Skeletal Muscle Energy Metabolism Research Articles

The Effect Of Eleutherococcus Senticosus On Metabolism-associated Protein Expressions In C2C12 Cells

PURPOSE: Eleutherococcus senticosus (ES) is a kind of Araliaceae and used as a medical plant. The principal component of ES is a glycoside such as triterpenoid and more than 16 kinds of components exist (e.g. sesamin, eleutheroside B, isoflavidin, chlorogenic acid). Given the finding that an intake of ES for 8 weeks enhances fat utilization and endurance exercise capacity in human study (Kuo et al., 2010), it is hypothesized that, in addition to fat mobilization from adipocytes, skeletal muscle energy metabolism is increased. However, the effect of ES on metabolic profile in a skeletal muscle cells is unknown. The aim of this study was to investigate the effect of ES on expressions of metabolism-associated proteins in differentiating C2C12. METHODS: During and after differentiation, C2C12 cells were treated with 0.1 mg/ml, 0.2 mg/ml, 0.5 or 1.0 mg/ml ES for 72 hours. The expressions of Mitochondrial lipid related proteins and energy metabolism associated proteins were analyzed by Western blotting. RESULTS: The expressions of mitochondrial lipid metabolism-associated proteins such as carnitine palmitoyltransferase I (CPT I), uncoupling protein 3 (UCP3), and cytochrome c oxidase (COX) did not change to ES treatments during and after C2C12 cell differentiation. However, the expression of phosphorylated AMP-activated protein kinase (AMPK), a metabolism-associated protein, was increased in response to 1.0 mg/ml ES (p<0.05) in both during and after cell differentiation. CONCLUSION: The finding suggests that ES may enhance skeletal muscle energy metabolism by means of augmented AMPK activity, and may relate to elevated endurance exercise capacity. Supported by Bizen Chemical Co.,LTD

Improved skeletal muscle energy metabolism relates to the recovery of β cell function by intensive insulin therapy in drug naïve type 2 diabetes.

Diminished energy turnover of skeletal muscle is involved in the development of type 2 diabetes. Intensive insulin therapy has been reported to maintain glycaemic control in newly diagnosed type 2 diabetes, while the underlying mechanism remains unclear. Herein, we aimed to characterize the contribution of muscular mitochondrial oxidative phosphorylation (OxPhos) activity to insulin-induced glycaemic control. There were 21 drug naïve patients with type 2 diabetes receiving continuous subcutaneous insulin infusion for 7days. Nine nondiabetics matched for age, body mass index, and physical activity were recruited as controls. We applied 31 P magnetic resonance spectroscopy to record in vivo muscular phosphocreatine (PCr) flux in controls and diabetics before and after insulin therapy. The mitochondrial OxPhos rate was calculated as ΔPCr/Δtime during the first 50seconds after cessation of exercise. In drug naïve type 2 diabetes, muscular mitochondrial OxPhos rate was restored after insulin therapy. Notably, this alteration was positively associated with the improvements of 1,5-anhydroglucitol, a serum marker for glucose control over the last 1week, as well as homeostasis model assessment of β cell function and C-peptide/glucose ratio t0 , two indices for basal insulin secretion. Furthermore, patients with diabetes family history and more severe glucotoxicity tend to achieve greater improvement in mitochondrial function by insulin. This study provides evidence that intensive insulin therapy facilitates muscular energy metabolism in drug naïve type 2 diabetes. It correlates to the recovery of β cell function, contributing to insulin-induced glucose control.

Effect of maternal feed restriction in dairy goats at different stages of gestation on skeletal muscle development and energy metabolism of kids at the time of births

The aim was to determine effects of maternal feed restriction in dairy goats at gestational different stages on skeletal muscle development and energy metabolism in kids at birth. Six pregnant goats were fed 50% of total digestible nutrients (TDN) and crude protein (CP) (NRC, 2007) recommendations in the first half of gestation and then fed to 100% of the recommendations in the second half of gestation (treatment R-M). In the other group, eight pregnant goats were fed 100% of TDN and CP in the first half of gestation and 50% of a restricted diet the second half of gestation (treatment M-R). Birth weight, blood glucose concentration, muscle fiber number, and size of kids at birth were not affected by maternal feed restriction. The mRNA and protein abundance of myogenic, adipogenic and fibrogenic markers were not affected (P > 0.05) by maternal diet. With regard to values for variables in kid energy metabolism, mRNA abundance of the glycolic enzyme HKII was less (P = 0.03) in the M-R group. In conclusion, maternal feed restriction in the first or second half of gestation had no affect mRNA abundance on myogenic, adipogenic, and fibrogenic markers nor were there changes in skeletal muscle mesenchymal stem cell population of kids at the time of birth. There, however, may be detrimental effects on energy metabolism by reducing HKII gene expression in skeletal muscle of dairy goat kids at the time of birth.

