C-reactive protein in peripheral arterial disease: Relation to severity of the disease and to future cardiovascular events

Novel Plasma Biomarkers Associated with Future Peripheral Atherosclerotic Disease and Abdominal Aortic Aneurysm-Insights from Contemporary Prospective Studies from the Malmö Diet and Cancer Study

INTRODUCTION

The potential utility of inflammatory and hemodynamic plasma biomarkers for the prediction of incident lower extremity arterial disease (LEAD), carotid artery stenosis (CAS), isolated atherosclerotic disease without concomitant abdominal aortic aneurysm (AAA), and isolated AAA without concomitant atherosclerotic disease has not yet been integrated in clinical practice. The main objective of this prospective study was to find predictive plasma biomarkers for cardiovascular disease and to evaluate differences in plasma biomarker profiles between asymptomatic and symptomatic CAS, as well as between isolated atherosclerotic disease and isolated AAA.

METHODS

Blood samples collected at baseline from participants in the prospective Malmö Diet and Cancer study (MDCS) cardiovascular cohort (n = 5550 middle-aged individuals; baseline 1991-1994) were used for plasma biomarker analysis. Validation of each incident cardiovascular diagnosis was performed by random sampling. Cox regression analysis was used to calculate hazard ratios (HRs) per one standard deviation increment of each respective log-transformed plasma biomarker with 95% confidence intervals (CI).

RESULTS

Adjusted lipoprotein-associated phospholipase A2 (Lp-PLA2) activity (HR 1.33; CI 1.17-1.52) and mass (HR 1.20; CI 1.05-1.37), C-reactive protein (CRP) (HR 1.55; CI 1.36-1.76), copeptin (HR 1.46; CI 1.19-1.80), N-terminal pro-B-type natriuretic peptide (N-BNP) (HR 1.28; 1.11-1.48), and cystatin C (HR 1.19; 95% 1.10-1.29) were associated with incident symptomatic LEAD. Adjusted N-BNP (HR 1.59; CI 1.20-2.11), mid-regional proadrenomedullin (HR 1.40; CI 1.13-1.73), cystatin C (HR 1.21; CI 1.02-1.43), and CRP (HR 1.53; CI 1.13-1.73) were associated with incident symptomatic but not asymptomatic CAS. Adjusted HR was higher for Lp-PLA2 (mass) for incident isolated AAA compared to for isolated atherosclerotic disease.

CONCLUSIONS

Plasma biomarker profile data support that subclinical vascular inflammation and cardiovascular stress seem to be relevant for the development of atherosclerotic disease and AAA.

Exercise Therapy in the Management of Peripheral Arterial Disease

The incidence and prevalence of peripheral artery disease (PAD) are increasing globally and have a marked economic burden in the United States. The American Heart Association/American College of Cardiology guidelines recommend exercise therapy as a Class 1A, but its utilization remains suboptimal. This state-of-the-art review aims to provide a comprehensive review of the most updated information available on PAD, along with its risk factors, management options, outcomes, economic burden, and the role of exercise therapy in managing PAD.

Increasing Awareness for Peripheral Artery Disease through the Identification of Novel Biomarkers

Peripheral artery disease (PAD) is a chronic atherosclerotic disorder that involves the lower extremity arteries, manifesting in claudication, rest pain, and tissue loss [...].

Monomeric C-Reactive Protein in Atherosclerotic Cardiovascular Disease: Advances and Perspectives

This review aimed to trace the inflammatory pathway from the NLRP3 inflammasome to monomeric C-reactive protein (mCRP) in atherosclerotic cardiovascular disease. CRP is the final product of the interleukin (IL)-1β/IL-6/CRP axis. Its monomeric form can be produced at sites of local inflammation through the dissociation of pentameric CRP and, to some extent, local synthesis. mCRP has a distinct proinflammatory profile. In vitro and animal-model studies have suggested a role for mCRP in: platelet activation, adhesion, and aggregation; endothelial activation; leukocyte recruitment and polarization; foam-cell formation; and neovascularization. mCRP has been shown to deposit in atherosclerotic plaques and damaged tissues. In recent years, the first published papers have reported the development and application of mCRP assays. Principally, these studies demonstrated the feasibility of measuring mCRP levels. With recent advances in detection techniques and the introduction of first assays, mCRP-level measurement should become more accessible and widely used. To date, anti-inflammatory therapy in atherosclerosis has targeted the NLRP3 inflammasome and upstream links of the IL-1β/IL-6/CRP axis. Large clinical trials have provided sufficient evidence to support this strategy. However, few compounds target CRP. Studies on these agents are limited to animal models or small clinical trials.

The prognostic capability of inflammatory proteins in predicting peripheral artery disease related adverse events

Background

Levels of inflammatory proteins and their prognostic potential have been inadequately studied in patients with peripheral artery disease (PAD). In this study, we quantified and assessed the ability of inflammatory proteins in predicting PAD-related adverse events.

Methods

In this prospective case-control study, blood samples were collected from patients without PAD (n = 202) and patients with PAD (n = 275). The PAD cohort was stratified by disease severity based on ankle brachial index (ABI): mild (n = 49), moderate (n = 164), and severe (n = 62). Patients were followed for 2 years. Plasma concentrations of 5 inflammatory proteins were measured: Alpha-2-Macroglobulin (A2M), Fetuin A, Alpha-1-Acid Glycoprotein (AGP), Serum Amyloid P component (SAP), and Adipsin. The primary outcome of our study was major adverse limb event (MALE), defined as the need for vascular intervention (open or endovascular revascularization) or major amputation. The secondary outcome was worsening PAD status, defined as a drop in ABI greater than or equal to 0.15 over the study period. Multivariable logistic regression was performed to assess the prognostic value of inflammatory proteins in predicting MALE, adjusting for confounding variables.

Results

Compared to patients without PAD, three inflammatory proteins were differentially expressed in patients with PAD (AGP, Fetuin A, and SAP). The primary outcome (MALE) and secondary outcome (worsening PAD) status were noted in 69 (25%) and 60 (22%) patients, respectively. PAD-related adverse events occurred more frequently in severe PAD patients. Based on our data, the inflammatory protein AGP was the most reliable predictor of primary and secondary outcomes. On multivariable analysis, there was a significant association between AGP and MALE in all PAD disease states [mild: adjusted HR 1.13 (95% CI 1.05-1.47), moderate: adjusted HR 1.23 (95% CI 1.16-1.73), severe: adjusted HR 1.37 (95% CI 1.25-1.85)]. High levels of AGP were associated with lower 2-year MALE-free survival in all PAD disease states [mild (64% vs. 100%, p = 0.02), moderate (64% vs. 85%, p = 0.02), severe (55% vs. 88%, p = 0.02), all PAD (62% vs. 88%, p = 0.01)].

