Effect of type 2 diabetes mellitus on exercise intolerance and the physiological responses to exercise in peripheral arterial disease

A Comprehensive Pilot Study to Elucidate the Distinct Gut Microbial Composition and Its Functional Significance in Cardio-Metabolic Disease

Cardio-metabolic disease is a significant global health challenge with increasing prevalence. Recent research underscores the disruption of gut microbial balance as a key factor in disease susceptibility. We aimed to characterize the gut microbiota composition and function in cardio-metabolic disease and healthy controls. For this purpose, we collected stool samples of 18 subjects (12 diseased, 6 healthy) and we performed metagenomics analysis and functional prediction using QIIME2 and PICRUSt. Furthermore, we carried out assessments of microbe-gene interactions, gene ontology, and microbe-disease associations. Our findings revealed distinct microbial patterns in the diseased group, particularly evident in lower taxonomic levels with significant variations in 14 microbial features. The diseased cohort exhibited an enrichment of Lachnospiraceae family, correlating with obesity, insulin resistance, and metabolic disturbances. Conversely, reduced levels of Clostridium, Gemmiger, and Ruminococcus genera indicated a potential inflammatory state, linked to compromised butyrate production and gut permeability. Functional analyses highlighted dysregulated pathways in amino acid metabolism and energy equilibrium, with perturbations correlating with elevated branch-chain amino acid levels-a known contributor to insulin resistance and type 2 diabetes. These findings were consistent across biomarker assessments, microbe-gene associations, and gene ontology analyses, emphasizing the intricate interplay between gut microbial dysbiosis and cardio-metabolic disease progression. In conclusion, our study unveils significant shifts in gut microbial composition and function in cardio-metabolic disease, emphasizing the broader implications of microbial dysregulation. Addressing gut microbial balance emerges as a crucial therapeutic target in managing cardio-metabolic disease burden.

Diabetes Is Negatively Associated With Meeting Physical Activity Time-Intensity Guidelines in Patients With Claudication

PURPOSES

We determined the percentage of patients with peripheral artery disease (PAD) and claudication who meet the 2018 physical activity (PA) time-intensity guidelines, and we identified the clinical characteristics associated with the status of meeting the guidelines.

METHODS

Five hundred seventy-two patients were assessed on their daily ambulatory activity for 1 wk with a step activity monitor, and were evaluated on whether or not they achieved 150 min/wk of moderate-intensity PA.

RESULTS

Thirty-one percent (n = 175) of the patients with PAD met the PA time-intensity guidelines and 69% (n = 397) did not. In a final multivariable logistic regression model identifying the independent predictors of meeting the PA time-intensity guidelines from clinical characteristics, diabetes was the only significant variable entered (OR = 0.310: 95% CI, 0.175-0.538; P < .001) and was associated with a 69% lower chance of meeting the guidelines. Patients with diabetes spent less daily time in moderate-intensity ambulatory PA than patients without diabetes (15 ± 13 vs 23 ± 20 min/d; P < .001).

CONCLUSIONS

Thirty-one percent of patients with PAD and claudication met the PA time-intensity guidelines. Furthermore, patients with diabetes were least likely to meet the PA time-intensity guidelines, as they had a 69% lower chance than patients without diabetes. The clinical significance is that PAD patients who have diabetes are particularly susceptible to being physically sedentary, and are therefore prime patients who should be encouraged to increase their daily PA.

The physiological and clinical importance of cardiorespiratory fitness in people with abdominal aortic aneurysm

New Findings

What is the topic of this review?

This review focuses on the physiological impact of abdominal aortic aneurysm (AAA) on cardiorespiratory fitness and the negative consequences of low fitness on clinical outcomes in AAA. We also discuss the efficacy of exercise training for improving cardiorespiratory fitness in AAA.

What advances does it highlight?

We demonstrate the negative impact of low fitness on disease progression and clinical outcomes in AAA. We highlight potential mechanistic determinants of low fitness in AAA and present evidence that exercise training can be an effective treatment strategy for improving cardiorespiratory fitness, postoperative mortality and disease progression.

