Serum miRNAs miR-23a, 206, and 499 as Potential Biomarkers for Skeletal Muscle Atrophy

Increased Expression of MiRNA-1 Contributes to Hypobaric Hypoxia-Induced Skeletal Muscle Loss

The present study aims to analyze the role of microRNA-1 in the regulation of skeletal muscle loss under hypobaric hypoxia (HH). Male Sprague Dawley rats (n = 10) weighing 230-250 g are divided into two groups, control and HH exposure for 7 days at 25 000 ft. After the hypoxia exposure, the animals are sacrificed and hindlimb skeletal muscles are excised for further analysis. Studies found the potential role of miR-1 (myomiR) as a biomarker under different atrophic conditions. Prolonged exposure to HH leads to enhanced expression of miR-1 in skeletal muscle as compared to unexposed controls. The Bioinformatics approach is used to identify the validated targets and the biological processes of miR-1. The target prediction tools identify PAX3 and HSP70 as major targets for miR-1. Exposure to HH significantly reduces PAX3 and HSP70 expression during 7 days of HH exposure, which further enhances the activity of FOXO3, MSTN, and ATROGIN known for the progression of skeletal muscle atrophy in relation to control rats. This study indicates the increased expressions of miR-1 and reduced expression of PAX3 and HSP70 lead to impaired myogenesis in skeletal muscle under HH. Further, enhanced expression of muscle degradation genes such as FOXO3, MSTN, and ATROGIN under HH exposure causes skeletal muscle protein loss.

Decreased expression of H19/miR-675 ameliorates muscle atrophy by regulating the IGF1R/Akt/FoxO signaling pathway

BACKGROUND

Long non-coding RNA (lncRNA) H19 is one of the most highly expressed and conserved transcripts in mammalian development, and its functions have been fully discussed in many contexts including tumorigenesis and skeletal muscle development. However, its exact role in muscle atrophy remains largely unknown. This study investigated the effect of lncRNA H19 on muscle atrophy and the potential underlying mechanism.

METHODS

Hindlimb suspension (HS) of C57BL/6 mice and starvation of C2C12 cells with PBS were conducted to induce atrophy. Real-time PCR and Western blotting were used to measure the expression of RNAs and proteins. LncRNA H19 and its encoded miR-675 were overexpressed or inhibited in different models of muscle atrophy. Immunofluorescence was carried out to examine the cross-sectional area (CSA) and minimal Feret's diameter (MFD) of myofibers and myotube diameter.

RESULTS

The expression levels of lncRNA H19 and miR-675 were significantly reduced in both the soleus and gastrocnemius muscles in response to HS. Overexpression of lncRNA H19 led to an increase in Atrogin-1 mRNA expression, and this effect was reversed by inhibiting miR-675. The overexpression of miR-675 aggravated both HS- and starving-induced muscle atrophy by inhibiting the IGF1R/Akt signaling pathway and promoting FoxO/Atrogin-1 expression. Conversely, miR-675 inhibition had the opposite effects.

CONCLUSION

The lncRNA H19/miR-675 axis can induce muscle atrophy, and its downregulation in mice with HS-induced muscle atrophy may act as a protective mechanism against this condition.

Profiling non-coding RNA expression in cerebrospinal fluid of amyotrophic lateral sclerosis patients

INTRODUCTION

Objective biomarkers for the fatal neurodegenerative disease amyotrophic lateral sclerosis or motor neuron disease (ALS/MND) are critical for diagnosis, drug development, clinical trials, and insight into disease pathology. Key candidates for biomarkers present in biofluids include non-coding RNA (ncRNA) transcripts including microRNA, piwi-interacting RNA and transfer RNA. To determine if the central nervous system was the source of the dysregulated ncRNA biomarkers we previously observed in serum, we sought to identify dysregulated ncRNA candidates in cerebrospinal fluid (CSF) which may provide new insight into the disease pathology.

METHODS AND MATERIALS

Small RNA sequencing (RNA-seq) was undertaken on CSF samples from healthy controls (n = 18), disease mimics (n = 8), and ALS patients (n = 40) in our Oxford Study for Biomarkers of ALS cohort, with RT-qPCR used to confirm their dysregulation.

