The Nitric Oxide System in Peripheral Artery Disease: Connection with Oxidative Stress and Biopterins

Oxidative stress and vascular dysfunction: Potential therapeutic targets and therapies in peripheral artery disease

Peripheral artery disease (PAD) is the manifestation of atherosclerosis characterized by the accumulation of plaques in the arteries of the lower limbs. Interestingly, growing evidence suggests that the pathology of PAD is multifaceted and encompasses both vascular and skeletal muscle dysfunctions, which contributes to blunted physical capabilities and diminished quality of life. Importantly, it has been suggested that many of these pathological impairments may stem from blunted reduction-oxidation (redox) handling. Of note, in those with PAD, excessive production of reactive oxygen species (ROS) outweighs antioxidant capabilities resulting in oxidative damage, which may have systemic consequences. It has been suggested that antioxidant supplementation may be able to assist in handling ROS. However, the activation of various ROS production sites makes it difficult to determine the efficacy of these antioxidant supplements. Therefore, this review focuses on the common cellular mechanisms that facilitate ROS production and discusses how excessive ROS may impair vascular and skeletal muscle function in PAD. Furthermore, we provide insight for current and potential antioxidant therapies, specifically highlighting activation of the Kelch-like ECH-associated protein 1 (Keap1) - Nuclear Factor Erythroid 2-related factor 2 (Nrf2) pathway as a potential pharmacological therapy to combat ROS accumulation and aid in vascular function, and physical performance in patients with PAD. Altogether, this review provides a better understanding of excessive ROS in the pathophysiology of PAD and enhances our perception of potential therapeutic targets that may improve vascular function, skeletal muscle function, walking capacity, and quality of life in patients with PAD.

The Promoter Polymorphism rs3918226 of the Endothelial Nitric Oxide Synthase Gene as a Novel Susceptibility Marker for Peripheral Artery Disease

BACKGROUND

This pilot study aimed to investigate the association between the single nucleotide polymorphism (SNP) rs3918226 in the promoter of the nitric oxide synthase (NOS3) gene and the risk of peripheral artery disease (PAD).

METHODS

DNA samples from 1,263 unrelated subjects of Slavic origin, including 620 patients with PAD and 643 controls, were genotyped for the SNP rs3918226 using the MassArray-4 system.

RESULTS

The rs3918226 polymorphism was found to be strongly associated with an increased risk of PAD regardless of coronary artery disease, hypertension, or cigarette smoking (odds ratio [OR] = 2.86; 95% confidence interval [CI] 1.89-4.32; Pperm < 0.0001). The SNP-PAD association was almost 3 times stronger in females (OR = 8.31; 95% CI 3.07-22.48) than in males (OR = 1.79; 95% CI 1.10-2.93). SNP rs3918226 was correlated with ankle-brachial index and total plasma cholesterol in patients with PAD (Рperm < 0.05). The NOS3 polymorphism was closely associated with SNPs rs7692387 and rs13139571 in guanylate cyclase soluble subunit alpha-3 (GUCY1A3) to determine the risk of PAD, suggesting that the rs3918226 polymorphism may disrupt signaling in the NO-soluble guanylyl cyclase pathway. Diplotypes with wild-type alleles, such as NOS3 rs3918226-C/C×GUCY1A1 rs7692387G/G and NOS3 rs3918226-C/C×GUCY1A1 rs13139571C/C, showed strong protection against disease risk (false discovery rate ≤ 0.001). Functional SNP annotation revealed that the allele rs3918226-T was associated with decreased expression of NOS3, most strongly in the tibial arteries than in the coronary artery or aorta.

CONCLUSIONS

The present study is the first to show that the rs3918226 polymorphism of NOS3 is a novel susceptibility marker for PAD. Further research in independent populations is necessary to reproduce the association between polymorphism rs3918226 and disease risk.

Dispel some mist on circulating biopterins: measurement, physiological interval and pathophysiological implication

BACKGROUND AND AIMS

Biopterins, including tetrahydrobiopterin (BH4), dihydrobiopterin (BH2), and biopterin (B), were crucial enzyme cofactors in vivo. Despite their recognized clinical significance, there remain notable research gaps and controversies surrounding experimental outcomes. This study aims to clarify the biopterins-related issues, including analytical art, physiological intervals, and pathophysiological implications.

