Thrombophilic risk factors for symptomatic peripheral arterial disease

Systematic review and meta-analysis of the genetics of peripheral arterial disease

Background

Peripheral artery disease (PAD) impacts more than 200 million people worldwide. The understanding of the genetics of the disease and its clinical implications continue to evolve. This systematic review provides a comprehensive summary of all DNA variants that have been studied in association with the diagnosis and progression of PAD, with a meta-analysis of the ones replicated in the literature.

Methods

A systematic review of all studies examining DNA variants associated with the diagnosis and progression of PAD was performed. Candidate gene and genome-wide association studies (GWAS) were included. A meta-analysis of 13 variants derived from earlier smaller candidate gene studies of the diagnosis of PAD was performed. The literature on the progression of PAD was limited, and a meta-analysis was not feasible because of the heterogeneity in the criteria used to characterize it.

Results

A total of 231 DNA variants in 112 papers were studied for the association with the diagnosis of PAD. There were significant variations in the definition of PAD and the selection of controls in the various studies. GWAS have established 19 variants associated with the diagnosis of PAD that were replicated in several large patient cohorts. Only variants in intercellular adhesion molecule-1 (rs5498), IL-6 (rs1800795), and hepatic lipase (rs2070895) showed significant association with the diagnosis of PAD. However, these variants were not noted in the published GWAS.

Conclusions

Genetic research in the diagnosis of PAD has significant heterogeneity, but recent GWAS have demonstrated variants consistently associated with the disease. More research focusing on the progression of PAD is needed to identify patients at risk of adverse events and develop strategies that would improve their outcomes.

Relationship between serum homocysteine, fibrinogen, lipoprotein-a level, and peripheral arterial disease: a dose-response meta-analysis

AIM

At present, the relationship between serum homocysteine (Hcy), fibrinogen (FIB), lipoprotein-a (LPa), and PAD is uncertain, and there has been no meta-analysis to establish the dose-response relationship between their exposure levels and PAD.

METHODS AND RESULTS

Relevant literature published in PubMed, Embase, and Web of Science was retrieved. The robust error meta-regression method was used to assess the linear and non-linear dose-response relationship between exposure level and PAD risk. A total of 68 articles, involving 565,209 participants, were included. Combined with continuous variables, the serum Hcy, FIB, and LPa levels of PAD patients were significantly higher than those of healthy individuals. The odds ratios (ORs) of PAD for individuals with high Hcy, FIB, and LPa levels compared with those with low levels were 1.47, 1.14, and 1.76, respectively. The study also showed that circulating Hcy, FIB, and LPa were significantly elevated in patients with PAD compared with controls. The level of Hcy and the risk of PAD presented a U-shaped distribution. The nonlinear dose-response model showed that each 1 μmol/L increase in serum Hcy increased the risk of PAD by 7%. Similarly, for each 10 mg/dL FIB and 10 mg/dL LPa increases, the risk of PAD increased by 3% and 6%, respectively.

CONCLUSIONS

This meta-analysis provided evidence that elevated Hcy, PIB, and LPa levels may increase the risk of PAD, and the risk of PAD increases with the increase in serum exposure within a certain range. By controlling Hcy level, the incidence of PAD may be reduced to control the PAD growing epidemic.

TRIAL REGISTRATION NUMBER

PROSPERO (CRD42021250501), https://www.crd.york.ac.uk/prospero/.

5,10-methylenetetrahydrofolate reductase C677T gene polymorphism and peripheral arterial disease: A meta-analysis

INTRODUCTION

Peripheral arterial disease is one common vascular disease most caused by atherosclerosis. As with stroke and coronary heart disease, peripheral arterial disease is one clinical type of atherosclerotic cardiovascular disease with many unmeasured environmental and genetic components. MTHFR C677T polymorphism is associated with the increased risk of ischemic stroke and coronary heart disease. MTHFR C677T polymorphism is associated with decreasing enzyme activity and increasing homocysteine levels. Meta-analysis of studies had demonstrated an association between elevated plasma homocysteine levels and peripheral arterial disease. Elevated plasma homocysteine level is closely related to MTHFR C677T polymorphism. Recent studies had clarified the relationship of MTHFR C677T polymorphism and peripheral arterial disease. So we performed a meta-analysis to investigate the association between MTHFR C677T polymorphism and peripheral arterial disease.

MATERIALS AND METHODS

We searched the database PubMed, Embase, and Cochrane Library for all English-language articles related to peripheral arterial disease and MTHFR C677T through 30 June 2020. Analysis results were shown by forest plot. Publication bias was estimated using funnel plot.

RESULTS

A total of 15 studies comprising 1929 patients with peripheral arterial disease and 2952 healthy controls were included in the meta-analysis. Significant associations between MTHFR C677T genetic polymorphism and peripheral arterial disease were found (OR = 1.31, 95% CI: 1.09-1.58, P <0.01). But there was no significant association (poor OR = 1.11, 95% CI: 0.98-1.26, P =0.11) between the T allele carrier and peripheral arterial disease.

CONCLUSION

Our meta-analysis suggested that MTHFR C677T genetic polymorphism TT genotype may be associated with increased peripheral arterial disease risk. But further studies with large sample sizes are needed to confirm our findings.

