Endothelial dysfunction: a key to the pathophysiology and natural history of peripheral arterial disease?

Role of long noncoding RNAs in diabetes-associated peripheral arterial disease

Diabetes mellitus (DM) is a metabolic disease that heightens the risks of many vascular complications, including peripheral arterial disease (PAD). Various types of cells, including but not limited to endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and macrophages (MΦs), play crucial roles in the pathogenesis of DM-PAD. Long non-coding RNAs (lncRNAs) are epigenetic regulators that play important roles in cellular function, and their dysregulation in DM can contribute to PAD. This review focuses on the developing field of lncRNAs and their emerging roles in linking DM and PAD. We review the studies investigating the role of lncRNAs in crucial cellular processes contributing to DM-PAD, including those in ECs, VSMCs, and MΦ. By examining the intricate molecular landscape governed by lncRNAs in these relevant cell types, we hope to shed light on the roles of lncRNAs in EC dysfunction, inflammatory responses, and vascular remodeling contributing to DM-PAD. Additionally, we provide an overview of the research approach and methodologies, from identifying disease-relevant lncRNAs to characterizing their molecular and cellular functions in the context of DM-PAD. We also discuss the potential of leveraging lncRNAs in the diagnosis and therapeutics for DM-PAD. Collectively, this review provides a summary of lncRNA-regulated cell functions contributing to DM-PAD and highlights the translational potential of leveraging lncRNA biology to tackle this increasingly prevalent and complex disease.

Integrated metabolomics and transcriptomics analysis reveals the mechanism of Tangbi capsule for diabetic lower extremities arterial disease

Objective

Tangbi capsule (TBC) is a traditional Chinese medicine prescription, which has the potential to improve the vascular insufficiency of lower extremities and limb numbness in diabetes. However, the potential mechanism remains unknown. This study aims to investigate the pharmacological effects and mechanism of TBC on rats with diabetic lower extremities arterial disease (LEAD).

Methods

The mechanism of TBC on diabetic LEAD was investigated through metabolomics and transcriptomics analysis, and the main components of TBC were determined by mass spectrometry. The efficacy and mechanism of TBC on diabetic LEAD rats were investigated through in vitro experiments, histopathology, blood flow monitoring, western blot, and real-time polymerase chain reaction.

Results

Mass spectrometry analysis identified 31 active chemical components in TBC including (2R)-2,3-Dihydroxypropanoic acid, catechin, citric acid, miquelianin, carminic acid, salicylic acid, formononetin, etc. In vitro analysis showed that TBC could reduce endothelial cell apoptosis and promote angiogenesis. Histopathological analysis showed that TBC led to an obvious improvement in diabetic LEAD as it improved fibrous tissue proliferation and reduced arterial wall thickening. In addition, TBC could significantly increase the expression levels of HIF-1α, eNOS, and VEGFA proteins and genes while reducing that of calpain-1 and TGF-β, suggesting that TBC can repair vascular injury. Compared with the model group, there were 47 differentially expressed genes in the whole blood of TBC groups, with 25 genes upregulated and 22 downregulated. Eighty-seven altered metabolites were identified from the serum samples. Combining the changes in differentially expressed genes and metabolites, we found that TBC could regulate arginine biosynthesis, phenylalanine metabolism, pyrimidine metabolism, arachidonic acid metabolism, pyrimidine metabolism, arachidonic acid metabolism, nucleotide metabolism, vitamin B6 metabolism and other metabolic pathways related to angiogenesis, immune-inflammatory response, and cell growth to improve diabetic LEAD.

Conclusion

TBC improved vascular endothelial injury, apoptosis, lipid accumulation, liver and kidney function, and restored blood flow in the lower extremities of diabetic LEAD rats. The mechanism of TBC in the treatment of diabetic LEAD may be related to the modulation of inflammatory immunity, lipid metabolism, and amino acid metabolism. This study presented preliminary evidence to guide the use of TBC as a therapy option for diabetic LEAD.

Polyvascular Disease Influences Long-Term Cardiovascular Morbidity in Carotid Endarterectomy

INTRODUCTION/OBJECTIVE

Carotid stenosis (CS) is an important cause of ischemic stroke. Secondary prevention lies in performing a carotid endarterectomy (CEA) procedure, the recommended treatment in most cases. When 2 or more vascular regions are simultaneously affected by atherosclerosis, mainly the carotid arteries, coronary arteries, or limb arteries, a multivessel disease polyvascular disease (PVD) is present. This study aims to assess the potential role of PVD as a long-term predictor of major adverse cardiovascular events (MACE) and all-cause mortality in patients submitted to CEA.

METHODS

From January 2012 to December 2021, patients submitted to CEA for carotid stenosis in a tertiary care and referral center were eligible from a prospective database. A posthoc survival analysis was performed using the Kaplan-Meier survival curve method. The primary outcome was the incidence of long-term MACE and all-cause mortality. Secondary outcomes included acute myocardial infarction (AMI), major adverse limb events (MALE), stroke, and acute heart failure (AHF).

RESULTS

A total of 207 patients were enrolled, with a median follow-up of 63 months. The mean age was 70.4 ± 8.9, and 163 (78.7%) were male. There were 65 (31.4%) patients that had 2 arterial vascular territories affected, and 29 (14.0%) patients had PVD in 3 arterial beds. On multivariable analysis, both MACE and all-cause mortality had as independent risk factors age (aHR 1.039, P = 0.003; aHR 1.041, P = 0.019), chronic kidney disease (aHR 2.524, P = 0.003; aHR 3.377, P < 0.001) and PVD2 (aHR 3.381, P < 0.001; aHR 2.665, P = 0.013). PVD1 was only associated with MACE as a statistically significant risk factor (aHR 2.531, 1.439-4.450, P < 0.001).

CONCLUSIONS

PVD in patients with cerebrovascular disease (CVD) was revealed to carry a 2-fold increased risk for all-cause mortality and MACE during long-term follow-up. PVD may be a simple yet valuable tool in predicting all-cause mortality, MACE, AMI, and MALE after CEA.

Association of Urine Albumin to Creatinine Ratio With Cardiovascular Outcomes in Patients With Type 2 Diabetes Mellitus

CONTEXT

The urinary albumin to creatinine ratio (UACR) is a widely used indicator of albuminuria and has predictive value for adverse cardiovascular events.

OBJECTIVE

To evaluate the correlation between the UACR and the risk of developing major adverse cardiovascular events (MACEs) and total mortality in patients with type 2 diabetes mellitus (T2DM).

METHODS

This post hoc analysis included 10 171 participants from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study and the ACCORD follow-up study (ACCORDION) with baseline UACR data. The natural logarithm (ln) of each UACR measurement was calculated. Univariate and multivariate Cox proportional hazard regression analyses were conducted to examine the association between the UACR and the risk of MACEs and total mortality. The additional predictive value of UACR was further evaluated. Similar methods were used to analyze the correlation between the UACR and MACEs and total mortality within the normal range.

RESULTS

During a median follow-up period of 8.83 years, 1808 (17.78%) participants experienced MACEs, and there were 1934 (19.01%) total deaths. After adjusting for traditional cardiovascular risk factors, the multivariate analysis revealed a significant association between the UACR and the risk of MACEs and total mortality. The inclusion of UACR in the conventional risk model enhanced the predictive efficacy for MACEs and total mortality.

CONCLUSION

An elevated UACR is associated with a higher risk of MACEs and total mortality in patients with T2DM, even when it falls within the normal range. The UACR improves prediction of MACE and total mortality risk in patients with T2DM.

Activation of the Aryl Hydrocarbon Receptor in Endothelial Cells Impairs Ischemic Angiogenesis in Chronic Kidney Disease

Rationale

Chronic kidney disease (CKD) is a strong risk factor for peripheral artery disease (PAD) that is associated with worsened clinical outcomes. CKD leads to accumulation of tryptophan metabolites that associate with adverse limb events in PAD and are ligands of the aryl hydrocarbon receptor (AHR) which may regulate ischemic angiogenesis.

Objectives

To test if endothelial cell-specific deletion of the AHR (AHRecKO) alters ischemic angiogenesis and limb function in mice with CKD subjected to femoral artery ligation.

Findings

Male AHRecKO mice with CKD displayed better limb perfusion recovery and enhanced ischemic angiogenesis compared to wildtype mice with CKD. However, the improved limb perfusion did not result in better muscle performance. In contrast to male mice, deletion of the AHR in female mice with CKD had no impact on perfusion recovery or angiogenesis. Using primary endothelial cells from male and female mice, treatment with indoxyl sulfate uncovered sex-dependent differences in AHR activating potential and RNA sequencing revealed wide ranging sex-differences in angiogenic signaling pathways.

Conclusion

Endothelium-specific deletion of the AHR improved ischemic angiogenesis in male, but not female, mice with CKD. There are sex-dependent differences in Ahr activating potential within endothelial cells that are independent of sex hormones.