Conclusion

Levels of inflammatory protein AGP may help in risk stratifying PAD patients at high risk of MALE and worsening PAD status and subsequently facilitate further vascular evaluation and initiation of aggressive medical/surgical management.

Circulating Biomarkers in Lower Extremity Artery Disease

Lower extremity artery disease (LEAD), a chronic condition with disturbed lower extremity circulation due to narrowing of the arteries, is predominantly caused by atherosclerosis and is associated with the presence of cardiovascular risk factors and an increased risk of cardiovascular events. LEAD is prevalent among older individuals and predicted to rise with the ageing population. In progressive disease, the patient experiences symptoms of ischaemia when walking and, in advanced critical limb-threatening ischaemia, even at rest. However, LEAD is asymptomatic in most patients, delaying diagnosis and treatment. In this setting, circulating biomarkers may facilitate earlier diagnosis in selected individuals. This review provides a broad overview of the circulating biomarkers investigated to date in relation to LEAD and discusses their usefulness in clinical practice.

Lower Plasma Albumin, Higher White Blood Cell Count and High-Sensitivity C-Reactive Protein are Associated with Femoral Artery Intima-Media Thickness Among Newly Diagnosed Patients with Type 2 Diabetes Mellitus

Introduction

Low albumin levels, high levels of high-sensitivity C-reactive protein (hs-CRP), and high white blood cell count were risk factors for changes in arterial intima-media thickness (IMT). Femoral artery IMT damages were one of the common peripheral artery type 2 diabetes. This study was conducted to determine the association between femoral artery IMT and plasma albumin, hs-CRP levels, and white blood cell count in newly diagnosed patients with type 2 diabetes mellitus (nT2D).

Materials and Methods

From January 2015 to May 2020, 306 patients with nT2D were recruited for this cross-sectional descriptive study at Vietnam's National Endocrinology Hospital. We measured IMT by Doppler ultrasound.

Results

There was a statistically significant difference in albumin, hs-CRP levels, hs-CRP-to-albumin ratio, and white blood cell counts between three different IMT groups namely normal IMT, thick IMT, and atherosclerosis (p = 0.003, p = 0.001, p = 0.001 and p = 0.049, respectively). In the multivariate linear regression analysis, white blood cell count, and hs-CRP levels showed a significantly positive correlation to IMT (standardized B and p of 0.17, 0.015 and 0.163, 0.024, respectively), but albumin levels were a significantly negative correlation to IMT (standardized B = -0.151, p = 0.029). The multivariate logistic regression analysis showed that albumin (OR = 0.79, 95% CI 0.65-0.90, p = 0.018), hs-CRP (OR = 1.09, 95% CI 1.01-1.18, p = 0.026), and white blood cell count (OR = 1.36, 95% CI 1.03-1.81, p = 0.033) had correlation to atherosclerosis of femoral artery.

Conclusion

Reduced plasma albumin, elevated hs-CRP, and white blood cell count associated with IMT increased the odds for atherosclerosis of femoral artery among nT2D.

Inflammatory Markers and Mortality in Diabetic Versus Idiopathic Gastroparesis

INTRODUCTION

Markers of systemic inflammation have been shown to be elevated in patients with gastroparesis (Gp). We hypothesized the presence of elevated markers of inflammation and/or coagulation can predict death in gastroparesis.

METHODS

Retrospective evaluation of 396 patients with symptoms of gastroparesis with baseline measures of inflammation and coagulation, using a database of patients from 2001 through 2011 followed for an additional 5 plus years. Patients were divided into two groups; diabetic (DM; n=137) and non-diabetic (non-DM; n=259). Inflammation, evaluated by C-reactive protein (CRP), and coagulation by fibrinogen by factor VIII assays, was compared to patient mortality, reported as death during the follow-up period.

RESULTS

Six DM and 13 non-DM patients died during the study period. DM patients had higher fibrinogen, CRP, and factor VIII levels of 454.0±135.2, 4.0±6.3, and 168±63.5, versus non-DM whose levels were 410.4±127.9, 2.6±4.9, 140.4±127.9, p=0.03, 0.001, and <0.001 respectively. Hypercoagulability risk differed by DM status (37% Vs. 29%, p=0.08). Compared to living non-DM, deceased non-DM/idiopathic patients had lower factor VIII (142.3±51.2 vs 117.7±40.3, p=0.07). The majority of deceased non-DM patients had abnormal fibrinogen (62%) but CRP and factor VIII were normal (80% and 85% respectively).

CONCLUSIONS

In this sample of 396 patients with symptoms of gastroparesis, systemic inflammation and coagulopathy appear related to diabetes mellitus. Patients who died had markers of inflammation and coagulation that differed from those still alive. Further analysis may suggest a link between inflammation, hypercoagulability, and the mechanism for mortality in gastroparesis or as a marker of disease severity.

Prognostic value of C-reactive protein to albumin ratio for long-term outcomes of patients with peripheral arterial disease underwent endovascular treatment

BACKGROUND

Peripheral artery disease (PAD) is part of the systemic atherosclerotic process that is highly associated with cardiovascular diseases. Despite successful endovascular treatment (EVT) strategies, mortality and morbidity rates still remain higher in PAD patients. C-reactive protein (CRP) and albumin are biomarkers of inflammation and malnutrition that play key roles in the progression of peripheral arterial disease. In this study, we aimed to investigate the relationship between CRP-to-albumin ratio (CAR) and mortality and amputation-free survival in patients with PAD after successful EVT.

METHOD

Our study enrolled 149 consecutive patients who underwent EVT on atherosclerotic obstruction of iliac, femoral, popliteal and/or below-knee arteries with the clinical features of PAD and/or chronic limb-threatening ischaemia between January 2015 and January 2020. Clinical and prognostic follow-up of patients had been done at the outpatient clinic and were collected from institution's medical records.

RESULTS

The mean follow-up period was 22 months (14-40). All-cause mortality and amputation rates of patients in the high CAR group were significantly higher than those in the low CAR group (21.3% vs. 6.8% and 18.7% vs. 5.4%, respectively). Kaplan-Meier survival analysis showed significantly better survival for patients in the low CAR group (log-rank p = 0.0058). In multivariate logistic regression analysis, CAR was found to be an independent predictor of amputation and all-cause mortality even after adjusting for other confounding risk factors. ROC curve analysis revealed the optimal cut-off value of CAR for predicting all-cause mortality and amputation to be >1.476 with a sensitivity of 48.5% and specificity of 94.0%.

