Exercise training reduces the acute inflammatory response associated with claudication

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.

Contemporary Medical Management of Peripheral Artery Disease

Peripheral artery disease (PAD) is a manifestation of systemic atherosclerosis. Modifiable risk factors including cigarette smoking, dyslipidemia, diabetes, poor diet quality, obesity, and physical inactivity, along with underlying genetic factors contribute to lower extremity atherosclerosis. Patients with PAD often have coexistent coronary or cerebrovascular disease, and increased likelihood of major adverse cardiovascular events, including myocardial infarction, stroke and cardiovascular death. Patients with PAD often have reduced walking capacity and are at risk of acute and chronic critical limb ischemia leading to major adverse limb events, such as peripheral revascularization or amputation. The presence of polyvascular disease identifies the highest risk patient group for major adverse cardiovascular events, and patients with prior critical limb ischemia, prior lower extremity revascularization, or amputation have a heightened risk of major adverse limb events. Medical therapies have demonstrated efficacy in reducing the risk of major adverse cardiovascular events and major adverse limb events, and improving function in patients with PAD by modulating key disease determining pathways including inflammation, vascular dysfunction, and metabolic disturbances. Treatment with guideline-recommended therapies, including smoking cessation, lipid lowering drugs, optimal glucose control, and antithrombotic medications lowers the incidence of major adverse cardiovascular events and major adverse limb events. Exercise training and cilostazol improve walking capacity. The heterogeneity of risk profile in patients with PAD supports a personalized approach, with consideration of treatment intensification in those at high risk of adverse events. This review highlights the medical therapies currently available to improve outcomes in patients with PAD.

Walking Training Improves Systemic and Local Pathophysiological Processes in Intermittent Claudication

OBJECTIVE

This study examined the impact of submaximal walking training (WT) on local and systemic nitric oxide (NO) bioavailability, inflammation, and oxidative stress in patients with intermittent claudication (IC).

METHODS

The study employed a randomised, controlled, parallel group design and was performed in a single centre. Thirty-two men with IC were randomly allocated to two groups: WT (n = 16, two sessions/week, 15 cycles of two minutes walking at an intensity corresponding to the heart rate obtained at the pain threshold interspersed by two minutes of upright rest) and control (CO, n = 16, two sessions/week, 30 minutes of stretching). NO bioavailability (blood NO and muscle nitric oxide synthase [eNOS]), redox homeostasis (catalase [CAT], superoxide dismutase [SOD], lipid peroxidation [LPO] measured in blood and muscle), and inflammation (interleukin-6 [IL-6], C-reactive protein [CRP], tumour necrosis factor α [TNF-α], intercellular adhesion molecules [ICAM], vascular adhesion molecules [VCAM] measured in blood and muscle) were assessed at baseline and after 12 weeks.

RESULTS

WT statistically significantly increased blood NO, muscle eNOS, blood SOD and CAT, and muscle SOD and abolished the increase in circulating and muscle LPO observed in the CO group. WT decreased blood CRP, ICAM, and VCAM and muscle IL-6 and CRP and eliminated the increase in blood TNF-α and muscle TNF-α, ICAM and VCAM observed in the CO group.

CONCLUSION

WT at an intensity of pain threshold improved NO bioavailability and decreased systemic and local oxidative stress and inflammation in patients with IC. The proposed WT protocol provides physiological adaptations that may contribute to cardiovascular health in these patients.

Asymptomatic peripheral artery disease: Silent but deadly

Peripheral Artery Disease (PAD) is a manifestation of atherosclerosis characterized by diminished perfusion of the limb and a state of dysmetabolism. The asymptomatic PAD phenotype is a relatively recent classification. It is unknown how many people currently live with asymptomatic PAD because there are no universal screening recommendations for patients at risk for PAD. Patients with asymptomatic PAD suffer from a similar risk profile of morbidity and mortality as their counterparts with claudication. Despite this increased risk, there is a dearth of clinical investigations into therapies that specifically benefit the asymptomatic PAD population. At present, current pharmacotherapies that have been studied in PAD patient populations do not stratify by symptom status. We believe that further investigation of the impact of existing therapies in this unique population presents an opportunity to reduce morbidity and mortality due to PAD. This can only be achieved in combination with wide-spread adoption of screening for asymptomatic PAD.

All Patients Benefit Equally From a Supervised Exercise Program for Claudication

This study assessed the effect of gender, diabetic status, statin use, smoking, hypertension, cardiac status, and use of cilostazol on the outcome of a supervised exercise program for patients with claudication. Patient risk factors were prospectively recorded in a group of patients who had completed 1 year on a supervised exercise program. In 165 claudicant patients, maximum walking distance increased ( P < .0001) from 67 meters (range, 17-196) to 122 meters (range, 43-409). Quality of life as measured by the Medical Outcome Study Short Form 36 increased ( P < .0001) from a median of 78 (range, 55-110) to 99 (range, 71-154). The improvements in claudication distance, maximal walking distance, and quality of life after the exercise program were not dependent on any of the measured patient factors. Patients referred to exercise programs for claudication are a heterogenous group. Despite this, they benefit equally from such a program.

Multi-dimensional flow cytometry analysis reveals increasing changes in the systemic neutrophil compartment during seven consecutive days of endurance exercise

Endurance exercise is associated with a transient increase in neutrophil counts in the peripheral blood. Here we investigate the impact of intensified endurance exercise on the neutrophil compartment. We hypothesized that intensified endurance exercise leads to mobilization of neutrophil subsets, which are normally absent in the blood. Furthermore, we followed the potential build-up of neutrophil activation and the impact on overnight recovery of the neutrophil compartment during a seven-day cycling tour. The neutrophil compartment was studied in 28 healthy amateur cyclists participating in an eight-day strenuous cycling tour. Blood samples were taken at baseline, after 4 days and after 7 days of cycling. The neutrophil compartment was analyzed in terms of numbers and its phenotype by deep phenotyping of flow cytometry data with the multi-dimensional analysis method FLOOD. Repeated endurance exercise led to a gradual increase in total neutrophil counts over the days leading to a 1.26 fold-increase (95%CI 1.01–1.51 p = 0.0431) in the morning of day 8. Flow cytometric measurements revealed the appearance of 2 additional neutrophil subsets: CD16^brightCD62L^dim and CD16^dimCD62L^bright. A complex change in neutrophil phenotypes was present characterized by decreased expression of both CD11b and CD62L and marked increased expression of LAIR-1, VLA-4 and CBRM1/5. The changes in expression were found on all neutrophils present in the blood. Strikingly, in strong contrast to our findings during acute inflammation evoked by LPS challenge, these neutrophils did not upregulate classical degranulation markers. In fact, our FLOOD analysis revealed that the exercise induced neutrophil phenotype did not overlap with the neutrophil subsets arising upon acute inflammation. In conclusion, during multiple days of endurance exercise the neutrophil compartment does not regain homeostasis overnight. Thereby our study supports the concept of a build-up of inflammatory cues during repeated endurance exercise training, causing a prolonged change of the systemic neutrophil compartment.