Antiphospholipid antibodies and lower extremity peripheral artery disease: A systematic review and meta-analysis

AIM

To evaluate the clinical relevance of antiphospholipid antibodies (aPL) in patients with lower extremity peripheral artery disease (PAD).

DATA SOURCES

EMBASE and MEDLINE databases were searched from inception to March 2020 for clinical studies reporting on the association between of aPL [IgG/IgM anticardiolipin (aCL) and lupus anticoagulant (LA)] and PAD.

METHODS

We determined the pooled prevalence (PP) of patients positive for aPL in PAD or the PP of PAD in patients positive for aPL; we employed Peto's odds ratio with random effect for the meta-analysis.

RESULTS

Twenty-one studies comprising 6,057 patients were evaluated: in patients with PAD, the PP of IgG aCL was 12% vs 4.1% in those without, IgM aCL was 13.2% vs 2.1%, and LA 13.3% vs 3.3%, respectively. The PP of patients with LA was greater in critical limb ischemia than in the control group (19.3% vs 4.2%). Also, the PP of patients with LA was greater in the failed than in the successful revascularisation group (35.8% vs 15.8%). The PP of post-procedural revascularisation failures was similar in the groups given or not given oral anticoagulation (59.2% vs 61.9%).

CONCLUSION

All the aPL related to PAD regardless of diagnostic definition used, whereas LA related also to critical limb ischaemia and failed revascularisation. Data expressed as percentage of participants positive for aPL limit the interpretation of these relationships.

Hypercoagulability predicts worse outcomes in young patients undergoing lower extremity revascularization

OBJECTIVE

Although we know that young patients with peripheral artery disease (PAD) have worse outcomes than older patients, there is a scarcity of information about the incidence of hypercoagulability in this population. Our aim was to analyze outcomes of young patients diagnosed with a hypercoagulable state (unusual tendency toward thrombosis) after lower extremity revascularization compared with similar patients without hypercoagulability.

METHODS

All patients 50 years of age or younger undergoing an initial procedure for lower extremity PAD from 2000 to 2015 at the Cleveland Clinic were retrospectively analyzed. Patients with a hypercoagulability panel were included and classified into groups as hypercoagulable positive (HP) or hypercoagulable negative (HN). Demographics, preoperative risk factors, form of presentation, level of disease, and type of intervention were analyzed in addition to perioperative complications, early failure, and length of stay. Primary outcomes were limb loss and primary, primary assisted, and secondary patencies. Outcomes were analyzed and Kaplan-Meier curves generated.

RESULTS

Ninety-one patients were included for a total of 118 limbs. Mean follow-up was 32 months; 55% of patients had a hypercoagulable disorder, with 59% having lupus anticoagulant and 32% hyperhomocysteinemia. In the HP group, 71% were men; 49% were men in the HN group. Patients overall had a high prevalence of smoking (86%), hypertension (36%), and hyperlipidemia (33%). Acute limb ischemia was the most common form of presentation for both groups (50% HP, 38% HN). The aortoiliac segment was the most commonly affected (38% HP, 50% HN). The most frequent operation in the HN group was endarterectomy or bypass (32%); in the HP group, it was an endovascular intervention (29%). Perioperative occlusion or failure was 18% in the HN group vs 30% in the HP group (P > .05). Primary patency, primary assisted patency, and secondary patency at 36 months were all better for the HN group (no statistical significance) in all treatment groups. Major amputation at 36 months was significantly worse for the HP group (40% vs 10% in the HN group; P < .005). There was no difference in perioperative complications or length of stay.

CONCLUSIONS

Young patients undergoing lower extremity revascularization for PAD have worse outcomes when associated with hypercoagulability. There are trends to decreased patency of revascularization in these patients, with significantly more major amputations. No clear differences between modalities of treatment were demonstrated.

Brachial artery thrombosis mimicking De Quervain's syndrome: a case report

Upper limb occlusions are rare and the clinical presentation may vary depending on the affected arteries. A detailed history and physical examination may reveal possible causes and can facilitate the differential diagnosis. It can be misdiagnosed as musculoskeletal diseases due to similar clinical manifestations. In this report, we present a case with wrist pain mimicking de Quervain's syndrome diagnosed as subacute brachial artery thrombosis due to factor II gene mutation. In conclusion, physicians should be cautious to avoid unnecessary delay in the diagnosis of thrombosis in young patients.

Markers of fibrinolysis may predict development of lower extremity arterial disease in patients with diabetes: A longitudinal prospective cohort study with 10 years of follow-up

BACKGROUND

A previous cross-sectional study suggested that tissue plasminogen activator-activity might be an early marker of asymptomatic lower extremity arterial disease, but the long-term relationship is unknown.

SUBJECTS AND METHODS

This study included 96 diabetic (48 type 1/48 type 2) and 62 non-diabetic subjects aged 30-70 years without previously known lower extremity arterial disease (age: 50.3 ± 9.3 years, gender: M/W 47.5/52.5% and body mass index: 26.6 ± 4.5 kg/m(2)). The relationships between asymptomatic lower extremity arterial disease and fibrinolytic markers (tissue plasminogen activator-activity, tissue plasminogen activator-mass, plasminogen activator inhibitor-1 activity) at baseline and after 10 years were assessed by logistic regression analysis adjusting for age, hypertension, statin treatment, HbA1c, triglycerides and low-density lipoprotein cholesterol as fixed covariates.