MATERIALS AND METHODS

A novel LC-MS/MS method was developed to comprehensively profile biopterins in plasma, utilizing chemical derivatization and cold-induced phase separation. Subsequently, apparently healthy individuals were enrolled to investigate the physiological ranges. And the relationships between biopterins and biochemical indicators were analyzed to explore the pathophysiological implications.

RESULTS

The developed method was validated as reliable for detecting biopterins across the entire physiological range. Timely anti-oxidation was found to be essential for accurate assessment of biopterins. The observed overall mean ± SDs levels were 3.51 ± 0.94, 1.54 ± 0.48, 2.45 ± 0.84 and 5.05 ± 1.14 ng/mL for BH4, BH2, BH4/BH2 and total biopterins. The status of biopterins showed interesting correlations with age, gender, hyperuricemia and overweight.

CONCLUSION

In conjunction with proper anti-oxidation, the newly developed method enables accurate determination of biopterins status in plasma. The observed physiological intervals and pathophysiological implications provide fundamental yet inspiring support for further clinical researches.

Oxidative damage in the gastrocnemius predicts long-term survival in patients with peripheral artery disease

Patients with peripheral artery disease (PAD) have increased mortality rates and a myopathy in their affected legs which is characterized by increased oxidative damage, reduced antioxidant enzymatic activity and defective mitochondrial bioenergetics. This study evaluated the hypothesis that increased levels of oxidative damage in gastrocnemius biopsies from patients with PAD predict long-term mortality rates. Oxidative damage was quantified as carbonyl adducts in myofibers of the gastrocnemius of PAD patients. The oxidative stress data were grouped into tertiles and the 5-year, all-cause mortality for each tertile was determined by Kaplan-Meier curves and compared by the Modified Peto test. A Cox-regression model was used to control the effects of clinical characteristics. Results were adjusted for age, sex, race, body mass index, ankle-brachial index, smoking, physical activity, and comorbidities. Of the 240 study participants, 99 died during a mean follow up of 37.8 months. Patients in the highest tertile of oxidative damage demonstrated the highest 5-year mortality rate. The mortality hazard ratios (HR) from the Cox analysis were statistically significant for oxidative damage (lowest vs middle tertile; HR = 6.33; p = 0.0001 and lowest vs highest; HR = 8.37; p < 0.0001). Survival analysis of a contemporaneous population of PAD patients identifies abundance of carbonyl adducts in myofibers of their gastrocnemius as a predictor of mortality rate independently of ankle-brachial index, disease stage and other clinical and myopathy-related covariates.

Risk of circulatory diseases associated with proton-pump inhibitors: a retrospective cohort study using electronic medical records in Thailand

Background

Proton-pump inhibitors (PPIs) are prescribed to treat gastric acid-related diseases, while they may also have potential risks to population health. Recent studies suggested that a potential mechanism explaining the association between PPIs and cardiovascular diseases (CVD) includes the inhibition of the nitrate-nitrite-nitric oxide (NO) pathway. However, previous observational studies showed controversial results of the association. In addition, the inhibition of the NO pathway due to PPIs use may lead to peripheral vascular diseases (PVD); however, none of the studies explore the PPI-PVD association. Therefore, this study aimed to evaluate the association of PPIs with circulatory diseases (CVD, ischemic strokes or IS, and PVD).

Methods

We conducted a retrospective hospital-based cohort study from Oct 2010 to Sep 2017 in Songkhla province, Thailand. PPIs and histamine 2-receptor antagonists (H2RAs) prescriptions were collected from electronic pharmacy records, while diagnostic outcomes were retrieved from electronic medical records at Songklanagarind hospital. Patients were followed up with an on-treatment approach. Cox proportional hazard models were applied to measure the association comparing PPIs vs H2RAs after 1:1 propensity-score-matching. Sub-group analysis, multi-bias E-values, and array-based sensitivity analysis for some covariates were used to assess the robustness of associations.

Results

A total of 3,928 new PPIs and 3,928 H2RAs users were included in the 1:1 propensity score-matched cohort. As compared with H2RAs, the association of PPIs with CVD, IS, and PVD, the hazard ratios were 1.76 95% CI = [1.40-2.20] for CVD, 3.53 95% CI = [2.21-5.64] for ischemic strokes, and 17.07 95% CI = [13.82-76.25] for PVD. The association between PPIs and each outcome was significant with medication persistent ratio of over 50%. In addition, the association between PPIs and circulatory diseases was robust to unmeasured confounders (i.e., smoking and alcohol).