Association between depression and macrovascular disease: a mini review

Depression and macrovascular diseases are globally recognized as significant disorders that pose a substantial socioeconomic burden because of their associated disability and mortality. In addition, comorbidities between depression and macrovascular diseases have been widely reported in clinical settings. Patients afflicted with coronary artery disease, cerebrovascular disease or peripheral artery disease exhibit an elevated propensity for depressive symptoms. These symptoms, in turn, augment the risk of macrovascular diseases, thereby reflecting a bidirectional relationship. This review examines the physiological and pathological mechanisms behind comorbidity while also examining the intricate connection between depression and macrovascular diseases. The present mechanisms are significantly impacted by atypical activity in the hypothalamic-pituitary-adrenal axis. Elevated levels of cortisol and other hormones may disrupt normal endothelial cell function, resulting in vascular narrowing. At the same time, proinflammatory cytokines like interleukin-1 and C-reactive protein have been shown to disrupt the normal function of neurons and microglia by affecting blood-brain barrier permeability in the brain, exacerbating depressive symptoms. In addition, platelet hyperactivation or aggregation, endothelial dysfunction, and autonomic nervous system dysfunction are important comorbidity mechanisms. Collectively, these mechanisms provide a plausible physiological basis for the interplay between these two diseases. Interdisciplinary collaboration is crucial for future research aiming to reveal the pathogenesis of comorbidity and develop customised prevention and treatment strategies.

Traditional Chinese medicine body constitution predicts new-onset diabetic albuminuria in patients with type 2 diabetes: Taichung diabetic body constitution prospective cohort study

This prospective cohort study explored whether body constitution (BC) independently predicts new-onset albuminuria in persons with type 2 diabetes mellitus (T2DM) enrolled in the diabetes care management program (DCMP) of a medical center, providing evidence of integrating traditional Chinese medicine into DCMP for improving care quality. Persons with T2DM (n = 426) originally without albuminuria enrolled in DCMP were recruited in 2010 and were then followed up to 2015 for detecting new-onset albuminuria. The participants received urinalysis and blood test annually. Albuminuria was determined by an elevated urinary albumin/creatinine ratio (≥ 30 µg/mg), and poor glucose control was defined as Glycosylated hemoglobin above or equal to 7%. BC type (Yin deficiency, Yang deficiency, and phlegm stasis) was assessed using a well-validated body constitution questionnaire at baseline. Risk factors for albuminuria (sociodemographic factors, diabetes history, lifestyle behaviors, lipid profile, blood pressure, and kidney function) were also recorded. Hazard ratios (HR) of albuminuria for BC were estimated using multivariate Cox proportional hazards model. During the 4-year follow-up period, albuminuria occurred in 30.5% of participants (n = 130). The HR indicated that Yin deficiency was significantly associated with an increased risk of new-onset albuminuria in persons with T2DM and good glucose control after adjustment for other risk factors (HR = 2.09; 95% confidence interval = 1.05-4.17, P = .04), but not in those with poor glucose control. In persons with T2DM and poor glucose control, phlegm stasis was also significantly associated with a higher risk of albuminuria (2.26; 1.03-4.94, P = .04) after multivariate adjustment, but not in those with good glucose control. In addition to already-known risk factors, BC is an independent and significant factor associated with new-onset albuminuria in persons with T2DM. Our results imply Yin deficiency and phlegm stasis interacting with glucose control status may affect new-onset albuminuria in persons with T2DM.

Inflammatory and Prothrombotic Biomarkers, DNA Polymorphisms, MicroRNAs and Personalized Medicine for Patients with Peripheral Arterial Disease

Classical risk factors play a major role in the initiation and development of atherosclerosis. However, the estimation of risk for cardiovascular events based only on risk factors is often insufficient. Efforts have been made to identify biomarkers that indicate ongoing atherosclerosis. Among important circulating biomarkers associated with peripheral arterial disease (PAD) are inflammatory markers which are determined by the expression of different genes and epigenetic processes. Among these proinflammatory molecules, interleukin-6, C-reactive protein, several adhesion molecules, CD40 ligand, osteoprotegerin and others are associated with the presence and progression of PAD. Additionally, several circulating prothrombotic markers have a predictive value in PAD. Genetic polymorphisms significantly, albeit moderately, affect risk factors for PAD via altered lipoprotein metabolism, diabetes, arterial hypertension, smoking, inflammation and thrombosis. However, most of the risk variants for PAD are located in noncoding regions of the genome and their influence on gene expression remains to be explored. MicroRNAs (miRNAs) are single-stranded, noncoding RNAs that modulate gene expression at the post-transcriptional level. Patterns of miRNA expression, to some extent, vary in different atherosclerotic cardiovascular diseases. miRNAs appear to be useful in the detection of PAD and the prediction of progression and revascularization outcomes. In conclusion, taking into account one’s predisposition to PAD, i.e., DNA polymorphisms and miRNAs, together with circulating inflammatory and coagulation markers, holds promise for more accurate prediction models and personalized therapeutic options.

Natural Activators of Autophagy Increase Maximal Walking Distance and Reduce Oxidative Stress in Patients with Peripheral Artery Disease: A Pilot Study

Trehalose, spermidine, nicotinamide, and polyphenols have been shown to display pro-autophagic and antioxidant properties, eventually reducing cardiovascular and ischemic complications. This study aimed to investigate whether a mixture of these components improves maximal walking distance (MWD) in peripheral artery disease (PAD) patients. Nitrite/nitrate (NOx), endothelin-1, sNOX2-dp, H2O2 production, H2O2 break-down activity (HBA), ATG5 and P62 levels, flow-mediated dilation (FMD), and MWD were evaluated in 20 PAD patients randomly allocated to 10.5 g of mixture or no-treatment in a single-blind study. The above variables were assessed at baseline and 60 days after mixture ingestion. Compared with baseline, mixture intake significantly increased MWD (+91%; p < 0.01) and serum NOx (+96%; p < 0.001), whereas it significantly reduced endothelin-1 levels (−30%, p < 0.01). Moreover, mixture intake led to a remarkable reduction in sNOX2dp (−31%, p < 0.05) and H2O2 (−40%, p < 0.001) and potentiated antioxidant power (+110%, p < 0.001). Finally, mixture ingestion restored autophagy by increasing ATG5 (+43%, p < 0.01) and decreasing P62 (−29%, p < 0.05). No changes in the above-mentioned variables were observed in the no-treatment group. The treatment with a mixture of trehalose, spermidine, nicotinamide, and polyphenols improves MWD in PAD patients, with a mechanism possibly related to NOX2-mediated oxidative stress downregulation and autophagic flux upregulation. Clinical Trial Registration unique identifier: NCT04061070.

Impact of Anticoagulation/Antiplatelet Therapy on Femoropopliteal Bypass Graft Outcomes

INTRODUCTION

Anticoagulant and antiplatelet (AC/AP) medications have been reported to improve bypass graft patency, however, the optimal AC/AP strategy remains unclear in the heterogenous peripheral artery disease population.

METHODS

A multi-institutional retrospective review utilizing the Research Patient Data Registry (RPDR) database from 1995-2020 was performed for all patients who underwent femoropopliteal bypass procedures. Electronic medical records were used to obtain demographic information, comorbidities, smoking status, operative details (bypass target), postoperative AC/AP medications, postoperative complications, and long-term outcomes were reviewed for the cohort. Cox proportional hazards model was used to determine independent risk factors for major adverse limb events (MALE) following bypass. MALE was defined as reintervention for patency or major amputation of index limb (above- or below-knee amputation).

RESULTS

A total of 1421 patients underwent femoropopliteal bypass between 1995-2020 throughout five institutions included in this study. Complete data was available for 1292/1421 (90.9%) patients. Indications for bypass included intermittent claudication (21.4%), rest pain (30.3%), tissue loss (33.5%), and non-atherosclerotic disease (14.8%). Distal bypass targets comprised above-knee (38.6%) and below-knee (61.4%) popliteal arteries. Patients were divided into six groups based on postoperative AC/AP use including none (n=57, 4.4%), mono-antiplatelet therapy (MAPT) (n=587, 45.4%), dual antiplatelet therapy (DAPT) (n=214, 16.6%), AC alone (n=73, 5.7%), AC+MAPT (n=319, 24.7%), and AC+DAPT (n=42, 3.3%). Postoperative bleeding complications were low for both hematoma (3.7%) and pseudoaneurysm (0.7%). There was no difference in bleeding complications across AC/AP groups (hematoma p=0.61, pseudoaneurysm p=0.31). After adjusting for patient factors, below-knee bypass target (HR 1.25 [1.04-1.52], p=0.019) and bypass for tissue loss (HR 1.40 [1.04-1.88], p=0.028) were independent predictors for MALE. Great saphenous vein conduit trended towards protection for MALE, compared with prosthetic grafts (HR 0.84 [0.70-1.01], p=0.06). No AC/AP regimen was associated with of MALE, even stratifying by above-knee and below-knee bypass cohorts. Median follow-up period was two years.

CONCLUSIONS

Among patients undergoing femoropopliteal bypass grafting, no combination of anticoagulation or antiplatelet medications was associated with improved graft patency, however, a below-knee target and tissue loss were associated with adverse limb events. Anticoagulation and antiplatelet regimen may be individualized post-bypass with regard to other concomitant medical comorbidities.

