Correlation Of Myostatin Gene Polymorphism And Lipid Metabolism

BackgroundWith the improvement of modern life, more and more people become heavier than before. And the topic on the onset of obesity is much more popular recently. In1997, myostatin was found by American scientists, which could inhibit the growth of skeletal muscles. So far, the skeletal muscles were considered as one of the most important issues that consume the energy, and without the function of inhibiting muscles growth by myostatin may increase the energy consumption in muscles. The pathway probably indicates a new direction to study the pathogenesis of obesity. In2007, Zhang and his team found the site+2278G>A of myostatin gene (MSTN) was correlated to the level of BMI, which may imply the correlation between the polymorphisms of MSTN and the onset of obesity and overweight. However, no report on this part has been published so far.ObjectiveTo study the correlation between the polymorphism of MSTN gene and the onset of obesity, we analyzed differences of alleles and genotypes frequencies between patients with overweight or obesity and normal participants. And we also analyzed differences of the indexes related to metabolism including the results of physical examination and laboratory tests among different genotypes of each SNPs.Methods1. Participants(1) Control group:302healthy Chinese (male=97, female=205) were selected in the study. The inclusive criteria:a. physical examination:systolic blood pressure (SBP)<140mmHg, diastolic blood pressure (DBP)<90mmHg, BMI<25Kg/m2; b. laboratory tests:ALT<100U/L, AST<92U/L, FBG<5.6mmol/L, TC<5.69mmol/L, TG<1.69mmol/L, LDL-C<3.62mmol/L, HDL-C>0.92mmol/L, Cr<132umol/L, BUN<7.14mmol/L. The exclusive criteria:Past medical history of disorders in liver.(2) Obesity group:597Chinese patients (male=284, female=313) suffered from obesity or over-weight were selected. The inclusive criteria:a. physical examination:BMI≥25Kg/m2; b. laboratory tests:ALT<100U/L, AST<92U/L, FBG<5.6mmol/L, Cr<132umol/L, BUN<7.14mmol/L. The exclusive criteria:Past medical history of disorders in liver.2. Target SNPs of MSTN(1) Sequencing of major segments:choose30participants from control group, and sequence11major segments that include all known SNPs.(2) Choose target SNPs:With the sequencing results, we could find out the SNPs in MSTN, and choose the suitable SNPs of which the minor allele frequency or heterozygosity is more than5%.3. The methods of identifying the target SNPs(1) RFLP:Use DNAassist2.2software to figure out all the sites could be cut by restriction endonuclease. The product of restriction endonuclease could be detected by Electrophoresis.(2) TaqMan(?) probe:Design the primers and probes for detecting SNPs, and amplify the target segment, then discriminate with type7900Fast PCR system.4. The statisticsUse SPSS (Version13.0) to analyze the enumeration data with chi square test, and analyze the measurement data with T-test and rank-sum test. If the p value is less than0.05, it indicates a significant difference.Results1. Choose the SNPs:The sequencing results indicated11SNPs of MSTN,5of them lie in both exons and introns, and1SNP lies in3’UTR. All the MAF (minor allele frequency) of the SNPs are more than1.0%. We chosen rs3791782(A/G), rs3791783(A/G) and rs35781413(G/A) as target SNPs for further study.2. Hardy-Weinberg Equilibrium:In the control group, the genotypes frequencies of all the three SNPs were consistent with those expected under Hardy-Weinberg Equilibrium test.3."Case-Control" association analysis:a) Alleles frequency:Between the Case and Control group, there were no significant differences in the allele frequencies of rs3791782, rs3791783and rs35781413.b) Genotypes frequency:Between the case and control group, there was a significant difference (p=0.032) in the genotype frequency of rs3791783, and no significant differences in the genotype frequencies of rs3791782and rs35781413.c) Dominant and recessive model:In the dominant model, between case and control group, there were no significant differences in the genotype frequency of rs3791782(AA vs. AG+GG), rs3791783(AA vs. AG+GG) and rs35781413(GG vs. GA+AA). In the recessive model, between the two group, there was a significant difference (p=0.012) in genotype frequency of rs3791783(AA+AG vs. GG), and the OR of genotype GG is less than1, which indicate there is a correlation between rs3791783and the onset of obesity and overweight. There were no significant differences in the genotype frequency of rs3791782(AA+AG vs. GG) and rs35781413(GG+GA vs. AA) in the recessive model.d) Analysis of Haplotype:The results of LD and R2of the three SNPs indicated rs3791782, rs3791783and rs35781413did not belong to the same block of linkage disequilibrium.4. Comparing the measurement data means in different genotypes of SNPs:We got the physical examination results and indexes of serum in laboratory tests of all the899participants in the study. The statistical results are below.e) Rs3791782:Among three genotypes of rs3791782, there was a significant difference (p=0.003) in the level of serum LDL-C.f) Rs3791783:Among three genotypes of rs3791783, there were significant differences in the levels of waist, BMI, serum LDL-C, TC and TG, and p values are0.041、0.009.0.005、0.030、0.046).g) Rs35781413:Among three genotypes of rs35781413, there was a significant difference (p=0.046) in the level of height.Conclusion1. There is a correlation between the rs3791783of MSTN and the onset of obesity and overweight, and GG genotype could reduce the risk of obesity and overweight. At the same time, rs3791783has a correlation with waist, BMI, serum TC, TG and LDL-C, and the participants with GG genotype in rs3791783have lower levels of these indexes above.2. There was no correlation between rs379782of MSTN and the onset of obesity and overweight. Rs3791782was correlated to the level of serum LDL-C, and the participants with GG genotype have lower level of serum LDL-C. 3. There was no correlation between rs35781413of MSTN and the onset of obesity and overweight.