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Changes in vascular and inflammatory biomarkers after exercise rehabilitation in patients with symptomatic peripheral artery disease

Open ArchivePublished:March 25, 2019DOI:https://doi.org/10.1016/j.jvs.2018.12.056

      Abstract

      Objective

      Home-based exercise is an alternative exercise mode to a structured supervised program to improve symptoms in patients with peripheral artery disease (PAD), but little is known about whether the slow-paced and less intense home program also elicits changes in vascular and inflammatory biomarkers. In an exploratory analysis from a randomized controlled trial, we compared changes in vascular and inflammatory biomarkers in patients with symptomatic PAD (typical and atypical of claudication) after home-based exercise and supervised exercise programs and in an attention-control group.

      Methods

      A total of 114 patients were randomized into one of the three groups (n = 38 per group). Two groups performed exercise interventions, consisting of home-based and supervised programs of intermittent walking to mild to moderate claudication pain for 12 weeks; a third group performed light resistance training as a nonwalking attention-control group. Before and after intervention, patients were characterized on treadmill performance and endothelial effects of circulating factors present in sera by a cell culture-based bioassay on primary human arterial endothelial cells, and they were further evaluated on circulating vascular and inflammatory biomarkers.

      Results

      Treadmill peak walking time increased (P = .008) in the two exercise groups but not in the control group (P > .05). Cultured endothelial cell apoptosis decreased after home-based exercise (P < .001) and supervised exercise (P = .007), and the change in the exercise groups combined was different from that in the control group (P = .005). For circulating biomarkers, increases were found in hydroxyl radical antioxidant capacity (P = .003) and vascular endothelial growth factor A (P = .037), and decreases were observed in E-selectin (P = .007) and blood glucose concentration (P = .012) after home-based exercise only. The changes in hydroxyl radical antioxidant capacity (P = .005), vascular endothelial growth factor A (P = .008), and E-selectin (P = .034) in the exercise groups combined were different from those in the control group.

      Conclusions

      This exploratory analysis found that both home-based and supervised exercise programs are efficacious to decrease cultured endothelial cell apoptosis in patients with symptomatic PAD. Furthermore, a monitored home-based exercise program elicits additional vascular benefits by improving circulating markers of endogenous antioxidant capacity, angiogenesis, endothelium-derived inflammation, and blood glucose concentration in patients with symptomatic PAD. The novel clinical significance is that important trends were found in this exploratory analysis that a contemporary home-based exercise program and a traditional supervised exercise program may favorably improve vascular and inflammatory biomarkers in addition to the well-described ambulatory improvements in symptomatic patients with PAD.

