Skeletal Muscle Gene Expression Research Articles

Beneficial effects of MgSO4 on TFAM, UPC3 and FNDC5 mRNA expressions in skeletal muscle of type 2 diabetic rats: a possible mechanism to improve insulin resistance

Hypomagnesemia has been associated with development of type 2 diabetesmellitus (T2DM) and its complications. Irisin has beneficial effects on glucose uptake and improves hepatic glucose and lipid metabolism. In this study, we aimed to evaluate the effects of long-term treatment of MgSO4 and insulin on insulin resistance, dyslipidemia, serum and hepatic irisin levels, skeletal muscle gene expression of fibronectin type III domain-containing protein 5 (FNDC5), mitochondrial transcription factor A (TFAM) and mitochondrial uncoupling protein 3 (UCP3) in T2DM rats. Twenty-four rats were divided into four groups: Control group, diabetic control (DC) using a high-fat diet + streptozotocin, insulin-treated diabetic group (DC + Ins), MgSO4-treated diabetic group (DC + Mg). At the end of therapies, serum concentrations of FBG, TG, insulin, Ox-LDL, along with serum and hepatic irisin levels were measured. FNDC5, TFAM, and UCP3 mRNA expressions were measured in the skeletal muscle by Real-time PCR. In comparison with DC group, MgSO4 therapy resulted in decreased FBG, TG, Ox-LDL, improved serum insulin and irisin levels, and increased mRNA expressions of FNDC5, UCP3 and TFAM. Insulin therapy significantly decreased FBG, Ox-LDL, FNDC5 and serum irisin levels compared with the control group. While, insulin therapy markedly increased TFAM and UCP3 compared with the DC group. In conclusion, MgSO4 can improve insulin resistance and hyperlipidemia partly through decreasing Ox-LDL, increasing serum irisin levels as well as increasing FNDC5, TFAM, and UCP3 mRNA expressions in T2DM rats. These findings can be considered in the management of diabetes treatment.

Growth performance, carcass traits, muscle fiber characteristics and skeletal muscle mRNA abundance in hair lambs supplemented with ferulic acid.

Ferulic acid (FA) is a phytochemical with various bioactive properties. It has recently been proposed that due to its phytogenic action it can be used as an alternative growth promoter additive to synthetic compounds. The objective of the present study was to evaluate the growth performance, carcass traits, fiber characterization and skeletal muscle gene expression on hair-lambs supplemented with two doses of FA. Thirty-two male lambs (n = 8 per treatment) were individually housed during a 32 d feeding trial to evaluate the effect of FA (300 and 600 mg d−1) or zilpaterol hydrochloride (ZH; 6 mg d−1) on growth performance, and then slaughtered to evaluate the effects on carcass traits, and muscle fibers morphometry from Longissimus thoracis (LT) and mRNA abundance of β2-adrenergic receptor (β2-AR), MHC-I, MHC-IIX and IGF-I genes. FA increased final weight and average daily gain with respect to non-supplemented animals (p < 0.05). The ZH supplementation increased LT muscle area, with respect to FA doses and control (p < 0.05). Cross-sectional area (CSA) of oxidative fibers was larger with FA doses and ZH (p < 0.05). Feeding ZH increased mRNA abundance for β2-AR compared to FA and control (p < 0.05), and expression of MHC-I was affected by FA doses and ZH (p < 0.05). Overall, FA supplementation of male hair lambs enhanced productive variables due to skeletal muscle hypertrophy caused by MHC-I up-regulation. Results suggest that FA has the potential like a growth promoter in lambs.