RESULTS

We found a range of ncRNA that were dysregulated in the RNA-seq screen, but these failed to be validated or detected in some cases using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Additionally, our previously identified serum ncRNA biomarker showed no change in CSF or correlation to serum.

CONCLUSIONS

This study suggests the CSF may not be the source of dysregulated ncRNA in the serum and highlights the difficulty in identifying ncRNA in CSF as biomarkers for ALS.KEY MESSAGESIn this current study, we investigated the expression of non-coding RNA transcripts in the cerebrospinal fluid of ALS patients compared to healthy controls.RNA-seq identified dysregulated non-coding RNA transcripts, but these were not validated with RT-qPCR.We conclude that cerebrospinal fluid is not a suitable source of diagnostic biomarkers.

Novel miRNA Biomarkers for Patients With Duchenne Muscular Dystrophy

Creatine kinase (CK) as a biomarker has long been expected to be replaced by other fluid biomarkers for Duchenne muscular dystrophy (DMD) because it is independent of disease severity. Growing evidence has demonstrated that muscle-specific microRNAs, known as myomiRs, can act as biomarkers for monitoring muscle pathology and disease severity of DMD patients. To gain insights into the relationship between serum myomiRs and clinical assessment, we measured serum levels of miR-1, miR-133a, miR-133b, miR-206, miR-208a, miR-208b, and miR-499 in 48 DMD patients by using real-time quantitative reverse transcription polymerase chain reaction. These were then compared with age, muscle strength, muscle functions, CK levels, cardiac manifestations, and mutation types (deletions, duplications, and small mutations). When compared to 53 controls, the expression levels of myomiRs were all significantly elevated (p < 0.05). The receiver operating characteristic curves of all seven myomiRs reflected marked differences between DMD patients and healthy controls (p < 0.05). We also showed that serum levels of myomiRs were positively correlated with lower limb distal muscle strength in patients of all age groups. The levels of miR-499, miR-208b, miR-133a, and miR-133b had significant negative correlations with the time to be upright from the supine position (Gowers' time) and the time taken to climb four stairs in DMD patients older than 7 years. Serum levels of miR-1, miR-133a, miR-133b, and miR-499 in patients with cardiac involvement were remarkably higher than those in non-cardiac-involved patients. There was no significant difference in levels of myomiRs between the different mutation groups. Our results indicated that serum myomiRs could be considered as novel biomarkers for monitoring pathology/pathophysiology of DMD patients. In particular, miR-499, miR-208b, miR-133a, and miR-133b might have the ability to reflect the extent of muscle impairment.

miR-30b-5p inhibits osteoblast differentiation through targeting BCL6

Human bone marrow mesenchymal stem cells (hBMSCs) are attractive candidates for new therapies to improve bone regeneration and repair. This study was to identify the function of the miR-30b-5p/BCL6 axis in osteogenic differentiation of hBMSCs. Realtime-quantitative PCR (RT-qPCR) and Western blotting were used to measure the relative expression of ALP, OCN, RUNX2, miR-30b-5p, and BCL6 during osteogenic differentiation of hBMSCs. The relationship between miR-30b-5p and BCL6 in hBMSCs was identified using dual-luciferase reporter system and RNA pull-down assay. Alizarin red S staining (ARS) was used to detect the calcium nodules in hBMSCs. We found that the expression of miR-30b-5p was downregulated, whereas that of BCL6 was upregulated during osteogenic differentiation of hBMSCs. Downregulating miR-30b-5p enhanced the expression of OCN, RUNX2, and ALP, and promoted calcium deposition. Conversely, transfection with si-BCL6 had the opposite effect that it inhibited osteogenic differentiation. However, the inhibitory effect of si-BCL6 was abrogated by miR-30b-5p inhibitor. miR-30b-5p inhibits the osteogenic differentiation of hBMSCs by targeting BCL6.