Conclusion

PPIs were associated with circulatory diseases, particularly ischemic strokes in this hospital-based cohort study, whereas, the strength of associations was robust to unmeasured confounders.

Oxidative stress and the role of redox signalling in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, underscoring a need to identify pathogenic mechanisms and potential therapeutic targets. Reactive oxygen species (ROS) are derivatives of oxygen molecules that are generated during aerobic metabolism and are involved in a variety of cellular functions that are governed by redox conditions. Low levels of ROS are required for diverse processes, including intracellular signal transduction, metabolism, immune and hypoxic responses, and transcriptional regulation. However, excess ROS can be pathological, and contribute to the development and progression of chronic diseases. Despite evidence linking elevated levels of ROS to CKD development and progression, the use of low-molecular-weight antioxidants to remove ROS has not been successful in preventing or slowing disease progression. More recent advances have enabled evaluation of the molecular interactions between specific ROS and their targets in redox signalling pathways. Such studies may pave the way for the development of sophisticated treatments that allow the selective control of specific ROS-mediated signalling pathways.

Translational Relevance of Advanced Age and Atherosclerosis in Preclinical Trials of Biotherapies for Peripheral Artery Disease

Approximately 6% of adults worldwide suffer from peripheral artery disease (PAD), primarily caused by atherosclerosis of lower limb arteries. Despite optimal medical care and revascularization, many PAD patients remain symptomatic and progress to critical limb ischemia (CLI) and risk major amputation. Delivery of pro-angiogenic factors as proteins or DNA, stem, or progenitor cells confers vascular regeneration and functional recovery in animal models of CLI, but the effects are not well replicated in patients and no pro-angiogenic biopharmacological procedures are approved in the US, EU, or China. The reasons are unclear, but animal models that do not represent clinical PAD/CLI are implicated. Consequently, it is unclear whether the obstacles to clinical success lie in the toxic biochemical milieu of human CLI, or in procedures that were optimized on inappropriate models. The question is significant because the former case requires abandonment of current strategies, while the latter encourages continued optimization. These issues are discussed in the context of relevant preclinical and clinical data, and it is concluded that preclinical mouse models that include age and atherosclerosis as the only comorbidities that are consistently present and active in clinical trial patients are necessary to predict clinical success. Of the reviewed materials, no biopharmacological procedure that failed in clinical trials had been tested in animal models that included advanced age and atherosclerosis relevant to PAD/CLI.

Proton pump inhibitors and gastroprotection in patients treated with antithrombotic drugs: A cardiologic point of view

Aspirin, other antiplatelet agents, and anticoagulant drugs are used across a wide spectrum of cardiovascular and cerebrovascular diseases. A concomitant proton pump inhibitor (PPI) treatment is often prescribed in these patients, as gastrointestinal complications are relatively frequent. On the other hand, a potential increased risk of cardiovascular events has been suggested in patients treated with PPIs; in particular, it has been discussed whether these drugs may reduce the cardiovascular protection of clopidogrel, due to pharmacodynamic and pharmacokinetic interactions through hepatic metabolism. Previously, the concomitant use of clopidogrel and omeprazole or esomeprazole has been discouraged. In contrast, it remains less known whether PPI use may affect the clinical efficacy of ticagrelor and prasugrel, new P2Y12 receptor antagonists. Current guidelines recommend PPI use in combination with antiplatelet treatment in patients with risk factors for gastrointestinal bleeding, including advanced age, concurrent use of anticoagulants, steroids, or non-steroidal anti-inflammatory drugs, and Helicobacter pylori (H. pylori) infection. In patients taking oral anticoagulant with risk factors for gastrointestinal bleeding, PPIs could be recommended, even if their usefulness deserves further data. H. pylori infection should always be investigated and treated in patients with a history of peptic ulcer disease (with or without complication) treated with antithrombotic drugs. The present review summarizes the current knowledge regarding the widespread combined use of platelet inhibitors, anticoagulants, and PPIs, discussing consequent clinical implications.