Abstract

An abdominal aortic aneurysm (AAA) is an abnormal enlargement of the aorta, below the level of the renal arteries, where the aorta diameter increases by >50%. As an aneurysm increases in size, there is a progressive increase in the risk of rupture, which ranges from 25 to 40% for aneurysms >5.5 cm in diameter. People with AAA are also at a heightened risk of cardiovascular events and associated mortality. Cardiorespiratory fitness is impaired in people with AAA and is associated with poor (postoperative) clinical outcomes, including increased length of hospital stay and postoperative mortality after open surgical or endovascular AAA repair. Although cardiorespiratory fitness is a well‐recognized prognostic marker of cardiovascular health and mortality, it is not assessed routinely, nor is it included in current clinical practice guidelines for the management of people with AAA. In this review, we discuss the physiological impact of AAA on cardiorespiratory fitness, in addition to the consequences of low cardiorespiratory fitness on clinical outcomes in people with AAA. Finally, we summarize current evidence for the effect of exercise training interventions on cardiorespiratory fitness in people with AAA, including the associated improvements in postoperative mortality, AAA growth and cardiovascular risk. Based on this review, we propose that cardiorespiratory fitness should be considered as part of the routine risk assessment and monitoring of people with AAA and that targeting improvements in cardiorespiratory fitness with exercise training might represent a viable adjunct treatment strategy for reducing postoperative mortality and disease progression.

Effects of exercise training and sex on dynamic responses of O2 uptake in type 2 diabetes

Effects of training and sex on oxygen uptake dynamics during exercise in type 2 diabetes mellitus (T2DM) are not well established. We tested the hypotheses that exercise training improves the time constant of the primary phase of oxygen uptake (τ_p oxygen uptake) and with greater effect in males than females. Forty-one subjects with T2DM were assigned to 2 training groups (T_male, T_female) and 2 control groups (C_male, C_female), and were assessed before and after a 12-week intervention period. Twelve weeks of aerobic/resistance training was performed 3 times per week, 60-90 min per session. Assessments included ventilatory threshold (VT), peak oxygen uptake, τ_p oxygen uptake (80%VT), and dynamic responses of cardiac output, mean arterial pressure and systemic vascular conductance (80%VT). Training significantly decreased τ_p oxygen uptake in males by a mean of 20% (T_male = 42.7 ± 6.2 to 34.3 ± 7.2 s) and females by a mean of 16% (T_female = 42.2 ± 9.3 to 35.4 ± 8.6 s); whereas τ_p oxygen uptake was not affected in controls (C_male = 41.6 ± 9.8 to 42.9 ± 7.6 s; C_female = 40.4 ± 12.2 to 40.6 ± 13.4 s). Training increased peak oxygen uptake in both sexes (12%-13%) but did not alter systemic cardiovascular dynamics in either sex. Training improved oxygen uptake dynamics to a similar extent in males and females in the absence of changes in systemic cardiovascular dynamics. Novelty Similar training improvements in oxygen uptake dynamics were observed in males and females with T2DM. In both sexes these improvements occurred without changes in systemic cardiovascular dynamics.

In peripheral artery disease, diabetes is associated with reduced physical activity level and physical function and impaired cardiac autonomic control: A cross-sectional study

BACKGROUND

Diabetes has been considered a major risk factor for peripheral artery disease (PAD). The effect of diabetes on daily physical activity level and cardiovascular function in PAD patients is poorly known.

OBJECTIVE

To analyze the effect of diabetes on physical activity level, physical function and cardiovascular health parameters in patients with PAD and claudication symptoms.

METHODS

Cross-sectional study of 267 PAD patients, 146 without and 121 with diabetes. Physical activity levels were objectively measured by using an accelerometer, and time spent in sedentary (0-100 counts/min), light (101-1040 counts/min) and moderate to vigorous (≥1041 counts/min) physical activity was obtained. Physical function assessment included the 6-min walk test, handgrip strength test and short physical performance battery. Cardiovascular health parameters measured were brachial blood pressure, heart rate variability, and arterial stiffness.

RESULTS

Diabetic PAD patients spent more time in sedentary behavior (P=0.001, effect size [ES] 0.234) and less time in light (P=0.003, ES=0.206) and moderate-to-vigorous physical activity (P<0.001, ES=0.258) than non-diabetic PAD patients. Diabetic PAD patients presented lower 6-min walk distance (P=0.005, ES=0.194) and impaired cardiac autonomic modulation (standard deviation of all NN intervals [SDNN], P<0.001, ES=0.357; square root of the mean of the sum of the squares of differences between adjacent NN intervals [RMSSD], P<0.001, ES=0.280; and NN50 count divided by the total number of all NN intervals [pNN50], P<0.001, ES=0.291) as compared with non-diabetic PAD patients. After adjustment for confounders, diabetes remained associated with sedentary behavior (P=0.011), light (P=0.020) and moderate-to-vigorous physical activity (P=0.008), 6-min walk distance (P=0.030), SDNN (P<0.001), RMSSD (P=0.004), and PNN50 (P=0.004).

