Impact of a cardiac rehabilitation program and inflammatory state on endothelial progenitor cells in acute coronary syndrome patients

Effects of cardiac rehabilitation on inflammatory biomarkers in unstable ischemic heart disease patients following percutaneous coronary intervention: a randomized controlled study

INTRODUCTION

Several blood inflammatory markers, such as high-sensitivity C-reactive protein (hs-CRP), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), are linked to increased risk for cardiovascular diseases. This study aimed to evaluate these inflammatory markers after cardiac rehabilitation (CR) in patients with unstable ischemic heart disease (UIHD) who underwent successful percutaneous coronary intervention (PCI).

METHODS

A cohort of 115 patients with successful PCI due to UIHD enrolled in the study from January 2018 to March 2021. We used a permuted block stratified randomization technique (2 : 1 ratio). Seventy-seven patients were randomized to the CR group and 38 patients to the control group. The CR group underwent a 12-week pre-specified CR regimen. Blood samples were taken at baseline and follow-up at 12 weeks for both groups.

RESULT

Among the 115 patients, 33 patients were female. The mean age was (53 ± 5.55 years) in the control and (53 ± 6.09 years) in the CR group. The two groups were comparable regarding their baseline characteristics and the values of the inflammatory markers. By contrast, at 12 weeks, the inflammatory marker values were significantly lower in the CR group compared to the control group; hs-CRP: 0.11 [0.08-0.14] vs. 0.21 [0.19-0.21], P -value <0.001; NLR: 2.17 [1.42-2.43] vs. 2.26 [2.07-2.6], P -value: 0.016; PLR: 91.2821 [63.3333-103.2000] vs. 92.600 [84.6154-110.0000], P -value: 0.027.

CONCLUSION

CR after PCI in UIHD patients may attenuate some inflammatory markers, which might benefit cardiovascular health. Further studies are required to evaluate these findings with longer follow-up and the powered to measure major cardiovascular event rates.

The Effects of a Cardiac Rehabilitation Program on Endothelial Progenitor Cells and Inflammatory Profile in Patients with Chronic Heart Failure of Different Severity

Endothelial dysfunction and inflammation are common pathophysiological characteristics of chronic heart failure (CHF). Endothelial progenitor cells (EPCs) are recognized as useful markers of vascular damage and endothelial repair. The aim of this study was to investigate the effects of a cardiac rehabilitation program on EPCs and inflammatory profile in CHF patients of different severity. Forty-four patients with stable CHF underwent a 36-session cardiac rehabilitation program. They were separated into two different subgroups each time, according to the median peak VO2, predicted peak VO2, VE/VCO2 slope, and ejection fraction. EPCs, C-reactive protein (CRP), interleukin 6 (IL-6), interleukin 10 (IL-10), and vascular endothelial growth factor (VEGF) were measured. Flow cytometry was used for the quantification of EPCs. Mobilization of EPCs increased and the inflammatory profile improved within each severity group (p < 0.05) after the cardiac rehabilitation program, but there were no statistically significant differences between groups (p > 0.05). A 36-session cardiac rehabilitation program has similar beneficial effects on the mobilization of EPCs and on the inflammatory profile in patients with CHF of different severity.

Aerobically trained older adults show impaired resting, but preserved exercise-induced circulating progenitor cell count, which was not improved by sprint interval training

Older adults exhibit a reduced number and function of CD34 + circulating progenitor cells (CPC), a known risk factor for cardiovascular disease. Exercise promotes the mobilisation of CPCs from bone marrow, so whether ageing per se or physical inactivity in older age reduces CPCs is unknown. Thus, this study examined the effect of age on resting and exercise-induced changes in CPCs in aerobically trained adults and the effect of 8 weeks of sprint interval training (SIT) on resting and exercise-induced CPCs in older adults. Twelve young (22-34 years) and nine older (63-70 years) adults participated in the study. Blood was sampled pre and immediately post a graded exercise test to exhaustion in both groups. Older participants repeated the process after 8 weeks of SIT (3 × 20 s 'all-out' sprints, 2 × a week). Total CPCs (CD34⁺) and endothelial progenitor cells (EPCs: CD34⁺KDR⁺) were determined by flow cytometry. Older adults exhibited lower basal total CD34⁺ CPCs (828 ± 314 vs. 1186 ± 272 cells·mL^-1, p = 0.0149) and CD34⁺KDR⁺ EPCs (177 ± 128 vs. 335 ± 92 cells·mL^-1, p = 0.007) than younger adults. The maximal exercise test increased CPCs in young (CD34⁺: p = 0.004; CD34⁺KDR⁺: p = 0.017) and older adults (CD34⁺: p < 0.001; CD34⁺KDR⁺: p = 0.008), without difference between groups (p = 0.211). SIT did not alter resting or exercise-induced changes in CPCs in the older cohort (p > 0.232). This study suggests age per se does not impair exercise-induced CPC counts, but does lower resting CPC counts.

Endothelial progenitor cell mobilization based on exercise volume in patients with cardiovascular disease and healthy individuals: a systematic review and meta-analysis

Endothelial progenitor cells (EPCs) play a vital role in protecting endothelial dysfunction and cardiovascular disease (CVD). Physical exercise stimulates the mobilization of EPCs, and along with vascular endothelial growth factor (VEGF), promotes EPC differentiation, and contributes to vasculogenesis. The present meta-analysis examines the exercise-induced EPC mobilization and has an impact on VEGF in patients with CVD and healthy individuals. Database research was conducted (PubMed, EMBASE, Cochrane Library of Controlled Trials) by using an appropriate algorithm to indicate the exercise-induced EPC mobilization studies. Eligibility criteria included EPC measurements following exercise in patients with CVD and healthy individuals. A continuous random effect model meta-analysis (PROSPERO-CRD42019128122) was used to calculate mean differences in EPCs (between baseline and post-exercise values or between an experimental and control group). A total of 1460 participants (36 studies) were identified. Data are presented as standard mean difference (Std.MD) and 95% confidence interval (95% CI). Aerobic training stimulates the mobilization of EPCs and increases VEGF in patients with CVD (EPCs: Std.MD: 1.23, 95% CI: 0.70-1.76; VEGF: Std.MD: 0.76, 95% CI:0.16-1.35) and healthy individuals (EPCs: Std.MD: 1.11, 95% CI:0.53-1.69; VEGF: Std.MD: 0.75, 95% CI: 0.01-1.48). Acute aerobic exercise (Std.MD: 1.40, 95% CI: 1.00-1.80) and resistance exercise (Std.MD: 0.46, 95%CI: 0.10-0.82) enhance EPC numbers in healthy individuals. Combined aerobic and resistance training increases EPC mobilization (Std.MD:1.84, 95% CI: 1.03-2.64) in patients with CVD. Adequate exercise volume (>60%VO_2max >30 min; P = 0.00001) yields desirable results. Our meta-analysis supports the findings of the literature. Exercise volume is required to obtain clinically significant results. Continuous exercise training of high-to-moderate intensity with adequate duration as well as combined training with aerobic and resistance exercise stimulates EPC mobilization and increases VEGF in patients with CVD and healthy individuals.

