A Study On Polymorphisms Of Matrix Metalloproteinases1,3,9 Gene And Pathogenesis In Chinese Han Patients With Isolated Systolic Hypertension

BackgroudIsolated systolic hypertension of the eldly was a subtype of essential hypertension and characteristiced by elevated systolic and pulse pressure, high mortality and high morbility. Even through, ISH has been an outcome of co-contribution of environment and inherit factors, unfortunately, the pathogenesis of ISH has not been fully understood. With the development of molecular genetics, the effect of inherit factor on the Essential Hypertension morbility has been emphasized. As yet,150 candidate genes for EH had been studied, which involved in renin-angiotensin-aldosterone system(RAAS), sympathetic nervous system(SNS), low-cerebral, ganglion-master, gland-axon, endothelin(ET), natriuretic peptide, KAL-kinin system, steroid hormone(STH), prostaglandin(PG), growth factor(GF), hormone, skeleton protein, adhesion molecule, intracellular messenger, lipide metabolism, glycometabolism, apolipoprotein(APO), ion channel, and so on. But no gene variant has been confirmed to be associated with EH. Owing to characteristic of the indefinite heredity model, high genetic heterogeneity, low penetrance, more genes participated, single gene effect feeble for the EH as some polygene diseases, and relatively low samples for the studies, it was all in the day’s work that the studies arrived at different results. Because of the EH including some subtypes, it is difficult to get confirmedly information about the gene association with EH, and may be as a breakthrough to interpret EH pathogenesis to chose a certain subtype.ISH was characterized by high artery stiffness and low artery compliance, it is reported that all the factors involved in promoting artery stiffness which might be lead to ISH. It had been confirmed that the change of structure and function of elastin located in the large artery media could caused artery stiffness, and some reports about the contributions of elastin to angio-development and cardiovascular diseases revoked our interest in studying elastin gene. a deletion involving 7q11.23 that results in hemizygosity of the elastin gene has been identified as the mechanism responsible for the Williams and Buren syndrome, which is characterized by supravalvular aortic stenosis, hypertension or peripheral stenoses. Li et al had reported that elastin is an essential determinant of arterial morphogenesis, the characterization of mice haploinsufficient for elastin (Eln+/-) revealed a role for elastin in the formation of vessel wall structure. The arteries of Eln+/-mice exhibited thinner elastic lamellae and an increased number of smooth muscle cell layers. Most interestingly, these identical changes have been observed in the arteries of patients with SVAS. D’Armiento J demonstrated that mice haploinsufficient for elastin develop structural changes in vessel walls similar to those seen in patients with mutations in the elastin gene. Due to mechanical changes in the vessel wall, these animals exhibit increased mean arterial pressures. The results evoke the possibility that alterations in elastin may contribute to the development of essential hypertension in patients.Some studies had also reported that elastin gene polymorphisms were associated with artery stiffness, Hanon O et al identified the relationship between the Ser422Gly polymorphism of the elastin gene in exon 16(rs2071307) and the distensibility of elastic arteries 9. Interestingly, Iwai N et al revealed the association of the rs34208922 polymorphism with hypertension and pulse wave velocity. Furthermore, Akagawa H et al reported that SNP(rs34208922) is involved in the reduction of elastin mRNA transcripts in vitro and ex vivo. Recently, elastin has also been suggested to be a potential candidate gene for familial intracranial aneurysms (IAs) and subarachnoid hemorrhages (SAH), which we also found defects in the internal elastic lamina. As a result, ELN may be considered as a functional candidate gene for ISH. Our study has confirmed that SNP rs34208922 and SNP rs2071307 are associated with the ISH by affecting the artery stiffness.Isolated systolic hypertension (ISH) is characterized by increased large artery stiffness and endothelial dysfunction. The factors that cause arterial stiffening and endothelial dysfunction are likely to be involved in the development of ISH. Large artery stiffness is influenced by the relative amounts of structural proteins (particularly elastin and collagens) and by smooth muscle tone. The matrix metalloproteinases (MMPs) are a family of zinc-dependent enzymes with proteolytic activity against connective tissue proteins such as collagens, proteoglycans and elastin. Increased expression and activity of MMPs has been identified in the change of relative amounts of structural proteins and vascular remodeling. Also, the activity of MMPs is influenced by tissue inhibitors of MMP (TIMP). In addition, there is a "functional" regulation of conduit artery stiffness by smooth muscle tone, which is influenced by circulating and endothelium-derived vasoactive mediators, including nitric oxide (NO) and endothelin-1(ET-1).Due to their major influence in vascular remodeling, MMPs have been confirmed to play an important role in the