Metabolomics of peripheral artery disease

The science of metabolomics has emerged as a novel tool for studying changes in metabolism that accompany different disease states. Several studies have applied this evolving field to the study of various cardiovascular disease states, which has led to improved understanding of metabolic changes that underlie heart failure and ischemic heart disease. A significant amount of progress has also been made in the identification of novel biomarkers of cardiovascular disease. Another common atherosclerotic disease, peripheral artery disease (PAD) affects arteries of the lower extremities. Although certain aspects of the disease pathophysiology overlap with other cardiovascular diseases in general, PAD patients suffer unique manifestations that lead to significant morbidity and mortality as well as severe functional limitations. Furthermore, because over half of PAD patients are asymptomatic, there is a need for improved diagnostic and screening methods. Identification of metabolites associated with the disease may thus be a promising approach for PAD. However, PAD remains highly understudied. In this chapter, we discuss the application of metabolomics to the study of PAD.

Systemic infection exacerbates cerebrovascular dysfunction in Alzheimer's disease

We studied the effects of systemic infection on brain cytokine level and cerebral vascular function in Alzheimer's disease and vascular dementia, in superior temporal cortex (Brodmann area 22) from Alzheimer's disease patients (n = 75), vascular dementia patients (n = 22) and age-matched control subjects (n = 46), stratified according to the presence or absence of terminal systemic infection. Brain cytokine levels were measured using Mesoscale Discovery Multiplex Assays and markers of cerebrovascular function were assessed by ELISA. Multiple brain cytokines were elevated in Alzheimer's disease and vascular dementia: IL-15 and IL-17A were maximally elevated in end-stage Alzheimer's disease (Braak tangle stage V-VI) whereas IL-2, IL-5, IL12p40 and IL-16 were highest in intermediate Braak tangle stage III-IV disease. Several cytokines (IL-1β, IL-6, TNF-α, IL-8 and IL-15) were further raised in Alzheimer's disease with systemic infection. Cerebral hypoperfusion-indicated by decreased MAG:PLP1 and increased vascular endothelial growth factor-A (VEGF)-and blood-brain barrier leakiness, indicated by raised levels of fibrinogen, were exacerbated in Alzheimer's disease and vascular dementia patients, and also in non-dementia controls, with systemic infection. Amyloid-β42 level did not vary with infection or in association with brain cytokine levels. In controls, cortical perfusion declined with increasing IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-12p70, IL-13 and tumour necrosis factor-α (TNF-α) but these relationships were lost with progression of Alzheimer's disease, and with infection (even in Braak stage 0-II brains). Cortical platelet-derived growth factor receptor-β (PDGFRβ), a pericyte marker, was reduced, and endothelin-1 (EDN1) level was increased in Alzheimer's disease; these were related to amyloid-β level and disease progression and only modestly affected by systemic infection. Our findings indicate that systemic infection alters brain cytokine levels and exacerbates cerebral hypoperfusion and blood-brain barrier leakiness associated with Alzheimer's disease and vascular dementia, independently of the level of insoluble amyloid-β, and highlight systemic infection as an important contributor to dementia, requiring early identification and treatment in the elderly population.

Effect of Sex on Vascular Adaptations to Isometric Handgrip Training in Elderly Patients with Peripheral Artery Disease: A Randomized Controlled Trial

BACKGROUND

Isometric handgrip training (IHT) promotes vascular adaptations in different populations.

AIMS

We assessed the sex differences in vascular adaptations of IHT in a sample of older adults with symptomatic peripheral artery disease (PAD).

METHODS

Fifty-three older patients with symptomatic PAD (6 women and 13 men in IHT and 13 women and 21 men in the control group) participated in this study. The IHT group performed 3 sessions per week, for 8 weeks, consisting of 4 sets of isometric contractions for 2 min at 30% of maximum voluntary contraction and a 4-min interval between sets. The control group received a compression ball in order to minimize the placebo effects, representing sham training. Blood flow and brachial flow-mediated dilation were analyzed at before and after 8 weeks of intervention. We compared the responses (Δ = post-pre values) of each group (women control, women IHT, men control, and men IHT) with a Kruskal-Wallis test.

RESULTS

There were no differences in all groups after 8 weeks of IHT in Δ brachial diameter (p = 0.850), Δ flow-mediated dilation (p = 0.241), Δ time to peak diameter (p = 0.528), and Δ FMD/AUC (p = 0.397).

CONCLUSIONS

There are no effects of sex on vascular adaptation after 8 weeks of IHT in older adults with symptomatic PAD.

Triglyceride-glucose index in the development of peripheral artery disease: findings from the Atherosclerosis Risk in Communities (ARIC) Study

Background

It remains unclear whether triglyceride-glucose (TyG) index, a surrogate marker of insulin resistance, is prospectively associated with incident peripheral arterial disease (PAD).

Methods

We included 12,320 Atherosclerosis Risk in Communities Study participants (aged 54.3 ± 5.7 years) free of a history of PAD at baseline (visit 1: 1987–1989). The TyG index was determined using ln (fasting triglycerides [mg/dL] × fasting glucose [mg/dL]/2), and measured at 5 visits between 1987 and 2013. Incident PAD was defined as the first hospitalization with PAD diagnosis or a new onset of measured ABI < 0.90 during follow-up visits. We quantified the association of both baseline and trajectories of TyG index with incident PAD using Cox regression and logistic regression analysis, respectively.

Results

Over a median follow-up of 23 years, 1300 participants developed PAD. After adjustment for traditional PAD risk factors, each 1-SD (0.58) increase in TyG index was associated with an 11.9% higher risk of incident PAD [hazard ratio, 1.119 (95% CI, 1.049–1.195)]. Results were similar when individuals were categorized by TyG index quartiles [hazard ratio, 1.239 (95% CI, 1.028–1.492); comparing extreme quartiles]. Four distinct trajectories of stable TyG indexes at various levels along the follow-up duration were identified [low (22.2%), moderate (43.2%), high (27.5%), and very high (7.1%) trajectory groups]. Compared with those with a TyG index trajectory at a low level, those participants with TyG index trajectories at high and very high levels had an even greater risk of future incident PAD [odds ratio (95%CI): 1.404 (1.132–1.740) and 1.742 (1.294–2.344), respectively] after multivariate adjustments for traditional PAD risk factors.

Conclusions

Higher TyG index is independently associated with an increased risk of incident PAD. Long-term trajectories of TyG index help identify individuals at a higher risk of PAD who deserve specific preventive and therapeutic approaches.

Trial registration: Clinical trial registration number: The ARIC trial was registered at clinicaltrials.gov as NCT00005131.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01319-1.

Accuracy of Peripheral Arterial Disease Registers in UK General Practice: Case-Control Study

Background:

Approximately 20% of the UK population aged 55 to 75 years have evidence of peripheral arterial disease (PAD). PAD affects quality of life and life expectancy if not appropriately diagnosed and managed. At risk patients require accurate diagnosis to ensure optimal treatment to slow disease progression and minimize adverse outcomes.

Aim:

To assess the accuracy of general practice (GP) registration of the diagnosis of peripheral arterial disease (PAD).

Design and Setting:

An observational analytic case-control study. As part of a National Institute for Health Research–funded (ISRCTN13301188) project assessing novel diagnostic methods set in GP practice.

Methods:

A total of 125 patients registered as having PAD and 125 age- and sex-matched controls were recruited from 15 general practices across North East England. The register was then assessed for accuracy of diagnosis. Duplex vascular ultrasound scanning (DUS) undertaken by vascular scientists was used as the gold standard reference for PAD.

Results:

The PAD register had a sensitivity of 86% (95% CI 77%-92%) and specificity of 74% (95% CI 67%-81%) when compared with DUS. The positive predictive value, however, was 69.6% (95% CI 63%-75%) and negative predictive value 88.8% (95% CI 82%-92%). The overall diagnostic effectiveness of the PAD register was 79.2% (95% CI 73%-84%).

Conclusion:

This analysis indicates that while PAD is detected with reasonable sensitivity in primary care, many patients registered with a diagnosis of PAD lacked DUS-proven disease. Improved approaches to the objective diagnosis of PAD may improve diagnosis and management of PAD in primary care.