Skeletal muscles of hibernating black bears show minimal atrophy and phenotype shifting despite prolonged physical inactivity and starvation.

Hibernating mammals experience prolonged periods of torpor and starvation during winter for up to 5–7 months. Though physical inactivity and malnutrition generally lead to profound loss of muscle mass and metabolic dysfunction in humans, hibernating bears show limited muscle atrophy and can successfully maintain locomotive function. These physiological features in bears allow us to hypothesize that hibernating bears uniquely alter the regulation of protein and energy metabolism in skeletal muscle which then contributes to “muscle atrophy resistance” against continued physical inactivity. In this study, alteration of signaling pathways governing protein and energy metabolisms was examined in skeletal muscle of the Japanese black bear (Ursus thibetanus japonicus). Sartorius muscle samples were collected from bear legs during late November (pre-hibernation) and early April (post-hibernation). Protein degradation pathways, through a ubiquitin-proteasome system (as assessed by increased expression of murf1 mRNA) and an autophagy-dependent system (as assessed by increased expression of atg7, beclin1, and map1lc3 mRNAs), were significantly activated in skeletal muscle following hibernation. In contrast, as indicated by a significant increase in S6K1 phosphorylation, an activation state of mTOR (mammalian/mechanistic target of rapamycin), which functions as a central regulator of protein synthesis, increased in post-hibernation samples. Gene expression of myostatin, a negative regulator of skeletal muscle mass, was significantly decreased post-hibernation. We also confirmed that the phenotype shifted toward slow-oxidative muscle and mitochondrial biogenesis. These observations suggest that protein and energy metabolism may be altered in skeletal muscle of hibernating bears, which then may contribute to limited loss of muscle mass and efficient energy utilization.

Angiotensin II suppresses autophagy and disrupts ultrastructural morphology and function of mitochondria in mouse skeletal muscle.

Angiotensin II (ANG II)-induced skeletal muscle wasting is characterized by activation of the ubiquitin-proteasome system. However, the potential involvement of proteolytic system macroautophagy/autophagy in this wasting process remains elusive. Autophagy is precisely regulated to maintain cell survival and homeostasis; thus its dysregulation (i.e., overactivation or persistent suppression) could lead to detrimental outcomes in skeletal muscle. Here we show that infusion of ANG II for 7 days in male FVB mice suppressed autophagy in skeletal muscle. ANG II blunted microtubule-associated protein 1 light chain 3B (LC3B)-I-to-LC3B-II conversion (an autophagosome marker), increased p62/SQSTM1 (an autophagy cargo receptor) protein expression, and decreased the number of autophagic vacuoles. ANG II inhibited UNC-51-like kinase 1 via inhibition of 5'-AMP-activated kinase and activation of mechanistic target of rapamycin complex 1, leading to reduced phosphorylation of beclin-1Ser14 and Autophagy-related protein 14Ser29, suggesting that ANG II impairs autophagosome formation in skeletal muscle. In line with ANG II-mediated suppression of autophagy, ANG II promoted accumulation of abnormal/damaged mitochondria, characterized by swelling and disorganized cristae and matrix dissolution, with associated increase in PTEN-induced kinase 1 protein expression. ANG II also reduced mitochondrial respiration, indicative of mitochondrial dysfunction. Together, these results demonstrate that ANG II reduces autophagic activity and disrupts mitochondrial ultrastructure and function, likely contributing to skeletal muscle wasting. Therefore, strategies that activate autophagy in skeletal muscle have the potential to prevent or blunt ANG II-induced skeletal muscle wasting in chronic diseases. NEW & NOTEWORTHY Our study identified a novel mechanism whereby angiotensin II (ANG II) impairs mitochondrial energy metabolism in skeletal muscle. ANG II suppressed autophagosome formation by inhibiting the UNC-51-like kinase 1(ULK1)-beclin-1 axis, resulting in accumulation of abnormal/damaged and dysfunctional mitochondria and reduced mitochondrial respiratory capacity. Therapeutic strategies that activate the ULK1-beclin-1 axis have the potential to delay or reverse skeletal muscle wasting in chronic diseases characterized by increased systemic ANG II levels.

4E-BP1 and 4E-BP2 double knockout mice are protected from aging-associated sarcopenia.