CONCLUSION

Diabetic PAD patients presented lower physical activity level, reduced physical function and impaired autonomic modulation as compared with non-diabetic PAD patients.

Effect of obesity on oxygen uptake and cardiovascular dynamics during whole-body and leg exercise in adult males and females

Obesity has been associated with a slowing of V˙O₂ dynamics in children and adolescents, but this problem has not been studied in adults. Cardiovascular mechanisms underlying this effect are not clear. In this study, 48 adults (18 males, 30 females) grouped according to body mass index (BMI) (lean < 25 kg·m⁻², overweight = 25–29.9 kg·m⁻², obese ≥30 kg·m⁻²) provided a fasting blood sample, completed a maximal graded exercise test and six bouts of submaximal exercise on a cycle ergometer, and performed two protocols of calf exercise. Dynamic response characteristics of V˙O₂ and leg vascular conductance (LVC) were assessed during cycling (80% ventilatory threshold) and calf exercise (30% MVC), respectively. Dynamic responses of cardiac output, mean arterial pressure and total systemic vascular conductance were also assessed during cycling based on measurements at 30 and 240 sec. The time constant of the second phase of the V˙O₂ response was significantly greater in obese than lean subjects (39.4 (9.2) vs. 29.1 (7.6) sec); whereas dynamic responses of cardiac output and systemic vascular conductance were not affected by BMI. For calf exercise, the time constant of the second growth phase of LVC was slowed significantly in obese subjects (22.1 (12.7) sec) compared with lean and overweight subjects (11.6 (4.5) sec and 13.4 (6.7) sec). These data show that obesity slows dynamic responses of V˙O₂ during cycling and the slower phase of vasodilation in contracting muscles of male and female adults.

Relationship between walking capacity and ambulatory blood pressure in patients with intermittent claudication

OBJECTIVE

Patients with intermittent claudication (IC) often have high blood pressure (BP), which increases their cardiovascular risk. However, whether walking capacity is associated with BP levels in patients with IC remains unknown. Therefore, this study was designed to investigate whether the total walking distance is associated with ambulatory BP in patients with IC.

PARTICIPANTS AND METHODS

This was a cross-sectional study of 75 patients with IC (58 men; 17 women). A maximal treadmill test (Gardner protocol) was performed to assess total walking distance in these patients. Furthermore, ambulatory BP, heart rate, rate-pressure product, and BP load were obtained over a 24-h period. One-way analysis of variance and multiple linear regression were carried out.

RESULTS

Walking capacity was correlated negatively with the following: (i) asleep systolic BP, diastolic BP, mean BP and heart rate; (ii) 24-h, awake and asleep RPP; and (iii) awake and asleep systolic BP load (all P<0.05). These associations occurred irrespective of confounders such as age, sex, BMI, smoking status, and number of antihypertensive medications.

CONCLUSION

A better walking capacity is associated with lower ambulatory BP parameters in patients with IC.

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 DIABETES ON AMBULATION AND INFLAMMATION IN MEN AND WOMEN WITH SYMPTOMATIC PERIPHERAL ARTERY DISEASE

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Diabetes and sex were correlated with ambulation and inflammation in patients with claudication.

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Men with diabetes have worse ambulation than men without diabetes.

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Women with diabetes have greater inflammation than women free of diabetes.

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Men and women with diabetes have evidence for high levels of angiogenic inhibition.

Objective

To determine whether diabetes and sex were factors associated with ambulatory function, endothelial cell inflammation, oxidative stress, and apoptosis, and with circulating biomarkers of inflammation and antioxidant capacity in patients with peripheral artery disease (PAD) and claudication.

Materials/Methods

Ambulatory function of 180 symptomatic men and women with PAD was assessed during a graded maximal treadmill test, 6-minute walk test, and 4-meter walk test. Patients were further characterized on endothelial effects of circulating factors present in the sera using a cell culture-based bioassay on primary human arterial endothelial cells, and on circulating inflammatory and vascular biomarkers.