Physical Exercise Reduces Cytotoxicity and Up-Regulates Nrf2 and UPR Expression in Circulating Cells of Peripheral Artery Disease Patients: An Hypoxic Adaptation?

Aim: Ischemia-reperfusion (I-R) produces reactive oxygen species (ROS) that damage cells and favour cytotoxicity and apoptosis in peripheral artery disease (PAD) patients. Since brief episodes of I-R (ischemic conditioning) protect cells against ischemic harms, we evaluated whether a short-course of supervised treadmill training, characterized by repeated episodes of I-R, makes peripheral blood mononuclear cells (PBMCs) from PAD patients with intermittent claudication more resistant to I-R injuries by reducing oxidative stress and by inducing an adaptative response of unfolded protein response (UPR) and nuclear factor-E2-related factor (Nrf2) pathway expression.

Methods: 24 PAD patients underwent 21 sessions of treadmill training and a treadmill test as indicator of acute response to I-R.

Results: Maximal and pain free walking distance improved (p < 0.01), whereas LDH leakage and apoptosis of PBMCs decreased (p < 0.01); plasma malondialdehyde and ROS generation in PBMCs declined, while plasma glutathione augmented (p < 0.01). Moreover we demonstrated an up-regulation of UPR and Nrf2 expression in PBMCs (p < 0.01). To understand whether treadmill training may act as a trigger of ischemic conditioning, we examined the effect of repeated episodes of I-R on adaptative response in PBMCs derived from the patients. We showed an up-regulation of UPR and Nrf2 gene expression (p < 0.01), while oxidative stress and cytotoxicity, after an initial increase, declined (p < 0.01). This positive effect on cytotoxicity was reduced after inhibition of UPR and Nrf2 pathways.

Conclusions: Treadmill training in PAD patients through UPR and Nrf2 up-regulation may trigger hypoxic adaptation similar to conditioning, thus modifying cell survival.

Exercise training in intermittent claudication: Effects on antioxidant genes, inflammatory mediators and proangiogenic progenitor cells

Exercise training remains a therapy of choice in intermittent claudication (IC). However, too exhaustive exercise may cause ischaemic injury and inflammatory response. We tested the impact of three-month treadmill training and single treadmill exercise on antioxidant gene expressions, cytokine concentrations and number of marrow-derived proangiogenic progenitor cells (PPC) in the blood of IC patients. Blood samples of 12 patients were collected before and after training, before and 1, 3 and 6 hours after the single exercise. PPCs were analysed with flow cytometry, cytokine concentrations were checked with Milliplex MAP, while expression of mRNAs and miRNAs was evaluated with qRT-PCR. Treadmill training improved pain-free walking time (from 144 ± 44 seconds [s] to 311 ± 134 s, p=0.02) and maximum walking time (from 578 ± 293 s to 859 ± 423 s, p=0.01) in IC patients. Before, but not after training, the single treadmill exercise increased the number of circulating CD45dimCD34+CD133-KDR+ PPCs (p=0.048), decreased expression of HMOX1 (p=0.04) in circulating leukocytes, reduced tumour necrosis factor-α (p=0.03) and tended to elevate myeloperoxidase (p=0.06) concentrations in plasma. In contrast, total plasminogen activator inhibitor-1 was decreased by single exercise only after, but not before training (p=0.02). Both before and after training the single exercise decreased monocyte chemoattractant protein (MCP)-1 (p=0.006 and p=0.03) concentration and increased SOD1 (p=0.001 and p=0.01) expression. Patients after training had also less interleukin-6 (p=0.03), but more MCP-1 (p=0.04) in the blood. In conclusion, treadmill training improves walking performance of IC patients, attenuates the single exercise-induced changes in gene expressions or PPC mobilisation, but may also lead to higher production of some proinflammatory cytokines.

Extracorporeal shockwave therapy for the treatment of lower limb intermittent claudication: study protocol for a randomised controlled trial (the SHOCKWAVE 1 trial)

Background

Peripheral arterial disease (PAD) has a population prevalence of 4.6% with intermittent claudication (IC) presenting as one of the earliest and most common symptoms. PAD has detrimental effects on patients’ walking ability in terms of maximum walking distance (MWD) and pain-free walking distance (PFWD). Research has suggested extracorporeal shockwave therapy (ESWT) may induce angiogenesis in treated tissue; therefore, our objective is to assess the tolerability and efficacy of ESWT as a novel treatment of intermittent claudication.

Methods/design

Patients with unilateral claudication will be randomised to receive either ESWT (PiezoWave 2 shockwave system) or sham treatment to the calf muscle bulk three times per week for 3 weeks. All patients are blinded to treatment group, and all assessments will be performed by a masked assessor. Treatment tolerability using a visual analogue scale, ankle-brachial pressure index, MWD, PFWD and safety will all be formally assessed as outcome measures at baseline and at 4, 8 and 12 weeks follow-up.

Discussion

This trial will be the first of its kind in terms of methodology in relation to ESWT for intermittent claudication. A double-masked randomised controlled trial will provide useful information about the potential for the use of ESWT as a non-invasive treatment option and the need for further robust research.

Trial registration

ClinicalTrials.gov, NCT02652078. Registered on 17 October 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1844-4) contains supplementary material, which is available to authorized users.

Association between daily walking and antioxidant capacity in patients with symptomatic peripheral artery disease

OBJECTIVE

The primary aim of the study was to assess whether both the amount and pace of daily walking were associated with circulating antioxidant capacity in symptomatic patients with peripheral artery disease (PAD).

METHODS

Community-based walking was measured in 244 men and women who were limited by symptomatic PAD during a 1-week period in which they wore an ankle-mounted step activity monitor. Patients were further characterized by circulating antioxidant capacity with the OxiSelect (Cell Biolabs Inc, San Diego, Calif) hydroxyl radical antioxidant capacity (HORAC) activity assay.