CONCLUSION

The inflammatory state reflected by CAR levels was strongly associated with all-cause mortality and amputation after EVT in patients with PAD. Furthermore, CAR was found to be an independent predictor of these clinical outcomes after adjusting for other clinically associated parameters.

Current Position on the Role of Monomeric C-reactive Protein in Vascular Pathology and Atherothrombosis

C-reactive Protein (CRP) is an acute phase reactant, belonging to the pentraxin family of proteins. Its level rises up to 1000-fold in response to acute inflammation. High sensitivity CRP level is utilized as an independent biomarker of inflammation and cardiovascular disease. The accumulating data suggests that CRP has two distinct forms. It is predominantly produced in the liver in a native pentameric form (nCRP). At sites of local inflammation and tissue injury it may bind to phosphocholine-rich membranes of activated and apoptotic cells and their microparticles, undergoing irreversible dissociation to five monomeric subunits, termed monomeric CRP (mCRP). Through dissociation, CRP deposits into tissues and acquires distinct proinflammatory properties. It activates both classic and alternative complement pathways, binding complement component C1q and factor H. mCRP actively participates in the development of endothelial dysfunction. It activates leukocytes, inducing cytokine release and monocyte recruitment. It may also play a role in the polarization of monocytes and T cells into proinflammatory phenotypes. It may be involved in low-density lipoproteins (LDL) opsonization and uptake by macrophages. mCRP deposits were detected in samples of atherosclerotic lesions from human aorta, carotid, coronary and femoral arteries. mCRP may also induce platelet aggregation and thrombus formation, thus contributing in multiple ways in the development of atherosclerosis and atherothrombosis. In this mini-review, we will provide an insight into the process of conformational rearrangement of nCRP, leading to dissociation, and describe known effects of mCRP. We will provide a rationalization for mCRP involvement in the development of atherosclerosis and atherothrombosis.

Plasma Biomarkers to Predict Cardiovascular Outcome in Patients With Peripheral Artery Disease: A Systematic Review and Meta-Analysis

Supplemental Digital Content is available in the text.

Patients with lower extremity peripheral artery disease (PAD) are at increased risk of major adverse cardiovascular events. Numerous plasma biomarkers have been investigated in lower extremity PAD, but none are used for clinical risk assessment. We aimed to provide a comprehensive overview of biomarker testing in PAD as a first step to improve risk stratification.

Assessment of the relation between C-reactive protein to albumin ratio and the severity and complexity of peripheral arterial disease

Background

Peripheral arterial disease is associated with increased cardiovascular mortality and morbidity. C-reactive protein and albumin are biomarkers of inflammation and malnutrition that play key roles in the pathophysiological pathways involved in the progression of atherosclerosis and peripheral arterial disease. In this study, we aimed to assess the relationship between C-reactive protein to albumin ratio and the suprapopliteal peripheral arterial disease severity and complexity as assessed by TransAtlantic Inter-Society Consensus-II (TASC-II) classification.

Method

Our study enrolled 224 consecutive patients referred for peripheral angiography with the clinical features of possible peripheral arterial disease at a tertiary care center between January 2016 and September 2019. Level of disease and lesion characteristics were defined with reference to angiographic findings according to the TASC-II classification.

Results

C-reactive protein/albumin ratio levels were significantly higher in TASC-II class C and D than in TASC-II class B patients with a median level of 1.8 to 2.1 vs 1.4, respectively ( p = 0.018). In multivariate regression analysis, C-reactive protein to albumin ratio remained an independent predictor of severe peripheral arterial disease. The predictive performance of C-reactive protein to albumin ratio, C-reactive protein, and albumin were compared by Receiver Operating Characteristic curve analysis. C-reactive protein to albumin ratio surpassed C-reactive protein and albumin in predicting peripheral arterial disease severity and complexity. A level of C-reactive protein to albumin ratio  > 0.14 predicted a higher grade of suprapopliteal TASC-II class with sensitivity and specificity of 68.2% and 56.0%, respectively.

Conclusion

C-reactive protein to albumin ratio was strongly associated with peripheral arterial disease severity and complexity, as assessed by TASC-II classification. Also, C-reactive protein to albumin ratio was found to be a more accurate marker than C-reactive protein and albumin alone in predicting more severe and complex lesions in patients with peripheral arterial disease.

Systematic Review and Meta-Analysis of the Association Between C-Reactive Protein and Major Cardiovascular Events in Patients with Peripheral Artery Disease

BACKGROUND

Patients with peripheral artery disease (PAD) are at substantial risk of cardiovascular events. There is interest in using blood markers, such as C-reactive protein (CRP), to monitor prognosis and treatment efficacy in PAD patients. The aim of this meta-analysis was to assess the association between CRP and major cardiovascular events in PAD patients.

METHOD

Studies evaluating the association between CRP and major cardiovascular events (myocardial infarction, stroke, cardiac revascularisation and mortality) were identified using MEDLINE and the Cochrane library. Studies that did not include participants with PAD, measure CRP, or follow-up patients for cardiovascular events were excluded. Meta-analyses of published adjusted hazard ratios (HR) were conducted using an inverse variance-weighted random effects model, and heterogeneity was assessed with the I² index.

RESULTS

A total of 16 studies involving 5041 participants met the inclusion criteria for the systematic review. Eight studies were included in the meta-analyses. Summary effect estimates were reported as HR comparing higher and lower quantiles, and HR per unit increase in log_eCRP. PAD patients with higher CRP had a significantly greater risk of major cardiovascular events compared with those with lower CRP (HR 2.26, 95% CI 1.65-3.09, p < 0.001). The HR for major cardiovascular events was 1.38 (95% CI 1.16-1.63, p < 0.001) per unit increase in log_eCRP.

CONCLUSIONS

The present findings suggest that high circulating CRP is predictive of major cardiovascular events in PAD patients.

Pain frequency, severity and QT dispersion in adult patients with sickle cell anemia: correlation with inflammatory markers

Background

Inflammatory markers are increased during vaso-occlusive crisis (VOC) in adult patients with sickle cell anemia (SCA), but this is not clear in clinical steady state.

Aim

The present study aims to establish the frequency and intensity of bone pain episodes in adult patients with SCA in clinical steady state and to determine the correlation between different inflammatory markers, other variables including QT dispersion (QTd) and pain frequency and intensity in SCA.

Patients and methods

Patients were classified into two groups: group 1, those with more than three hospital admissions in the last 6 months, and group 2, those with no hospital admission. Pearson correlation between variables such as body mass index (BMI), level of tumor necrosis factor (TNF-α), interleukin-1 (IL-1), C-reactive protein (CRP), hemoglobin (Hb), reticulocyte count, white blood cell count (WBC), ferritin, lactate dehydrogenase (LDH), parathormone (PTH), vitamin D3 (25-OH cholecalciferol) and bone pain frequency with severity was evaluated.

