Plasma levels of microRNA in chronic kidney disease: patterns in acute and chronic exercise

Meta-analysis of Circulatory mitomiRs in stress Response: Unveiling the significance of miR-34a and miR-146a

BACKGROUND

MicroRNAs (miRNAs) are short, noncoding RNAs with essential roles in cellular pathways and are often associated with various diseases and stress conditions. Recently, they have been discovered in mitochondria, termed "mitomiRs," with unique functions. Mitochondria, crucial organelles for energy production and stress responses, Dysregulated mitomiRs functions and expression has been evident in stress conditions such as cardiovascular and neurodegenerative. In this meta-analysis we have systematically identified miR-34a & miR-146a as possible potential biomarkers for affliction.

METHODS

A meta-analysis was conducted to assess the potential role of miR-34a and miR-146a, two specific mitomiRs, as biomarkers in stress-related conditions. The study followed PRISMA guidelines, involving comprehensive database searches in May and September 2023. Twelve studies meeting predefined inclusion criteria were selected, and data analysis included the evaluation of miR-34a and miR-146a expression levels in various stress conditions compared to control groups. We also performed Gene ontology (GO) and Pathway enrichment analysis to observe how mitomiRs affects our body.

RESULTS

The meta-analysis revealed a significant increase in overall mitomiRs (miR-34a and miR-146a) expression levels in experimental groups experiencing different stress conditions compared to control groups (Z = 3.54, p < 0.05 using RevMan software). miR-34a demonstrated more pronounced upregulation and exhibited potential as a specific biomarker in certain stress-related conditions (Z = 2.22, p < 0.05). However, miR-146a did not show a significant difference, requiring further investigation in various stress-related contexts. The Analysis indicated a high degree of heterogeneity among the studies.

CONCLUSION

This meta-analysis emphasises the importance of mitomiRs, especially miR-34a, as potential biomarkers in the intricate interplay between stress, mitochondrial function, and disease. The study opens new avenues for exploring miRNAs' diagnostic and therapeutic applications in stress-related diseases, highlighting their pivotal role at the crossroads of molecular biology, psychology, and medicine.

Non-coding RNAs in exercise immunology: A systematic review

Regular physical exercise has been recognized as a potent modulator of immune function, with its effects including enhanced immune surveillance, reduced inflammation, and improved overall health. While strong evidence exists that physical exercise affects the specific expression and activity of non-coding RNAs (ncRNAs) also involved in immune system regulation, heterogeneity in individual study designs and analyzed exercise protocols exists, and a condensed list of functional, exercise-dependent ncRNAs with known targets in the immune system is missing from the literature. A systematic review and qualitative analysis was used to identify and categorize ncRNAs participating in immune modulation by physical exercise. Two combined approaches were used: (a) a systematic literature search for "ncRNA and exercise immunology", (b) and a database search for microRNAs (miRNAs) (miRTarBase and DIANA-Tarbase v8) aligned with known target genes in the immune system based on the Reactome database, combined with a systematic literature search for "ncRNA and exercise". Literature searches were based on PubMed, Web of Science, and SPORTDiscus; and miRNA databases were filtered for targets validated by in vitro experimental data. Studies were eligible if they reported on exercise-based interventions in healthy humans. After duplicate removal, 95 studies were included reporting on 164 miRNAs, which were used for the qualitative synthesis. Six studies reporting on long-noncoding RNAs (lncRNAs) or circular RNAs were also identified. Results were analyzed using ordering tables that included exercise modality (endurance/resistance exercise), acute or chronic interventions, as well as the consistency in reported change between studies. Evaluation criteria were defined as "validated" with 100% of ≥3 independent studies showing identical direction of regulation, "plausible" (≥80%), or "suggestive" (≥70%). For resistance exercise, upregulation of miR-206 was validated while downregulation of miR-133a appeared plausible. For endurance exercise, 15 miRNAs were categorized as validated, with 12 miRNAs being consistently elevated and 3 miRNAs being downregulated, most of them after acute exercise training. In conclusion, our approach provides evidence that miRNAs play a major role in exercise-induced effects on the innate and adaptive immune system by targeting different pathways affecting immune cell distribution, function, and trafficking as well as production of (anti-)inflammatory cytokines. miRNAs miR-15, miR-29c, miR-30a, miR-142/3, miR-181a, and miR-338 emerged as key players in mediating the immunomodulatory effects of exercise predominantly after acute bouts of endurance exercise.

The role of fibrosis in cardiomyopathies: An opportunity to develop novel biomarkers of disease activity

Cardiomyopathies encompass a spectrum of heart disorders with diverse causes and presentations. Fibrosis stands out as a shared hallmark among various cardiomyopathies, reflecting a common thread in their pathogenesis. This prevalent fibrotic response is intricately linked to the consequences of dysregulated extracellular matrix (ECM) remodeling, emphasizing its significance in the development and progression the disease. This review explores the ECM involvement in various cardiomyopathies and its impact on myocardial stiffness and fibrosis. Additionally, we discuss the potential of ECM fragments as early diagnosis, prognosis, and risk stratification. Biomarkers deriving from turnover of collagens and other ECM proteins hold promise in clinical applications. We outline current clinical management, future directions, and the potential for personalized ECM-targeted therapies with specific focus on microRNAs. In summary, this review examines the role of the fibrosis in cardiomyopathies, highlighting the potential of ECM-derived biomarkers in improving disease management with implications for precision medicine.

Exercise for patients with chronic kidney disease: from cells to systems to function

Chronic kidney disease (CKD) is among the leading causes of death and disability, affecting an estimated 800 million adults globally. The underlying pathophysiology of CKD is complex creating challenges to its management. Primary risk factors for the development and progression of CKD include diabetes mellitus, hypertension, age, obesity, diet, inflammation, and physical inactivity. The high prevalence of diabetes and hypertension in patients with CKD increases the risk for secondary consequences such as cardiovascular disease and peripheral neuropathy. Moreover, the increased prevalence of obesity and chronic levels of systemic inflammation in CKD have downstream effects on critical cellular functions regulating homeostasis. The combination of these factors results in the deterioration of health and functional capacity in those living with CKD. Exercise offers protective benefits for the maintenance of health and function with age, even in the presence of CKD. Despite accumulating data supporting the implementation of exercise for the promotion of health and function in patients with CKD, a thorough description of the responses and adaptations to exercise at the cellular, system, and whole body levels is currently lacking. Therefore, the purpose of this review is to provide an up-to-date comprehensive review of the effects of exercise training on vascular endothelial progenitor cells at the cellular level; cardiovascular, musculoskeletal, and neural factors at the system level; and physical function, frailty, and fatigability at the whole body level in patients with CKD.

