Exercise in claudicants increase or decrease walking ability and the response relates to mitochondrial function

Mitochondrial respiration in peripheral arterial disease depends on stage severity

Peripheral arterial disease (PAD) is an increasing cause of morbidity and its severity is graded based on clinical manifestation. To investigate the influence of the different stages on myopathy of ischemic muscle we analysed severity-dependent effects of mitochondrial respiration in PAD. Eighteen patients with severe PAD, defined as chronic limb-threatening ischemia, 47 patients with intermittent claudication (IC) and 22 non-ischemic controls were analysed. High-resolution respirometry (HRR) was performed on muscle biopsies of gastrocnemius and vastus lateralis muscle of patients in different PAD stages to investigate different respiratory states. Results from HRR are given as median and interquartile range and were normalized to citrate synthase activity (CSA), a marker for mitochondrial content. In order to account for inter-individual differences between patients and controls, we calculated the ratio of O₂-flux in gastrocnemius muscle over vastus muscle ('GV ratio'). CSA of the gastrocnemius muscle as a proxy for mitochondrial content was significantly lower in critical ischemia compared to controls. Mitochondrial respiration normalized to CSA was higher in IC compared to controls. Likewise, the GV ratio was significantly higher in IC compared to control. Mitochondrial respiration and CSA of PAD patients showed stage-dependent modifications with greater changes in the mild PAD stage group (IC).

Trainability for cardiopulmonary fitness is low in patients with peripheral artery disease

AIMS

In patients with peripheral arterial disease (PAD), exercise therapy is recommended to relieve leg symptoms, as noted in the 2016 AHA/ACC and 2017 ESC/ESVS guidelines. We assessed the trainability for cardiopulmonary fitness (CPF) and quality of life (QOL); three distinct patient types, namely, PAD, heart failure (HF), and stroke, were compared.

METHODS AND RESULTS

This is a multicentre, retrospective analysis of prospectively collected data from three clinical studies. Data collected from 123 patients who completed 36 sessions of supervised aerobic training of moderate intensity were analysed, with 28 PAD, 55 HF, and 40 stroke patients totalling 123. Before and after training, cardiopulmonary exercise testing with non-invasive cardiac output monitoring and QOL evaluation using a 36-Item Short Form Survey (SF-36) were performed. Non-response was defined as a negative change in the post-training value compared with that in the pre-training value. The result showed an improvement in CPF in all three groups. However, cardiorespiratory fitness (CRF) increased by a lesser extent in the PAD group than in the HF and stroke groups; the physical and mental component scores (MCS) of SF-36 exhibited a similar pattern. Non-response rates of peak V˙O2, oxygen uptake efficiency slope, and MCS were higher in the PAD group. In the PAD group, non-responders regarding peak V˙O2 had a higher pulse wave velocity than responders.

CONCLUSION

In patients with PAD following exercise therapy, CRF and QOL improved to a lesser extent on average; their non-response rate was also higher compared with that of HF or stroke patients. Therefore, a higher dose of exercise might be needed to elicit adaptation in PAD patients, especially those with high pulse wave velocity.

Changes in miRNA expression in patients with peripheral arterial vascular disease during moderate- and vigorous-intensity physical activity

BACKGROUND

Walking is the preferred therapy for peripheral arterial disease in early stage. An effect of walking exercise is the increase of blood flow and fluid shear stress, leading, triggered by arteriogenesis, to the formation of collateral blood vessels. Circulating micro-RNA may act as an important information transmitter in this process. We investigated the acute effects of a single bout of 1) aerobic walking with moderate intensity; and 2) anaerobic walking with vigorous intensity on miRNA parameters related to vascular collateral formation.

METHODS

Ten (10) patients with peripheral arterial disease with claudication (age 72 ± 7 years) participated in this two-armed, randomized-balanced cross-over study. The intervention arms were single bouts of supervised walking training at (1) vigorous intensity on a treadmill up to volitional exhaustion and (2) moderate intensity with individual selected speed for a duration of 20 min. One week of washout was maintained between the arms. During each intervention, heart rate was continuously monitored. Acute effects on circulating miRNAs and lactate concentration were determined using pre- and post-intervention measurement comparisons.