RESULTS

To assess the amount of walking, patients were grouped into low (≤2440 strides/d), middle (2441-3835 strides/d), and high (>3835 strides/d) stride tertiles. HORAC was higher in the middle (P = .03) and high (P = .01) stride tertiles than in the low tertile, but there was no difference between middle and high tertiles (P = .44). To assess the pace of walking, patients were grouped into slow (<25.0 strides/min), middle (25.0-31.6 strides/min), and fast (>31.6 strides/min) cadence tertiles. HORAC was higher in the high cadence tertile than in the low (P < .01) and middle (P < .01) tertiles, but there was no difference between low and middle tertiles (P = .48). Similar findings were obtained on group differences in HORAC after adjusting for age, sex, race, and ankle-brachial index for both the amount and pace of daily walking.

CONCLUSIONS

Walking >2440 strides each day and walking at a cadence faster than 31.6 strides/min for 30 minutes each day are both associated with greater circulating antioxidant capacity in symptomatic patients with PAD. The clinical significance is that a home-based walking program may be one approach to increase endogenous antioxidant capacity.

A randomised controlled trial of two supervised exercise regimens and their impact on inflammatory burden in patients with intermittent claudication

Objective

This study assesses the impact of treadmill-based SET alone or in combination with resistance training on systemic inflammatory response, in patients with intermittent claudication (IC).

Methods

Thirty-five patients with IC were randomised to 12 weeks of treadmill-only SET (Group 1) or a combination of treadmill and lower-limb resistance SET (Group 2). A panel of pro- and anti-inflammatory markers were assessed before, during and after the SET.

Results

Over the duration of SET, homocysteine increased within Group 1 (12.0–15.5 µmol/L, p = 0.003) but not Group 2, (13.7–14.7 µmol/) while neutrophil elastase (NE) increased within Group 2 (174.5–238.2 ng/mL, p = 0.007) but not Group 1 (300.8–312.0 ng/mL). In both groups NE increased following acute exercise at the start of the SET. Differences in cytokine expression was evident between the two groups (in Group 1, pro-inflammatory cytokines interleukin-12 and interferon-gamma decreased following an acute bout of exercise at the end of SET, where as in Group 2 pro-inflammatory cytokines interleukin-6 and 8 were seen to increase after an acute bout of exercise at the end of SET).

Conclusion

SET in patients with IC influences the complex immune-modulatory state of atherosclerosis through inflammatory pathways that induce both pro-inflammatory and immunosuppressive responses.

Effects of oral N-acetylcysteine on walking capacity, leg reactive hyperemia, and inflammatory and angiogenic mediators in patients with intermittent claudication

Increased oxidative stress and inflammation contribute to impaired walking capacity and endothelial dysfunction in patients with intermittent claudication (IC). The goal of the study was to determine the effects of oral treatment with the antioxidant N-acetylcysteine (NAC) on walking capacity, leg postocclusive reactive hyperemia, circulating levels of inflammatory mediators, and whole blood expression of angiogenic mediators in patients with IC. Following a double-blinded randomized crossover design, 10 patients with IC received NAC (1,800 mg/day for 4 days plus 2,700 mg before the experimental session) and placebo (PLA) before undergoing a graded treadmill exercise test. Leg postocclusive reactive hyperemia was assessed before and after the test. Blood samples were taken before and after NAC or PLA ingestions and 5 and 30 min after the exercise test for the analysis of circulating inflammatory and angiogenic markers. Although NAC increased the plasma ratio of reduced to oxidized glutathione, there were no differences between experimental sessions for walking tolerance and postocclusive reactive hyperemia. Plasma concentrations of soluble vascular cell adhesion protein-1, monocyte chemotactic protein-1, and endothelin-1 increased similarly following maximal exercise after PLA and NAC (P < 0.001). Whole blood expression of pro-angiogenic microRNA-126 increased after maximal exercise in the PLA session, but treatment with NAC prevented this response. Similarly, exercise-induced changes in whole blood expression of VEGF, endothelial nitric oxide synthase and phosphatidylinositol 3-kinase R2 were blunted after NAC. In conclusion, oral NAC does not increase walking tolerance or leg blood flow in patients with IC. In addition, oral NAC prevents maximal exercise-induced increase in the expression of circulating microRNA-126 and other angiogenic mediators in patients with IC.

A review of the pathophysiology and potential biomarkers for peripheral artery disease

Peripheral artery disease (PAD) is due to the blockage of the arteries supplying blood to the lower limbs usually secondary to atherosclerosis. The most severe clinical manifestation of PAD is critical limb ischemia (CLI), which is associated with a risk of limb loss and mortality due to cardiovascular events. Currently CLI is mainly treated by surgical or endovascular revascularization, with few other treatments in routine clinical practice. There are a number of problems with current PAD management strategies, such as the difficulty in selecting the appropriate treatments for individual patients. Many patients undergo repeated attempts at revascularization surgery, but ultimately require an amputation. There is great interest in developing new methods to identify patients who are unlikely to benefit from revascularization and to improve management of patients unsuitable for surgery. Circulating biomarkers that predict the progression of PAD and the response to therapies could assist in the management of patients. This review provides an overview of the pathophysiology of PAD and examines the association between circulating biomarkers and PAD presence, severity and prognosis. While some currently identified circulating markers show promise, further larger studies focused on the clinical value of the biomarkers over existing risk predictors are needed.

Physiology in medicine: peripheral arterial disease

Peripheral arterial disease (PAD) is an atherosclerotic condition that can provoke symptoms of leg pain ("intermittent claudication") during exercise. Because PAD is often observed with comorbid conditions such hypertension, dyslipidemia, diabetes, cigarette smoking, and/or physical inactivity, the pathophysiology of PAD is certainly complex and involves multiple organ systems. Patients with PAD are at high risk for myocardial infarction, stroke, and all-cause mortality. For this reason, a better physiological understanding of the pathogenesis and treatment options for PAD patients is necessary and forms the basis of this Physiology in Medicine review.