Decreased miR-497-5p Suppresses IL-6 Induced Atrophy in Muscle Cells

Interleukin-6 (IL-6) is a pro-inflammatory cytokine associated with skeletal muscle wasting in cancer cachexia. The control of gene expression by microRNAs (miRNAs) in muscle wasting involves the regulation of thousands of target transcripts. However, the miRNA-target networks associated with IL6-induced muscle atrophy remain to be characterized. Here, we show that IL-6 promotes the atrophy of C2C12 myotubes and changes the expression of 20 miRNAs (5 up-regulated and 15 down-regulated). Gene Ontology analysis of predicted miRNAs targets revealed post-transcriptional regulation of genes involved in cell differentiation, apoptosis, migration, and catabolic processes. Next, we performed a meta-analysis of miRNA-published data that identified miR-497-5p, a down-regulated miRNAs induced by IL-6, also down-regulated in other muscle-wasting conditions. We used miR-497-5p mimics and inhibitors to explore the function of miR-497-5p in C2C12 myoblasts and myotubes. We found that miR-497-5p can regulate the expression of the cell cycle genes CcnD2 and CcnE1 without affecting the rate of myoblast cellular proliferation. Notably, miR-497-5p mimics induced myotube atrophy and reduced Insr expression. Treatment with miR-497-5p inhibitors did not change the diameter of the myotubes but increased the expression of its target genes Insr and Igf1r. These genes are known to regulate skeletal muscle regeneration and hypertrophy via insulin-like growth factor pathway and were up-regulated in cachectic muscle samples. Our miRNA-regulated network analysis revealed a potential role for miR-497-5p during IL6-induced muscle cell atrophy and suggests that miR-497-5p is likely involved in a compensatory mechanism of muscle atrophy in response to IL-6.

MicroRNAs associated with signaling pathways and exercise adaptation in sarcopenia

Considering the expansion of human life-span over the past few decades; sarcopenia, a physiological consequence of aging process characterized with a diminution in mass and strength of skeletal muscle, has become more frequent. Thus, there is a growing need for expanding our knowledge on the molecular mechanisms of muscle atrophy in sarcopenia which are complex and involve many signaling pathways associated with protein degradation and synthesis. MicroRNAs (miRNAs) as evolutionary conserved small RNAs, could complementarily bind to their target mRNAs and post-transcriptionally inhibit their translation. Aberrant expression of miRNAs contributes to the development of sarcopenia by regulating the expression of critical genes involved in age-related skeletal muscle mass loss. Here we have a review on the signaling pathways along with the miRNAs controlling their components expression and subsequently we provide a brief overview on the effects of exercise on expression pattern of miRNAs in sarcopenia.

Emerging role of MyomiRs as biomarkers and therapeutic targets in skeletal muscle diseases

Several chronic diseases lead to skeletal muscle loss and a decline in physical performance. MicroRNAs (miRNAs) are small, noncoding RNAs, which have exhibited their role in the development and diseased state of the skeletal muscle. miRNA regulates gene expression by binding to the 3' untranslated region of its target mRNA. Due to the robust stability in biological fluids, miRNAs are ideal candidate as biomarker. These miRNAs provide a novel avenue in strengthening our awareness and knowledge about the factors governing skeletal muscle functions such as development, growth, metabolism, differentiation, and cell proliferation. It also helps in understanding the therapeutic strategies in improving or conserving skeletal muscle health. This review outlines the evidence regarding the present knowledge on the role miRNA as a potential biomarker in skeletal muscle diseases and their exploration might be a unique and potential therapeutic strategy for various skeletal muscle disorders.

Identification of potential microRNAs and KEGG pathways in denervation muscle atrophy based on meta-analysis