Results

Forty-six patients were enrolled in this study with a mean age of 18.47±5.78 years, with 23 patients in each group. Vitamin D3 and Hb were lower (17.04±5.77 vs 37.59±4.83 ng/L, P<0.01 and 7.96±0.3 vs 8.44±0.27 g/dL, P<0.01, respectively); the inflammatory markers showed significantly higher level of TNF-α, IL-1 and CRP (56.52±5.43 pg/ml, 44.17±4.54 pg/ml and 3.20±0.72 mg/L, respectively, P<0.05); WBC, LDH and reticulocyte count were also significantly higher and the QTd was higher (45.0±2.22 vs 41.55±0.8 ms, P<0.05) in group 1 when compared with group 2. Pearson correlation coefficient showed significant positive correlation between serum level of TNF-α and bone pain frequency (r=0.414, P<0.005) and serum level of IL-1 (r=0.39, P<0.008).

Conclusion

There is a strong positive correlation between TNF-α, IL-1 and WBC and bone pain frequency in steady state in adult patients with SCA. CRP and low hemoglobin had weak positive correlation. QTd was significantly longer in patients who had hospitalizations with VOC.

Outcomes Following Advanced Wound Care for Diabetic Foot Ulcers: A Canadian Study

OBJECTIVES

Data concerning outcomes of Canadian patients with diabetic foot ulcers (DFUs) are limited. The objectives of this study were to evaluate the healing rates and identify the predictors of poor outcomes following advanced wound care in patients presenting with DFUs.

METHODS

We conducted retrospective cohort study of adult patients who had DFUs and were referred to a single Canadian advanced diabetic foot and wound care centre between January 1, 2010, and December 31, 2010. The primary outcome was the healing rate at 52 weeks. The generalized estimating equation model was used to identify potential risk factors associated with delayed healing of DFUs.

RESULTS

Of the 40 patients for whom there were complete follow ups, 35 (87.5%) had healing of all DFUs by 52 weeks. Predictors of poor healing were the presence of chronic ulcers, ulcer sizes >1 cm², peripheral vascular disease and multiple ulcers at first presentation. Of the patients, 7.1% required amputation, and 8.9% of patients receiving our treatment died before 52 weeks. At 52 weeks of follow up, 16 of 17 recurrent ulcers and 68 of 108 pre-existing ulcers had healed. Compared to the unadjusted healing rate of preexisting ulcers (63.0%), the unadjusted healing rate of recurrent ulcers (94.1%) was significantly higher (p=0.01).

CONCLUSIONS

Our findings demonstrate that patients with DFUs in Canada who receive early and continued care from specialized, outpatient, advanced wound care centres experience significantly improved rates of healing of recurrent DFUs compared to pre-existing DFUs.

Biochemical indices of oxidative stress and inflammation in the evaluation of peripheral artery disease

BACKGROUND

The aims of this study were: (1) to investigate changes in indices of oxidative stress and inflammation in the evaluation of peripheral artery disease (PAD); (2) to compare the diagnostic efficacy of these parameters with that of classical clinical laboratory routine parameters.

DESIGN AND METHODS

We studied 115 patients with PAD and 300 healthy volunteers.

RESULTS

PAD patients had significantly increased circulating concentrations of F2-isoprostanes, protein carbonyls, chemokine (C-C motif) ligand 2 (CCL2), high-sensitivity C-reactive protein (hs-CRP), β-2-microglobulin (B2M), and decreased paraoxonase-1 (PON1) levels. When patients were classified according to the Fontaine score, we observed important increases in plasma F2-isoprostanes and CCL2 that appeared in milder stages of the disease, and remained so at similar levels in more advanced stages; almost no overlapping with the control group was noted. Receiver operating characteristics analysis comparing patients and controls revealed that the areas under the curve for F2-isoprostanes and CCL2 approached unity [0.999 (0.998-1.000) and 0.993 (0.985-1.000)], respectively, and significantly higher to those of the other measured parameters.

CONCLUSION

Our data suggest that F2-isoprostanes and CCL2 measurements may be useful tools for the diagnosis of PAD.

The role of inflammation in cardiovascular diseases: the predictive value of neutrophil-lymphocyte ratio as a marker in peripheral arterial disease

Peripheral arterial disease (PAD) is an important manifestation of atherosclerosis, with increasing prevalence worldwide. A growing body of evidence shows that the systemic inflammatory response is closely related to the development, progression, and prognosis of atherosclerosis. In the last decade, several studies have suggested the role of measured inflammatory biomarkers as predictors of severity and prognosis in PAD in an effort to stratify the risk of these patients, to improve treatment selection, and to predict the results after interventions. A simple inflammatory marker, more available than any other, is the neutrophil-lymphocyte ratio (NLR), which can be easily obtained in clinical practice, based on the absolute count of neutrophils and lymphocytes from the differential leukocytes count. Many researchers evaluated vigorously the NLR as a potential prognostic biomarker predicting pathological and survival outcomes in patients with atherosclerosis. In this work, we aim to present the role of NLR as a prognostic marker in patients with PAD through a thorough review of the literature.

Multiple biomarkers for mortality prediction in peripheral arterial disease

Few studies have assessed which biomarkers influence mortality risk among those with peripheral arterial disease (PAD). We analyzed data from 556 individuals identified to have PAD (i.e. ankle–brachial index ⩽0.9) with available measurements of C-reactive protein, the neutrophil-to-lymphocyte ratio (NLR), homocysteine, and the urinary albumin-to-creatinine ratio (UACR) in the 1999–2004 National Health and Nutrition Examination Survey. We investigated whether a combination of these biomarkers improved the prediction of all-cause and cardiovascular mortality beyond conventional risk factors. During follow-up (median, 8.1 years), 277 of 556 participants died; 63 deaths were attributed to cardiovascular disease. After adjusting for conventional risk factors, Cox proportional-hazards models showed the following to be most strongly associated with all-cause mortality (each is followed by the adjusted hazard ratio [HR] per 1 standard deviation increment in the log values): homocysteine (1.31), UACR (1.21), and NLR (1.20). UACR alone significantly predicted cardiovascular mortality (1.53). Persons in the highest quintile of multimarker scores derived from regression coefficients of significant biomarkers had elevated risks of all-cause mortality (adjusted HR, 2.45; 95% CI, 1.66–3.62; p for trend, <0.001) and cardiovascular mortality (adjusted HR, 2.20; 95% CI, 1.02–4.71; p for trend, 0.053) compared to those in the lowest two quintiles. The addition of continuous multimarker scores to conventional risk factors improved risk stratification of all-cause mortality (integrated discrimination improvement [IDI], 0.162; p<0.00001) and cardiovascular mortality (IDI, 0.058; p<0.00001). In conclusion, the addition of a continuous multimarker score to conventional risk factors improved mortality prediction among patients with PAD.