Effect of Dietary Supplements Which Upregulate Nitric Oxide on Walking and Quality of Life in Patients with Peripheral Artery Disease: A Meta-Analysis

This systematic review pooled evidence from randomised controlled trials (RCTs) on the effectiveness of dietary upregulators of nitric oxide (NO) in improving the walking and quality of life of patients with peripheral artery disease (PAD). RCTs examining the effect of dietary upregulators of NO in patients with PAD were included. The primary outcome was the maximum walking distance. Secondary outcomes were the initial claudication distance, the six-minute walking distance, quality of life, the ankle-brachial pressure index (ABI), adverse events and risk of mortality, revascularisation or amputation. Meta-analyses were performed using random effects models. The risk of bias was assessed using Cochrane's ROB-2 tool. Leave-one-out and subgroup analyses were conducted to assess the effect of individual studies, the risk of bias and intervention type on pooled estimates. Thirty-four RCTs involving 3472 participants were included. Seven trials tested NO donors, nineteen tested antioxidants, three tested NO synthase inducers and five tested enhancers of NO availability. Overall, the dietary supplements significantly improved the initial claudication (SMD 0.34; 95%CI 0.04, 0.64; p = 0.03) but not maximum walking (SMD 0.13; 95%CI -0.17, 0.43; p = 0.39) distances. Antioxidant supplements significantly increased both the maximum walking (SMD 0.36; 95%CI 0.14, 0.59; p = 0.001) and initial claudication (SMD 0.58; 95%CI 0.26, 0.90; p < 0.001) distances. The dietary interventions did not improve the physical function domain of the Short Form-36 (SMD -0.16; 95%CI -0.32, 0.00; p = 0.38), ABI or risk of adverse events, mortality, revascularisation or amputation. Dietary NO upregulators, especially antioxidants, appear to improve the initial claudication distance in patients with PAD. Larger high-quality RCTs are needed to fully examine the benefits and risks of these treatments. PROSPERO Registration: CRD42022256653.

Myoglobinemia, Peripheral Arterial Disease, and Patient Mortality

BACKGROUND

Peripheral arterial disease (PAD) causes leg muscle damage due to inadequate perfusion and increases cardiovascular events and mortality 2- to 3-fold. It is unclear if PAD is a biomarker for high-risk cardiovascular disease or if skeletal muscle injury harms arterial health. The objective of this work is to test if serum myoglobin levels (myoglobinemia) are a marker of PAD, and if so, whether myoglobin impairs vascular health.

STUDY DESIGN

Patient blood samples were collected from PAD and control (no PAD) patients and interrogated for myoglobin concentrations and nitric oxide bioavailability. Patient mortality over time was captured from the medical record. Myoglobin activity was tested on endothelial cells and arterial function.

RESULTS

Myoglobin is a biomarker for symptomatic PAD and was inversely related to nitric oxide bioavailability; 200 ng/mL myoglobin in vitro increased endothelial cell permeability in vitro and decreased nitrate bioavailability. Ex vivo, 100 ng/mL myoglobin increased vascular tone in naive murine aortas approximately 1.5 times, impairing absolute vessel relaxation. In vivo, we demonstrated that myoglobinemia caused impaired flow-mediated dilation in a porcine model. Patients presenting with myoglobin levels of 100 ng/mL or greater had significantly more deaths than those with myoglobin levels of less than 100 ng/mL.

CONCLUSIONS

Using a combination of patient data, in vitro, ex vivo, and in vivo testing, we found that myoglobin is a biomarker for symptomatic PAD and a potent regulator of arterial health that can increase vascular tone, increase vascular permeability, and cause endothelial dysfunction, all of which may contribute to the vulnerability of PAD patients to cardiovascular events and death.

