<p>Background: Genome wide association studies (GWAS) performed in Caucasian populations have identified several single nucleotide polymorphisms (SNPs) associated with coronary artery disease (CAD), although their cumulative impact in other ethnicities is unknown. Using a genetic risk score (GRS), we examined the impact of CAD related SNPs on myocardial infarction (MI) in a multi-ethnic population.</p> <p>Methods: We included 4083 MI cases and 4473 controls from the INTERHEART case: control study, stratified by six ethnic groups: European, South Asian, other Asian, Arab, Latin American, and African. We created a GRS comprised of 25 SNPS, and tested its association with MI in individual ethnicities using logistic regression, and across ethnic groups through meta-analyses. Results were adjusted for age, sex, and modifiable risk factors.</p> <p>Results: The GRS was significantly associated with MI in Europeans (odds ratio [OR] = 1.08, 95% confidence interval [CI] 1.04-1.12 per risk allele), South Asians (OR = 1.09, 95% CI 1.05-1.14), other Asians (OR = 1.09, 95% CI 1.04-1.15), and Arabs (OR = 1.07, 95% CI 1.03-1.12). In Latin Americans and Africans the GRS was not significant. Meta-analysis of ethnic groups demonstrated a 1.06 (95% CI 1.03-1.09) increase in the odds of MI with the GRS per risk allele. Significant heterogeneity was observed, which was reduced by exclusion of Latin Americans (I2=63% to 0%). Above clinical risk factors, the GRS modestly increased population attributable risk (PAR) (0.92 to 0.94), concordance statistic (0.73 to 0.74), net reclassification improvement (0.14), and integrated discriminatory improvement (0.007).</p> <p>Conclusions:<strong> </strong>The GRS was associated with a significant increase in the odds of MI in multiple ethnic groups. Improvements in PAR, discrimination and reclassification were modest above clinical factors.</p> / Master of Science (MSc)

The physiological and psychosocial benefits of sustained exercise adherence among individuals with coronary artery disease (CAD) have been well-documented (e.g., Blumenthal et al., 1997; Rozanski et al., 1999; Wenger et al., 1995). Despite these known benefits, approximately 80% of patients who enter the maintenance phase of cardiac rehabilitation drop out after one year (Balady et al., 1994; Hedback, Perk, Wodlin, 1993 ). Among this 80%, less than 25% continue to exercise at levels that will maintain or improve cardiorespiratory fitness (Daltroy, 1985; Radtke, 1989). Self-efficacy has been identified as a significant predictor of adherence to exercise beyond the initial 6 months of participation. In addition to self-efficacy, outcome satisfaction has been suggested as a potentially significant predictor of adherence to exercise beyond the initiation phase (i.e., beyond the first 6 months). Unfortunately, most research examining these predictors of adherence has been conducted among asymptomatic populations. Thus, little is known about the predictive utility of self-efficacy and outcome satisfaction in relation to sustained exercise adherence among the CAD population. The purpose of the present study was to examine self-efficacy (Bandura, 1986) and outcome satisfaction (Rothman, 2000) in the prediction of adherence to maintenance cardiac rehabilitation in 101 men (M age= 68.15 ± 8.03) with coronary artery disease (CAD). A series of three hierarchical multiple regression analyses were conducted to predict onsite, offsite and total adherence to the maintenance cardiac rehabilitation exercise prescription. Interestingly, Exercise Beliefs (i.e., days of aerobic exercise per week believed necessary to maintain cardiovascular health), one of the study covariates, emerged as an important predictor of both offsite and total exercise adherence and explained a significant amount of variance in these variables (R2 = .25 [offsite], .23 [total],ps < .01). As predicted, self-regulatory efficacy was a significant predictor and explained a significant amount of variance in onsite exercise adherence (R2 = .17 [scheduling],p < .001). Task self-efficacy was not