Exercise training and peripheral arterial disease

Eight weeks of nitrate supplementation improves blood flow and reduces the exaggerated pressor response during forearm exercise in peripheral artery disease

Peripheral artery disease (PAD) is characterized by a reduced blood flow (BF) and an elevated blood pressure (pressor) response during lower extremity exercise. Although PAD is evident in the upper extremities, no studies have determined BF and pressor responses during upper extremity exercise in PAD. Emerging evidence suggests that inorganic nitrate supplementation may serve as an alternative dietary strategy to boost nitric oxide bioavailability, improving exercising BF and pressor responses during exercise. The present study investigated 1) BF and pressor responses to forearm exercise in patients with PAD ( n = 21) relative to healthy age-matched control subjects ( n = 16) and 2) whether 8 wk of NaNO₃ supplementation influenced BF and pressor responses to forearm exercise in patients with PAD. Patients with moderate to severe PAD were randomly assigned to a NaNO₃ (1 g/day, n = 13)-treated group or a placebo (microcrystalline cellulose, n = 8)-treated group. Brachial artery forearm BF (FBF; via Doppler) and blood pressure (via finger plethysmography) were measured during mild-intensity (~3.5-kg) and moderate-intensity (~7-kg) handgrip exercise. The absolute change (from baseline) in FBF was reduced (except in the 3.5-kg condition) and BP responses were increased in patients with PAD compared with healthy control subjects in 3.5- and 7-kg conditions (all P < 0.05). Plasma nitrate and nitrite were elevated, exercising (7-kg) ΔFBF was improved (from 141 ± 17 to 172 ± 20 ml/min), and mean arterial pressure response was reduced (from 13 ± 1 to 9 ± 1 mmHg, P < 0.05) in patients with PAD that received NaNO₃ supplementation for 8 wk relative to those that received placebo. These results suggest that the BF limitation and exaggerated pressor response to moderate-intensity forearm exercise in patients with PAD are improved with 8 wk of NaNO₃ supplementation. NEW & NOTEWORTHY Peripheral artery disease (PAD) results in an exaggerated pressor response and reduced blood flow during lower limb exercise; however, the effect of PAD in the upper limbs has remained unknown. These results suggest that 8 wk of inorganic nitrate supplementation improves the blood flow limitation and exaggerated pressor response to moderate-intensity forearm exercise in PAD.

Exercise for intermittent claudication

BACKGROUND

Exercise programmes are a relatively inexpensive, low-risk option compared with other, more invasive therapies for treatment of leg pain on walking (intermittent claudication (IC)). This is the fourth update of a review first published in 1998.

OBJECTIVES

Our goal was to determine whether an exercise programme was effective in alleviating symptoms and increasing walking treadmill distances and walking times in people with intermittent claudication. Secondary objectives were to determine whether exercise was effective in preventing deterioration of underlying disease, reducing cardiovascular events, and improving quality of life.

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (last searched 15 November 2016) and the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 10) via the Cochrane Register of Studies Online, along with trials registries.

SELECTION CRITERIA

Randomised controlled trials of an exercise regimen versus control or versus medical therapy for people with IC due to peripheral arterial disease (PAD). We included any exercise programme or regimen used for treatment of IC, such as walking, skipping, and running. Inclusion of trials was not affected by duration, frequency, or intensity of the exercise programme. Outcome measures collected included treadmill walking distance (time to onset of pain or pain-free walking distance and maximum walking time or maximum walking distance), ankle brachial index (ABI), quality of life, morbidity, or amputation; if none of these was reported, we did not include the trial in this review.

DATA COLLECTION AND ANALYSIS

For this update (2017), RAL and AH selected trials and extracted data independently. We assessed study quality by using the Cochrane 'Risk of bias' tool. We analysed continuous data by determining mean differences (MDs) and 95% confidence intervals (CIs), and dichotomous data by determining risk ratios (RRs) and 95% CIs. We pooled data using a fixed-effect model unless we identified significant heterogeneity, in which case we used a random-effects model. We used the GRADE approach to assess the overall quality of evidence supporting the outcomes assessed in this review.

MAIN RESULTS

We included two new studies in this update and identified additional publications for previously included studies, bringing the total number of studies meeting the inclusion criteria to 32, and involving a total of 1835 participants with stable leg pain. The follow-up period ranged from two weeks to two years. Types of exercise varied from strength training to polestriding and upper or lower limb exercises; supervised sessions were generally held at least twice a week. Most trials used a treadmill walking test for one of the primary outcome measures. The methodological quality of included trials was moderate, mainly owing to absence of relevant information. Most trials were small and included 20 to 49 participants. Twenty-seven trials compared exercise versus usual care or placebo, and the five remaining trials compared exercise versus medication (pentoxifylline, iloprost, antiplatelet agents, and vitamin E) or pneumatic calf compression; we generally excluded people with various medical conditions or other pre-existing limitations to their exercise capacity.Meta-analysis from nine studies with 391 participants showed overall improvement in pain-free walking distance in the exercise group compared with the no exercise group (MD 82.11 m, 95% CI 71.73 to 92.48, P < 0.00001, high-quality evidence). Data also showed benefit from exercise in improved maximum walking distance (MD 120.36 m, 95% CI 50.79 to 189.92, P < 0.0007, high-quality evidence), as revealed by pooling data from 10 studies with 500 participants. Improvements were seen for up to two years.Exercise did not improve the ABI (MD 0.04, 95% CI 0.00 to 0.08, 13 trials, 570 participants, moderate-quality evidence). Limited data were available for the outcomes of mortality and amputation; trials provided no evidence of an effect of exercise, when compared with placebo or usual care, on mortality (RR 0.92, 95% CI 0.39 to 2.17, 5 trials, 540 participants, moderate-quality evidence) or amputation (RR 0.20, 95% CI 0.01 to 4.15, 1 trial, 177 participants, low-quality evidence).Researchers measured quality of life using Short Form (SF)-36 at three and six months. At three months, the domains 'physical function', 'vitality', and 'role physical' improved with exercise; however this was a limited finding, as it was reported by only two trials. At six months, meta-analysis showed improvement in 'physical summary score' (MD 2.15, 95% CI 1.26 to 3.04, P = 0.02, 5 trials, 429 participants, moderate-quality evidence) and in 'mental summary score' (MD 3.76, 95% CI 2.70 to 4.82, P < 0.01, 4 trials, 343 participants, moderate-quality evidence) secondary to exercise. Two trials reported the remaining domains of the SF-36. Data showed improvements secondary to exercise in 'physical function' and 'general health'. The other domains - 'role physical', 'bodily pain', 'vitality', 'social', 'role emotional', and 'mental health' - did not show improvement at six months.Evidence was generally limited in trials comparing exercise versus antiplatelet therapy, pentoxifylline, iloprost, vitamin E, and pneumatic foot and calf compression owing to small numbers of trials and participants.Review authors used GRADE to assess the evidence presented in this review and determined that quality was moderate to high. Although results showed significant heterogeneity between trials, populations and outcomes were comparable overall, with findings relevant to the claudicant population. Results were pooled for large sample sizes - over 300 participants for most outcomes - using reproducible methods.