Exercise and chronic kidney disease: potential mechanisms underlying the physiological benefits

Increasing evidence indicates that exercise has beneficial effects on chronic inflammation, cardiorespiratory function, muscle and bone strength and metabolic markers in adults with chronic kidney disease (CKD), kidney failure or kidney transplants. However, the mechanisms that underlie these benefits have received little attention, and the available clinical evidence is mainly from small, short-duration (<12 weeks) exercise intervention studies. The available data, mainly from patients with CKD or on dialysis, suggest that exercise-mediated shifts towards a less inflammatory immune cell profile, enhanced activity of the NRF2 pathway and reduced monocyte infiltration into adipose tissue may underlie improvements in inflammatory biomarkers. Exercise-mediated increases in nitric oxide release and bioavailability, reduced angiotensin II accumulation in the heart, left ventricular remodelling and reductions in myocardial fibrosis may contribute to improvements in left ventricular hypertrophy. Exercise stimulates an anabolic response in skeletal muscle in CKD, but increases in mitochondrial mass and satellite cell activation seem to be impaired in this population. Exercise-mediated activation of the canonical wnt pathway may lead to bone formation and improvements in the levels of the bone-derived hormones klotho and fibroblast growth factor 23 (FGF23). Longer duration studies with larger sample sizes are needed to confirm these mechanisms in CKD, kidney failure and kidney transplant populations and provide evidence for targeted exercise interventions.

Clinical effect and biological mechanism of exercise for rheumatoid arthritis: A mini review

Rheumatoid arthritis (RA) is a common systematic, chronic inflammatory, autoimmune, and polyarticular disease, causing a range of clinical manifestations, including joint swelling, redness, pain, stiffness, fatigue, decreased quality of life, progressive disability, cardiovascular problems, and other comorbidities. Strong evidence has shown that exercise is effective for RA treatment in various clinical domains. Exercise training for relatively longer periods (e.g., ≥ 12 weeks) can decrease disease activity of RA. However, the mechanism underlying the effectiveness of exercise in reducing RA disease activity remains unclear. This review first summarizes and highlights the effectiveness of exercise in RA treatment. Then, we integrate current evidence and propose biological mechanisms responsible for the potential effects of exercise on immune cells and immunity, inflammatory response, matrix metalloproteinases, oxidative stress, and epigenetic regulation. However, a large body of evidence was obtained from the non-RA populations. Future studies are needed to further examine the proposed biological mechanisms responsible for the effectiveness of exercise in decreasing disease activity in RA populations. Such knowledge will contribute to the basic science and strengthen the scientific basis of the prescription of exercise therapy for RA in the clinical routine.

Epigenetics in the primary and secondary prevention of cardiovascular disease: influence of exercise and nutrition

Increasing evidence links changes in epigenetic systems, such as DNA methylation, histone modification, and non-coding RNA expression, to the occurrence of cardiovascular disease (CVD). These epigenetic modifications can change genetic function under influence of exogenous stimuli and can be transferred to next generations, providing a potential mechanism for inheritance of behavioural intervention effects. The benefits of exercise and nutritional interventions in the primary and secondary prevention of CVD are well established, but the mechanisms are not completely understood. In this review, we describe the acute and chronic epigenetic effects of physical activity and dietary changes. We propose exercise and nutrition as potential triggers of epigenetic signals, promoting the reshaping of transcriptional programmes with effects on CVD phenotypes. Finally, we highlight recent developments in epigenetic therapeutics with implications for primary and secondary CVD prevention.

Physical exercise and the functions of microRNAs

MicroRNAs (miRNAs) control RNA translation and are a class of small, tissue-specific, non-protein-coding RNAs that maintain cellular homeostasis through negative gene regulation. Maintenance of the physiological environment depends on the proper control of miRNA expression, as these molecules influence almost all genetic pathways, from the cell cycle checkpoint to cell proliferation and apoptosis, with a wide range of target genes. Dysregulation of the expression of miRNAs is correlated with several types of diseases, acting as regulators of cardiovascular functions, myogenesis, adipogenesis, osteogenesis, hepatic lipogenesis, and important brain functions. miRNAs can be modulated by environmental factors or external stimuli, such as physical exercise, and can eventually induce specific and adjusted changes in the transcriptional response. Physical exercise is used as a preventive and non-pharmacological treatment for many diseases. It is well established that physical exercise promotes various benefits in the human body such as muscle hypertrophy, mental health improvement, cellular apoptosis, weight loss, and inhibition of cell proliferation. This review highlights the current knowledge on the main miRNAs altered by exercise in the skeletal muscle, cardiac muscle, bone, adipose tissue, liver, brain, and body fluids. In addition, knowing the modifications induced by miRNAs and relating them to the results of prescribed physical exercise with different protocols and intensities can serve as markers of physical adaptation to training and responses to the effects of physical exercise for some types of chronic diseases. This narrative review consists of randomized exercise training experiments with humans and/or animals, combined with analyses of miRNA modulation.

Regulation of microRNAs in Alzheimer´s disease, type 2 diabetes, and aerobic exercise training

Alzheimer's disease (AD) is the most common type of dementia. The evolution and aggregation of amyloid beta (β) oligomers is linked to insulin resistance in AD, which is also the major characteristic of type 2 diabetes (T2D). Being physically inactive can contribute to the development of AD and/or T2D. Aerobic exercise training (AET), a type of physical exercise, can be useful in preventing or treating the negative outcomes of AD and T2D. AD, T2D and AET can regulate the expression of microRNAs (miRNAs). Here, we review some of the changes in miRNAs expression regulated by AET, AD and T2D. MiRNAs play an important role in the gene regulation of key signaling pathways in both pathologies, AD and T2D. MiRNA dysregulation is evident in AD and has been associated with several neuropathological alterations, such as the development of a reactive gliosis. Expression of miRNAs are associated with many pathophysiological mechanisms involved in T2D like insulin synthesis, insulin resistance, glucose intolerance, hyperglycemia, intracellular signaling, and lipid profile. AET regulates miRNAs levels. We identified 5 miRNAs (miR-21, miR-29a/b, miR-103, miR-107, and miR-195) that regulate gene expression and are modulated by AET on AD and T2D. The identified miRNAs are potential targets to treat the symptoms of AD and T2D. Thus, AET is a non-pharmacological tool that can be used to prevent and fight the negative outcomes in AD and T2D.

MicroRNA levels in hemodialysis patients following resistance training: Associations with functional performance, inflammatory profile, sestrins-2, and nitric oxide

OBJECTIVE

Investigate the effects of long-term resistance training (RT) on expression of the four selected microRNAs (miRNA or mir) and further association with biomarkers related to functional performance in older end-stage renal disease (ESRD) patients undergoing hemodialysis.