Inflammatory biomarkers in peripheral arterial disease

Biochemical markers have the potential to aid the vascular specialist in many ways. On a daily basis, we rely on such markers as d-dimer to help exclude thromboembolic disease and thus limit low-probability ultrasound imaging. Additionally, we use troponin levels to determine myocardial events perioperatively. During the past decade, use of the inflammatory marker C-reactive protein has been recommended by the American Heart Association to further stratify patient cardiovascular risk, and has been studied more extensively in patients with peripheral vascular disease. This review details clinical information published during the past several decades on the application of serum C-reactive protein levels in peripheral arterial disease patients in correlation with disease severity and likelihood of future cardiovascular events, including recent predictive models.

Predictive value of neutrophil to lymphocyte ratio for the presence of coronary artery ectasia in patients with aortic aneurysms

Background

Both aortic aneurysms and coronary artery ectasia (CAE) frequently coexist and are associated with more pronounced inflammation. Neutrophil to lymphocyte ratio (NL ratio) is widely used as a marker of inflammation. However, relation between CAE and NL ratio in patients with aortic aneurysms is not fully understood. This study was undertaken to assess relation between CAE and NL ratio in patients with aortic aneurysms.

Methods

This study consisted of 93 consecutive patients with aortic aneurysms (AA group) and 79 patients without aortic aneurysms who had angiographically normal coronary arteries as the control group. Moreover, patients with aortic aneurysms were classified into two groups based on the presence of CAE; CAE (+) group (n = 44) and CAE (−) group (n = 49). We compared blood chemical parameters in both groups.

Results

In the AA group, 44 patients (47.3%) had CAE. The AA group had a significantly higher NL ratio than the control group (2.93 ± 1.43 vs. 2.45 ± 1.05, p = 0.027). Furthermore, the CAE (+) group had a significantly higher NL ratio than the CAE (−) group (3.39 ± 1.67 vs. 2.52 ± 1.04, p < 0.01). Multivariate logistic regression analysis revealed that the high NL ratio was an independent predictor for CAE in patients with aortic aneurysms (odds ratio 1.76, 95% confidence interval 1.24–2.69, p = 0.001).

Conclusions

Patients with aortic aneurysms had a significantly higher NL ratio than those without aortic aneurysms. Furthermore, the NL ratio might predict the presence of CAE in patients with aortic aneurysms.

Testosterone and high-sensitive C-reactive protein in coronary artery disease patients awaiting coronary artery bypass graft

Natural androgens inhibit atherosclerosis in men. This study aimed to examine whether testosterone and high-sensitive C-reactive protein differ between patients with coronary artery disease and those without coronary artery disease and to determine the association with the severity of coronary artery disease. Two hundred and six male subjects were recruited. Serum total testosterone and high-sensitive C-reactive protein were estimated. Severity of coronary artery disease was assessed by angiographic scores. Total testosterone level in patients was significantly different from controls (11.4 ± 2.7 vs. 18.1 ± 7.2 nmP = 0.001) and high-sensitive protein level in cases was significantly higher compared to controls (3.37 ± 1.62 mg l(-1) vs. 1.71 ± 0.60 mg l(-1) , P = 0.001). Testosterone levels were not significantly different with vessel (P = 0.592), Leaman (P = 0.694) and Gensini (P = 0.329) score groups, but high-sensitive C-reactive protein showed significant positive correlation among the respective groups (P = 0.005, P = 0.028, P = 0.015). Testosterone was lower, while high-sensitive C-reactive protein was higher in patients compared to controls. Testosterone showed no correlation with the severity of atherosclerosis, but high-sensitive C-reactive protein showed significant positive correlation.

C-reactive protein and brain natriuretic peptide as predictors of adverse events after lower extremity endovascular revascularization

BACKGROUND

High-sensitivity C-reactive protein (hsCRP) and brain natriuretic peptide (BNP) have been shown to be independent predictors of adverse cardiovascular outcomes and increased risk of secondary interventions or limb loss in patients with peripheral arterial disease (PAD). To assist clinicians in decision-making about treatment approaches and predicting postprocedure mortality and morbidity, we retrospectively examined patients with preprocedure hsCRP and BNP levels who underwent elective angioplasty or stent placement for lower extremity PAD.

METHODS

The study period was from January 1, 2007, to December 31, 2012, and patients were included who had angioplasty or stenting for PAD. Minimal required follow-up for study inclusion was at least one postoperative ankle-brachial index, contrast angiography, or duplex imaging of the treated limb. Events of interest included major adverse limb events (MALE), defined as target vessel revascularization, amputation, or disease progression by 1 year, and major adverse cardiovascular events (MACE; stroke, myocardial infarction, or death) by 2 years. Elevated/abnormal values for our biomarkers of interest were established by the upper limits of our institution's clinical laboratory reference range (hsCRP, >0.80 mg/dL; BNP, >100 pg/mL).

RESULTS

A total of 159 limbs in 118 patients were included in analysis (42% men; median age [range], 64 [42-87] years). All limbs were symptomatic (Rutherford classification: 1-6). Iliac artery revascularization without other adjunct lower extremity intervention was performed in 60% of the limbs. High hsCRP levels (>0.80 mg/dL) were present in 32 patients (27%) and high BNP values (>100 pg/mL) in 24 patients (20%). Kaplan-Meier analysis with log-rank comparison demonstrated that elevated hsCRP levels were associated with MALE but only in limbs receiving interventions distal to the iliac arteries (P = .005). High BNP levels did not affect MALE rates (P = .821). Conversely, both elevated BNP levels (hazard ratio, 5.6; 95% confidence interval [CI], 2.0-5.8; P = .001) and hsCRP levels (hazard ratio, 2.9; 95% CI, 1.1-7.6; P = .034) predicted MACE at 2 years in the presence of confounders in Cox proportional hazards multivariate analysis. Patients with high preintervention values of hsCRP and BNP were 10.6 times (95% CI, 2.6-42.9; P = .001) more likely to experience MACE than were patients with normal hsCRP and BNP values.

CONCLUSIONS

After lower extremity endovascular interventions, elevated preprocedural hsCRP levels are associated with MALE (femoral-popliteal interventions), and elevated levels of hsCRP and BNP are associated with late cardiovascular events.

