development of MetS by affecting adipocyte differentiation, endocrine hormone.Increasingly evidence confirms that SNPs in3’untranslated regions (3’UTRs)targeted by miRNAs alter the strength of miRNA binding, with consequences onregulation of target genes thereby affecting the individual’s diseases. Therefore, wewill better understand the pathogenesis of MetS by investigate the relationshipbetween SNPs in miRNA binding sites and MetS. Furthermore, there are a number ofalgorithms and bioinformatics data banks to help identify putative miRNA bindingsites.In this study, we conducted a case-control study of the Chinese southeast Hanpopulation, and analyzed the SNPs in lipid metabolism related miRNA binding sitesand haplotype analysis, combined with environmental factors, to find whether thepolymorphisms and its phenotype are associated with the MetS. We furtherresearched the association between these SNPs and the components of MetS. A betterunderstanding of the functional role of polymorphisms in miRNA binding sites willbe a key step to allow us to fully exploit these new data to provide the scientificevidence for the prevention of MetS and screening of high-risk population.Part ⅠScreening microRNAs target SNPs and investigatingtheir associations with MetS susceptibilityWe conducted a case-control study of the Chinese southeast Han population. PotentialmiRNA binding sites in genomic sequences for the list of miRNAs were assessed bybioinformatics data bank (http://www.mirbase.org/) and NCBI data bank(http://www.ncbi.nlm. nih.gov/) using4bioinformatics software. Eventually,8SNPswere selected for subsequent genotyping and association analyses. By utilizingTaqMan assay detection technology, we detect all subjects (1026MetS patients,1032health controls) and analyzed the association between these11SNPs and MetS in the Chinese Han population. Associations between genotypes and MetS risk (ORsand95%CI) were estimated by logistic regression. The main results were as follows:1. Lipid metabolism related miRNA target SNP selectionWe selected7miRNAs which were previously identified related to lipidmetabolism,11target SNPs were assessed by bioinformatics data bank includingrs1042094,rs741191,rs5750146,rs11724758,rs6710015,rs4597342,rs2292899,rs5999924.2. The distribution in cases and controls of SNPs in miRNA binding sitesThe genotype distribution for all the11SNPs did not show any deviation fromthe Hardy-Weinberg equilibrium (all P>0.05in controls). Compared with thegenotypes GG homozygote, the variant genotypes GA and the combined genotypeGA/AA of rs5750146were all associated with a significant risk effect for MetS[Adjusted ORs(95%CIs)=1.31(1.08-1.58),1.24(1.03-1.49)]. Similarly, the variantgenotypes AT and the combined genotype AT/TT of rs5999924compared with the AAgenotype were all associated with a significantly increased risk of MetS [AdjustedORs(95%CIs)=1.27(1.05-1.54),1.22(1.01-1.46)]. The rs11724758AA genotypecarriers were significantly associated with a decreased risk of MetS [AdjustedORs(95%CIs)=0.65(0.50-0.86)]. After inspected by five thousand times permutationtest, the frequency distribution of those sites genotype between the case group andcontrol group still existed statistical differences. No evidence suggested other SNPswere associated with MetS(P>0.05).3. Stratified analysis by gender of miRNA target SNPThe stratified analysis by gender show that the variant genotypes GA[AdjustedORs(95%CIs)=1.37(1.06-1.72)] and the combined genotype GA/AA[AdjustedORs(95%CIs)=1.33(1.03-1.71)] of rs5750146were still all associated with asignificant risk effect for MetS compared with the GG genotype in the female subjects. Similar changes in rs5999924were seen. On the contrary, the variantgenotypes AA of rs11724758was not associated with a decreased risk effect for MetSin the female subjects, association still existed in the male subjects [AdjustedORs(95%CIs)=0.52(0.34-0.80)]. For both males and females, other SNPs were notsignificantly associated with MetS.4. Haplotype analysis on APOL6variationsWe performed haplotype analysis on APOL6variations. There were nohaplotypes which may increase or decrease risk of MetS compared with the mostcommon haplotype GArs5750146-rs5999924, even after adjusting for age, gender, smoking,drinking and physical activity5. Conjoint analysis between SNPs rs5750146and rs11724758and MetS risk.Compared with the wild homozygote of rs5750146and rs11724758, subjectswith variant alleles of the two SNPs had increased risk for MetS susceptibility in adose-response manner (P trend=5.4×10-5).Part ⅡAssociation of polymorphisms in lipid metabolismrelated miRNA binding and the components of MetSIn this study, we based on the PartⅠof Association of Polymorphisms in lipidmetabolism related miRNA binding and the susceptibility of MetS, and selectedrs5750146and rs11724758which had shown the association with MetS in the logisticregression analysis. We further researched the association of these tow SNPs and thecomponents of MetS in group case and control. The main results were as follows:1. Comparison of the levels of triglycerides (TG) of SNPs in miRNA binding sites.In control group, people who carriers with rs5750146AA had higher levels ofTG (1.48±0.95mmol/L)than those with the genotype GG (1.23±0.77mmol/L) (P=0.034), after adjusting for age, gender, HDL-C, FPG, BP and WC, smoking,drinking, physical activity.2. Comparison of the levels of fasting glucose (FPG) of SNPs in miRNA bindingsites.Patients who carriers with rs11724758AA had lower levels of FPG(7.66±3.46mmol/L) than those with the genotype GG(8.99±3.93mmol/L),(P=0.002), after adjusting for age, gender, TG, HDL-C, WC, smoking, drinking andphysical activity.3. Conjoint analysis between SNPs rs5750146and rs11724758and levels of fastingglucose (FPG).Compared with the wild homozygote of rs5750146and rs11724758, Patientswith variant alleles of the two SNPs had increased levels of fasting glucose in adose-response manner (β=0.43295%CI=0.043-0.820, P=0.030).