METHODS

Twenty-five older hemodialysis patients (glomerular filtration rate <15 mL/min/1.73 m² aged 68.28 ± 1.06) were recruited for the study. Patients were allocated to two groups (control, n = 12 and RT, n = 13). The RT group completed 24 weeks of training, with sessions held three times per week on alternate days. Blood samples were collected pre- and post- intervention for miRNA and biochemical assays. Results were considered significant at P < 0.05.

RESULTS

RT promoted benefits in inflammatory profile, nitric oxide, sestrins-2, anthropometric data, and functional performance. Trained subjects presented a 51% decrease in miRNA-31 after intervention. In addition, miRNA-1 increased 128% after RT protocol. miRNA-1 significantly correlated with functional performance, inflammatory profile, sestrins-2, and nitric oxide (all P < 0.05).

CONCLUSIONS

These results suggest that the upregulation of miRNA-1 could be associated with physiological benefits promoted by RT in hemodialysis patients, providing novel understanding for potential regulatory miRNA effects on physiological RT response. These findings might point out to strategic direction for future studies.

Plasma-Derived microRNAs Are Influenced by Acute and Chronic Exercise in Patients With Heart Failure With Reduced Ejection Fraction

Background: Exercise training improves VO₂peak in heart failure with reduced ejection fraction (HFrEF), but the effect is highly variable as it is dependent on peripheral adaptations. We evaluated changes in plasma-derived miRNAs by acute and chronic exercise to investigate whether these can mechanistically be involved in the variability of exercise-induced adaptations.

Methods: Twenty-five male HFrEF patients (left ventricular ejection fraction < 40%, New York Heart Association class ≥ II) participated in a 15-week combined strength and aerobic training program. The effect of training on plasma miRNA levels was compared to 21 male age-matched sedentary HFrEF controls. Additionally, the effect of a single acute exercise bout on plasma miRNA levels was assessed. Levels of 5 miRNAs involved in pathways relevant for exercise adaptation (miR-23a, miR-140, miR-146a, miR-191, and miR-210) were quantified using RT-qPCR and correlated with cardiopulmonary exercise test (CPET), echocardiographic, vascular function, and muscle strength variables.

Results: Expression levels of miR-146a decreased with training compared to controls. Acute exercise resulted in a decrease in miR-191 before, but not after training. Baseline miR-23a predicted change in VO₂peak independent of age and left ventricular ejection fraction (LVEF). Baseline miR-140 was independently correlated with change in load at the respiratory compensation point and change in body mass index, and baseline miR-146a with change in left ventricular mass index.

Conclusion: Plasma-derived miRNAs may reflect the underlying mechanisms of exercise-induced adaptation. In HFrEF patients, baseline miR-23a predicted VO₂peak response to training. Several miRNAs were influenced by acute or repeated exercise. These findings warrant exploration in larger patient populations and further mechanistic in vitro studies on their molecular involvement.

miRNA biomarkers in renal disease

Chronic kidney disease (CKD), which is characterized by the gradual loss of kidney function, is a growing worldwide problem due to CKD-related morbidity and mortality. There are no reliable and early biomarkers enabling the monitoring, the stratification of CKD progression and the estimation of the risk of CKD-related complications, and therefore, the search for such molecules is still going on. Numerous studies have provided evidence that miRNAs are potentially important particles in the CKD field. Studies indicate that some miRNA levels can be increased in patients with CKD stages III–V and hemodialysis and decreased in renal transplant recipients (miR-143, miR-145 and miR-223) as well as elevated in patients with CKD stages III–V, decreased in hemodialysis patients and even more markedly decreased in renal transplant recipients (miR-126 and miR-155). miRNA have great potential of being sensitive and specific biomarkers in kidney diseases as they are tissue specific and stable in various biological materials. Some promising non-invasive miRNA biomarkers have already been recognized in renal disease with the potential to enhance diagnostic accuracy, predict prognosis and monitor the course of disease. However, large-scale clinical trials enrolling heterogeneous patients are required to evaluate the clinical value of miRNAs.

Expression levels of specific microRNAs are increased after exercise and are associated with cognitive improvement in Parkinson's disease

There is a consensus regarding the efficacy of physical exercise in maintaining or improving human health; however, there are few studies examining the effect of physical exercise on the expression levels of microRNAs (miRNA/miRs) in Parkinson's disease (PD). The aim of the present study was to investigate the effects of an interval training program on a cycle ergometer on the expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in serum samples from men with PD. This was a quasi‑experimental study with pre‑ and post‑testing and with a non‑equivalent group design. The participants were selected based on the eligibility criteria and subsequently classified into two groups: Experimental group and control group. The evaluations were performed at the beginning of the study (week 0) and after 8 weeks of the intervention program (week 9). The interval training program was performed on a cycle ergometer for 30 min, three times a week during an 8‑week period. The expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in the experimental group were increased after physical exercise and were associated with cognitive improvement in men with PD. However, further studies are required to clarify the potential use of these circulating miRNAs as markers of adaptation to physical exercise. Collectively, the present results indicated that these three miRNAs may be associated with the exercise response and cognitive improvement in men with PD.

The effects of biophysical stimulation on osteogenic differentiation and the mechanisms from ncRNAs

Ample proof showed that non-coding RNAs (ncRNAs) play a crucial role in proliferation and differentiation of osteoblasts and bone marrow stromal cells (BMSCs). Varied forms of biophysical stimuli like mechanical strain, fluid shear stress (FSS), microgravity and vibration are verified to regulate ncRNAs expression in osteogenic differentiation and influence the expression of target genes associated with osteogenic differentiation and ultimately regulate bone formation. The consequences of biophysical stimulation on osteogenic differentiation validate the prospect of exercise for the prevention and treatment of osteoporosis. In this review, we tend to summarize the studies on regulation of osteogenic differentiation by ncRNAs beneath biophysical stimulation and facilitate to reveal the regulatory mechanism of biophysical stimulation on ncRNAs, and provide an update for the prevention of bone metabolism diseases by exercise.

Circulating microRNA as predictors for exercise response in heart failure with reduced ejection fraction

AIMS

Exercise training is a powerful adjunctive therapy in patients with heart failure with reduced ejection fraction (HFrEF), but ca. 55% of patients fail to improve VO2peak. We hypothesize that circulating microRNAs (miRNAs), as epigenetic determinants of VO2peak, can distinguish exercise responders (ER) from exercise non-responders (ENR).