Mechanisms and Clinical Implications of Endothelial Dysfunction in Arterial Hypertension

The endothelium is composed of a monolayer of endothelial cells, lining the interior surface of blood and lymphatic vessels. Endothelial cells display important homeostatic functions, since they are able to respond to humoral and hemodynamic stimuli. Thus, endothelial dysfunction has been proposed as a key and early pathogenic mechanism in many clinical conditions. Given the relevant repercussions on cardiovascular risk, the complex interplay between endothelial dysfunction and systemic arterial hypertension has been a matter of study in recent years. Numerous articles have been published on this issue, all of which contribute to providing an interesting insight into the molecular mechanisms of endothelial dysfunction in arterial hypertension and its role as a biomarker of inflammation, oxidative stress, and vascular disease. The prognostic and therapeutic implications of endothelial dysfunction have also been analyzed in this clinical setting, with interesting new findings and potential applications in clinical practice and future research. The aim of this review is to summarize the pathophysiology of the relationship between endothelial dysfunction and systemic arterial hypertension, with a focus on the personalized pharmacological and rehabilitation strategies targeting endothelial dysfunction while treating hypertension and cardiovascular comorbidities.

The impact of different forms of exercise on circulating endothelial progenitor cells in cardiovascular and metabolic disease

Circulating endothelial progenitor cells (EPCs) contribute to vascular repair and their monitoring could have prognostic clinical value. Exercise is often prescribed for the management of cardiometabolic diseases, however, it is not fully understood how it regulates EPCs.

OBJECTIVES

to systematically examine the acute and chronic effects of different exercise modalities on circulating EPCs in patients with cardiovascular and metabolic disease.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed.

RESULTS

six electronic databases and reference lists of eligible studies were searched to April 2021. Thirty-six trials met the inclusion criteria including 1731 participants. Acute trials: in chronic heart failure (CHF), EPC mobilisation was acutely increased after high intensity interval or moderate intensity continuous exercise training, while findings were inconclusive after a cardiopulmonary cycling exercise test. Maximal exercise tests acutely increased EPCs in ischaemic or revascularized coronary artery disease (CAD) patients. In peripheral arterial disease (PAD), EPC levels increased up to 24 h post-exercise. In patients with compromised metabolic health, EPC mobilisation was blunted after a single exercise session. Chronic trials: in CHF and acute coronary syndrome, moderate intensity continuous protocols, with or without resistance exercise or calisthenics, increased EPCs irrespective of EPC identification phenotype. Findings were equivocal in CAD regardless of exercise mode, while in severe PAD disease EPCs increased. High intensity interval training increased EPCs in hypertensive metabolic syndrome and heart failure reduced ejection fraction.

CONCLUSION

the clinical condition and exercise modality influence the degree of EPC mobilisation and magnitude of EPC increases in the long term.

Serial Changes in Exercise Capacity, NT-proBNP, and Adiponectin in Patients with Acute Coronary Syndrome before and after Phase II Rehabilitation as well as at the 12-Month Follow-Up

Background. Acute coronary syndrome (ACS) causes pathophysiological changes in exercise capacity, N-terminal part of pro-brain natriuretic peptide (NT-proBNP), and adiponectin that impact the course of coronary artery disease and clinical outcomes after cardiac rehabilitation (CR). However, the serial changes and the relationship between the changes in these parameters for a prolonged term remain uninvestigated. Methods. Eighty-one patients with ACS underwent a three- or four-week CR program after acute care and were followed up for 12 months. Exercise capacity on a cycle ergometer and blood levels of NT-proBNP and adiponectin were determined before and after CR as well as at the 12-month follow-up. Results. Exercise capacity increased from 100 watts (in median) before CR to 138 watts after CR and 150 watts at 12 months. The NT-proBNP level (526 pg/ml before CR) remained almost unchanged after CR (557 pg/ml) and then decreased at 12 months (173 pg/ml). The adiponectin level (14.5 µg/ml before CR) increased after CR (16.0 µg/ml) and at 12 months (17.2 µg/ml). There was no significant correlation among the changes in these parameters at each observation time point. Conclusion. During the observation period from before CR to the 12-month follow-up, exercise capacity, NT-proBNP, and adiponectin underwent significant changes; however, these changes were independent from each other and not correlated linearly, and they provide complementary information in clinical practice. Thus, all these parameters should be included and determined at different time points for a prolonged period of time.

The impact of different forms of exercise on circulating endothelial progenitor cells in cardiovascular and metabolic disease

Circulating endothelial progenitor cells (EPCs) contribute to vascular repair and their monitoring could have prognostic clinical value. Exercise is often prescribed for the management of cardiometabolic diseases, however, it is not fully understood how it regulates EPCs.

OBJECTIVES

to systematically examine the acute and chronic effects of different exercise modalities on circulating EPCs in patients with cardiovascular and metabolic disease.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed.

RESULTS

six electronic databases and reference lists of eligible studies were searched to April 2021. Thirty-six trials met the inclusion criteria including 1731 participants. Acute trials: in chronic heart failure (CHF), EPC mobilisation was acutely increased after high intensity interval or moderate intensity continuous exercise training, while findings were inconclusive after a cardiopulmonary cycling exercise test. Maximal exercise tests acutely increased EPCs in ischaemic or revascularized coronary artery disease (CAD) patients. In peripheral arterial disease (PAD), EPC levels increased up to 24 h post-exercise. In patients with compromised metabolic health, EPC mobilisation was blunted after a single exercise session. Chronic trials: in CHF and acute coronary syndrome, moderate intensity continuous protocols, with or without resistance exercise or calisthenics, increased EPCs irrespective of EPC identification phenotype. Findings were equivocal in CAD regardless of exercise mode, while in severe PAD disease EPCs increased. High intensity interval training increased EPCs in hypertensive metabolic syndrome and heart failure reduced ejection fraction.