BackgroundSarcopenia is the loss of muscle mass/function that occurs during the aging process. The links between mechanistic target of rapamycin (mTOR) activity and muscle development are largely documented, but the role of its downstream targets in the development of sarcopenia is poorly understood. Eukaryotic initiation factor 4E‐binding proteins (4E‐BPs) are targets of mTOR that repress mRNA translation initiation and are involved in the control of several physiological processes. However, their role in skeletal muscle is still poorly understood. The goal of this study was to assess how loss of 4E‐BP1 and 4E‐BP2 expression impacts skeletal muscle function and homeostasis in aged mice and to characterize the associated metabolic changes by metabolomic and lipidomic profiling.MethodsTwenty‐four‐month‐old wild‐type and whole body 4E‐BP1/4E‐BP2 double knockout (DKO) mice were used to measure muscle mass and function. Protein homeostasis was measured ex vivo in extensor digitorum longus by incorporation of l‐[U‐14C]phenylalanine, and metabolomic and lipidomic profiling of skeletal muscle was performed by Metabolon, Inc.ResultsThe 4E‐BP1/2 DKO mice exhibited an increase in muscle mass that was associated with increased grip strength (P < 0.05). Protein synthesis was higher under both basal (+102%, P < 0.05) and stimulated conditions (+65%, P < 0.05) in DKO skeletal muscle. Metabolomic and complex lipid analysis of skeletal muscle revealed robust differences pertaining to amino acid homeostasis, carbohydrate abundance, and certain aspects of lipid metabolism. In particular, levels of most free amino acids were lower within the 4E‐BP1/2 DKO muscle. Interestingly, although glucose levels were unchanged, differences were observed in the isobaric compound maltitol/lactitol (33‐fold increase, P < 0.01) and in several additional carbohydrate compounds. 4E‐BP1/2 depletion also resulted in accumulation of medium‐chain acylcarnitines and a 20% lower C2/C0 acylcarnitine ratio (P < 0.01) indicative of reduced β‐oxidation.ConclusionsTaken together, these findings demonstrate that deletion of 4E‐BPs is associated with perturbed energy metabolism in skeletal muscle and could have beneficial effects on skeletal muscle mass and function in aging mice. They also identify 4E‐BPs as potential targets for the treatment of sarcopenia.

Lifelong physical activity is associated with promoter hypomethylation of genes involved in metabolism, myogenesis, contractile properties and oxidative stress resistance in aged human skeletal muscle

Lifelong regular physical activity is associated with reduced risk of type 2 diabetes (T2D), maintenance of muscle mass and increased metabolic capacity. However, little is known about epigenetic mechanisms that might contribute to these beneficial effects in aged individuals. We investigated the effect of lifelong physical activity on global DNA methylation patterns in skeletal muscle of healthy aged men, who had either performed regular exercise or remained sedentary their entire lives (average age 62 years). DNA methylation was significantly lower in 714 promoters of the physically active than inactive men while methylation of introns, exons and CpG islands was similar in the two groups. Promoters for genes encoding critical insulin-responsive enzymes in glycogen metabolism, glycolysis and TCA cycle were hypomethylated in active relative to inactive men. Hypomethylation was also found in promoters of myosin light chain, dystrophin, actin polymerization, PAK regulatory genes and oxidative stress response genes. A cluster of genes regulated by GSK3β-TCF7L2 also displayed promoter hypomethylation. Together, our results suggest that lifelong physical activity is associated with DNA methylation patterns that potentially allow for increased insulin sensitivity and a higher expression of genes in energy metabolism, myogenesis, contractile properties and oxidative stress resistance in skeletal muscle of aged individuals.

Reduced hepatocellular lipid accumulation and energy metabolism in patients with long standing type 1 diabetes mellitus

The prevalence of obesity and metabolic syndrome increases in patients with type 1 diabetes mellitus (T1DM). In the general population this is linked with ectopic lipid accumulation in liver (HCL) and skeletal muscle (IMCL), representing hallmarks in the development of insulin resistance. Moreover, hepatic mitochondrial activity is lower in newly diagnosed patients with T1DM. If this precedes later development of diabetes related fatty liver disease is currently not known. This study aims to investigate energy metabolism in liver (kATP) and skeletal muscle (kCK) and its impact on HCL, IMCL, cardiac fat depots and heart function in 10 patients with long standing T1DM compared to 11 well-matched controls by 31P/1H magnetic resonance spectroscopy. HCL was almost 70% lower in T1DM compared to controls (6.9 ± 5% vs 2.1 ± 1.3%; p = 0.030). Also kATP was significantly reduced (0.33 ± 0.1 s−1vs 0.17 ± 0.1 s−1; p = 0.018). In T1DM, dose of basal insulin strongly correlated with BMI (r = 0.676, p = 0.032) and HCL (r = 0.643, p = 0.045), but not with kATP. In the whole cohort, HCL was significantly associated with BMI (r = 0.615, p = 0.005). In skeletal muscle kCK was lower in patients with T1DM (0.25 ± 0.05 s−1vs 0.31 ± 0–04 s−1; p = 0.039). No significant differences were found in IMCL. Cardiac fat depots as well as heart function were not different. Our results in patients with long standing T1DM show that HCL is lower compared to matched controls, despite reduced energy metabolism in liver and skeletal muscle.