METHODS AND RESULTS

We analysed 377 miRNAs in 18 male HFrEF patients (9 ER and 9 ENR) prior to 15 weeks of exercise training using a miRNA array. ER and ENR were defined as change in VO2peak of >20% or <6%, respectively. First, unsupervised clustering analysis of the miRNA pattern was performed. Second, differential expression of miRNA in ER and ENR was analysed and related to percent change in VO2peak. Third, a gene set enrichment analysis was conducted to detect targeted genes and pathways. Baseline characteristics and training volume were similar between ER and ENR. Unsupervised clustering analysis of miRNAs distinguished ER from ENR with 83% accuracy. A total of 57 miRNAs were differentially expressed in ENR vs. ER. A panel of seven miRNAs up-regulated in ENR (Let-7b, miR-23a, miR-140, miR-146a, miR-191, miR-210, and miR-339-5p) correlated with %changeVO2peak (all P < 0.05) and predicted ENR with area under the receiver operating characteristic curves ≥0.77. Multiple pathways involved in exercise adaptation processes were identified.

CONCLUSION

A fingerprint of seven miRNAs involved in exercise adaptation processes is highly correlated with VO2peak trainability in HFrEF, which holds promise for the prediction of training response and patient-targeted exercise prescription.

Effects of physical activity on cell-to-cell communication during type 2 diabetes: A focus on miRNA signaling

Type 2 diabetes (TD2) is a progressive disease characterized by hyperglycemia that results from alteration in insulin secretion, insulin resistance, or both. A number of alterations involving different tissues and organs have been reported to the development and the progression of T2D, and more relevantly, through cell-to-cell communication pathways. Recent studies demonstrated that miRNAs are considerably implicated to cell-to-cell communication during T2D. Physical activity (PA) is associated with decreasing risks of developing T2D and acts as insulin-like factor. Cumulative evidence suggests that this effect could be mediated in part through improving insulin sensitivity in T2D and obese patients and modulating miRNAs synthesis and release in healthy patients. Therefore, the practice of PA should ideally be established before the initiation of T2D. This review describes cell-to-cell communications involved in the pathophysiology of T2D during PA.

The impacts of garlic and voluntary training alone or together on myocardial miR-126 and miR-210 gene expressions and angiogenesis in healthy rats

Introduction: microRNAs (miRs) play a critical role in both physiological and pathological processes. Recent studies have shown that garlic and exercise training have many beneficial effects in different disorders including cardiovascular disease. However, their mechanisms have not been fully understood. This study sought to investigate the impact of garlic and voluntary training alone or together on themiR-126 and miR-210 gene expressions and cardiac angiogenesis. Methods: Male Wistar rats were divided into four groups (n=7): (1) Control, (2) Garlic, (3) Exercise, and (4) Garlic+ Exercise. Animals were gavaged with raw fresh garlic homogenate (250 mg/kg body weight/day) or were subjected to voluntary training alone or together for about 6 weeks. The expressions of miR-126 and miR-210 in the heart tissue were measured by real-time PCR and lipid profile in serum was assessed by enzymatic kits. Angiogenesis was determined by immuno staining detection of PECAM-1 and CD31 in the heart tissue. Results: Garlic and exercise up-regulated myocardial miR-126 (P < 0.01), miR-210 (P < 0.001)expressions, and angiogenesis (P < 0.001) which was evidenced by higher CD31 expression. Besides, combination of garlic and exercise amplified their effects on those parameters (P < 0.001). Moreover, both voluntary exercise and garlic alone (P < 0.01) or together (P < 0.001) markedly modulated serum lipid profile. Conclusion: Voluntary exercise and garlic treatment for 6 weeks enhanced myocardial angiogenesis. These alterations were partly due to the increment of miR-126 and miR-210 expressions in the heart tissue in relation to improvement in lipid profile.

Effects of Physical Exercise on the Expression of MicroRNAs: A Systematic Review

Silva, FCd, Iop, RdR, Andrade, A, Costa, VP, Gutierres Filho, PJB, and Silva, Rd. Effects of physical exercise on the expression of microRNAs: A systematic review 34(1): 270-280, 2020-Studies have detected changes in the expression of miRNAs after physical exercise, which brings new insight into the molecular control of adaptation to exercise. Therefore, the objective of the current systematic review of experimental and quasiexperimental studies published in the past 10 years was to assess evidence related to acute effects, chronic effects, and both acute and chronic effects of physical exercise on miRNA expression in humans, as well as its functions, evaluated in serum, plasma, whole blood, saliva, or muscle biopsy. For this purpose, the following electronic databases were selected: MEDLINE by Pubmed, SCOPUS, Web of Science, and also a manual search in references of the selected articles to April 2017. Experimental and quasiexperimental studies were included. Results indicate that, of the 345 studies retrieved, 40 studies met the inclusion criteria and two articles were included as a result of the manual search. The 42 studies were analyzed, and it can be observed acute and chronic effects of physical exercises (aerobic and resistance) on the expression of several miRNAs in healthy subjects, athletes, young, elderly and in patients with congestive heart failure, chronic kidney disease, diabetes mellitus type 2 associated with morbid obesity, prediabetic, and patients with intermittent claudication. It is safe to assume that miRNA changes, both in muscle tissues and bodily fluids, are presumably associated with the benefits induced by acute and chronic physical exercise. Thus, a better understanding of changes in miRNAs as a response to physical exercise might contribute to the development of miRNAs as therapeutic targets for the improvement of exercise capacity in individuals with any given disease. However, additional studies are necessary to draw accurate conclusions.

Exercise, redox homeostasis and the epigenetic landscape

Physical exercise represents one of the strongest physiological stimuli capable to induce functional and structural modifications in all biological systems. Indeed, beside the traditional genetic mechanisms, physical exercise can modulate gene expression through epigenetic modifications, namely DNA methylation, post-translational histone modification and non-coding RNA transcripts.

Initially considered as merely damaging molecules, it is now well recognized that both reactive oxygen (ROS) and nitrogen species (RNS) produced under voluntary exercise play an important role as regulatory mediators in signaling processes. While robust scientific evidences highlight the role of exercise-associated redox modifications in modulating gene expression through the genetic machinery, the understanding of their specific impact on epigenomic profile is still at an early stage. This review will provide an overview of the role of ROS and RNS in modulating the epigenetic landscape in the context of exercise-related adaptations.

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Physical exercise can modulate gene expression through epigenetic modifications.

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Epigenetic regulation of ROS/RNS generating, sensing and neutralizing enzymes can impact the cellular levels of ROS and RNS.

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ROS might act as modulators of epigenetic machinery, interfering with DNA methylation, hPTMs and ncRNAs expression.

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Redox homeostasis might hold a relevant role in the epigenetic landscape modulating exercise-related adaptations.