RESULTS

The tissue plasminogen activator-activity at baseline and at the 10-year follow-up significantly predicted the presence of sign(s) of lower extremity arterial disease (odds ratio = 1.78, 95% confidence interval: 1.02-3.10, p = 0.043 and odds ratio = 1.78, 95% confidence interval: 1.12-2.23, p = 0.014, respectively). In addition, tissue plasminogen activator-mass at the 10-year follow-up was associated with signs of lower extremity arterial disease (odds ratio = 1.07, 95% confidence interval: 1.00-1.15, p = 0.046). Baseline age, hypertension and HbA1c were independently associated with sign(s) of lower extremity arterial disease at 10 years (odds ratio = 1.09, 95% confidence interval: 1.04-1.14, p = < 0.001; odds ratio = 3.68, 95% confidence interval: 1.67-8.12, p = 0.001 and odds ratio = 1.54, 95% confidence interval: 1.21-1.95, p = < 0.001, respectively).

CONCLUSION

This long-term study supports previous findings of a significant association between asymptomatic lower extremity arterial disease and tissue plasminogen activator-activity. Thus, tissue plasminogen activator-activity may be an early marker of lower extremity arterial disease although the mechanism of this relationship remains unclear.

The relationship between plasma homocysteine level and HLA-B51 in patients with Behcet's disease: a case-control study

BACKGROUND

Various coagulation disorders have been reported to explain hypercoagulability state in Behcet's disease (BD). A possible negative association between human leukocyte antigen (HLA)-B51 and increased homocysteine level has been suggested in a previous report from Iranian patients with BD. The aim of this study was to find any possible relationship between plasma homocysteine levels and HLA-B51.

METHODS

In a case-control study, BD patients (fulfilling the new International Criteria for BD) and controls (who had similar clinical symptoms but BD was clinically excluded in them) were included. Mean plasma homocysteine levels measured by enzyme-linked immunosorbent assay in HLA-B51 positive and negative individuals both in patients and controls were compared by t-test, Mann-Whitney test and analysis of variance (F-test).

RESULTS

Ninety-six BD patients and 152 controls were recruited. There was no significant difference between HLA-B51 positive and negative individuals either in the mean plasma homocysteine levels (13.59 ± 9.03 vs. 12.95 ± 4.98 μmol/L, P = 0.514), or in the prevalence of hyperhomocysteinemia (17% vs. 21.4%, P = 0.504). This was true both for BD and control groups. In HLA-B51 positive and negative BD patients, mean plasma homocysteine levels were 14.29 ± 12.02 and 12.62 ± 4.79 μmol/L, respectively (P = 0.33), and the prevalence of hyperhomocysteinemia was 20.8% versus 19.5% (P = 0.55). In the control group, the mean plasma homocysteine levels in HLA-B51 positive and negative individuals were 12.85 ± 4.28 and 13.14 ± 5.10 μmol/L, respectively (P = 0.794), and the prevalence of hyperhomocysteinemia was 13% versus 22.1% (P = 0.23). The difference was non-significant regarding sex (P > 0.71) and disease activity (P > 0.31).

CONCLUSION

In contrast to our previous report, we found no relationship between plasma homocysteine levels and HLA-B51 in this study, either in BD or in the control group.

Plasma homocysteine levels are independently associated with the severity of peripheral polyneuropathy in type 2 diabetic subjects

Peripheral polyneuropathy (PN) is a frequent complication of diabetes. However, mechanisms underlying the development of PN are multifactorial and not well understood. Our aim was to examine the association of plasma homocysteine (Hcy) with the prevalence and grade of peripheral PN in patients with type 2 diabetes (T2DM). We studied a cohort of 196 subjects with T2DM classified according to the grade of PN (Neuropathy Disability Score, NDS). Subjects with the highest grade of PN were older and had significantly increased levels of creatinine, microalbuminuria, HbA1c, and plasma Hcy compared to the other two groups. The differences in plasma Hcy values were maintained after correcting for confounding factors. Plasma Hcy, HbA1c, duration of diabetes, and age were predictors of the grade of PN. In conclusion, for each increase of 1 µmol in plasma Hcy there was a 23% increase of the risk of diabetic PN evaluated by NDS. Moreover, the grade of PN was predicted by plasma Hcy and HbA1c values, age and duration of diabetes. Further prospective studies should be conducted to confirm the association of plasma Hcy levels with the grade of PN in subjects with T2DM.

The role of nutrition and body composition in peripheral arterial disease

Peripheral arterial disease (PAD) has not been as extensively investigated as other cardiovascular diseases. However, the available data suggest that nutrition-based treatment strategies have the potential to reduce the cost-economic burden of PAD substantially. Abdominal obesity is associated with PAD and prospective and cross-sectional studies have shown that a low dietary intake of folate and reduced synthesis of vitamin D are associated with an increased risk of PAD and severe walking impairment in patients who have the disease. However, dietary patterns that are associated with decreased cardiovascular risk might protect against PAD. A small number of clinical trials have provided evidence that increased intakes of niacin and insoluble fiber might be associated with decreased levels of LDL cholesterol and thrombogenic biomarkers, as well as increased serum levels of HDL cholesterol in patients with PAD. However, little evidence that antioxidants, vitamins B(6) and B(12), or essential fatty acid supplements improve clinical outcomes in these patients exists. Overall, data on the effects of nutrition, body composition, and nutritional supplementation on the risk, progression, and prognosis of PAD are scarce. Further research into these areas is required to allow the development of evidence-based nutritional guidelines for the prevention and treatment of the disease.