Peripheral arterial disease

Peripheral arterial disease (PAD) is an atherosclerotic-driven condition that remains underdiagnosed and undertreated. In diabetic patients, PAD begins early, progresses rapidly, and is frequently asymptomatic, making it difficult to diagnose. Strict management of the metabolic instigators and use of screening techniques for PAD in diabetes can facilitate early diagnosis and reduce progression. Exercise is an equally effective treatment option in improving walking distance. Early revascularization must be offered early in suitable patients. Surgical bypass and endovascular revascularization are complementary and the choice of intervention should be applied appropriately by a multidisciplinary vascular team on a selective, patient-specific basis.

Inflammatory biomarkers for predicting cardiovascular disease

The pathology of cardiovascular disease (CVD) is complex; multiple biological pathways have been implicated, including, but not limited to, inflammation and oxidative stress. Biomarkers of inflammation and oxidative stress may serve to help identify patients at risk for CVD, to monitor the efficacy of treatments, and to develop new pharmacological tools. However, due to the complexities of CVD pathogenesis there is no single biomarker available to estimate absolute risk of future cardiovascular events. Furthermore, not all biomarkers are equal; the functions of many biomarkers overlap, some offer better prognostic information than others, and some are better suited to identify/predict the pathogenesis of particular cardiovascular events. The identification of the most appropriate set of biomarkers can provide a detailed picture of the specific nature of the cardiovascular event. The following review provides an overview of existing and emerging inflammatory biomarkers, pro-inflammatory cytokines, anti-inflammatory cytokines, chemokines, oxidative stress biomarkers, and antioxidant biomarkers. The functions of each biomarker are discussed, and prognostic data are provided where available.

Peripheral arterial disease in the Middle East: Underestimated predictor of worse outcome

Peripheral arterial disease (PAD) is a common manifestation of systemic atherosclerosis and is associated with significant morbidity and mortality. The prevalence of PAD in the developed world is approximately 12% among adult population, which is age-dependent and with men being affected slightly more than women. Despite the strikingly high prevalence of PAD, the disease is underdiagnosed. Surprisingly, more than 70% of primary health care providers in the US were unaware of the presence of PAD in their patients. The clinical presentation of PAD may vary from asymptomatic to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Claudication is the typical symptomatic expression of PAD. However, the disease may remains asymptomatic in up to 50% of all PAD patients. PAD has also been reported as a marker of poor outcome among patients with coronary artery disease. Despite the fact that the prevalence of atherosclerotic disease is increasing in the Middle East with increasing cardiovascular risk factors (tobacco use, diabetes mellitus and the metabolic syndrome), data regarding PAD incidence in the Middle East are scarce.

Thirty-day vein remodeling is predictive of midterm graft patency after lower extremity bypass

OBJECTIVE

Successful adaptation of a vein graft to an arterial environment is incompletely understood. We sought to investigate whether early vein graft remodeling is predictive of subsequent patency.

METHODS

A prospective longitudinal study was conducted of 67 patients undergoing lower extremity bypass with autogenous vein between February 2004 and April 2008. Preoperative blood samples were drawn for biomarkers. During the bypass operation, a 5-cm index segment of the graft was registered for serial lumen diameter measurements at 0, 1, 3, 6, 9, and 12 months using duplex ultrasound imaging. The imaging substudy analysis included patients with at least two ultrasound assessments.

RESULTS

Patients (55% male) were a median age of 70 years (interquartile range [IQR], 59-76 years), 40% had diabetes mellitus, 49% had critical limb ischemia, 75% were taking a statin, and 91% were taking an antiplatelet medication. Median follow-up was 32 months (IQR, 15-47 months). The median baseline high-sensitivity C-reactive protein level (hsCRP) was 3.2 mg/L (IQR, 1.4-9.7 mg/L). The average intraoperative, postimplantation vein lumen diameter was 3.9±1.0 mm, increasing to 4.7±1.1 mm at 1 month, an average 24%±27% change per patient. By 3 months, the average lumen diameter was 5.1±1.6 mm, with little subsequent change observed to 12 months. Nonwhite race, baseline hsCRP ≥5 mg/L, statin use, and initial lumen diameter were significantly associated with early (0- to 1-month) vein remodeling in a multivariable regression model. The primary patency rate for the cohort was 60%±6.3% at 2 years. Initial lumen diameter of the index segment was not associated with primary patency, whereas larger lumen diameter achieved at 1 month (≥5.1 mm) was positively associated with primary patency (log-rank, P=.03). Early (30-day) remodeling behavior was used to divide patients into "poor remodelers" (<-5% lumen diameter change, n=6), "modest remodelers" (-5% to 25% change, n=29), and "robust remodelers" (>+25% change, n=30). Early remodeling category was significantly associated with primary patency rate at 2 years (log-rank, P=.02). A multivariable Cox proportional hazards model showed that modest remodelers (hazard ratio, 3.9; 95% confidence interval, 1.02-15; P=.04) and poor remodelers (hazard ratio, 13; 95% confidence interval; P=.008) had significantly higher hazard ratios for graft failure than robust early remodelers.

CONCLUSIONS

Early remodeling of the arterialized vein appears to predict midterm bypass graft patency. In addition to baseline diameter, race, inflammation, hsCRP, and statin use are associated with early adaptive remodeling, but the mechanisms for these observations are not understood.

Inflammation and platelet activation in peripheral arterial occlusive disease

OBJECTIVES

Epidemiological evidence indicates that inflammation accompanies the progression of atherosclerosis. The aim of the present cross-sectional study was to define relationships between platelet activation and inflammation in patients with mild to severe (stages II to IV) peripheral arterial occlusive disease (PAOD) and matched controls. The effect of chronic administration of low-dose acetylsalicylic acid was investigated.

METHODS

Subjects were studied on a single occasion. C-reactive protein (CRP) and two indexes of in vivo platelet activation were measured - the urinary excretion of 11-dehydrothromboxane (TX) B(2) by immunoassay and circulating platelet-monocyte aggregates (PMAs) by flow cytometry.

RESULTS

Plasma PMAs and urinary 11-dehydro-TXB(2) were significantly increased in PAOD patients compared with controls (P<0.01 for all). A positive correlation between 11-dehydro-TXB(2) and CRP was found in the study population (r(s)=0.63, P<0.001). Using logistic regression analysis, CRP was the only independent correlate of 11-dehydro-TXB(2) (β(CRP)=11.9, P<0.01), whereas only the presence of PAOD was an independent predictor of high PMA levels (β(PAOD)=13.7, P=0.001). Chronic administration of acetylsalicylic acid reduced 11-dehydro-TXB(2), but not PMA and CRP.

