Mitochondrial Function Gene Bmal1 Gene Regulation Mfn2, Esrra And Biological Clock, Clock, And Genetic Susceptibility To Type 2 Diabetes Research

BackgroundType2diabetes (T2D) is a metabolic disease mainly characterized by high blood glucose which is induced by both insulin resistance and relative insulin deficiency, and the complications of T2D, such as cardiovascular disease, renal failure and blindness, always bring heavy burden to socity and patients with T2D. T2D is always due to a combination of lifestyle and genetic factors.The peroxisome proliferator-activated receptor-y (PPARy) coactivator-1a (PGC-la) is originally identified as a coactivator of PPARy. It is a multifunctional regulatory factor. Estrogen-related receptor-a (ESRRA) is an orphan nuclear receptor involved in a wide variety of cell functions. Mitofusin-2(MFN2) severs as a mitochondrial fusion protein regulating their morphology and distribution. It was reported that ESRRA binding PGC-1α could regulate the expression of MFN2in muscle cell.Studies revealed that disruption insulin secretion, a hallmark of diabetes, play an important role in the development of T2D. Central factors among circadian Clocks are heterodimer partner brain-muscle-arnt-like protein1(Bmall) and the circadian locomotor output cycle kaput (Clock), which are both transcription factors. Bmall and Clock have similar transcriptional regulatory machinery for giving rise to intrinsic circadian oscillatory rhythms through coordinating activation/inactivation of a set of transcription factors.We use the case-control study to test the associations between the mitochondrial function gene(MFN2, ESRRA), circadian clock gene (Bmall, Clock) and T2D in Han Chinese, and interactions between genetic variants of MFN2-ESRRA-PGC-1α and Bmall-Clock gene in the pathogenesis of T2D.MethodsWe made use of the case-control study. The subjects include571T2D patients and649non-diabetic controls. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and TaqMan technology methods, single nucleotide polymorphisms (SNPs) of the MFN2, ESRRA, Clock and Bmall genes were genotyped. Replicating the associated SNPs was performed in the stage2populations including546T2D patients and419non-diabetic controls.We evaluated the frequencies of alleles, genotypes and haplotypes, LD values (D’), r2values using the SHEsis online software (http://analysis.bio-x.cn/myAnalysis.php). Statistical analyses were adjusted using the SPSS statistical package, version16.0. Analysis of gene-gene interaction on the risk of T2D was carried out by multifactor dimensionality reduction (MDR) version2.0beta6(http://www.epistasis.org). A P value of less than0.05was considered statistically significant.Results1. Mitochondrial function genes MFN2and ESRRA(1) Associations of polymorphisms in MFN2gene with T2DFive SNPs (rs873458, rs2878677, rs2236058, rs3766742, rs3766741) in MFN2were selected to genotyped. In stage1population, we found that the frequencies of rs873458-G and rs2878677-T of MFN2gene in the case group were higher than that in the control group (65.6%vs.60.0%, P=0.005, OR=1.27,95%CI=1.08-1.49;44.4%vs.39.1%, P=0.01, OR=1.23,95%CI=1.05-1.47). The genotype distribution of rs873458and rs2878677were significantly different in case-control groups (P=0.0007, P=0.03). After adjusting for age, sex and BMI (body mass index) using analysis of logistic regression with additive model, data showed that the genotype distribution of rs873458and rs2878677of MFN2gene were still significantly different in case-control groups (P=0.01; P=0.02). Replicating the two associated SNPs in the stage2population, data suggested that allele frequency and genotype distribution of rs2878677were still significantly different in case-control groups (P=0.01; P=0.05). Analysis of logistic regression revealed that genotype of rs2878677had significant association of T2D (P=0.02). The allele and genotype of rs873458were not associated with T2D. In the combined