CONCLUSION

the clinical condition and exercise modality influence the degree of EPC mobilisation and magnitude of EPC increases in the long term.

A Meta-Analysis of the Effects of Aerobic Exercise on the Basal Level of Endothelial Progenitor Cells in Middle-Aged and Older Adults

Circulatory endothelial progenitor cells (EPCs) play an important role in repairing damaged vascular endothelium and preventing cardiovascular diseases. The decrease in level of circulating EPCs in middle-aged and older adults can lead to an increase in cardiovascular events. Researchers have carried out several studies on the effects of aerobic exercise on circulating EPCs in middle-aged and older adults, but the results vary from one study to another. The aim of this study therefore is to systematically evaluate the effect of aerobic exercise on the basal level of circulating EPCs in middle-aged and older adults by meta-analysis. Randomized controlled trial studies on the effects of aerobic exercise on EPCs were searched for from CNKI, PubMed, EBSCO, Cochrane Library, Web of Science, and Embase databases. The literature was screened according to inclusion and exclusion criteria, research data were extracted, and the literature quality was evaluated by Cochrane scale. Software Review Manager (version 5.3) and Stata (version 15.0) were used for data analysis. A total of nine articles were included in this analysis, including 165 participants (40 healthy adults and 125 patients) who received exercise interventions and 162 participants (40 healthy adults and 122 patients) who served as the control, with an age range from 58 to 70 years. The meta-analysis found that long-term (≥12 weeks) aerobic exercise could improve the level of EPCs in the peripheral circulation (standardized mean differences [SMD] = 0.53, 95% confidence interval [0.30, 0.76], p < .01). The subgroup analysis found that aerobic exercise improved EPCs in healthy people better than in people with cardiovascular disease and that the intervention time needs to be over 12 weeks to have a significant impact. In conclusion, the authors suggest that middle-aged and older adults can improve their EPCs quantity by engaging in moderate-intensity aerobic exercise four to five times per week for no less than 12 weeks to reduce the risk of cardiovascular disease.

CD34+ progenitors are predictive of mortality and are associated with physical activity in cardiovascular disease patients

BACKGROUND AND AIMS

Circulating progenitor cells (CPCs) play an important role in vascular repair and can influence cardiovascular (CV) health and longevity. Exercise is known to modulate these cells via mobilization from the bone marrow. The primary aims of this study were to evaluate the association of CPCs with mortality and explore the association between physical activity (PA) and CPCs.

METHODS

1751 individuals from the Framingham Offspring cohort (66 ± 9 years [40-92 years], 54% female) were included in the study. CPCs (CD34^+, CD34⁺CD133⁺, CD34⁺CD133⁺KDR⁺) were measured by flow cytometry. Multivariable Cox regression analyses were performed to investigate relationship of CPCs with future CV event and mortality. Multivariate regression analyses were performed to determine the relationship between self-reported PA and CPC counts.

RESULTS

Following adjustment for standard risk factors, there was an inverse association between CD34⁺ CPCs and all-cause mortality (hazard ratio (HR) per unit increase in CD34⁺, 0.79; 95% CI 0.64-0.98, p = 0.036). CD34⁺CD133⁺ CPCs were inversely associated with CV mortality (HR 0.63, 95% CI 0.44-0.91, p = 0.013). Associations of CD34⁺ and CD34⁺CD133⁺ with mortality were strongest in participants with pre-existing CVD. PA was associated with CD34⁺ CPCs only in CVD participants (PA Index: β = 0.176, p = 0.003; moderate-to-vigorous [MVPA]: β = 0.159, p = 0.007). This relationship was maintained after adjustment for confounding variables.

CONCLUSIONS

A higher number of CD34⁺ and CD34⁺ CD133⁺ CPCs was inversely associated with all-cause and CV mortality. These associations were strongest in participants with CVD. PA is independently associated with CD34⁺ CPCs in individuals with CVD only, suggestive of greater benefit for this population group.

Effects of Exercise Therapy for Adults With Coronary Heart Disease: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Exercise therapy has been recommended as a core element for the prevention of coronary heart disease (CHD). However, the independent impact of exercise therapy remains unclear.

OBJECTIVE

The aim of this study was to assess the effects of exercise therapy compared with no exercise control in patients with CHD.

METHODS

We searched 8 electronic databases from January 2000 to March 2020. Randomized controlled trials with at least 6 months of follow-up that evaluated the effects of exercise therapy on hospital admissions, health-related quality of life (HRQoL), mortality, and morbidity in adults with CHD were included. Two reviewers independently screened records for eligibility, extracted data, and assessed risks of bias using the Cochrane tool. Meta-analyses were conducted using the random-effects model.

RESULTS

We included 22 randomized controlled trials involving 4465 participants. Compared with no exercise control, exercise therapy reduced all-cause hospital admissions (10 studies; risk ratio, 0.46; 95% confidence interval, 0.25-0.83; I = 64%) and cardiovascular mortality (9 studies; risk ratio, 0.44; 95% confidence interval, 0.22-0.89; I= 0%) across all studies reporting these outcomes at their longest follow-up. Eight of 14 studies that assessed HRQoL observed a significant improvement in at least 1 domain or overall HRQoL with exercise therapy compared with control. There were no significant reductions in cardiovascular hospital admissions, all-cause mortality, incidence of myocardial infarction, or revascularization.

CONCLUSIONS

This review shows the independent benefits of exercise therapy in reducing all-cause hospital admissions and cardiovascular mortality for adults with CHD.

[Modern strategies for cardiac rehabilitation after myocardial infarction and percutaneous coronary intervention]

Modern cardiac rehabilitation represents a structured, multicomponent program, which includes physical activity, education of the patient, modification of the health behavior, and psychological and social support. In EU countries, only 44.8% of patients with ischemic heart disease receive a recommendation to participate in any form of rehabilitation, and only 36.5% of all patients presently have an access to any rehabilitation program. Systematic analysis of programs for prevention of cardiovascular diseases and for rehabilitation in patients with myocardial infarction (MI) and percutaneous coronary intervention showed that complex programs can still reduce all-cause and cardiovascular mortality and frequency of recurrent MI and stroke. These programs include key components of cardiac rehabilitation, reduction of six or more risk factors, and effective control by drug therapy.