Pre-Operative Physical Function Predicts Post-Operative Skeletal Muscle Gene Expression in Old Mice

In older adults, pre-operative physical function predicts post-operative outcomes. The biological mechanisms underlying vulnerability to physical decline remain poorly understood. Using a mouse model of laparotomy, we sought to identify biological correlates of post-operative function. 24-month-old male C57BL/6N mice were categorized as high functioning (HF) or low functioning (LF) based on pre-operative performance on the accelerating rotarod. On post-operative days (POD) 2 and 4, LF mice had lower rotarod latency to fall times than HF mice did. Forelimb grip strength was reduced after laparotomy in both HF and LF groups on POD 1 and 3 and did not differ significantly between these groups. Whole transcriptome sequencing analysis (RNAseq) of soleus muscles collected on POD 5 showed 224 and 228 differentially expressed genes (DEGs) for HF and LF, respectively, compared to their respective controls. Only 21 DEGs were observed in both groups, including Pparα, Fst and Pla2g15. Such changes may be hallmarks of the post-surgical response in aging. Pathway analysis of DEGs using Ingenuity Pathway Analysis software (Qiagen) revealed one pathway common to HF and LF (osteoarthritis) whereas activation of GP6 signaling and apoptosis signaling was observed in HF and inhibition of PPARα/RXR activation and PPARα signaling was noted in LF. We conclude that pre-operative performance on the accelerating rotarod correlates with differences in skeletal muscle gene expression, which may contribute to the differences in functional outcomes post-operatively in HF and LF mice. Further studies are needed to delineate the roles of these signaling pathways in physical resilience to surgery.

Physiological Doses of Hydroxytyrosol Modulate Gene Expression in Skeletal Muscle of Exercised Rats.

We tested whether physiological doses of hydroxytyrosol (HT) may alter the mRNA transcription of key metabolic genes in exercised skeletal muscle. Two groups of exercise-trained Wistar rats, HTlow and HTmid, were supplemented with 0.31 and 4.61 mg/kg/d of HT, respectively, for 10 weeks. Another two groups of rats were not supplemented with HT; one remained sedentary and the other one was exercised. After the experimental period, the soleus muscle was removed for qRT-PCR and western blot analysis. The consumption of 4.61 mg/kg/d of HT during exercise increased the mRNA expression of important metabolic proteins. Specifically, 4.61 mg/kg/d of HT may upregulate long-chain fatty acid oxidation, lactate, and glucose oxidation as well as mitochondrial Krebs cycle in trained skeletal muscle. However, a 4.61 mg/kg/d of HT may alter protein translation, as in spite of the increment showed by CD36 and GLUT4 at the mRNA level this was not translated to higher protein content.

The ELSA trial: single versus combinatory effects of non-prohibited beta-2 agonists on skeletal muscle metabolism, cardio-pulmonary function and endurance performance\u2014study protocol for a randomized 4-way balanced cross-over trial

BackgroundAsthma and/or airway hyper-responsiveness (AHR) are common in elite endurance athletes with a high prevalence rate of beta-2 adrenoreceptor (beta-2) agonists use. Nevertheless, there are data on dose-dependent ergogenic effects of beta-2 agonists suggesting increased muscle strength, endurance and neuromuscular performance. Therefore, most beta-2 agonists belong to the World Anti Doping Agency (WADA) list of prohibited substances and it is tempting to speculate that illegitimate use of beta-2 agonists might be a common practice to boost performance in competitive sports. It is currently unknown whether or not inhaled beta-2 agonists enhance performance by stimulatory effects in skeletal and cardiac muscle.MethodsThe ELSA trial is a double-blinded, placebo-controlled, randomized, balanced, four-way cross-over study. Study participants (n=24, 12 ♀, 12 ♂) complete four study arms (i.e. periods with treatment A, placebo; B, salbutamol; C, formoterol; D, formoterol + salbutamol) in random order after an initial preliminary testing session. Participants inhale the study medication 20 min before the 10-min time trial (TT; exercise performance test), where participants cycle 10 min at the highest possible workload. Cardiac output is measured continuously. A skeletal muscle biopsy is collected 3 h after the TT. Study endpoints include measures of skeletal muscle expression of nuclear receptors, hormones and cytokine levels, urinary and plasma concentrations of salbutamol and formoterol, circulating cardiac markers, cardiopulmonary function and exercise performance (average power and peak power during the TT). Blood and urine are collected and respiratory testing is performed 24 h post TT.Summary/conclusionsThis clinical trial evaluates the potential performance-enhancing effects of non-prohibited, not medically indicated inhaled short- and long-acting beta-2 agonists on skeletal muscle gene expression, endocrine regulation, cardiac biomarkers, cardiopulmonary function and acute endurance exercise performance. These data will be used by WADA to adapt the annually published list of prohibited substances (WADA 2021) and will be published in scientific journals.Trial registrationThe trial is registered at the European Clinical Trials Database (Eudra CT) with the number: 2015-005598-19 as well as at the German register for clinical studies (DRKS number 00010574).

