Physiologically assessed coronary collateral flow and intracoronary growth factor concentrations in patients with 1- to 3-vessel coronary artery disease

Leptin-VEGF crosstalk in excess body mass and related disorders: A systematic review

By 2030, it is expected that a billion people will have suffer from obesity. Adipose tissue synthesizes leptin, an adipokine that affects cardiovascular risk. Leptin intensifies the synthesis of vascular endothelial growth factor (VEGF). Our study reviews recent reports on leptin-VEGF crosstalk in obesity and related disorders. PubMed, Web of Science, Scopus, and Google Scholar were searched. One hundred and one articles involving human, animal, and in vitro research were included. In vitro studies show the crucial role of interaction between endothelial cells and adipocytes and hypoxia as a factor that intensifies leptin's effects on VEGF. Leptin-VEGF crosstalk promotes the progression of cancer. The animal research reveal that a high-fat diet enhances leptin and VEGF crosstalk. Genetic and epigenetic mechanisms and procreator-offspring programming may be involved in leptin-VEGF crosstalk. Some female-specific characteristics of leptin-VEGF relation in obesity were observed. The human studies have shown that increased leptin and VEGF synthesis and leptin-VEGF crosstalk are factors linking obesity with elevated cardiovascular risk. The studies of the last 10 years documented a range of significant aspects of leptin-VEGF crosstalk specific for obesity and related disorders, shedding new light on the link between obesity and increased cardiovascular risk.

Association of rs699947 (-2578 C/A) and rs2010963 (-634 G/C) Single Nucleotide Polymorphisms of the VEGF Gene, VEGF-A and Leptin Serum Level, and Cardiovascular Risk in Patients with Excess Body Mass: A Case-Control Study

Background: Two single nucleotide polymorphisms (SNPs) of the VEGF gene, rs699947 and rs2010963, are responsible for differentiated gene expression. A mutual dependence between VEGF and leptin serum level has been observed. This study investigated the associations between the rs699947 and rs2010963 SNPs of VEGF gene, VEGF-A, and leptin serum concentrations, and cardiometabolic risk of body mass excess. Methods: In this case–control study, 212 subjects with excess body mass and 145 normal-weight controls gave blood samples and underwent anthropometric and pulse wave analysis. Genotyping of VEGF gene was carried out to analyze the rs699947 (−2578 C/A) and rs2010963 (−634 G/C) SNPs. (ClinicalTrials.gov ID: NCT04077554). Results: This study showed a significant positive correlation between serum levels of VEGF-A and leptin in individuals with excess body mass possessing the CC genotype of the rs699947 variant of the VEGF gene. It has been registered that an increase in VEGF-A serum level correlates with an increase in arterial stiffness in excess body mass patients harboring AA genotype of the rs699947 (−2578 C/A) variant of the VEGF gene. No differences in VEGF-A and leptin serum concentrations were noted between particular genotypes. Conclusions: The CC genotype of the rs699947 variant of the VEGF gene promotes a positive interdependency between leptin and VEGF-A serum levels in subjects with excess body mass.

Biomarkers of coronary endothelial health: correlation with invasive measures of collateral function, flow and resistance in chronically occluded coronary arteries and the effect of recanalization

OBJECTIVES

In the presence of a chronically occluded coronary artery, the collateral circulation matures by a process of arteriogenesis; however, there is considerable variation between individuals in the functional capacity of that collateral network. This could be explained by differences in endothelial health and function. We aimed to examine the relationship between the functional extent of collateralization and levels of biomarkers that have been shown to relate to endothelial health.

METHODS

We measured four potential biomarkers of endothelial health in 34 patients with mature collateral networks who underwent a successful percutaneous coronary intervention (PCI) for a chronic total coronary occlusion (CTO) before PCI and 6-8 weeks after PCI, and examined the relationship of biomarker levels with physiological measures of collateralization.

RESULTS

We did not find a significant change in the systemic levels of sICAM-1, sE-selectin, microparticles or tissue factor 6-8 weeks after PCI. We did find an association between estimated retrograde collateral flow before CTO recanalization and lower levels of sICAM-1 (r=0.39, P=0.026), sE-selectin (r=0.48, P=0.005) and microparticles (r=0.38, P=0.03).

CONCLUSION

Recanalization of a CTO and resultant regression of a mature collateral circulation do not alter systemic levels of sICAM-1, sE-selectin, microparticles or tissue factor. The identified relationship of retrograde collateral flow with sICAM-1, sE-selectin and microparticles is likely to represent an association with an ability to develop collaterals rather than their presence and extent.

Insufficient glucocorticoid signaling and elevated inflammation in coronary heart disease patients with comorbid depression

Coronary heart disease (CHD) and depression are very common and often co-existing disorders. In addition to psychological and social morbidity, depression exacerbates adverse cardiac outcomes in CHD patients. Inflammation has been proposed as one of the mechanisms involved in the association between these two debilitating diseases. Therefore, the present study aimed to evaluate inflammatory responses as well as to investigate the pathophysiological mechanisms underlying the putative inflammatory activation in CHD patients with and without depression, by assessing the function of two important biological factors regulating inflammation, the hypothalamus-pituitary-adrenal (HPA) axis and the glucocorticoid receptor (GR). Eighty-three CHD patients with (n=28) and without (n=55) comorbid depression were recruited from primary care services in South London. Depression status was assessed by means of Clinical Interview Schedule Revised for diagnosis of depression, and Beck Depression Inventory for the presence of depressive symptoms. Serum C-reactive protein (CRP), plasma vascular endothelial growth factor (VEGF), and plasma and salivary cortisol were measured using commercially available ELISA kits. Gene expression of GR and interleukin-6 (IL-6) were conducted via qPCR. GR sensitivity was evaluated in vitro in isolated peripheral blood mononuclear cells using the dexamethasone inhibition of lipopolysaccharide-stimulated IL-6 levels. Serum levels of kynurenine pathway metabolites were measured using high performance liquid chromatography. Our results show that CHD patients with depression had higher levels of CRP, IL-6 gene expression, and VEGF compared with CHD non-depressed, as well as lower plasma and saliva cortisol levels. The CHD depressed group also exhibited a reduction in GR expression and sensitivity. Finally, tryptophan levels were significantly lower in patients with depression, who also showed an increased kynurenine/tryptophan ratio. In conclusion, CHD patients with depression had elevated levels of inflammation in the context of HPA axis hypoactivity, GR resistance, and increased activation of the kynurenine pathway. Reduced cortisol bioavailability and attenuated glucocorticoid responsiveness due to decreased expression and sensitivity of GR may lead to insufficient glucocorticoid signaling and thus elevation of inflammation in these patients.