AUTHORS' CONCLUSIONS

High-quality evidence shows that exercise programmes provided important benefit compared with placebo or usual care in improving both pain-free and maximum walking distance in people with leg pain from IC who were considered to be fit for exercise intervention. Exercise did not improve ABI, and we found no evidence of an effect of exercise on amputation or mortality. Exercise may improve quality of life when compared with placebo or usual care. As time has progressed, the trials undertaken have begun to include exercise versus exercise or other modalities; therefore we can include fewer of the new trials in this update.

Peripheral Vascular Disease: The Beneficial Effect of Exercise in Peripheral Vascular Diseases Based on Clinical Trials

Intermittent claudication (IC) due to peripheral artery diseases (PAD) is one of the disabling disease that can affect quality of life (QOL) and functional status of capacity. It is characterized by cramping pain which develops with exercise and eliminated by rest secondary to decrease blood flow to the muscles. The annual incidence rate is increased with age. Exercise rehabilitation has a great impact in improving the functional capacity and prevent the functional disability. The available evidences from current studies have showed that exercise therapy is considered the primary treatment in PAD, which in consequently improves the QOL. In this chapter we will illustrate the current available evidences which support exercise benefit and outcomes in PAD with IC.

Chronic femoral artery ligation exaggerates the pressor and sympathetic nerve responses during dynamic skeletal muscle stretch in decerebrate rats

Mechanical and metabolic signals arising during skeletal muscle contraction reflexly increase sympathetic nerve activity and blood pressure (i.e., the exercise pressor reflex). In a rat model of simulated peripheral artery disease in which a femoral artery is chronically (~72 h) ligated, the mechanically sensitive component of the exercise pressor reflex during 1-Hz dynamic contraction is exaggerated compared with that found in normal rats. Whether this is due to an enhanced acute sensitization of mechanoreceptors by metabolites produced during contraction or involves a chronic sensitization of mechanoreceptors is unknown. To investigate this issue, in decerebrate, unanesthetized rats, we tested the hypothesis that the increases in mean arterial blood pressure and renal sympathetic nerve activity during 1-Hz dynamic stretch are larger when evoked from a previously "ligated" hindlimb compared with those evoked from the contralateral "freely perfused" hindlimb. Dynamic stretch provided a mechanical stimulus in the absence of contraction-induced metabolite production that closely replicated the pattern of the mechanical stimulus present during dynamic contraction. We found that the increases in mean arterial blood pressure (freely perfused: 14 ± 1 and ligated: 23 ± 3 mmHg, P = 0.02) and renal sympathetic nerve activity were significantly greater during dynamic stretch of the ligated hindlimb compared with the increases during dynamic stretch of the freely perfused hindlimb. These findings suggest that the exaggerated mechanically sensitive component of the exercise pressor reflex found during dynamic muscle contraction in this rat model of simulated peripheral artery disease involves a chronic sensitizing effect of ligation on muscle mechanoreceptors and cannot be attributed solely to acute contraction-induced metabolite sensitization. NEW & NOTEWORTHY We found that the pressor and sympathetic nerve responses during dynamic stretch were exaggerated in rats with a ligated femoral artery (a model of peripheral artery disease). Our findings provide mechanistic insights into the exaggerated exercise pressor reflex in this model and may have important implications for peripheral artery disease patients.

Exaggerated cardiovascular responses to treadmill running in rats with peripheral arterial insufficiency

Patients with atherosclerotic peripheral artery disease have an augmented pressor response to treadmill walking, but the underlying mechanisms remain poorly understood and difficult to isolate because of the confounding presence of numerous cardiovascular risk factors. In the present study, we tested the hypothesis that a chronic deficit in muscle blood flow capacity would be sufficient to trigger an exaggerated pressor response to dynamic exercise. Sprague-Dawley rats (5 male and 5 female) were instrumented with radiotelemetry devices to measure the cardiovascular responses to treadmill running before and after bilateral femoral artery ligation, which has been previously shown to reduce the blood flow capacity of distal hindlimb muscles by >60%. Treadmill running evoked reproducible increases in mean arterial pressure (MAP) and heart rate (HR), which were significantly augmented 3 days after femoral artery ligation in both male rats [ΔMAP: +10 ± 1 (SE) vs. +18 ± 3 mmHg and ΔHR: +94 ± 12 vs. +148 ± 15 beats/min, P < 0.05] and female rats (ΔMAP: +16 ± 3 vs. +30 ± 5 mmHg and ΔHR: +128 ± 20 vs. +178 ± 19 beats/min, P < 0.05). Similar exaggerated MAP and HR responses were observed at repeated intervals between 3 and 65 days postligation. These findings indicate that a chronic deficit in muscle blood flow capacity is an important, persistent cause of the abnormal pressor and cardioaccelerator responses to dynamic exercise in both male and female rats with peripheral arterial insufficiency. NEW & NOTEWORTHY Using radiotelemetry to assess cardiovascular effects of exercise, we showed that femoral artery obstruction in male and female rats is an important, persistent cause of exaggerated pressor and cardioaccelerator responses to treadmill running. This translational model reproduces the abnormal cardiovascular response to exercise seen in patients with peripheral artery disease. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/treadmill-bp-in-simulated-peripheral-artery-disease/ .