Body mass-normalized moderate dose of dietary nitrate intake improves endothelial function and walking capacity in patients with peripheral artery disease

Peripheral artery disease (PAD) is characterized by the accumulation of atherosclerotic plaques in the lower extremity conduit arteries, which impairs blood flow and walking capacity. Dietary nitrate has been used to reduce blood pressure (BP) and improve walking capacity in PAD. However, a standardized dose for PAD has not been determined. Therefore, we sought to determine the effects of a body mass-normalized moderate dose of nitrate (0.11 mmol nitrate/kg) as beetroot juice on serum nitrate/nitrite, vascular function, walking capacity, and tissue oxygen utilization capacity in patients with PAD. A total of 11 patients with PAD received either nitrate supplement or placebo in a randomized crossover design. Total serum nitrate/nitrite, resting BP, brachial and popliteal artery endothelial function (flow-mediated dilation, FMD), arterial stiffness (pulse-wave velocity, PWV), augmentation index (AIx), maximal walking distance and time, claudication onset time, and skeletal muscle oxygen utilization were measured pre- and postnitrate and placebo intake. There were significant group × time interactions (P < 0.05) for serum nitrate/nitrite, FMD, BP, walking distance and time, and skeletal muscle oxygen utilization. The nitrate group showed significantly increased serum nitrate/nitrite (Δ1.32 μM), increased brachial and popliteal FMD (Δ1.3% and Δ1.7%, respectively), reduced peripheral and central systolic BP (Δ-4.7 mmHg and Δ-8.2 mmHg, respectively), increased maximal walking distance (Δ92.7 m) and time (Δ56.3 s), and reduced deoxygenated hemoglobin during walking. There were no changes in PWV, AIx, or claudication (P > 0.05). These results indicate that a body-mass normalized moderate dose of nitrate may be effective and safe for reducing BP, improving endothelial function, and improving walking capacity in patients with PAD.

Estimated Glomerular Filtration Rate as a Predictor of Restenosis After Carotid Stenting Using First-Generation Stents

This study evaluated the impact of the baseline estimated glomerular filtration rate (eGFR) on clinical and angiographic outcomes and long-term in-stent restenosis (ISR) rates in patients undergoing elective carotid artery stenting (CAS) procedures. Consecutive patients who underwent CAS were retrospectively enrolled (n = 456). At the end of 3 years of follow-up, patients who had died or were lost follow-up were excluded from the study and a final analysis was performed using data from the remaining 405 patients. The study population (n = 405) was divided into 3 tertiles based on the tertile values of the eGFR level (T1, T2, and T3); then, clinical and procedural characteristics and 3-year ISR rates were compared between the groups. An ISR of 50% was detected in 49 (12%) surviving patients. The 3-year ISR was higher among patients with the lowest eGFR values (T1) by 3.7 times (95% CI: 2.01-11.38) than that among patients with the highest eGFR values (T3). These significant relationships persisted following adjustment for confounders. A lower baseline eGFR level was significantly associated with an increased ISR rate. Decreased renal function may be a predictor of ISR after CAS using first-generation stents.

Walking-induced endothelial dysfunction predicts ischemic cardiovascular events in patients with intermittent claudication

Endothelial dysfunction, evaluated by flow-mediated dilatation (FMD), predicts adverse cardiovascular events in patients with intermittent claudication (IC). IC is an example of repeated ischemia/reperfusion injury that may contribute to the progression of vascular disease by worsening endothelial function, a trigger for acute cardiovascular events. The predictive value of effort-induced endothelial dysfunction for cardiovascular events in patients with IC has not been studied previously. The objective of this study was to assess whether exercise-induced endothelial dysfunction is predictive of adverse cardiovascular outcome in IC. In 44 patients with IC, we measured brachial artery FMD by B-mode ultrasonography at rest and 10 minutes after a maximal treadmill exercise. Treadmill exercise halved the FMD (from 3.5 ± 0.6% to 1.45 ± 0.46%, p < 0.05). After a follow-up period of 85 (72-98) months, a total of 20 major cardiovascular events occurred. In a multivariate analysis, a post-exercise reduction of brachial FMD > 1.3% was predictive for cardiovascular events. Maximal exercise-induced endothelial dysfunction is predictive of cardiovascular events in patients with IC.

The area under curve for time-course analysis parameters is associated with abdominal aortic aneurysms and the severity of peripheral artery disease in men

Background

Abdominal aortic aneurysm (AAA) and peripheral artery disease (PAD) are associated with vascular endothelial dysfunction. To date, flow-mediated vasodilatation (FMD) and nitroglycerin-mediated vasodilatation (NMD) have been used to evaluate vascular function. Recently, parameters of time-course analysis have been proposed as useful evaluations for arteriosclerotic diseases. In this study, the correlation between the parameters of time-course analysis, to the degree of vascular endothelial damage in AAA and PAD, together with their applicability as a vascular function test, was investigated.

Methods

Brachial artery vasoreactivity was assessed in male patients with AAA (n = 150) and PAD (n = 50). The percentage change in peak diameters (ΔFMD and ΔNMD), the time to diameter change, the time to peak diameter from the diameter change, the blood flow decay time constant, the area under the curve (AUC), the maximum dilation rate and the extended time constant were measured.

Results

Among the groups of aneurysm diameter in AAA, the FMD-AUC was highly different (p = .01), while the ΔFMD was not significantly different (p = .36). Among the Fontaine stages in PAD, the FMD-AUC was inversely associated with severity (p = .01) although the ΔFMD was not significantly different (p = .71). Among the Fontaine stages, the NMD-AUC was also inversely associated with severity (p = .03) although the ΔNMD was not significantly different (p = .11).

Conclusion

This study suggests that FMD-AUC and NMD-AUC are useful for estimating vascular endothelial and vascular smooth muscle dysfunction, serving as supplementary markers for the diagnosis and evaluation of PAD and AAA.

Endothelial Dysfunction as a Primary Consequence of SARS-CoV-2 Infection

A number of different viral species are known to have effects on the endothelium. These include dengue, Ebola, Marburg, Lassa fever, yellow fever and influenza viruses, cytomegalovirus and coronaviruses. There are currently seven human endemic coronaviruses, all of which cause respiratory diseases and bind to receptors found within the endothelium. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the coronavirus disease 2019 (COVID-19) is highly infectious. Like its predecessor, SARS-CoV, it binds to angiotensin-converting enzyme-2 (ACE-2), which is expressed in many cell types, particularly in the lung, including endothelial cells. The initiation of a cytokine storm by the virus along with infection of endothelial cells leads to apoptosis and structural and functional changes that attenuate vascular integrity in many organs including the lungs, heart, liver and kidney. Endothelial damage also enhances the coagulation pathway leading to thrombus formation in major vessels and capillaries. Infection with SARS-CoV-2 has an adverse outcome for individuals with particular comorbid diseases, e.g. hypertension, obesity, type 2 diabetes and cardiovascular disease. It is possible that this is due to the presence of pre-existing endothelial dysfunction and systemic inflammation in subjects with these diseases. Therapies for COVID-19 that target the endothelium, the inflammatory response and the coagulation pathway are currently under trial.

Independent associations of urinary albumin-to-creatinine ratio and serum cystatin C with carotid intima-media thickness in community-living Taiwanese adults

Background

Renal function is a key factor of cardiovascular disease. Carotid intima-media thickness (IMT) has been widely used as a marker of early subclinical atherosclerosis. The determinants of cystatin C, a novel marker of renal function, have not been extensively studied in the Asian population. This study aimed to assess the determinants of cystatin C and explore whether carotid thickening was associated with urinary albumin-creatinine ratio and cystatin C in community-living Taiwanese adults.

Methods

A cross-sectional study was conducted on participants from Taichung City, Taiwan. All the participants underwent carotid ultrasonography. Carotid IMT-mean and IMT-maximum were derived. Kidney biomarkers were measured on the basis of urinary albumin-to-creatinine ratio (ACR) and cystatin C. Multiple linear regression analysis was used.

Results

A total of 1032 individuals were recruited, and 469 (45.44%) of them were men. An increased cystatin C level was significantly associated with older age, male gender, lack of physical activity, low HDL cholesterol, abdominal obesity, high hs-CRP, and high ACR. The multivariate-adjusted mean carotid IMT-mean and IMT-maximum values significantly increased by 80.49 and 195.23 μm for every one unit of increase in cystatin C level and by 0.07 and 0.14 μm for every one unit of increase in ACR, respectively (all p < 0.001 except ACR on IMT-maximum with p < 0.01). Lack of physical activity, low HDL, abdominal obesity, high hs-CRP, and high ACR were the determinants of cystatin C.

Conclusion

Cystatin C and ACR were strongly and linearly associated with carotid thickening, a marker of subclinical atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-020-02123-x.

Biomarker Utility for Peripheral Artery Disease Diagnosis in Real Clinical Practice: A Prospective Study

Peripheral arterial disease (PAD) is a common manifestation of generalized atherosclerosis, which affects more than 200 million patients worldwide. Currently, there is no ideal biomarker for PAD risk stratification and diagnosis. The goal of this research was to investigate the levels of inflammation biomarkers and cystatin C and to explore their utility for the diagnosis of PAD. The study included 296 participants, distributed in two groups: 216 patients diagnosed with PAD and 80 patients without PAD as controls. All studied biomarker levels (C-reactive protein, CRP; fibrinogen; erythrocyte sedimentation rate, ESR; neopterin; beta 2-microglobulin, B2-MG; and cystatin C) were significantly higher in the PAD group and indirectly correlated with the ankle-brachial index (ABI). The final logistic regression model included an association of neopterin, fibrinogen, and cystatin C as the most efficient markers for the prediction of PAD diagnosis. When comparing the area under the curve (AUC) for all biomarkers, the value for neopterin was significantly higher than those of all the other analyzed biomarkers. In agreement with previous studies, this research shows that markers such as fibrinogen, CRP, ESR, B2-MG, and cystatin C have significant value for the diagnosis of PAD, and also clearly underlines the accuracy of neopterin as a leading biomarker in PAD prediction.