Do skeletal muscle composition and gene expression as well as acute exercise-induced serum adaptations in older adults depend on fitness status?

BackgroundInactive physical behavior among the elderly is one risk factor for cardiovascular disease, immobility and increased all-cause mortality. We aimed to answer the question whether or not circulating and skeletal muscle biomarkers are differentially expressed depending on fitness status in a group of elderly individuals.MethodsTwenty-eight elderly individuals (73.36 ± 5.46 years) participated in this exploratory study after participating as part of the multinational SITLESS-clinical trial (implementation of self-management and exercise programs over 16 weeks). A cardiopulmonary exercise test (CPX) and resting skeletal muscle biopsy were performed to determine individual physiological performance capacity. Participants were categorized into a high physical fitness group (HPF) and a low physical fitness group (LPF) depending on peak oxygen uptake (VO2peak). Serum blood samples were taken before (pre) and after (post) CPX and were examined regarding serum BDNF, HSP70, Kynurenine, Irisin and Il-6 concentrations. Skeletal muscle tissue was analyzed by silver staining to determine the myosin heavy chain (MyHC) composition and selected genes by qRT-PCR.ResultsHPF showed lower body weight and body fat, while skeletal muscle mass and oxygen uptake at the first ventilatory threshold (VO2T1) did not differ between groups. There were positive associations between VO2peak and VO2VT1 in HPF and LPF. MyHC isoform quantification revealed no differences between groups. qRT-PCR showed higher expression of BDNF and BRCA1 in LPF skeletal muscle while there were no differences in other examined genes regarding energy metabolism. Basal serum concentrations of Irisin were higher in HPF compared to LPF with a trend towards higher values in BDNF and HSP70 in HPF. Increases in Il-6 in both groups were observed post.ConclusionsAlthough no association between muscle composition/VO2peak with fitness status in older people was detected, higher basal Irisin serum levels in HPF revealed slightly beneficial molecular serum and muscle adaptations.Trial registrationClinicalTrials.gov, NCT02629666. Registered 19 November 2015.

Beta-adrenergic agonists and heat stress impact skeletal muscle gene expression and mitochondrial function in beef cattle

Beta-adrenergic agonists and heat stress impact skeletal muscle gene expression and mitochondrial function in beef cattle

Effects of Training Status and Exercise Mode on Global Gene Expression in Skeletal Muscle.

The aim of this study was to investigate differences in skeletal muscle gene expression of highly trained endurance and strength athletes in comparison to untrained individuals at rest and in response to either an acute bout of endurance or strength exercise. Endurance (ET, n = 8, VO2max 67 ± 9 mL/kg/min) and strength athletes (ST, n = 8, 5.8 ± 3.0 training years) as well as untrained controls (E-UT and S-UT, each n = 8) performed an acute endurance or strength exercise test. One day before testing (Pre), 30 min (30′Post) and 3 h (180′Post) afterwards, a skeletal muscle biopsy was obtained from the m. vastus lateralis. Skeletal muscle mRNA was isolated and analyzed by Affymetrix-microarray technology. Pathway analyses were performed to evaluate the effects of training status (trained vs. untrained) and exercise mode-specific (ET vs. ST) transcriptional responses. Differences in global skeletal muscle gene expression between trained and untrained were smaller compared to differences in exercise mode. Maximum differences between ET and ST were found between Pre and 180′Post. Pathway analyses showed increased expression of exercise-related genes, such as nuclear transcription factors (NR4A family), metabolism and vascularization (PGC1-α and VEGF-A), and muscle growth/structure (myostatin, IRS1/2 and HIF1-α. The most upregulated genes in response to acute endurance or strength exercise were the NR4A genes (NR4A1, NR4A2, NR4A3). The mode of acute exercise had a significant effect on transcriptional regulation Pre vs. 180′Post. In contrast, the effect of training status on human skeletal muscle gene expression profiles was negligible compared to strength or endurance specialization. The highest variability in gene expression, especially for the NR4A-family, was observed in trained individuals at 180′Post. Assessment of these receptors might be suitable to obtain a deeper understanding of skeletal muscle adaptive processes to develop optimized training strategies.