a significant predictor and did not account for a significant amount of variance in onsite exercise adherence. Also as predicted, task self-efficacy was a significant predictor and explained a significant amount of variance in offsite exercise adherence (R2= .10,p < .05). Self-regulatory efficacy was not a significant predictor and did not account for a significant amount of variance in offsite exercise adherence. In addition, consistent with hypothesis, both task self-efficacy and self-regulatory efficacy were significant predictors of total exercise adherence and explained a significant amount of the variance in this variable (R2 = .12 [task], .07 [scheduling],ps < .05). Contrary to hypothesis, outcome satisfaction did not explain a significant amount of variance in exercise adherence (onsite, offsite, and total) beyond that explained by self-efficacy (task and self-regulatory) alone. Taken together, this research has enhanced our knowledge of the psychosocial predictors of adherence to the maintenance cardiac rehabilitation exercise prescription among men with CAD. These findings also have important implications for health care professionals working in the area of cardiac rehabilitation. Specifically, it is up to health care professionals to ensure that patient beliefs regarding the maintenance cardiac rehabilitation exercise prescription are accurate, and that patients are efficacious in their ability to engage in the elemental physical aspects of exercise and to effectively schedule exercise into their daily lives. / Thesis / Master of Science (MS)

Não há evidência conclusiva da vantagem da revascularização cirúrgica do miocárdio (RCM) ou angioplastia percutânea coronária (APC) sobre o tratamento clínico (TC) em pacientes sintomáticos, com doença arterial coronária (DAC) multiarterial e função ventricular esquerda (FVE) preservada. O objetivo deste estudo foi comparar os resultados em longo prazo da RCM ou APC com o TC em pacientes portadores de DAC em múltiplos vasos e FVE preservada. Os desfechos primários do estudo foram a combinação de morte por qualquer origem, infarto do miocárdio não fatal (IAM) e angina refratária com necessidade de intervenção mecânica. O desfecho secundário foi o estado anginoso ao final do estudo. Todos os eventos foram analisados de acordo com o princípio de intenção de tratar. De 2.077 pacientes elegíveis para randomização dentre 20.769 pacientes avaliados para participar do estudo, 611 foram efetivamente randomizados para se submeterem à RCM (n=203), APC (n=205) ou TC (n=203). Em 10 anos de seguimento desfechos primários ocorreram em 37,9% dos pacientes submetidos à RCM em comparação a 56,1% dos submetidos à APC e 69% dos que receberam TC (p<0,0001). Não foi encontrada nenhuma diferença com relação à morte por qualquer origem entre RCM (25,1%), APC (23,9%) e TC (31%) (p=0,230). Intervenção mecânica por causa de angina refratária foi necessária em 38,9% dos que receberam TC, comparada a 40% dos submetidos à APC e 7,4% dos que se submeteram à RCM (p<0,0001). Em adição, 20,7% dos pacientes que receberam TC tiveram IAM, em comparação a 13,2% dos submetidos à APC e 9,9% dos submetidos à RCM (p=0,008). Pacientes submetidos à TC tiveram maior incidência de morte por origem cardíaca (20,7%) do que os submetidos à APC (14,1%) e RCM (10,8%) (p=0,021), no entanto, essa diferença só foi significativa entre RCM e TC (p=0,009). Nenhuma diferença significativa foi encontrada na incidência de AVE entre os três grupos de tratamento (p=0,303). Ao final do seguimento, angina estava presente em 14,8% dos pacientes alocados para TC em comparação a 9,3% dos submetidos à APC e 6,4% dos submetidos à RCM (p=0,022). A RCM reduziu de modo significativo e independente a incidência de eventos combinados em comparação ao TC (HR=0,449; IC95%=0,346 - 0,583) e à APC (HR=0,560; IC95%=0,431 0,726), sobretudo à custa de redução da intervenção mecânica em comparação ao TC (HR=0,162; IC95%=0,113-0,232) e à APC (HR=0,150;IC95%=0,111-0,228). A RCM também reduziu significativamente a incidência de IAM e o estado anginoso em