Monitored daily ambulatory activity, inflammation, and oxidative stress in patients with claudication

We determined the association between daily ambulatory activity and markers of inflammation and oxidative stress in patients with peripheral artery disease (PAD) and claudication. Patients with PAD (n = 134) limited by claudication were studied. Patients took 3275 ± 1743 daily strides for 273 ± 112 minutes each day, and their average daily cadence was 11.7 ± 2.7 strides/min. High-sensitivity C-reactive protein was significantly and negatively associated with the total number of daily strides (P < .001), total daily ambulatory time (P < .01), peak activity index (P < .01), daily average cadence (P < .05), and the maximum cadences for 60 minutes (P < .05), 30 minutes (P < .05), 20 minutes (P < .05), and 5 minutes (P < .01). Oxidized low-density lipoprotein and soluble vascular cell adhesion molecule 1 were not significantly associated with any of the ambulatory measures (P > .05). We conclude that higher levels of community-based, daily ambulatory activity are associated with lower levels of inflammation but are not associated with markers of oxidative stress.

Exercise training and peripheral arterial disease

Peripheral arterial disease (PAD) is a common vascular disease that reduces blood flow capacity to the legs of patients. PAD leads to exercise intolerance that can progress in severity to greatly limit mobility, and in advanced cases leads to frank ischemia with pain at rest. It is estimated that 12 to 15 million people in the United States are diagnosed with PAD, with a much larger population that is undiagnosed. The presence of PAD predicts a 50% to 1500% increase in morbidity and mortality, depending on severity. Treatment of patients with PAD is limited to modification of cardiovascular disease risk factors, pharmacological intervention, surgery, and exercise therapy. Extended exercise programs that involve walking approximately five times per week, at a significant intensity that requires frequent rest periods, are most significant. Preclinical studies and virtually all clinical trials demonstrate the benefits of exercise therapy, including improved walking tolerance, modified inflammatory/hemostatic markers, enhanced vasoresponsiveness, adaptations within the limb (angiogenesis, arteriogenesis, and mitochondrial synthesis) that enhance oxygen delivery and metabolic responses, potentially delayed progression of the disease, enhanced quality of life indices, and extended longevity. A synthesis is provided as to how these adaptations can develop in the context of our current state of knowledge and events known to be orchestrated by exercise. The benefits are so compelling that exercise prescription should be an essential option presented to patients with PAD in the absence of contraindications. Obviously, selecting for a lifestyle pattern that includes enhanced physical activity prior to the advance of PAD limitations is the most desirable and beneficial.

Supervised Exercise in Intermittent Claudication: A Sedentary Notion?

The benefit of exercise in the management of intermittent claudication has been explored through extensive research in the preceding decades. Within the clinical setting, there is often little differentiation between home-based and supervised exercise regimens. We examined the history and qualification of supervised exercise as a distinct treatment modality from nonsupervised exercise in intermittent claudication. A Medline, Embase, Ovid, Cochrane Database, and Google Scholar search was performed on all studies published until December 31, 2007, investigating the use of supervised exercise in peripheral arterial disease. Supervised exercise is well grounded in evidence to support its superiority over nonsupervised exercise in the management of intermittent claudication, conveying marked improvement in symptomatology, function, and quality of life. Further research is required to determine the nature of the advantage that supervision affords.

Physical activity during daily life and circulating biomarker levels in patients with peripheral arterial disease

Higher levels of inflammation are associated with adverse outcomes in patients with lower extremity peripheral arterial disease (PAD). This study evaluated associations of physical activity during daily life with levels of inflammatory biomarkers, D-dimer, and homocysteine in patients with PAD. Participants were 244 men and women (mean age 74.4 +/- 8.2 years) with PAD (ankle brachial index <0.90). C-reactive protein, interleukin-6, soluble intracellular adhesion molecule-1, soluble vascular cellular adhesion molecule-1, D-dimer, and homocysteine were assessed at study entry. Physical activity was objectively assessed with a vertical accelerometer, which participants wore continuously for 7 days. After adjusting for age, gender, race, body mass index, smoking, co-morbidities, ankle brachial index, and other potential confounders, higher physical activity levels were associated linearly and significantly with lower levels of all measured circulating biomarkers: soluble vascular cellular adhesion molecule-1 (p trend = 0.001), D-dimer (p trend = 0.005), homocysteine (p trend = 0.006), interleukin-6 (p trend = 0.010), C-reactive protein (p trend = 0.028), and soluble intracellular adhesion molecule-1 (p trend = 0.033). In conclusion, higher levels of physical activity were associated independently with lower levels of inflammatory markers, homocysteine, and D-dimer in patients with PAD.

Measurement of ischaemia-reperfusion in patients with intermittent claudication using NMR-based metabonomics

Intermittent claudication has proved to be a good in vivo model for ischaemia-reperfusion. For assessment of ischaemia-reperfusion damage, the known biochemical markers all have disadvantages with respect to sensitivity and interference with other physiological events. In this work, we studied the metabolic effects of ischaemia-reperfusion in patients with intermittent claudication, and the effects of vitamin C and E intervention, using both traditional biochemical measurements and 1H-NMR-based metabonomics on urine and plasma. The 1H-NMR spectra were subjected to multivariate modelling using principal components discriminant analysis, and the observed clusters were validated using joint deployment of univariate analysis of variance and Tukey-Kramer honestly significant difference (HSD) testing. The study involved 14 patients with intermittent claudication and three healthy volunteers, who were monitored during a walking test, before and after a vitamin C/E intervention, and after a washout period. The effect of exercise was only observable for a limited number of biochemical markers, whereas 1H NMR revealed an effect in line with anaerobic ATP production via glycolysis in exercising (ischaemic) muscle of the claudicants. Thus, the beneficial effect of vitamins C and E in claudicants was more pronounced when observed by metabonomics than by traditional biochemical markers. The main effect was more rapid recovery from exercise to resting state metabolism. Furthermore, after intervention, claudicants tended to have lower concentrations of lactate and glucose and several other citric acid cycle metabolites, whereas acetoacetate was increased. The observed metabolic changes in the plasma suggest that intake of vitamin C/E leads to increased muscle oxidative metabolism.

Mitochondriopathy of peripheral arterial disease

The signs and symptoms of peripheral arterial occlusive disease (PAD), including claudication, rest pain, and tissue loss, are consequences of compromised bioenergetics and oxidative tissue injury within the affected lower extremities. Compromised bioenergetics is the result of a combination of low blood flow through diseased arteries and diminished adenosine triphosphate production by dysfunctional mitochondria. The tissue injury appears to be secondary to increased production of reactive oxygen species by dysfunctional mitochondria and by inflammation, in association with ischemia and ischemia/reperfusion. In this review, we present the current histomorphologic, physiologic, and biochemical evidence defining the nature of this mitochondriopathy and discuss its contribution to the pathogenesis and clinical manifestations of PAD.