      Keywords

      Article Highlights
      • Type of Research: Single-center, prospective, randomized controlled trial
      • Key Findings: In 114 patients, a monitored home-based walking program and a supervised walking program both decreased cultured endothelial cell apoptosis in patients with symptomatic peripheral artery disease. The home-based program further improved circulating markers of endogenous antioxidant capacity, angiogenesis, endothelium-derived inflammation, and blood glucose concentration.
      • Take Home Message: Participating in 3 months of a monitored home-based walking program, typically done at lower exercise intensity than a traditional supervised treadmill walking program, may favorably improve vascular and inflammatory biomarkers in addition to the well-described ambulatory improvements in symptomatic patients with peripheral artery disease.
      Peripheral artery disease (PAD) is highly prevalent,
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      Endothelial cell inflammation and antioxidant capacity are associated with exercise performance and microcirculation in patients with symptomatic peripheral artery disease.
      a 6-minute walk test,
      • McDermott M.M.
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      Circulating blood markers and functional impairment in peripheral arterial disease.
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      Association between gait characteristics and endothelial oxidative stress and inflammation in patients with symptomatic peripheral artery disease.
      Physical activity reduces oxidative stress and increases the ability to respond to oxidative challenges in older adults,
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      Oxidative stress in older adults: effects of physical fitness.
      suggesting that ischemic preconditioning may occur with repeated episodes of exercise.
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      • Martini R.
      Acute impairment of the endothelial function by maximal treadmill exercise in patients with intermittent claudication, and its improvement after supervised physical training.
      We previously found that higher levels of community-based daily ambulatory activity are associated with higher levels of circulating antioxidant capacity,
      • Gardner A.W.
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      • Silva-Palacios F.
      • Ungvari Z.
      • Csiszar A.
      • et al.
      Association between daily walking and antioxidant capacity in patients with symptomatic peripheral artery disease.
      lower levels of inflammation determined by high-sensitivity C-reactive protein,
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      • Teague A.M.
      • Casanegra A.I.
      Monitored daily ambulatory activity, inflammation, and oxidative stress in patients with claudication.
      and no increase in oxidative stress markers
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      • Teague A.M.
      • Casanegra A.I.
      Monitored daily ambulatory activity, inflammation, and oxidative stress in patients with claudication.
      in symptomatic patients with PAD. These data suggest that chronic exercise may improve antioxidant capacity and inflammation without negatively influencing oxidative stress in symptomatic patients with PAD.
      Previous exercise training studies reported that supervised exercise lowers circulating vascular and inflammatory biomarkers, such as E-selectin,
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      Supervised exercise training reduces plasma levels of the endothelial inflammatory markers E-selectin and ICAM-I in patients with peripheral arterial disease.
      intercellular adhesion molecule 1,
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      • et al.
      Supervised exercise training reduces plasma levels of the endothelial inflammatory markers E-selectin and ICAM-I in patients with peripheral arterial disease.
      and interleukin-6,
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      • Bukowska-Strakova K.
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      Exercise training in intermittent claudication: effects on antioxidant genes, inflammatory mediators and proangiogenic progenitor cells.
      and may
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      The effect of treadmill training on endothelial function and walking abilities in patients with peripheral arterial disease.
      or may not
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      • Mika A.
      • Nowobilski R.
      • et al.
      Comparison of two treadmill training programs on walking ability and endothelial function in intermittent claudication.
      lower high-sensitivity C-reactive protein levels. Home-based exercise has recently been found to be an alternative mode of exercise to improve symptoms in patients with PAD.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      • McDermott M.M.
      • Liu K.
      • Guralnik J.M.
      • Criqui M.H.
      • Spring B.
      • Tian L.
      • et al.
      Home-based walking exercise intervention in peripheral artery disease: a randomized clinical trial.
      • McDermott M.M.
      • Guralnik J.M.
      • Criqui M.H.
      • Ferrucci L.
      • Zhao L.
      • Liu K.
      • et al.
      Home-based walking exercise in peripheral artery disease: 12-month follow-up of the GOALS randomized trial.
      A monitored home-based exercise program has numerous advantages to a supervised program for both patients and clinical staff as less time, effort, and resources are required to implement home-based exercise. However, minimal work has examined whether home-based exercise, which is done at a slower pace and lower exercise intensity than supervised exercise,
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      elicits changes in both vascular and inflammatory biomarkers and whether these changes are different from those of supervised exercise programs. A direct assessment of home-based and supervised exercise programs compared with a control group has not been done on their effects on circulating antioxidant capacity, inflammation, and oxidative stress biomarkers and on endothelial cell biomarkers.
      Therefore, in an exploratory analysis from our randomized controlled trial, we compared changes in vascular and inflammatory biomarkers in patients with symptomatic PAD after home-based exercise and supervised exercise programs and in an attention-control group who performed light resistance training exercise.

      Methods

       Patients

       Approval and informed consent

      The procedures of this study were approved by the Institutional Review Board at the University of Oklahoma Health Sciences Center. Written informed consent was obtained from each patient at the beginning of investigation.

       Recruitment

      Patients who were not currently exercising were recruited from vascular laboratories and vascular clinics from the university for possible enrollment into exercise rehabilitation programs to treat leg pain secondary to PAD.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.

       Medical screening through history and physical examination

      Patients were evaluated in the morning at the Clinical Research Center.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      Patients arrived fasted but were permitted to take their usual medications. Patients were evaluated with a medical history and physical examination in which demographic information, height, weight, waist circumference, cardiovascular risk factors, comorbid conditions, claudication history, ankle-brachial index, and list of current medications were obtained. Blood samples were drawn by venipuncture from an antecubital vein and were analyzed on routine clinical panels. Additional samples were obtained, and the serum was stored at −80°C for subsequent batched analyses in duplicate of circulating and cultured endothelial cell biomarkers. In the event of an acute illness on days of baseline and post-testing evaluation, patients had their study visit rescheduled because of the possible influence that illness could have on study results, particularly with the blood biomarker analyses.

       Inclusion and exclusion criteria

      According to inclusion and exclusion criteria previously listed and described in detail for this trial,
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      patients with symptomatic PAD were examined and randomized into this study. A total of 180 patients were randomized in this clinical trial, in which 60 patients were assigned into each of the three groups, as detailed in our original report
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      and shown in the Fig. Because of initial budgetary constraints, the additional biomarker samples included in the current investigation were obtained from only the final 114 randomized patients, consisting of the final 38 patients randomized into each group (Fig). All biomarkers were selected during study design and were planned for exploratory analyses after the primary outcome analyses. A computer-generated random allocation sequence was created by the biostatistician at the beginning of the study using the NCSS statistical package (Kaysville, Utah). The allocation sequence was concealed from the research staff enrolling and assessing patients. At completion of baseline testing, patients were randomized to one of three groups within blocks to ensure that no more than two sequential participants were assigned to the same group.
      Figure thumbnail gr1
      FigConsolidated Standards of Reporting Trials flow diagram of patients through the trial. ITT, Intention to treat.

       Intervention and control groups

       Home-based exercise rehabilitation program

      The home-based exercise program consisted of 3 months of intermittent walking to mild to moderate claudication pain at least 3 days per week at a self-selected pace, in which exercise session duration was progressively increased with the aid of a step activity monitor.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      Patients wore the step activity monitor during each exercise session and returned the monitor and a logbook to the research staff at the end of week 1, 4, 8, and 12.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      During these brief 15-minute meetings, monitor data were downloaded, results were reviewed and sessions were recorded, and feedback was provided for the subsequent month of training.