comparação ao TC (HR=0,467; IC95%=0,280 0,780; p=0,013 e HR=0,397; IC95=0,200 0,785; p=0,009, respectivamente). O estudo revelou que os três tipos de tratamento alcançaram índices elevados e semelhantes de sobrevivência em 10 anos de seguimento. Todavia, a cirurgia foi superior ao tratamento clínico na prevenção do infarto do miocárdio não fatal, na diminuição da incidência de angina e na prevenção da intervenção mecânica guiada por angina refratária. A angioplastia e o tratamento clínico mostraram resultados semelhantes em relação ao alívio dos sintomas anginosos e na prevenção dos eventos combinados definidos como morte por qualquer origem, infarto do miocárdio não fatal e a necessidade de intervenção mecânica / There was no conclusive evidence that coronary artery bypass graft surgery (CABG) or percutaneous coronary intervention (PCI) is superior to medical therapy (MT) alone in symptomatic patients with multivessel coronary artery disease (CAD), and preserved left ventricular function. The objective of this study is to compare the long-term results of CABG or PCI versus MT in patients with multivessel CAD and preserved left ventricular function. The primary end-points were the combination (MACE) of overall mortality, non fatal acute myocardial infarction (AMI), and refractory angina requiring revascularization. Secondary end-point was the angina status at the end of follow-up. All events were analyzed according to the intention to treat principle. From 2.077 eligible patients for randomization among 20.769 patients screened for the trial, 611 could be randomized to CABG (n=203), PCI (n=205), and MT (n=203). At 10-year follow-up, MACE occurred in 69% of patients who underwent MT, compared to 56% treated with PCI, and 37.9% receiving CABG (p<0.0001). There were no statistical differences in overall mortality among the three groups (31% in MT, 23.9% in PCI, and 25.1% in CABG; p=0.230). Mechanical intervention driven by refractory angina were necessary in 38.9% of patients in the MT, compared to 40% in the PCI, and 7.4% in the CABG group (p<0.0001). In addition, non-fatal acute myocardial infarction (AMI) were experienced by 20.7% of patients receiving MT, in comparison to 13.2% of patients submitted to PCI and 9.9% of those submitted to CABG (p=0.008). Patients who underwent MT had higher cardiac mortality (20.7%), than patients receiving PCI (14.1%) or CABG (10.8%) (p=0.021), however this difference was significant only between CABG and MT (p=0,009). No statistical differences were observed in the incidence of stroke among the three groups of treatment (p=0.303). At the end of follow-up angina was present in 14.8% of MT patients, compared to 9.3% of PCI patients, and 6.4% of CABG patients (p=0.022). CABG independently reduced the incidence of MACE in comparison to MT (HR=0.449; CI95%=0.346 0.583) and PCI (HR=0.560; CI95%=0.431 0.726). This reduction is mainly driven by reduction in the rate of mechanical intervention in comparison to MT (HR=0.162; CI95%=0.113-0.232), and PCI (HZ=0.150; CI95%=0.111-0.228). CABG also reduced the incidence of AMI and angina status in comparison to MT (HR=0.150; IC95%=0.280 0.780; p=0.013; HR=0.397; IC95%=0.200 0.785; p=0.009, respectively). Our study has shown that the three treatment options yielded comparable and elevated rates of survival in 10-year follow-up. However, CABG was superior to MT in the prevention of AMI, in the reduction of the angina incidence, and in the prevention of mechanical intervention. Angioplasty and MT have shown similar results in relation to angina alleviation and prevention from MACE defined as the combination of all cause mortality, AMI, and the need of mechanical intervention