The myopathy of peripheral arterial occlusive disease: Part 2. Oxidative stress, neuropathy, and shift in muscle fiber type

In recent years, an increasing number of studies have demonstrated that a myopathy is present, contributes, and, to a certain extent, determines the pathogenesis of peripheral arterial occlusive disease. These works provide evidence that a state of repetitive cycles of exercise-induced ischemia followed by reperfusion at rest operates in patients with peripheral arterial occlusive disease and mediates a large number of structural and metabolic changes in the muscle, resulting in reduced strength and function. The key players in this process appear to be defective mitochondria that, through multilevel failure in their roles as energy, oxygen radical species, and apoptosis regulators, produce and sustain a progressive decline in muscle performance. In this 2-part review, the currently available evidence that characterizes the nature and mechanisms responsible for this myopathy is highlighted. In part 1, the functional and histomorphological characteristics of the myopathy were reviewed, and the main focus was on the biochemistry and bioenergetics of its mitochondriopathy. In part 2, accumulating evidence that oxidative stress related to ischemia reperfusion is probably the major operating mechanism of peripheral arterial occlusive disease myopathy is reviewed. Important new findings of a possible neuropathy and a shift in muscle fiber type are also reviewed. Learning more about these mechanisms will enhance our understanding of the degree to which they are preventable and treatable.

Antioxidants attenuate oxidative damage in rat skeletal muscle during mild ischaemia

We have previously shown oxidative stress and oedema, caused by both xanthine oxidase-derived oxidants and infiltrating neutrophils, within skeletal muscle after contractile-induced claudication. The purpose of this study was to determine whether supplementation with antioxidant vitamins attenuates the oxidative stress, neutrophil infiltration and oedema associated with an acute bout of contractile-induced claudication. Rats received vehicle, vitamin C, vitamin E or vitamin C + E for 5 days prior to contractile-induced claudication. Force production was significantly reduced in the claudicant limbs of all groups compared with the control (sham) limb of control animals. Contractile-induced claudication caused a significant increase in protein oxidation, lipid peroxidation, neutrophil infiltration and oedema compared with sham muscles. Supplementation with vitamin C, E or C + E prevented the increases in each of these, and there were no differences between groups. These findings suggest that, in an animal model of exercise-induced claudication, neutrophil chemotaxis is caused by oxidizing species and that antioxidant supplementation can prevent oxidative damage, neutrophil infiltration and oedema following an acute bout of contractile-induced claudication.

Supervised Exercise Training for Intermittent Claudication: Lasting Benefit at Three Years

OBJECTIVES

To assess the long-term outcome of supervised exercise training for intermittent claudication.

METHODS

A prospective study was undertaken of all patients referred to a single centre with intermittent claudication (>46 m). Patients underwent supervised exercise training twice weekly for 10 weeks, with regular follow-up to 3 years. Actual Claudication Distance (ACD), Maximum Walking Distance (MWD) and ankle-brachial pressure indices (ABPI) were measured.

RESULTS

In 202 patients the initial median ACD and MWD were 112 m and 197 m. Following exercise therapy both the median ACD and MWD increased to 266 m and 477 m at three months, increases of 237% and 242% respectively (p<0.001). At three years the median ACD and MWD were 250 m and 372 m, increases of 223% and 188% respectively (p<0.001). There was no significant change in ACD or MWD at 3 months compared to 1, 2 or 3 years. ABPI remained unchanged throughout.

CONCLUSIONS

Supervised exercise training has long term benefit in patients with intermittent claudication. Results seen at 12 weeks are sustained at three years.

Colitis-induced oxidative damage of the colon and skeletal muscle is ameliorated by regular exercise in rats: the anxiolytic role of exercise

Epidemiological studies have shown that exercise protects the gastrointestinal tract, reducing the risk of diverticulosis, gastrointestinal haemorrhage and inflammatory bowel disease, while many digestive complaints occurring during exercise are attributed to the adverse effects of exercise on the colon. In order to assess the effects of regular exercise on the pathogenesis of colitis, Sprague-Dawley rats of both sexes were either kept sedentary or given exercise on a running wheel (0.4 km h(-1), 30 min for 3 days week(-1)). At the end of 6 weeks, under anaesthesia, either saline or acetic acid (4%, 1 ml) was given intracolonically. Holeboard tests were performed for the evaluation of anxiety at 24 h before and 48 h after induction of colitis. Increased 'freezing time' in the colitis-induced sedentary group, representing increased anxiety, was reduced in the exercised colitis group (P < 0.05). On the third day following the colonic instillation, the rats were decapitated under brief ether anesthesia and the distal 8 cm of the colons were removed. In the sedentary colitis group, macroscopic and microscopic damage scores, malondialdehyde level and myeloperoxidase activity were increased when compared to the control group (P < 0.01-0.001), while exercise prior to colitis reduced all the measurements with respect to sedentary colitis group (P < 0.05-0.001). The results demonstrate that low-intensity, repetitive exercise protects against oxidative colonic injury, and that this appears to involve the anxiolytic effect of exercise, suggesting that exercise may have a therapeutic value in reducing stress-related exacerbation of colitis.

Haemostasis, inflammation and renal function following exercise in patients with intermittent claudication on statin and aspirin therapy

Background

Previous studies have suggested that exercise in patients with intermittent claudication (IC) may induce a systemic thrombo-inflammatory response. The effect of secondary prevention therapy on this response is unknown. This study aimed to investigate the effects of treadmill exercise on markers of coagulation activation, inflammation and renal function in patients with IC, receiving aspirin and statin therapy compared to healthy controls.

Methods

Samples were taken before, immediately and 1 hour after exercising on a treadmill in 20 patients with IC and 20 healthy volunteers. Interleukin-6 (IL-6), thrombin-anti-thrombin complex (TAT) and fibrin D-dimer were measured by ELISA. High sensitivity CRP (HsCRP) and urinary albumin were measured via a nephelometric technique, urinary protein via a turbidometric assay and N-acetyl-β-D-glucosaminidase (NAG) via a colorimetric assay.