population, analysis of logistic regression showed that the genotype distribution of rs873458and rs2878677were still significantly different in case-control groups (P=0.002; P=0.0004). We estimated the frequencies of haplotype of the case-control groups in stage1population. The frequencies of common haplotype A-C-G-T-C and G-T-C-T-C were significantly different in the case-control groups (31.9%vs.37.7%, P=0.007, OR=0.79,95%CI=0.66-0.94;40.6%vs.36.2%, P=0.009, OR=1.26,95%CI=1.06-1.49). Therefore, these results suggested that the polymorphisms of MFN2gene were significantly associated with T2D.(2) Associations of polymorphisms in ESRRA gene with T2DThree SNPs (rs731703, rs650008, rs11600990) in ESRRA gene were selected to genotyped. The frequencies of alleles, genotypes and haplotypes in ESRRA gene were not significantly different in case-control groups of stage1population. Therefore, it suggested that the polymorphisms of ESRRA gene were not significantly associated with T2D.(3) The interaction of MFN2, ESRRA, PGC-1α gene in the pathogenesis of T2DThe analysis between MFN2-ESRRA and MFN2-PGC-1α gene interaction showed that the rs2878677/rs3766741/rs731703/rsl1600990model (testing accuracy=57.7%, CV consistency=3/10) in MFN2-ESRRA, the rs2878677/rs3774923/rs7656250/rs13131226model (testing accuracy=63.9%, CV consistency=9/10) in MFN2-PGC-1α gene, data of PGC-1α gene from our previously study, suggested that there may be interaction between genetic variants in the MFN2, ESRRA and PGC-1α gene. The positive result of association analysis regarding single SNP rs2878677in MFN2gene indicated MFN2gene may be the main factor during the interaction.2. Circandian clock genes Bmall and Clock(1) Associations of polymorphisms in Bmall gene with T2DEight SNPs (rs4414197, rs7950226, rs4757144, rs7126303, rs11022776, rs3789327, rs969485, rs12364562) in Bmall were selected to genotyped. Distribution of rs7950226-GG in case group was higher than that in the control group (19.3%vs.15.4%, P=0.02). Adjusting for age, sex and BMI using analysis of logistic regression, we found there was no significant association between the rs7950226and T2D. Haplotype analysis with multiple loci indicated that frequency of G-A-G-G-G-A-C-A in the Bmall gene was significantly different in case-control groups (10.6%vs13.7%, P=0.04, OR=0.76,95%CI=0.58-0.99). Therefore, it suggested that the polymorphisms of Bmall gene were significantly associated with T2D.(2) Associations of polymorphisms in Clock gene with T2DThree SNPs (rs11240, rs10002541, rs11133391) in Clock were selected to genotyped. The frequencies of alleles, genotypes and haplotypes in Clock gene were not significantly different in case-control groups. Therefore, it suggested that the polymorphisms of Clock gene were not significantly associated with T2D.(3) The interaction of Bmall and Clock gene in the pathogenesis of T2DThe analysis of interaction between genetic variants in Bmall and Clock gene showed that rs7950226/rsl1133391(testing accuracy=51.0%, CV consistency=7/10) suggested that there may be interaction between genetic variants in the Bmall and Clock gene in the pathogenesis of type2diabetes. The positive result of association analysis in Bmall gene indicated Bmall gene may be the main factor during the interaction. ConclusionsThe present study suggested that rs873458-G, rs287867-T and haplotype G-T-C-T-C were risk factors of T2D, haplotype A-C-G-T-C is the protective factor of T2D. And we hold the opinion that MFN2and ESRRA, MFN2and PGC-1α may interact with each other in the pathogensis of T2D. We also found that haplotype G-A-G-G-G-A-C-A in Bmall was protection factor of T2D. And Bmall and Clock gene may interact with each other in the pathogensis of T2D. Associations between polymorphisms in the ESRRA and Clock gene and T2D were not found. Therefore, the present study revealed that the polymorphisms of MFN2and Bmall genes were significantly associated with T2D in Han Chinese.