Circulating microRNAs as potential biomarkers of chronic kidney disease

Chronic kidney disease (CKD) is a supra - nosological term that reflects the progressive nature of chronic kidney diseases, which are based on the mechanisms of nephrosclerosis. Diagnosis of CKD at the earliest stages is of great importance, because it allows, by using therapeutic agents, to slow the progression of renal dysfunction and the development of cardiovascular complications. However, the currently available methods for diagnosing renal function impairment, including the determination of endogenous creatinine clearance, can detect renal dysfunction too late, when around 40-50% of the renal parenchyma is already reversibly or irreversibly damaged. In this regard, there is an active search for new, more sensitive and specific biomarkers for early diagnosis of CKD. Recent studies in cellular and animal models of CKD have demonstrated the important role of microRNA, a new class of posttranscriptional regulators of gene expression, in physiology and pathophysiology of kidneys. In particular, it has been shown that their expression profile in blood or urine can reflect changes in cells involved in a particular pathological process, since these cells can secrete a specific population of microRNAs, for example, through secretion of microRNA-containing exosomes. This gave grounds for considering increased or decreased expression of individual microRNAs in renal tissue or biological fluids (including urine) as new biomarkers for the diagnosis and monitoring of CKD. This review presents the results of recent experimental and clinical studies on these issues.

Heart Failure With Preserved Ejection Fraction: A Review of Cardiac and Noncardiac Pathophysiology

Heart failure with preserved ejection fraction (HFpEF) is one of the largest unmet clinical needs in 21st-century cardiology. It is a complex disorder resulting from the influence of several comorbidities on the endothelium. A derangement in nitric oxide bioavailability leads to an intricate web of physiological abnormalities in the heart, blood vessels, and other organs. In this review, we examine the contribution of cardiac and noncardiac factors to the development of HFpEF. We zoom in on recent insights on the role of comorbidities and microRNAs in HFpEF. Finally, we address the potential of exercise training, which is currently the only available therapy to improve aerobic capacity and quality of life in HFpEF patients. Unraveling the underlying mechanisms responsible for this improvement could lead to new biomarkers and therapeutic targets for HFpEF.

The effects of intradialytic resistance training on muscle strength, psychological well-being, clinical outcomes and circulatory micro-ribonucleic acid profiles in haemodialysis patients: Protocol for a quasi-experimental study

BACKGROUND

Intradialytic resistance training (IRT) protects patients' muscle mass and functions against protein-energy wasting, malnutrition and cachexia. However, the evidence of the effects of such an intervention in haemodialysis patients is limited and not conclusive. To improve the applicability of such interventions, we need a better understanding of molecular, functional and psycho-social adaptation in dialysed patients following a physical training. Therefore, the aim of this study is to investigate the effects of IRT on lower extremity muscle functions, quality of life, and anxiety and depression, clinical outcomes and circulatory micro-ribonucleic acid (miRNA) profiles in patients on chronic haemodialysis therapy.

METHODS

We will perform a quasi-experimental study in 3 dialysis centres. Patients will be recruited via their nephrologists and will be allocated to an experimental and a control group based on the location of the patients' dialysis centre. Patients allocated to the experimental group will undergo a 12-week IRT, while the control group will remain physically inactive during dialysis. The primary outcome is the change in the maximal force produced during an isometric contraction of lower extremity muscles. Secondary outcomes regard quality of life, anxiety and depression, clinical outcomes and circulatory miRNA profiles. Patients' level of health literacy defined as the ability to get and understand health information will be also measured in the study as a potential modifier of effects.

DISCUSSION

This quasi-experimental study can add in an important way to our understanding of the effects of resistance training on dialysis patients' muscle strength, quality of life and disease-specific outcomes.

Small non-coding RNAs are altered by short-term sprint interval training in men

Small non-coding RNAs (ncRNAs) are emerging as important molecules for normal biological processes and are deregulated in disease. Exercise training is a powerful therapeutic strategy that prevents cardiometabolic disease and improves cardiorespiratory fitness and performance. Despite the known systemic health benefits of exercise training, the underlying molecular mechanisms are incompletely understood. Recent evidence suggests a role for epigenetic mechanisms, such as microRNAs, but whether other small ncRNAs are modulated by chronic exercise training is unknown. Here, we used small RNA sequencing to explore whether sprint interval training (SIT) controls the abundance of circulating small ncRNAs in human whole blood samples. Ten healthy men performed SIT three times a week for 6 weeks. After training, subjects showed marked improvements in maximal oxygen consumption and cycling performance with concurrent changes to the abundance of diverse species of circulating small ncRNAs (n = 1266 small ncRNAs, n = 13 microRNAs, q < 0.05). Twelve microRNAs altered by 6 weeks of SIT were ubiquitously expressed microRNAs and two regulated important signaling pathways, including p53, thyroid hormone and cell cycle signaling. MicroRNAs altered by 6 weeks of SIT were unchanged after a single session of SIT (n = 24, all P > 0.05). Relative to older individuals, younger subjects exhibited an increased acute SIT-induced fold change in miR-1301-3p (P = 0.02) - a microRNA predicted to target mRNAs involved in alternative splicing, phosphoprotein and chromosomal rearrangement processes (all P < 0.001). Our findings indicate many species of circulating small ncRNAs are modulated by exercise training and that they could control signaling pathways responsible for health benefits achieved from exercise.

Associations of Circulating MicroRNAs (miR-17, miR-21, and miR-150) and Chronic Kidney Disease in a Japanese Population

Background

MicroRNAs (miRNAs) play crucial roles in the development of various diseases, including chronic kidney disease (CKD). Although previous studies in clinically severe patients have investigated associations between CKD and miRNAs, with particular attention on renal fibrosis, relationships in a general population have yet to be established. The aim of this study was to examine the relationship between expression level of circulating miRNAs and CKD in a middle-aged Japanese population.

Methods

A final total of 513 individuals (216 men and 297 women) who participated in the health check-up program in 2012 were included in our analysis. Quantitative real-time polymerase chain reaction was used to determine expression levels of 22 miRNAs. Estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine level, sex, and age. Participants with eGFR <60 mL/min/1.73 m² were defined as having CKD.

Results

Three different miRNAs (miR-17, miR-21, and miR-150) showed significant correlations with eGFR after Bonferroni correction and were selected for further analyses. Expression levels of miR-17, miR-21, and miR-150 miRNAs were positively associated with eGFR after adjusting for potential confounders (P = 0.004, 0.002, and 0.004, respectively). Logistic regression analyses showed significantly lower odds ratios for CKD (eGFR <60 mL/min/1.73 m²) in the highest tertile of all three miRNAs (miR-17, miR-21, and miR-150) compared with the lowest tertile (P = 0.003, 0.01, and 0.02, respectively).

Conclusions

We found that three circulating miRNAs were significantly associated with CKD in a general Japanese population, which suggested that these miRNAs may be biomarkers for CKD among general adults.

