Large artery stiffness: structural and genetic aspects

Functionally significant polymorphisms of the MMP9 gene are associated with primary open-angle glaucoma in the population of Russia

PURPOSE

The aim of this study was to investigate the role of functionally significant loci of the matrix metalloproteinases genes 1, 3, 9 (MMP1, MMP3, and MMP9) in the development of primary open-angle glaucoma (POAG) in Caucasians of the Central region of Russia.

METHODS

In total 604 participants were recruited for the study, including 208 patients with POAG and 396 healthy controls. They were genotyped at eight single nucleotide polymorphisms (SNPs) of the three MMP genes. The association was analyzed using logistic and log-linear regression. POAG-associated loci and their proxies were in silico assessed for their functional prediction.

RESULTS

Variant allele G*rs2250889 of MMP9 was significantly associated with higher risk of POAG (OR_cov = 1.57-1.71). Haplotype CCA [rs3918242-rs3918249-rs17576] of the MMP9 gene was associated with lower risk of POAG (OR_cov = 0.33). Allele А*rs3787268 of MMP9 was associated with the low intraocular pressure in the POAG patients (β_cov = -0.176 - -0.272), and so were haplotypes AA [rs17576-rs3787268] (β_cov = -0.577) and AAC [rs17576-rs3787268- rs2250889] (β_cov = -0.742) of the same gene, whereas allele 2G*rs1799750 of MMP1 was associated with the earlier onset of the disease (β_cov = -0.112 - -0.218). In silico analysis of the polymorphisms suggested the functionality of POAG-associated SNPs and their proxies (epigenetic potential, expression and alternative splicing effects for several genes).

CONCLUSIONS

The MMP9 gene polymorphisms are associated with POAG and intraocular pressure in POAG patients; rs1799750 of MMP1 was associated with the earlier age of manifestation of the disease symptoms.

Serum MMP-3 and its association with central arterial stiffness among young adults is moderated by smoking and BMI

Central arterial stiffness is an independent predictor of cardiovascular disease. It is characterized by a marked reduction in the elastin-collagen ratio of the arterial wall extracellular matrix (ECM), and is largely the result of degradation of various ECM components. Matrix metalloproteinase-3 (MMP-3) may contribute to central arterial stiffness via its involvement in ECM homeostasis and remodeling. This study examined the association between serum MMP-3 concentrations and central arterial stiffness and potential interactions of MMP-3 and traditional cardiovascular risk factors in a population of healthy young adults. A total of 206 participants (n = 109 females) aged 19-25 years were included in the current study. Central arterial stiffness was measured non-invasively as carotid-femoral pulse wave velocity (cfPWV) (m/s). MMP-3 concentrations (ng/ml) were measured using ELISA techniques. Regression analyses were used to examine the association between cfPWV and MMP-3, adjusting for age, sex, smoking status, body mass index (BMI), instantaneous mean arterial pressure (MAP) and heart rate, and serum C-reactive protein. Interactions between MMP-3 with smoking, BMI, sex, and MAP were analyzed in subsequent regression models. MMP-3 was an independent predictor of cfPWV (β = 0.187, p = 0.007), and significant interactions between MMP-3 and regular smoking (β = 0.291, p = 0.022), and MMP-3 and BMI (β = 0.210, p = 0.013) were observed. Higher serum MMP-3 concentrations were associated with a faster cfPWV and thus, greater central arterial stiffness. Interactions between MMP-3 and smoking, and MMP-3 and BMI may, in part, drive the association between MMP-3 and central arterial stiffness.

Matrix Metalloproteinases and Hypertension-Mediated Organ Damage: Current Insights

Matrix metalloproteinases (MMPs) are important extracellular enzymes involved in many physiological and pathological processes. Changes in the activity and concentration of specific MMPs, as well as the unbalance with their inhibitors (tissue inhibitors of metalloproteinases – TIMPs), have been described as a part of the pathogenic cascade promoted by arterial hypertension. MMPs are able to degrade various protein substrates in the extracellular matrix, to influence endothelial cells function, vascular smooth muscle cells migration, proliferation and contraction, and to stimulate cardiomyocytes changes. All these processes can be activated by chronically elevated blood pressure values. Animal and human studies demonstrated the key function of MMPs in the pathogenesis of hypertension-mediated vascular, cardiac, and renal damage, besides age and blood pressure values. Thus, the role of MMPs as biomarkers of hypertension-mediated organ damage and potential pharmacological treatment targets to prevent further cardiovascular and renal complications in hypertensive population is increasingly supported. In this review, we aimed to describe the main scientific evidence about the behavior of MMPs in the development of vascular, cardiac, and renal damage in hypertensive patients.