Oxidative Stress and Inflammation, Key Targets of Atherosclerotic Plaque Progression and Vulnerability: Potential Impact of Physical Activity

Atherosclerosis, a complex cardiovascular disease, is a leading cause of mortality and morbidity worldwide. Oxidative stress and inflammation are both involved in the development of atherosclerotic plaque as they increase the biological processes associated with this pathology, such as endothelial dysfunction and macrophage recruitment and adhesion. Atherosclerotic plaque rupture leading to major ischemic events is the result of vulnerable plaque progression, which is a result of the detrimental effect of oxidative stress and inflammation on risk factors for atherosclerotic plaque rupture, such as intraplaque hemorrhage, neovascularization, and fibrous cap thickness. Thus, both are key targets for primary and secondary interventions. It is well recognized that chronic physical activity attenuates oxidative stress in healthy subjects via the improvement of antioxidant enzyme capacities and inflammation via the enhancement of anti-inflammatory molecules. Moreover, it was recently shown that chronic physical activity could decrease oxidative stress and inflammation in atherosclerotic patients. The aim of this review is to summarize the role of oxidative stress and inflammation in atherosclerosis and the results of therapeutic interventions targeting them in both preclinical and clinical studies. The effects of chronic physical activity on these two key processes are then reviewed in vulnerable atherosclerotic plaques in both coronary and carotid arteries.

Effects of Catheterization on Artery Function and Health: When Should Patients Start Exercising Following Their Coronary Intervention?

Coronary artery disease (CAD) is a leading cause of death worldwide, and percutaneous transluminal coronary angiography (PTCA) and/or percutaneous coronary intervention (PCI; angioplasty) are commonly used to diagnose and/or treat the obstructed coronaries. Exercise-based rehabilitation is recommended for all CAD patients; however, most guidelines do not specify when exercise training should commence following PTCA and/or PCI. Catheterization can result in arterial dysfunction and acute injury, and given the fact that exercise, particularly at higher intensities, is associated with elevated inflammatory and oxidative stress, endothelial dysfunction and a pro-thrombotic milieu, performing exercise post-PTCA/PCI may transiently elevate the risk of cardiac events. This review aims to summarize extant literature relating to the impacts of coronary interventions on arterial function, including the time-course of recovery and the potential deleterious and/or beneficial impacts of acute versus long-term exercise. The current literature suggests that arterial dysfunction induced by catheterization recovers 4-12 weeks following catheterization. This review proposes that a period of relative arterial vulnerability may exist and exercise during this period may contribute to elevated event susceptibility. We therefore suggest that CAD patients start an exercise training programme between 2 and 4 weeks post-PCI, recognizing that the literature suggest there is a 'grey area' for functional recovery between 2 and 12 weeks post-catheterization. The timing of exercise onset should take into consideration the individual characteristics of patients (age, severity of disease, comorbidities) and the intensity, frequency and duration of the exercise prescription.

Endothelial Regenerative Capacity and Aging: Influence of Diet, Exercise and Obesity

Background:

The endothelium plays an important role in cardiovascular regulation, from blood flow to platelet aggregation, immune cell infiltration and demargination. A dysfunctional endo-thelium leads to the onset and progression of Cardiovascular Disease (CVD). The aging endothelium displays significant alterations in function, such as reduced vasomotor functions and reduced angio-genic capabilities. This could be partly due to elevated levels of oxidative stress and reduced endothe-lial cell turnover. Circulating angiogenic cells, such as Endothelial Progenitor Cells (EPCs) play a significant role in maintaining endothelial health and function, by supporting endothelial cell prolifera-tion, or via incorporation into the vasculature and differentiation into mature endothelial cells. Howev-er, these cells are reduced in number and function with age, which may contribute to the elevated CVD risk in this population. However, lifestyle factors, such as exercise, physical activity obesity, and dietary intake of omega-3 polyunsaturated fatty acids, nitrates, and antioxidants, significantly af-fect the number and function of these circulating angiogenic cells.

Conclusion:

This review will discuss the effects of advancing age on endothelial health and vascular regenerative capacity, as well as the influence of diet, exercise, and obesity on these cells, the mecha-nistic links and the subsequent impact on cardiovascular health

Insights into Endothelial Progenitor Cells: Origin, Classification, Potentials, and Prospects

With the discovery of endothelial progenitor cells (EPCs) in the late 1990s, a paradigm shift in the concept of neoangiogenesis occurred. The identification of circulating EPCs in peripheral blood marked the beginning of a new era with enormous potential in the rapidly transforming regenerative field. Overwhelmed with the revelation, researchers across the globe focused on isolating, defining, and interpreting the role of EPCs in various physiological and pathological conditions. Consequently, controversies emerged regarding the isolation techniques and classification of EPCs. Nevertheless, the potential of using EPCs in tissue engineering as an angiogenic source has been extensively explored. Concomitantly, the impact of EPCs on various diseases, such as diabetes, cancer, and cardiovascular diseases, has been studied. Within the limitations of the current knowledge, this review attempts to delineate the concept of EPCs in a sequential manner from the speculative history to a definitive presence (origin, sources of EPCs, isolation, and identification) and significance of these EPCs. Additionally, this review is aimed at serving as a guide for investigators, identifying potential research gaps, and summarizing our current and future prospects regarding EPCs.

Effect of cardiac rehabilitation on inflammation: A systematic review and meta-analysis of controlled clinical trials

BACKGROUND

This systematic review and meta-analysis aimed to assess the effect of cardiac rehabilitation (CR) on serum C-reactive protein (CRP) as an indicator of the inflammatory state and predictor of recurrent cardiovascular events.

METHODS

PubMed, SCOPUS, Cochrane library, and Google Scholar databases were searched up to January 2014 for original articles which investigated the effect of CR on CRP among adult patients with previous cardiovascular events. The random effects model was used to assess the overall effect of CR on the variation in serum CRP levels.