RESULTS

Vigorous-intensity walking resulted in a higher heart rate (125 ± 21 bpm) than the moderate-intensity intervention (88 ± 9 bpm) (p < 0.05). Lactate concentration was increased after vigorous-intensity walking (p = 0.005; 3.3 ± 1.2 mmol/l), but not after moderate exercising (p > 0.05; 1.7 ± 0.6 mmol/l). The circulating levels of miR-142-5p and miR-424-5p were up-regulated after moderate-intensity (p < 0.05), but not after vigorous-intensity training (p > 0.05).

CONCLUSION

Moderate-intensity walking seems to be more feasible than vigorous exercises to induce changes of blood flow and endurance training-related miRNAs in patients with peripheral arterial disease. Our data thus indicates that effect mechanisms might follow an optimal rather than a maximal dose response relation. Steady state walking without the necessity to reach exhaustion seems to be better suited as stimulus.

Inequity in exercise-based interventions for adults with intermittent claudication due to peripheral arterial disease: a systematic review

PURPOSE

To determine the equity in access to trials of exercise interventions for adults with intermittent claudication due to peripheral arterial disease.

METHODS

Systematic electronic database searches of MEDLINE, Embase, CINAHL, Cochrane Central Register of Controlled Clinical Trials, PEDRO, Opengrey, ISRCTN and ClinincalTrials.gov for randomised controlled trials of exercise interventions for adults with intermittent claudication were conducted. Data extraction was informed by Cochrane's PROGRESS-Plus framework.

RESULTS

Searches identified 6412 records. Following the screening of 262 full texts, 49 trials including 3695 participants were included. All trials excluded potential participants on at least one equity factor. This comprised place of residence, language, sex, personal characteristics (e.g., age and disability), features of relationships (e.g., familial risk factors) and time-dependent factors, (e.g., time since revascularisation). Overall, 1839 of 7567 potential participants (24.3%) were excluded based on equity factors. Disability was the most frequently reported factor for exclusions.

CONCLUSION

Trialists endeavour to enrol a representative sample in exercise trials whilst preserving the safety profile of the intervention. This review highlights that these efforts can inadvertently lead to inequities in access as all trials excluded potential participants on at least one equity factor. Future exercise trials should optimise participation to maximise generalisability of findings. PROSPERO registration no. CRD42020189965.Implications for rehabilitationEquity factors influence health opportunities and outcomes.All trials of exercise for people with intermittent claudication excluded adults on at least one equity factor.Disability was the predominant factor for exclusions from trials.Trials should optimise participation to maximise generalisability of results as these findings are used to inform treatment and service design.

The Effect of Long-Lasting Swimming on Rats Skeletal Muscles Energy Metabolism after Nine Days of Dexamethasone Treatment

This study investigates the effect of Dexamethasone (Dex) treatment on blood and skeletal muscle metabolites level and skeletal muscle activity of enzymes related to energy metabolism after long-duration swimming. To evaluate whether Dex treatment, swimming, and combining these factors act on analyzed data, rats were randomly divided into four groups: saline treatment non-exercise and exercise and Dex treatment non-exercised and exercised. Animals in both exercised groups underwent long-lasting swimming. The concentration of lipids metabolites, glucose, and lactate were measured in skeletal muscles and blood according to standard colorimetric and fluorimetric methods. Also, activities of enzymes related to aerobic and anaerobic metabolism were measured in skeletal muscles. The results indicated that Dex treatment induced body mass loss and increased lipid metabolites in the rats’ blood but did not alter these changes in skeletal muscles. Interestingly, prolonged swimming applied after 9 days of Dex treatment significantly intensified changes induced by Dex; however, there was no difference in skeletal muscle enzymatic activities. This study shows for the first time the cumulative effect of exercise and Dex on selected elements of lipid metabolism, which seems to be essential for the patient’s health due to the common use of glucocorticoids like Dex.