The Role of VEGF in the Diabetic Patients Undergoing Endovascular Therapy of Symptomatic Aortic Valve Stenosis

The aim of this study was to explore changes in plasma vascular endothelial growth factor (VEGF) in aged patients who undergone transcatheter aortic valve implantation or balloon angioplasty for the treatment of aortic stenosis. Plasma VEGF was measured in subjects with diabetes mellitus type 2 (DM) (n=21, age 79.2±1.6 years) and in non-diabetic subjects (non-DM) (n=23, age 84.4±0.7 years), using an ELISA kit. Before the procedure plasma levels of VEGF were significantly lower in DM than in non-DM patients (P<0.05). Plasma VEGF significantly increased in both groups (DM and non-DM) 24 h (387±64 vs. 440±30 pg/ml, P<0.05) and 72 h (323±69 vs. 489±47 pg/ml, P<0.05) after the endovascular procedure. However, the VEGF in DM patients was significantly lower compared to non-DM subjects up to one month after the endovascular procedure (283±47 vs. 386±38 pg/ml, P<0.05). We conclude that increased plasma VEGF in aged patients associates with atherosclerotic aortic valve stenosis. In spite of that plasma VEGF in DM was constantly significantly lower than in non diabetic patients, both before and after the endovascular procedure, possibly reflecting a disturbance of angiogenic/anti-angiogenic balance in diabetes.

Angiotensin converting enzyme insertion/deletion (I/D) (rs4646994) and Vegf polymorphism (+405G/C; rs2010963) in type II diabetic patients: Association with the risk of coronary artery disease

HYPOTHESIS

Little is known about the concomitant presence of the angiotensin-converting enzyme (ACE) (rs4646994) D allele and vascular endothelial growth factor(VEGF) (+405G/C; rs2010963) G allele on the susceptibility of coronary artery disease (CAD). Here we examined the hypothesis that ACE-D and VEGF-G alleles act synergistically to increase the severity of CAD in patients with type II diabetes mellitus (T2DM).

MATERIALS AND METHODS

The VEGF (rs2010963) and ACE (rs4646994) genotypes were detected by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) and PCR, respectively in 510 T2DM patients undergoing their first coronary angiography. Diabetic patients were classified as T2DM patients with and without CAD (control).

RESULTS

The crude odds ratio (OR) for the presence of CAD in ID+DD and D allele carriers were 1.98 (p=0.01) and 1.55 (p=0.001), respectively. Also, adjusted ORs in the presence of normolipidemia and the absence of history of hypertension for the risk of CAD in the either ACE(rs4646994) D allele or VGEF(rs2010963)-G alleles were 2.08 (p=0.004) and 1.75 (p=0.024), respectively. In addition, the concomitant presence of the ACE-D and VEGF-G alleles increased the risk of CAD 2.25-fold (p=0.043).

CONCLUSION

Our results indicated that ACE(rs4646994)-D allele alone and in the presence of VEGF(rs2010963)-G allele can be an important independent risk factor for susceptibility of CAD in T2DM patients even after correcting for conventional risk factors in a population of Iran.

Serum erythropoietin: a useful biomarker for coronary collateral development and potential target for therapeutic angiogenesis among the patients with coronary chronic total occlusion

The study was to investigate the association of endogenous erythropoietin (EPO) and coronary collateral development. Forty-nine patients (31 with chronic total occlusion (CTO), 18 with normal coronary artery) were consecutively enrolled. The serum EPO was positively related with Rentrop class. Increased serum EPO was one of the independent predictors of good collateral development (odds ratio 1.31; p = 0.025). A significantly positive correlation was seen between serum EPO and vascular endothelial growth factor (VEGF) levels (r = 0.96, p < 0.001). Circulatory EPO may be a useful biomarker for coronary collateral development and potential target for therapeutic angiogenesis in patients with CTO.

Mechanistic, technical, and clinical perspectives in therapeutic stimulation of coronary collateral development by angiogenic growth factors

Stimulation of collateral vessel development in the heart by angiogenic growth factor therapy has been tested in animals and humans for almost two decades. Discordance between the outcome of preclinical studies and clinical trials pointed to the difficulties of translation from animal models to patients. Lessons learned in this process identified specific mechanistic, technical, and clinical hurdles, which need to be overcome. This review summarizes current understanding of the mechanisms leading to the establishment of a functional coronary collateral network and the biological processes growth factor therapies should stimulate even under conditions of impaired natural adaptive vascular response. Vector delivery methods are recommended to maximize angiogenic gene therapy efficiency and reduce side effects. Optimization of clinical trial design should include the choice of clinical end points which provide mechanistic proof-of-concept and also reflect clinical benefits (e.g., surrogates to assess increased collateral flow reserve, such as myocardial perfusion imaging). Guidelines are proposed to select patients who may respond to the therapy with high(er) probability. Both short and longer term strategies are outlined which may help to make therapeutic angiogenesis (TA) work in the future.

Circulating neuregulin-1β levels vary according to the angiographic severity of coronary artery disease and ischemia

BACKGROUND

Coronary artery disease (CAD) is the leading killer in the United States. Patients with severe CAD and ischemia have worse prognosis. Therefore expansion of biomarker research, to identify at-risk individuals and explain the complex biology between cardiovascular growth factors and atherosclerosis is needed. Neuregulin-1β (NRG-1β) is a myocardial stress activated growth and survival factor released from endocardial and endothelial cells. NRG-1β is essential for cardiovascular development and a regulator of angiogenesis. We postulated that plasma and serum levels of NRG-1β would vary in relation to CAD severity and the presence of stress-induced ischemia.