The impact of blood coagulability on atherosclerosis and cardiovascular disease

Although the link between blood coagulation and atherogenesis has been long postulated, only recently, and through the extensive work on transgenic mice, crossbred on an atherogenic background, has the direction of this interaction become visible. In general, hypercoagulability in mice tends to increase atherosclerosis, whereas hypocoagulability reduces the atherosclerotic burden, depending on the mouse model used. The information on a direct relationship between coagulation and atherosclerosis in humans, however, is not that clear. Almost all coagulation proteins, including tissue factor, are found in atherosclerotic lesions in humans. In addition to producing local fibrin, a matrix for cell growth, serine proteases such as thrombin may be very important in cell signaling processes, acting through the activation of protease-activated receptors (PARs). Activation of PARs on vascular cells drives many complex processes involved in the development and progression of atherosclerosis, including inflammation, angiogenesis, and cell proliferation. Although current imaging techniques do not allow for a detailed analysis of atherosclerotic lesion phenotype, hypercoagulability, defined either by gene defects of coagulation proteins or elevated levels of circulating markers of activated coagulation, has been linked to atherosclerosis-related ischemic arterial disease. New, high-resolution imaging techniques and sensitive markers of activated coagulation are needed in order to study a causal contribution of hypercoagulability to the pathophysiology of atherosclerosis. Novel selective inhibitors of coagulation enzymes potentially have vascular effects, including inhibition of atherogenesis through attenuation of inflammatory pathways. Therefore, we propose that studying the long-term vascular side effects of this novel class of oral anticoagulants should become a clinical research priority.

Association analysis of genetic polymorphisms of factor V, factor VII and fibrinogen β chain genes with human abdominal aortic aneurysm

Increased activity of the coagulation system is associated with the increased risk of many arterial thrombotic diseases and atherosclerosis. The purpose of this study was to evaluate the influence of selected polymorphisms in genes coding for coagulation factor V (1691 G/A, the so-called Leiden mutation), factor VII (−323 0/10 bp insertion/deletion) and fibrinogen β chain (−455 G/A) on the risk of abdominal aortic aneurysm, a particular form of atherothrombosis. We conducted a case-control study of 153 Polish patients hospitalized due to abdominal aortic aneurysm (AAA) and compared the results to those obtained from matched healthy control subjects. The polymorphisms were ascertained through genotyping by polymerase chain reaction and restriction digestion of amplified fragments. The study revealed that individuals carrying heterozygous genotype GA for the fibrinogen β chain −455 G/A mutation had at least a 2-fold greater likelihood of AAA development compared to control subjects (OR=3.01; 95% CI 1.83–4.96). The cases possessing homozygous mutant genotype (AA) had no significant risk of developing AAA compared to the control subjects (OR=1.12; 95% CI 0.33–2.44; p=0.83). Concerning factor V 1691 G/A and factor VII −323 0/10 bp mutations, we did not find any statistically significant correlation between them and AAA occurrence. In conclusion, we suggest that the −455G/A polymorphism of the fibrinogen β chain gene is a potential genetic marker to identify the risk of AAA.

Genetic cardiovascular risk factors and age-related macular degeneration

PURPOSE

To investigate the association between genetic cardiovascular risk factors and exudative age-related macular degeneration (AMD) in a White Austrian population.

METHODS

Seventy-five unrelated AMD patients and 75 unrelated healthy, sex- and age-matched control patients were genotyped for the following 19 single nucleotide polymorphisms (SNPs) in 14 different genes: blood coagulation factor V (FV) R506Q, factor II (prothrombin) G20210A and factor XIII (FXIII) V34L; 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T, A1298C; plasminogen activator inhibitor 1 (PAI-1) 4G/5G; endothelial protein C receptor (EPCR) 4600 A>G (A3 haplotype), 4678 G>C (A1 haplotype); apolipoprotein B (ApoB) R3500Q; apolipoprotein E (ApoE) E2/E3/E4; β-fibrinogen -455 G>A; human platelet antigen 1 (HPA1) a/b; angiotensin-converting enzyme (ACE) I/D; endothelial nitric oxide synthase (eNOS) 786 T>C, 894 G>T; lymphotoxin alpha (LTA) 804 C>A and 9p21 rs10757278. Genotyping was carried out by polymerase chain reaction (PCR) followed by reverse hybridization (CVD StripAssays; ViennaLab Diagnostics, Vienna, Austria).

RESULTS

No statistically significant association could be observed between AMD and the investigated genetic risk factors for cardiovascular disease (CVD). All factors seem to be uniformly distributed in the two groups of AMD patients and healthy controls. Two variables -β-fibrinogen: -455 G>A (p = 0.0786) and apolipoprotein E4 (p = 0.0636) - were not as far from association as the others.

CONCLUSION

Our data show that the 19 tested CVD risk markers do not play a significant role in AMD. β-Fibrinogen and apolipoprotein E4 should be examined in a larger cohort.