Acute mitochondrial antioxidant intake improves endothelial function, antioxidant enzyme activity, and exercise tolerance in patients with peripheral artery disease

The results of this study reveal for the first time that acute oral intake of mitochondrial-targeted antioxidant (MitoQ, 80 mg) is effective for improving vascular endothelial function and superoxide dismutase in patients with peripheral artery disease (PAD). Acute MitoQ intake is also effective for improving maximal walking capacity and delaying the onset of claudication in patients with PAD. These findings suggest that the acute oral intake of MitoQ-mediated improvements in vascular mitochondria play a pivotal role for improving endothelial function, the redox environment, and skeletal muscle performance in PAD.

Subclinical Atherosclerosis Markers of Carotid Intima-Media Thickness, Carotid Plaques, Carotid Stenosis, and Mortality in Community-Dwelling Adults

Carotid intima–media thickness (IMT), plaque, and stenosis are widely used as early surrogate markers of subclinical atherosclerosis and strong predictors of future deaths and cardiovascular events. Albuminuria is an indicator of generalized endothelial dysfunction that speeds up atherosclerosis. However, previous studies reporting these associations cannot rule out the confounding effect of albuminuria. We aimed to examine the independent and joint relationships between IMT markers and 10-year mortality in community-dwelling Taiwanese adults. This work was a community-based prospective cohort study consisting of 2956 adults aged at least 30 years recruited in 2007 and followed up through 2019. Cox proportional hazard regression models were used to examine associations of these subclinical atherosclerosis markers with mortality. During an average of 9.41 years of follow up, 242 deaths occurred. The mortality rate was 8.70 per 1000 person-years. Compared with those with carotid IMT less than 1.0 mm, persons with severely increased carotid IMT (≥2.0 mm) had an increased risk for death (hazard ratio (HR): 1.79; 95% confidence interval (CI): 1.07, 3.00). Compared with those without carotid plaque, persons with carotid plaque were more likely to have an increased risk for death (1.65; 1.21–2.32). Compared with those with carotid stenosis less than 25%, persons with carotid stenosis of 25–36% had a significant increased risk for death (1.57; 1.12–2.22). Considering these three IMT markers along with the traditional risk factors (c-statistic: 0.85) significantly increased their predictive ability of mortality compared with any individual variable’s predictive ability (all p-values < 0.001 for comparisons of c-statistic values). Carotid IMT measures, including IMT thickness, carotid plaque, and carotid stenosis were significant independent predictors of mortality. Our study supports evidence of blood pressure-related media thickening markers to assess future mortality risks in Chinese adults of general population.

Pathophysiology of Peripheral Arterial Disease (PAD): A Review on Oxidative Disorders

Peripheral arterial disease (PAD) is an atherosclerotic disease that affects a wide range of the world’s population, reaching up to 200 million individuals worldwide. PAD particularly affects elderly individuals (>65 years old). PAD is often underdiagnosed or underestimated, although specificity in diagnosis is shown by an ankle/brachial approach, and the high cardiovascular event risk that affected the PAD patients. A number of pathophysiologic pathways operate in chronic arterial ischemia of lower limbs, giving the possibility to improve therapeutic strategies and the outcome of patients. This review aims to provide a well detailed description of such fundamental issues as physical exercise, biochemistry of physical exercise, skeletal muscle in PAD, heme oxygenase 1 (HO-1) in PAD, and antioxidants in PAD. These issues are closely related to the oxidative stress in PAD. We want to draw attention to the pathophysiologic pathways that are considered to be beneficial in order to achieve more effective options to treat PAD patients.

Effects of n-3 PUFA on endothelial function in patients with peripheral arterial disease: a randomised, placebo-controlled, double-blind trial

As only limited evidence is available for potential benefits of n-3 PUFA supplementation in patients with peripheral arterial disease (PAD), we studied the effects of 4 g n-3 PUFA on endothelial function and inflammatory markers. Seventy patients with stable PAD classified as Rutherford stage 2 or 3 and good control of cardiovascular factors were randomised to receive either 4 g n-3 PUFA or placebo daily for 3 months in a double-blind fashion. Primary endpoint was endothelial function assessed by flow-mediated vasodilation (FMD). In addition, ankle-brachial index, maximum and pain-free walking distances were determined. Lipid parameters including the omega-3 index reflecting n-3 PUFA intake as well as pro-inflammatory, endothelial and platelet activation markers were measured over the same time interval. After 3 months of treatment with 4 g n-3 PUFA daily, a significant improvement of FMD was observed compared with placebo (n-3 PUFA, median Δ 3·7 (interquartile range (IQR) -1·8, 7·1) % v. placebo, Δ -0·5 (IQR -6·5, 3·0) %, P = 0·01 between the groups). After a 3-month washout period, this benefit was not sustained (n-3 PUFA, median Δ 0·6 (IQR -2·2, 5·6) % v. placebo, Δ -0·9 (IQR -6·6, 6·7) %, P = 0·20). In response to n-3 PUFA, an improvement of lipid parameters with a pronounced increase in the omega-3 index was seen. No changes were found for other parameters. In conclusion, in patients with PAD, 4 g/d n-3 PUFA improved cardiovascular risk in PAD patients, which needs testing in large-scale trials.

Imaging the Landmarks of Vascular Recovery

Background: Peripheral arterial disease (PAD) is a major worldwide health concern. Since the late 1990s therapeutic angiogenesis has been investigated as an alternative to traditional PAD treatments. Although positive preclinical results abound in the literature, the outcomes of human clinical trials have been discouraging. Among the challenges the field has faced has been a lack of standardization of the timings and measures used to validate new treatment approaches.

Methods: In order to study the spatiotemporal dynamics of both perfusion and neovascularization in mice subjected to surgically-induced hindlimb ischemia (n= 30), we employed three label-free imaging modalities (a novel high-sensitivity ultrasonic Power Doppler methodology, laser speckle contrast, and photoacoustic imaging), as well as a tandem of radio-labeled molecular probes, ^99mTc-NC100692 and ^99mTc-BRU-5921 respectively, designed to detect two key modulators of angiogenic activity, α_Vβ₃ and HIF-1α , via scintigraphic imaging.

Results: The multimodal imaging strategy reveals a set of “landmarks”—key physiological and molecular events in the healing process—that can serve as a standardized framework for describing the impact of emerging PAD treatments. These landmarks span the entire process of neovascularization, beginning with the rapid decreases in perfusion and oxygenation associated with ligation surgery, extending through pro-angiogenic changes in gene expression driven by the master regulator HIF-1α , and ultimately leading to complete functional revascularization of the affected tissues.

Conclusions: This study represents an important step in the development of multimodal non-invasive imaging strategies for vascular research; the combined results offer more insight than can be gleaned through any of the individual imaging methods alone. Researchers adopting similar imaging strategies and will be better able to describe changes in the onset, duration, and strength of each of the landmarks of vascular recovery, yielding greater biological insight, and enabling more comprehensive cross-study comparisons. Perhaps most important, this study paves the road for more efficient translation of PAD research; emerging experimental treatments can be more effectively assessed and refined at the preclinical stage, ultimately leading to better next-generation therapies.

Pathophysiology of chronic peripheral ischemia: new perspectives

Peripheral arterial disease (PAD) affects individuals particularly over 65 years old in the more advanced countries. Hemodynamic, inflammatory, and oxidative mechanisms interact in the pathophysiological scenario of this chronic arterial disease. We discuss the hemodynamic, muscle tissue, and oxidative stress (OxS) conditions related to chronic ischemia of the peripheral arteries. This review summarizes the results of evaluating both metabolic and oxidative markers, and also therapy to counteract OxS. In conclusion, we believe different pathways should be highlighted to discover new drugs to treat patients suffering from PAD.

Oxidative Stress in Peripheral Arterial Disease (PAD) Mechanism and Biomarkers

Hemodynamic dysfunction mainly characterizes pathophysiology of peripheral arterial disease (PAD) leading to chronic ischemia. Hemodynamic dysfunction is the origin of intermittent claudication (chronic PAD) or of critical limb ischemia (very severe PAD). Notably, it is well known that oxidative stress (OxS) plays a pathophysiological role in PAD. The higher production of reactive oxygen species (ROS) from OxS and reduced redox capability are two crucial players in initiating and progressing PAD. A number of biomarkers highlight OxS and monitor it in PAD. The present review summarizes data on OxS, on biomarkers available to mark OxS occurrence and to monitor on PAD progression, as well as to evaluate the effects treatments in PAD patients. In conclusion, by detailing OxS and its biomarkers, we hope to encourage more studies to focus on drugs which combat OxS and inflammation.