The effects of RSR13 on microvascular Po2 kinetics and muscle contractile performance in the rat arterial ligation model of peripheral arterial disease

Exercise intolerance and claudication are symptomatic of peripheral arterial disease. There is a close relationship between muscle O2 delivery, microvascular oxygen partial pressure (P mvO2), and contractile performance. We therefore hypothesized that a reduction of hemoglobin-oxygen affinity via RSR13 would maintain a higher P mvO2 and enhance blood-muscle O2 transport and contractile function. In male Wistar rats (12 wk of age), we created hindlimb ischemia via right-side iliac artery ligation (AL). The contralateral (left) muscle served as control (CONT). Seven days after AL, phosphorescence-quenching techniques were used to measure P mvO2 at rest and during contractions (electrical stimulation; 1 Hz, 300 s) in tibialis anterior muscle (TA) under saline ( n = 10) or RSR13 ( n = 10) conditions. RSR13 at rest increased TA P mvO2 in CONT (13.9 ± 1.6 to 19.3 ± 1.9 Torr, P < 0.05) and AL (9.0 ± 0.5 to 9.9 ± 0.7 Torr, P < 0.05). Furthermore, RSR13 extended maintenance of the initial TA force (i.e., improved contractile performance) such that force was not decreased significantly until contraction 240 vs. 150 in CONT and 80 vs. 20 in AL. This improved muscle endurance with RSR13 was accompanied by a greater ΔP mvO2 (P mvO2 decrease from baseline) (CONT, 7.4 ± 1.0 to 11.2 ± 1.3; AL, 6.9 ± 0.5 to 8.6 ± 0.6 Torr, both P < 0.05). Whereas RSR13 did not alter the kinetics profile of P mvO2 (i.e., mean response time) substantially during contractions, muscle force was elevated, and the ratio of muscle force to P mvO2 increased. In conclusion, reduction of hemoglobin-oxygen affinity via RSR13 in AL increased P mvO2 and improved muscle contractile performance most likely via enhanced blood-muscle O2 diffusion.

NEW & NOTEWORTHY This is the first investigation to examine the effect of RSR13 (erythrocyte allosteric effector) on skeletal muscle microvascular oxygen partial pressure kinetics and contractile function using an arterial ligation model of peripheral arterial disease in experimental animals. The present results provide strong support for the concept that reducing hemoglobin-O2 affinity via RSR13 improved tibialis anterior muscle contractile performance most likely via enhanced blood-muscle O2 diffusion.

The efficacy of transcutaneous electrical nerve stimulation on the improvement of walking distance in patients with peripheral arterial disease with intermittent claudication: study protocol for a randomised controlled trial: the TENS-PAD study

Background

In patients with peripheral arterial disease (PAD), walking improvements are often limited by early pain onset due to vascular claudication. It would thus appear interesting to develop noninvasive therapeutic strategies, such as transcutaneous electrical nerve stimulation (TENS), to improve the participation of PAD patients in rehabilitation programmes, and thus improve their quality of life. Our team recently tested the efficacy of a single 45-min session of 10-Hz TENS prior to walking. TENS significantly delayed pain onset and increased the pain-free walking distance in patients with class-II PAD. We now seek to assess the efficacy of a chronic intervention that includes the daily use of TENS for 3 weeks (5 days a week) on walking distance in Leriche-Fontaine stage-II PAD patients.

Methods/design

This is a prospective, double-blind, multicentre, randomised, placebo-controlled trial. One hundred subjects with unilateral PAD (Leriche-Fontaine stage II) will be randomised into two groups (1:1). For the experimental group (TENS group): the treatment will consist of stimulation of the affected leg (at a biphasic frequency of 10 Hz, with a pulse width of 200 μs, maximal intensity below the motor threshold) for 45 min per day, in the morning before the exercise rehabilitation programme, for 3 weeks, 5 days per week. For the control group (SHAM group): the placebo stimulation will be delivered according to the same modalities as for the TENS group but with a voltage level automatically falling to zero after 10 s of stimulation. First outcome: walking distance without pain. Secondary outcomes: transcutaneous oxygen pressure (TcPO₂) measured during a Strandness exercise test, peak oxygen uptake (VO₂ peak), endothelial function (EndoPAT®), Ankle-brachial Pressure Index, Body Mass Index, lipid profile (LDL-C, HDL-C, triglycerides), fasting glycaemia, HbA1c level, and the WELCH questionnaire.

Discussion

TENS-PAD is the first randomised controlled trial that uses transcutaneous electrical therapy as an adjuvant technique to improve vascular function in the treatment of PAD. If the results are confirmed, this technique could be incorporated into the routine care in cardiovascular rehabilitation centers and used in the long term by patients to improve their walking capacity.

Trial registration

ClinicalTrials.gov, ID: NCT02678403. Registered on 9 February 2016. Sponsor: Toulouse University Hospital.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1997-1) contains supplementary material, which is available to authorized users.

Moderate Exercise Allows for shorter Recovery Time in Critical Limb Ischemia

Whether and how moderate exercise might allow for accelerated limb recovery in chronic critical limb ischemia (CLI) remains to be determined. Chronic CLI was surgically induced in mice, and the effect of moderate exercise (training five times per week over a 3-week period) was investigated. Tissue damages and functional scores were assessed on the 4th, 6th, 10th, 20th, and 30th day after surgery. Mice were sacrificed 48 h after the last exercise session in order to assess muscle structure, mitochondrial respiration, calcium retention capacity, oxidative stress and transcript levels of genes encoding proteins controlling mitochondrial functions (PGC1α, PGC1β, NRF1) and anti-oxidant defenses markers (SOD1, SOD2, catalase). CLI resulted in tissue damages and impaired functional scores. Mitochondrial respiration and calcium retention capacity were decreased in the ischemic limb of the non-exercised group (V_max = 7.11 ± 1.14 vs. 9.86 ± 0.86 mmol 02/min/g dw, p < 0.001; CRC = 7.01 ± 0.97 vs. 11.96 ± 0.92 microM/mg dw, p < 0.001, respectively). Moderate exercise reduced tissue damages, improved functional scores, and restored mitochondrial respiration and calcium retention capacity in the ischemic limb (V_max = 9.75 ± 1.00 vs. 9.82 ± 0.68 mmol 02/min/g dw; CRC = 11.36 ± 1.33 vs. 12.01 ± 1.24 microM/mg dw, respectively). Exercise also enhanced the transcript levels of PGC1α, PGC1β, NRF1, as well as SOD1, SOD2, and catalase. Moderate exercise restores mitochondrial respiration and calcium retention capacity, and it has beneficial functional effects in chronic CLI, likely by stimulating reactive oxygen species-induced biogenesis and anti-oxidant defenses. These data support further development of exercise therapy even in advanced peripheral arterial disease.