The molecular mechanism of muscle atrophy has been studied a lot, but there is no comprehensive analysis focusing on the denervated muscle atrophy. The gene network that controls the development of denervated muscle atrophy needs further elucidation. We examined differentially expressed genes (DEGs) from five denervated muscle atrophy microarray datasets and predicted microRNAs that target these DEGs. We also included the differentially expressed microRNAs datasets of denervated muscle atrophy in previous studies as background information to identify potential key microRNAs. Finally, we compared denervated muscle atrophy with disuse muscle atrophy caused by other reasons, and obtained the Den-genes which only differentially expressed in denervated muscle atrophy. In this meta-analysis, we obtained 429 up-regulated genes, 525 down-regulated genes and a batch of key microRNAs in denervated muscle atrophy. We found eight important microRNA-mRNA interactions (miR-1/Jun, miR-1/Vegfa, miR-497/Vegfa, miR-23a/Vegfa, miR-206/Vegfa, miR-497/Suclg1, miR-27a/Suclg1, miR-27a/Mapk14). The top five KEGG pathways enriched by Den-genes are Insulin signaling pathway, T cell receptor signaling pathway, MAPK signaling pathway, Toll-like receptor signaling pathway and B cell receptor signaling pathway. Our research has delineated the RNA regulatory network of denervated muscle atrophy, and uncovered the specific genes and terms in denervated muscle atrophy.

Functional roles of non-coding RNAs in atrophy

Atrophy is defined as a reduction in cell, organ, or tissue size after reaching their normal mature sizes because of loss of organelles, cytoplasmic compartments, and proteins. This process is also involved in the pathogenesis of human disorders. Inadequate nourishment, poor circulation, inadequate hormonal support, defects in nerve supply of the tissue, disproportionate induction of apoptosis in the tissue, and absence of exercise are some underlying causes of atrophy. Recently, several non-coding RNAs (ncRNAs) have been identified that regulate atrophy, thus participating in the pathobiology of related disorders such as neurodegenerative/ neuromuscular diseases, age-related muscle atrophy, and cardiac tissue atrophy. In the current review, we have focused on two classes of ncRNAs namely long ncRNAs (lncRNAs) and microRNAs (miRNAs) to unravel their participation in atrophy-associated disorders.

The role of physical activity and miRNAs in the vascular aging and cardiac health of dialysis patients

Cardiovascular comorbidities are independent risk factors for mortality in dialysis patients. MicroRNA signaling has an important role in vascular aging and cardiac health, while physical activity is a primary nonpharmacologic treatment for cardiovascular comorbidities in dialysis patients. To identify the relationships between muscle function, miRNA signaling pathways, the presence of vascular calcifications and the severity of cardiovascular comorbidities, we initially enrolled 90 subjects on hemodialysis therapy and collected complete data from 46 subjects. A group of 26 subjects inactiv group (INC) was monitored during 12 weeks of physical inactivity and another group of 20 patients exercise group (EXC) was followed during 12 weeks of intradialytic, moderate intensity, resistance training intervention applied three times per week. In both groups, we assessed the expression levels of myo‐miRNAs, proteins, and muscle function (MF) before and after the 12‐week period. Data on the presence of vascular calcifications and the severity of cardiac comorbidities were collected from the patients’ EuCliD^® records. Using a full structural equitation modelling of the total study sample, we found that the higher the increase in MF was observed in patients, the higher the probability of a decrease in the expression of miR‐206 and TRIM63 and the lower severity of cardiac comorbidities. A reduced structural model in INC patients showed that the higher the decrease in MF, the higher the probability of the presence of calcifications and the higher severity of cardiac comorbidities. In EXC patients, we found that the higher the increase in MF, the lower the probability of higher severity of cardiovascular comorbidities.

Molecular Mechanisms of Muscle Tone Impairment under Conditions of Real and Simulated Space Flight

Kozlovskaya et al. [1] and Grigoriev et al. [2] showed that enormous loss of muscle stiffness (atonia) develops in humans under true (space flight) and simulated microgravity conditions as early as after the first days of exposure. This phenomenon is attributed to the inactivation of slow motor units and called reflectory atonia. However, a lot of evidence indicating that even isolated muscle or a single fiber possesses substantial stiffness was published at the end of the 20th century. This intrinsic stiffness is determined by the active component, i.e. the ability to form actin-myosin cross-bridges during muscle stretch and contraction, as well as by cytoskeletal and extracellular matrix proteins, capable of resisting muscle stretch. The main facts on intrinsic muscle stiffness under conditions of gravitational unloading are considered in this review. The data obtained in studies of humans under dry immersion and rodent hindlimb suspension is analyzed. The results and hypotheses regarding reduced probability of cross-bridge formation in an atrophying muscle due to increased interfilament spacing are described. The evidence of cytoskeletal protein (titin, nebulin, etc.) degradation during gravitational unloading is also discussed. The possible mechanisms underlying structural changes in skeletal muscle collagen and its role in reducing intrinsic muscle stiffness are presented. The molecular mechanisms of changes in intrinsic stiffness during space flight and simulated microgravity are reviewed.