       Supervised exercise rehabilitation program

      Exercise sessions in our supervised, on-site, treadmill exercise program were also performed with wearing of a step activity monitor.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      The supervised program consisted of 3 months of intermittent treadmill walking to mild to moderate claudication pain 3 days per week in which exercise session duration was progressively increased under the direct on-site supervision of the research staff.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Efficacy of quantified home-based exercise and supervised exercise in patients with intermittent claudication: a randomized controlled trial.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.

       Attention-control, light resistance program

      Light resistance training was performed three times per week, without any walking exercise, using a Pro-Form Fusion 6.0 LX weight system (ICON Health and Fitness, Inc, Logan, Utah).
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      Step-monitored home exercise improves ambulation, vascular function, and inflammation in symptomatic patients with peripheral artery disease: a randomized controlled trial.
      Resistance training consisted of performing both upper and lower extremity exercises. One set of 15 repetitions was performed for each exercise. If the resistance from the exercise machine could not be lifted, resistance bands were used instead. Each light resistance exercise session was performed under the direct on-site supervision of the research staff (ie, attention).

       Tests and outcome measurements

       Graded maximal treadmill test

      Patients performed a graded treadmill protocol to determine study eligibility as well as to obtain outcome measures related to exercise performance.
      • Gardner A.W.
      • Skinner J.S.
      • Cantwell B.W.
      • Smith L.K.
      Progressive vs single-stage treadmill tests for evaluation of claudication.
      The claudication onset time (COT), defined as the walking time at which the patients first experienced pain, and the peak walking time (PWT), defined as the walking time at which ambulation could not continue because of maximal pain, were both recorded to quantify the severity of claudication. Calf muscle hemoglobin oxygen saturation (StO2) was also measured during the treadmill test using a continuous-wave, near-infrared spectroscopy unit.
      • Gardner A.W.
      • Parker D.E.
      • Webb N.
      • Montgomery P.S.
      • Scott K.J.
      • Blevins S.M.
      Calf muscle hemoglobin oxygen saturation characteristics and exercise performance in patients with intermittent claudication.
      The time taken to reach the minimum calf StO2 value during exercise was assessed.

       Six-minute walk test

      On a separate day, typically within 1 week from the treadmill test, patients performed an overground, 6-minute walk test in which two cones were placed 100 feet apart in a marked corridor, as previously described.
      • Montgomery P.S.
      • Gardner A.W.
      The clinical utility of a six-minute walk test in peripheral arterial occlusive disease patients.
      The total distance walked was recorded.

       Endothelial cell culture bioassay

      We used a cell culture-based bioassay approach. Cultured primary human arterial endothelial cells were used to characterize the endothelial effects of circulating factors present in the sera, as previously described.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

       Apoptosis assay

      Cultured endothelial cells were treated for 24 hours with sera of patients to determine whether circulating factors in the sera exerted proapoptotic effects. Apoptotic cell death was assessed by caspase activities using Caspase-Glo 3/7 assay kit (Promega, Madison, Wisc).
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

       Cellular oxidative stress production

      To assess cellular oxidative stress induced by factors present in the sera, hydrogen peroxide production in detector endothelial cells was measured fluorometrically using the Amplex red/horseradish peroxidase assay.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

       Transient transfection, nuclear factor κ-light-chain-enhancer of activated B (NF-κB) cultured endothelial cells reporter gene assay

      To assess cellular proinflammatory effects induced by factors in the sera, transcriptional activity of NF-κB was tested in serum-treated detector endothelial cells by a reporter gene assay.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

       Circulating biomarkers of antioxidant capacity and inflammation

       Serum antioxidant capacity

      Hydroxyl radical antioxidant capacity (HORAC) was measured using the OxiSelect HORAC Activity Assay (Cell Biolabs Inc, San Diego, Calif) to determine the capacity of antioxidant enzymes and other redox molecules to counterbalance the deleterious effects of oxidative stress.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

       Circulating inflammatory and vascular biomarkers
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Sosnowska D.
      • Casanegra A.I.
      • Esponda O.L.
      • et al.
      Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease.

      A Milliplex Human Adipokine Magnetic Bead Kit was used for determining tumor necrosis factor α, interleukin-1B, and interleukin-6. A Milliplex Human Cardiovascular Disease Panel 1 Kit was used for E-selectin. A Milliplex Human Apolipoprotein Kit was used for apolipoprotein B. The Millipore kits were purchased from EMD Millipore (Billerica, Mass). Affymetrix Procarta Immunoassay was used to detect vascular endothelial growth factor A (VEGF-A). These assays were performed according to the manufacturer's protocols by a Bio-Plex 200 System (Bio-Rad, Hercules, Calif). Sample protein content was determined for normalization purposes by a spectrophotometric quantification method using BCA reagent (Pierce Chemical Co, Rockford, Ill).