Exercise Training Increases Resting Calf Muscle Oxygen Metabolism in Patients with Peripheral Artery Disease

Exercise training can mitigate symptoms of claudication (walking-induced muscle pain) in patients with peripheral artery disease (PAD). One adaptive response enabling this improvement is enhanced muscle oxygen metabolism. To explore this issue, we used arterial-occlusion diffuse optical spectroscopy (AO-DOS) to measure the effects of exercise training on the metabolic rate of oxygen (MRO₂) in resting calf muscle. Additionally, venous-occlusion DOS (VO-DOS) and frequency-domain DOS (FD-DOS) were used to measure muscle blood flow (F) and tissue oxygen saturation (StO₂), and resting calf muscle oxygen extraction fraction (OEF) was calculated from MRO₂, F, and blood hemoglobin. Lastly, the venous/arterial ratio (γ) of blood monitored by FD-DOS was calculated from OEF and StO₂. PAD patients who experience claudication (n = 28) were randomly assigned to exercise and control groups. Patients in the exercise group received 3 months of supervised exercise training. Optical measurements were obtained at baseline and at 3 months in both groups. Resting MRO₂, OEF, and F, respectively, increased by 30% (12%, 44%) (p < 0.001), 17% (6%, 45%) (p = 0.003), and 7% (0%, 16%) (p = 0.11), after exercise training (median (interquartile range)). The pre-exercise γ was 0.76 (0.61, 0.89); it decreased by 12% (35%, 6%) after exercise training (p = 0.011). Improvement in exercise performance was associated with a correlative increase in resting OEF (R = 0.45, p = 0.02).

The Role of Mitochondrial Function in Peripheral Arterial Disease: Insights from Translational Studies

Recent evidence demonstrates an involvement of impaired mitochondrial function in peripheral arterial disease (PAD) development. Specific impairments have been assessed by different methodological in-vivo (near-infrared spectroscopy, ³¹P magnetic resonance spectroscopy), as well as in-vitro approaches (Western blotting of mitochondrial proteins and enzymes, assays of mitochondrial function and content). While effects differ with regard to disease severity, chronic malperfusion impacts subcellular energy homeostasis, and repeating cycles of ischemia and reperfusion contribute to PAD disease progression by increasing mitochondrial reactive oxygen species production and impairing mitochondrial function. With the leading clinical symptom of decreased walking capacity due to intermittent claudication, PAD patients suffer from a subsequent reduction of quality of life. Different treatment modalities, such as physical activity and revascularization procedures, can aid mitochondrial recovery. While the relevance of these modalities for mitochondrial functional recovery is still a matter of debate, recent research indicates the importance of revascularization procedures, with increased physical activity levels being a subordinate contributor, at least during mild stages of PAD. With an additional focus on the role of revascularization procedures on mitochondria and the identification of suitable mitochondrial markers in PAD, this review aims to critically evaluate the relevance of mitochondrial function in PAD development and progression.

Urolithin A improves muscle function by inducing mitophagy in muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy, and despite advances in genetic and pharmacological disease-modifying treatments, its management remains a major challenge. Mitochondrial dysfunction contributes to DMD, yet the mechanisms by which this occurs remain elusive. Our data in experimental models and patients with DMD show that reduced expression of genes involved in mitochondrial autophagy, or mitophagy, contributes to mitochondrial dysfunction. Mitophagy markers were reduced in skeletal muscle and in muscle stem cells (MuSCs) of a mouse model of DMD. Administration of the mitophagy activator urolithin A (UA) rescued mitophagy in DMD worms and mice and in primary myoblasts from patients with DMD, increased skeletal muscle respiratory capacity, and improved MuSCs' regenerative ability, resulting in the recovery of muscle function and increased survival in DMD mouse models. These data indicate that restoration of mitophagy alleviates symptoms of DMD and suggest that UA may have potential therapeutic applications for muscular dystrophies.