Palmitic Acid Impairs Myogenesis and Alters Temporal Expression of miR-133a and miR-206 in C2C12 Myoblasts

Palmitic acid (PA), a saturated fatty acid enriched in high-fat diet, has been implicated in the development of sarcopenic obesity. Herein, we chose two non-cytotoxic concentrations to better understand how excess PA could impact myotube formation or diameter without inducing cell death. Forty-eight hours of 100 µM PA induced a reduction of myotube diameter and increased the number of type I fibers, which was associated with increased miR-206 expression. Next, C2C12 myotube growth in the presence of PA was evaluated. Compared to control cells, 150 µM PA reduces myoblast proliferation and the expression of MyoD and miR-206 and miR-133a expression, leading to a reduced number and diameter of myotubes. PA (100 µM), despite not affecting proliferation, impairs myotube formation by reducing the expression of Myf5 and miR-206 and decreasing protein synthesis. Interestingly, 100 and 150 µM PA-treated myotubes had a higher number of type II fibers than control cells. In conclusion, PA affects negatively myotube diameter, fusion, and metabolism, which may be related to myomiRs. By providing new insights into the mechanisms by which PA affects negatively skeletal muscle, our data may help in the discovery of new targets to treat sarcopenic obesity.

MIR-190B Alleviates Cell Autophagy and Burn-Induced Skeletal Muscle Wasting via Modulating PHLPP1/Akt/FoxO3A Signaling Pathway

INTRODUCTION

Cell autophagy is an important material recycling process and is involved in regulating many vital activities under both physiological and pathological conditions. However, the mechanism of autophagy regulating burn-induced skeletal muscle wasting still needs to be elucidated.

METHODS

The rat burn model with 30% total body surface area and L6 cell line were used in this study. An immunofluorescence assay was used to detect autophagic levels. MicroRNA array and real-time PCR were employed to measure miR-190b levels, and its influence on PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1) protein translation was estimated using luciferase reporter assay. The expression levels of autophagy-related proteins were analyzed by Western blot. Skeletal muscle wasting was evaluated by the ratio of tibias anterior muscle weight to body weight.

RESULTS

Our study demonstrates that burn injury promotes expression of the autophagy-related proteins light chain 3 (LC3) and Beclin-1, suppresses expression of Akt and Forkhead box O (FoxO) 3a protein phosphorylation, and increases PHLPP1 protein level which is required for Akt dephosphorylation. miR-190b, the regulator of PHLPP1 protein translation, also significantly decreases after burn injury. Ectopic expression of miR-190b in L6 myoblast cell downregulates PHLPP1 protein expression, elevates Akt and FoxO3a phosphorylation, and subsequently reduces cell autophagy. Finally, suppressing autophagy with 3-methyladenine represses the protein expression of LC3 and Beclin-1 and mitigates burn-induced skeletal muscle wasting.

CONCLUSION

Burn injury induced skeletal muscle cell autophagy and subsequently resulted in skeletal muscle wasting via regulating miR-190b/PHLPP1/Akt/FoxO3a signaling pathway.

Serum miR-206 as a biomarker for drug-induced skeletal muscle injury in rats

Creatine kinase (CK) and lactate dehydrogenase (LDH) serve as biomarkers for skeletal muscle injury in preclinical toxicity studies, but have a limitation regarding tissue specificity. Circulating miR-206 was recently reported to be a useful biomarker for skeletal muscle disorders in humans. Here, we sought to determine whether serum miR-206 can be used as a biomarker in preclinical toxicity studies to detect drug-induced skeletal muscle injury with higher sensitivity and specificity than the biomarkers CK, LDH, skeletal troponin I (sTnI), and myosin light chain 3 (Myl3). We established rat models of skeletal muscle injury through treatment with the muscle toxicant 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD) as well as four in-house compounds. We found that serum miR-206 levels significantly increased after treatment with TMPD, and tended to be higher in rats treated with in-house compounds than in control rats. ROC analysis revealed that the specificity of serum miR-206 for detection of skeletal muscle injury was higher compared with those of other markers. Further, serum miR-206 levels were unchanged in rats with isoproterenol-induced cardiotoxicity. These findings demonstrate that serum miR-206 may serve as a highly specific biomarker for preclinical analysis of rats with drug-induced skeletal muscle injuries.