Non-cell autonomous mechanisms control mitochondrial gene dysregulation in polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with insulin resistance and impaired energy metabolism in skeletal muscle, the aetiology of which is currently unclear. Here, we mapped the gene expression profile of skeletal muscle from women with PCOS and determined if cultured primary myotubes retain the gene expression signature of PCOS in vivo. Transcriptomic analysis of vastus lateralis biopsies collected from PCOS women showed lower expression of genes associated with mitochondrial function, while the expression of genes associated with the extracellular matrix was higher compared to controls. Altered skeletal muscle mRNA expression of mitochondrial-associated genes in PCOS was associated with lower protein expression of mitochondrial complex II–V, but not complex I, with no difference in mitochondrial DNA content. Transcriptomic analysis of primary myotube cultures established from biopsies did not display any differentially expressed genes between controls and PCOS. Comparison of gene expression profiles in skeletal muscle biopsies and primary myotube cultures showed lower expression of mitochondrial and energy metabolism-related genes in vitro, irrespective of the group. Together, our results show that the altered mitochondrial-associated gene expression in skeletal muscle in PCOS is not preserved in cultured myotubes, indicating that the in vivo extracellular milieu, rather than genetic or epigenetic factors, may drive this alteration. Dysregulation of mitochondrial-associated genes in skeletal muscle by extracellular factors may contribute to the impaired energy metabolism associated with PCOS.

Impaired Muscle Mitochondrial Function in Familial Partial Lipodystrophy.

Familial partial lipodystrophy (FPL), Dunnigan variety is characterized by skeletal muscle hypertrophy and insulin resistance besides fat loss from the extremities. The cause for the muscle hypertrophy and its functional consequences is not known. To compare muscle strength and endurance, besides muscle protein synthesis rate between subjects with FPL and matched controls (n = 6 in each group). In addition, we studied skeletal muscle mitochondrial function and gene expression pattern to help understand the mechanisms for the observed differences. Body composition by dual-energy X-ray absorptiometry, insulin sensitivity by minimal modelling, assessment of peak muscle strength and fatigue, skeletal muscle biopsy and calculation of muscle protein synthesis rate, mitochondrial respirometry, skeletal muscle transcriptome, proteome, and gene set enrichment analysis. Despite increased muscularity, FPL subjects did not demonstrate increased muscle strength but had earlier fatigue on chest press exercise. Decreased mitochondrial state 3 respiration in the presence of fatty acid substrate was noted, concurrent to elevated muscle lactate and decreased long-chain acylcarnitine. Based on gene transcriptome, there was significant downregulation of many critical metabolic pathways involved in mitochondrial biogenesis and function. Moreover, the overall pattern of gene expression was indicative of accelerated aging in FPL subjects. A lower muscle protein synthesis and downregulation of gene transcripts involved in muscle protein catabolism was observed. Increased muscularity in FPL is not due to increased muscle protein synthesis and is likely due to reduced muscle protein degradation. Impaired mitochondrial function and altered gene expression likely explain the metabolic abnormalities and skeletal muscle dysfunction in FPL subjects.

Research Progress on the Effect of Exercise Rehabilitation on Functional Level and Physical Fitness