Results

Men and women with diabetes had greater prevalence (p = 0.007 and p = 0.015, respectively) of coronary artery disease (CAD) than patients without diabetes. To assure that this difference did not influence planned comparisons, the data set was stratified on CAD. Diabetic men with CAD had a lower peak walking time (PWT) during the treadmill test and a slower 4-meter gait speed compared to non-diabetic men with CAD (p < 0.05). Diabetic women with CAD had a lower PWT compared to their non-diabetic counterparts (p < 0.01). Additionally, diabetic men with CAD had higher pigment epithelium-derived factor (p < 0.05) than their non-diabetic counterparts, and diabetic women with CAD had higher leptin (p < 0.01) and interleukin-8 levels (p < 0.05).

Conclusions

In patients with PAD, diabetic men and women with CAD had more severe claudication than their non-diabetic counterparts, as measured by shorter PWT, and the men had further ambulatory impairment manifested by slower 4-meter gait speed. Furthermore, the diabetic patients with CAD had elevations in interleukin-8, leptin, and PEDF.

Reliability of the Vascular Claudication Reporting in Diabetic Patients With Peripheral Arterial Disease

We evaluated whether altered reporting of ischemic symptoms occurs in diabetic patients with peripheral arterial disease (PAD) and stable claudication. Patients (n = 152) with claudication were enrolled (120 males; mean age: 71.0 ± 8.6 years): 74 with diabetes (DM-PAD) and 78 without (DMfree-PAD). The degree of muscle oxygenation at symptom onset and maximal speed (Smax) during an incremental treadmill test was recorded at the gastrocnemius by near-infrared spectroscopy (NIRS) and quantified by area under the curve of oxygenated hemoglobin (AUC-Hbo2) and area under the curve of differential hemoglobin (AUC-dHb). The DM-PAD and DMfree-PAD showed similar exercise capacities inversely correlated with the degree of muscle oxygenation but significantly lower values of AUC-Hbo2 and AUC-dHb for DM-PAD at symptom onset and Smax (−356 vs −122 and −1200 vs −359, P < .0001). During a NIRS-assisted test, the report of claudication in the presence of diabetes was delayed, occurring at a lower degree of oxygenation than in patients with PAD only, with potential implications for testing, functional staging, and balance disorders.

Regulation of pyruvate metabolism and human disease

Pyruvate is a keystone molecule critical for numerous aspects of eukaryotic and human metabolism. Pyruvate is the end-product of glycolysis, is derived from additional sources in the cellular cytoplasm, and is ultimately destined for transport into mitochondria as a master fuel input undergirding citric acid cycle carbon flux. In mitochondria, pyruvate drives ATP production by oxidative phosphorylation and multiple biosynthetic pathways intersecting the citric acid cycle. Mitochondrial pyruvate metabolism is regulated by many enzymes, including the recently discovered mitochondria pyruvate carrier, pyruvate dehydrogenase, and pyruvate carboxylase, to modulate overall pyruvate carbon flux. Mutations in any of the genes encoding for proteins regulating pyruvate metabolism may lead to disease. Numerous cases have been described. Aberrant pyruvate metabolism plays an especially prominent role in cancer, heart failure, and neurodegeneration. Because most major diseases involve aberrant metabolism, understanding and exploiting pyruvate carbon flux may yield novel treatments that enhance human health.

Do behaviour-change techniques contribute to the effectiveness of exercise therapy in patients with intermittent claudication? A systematic review

This systematic narrative review of randomised controlled trials (RCTs) identifies and evaluates the efficacy of behaviour-change techniques explicitly aimed at walking in individuals with intermittent claudication. An electronic database search was conducted up to December 2012. RCTs were included comparing interventions incorporating behaviour-change techniques with usual care, walking advice or exercise therapy for increasing walking in people with intermittent claudication. Studies were evaluated using the Cochrane Collaboration risk of bias tool. The primary outcome variable was maximal walking ability at least 3 months after the start of an intervention. Secondary outcome variables included pain-free walking ability, self-report walking ability and daily walking activity. A total of 3,575 records were retrieved. Of these, six RCTs met the inclusion criteria. As a result of substantial heterogeneity between studies, no meta-analysis was conducted. Overall, 11 behaviour-change techniques were identified; barrier identification with problem solving, self-monitoring and feedback on performance were most frequently reported. There was limited high-quality evidence and findings were inconclusive regarding the utility of behaviour-change techniques for improving walking in people with intermittent claudication. Rigorous, fully powered trials are required that control for exercise dosage and supervision in order to isolate the effect of behaviour-change techniques alongside exercise therapy.