Circulating 20S proteasome for assessing protein energy wasting syndrome in hemodialysis patients

Protein energy wasting (PEW) including muscle atrophy is a common complication in chronic hemodialysis patients. The ubiquitin proteasome system (UPS) is the main proteolytic system causing muscle atrophy in chronic kidney disease and proteasome 20S is the catalytic component of the UPS. Circulating proteasome 20S (c20S proteasome) is present in the blood and its level is related to disease severity and prognosis in several disorders. We hypothesized that c20S proteasome could be related with muscle mass, other PEW criteria and their evolution in hemodialysis patients. Stable hemodialysis patients treated at our center for more than 3 months were followed over 2 years. C20S proteasome assay was performed at baseline. Biological and clinical data were collected, muscle mass was assessed by multi-frequency bio-impedancemetry, and nutritional scores were calculated at baseline, 1 year and 2 years. Hospitalizations and mortality data were collected over the 2 years. Forty-nine patients were included. At baseline, the c20S proteasome level was 0.40[0.26–0.55] μg/ml. Low muscle mass as defined by a lean tissue index (LTI) < 10th in accordance with the International Society of Renal Nutrition and Metabolism guidelines was observed in 36% and PEW in 62%. Increased c20S proteasome levels were related with LTI at baseline (R = 0.43, p = 0.004) and with its 2 year-variation (R = -0.56, p = 0.003). Two-year survival rate was not different between higher and lower c20S proteasome values (78.9 vs 78.4%, p = 0.98 log-rank test). C20S proteasome is not a good marker for assessing nutritional status in hemodialysis patients and predicting patient outcomes.

Identification of a potential non-coding RNA biomarker signature for amyotrophic lateral sclerosis

Objective biomarkers for the clinically heterogeneous adult-onset neurodegenerative disorder amyotrophic lateral sclerosis are crucial to facilitate assessing emerging therapeutics and improve the diagnostic pathway in what is a clinically heterogeneous syndrome. With non-coding RNA transcripts including microRNA, piwi-RNA and transfer RNA present in human biofluids, we sought to identify whether non-coding RNA in serum could be biomarkers for amyotrophic lateral sclerosis. Serum samples from our Oxford Study for Biomarkers in motor neurone disease/amyotrophic lateral sclerosis discovery cohort of amyotrophic lateral sclerosis patients (n = 48), disease mimics (n = 16) and age- and sex-matched healthy controls (n = 24) were profiled for non-coding RNA expression using RNA-sequencing, which showed a wide range of non-coding RNA to be dysregulated. We confirmed significant alterations with reverse transcription-quantitative PCR in the expression of hsa-miR-16-5p, hsa-miR-21-5p, hsa-miR-92a-3p, hsa-piR-33151, TRV-AAC4-1.1 and TRA-AGC6-1.1. Furthermore, hsa-miR-206, a previously identified amyotrophic lateral sclerosis biomarker, showed a binary-like pattern of expression in our samples. Using the expression of these non-coding RNA, we were able to discriminate amyotrophic lateral sclerosis samples from healthy controls in our discovery cohort using a random forest analysis with 93.7% accuracy with promise in predicting progression rate of patients. Importantly, cross-validation of this novel signature using a new geographically distinct cohort of samples from the United Kingdom and Germany with both amyotrophic lateral sclerosis and control samples (n = 156) yielded an accuracy of 73.9%. The high prediction accuracy of this non-coding RNA-based biomarker signature, even across heterogeneous cohorts, demonstrates the strength of our approach as a novel platform to identify and stratify amyotrophic lateral sclerosis patients.