INFLUENCE OF PATRINIA SCABIOSIFOLIA ON THE RESISTANCE OF MICE TO WHOLE-BODY VIBRATION

The aim of the study was to evaluate the effectiveness of P. scabiosifolia in correcting the physiological and psychosomatic state of mice exposed to acute and prolonged whole-body vibration. The effect of a 40% water-alcohol tincture from the roots of P. scabiosifolia was investigated in CD-1 mice under the influence of whole-body vibration induced by a shaker or exposure to road transportation. Emotional, exploratory-oriented and motor behavioral components were observed in the open field. Physical performance was evaluated by the duration of swimming until fatigue with a 7% weight attached to the tail root. Metabolic indices were serum corticosterone, glycogen, lactate and adenosine triphosphate of the liver and skeletal muscle. The orally administered drug at a dose of 5 ml/kg optimized the behavioral reactions of the animals, increased their exercise performance, improved hormonal status, and energy metabolism in liver and skeletal muscle and tissues under the influence of whole-body vibration. The P. scabiosifolia tincture possesses a vibroprotectiveeffect and can be recommended for the prevention and treatment of neurophysiological disorders caused by whole-body vibration, in combination with basic therapy.

Swim Training Modulates Mouse Skeletal Muscle Energy Metabolism and Ameliorates Reduction in Grip Strength in a Mouse Model of Amyotrophic Lateral Sclerosis.

Metabolic reprogramming in skeletal muscles in the human and animal models of amyotrophic lateral sclerosis (ALS) may be an important factor in the diseases progression. We hypothesized that swim training, a modulator of cellular metabolism via changes in muscle bioenergetics and oxidative stress, ameliorates the reduction in muscle strength in ALS mice. In this study, we used transgenic male mice with the G93A human SOD1 mutation B6SJL-Tg (SOD1G93A) 1Gur/J and wild type B6SJL (WT) mice. Mice were subjected to a grip strength test and isolated skeletal muscle mitochondria were used to perform high-resolution respirometry. Moreover, the activities of enzymes involved in the oxidative energy metabolism and total sulfhydryl groups (as an oxidative stress marker) were evaluated in skeletal muscle. ALS reduces muscle strength (−70% between 11 and 15 weeks, p < 0.05), modulates muscle metabolism through lowering citrate synthase (CS) (−30% vs. WT, p = 0.0007) and increasing cytochrome c oxidase and malate dehydrogenase activities, and elevates oxidative stress markers in skeletal muscle. Swim training slows the reduction in muscle strength (−5% between 11 and 15 weeks) and increases CS activity (+26% vs. ALS I, p = 0.0048). Our findings indicate that swim training is a modulator of skeletal muscle energy metabolism with concomitant improvement of skeletal muscle function in ALS mice.

Effects of FABP knockdown on flight performance of the desert locust, Schistocerca gregaria.

During migratory flight, desert locusts rely on fatty acids as their predominant source of energy. Lipids mobilized in the fat body are transported to the flight muscles and enter the muscle cells as free fatty acids. It has been postulated that muscle fatty acid binding protein (FABP) is needed for the efficient translocation of fatty acids through the aqueous cytosol towards mitochondrial β-oxidation. To assess whether FABP is required for this process, dsRNA was injected into freshly emerged adult males to knock down the expression of FABP. Three weeks after injection, FABP and its mRNA were undetectable in flight muscle, indicating efficient silencing of FABP expression. At rest, control and treated animals exhibited no morphological or behavioral differences. In tethered flight experiments, both control and treated insects were able to fly continually in the initial, carbohydrate-fueled phase of flight, and in both groups, lipids were mobilized and released into the hemolymph. Flight periods exceeding 30min, however, when fatty acids become the main energy source, were rarely possible for FABP-depleted animals, while control insects continued to fly for more than 2 h. These results demonstrate that FABP is an essential element of skeletal muscle energy metabolism in vivo.

Keeping the Heart Fitm2 during Chemotherapy.