The essence of rehabilitation is the recovery and reconstruction of body function,and cardiopulmonary function is not only the core of body function, but also the core element of physical fitness. As one of the important interventions of modern rehabilitation treatment, exercise rehabilitation is the fundamental way to improve the level of body function, and plays a key role in the process of disease rehabilitation. The forms of exercise rehabilitation are widely used in clinic including aerobic exercise, high intensity interval training,muscle strength training, and traditional exercise and so on. Different forms of exercise rehabilitation can improve the level of body function and promote physical fitness in varying degrees. The main functions include regulating blood pressure, blood lipids and blood glucose, improving balance and muscle strength,increasing bone mineral density, enhancing cardiorespiratory fitness and walking ability, improving cognitive and memory functions,regulating emotions, promoting mental health, and improving the quality of life, etc., so as to achieve the goal of shortening the process of disease rehabilitation and improving its curative effect. However, there are differences in the dimensions and degrees of the influence of different forms of exercise rehabilitation on functional level and physical fitness. Among them, aerobic exercise mainly has a positive impact on cardiorespiratory fitness, glucose and lipid metabolism,emotional regulation, cognition and memory and other dimensions, and its mechanism involves the increase of endogenous cannabinoid in circulation and the integrity of white matter fibers and so on. Compared with moderate intensity aerobic exercise, high intensity interval training can improve cardiorespiratory fitness and cardiac metabolic health more timely and its mechanism involves the increase of muscle mitochondrial production capacity and the regulation of partial gene expression in skeletal muscle. Muscle strength training can improve blood glucose control and reduce the risk of chronic diseases and death by increasing muscle strength and endurance, especially for postmenopausal women and overweight/obese elderly. Traditional exercises, such as Taijiquan and Baduanjin, are important interventions of rehabilitation in traditional Chinese medicine, which have definite effect in improving balance, cognition and memory, and are worthy of clinical promotion and application. At present, how to choose the best form of exercise rehabilitation and the best course of treatment for people with different functional disorders and different disease status remains to be further clarified by follow-up clinical and basic research.

Systemic delivery of a DUX4-targeting antisense oligonucleotide to treat facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most prevalent skeletal muscle dystrophies. Skeletal muscle pathology in individuals with FSHD is caused by inappropriate expression of the transcription factor DUX4, which activates different myotoxic pathways. At the moment there is no molecular therapy that can delay or prevent skeletal muscle wasting in FSHD. In this study, a systemically delivered antisense oligonucleotide (ASO) targeting the DUX4 transcript was tested in vivo in ACTA1-MCM;FLExDUX4 mice that express DUX4 in skeletal muscles. We show that the DUX4 ASO was well tolerated and repressed the DUX4 transcript, DUX4 protein, and mouse DUX4 target gene expression in skeletal muscles. In addition, the DUX4 ASO alleviated the severity of skeletal muscle pathology and partially prevented the dysregulation of inflammatory and extracellular matrix genes. DUX4 ASO-treated ACTA1-MCM;FLExDUX4 mice performed better on a treadmill; however, the hanging grid and four-limb grip strength tests were not improved compared to control ASO-treated ACTA1-MCM;FLExDUX4 mice. This study shows that systemic delivery of ASOs targeting DUX4 is a promising therapeutic strategy for FSHD and strategies that further improve the ASO efficacy in skeletal muscle are warranted.

A Modular Mathematical Model of Exercise-Induced Changes in Metabolism, Signaling, and Gene Expression in Human Skeletal Muscle.

Skeletal muscle is the principal contributor to exercise-induced changes in human metabolism. Strikingly, although it has been demonstrated that a lot of metabolites accumulating in blood and human skeletal muscle during an exercise activate different signaling pathways and induce the expression of many genes in working muscle fibres, the systematic understanding of signaling–metabolic pathway interrelations with downstream genetic regulation in the skeletal muscle is still elusive. Herein, a physiologically based computational model of skeletal muscle comprising energy metabolism, Ca2+, and AMPK (AMP-dependent protein kinase) signaling pathways and the expression regulation of genes with early and delayed responses was developed based on a modular modeling approach and included 171 differential equations and more than 640 parameters. The integrated modular model validated on diverse including original experimental data and different exercise modes provides a comprehensive in silico platform in order to decipher and track cause–effect relationships between metabolic, signaling, and gene expression levels in skeletal muscle.