Protein Nutritional Support: The Classical and Potential New Mechanisms in the Prevention and Therapy of Sarcopenia

Sarcopenia commonly occurs in the elderly and patients with wasting diseases. The main reason is an imbalance in protein metabolism (protein degradation exceeding protein synthesis). It causes a serious decline in muscle strength and motion ability, even leading to long-term bed rest. Recent studies indicate that nutritional support is beneficial for ameliorating sarcopenia and restoring muscle function. This review will summarize the classical mechanisms of protein nutritional support for alleviating sarcopenia, such as modulating the ubiquitin-proteasome system, oxidative response, and cell autophagy, as well as the potential new mechanisms, including altering miRNA profiles and gut microbiota. In addition, the clinical application and outcome of protein nutritional support in the elderly and patients with wasting diseases are also introduced. Protein nutritional support is expected to provide new approaches for the prevention and adjuvant therapy of sarcopenia.

Non-Coding RNA Regulates the Myogenesis of Skeletal Muscle Satellite Cells, Injury Repair and Diseases

Skeletal muscle myogenesis and injury-induced muscle regeneration contribute to muscle formation and maintenance. As myogenic stem cells, skeletal muscle satellite cells have the ability to proliferate, differentiate and self-renew, and are involved in muscle formation and muscle injury repair. Accumulating evidence suggests that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), are widely involved in the regulation of gene expression during skeletal muscle myogenesis, and their abnormal expression is associated with a variety of muscle diseases. From the perspective of the molecular mechanism and mode of action of ncRNAs in myogenesis, this review aims to summarize the role of ncRNAs in skeletal muscle satellite cells’ myogenic differentiation and in muscle disease, and systematically analyze the mechanism of ncRNAs in skeletal muscle development. This work will systematically summarize the role of ncRNAs in myogenesis and provide reference targets for the treatment of various muscle diseases, such as muscle dystrophy, atrophy and aberrant hypertrophy.

Differential MicroRNA expression following head-down tilt bed rest: implications for cardiovascular responses to microgravity

Head-down tilt bedrest (HDBR), an analog of spaceflight, elicits changes in cardiovascular function that adversely affect astronaut performance. It is therefore fundamental to elucidate the molecular regulators of these changes. Study aim was to determine if cardiovascular-related circulating microRNA (miRNA) are altered following HDBR and if they relate to changes in cardiac function and peak aerobic capacity. Eleven participants completed 30-days HDBR at an ambient CO2 of 0.5% (replicate the in-flight CO2 levels). Blood samples were obtained 3 days (BDC-3) prior to and immediately (R + 0) following HDBR. 44-targeted circulating miRNAs (c-miRNA) identified from published roles in cardiovascular structure/function were analyzed via RT-qPCR. Resting stroke volume was evaluated via ultrasonography. Peak oxygen uptake ( V ˙ O 2 peak ) was determined using a graded exercise test on an electronically braked cycle ergometer. Ten cardiovascular-related miRNA were significantly increased following HDBR. The differentially expressed c-miRNA were grouped into clusters according to their expression profile. Cluster A included c-miRNA that have been identified as regulators of cardiac function and hypertrophy (c-miRNA-133), atrial fibrillation and mitochondrial function (c-miRNA-1), skeletal muscle atrophy (c-miRNA-1), and vascular control (c-miRNA-155). Cluster B contained c-miRNA identified as regulators of cardiac hypertrophy (c-miRNA-30, -15), fibrosis (c-miRNA-22, -18), mitochondrial function (miRNA-181), and aerobic capacity (c-miRNA-20a). Following HDBR resting stroke volume was decreased and correlated with changes in c-miRNA-378a and -18a. V ˙ O 2 peak was decreased and correlated with changes c-miRNA-133. In conclusion, we found that HDBR induced a distinct and specific cardiovascular-related miRNA response, which were associated with changes in cardiac function and peak aerobic capacity.