The Effects of Acute High-Intensity Interval Training on Hematological Parameters in Sedentary Subjects

The objective of the study was to determine the effects of acute high-intensity interval training (HIIT) on hematological parameters in sedentary men. Ten healthy, non-smoker, and sedentary men aged between 18 and 24 years participated in the study. All subjects performed four Wingate tests with 4 min intervals between the tests. Blood samples were collected at pre-exercise, immediately after, 3 and 6 h after the fourth Wingate test. Hematological parameters were analyzed in these samples. The results showed that hematocrit percentage, hemoglobin values, red cell count, mean cell volume, platelet count, total white cell count, and counts of the white cell subgroups increased immediately after the acute HIIT and their values began to return to resting levels 3 h after exercise, and completely returned to resting levels 6 h after exercise. In conclusion, acute HIIT causes an inflammatory response in blood.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

An Approach to Transmetatarsal Amputation to Encourage Immediate Weightbearing in Diabetic Patients

Transmetatarsal amputation remains the standard treatment for the unsalvageable diabetic forefoot; however, this operation is often complicated by wound dehiscence, ulceration, and the need for additional surgery and tendon balancing. The technique described in the present report provides an uncomplicated suturing method for closure of a standard transmetatarsal amputation. A drill hole is created through the first, second, and fourth metatarsals, which facilitates added stability to the plantar flap of the residual metatarsals. The patients are encouraged to begin protected weightbearing as early as the first postoperative day. The security of the flap promotes immediate weightbearing, which could result in fewer postoperative complications of transmetatarsal amputations. Early weightbearing will not only encourage tendon rebalancing, but also could improve angiogenesis through capillary ingrowth.

A Home-Based Walking Program Improves Respiratory Endurance in Patients With Acute Myocardial Infarction: A Randomized Controlled Trial

BACKGROUND

The purpose of this study was to evaluate respiratory muscle strength and endurance in the inpatient period in patients who recently experienced myocardial infarction (MI) and investigate the effects of a home-based walking program on respiratory strength and endurance in low-risk patients after MI.

METHODS

Patients were randomized into a usual-care group (UCG) entailing regular care (n = 23) and an intervention group (IG) entailing an outpatient home-based walking program (n = 31). Healthy sex- and age-matched participants served as a control group for respiratory endurance variables. Respiratory muscle strength was evaluated through maximal inspiratory pressure (MIP) and endurance during the inpatient period, at 15 days, and at 60 days after MI. Submaximal functional capacity was determined by a 6-minute walk test (6MWT) at hospital discharge and 60 days after MI.

RESULTS

Both groups showed impaired inspiratory muscle strength at hospital discharge. When compared with healthy individuals, after MI, patients had worse respiratory muscle endurance pressure (PTH_max = 73.02 ± 8.40 vs 44.47 ± 16.32; P < 0.05) and time (Tlim = 324.1 ± 12.2 vs 58.7 ± 93.3; P < 0.05). Only the IG showed a significant improvement in MIP and PTH_max at 15 days and 60 days after MI (P < 0.05). When comparing groups, the IG achieved higher values for MIP, PTH_max, and Tlim 15 and 60 days after MI (P < 0.01). The 60-day assessment revealed that the 6MWT distance and level of physical activity was significantly higher in the IG compared with the UCG.

CONCLUSIONS

Low-risk patients recently experiencing MI demonstrate impaired MIP and respiratory endurance compared with healthy participants. A home-based walking program improved respiratory endurance and functional capacity.

Inflammation is associated with a reduced number of pro-angiogenic Tie-2 monocytes and endothelial progenitor cells in patients with critical limb ischemia

BACKGROUND

Inflammation is the driving force in atherosclerosis. One central strategy in the treatment for PAD is the promotion of angiogenesis. Here, pro-angiogenic Tie-2-expressing monocytes (TEM) and endothelial progenitor cells (EPC) play a crucial role. Critical limb ischemia (CLI) is characterized by a severe, chronic inflammatory response; thus, progression of the disease might be related to the deleterious effects of inflammation on pro-angiogenic cells.

METHODS

Forty-five patients with intermittent claudication (IC) [three groups: Rutherford (R)-1, -2, or -3; each n = 15], 20 patients with CLI [n = 20; Rutherford 4 (15 %), 5 (40 %), and 6 (45 %)], and 20 healthy controls were included in the study. Analysis of TEM and EPC was performed from whole blood by flow cytometry. Treatment for IC patients was conservative, and CLI patients underwent surgical revascularization. Follow-up was performed after mean of 7.1 months.

RESULTS

In comparison with healthy controls, we found increased proportions of TEM and EPC in dependence of the severity of PAD, with the highest level in patients with severe claudication (R3) (p < 0.01). In contrast, for patients with CLI, we found a significantly reduced expression of both TEM and EPC in comparison with healthy controls (p < 0.05) or IC patients (R-1, R-2, and R-3) (all p < 0.001). At follow-up, TEM and EPC in CLI patients increased significantly (both p < 0.001). Serum levels of fibrinogen and CRP were significantly increased in CLI patients (all p < 0.001), but decreased at follow-up (all p < 0.05). TEM and EPC proportions correlated inversely with levels of fibrinogen [(TEM: r = −0.266; p < 0.01) (EPC: r = −0.297; p < 0.001)], CRP (TEM: r = −0.283; p < 0.01) (EPC: r = −0.260; p < 0.01).

CONCLUSIONS

We found a strong association of diverse inflammatory markers with a reduced proportion of pro-angiogenic TEM or EPC in patients with CLI, giving rise to the speculation that a severe chronic inflammation might lead to deleterious effects on TEM and EPC, possibly interfering with angiogenesis, thus promoting an aggravation of the disease.

Walking performance is positively correlated to calf muscle fiber size in peripheral artery disease subjects, but fibers show aberrant mitophagy: an observational study

BACKGROUND

Patients with lower extremity peripheral artery disease (PAD) have decreased mobility, which is not fully explained by impaired blood supply to the lower limb. Additionally, reports are conflicted regarding fiber type distribution patterns in PAD, but agree that skeletal muscle mitochondrial respiration is impaired.

METHODS

To test the hypothesis that reduced muscle fiber oxidative activity and type I distribution are negatively associated with walking performance in PAD, calf muscle biopsies from non-PAD (n = 7) and PAD participants (n = 26) were analyzed immunohistochemically for fiber type and size, oxidative activity, markers of autophagy, and capillary density. Data were analyzed using analysis of covariance.

RESULTS

There was a wide range in fiber type distribution among subjects with PAD (9-81 % type I fibers) that did not correlate with walking performance. However, mean type I fiber size correlated with 4-min normal- and fastest-paced walk velocity (r = 0.4940, P = 0.010 and r = 0.4944, P = 0.010, respectively). Although intensity of succinate dehydrogenase activity staining was consistent with fiber type, up to 17 % of oxidative fibers were devoid of mitochondria in their cores, and the core showed accumulation of the autophagic marker, LC3, which did not completely co-localize with LAMP2, a lysosome marker.

CONCLUSIONS

Calf muscle type I fiber size positively correlates with walking performance in PAD. Accumulation of LC3 and a lack of co-localization of LC3 with LAMP2 in the area depleted of mitochondria in PAD fibers suggests impaired clearance of damaged mitochondria, which may contribute to reduced muscle oxidative capacity. Further study is needed to determine whether defective mitophagy is associated with decline in function over time, and whether interventions aimed at preserving mitochondrial function and improving autophagy can improve walking performance in PAD.