Não há evidência conclusiva da vantagem da revascularização cirúrgica do miocárdio (RCM) ou angioplastia percutânea coronária (APC) sobre o tratamento clínico (TC) em pacientes sintomáticos, com doença arterial coronária (DAC) multiarterial e função ventricular esquerda (FVE) preservada. O objetivo deste estudo foi comparar os resultados em longo prazo da RCM ou APC com o TC em pacientes portadores de DAC em múltiplos vasos e FVE preservada. Os desfechos primários do estudo foram a combinação de morte por qualquer origem, infarto do miocárdio não fatal (IAM) e angina refratária com necessidade de intervenção mecânica. O desfecho secundário foi o estado anginoso ao final do estudo. Todos os eventos foram analisados de acordo com o princípio de intenção de tratar. De 2.077 pacientes elegíveis para randomização dentre 20.769 pacientes avaliados para participar do estudo, 611 foram efetivamente randomizados para se submeterem à RCM (n=203), APC (n=205) ou TC (n=203). Em 10 anos de seguimento desfechos primários ocorreram em 37,9% dos pacientes submetidos à RCM em comparação a 56,1% dos submetidos à APC e 69% dos que receberam TC (p<0,0001). Não foi encontrada nenhuma diferença com relação à morte por qualquer origem entre RCM (25,1%), APC (23,9%) e TC (31%) (p=0,230). Intervenção mecânica por causa de angina refratária foi necessária em 38,9% dos que receberam TC, comparada a 40% dos submetidos à APC e 7,4% dos que se submeteram à RCM (p<0,0001). Em adição, 20,7% dos pacientes que receberam TC tiveram IAM, em comparação a 13,2% dos submetidos à APC e 9,9% dos submetidos à RCM (p=0,008). Pacientes submetidos à TC tiveram maior incidência de morte por origem cardíaca (20,7%) do que os submetidos à APC (14,1%) e RCM (10,8%) (p=0,021), no entanto, essa diferença só foi significativa entre RCM e TC (p=0,009). Nenhuma diferença significativa foi encontrada na incidência de AVE entre os três grupos de tratamento (p=0,303). Ao final do seguimento, angina estava presente em 14,8% dos pacientes alocados para TC em comparação a 9,3% dos submetidos à APC e 6,4% dos submetidos à RCM (p=0,022). A RCM reduziu de modo significativo e independente a incidência de eventos combinados em comparação ao TC (HR=0,449; IC95%=0,346 - 0,583) e à APC (HR=0,560; IC95%=0,431 0,726), sobretudo à custa de redução da intervenção mecânica em comparação ao TC (HR=0,162; IC95%=0,113-0,232) e à APC (HR=0,150;IC95%=0,111-0,228). A RCM também reduziu significativamente a incidência de IAM e o estado anginoso em comparação ao TC (HR=0,467; IC95%=0,280 0,780; p=0,013 e HR=0,397; IC95=0,200 0,785; p=0,009, respectivamente). O estudo revelou que os três tipos de tratamento alcançaram índices elevados e semelhantes de sobrevivência em 10 anos de seguimento. Todavia, a cirurgia foi superior ao tratamento clínico na prevenção do infarto do miocárdio não fatal, na diminuição da incidência de angina e na prevenção da intervenção mecânica guiada por angina refratária. A angioplastia e o tratamento clínico mostraram resultados semelhantes em relação ao alívio dos sintomas anginosos e na prevenção dos eventos combinados definidos como morte por qualquer origem, infarto do miocárdio não fatal e a necessidade de intervenção mecânica / There was no conclusive evidence that coronary artery bypass graft surgery (CABG) or percutaneous coronary intervention (PCI) is superior to medical therapy (MT) alone in symptomatic patients with multivessel coronary artery disease (CAD), and preserved left ventricular function. The objective of this study is to compare the long-term results of CABG or PCI versus MT in patients with multivessel CAD and preserved left ventricular function. The primary end-points were the combination (MACE) of overall mortality, non fatal acute myocardial infarction (AMI), and refractory angina requiring revascularization. Secondary end-point was the angina status at the end of follow-up. All events were analyzed according to the intention to treat principle. From 2.077 eligible patients for randomization among 20.769 patients screened for the trial, 611 could be randomized to CABG (n=203), PCI (n=205), and MT (n=203). At 10-year follow-up, MACE occurred in 69% of patients who underwent MT, compared to 56% treated with PCI, and 37.9% receiving CABG (p<0.0001). There were no statistical differences in overall mortality among the three groups (31% in MT, 23.9% in PCI, and 25.1% in CABG; p=0.230). Mechanical intervention driven by refractory angina were