METHODS

We measured serum and plasma levels of NRG-1β and vascular endothelial growth factor (VEGF) in 60 patients undergoing cardiac catheterization. CAD severity was calculated from angiographic results using a modified Duke jeopardy score.

RESULTS

Serum NRG-1β (sNRG-1β), plasma NRG-1β (pNRG-1β), serum VEGF, and plasma VEGF were detectable in the majority of patients. The pNRG-1β levels were approximately two-fold higher than sNRG-1β. Both sNRG-1β and pNRG-1β correlated inversely with CAD severity. pNRG-1β levels were statistically higher in patients with stress-induced ischemia denoted by a positive myocardial perfusion imaging study that correlated with angiographic findings (P=0.02).

CONCLUSION

Both sNRG-1β and pNRG-1β correlated inversely with angiographic severity of CAD. pNRG-1β levels were two-fold higher than serum and were higher in patients with stress-induced ischemia. Therefore we conclude that plasma is the optimal source for the further exploration of the biological significance of NRG-1β as a biomarker of CAD severity and ischemia.

The relationship of serum erythropoietin level with coronary collateral grade

BACKGROUND

Erythropoietin has been shown to induce neovascularization and protect against ischemic vascular injury. We investigated whether a higher serum erythropoietin (EPO) level is related to better coronary collateral vessel grade.

METHODS

Ninety-nine patients with stable angina pectoris who have at least 1 coronary stenosis of equal to or greater than 70% at coronary angiography were prospectively enrolled. Serum EPO and vascular endothelial growth factor (VEGF) levels were studied. Coronary collateral degree was graded according to the Rentrop method. Patients with grade 2-3 collateral degree were included in the good collateral group and formed Group I. The patients with grade 0-1 collateral degree were included in the poor collateral group and formed Group II.

RESULTS

The serum EPO level was significantly higher in the good collateral group (17.3 ± 9.3 mU/mL vs 11.7 ± 5.0 mU/mL; P < 0.001). There was also a positive correlation between serum EPO level and Rentrop score (r = 0.39; P < 0.001). In multivariate analysis, serum EPO level (odds ratio [OR] 1.336; 95% confidence interval [CI], 1.120-1.593; P = 0.001), oxygen saturation (OR 0.638; 95% CI, 0.422-0.963; P = 0.033) and presence of chronic total occlusion (CTO) (OR 26.7; 95% CI, 3.874-184.6; P = 0.001) were independently related to well-developed coronary collaterals.

CONCLUSIONS

Higher serum EPO level is related to better coronary collateral development. Erythropoietin may have a positive effect on the development of collaterals and may provide a new agent for the treatment strategies to enhance coronary collateral vessel development.

Plasma chemokine levels are associated with the presence and extent of angiographic coronary collaterals in chronic ischemic heart disease

BACKGROUND

In patients with chronic ischemic heart disease (IHD), the presence and extent of spontaneously visible coronary collaterals are powerful determinants of clinical outcome. There is marked heterogeneity in the recruitment of coronary collaterals amongst patients with similar degrees of coronary artery stenoses, but the biological basis of this heterogeneity is not known. Chemokines are potent mediators of vascular remodeling in diverse biological settings. Their role in coronary collateralization has not been investigated. We sought to determine whether plasma levels of angiogenic and angiostatic chemokines are associated with of the presence and extent of coronary collaterals in patients with chronic IHD.

METHODOLOGY/PRINCIPAL FINDINGS

We measured plasma concentrations of angiogenic and angiostatic chemokine ligands in 156 consecutive subjects undergoing coronary angiography with at least one ≥90% coronary stenosis and determined the presence and extent of spontaneously visible coronary collaterals using the Rentrop scoring system. Eighty-eight subjects (56%) had evidence of coronary collaterals. In a multivariable regression model, the concentration of the angiogenic ligands CXCL5, CXCL8 and CXCL12, hyperlipidemia, and an occluded artery were associated with the presence of collaterals; conversely, the concentration of the angiostatic ligand CXCL11, interferon-γ, hypertension and diabetes were associated with the absence of collaterals (ROC area 0.91). When analyzed according to extent of collateralization, higher Rentrop scores were significantly associated with increased concentration of the angiogenic ligand CXCL1 (p<0.0001), and decreased concentrations of angiostatic ligands CXCL9 (p<0.0001), CXCL10 (p = 0.002), and CXCL11 (p = 0.0002), and interferon-γ (p = 0.0004).

CONCLUSIONS/SIGNIFICANCE

Plasma chemokine concentrations are associated with the presence and extent of spontaneously visible coronary artery collaterals and may be mechanistically involved in their recruitment.

Relation between serum monocyte chemoattractant protein-1 and coronary collateral development

BACKGROUND

The degree of coronary collateral development is not same in every patient with similar degree of coronary stenosis. In animal studies monocyte chemoattractant protein-1 (MCP-1) has been found to be related to collateral vessel development. In this study we investigated whether a higher serum MCP-1 level is related to better coronary collateral vessel development in patients with stable coronary artery disease.

METHOD

Eighty-three patients with stable angina pectoris, who have at least one coronary stenosis equal to or greater than 70% at coronary angiography, were prospectively enrolled. Serum MCP-1 and vascular endothelial growth factor (VEGF) levels were studied. Coronary collateral development was graded according to the Rentrop method. Patients with grade 2-3 collateral developments were included in good collateral group and formed group I. The patients with grade 0-1 collateral developments were included in poor collateral group and formed group II.