The Effect of Acute and Chronic Thermotherapy on Type 2 Diabetic Skeletal Muscle Gene Expression and Inflammatory Markers

Background: Type 2 diabetes (T2D) is a chronic illness associated with resistance to or defective insulin secretion. This study investigates the effects of thermotherapy on cell viability, gene expression and inflammation in skeletal muscle cell lines. Methods: Healthy and T2D human skeletal muscle cell lines (HSMM and D-HSMM, respectively) were subjected to acute or chronic thermo-therapy (AT or CT, respectively). CT consisted of a 30 min exposure to 40 °C, three times a week for three weeks; AT was a one-time exposure. Results: A significant decrease in D-HSMM cell viability percentage followed AT; however, no significant change occurred in CT. HSMM yielded the highest elevations of genes following CT. In D-HSMM, both treatments yielded gene upregulation. Both treatments significantly down-regulated IL-1β, IL-6, IL-10 and TNF-α in HSMM. AT significantly decreased IL-1β, IL-6 and upregulated IL-10 and TNF-α levels in D-HSMM, while CT yielded a reduction in IL-4, TNF-α and an upregulation of IL-6 and IL-10. Conclusions: An increase in gene expression indicates actin activity and cellular responses, suggesting an increase in transcriptional regulation. The upregulation of IL-6 and IL-10 in D-HSMM negatively correlated with a decrease in TNF-α and IL-1β, indicating improved adverse inflammatory effects associated with the disease.

AMP-Activated Protein Kinase Abundance and Activation is increased with the β-Adrenergic agonist Zilpaterol Hydrochloride in Muscle from Feedlot Cattle

The objective of this research was to evaluate the effect of Zilpaterol Hydrochloride (ZH) on myogenic or adipogenic gene and protein expression in skeletal muscle. Two feeding trials and one cell culture experiments were conducted. Semimembranosus muscle tissue was collected from steers that had been fed a diet containing 8.3 mg of ZH/kg DM for the last 0 or 20 d of the finishing period with a 3 d withdrawal period. To test the mode of action an in vitromodel was used with, isolated bovine satellite cells isolated from muscle tissue. Real Time-QPCR (RTQPCR) was used to measure the relative mRNA abundance of Adenosine Monophosphate Protein Kinase α (AMPK), Myosin Heavy Chain (MHC) I, MHCIIA, MHCIIX, Insulin-like Growth Factor I (IGF-I), β-adrenergic receptor (βAR) 1 and 2, peroxisome proliferator-activated receptor gamma (PPARγ), and Stearoyl-CoA Desaturase (SCD). Western blotting was used to measure the relative protein abundance of AMPK and Phosphorylated-AMPK (pAMPK). No differences were detected in relative mRNA abundance of AMPK, MHCIIA, IGF-I, βAR1 and βAR2. However, MHCI, SCD, and PPARγ mRNA expression was decreased and MHCIIX mRNA increased from ZH fed cattle compared to non-ZH. For one experiment, AMPK protein expression increased, while in another experiment, AMPK phosphorylation increased with ZH fed animals. The increase in MHCIIX mRNA with ZH fed cattle indicated the start of a fiber type shift towards larger diameter fibers. This shift may have been due to increased expression and phosphorylation of AMPK. These data suggest that the shift increase in MHCIIX was likely due to the ZH administration.

Effect of repeated bouts of fasting and refeeding on body composition and proteolysis gene expression in skeletal muscles and liver of C57BL/6J mice

Effect of repeated bouts of fasting and refeeding on body composition and proteolysis gene expression in skeletal muscles and liver of C57BL/6J mice

Retinoic acid exerts sexually dimorphic effects on muscle energy metabolism and function