       Oxidized low-density lipoprotein

      Plasma oxidized low-density lipoprotein was measured by immunoassay (Mercodia, Uppsala, Sweden) according to the manufacturer's protocol.
      • Gardner A.W.
      • Parker D.E.
      • Montgomery P.S.
      • Blevins S.M.
      • Teague A.M.
      • Casanegra A.I.
      Monitored daily ambulatory activity, inflammation, and oxidative stress in patients with claudication.

       Statistical analyses

      Measurement variables in Table I were summarized as means and standard deviations, and groups were compared with a one-way analysis of variance. Dichotomized variables were summarized as percentage with characteristic. Groups were compared using a 2 × 3 χ2 test. Only the prevalence of cerebrovascular accident and chronic kidney disease variables indicated a significant difference among groups, whereas none of the remaining variables were different. These were used as covariates in group comparisons in subsequent analyses. Changes from baseline (deltas) were computed as post-test value minus pre-test value for all variables. The missing values routine of NCSS Computer Package was used to impute missing values to produce complete delta sets for intention-to-treat (ITT) comparison. For statistical purposes, the study is viewed as a one-way design with three groups and with change scores as the response variables. Changes were selected as the response variable because this metric addresses the research questions.
      Table IBaseline clinical characteristics
      VariablesControl group (n = 38)Supervised exercise group (n = 38)Home-based exercise group (n = 38)
      Age, years63 (8)64 (10)67 (11)
      Weight, kg84.5 (17.3)81.8 (21.0)82.7 (22.0)
      Body mass index, kg/m229.4 (5.5)29.3 (6.8)28.7 (6.4)
      Ankle-brachial index0.76 (0.21)0.69 (0.24)0.68 (0.28)
      Sex, male585055
      Race, white504558
      Current smoking454034
      Hypertension899287
       Medication use878784
      Dyslipidemia929297
       Medication use687684
      Diabetes425534
       Medication use424526
      Abdominal obesity585555
      Metabolic syndrome848484
      Obesity453742
      Lower extremity revascularization393939
      Coronary artery disease293234
      Myocardial infarction182418
      Cerebrovascular disease111832
      Cerebrovascular accident
      Different between groups, P < .05.
      51832
      Chronic kidney disease
      Different between groups, P < .01.
      191645
      Chronic obstructive pulmonary disease213218
      Dyspnea585853
      Arthritis666363
      Values are presented as means (standard deviation) or percentage of patients.
      a Different between groups, P < .05.
      b Different between groups, P < .01.
      The variables in Table II were summarized as means and standard deviations. Within each group, delta means were examined for difference from 0 with one-sample t-test as changes in variables did not reveal any extreme departures from normal distribution. Comparisons of delta means among groups were made by an analysis of covariance followed by two orthogonal contrasts. For each variable, an ITT analysis among groups was examined for the group main effect. Contrast 1 compared the two exercise groups. Contrast 2 compared the two exercise groups combined with the control group. Variables in Tables III and IV exhibited significant departures from normal distribution. Therefore, these were summarized as medians and interquartile ranges. Within each group, delta medians were examined for difference from 0 with one-sample Wilcoxon test. For each variable, an ITT analysis among groups was examined for the group main effect using Kruskal-Wallis procedure. Note that no nonparametric analogue of analysis of covariance is available. Therefore, the main effect P values were not adjusted for covariates. However, because the Wilcoxon two-sample test and Spearman correlations of variable with a dichotomous variable yield the same P values, partial Spearman correlations controlled for two covariates were used as a nonparametric analogue for Contrast 1 comparison of the two exercise groups. A similar procedure was used for analogue of Contrast 2 with the two exercise groups combined compared with controls. For the ITT main effect of this analysis, the range of difference for a one-way design for three groups with 38 patients available per group was, for 80% power, between 0.62 and 0.72 standard deviation of within-cell variation. Because of the exploratory nature of this investigation, these analyses are designed as hypothesis generating more than hypothesis confirming.
      Table IILipids and glucose metabolism measurements in patients in the control, supervised exercise, and home-based exercise groups
      VariablesPre-test valuePost-test valueMean change scoreMain effect P values
      Cholesterol, mg/dL
       Control group176 (44)178 (51)1 (28)
       Supervised exercise group166 (41)166 (46)0 (24)
       Home-based exercise group162 (41)160 (56)−2 (44).607
      HDL-C, mg/dL
       Control group45 (13)45 (14)0 (6)
       Supervised exercise group39 (9)39 (10)−1 (6)
       Home-based exercise group46 (17)46 (19)−0 (8).793
      LDL-C, mg/dL
       Control group104 (41)99 (49)−4 (38)
       Supervised exercise group99 (35)94 (47)−5 (32)
       Home-based exercise group85 (31)78 (26)−7 (33).592
      LDL-C/HDL-C
       Control group2.4 (1.0)2.3 (1.3)−0.1 (1.1)
       Supervised exercise group2.7 (1.3)2.6 (1.6)−0.1 (1.0)
       Home-based exercise group2.2 (1.3)2.0 (1.0)−0.2 (0.9).370
      Non-HDL-C, mg/dL
       Control group132 (41)134 (56)2 (31)
       Supervised exercise group127 (41)128 (46)0 (21)