Results

Elevated baseline levels of Hs-CRP, IL-6, white cell counts, D-dimer and urinary NAG occurred in patients with IC compared to volunteers (p > 0.05). Following exercise there was no increase in Hs CRP or IL-6. D-dimer levels significantly increased following exercise in the patients and volunteers. TAT levels increased immediately after exercise in the patient group only and were significantly increased at 1 hour in both patients and volunteers. A transient rise in the protein creatinine ratio occurred in both groups (p < 0.007), and in albumin creatinine ratio in the patient group. There was no change in urinary NAG.

Conclusion

Elevated markers of inflammation occurred in patients with IC on statin and aspirin therapy but these did not increase following exercise. However, acute exercise resulted in a prothrombotic state evident in both groups, although this was more prolonged in patient with IC. The clinical significance of these findings in patients who are known to be at an increased risk of cardiac and other thrombotic event are unclear.

A Preliminary Study on the Effects of Exercising to Maximum Walking Distance on Platelet and Endothelial Function in Patients with Intermittent Claudication

BACKGROUND

Platelet and endothelial activation has been shown to be increased in patients with intermittent claudication (IC). Recent studies have suggested that exercise may induce further platelet activation. The aims of this study were to investigate the effect of exercising to maximum walking distance on platelet and endothelial function in patients with intermittent claudication who were receiving statin and aspirin therapy compared with age matched healthy controls.

METHODS

Platelet aggregation through COX-mediated and thrombin receptor activator peptide (TRAP)-stimulated GPIIb/IIIa pathways was measured by the Ultegra point of care system in 20 patients with IC on aspirin and 20 healthy volunteers before, immediately and 1h after exercising to treadmill maximal walking distance (MWD). Soluble P-selectin, vWF and sICAM were measured using an enzyme linked immuno-sorbent assay technique.

RESULTS

Baseline platelet aggregation was significantly reduced in patients with IC compared to volunteers (p<0.05). In patients, exercising to MWD significantly reduced platelet aggregation (COX, median -5% [range -24 to 13%]; p = 0.02; GPIIIa/IIb, median -13% [range -72 to 33%]; p = 0.02) immediately post-exercise which returned to baseline values at 1 h. There was no change in the healthy volunteers following the same median duration of exercise. Baseline sP-selectin levels were higher in the patients with IC compared to the healthy volunteers [Median values (interquartile range), 42.72 (33.28-54.24) versus 29.16 (24.40-34.10), p = 0.0003] but there were no differences in vWF levels. Both sP-selectin and vWF levels increased significantly in the control and patient group following exercise (p<0.005). sICAM were higher at baseline in the patients with IC but were unchanged following exercise [Median values (interquartile range),560.9 (405.5-739.4) versus 467.0 (325.7-643.4), p<0.05].

CONCLUSION

This study is the first to show that platelet aggregation is reduced immediately following treadmill exercise to maximum walking distance in patients with IC despite a rise in sP-selectin and vWF, suggesting endothelial activation. The inhibition of platelet aggregation after exercise in subjects on antiplatelet and statin therapy suggests that exercise is unlikely to exacerbate platelet thrombus formation in patients with IC.

The constitutive procoagulant and hypofibrinolytic state in patients with intermittent claudication due to infrainguinal disease significantly improves with percutaneous transluminal balloon angioplasty

BACKGROUND

Patients with intermittent lower limb claudication (IC) exhibit a prothrombotic diathesis that is acutely exacerbated by exercise. This may occur because of ischemia/reperfusion injury within the leg muscles during walking and may contribute to the increased risk of thrombotic vascular events in this group of patients. This randomized study compared the effect of lower limb revascularization by percutaneous transluminal balloon angioplasty (PTA), supervised exercise, and best medical therapy (BMT) alone on this prothrombotic state.

METHODS

Twenty-three patients (16 men and 7 women; median age, 67 years; range, 57-77 years) with IC due to infrainguinal disease were randomized to receive BMT alone (n = 7), BMT plus PTA (n = 9), or BMT plus supervised exercise (n = 7) as part of the Health Technology Assessment-funded EXercise vs Angioplasty in Claudication Trial (EXACT). Patients were assessed at baseline and at 3 and 6 months. Thrombin-antithrombin complex (TAT) was determined as a marker of thrombin generation, and plasminogen activator inhibitor (PAI) antigen was determined as a marker of fibrinolysis. Increased TAT indicates a procoagulant state, and increased PAI antigen indicates a hypofibrinolytic state.

RESULTS

At 6 months, subjects randomized to BMT plus PTA demonstrated a significant improvement in ankle-brachial pressure index (P = .013) and maximal walking distance (P = .008), a significant decline in resting thrombin generation (median [interquartile range] TAT, 6.4 microg/L [2.7-13.5 microg/L] to 1.5 microg/L [0.3-2.9 microg/L]; P = .038), and an improvement in resting fibrinolysis (median [interquartile range] PAI-1, 10.0 ng/mL [1.0-20.5 ng/mL] to 1.0 ng/mL [1.0-14.8 ng/mL]; P = .043). There was no significant change in any of these parameters in patients randomized to BMT plus supervised exercise or to BMT alone.

CONCLUSIONS

The addition of lower limb revascularization by PTA to BMT in patients with IC due to infra-inguinal disease results in a medium-term improvement in the resting procoagulant and hypofibrinolytic state. This may translate into a reduction in morbidity and mortality from thrombotic vascular events in this group of patients.

Experimental Model of Pain-Free Treadmill Training in Patients with Claudication

OBJECTIVE

Treadmill training in claudication is often based on walking exercise to a pain threshold or longer to the maximum muscle pain of the lower limbs. This kind of exercise may cause an inflammatory response. The purpose of this study was to determine whether pain-free treadmill training using walking exercise to 85% of the distance to onset of claudication pain can significantly improve pain-free walking distance in patients with intermittent claudication and to evaluate whether this kind of program may induce an inflammatory response leading to the progression of atherosclerosis.

DESIGN

A total of 98 patients aged 50-70 yrs with stable intermittent claudication were randomized into a supervised treadmill training program or a comparison group. Patients in the treatment group participated in 12 wks of supervised treadmill training. We examined the effects of 12 wks of pain-free treadmill training on pain-free walking distance, total leukocyte count, neutrophil count, and microalbuminuria in patients with claudication.