RESULTS

The serum MCP-1 level was significantly higher in good collateral group (288 ± 277 pg/ml vs. 132 ± 64 pg/ml; P<0.001). There was also a positive correlation between serum MCP-1 level and Rentrop score (r=0.39, P<0.001). The patients in the good collateral group also had a significantly higher number of coronary arteries with significant stenosis (1.7 ± 0.7 vs. 1.4 ± 0.6, P=0.049), and higher VEGF levels (322 ± 147 pg/ml vs. 225 ± 161 pg/ml, P=0.007). In multivariate analysis, only serum MCP-1 level (P=0.014, odds ratio: 1.01, 95% confidence interval: 1.002-1.019) was independently related to good coronary collateral development.

CONCLUSION

Higher serum MCP-1 level is related to better coronary collateral development.

Soluble fms-like tyrosine kinase-1 and the progression of carotid intima-media thickness – 24-month follow-up study –

BACKGROUND

The relationship between fms-like tyrosine kinase-1 (sFlt-1), a soluble receptor for vascular endothelial growth factor (VEGF), and vascular disease has not been established, so this study aimed to elucidate the association between sFlt-1 and the progression of carotid intima - media thickness (IMT) in hypertensive patients.

METHODS AND RESULTS

The 120 hypertensive patients under medical control were enrolled and 112 completed the study (age 59 ± 9 years, 57 females). Plasma VEGF and sFlt-1 levels were measured at enrollment. At baseline and 24-month visit, carotid IMT was measured and the association between sFlt-1 and IMT progression was assessed by linear regression. At baseline, age (r=0.186) and low level of high-density lipoprotein-cholesterol (HDL-C <40 mg/dl, r=0.214) were significantly related to carotid IMT. Over the 24 months, carotid IMT increased from 0.670 ± 0.089 mm to 0.696 ± 0.095 mm. There was a positive correlation between sFlt-1 tertiles and IMT change (P=0.05 by ANOVA). Upon multivariate analysis, log-transformed sFlt-1 level (β=0.137, P=0.003) and low HDL-C (β=0.048, P=0.04) were identified as predictors of IMT progression, independent of other confounding variables.

CONCLUSIONS

High sFlt-1 level is predictive of carotid IMT progression in hypertensive patients. Low HDL-C level was also associated with IMT change. These observations support a high sFlt-1 level being indicative of progression of atherosclerosis. 

Vascular Endothelial Growth Factor, Soluble Fms-Like Tyrosine Kinase 1, and the Severity of Coronary Artery Disease

Background: The association between vascular endothelial growth factor (VEGF), soluble fms-like tyrosine kinase 1 (sFlt-1), and coronary artery disease (CAD) was investigated. Methods: We enrolled 112 hypertensive patients with proven CAD and 112 hypertensive controls matched for age and gender. The severity of CAD was assessed by the most severe clinical presentation of CAD in patients’ history and by the number of diseased vessels. Results: Vascular endothelial growth factor level was lower, whereas sFlt-1 level was higher in the CAD group compared to the controls. Diabetes mellitus (P = .001), smoking (P = .004), and higher sFlt-1 level (P = .01) were independently associated with CAD. Younger age (P = .02), smoking (P = .049), and higher VEGF levels (P = .02) were independently associated with a history of myocardial infarction (MI), whereas higher sFlt-1 level (P = .01) was independently associated with multivessel disease. Conclusion: Plasma sFlt-1 levels are positively associated with the presence of CAD and are associated with angiographical severity of CAD.

Vascular endothelial growth factor in coronary sinus: Evidence for its association with coronary collaterals

OBJECTIVES

To explore whether local growth factors concentration, including vascular endothelial growth factor (VEGF) and transforming growth factor beta one (TGF-beta(1)), influence the formation of coronary collaterals.

DESIGN

Thirty-six patients scheduled for coronary angiography received a 6F Goodale-Lubin catheterization to collect blood from the coronary sinus (CS) and right atrium (RA).

RESULTS

Patients with coronary collaterals had a higher number of diseased vessels (2.6+/-0.2 vs. 1.4+/-0.3, p = 0.005), higher percentage of severity of stenosis (93+/-2 vs. 48+/-8, P < 0.001) and higher VEGF concentrations in CS (38.9+/-3.9 pg/ml vs. 20.8+/-1.4 pg/ml, P < 0.001) and in RA (31.7+/-3.1 pg/ml vs. 22.0+/-2.3 pg/ml, p = 0.004). There was no significant relationship between coronary collateral formation and TGF-beta(1) concentration. By binary logistic regression analysis, VEGF concentrations in CS (p = 0.030) and stenosis severity (p = 0.042) are correlated positively with collateral formation.

CONCLUSIONS

The association between local, endogenous secretion of VEGF and coronary collateral formation is compatible with a paracrine role for this growth factor in pathophysiologic collateral formation.

Local cytokine concentrations and oxygen pressure are related to maturation of the collateral circulation in humans

OBJECTIVES

Our aim was to determine cytokine and oxygen gradients over the collateral circulation in humans.

BACKGROUND

The molecular background of the maturation of the collateral circulation in response to coronary narrowing is poorly understood in humans, partly because of difficulties in obtaining local samples from the human collateral circulation.

METHODS

Coronary collateral blood was sampled in 60 patients with nontotal (n = 25) or total coronary occlusions (n = 35) using a special wide-lumen catheter. Coronary collateral flow index (CFI) was assessed by intracoronary pressure measurements. Oxygenation and lactate content was measured as well as 30 cytokines potentially involved in collateral artery growth, using a custom-made multiplex assay.

RESULTS

No rise in lactate or change in pH was found in collateral blood. Oxygen gradient between coronary and collateral arterial blood correlated inversely with CFI (r = -0.61, p < 0.001). Locally increased plasma levels were found for basic fibroblast growth factor, eotaxin, macrophage migration inflammatory factor, monocyte chemoattractant protein-1, and transforming growth factor-beta, while stem cell factor and stem cell growth factor-beta were significantly decreased. The highest cytokine gradients were found in patients with the least developed collateral circulation. The majority of cytokines correlated more strongly with the pO(2) gradient across the collateral bed than with CFI.