       Home-based exercise group118 (46)116 (60)−2 (42).510
      Triglycerides, mg/dL
       Control group138 (152)154 (206)16 (68)
       Supervised exercise group145 (104)153 (105)8 (41)
       Home-based exercise group171 (199)229 (564)58 (376).803
      Glucose, mg/L
       Control group111 (51)115 (44)4 (36)
       Supervised exercise group105 (32)110 (37)5 (38)
       Home-based exercise group100 (36)90 (35)−10 (26)
      Change from pre-test value, P < .05.
      ,
      Different from supervised exercise group, P < .05.
      .041
      Insulin, mg/L
       Control group12.7 (13.6)12.1 (8.9)−0.6 (11.7)
       Supervised exercise group17.6 (19.9)18.7 (19.5)1.2 (10.7)
       Home-based exercise group15.5 (21.6)19.7 (35.2)4.2 (17.6).155
      HOMA-IR, mg/L
       Control group3.98 (6.07)3.84 (3.87)−0.15 (5.78)
       Supervised exercise group5.40 (6.88)5.64 (5.73)0.24 (4.86)
       Home-based exercise group3.94 (5.24)5.05 (9.12)1.10 (5.57).341
      HDL-C, High-density lipoprotein cholesterol; HOMA-IR, homeostasis model assessment of insulin resistance; LDL-C, low-density lipoprotein cholesterol.
      Values are presented as means (standard deviation).
      a Change from pre-test value, P < .05.
      b Different from supervised exercise group, P < .05.
      Table IIIMeasurements from cultured endothelial cells treated with sera in patients in the control, supervised exercise, and home-based exercise groups
      VariablesPre-test valuePost-test valueMedian change scoreMain effect P values
      Apoptosis, AU
       Control group1.11 (0.32)1.20 (0.48)0.15 (0.52)
      Different from exercise groups, P < .01.
       Supervised exercise group1.05 (0.37)0.98 (0.70)−0.20 (0.38)
      Change from pre-test value, P < .01.
       Home-based exercise group1.11 (0.29)0.77 (0.57)−0.26 (0.63)
      Change from pre-test value, P < .001.
      .016
      Cellular oxidative stress, AU
       Control group27.63 (6.63)23.74 (7.67)−0.96 (6.97)
       Supervised exercise group27.50 (5.26)23.92 (6.29)−2.63 (5.74)
      Change from pre-test value, P < .01.
       Home-based exercise group26.15 (9.51)24.65 (5.65)−2.26 (6.38)
      Change from pre-test value, P < .01.
      .971
      NF-κB activity, AU
       Control group1.18 (0.71)1.43 (0.94)0.37 (0.62)
      Change from pre-test value, P < .01.
      ,
      Different from exercise groups, P < .001.
       Supervised exercise group1.61 (1.08)1.29 (0.69)−0.15 (0.51)
       Home-based exercise group1.11 (0.89)1.26 (1.19)−0.29 (0.84)<.001
      NF-κB, Nuclear factor κ-light-chain-enhancer of activated B cells.
      Values are presented as medians (interquartile ranges).
      a Different from exercise groups, P < .01.
      b Change from pre-test value, P < .01.
      c Change from pre-test value, P < .001.
      d Different from exercise groups, P < .001.
      Table IVCirculating inflammatory, antioxidant capacity, and vascular biomarkers in patients in the control, supervised exercise, and home-based exercise groups
      VariablesPre-test valuePost-test valueMedian change scoreMain effect P values
      TNF-α, pg/mL
       Control group56.0 (31.0)51.0 (22.5)−5.0 (30.5)
       Supervised exercise group56.5 (27.0)50.0 (21.5)−12.5 (21.5)
      Change from pre-test value, P < .01.
       Home-based exercise group46.5 (25.0)49.0 (35.0)−7.5 (26.0).269
      Interleukin-1B, pg/mL
       Control group15.0 (5.5)16.0 (5.0)−1.0 (4.0)
       Supervised exercise group16.0 (4.0)14.0 (4.0)−2.0 (4.0)
       Home-based exercise group15.0 (4.5)15.0 (5.0)−1.0 (6.0).325
      Interleukin-6, pg/mL
       Control group23.0 (11.5)23.5 (13.5)3.0 (11.0)
       Supervised exercise group25.0 (17.0)21.5 (14.0)−2.0 (13.5)
       Home-based exercise group23.0 (13.0)22.0 (9.5)−2.0 (15.0).754
      Oxidized LDL, U/L
       Control group70.8 (22.5)71.0 (39.3)−2.2 (14.4)
       Supervised exercise group71.3 (42.2)66.3 (36.3)−1.0 (13.5)
       Home-based exercise group63.0 (30.0)61.8 (27.3)−0.9 (18.2).108
      HORAC, AU
       Control group0.98 (0.35)0.94 (0.20)−0.06 (0.30)
      Different from exercise groups, P < .01.
       Supervised exercise group0.92 (0.17)0.95 (0.41)0.03 (0.40)
       Home-based exercise group0.95 (0.25)1.19 (0.40)0.15 (0.32)
      Change from pre-test value, P < .01.
      .005
      E-selectin, pg/mL
       Control group43.0 (52.0)35.0 (67.0)−1.5 (40.0)
      Different from exercise groups, P < .05.
       Supervised exercise group40.0 (40.5)45.0 (30.0)−4.5 (20.5)
       Home-based exercise group36.0 (26.5)36.5 (23.0)−8.0 (26.0)
      Change from pre-test value, P < .01.
      .040
      VEGF-A, pg/mL
       Control group28.0 (24.0)24.0 (21.5)−6.0 (18.0)
      Different from exercise groups, P < .01.
       Supervised exercise group25.5 (19.5)31.0 (28.5)2.0 (29.0)
       Home-based exercise group26.0 (34.0)35.0 (59.5)9.0 (45.5)
      Change from pre-test value, P < .05.
      .003
      Apolipoprotein B, ng/mL
       Control group67.0 (55.0)50.5 (51.0)−15.5 (34.5)
       Supervised exercise group71.0 (51.0)47.0 (33.5)−10.5 (28.0)
      Change from pre-test value, P < .05.
       Home-based exercise group63.0 (69.0)41.0 (46.0)−16.0 (49.5)
      Change from pre-test value, P < .05.
      .965
      HORAC, Hydroxyl radical antioxidant capacity; LDL, low-density lipoprotein; TNF-α, tumor necrosis factor α; VEGF-A, vascular endothelial growth factor A.
      Values are presented as medians (interquartile ranges).
      a Change from pre-test value, P < .01.
      b Different from exercise groups, P < .01.
      c Different from exercise groups, P < .05.
      d Change from pre-test value, P < .05.