Type 2 Diabetes and Cardiovascular Factors Contrasted with Fibrinolysis Disorders in the Blood of Patients with Peripheral Arterial Disease

Background and objectives: Both in the pathogenesis of type 2 diabetes (DM 2) and Peripheral Arterial Disease (PAD), a vital role is played by endothelial dysfunction. Metabolic disorders found in DM 2 (hyperglycemia, insulin resistance), endothelial dysfunction, and increased inflammation lead to intensified atherothrombosis. The fibrinolysis system comprises a natural compensatory mechanism in case of hypercoagulability. The aim of this study was to assess concentrations of selected fibrinolysis parameters in the blood of patients with symptomatic PAD, including in particular concurrent DM 2 and other cardiovascular factors. Materials and Methods: In the group of 80 patients with PAD (27 F/53 M) and 30 healthy volunteers (10 F/20 M), the following parameters were measured: Concentrations of fibrinogen, tissue-Plasminogen Activator (t-PA Ag), Plasminogen Activator Inhibitor-1 (PAI-1 Ag), D-dimer, and platelet (PLT) count. Results: In the blood of patients with PAD and concomitant DM 2 significantly higher concentrations of fibrinogen were found in comparison with patients with PAD and without diabetes (p = 0.044). No significant impact was observed in individuals with atherosclerotic complications (manifested by coronary artery disease, atherosclerosis of cerebral arteries) and selected cardiovascular risk factors (smoking, LDL and triglyceride concentrations, BP values) on the levels of t-PA, PAI-1, D-dimer, and PLT count. It was found that t-PA Ag and PAI-1 Ag values tended to rise along with a BMI increase in the subgroups of subjects (with normal body mass, overweight, and obesity), but no statistically significant differences were observed. However, two significant positive correlations were reported between t-PA Ag and BMI, as well as between PAI-1 Ag and BMI. Conclusions: Type 2 diabetes in peripheral arterial disease affects the concentration of fibrinogen causing its increase, which is connected with the inflammation and prothrombotic process in the course of both conditions. The concurrence of atherosclerosis of coronary or cerebral arteries, smoking, LDL and TG concentrations, and BP value do not have a significant impact on the levels of analyzed fibrinolysis parameters. A positive correlation between BMI and t-PA Ag and PAI-1 Ag concentrations needs to be supported in further studies on a larger number of overweight and obese patients.

Role of microcirculatory function and plasma biomarkers in determining the development of cardiovascular adverse events in patients with peripheral arterial disease: A 5-year follow-up

OBJECTIVE

The aim of this long-term follow-up study was to investigate the association of local and systemic cardiovascular complications with endothelium-dependent and-independent microvascular relaxations and blood biomarkers and biochemicals in patients with peripheral arterial disease (PAD) caused by atherosclerosis.

METHODS

This prospective study included 67 patients with PAD who had not undergone any endovascular intervention, peripheral arterial surgery, or major amputation. Changes in the microvascular blood flow were measured using laser Doppler imaging after iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). The biochemical markers of high sensitivity C reactive protein (hs-CRP), nitric oxide (NO), total antioxidant capacity (TAC), asymmetric dimethyl arginine (ADMA), and hydrogen sulfide (H2S) levels were measured from blood samples. All the patients were followed up for 5 years to determine the development of cardiovascular adverse events (CVAEs) and major amputation. At the end of the follow-up period, the patients were classified into two groups: those who had a CVAE [CVAE (+)] and those who did not experience CVAE [CVAE (-)]. Parameters such as demographic features, atherosclerotic risk factors, chronic ischemia category, microvascular endothelial functions, and plasma biomarkers were compared between the groups.

RESULTS

A total of 67 patients comprising 61 (91%) males and 6 (9%) females with a mean age of 62.3±9.7 years were included. During the follow-up period, 29 patients had CVAE (43.3%) and 38 patients did not have CVAE (56.7%). There was no difference between the groups in terms of ACh and SNP-induced vasodilation responses. Plasma high density lipoprotein (HDL) cholesterol values were lower in the CVAE (+) group [(CVAE+HDL: 38.4±9.1), (CVAE-HDL: 44.7±11.1), p=0.02]. Plasma hs-CRP values were significantly higher in the CVAE (+) group [(CVAE+ hs-CRP: 14.3±20.6), (CVAE-hs-CRP: 5.9±10.9), p=0.004]. No significant difference was observed between the groups in terms of plasma biomarkers and other biochemical levels.

CONCLUSION

Based on the study findings, it was concluded that only low plasma HDL and high hs-CRP levels were risk factors for the development of CVAEs during follow-up of patients with PAD.

Inflammation and Peripheral Arterial Disease

Peripheral arterial disease (PAD) is an atherosclerotic disease closely associated with high morbidity and mortality in cardiac events. Inflammation is crucial in atherosclerosis both at triggering and in progression. Numerous inflammatory biomarkers (cytokines, matrix metalloproteinases (MMPs), selectin, intracellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) C-reactive protein (CRP), fibrinogen) have been measured in atherosclerotic diseases including PAD. This paper summarizes the data on the inflammatory biomarkers for PAD pathophysiology and highlights the most useful markers in monitoring PAD outcomes.

Radial Artery Tonometry is Associated With Major Adverse Cardiac Events in Patients With Peripheral Artery Disease

BACKGROUND

Peripheral artery disease (PAD) is associated with increased arterial stiffness, as measured by an increasing radial artery augmentation index (AIX). However, it has not yet been clearly demonstrated whether AIX is associated with adverse cardiovascular outcomes in a PAD population.

MATERIALS AND METHODS

Seventy-two patients with PAD were recruited between 2011 and 2016. Radial artery applanation tonometry was performed at a baseline visit, and the central AIX, normalized to 75 beats/min, and the peripheral AIX were calculated using pulse wave analysis. Incident major adverse cardiac events (MACEs) were identified by subsequent chart review.

RESULTS

Study subjects had comorbidities commonly associated with PAD including a high prevalence of hypertension (93%), hyperlipidemia (85%), coronary artery disease (39%), and diabetes mellitus (39%). During a median follow-up period of 34 mo (interquartile range 29-38), 14 patients experienced a MACE. In a univariate Cox proportional hazards model, a 10-unit increase in the peripheral AIX was significantly associated with a 54% increased rate of MACE (hazard ratio [HR] 1.54, 95% confidence interval [CI] 1.06-2.22, P = 0.02), but central AIX, normalized to 75 beats/min, was not (HR 1.33, 95% CI 0.71-2.47, P = 0.37). In a multivariable model adjusted for coronary artery disease, age, and Rutherford category the peripheral AIX remained significantly associated with MACE (HR 1.70, 95% CI 1.10-2.62, P = 0.02).

CONCLUSIONS

Increased arterial stiffness, as measured by the peripheral AIX, was independently associated with an increased rate of MACE in patients with PAD. The use of radial artery tonometry should be contemplated as a tool for risk stratification in patients with PAD.

Deciphering Endothelial Dysfunction in the HIV-Infected Population

Cardiovascular disease (CVD), as a possible consequence of endothelial dysfunction, is prevalent among HIV-infected patients despite successful administration of antiretroviral drugs. This warrants the routine clinical assessment of endothelial function in HIV-positive patients to circumvent potential CVD events. Several different non-invasive strategies have been employed to assess endothelial function in clinical research studies yielding inconsistencies among these reports. This review summarises the different techniques used for assessing endothelial function, with a focus on proposed blood-based biomarkers, such as endothelial leukocyte adhesion molecule-1 (E-selectin), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), TNF-α, interleukin 6 (IL6) and soluble thrombomodulin (sTM). The identification of suitable blood-based biomarkers, especially those that can be measured using a point-of-care device, would be more applicable in under-resourced countries where the prevalence of HIV is high.

Leg blood flow and skeletal muscle microvascular perfusion responses to submaximal exercise in peripheral arterial disease

Peripheral arterial disease (PAD) is characterized by stenosis and occlusion of the lower limb arteries. Although leg blood flow is limited in PAD, it remains unclear whether skeletal muscle microvascular perfusion is affected. We compared whole leg blood flow and calf muscle microvascular perfusion after cuff occlusion and submaximal leg exercise between patients with PAD ( n = 12, 69 ± 9 yr) and healthy age-matched control participants ( n = 12, 68 ± 7 yr). Microvascular blood flow (microvascular volume × flow velocity) of the medial gastrocnemius muscle was measured before and immediately after the following: 1) 5 min of thigh-cuff occlusion, and 2) a 5-min bout of intermittent isometric plantar-flexion exercise (400 N) using real-time contrast-enhanced ultrasound. Whole leg blood flow was measured after thigh-cuff occlusion and during submaximal plantar-flexion exercise using strain-gauge plethysmography. Postocclusion whole leg blood flow and calf muscle microvascular perfusion were lower in patients with PAD than control participants, and these parameters were strongly correlated ( r = 0.84, P < 0.01). During submaximal exercise, total whole leg blood flow and vascular conductance were not different between groups. There were also no group differences in postexercise calf muscle microvascular perfusion, although microvascular blood volume was higher in patients with PAD than control participants (12.41 ± 6.98 vs. 6.34 ± 4.98 arbitrary units, P = 0.03). This study demonstrates that the impaired muscle perfusion of patients with PAD during postocclusion hyperemia is strongly correlated with disease severity and is likely mainly determined by the limited conduit artery flow. In response to submaximal leg exercise, microvascular flow volume was elevated in patients with PAD, which may reflect a compensatory mechanism to maintain muscle perfusion and oxygen delivery during recovery from exercise.