necessary in 38.9% of patients in the MT, compared to 40% in the PCI, and 7.4% in the CABG group (p<0.0001). In addition, non-fatal acute myocardial infarction (AMI) were experienced by 20.7% of patients receiving MT, in comparison to 13.2% of patients submitted to PCI and 9.9% of those submitted to CABG (p=0.008). Patients who underwent MT had higher cardiac mortality (20.7%), than patients receiving PCI (14.1%) or CABG (10.8%) (p=0.021), however this difference was significant only between CABG and MT (p=0,009). No statistical differences were observed in the incidence of stroke among the three groups of treatment (p=0.303). At the end of follow-up angina was present in 14.8% of MT patients, compared to 9.3% of PCI patients, and 6.4% of CABG patients (p=0.022). CABG independently reduced the incidence of MACE in comparison to MT (HR=0.449; CI95%=0.346 0.583) and PCI (HR=0.560; CI95%=0.431 0.726). This reduction is mainly driven by reduction in the rate of mechanical intervention in comparison to MT (HR=0.162; CI95%=0.113-0.232), and PCI (HZ=0.150; CI95%=0.111-0.228). CABG also reduced the incidence of AMI and angina status in comparison to MT (HR=0.150; IC95%=0.280 0.780; p=0.013; HR=0.397; IC95%=0.200 0.785; p=0.009, respectively). Our study has shown that the three treatment options yielded comparable and elevated rates of survival in 10-year follow-up. However, CABG was superior to MT in the prevention of AMI, in the reduction of the angina incidence, and in the prevention of mechanical intervention. Angioplasty and MT have shown similar results in relation to angina alleviation and prevention from MACE defined as the combination of all cause mortality, AMI, and the need of mechanical intervention

Activation of A3 adenosine receptors has been shown to protect the myocardium from ischaemia reperfusion injury in a number of animal models. The PI3K - AKT and MEK1/2 - ERK1/2 cell survival pathways have been shown to play a critical role in regulating myocardial ischaemia reperfusion injury. In this study we investigated whether the A3 adenosine receptor agonist 2-CL-IB-MECA protects the myocardium from ischaemia reperfusion injury, when administered at reperfusion or post reperfusion and whether the protection involved the PI3K – AKT or MEK 1/2 – ERK1/2 cell survival pathways. In the Langendorff model of ischaemia reperfusion injury isolated perfused rat hearts underwent 35 minutes of ischaemia and 120 minutes of reperfusion. Administration of 2-CL-IB-MECA (1nM) at reperfusion significantly decreased infarct size to risk ratio compared to non-treated ischeamic reperfused control hearts. This protection was abolished in the presence of the PI3K inhibitor Wortmannin or MEK1/2 inhibitor UO126. Western blot analysis determined that administration of 2-CL-IB-MECA (1 nM) upregulated ERK1/2 phosphorylation. In the adult rat cardiac myocyte model of hypoxia/reoxygenation cells underwent 6 hours of hypoxia and 18 hours of reoxygenation. Administration of 2-CL-IB-MECA (1 nM) at the onset of reoxygenation significantly decreased cellular apoptosis and necrosis. Administration of 2-CL-IB-MECA (1nM) in the presence of the Wortmannin or UO126 significantly reversed this anti-apoptotic effect and anti-necrotic effect. Our data further showed that 2-CL-IB-MECA protects myocytes subjected to hypoxia/reoxygenation injury via decreasing cleaved-caspase 3 activity that was abolished in presence of the PI3K inhibitor but not in the presence of the MEK1/2 inhibitor UO126. Administration of 2-CL-IB-MECA (100nM) at the onset of reperfusion also significantly decreased infarct size to risk ratio in the ischaemic reperfused rat heart compared to controls that was reversed in the presence of Wortmannin or Rapamycin. This protection was associated with an increase in PI3K-AKT / p70S6K / BAD phosphorylation. 