The retinol dehydrogenase Rdh10 catalyzes the rate-limiting reaction that converts retinol into retinoic acid (RA), an autacoid that regulates energy balance and reduces adiposity. Skeletal muscle contributes to preventing adiposity, by consuming nearly half the energy of a typical human. We report sexually dimorphic differences in energy metabolism and muscle function in Rdh10+/− mice. Relative to wild-type (WT) controls, Rdh10+/− males fed a high-fat diet decrease reliance on fatty-acid oxidation and experience glucose intolerance and insulin resistance. Running endurance decreases 40%. Rdh10+/− females fed this diet increase fatty acid oxidation and experience neither glucose intolerance nor insulin resistance. Running endurance increases 220%. We therefore assessed RA function in the mixed-fiber type gastrocnemius muscles (GM), which contribute to running, rather than standing, and are similar to human GM. RA levels in Rdh10+/− male GM decrease 38% relative to WT. Rdh10+/− male GM increase expression of Myog and reduce Eif6 mRNAs, which reduce and enhance running endurance, respectively. Cox5A, complex IV activity, and ATP decrease. Increased centralized nuclei reveal existence of muscle malady and/or repair in GM fibers. Comparatively, RA in Rdh10+/− female GM decreases by less than half the male decrease, from a more modest decrease in Rdh10 and an increase in the estrogen-induced retinol dehydrogenase Dhrs9. Myog mRNA decreases. Cox5A, complex IV activity, and ATP increase. Centralized GM nuclei do not increase. We conclude that Rdh10/RA affects whole body energy use and insulin resistance partially through sexual dimorphic effects on skeletal muscle gene expression, structure, and mitochondria activity.

Altered skeletal muscle metabolic pathways, age, systemic inflammation, and low cardiorespiratory fitness associate with improvements in disease activity following high-intensity interval training in persons with rheumatoid arthritis

BackgroundExercise training, including high-intensity interval training (HIIT), improves rheumatoid arthritis (RA) inflammatory disease activity via unclear mechanisms. Because exercise requires skeletal muscle, skeletal muscle molecular pathways may contribute. The purpose of this study was to identify connections between skeletal muscle molecular pathways, RA disease activity, and RA disease activity improvements following HIIT.MethodsRA disease activity assessments and vastus lateralis skeletal muscle biopsies were performed in two separate cohorts of persons with established, seropositive, and/or erosive RA. Body composition and objective physical activity assessments were also performed in both the cross-sectional cohort and the longitudinal group before and after 10 weeks of HIIT. Baseline clinical assessments and muscle RNA gene expression were correlated with RA disease activity score in 28 joints (DAS-28) and DAS-28 improvements following HIIT. Skeletal muscle gene expression changes with HIIT were evaluated using analysis of covariance and biological pathway analysis.ResultsRA inflammatory disease activity was associated with greater amounts of intramuscular adiposity and less vigorous aerobic exercise (both p < 0.05). HIIT-induced disease activity improvements were greatest in those with an older age, elevated erythrocyte sedimentation rate, low cardiorespiratory fitness, and a skeletal muscle molecular profile indicative of altered metabolic pathways (p < 0.05 for all). Specifically, disease activity improvements were linked to baseline expression of RA skeletal muscle genes with cellular functions to (1) increase amino acid catabolism and interconversion (GLDC, BCKDHB, AASS, PYCR, RPL15), (2) increase glycolytic lactate production (AGL, PDK2, LDHB, HIF1A), and (3) reduce oxidative metabolism via altered beta-oxidation (PXMP2, ACSS2), TCA cycle flux (OGDH, SUCLA2, MDH1B), and electron transport chain complex I function (NDUFV3). The muscle mitochondrial glycine cleavage system (GCS) was identified as critically involved in RA disease activity improvements given upregulation of multiple GCS genes at baseline, while GLDC was significantly downregulated following HIIT.ConclusionIn the absence of physical activity, RA inflammatory disease activity is associated with transcriptional remodeling of skeletal muscle metabolism. Following exercise training, the greatest improvements in disease activity occur in older, more inflamed, and less fit persons with RA. These exercise training-induced immunomodulatory changes may occur via reprogramming muscle bioenergetic and amino acid/protein homeostatic pathways.Trial registrationClinicalTrials.gov, NCT02528344. Registered on 19 August 2015.