Walking Exercise Therapy Effects on Lower Extremity Skeletal Muscle in Peripheral Artery Disease

Walking exercise is the most effective noninvasive therapy that improves walking ability in peripheral artery disease (PAD). Biologic mechanisms by which exercise improves walking in PAD are unclear. This review summarizes evidence regarding effects of walking exercise on lower extremity skeletal muscle in PAD. In older people without PAD, aerobic exercise improves mitochondrial activity, muscle mass, capillary density, and insulin sensitivity in skeletal muscle. However, walking exercise increases lower extremity ischemia in people with PAD, and therefore, mechanisms by which this exercise improves walking may differ between people with and without PAD. Compared with people without PAD, gastrocnemius muscle in people with PAD has greater mitochondrial impairment, increased reactive oxygen species, and increased fibrosis. In multiple small trials, walking exercise therapy did not consistently improve mitochondrial activity in people with PAD. In one 12-week randomized trial of people with PAD randomized to supervised exercise or control, supervised treadmill exercise increased treadmill walking time from 9.3 to 15.1 minutes, but simultaneously increased the proportion of angular muscle fibers, consistent with muscle denervation (from 7.6% to 15.6%), while angular myofibers did not change in the control group (from 9.1% to 9.1%). These findings suggest an adaptive response to exercise in PAD that includes denervation and reinnervation, an adaptive process observed in skeletal muscle of people without PAD during aging. Small studies have not shown significant effects of exercise on increased capillary density in lower extremity skeletal muscle of participants with PAD, and there are no data showing that exercise improves microcirculatory delivery of oxygen and nutrients in patients with PAD. However, the effects of supervised exercise on increased plasma nitrite abundance after a treadmill walking test in people with PAD may be associated with improved lower extremity skeletal muscle perfusion and may contribute to improved walking performance in response to exercise in people with PAD. Randomized trials with serial, comprehensive measures of muscle biology, and physiology are needed to clarify mechanisms by which walking exercise interventions improve mobility in PAD.

The effect of revascularization on recovery of mitochondrial respiration in peripheral artery disease: a case control study

Background

Peripheral arterial disease (PAD) is accompanied by myopathy characterized by mitochondrial dysfunction. The aim of this experimental study was to investigate the effect of revascularization procedures on mitochondrial function in ischemic and non-ischemic muscle.

Methods

Muscle biopsies from patients with symptomatic stage IIB/III PAD caused by isolated pathologies of the superficial femoral artery were obtained from muscle regions within the chronic ischemic muscle (gastrocnemius) and from non-ischemic muscle (vastus lateralis) before and 6 weeks after invasive revascularization. High-resolution respirometry was used to investigate mitochondrial function and results were normalized to citrate synthase activity (CSA). Results are given in absolute values and fold over basal (FOB).

Results

Respiratory states (OXPHOS (P) and electron transfer (E) capacity) normalized to CSA decreased while CSA was increased in chronic ischemic muscle after revascularization. There were no changes in in non-ischemic muscle. The FOB of chronic ischemic muscle was significantly higher for CSA (chronic ischemic 1.37 (IQR 1.10–1.64) vs. non-ischemic 0.93 (IQR 0.69–1.16) p = 0.020) and significantly lower for respiratory states normalized to CSA when compared to the non-ischemic muscle (P per CSA chronic ischemic 0.64 (IQR 0.46–0.82) vs non-ischemic 1.16 (IQR 0.77–1.54) p = 0.011; E per CSA chronic ischemic 0.61 (IQR 0.47–0.76) vs. non-ischemic 1.02 (IQR 0.64–1.40) p = 0.010).

Conclusions

Regeneration of mitochondrial content and function following revascularization procedures only occur in muscle regions affected by malperfusion. This indicates that the restoration of blood and oxygen supply are important mediators aiding mitochondrial recovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02908-0.

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

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

Individual Differences in Response to Supervised Exercise Therapy for Peripheral Artery Disease

Nonresponse to exercise has been extensively examined in young athletes but is seldom reported in studies of aerobic exercise interventions in older adults. This study examined the prevalence of nonresponse and poor response to exercise in functional and quality of life outcomes and response patterns between and among older adults undergoing 12-weeks of supervised exercise therapy for the management of peripheral artery disease (N = 44, mean age 72.3 years, 47.7% female). The prevalence of nonresponse (no change/decline in performance) in walking distance was 31.8%. The prevalence of poor response (lack of a clinically meaningful improvement) was 43.2%. Similar patterns of response were observed in both objective and patient-reported measures of physical function. All participants improved in at least one outcome; only two participants improved in all measured outcomes. Additional research should examine modifiable predictors of response to inform programming and maximize an individual's potential benefit from exercise therapy.