Can yoga therapy stimulate stem cell trafficking from bone marrow?

It has been established that mesenchymal stromal cells (MSCs) from bone marrow enter the peripheral circulation intermittently for possible tissue regeneration, repair and to take care of daily wear and tear. This is evident from the detection of MSCs from peripheral blood. The factors governing this migration remain elusive. These MSCs carry out the work of policing and are supposed to repair the injured tissues. Thus, these cells help in maintaining the tissue and organ homeostasis. Yoga and pranayama originated in India and is now being practiced all over the world for positive health. So far, the chemical stimulation of bone marrow has been widely used employing injection of colony stimulating factor. However, the role of physical factors such as mechanical stimulation and stretching has not been substantiated. It is claimed that practicing yoga delays senescence, improves the physiological functions of heart and lung and yoga postures make the body elastic. It remains to be seen whether the yoga therapy promotes trafficking of the stem cells from bone marrow for possible repair and regeneration of worn out and degenerating tissues. We cover in this short review, mainly the role of physical factors especially the yoga therapy on stem cells trafficking from bone marrow.

Pericapillary basement membrane thickening in human skeletal muscles

The basement membrane (BM) surrounding capillaries in skeletal muscles varies physiologically in thickness according to age, physical fitness, and anatomical site in humans. Furthermore, the pericapillary BM thickness (CBMT) increases pathophysiologically during several common disease states, including peripheral arterial disease and diabetes mellitus. This review on CBM thickening in human skeletal muscles is two pronged. First, it addresses the advantages/disadvantages of grid- and tablet-based measuring and morphometric techniques that are implemented to assess the CBMT on transmission electron micrographs. Second, it deals with the biology of CBM thickening in skeletal muscles, particularly its possible causes, molecular mechanisms, and functional impact. CBM thickening is triggered by several physical factors, including diabetes-associated glycation, hydrostatic pressure, and inflammation. Increased biosynthesis of type IV collagen expression or repetitive cycles in pericyte or endothelial cell degeneration/proliferation appear to be most critical for CBM accumulation. A thickened CBM obviously poses a greater barrier for diffusion, lowers the microvascular elasticity, and impedes transcytosis of inflammatory cells. Our own morphometric data reveal the CBM enlargement to be not accompanied by the pericyte coverage. Owing to an overlap or redundancy in the capillary supply, CBM thickening in skeletal muscles might not be such a devastating occurrence as in organs with endarterial circulation (e.g., kidney and retina). CBM growth in skeletal muscles can be reversed by training or administration of antidiabetic drugs. In conclusion, CBM thickening in skeletal muscles is a microvascular remodeling process by which metabolic, hemodynamic, and inflammatory forces are integrated together and which could play a hitherto underestimated role in etiology/progression of human diseases.

Evidence of a broad histamine footprint on the human exercise transcriptome

KEY POINTS

Histamine is a primordial signalling molecule, capable of activating cells in an autocrine or paracrine fashion via specific cell surface receptors, in a variety of pathways that probably predate its more recent role in innate and adaptive immunity. Although histamine is normally associated with pathological conditions or allergic and anaphylactic reactions, it may contribute beneficially to the normal changes that occur within skeletal muscle during the recovery from exercise. We show that the human response to exercise includes an altered expression of thousands of protein-coding genes, and much of this response appears to be driven by histamine. Histamine may be an important molecular transducer contributing to many of the adaptations that accompany chronic exercise training.

ABSTRACT

Histamine is a primordial signalling molecule, capable of activating cells in an autocrine or paracrine fashion via specific cell surface receptors. In humans, aerobic exercise is followed by a post-exercise activation of histamine H1 and H2 receptors localized to the previously exercised muscle. This could trigger a broad range of cellular adaptations in response to exercise. Thus, we exploited RNA sequencing to explore the effects of H1 and H2 receptor blockade on the exercise transcriptome in human skeletal muscle tissue harvested from the vastus lateralis. We found that exercise exerts a profound influence on the human transcriptome, causing the differential expression of more than 3000 protein-coding genes. The influence of histamine blockade post-exercise was notable for 795 genes that were differentially expressed between the control and blockade condition, which represents >25% of the number responding to exercise. The broad histamine footprint on the human exercise transcriptome crosses many cellular functions, including inflammation, vascular function, metabolism, and cellular maintenance.

Capillary ultrastructure and mitochondrial volume density in skeletal muscle in relation to reduced exercise capacity of patients with intermittent claudication

Intermittent claudication (IC) is the most commonly reported symptom of peripheral arterial disease (PAD). Impaired limb blood flow is a major casual factor of lower exercise tolerance in PAD but cannot entirely explain it. We hypothesized that IC is associated with structural changes of the capillary-mitochondria interface that could contribute to the reduction of exercise tolerance in IC patients. Capillary and mitochondrial morphometry were performed after light and transmission electron microscopy using vastus lateralis muscle biopsies of 14 IC patients and 10 age-matched controls, and peak power output (PPO) was determined for all participants using an incremental single-leg knee-extension protocol. Capillary density was lower (411 ± 90 mm−2 vs. 506 ± 95 mm−2; P ≤ 0.05) in the biopsies of the IC patients than in those of the controls. The basement membrane (BM) around capillaries was thicker (543 ± 82 nm vs. 423 ± 97 nm; P ≤ 0.01) and the volume density of mitochondria was lower (3.51 ± 0.56% vs. 4.60 ± 0.74%; P ≤ 0.01) in the IC patients than the controls. In the IC patients, a higher proportion of capillaries appeared with collapsed slit-like lumen and/or swollen endothelium. PPO was lower (18.5 ± 9.9 W vs. 33.5 ± 9.4 W; P ≤ 0.01) in the IC patients than the controls. We suggest that several structural alterations in skeletal muscle, either collectively or separately, contribute to the reduction of exercise tolerance in IC patients.