RESULTS

A total of 80 participants completed the program. Exercise rehabilitation increased the time to onset of claudication pain by 119.2%, from 87.4 +/- 38 m to 191.6 +/- 94.8 m (P < 0.001). There was no increase in total leukocyte count, neutrophil count, or microalbuminuria after 12 wks of treadmill exercise (P > 0.05)

CONCLUSION

A pain-free training program can be used in the treatment of claudication as a low-risk program, increasing walking ability without potential harmful effects of ischemia-reperfusion injury.

Effects of warm-up on exercise capacity, platelet activation and platelet-leucocyte aggregation in patients with claudication

BACKGROUND

The effects of exercise and warm-up were investigated in patients with claudication.

METHODS

This case-control crossover study involved two treadmill exercise tests, one preceded by a warm-up. Exercise continued until maximal leg pain (patients with claudication) or exhaustion (controls). Blood was taken before, and 5 and 60 min after exercise for flow cytometric analysis of platelet activation and platelet-leucocyte aggregation.

RESULTS

Both cohorts (eight patients with claudication of median age 63 years and eight healthy controls of median age 63.5 years) demonstrated improvement in exercise capacity after warm-up (13.1 per cent, P = 0.012 and 15.6 per cent, P = 0.008 respectively). Platelet activation increased after exercise in patients with claudication (fibrinogen binding: 1.11 per cent before exercise versus 2.63 per cent after exercise, P = 0.008; P-selectin: 0.68 versus 1.11 per cent, P = 0.028). Neither agonist stimulation nor warm-up altered this trend. Platelet-leucocyte (PLA) and platelet-neutrophil (PNA) aggregation were similarly increased immediately after exercise in patients with claudication (PLA: 7.6 versus 13.0 per cent, P = 0.004; PNA: 6.8 versus 10.2 per cent, P = 0.012). These remained high 60 min after exercise only in patients with claudication, but recovered to baseline levels when preceded by warm-up. Warm-up significantly desensitized PNA after stimulation with 10 micromol/l adenosine 5'-diphosphate at all time points.

CONCLUSION

Warm-up increased the exercise capacity of patients with claudication. Exercise induced a thromboinflammatory response, with PLA and PNA persistently increased after 60 min in patients with claudication, an effect diminished after warm-up.

Inflammatory status and endothelial function in asymptomatic and symptomatic peripheral arterial disease

Peripheral arterial disease (PAD) is a predictor of cardiovascular risk. However, it is unknown whether PAD severity influences inflammatory status and endothelial function, which play a major role in atherosclerosis. Accordingly, we measured brachial artery flow-mediated dilation (FMD), and plasma levels of several inflammatory markers in 15 control subjects, and 19 asymptomatic and 19 symptomatic PAD patients. Each symptomatic patient was matched to an asymptomatic patient for age, sex, risk factors, presence of cardiovascular disease, and pharmacological treatments. Asymptomatic patients had similar inflammatory profiles as controls, but lower median FMD (11.7% vs 8.5%, p < 0.01). Compared with asymptomatic patients, symptomatic patients had higher median C-reactive protein (1.5 mg/l vs 6.0 mg/l, p < 0.05) and interleukine-6 (1.5 pg/ml vs 3.5 pg/ml, p < 0.05), and lower FMD (8.5% vs 5.1%, p < 0.01). In the 38 PAD patients, the ankle/brachial pressure index correlated positively with FMD (p < 0.01), and negatively with C-reactive protein (p < 0.05), soluble intercellular adhesion molecule-1 (p < 0.05) and soluble vascular cell adhesion molecule-1 (p < 0.05). Thus, in PAD, endothelial function and inflammatory status are related to the severity of the circulatory impairment. This finding may contribute to the explanation of the increasingly poor prognosis with increased PAD severity.

Xanthine oxidase and activated neutrophils cause oxidative damage to skeletal muscle after contractile claudication

We previously showed oxidative damage and edema within skeletal muscle after contractile claudication. To investigate the sources of this oxidative damage in the gastrocnemius muscle, we administered allopurinol (Allo, to inhibit xanthine oxidase) and cyclophosphamide (Cyclo, to deplete neutrophils) before inducing contractile claudication in male Sprague Dawley rats. Contractile claudication (ligated stimulated, LS) caused a significant increase in xanthine oxidase activity [sham ligated stimulated (SS) = 2.57 +/- 0.07; LS = 3.22 +/- 0.07] and neutrophil infiltration (SS = 0.47 +/- 0.03; LS = 0.91 +/- 0.10) compared with controls (SS), and this was associated with increased lipid peroxidation, protein oxidation, muscle damage, and edema. Pretreatment with Allo attenuated the increase in xanthine oxidase activity and attenuated lipid hydroperoxides (control LS = 12.85 +/- 0.50; Allo LS = 9.96 +/- 0.71), muscle damage, and neutrophil infiltration (control LS = 0.91 +/- 0.10; Allo LS = 0.61 +/- 0.07). This latter finding suggests that xanthine oxidase-derived oxidants are chemotactic to neutrophils. Pretreatment with Cyclo reduced neutrophil infiltration (control LS = 0.91 +/- 0.10; Cyclo LS = 0.55 +/- 0.02) and attenuated lipid peroxidation (control LS = 12.85 +/- 0.50; Cyclo LS = 6.462 +/- 0.62), protein oxidation (control LS = 2.59 +/- 0.47; Cyclo LS = 1.77 +/- 0.60), muscle damage, and edema. Together, these data indicate that contractile claudication causes an increase in xanthine oxidase activity and neutrophils in muscle and that inhibition of these oxidant sources protects against oxidative stress, muscle damage, and edema.

Oxidative damage to skeletal muscle following an acute bout of contractile claudication

The purpose of this study was to determine the extent and sources of oxidative stress within skeletal muscle following an acute bout of contractile claudication. Twenty-four hours after unilateral ligation of the femoral artery, rat hind limbs were stimulated in vivo for 30 min, and force production measured. One-hour post-stimulation, animals were sacrificed and soleus and gastrocnemius muscles removed. There was significant reduction in force in the control limb (sham ligated/stimulated (SS)), while force in the ligated limb (ligated/stimulated (LS)) was reduced by 72%. There was an increase in skeletal muscle lipid hydroperoxides (53 and 47%) and protein carbonyls (57 and 54%) in the soleus and gastrocnemius muscles, respectively, and the muscle wet/dry weight ratio was increased in the gastrocnemius muscles. Total glutathione (GHS) was reduced, while xanthine oxidase (XO) activity and neutrophil levels were increased, in LS compared to SS in both soleus and gastrocnemius muscles. These data suggest that an acute bout of contractile claudication causes significant oxidative damage and edema to skeletal muscle. This is associated with both an increase in the activity of the radical-producing enzyme xanthine oxidase and an increase in activated neutrophils.