pathogenesis and prognosis of cardiovascular (CV) diseases, including atherosclerotic plaque progression, myocardial infarction and strokes. Furthermore, studies have demonstrated that MMPs gene polymorphisms are associated with artery stiffness and high blood pressure. MMP-3 plays a pivotal role in large artery matrix homeostasis; Moreover, MMP-3 can activate several other matrix metalloproteinases. This versatile enzyme is believed to play important roles in vascular and cardiac matrix remodeling. Clinical investigations have shown that MMP-3 gene polymorphisms (5A/6A) are associated with coronary atherosclerosis and risk of myocardial infarction. Additionally, MMP-3 mRNA and protein level studies from ex vivo tissue, including vascular tissue from individuals of different genotypes for the 5A/6A polymorphism(rs3025058), showed that MMP-3 expression levels are highest in 5A homozygotes, intermediate in heterozygotes and lowest in 6A homozygotes. Furthermore, individuals with 5A allele homozygotes have increased large artery stiffness and higher blood pressure compared with 5A/6A heterozygotes and 6A homozygotes. In agreement, plasma concentrations and different genotypes for the-1562 C>T polymorphism(rs3918242) of MMP-9 are not only associated with the pathogenesis of coronary disease and prognosis of patients with cardiovascular disease, but also these T-1562 allele carriers have significantly greater aortic stiffness and higher brachial systolic and pulse pressure, in addition to carotid systolic and pulse pressure. Yasmin et al demonstrated that MMP-9 levels are related to aortic stiffness, not only in ISH patients, but also in younger and healthier individuals. Furthermore, studies have revealed the MMP-9 polymorphism (-1562 C/T) seems to play a key role in the early stages of hypertensive vascular remodeling and the process of large artery stiffening. Armstrong et al revealed that MMP-9 R279Q(rs17576) is associated with internal carotid artery bulb IMT, while MMP-1 A-519G(rs494379), TIMP-3 T-1296C (rs5749511) are significantly associated with hypertension and artery stiffness. As a result, MMP-1, MMP-3, MMP-9 and TIMP-3 genes may be considered as functional candidate genes for ISH.Pulse wave velocity (PWV) is a known marker of arterial stiffness and defined as the speed in which the pulse wave travels along the length of an artery. Recently, a role for advanced glycation end products (AGEs) in the development of arterial stiffening has been suggested, in that the resultant cross-bridge formation between AGEs and structural proteins leads to increased arterial stiffness in the model of hypertension. Endothelial function, defined as flow mediated dilatation (FMD), is estimated as the percentage increase in vessel diameter from baseline conditions to maximum vessel diameter during hyperaemia and used as a measure of endothelium-dependent vasodilatation. Clinical investigation has demonstrated the presence of impaired endothelium-dependent vasodilation in patients with hypertension as flow-mediated dilatation is inversely correlated with PWV. Nitric oxide (NO) and endothelin-1 (ET-1), the major endothelium-derived relaxing and contracting factors that regulate endothelium-dependent vasodilation, are involved in the pathogenesis of artery stiffness and hypertension. We hypothesized that MMP-1, MMP-3, MMP-9 and TIMP-3 genes polymorphism would be involved in the development of ISH by affecting PWV, FMD, plasma AGEs, ET-1 or NO. The aim of this study was to test these hypotheses in a group of subjects with ISH, EH subjects(no ISH) and age-matched normotensive control(NT).Part one Associations of MMP1,3,9 and TIMP3 Genes Polymorphism with Isolated Systolic Hypertension in Chinese Han PopulationObjective To investigate the relationship of MMP1,3,9 and TIMP3 genes polymorphism with isolated systolic hypertension in Chinese Han population.Methods and results We identified the genotype of the genes in 503 patients with isolated systolic hypertension,481 essential hypertension patients with elevated diastolic blood pressure and 244 age-matched normotensive controls for 5 SNPs among the participants. Multinomial logistic analyses showed that the 5A allele of rs3025058(5A/6A) in MMP3 and the T allele of rs3918242(C-1562T) in MMP9 were significantly associated with isolated systolic hypertension after adjusted by age, triglyceride, low-density lipoprotein (P< 0.001,Pcorr< 0.003;P=0.009, Pcorr=0.027). The 5A/G/C was associated with essential hypertension and 6A/A/T haplotypes were significantly associated with isolated systolic hypertension (Permutation P=0.0258; Permutation P=0.000002). Conclusion MMP3 and MMP9 genes variant seem to contribute to the development of isolated systolic hypertensionPart two Association of Polymorphisms of matrix metalloproteinasesl,3,9 Gene with artery stiffness and endothelial function in Chinese Han Patients with Isolated Systolic Hypertension Objective To investigate the relationship of polymorphisms of matrix metalloproteinasesl,3,9 gene with pulse wave velocity(PWV), advanced glycation end products(AGEs), flow mediated dilatation(FMD), endothelin-1(ET-1) and nitric oxide(NO) in Chinese Han patients with isolated systolic hypertension.Methods We identified the genotype of the genes in 169 patients with isolated systolic