Muscle metaboreflex and cerebral blood flow regulation in humans: implications for exercise with blood flow restriction

We investigated the effect of activating metabolically sensitive skeletal muscle afferents (muscle metaboreflex) on cerebral blood flow and the potentially confounding influence of concomitant changes in the partial pressure of arterial carbon dioxide. Eleven healthy males (25 ± 4 yr) performed submaximal leg cycling exercise on a semirecumbent cycle ergometer (heart rate: ∼120 beats/min), and assessments were made of the partial pressure of end-tidal carbon dioxide (PetCO2), internal carotid artery blood flow (ICAQ) and conductance (ICACVC), and middle cerebral artery mean blood velocity (MCAvm) and conductance index (MCACVCi).The muscle metaboreflex was activated during cycling with leg blood flow restriction (BFR) or isolated with postexercise ischemia (PEI). In separate trials, PetCO2was either permitted to fluctuate spontaneously (control trial) or was clamped at 1 mmHg above resting levels (PetCO2clamp trial). In the control trial, leg cycling with BFR decreased PetCO2(Δ−4.8 ± 0.9 mmHg vs. leg cycling exercise) secondary to hyperventilation, while ICAQ, ICACVC, and MCAvmwere unchanged and MCACVCidecreased. However, in the PetCO2clamp trial, leg cycling with BFR increased both MCAvm(Δ5.9 ± 1.4 cm/s) and ICAQ(Δ20.0 ± 7.8 ml/min) and attenuated the decrease in MCACVCi, while ICACVCwas unchanged. In the control trial, PEI decreased PetCO2(Δ−7.0 ± 1.3 mmHg vs. rest), MCAvmand MCACVCi, whereas ICAQand ICACVCwere unchanged. In contrast, in the PetCO2clamp trial both ICAQ(Δ18.5 ± 11.9 ml/min) and MCAvm(Δ8.8 ± 2.0 cm/s) were elevated, while ICACVCand MCACVCiwere unchanged. In conclusion, when hyperventilation-related decreases in PetCO2are prevented the activation of metabolically sensitive skeletal muscle afferent fibers increases cerebral blood flow.

Advances in our understanding of the influence of gender on patient outcomes with peripheral arterial disease co-occurring with diabetes

Peripheral arterial disease is an important predictor of cardiovascular morbidity and mortality. Patients with peripheral arterial disease are at a higher risk of myocardial infarction and stroke. The well-known coronary artery disease risk factors such as diabetes, hypertension, smoking and dyslipidemia are also risk factors for peripheral arterial disease. Hyperglycemia is an important mediator in the pathogenesis of this disease in diabetics, more so in women. The morbidity and poor outcomes associated with peripheral arterial disease in women are emerging. Women are more likely to present at an older age are often asymptomatic and have poorer outcomes with revascularization. Women experience specific sex-related challenges in the various diagnostic methods which could lead to a delay in diagnosis. This is a group which needs close attention and aggressive risk factor modification.

Intensive walking exercise for lower extremity peripheral arterial disease: A systematic review and meta-analysis

BACKGROUND

Supervised treadmill exercise is the recommended therapy for peripheral arterial disease (PAD) patients with intermittent claudication (IC). However, most PAD patients do not exhibit typical symptoms of IC. The aim of the present study was to explore the efficacy and safety of intensive walking exercise in PAD patients with and without IC.

METHODS

The PubMed, Embase and Cochrane Library databases were systematically searched. Randomized controlled trials comparing the effects of intensive walking exercise with usual care in patients with PAD were included for systematic review and meta-analysis.

RESULTS

Eighteen trials with 1200 patients were eligible for the present analysis. Compared with usual care, intensive walking exercise significantly improved the maximal walking distance (MWD), pain-free walking distance, and the 6-min walking distance in patients with PAD (P < 0.00001 for all). Subgroup analyses indicated that a lesser improvement in MWD was observed in the subgroup with more diabetes patients, and that the subgroup with better baseline walking ability exhibited greater improvement in walking performance. In addition, similar improvements in walking performance were observed for exercise programs of different durations and modalities. No significant difference was found in adverse events between the intensive walking and usual care groups (relative risk 0.84; 95% confidence interval 0.51, 1.39; P = 0.50).

CONCLUSIONS

Regardless of exercise length and modality, regularly intensive walking exercise improves walking ability in PAD patients more than usual care. The presence of diabetes may attenuate the improvements in walking performance in patients with PAD following exercise.

Influence of exercise training on proangiogenic TIE-2 monocytes and circulating angiogenic cells in patients with peripheral arterial disease

BACKGROUND

Inflammation is the driving force in atherosclerosis. One central strategy in the treatment of peripheral arterial disease (PAD) is the promotion of angiogenesis. Here, proangiogenic Tie-2 expressing monocytes (TEM) and circulating angiogenic cells (CAC) play a crucial role. Exercise training (ET) is recommended in PAD patients at Fontaine stage II to promote angiogenesis.

METHODS

40 patients with intermittend claudication (IC) [2 groups: supervised ET (SET) vs. non-supervised ET (nSET), each n = 20] and 20 healthy controls were included in the study. Analysis of TEM and CAC was performed from whole blood by flow-cytometry. TEM were identified via CD45, CD86, CD14, CD16 and analysed for the expression of Tie-2. CAC were identified via their expression of CD45 (CD45dim), CD34 and VEGF-R2 (CD309/KDR). Follow up was performed after mean of 7.65 ± 1.62 months.

RESULTS

In comparison to healthy controls, we found increased proportions of CAC (p < 0.0001) and similar TEM numbers in both ET groups. At follow-up (FU) TEM poroportions increased (p < 0.001) and CAC proportions decreased (p < 0.01), but both more significantly in SET (p < 0.001) than nSET (p = 0.01). Only in SET fibrinogen levels decreased and VEGF-A increased (both p < 0.05). Finally, we found in both ET groups a significant increase in absolute walking distance but with a higher individual increase in SET (p < 0.01). TEM and CAC proportions correlated inversely with the absolute walking distance (CAC: r = -0.296, p = 0.02; TEM: r = -0.270, p = 0.04) as well as with ABI (CAC: r = -0.394, p < 0.01; TEM: r = -0.382, p < 0.01).

CONCLUSIONS

ET influences the distribution of CAC and TEM proportions. nSET, although still effective in regard to an improved walking distance, is less effective in the influence of proangiogenic cells and inflammatory burden than SET. Our results indicate SET to be a more preferential exercise form, supporting the necessity to establish more SET programs.