RESULTS

In the present systematic review and meta-analysis, 15 studies were included. The analysis showed that CR might significantly reduce high-sensitivity CRP (hs-CRP) levels [Difference in means (DM) = -1.81 mg/l, 95% confidence interval (CI): -2.65, -0.98; P = 0.004). However, the heterogeneity between studies was significant (Cochran's Q test, P < 0.001, I-squared = 84.9%). To find the source of variation, the studies were categorized based on study design (quality) and duration. The negative effect was higher among studies which followed their participants for 3 weeks or less (DM = -2.75 mg/l, 95% CI: -3.86, -1.64; P < 0.001) compared to studies which investigated the effect of CR for 3-8 weeks (DM = -0.89 mg/l, 95% CI: -1.35, -0.44; P < 0.001) and those which lasted more than 8 weeks (DM = -1.71 mg/l, 95% CI: -2.53, -0.89; P < 0.001). There was no evidence of heterogeneity when the categorization was based on the follow-up period.

CONCLUSION

Both short- and long-term CR have resulted in improvement in serum hs-CRP levels. CR can be perceived as a beneficial tool to reduce inflammatory markers among patients with previous cardiac events.

Cardiac rehabilitation in acute myocardial infarction patients after percutaneous coronary intervention: A community-based study

BACKGROUND

Acute myocardial infarction (AMI) is one of the leading causes of death and physical disability worldwide. However, the development of community- based cardiac rehabilitation (CR) in AMI patients is hysteretic. Here, we aimed to evaluate the safety and efficacy of CR applied in the community in AMI patients who underwent percutaneous coronary intervention (PCI).

METHODS

A total of 130 ST-segment elevated myocardial infarction (STEMI) patients after PCI were randomly divided into 2 groups in the community, rehabilitation group (n = 65) and control group (n = 65). Cardiac function, a 6-minute walk distance, exercise time and steps, cardiovascular risk factors were monitored respectively and compared before and after the intervention of 2 groups. The software of EpiData 3.1 was used to input research data and SPSS16.0 was used for statistical analysis.

RESULTS

After a planned rehabilitation intervention, the rehabilitation group showed better results than the control group. The rehabilitation group had a significant improvement in recurrence angina and readmission (P < .01). Left ventricular ejection fraction (LVEF) of rehabilitation group showed improvement in phase II (t = 4.963, P < .01) and phase III (t = 11.802, P < .01), and the New York Heart Association (NYHA) classification was recovered within class II. There was a significant difference compared with before (Z = 7.238, P < .01). Six minutes walking distance, aerobic exercise time, and steps all achieved rehabilitation requirements in rehabilitation group in phase II and III, there existed distinct variation between 2 phases. Rehabilitation group had a better result in cardiovascular risk factors than control group (P < .05).

CONCLUSION

Community-based CR after PCI through simple but safe exercise methods can improve the AMI patient's living quality, which includes increasing cardiac ejection fraction, exercise tolerance, and physical status. It must be emphasized that the good result should be established by the foundation of close cooperation between cardiologists and general practitioners, also the importance of cooperation of patients and their families should not be ignored. The rehabilitation program we used is feasible, safe, and effective.

Adherence to lifestyle modifications after a cardiac rehabilitation program and endothelial progenitor cells

An increase of endothelial progenitor cells (EPCs) among acute myo-cardial infarction (AMI) patients participating in a cardiac rehabilitation (CR) program has been reported, but no data on the impact of adherence to lifestyle recommendations provided during a CR program on EPCs are available. It was our aim to investigate the effect of adherence to lifestyle recommendations on EPCs, inflammatory and functional parameters after six months of a CR program in AMI patients. In 110 AMI patients (90 male/20 female; mean age 57.9 ± 9.4 years) EPCs, high sensitivity C-reactive protein (hsCRP), N-terminal pro-brain natriuretic peptide (NT-ProBNP) levels, and cardiopulmonary testings were determined at the end of the CR (T1) and at a six-month follow-up (T2). At T2 we administered a questionnaire assessing dietary habits and physical activity. At T2, we observed a decrease of EPCs (p<0.05), of hsCRP (p=0.009) and of NT-ProBNP (p<0.0001). Patient population was divided into three categories by Healthy Lifestyle (HL) score (none/low, moderate and high adherence to lifestyle recommendations). We observed a significant association between adherence to lifestyle recommendations, increase in EPCs and exercise capacity between T1 and T2 (Δ EPCs p for trend <0.05; ΔWatt max p for trend=0.004). In a multivariate logistic regression analyses, being in the highest tertile of HL score affected the likelihood of an increase of EPC levels at T2 [OR (95% confidence interval): 3.36 (1.0–10.72) p=0.04]. In conclusion, adherence to lifestyle recommendations provided during a CR program positively influences EPC levels and exercise capacity.

Endothelial and cardiac progenitor cells for cardiovascular repair: A controversial paradigm in cell therapy

Stem cells have the potential to differentiate into cardiovascular cell lineages and to stimulate tissue regeneration in a paracrine/autocrine manner; thus, they have been extensively studied as candidate cell sources for cardiovascular regeneration. Several preclinical and clinical studies addressing the therapeutic potential of endothelial progenitor cells (EPCs) and cardiac progenitor cells (CPCs) in cardiovascular diseases have been performed. For instance, autologous EPC transplantation and EPC mobilization through pharmacological agents contributed to vascular repair and neovascularization in different animal models of limb ischemia and myocardial infarction. Also, CPC administration and in situ stimulation of resident CPCs have been shown to improve myocardial survival and function in experimental models of ischemic heart disease. However, clinical studies using EPC- and CPC-based therapeutic approaches have produced mixed results. In this regard, intracoronary, intra-myocardial or intramuscular injection of either bone marrow-derived or peripheral blood progenitor cells has improved pathological features of tissue ischemia in humans, despite modest or no clinical benefit has been observed in most cases. Also, the intriguing scientific background surrounding the potential clinical applications of EPC capture stenting is still waiting for a confirmatory proof. Moreover, clinical findings on the efficacy of CPC-based cell therapy in heart diseases are still very preliminary and based on small-size studies. Despite promising evidence, widespread clinical application of both EPCs and CPCs remains delayed due to several unresolved issues. The present review provides a summary of the different applications of EPCs and CPCs for cardiovascular cell therapy and underlies their advantages and limitations.

Permanent atrial fibrillation impairs the function of circulating endothelial progenitor cells

OBJECTIVE

to determine whether functions of endothelial progenitor cells (EPCs) were impaired in patients with permanent atrial fibrillation (AF).