Novel Data about Association of the Functionally Significant Polymorphisms of the MMP9 Gene with Exfoliation Glaucoma in the Caucasian Population of Central Russia

AIM

This study aimed to investigate the role of functionally significant polymorphisms of the MMP1, MMP3, and MMP9 genes in the development of exfoliation glaucoma (XFG) in the Caucasian population of Central Russia.

METHODS

The study sample consisted of 724 participants, including 328 patients with XFG and 396 individuals in the control group. The participants were of Russian ethnicity (self-reported) born in Central Russia. The participants were genotyped at 8 functionally significant polymorphisms of the MMP genes (rs3918242, rs3918249, rs17576, rs3787268, rs2250889, rs17577 MMP9, rs679620 MMP3, and rs1799750 MMP1). The association analysis was performed using logistic regression. Two polymorphisms, which were associated with XFG, and 12 polymorphisms linked to them (r2 ≥ 0.8) were analyzed for their functional significance in silico.

RESULTS

Allele C of rs3918249 MMP9 was associated with XFG according to the additive model (OR = 0.75, 95% CI: 0.56-0.93, pperm = 0.015), and allele G of the rs2250889 MMP9 locus was associated with XFG according to the additive (OR = 1.59, 95% CI: 1.10-2.29, pperm = 0.013) and dominant (OR = 1.68, 95% CI: 1.11-2.56, pperm = 0.016) models. Two XFG-associated loci of the MMP9 gene and 12 SNPs linked to them had a significant regulatory potential (they are located in the evolutionarily conserved regions, promoter and enhancer histone marks, the DNAase-hypersensitivity regions, a region binding to regulatory protein, and a region of regulatory motifs) and may influence the expression of 13 genes and alternative splicing of 4 genes in various tissues and organs related to the pathogenesis of XFG.

CONCLUSION

Allele C rs3918249 MMP9 decreased risk for XFG (OR = 0.75), and allele G of the rs2250889 MMP9 locus increased risk for XFG (OR = 1.59-1.68) in the Caucasian population of Central Russia.

Effects of aquarobic exercise and burdock intake on serum blood lipids and vascular elasticity in Korean elderly women

BACKGROUND

The elderly's health issues are often complex and tend to lead to chronic diseases; such issues can be due to a fitness decline resulting from a lack of physical activities. The burdock root is a blood purifier, lymphatic system strengthener, and natural diuretic. The purpose of this study was to analyze the effects of aquarobic exercise and burdock intake on serum blood lipids and vascular elasticity in elderly women by implementing a 12-week program with these interventions.

METHODS

Forty elderly female volunteer subjects aged 70 to 80years comprised the control group (n=8), aquarobic exercise group (n=11), aquarobic exercise and burdock intake combination group (n=11), and burdock intake group (n=10). The variables of serum blood lipids, and vascular elasticity were measured in all participants before and after the 12-week study.

RESULTS

Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels significantly decreased in the aquarobic exercise group and aquarobic exercise and burdock intake combination group (p<0.05, p<0.01, p<0.001). No statistically significant changes in pulse wave velocity were also found within or between the groups before and after participation in the 12-week program.

CONCLUSIONS

Our findings indicate that aquarobic exercise and burdock intake improved the serum blood lipid levels and vascular elasticity of Korean elderly women. Additionally, burdock extract intake may be useful in vascular health by playing a secondary role in disease prevention and health promotion.