NEW & NOTEWORTHY This study suggests that peripheral arterial disease (PAD) has different effects on the microvascular perfusion responses to cuff occlusion and submaximal leg exercise. Patients with PAD have impaired microvascular perfusion after cuff occlusion, similar to that previously reported after maximal exercise. In response to submaximal exercise, however, the microvascular flow volume response was elevated in patients with PAD compared with control. This finding may reflect a compensatory mechanism to maintain perfusion and oxygen delivery during recovery from exercise.

Lower extremity arterial disease in patients with diabetes: a contemporary narrative review

Lower-extremity arterial disease (LEAD) is a major endemic disease with an alarming increased prevalence worldwide. It is a common and severe condition with excess risk of major cardiovascular events and death. It also leads to a high rate of lower-limb adverse events and non-traumatic amputation. The American Diabetes Association recommends a widespread medical history and clinical examination to screen for LEAD. The ankle brachial index (ABI) is the first non-invasive tool recommended to diagnose LEAD although its variable performance in patients with diabetes. The performance of ABI is particularly affected by the presence of peripheral neuropathy, medial arterial calcification, and incompressible arteries. There is no strong evidence today to support an alternative test for LEAD diagnosis in these conditions. The management of LEAD requires a strict control of cardiovascular risk factors including diabetes, hypertension, and dyslipidaemia. The benefit of intensive versus standard glucose control on the risk of LEAD has not been clearly established. Antihypertensive, lipid-lowering, and antiplatelet agents are obviously worthfull to reduce major cardiovascular adverse events, but few randomised controlled trials (RCTs) have evaluated the benefits of these treatments in terms of LEAD and its related adverse events. Smoking cessation, physical activity, supervised walking rehabilitation and healthy diet are also crucial in LEAD management. Several advances have been achieved in endovascular and surgical revascularization procedures, with obvious improvement in LEAD management. The revascularization strategy should take into account several factors including anatomical localizations of lesions, medical history of each patients and operator experience. Further studies, especially RCTs, are needed to evaluate the interest of different therapeutic strategies on the occurrence and progression of LEAD and its related adverse events in patients with diabetes.

Oxidative Stress and Arterial Dysfunction in Peripheral Artery Disease

Peripheral artery disease (PAD) is an atherosclerotic disease characterized by a narrowing of the arteries in the lower extremities. Disease manifestations are the result of more than just reduced blood flow, and include endothelial dysfunction, arterial stiffness, and inflammation. Growing evidence suggests that these factors lead to functional impairment and decline in PAD patients. Oxidative stress also plays an important role in the disease, and a growing amount of data suggest a link between arterial dysfunction and oxidative stress. In this review, we present the current evidence for the involvement of endothelial dysfunction, arterial stiffness, and inflammation in the pathophysiology of PAD. We also discuss the links between these factors and oxidative stress, with a focus on nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2)-derived reactive oxygen species (ROS) and decreased nitric oxide (NO) bioavailability. Finally, the potential therapeutic role of NOX2 antioxidants for improving arterial function and functional status in PAD patients is explored.

Computing the ankle-brachial index with parallel computational fluid dynamics

The ankle-brachial index (ABI), a ratio of arterial blood pressure in the ankles and upper arms, is used to diagnose and monitor circulatory conditions such as coarctation of the aorta and peripheral artery disease. Computational simulations of the ABI can potentially determine the parameters that produce an ABI indicative of ischemia or other abnormalities in blood flow. However, 0- and 1-D computational methods are limited in describing a 3-D patient-derived geometry. Thus, we present a massively parallel framework for computational fluid dynamics (CFD) simulations in the full arterial system. Using the lattice Boltzmann method to solve the Navier-Stokes equations, we employ highly parallelized and scalable methods to generate the simulation domain and efficiently distribute the computational load among processors. For the first time, we compute an ABI with 3-D CFD. In this proof-of-concept study, we investigate the dependence of ABI on the presence of stenoses, or narrowed regions of the arteries, by directly modifying the arterial geometry. As a result, our framework enables the computation a hemodynamic factor characterizing flow at the scale of the full arterial system, in a manner that is extensible to patient-specific imaging data and holds potential for treatment planning.

Microvascular Dysfunction Following Multiwalled Carbon Nanotube Exposure Is Mediated by Thrombospondin-1 Receptor CD47

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation. Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 µg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours postexposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT + MWCNT group compared with control (57 ± 9 vs 90 ± 2% relaxation), while CD47 KO animals showed no impairment (108 ± 8% relaxation). Venular leukocyte adhesion and rolling increased by >2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT + MWCNT group. Lung and plasma NOx were reduced in the WT + MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47 + MWCNT group only. In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (•NO) signaling and promotes leukocyte-endothelial interactions. Impaired •NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.

Anthocyanins and their gut metabolites attenuate monocyte adhesion and transendothelial migration through nutrigenomic mechanisms regulating endothelial cell permeability

Cardioprotective effects of dietary anthocyanins are partly attributed to their ability to maintain endothelial function. However, the underlying cellular and molecular mechanisms of action are not fully understood. This study aimed to evaluate the effect of anthocyanins and their gut metabolites, at physiologically-relevant conditions, on endothelial cell (EC) function and decipher the underlying molecular mechanisms of action using integrated omics approaches. Primary EC were treated with a mixture of 0.1 μM cyanidin-3-arabinoside, 0.1 μM cyanidin-3-galactoside, 0.1 μM cyanidin-3-glucoside, 0.1 μM delphinidin-3-glucoside, 0.1 μM peonidin-3-glucoside and 0.5 μM 4-hydroxybenzaldehyde for 3 h or a mixture of gut metabolites: 0.2 μM protocatechuic, 2 μM vanillic, 1 μM ferulic and 2 μM hippuric acids for 18 h. Also, successive exposure of EC to both mixtures was performed to mimic anthocyanin pharmacokinetics following their intake. Inflammatory stress was induced using TNFα and monocytes added to assess adhesion and transmigration. Effects of these mixtures on gene, miRNA expression and their potential interaction with cell signalling were investigated. Anthocyanins and their gut metabolites significantly reduced monocyte adhesion and transendothelial migration. Gene expression analysis, using macroarrays, showed that tested compounds modulated the expression of genes involved in cell-cell adhesion, cytoskeleton organisation or focal adhesion. Bioinformatics analyses of gene expression data identified potential transcription factors involved in the observed nutrigenomic effects and signalling proteins regulating their activity. Molecular docking revealed cell signalling proteins to which these bioactives may bind to and potentially affect their activity and the activation of downstream signalling, effects that were in agreement with the results of Western blot analyses. Microarray analysis showed that anthocyanins and their gut metabolites affected miRNA expression in EC, especially those involved in regulation of EC permeability, contributing to the observed changes in EC function. Integration of these results revealed endothelial-protective properties of anthocyanins and their gut metabolites and deciphered new underlying multi-target and multi-layered mode of action.

Baicalein protects against oxLDL-caused oxidative stress and inflammation by modulation of AMPK-alpha

Atherosclerosis is considered to be a form of chronic inflammation and a disorder of lipid metabolism. Oxidative transformations in the lipid and apolipoprotein B (Apo B) constituent of low density lipoprotein drive the initial step in atherogenesis due to macrophage scavenger receptors identify oxidized LDL (oxLDL) but non-oxidized LDL. The human vascular endothelial cells fact a critical role in vasodilation, provides a nonadhesive surface for circulation, reduces vascular smooth muscle proliferation, inflammation, thrombus formation and platelet aggregation. Assembly of oxLDL contribute to stimulation of endothelial cells with up-regulation of adhesion molecules, increase oxidative stress to the vascular endothelium and inhibition of NO-mediated vasodilation. When adhesion molecules are over-expressed on the surface of endothelial cells under oxLDL stimulation, it will recruit monocytes to the arterial wall. Then adherent monocytes will migrate into the subendothelial space and subsequently differentiate into macrophages. In the subendothelial space, oxLDL will be taken up by macrophages, thereby causing the substantial cholesterol accumulation and the foam cells production.

Metformin regulates oxLDL-facilitated endothelial dysfunction by modulation of SIRT1 through repressing LOX-1-modulated oxidative signaling

It is suggested that oxLDL is decisive in the initiation and development of atherosclerotic injuries. The up-regulation of oxidative stress and the generation of ROS act as key modulators in developing pro-atherosclerotic and anti-atherosclerotic processes in the human endothelial wall. In this present study, we confirmed that metformin enhanced SIRT1 and AMPK expression in human umbilical vein endothelial cells (HUVECs). Metformin also inhibited oxLDL-increased LOX-1 expression and oxLDL-collapsed AKT/eNOS levels. However, silencing SIRT1 and AMPK diminished the protective function of metformin against oxidative injuries. These results provide a new insight regarding the possible molecular mechanisms of metformin.