hypertension,134 essential hypertension patients with elevated diastolic blood pressure and 71 age-matched normotensive controls whom recruited from July 2007 to December 2008 for 2 SNPs and detected the brachial-ankle pulse wave velocity, advanced glycation end products, flow-mediated dilatation, endothelin-1 and nitric oxide among the participants.Results The baPWV, AGEs and ET-1 in ISH patients were significantly higher compared with EH patients and NT controls(P<0.01, Pcorr<0.05), the FMD and NO in ISH patients and EH patients were markedly lower than NT controls(P<0.01, Pcorr<0.05), although FMD and NO in ISH patients were not significantly different with EH patients. The baPWV of different genotypes for the 5 A/6 A and C-1562T polymorphisms were significantly highest in 5A or T homozygotes, intermediate in heterozygotes and lowest in 6A or C homozygotes(P<0.01, Pcorr<0.05).By contrast, the FMD and NO were markedly lowest in 5A·or T homozygotes, intermediate in heterozygotes and highest in 6A or C homozygotes (P<0.01, Pcorr<0.05), however, there were no difference for AGEs and ET-1 in different genotype of 5A/6A and C-1562T polymorphisms.Conclusion MMP3 and MMP9 genes variant seem to contribute to the development of isolated systolic hypertension by affecting arterial stiffness and endothelial function.Part three The Correlation of AGEs and Vascular Function in Patients with Isolated Systolic Hypertension Objective To investigate the correlation of advanced glycation end products(AGEs) with flow-mediated diavasoculation(FMD) and the effects of AGEs on endothelium dysfunction in patients with isolated systolic hypertension.Methods Overall,310 subjects were enrolled in this study,120 patients with isolated systolic hypertension(ISH),120 patients with essential hypertension (DH) and 70 age-matched NT(normotension control) subjects. All of them were detected pulse wave velocity(PWV) and FMD, and the serum concentration of AGEs, ET-1 were measured by ELISA, and NO by Griess’method.Results The PWV, AGEs and ET-1 were significantly higher in ISH patients compared with NT controls and DH patients, however, the FMD and NO in ISH patients and DH patients were markedly lower than those in NT controls. AGEs was significantly positively correlated with PWV and ET-1(r=0.525,P=0.000; r=0.863,P=0.000),but negatively correlated with FMD and NO(r=-0.635,P=0.000; r=-0.669,P=0.000);furthermore, multiple linear regression analysis showed AGEs, cfPWV were risk factors predisposed for FMD.Conclusion AGEs was the independent risk factor of endothelium dysfunction, and may be involved in the development of ISH.Part four Association of Endothelium-dependent Vasodilation and Left Ventricular Hypertrophy in patients with isolated systolic hypertensionObjective To investigate the correlation of endothelium-dependent vasodilation and left ventricular hypertrophy in patients with isolated systolic hypertension.Methods Overall,250 subjects were enrolled in this study,73 isolated systolic hypertension patients (ISH) with left ventricular hypertrophy,127 ISH patients without left ventricular hypertrophy and 50 age-matched NT(normotension control) subjects according to LVMI. All of them were detected FMD by echocardiography, and the serum concentration of AGEs, ET-1 were measured by ELISA, and NO by Griess reaction.Results The FMD and NO in ISH patients with left ventricular hypertrophy were significantly decreased(P<0.01), however, the AGEs and ET-1 were markedly increased(P<0.01); Correlation analysis showed that LVMI were negatively correlated with FMD and NO (r=-0.718,P=0.003;r=-0.337,P=0.041), and positively correlated with AGEs and ET-1(r=0.639,.P=0.015;r=0.428,P=0.036);the logistic analysis showed that FMD and AGEs were dependently associated with LVH (P=0.027,P=0.035),respectively. With the decreasing of FMD and increasing of AGEs, the odds ratio of morbidity of LVH were significantly increased.Conclusion Endothelium-dependent Vasodilation impaired and large artery stiffness were regarded as the dependent risk factors of LVH.Part five The study of heredity difference of elastin and matrix metalloproteinase gene polymorphism between Han patients and Uigur patients with isolated systolic hypertensionObjective To investigate the heredity difference of elastin and matrix metalloproteinase gene polymorphism(SNP) between Han patients and Uigur patients with isolated systolic hypertension(ISH).Methods 358 Han patients with ISH were recruited from Nanfang hospital and 200 Uigur patients with ISH were recruited from People’s Hospital of Xinjiang Uygur Autonomous Region. The genotypes of 4 SNPs were detected with LDR-PCR and the allele frequencies of each SNP in Han and Uigur patients with ISH were analyzed. Results The frequencies of A allele of rs2071307 and rs34208922 and T allele of rs3918242 in Uigur patients with ISH were significantly higher than those in Han patients with ISH, however, there was no difference of 5A allele of rs3025058 between Han and Uigur patients with ISH. Furthermore, the frequencies of A allele of rs2071307 and rs34208922 were markedly increased with the increase of systolic blood pressure(P=0.0079, P=0.0040).Conclusion Elastin gene polymorphism of rs2071307 and rs34208922 may be involved in the development of Han patients and Uigur patients with ISH.