Association of matrix metalloproteinase-3 gene 5A/6A polymorphism with the recurrence of ischemic stroke: A prospective observational study

Studies have demonstrated that matrix metalloproteinase-3 (MMP-3) is involved in the development and progression of atherosclerosis. However, there is no information available on the association of MMP-3 5A/6A polymorphism with recurrent ischemic stroke (IS) in different IS subtypes. We investigated the potential associations between MMP-3 serum level and -1171 5A/6A polymorphism and the recurrence of IS in a Chinese population. Consecutive acute first-ever IS patients were enrolled between August 2008 and October 2013. The genotypes of MMP-3 5A/6A polymorphism were determined using polymerase chain reaction-restriction fragment length polymorphism. IS recurrence was monitored after the index event and multivariate Cox proportional hazards model was constructed to identify factors related to future IS recurrence. A total of 1282 eligible patients were enrolled. During a 2-year follow-up period, 157 (12.25%) patients had recurrent events. MMP-3 level was significantly higher in patients with 5A/6A or 5A/5A genotype (22.72±7.29ng/ul) than in patients with 6A/6A genotype (20.48±7.58ng/ul), P<0.001. No interaction between MMP-3 5A/6A polymorphism and the risk of recurrence in total IS patients was found. The variant 5A/6A+5A/5A genotype and the 5A allele were significantly associated with a high risk of recurrence for large-artery atherosclerosis (LAA) (multivariate-adjusted, P=0.002, 0.001, respectively), but not for small-artery occlusion and cardioembolism. Our finding showed that MMP-3 5A/6A may be a useful biomarker for predicting recurrence for LAA stroke patients and 5A allele carrier may bear a higher risk of recurrence among patients with the subtype of LAA.

The effect of antihypertensive treatment on arterial stiffness and serum concentration of selected matrix metalloproteinases

INTRODUCTION

The aim of the study was to assess the arterial stiffness and serum levels of selected metalloproteinases (MMPs) in hypertensive patients and their changes following antihypertensive therapy.

MATERIAL AND METHODS

The study group consisted of 95 patients with essential arterial hypertension (HT) stage 1 or 2 (mean age: 53.1 ±13.0 years). The control group consisted of 31 normotensives of the same age range. Hypertension patients were randomized to one of the following monotherapies for 6 months: quinapril, losartan, amlodipine, hydrochlorothiazide or bisoprolol. Carotid-femoral pulse wave velocity (PWV) was measured using a Complior device. Serum concentrations of MMPs (proMMP-1, MMP-2, MMP-3, MMP-9) and plasma concentration of tissue inhibitor of MMPs (TIMP-1) were measured using ELISA.

RESULTS

Pulse wave velocity and serum concentrations of MMP-2 and MMP-9 were higher in HT patients than in the control group. In HT patients PWV was significantly associated (R² = 0.41) with age (B = 0.408, p = 0.00027), systolic blood pressure (SBP) (B = 0.441, p = 0.0011), and MMP-3 (B = 0.204, p = 0.0459). After 6 months of treatment, regardless of the agent used, we observed a significant decrease of PWV, SBP, MMP-2 and MMP-3 and an increase of TIMP-1 plasma concentration. The decrease of PWV was significantly associated with a decrease of SBP (R² = 0.07, B = 0.260, p = 0.015) only.

CONCLUSIONS

In patients with arterial hypertension, beside age and systolic blood pressure, the determinants of arterial stiffness include serum MMP-3 concentration. For drugs compared in the study with the same hypotensive effect obtained, the arterial stiffness reduction effect is not dependent on the drug used. Systolic blood pressure is one of the independent factors responsible for the reduction of arterial stiffness in the course of antihypertensive treatment.

The Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure (InterGEN) Study: Design and Methods for Complex DNA Analysis

The Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure (InterGEN) study aims to delineate the independent and interaction effects of genomic (genetic and epigenetic) and psychological-environmental (maternally perceived racial discrimination, mental health, and parenting behavior) factors on blood pressure (BP) among African American mother-child dyads over time. The purpose of this article is to describe the two-step genetic and epigenetic approach that will be executed to explore Gene × Environment interactions on BP using a longitudinal cohort design. Procedure for the single collection of DNA at Time 1 includes the use of the Oragene 500-format saliva sample collection tube, which provides enough DNA for both the Illumina Multi-Ethnic Genotyping and 850K EPIC methylation analyses. BP readings, height, weight, percentage of body fat, and percentage of body water will be measured on all participants every 6 months for 2 years for a total of 4 time points. Genomic data analyses to be completed include multivariate modeling, assessment of population admixture and structure, and extended analyses including Bonferroni correction, false discovery rate methods, Monte Carlo approach, EIGENSTRAT methods, and so on, to determine relationships among both main and interaction effects of genetic, epigenetic, and psychological environmental factors on BP.