Modes of exercise training for intermittent claudication

BACKGROUND

According to international guidelines and literature, all patients with intermittent claudication should receive an initial treatment of cardiovascular risk modification, lifestyle coaching, and supervised exercise therapy. In the literature, supervised exercise therapy often consists of treadmill or track walking. However, alternative modes of exercise therapy have been described and yielded similar results to walking. This raises the following question: which exercise mode produces the most favourable results? This is the first update of the original review published in 2014.

OBJECTIVES

To assess the effects of alternative modes of supervised exercise therapy compared to traditional walking exercise in patients with intermittent claudication.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 4 March 2019. We also undertook reference checking, citation searching and contact with study authors to identify additional studies. No language restriction was applied.

SELECTION CRITERIA

We included parallel-group randomised controlled trials comparing alternative modes of exercise training or combinations of exercise modes with a control group of supervised walking exercise in patients with clinically determined intermittent claudication. The supervised walking programme needed to be supervised at least twice a week for a consecutive six weeks of training.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, extracted data, and assessed the risk of bias for each study. As we included studies with different treadmill test protocols and different measuring units (metres, minutes, or seconds), the standardised mean difference (SMD) approach was used for summary statistics of mean walking distance (MWD) and pain-free walking distance (PFWD). Summary estimates were obtained for all outcome measures using a random-effects model. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

For this update, five additional studies were included, making a total of 10 studies that randomised a total of 527 participants with intermittent claudication (IC). The alternative modes of exercise therapy included cycling, lower-extremity resistance training, upper-arm ergometry, Nordic walking, and combinations of exercise modes. Besides randomised controlled trials, two quasi-randomised trials were included. Overall risk of bias in included studies varied from high to low. According to GRADE criteria, the certainty of the evidence was downgraded to low, due to the relatively small sample sizes, clinical inconsistency, and inclusion of three studies with risk of bias concerns. Overall, comparing alternative exercise modes versus walking showed no clear differences for MWD at 12 weeks (standardised mean difference (SMD) -0.01, 95% confidence interval (CI) -0.29 to 0.27; P = 0.95; 6 studies; 274 participants; low-certainty evidence); or at the end of training (SMD -0.11, 95% CI -0.33 to 0.11; P = 0.32; 9 studies; 412 participants; low-certainty evidence). Similarly, no clear differences were detected in PFWD at 12 weeks (SMD -0.01, 95% CI -0.26 to 0.25; P = 0.97; 5 studies; 249 participants; low-certainty evidence); or at the end of training (SMD -0.06, 95% CI -0.30 to 0.17; P = 0.59; 8 studies, 382 participants; low-certainty evidence). Four studies reported on health-related quality of life (HR-QoL) and three studies reported on functional impairment. As the studies used different measurements, meta-analysis was only possible for the walking impairment questionnaire (WIQ) distance score, which demonstrated little or no difference between groups (MD -5.52, 95% CI -17.41 to 6.36; P = 0.36; 2 studies; 96 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

This review found no clear difference between alternative exercise modes and supervised walking exercise in improving the maximum and pain-free walking distance in patients with intermittent claudication. The certainty of this evidence was judged to be low, due to clinical inconsistency, small sample size and risk of bias concerns. The findings of this review indicate that alternative exercise modes may be useful when supervised walking exercise is not an option. More RCTs with adequate methodological quality and sufficient power are needed to provide solid evidence for comparisons between each alternative exercise mode and the current standard of supervised treadmill walking. Future RCTs should investigate outcome measures on walking behaviour, physical activity, cardiovascular risk, and HR-QoL, using standardised testing methods and reporting of outcomes to allow meaningful comparison across studies.