An Overview of MicroRNAs as Biomarkers of ALS

Amyotrophic lateral sclerosis (ALS; MND, motor neuron disease) is a debilitating neurodegenerative disease affecting 4.5 per 100,000 people per year around the world. There is currently no cure for this disease, and its causes are relatively unknown. Diagnosis is based on a battery of clinical tests up to a year after symptom onset, with no robust markers of diagnosis or disease progression currently identified. A major thrust of current research is to identify potential non-invasive markers (“biomarkers”) in body fluids such as blood and/or cerebrospinal fluid (CSF) to use for diagnostic or prognostic purposes. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), are found at detectable and stable levels in blood and other bodily fluids. Specific ncRNAs can vary in levels between ALS patients and non-ALS controls without the disease. In this review, we will provide an overview of early findings, demonstrate the potential of this new class as biomarkers, and discuss future challenges and opportunities taking this forward to help patients with ALS.

Formoterol treatment prevents the effects of endotoxin on muscle TNF/NF-kB, Akt/mTOR, and proteolytic pathways in a rat model. Role of IGF-I and miRNA 29b

Inflammatory diseases are associated with muscle wasting as a result of an increase in proteolysis. The purpose of this study was to elucidate whether administration of a β2 adrenergic agonist, formoterol, was able to prevent the acute effects of sepsis induced by liposaccharide (LPS) injection on rat gastrocnemius muscle and to evaluate the possible roles of corticosterone, IGF-I, miR-23a, and miR-29b. For this purpose, male Wistar rats were injected with LPS and/or formoterol. Formoterol treatment decreased LPS-induced increase in serum corticosterone, TNFα upregulation, and NF-κB(p65) and Forkhead box protein O1 activation in the gastrocnemius. Atrogin-1, muscle RING-finger protein-1, microtubule-associated protein-1 light chain 3b (LC3b), and the lipidation of LC3b-I to LC3b-II were increased by LPS, and formoterol blocked these effects. Serum IGF-I and its mRNA levels in the gastrocnemius were decreased, whereas mecano growth factor and IGF binding protein 3 mRNA levels were increased in the rats injected with LPS but not in the rats that received LPS and formoterol. Similarly, LPS decreased Akt and mammalian target of rapamycin phosphorylation, and formoterol blocked these decreases. Finally, miR-29b expression in the gastrocnemius was upregulated by endotoxin injection, whereas miR-23a was not significantly different. Formoterol treatment did not significantly modify LPS-induced increase in muscle miR-29b. Furthermore, in control rats formoterol increased the expression of this miRNA. We conclude that formoterol decreases endotoxin-induced inflammation and proteolysis in rat skeletal muscle. Those responses can be a direct effect of β2 adrenergic receptor stimulation or/and of blocking the effects of LPS on corticosterone and IGF-I. Muscle miR-23a and -29b do not seem to play an important role in those responses.

miR-30 Family: A Promising Regulator in Development and Disease

MicroRNAs (miRNAs) are small noncoding RNAs that negatively regulate posttranscriptional expression of target genes. Accumulating evidences have demonstrated that the miR-30 family, as a member of microRNAs, played a crucial regulating role in the development of tissues and organs and the pathogenesis of clinical diseases, which indicated that it may be a promising regulator in development and disease. This review aims to clarify the current progress on the regulating role of miR-30 family in tissues and organs development and related disease and highlight their research prospective in the future.

Noncoding RNAs in Muscle Atrophy

Denervation, disuse, fasting, and various diseases could induce skeletal muscle atrophy, which results in the decline of life quality and increase of the mortality risk for patients. Noncoding RNAs (ncRNAs) are implicated important in regulating gene expression. Thus, ncRNAs, especially microRNAs and long noncoding RNAs (lncRNAs), have gained widespread attention as crucial players in numerous physiological and pathological processes, including skeletal muscle atrophy. In this review, we comprehensively described the potential of circulating microRNAs as biomarkers, summarized the profiling of microRNAs and lncRNAs in atrophying muscles, as well as discussed the effects and underlying mechanisms of microRNA machinery proteins, microRNAs, and lncRNAs in skeletal muscle atrophy. Considering the large quantity and variety of ncRNAs, the understanding of ncRNAs in muscle atrophy is still very limited. Future studies are needed to elucidate the possibility of ncRNAs as diagnosis biomarkers and therapeutic targets in muscle atrophy.