2-CL-IB-MECA (100nM) administered at reoxygenation also significantly protected adult rat cardiac myocytes from hypoxia/reoxygenation injury 28 in an anti-apoptotic and anti-necrotic manner. This anti-apoptotic/necrotic effect of 2-CL-IB-MECA was abolished in the presence Wortmannin. Furthermore, that this protection afforded by 2-CL-IB-MECA (100nM) when administered at reoxygenation was associated with a decrease in cleaved caspase 3 activity that was abolished in the presence of the Wortmannin Interestingly, postponing the administration of 2-CL-IB-MECA to 15 or 30 minutes after the onset of reperfusion significantly protected the isolated perfused rat heart from ischaemia reperfusion injury in a Wortmannin and UO126 sensitive manner. This protection was associated with an increase in AKT and ERK1/2 phosphorylation. Administration of the A3 agonist 2-CL-IB-MECA 15 or 30 minutes after the onset of reoxygenation significantly protected isolated adult rat cardiac myocytes subjected to 6 hours of hypoxia and 18 hours of reoxygenation from injury in an anti-apoptotic/necrotic manner. This anti-apoptotic was abolished upon PI3K inhibition with Wortmannin or MEK1/2 inhibition with UO126. The anti-necrotic effect of 2-CL-IB-MECA when administered 15 or 30 minutes post-reperfusion was not abolished in the presence of the inhibitors. Delaying the administration of 2-CL-IB-MECA to 15 or 30 minutes after reoxygenation was associated with a decrease in cleaved-caspase 3 activity that was abolished in the presence of Wortmannin but not in the presence of the MEK 1/2inhibitor UO126. Collectively, we have demonstrated for the first time that administration of 2-CL-IB-MECA at the onset of reperfusion protects the ischaemic reperfused rat myocardium from lethal ischaemia reperfusion injury in a PI3K and MEK1/2 sensitive manner. Delaying the administration of 2-CL-IB-MECA to 15 or 30 minutes after the onset of reperfusion of reoxygenation also significantly protects the isolated perfused rat heart from ischaemia reperfusion injury and the adult rat cardiac myocyte from hypoxia/reoxygenation injury in an anti apoptotic / necrotic manner. Furthermore, that this protection is associated with recruitment of the PI3K-AKT and MEK1/2 – ERK1/2 cell survival pathways.

3-nitrotyrosine (3NT), a stable end product arising from the interaction of proteins and reactive nitrogen species such as peroxynitrite, is produced during periods of oxidative stress. 3NT is, therefore, of interest as a potential biomarker in a variety of disease states where oxidative stress is known to be involved in the pathology, for example intermittent claudication. The aim of this thesis was to develop sensitive and specific immunoassays to assess the levels of 3NT in plasma samples from claudicants and to investigate the protein nitration profile. Clinical data and plasma samples were collected from claudicant (n=33) and control (n=6) subjects. Analysis of data confirmed the difficulty of using parameters such as ankle brachial index (ABI) in diagnosis, supporting the need for investigations into potential biomarkers. Development of indirect and competitive ELISAs using electrochemically nitrated bovine serum albumin as the standard revealed that the detection of 3NT was dependent on the antibody being able to access the 3NT-residues within the protein. Various denaturing conditions and different types of microtitre plate were utilised during development. Initially the presence of 3NT in claudicant or control whole plasma samples could only be detected using dot blot immunodetection. Affinity purification techniques for the fractionation of the plasma proteins were therefore applied. Subsequently, 3NT-containing plasma proteins were found to be present in all of the claudicant and control samples using the developed competitive ELISA. Proteomic analysis of the 3NT-affinity purified samples, using MALDI-MS and LC-ESI-MS/MS, confirmed the presence of human serum albumin, serotransferrin and apolipoprotein A1 and A2 precursors within those protein bands staining immunopositive for 3NT on SDS-PAGE gels. The identification of apolipoprotein A1 within 3NT-immunopositive bands confirms previous reports suggesting the oxidative modification of HDL may contribute to the link between inflammation and the pathology of atherosclerosis.