The α7 Nicotinic Acetylcholine Receptor: A Promising Target for the Treatment of Fibrotic Skin Disorders

Targeting neuroendocrine receptors can be considered as another interesting approach to treating fibrotic disorders. Previously, we could demonstrate that tropisetron, a classical serotonin receptor blocker, can modulate collagen synthesis and acts in vitro through the α7 nicotinic acetylcholine receptor (α7nAchR). Here, we used a pharmacologic approach with specific α7nAchR agonists to validate this hypothesis. PHA-543613, an α7nAchR-specific agonist, not only prevented but also reversed established skin fibrosis of mice injected with bleomycin. Interestingly, agonistic stimulation of α7nAchR also attenuated experimental skin fibrosis in the non-inflammation driven adenovirus coding for TGFβ receptor I^act mouse model, indicating fibroblast-mediated and not only anti-inflammatory effects of such agents. The fibroblast-mediated effects were confirmed in vitro using human dermal fibroblasts, in which the α7nAchR-specific agonists strongly reduced the impact of TGFβ1-mediated expression on collagen and myofibroblast marker expression. These actions were linked to modulation of the redox-sensitive transcription factor JunB and impairment of the mitochondrial respiratory system. Our results indicate that pharmacologic stimulation of the α7nAchR could be a promising target for treatment of patients with skin fibrotic diseases. Moreover, our results suggest a mechanistic axis of collagen synthesis regulation through the mitochondrial respiratory system.

Regeneration of Mitochondrial Function in Gastrocnemius Muscle in Peripheral Arterial Disease After Successful Revascularisation

OBJECTIVE

Myopathy, characterised by altered mitochondrial function, is a central part of the pathophysiology of peripheral arterial disease and the aim of this study was to investigate the effect of revascularisation on mitochondrial function.

METHODS

High resolution respirometry was used to investigate mitochondrial respiration and the results were normalised to citrate synthase activity (CSA), a marker of mitochondrial content. Ten patients with symptomatic peripheral arterial disease (study group) and 10 subjects without ischaemia (control group) were included. Ankle brachial index and ultrasound imaging were performed before and after vascular intervention to confirm technically successful revascularisation. Within the study group, muscle biopsies from the gastrocnemius muscle were taken before vascular intervention and six weeks after revascularisation. Within the control group, tissue was harvested once.

RESULTS

There were no significant group differences regarding anthropometric data. CSA showed a significant increase after successful revascularisation (CSA pre-operative 281.4 (252.4-391.8) nmol/min/mg protein vs. CSA post-operative 438.5 (361.4-471.3) nmol/min/mg protein; p = .01) with post-operative return of values to the range of control subjects (CSA control 396.6 (308.2-435.9)). Mitochondrial respiration normalised to CSA in oxidative phosphorylation (P) as well as in electron transfer (E) capacity were significantly reduced post-operatively when compared with pre-operative values (P pre-operative 0.218 (0.196-0.266) pmol/(sec×mg) per CSA vs. post-operative 0.132 (0.116-0.150) pmol/(sec×mg) per CSA, p = .007; E pre-operative 0.230 (0.195-0.279) pmol/(sec×mg) per CSA vs. post-operative 0.129 (0.120-0.154) pmol/(sec×mg) per CSA, p = .005) meaning a post-operative return of values to within the range of control subjects (P control 0.124 (0.080-0.155) pmol/(sec×mg) per CSA; E control 0.121 (0.079-0.125) pmol/(sec×mg) per CSA).

CONCLUSION

With these results, it has been shown that the initially impaired mitochondrial function and content can normalise after revascularisation.

Experience Implementing Supervised Exercise Therapy for Peripheral Artery Disease

Background

Supervised exercise therapy (SET) is a cornerstone of treatment for improving walking distance for individuals with symptomatic peripheral artery disease and claudication. High quality randomized controlled trials have documented the efficacy of SET as a claudication treatment and led to the recent Centers for Medicare and Medicaid decision to cover supervised exercise therapy (SET). However, to date, the translation of highly controlled, laboratory based SET programs in real world cardiopulmonary rehabilitation settings has been unexplored.