With increasing cancer survival rates due to improved treatment options, attention to the chronic sequelae of chemotherapy is becoming increasingly more relevant. Cardiotoxicity is an important complication of several cancer therapeutic agents, but, so far, approaches to reduce cardiotoxicity have shown limited success. In this issue of Molecular Therapy, Gupta et al.1Gupta S.K. Garg A. Avramopoulos P. Engelhardt S. Streckfuss-Bömeke K. Batkai S. Thum T. miR-212/132 cluster modulation prevents doxorubicin-mediated atrophy and cardiotoxicity.Mol. Ther. 2018; 27 (Published online January 2019)https://doi.org/10.1016/j.ymthe.2018.11.004Abstract Full Text Full Text PDF Scopus (27) Google Scholar report a potential new strategy to counteract doxorubicin-induced myocardial atrophy and apoptosis: treatment with the pro-hypertrophic miR-132-212 cluster. The results unveil a new pathophysiological aspect of doxorubicin-induced cardiotoxicity and may provide a promising starting point for the development of new therapies. Anthracycline drugs, such as doxorubicin, are highly effective, broad-spectrum anti-cancer agents, but cardiac side effects pose a major limitation to their use. These agents can cause severe cardiomyocyte damage, leading to degradation of the sarcomere, swelling of mitochondria, vacuolar degradation of the sarcoplasmic reticulum, and, eventually, cardiomyocyte death. Cell death may also occur in cell types other than cardiomyocytes, potentially limiting the adaptive capacity of the heart and thereby increasing the risk of future cardiovascular disease and toxicity with future administration of cardiotoxic drugs.2Geisberg C.A. Sawyer D.B. Mechanisms of anthracycline cardiotoxicity and strategies to decrease cardiac damage.Curr. Hypertens. Rep. 2010; 12: 404-410Crossref PubMed Scopus (99) Google Scholar Together, these effects result in symptomatic heart failure in 2%–4% of patients treated with anthracyclines and an asymptomatic reduction of left ventricular ejection fraction (LVEF) in 9%–11% of patients.3McGowan J.V. Chung R. Maulik A. Piotrowska I. Walker J.M. Yellon D.M. Anthracycline Chemotherapy and Cardiotoxicity.Cardiovasc. Drugs Ther. 2017; 31: 63-75Crossref PubMed Scopus (488) Google Scholar While anthracycline-induced cardiotoxicity (AIC) was initially believed to comprise both an early and a late component, recent data by Cardinale et al.4Cardinale D. Colombo A. Bacchiani G. Tedeschi I. Meroni C.A. Veglia F. Civelli M. Lamantia G. Colombo N. Curigliano G. et al.Early detection of anthracycline cardiotoxicity and improvement with heart failure therapy.Circulation. 2015; 131: 1981-1988Crossref PubMed Scopus (872) Google Scholar indicated that 98% of patients with an asymptomatic decline in LVEF already showed a decrease at 12 months after chemotherapy. This suggests that most of the cardiotoxicity caused by anthracyclines is established rather soon after the onset of treatment. Despite extensive research, the mechanisms underlying AIC have not been fully elucidated. A potential explanation for the cardiotocixity is linked to the known function of anthracyclines. Anthracyclines cause their intended cytotoxic effect in cancer cells by binding to topoisomerase 2 (Top2). Top2 is an enzyme that is important for the organization of DNA and exists in an α- and β-isoform in humans. Top2α expression is co-regulated with the cell cycle and peaks in G2/M phase. Binding of anthracyclines to Top2α inhibits DNA replication, thereby arresting the cell cycle in G1/G2 and leading to apoptosis.3McGowan J.V. Chung R. Maulik A. Piotrowska I. Walker J.M. Yellon D.M. Anthracycline Chemotherapy and Cardiotoxicity.Cardiovasc. Drugs Ther. 2017; 31: 63-75Crossref PubMed Scopus (488) Google Scholar However, Top2β is also expressed in non-proliferating cells, such as cardiomyocytes, where binding of anthracyclines leads to the suppression of peroxisome proliferator-activated receptors (PPARs), resulting in mitochondrial dysfunction and eventually cell death.5Yang Y. Zhang H. Li X. Yang T. Jiang Q. Effects of PPARα/PGC-1α on the energy metabolism remodeling and apoptosis in the doxorubicin induced mice cardiomyocytes in vitro.Int. J. Clin. Exp. Pathol. 2015; 8: 12216-12224PubMed Google Scholar Additionally, it has been shown that anthracyclines can downregulate transcription factors, such as GATA4, that are essential for sarcomere maintenance.6Park A.-M. Nagase H. Liu L. Vinod Kumar S. Szwergold N. Wong C.-M. Suzuki Y.J. Mechanism of anthracycline-mediated down-regulation of GATA4 in the heart.Cardiovasc. Res. 2011; 90: 97-104Crossref PubMed Scopus (26) Google Scholar Another potential underlying mechanism for AIC is through the production of reactive oxygen species (ROS). Anthracyclines interact with ferric iron to convert molecular oxygen into superoxide radicals, but can additionally interfere with enzymes in the mitochondrial respiratory chain, leading to the production of ROS. The ROS then damage cellular components that can ultimately lead to apoptosis.2Geisberg C.A. Sawyer D.B. Mechanisms of anthracycline cardiotoxicity and strategies to decrease cardiac damage.Curr. Hypertens. Rep. 2010; 12: 404-410Crossref PubMed Scopus (99) Google Scholar So far, no effective prevention or therapy has been found for AIC. A 