Expression Profiling and Clinical Significance of Plasma MicroRNAs in Diabetic Nephropathy

AIMS

MicroRNAs (miRNAs) stably and abundantly exist in body fluids and have been considered as novel and noninvasive biomarkers for several diseases. The present study is aimed at investigating the expression profiling and clinical significance of plasma miRNAs in the pathogenesis and progression of diabetic nephropathy (DN).

METHODS

Plasma samples were obtained from 66 DN patients (36 had microalbuminuria and 30 had macroalbuminuria), 36 diabetic patients with normoalbuminuria, and 40 healthy controls. The plasma miRNA profiles were obtained by miRNA low-density array chip and validated by quantitative real-time polymerase chain reaction. The correlations between the differential expression of plasma miRNAs and clinicopathological parameters were explored.

RESULTS

miR-150-5p, miR-155-5p, miR-30e, miR-320e, and miR-3196 were found to be differentially expressed in plasma samples among these three groups: diabetic patients with microalbuminuria, diabetic patients with normoalbuminuria, and healthy controls (P < 0.05). The expression levels of miR-150-5p and miR-155-5p in patients with macroalbuminuria were 2.3-fold (P = 0.001) and 1.5-fold (P = 0.033) higher than patients with microalbuminuria, respectively. However, the expression levels of miR-30e, miR-3196, miR-320, and let-7a-5p were not significantly different between these two groups (P > 0.05). Furthermore, plasma miR-150-5p (P = 0.016, r = -0.460) and miR-155-5p (P = 0.014, r = -0.467) were negatively correlated with the albuminuria excretion rate, while plasma miR-150-5p (P = 0.01, r = 0.318) and miR-155-5p (P = 0.030, r = 0.271) were positively correlated with the estimated glomerular filtration rate.

CONCLUSION

miR-150-5p, miR-155-5p, miR-30e, miR-320e, and miR-3196 are potentially new diagnostic biomarkers for early DN. miR-150-5p and miR-155-5p may be involved in the pathogenesis and progression of DN. Further research is required to verify these findings and clarify the specific molecular mechanisms.

The Effect of Garlic and Voluntary Exercise on Cardiac Angiogenesis in Diabetes: The Role of MiR-126 and MiR-210

BACKGROUND

Diabetes mellitus (DM) is one of the major risk factors for cardiovascular disease, leading to endothelial dysfunction and angiogenesis impairment . MiR-126 and miR-210 support angiogenic response in endothelial cells.

OBJECTIVE

The present study sought to explore the effect of garlic and voluntary exercise, alone or together, on miR-126 and miR-210 expressions and cardiac angiogenesis in rats with type 1 diabetes.

METHODS

Male Wistar rats were divided into five groups (n = 7): Control, Diabetes, Diabetes+Garlic, Diabetes+Exercise, and Diabetes+Garlic+Exercise. Diabetes was induced in the animals by streptozotocin (ip, 50 mg/kg). The rats were then fed raw fresh garlic homogenate (250 mg/kg) or were subjected to voluntary exercise, or to combined garlic and voluntary exercise for 6 weeks. MiR-126 and miR-210 expressions in the myocardium were determined by real time PCR, and the serum lipid profile was measured by enzymatic kits. Angiogenesis was evaluated by immunostaining for PECAM-1/ CD31 in the myocardium.

RESULTS

Diabetes reduced both cardiac miR-126 expression and angiogenesis (p < 0.05). On the other hand, there was a miR-210 expression increase in the myocardium of diabetic animals (p < 0.001). However, those effects reversed either with garlic or voluntary exercise (p < 0.01). Moreover, treating diabetic rats with garlic and voluntary exercise combined had an additional effect on the expressions of miR-126 and miR-210 (p < 0.001). Furthermore, both voluntary exercise and garlic significantly improved serum lipid profiles (p < 0.001).

CONCLUSION

The induction of diabetes decreased angiogenesis in the myocardium, whereas our treatment using long-term voluntary exercise and garlic improved myocardial angiogenesis. These changes were possibly owing to the enhancement of myocardial miR-126 and miR-210 expressions.

Circulating microRNA as Emerging Biomarkers of Exercise

An interest has recently emerged in the role of circulating microRNAs (c-miRNAs) as posttranscriptional regulators, intercellular communicators and, especially, as potential biomarkers of the systemic response to acute exercise and training. We propose that, with the limited, heterogeneous, and mainly descriptive information currently available, c-miRNAs do not provide a reliable biomarker of exercise in healthy or diseased individuals.

Benefits of exercise training on cardiovascular dysfunction: molecular and integrative

Exercise training has been shown to ameliorate a wide variety of cardiovascular disorders. The mechanisms by which long-term benefits of exercise training are mediated remains incomplete, despite intense research in this area. Exactly how the act of chronic exercise improves function in every tissue is unknown, but many of the cellular, molecular, and genetic mechanisms are becoming progressively clearer. This "Perspectives" article reviews the contributions of 15 articles published in the American Journal of Physiology-Heart and Circulatory Physiology in response to a Call for Papers in this area. Here, we summarize the contributions of these studies at the cardiac, vascular, immune, and molecular levels. We discuss the translational benefit of these studies and conclude that the beneficial effects of exercise training in cardiovascular disease is due to a large interplay of cellular and molecular mediators in the heart and peripheral vasculature as well as changes in neural elements that regulate blood pressure and blood flow. Readers are encouraged to evaluate and learn from this collection of novel studies.

Transforming growth factor-β signalling in renal fibrosis: from Smads to non-coding RNAs

Transforming growth factor-β (TGF-β) is the key player in tissue fibrosis. However, antifibrotic therapy targeting this multifunctional protein may interfere with other physiological processes to cause side effects. Thus, precise therapeutic targets need to be identified by further understanding the underlying mechanisms of TGF-β1 signalling during fibrogenesis. Equilibrium of Smad signalling is crucial for TGF-β-mediated renal fibrosis, where Smad3 is pathogenic but Smad2 and Smad7 are protective. The activation of TGF-β1/Smad signalling triggers extracellular matrix deposition, and local myofibroblast generation and activation. Mechanistic studies have shown that TGF-β/Smad3 transits the microRNA profile from antifibrotic to profibrotic and therefore promotes renal fibrosis via regulating non-coding RNAs at transcriptional levels. More importantly, disease-specific Smad3-dependent long non-coding RNAs have been recently uncovered from mouse kidney disease models and may represent novel precision therapeutic targets for chronic kidney disease. In this review, mechanisms of TGF-β-driven renal fibrosis via non-coding RNAs and their translational capacities will be discussed in detail.