CONCLUSIONS

Intravascular ischemia during brief balloon coronary occlusion is absent in human coronary collateral arteries. The oxygen gradient found over the collateral circulation is increased in patients with a less matured collateral circulation and relates to local levels of several known pro-arteriogenic cytokines. In case of a more developed collateral circulation, relatively low levels of cytokines are present, suggesting that growth factor therapy might be beneficial at this stage.

Vascular endothelial growth factors in cardiovascular medicine

The discovery of vascular endothelial growth factors (VEGFs) and their receptors has considerably improved the understanding of the development and function of endothelial cells. Each member of the VEGF family appears to have a specific function: VEGF-A induces angiogenesis (i.e. growth of new blood vessels from preexisting ones), placental growth factor mediates both angiogenesis and arteriogenesis (i.e. the formation of collateral arteries from preexisting arterioles), VEGF-C and VEGF-D act mainly as lymphangiogenic factors. The study of the biology of these endothelial growth factors has allowed a major progress in the comprehension of the genesis of the vascular system and its abnormalities observed in various pathologic conditions (atherosclerosis and coronary artery disease). The role of VEGF in the atherogenic process is still unclear, but actual evidence suggests both detrimental (development of a neoangiogenetic process within the atherosclerotic plaque) and beneficial (promotion of collateral vessel formation) effects. VEGF and other angiogenic growth factors (fibroblast growth factor), although initially promising in experimental studies and in initial phase I/II clinical trials in patients with ischemic heart disease or peripheral arterial occlusive disease, have subsequently failed to show significant therapeutic improvements in controlled clinical studies. Challenges still remain about the type or the combination of angiogenic factors to be administered, the form (protein vs. gene), the route, and the duration of administration.

Vascular endothelial growth factor genetic variability and coronary artery disease in Brazilian population

Atherosclerosis results from a complex interaction between environment and genetic risk factors. The gene encoding vascular endothelial growth factor (VEGF) is associated with differential protein expression and has been investigated in coronary artery disease (CAD) studies. Based on this, we aimed at determining if patients with CAD are affected by polymorphisms (-2 578, -1 154, and 936) in the VEGF gene, and also if these polymorphisms are associated with the number of diseased vessels and degree of arterial obstruction. The case group was formed by 175 Caucasian patients with angiographically confirmed CAD, and the control group involved 108 Caucasian patients with normal coronary angiograms. Polymerase chain reaction (PCR) was used for genotyping. Allele frequencies for VEGF -2 578A, -1 154A, and 936T were 0.46, 0.38, and 0.14 in cases and 0.49, 0.30, and 0.13 in control subjects. Allele and genotype distribution did not significantly differ between groups. A higher frequency of the VEGF -2 578AA genotype was observed in the group with three vessel disease (P = 0.008). No association between the VEGF -2 578, -1 154, and 936 polymorphisms and degree of arterial obstruction was observed. The frequency of carriers of two copies of the haplotype AG (-2 578/-1 154) were higher in the group with three-vessel disease (P = 0.05). In summary, our report shows that the VEGF -2 578 polymorphism has an influence on CAD severity, possibly because of a reduced VEGF expression, suggesting a protective effect of VEGF in atherosclerosis.

The relationship between severity of coronary artery disease and plasma level of vascular endothelial growth factor

OBJECTIVE

It has been known that ischemia or occlusion of coronary arteries in animal models increases the production of vascular endothelial growth factor (VEGF); however, little is known about the relationship between coronary artery disease and VEGF in humans. In this study, our aim was to evaluate the relationships between the degree of coronary occlusion and plasma VEGF level as well as other risk factors, including age, weight, arterial blood pressure, cholesterol, triglyceride, blood glucose, and high-sensitive C-reactive protein (hsCRP) in patients with established coronary artery disease.

MATERIALS AND METHODS

Our study group consisted of 77 patients. Of these, 38 patients had normal coronary angiography (control group; group C) and 39 had abnormal angiography (17 critical lesion; group CL, 22 noncritical lesion; non-CL group).

RESULTS

Plasma VEGF level was 116.95+/-30.12 pg/ml in the control group, 212.47+/-75.28 pg/ml in group CL, and 138.89+/-45.18 pg/ml in the non-CL group. Plasma VEGF level of group C was found to be lower than that of group CL (P<.05), but the difference between groups C and non-CL was insignificant (P>.05). However, logistic regression analysis showed that VEGF level of group CL was significantly higher (P<.001). There was a negative correlation between VEGF and haemoglobin (r=-0.58, P<.01), and positive correlation between VEGF and age (r=0.29, P<.04). There was no relationship between plasma VEGF level and other cardiac risk parameters. Group CL had a higher level of total and LDL-cholesterol levels.

CONCLUSION

Increased plasma VEGF levels in patients with coronary artery disease may point that the coronary lesion is critical, and VEGF increase in patients with established coronary artery disease may be used as an indicator of the need for revascularization.

Angiopoietin-1, Angiopoietin-2 and Tie-2 in the Coronary Circulation of Patients With and Without Coronary Collateral Vessels

BACKGROUND

The role of the angiopoietin (Ang)/Tie-2 system in coronary collateral growth is not well understood, so the purpose of this study was to investigate and elucidate the relationship of this system to coronary collateral formation in patients with coronary artery disease (CAD).

METHODS AND RESULTS

Fifty-nine patients with CAD were recruited. Blood samples from the left ventricle (LV) and coronary sinus (CS) were obtained during cardiac catheterization, and serum concentrations of Ang-1, Ang-2, and Tie-2 were measured by enzyme-linked immunosorbent assay. Patients were then classified as mild CAD (n=30), defined as </=90% stenosis of the coronary arterial luminal diameter, or severe CAD (n=29), which was total (or near total) coronary occlusion requiring coronary collateral growth. Ang-1, Ang-2, and Tie-2 in the LV and CS sera were not significantly different between groups. In the severe CAD group, spillover of Tie-2 (CS-LV value) from the coronary circulation was found in comparison with the mild CAD group (3.43+/-2.22 vs -3.29+/-1.54 ng/ml, p=0.01), whereas the CS-LV values of Ang-1 and Ang-2 did not differ between groups. Tie-2 production was markedly increased in patients with well-developed collaterals. A positive and significant correlation was found between coronary Ang-2 and Tie-2 levels (r=0.44, p<0.001).