2016 position paper by the European Society of Cardiology7Zamorano J.L. Lancellotti P. Rodriguez Muñoz D. Aboyans V. Asteggiano R. Galderisi M. Habib G. Lenihan D.J. Lip G.Y.H. Lyon A.R. et al.ESC Scientific Document Group2016 ESC Position Paper on cancer treatments and cardiovascular toxicity developed under the auspices of the ESC Committee for Practice Guidelines: The Task Force for cancer treatments and cardiovascular toxicity of the European Society of Cardiology (ESC).Eur. Heart J. 2016; 37: 2768-2801Crossref PubMed Scopus (1516) Google Scholar suggested limiting cardiotoxicity by minimizing the total dose of anthracyclines, using less cardiotoxic doxorubicin analogs or formulations, or employing a non-anthracycline regimen. A cardiac protective treatment option, the use of the iron chelator dexrazoxane, has shown some therapeutic benefit.8van Dalen E.C. Caron H.N. Dickinson H.O. Kremer L.C.M. Cardioprotective interventions for cancer patients receiving anthracyclines.Cochrane Database Syst. Rev. 2005; CD003917: CD003917Google Scholar Some clinical trials also suggest potential benefits of the use of ACE-inhibitors and/or beta-blockers,9Bosch X. Rovira M. Sitges M. Domènech A. Ortiz-Pérez J.T. de Caralt T.M. et al.Enalapril and carvedilol for preventing chemotherapy-induced left ventricular systolic dysfunction in patients with malignant hemopathies: the OVERCOME trial (preventiOn of left Ventricular dysfunction with Enalapril and caRvedilol in patients submitted t.J. Am. Coll. Cardiol. 2013; 61: 2355-2362Crossref PubMed Scopus (432) Google Scholar, 10Gulati G. Heck S.L. Ree A.H. Hoffmann P. Schulz-Menger J. Fagerland M.W. Gravdehaug B. von Knobelsdorff-Brenkenhoff F. Bratland Å. Storås T.H. et al.Prevention of cardiac dysfunction during adjuvant breast cancer therapy (PRADA): a 2 × 2 factorial, randomized, placebo-controlled, double-blind clinical trial of candesartan and metoprolol.Eur. Heart J. 2016; 37: 1671-1680Crossref PubMed Scopus (395) Google Scholar but further studies are currently ongoing. In recent years, research has focused on the function of non-coding RNAs (ncRNAs) in AIC. microRNAs (miRs) are short strands of RNA that influence the translation of mRNA into protein by causing either translational repression or degradation of mRNA.11van Rooij E. Olson E.N. MicroRNA therapeutics for cardiovascular disease: opportunities and obstacles.Nat. Rev. Drug Discov. 2012; 11: 860-872Crossref PubMed Scopus (490) Google Scholar miR-208a was shown to be upregulated by doxorubicin, and inhibition of this miR resulted in a reduction in apoptosis through the derepression of Gata4 and Bcl2.12Tony H. Yu K. Qiutang Z. MicroRNA-208a Silencing Attenuates Doxorubicin Induced Myocyte Apoptosis and Cardiac Dysfunction.Oxid. Med. Cell. Longev. 2015; 2015: 597032Crossref PubMed Scopus (55) Google Scholar In a similar fashion, the miR-30 family was found to be downregulated in response to doxorubicin, while overexpression of miR-30e proved beneficial by reducing apoptosis and ROS production.13Chatterjee S. Gupta S.K. Bär C. Thum T. Non-coding RNAs: potential regulators in cardio-oncology.Am. J. Physiol. Heart Circ. Physiol. 2018; (Published online November 9, 2018)https://doi.org/10.1152/ajpheart.00418.2018Crossref PubMed Scopus (12) Google Scholar In the current study, Gupta et al.1Gupta S.K. Garg A. Avramopoulos P. Engelhardt S. Streckfuss-Bömeke K. Batkai S. Thum T. miR-212/132 cluster modulation prevents doxorubicin-mediated atrophy and cardiotoxicity.Mol. Ther. 2018; 27 (Published online January 2019)https://doi.org/10.1016/j.ymthe.2018.11.004Abstract Full Text Full Text PDF Scopus (27) Google Scholar hypothesized that overexpression of pro-hypertrophic miRs would be able to counteract AIC-induced atrophy. They show that doxorubicin causes apoptosis and a reduction in cell size in isolated neonatal rat ventricular myocytes (NRVMs). While miR-132 and miR-212 levels do not change during doxorubicin-induced cardiomyocyte toxicity, cotreatment with pre-miR-132 or pre-miR-212 protected the cells against these effects. And while in vivo AAV9-mediated overexpression of the cluster, as expected, resulted in cardiac hypertrophy in doxorubicin-naive animals,14Ucar A. Gupta S.K. Fiedler J. Erikci E. Kardasinski M. Batkai S. Dangwal S. Kumarswamy R. Bang C. Holzmann A. et al.The miRNA-212/132 family regulates both cardiac hypertrophy and cardiomyocyte autophagy.Nat. Commun. 2012; 3: 1078Crossref PubMed Scopus (446) Google Scholar viral overexpression of miR-132-212 during doxorubicin treatment actually ameliorated the doxorubicin-induced reduction in ejection fraction, remodeling, myofibril loss, and apoptosis. To elucidate the mechanism behind the cardioprotective effect of the miR-132-212 on doxorubicin-treated hearts, the authors analyzed the cardiac transcriptomes of doxorubicin-treated mice with or without viral overexpression of miR-132-212. Among the differentially regulated genes, cell-death related processes were enriched and the gene fat storage-inducing transmembrane protein 2 (Fitm2) was identified as a potential direct target of miR-132 and miR-212. Follow-up in vitro experiments showed that overexpression of Fitm2 was able to block the protective effects of miR-132 or miR-212 during doxorubicin-induced