Endothelial dysfunction due to eNOS uncoupling: molecular mechanisms as potential therapeutic targets

Nitric oxide (NO) is one of the most important molecules released by endothelial cells, and its antiatherogenic properties support cardiovascular homeostasis. Diminished NO bioavailability is a common hallmark of endothelial dysfunction underlying the pathogenesis of the cardiovascular disease. Vascular NO is synthesized by endothelial nitric oxide synthase (eNOS) from the substrate L-arginine (L-Arg), with tetrahydrobiopterin (BH₄) as an essential cofactor. Cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, aging, or smoking increase vascular oxidative stress that strongly affects eNOS activity and leads to eNOS uncoupling. Uncoupled eNOS produces superoxide anion (O₂^-) instead of NO, thus becoming a source of harmful free radicals exacerbating the oxidative stress further. eNOS uncoupling is thought to be one of the major underlying causes of endothelial dysfunction observed in the pathogenesis of vascular diseases. Here, we discuss the main mechanisms of eNOS uncoupling, including oxidative depletion of the critical eNOS cofactor BH₄, deficiency of eNOS substrate L-Arg, or accumulation of its analog asymmetrical dimethylarginine (ADMA), and eNOS S-glutathionylation. Moreover, potential therapeutic approaches that prevent eNOS uncoupling by improving cofactor availability, restoration of L-Arg/ADMA ratio, or modulation of eNOS S-glutathionylation are briefly outlined.

Endothelial cell dysfunction: Implications for the pathogenesis of peripheral artery disease

Peripheral artery disease (PAD) is caused by occluded or narrowed arteries that reduce blood flow to the lower limbs. The treatment focuses on lifestyle changes, management of modifiable risk factors and vascular surgery. In this review we focus on how Endothelial Cell (EC) dysfunction contributes to PAD pathophysiology and describe the largely untapped potential of correcting endothelial dysfunction. Moreover, we describe current treatments and clinical trials which improve EC dysfunction and offer insights into where future research efforts could be made. Endothelial dysfunction could represent a target for PAD therapy.

Early ascorbic acid administration prevents vascular endothelial cell damage in septic mice

Oxidation of BH₄, a cofactor of nitric oxide synthase (NOS), produces reactive oxygen species (ROS) through uncoupling of NOS and affects vascular endothelial dysfunction. Ascorbic acid (AsA) inhibits the oxidation of BH₄ and reduces ROS. However, the kinetic changes of BH₄ in sepsis and its effect on the kinetic changes in AsA administration therapy, as well as the appropriate timing of AsA administration for AsA therapy to be effective, are unclear. Mice with sepsis, induced by cecal ligation and puncture (CLP), were examined for the effect of AsA administration (200 mg/kg) on vascular endothelial cell dysfunction at two administration timings: early group (AsA administered immediately after CLP) and late group (AsA administered 12 h after CLP). Survival rates were compared between the early and late administration groups, and vascular endothelial cell damage, indicated by the dihydrobiopterin/tetrahydrobiopterin ratio, serum syndecan-1, and endothelial nitric oxide synthase, as well as liver damage, were examined. The early group showed significantly improved survival compared to the non-treatment group (p < 0.05), while the late group showed no improved survival compared to the non-treatment group. Compared to the non-treated group, the early AsA group showed less oxidation of BH₄ in sepsis. Syndecan1, a marker of vascular endothelial cell damage, was less elevated and organ damage was reduced in the early AsA-treated group. In septic mice, early AsA administration immediately after CLP may protect vascular endothelial cells by inhibiting BH₄ oxidation, thereby reducing organ dysfunction and improving survival.

The Genetic Architecture of the Etiology of Lower Extremity Peripheral Artery Disease: Current Knowledge and Future Challenges in the Era of Genomic Medicine

Lower extremity artery disease (LEAD), caused by atherosclerotic obstruction of the arteries of the lower limb extremities, has exhibited an increase in mortality and morbidity worldwide. The phenotypic variability of LEAD is correlated with its complex, multifactorial etiology. In addition to traditional risk factors, it has been shown that the interaction between genetic factors (epistasis) or between genes and the environment potentially have an independent role in the development and progression of LEAD. In recent years, progress has been made in identifying genetic variants associated with LEAD, by Genome-Wide Association Studies (GWAS), Whole Exome Sequencing (WES) studies, and epigenetic profiling. The aim of this review is to present the current knowledge about the genetic factors involved in the etiopathogenic mechanisms of LEAD, as well as possible directions for future research. We analyzed data from the literature, starting with candidate gene-based association studies, and then continuing with extensive association studies, such as GWAS and WES. The results of these studies showed that the genetic architecture of LEAD is extremely heterogeneous. In the future, the identification of new genetic factors will allow for the development of targeted molecular therapies, and the use of polygenic risk scores (PRS) to identify individuals at an increased risk of LEAD will allow for early prophylactic measures and personalized therapy to improve their prognosis.