Analysis of the microcirculatory pulse wave: age-related alterations

Morphological analysis of the pulse wave of central blood pressure signal is commonly used for the study of cardiac and vascular properties, but very few attempts were performed for analyzing the peripheral pulse wave of blood flow. In this work, we analyzed this waveform using classical methods, based on the application of FFT, followed by principal components analysis, for assessing the properties of the blood flow. As a sample problem, we evaluated the capability of the proposed method of assessing the alterations correlated with the aging of the vascular system. Results show a good discrimination between the different age groups, confirming the validity of the approach.

Shape analysis of the microcirculatory flow wave

The cardiovascular system and its alterations are a crucial aspect of physiology and medicine. Non-invasive assessment of the functional properties of circulation is of considerable interest to clinicians and physiologists. In this work we investigate the possibility of detecting alterations of the flow waveform in microcirculation, using non-invasive measurements based on a laser Doppler flowmeter. As a test case, we focus on the effect of ageing. Skin is warmed up to a fixed temperature (44 °C) during measurement, to increase blood flow. The shape of the perfusion waveform during each heart beat after the flow was stabilized was used to estimate dynamic parameters of the microcirculatory system. Both the wave rise time, defined as the delay between the diastolic minimum and the following systolic maximum, and the oscillation fraction, defined as the normalized difference between the maximum and minimum flow, present significant variation with age.

Pharmacogenetic effect of the stromelysin (MMP3) polymorphism on stroke risk in relation to antihypertensive treatment: the genetics of hypertension associated treatment study

BACKGROUND AND PURPOSE

Atherothrombotic diseases including stroke share a common etiology of atherosclerosis, and susceptibility to atherosclerosis has a genetic component. Stromelysin-1 (matrix metalloproteinase-3 [MMP3]) regulates arterial matrix composition and is a candidate gene for atherothrombosis. A common polymorphism of MMP3 alters expression levels and affects atherosclerotic progression and plaque stability. As part of the Genetics of Hypertension Associated Treatment study, ancillary to the Antihypertensive and Lipid Lowering to Prevent Heart Attack Trial, we evaluated the 5A/6A polymorphism in MMP3 to determine its association with stroke and determine whether it modifies clinical outcome response to blood pressure-lowering drugs.

METHODS

The effect of the MMP3 5A/6A polymorphism on stroke rates was examined by using multivariate-adjusted Cox regression models, including a test for interactions between genotype and antihypertensive drug class.

RESULTS

Compared with participants treated with chlorthalidone with the 6A/6A genotype, individuals with the 6A/6A genotype randomized to lisinopril had higher stroke rates (hazard ratio=1.32; 95% CI, 1.08 to 1.61; P=0.007) and 5A/6A individuals taking lisinopril had lower stroke rates (hazard ratio(interaction)=0.74; 95% CI, 0.53 to 1.04; P(interaction)=0.08), whereas 5A/5A individuals taking lisinopril had the lowest stroke rate (hazard ratio(interaction)=0.51; 95% CI, 0.31 to 0.85; P(interaction)=0.009). There were no pharmacogenetic differences in stroke rate by genotype in patients taking amlodipine or doxazosin vs chlorthalidone.

CONCLUSIONS

The MMP3 6A/6A genotype is associated with an increased risk of stroke in hypertensive subjects taking lisinopril compared with patients treated with chlorthalidone, whereas a protective effect was found for 5A/5A individuals treated with lisinopril. Genetic screening for the MMP3 5A/6A genotype might be a useful tool to select optimal antihypertensive therapy if this finding is replicated. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00563901.