CONCLUSIONS

Tie-2 is probably produced in the coronary circulation and may induce the development or maintenance of coronary collaterals in CAD patients. Furthermore, the role of Ang-2 in the formation of coronary collaterals may be more important than that of Ang-1.

Relation of various plasma growth factor levels in patients with stable angina pectoris and total occlusion of a coronary artery to the degree of coronary collaterals

We assessed (1) angiogenic factors in patients with stable angina and longstanding (> or =24 months) total occlusion of a single coronary artery and (2) the relation between plasma levels of angiogenic factors and the development of collateral vessels as evaluated by coronary angiography. Plasma concentrations of vascular endothelial growth factor (VEGF(165)), fibroblast growth factor, placenta-derived growth factors (PlGFs), and hepatocyte growth factor were assessed in 96 patients with stable angina and longstanding (> or =24 months) total occlusion of a single coronary artery. According to coronary angiographic results, 18 patients had no visible collaterals (group 0), 21 patients had visible collaterals but no filling of the recipient epicardial vessel (group 1), and 57 patients showed filling (partial or complete) of the recipient epicardial vessel by collaterals (group 2). Plasma VEGF(165) and PlGF concentrations were higher in group 1 than in groups 0 and 2 (VEGF(165) 75 pg/ml, range 24 to 105, vs 23 pg/ml, range 15 to 29, and 19 pg/ml, range 10 to 41, respectively, F = 5.53, p = 0.006; PlGF 35 pg/ml, range 3.5 to 105, vs 1 pg/ml, range 1 to 38, and 1 pg/ml, range 1 to 5, respectively, F = 7.09, p = 0.008). Plasma VEGF(165) and PlGF levels were similar in groups 0 and 2. There was no significant difference in plasma levels of fibroblast and hepatocyte growth factor concentrations across the 3 groups. In conclusion, plasma levels of angiogenic growth factors differ among patients with stable angina pectoris and longstanding total coronary occlusion.

Simvastatin Reduces Serum Level of Vascular Endothelial Growth Factor in Hypercholesterolemic Patients

Vascular endothelial growth factor plays a pivotal role in the progression of atherosclerotic lesions and causes instability of atherosclerotic plaques by inducing neoangiogenesis inside the current plaque. The pro-inflammatory cytokine interleukin (IL-) 6 induces vascular endothelial growth factor in smooth muscle cells (SMC). HMG-CoA reductase inhibitors (statins), display beside their lipid-lowering potency various pleiotropic effects. Such pleiotropic effects include improvement of endothelial dysfunction, increased nitric oxide bioavailability, antioxidant properties, inhibition of inflammatory responses, and stabilization of atherosclerotic plaques. In this study we investigate the influence of statin treatment on the serum levels of VEGF in hypercholesterolemic patients. One hundred and seven hypercholesterolemic patients were treated with 20 (n = 52) or 40 mg (n = 55) simvastatin daily. Six weeks of treatment resulted in a significant decrease of VEGF from 1017.1 +/- 297.8 pg/mL at baseline to 543.5 +/- 317.4 pg/mL after 6 weeks (-47.7%) and to 211.8 +/- 155.3 pg/mL after 6 months (-79.7%; all P < 0.001). IL-6 induced the expression of vascular endothelial growth factor in human SMC as analyzed by rt-PCR and flow cytometry. Statins decreased the stimulatory effect of IL-6 on mRNA and protein levels. This effect could be inhibited by co-incubation with mevalonate acid. This study contributes in understanding the pleiotropic effects of statins particularly with regard to their use in treatment and prevention of cardiovascular disease.

Plasma vascular endothelial growth factor as a marker for early vascular damage in hypertension

Elevation of plasma VEGF (vascular endothelial growth factor) has been noted in patients with hypertension or atherosclerosis. VEGF has been regarded as a marker for endothelial dysfunction. However, the role of VEGF in hypertension-induced vascular injury and its relationship with endothelial function have not been studied. This study included 20 untreated hypertensive men with grade 1 or 2 hypertensive retinopathy, 10 untreated hypertensive men without hypertensive retinopathy and 10 healthy controls. None of the hypertensive patients had diabetes, renal impairment or overt vascular diseases. Plasma VEGF and adhesion molecules were measured using ELISAs. Endothelial function was measured by FMD (flow-mediated vasodilation) of the brachial artery. Plasma levels of VEGF, excluding adhesion molecules, were significantly higher in hypertensive patients with retinopathy when compared with patients without retinopathy (152.4+/-80.8 pg/ml versus 104.7+/-27.2 pg/ml, P = 0.035) or controls (152.4+/-80.8 pg/ml versus 98.9+/-23.7 pg/ml, P = 0.025). Levels of FMD were significantly lower in hypertensive patients than controls, but there were no significant differences between patients with or without retinopathy. Degrees of FMD were inversely correlated with VEGF levels (r = -0.351, P = 0.031). Elevation of plasma VEGF was associated with hypertensive retinopathy. Plasma VEGF could be used as a marker of early vascular damage induced by hypertension.

Collateral vessel physiology and functional impact–in vivo assessment of collateral channels

The existence and recruitment of collateral vessels within the coronary circulation may account for the tremendous variability in presentation, symptoms and outcome in patients with coronary atherosclerosis. Multiple episodes of ischemia have been found to produce the stimuli necessary for the growth of new vessels which result in collateral blood flow. Furthermore, there is also a subset of patients with readily recruitable collateral vessels that function to limit myocardial necrosis during an acute ischemic event. Promising early studies have utilized angiogenic growth factors as a means to stimulate collateral growth, bringing a renewal interest in their assessment and significance. We review, in brief, the significance and understanding of the development of coronary collaterals as well as the available means to assess them.