cardiomyocyte toxicity. Based on these data, the authors conclude that increasing the miR-132-212 cluster might be a good therapeutic means for reducing AIC and that these effects are at least partially due to a decrease in Fitm2. Fitm2 is known to be involved in the formation of cytosolic lipid droplets and has been shown to have an important role in skeletal muscle energy metabolism.15Miranda D.A. Koves T.R. Gross D.A. Chadt A. Al-Hasani H. Cline G.W. Schwartz G.J. Muoio D.M. Silver D.L. Re-patterning of skeletal muscle energy metabolism by fat storage-inducing transmembrane protein 2.J. Biol. Chem. 2011; 286: 42188-42199Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar Since it has not been studied for its function in cardiomyocyte biology, future studies are required to examine how its decrease would trigger hypertrophy or block AIC. As this gene was not found to be upregulated by the miR-132-212 cluster during doxorubicin treatment in vivo, a logical explanation might be that additional mechanisms are at play, which can explain the observed cardioprotective effects. Another important biological question that remains relates to the long-term effect of blocking doxorubicin-induced cardiomyocyte apoptosis. Since a major cause of cardiomyocyte loss in AIC is apoptosis in response to intracellular damage, inhibition of this process by a transient early increase in miR-132/212 might be beneficial, but long-term expression might be detrimental since damaged cells are not removed. In addition, the fact that long-term overexpression of the miR-132/212 cluster under baseline conditions previously was shown to result in heart failure could underscore a level of caution regarding a long-term increase in the miRs.14Ucar A. Gupta S.K. Fiedler J. Erikci E. Kardasinski M. Batkai S. Dangwal S. Kumarswamy R. Bang C. Holzmann A. et al.The miRNA-212/132 family regulates both cardiac hypertrophy and cardiomyocyte autophagy.Nat. Commun. 2012; 3: 1078Crossref PubMed Scopus (446) Google Scholar From a therapeutic perspective, some hurdles must be overcome before increasing levels of miR-132 and -212 can be considered a viable option for treating AIC. Increasing miR levels is possible through oligonucleotide therapy (mimicry), but targeting a specific cell type or organ is difficult. and the stability of these compounds is limited because stabilizing modifications generally preclude incorporation into RNA-induced silencing complex (RISC).16van Rooij E. Purcell A.L. Levin A.A. Developing microRNA therapeutics.Circ. Res. 2012; 110: 496-507Crossref PubMed Scopus (415) Google Scholar Viral gene therapy circumvents the stability and delivery issues, but has the risk of the patient having or developing immunity to the virus being used.17Boutin S. Monteilhet V. Veron P. Leborgne C. Benveniste O. Montus M.F. Masurier C. Prevalence of serum IgG and neutralizing factors against adeno-associated virus (AAV) types 1, 2, 5, 6, 8, and 9 in the healthy population: implications for gene therapy using AAV vectors.Hum. Gene Ther. 2010; 21: 704-712Crossref PubMed Scopus (623) Google Scholar Additionally, even when local delivery could be achieved, sustained overexpression of miRs could have all types of unwanted off-target effects, since each miR is predicted to regulate multiple (sometimes unrelated) mRNA targets. Currently, to avoid AIC, clinicians limit anthracycline dose, use less toxic formulations, or avoid anthracyclines altogether, even though they are very potent drugs. Therefore, there is a dire need for approaches to circumvent cardiotoxicity during anthracycline regimens. The use of a prohypertrophic miR cluster to counter the atrophy in AIC is an intriguing choice. It will be very interesting to see what future studies will reveal regarding the durability of this protective effect as well as the mechanism underlying these effects. Will it turn out that Fitm2 fits in with the ROS paradigm because it influences ROS production by influencing cardiomyocyte energy metabolism or will a completely new mechanism of cardioprotection be revealed? Regardless of what the final outcomes will be, the work of Gupta et al.1Gupta S.K. Garg A. Avramopoulos P. Engelhardt S. Streckfuss-Bömeke K. Batkai S. Thum T. miR-212/132 cluster modulation prevents doxorubicin-mediated atrophy and cardiotoxicity.Mol. Ther. 2018; 27 (Published online January 2019)https://doi.org/10.1016/j.ymthe.2018.11.004Abstract Full Text Full Text PDF Scopus (27) Google Scholar presented here paves the way for a new avenue of promising research into AIC. E.v.R. is a scientific co-founder and member of the Scientific Advisory Board of miRagen Therapeutics, Inc. E.v.R. was supported by a consolidator grant from the European Research Council (ERC CoG 615708 MICARUS) and a network grant from Fondation Leducq and CVON REMAIN (2014-27). miR-212/132 Cluster Modulation Prevents Doxorubicin-Mediated Atrophy and CardiotoxicityGupta et al.Molecular TherapyNovember 12, 2018In BriefDoxorubicin is known to cause dose-dependent cardiotoxicity in cancer patients. Here, Thum and colleagues show that overexpression of a pro-hypertrophic microRNA cluster, miR-212/132, can reduce the doxorubicin-induced cardiotoxic effects by reversing cardiac atrophy and apoptosis. Full-Text PDF Open Archive