MicroRNA profiling in plasma samples using qPCR arrays: Recommendations for correct analysis and interpretation

MicroRNA (miRNA) regulate gene expression through posttranscriptional mRNA degradation or suppression of translation. Many (pre)analytical issues remain to be resolved for miRNA screening with TaqMan Low Density Arrays (TLDA) in plasma samples, such as optimal RNA isolation, preamplification and data normalization. We optimized the TLDA protocol using three RNA isolation protocols and preamplification dilutions. By using 100μL elution volume during RNA isolation and adding a preamplification step without dilution, 49% of wells were amplified. Informative target miRNA were defined as having quantification cycle values ≤35 in at least 20% of samples and low technical variability (CV across 2 duplicates of 1 sample <4%). A total of 218 miRNA was considered informative (= 59% of all target miRNA). Different normalization strategies were compared: exogenous Ath-miR-159a, endogenous RNA U6, and three mathematical normalization techniques: geNorm (Qbase, QB) and NormFinder (NF) normalization algorithms, and global mean calculation. To select the best normalization method, technical variability, biological variability, stability, and the extent to which the normalization method reduces data dispersion were calculated. The geNorm normalization algorithm reduced data dispersion to the greatest extent, while endogenous RNA U6 performed worst. In conclusion, for miRNA profiling in plasma samples using TLDA cards we recommend: 1. Implementing a preamplification step in the TLDA protocol without diluting the final preamplification product 2. A stepwise approach to exclude non-informative miRNA based on quality control parameters 3. Against using snoRNA U6 as normalization method for relative quantification 4. Using the geNorm algorithm as normalization method for relative quantification.

Epigenetic effects of physical activity in elderly patients with cardiovascular disease

Cardiovascular disease (CVD) is an important public health problem affecting especially the elderly. Over the past 20years, an increasing number of studies have examined its underlying pathophysiological mechanisms and new therapies are continually being discovered. However, despite considerable progress in CVD management, mortality and morbidity remain a major healthcare concern, and frequent hospital admissions compromise the daily life and social activities of these patients. Physical activity has emerged as an important non-pharmacological adjunctive therapy for CVD in older patients, especially for heart failure patients, exerting its beneficial effects on mortality, morbidity, and functional capacity. The mechanisms underlying the cardiovascular benefits of exercise are not wholly clear. Mounting evidence suggest that epigenetic modifications, such as DNA methylation, histone post-translational modifications (hPTMs) and non-coding RNA, especially microRNAs (miRNAs), may be induced by physical activity. Recently, a number of miRNAs have been identified as key players in gene expression modulation by exercise. MiRNAs are synthesized by living cells and actively released into the bloodstream through different shuttles. The epigenetic information, thus carried and delivered, is involved in the interplay between environmental factors, including physical activity, and individual genetic make-up. We review and discuss the effects of exercise on age-related CVDs, focusing on circulating miRNA (c-miRNAs) modulation. Epigenetic mechanisms may have clinical relevance in CVD prevention and management; since they can be modified, insights into the implications of lifestyle-related epigenetic changes in CVD etiology may help develop therapeutic protocols of exercise training that can be suitable and effective for elderly patients.

The Management of Cardiovascular Risk through Epigenetic Biomarkers

Epigenetic sciences study heritable changes in gene expression not related to changes in the genomic DNA sequence. The most important epigenetic mechanisms are DNA methylation, posttranslational histone modification, and gene regulation by noncoding RNAs, such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). Cardiovascular diseases (CVD) are responsible for at least one-third of premature deaths worldwide and represent a heavy burden of healthcare expenditure. We will discuss in this review the most recent findings dealing with epigenetic alterations linked to cardiovascular physiopathology in patients. A particular focus will be put on the way these changes can be translated in the clinic, to develop innovative and groundbreaking biomarkers in CVD field.

Current epigenetic aspects the clinical kidney researcher should embrace

Chronic kidney disease (CKD), affecting 10–12% of the world’s adult population, is associated with a considerably elevated risk of serious comorbidities, in particular, premature vascular disease and death. Although a wide spectrum of causative factors has been identified and/or suggested, there is still a large gap of knowledge regarding the underlying mechanisms and the complexity of the CKD phenotype. Epigenetic factors, which calibrate the genetic code, are emerging as important players in the CKD-associated pathophysiology. In this article, we review some of the current knowledge on epigenetic modifications and aspects on their role in the perturbed uraemic milieu, as well as the prospect of applying epigenotype-based diagnostics and preventive and therapeutic tools of clinical relevance to CKD patients. The practical realization of such a paradigm will require that researchers apply a holistic approach, including the full spectrum of the epigenetic landscape as well as the variability between and within tissues in the uraemic milieu.

Failed Downregulation of Circulating MicroRNA-155 in the Early Phase after ST Elevation Myocardial Infarction Is Associated with Adverse Left Ventricular Remodeling

BACKGROUND

MicroRNA are noncoding RNA that have a significant role in both inflammatory and cardiovascular diseases.

AIMS

We aimed to assess whether the inflammation-related microRNA-155 is associated with the development of adverse left ventricular (LV) remodeling following ST elevation myocardial infarction (STEMI).

METHODS

Peripheral blood samples were collected in the inflammatory (day 2), proliferative (day 5), and maturation phases (6 months) after STEMI (n = 20). Granulocytes, monocytes, and lymphocytes were enumerated with flow cytometry. The changes in LV volumes were assessed with 3-D echocardiography on day 1 and after 6 months. Adverse remodeling was defined as a >20% increase in end-diastolic volume. Healthy subjects were recruited as controls.

RESULTS

MicroRNA-155 measured on day 5 correlated positively with the relative change in end-diastolic volume (ρ = 0.490, p = 0.028). MicroRNA-155 (day 5) was significantly higher in patients with compared to patients without adverse LV remodeling. The expression level was similar in healthy subjects (n = 8) and in patients with LV remodeling. There was a positive correlation between microRNA-155 and the amount of monocytes (day 5, ρ = 0.463, p = 0.046).

CONCLUSION

Impaired downregulation of microRNA-155 during the second phase of the post- STEMI inflammatory response is a determinant of the development of adverse LV remodeling.