      Results

       Baseline clinical characteristics and patient flow

      In Table I, none of the baseline characteristics, including cardiovascular risk factors and treatment with medications, were significantly different among the groups, except for chronic kidney disease (P = .004) and a history of cerebrovascular accident (P = .018), in which the home-based exercise group had the highest prevalence. Of the 114 patients, 14 did not complete the study, consisting of 5 from the control group, 5 from the supervised exercise group, and 4 from the home-based exercise group (Fig). Of these 14 patients, 11 discontinued because of personal decisions, and only 3 discontinued because of an adverse event in which all were deemed unrelated to the 3-month exercise intervention.

       Exercise measures

      During the interventions, the attention-control group completed 71% of the light resistance training sessions, the supervised exercise group completed 86% of their walking sessions, and the home-based exercise group completed 70% of their walking sessions (data not shown). Significant differences were found in the adjusted change scores (mean ± standard error of the mean) for COT in the attention-control, supervised exercise, and home-based exercise groups (47 ± 34 seconds, 213 ± 33 seconds, and 106 ± 35 seconds, respectively; P = .003), the adjusted change scores for PWT (28 ± 34 seconds, 208 ± 34 seconds, and 52 ± 36 seconds; P < .001), and the adjusted change scores for 6-minute walk distance (12 ± 10 m, 22 ± 10 m, and 72 ± 10 m; P < .001). All change scores were significant in the two exercise groups (P = .009, P = .008, and P = .016 for COT, PWT, and 6-minute walk distance, respectively) but not in the control group. The increases in COT (P = .029) and PWT (P = .002) were greater in the supervised exercise group than in the home-based exercise group, whereas the increase in 6-minute walk distance was greater in the home-based exercise group than in the supervised exercise group (P < .001). A significant difference was found in the adjusted change scores for the time to minimum calf StO2 during the treadmill test in the attention-control, supervised exercise, and home-based exercise groups (10 ± 55 seconds, 169 ± 53 seconds, and 125 ± 46 seconds, respectively; P = .002). The change scores were significant in the two exercise groups (P = .044) but not in the control group, and there was no difference between the two exercise groups.

       Outcome measures

      In Table II, the change score for glucose was significantly different among the three groups. Glucose concentration decreased in the home-based exercise group (P = .012), and this change was different from the change in the supervised exercise group (P = .020). None of the change scores for the remaining variables in Table II were significantly different among the three groups. In addition, the change scores were not significantly different among groups for fibrinolytic variables consisting of tissue plasminogen activator activity, tissue plasminogen activator antigen, plasminogen activator inhibitor 1 activity, and fibrinogen (data not shown).
      In Table III, the change score for endothelial cell apoptosis was significantly different among the three groups as the median decreased in the home-based exercise group (P < .001) and in the supervised exercise group (P = .007), and these changes in apoptosis were different from the change score in the control group (P = .005). The change score for NF-κB activity was significantly different among the three groups (P < .001) as the median increased in the control group (P = .003), and this change score was significantly different from that of the two exercise groups (P < .001), both of which did not experience a significant change. The change score for cellular oxidative stress was not significantly different among the three groups (P = .971); however, the within-group median decreased in both exercise groups (P = .008).
      In Table IV, the median change scores were significantly different among the three groups for HORAC, E-selectin, and VEGF-A. In the home-based exercise group, the median values increased for HORAC (P = .003) and VEGF-A (P = .037) and decreased for E-selectin (P = .007). Furthermore, these change scores were different between the control group and the two exercise groups combined for HORAC (P = .005), VEGF-A (P = .008), and E-selectin (P = .034). No significant group differences were seen for the remaining biomarkers.