Peripheral arterial disease in diabetes: is there a role for genetics?

Atherosclerotic occlusion of vessels outside of the heart is commonly referred to as peripheral arterial disease (PAD). The lower extremity is the most common site of PAD and its development is associated with the same risk factors involved in general atherosclerosis. However, there is emerging evidence that other risk factors may play a key role in the development of PAD. Over the past decade polymorphism in a number of genes has been shown to contribute to the risk of developing PAD. These genes can be classified into proartherosclerosis or proatherothrombosis based on the known gene function. Moreover, they can be categorized as "novel" polymorphism when the function of the genes is not known or when the specific gene within an associated genetic locus is not known. It is intriguing that not only are gene polymorphisms associated with PAD being identified, but more recently studies are now finding gene polymorphisms that may be important in development of this syndrome only in the contest of certain environmental factors such as diabetes. Currently how these gene-environment interactions contribute to the pathogenesis of PAD is poorly understood but will likely play a critical role in future understanding of this complex disease.

High thrombin activatable fibrinolysis inhibitor levels are associated with an increased risk of premature peripheral arterial disease

BACKGROUND

Previous studies suggested that hypofibrinolysis is associated with increased risk of peripheral arterial disease. Thrombin activatable fibrinolysis inhibitor (TAFI) has been identified as an important inhibitor of fibrinolysis. The aim of our study was to assess the role of TAFI in young patients with peripheral arterial disease.

METHODS

In a single-center case-control study we measured plasma TAFI antigen levels and functional TAFI in consecutive young patients (men 18-45 years and women 18-55 years) with a first manifestation of peripheral arterial disease and compared these with a population-based control group.

RESULTS

A total of 47 peripheral arterial disease patients and 141 controls (mean age 43) were included. Intact TAFI antigen levels were significantly higher in patients with peripheral arterial disease (112.4±21.1%) than in controls (104.9±19.9%, p=0.03). The risk of peripheral arterial disease increased with 18% (OR 1.18; CI 1.01-1.34) per 10% increase of TAFI antigen. Functional TAFI levels were slightly higher in patients compared to controls, however this difference was not significant. For individuals with the highest functional TAFI levels, above the 90th percentile, the increased risk for peripheral arterial disease was most pronounced (OR 3.1; CI 1.02-9.41).

CONCLUSION

High TAFI levels are associated with increased risk of premature peripheral arterial disease.

Peripheral artery disease and genetics: is there a cause-and-effect relationship?

Peripheral artery disease (PAD) is a major health problem worldwide, affecting millions of patients. Although cardiovascular risk factors, such as diabetes, tobacco use, hypertension, and hypercholesterolemia have been associated with the development of PAD, the possible existence of an inherited genetic predisposition to PAD has been investigated in numerous familial aggregation studies. A link between genetics and PAD may open new avenues for the prevention of this morbid and mortal disorder. This is an overview of the potential association between genetics and PAD.

Homocysteine in vascular Behcet disease: a meta-analysis

OBJECTIVE

Behçet disease (BD) is a vasculitis of unknown etiology, characterized by oral or genital aphtosis and uveitis. Homocysteine (hcy) is an independent risk factor for venous and arterial thrombosis. The association between hyperhomocysteinemia and thrombosis has been investigated in some studies in BD patients. However, information on this association is based only on the results of small studies with conflicting results. To overcome such limitations, we performed a metaanalysis comparing the plasma levels of hcy in BD patients with and without history of thrombosis.

METHODS AND RESULTS

We searched for all published studies using the Medline and Embase databases. Two reviewers performed study selection independently. Studies were included if hcy was measured in adult BD patients with and without thrombosis. Two reviewers independently extracted data on study and population characteristics. The mean value of hcy in BD patients and the presence of hyperhomocysteinemia in patients with and without thrombosis were collected. Association between thrombosis and hyperhomocysteinemia, and the mean difference of hcy levels in BD patients with and without thrombosis were calculated. Sixteen studies, for a total of 979 patients, were included. Hyperhomocysteinemia was more prevalent in patients with thrombosis than in those without (odds ratio 3.14; 95% CI 1.26 to 7.80) Mean levels of hcy were significantly higher in patients with thrombosis in comparison with patients without (mean difference 3.30 μmol/L; 95% CI 2.09 to 4.51).

CONCLUSIONS

Our results suggest that hyperhomocysteinemia may be considered to be associated with thrombosis in BD patients.

Plasma homocysteine levels are associated with ulceration of the foot in patients with type 2 diabetes mellitus

BACKGROUND

To examine the association of biochemical markers of risk (plasma Hcy, microalbuminuria, lipoprotein (a)(Lp(a)) and diabetic dyslipidaemia) with the prevalence of diabetic foot ulceration in type 2 diabetic patients.

METHODS

Case/control study conducted in 198 type 2 diabetic patients. 89 patients have foot ulcers and 109 have no foot ulcers (control group), in order to establish ORs for diabetic foot ulceration. In all subjects plasma Hcy, Lp(a), total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoprotein B, HbA(1c) and microalbuminuria were measured using standard procedures.