Exercise and diabetes-related cardiovascular disease: systematic review of published evidence from observational studies and clinical trials

The cost of treating cardiovascular disease (CVD) and diabetes is enormous and is set to rise in the coming years. Physical inactivity and sedentary behaviors are major risk factors for these diseases and are estimated to account for several million global deaths annually. Lifestyle interventions, particularly those aimed at enhancing physical activity levels, have a substantial favorable impact on diabetes progression in people at high risk of the disease. Although observational studies and small intervention studies suggest that physical activity might also prevent CVD in people with diabetes, this is not supported by the results of larger randomized controlled trials of lifestyle intervention. The purpose of this review is to provide an overview of the published studies focused on the role of physical activity in CVD prevention in persons with diabetes, and to discuss the implications of these studies' findings. Our review identified almost 100 studies published in the past decade relevant to this topic.

Exercise training and peripheral arterial disease

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

Similar level of impairment in exercise performance and oxygen uptake kinetics in middle-aged men and women with type 2 diabetes

The present study tested the hypothesis that the magnitude of the type 2 diabetes-induced impairments in peak oxygen uptake (V̇o2) and V̇o2 kinetics would be greater in females than males in middle-aged participants. Thirty-two individuals with type 2 diabetes (16 male, 16 female), and 32 age- and body mass index (BMI)-matched healthy individuals (16 male, 16 female) were recruited. Initially, the ventilatory threshold (VT) and peak V̇o2 were determined. On a separate day, subjects completed four 6-min bouts of constant-load cycling at 80% VT for the determination of V̇o2 kinetics using standard procedures. Cardiac output (CO) (inert gas rebreathing) was recorded at rest, 30, and 240 s during two additional bouts. Peak V̇o2 (ml·kg−1·min−1) was significantly reduced in men and women with type 2 diabetes compared with their respective nondiabetic counterparts (men, 27.8 ± 4.4 vs. 31.1 ± 6.2 ml·kg−1·min−1; women, 19.4 ± 4.1 vs. 21.4 ± 2.9 ml·kg−1·min−1). The time constant (s) of phase 2 (τ2) and mean response time (s) of the V̇o2 response (MRT) were slowed in women with type 2 diabetes compared with healthy women (τ2, 43.3 ± 9.8 vs. 33.6 ± 10.0 s; MRT, 51.7 ± 9.4 vs. 43.5 ± 11.4s) and in men with type 2 diabetes compared with nondiabetic men (τ2, 43.8 ± 12.0 vs. 35.3 ± 9.5 s; MRT, 57.6 ± 8.3 vs. 47.3 ± 9.3 s). The magnitude of these impairments was not different between males and females. The steady-state CO responses or the dynamic responses of CO were not affected by type 2 diabetes among men or women. The results suggest that the type 2 diabetes-induced impairments in peak V̇o2 and V̇o2 kinetics are not affected by sex in middle aged participants.

Bone marrow mobilization with granulocyte macrophage colony-stimulating factor improves endothelial dysfunction and exercise capacity in patients with peripheral arterial disease

BACKGROUND

We hypothesized that granulocyte macrophage colony-stimulating factor (GM-CSF) administration will be safe and will improve endothelial dysfunction and exercise capacity by mobilizing progenitor cells in patients with peripheral arterial disease (PAD).

METHODS

Forty-five patients with PAD received thrice-weekly injections for 2 weeks of 3, 6, or 10 microg/kg per day of GM-CSF or placebo in successive cohorts of 15 subjects randomized 2:1 to drug or placebo. CD34+ mononuclear cell subsets and colony formation assay, endothelial function, ankle-brachial index, and walking capacity were measured.

RESULTS

Granulocyte macrophage colony-stimulating factor administration was safe. After pooling data from GM-CSF cohorts, at 2 weeks, there was a significant increase in total leukocytes (43%, P < .0001), CD34+ cells (46%, P = .035), and colony-forming units (31%, P = .026, week 1). At 12 weeks, endothelial function improved with GM-CSF (flow-mediated vasodilation increased by 59%, P < .01) as did pain-free treadmill walking time (38 seconds, P = .008) and total treadmill walking time (55 seconds, P = .016). Corresponding changes were not observed in the placebo group.

CONCLUSIONS

Granulocyte macrophage colony-stimulating factor therapy in patients with PAD was associated with mobilization of progenitor cells, improvement of endothelial dysfunction, and exercise capacity. The efficacy of strategies designed to mobilize bone marrow progenitors warrants further study in patients with PAD.