Methods

In this article, we describe our experience integrating SET into existing cardiopulmonary rehabilitation programs, focusing on patient evaluation, exercise prescription, outcome assessments, strategies to maximize program adherence, and transitioning to home and community-based exercise training.

Results

Our team has over 3 years experience successfully implementing SET in cardiac rehabilitation settings. The experiences communicated within can serve as a model for rehabilitation therapists to follow as they begin to incorporate SET in their rehabilitation programs.

Conclusions

CMS reimbursement has the potential to change clinical practice and utilization of SET for patients with symptomatic peripheral artery disease. The experience we have gained through implementation of SET programs across the M Health and Fairview Health Systems and in other Minnesota communities, including specific elements in our programs and the lessons learned from our clinical experience, can inform and help to guide development of new programs.

Brief Abstract

The recent Centers for Medicare and Medicaid decision to cover supervised exercise therapy (SET) for beneficiaries with peripheral artery disease (PAD) has the potential to transform practice. In this article, we describe our experience integrating SET into existing cardiopulmonary rehabilitation programs, which could serve as a model for new programs.

Swim Training Modulates Mouse Skeletal Muscle Energy Metabolism and Ameliorates Reduction in Grip Strength in a Mouse Model of Amyotrophic Lateral Sclerosis

Metabolic reprogramming in skeletal muscles in the human and animal models of amyotrophic lateral sclerosis (ALS) may be an important factor in the diseases progression. We hypothesized that swim training, a modulator of cellular metabolism via changes in muscle bioenergetics and oxidative stress, ameliorates the reduction in muscle strength in ALS mice. In this study, we used transgenic male mice with the G93A human SOD1 mutation B6SJL-Tg (SOD1^G93A) 1Gur/J and wild type B6SJL (WT) mice. Mice were subjected to a grip strength test and isolated skeletal muscle mitochondria were used to perform high-resolution respirometry. Moreover, the activities of enzymes involved in the oxidative energy metabolism and total sulfhydryl groups (as an oxidative stress marker) were evaluated in skeletal muscle. ALS reduces muscle strength (-70% between 11 and 15 weeks, p < 0.05), modulates muscle metabolism through lowering citrate synthase (CS) (-30% vs. WT, p = 0.0007) and increasing cytochrome c oxidase and malate dehydrogenase activities, and elevates oxidative stress markers in skeletal muscle. Swim training slows the reduction in muscle strength (-5% between 11 and 15 weeks) and increases CS activity (+26% vs. ALS I, p = 0.0048). Our findings indicate that swim training is a modulator of skeletal muscle energy metabolism with concomitant improvement of skeletal muscle function in ALS mice.

Melatonin and Its Metabolites Ameliorate UVR-Induced Mitochondrial Oxidative Stress in Human MNT-1 Melanoma Cells

Melatonin (Mel) is the major biologically active molecule secreted by the pineal gland. Mel and its metabolites, 6-hydroxymelatonin (6(OH)Mel) and 5-methoxytryptamine (5-MT), possess a variety of functions, including the scavenging of free radicals and the induction of protective or reparative mechanisms in the cell. Their amphiphilic character allows them to cross cellular membranes and reach subcellular organelles, including the mitochondria. Herein, the action of Mel, 6(OH)Mel, and 5-MT in human MNT-1 melanoma cells against ultraviolet B (UVB) radiation was investigated. The dose of 50 mJ/cm² caused a significant reduction of cell viability up to 48%, while investigated compounds counteracted this deleterious effect. UVB exposure increased catalase activity and led to a simultaneous Ca⁺⁺ influx (16%), while tested compounds prevented these disturbances. Additional analysis focused on mitochondrial respiration performed in isolated mitochondria from the liver of BALB/cJ mice where Mel, 6(OH)Mel, and 5-MT significantly enhanced the oxidative phosphorylation at the dose of 10⁻⁶ M with lower effects seen at 10⁻⁹ or 10⁻⁴ M. In conclusion, Mel, 6(OH)Mel and 5-MT protect MNT-1 cells, which express melatonin receptors (MT1 and MT2) against UVB-induced oxidative stress and mitochondrial dysfunction, including the uncoupling of oxidative phosphorylation.