Combined Dietary Nitrate and Exercise Intervention in Peripheral Artery Disease: Protocol Rationale and Design

Background

Peripheral artery disease (PAD) is caused by atherosclerotic occlusions in the legs. It affects approximately 8-12 million people in the United States alone, one-third of whom suffer from intermittent claudication (IC), defined as ischemic leg pain that occurs with walking and improves with rest. Patients with IC suffer a markedly impaired quality of life and a high perception of disability. Improving pain-free walking time is a primary goal of rehabilitation in this population.

Objective

The nitric oxide (NO)-PAD trial is designed to compare the effects that 12 weeks of supervised exercise training, in combination with a high inorganic nitrate-content (beetroot [BR] juice) beverage or placebo (PL) beverage, has on clinical outcomes of exercise and functional capacity in two groups of PAD+IC patients: exercise training plus beetroot (EX+BR) and exercise training plus placebo (EX+PL). The primary aims of this randomized controlled, double-blind pilot study are to determine group differences following 12 weeks of EX+BR versus EX+PL in the changes for (1) exercise capacity: pain-free walking time (claudication onset time, COT), peak walk time (PWT), and maximal exercise capacity (peak oxygen uptake, VO_2peak) during a maximal-graded cardiopulmonary exercise test (max CPX) and (2) functional capacity: 6-minute walk (6MW) distance. The secondary aims will provide mechanistic insights into the exercise outcome measures and will include (1) gastrocnemius muscle oxygenation during exercise via near-infrared spectroscopy (NIRS); (2) gastrocnemius muscle angiogenesis: capillaries per unit area and per muscle fiber, and relative fraction of type I, IIa, IIb, and IId/x fibers; and (3) vascular health/function via brachial artery flow-mediated dilation, lower-limb blood flow via plethysmography, and pulse wave velocity and reflection.

Methods

A total of 30 subjects between 40 and 80 years of age with PAD who are limited by IC will undergo exercise training 3 days per week for 12 weeks (ie, 36 sessions). They will be randomized to either the EX+BR or EX+PL group where participants will consume a beverage high in inorganic nitrate (4.2 mmol) or a low-nitrate placebo, respectively, 3 hours prior to each training session.

Results

Data collection from this study has been completed and is in the process of analysis and write-up. While the study is too underpowered—EX+BR, n=11; EX+PL, n=13—to determine between-group differences in the primary outcomes of COT, PWT, and 6MW, preliminary observations are promising with Cohen d effect sizes of medium to large.

Conclusions

Exercise training is currently the most effective therapy to increase functional capacity in PAD+IC. If the addition of inorganic nitrate to an exercise regimen elicits greater benefits, it may redefine the current standard of care for PAD+IC.

Trial Registration

ClinicalTrials.gov NCT01684930; https://clinicaltrials.gov/ct2/show/NCT01684930 (Archived by WebCite at http://www.webcitation.org/6raXFyEcP)

Plasma nitric oxide level is correlated with microvascular functions in the peripheral arterial disease

At present there is no widely accepted biomarker for monitoring of vascular functions. The purpose of this prospective study was to investigate the association of some blood biomarkers with vascular reactivity in patients with peripheral arterial diseases (PAD). A prospective evaluation was made of 3 groups comprising a control group of healthy individuals, and patients with PAD caused by either atherosclerosis or Buerger's disease. Microvascular perfusion was examined using laser Doppler imaging of cutaneous erythrocyte flux after iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). The correlation of microvascular reactivity with endothelium-related biomarkers was assessed. ACh-induced and SNP-induced vasodilations were significantly diminished in the PAD groups. The plasma nitric oxide (NO) levels of PAD patients were significantly higher than those of the control group, but asymmetric dimethylarginine, total antioxidant capacity and hydrogen sulphide levels were similar. Plasma NO level was negatively correlated with ACh and SNP-stimulated microvascular flow increase, whereas a positive correlation was detected with blood glucose and glycated hemoglobin (HbA1c) levels in all groups. These results indicate that a high plasma level of NO in PAD patients is associated with diminished endothelium-dependent and independent flow increase in the microvascular bed. An excessive amount of NO-induced nitrosative stress in an inflammatory condition that might be a reason for vascular dysfunction should be taken into consideration in the diagnostic and therapeutic approaches to PAD.

Hemorrhoid is associated with increased risk of peripheral artery occlusive disease: A nationwide cohort study

BACKGROUND

This study was conducted to evaluate the association between hemorrhoid and risk of incident peripheral artery occlusive disease (PAOD).

METHODS

Using the Taiwanese Longitudinal Health Insurance Database 2000, we compared the incident PAOD risk between the hemorrhoid and the non-hemorrhoid cohorts. Both of these cohorts were followed up from the index date until the date of PAOD diagnosis, withdrawal from the National Health Insurance program, or the end of 2011.

RESULTS

The mean follow-up period was 6.82 (standard deviation [SD], 3.22) and 6.70 (SD, 3.23) years in the hemorrhoid and non-hemorrhoid cohorts, respectively. The plot of the Kaplan-Meier analysis showed that, by the end of the 12-year follow-up period, the cumulative incidence of PAOD was significantly higher for the hemorrhoid cohort than for the non-hemorrhoid cohort (log-rank test: P < 0.001).

CONCLUSIONS

A significantly increased PAOD risk in patients with hemorrhoids was found in this nationwide cohort study.

Assessment of Renal Function and Risk Factors for Chronic Kidney Disease in Patients With Peripheral Arterial Disease

Chronic kidney disease (CKD) and peripheral arterial disease (PAD) share common risk factors. We assessed renal function and the prevalence of CKD in patients with PAD and investigated the characteristics of the risk factors for CKD in this population. Renal function of 421 patients with PAD was evaluated. Among the participants, 194 (46.1%) patients had decreased estimated glomerular filtration rate (eGFR). The prevalence of CKD was much higher among patients with PAD. Hypertension (odds ratios [ORs] 2.156, 95% confidence interval [CI] 1.413-3.289, P < .001), serum uric acid (OR 3.794, 95% CI 2.220-6.450, P < .001), and dyslipidemia (OR 1.755, 95% CI 1.123-2.745, P = .014) were significantly associated with CKD and the independent risk factors for CKD in patients with PAD. CKD is common and has a high prevalence in a population with PAD. Patients with PAD may be considered as a high-risk population for CKD. Recognition and modification of risk factors for CKD might beneficially decrease CKD incidence and improve prognosis in patients with PAD.

The Central Role of Endothelial Dysfunction in Cardiorenal Syndrome

BACKGROUND

Endothelial dysfunction (ED) has emerged as a critical process in cardiorenal syndrome (CRS). The concept that ED is closely linked with cardiac and renal dysfunction has become an important target for CRS-related research and clinical practice.

SUMMARY

The sequence of events leading to ED is initiated by type I endothelial activation (almost immediately) and type II endothelial activation (over hours, days, and even months), followed by endothelial apoptosis and endothelial necrosis. The fact that ED is a continual cellular event divides this process into reversible ED (endothelial activation) and irreversible ED (endothelial apoptosis and necrosis). This basic research-defined concept may have clinical implications. Although most antihypertensive drugs (ACE inhibitors, statins, etc.) are effective in patients with hypertension and diabetes, some of them have proved to be ineffective, which may partly be attributed to irreversible ED. Even though the etiology of ED consists mainly of asymmetric dimethylarginine, nitric oxide, oxidative stress, and anti-endothelial cell antibodies, many other inducers of ED have been identified. In addition, a distinct role of ED has been reported for each type of CRS in humans.

KEY MESSAGES

Further study is warranted to prove whether ED holds promise as a pharmacological target in CRS patients.

Leptospirosis and Peripheral Artery Occlusive Disease: A Nationwide Cohort Analysis

Data on the association between peripheral artery occlusive disease (PAOD) and leptospirosis are limited. We conducted a retrospective cohort study for determining whether leptospirosis is one of the possible risk factors for PAOD. Patients diagnosed with leptospirosis by using 2000 to 2010 data from the Taiwan National Health Insurance Research Database. Patients with leptospirosis without a history of PAOD were selected. For each leptospirosis patient, 4 controls without a history of leptospirosis and PAOD were randomly selected and frequency-matched for sex, age, the year of the index date, and comorbidity diseases. The follow-up period was from the time of the initial diagnosis of leptospirosis to the diagnosis date of PAOD, or December 31, 2011. The Cox proportional hazard regression models were used for analyzing the risk of PAOD. During the follow-up period, the cumulative incidence of PAOD was higher among the patients from the leptospirosis cohort than among the nonleptospirosis cohort (log-rank test, P < 0.001). In total, 29 patients with PAOD from the leptospirosis cohort and 81 from the nonleptospirosis cohort were observed with the incidence rates of 2.1 and 1.3 per 1000 person-years, respectively, yielding a crude hazards ratio (HR) of 1.62 (95% confidence interval [CI] = 1.44-1.81) and adjusted HR (aHR) of 1.75 (95% CI = 1.58-1.95).The risk of PAOD was 1.75-fold higher in the patients with leptospirosis than in the general population.