Cognitive impairment in coronary artery disease (CAD) patients can predict poorer quality of life, dementia, and increased mortality. This study aimed to determine the association between long-term cortisol elevations and cognitive function in CAD patients. Participants were recruited at the beginning of a 1 year cardiac rehabilitation program and followed forward. Composite Z-scores were computed from tests measuring memory and executive function at baseline and 1 year. Cortisol deposition (3 months) was measured from a 20 mg, 3 cm hair sample. Analyses of covariance showed less improvement in memory function (F1,50=4.721, p=0.035) but not executive function (F1,49=0.318, p=0.575) in patients dichotomized into a high cortisol group based on a previously established reference range. Prolonged cortisol elevation may be associated with cognitive changes in subjects with CAD.

Cognitive impairment in coronary artery disease (CAD) patients can predict poorer quality of life, dementia, and increased mortality. This study aimed to determine the association between long-term cortisol elevations and cognitive function in CAD patients. Participants were recruited at the beginning of a 1 year cardiac rehabilitation program and followed forward. Composite Z-scores were computed from tests measuring memory and executive function at baseline and 1 year. Cortisol deposition (3 months) was measured from a 20 mg, 3 cm hair sample. Analyses of covariance showed less improvement in memory function (F1,50=4.721, p=0.035) but not executive function (F1,49=0.318, p=0.575) in patients dichotomized into a high cortisol group based on a previously established reference range. Prolonged cortisol elevation may be associated with cognitive changes in subjects with CAD.

Angiogenic cell therapy is currently being developed as a treatment for coronary artery disease (CAD); however, endothelial dysfunction (ED), commonly found in patients with CAD, impairs the ability for revascularization to occur. We hypothesized that culture on a collagen matrix will improve survival and function of circulating progenitor cells (CPCs) isolated from a mouse model of ED. Overall, ED decreased the expression of endothelial markers in CPCs and impaired their function, compared to normal mice. Culture of CPCs from ED mice on collagen was able to increase cell marker expression, and improve migration and adhesion potential, compared to CPCs on fibronectin. Nitric oxide production was reduced for CPCs on collagen for the ED group; however, CPCs on collagen had better viability under conditions of serum deprivation and hypoxia, compared to fibronectin. This study suggests that a collagen matrix may improve the function of therapeutic CPCs that have been exposed to ED.

The endothelial nitric oxide synthase (eNOS) co-factor tetrahydrobiopterin (BH4) has been shown to play a pivotal role in maintaining endothelial function in experimental vascular disease models. In BH4-deficient states, eNOS becomes enzymatically ‘uncoupled’, generating reactive oxygen species instead of nitric oxide, thus promoting endothelial dysfunction. In humans with coronary artery disease (CAD), higher vascular BH4 levels have been shown to be associated with improved endothelial function, and genetic variation in endogenous BH4 synthesis has implicated a causal role. Accordingly, BH4 has been proposed as a potential therapeutic target in vascular disease states. The work in this thesis aims to further elucidate the roles of exogenous and endogenous BH4 in humans. In a randomised, placebo-controlled clinical trial of oral BH4 therapy in patients with CAD, exogenous BH4 had no effect on endothelial function or vascular oxidative stress. Subsequent pharmacokinetic and pharmacodynamic analysis revealed that oral BH4 significantly augmented BH4 levels in plasma and in venous tissue (but not in arterial tissue), but also increased levels of the oxidation product dihydrobiopterin (BH2), which lacks eNOS cofactor activity. Thus, there was a null effect on overall biopterin redox status. To further understand the mechanics of exogenous BH4 oxidation, ex vivo studies of human blood and vascular tissue demonstrated that exogenous BH4 is very rapidly oxidised to BH2; co-administration with an antioxidant had only a modest effect on preventing BH4 oxidation in blood, with no beneficial effect on biopterin redox state in the vasculature. Finally, using a “Mendelian randomisation” approach, I studied the effects of a haplotype of GCH1 (the gene encoding the rate limiting enzyme in BH4 synthesis) on endogenous BH4 bioavailability and vascular function in healthy individuals. In patients with CAD, this haplotype has been associated with decreased BH4 bioavailability and eNOS uncoupling, however in healthy individuals the haplotype exerted no significant effect, likely due to reduced inflammatory stimulation of GCH1.