Redox Potential Correlates with Changes in Metabolite Concentrations Attributable to Pathways Active in Oxidative Stress Response in Swine Traumatic Shock

INTRODUCTION

Oxidation-reduction (redox) reactions, and the redox potential (RP) that must be maintained for proper cell function, lie at the heart of physiologic processes in critical illness. Imbalance in RP reflects systemic oxidative stress, and whole blood RP measures have been shown to correlate with oxygen debt level over time in swine traumatic shock. We hypothesize that RP measures reflect changing concentrations of metabolites involved in oxidative stress. To test this hypothesis, we compared blood and urine RP with concentrations of multiple metabolites in a swine traumatic shock model to identify meaningful RP-metabolite relationships.

METHODS

Seven swine were subjected to traumatic shock. Mixed venous (MV) RP, urine RP, and concurrent MV and urine metabolite concentrations were assessed at baseline, max O 2 Debt (80 mL/kg), end resuscitation, and 2 h post-resuscitation. RP was measured at collection via open circuit potential using nanoporous gold electrodes with Ag/AgCl reference and a ParstatMC potentiostat. Metabolite concentrations were measured by quantitative 1 H-NMR spectroscopy. MV and urine RP were compared with time-matched metabolites across all swine. LASSO regression with leave-one-out cross validation was used to determine meaningful RP/metabolite relationships. Metabolites had to maintain magnitude and direction of coefficients across 6 or more swine to be considered as having a meaningful relationship. KEGG IDs of these metabolites were uploaded into Metscape for pathway identification and evaluation for physiologic function.

RESULTS

Meaningful metabolite relationships (and mean coefficients across cross-validation folds) with MV RP included: choline (-6.27), ATP (-4.39), glycine (5.93), ADP (1.84), glucose (15.96), formate (-13.09), pyruvate (6.18), and taurine (-7.18). Relationships with urine RP were: betaine (4.81), urea (4.14), glycine (-2.97), taurine (10.32), 3-hydroxyisobutyrate (-7.67), N-phenylacetylglycine, PAG (-14.52), hippurate (12.89), and formate (-5.89). These meaningful metabolites were found to scavenge extracellular peroxide (pyruvate), inhibit ROS and activate cellular antioxidant defense (taurine), act as indicators of antioxidant mobilization against oxidative stress (glycine + PAG), and reflect renal hydroxyl radical trapping (hippurate), among other activities.

CONCLUSIONS

Real-time RP measures demonstrate significant relationships with metabolites attributable to metabolic pathways involved in systemic responses to oxidative stress, as well as those involved in these processes. These data support RP measures as a feasible, biologically relevant marker of oxidative stress. As a direct measure of redox state, RP may be a useful biomarker and clinical tool in guiding diagnosis and therapy in states of increased oxidative stress and may offer value as a marker for organ injury in these states as well.

Endothelial colony forming cells' tetrahydrobiopterin level in coronary artery disease patients and its association with circulating endothelial progenitor cells

Endothelial colony forming cells (ECFCs) participate in neovascularization. Endothelial nitric oxide synthase (eNOS) derived NO· helps in homing of endothelial progenitor cells (EPCs) at the site of vascular injury. The enzyme cofactor tetrahydrobiopterin (BH4) stabilizes the catalytic active state of eNOS. Association of intracellular ECFCs biopterins and ratio of reduced to oxidized biopterin (BH4:BH2) with circulatory EPCs and ECFCs functionality have not been studied. We investigated ECFCs biopterin levels and its association with circulatory EPCs as well as ECFCs proliferative potential in terms of day of appearance in culture. Circulatory EPCs were enumerated by flowcytometry in 53 coronary artery disease (CAD) patients and 42 controls. ECFCs were cultured, characterized, and biopterin levels assessed by high performance liquid chromatography. Appearance of ECFCs' colony and their number were recorded. Circulatory EPCs were significantly lower in CAD and ECFCs appeared in 56% and 33% of CAD and control subjects, respectively. Intracellular BH4 and BH4:BH2 were significantly reduced in CAD. BH4:BH2 was positively correlated with circulatory EPCs (p = 0.01), and negatively with day of appearance of ECFCs (p = 0.04). Circulatory EPCs negatively correlated with ECFCs appearance (p = 0.02). These findings suggest the role of biopterins in maintaining circulatory EPCs and functional integrity of ECFCs.