METHODS

35 patients with permanent AF (AF group) and 35 age and sex matched controls (control group) were collected. The numbers of circulating CD34⁺/KDR⁺ cells were determined with flow cytometry in the two groups. Cell proliferation, tube formation, nitric oxygen (NO) and vascular endothelial growth factor (VEGF) were assayed.

RESULTS

the numbers of CD34⁺/KDR⁺ cells were lower in the AF group than the control group (20.01 ± 12.66 /10⁵ vs 77.93 ± 58.93 /10⁵，p = 0.022). Colony formation unit (CFU) of EPCs were decreased in AF group compared to the control group（1.76 ± 0.59 CFU vs 3.45 ± 0.82 CFU, p = 0.0000). The AF group had lower cell proliferation ability than control group（0.401 ± 0.113 A vs 0.558 ± 0.130 A, p = 0.004). Tube formation ability was decreased in AF patients compared to controls（434.30 ± 96.22μm/mm² vs 568.09 ± 196.17μm/mm²，p = 0.041). AF patients had lower VEGF secretion than controls (27.35 ± 9.93 ng/L vs 41.86 ± 7.31 ng/L，p = 0.001），they also had lower NO secretion than controls（16.55 ± 6.92μmol/l vs 23.65 ± 5.48，p = 0.012).

CONCLUSIONS

proliferation, tube formation and paracrine of EPCs were reduced in patients with permanent AF.

Association of CXCR4 expression with coronary collateralization in patients with chronic total coronary occlusion: A nested case-control study

OBJECTIVE

CXCR4 signaling contributes to the development and progression of neovascularization. The objective of this study was to investigate whether CXCR4 expression in peripheral CD34+ cells associated with the coronary collateralization (CC) in patients with chronic total coronary occlusion (CTO).

METHODS AND RESULTS

We measured CXCR4 expression in peripheral CD34+ cells and assessed its relation with CC in a nested case-control study including 78 cases and 78 matched controls aged 38-69years, assessed in January 2011 to December 2012 and with at least 1year of follow-up before the index date. Cases were defined as good coronary collateralization (GCC) according to the Rentrop scoring system (Rentrop score of 2 or 3); for each case, one age-matched control with poor coronary collateralization (PCC) (Rentrop score 0 or 1) was randomly selected from the study participants. Demographic, biochemical, and angiographic variables were collected. In multivariate analysis, the OR (95% CI) of CXCR4 expression was 0.018 (0.017 to 0.020) in patients with GCC versus PCC. Independent effect of CXCR4 expression on CC was (OR 0.012, 95% CI 0.010-0.014) when adjusted for other variables. A nonlinear relationship between CXCR4 expression and CC was observed. The CC degree increased when CXCR4 expression exceeded the turning point (30%) (OR 0.025, 95% CI 0.022-0.028; p<0.001). When the CXCR4 expression exceeded 75%, increased CXCR4 level could not promoted CC (OR 0.000, 95% CI 0.008-0.007; p=0.974).

CONCLUSION

Increased CXCR4 level in peripheral CD34+ cells was associated with GCC in patients with CTO.

Relation Between C-X-C Motif Chemokine Receptor 4 Levels and the Presence and Extent of Angiographic Coronary Collaterals in Patients With Chronic Total Coronary Occlusion

Coronary collateral circulation is an alternative source of blood supply to the myocardium in the presence of chronic total coronary occlusion (CTO). C-X-C motif chemokine receptor 4 (CXCR4) signaling usually contributes to neovascularization. Here, we investigate the relation between CXCR4 levels in peripheral blood CD34+ cells and the formation of angiographic coronary collaterals and determine the risk factors that affect CXCR4 expression in patients with CTO. Demographic, biochemical, and angiographic variables were collected from 324 patients with CTO and 90 negative controls. The presence and extent of collaterals were scored according to the Rentrop scoring system (Rentrop's). CXCR4 levels and plasma biochemical factors were detected. Clinical outcomes were collected during a 12-month follow-up. Results show that low (Rentrop's 0 or 1) and high (Rentrop's of 2 or 3) coronary collateralizations were detected in 183 and 141 patients, respectively. The Rentrop scores were positively correlated with CXCR4 levels in patients with CTO. Patients with low CXCR4 expression exhibited worse clinical outcomes compared with those with high CXCR4 expression. Univariate correlation analysis revealed that age of ≥65 years, women, diabetes, increased plasma level of high-sensitivity C-reactive protein (hs-CRP), and N-terminal brain-type natriuretic peptide were associated with low CXCR4 levels. In conclusion, CXCR4 levels were positively correlated with the presence and extent of angiographic coronary collaterals in patients with CTO. Elder age, women, diabetes, increased plasma level of high-sensitivity C-reactive protein, and N-terminal brain-type natriuretic peptide may be risk factors of CXCR4 expression.

The Beneficial Effects of Cardiac Rehabilitation on the Function and Levels of Endothelial Progenitor Cells

Cardiac rehabilitation (CR) is a comprehensive program, which mainly focusses on exercise training, disease evaluation, cardiovascular risk factors control, medication therapy, psychosocial intervention, and patient education. Although the beneficial properties of CR have been widely evidenced, its mechanism is still not completely clarified. To date, endothelial progenitor cells (EPCs) have been explored by emerging studies, and evidence has suggested that CR, especially exercise training, significantly increases the function and levels of EPCs, which is likely to elucidate the profiting mechanism of CR. Thus, this review summarises the potential relationship between CR and EPCs with an aim of providing novel directions for future CR research.

Exercise training-induced different improvement profile of endothelial progenitor cells function in mice with or without myocardial infarction

BACKGROUND

Neovascularization in response to ischemia after myocardial infarction (MI) has been widely considered as being initiated by endothelial progenitor cells (EPCs). Well-documented evidences in recent years have proved exercise training (ET) improving EPC function. However, whether ET-induced improvement of EPC function under or without ischemic state is different has not been reported.

METHODS

Mice performed ET following an exercise prescription 1week after MI or non-MI surgery respectively. Bone marrow-derived EPCs were isolated at 0day, 3days, 1week, 2weeks, 4weeks, and 8weeks of ET. After 7days cultivation, EPC functions including proliferation, adhesion, migration, and in vitro angiogenesis were measured. AKT/glycogen synthase kinase 3β (GSK3β) signaling pathway was tested by western blotting.