Plasma levels of matrix metalloproteinase-9 are independently associated with psychosocial factors in a middle-aged normal population

OBJECTIVE

To test the association between psychosocial factors and circulating levels of matrix metalloproteinase-9 (MMP-9) in a normal population sample. Psychosocial factors have been associated with inflammatory markers and are of prognostic significance for coronary artery disease (CAD). The degrading enzyme MMP-9 is upregulated in inflammatory processes and hypothesized to play a role in the rupture of atherosclerotic plaques.

METHODS

A total of 402 participants (50% women), aged 45 to 69 years, were drawn randomly from a normal population. Psychosocial instruments covered depression (Center for Epidemiological Studies Depression Questionnaire, CES-D), vital exhaustion, hostile affect, cynicism, mastery, self-esteem, sense of coherence (SOC), emotional support, and social integration. Plasma MMP-9 was measured by an enzyme-linked immunosorbent assay method. Linear regression models were adjusted for age, sex, known CAD, rheumatoid arthritis, cancer, cardiovascular risk factors including C-reactive protein and ongoing medication.

RESULTS

After full adjustment, there were independent associations of elevated MMP-9 levels with CES-D (+2.9 ng/ml per SD, p = .02), hostile affect (+3.0 ng/ml per SD, p = .02), cynicism (+3.5 ng/ml per SD, p = .006), and SOC (-2.5 ng/ml per SD, p = .046). A principal component analysis extracted three components. The first was mainly extracted from CES-D, vital exhaustion, self-esteem, mastery, and SOC; the second was mainly extracted from hostile affect and cynicism. Both were independently associated with MMP-9 (p = .02, p = .04) when run in the same model.

CONCLUSIONS

MMP-9 levels were associated with psychosocial factors in a middle-aged normal population sample, independently of traditional risk factors. The findings may constitute a possible link between psychosocial factors and cardiovascular risk.

Interactions between metallopeptidase 3 polymorphism rs679620 and BMI in predicting blood pressure in African-American women with hypertension

BMI represents an internal metabolic and physiological environment that plays a key role in development of high blood pressure (BP) for many Americans. African-American women have a higher prevalence of high BP and being overweight than men or other ethnic groups. This study examines the genetic-environmental interaction effects of single nucleotide polymorphisms and BMI on BP among African-American women using 1418 African-American women and men from the Genetic Epidemiology Network of Arteriopathy study. A total of 403 tests of single nucleotide polymorphism-BMI interaction were conducted using methods of internal replication, cross-validation, and false discovery rate. One single nucleotide polymorphism (located in the ATP6B1 gene, rs2266917) passed adjustments for multiple testing and had a significant independent main effect (P = 0.0018) on diastolic BP among African-American women. A significant sex-specific interaction effect was found between MMP3_rs679620 and BMI in African-American women (P = 0.0009). MMP3_rs679620 (A-G polymorphism) encodes a Lys-Glu nonsynonymous variant at the 45th amino acid of metallopeptidase 3 and indicates a putative functional modification of metallopeptidase 3. These findings were not identified in African-American men. MMP3_rs679620 appears to have a protective effect on diastolic BP in women with high BMI. Surprisingly, MMP3_rs679620 had the opposite effect on women with low BMI, resulting in higher diastolic BP.

A whole genome scan for pulse pressure/stroke volume ratio in African Americans: the HyperGEN study

BACKGROUND

Arterial stiffness is reported in numerous family studies to be heritable. Linkage analysis has identified genomic regions that likely harbor genes contributing to its phenotypic expression. We sought to identify loci contributing to arterial stiffness in a large group of African-American hypertensive families.

METHODS

We performed a genome scan on 1251 African Americans in families participating in the HyperGEN (Hypertension Genetic Epidemiology Network) study. Children of the hypertensive proband generation were also included in the analysis. Arterial stiffness was estimated as pulse pressure (PP; systolic - diastolic blood pressure [BP]) divided by echocardiographically determined stroke volume (SV). The PP/SV ratio was adjusted for several nongenetic sources of variation, including demographic and lifestyle factors. The residual phenotype was analyzed using multipoint variance components linkage implemented in SOLAR 2.0.3.