      Discussion

      A primary novel finding from this exploratory analysis is that both the home-based exercise and supervised exercise programs decreased cultured endothelial cell apoptosis. In addition, the home-based exercise program elicited an increase in circulating antioxidant capacity (HORAC) and VEGF-A and a decrease in E-selectin and blood glucose.

       Exercise-mediated changes in cultured endothelial cells

      PAD induces mitochondriopathy,
      • Pipinos II,
      • Judge A.R.
      • Selsby J.T.
      • Zhu Z.
      • Swanson S.A.
      • Nella A.A.
      • et al.
      The myopathy of peripheral arterial occlusive disease: part 1. Functional and histomorphological changes and evidence for mitochondrial dysfunction.
      which leads to increased production of oxidative stress within myocytes and damaging effects on muscle and other tissues.
      • Pipinos II,
      • Judge A.R.
      • Selsby J.T.
      • Zhu Z.
      • Swanson S.A.
      • Nella A.A.
      • et al.
      The myopathy of peripheral arterial occlusive disease: part 2. Oxidative stress, neuropathy, and shift in muscle fiber type.
      It has been proposed that repeated episodes of ischemia and reperfusion that occur with acute bouts of walking by PAD patients, particularly at relatively high intensities, may worsen the oxidative stress and inflammatory responses.
      • Andreozzi G.M.
      • Leone A.
      • Laudani R.
      • Deinite G.
      • Martini R.
      Acute impairment of the endothelial function by maximal treadmill exercise in patients with intermittent claudication, and its improvement after supervised physical training.
      However, our results of reduced endothelial cell apoptosis after home-based and supervised exercise programs support the notion that chronic cycles of ischemia and reperfusion from 3 months of exercise training elicit a preconditioning ischemic stimulus,
      • Andreozzi G.M.
      • Leone A.
      • Laudani R.
      • Deinite G.
      • Martini R.
      Acute impairment of the endothelial function by maximal treadmill exercise in patients with intermittent claudication, and its improvement after supervised physical training.
      • Capecchi P.L.
      • Pasini F.L.
      • Cati G.
      • Colafati M.
      • Acciavatti A.
      • Ceccatelli L.
      • et al.
      Experimental model of short-time exercise-induced preconditioning in POAD patients.
      resulting in an overall reduction in endothelial apoptosis.