RESULTS

Plasma Hcy, microalbuminuria, HbA(1c) and apolipoprotein B levels were significantly higher in patients with foot ulceration compared with the control group. Plasma lipids, Lp(a), vitamin B12 and folic acid values were similar in both groups. In the logistic regression model, plasma Hcy (OR 1.09; 95% CI 1.04-1.69), microalbuminuria (OR 1,01; 95% CI 1.01-1.17) and HbA(1c) levels (OR 1.33; 95% CI 1.04-1.69) were independent risk factors for the presence of diabetic foot ulceration.

CONCLUSIONS

In our study, for each micromol increase in plasma Hcy levels there was a 10% increase in the risk of diabetic foot ulceration. In addition, plasma homocysteine, HbA(1c) and microalbuminuria accounted for 50% prevalence risk of diabetic foot ulceration. Further prospective studies should be conducted to confirm the association of plasma Hcy levels with the risk of foot ulceration.

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.

Is Increased Thrombin Activation in Patients With Abdominal Aortic Aneurysms Dependent on Area or Volume of Aneurysm Thrombus Mass?

Objectives: Does thrombin activation seen in patients with abdominal aortic aneurysms (AAA) relate to the thrombus surface area or volume within the aneurysm? Patients and methods: A total of 130 patients with AAA were analyzed regarding levels of the complex between activated protein C—protein C inhibitor (APC-PCI) and AAA morphology. Analysis of APC-PCI complex was made using a sandwich immunofluorometric method. Results: Increased APC-PCI concentrations were seen in patients with AAA (0.44 μg/L; P < .001 compared with controls). The correlations of APC-PCI values were r = .13, P = .13 for aneurysm size, r = .08, P = .35 for thrombus surface area, and r = .13, P = .14 for thrombus volume. APC-PCI values elevated to 0.45 μg/L in 10 patients with AAA having no or very little thrombus mass. Conclusion: Disappointingly, no correlation was found between thrombus surface area or volume and levels of the APC-PCI complex. Mechanisms other than the AAA-sac thrombus must be evaluated as cause of thrombin activation in patients with AAA.

A field synopsis and meta-analysis of genetic association studies in peripheral arterial disease: The CUMAGAS-PAD database

In an electronic search of the literature, the authors systematically retrieved all published studies that investigated genetic susceptibility to peripheral arterial disease (PAD). They created a comprehensive database of all eligible studies, collecting detailed genetic and bioinformatics data on each polymorphism. Data from eligible studies were synthesized using meta-analysis techniques. Gene variants were classified into distinct pathophysiologic pathways, and their potential involvement in PAD pathogenesis was determined. Forty-one publications that examined 44 gene polymorphisms were included. For 37 polymorphisms, the variant form had a functional effect. Twenty-three polymorphisms in 22 potential PAD candidate genes (F2, FGB, MTHFR, ITGB3, ACE, AGT, IL6, CCL2, ICAM1, SELE, MMP9, PPARG, MMP1, ADD1, P2RY12, LIPC, PLA2G7, SCARB1, MMP3, MTTP, LPA, CHRNA3) showed a significant association in individual studies. Eighty-eight percent of the studies had statistical power of less than 50%, and in 15 studies the genotype distribution in the control group did not conform to Hardy-Weinberg equilibrium. Data on 12 polymorphisms (F5 1691 G/A, MTHFR 677C/T, F2 20210 G/A, ITGB3 1565 T/C, ACE I/D, AGT 704C/T, AGT -6G/A, AGT 733C/T, IL6 -174 G/C, MMP9 -1562C/T, ICAM1 1462A/G, CHRNA3 831C/T) were synthesized, and a positive association was found for 3 (IL6 -174 G/C, ICAM1 1462A/G, CHRNA3 831C/T).

Peripheral arterial disease and methylenetetrahydrofolate reductase (MTHFR) C677T mutations: A case-control study and meta-analysis

OBJECTIVE

Hyperhomocysteinaemia is associated with peripheral arterial disease (PAD). There are inter-individual variations in the metabolism of homocysteine because of genetic polymorphisms. This study analyzed the role of one polymorphism that is associated with raised homocysteine, as a risk factor for PAD.

METHODS

This study considered the association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms with the incidence of PAD by performing a case-control study and a cross sectional study of homocysteine levels. We recruited 133 patients with PAD in Norfolk and compared the MTHFR allele distribution with 457 healthy individuals. We also carried out a meta-analysis to place our data within the context of other published studies. We searched Medline, Embase, and Cochrane databases up to March 2008 for any studies on the association between MTHFR C677T polymorphism and PAD.

RESULTS

The MTHFR C677T allele frequencies in the cases and controls were 0.37 and 0.33, and the odds ratios for the association of the 677 T allele or TT genotype with PAD were 1.18 (95% Confidence Interval [CI] 0.89, 1.58) and 1.99 (95% CI 1.09, 3.63). Homozygotes for the MTHFR C677T mutation had higher concentrations of plasma total homocysteine, odds ratio 2.82 (95% CI 1.03, 7.77) compared to homozygotes for the MTHFR 677 CC genotype. Twelve of 72 articles retrieved from the database search reported the prevalence of mutations in PAD patients. A meta-analysis of 9 appropriate studies, including our own, showed that being homozygous for the C677T allele was associated with an increased risk of PAD, pooled odds ratio 1.36 (95% CI 1.09, 1.68).