RESULTS

Arterial stiffness was 20% heritable in African Americans. Two regions were highly suggestive of linkage, one between markers D1S1665 and D1S1728 in the 215-cM region of chromosome 1 (LOD = 3.08), and another between D14S588 and D14S606 in the 85-cM region of chromosome 14 (LOD = 2.42). Two candidate genes (GPR-25, SMOC-1) are located in the linked regions. SMOC-1 is of physiological interest because it codes a secreted glycoprotein with five domains, each containing regions homologous to those on other proteins that mediate cell-matrix interactions. GPR-25 is homologous to receptors involved in BP regulation.

CONCLUSIONS

At least two chromosomal regions in humans are likely to harbor genes contributing to interindividual variation in PP/SV ratio, an index of arterial stiffness, in African Americans.

Ageing and vascular ageing

There is an age related decline in various physiological processes. Vascular ageing is associated with changes in the mechanical and the structural properties of the vascular wall, which leads to the loss of arterial elasticity and reduced arterial compliance. Arterial compliance can be measured by different parameters like pulse wave velocity, augmentation index, and systemic arterial compliance. There is evidence that arterial compliance is reduced in disease states such as hypertension, diabetes, and end stage renal failure. Changes in arterial compliance can be present before the clinical manifestation of cardiovascular disease. Pharmacological and non-pharmacological measures have been shown to improve arterial compliance. Arterial compliance may constitute an early cardiovascular risk marker and may be useful in assessing the effects of drugs on the cardiovascular system. Pharmacogenetics and genetics of arterial compliance in the future will improve our knowledge and understanding about vascular ageing.

Mechanical testing of human cardiac tissue: some implications for MRI safety

PURPOSE

The effects of aging on tissue strength and its ability to withstand forces associated with MRI have not been investigated. This study aimed to determine the forces required to cause partial or total detachment of a heart valve prosthesis in patients with age-related degenerative diseases exposed to MRI.

METHODS

Eighteen tissue samples excised during routine heart valve replacement surgery were subjected to a suture pull-out test using a tensile materials testing machine. Five preconditioning cycles were applied before commencing the final destructive test. The test was complete when the sample ruptured and the suture was pulled completely free from the tissue. Results were compared with previously calculated magnetically induced forces at 4.7 T.

RESULTS

All tissue samples displayed a basic failure pattern. Mean forces required to cause initial yield and total rupture were 4.0 N (+/- 3.3 N) and 4.9 N (+/- 3.6 N), respectively. Significant factors determining initial yield were stenosed calcific tissue (p < .01), calcific degeneration (single pathology) (p < .04) and tissue stiffness (p < .01). Calcific degeneration (p < .03) and tissue stiffness (p < .03) were also significant in determining maximum force required to cause total rupture.

CONCLUSION

Specific age-related degenerative cardiac diseases stiffen and strengthen tissue resulting in significant forces being required to pull a suture through valve annulus tissue. These forces are significantly greater than magnetically induced < 4.7 T. Therefore, patients with degenerative valvular diseases are unlikely to be at risk of valve dehiscence during exposure to static magnetic field < or = 4.7 T.

Endothelial NOS G894 T and MMP-3 5A/6A gene polymorphisms and hypertension in Serbian population

The incidence of hypertension is increasing and it is more common in man than in women. Up to date, MMP-3 5A/6A polymorphism has been associated with artery stiffening and elevated blood pressure, whereas results considering association of endothelial NOS (eNOS) G894 T polymorphism with hypertension are controversial. The aim of our study was to analyze the possible association of eNOS G894 T and MMP-3 5A/6A gene polymorphisms with hypertension in Serbian population. Study sample consisted of 172 hypertensive and 200 normotensive subjects divided by gender. Both female and male group was truncated according to age. All subjects were genotyped for MMP-3 5A/6A and eNOS G894 T polymorphism. There was a significantly higher (P < 0.05) prevalence of 5A/5A genotype in hypertensive females compared to normotensive ones (19.30 % vs. 10.84%) even more pronounced in group > or =50 years, according to its recessive effect. In young males (<40 years), we found 3.7-fold increased risk for hypertension associated with allele 6A (P < 0.01), and 8.1-fold with genotype 6A/6A (P = 0.01) according to recessive model. We found no association of eNOS G894 T polymorphism with hypertension. These results indicate that there were gender- and age-specific differences in association of MMP-3 5A/6A polymorphism with hypertension in Serbian population.