RESULTS

EPC function in mice underwent non-MI surgery was attenuated overtime, while ET ameliorated this tendency. EPC function was peaked at 4weeks ET in non-MI surgery mice and maintained with an extended exercise time. Besides, simple ischemia was sufficient to enhanced EPC function, with a maximum at 2weeks of MI surgery. In MI mice, ET further improved EPC function and achieved peak at 2weeks exercise. Furthermore, AKT/GSK3β signaling pathway activation was consistent with EPC function change after ischemia, which was further promoted by 4weeks exercise.

CONCLUSION

ET significantly increased EPC function in mice both with and without MI, but the time points of peak function were different.

Effects of aerobic interval training and continuous training on cellular markers of endothelial integrity in coronary artery disease: a SAINTEX-CAD substudy

In this large multicenter trial, we aimed to assess the effect of aerobic exercise training in stable coronary artery disease (CAD) patients on cellular markers of endothelial integrity and to examine their relation with improvement of endothelial function. Two-hundred CAD patients (left ventricular ejection fraction > 40%, 90% male, mean age 58.4 ± 9.1 yr) were randomized on a 1:1 base to a supervised 12-wk rehabilitation program of either aerobic interval training or aerobic continuous training on a bicycle. At baseline and after 12 wk, numbers of circulating CD34+/KDR+/CD45dim endothelial progenitor cells (EPCs), CD31+/CD3+/CXCR4+ angiogenic T cells, and CD31+/CD42b− endothelial microparticles (EMPs) were analyzed by flow cytometry. Endothelial function was assessed by flow-mediated dilation (FMD) of the brachial artery. After 12 wk of aerobic interval training or aerobic continuous training, numbers of circulating EPCs, angiogenic T cells, and EMPs were comparable with baseline levels. Whereas improvement in peak oxygen consumption was correlated to improvement in FMD (Pearson r = 0.17, P = 0.035), a direct correlation of baseline or posttraining EPCs, angiogenic T cells, and EMP levels with FMD was absent. Baseline EMPs related inversely to the magnitude of the increases in peak oxygen consumption (Spearman rho = −0.245, P = 0.027) and FMD (Spearman rho = −0.374, P = 0.001) following exercise training. In conclusion, endothelial function improvement in response to exercise training in patients with CAD did not relate to altered levels of EPCs and angiogenic T cells and/or a diminished shedding of EMPs into the circulation. EMP flow cytometry may be predictive of the increase in aerobic capacity and endothelial function.

Vascular Ageing and Exercise: Focus on Cellular Reparative Processes

Ageing is associated with an increased risk of developing noncommunicable diseases (NCDs), such as diabetes and cardiovascular disease (CVD). The increased risk can be attributable to increased prolonged exposure to oxidative stress. Often, CVD is preceded by endothelial dysfunction, which carries with it a proatherothrombotic phenotype. Endothelial senescence and reduced production and release of nitric oxide (NO) are associated with “vascular ageing” and are often accompanied by a reduced ability for the body to repair vascular damage, termed “reendothelialization.” Exercise has been repeatedly shown to confer protection against CVD and diabetes risk and incidence. Regular exercise promotes endothelial function and can prevent endothelial senescence, often through a reduction in oxidative stress. Recently, endothelial precursors, endothelial progenitor cells (EPC), have been shown to repair damaged endothelium, and reduced circulating number and/or function of these cells is associated with ageing. Exercise can modulate both number and function of these cells to promote endothelial homeostasis. In this review we look at the effects of advancing age on the endothelium and these endothelial precursors and how exercise appears to offset this “vascular ageing” process.

The inflammation, vascular repair and injury responses to exercise in fit males with and without Type 1 diabetes: an observational study

BACKGROUND

Type 1 diabetes is associated with raised inflammation, impaired endothelial progenitor cell mobilisation and increased markers of vascular injury. Both acute and chronic exercise is known to influence these markers in non-diabetic controls, but limited data exists in Type 1 diabetes. We assessed inflammation, vascular repair and injury at rest and after exercise in physically-fit males with and without Type 1 diabetes.

METHODS

Ten well-controlled type 1 diabetes (27 ± 2 years; BMI 24 ± 0.7 kg.m(2); HbA1c 53.3 ± 2.4 mmol/mol) and nine non-diabetic control males (27 ± 1 years; BMI 23 ± 0.8 kg.m(2)) matched for age, BMI and fitness completed 45-min of running. Venous blood samples were collected 60-min before and 60-min after exercise, and again on the following morning. Blood samples were processed for TNF-α using ELISA, and circulating endothelial progenitor cells (cEPCs; CD45(dim)CD34(+)VEGFR2(+)) and endothelial cells (cECs; CD45(dim)CD133(-)CD34(+)CD144(+)) counts using flow-cytometry.

RESULTS

TNF-α concentrations were 4-fold higher at all-time points in Type 1 diabetes, when compared with control (P < 0.001). Resting cEPCs were similar between groups; after exercise there was a significant increase in controls (P = 0.016), but not in Type 1 diabetes (P = 0.202). CEPCs peaked the morning after exercise, with a greater change in controls vs. Type 1 diabetes (+139 % vs. 27 %; P = 0.01). CECs did not change with exercise and were similar between groups at all points (P > 0.05). Within the Type 1 diabetes group, the delta change in cEPCS from rest to the following morning was related to HbA1c (r = -0.65, P = 0.021) and TNF-α (r = -0.766, P = 0.005).

CONCLUSIONS

Resting cEPCs and cECs in Type 1 diabetes patients with excellent HbA1c and high physical-fitness are comparable to healthy controls, despite eliciting 4-fold greater TNF-α. Furthermore, Type 1 diabetes patients appear to have a blunted post-exercise cEPCs response (vascular repair), whilst a biomarker of vascular injury (cECs) remained comparable to healthy controls.