Abstract 133: Skeletal muscle transcriptome profiling of human pancreatic cancer cachexia: single largest study in cachexia

Abstract Cancer cachexia is a devastating syndrome characterized by severe depletion of muscle and fat loss. More than 80% of patients with pancreatic ductal adenocarcinoma (PDAC) cancer suffer from cachexia. Virtually all of the mechanistic understanding of cachexia comes from preclinical models; it remains to be seen how much of these molecular findings reflect in human cachexia. To translate the findings, it is important to have a better understanding of the human biology of cachexia. To address this knowledge gap, we performed a single large transcriptome profiling of skeletal muscle biopsies from 18 controls and 55 patients with resectable PDAC. RNA was isolated from rectus abdominus muscle and subjected to total RNA sequencing. Each sample was sequenced to 100 million reads. Differentially expressed (DE) genes were identified using Deseq2 and were subjected to pathway analysis. Further, we performed a sex-stratified analysis to understand if a sex-specific gene pattern exists. To better understand the relationship between clinical variables of cachexia such as 1- and 6-month weight loss, BMI, and skeletal muscle index versus gene expression, we built a sex-specific correlation network using weighted gene co-expression network analysis (WGCNA). As age was significantly different between controls and PDAC, we also performed age-adjusted gene expression analysis. In the overall analysis, 598 genes were DE between controls and PDAC groups. Novel upstream transcription factors including EGR1, EGR2 and EGR3 were identified. Many inflammatory pathways such as IL-6, IL-8, JAK/STAT, and p53 signaling were identified. In sex-specific analyses, 802 genes were DE in males, and 511 in females. Only 86 genes overlapped between males and females, suggesting that gene expression is modulated in a sex-specific fashion. WGCNA identified many significant modules at 1-month weight loss indicating that the gene changes could be dynamic in early stages of weight loss. The key correlated modules in males were enriched for pathways such as Wnt signaling, IL-6 signaling, lipid metabolism and hypoxia signaling. In females, the correlated modules were predominantly associated with DNA repair pathways and epigenetic pathways such as chromatin organization and apoptosis. Overall, this is the single largest cachexia-specific transcriptome profiling performed to date to comprehensively document RNA changes in PDAC cachexia. Our results suggest a strong sex influence at the gene, pathway, and WGCNA analysis levels. The catalog of genes identified from the study can be used be a rich resource for validation of pre-clinical observations and hypothesis generation. Efforts are underway to build an interactive database for public access. Citation Format: Ashok Narasimhan, Xiaoling Zhong, Jun Wan, Sheng Liu, Leonidas G. Koniaris, Teresa A. Zimmers. Skeletal muscle transcriptome profiling of human pancreatic cancer cachexia: single largest study in cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 133.

Impact of Hypoxic Exercise Recovery on Skeletal Muscle Glycogen and Gene Expression.

Slivka, Dustin, Charles Dumke, Walter Hailes, and Brent Ruby. Impact of hypoxic exercise recovery on skeletal muscle glycogen and gene expression. High Alt Med Biol. 22:300-307, 2021. Background: The impact of altitude during recovery from exercise is largely unknown. The purpose of this study was to determine the acute gene response and muscle glycogen re-synthesis after exercise when exposed to simulated high altitude during recovery. Materials and Methods: Twelve male participants (age, 25 ± 2 years; height, 178 ± 7 cm; weight, 78.8 ± 7.8 kg; VO2peak, 4.25 ± 0.59 l/min; Wpeak 307 ± 44 W; and body fat, 13.1% ± 1.2%) completed two trials (random order), which consisted of cycling for 90 minutes in laboratory conditions and then recovering for 6 hours in laboratory conditions (975 m; normoxia) or at a high simulated altitude (5,000 m; hypoxia). Results: Skeletal muscle biopsies from the vastus lateralis were obtained before exercise, after exercise, and 6 hours after exercise for the measurement of metabolic gene expression and muscle glycogen. Muscle glycogen decreased with exercise (61% ± 13%, p < 0.05) and increased with recovery (78% ± 35%, p < 0.05) with no difference between trials (p > 0.05). Hypoxia-inducible factor (HIF)-1α, HIF-2α, optic atrophy gene 1 (OPA-1), mitofusin 2 (MFN-2), and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) gene expression were suppressed after altitude exposure (p < 0.05), while mitochondrial fission 1 protein (FIS-1), phosphofructokinase (PFK), Cytochrome c oxidase (COX), and hexokinase (HK) were unaffected by altitude exposure (p > 0.05). Conclusions: High-altitude exposure during recovery from exercise inhibits gene expression associated with mitochondrial development without affecting muscle glycogen re-synthesis.