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.

Update on the pathophysiology and medical treatment of peripheral artery disease

Approximately 6% of adults worldwide have atherosclerosis and thrombosis of the lower limb arteries (peripheral artery disease (PAD)) and the prevalence is rising. PAD causes leg pain, impaired health-related quality of life, immobility, tissue loss and a high risk of major adverse events, including myocardial infarction, stroke, revascularization, amputation and death. In this Review, I describe the pathophysiology, presentation, outcome, preclinical research and medical management of PAD. Established treatments for PAD include antithrombotic drugs, such as aspirin and clopidogrel, and medications to treat dyslipidaemia, hypertension and diabetes mellitus. Randomized controlled trials have demonstrated that these treatments reduce the risk of major adverse events. The drug cilostazol, exercise therapy and revascularization are the current treatment options for the limb symptoms of PAD, but each has limitations. Novel therapies to promote collateral and new capillary growth and treat PAD-related myopathy are under investigation. Methods to improve the implementation of evidence-based medical management, novel drug therapies and rehabilitation programmes for PAD-related pain, functional impairment and ischaemic foot disease are important areas for future research.

MicroRNAs in peripheral artery disease: potential biomarkers and pathophysiological mechanisms

Peripheral artery disease (PAD) is a disease of atherosclerosis in the lower extremities. PAD carries a massive burden worldwide, while diagnosis and treatment options are often lacking. One of the key points of research in recent years is the involvement of microRNAs (miRNAs), which are short 20-25 nucleotide single-stranded RNAs that can act as negative regulators of post-transcriptional gene expression. Many of these miRNAs have been discovered to be misregulated in PAD patients, suggesting a potential utility as biomarkers for PAD diagnosis. miRNAs have also been shown to play an important role in many different pathophysiological aspects involved in the initiation and progression of the disease including angiogenesis, hypoxia, inflammation, as well as other cellular functions like cell proliferation and migration. The research on miRNAs in PAD has the potential to lead to a whole new class of diagnostic tools and treatments.

Recent Insights into the Nutritional Antioxidant Therapy in Prevention and Treatment of Diabetic Vascular Complications - A comprehensive Review

Diabetes mellitus (DM) and DM-induced vascular complications are a significant global healthcare problem causing a decrease in patient quality of life. The main reason for the disability and mortality of patients is rapidly progressing micro- and macroangiopathies. Currently, free radical oxidation is recognized as one of the main mechanisms in the development of DM and associated complications. Under normal physiological conditions, the level of free radicals and antioxidant defense capabilities is balanced. However, imbalance occurs between the antioxidant defense system and pro-oxidants during chronic hyperglycemia and may invoke formation of excess free radicals, leading to activation of lipid peroxidation and accumulation of highly toxic products of free radical oxidation. This is accompanied by varying degrees of insulin deficiency and insulin resistance in DM patients. Simultaneously with the activation of free radical generation, a decrease in the activity of antioxidant defense factors (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, vitamins C and E) and an acceleration of diabetic complications is seen. Therefore, we hypothesize that antioxidants may play a positive role in the treatment of DM patients to prevent DM-induced vascular complications. However this has not been sufficiently studied. In this review, we discuss recent insights into the potential underlying mechanisms of oxidative stress induced diabetic complications, and implications of antioxidants in mitigation of DM-induced vascular complications.

Phytochemicals as Therapeutic Interventions in Peripheral Artery Disease

Peripheral artery disease (PAD) affects over 200 million people worldwide, resulting in significant morbidity and mortality, yet treatment options remain limited. Among the manifestations of PAD is a severe functional disability and decline, which is thought to be the result of different pathophysiological mechanisms including oxidative stress, skeletal muscle pathology, and reduced nitric oxide bioavailability. Thus, compounds that target these mechanisms may have a therapeutic effect on walking performance in PAD patients. Phytochemicals produced by plants have been widely studied for their potential health effects and role in various diseases including cardiovascular disease and cancer. In this review, we focus on PAD and discuss the evidence related to the clinical utility of different phytochemicals. We discuss phytochemical research in preclinical models of PAD, and we highlight the results of the available clinical trials that have assessed the effects of these compounds on PAD patient functional outcomes.