CONCLUSIONS

There is evidence that platelet activation in patients with PAOD is related to the vascular disease and is dependent on the severity of inflammation.

An integrated biochemical prediction model of all-cause mortality in patients undergoing lower extremity bypass surgery for advanced peripheral artery disease

BACKGROUND

Patients with advanced peripheral artery disease (PAD) have a high prevalence of cardiovascular (CV) risk factors and shortened life expectancy. However, CV risk factors poorly predict midterm (<5 years) mortality in this population. This study tested the hypothesis that baseline biochemical parameters would add clinically meaningful predictive information in patients undergoing lower extremity bypass operations.

METHODS

This was a prospective cohort study of patients with clinically advanced PAD undergoing lower extremity bypass surgery. The Cox proportional hazard model was used to assess the main outcome of all-cause mortality. A clinical model was constructed with known CV risk factors, and the incremental value of the addition of clinical chemistry, lipid assessment, and a panel of 11 inflammatory parameters was investigated using the C statistic, the integrated discrimination improvement index, and Akaike information criterion.

RESULTS

The study monitored 225 patients for a median of 893 days (interquartile range, 539-1315 days). In this study, 50 patients (22.22%) died during the follow-up period. By life-table analysis (expressed as percent surviving ± standard error), survival at 1, 2, 3, 4, and 5 years, respectively, was 90.5% ± 1.9%, 83.4% ± 2.5%, 77.5% ± 3.1%, 71.0% ± 3.8%, and 65.3% ± 6.5%. Compared with survivors, decedents were older, diabetic, had extant coronary artery disease, and were more likely to present with critical limb ischemia as their indication for bypass surgery (P < .05). After adjustment for the above, clinical chemistry and inflammatory parameters significant (hazard ratio [95% confidence interval]) for all-cause mortality were albumin (0.43 [0.26-0.71]; P = .001), estimated glomerular filtration rate (0.98 [0.97-0.99]; P = .023), high-sensitivity C-reactive protein (hsCRP; 3.21 [1.21-8.55]; P = .019), and soluble vascular cell adhesion molecule (1.74 [1.04-2.91]; P = .034). Of the inflammatory molecules investigated, hsCRP proved most robust and representative of the integrated inflammatory response. Albumin, eGFR, and hsCRP improved the C statistic and integrated discrimination improvement index beyond that of the clinical model and produced a final C statistic of 0.82.

CONCLUSIONS

A risk prediction model including traditional risk factors and parameters of inflammation, renal function, and nutrition had excellent discriminatory ability in predicting all-cause mortality in patients with clinically advanced PAD undergoing bypass surgery.

Relationship between high-sensitivity C-reactive protein and risk factors in patients with peripheral arterial disease--a cross-sectional study

We investigated whether patients with peripheral arterial disease (PAD) with various serum levels of high-sensitivity C-reactive protein (hsCRP) differ in the frequency of atherosclerotic risk factors. Among 388 patients, hsCRP levels were (1) low, <1 mg/L, in 41 (10.6%) participants; (2) medium, from 1 to 3 mg/L, in 152 (39.2%) participants, and (3) high, >3 mg/L, in 195 (50.2%) individuals. According to multivariate logistic regression analysis, in comparison with patients with hsCRP level ≤3.0 mg/L, those with higher hsCRP levels had more frequently a severe form of PAD (gangrene, P ranged from .045 to <.001; ankle-brachial index ≤.40, P = .059) and had more frequently some of atherosclerotic risk factors (metabolic syndrome, P = .007; hypertension, P = .013; abdominal obesity, P = .007; high levels of uric acid, P = .022; high level of fibrinogen, P < .001; and depression, P = .015).

Anti-Inflammatory Activity of Hyperoside Through the Suppression of Nuclear Factor-κB Activation in Mouse Peritoneal Macrophages

Hyperoside (quercetin-3-O-galactoside) is a flavonoid compound mainly found in the herb plants Hypericum perforatum L and Crataegus pinnatifida. Although hyperoside has a variety of pharmacological effects including anti-viral, anti-oxidative, and anti-apoptotic activities, the anti-inflammatory mechanism of hyperoside in mouse peritoneal macrophages remains unclear. In this study, hyperoside was shown to exert an anti-inflammatory action through suppressed production of tumor necrosis factor, interleukin-6, and nitric oxide in lipopolysaccharide-stimulated mouse peritoneal macrophages. The maximal inhibition rate of tumor necrosis factor-α, interleukin-6, and nitric oxide production by 5 μM hyperoside was 32.31 ± 2.8%, 41.31 ± 3.1%, and 30.31 ± 4.1%, respectively. In addition, hyperoside inhibited nuclear factor-κB activation and IκB-α degradation. The present study suggests that an important molecular mechanism by hyperoside reduces inflammation, which might explain its beneficial effect in the regulation of inflammatory reactions.

LDL lowering in peripheral arterial disease: are there benefits beyond reducing cardiovascular morbidity and mortality?

Peripheral arterial disease affecting the lower extremities is associated with increased mortality due to cardiovascular events and reduced functional capacity due to claudication. There is abundant evidence to support the role of lipid lowering with statins in preventing cardiovascular events in patients with peripheral arterial disease. Over the last 10 years, multiple studies have been designed to test the theory that LDL C lowering with statins could result in improved exercise performance in patients with peripheral arterial disease. However, this remains an active area of investigation to better understand how the pleiotropic effects of statins could lead to enhanced functional capacity for patients with claudication. Furthermore, new insights into the complex pathophysiology of claudication may help us to understand the potential role of lipid lowering therapy in alleviating exercise induced symptoms.

High-sensitive C-reactive protein: universal prognostic and causative biomarker in heart disease?

C-reactive protein (CRP), a pentraxin protein, is an established marker of acute phase reactions. There is some experimental evidence that the CRP molecule could be causative in all stages of atherosclerotic disease starting from endothelial dysfunction, continuing to plaque formation and destabilization, and to atherothrombotic complications. However, each claim of causality has elicited a counterpoint argument, and Mendelian randomization studies have confidently shown that the concentration of CRP is unlikely to be causative. Meta-analyses have attributed a 1.5–1.7-fold risk to one standard deviation increase of high-sensitive CRP (a high-sensitivity CRP assay) for major cardiovascular events after adjustments for classical risk factors. Additional adjustments for metabolic factors reduced the risk to approximately 1.2–1.4-fold, which is still significant. Of interest, high-sensitive CRP also predicted all-cause and cancer mortality. Driven by the JUPITER trial that showed a benefit on outcome for treatment with rosuvastatin in primary prevention, treatment has been recommended in patients with a moderate Framingham Risk Score with a high-sensitive CRP of >2 mg/l. However, adding CRP to risk charts and biomarker panels mostly yielded small and inconsistent improvements.