Collateralization and the response to obstruction of epicardial coronary arteries

Occlusive coronary disease is an important cause of global morbidity and mortality. While mechanical revascularization is effective, some individuals are not amenable to such interventions, and have a poorer prognosis. However, collateral circulation can protect and preserve myocardium around the time of coronary occlusion, contribute to better residual myocardial contractility, and lessen symptoms. We describe the anatomy and physiology of coronary collateralization, its component parts (angiogenesis and arteriogenesis), the current methods for definition of the collateral response and how this might be manipulated. The manipulation of this process is a realistic possibility for future adjuvant treatment of coronary artery disease.

Angiogenesis, thrombogenesis, endothelial dysfunction and angiographic severity of coronary artery disease

BACKGROUND

Thrombogenesis, angiogenesis, and endothelial damage/dysfunction are components in the pathogenesis of atherosclerosis.

OBJECTIVE

To investigate the relation of these variables to atherosclerotic disease severity and the possible interrelations between the three.

METHODS

111 patients attending for coronary angiography were studied (85 male, 26 female; mean (SD) age, 61.6 (10.0) years). Plasma concentrations of von Willebrand factor (vWf, a marker of endothelial damage/dysfunction), vascular endothelial growth factor (VEGF, associated with angiogenesis), soluble VEGF receptor Flt-1 (sFlt-1), and tissue factor (TF, a key component of coagulation) were measured by an enzyme linked immunosorbent assay. Following angiography, disease severity was assessed by the number of coronary vessels diseased (> 50% stenosis) and by a coronary atheroma score.

RESULTS

All indices were raised in the patients compared with 34 healthy controls except sFlt-1, which was lower in the patients. No significant correlations were found between the coronary atheroma score and values of vWf (Spearman correlations: r = 0.21, p = 0.83), VEGF (r = 0.11, p = 0.27), or TF (r = -0.04, p = 0.68). However, there was an inverse correlation between plasma sFlt-1 and coronary atheroma score (r = -0.19, p = 0.049). The number of vessels diseased had no relation to any marker. Correlations were found between TF and VEGF (r = 0.25, p = 0.008) and between TF and sFlt-1 (r = 0.42, p < 0.001) in the patients.

CONCLUSIONS

Despite evidence of abnormal angiogenesis (VEGF and sFlt-1), thrombogenesis (TF), and endothelial damage/dysfunction (vWf) in the patients with coronary artery disease, there was no correlation between VEGF, sFlt-1, vWf, or TF and angiographically defined disease severity.

Evidence for association of coronary sinus levels of hepatocyte growth factor and collateralization in human coronary disease

The therapeutic use of angiogenic factors to protect ischemic myocardium is limited by our incomplete understanding of their endogenous production. We determined the association between angiogenic factors and collateral formation in patients with coronary artery disease (CAD). A total of 71 patients underwent catheterization with sampling of the pulmonary artery, aorta, and coronary sinus (CS) to determine the levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). VEGF and HGF levels were not different in the three vascular sites, suggesting that the heart is not a major source of these cytokines in the circulation. CS VEGF and HGF levels were similar in patients with and without CAD. Elevated CS HGF levels were associated with collateral formation, whereas VEGF levels were not. Additionally, CS HGF was significantly elevated in patients with left ventricular dysfunction. These data map for the first time the concentration of endogenous angiogenic factors in the coronary circulation and support further studies to determine whether HGF may be an endogenous cardioprotective angiogenic factor.

Angiogenesis of the heart

Despite continued advances in the prevention and treatment of coronary artery disease, there are still a large number of patients who are not candidates for the conventional revascularization techniques of balloon angioplasty and stenting, or coronary artery bypass grafting (CABG). Therapeutic angiogenesis, in the form of the administration of growth factor protein or gene therapy, has emerged as a promising new method of treatment for patients with coronary artery disease. The goal of this strategy is to promote the development of supplemental blood conduits that will act as endogenous bypass vessels. New vessel formation occurs through the processes of angiogenesis, vasculogenesis, and arteriogenesis, under the control of growth factors such as those that belong to the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and angiopoeitin (Ang) families of molecules. Preclinical studies have suggested that such an approach is both feasible and effective; however many questions remain to be answered. This review will address the elements of pharmacologic revascularization, focusing on gene and protein-based therapy. The important growth factors, the vector (for gene therapy), routes of delivery, the desired therapeutic effect, and quantifiable clinical end points for trials of angiogenesis will all be addressed.

Blood monocyte concentration is critical for enhancement of collateral artery growth

Arteriogenesis has been associated with the presence of monocytes/macrophages within the collateral vessel wall. We tested the hypothesis that arteriogenesis is functionally linked to the concentration of circulating blood monocytes. Monocyte concentrations in peripheral blood were manipulated by single injections of the antimetabolite 5-fluorouracil (5-FU), resulting in a marked rebound effect in New Zealand White rabbits. Collateral artery growth was assessed by the use of a model of acute femoral artery ligation. Seven days after ligation, collateral conductance and the number of visible collateral arteries were increased in the rebound group. This increase was accompanied by an increased monocyte accumulation as demonstrated by immunohistology in the thigh 3 days after surgery. In a second animal model (129S2/SvHsd mice), 5-FU treatment caused a remarkable decrease in blood monocyte numbers at day 4, followed by a rebound effect at day 12. Foot blood flow, assessed by laser-Doppler imaging before and at various time points after surgery, increased from day 7 through day 21 in mice from the rebound group. In contrast, ligation during the phase of monocyte depletion resulted in a reduction of blood flow reconstitution. This inhibition could be reversed by an injection of isolated monocytes. In conclusion, we have demonstrated a functional link between the monocyte concentration in the peripheral blood and the enhancement of arteriogenesis.

