| BackgroundCardiac hypertrophy is recognized as an adaptive process to a variety of physiological and pathological conditions. Prolonged cardiac hypertrophy can depress cardiac function, known as decompensation of hypertrophy, and lead to heart failure. Left ventricular hypertrophy is a complex pathological process, and the molecular mechanisms underlying the development of heart failure are still not clearly understood. It is necessary to explore signals and pathways that play an important role in pathological hypertrophy. Myotrophin, a12-kDa protein, was identified in spontaneously hypertensive rat hearts. It is expressed ubiquitously in mammalian tissues. Several lines of evidence have shown that myotrophin plays a vital role in the initiation of cardiac hypertrophy that transits to heart failure.Nucleotide polymorphisms rs17168525of MTPN as one of miRNA target sites can contribute to alterations in the structure of regions flanking them, then miRNAs binding. Notably, the critical region for a miRNA is nucleotides2-7from the5'end of the miRNA, called as "seed" region, which most often binds to a target site in the3'-UTR of the given mRNA by perfect Watson-Crick complementarity. Variant rs17168525is located in the let-7/miR-98complementarity seed binding sequence and has the potential to alter the base-pairing patterns which in turn would affect the accessibility of the miRNA at the target site and gene activity. We presumed that variant rs17168525able to interrupt myotrophin expression would modify the genetic susceptibility to left ventricular hypertrophy. ObjectiveThe purpose of the study was to determine whether variant rs17168525could modify miRNA binding to myotrophin and contribute to the genetic susceptibility to left ventricular hypertrophy in patients with essential hypertension.MethodsTo construct myotrophin3'-UTR-luciferase reporter plasmids, a46bp sequence carrying either the wild type or the variant genotype of rs17168525was synthesized and cloned into the pMIR-REPORT vector. Hela cells were cotransfected with reconstructed plasmid, Renilla luciferase and PremiR miRNA precursor of let-7c or PremiR Negative Control. Luciferase activities were measured using a luminometer. Western blot examine whether let-7c downregulates myotrophin in cardiomyocytes.Genetic variant rs17168525was genotyped in an independent case-control studies, subjects consisted of552hypertensive patients with LVH and1,062hypertensive patients without LVH and591controls. Echocardiographic measurements were obtained in all the hypertensive patients.ResultsWe show that the TT genotype of variant rs17168525in MTPN was resistant to let-7/miR-98-induced downregulation of myotrophin (41%of the negative control; p<0.05). Let-7c mimic overexpression caused a significant decrease in the level of the myotrophin protein.In the present case-control study, the distributions were in agreement with the Hardy-Weinberg equilibrium in both patients and controls. No differences were found in either genotype frequency distribution between hypertensive patients with LVH and hypertensive patients without LVH or controls. The echocardiographic parameters were not statistically different among the patients carrying the different genotypes (all p>0.05).ConclusionOur experimental results provide evidence that the T allele of rs17168525in the3'-UTR of myotrophin might influence in the level of myotrophin protein by interfering with let-7/miR-98binding. BackgroundAtherosclerosis is pathologic basis of coronary artery disease (CAD). Based on the inflammatory theory, atherosclerosis has been considered as a chronic inflammatory process with multiple immune cells involvement, such as monocytes, macrophage cells and lymphocytes. Monocyte chemoattractant protein-1(MCP-1) is considered as a critical factor in the early formation of atherosclerotic plaques. Interactions between MCP-1and its receptor (C-C motif) chemokine receptor2(CCR2) mediate monocytes recruitment into the subendothelial space where they accumulate lipids and differentiate into macrophages and foam cells. Evidence in animal studies show that the deletion of MCP-1can attenuate diet-induced atherosclerosis, and the deletion of CCR2in apoE-deficient mice afford significant protection from both macrophage accumulation and atherosclerotic lesions formation. Many studies have investigated the association of genetic variants in the MCP-1and CCR2genes with CAD. Variant A-2518G in the MCP-1has been found to increase transcriptional activity and up-regulate the expression of MCP-1. The substitution (Val>Ile) at the64amino acid residue in the CCR2has been reported to be associated with the risk of CAD. However, the results are inconsistent.ObjectiveThe objective of the present study was to clarify this inconsistency and to establish a comprehensive picture of the relationship between these two polymorphisms and the risk of CAD.MethodsA meta-analysis of genetic association studies was conducted to evaluate the association between variants of the MCP-1gene or CCR2gene and risk of CAD. Publications were searched in PubMed, Embase, Web of Science, reviews and reference lists of relevant articles. Pooled effects (OR together with95%CI) were calculated by using random-effect models or fixed-effects model. Subgroup analysis and sensitivity analysis were performed to identify the source of heterogeneity.ResultsA total of20eligible original reports were involved, including a total of9,844patients with CAD and11,821controls. Overall, the-2518GG genotype was weakly associated with CAD risk compared with the wild-type A allele by using random effects model, and the pooled OR was1.42(95%CI:1.06-1.92, P=0.02) in Caucasian studies. Significant heterogeneity was found among the Caucasian studies (Chi2=24.38, I2=67.2%, P=0.002). To clarify the heterogeneity, subgroup analyses were performed to investigate the source of heterogeneity. Sample size (P=0.033) and status of HWE of variant distribution in both cases and controls (P<0.001) explained a large part of the heterogeneity, where as types of coronary heart disease end-points (myocardial infarction versus coronary stenosis) and genotyping method (PCR-RFLP versus others) explained little heterogeneity. In order to minimize the selection bias, analysis restricted to the2studies with more than500patients and yielded an OR of1.08(95%CI:0.85-1.37, P=0.54), which there was no heterogeneity (Chi2=0.64,I2=0%, P=0.43). The pooled ORs (95%CI) for subgroups with200-499and<200were1.86(95%CI:1.06-3.25, P=0.03) and1.46(95%CI:0.82-2.62, P=0.20) respectively. A funnel plot of these9studies suggest possibility of the preferential publication of positive findings in smaller studies (Egger's test, P=0.018). The pooled OR of-2518G compared to A allele was0.93(95%CI:0.73-1.17, P=0.52) in East Asian studies. The pooled OR of641variant for CAD was1.27(95%CI:0.81-1.99, P=0.31) compared to64V in recessive genetic model, and was1.06(95%CI:0.95-1.19, P=0.30) in dominant genetic model. Funnel plots of all enrolled studies suggested no publication bias (Egger's test, P=0.538).ConclusionThe results indicate that MCP-1-2518G allele had probably increased risk of CAD in Caucasian but this is likely to be due to publication bias and insufficient sample size. The CCR2V64I has not been found any association with CAD.
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