CONCLUSION

We have found a strong association between raised homocysteine, the TT genotype, and PAD.

[Thrombophilias and peripheral arterial occlusive disease]

Peripheral arterial occlusive disease is a frequent disease due to the classical vascular risk factors such as smoking, diabetes mellitus, dyslipidemia, and hypertension. Despite these risk factors, many thrombophilias (physiological inhibitors defects, Factor V Leiden and 20210A prothrombin gene variant, antiphospholipid antibodies, mild hyperhomocysteinemia 15-30micromol/l) can be evoked in some clinical forms of peripheral arterial occlusive disease. This paper provides a synthesis of the published data about this topic. Screening for these thrombophilias is justified in patients with venous thromboembolic disease, or signs of antiphospholipid syndrome and possibly in different situations such as premature atheroma of lower limbs, chronic ischaemia, evolutive disease despite adapted treatment and revascularisation failures without evident technical explanation. Except for the antiphospholipid syndrome, there is currently no consensus for systematic screening of thrombophilia and treatment in patients with peripheral arterial occlusive disease.

Association of novel risk factors with the ankle brachial index in African American and non-Hispanic white populations

OBJECTIVES

To investigate whether novel risk factors, including C-reactive protein (CRP), fibrinogen, lipoprotein(a) [Lp(a)], and homocysteine levels, are associated with the ankle brachial index (ABI) in African American and non-Hispanic white populations and whether novel risk factors account for ethnic differences in peripheral arterial disease (PAD).

PARTICIPANTS AND METHODS

Between December 2000 and October 2004, original participants in the Genetic Epidemiology Network of Arteriopathy study returned for a second study visit to undergo measurement of risk factors and ABI. The CRP, Lp(a), and homocysteine levels were log transformed to reduce skewness. Multivariable regression analyses were used to assess whether a novel risk factor was associated with ABI after adjustment for conventional risk factors and whether ethnicity was associated with PAD (ABI, <or=0.95) after adjustment for conventional and novel risk factors.

RESULTS

Of 2229 study participants, the ABI was determined in 1395 African American participants (mean +/- SD age, 63 +/- 9 years; 71% women) and 834 white participants (mean +/- SD age, 58 +/- 9 years; 62% women) who belonged to hypertensive sibships. The mean ABI was lower in African American than in white individuals (0.99 +/- 0.1 vs 1.13 +/- 0.1; P < .001). In both ethnic groups, higher levels of CRP, fibrinogen, and homocysteine were each associated with a lower ABI after adjustment for conventional risk factors. In African American participants, the Lp(a) level was also significantly associated with the ABI. African American ethnicity was associated with the presence of PAD after adjustment for conventional risk factors (men: odds ratio [OR], 3.04; 95% confidence interval [CI], 1.80-5.15; women: OR, 2.82; 95% CI, 1.85-4.29), but the risk was significantly attenuated after additional adjustment for novel risk factors (men: OR, 2.11; 95% CI, 1.21-3.70; women: OR, 1.98; 95% CI, 1.26-3.11).

CONCLUSION

Novel risk factors are associated with interindividual variation in ABI in African American and non-Hispanic white populations and partly account for the increased risk of PAD associated with African American ethnicity.

Inherited Thrombophilia in Arterial Disease: A Selective Review

Thrombophilia may be defined as an acquired or congenital abnormality of hemostasis predisposing to thrombosis. Because arterial thrombosis is usually linked with classical risk factors such as smoking, hypertension, dyslipidemia, or diabetes, a thrombophilia workup is usually not considered in case of arterial thrombosis. The most accepted inherited hemostatic abnormalities associated with venous thromboembolism are factor V Leiden (FVL) and factor II (FII) G20210A mutations, as well as deficiencies in antithrombin (AT), protein C (PC), and protein S (PS). This review focuses on the link between these abnormalities and arterial thrombosis. Overall, the association between these genetic disorders and the three main arterial complications (myocardial infarction [MI], ischemic stroke [IS], and peripheral arterial disease [PAD]) is modest. Routine screening for these disorders is therefore not warranted in most cases of arterial complications. However, when such an arterial event occurs in a young person, inherited abnormalities of hemostasis seem to play a role, particularly when associated with smoking or oral contraceptive use. These abnormalities also seem to play a role in the risk of premature occlusion after revascularization procedures. Therefore thrombophilia tests may be informative in a very restricted population with arterial events. Anticoagulants rather than antiplatelet therapy may be preferable for these patients, although this remains to be proven.

MTHFR C677T and A1298C gene polymorphisms and hyperhomocysteinemia as risk factors of diabetic nephropathy in type 2 diabetes patients

Point mutations in methylenetetrahydrofolate reductase (MTHFR) and hyperhomocysteinemia were implicated in the pathogenesis of diabetic nephropathy (DN) in many ethnic groups. This study addressed the association of C677T and A1298C single nucleotide polymorphisms (SNPs) of MTHFR gene with DN in Tunisian type 2 diabetes (T2DM) patients. Study subjects comprised 93 DN patients, 267 patients with normoalbuminuria, and 400 control subjects. C677T and A1298C genotypes were determined by PCR-RFLP analysis, and homocysteine levels were measured by ELISA. A1298C and C677T were highly prevalent among T2DM patients, with allele frequencies of 0.26 and 0.36, respectively. Higher mutant 677T allele and 677C/T and 677T/T genotypes of C677T SNP, but not A1298C SNP, together with 677C/1298A, 677C/1298C, and 677T/1298A haplotypes were seen in DN patients compared to normoalbuminuric patients, (p<0.001). Plasma homocysteine was positively associated with MTHFR 677T/T genotype among the three groups, and was significantly elevated in double heterozygous DN patients but not in normoalbuminuric patients or controls. Logistic regression analysis with DN as dependent variable showed that homocysteine (OR, 1.153) and MTHFR 677T/T (OR, 9.799) were the only variables associated with DN, after adjusting for possible confounding variables. C677T, but not A1298C, SNP, is a risk factor for DN, presumably acting by elevating homocysteine levels.