Basic fibroblast growth factor changes in response to coronary angioplasty in patients with stable angina

Basic fibroblast growth factor (bFGF) has been implicated in the pathogenesis of coronary atherosclerosis and in angiogenesis. We assessed the changes in serum bFGF before, immediately after, and 6 months after coronary angioplasty (PTCA). Using the ELISA methods we measured plasma bFGF in 28 patients who underwent PTCA, in 20 patients with coronary artery disease who underwent elective coronary angiography and in 28 healthy subjects. Before PTCA and coronary angiography, bFGF plasma levels were similar in both patient groups (4.4+/-1.0 vs. 3.3+/-0.5 pg/ml), but were significantly higher compared with those of the control group (0.8+/-0.1 pg/ml, P<0.05). By 24 h, 3 months and 6 months after PTCA, bFGF levels had decreased significantly in the PTCA group (3.2+/-0.6, 1.7+/-0.3 and 2.7+/-0.6 pg/ml, respectively, P<0.05). In conclusion, these findings show that bFGF levels are elevated in patients with coronary artery disease. Following PTCA, bFGF levels decreased significantly and remained stable for 6 months after the procedure. Thus, bFGF level may change in response to PTCA in patients with coronary artery disease and stable angina.

Atorvastatin decreases vascular endothelial growth factor in patients with coronary artery disease

OBJECTIVES

The aim of this study was to test a possible influence of atorvastatin on the production of vascular endothelial growth factor (VEGF) in patients with coronary artery disease (CAD) and in vitro.

BACKGROUND

Vascular endothelial growth factor is suggested to be involved in the growth of atherosclerotic plaque by inducing its neovascularization. Hepatic hydroxymethyl glutaryl-coenzyme A reductase inhibitors (statins) are known to have atheroprotective effects beyond lipid lowering.

METHODS

Blood was collected from 14 male hypercholesterolemic patients with angiographically confirmed CAD at baseline and after two months of atorvastatin therapy (20 mg/d) and from eight male control patients. In an ex vivo assay, human coronary artery smooth muscle cells (HCASMC) were incubated with the patient plasma collected before and after atorvastatin therapy. To test the direct effect of atorvastatin on VEGF synthesis in vitro, HCASMC were treated with atorvastatin (1, 3 and 10 microM). The VEGF concentration was measured by enzyme-linked immunosorbent assay.

RESULTS

Atorvastatin therapy reduced VEGF plasma levels in CAD patients (from 31.1 +/- 6.1 to 19.0 +/- 3.6 pg/ml; p < 0.05). The VEGF plasma concentration tended to be higher in CAD patients before treatment compared to control patients (31.1 +/- 6.1 vs. 23.4 +/- 3.6 pg/ml; p = NS). Plasma collected before therapy induced significantly more VEGF in HCASMC compared to the plasma collected after treatment and compared to control cells. In vitro, atorvastatin decreased both the basal and the interleukin-1beta-induced VEGF release in HCASMC.

CONCLUSIONS

These data suggest that atorvastatin may lower the plasma level of VEGF in CAD patients, which could represent a novel beneficial effect of this and perhaps other statins.

Frequency distribution of collateral flow and factors influencing collateral channel development. Functional collateral channel measurement in 450 patients with coronary artery disease

OBJECTIVES

We sought to determine the pathogenetic predictors of collateral channels in a large cohort of patients with coronary artery disease (CAD).

BACKGROUND

The frequency distribution of collateral flow in patients with CAD is unknown. Only small qualitative studies have investigated which factors influence the development of collateral channels.

METHODS

In 450 patients with one- to three-vessel CAD undergoing percutaneous transluminal coronary angioplasty (PTCA), collateral flow was measured. A collateral flow index (CFI; no unit) expressing collateral flow relative to normal anterograde flow was determined using coronary wedge pressure or Doppler measurements through sensor-tipped PTCA guide wires. Frequency distribution analysis of CFI and univariate and multivariate analyses of 32 factors, including gender, age, patient history, cardiovascular risk factors, medication and coronary angiographic data, were performed.

RESULTS

Two-thirds of the patients had a CFI < 0.25 and approximately 40% of patients had a CFI < 0.15, but only approximately 10% of the patients had a recruitable CFI > or =0.4. By univariate analysis, the following were predictors of CFI > or =0.25: high levels of high-density lipoprotein cholesterol, the absence of previous non-Q-wave myocardial infarction, angina pectoris during an exercise test, angiographic indicators of severe CAD and the left circumflex or right coronary artery as the collateral-receiving vessel. Percent diameter stenosis of the lesion undergoing PTCA was the only independent predictor of a high CFI.

CONCLUSIONS

This large clinical study of patients with CAD in whom collateral flow was quantitatively assessed reveals that two-thirds of the patients do not have enough collateral flow to prevent myocardial ischemia during coronary occlusion, and that coronary lesion severity is the only independent pathogenetic variable related to collateral flow.

Influence on collateral flow of recanalising chronic total coronary occlusions: a case-control study

OBJECTIVE

To assess the effect of recanalisation on collateral flow in a case-control study in patients with and without chronic total coronary occlusions.

DESIGN

In 54 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) (mean (SD) age 61 (6) years), coronary collateral flow was measured by intracoronary pressure or Doppler guide wires at the end of repeated balloon occlusions. Coronary collateral flow index (collateral flow relative to normal antegrade flow) during the first two balloon inflations in 27 patients with a chronic total occlusion (occlusion group) was compared with that of 27 patients matched for age, sex, and collateral flow index at the first occlusion and with a coronary artery diameter stenosis </= 80% (stenosis group).

RESULTS

Following revascularisation, collateral flow index decreased in 17 of the patients in the occlusion group (63%) and in eight of the patients in the stenosis group (30%) (p = 0.03 between groups). The overall change of collateral flow index between the first and the second balloon occlusion was -0.04 (0.01) in the occlusion group (p = 0.07 for paired comparison; from 0.29 (0.17) to 0.25 (0.14)), and +0.02 (0.06) in the stenosis group (p = 0.06 for paired comparison; from 0.27 (0.13) to 0.30 (0.15)). The trend to collateral enhancement in the stenosis group differed significantly from the occlusion group (p = 0.01).

CONCLUSIONS

While repeated coronary balloon occlusions induce collateral recruitment in the majority of patients with moderate stenoses, recanalisation of chronic total coronary occlusions is more often associated with collateral flow reduction. A later decrease in collateral flow by involution of collateral channels cannot be excluded by this study but has not been reported so far.