Extracellular Matrix Hydrogel Promotes Tissue Remodeling, Arteriogenesis, and Perfusion in a Rat Hindlimb Ischemia Model

Although surgical and endovascular revascularization can be performed in peripheral arterial disease (PAD), 40% of patients with critical limb ischemia do not have a revascularization option. This study examines the efficacy and mechanisms of action of acellular extracellular matrix-based hydrogels as a potential novel therapy for treating PAD. We tested the efficacy of using a tissue-specific injectable hydrogel derived from decellularized porcine skeletal muscle (SKM) and compared this to a new human umbilical cord-derived matrix (hUC) hydrogel, which could have greater potential for tissue regeneration because of the younger age of the tissue source. In a rodent hindlimb ischemia model, both hydrogels were injected 1-week post-surgery and perfusion was regularly monitored with laser speckle contrast analysis to 35 days post-injection. There were significant improvements in hindlimb tissue perfusion and perfusion kinetics with both biomaterials. Histologic analysis indicated that the injected hydrogels were biocompatible, and resulted in arteriogenesis, rather than angiogenesis, as well as improved recruitment of skeletal muscle progenitors. Skeletal muscle fiber morphology analysis indicated that the muscle treated with the tissue-specific SKM hydrogel more closely matched healthy tissue morphology. Whole transcriptome analysis indicated that the SKM hydrogel caused a shift in the inflammatory response, decreased cell death, and increased blood vessel and muscle development. These results show the efficacy of an injectable ECM hydrogel alone as a potential therapy for treating patients with PAD. Our results indicate that the SKM hydrogel improved functional outcomes through stimulation of arteriogenesis and muscle progenitor cell recruitment.

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Although surgical and endovascular revascularization can be performed in patients with peripheral arterial disease (PAD), 40% of patients with critical limb ischemia do not have a revascularization option.

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The efficacy of an injectable tissue-specific skeletal muscle extracellular matrix (ECM) hydrogel and a human umbilical cord-derived ECM hydrogel were examined in a rodent hindlimb ischemia model.

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Although both biomaterials increased tissue perfusion 35 days post-injection, likely through arteriogenesis, the skeletal muscle ECM hydrogel more closely matched healthy tissue morphology.

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Transcriptomic analysis indicates the skeletal muscle ECM hydrogel shifted the inflammatory response, decreased necrosis/apoptosis, and increased blood vessel and muscle development.

Regulation of skeletal muscle capillary growth in exercise and disease

Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations.

Computational drug repositioning for peripheral arterial disease: prediction of anti-inflammatory and pro-angiogenic therapeutics

Peripheral arterial disease (PAD) results from atherosclerosis that leads to blocked arteries and reduced blood flow, most commonly in the arteries of the legs. PAD clinical trials to induce angiogenesis to improve blood flow conducted in the last decade have not succeeded. We have recently constructed PADPIN, protein-protein interaction network (PIN) of PAD, and here we combine it with the drug-target relations to identify potential drug targets for PAD. Specifically, the proteins in the PADPIN were classified as belonging to the angiome, immunome, and arteriome, characterizing the processes of angiogenesis, immune response/inflammation, and arteriogenesis, respectively. Using the network-based approach we predict the candidate drugs for repositioning that have potential applications to PAD. By compiling the drug information in two drug databases DrugBank and PharmGKB, we predict FDA-approved drugs whose targets are the proteins annotated as anti-angiogenic and pro-inflammatory, respectively. Examples of pro-angiogenic drugs are carvedilol and urokinase. Examples of anti-inflammatory drugs are ACE inhibitors and maraviroc. This is the first computational drug repositioning study for PAD.

Pain-free treadmill exercise for patients with intermittent claudication: Are there gender differences?

Intermittent claudication, a common symptom of peripheral arterial disease, results in insufficient blood flow and oxygen supply to lower extremity muscles. Compared to men, women with peripheral arterial disease have a higher rate of mobility loss with peripheral arterial disease due to poorer lower extremity functioning. This study evaluates the effect of supervised pain-free treadmill exercise on improving performance in women with intermittent claudication due to peripheral arterial disease in comparison to men. A total of 26 participants (women, n = 9, 34.62%; mean age = 67.58 ± 5.59 years; averaging 23.46 ± 3.91 visits and 10.46 ± 0.99 weeks in the program) diagnosed with peripheral arterial disease, with symptoms of intermittent claudication, partook in a 45 min treadmill walk, twice per week, below the participant's minimal pain threshold. Female participants' change scores showed 752%, 278% and 115% improvement in mean walking distance, duration and rate, respectively. Men improved 334%, 149% and 80%, respectively. Significant differences (p < 0.05) in pre and post measurements within each group support positive outcomes. No significant differences between groups were observed (Cohen's d effect size > 0.80). Our results suggest that women reap similar benefits from this low-intensity treadmill program in comparison to men.

Impaired Coronary Endothelial Vasorelaxation in a Preclinical Model of Peripheral Arterial Insufficiency

The present study was designed to determine whether adult swine with peripheral artery insufficiency (PAI) would exhibit vascular dysfunction in vessels distinct from the affected distal limbs, the coronary conduit arteries. Moreover, we sought to evaluate the effect of exercise training on coronary vasomotor function in PAI. Eighteen female healthy young Yucatan miniature swine were randomly assigned to either occluded exercise trained (Occl-Ex, n=7), or occluded-sedentary (Occl-Sed, n=5), or non-occluded, non-exercised control (Non-Occl-Con, n=6) groups. Occl-Ex pigs were progressively trained by running on a treadmill (5days/week, 12 weeks). The left descending artery (LAD) and left circumflex (LCX) coronary arteries were harvested. Vasorelaxation to adenosine diphosphate (ADP), bradykinin (BK), and sodium nitro-prusside (SNP) were assessed in LAD’s; while constrictor responses to phenylephrine (PE), angiotensin II (Ang II), and endothelin-1 (ET-1) were assessed in LCX’s. Vasorelaxation to ADP was reduced in LADs from Occl-Sed and Occl-Ex pigs (P<0.001) as compared to Non-Occl-Con pigs; however, Occl-Ex pigs exhibited partial recovery (P<0.001) intermediate to the other two groups. BK induced relaxation was reduced in LADs from Occl-Ex and Occl-Sed pigs (P<0.001), compared to Non-Occl-Con, and exercise modestly increased responses to BK (P<0.05). In addition, SNP, PE, Ang II, and ET-1 responses were not significantly different among the groups. Our results indicate that ‘simple’ occlusion of the femoral arteries induces vascular dysfunction in conduit vessels distinct from the affected hindlimbs, as evident in blunted coronary vasorelaxation responses to ADP and BK. These findings imply that PAI, even in the absence of frank atherogenic vascular disease, contributes to vascular dysfunction in the coronary arteries that could exacerbate disease outcome in patients with peripheral artery disease. Further, regular daily physical activity partially recovered the deficit observed in the coronary arteries.

Coronary and muscle blood flow during physical exercise in humans; heterogenic alliance

In this review, we present the relation between power generation capabilities and pulmonary oxygen uptake during incremental cycling exercise in humans and the effect of exercise intensity on the oxygen cost of work. We also discuss the importance of oxygen delivery to the working muscles as a factor determining maximal oxygen uptake in humans. Subsequently, we outline the importance of coronary blood flow, myocardial oxygen uptake and myocardial metabolic stability for exercise tolerance. Finally, we describe mechanisms of endothelium-dependent regulation of coronary and skeletal muscle blood flow, dysregulation of which may impair exercise capacity and increase the cardiovascular risk of exercise.