MicroRNAs 223-3p and 93-5p in patients with chronic kidney disease before and after renal transplantation

Chronic kidney disease (CKD) is associated with a multifactorial dysregulation of bone and vascular calcification and closely linked to increased cardiovascular mortality and concomitant bone disease. We aimed to investigate specific microRNA (miRNA) signatures in CKD patients to find indicators for vascular calcification and/or bone mineralization changes during CKD and after kidney transplantation (KT). A miRNA array was used to investigate serum miRNA profiles in CKD patients, then selected miRNAs were quantified in a validation cohort comprising 73 patients in CKD stages 3 to 5, 67 CKD patients after KT, and 36 healthy controls. A spectrum of biochemical parameters including markers for kidney function, inflammation, glucose, and mineral metabolism was determined. The relative expression of miR-223-3p and miR-93-5p was down-regulated in patients with CKD stage 4 and 5 compared to healthy controls. This down-regulation disappeared after kidney transplantation even when lower glomerular filtration rates (eGFR) persisted. MiR-223-3p and miR-93-5p were associated with interleukin-6 (IL-6) and eGFR levels, and by trend with interleukin-8 (IL-8), C-peptide, hematocrit, and parathyroid hormone (PTH). This study contributes new knowledge of serum miRNA expression profiles in CKD, potentially reflecting pathophysiological changes of bone and calcification pathways associated with inflammation, vascular calcification, mineral and glucose metabolism. Identified miRNA signatures can contribute to future risk markers or future therapeutic targets in bone and kidney disease.

Circulating microRNAs in acute and chronic exercise: more than mere biomarkers

MicroRNAs (miRNAs) are short, noncoding RNAs that influence biological processes by regulating gene expression after transcription. It was recently discovered that miRNAs are released into the circulation (ci-miRNAs) where they are highly stable and can act as intercellular messengers to affect physiological processes. This review provides a comprehensive summary of the studies to date that have investigated the effects of acute exercise and exercise training on ci-miRNAs in humans. Findings indicate that specific ci-miRNAs are altered in response to different protocols of acute and chronic exercise in both healthy and diseased populations. In some cases, altered ci-miRNAs correlate with fitness and health parameters, suggesting causal mechanisms by which ci-miRNAs may facilitate adaptations to exercise training. However, strong data supporting such mechanisms are lacking. Thus, a purpose of this review is to guide future studies by discussing current and novel proposed roles for ci-miRNAs in adaptations to exercise training. In addition, substantial, fundamental gaps in the field need to be addressed. The ultimate goal of this research is that an understanding of the roles of ci-miRNAs in physiological adaptations to exercise training will one day translate to therapeutic interventions.

microRNAs in the pathophysiology of CKD-MBD: Biomarkers and innovative drugs

microRNAs comprise a novel class of endogenous small non-coding RNAs that have been shown to be implicated in both vascular damage and bone pathophysiology. Chronic kidney disease-mineral bone disorder (CKD-MBD) is characterized by vessel and bone damage secondary to progressive loss of kidney function. In this review, we will describe how several microRNAs have been implicated, in recent years, in cellular and animal models of CKD-MBD, and have been very recently shown to be deregulated in patients with CKD. Particular emphasis has been placed on the endothelial-specific miR-126, a potential biomarker of endothelial dysfunction, and miR-155 and miR-223, which play a role in both vascular smooth muscle cells and osteoclasts, with an impact on the vascular calcification and osteoporosis process. Finally, as these microRNAs may constitute useful targets to prevent or treat complications of CKD-MBD, we will discuss their potential as innovative drugs, describe how they could be delivered in a timely and specific way to vessels and bone by using the most recent techniques such as nanotechnology, viral vectors or CRISPR gene targeting.

Circulating MicroRNAs as Potential Biomarkers of Exercise Response

Systematic physical activity increases physical fitness and exercise capacity that lead to the improvement of health status and athletic performance. Considerable effort is devoted to identifying new biomarkers capable of evaluating exercise performance capacity and progress in training, early detection of overtraining, and monitoring health-related adaptation changes. Recent advances in OMICS technologies have opened new opportunities in the detection of genetic, epigenetic and transcriptomic biomarkers. Very promising are mainly small non-coding microRNAs (miRNAs). miRNAs post-transcriptionally regulate gene expression by binding to mRNA and causing its degradation or inhibiting translation. A growing body of evidence suggests that miRNAs affect many processes and play a crucial role not only in cell differentiation, proliferation and apoptosis, but also affect extracellular matrix composition and maintaining processes of homeostasis. A number of studies have shown changes in distribution profiles of circulating miRNAs (c-miRNAs) associated with various diseases and disorders as well as in samples taken under physiological conditions such as pregnancy or physical exercise. This overview aims to summarize the current knowledge related to the response of blood c-miRNAs profiles to different modes of exercise and to highlight their potential application as a novel class of biomarkers of physical performance capacity and training adaptation.

Circulating miRNAs as biomarkers of kidney disease

Interest in microRNAs (miRNAs) has dramatically increased in recent years not only because they regulate mRNA expression, and thus many physiological or pathophysiological processes, but also because they could serve as biomarkers. Next to analysis of tissue miRNA expression, measurement in body fluids such as blood or urine is attractive because miRNA in microvesicles or bound to protein is very stable. Currently it is unclear whether these circulating miRNAs are tissue and disease specific or represent more general pathologies like inflammation. In addition pre-analytical sample handling and variable analysis techniques affect the results and thus much more work needs to be done before one can draw a final conclusion about their clinical utility.

Impaired vascular function contributes to exercise intolerance in chronic kidney disease

BACKGROUND

Exercise intolerance is an important feature in patients with chronic kidney disease (CKD) and is prognostic for both increased morbidity and mortality. Little is known about the underlying mechanisms in predialysis CKD. This study aimed to gain more insight into the role of vascular dysfunction in the exercise intolerance of predialysis CKD. In addition, vascular-related microRNAs (miRNAs)-as epigenetic regulators of exercise capacity-were analysed.

METHODS

Sixty-three patients with CKD stages 1-5 and 18 healthy controls were included. Peak oxygen consumption (VO₂peak) was determined by cardiopulmonary exercise testing, endothelial function by flow-mediated dilation (FMD) and arterial stiffness by carotid-femoral pulse wave velocity (PWV). Plasma miRNA levels (miR-21, miR-126, miR-146a, miR-150 and miR-210) were quantified by quantitative RT-PCR.

RESULTS

VO₂peak was already impaired in mild CKD (stages 1-3A) and significantly correlated with estimated glomerular filtration rate (eGFR; r = 0.525, P < 0.001). Likewise, both FMD and PWV were significantly correlated with eGFR (r = 0.319, P = 0.007 and r = -0.365, P = 0.001, respectively). In multiple regression analysis, PWV remained one of the strongest independent determinants of VO₂peak (β = -0.301, P = 0.01). Of the studied miRNA, circulating levels of miR-146a and miR-150 correlated with eGFR, PWV and VO₂peak, but the association with the latter was lost when correcting for PWV.

CONCLUSIONS

Arterial stiffness contributes to the observed reduced aerobic capacity in predialysis CKD, independent of age, haemoglobin levels and endothelial function and represents a promising therapeutic target for improving exercise capacity in this population. Future work is required to elucidate why higher circulating levels of miR-146a and miR-150 are associated with impaired renal function and increased arterial stiffness.