The effect of novel cardiovascular risk factors on the ethnic-specific odds for peripheral arterial disease in the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVES

The purpose of this study was to: 1) determine the significance and magnitude of associations between novel cardiovascular disease (CVD) risk factors and peripheral arterial disease (PAD) after adjustment for traditional risk factors; and 2) ascertain the extent to which novel risk factors explain the excess or lower risk for PAD in different ethnic groups.

BACKGROUND

Previous reports have found a significant difference in the risk of PAD by ethnic group, with some of the risk difference attributed to different levels of traditional CVD risk factors.

METHODS

A total of 6,814 individuals free of clinically apparent CVD were enrolled in the MESA (Multiethnic Study of Atherosclerosis) and underwent standardized testing for the presence of PAD by the ankle-brachial index. These subjects also had fasting blood drawn for serum cholesterol, glucose, and a number of novel biomarkers for CVD. Non-Hispanic whites were the largest ethnic group (38%), followed by African Americans (28%), Hispanics (22%), and Chinese (12%).

RESULTS

In this cross-sectional analysis, 6,653 subjects with an ankle brachial index <1.40 were analyzed. The mean (SD) age was 62.2 (10.2) years, and 52.9% were women. Interleukin-6, fibrinogen, D-dimer, and homocysteine were significantly associated with PAD after adjustment for traditional CVD risk factors. Compared with non-Hispanic whites and after adjustment for traditional and "novel" risk factors, the odds for PAD were 1.47 (95% confidence interval [CI]: 1.07 to 2.02) times higher in African Americans, while being 0.45 (95% CI: 0.29 to 0.70) and 0.44 (95% CI: 0.24 to 0.78) in Hispanics and Chinese, respectively.

CONCLUSIONS

Ethnic associations with PAD remained significant even after adjustment for traditional and novel risk factors. This suggests that unknown factors may account for the residual ethnic differences in PAD.

Activated protein C-protein C inhibitor complex: A new biological marker for aortic aneurysms

OBJECTIVE

The concentration of the complex between activated protein C (APC) and protein C inhibitor (PCI) is a measure of thrombin generation. We studied whether it can provide information useful for the diagnosis and treatment of arterial vascular disease.

METHODS

Blood was obtained from 429 vascular patients admitted consecutively during September 2004 to March 2005. The APC-PCI complex was measured by using a sandwich immunofluorometric method. The patients were divided into cohorts according to the planned treatment and compared with a control group of healthy individuals.

RESULTS

The APC-PCI complex concentration varied from 0.08 to 2.50 microg/L. In the cohort of patients with aortic aneurysms (n = 78), the median APC-PCI value was 0.45 (10th to 90th percentile, 0.24-1.47), and values were clearly increased compared with all other cohorts (P < .0001). Patients with carotid disease (n = 73) yielded a median of 0.22 (10th to 90th percentile, 0.15-0.48). The median for claudicants (n = 74) was 0.26 microg/L (10th to 90th percentile, 0.15-0.75), which was higher than in those (n = 97) with critical ischemia (0.20; 10th to 90th percentile, 0.13-0.36; P < .0023). The cohort with other forms of atherosclerotic disease (n = 40) had a median of 0.23 (10th to 90th percentile, 0.14-0.42), whereas the value for a cohort of 21 patients with venous disease was 0.19 (10th to 90th percentile, 0.10-0.34). The median was 0.15 (10th to 90th percentile, 0.10-0.23) for the control group (n = 121).

CONCLUSIONS

Patients with atherosclerosis had an increased APC-PCI concentration that corresponded to increased generation of thrombin. Patients with aortic aneurysm had a threefold higher median concentration than the control group. We suggest that this remarkable increase is caused by the local activation of coagulation, and we surmise that APC-PCI measurements can be used as a screening tool to identify patients with aortic aneurysms.

Arterial thrombosis associated with heterozygous factor V Leiden disorder, hyperhomocysteinemia, and peripheral arterial disease: Importance of synergistic factors

A 47-year-old man with heterozygous factor V Leiden disorder and intermittent hyperhomocysteinemia developed spontaneous acute popliteal artery thrombosis. Homocysteine levels were above normal limits at presentation. Intra-arterial thrombolysis was used successfully to treat the acute thrombosis; long-term treatment included anticoagulation, folic acid, and risk factor modification. Although factor V Leiden is strongly associated with deep venous thrombosis, additional cofactors such as hyperhomocysteinemia may predispose to an increased risk of acute arterial thrombosis in areas of pre-existing peripheral arterial disease.