Effectiveness of a new exercise program after lower limb arterial blood flow surgery in patients with peripheral arterial disease: a randomized clinical trial

OBJECTIVE

The aim of this study was to evaluate the effectiveness of a supervised exercise program (SEP) plus at home nonsupervised exercise therapy (non-SET) on functional status, quality of life (QoL) and hemodynamic response in post-lower-limb bypass surgery patients.

RESULTS

One hundred and seventeen patients were randomized to an intervention (n = 57) or a control group (n = 60). A new individual SEP was designed for patients with peripheral arterial disease (PAD) and applied to the studied subjects of the intervention group who also continued non-SET at home, whereas those assigned to the control group received just usual SEP according to a common cardiovascular program. The participants of the study were assessed by a 6-min walking test (6 MWT), an ankle-brachial index (ABI), and the Medical Outcomes Study Short Form-36 (SF-36) of QoL at baseline, at 1 and 6 months after surgery. A significant improvement was observed in the walked distance in the intervention group after 6 months compared with the control group (p < 0.001). The intervention group had significantly higher QoL score in the physical and mental component of SF-36 (p < 0.05).

CONCLUSIONS

A 6-month application of the new SEP and non-SET at home has yielded significantly better results in walking distance and QoL in the intervention group than in the controls.

Forkhead BoxO transcription factors restrain exercise-induced angiogenesis

The physiological process of exercise-induced angiogenesis involves the orchestrated upregulation of angiogenic factors together with repression of angiostatic factors. The Forkhead Box 'O' (FoxO) transcription factors promote an angiostatic environment in pathological contexts. We hypothesized that endothelial FoxO1 and FoxO3a also play an integral role in restricting the angiogenic response to aerobic exercise training. A single exercise bout significantly increased levels of FoxO1 and FoxO3a mRNA (5.5- and 1.7-fold, respectively) and protein (1.7- and 2.2-fold, respectively) within the muscles of mice 2 h post-exercise compared to sedentary. Training abolished the exercise-induced increases in both FoxO1 and FoxO3a mRNA and proteins, and resulted in significantly lower nuclear levels of FoxO1 and FoxO3a protein (0.5- and 0.4-fold, respectively, relative to sedentary). Thrombospondin 1 (THBS1) protein level closely mirrored the expression pattern of FoxO proteins. The 1.7-fold increase in THBS1 protein following acute exercise no longer occurred after 10 days of repeated exercise. Endothelial cell-directed conditional deletion of FoxO1/3a/4 in mice prevented the increase in THBS1 mRNA following a single exercise bout. Mice harbouring the endothelial FoxO deletion also demonstrated a significant 20% increase in capillary to muscle fibre ratio after only 7 days of training while 14 days of training was required to elicit a similar increase in wildtype littermates. Our results demonstrate that the downregulation of FoxO1 and FoxO3a proteins facilitates angiogenesis in response to repeated exercise. In conclusion, FoxO proteins can delay exercise-induced angiogenesis, and thus are critical regulators of the physiological angiogenic response in skeletal muscle.

Exercise for intermittent claudication

BACKGROUND

Exercise programmes are a relatively inexpensive, low-risk option compared with other more invasive therapies for leg pain on walking (intermittent claudication (IC)). This is an update of a review first published in 1998.

OBJECTIVES

The prime objective of this review was to determine whether an exercise programme in people with intermittent claudication was effective in alleviating symptoms and increasing walking treadmill distances and walking times. Secondary objectives were to determine whether exercise was effective in preventing deterioration of underlying disease, reducing cardiovascular events and improving quality of life.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched September 2013) and CENTRAL (2013, Issue 8).

SELECTION CRITERIA

Randomised controlled trials of an exercise regimen versus control or versus medical therapy in people with IC due to peripheral arterial disease. Any exercise programme or regimen used in the treatment of intermittent claudication was included, such as walking, skipping and running. Inclusion of trials was not affected by the duration, frequency or intensity of the exercise programme. Outcome measures collected included treadmill walking distance (time to onset of pain or pain-free walking distance and maximum walking time or maximal walking distance), ankle brachial index (ABI), quality of life, morbidity or amputation; if none of these were reported the trial was not included in this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality.

MAIN RESULTS

Eleven additional studies were included in this update making a total of 30 trials which met the inclusion criteria, involving a total of 1816 participants with stable leg pain. The follow-up period ranged from two weeks to two years. The types of exercise varied from strength training to polestriding and upper or lower limb exercises; generally supervised sessions were at least twice a week. Most trials used a treadmill walking test for one of the outcome measures. Quality of the included trials was moderate, mainly due to an absence of relevant information. The majority of trials were small with 20 to 49 participants. Twenty trials compared exercise with usual care or placebo, the remainder of the trials compared exercise to medication (pentoxifylline, iloprost, antiplatelet agents and vitamin E) or pneumatic calf compression; people with various medical conditions or other pre-existing limitations to their exercise capacity were generally excluded.Overall, when taking the first time point reported in each of the studies, exercise significantly improved maximal walking time when compared with usual care or placebo: mean difference (MD) 4.51 minutes (95% confidence interval (CI) 3.11 to 5.92) with an overall improvement in walking ability of approximately 50% to 200%. Walking distances were also significantly improved: pain-free walking distance MD 82.29 metres (95% CI 71.86 to 92.72) and maximum walking distance MD 108.99 metres (95% CI 38.20 to 179.78). Improvements were seen for up to two years, and subgroup analyses were performed at three, six and 12 months where possible. Exercise did not improve the ABI (MD 0.05, 95% CI 0.00 to 0.09). The effect of exercise, when compared with placebo or usual care, was inconclusive on mortality, amputation and peak exercise calf blood flow due to limited data. No data were given on non-fatal cardiovascular events.Quality of life measured using the Short Form (SF)-36 was reported at three and six months. At three months, physical function, vitality and role physical all significantly improved with exercise, however this was a limited finding as this measure was only reported in two trials. At six months five trials reported outcomes of a significantly improved physical summary score and mental summary score secondary to exercise. Only two trials reported improvements in other domains, physical function and general health.Evidence was generally limited for exercise compared with antiplatelet therapy, pentoxifylline, iloprost, vitamin E and pneumatic foot and calf compression due to small numbers of trials and participants.

AUTHORS' CONCLUSIONS

Exercise programmes are of significant benefit compared with placebo or usual care in improving walking time and distance in people with leg pain from IC who were considered to be fit for exercise intervention.