       Exercise-mediated changes in circulating biomarkers

      Another novel finding of this investigation is that the home-based exercise program increased circulating HORAC, indicating that the total antioxidant capacity was increased. This observation supports our previous report that baseline daily activity level is positively associated with HORAC in patients with symptomatic PAD
      • Gardner A.W.
      • Montgomery P.S.
      • Zhao Y.D.
      • Silva-Palacios F.
      • Ungvari Z.
      • Csiszar A.
      • et al.
      Association between daily walking and antioxidant capacity in patients with symptomatic peripheral artery disease.
      and suggests that ischemic preconditioning may play a role in the beneficial influences of habitual exercise on circulating antioxidant capacity.
      • Pickering A.M.
      • Vojtovich L.
      • Tower J.
      • Davies K.J.
      Oxidative stress adaptation with acute, chronic, and repeated stress.
      Furthermore, home-based exercise training resulted in an increase in circulating VEGF-A and a decrease in E-selectin and blood glucose, suggesting that home-based exercise elicited an increase in angiogenesis and decreases in endothelium-derived inflammation and insulin resistance. Our finding of exercise-mediated reduction in E-selectin supports a previous report that found E-selectin decreased in PAD patients after 8 weeks of supervised exercise training.
      • Saetre T.
      • Enoksen E.
      • Lyberg T.
      • Stranden E.
      • Jorgensen J.J.
      • Sundhagen J.O.
      • et al.
      Supervised exercise training reduces plasma levels of the endothelial inflammatory markers E-selectin and ICAM-I in patients with peripheral arterial disease.
      The effect of exercise on VEGF-A in patients with symptomatic PAD is inconsistent. Our findings of increased serum VEGF-A after home-based exercise differ from those of a nonrandomized exercise trial that found serum VEGF-A did not change with a program of nonsupervised exercise, but it was increased with a program of supervised exercise.
      • Dopheide J.F.
      • Geissler P.
      • Rubrech J.
      • Trumpp A.
      • Zeller G.C.
      • Daiber A.
      • et al.
      Influence of exercise training on proangiogenic TIE-2 monocytes and circulating angiogenic cells in patients with peripheral arterial disease.
      However, an earlier report found that skeletal muscle VEGF-A was decreased after 12 weeks of supervised exercise and remained unchanged after a home-based exercise program.
      • Jones W.S.
      • Duscha B.D.
      • Robbins J.L.
      • Duggan N.N.
      • Regensteiner J.G.
      • Kraus W.E.
      • et al.
      Alteration in angiogenic and anti-angiogenic forms of vascular endothelial growth factor-A in skeletal muscle of patients with intermittent claudication following exercise training.
      Our observation of a reduction in blood glucose after a home-based exercise program is novel, and the finding that blood glucose concentration does not change after supervised treadmill exercise supports prior work from our laboratory.
      • Izquierdo-Porrera A.M.
      • Gardner A.W.
      • Powell C.C.
      • Katzel L.I.
      Effects of exercise rehabilitation on cardiovascular risk factors in older patients with peripheral arterial occlusive disease.
      Given that we have previously found that elevated fasting glucose in patients with symptomatic PAD is associated with peripheral circulation, patient-perceived walking ability, health-related quality of life, and sedentary behavior,
      • Gardner A.W.
      • Montgomery P.S.
      The effect of metabolic syndrome components on exercise performance in patients with intermittent claudication.
      • Farah B.Q.
      • Ritti-Dias R.M.
      • Montgomery P.S.
      • Casanegra A.I.
      • Silva-Palacios F.
      • Gardner A.W.
      Sedentary behavior is associated with impaired biomarkers in claudicants.
      the reduction of blood glucose after home-based exercise has particular clinical significance for these patients. These results are supported by previous reports that diabetes impairs microcirculation
      • Mohler III, E.R.
      • Lech G.
      • Supple G.E.
      • Wang H.
      • Chance B.
      Impaired exercise-induced blood volume in type 2 diabetes with or without peripheral arterial disease measured by continuous-wave near-infrared spectroscopy.
      and metabolic syndrome impairs ankle-brachial index and claudication distances in patients with PAD.
      • Golledge J.
      • Leicht A.
      • Crowther R.G.
      • Clancy P.
      • Spinks W.L.
      • Quigley F.
      Association of obesity and metabolic syndrome with the severity and outcome of intermittent claudication.
      In this study, the fact that monitored home-based exercise training improved circulating markers of antioxidant capacity, angiogenesis, endothelium-derived inflammation, and blood glucose concentration suggests that a home-based exercise program, typically done at lower exercise intensity than a traditional supervised treadmill training program, can be used to improve these biomarkers.

       Limitations

      Several study limitations exist. Patients were volunteers, and their participation may represent a self-selection bias (eg, those most interested in their health were more likely to participate). A second limitation is that the study results may not be applicable to patients with either less severe (ie, asymptomatic) or more severe (ie, critical limb ischemia) PAD. Another limitation is that we used an indirect assay for the cultured endothelial cell data. Using this approach, the sera of patients were incubated with primary human endothelial cells and thus were not the endothelial cells of each patient. A fourth limitation is that patients were not observed long term after completing the exercise interventions, and it cannot be determined whether exercise-mediated changes in vascular and inflammatory biomarkers alter the progression of PAD or the observed declines in function.
      • McDermott M.M.
      • Ferrucci L.
      • Liu K.
      • Criqui M.H.
      • Greenland P.
      • Green D.
      • et al.
      D-dimer and inflammatory markers as predictors of functional decline in men and women with and without peripheral arterial disease.
      • McDermott M.M.
      • Liu K.
      • Guralnik J.M.
      • Ferrucci L.
      • Green D.
      • Greenland P.
      • et al.
      Functional decline in patients with and without peripheral arterial disease: predictive value of annual changes in levels of C-reactive protein and D-dimer.
      A final limitation was that because of the expense of the assay analyses, we studied the biomarker data of only the final 114 patients who were randomized into this study, and thus we may have had insufficient power to detect significant changes in some biomarkers. However, this was an exploratory analysis in which we found a number of significant changes in biomarkers with the exercise interventions, thereby providing a groundwork for future trials.

      Conclusions

      This exploratory analysis found that both home-based and supervised exercise programs are efficacious to decrease cultured endothelial cell apoptosis in patients with symptomatic PAD. Furthermore, a monitored home-based walking program improves circulating markers of endogenous antioxidant capacity, angiogenesis, endothelium-derived inflammation, and blood glucose concentration in patients with symptomatic PAD. The novel clinical significance is that important trends were found in this exploratory analysis that a contemporary home-based exercise program and a traditional supervised exercise program may favorably improve vascular and inflammatory biomarkers in addition to the well-described ambulatory improvements in symptomatic patients with PAD.

      Author contributions

      Conception and design: AG
      Analysis and interpretation: AG, DP
      Data collection: PM
      Writing the article: AG, DP
      Critical revision of the article: AG, DP, PM
      Final approval of the article: AG, DP, PM
      Statistical analysis: DP
      Obtained funding: AG
      Overall responsibility: AG

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