C-reactive protein concentration is associated with prognosis in patients suffering from peritoneal carcinomatosis of colorectal origin

PURPOSE

Only a limited number of patients with peritoneal carcinomatosis (PC) of colorectal origin benefit from palliative chemotherapy. Identification of prognostic factors may aid in patient selection. The plasma concentration of C-reactive protein (CRP) is increasingly recognized as prognostic factor in a variety of malignancies. However, its value in peritoneal PC of colorectal origin is currently unknown. The aim of the present study was to investigate the association of plasma CRP concentrations with survival in patients suffering from PC of colorectal origin who receive palliative chemotherapy.

METHODS

Fifty patients with colorectal PC were identified from the Eindhoven Cancer Registry. Relevant data were retrieved from their clinical records. The most discriminatory CRP concentration was identified and patients were stratified accordingly, resulting in a group with low and a group with high CRP concentrations. Further comparisons were made between these groups.

RESULTS

A CRP concentration <35 mg/L was associated with a better prognosis (median survival 22.4 months) than a CRP concentration ≥35 mg/L (7.9 months) (p = 0.0002). CRP concentrations were inversely related to albumin concentrations which could predict survival at a cut-off value of 35 g/L (median survival 7.2 vs. 12.9 months, p = 0.01). High CRP concentrations were related to a decreased resectability rate of the primary tumor.

CONCLUSION

Elevated CRP plasma concentrations are associated with decreased survival in patients with colorectal PC. This reflects the importance of inflammation in cancer survival. Further research is warranted to assess the clinical applicability of the current findings.

Inflammatory cytokines imbalance in the very early phase of acute coronary syndrome: correlations with angiographic findings and in-hospital events

The aim of this study is to investigate the release of some inflammatory cytokines (Cks) during the very early phase (first 24 h) of acute coronary syndrome (ACS). Twenty-six consecutive subjects admitted to coronary care unit with ACS underwent serial blood sampling in order to evaluate concentrations of interleukin (IL)-2, IL-10, IL-18, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ. Blood samples were taken within 6 h after onset of chest pain (T₀), at 12 h (T₁), and at 24 h (T₂). Patients were thus divided into four groups comparing pro-inflammatory Ck release (IL-2, TNF-α, and IFN-γ) and anti-inflammatory activity (IL-10). Clinical features, risk factors, incidence of adverse events, and coronary angiography findings were compared with Ck activation. Ck levels were significantly increased if compared with baseline. Subjects with marked inflammatory response showed a higher incidence of left anterior descending coronary disease (IL-2, p < 0.001; TNF-α and IFN-γ, p < 0.05) and more often incurred early complications (IL-2, p < 0.05; IFN-γ, p < 0.001). A correlation was detectable between IL-18 levels and myocardial enzyme release (creatine kinase, r = 0.47; lactate dehydrogenase, r = 0.54; troponin I, r = 0.58; p < 0.05). TNF-α levels were associated with a worse prognosis at follow-up (Log rank, p < 0.05). A Ck activation characterizes the early phase of ACS. Early inflammatory reaction seems to correlate with coronary disease and adverse events.

Biomarkers of peripheral arterial disease

Atherosclerotic arterial occlusive disease affecting the lower extremities is also known as peripheral artery disease (PAD). This disorder affects 8 to 12 million individuals in the U.S. and is increasingly prevalent in Europe and Asia. Unfortunately, most patients are not diagnosed and are not optimally treated. A blood test for PAD, if sufficiently sensitive and specific, would be expected to improve recognition and treatment of these individuals. Even a biomarker panel of moderate sensitivity and specificity for PAD could refine risk stratification to select individuals for diagnostic vascular examination. Alternatively, biomarkers for PAD may be useful in determining prognosis, the risk for progression, or the response to therapy. Finally, the discovery of biomarkers associated with PAD may provide novel insights into the pathophysiology of PAD and new therapeutic avenues to pursue. Biomarkers may be derived from studies of the genome, transcriptome, proteome, or metabolome. The focus of this review is on proteomic biomarkers associated with PAD.

VEGF and soluble VEGF receptor-1 (sFlt-1) distributions in peripheral arterial disease: an in silico model

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis, the growth of new capillaries from existing microvasculature. In peripheral arterial disease (PAD), lower extremity muscle ischemia develops downstream of atherosclerotic obstruction. A working hypothesis proposed that the maladaptive overexpression of soluble VEGF receptor 1 (sVEGFR1) in ischemic muscle tissues, and its subsequent antagonism of VEGF bioactivity, may contribute to the deficient angiogenic response in PAD, as well as the limited success of therapeutic angiogenesis strategies where exogenous VEGF genes/proteins are delivered. The objectives of this study were to develop a computational framework for simulating the systemic distributions of VEGF and sVEGFR1 (e.g., intramuscular vs. circulating, free vs. complexed) as observed in human PAD patients and to serve as a platform for the systematic optimization of diagnostic tools and therapeutic strategies. A three-compartment model was constructed, dividing the human body into the ischemic calf muscle, blood, and the rest of the body, connected through macromolecular biotransport processes. Detailed molecular interactions between VEGF, sVEGFR1, endothelial surface receptors (VEGFR1, VEGFR2, NRP1), and interstitial matrix sites were modeled. Our simulation results did not support a simultaneous decrease in plasma sVEGFR1 during PAD-associated elevations in plasma VEGF reported in literature. Furthermore, despite the overexpression in sVEGFR1, our PAD control demonstrated increased proangiogenic signaling complex formation, relative to our previous healthy control, due to sizeable upregulations in VEGFR2 and VEGF expression, thus leaving open the possibility that impaired angiogenesis in PAD may be rooted in signaling pathway disruptions downstream of ligand-receptor binding.

Novel markers of peripheral arterial disease

Peripheral arterial disease (PAD), a relatively common manifestation of atherosclerotic vascular disease, is associated with significant morbidity and mortality. Although conventional risk factors contribute to the onset and progression of PAD, the role of 'novel' biomarkers in pathways of inflammation, thrombosis, lipoprotein metabolism, and oxidative stress in determining susceptibility to PAD is being increasingly recognized. Validation of novel risk factors for PAD may allow earlier detection, an improved understanding of disease etiology and progression, and the development of new therapies. In this review, we discuss available evidence for associations between novel circulating markers and several aspects of PAD including disease susceptibility, progression, functional limitation, and adverse outcomes.