Effect of exercise-based cardiac rehabilitation on non-culprit mild coronary plaques in the culprit coronary artery of patients with acute coronary syndrome

Approximately, 70 % of acute myocardial infarctions are known to develop from mild atherosclerotic lesions. Therefore, it is important to evaluate mild coronary plaques to prevent acute coronary syndrome (ACS). The aim of the present study was to investigate the effects of exercise-based cardiac rehabilitation (CR) on mild coronary atherosclerosis in non-culprit lesions in patients with ACS. Forty-one men with ACS who underwent emergency percutaneous coronary interventions and completed a 6-month follow-up were divided into CR and non-CR groups. Quantitative coronary angiography (QCA) was performed using the automatic edge detection program. The target lesion was a mild stenotic segment (10-50 % stenosis) at the distal site of the culprit lesion, and the segment to be analyzed was determined at a segment length ranging from 10 to 15 mm. The plaque area was significantly decreased in the CR group after 6 months, but was significantly increased in the non-CR group (P < 0.05). The low-density lipoprotein (LDL) cholesterol, LDL/high-density lipoprotein (HDL) ratio and high-sensitivity C-reactive protein (Hs-CRP) levels were significantly reduced in both groups (P < 0.01). Peak VO2 in the CR group was significantly increased (P < 0.01). Changes in the plaque area correlated with those in Hs-CRP in both groups, while that association with those in HDL-C was observed in only CR group. Stepwise regression analysis revealed the decrease in Hs-CRP as an independent predictor of plaque area regression in the CR group. CR prevented the progression of mild coronary atherosclerosis in patients with ACS.

Impact of depression on circulating endothelial progenitor cells in patients with acute coronary syndromes: a pilot study

AIMS

Depression has been identified as a risk factor for an adverse prognosis and reduced survival in patients with acute coronary syndrome (ACS). The number of endothelial progenitor cells (EPCs) is an independent predictor of clinical outcomes in patients with ACS. The aim of this study was to evaluate the impact of depression on EPC levels in patients with ACS.

METHODS

Out of 74 ACS patients [23 non-ST-segment elevation myocardial infarction (NSTEMI), 48 STEMI], 36 had a diagnosis of major depressive episode (MDE) according to the Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV) criteria at the time of the inclusion in the study. Control groups were as follows: 15 healthy individuals and 18 patients with current MDE without a history of cardiovascular diseases. EPCs were defined as CD34CD133KDR and evaluated by flow cytometry. All patients underwent standardized cardiological and psychopathological evaluations. Parametric and nonparametric statistical tests were performed wherever appropriate.

RESULTS

ACS patients with MDE showed a significant decrease in circulating EPC number compared with ACS patients without MDE (P < 0.001). The ACS study population was then subdivided into STEMI and NSTEMI groups, and within each group patients with MDE again showed a significant decrease in circulating CD34CD133KDR EPCs compared with others (P <0.001).

CONCLUSION

We showed that ACS patients with MDE have a reduced number of circulating CD34CD133KDR cells compared with ACS patients without MDE, suggesting that the presence of MDE reduces the response of bone marrow to acute ischemic events. Considering the reparative role of EPCs in ACS patients, we propose that patients with MDE might be protected less than patients without MDE.

Effects of simvastatin/ezetimibe on microparticles, endothelial progenitor cells and platelet aggregation in subjects with coronary heart disease under antiplatelet therapy

It is not known whether the addition of ezetimibe to statins adds cardiovascular protection beyond the expected changes in lipid levels. Subjects with coronary heart disease were treated with four consecutive 1-week courses of therapy (T) and evaluations. The courses were: T1, 100 mg aspirin alone; T2, 100 mg aspirin and 40 mg simvastatin/10 mg ezetimibe; T3, 40 mg simvastatin/10 mg ezetimibe, and 75 mg clopidogrel (300 mg initial loading dose); T4, 75 mg clopidogrel alone. Platelet aggregation was examined in whole blood. Endothelial microparticles (CD51), platelet microparticles (CD42/CD31), and endothelial progenitor cells (CD34/CD133; CDKDR/CD133, or CD34/KDR) were quantified by flow cytometry. Endothelial function was examined by flow-mediated dilation. Comparisons between therapies revealed differences in lipids (T2 and T3<T1 and T4 for total cholesterol, LDL-C, and triglycerides; P<0.002 for all), as well as for endothelial function (T2>T1 and T4, P=0.001). Decreased platelet aggregation was observed after aspirin (arachidonic acid, T1<T3 and T4, P=0.034) and clopidogrel (adenosine, T3 and T4<T1 and T2, P<0.0001) therapy. Simvastatin/ezetimibe diphosphate did not change platelet aggregation, the amount of circulating endothelial and platelet microparticles, or endothelial progenitor cells. Cardiovascular protection following therapy with simvastatin/ezetimibe seems restricted to lipid changes and improvement of endothelial function not affecting the release of microparticles, mobilization of endothelial progenitor cells or decreased platelet aggregation.

Effects of physical activity on endothelial progenitor cells (EPCs)

Physical activity has a therapeutic role in cardiovascular disease (CVD), through its beneficial effects on endothelial function and cardiovascular system. Circulating endothelial progenitor cells (EPCs) are bone marrow (BM) derived cells that represent a novel therapeutic target in CVD patients, because of their ability to home to sites of ischemic injury and repair the damaged vessels. Several studies show that physical activity results in a significant increase in circulating EPCs, and, in particular, there are some evidence of the beneficial exercise-induced effects on EPCs activity in CVD settings, including coronary artery disease (CAD), heart failure (HF), and peripheral artery disease (PAD). The aim of this paper is to review the current evidence about the beneficial effects of physical exercise on endothelial function and EPCs levels and activity in both healthy subjects and patients with CVD.

Circulating endothelial and progenitor cells: Evidence from acute and long-term exercise effects

Circulating bone-marrow-derived cells, named endothelial progenitor cells (EPCs), are capable of maintaining, generating, and replacing terminally differentiated cells within their own specific tissue as a consequence of physiological cell turnover or tissue damage due to injury. Endothelium maintenance and restoration of normal endothelial cell function is guaranteed by a complex physiological procedure in which EPCs play a significant role. Decreased number of peripheral blood EPCs has been associated with endothelial dysfunction and high cardiovascular risk. In this review, we initially report current knowledge with regard to the role of EPCs in healthy subjects and the clinical value of EPCs in different disease populations such as arterial hypertension, obstructive sleep-apnea syndrome, obesity, diabetes mellitus, peripheral arterial disease, coronary artery disease, pulmonary hypertension, and heart failure. Recent studies have introduced the novel concept that physical activity, either performed as a single exercise session or performed as part of an exercise training program, results in a significant increase of circulating EPCs. In the second part of this review we provide preliminary evidence from recent studies investigating the effects of acute and long-term exercise in healthy subjects and athletes as well as in disease populations.