Effect of transdermal nitroglycerin on inflammatory mediators in patients with peripheral atherosclerotic vascular disease

OBJECTIVE

To demonstrate that nitroglycerin improves biological markers of arterial inflammation in patients with peripheral vascular disease.

BACKGROUND

Atherosclerosis is an inflammatory disease in which there is an increase in active inflammation markers such as C-reactive protein and other factors released by endothelial cells. Nitroglycerin acts by a chemical liberation of nitric oxide. We have previously published the results from several controlled clinical trials confirming an anti-inflammatory action of nitroglycerin.

METHODS

Forty patients with peripheral vascular disease entered a randomized, double-blind, placebo-controlled pilot study for 6 weeks. Twenty-one patients were treated with continuous application of a transdermal nitroglycerin patch (15 mg/24 hours) on the anterior face of the thigh. Venous blood samples were obtained before treatment and 2 and 6 weeks after. We measured plasma levels of C-reactive protein, cGMP (also intraplatelet cGMP), E-selectin, ICAM, VCAM-1, IL-6, and nitrites/nitrates.

RESULTS

No biological parameter was modified in the placebo group. On the contrary, nitroglycerin significantly reduced plasma levels of C-reactive protein and sE-selectin and increased the levels of intraplatelet cGMP.

CONCLUSIONS

The results of this preliminary study show that nitroglycerin has an anti-inflammatory action in patients with peripheral vascular disease. This may provide a new therapeutic approach to understanding the efficacy of nitrovasodilators in the improvement of atherosclerotic syndromes.

Medical treatment of peripheral arterial disease

PURPOSE OF REVIEW

The evolution of interventional treatments of peripheral arterial disease is progressing at a dizzying pace. However, optimized medical therapy of these patients may be neglected. Recent advances in our understanding of atherosclerosis and the epidemiology of vascular disease reemphasize the importance of a consistent and complete medical regimen. They have also opened new avenues for potential therapy.

RECENT FINDINGS

A diagnosis of peripheral arterial disease confers an increased risk of morbidity and mortality that can be at least partially mitigated with a properly designed medical regimen. New evidence supports the importance of risk factor modification including controlling hypertension, lowering lipid levels, and the routine use of antiplatelet agents. For claudication symptoms, several newer drugs and the use of immune-modifying therapy are showing some improvement in symptoms. The use of gene therapy and other means to achieve improved collateral formation in ischemic tissues are showing some promise in the early stages of study.

SUMMARY

Peripheral arterial disease is a marker of cardiovascular morbidity and mortality risk. An individualized plan should be devised to include smoking cessation, exercise, lowering serum lipids, lowering high blood pressure, and daily antiplatelet therapy. Supervised exercise programs and cilostazol remain the first-line medical therapies for claudication symptoms, and anticoagulants are added to patients who have bypasses at high risk for thrombosis. The utilities of immune-modifying, antibiotic, and angiogenic therapies remain to be proven.

Exercise in claudicants is accompanied by excessive thrombin generation

BACKGROUND

exercise in IC leads to ischaemia-reperfusion injury of leg muscles and a systemic inflammatory response, but the effect of on coagulation is unknown.

OBJECTIVE

to compare the effect of exercise on thrombin formation and fibrin turnover in patients with IC (n = 10), and age and sex matched smokers ([S] n = 5) and non-smokers ([NS] n = 5) without peripheral vascular disease.

METHODS

blood was taken from subjects 60 and 30 min before, and 1, 5, 20, 40, 60 and 120 min after, treadmill exercise. Markers of thrombin generation (thrombin-antithrombin complexes [TAT] and prothrombin fragments 1 + 2 [PF1 + 2]) and fibrin turnover (D-dimer and fibrin degradation products [FbDP]) were assayed at each time point.

RESULTS

following exercise, thrombin generation was significantly greater in the claudicant group compared to the control groups (Area Under Curve [AUC] post exercise IC vs S vs NS; TAT 3960 vs 1623 vs 1476 vs = 0.007 Kruskal-Wallis [KW]; PF1 + 2 163 vs 107 vs 123 p = 0.024 KW). Pre and post-exercise, fibrin turnover in claudicants was similar to smoking controls, but higher than non-smoking controls. (AUC post exercise IC vs NS; D-dimer 6340 vs 2754 p = 0.055 Mann-Whitney U[MW]; FbDP 45113 vs 21511 p = 0.009 MW).

CONCLUSION

when compared to non-claudicants, exercise in IC is associated with excessive production of thrombin. Despite this, claudicants have a similar level of fibrin turnover suggesting a possible defect in fibrinolysis. This prothrombotic state may contribute to the excess thrombotic morbidity and mortality suffered by claudicants.

Vitamin C prevents endothelial dysfunction induced by acute exercise in patients with intermittent claudication

In patients with intermittent claudication, exercise is associated with a marked increase in oxidative stress, likely responsible for systemic endothelial perturbation. In 31 claudicant patients, we assessed the effect of vitamin C administration on the acute changes induced by maximal and submaximal exercise in endothelium-dependent, flow-mediated dilation (FMD), and in plasma levels of thiobarbituric acid-reactive substances (TBARS) and soluble intercellular adhesion molecule-1 (sICAM-1). In 16 claudicants, maximal exercise reduced FMD (from 8.5+/-0.9 to 3.7+/-0.8%, P<0.01), and increased plasma levels of TBARS (from 1.93+/-0.06 to 2.22+/-0.1 nmol/ml, P<0.02) and of sICAM-1 (from 282+/-17 to 323+/-19 ng/ml, P<0.01). In eight of these patients, randomized to vitamin C, exercise-induced changes in FMD and biochemistry were abolished. This beneficial effect was not observed in the eight patients randomized to saline. In 15 patients, who walked until the onset of claudication pain (submaximal exercise), and in ten control subjects, who performed maximal exercise, no changes were observed with exercise. Thus, in claudicants, vitamin C prevents the acute, systemic impairment in endothelial function induced by maximal exercise. This finding provides a rationale for trials investigating antioxidant therapy and cardiovascular risk in patients with intermittent claudication.