Flow-mediated changes in pulse wave velocity: a new clinical measure of endothelial function

AIMS

To test whether measuring hyperaemic changes in pulse wave velocity (PWV) could be used as a new method of assessing endothelial function for use in clinical practice.

METHODS AND RESULTS

Flow-mediated changes in vascular tone may be used to assess endothelial function and may be induced by distal hyperaemia, while endothelium-mediated changes in vascular tone can influence PWV. These three known principles were combined to provide and test a novel method of measuring endothelial function by the acute effects of distal hyperaemia on upper and lower limb PWV (measured by a recently developed method). Flow-mediated changes in upper and lower limb PWV were compared in 17 healthy subjects and seven patients with stable chronic heart failure (CHF), as a condition where endothelial function is impaired but endothelium-independent dilator responses are retained. Corroborative measurements of PWV and brachial artery diameter responses to endothelium-dependent and -independent pharmacological stimuli were performed in a further eight healthy subjects. Flow-mediated reduction of PWV (by 14% with no change in blood pressure) was found in normal subjects but was almost abolished in patients with CHF. PWV responses appear to be inversely related to and relatively greater than brachial artery diameter responses.

CONCLUSION

The method may offer potential advantages of practical use and sensitivity over conduit artery diameter responses to measure endothelial dysfunction.

Stromelysin-1 (MMP-3) gene 5A/6A promoter polymorphism is associated with blood pressure in a community population

BACKGROUND AND OBJECTIVES

Arterial remodelling contributes to the development of hypertension. Stromelysin-1 (MMP-3), a member of the matrix metalloproteinase family may contribute to this process. Stromelysin-1 gene expression is partly regulated by a common polymorphism in the promoter region of either five or six consecutive adenosine bases (5A/6A).

METHODS AND RESULTS

A cross-sectional study of 1111 randomly selected male and female community subjects (27-77 years), were assessed for conventional cardiovascular risk factors and stromelysin-1 5A-1171-6A genotype. Multivariate analysis showed an independent association between the stromelysin-1 genotype and blood pressure that was recessive for the 5A/5A genotype. Subjects with the 5A/5A genotype had a higher mean systolic blood pressure (SBP) (+4.2 mmHg) and diastolic blood pressure (DBP) (+2.2 mmHg) compared to subjects with 5A/6A and 6A/6A genotypes. Subgroup analysis revealed an independent association of the 5A/5A genotype with SBP (+3.6 mmHg, P = 0.001) and DBP (+2.0 mmHg, P = 0.004) in subjects not on blood pressure medication. Whereas subjects with the 5A/5A genotype and taking medication had a higher mean SBP (+7.4 mmHg, P = 0.02) and DBP (+2.7 mmHg, P = 0.11). Multivariate analysis in the whole population showed there was no association between genotypes and mean intimal-medial wall thickness (IMT) (P = 0.87) or the likelihood of carotid plaque formation.

CONCLUSIONS

The stromelysin-1 5A-1171-6A genotype is an important determinant of blood pressure in this general population sample.

Acute effects of resistance exercise on arterial compliance

Decreased central arterial compliance is an emerging risk factor for cardiovascular disease. Resistance training is associated with reductions in the elastic properties of central arteries. Currently, it is not known whether this reduction is from one bout of resistance exercise or from an adaptation to multiple bouts of resistance training. Sixteen healthy sedentary or recreationally active adults (11 men and 5 women, age 27 ± 1 yr) were studied under parallel experimental conditions on 2 separate days. The order of experiments was randomized between resistance exercise (9 resistance exercises at 75% of 1 repetition maximum) and sham control (seated rest in the exercise room). Baseline hemodynamic values were not different between the two experimental conditions. Carotid arterial compliance (via simultaneous B-mode ultrasound and applanation tonometry) decreased and β-stiffness index increased ( P < 0.01) immediately and 30 min after resistance exercise. Immediately after resistance exercise, carotid systolic blood pressure increased ( P < 0.01), although no changes were observed in brachial systolic blood pressure at any time points. These measures returned to baseline values within 60 min after the completion of resistance exercise. No significant changes in these variables were observed during the sham control condition. These results indicate that one bout of resistance exercise acutely decreases central arterial compliance, but this effect is sustained for <60 min after the completion of resistance exercise.

