A Study Of The Association Between Polymorphisms Of The MMP-2 Gene And Type 2 Diabetic Retinopathy

Objective:Diabetes(diabetes mellitus,DM) widely spreads in the world,it is a metabolic disorder symdrone diagnosed by increased sugar level in the blood and urine.It is one of the major chronic diseases which treat to human health. Diabetic retinopathy(DR) is a serious complication of diabete, and it is an important cause for blindness.The pathogenesy of DR is still unclearly,some research indicated that DR is a diabetic microvasalar complication which caused by multiple factors.Long-term chronic hyperglycemia will lead to a series of metabolic disorders which are associated with DR.But the morbidity time and severity of DR can't completely explained by physiology biochemistry and environmental factors.The invasion of DR and DM almost happened at the same time in some patients while DR may happen ten or more years after invasion of DM in other patients.The incidence of DR is different in different ethnic people and different geographical regions.So genetic factor may plays an important role in the invasion and development of DR.At present,scholars domestic or foreign mainly proceed their study on the pathophysiology of the invasion and development of DR.They screened the possible candidate genes which may affect the invasion and development of DR,and analysised the hereditary susceptibility of DR by gene polymorplism and the regulation of gene expression.So our purpose of this study is to research the relationship between matrix metallopro- teinase-2 and type 2 Diabetic retinopathy.Matrix metalloproteinase(MMPs) are an important family of proteolytic enzymes which are important in many processes of physiologies and pathologies.The MMPs can degrade all kinds of contents of extracell matrix(ECM) and basement membrane(BM).The single nucleotide polymerphism (SNP)of MMP-2 gene may influence it's transcriptional level and protein expression,consequently it may influence the invasion of diseases.The aim of our study is to approach the relationship between the -1306C/T and -735C/T polymerphisms in promoter region of MMP-2 gene and DR in North Chinese han people.Methods:Our study applys case-control studing method. All the patients were recruited from the department of ophthalmology and endocrinology in the Fourth Affiliated Hospital of Hebei Medical University and from DM screening in the city of Shi Jiazhuang and surrounding counties from March 2006 to February 2008,including 139 cases of diabetes mellitus without diabetic retinopathy(DM),151cases of diabetic retinopathy(DR),and there are 118 cases of non proliferation diabetic retinopathy(NPDR) and 33 cases of proliferation diabetic retinopathy(PDR).All the cases were confirmed by the international WHO diagnostic criteria for diabetes and international diabetic retinopathy classification standard.150 cases of healthy volunteers(Control),who had no evidence of diabetes mellitus or any other diseases were randomly selected from Chinese blood donors as control subjects.All cases and controls were from North Chinese Han population.The informed consent was got from all the recruited subjects.Four milliter of venous blood from each subject was drawn in Vacutainer tubes containing 3.2%sodium citrate and stored at 4℃.The genomic DNA was extracted within one week after bleeding by using proteinase K digestion followed by a salting out procedure.Genotypes of the MMP-2 gene were analyzed by PCR-restriction fragment length polymorphism analysis(RFLP) Statistical analysis was performed using SPSS11.5 software package.P＜α=0.05 was considered significant for all statistical analyses and in the method of Chi-square division test P＜α'=0.0125 was Considered significant.Comparison of the MMP-2 genotype,allelotype distribution in patients and healthy controls was performed by means of two-sided contingency tables using Chi-square test.The odds ratio(OR) and 95% confidence Interval(CI) were calculated using an unconditional logistic regression model.Results:1.The allelotype frequencies and the genotype frequencies of MMP-2 in the group of healthy controls were found in Hardy-weinberg equilibrium.2.Association between the MMP-2 -1306C/T SNP in promoter region and diabetic retinopathy:the C and T allele frequencies in Control,DM,DR groups are 90%,10%;92.1%,7.9%;94.7%,5.3%,respectively.And the results have no significant deviation(χ2=4.686,P=0.096).The C/C,C/T,T/T genotypic frequencies of cases in the three groups are 80%,20%,0%;86.3%,11.5%,2.2%;90.7%,7.9%,1.3%, respectively.The results have significant deviation(χ2=7.130, P=0.028).There's no significant deviation of C/C,C/T,T/T genotypic frequencies between the Control group and DM group(χ2=2.054,P＞0.0125),or the DM group and DR group(χ2=1.388,P＞0.0125),while there is significant deviation between the Control group and DR group(χ2=6.939,P＜0.0125). Compared with the C/T+T/T genotype,the C/Cgenotype may increase the onset risk of diabetic retinopathy.The odds ratio (OR) between the Control group and DR group is 2.446(95%CI =1.239-4.829);between the DM group and DR group is 1.549 (95%CI=0.745-3.223)(Table 3).3.Association between the MMP-2 735C/T SNP in promoter region and diabetic retinopathy:the C and T allele frequencies in Control,DM,DR groups are 84%,16%; 84.9%,15.1%;80.1%,19.9%,respectively.And there's no significant deviation between them(χ2=2.671,P=0.263).The C/C,C/T,T/T genotypic frequencies of cases in the three groups are 70.7%,26.7%,2.7%;71.9%,25.9%,2.2%;63.6%, 33.1%,3.3%,respectively.Also,there's no significant deviation between them(χ2=2.789,P=0.248).Compared with the C/T+T/T genotype,the C/C genotype won't increase the onset risk of diabetic retinopathy.The odds ratio(OR) between the Control group and DR group is 0.725(95%CI=0.447-1.175); Between the DM group and DR group is 0.681(95%CI=0.414-1.119).4.Stratified by international diabetic retinopathy typing: The C/C,C/T,T/T genotypic frequencies of MMP-2 1306 C/T site in NPDR group are 90.7%,7.6%,1.7%,respectively,and there's no significant deviation when compared with the PDR group(90.9%,9.1%,0%)(χ2=0.002,P=0.968).Compared with the C/T+T/T genotype,the C/C genotype won't increase the onset risk of PDR,OR=1.028(95%CI=0.269-3.923).The C and T allele frequencies in the two groups are 94.5%,5.5%;95.5%, 4.5%,respectively,and there's no significant deviation between them(χ2=0.095,P=0.758).The C/C,C/T,T/T genotypic frequencies of MMP-2 735 C/T site in NPDR group are 62.7%,33.9%,3.4%,respectively,and there's no significant deviation when compared with the PDR group (66.7%,30.3%,13.0%)(χ2=0.174,P=0.676).Compared with the C/T+T/T genotype,the C/C genotype won't increase the onset risk of PDR,OR=1.189(95%CI=0.527-2.685).The C and T allele frequencies in the two groups are 79.7%,20.3%; 81.8%,18.2%,respectively,and there's no significant deviation bet-ween them(χ2=0.151,P=0.698).Conclusions:1.The MMP-2 C/T SNP may play a role in the genetic susceptibility to the invasion of diabetic retinopathy.Compared with the -1306C/T,T/T genotype,the MMP-2 -1306C/C genotype did significantly increase the risk of the development of the diseases.2.The MMP-2 -735C/T SNP is not associated with the susceptibility of DR in North Chinese han population.3.The MMP-2 -1306C/T SNP and -735C/T SNP is not associated with the development of NPDR to PDR of DR in North Chinese han population.