Pharmacogenomics of multigenic diseases: sex-specific differences in disease and treatment outcome

Numerous genetic variations have been shown to affect disease susceptibility and drug response. Pharmacogenomics aims at improving therapy on the basis of genetic information for each individual patient. Furthermore, sex chromosomes broadly determine biological differences between males and females. Consequently, substantial sex differences exist in phenotypic manifestation of disease and treatment response. This review discusses the role of sex in coronary artery disease, schizophrenia, and depression--complex multigenic disorders with considerable sex differences in frequency and presentation. Moreover, genetic factors underlying disease and drug response appear to differ between male and female patients. This appears to result at least in part from different physiological effects exerted by sex hormones such that polymorphisms in susceptibility genes may have physiological relevance only in males or females. However, few examples have been discovered to play a role in complex multigenic diseases, and the mechanistic basis of genetic variants as sex-dependent susceptibility factors has yet to be explored. Therefore, pharmacogenomic studies must consider sex differences in an effort to optimize individual drug therapy.

Cardiovascular risk in women with type 2 diabetes

Type 2 DM appears to eliminate the relative survival advantage experienced by premenopausal nondiabetic women compared with men with regard to CVD. The role of traditional cardiovascular risk factors, while important, cannot fully account for the disparate increase in CVD among women with type 2 DM compared with nondiabetic women. The interplay between type 2 DM and female hormones may prove important. Other less traditional risk factors such as endothelial dysfunction and impaired fibrinolysis may also play a role. Impairments in cardiovascular exercise performance in women with type 2 DM may provide insight in the future as representative of a pre-CVD state. Future research should focus on the specific causes of CVD in women with DM. In the meantime, it is important to aggressively treat modifiable risk factors in this population (Table 1). The impact of this health problem will continue to increase in our aging society, because a steadily increasing proportion of the population will be women; furthermore, an increasing percentage of these women will have diabetes if current trends continue.

Vascular and metabolic response to isolated small muscle mass exercise: effect of age

To determine the effect of age on quadriceps muscle blood flow (QMBF), leg vascular resistance (LVR), and maximum oxygen uptake (QVO2 max), a thermal dilution technique was used in conjunction with arterial and venous femoral blood sampling in six sedentary young (19.8 +/- 1.3 yr) and six sedentary old (66.5 +/- 2.1 yr) males during incremental knee extensor exercise (KE). Young and old attained a similar maximal KE work rate (WRmax) (young: 25.2 +/- 2.1 and old: 24.1 +/- 4 W) and QVO2 max (young: 0.52 +/- 0.03 and old: 0.42 +/- 0.05 l/min). QMBF during KE was lower in old subjects by approximately 500 ml/min across all work rates, with old subjects demonstrating a significantly lower QMBF/W (old: 174 +/- 20 and young: 239 +/- 46 ml. min-1. W-1). Although the vasodilatory response to incremental KE was approximately 142% greater in the old (young: 0.0019 and old: 0.0046 mmHg. min. ml-1. W-1), consistently elevated leg vascular resistance (LVR) in the old, approximately 80% higher LVR in the old at 50% WR and approximately 40% higher LVR in the old at WRmax (young: 44.1 +/- 3.6 and old: 31.0 +/- 1.7 mmHg. min. ml-1), dictated that during incremental KE the LVR of the old subjects was never less than that of the young subjects. Pulse pressures, indicative of arterial vessel compliance, were approximately 36% higher in the old subjects across all work rates. In conclusion, well-matched sedentary young and old subjects with similar quadriceps muscle mass achieved a similar WRmax and QVO2 max during incremental KE. The old subjects, despite a reduced QMBF, had a greater vasodilatory response to incremental KE. Given that small muscle mass exercise, such as KE, utilizes only a fraction of maximal cardiac output, peripheral mechanisms such as consistently elevated leg vascular resistance and greater pulse pressures appear to be responsible for reduced blood flow persisting throughout graded KE in the old subjects.