Increased triacylglycerol - Fatty acid substrate cycling in human skeletal muscle cells exposed to eicosapentaenoic acid.

It has previously been shown that pretreatment of differentiated human skeletal muscle cells (myotubes) with eicosapentaenoic acid (EPA) promoted increased uptake of fatty acids and increased triacylglycerol accumulation, compared to pretreatment with oleic acid (OA) and palmitic acid (PA). The aim of the present study was to examine whether EPA could affect substrate cycling in human skeletal muscle cells by altering lipolysis rate of intracellular TAG and re-esterification of fatty acids. Fatty acid metabolism was studied in human myotubes using a mixture of fatty acids, consisting of radiolabelled oleic acid as tracer (14C-OA) together with EPA or PA. Co-incubation of myotubes with EPA increased cell-accumulation and incomplete fatty acid oxidation of 14C-OA compared to co-incubation with PA. Lipid distribution showed higher incorporation of 14C-OA into all cellular lipids after co-incubation with EPA relative to PA, with most markedly increases (3 to 4-fold) for diacylglycerol and triacylglycerol. Further, the increases in cellular lipids after co-incubation with EPA were accompanied by higher lipolysis and fatty acid re-esterification rate. Correspondingly, basal respiration, proton leak and maximal respiration were significantly increased in cells exposed to EPA compared to PA. Microarray and Gene Ontology (GO) enrichment analysis showed that EPA, related to PA, significantly changed i.e. the GO terms “Neutral lipid metabolic process” and “Regulation of lipid storage”. Finally, an inhibitor of diacylglycerol acyltransferase 1 decreased the effect of EPA to promote fatty acid accumulation. In conclusion, incubation of human myotubes with EPA, compared to PA, increased processes of fatty acid turnover and oxidation suggesting that EPA may activate futile substrate cycling of fatty acids in human myotubes. Increased TAG—FA cycling may be involved in the potentially favourable effects of long-chain polyunsaturated n-3 fatty acids on skeletal muscle and whole-body energy metabolism.

Ghrelin forms in the modulation of energy balance and metabolism.

Ghrelin is a gastric hormone circulating in acylated (AG) and unacylated (UnAG) forms. This narrative review aims at presenting current emerging knowledge on the impact of ghrelin forms on energy balance and metabolism. AG represents ~ 10% of total plasma ghrelin, has an appetite-stimulating effect and is the only form for which a receptor has been identified. Moreover, other metabolic AG-induced effects have been reported, including the modulation of glucose homeostasis with stimulation of liver gluconeogenesis, the increase of fat mass and the improvement of skeletal muscle mitochondrial function. On the other hand, UnAG has no orexigenic effects, however recent reports have shown that it is directly involved in the modulation of skeletal muscle energy metabolism by improving a cluster of interlinked functions including mitochondrial redox activities, tissue inflammation and insulin signalling and action. These findings are in agreement with human studies which show that UnAG circulating levels are positively associated with insulin sensitivity both in metabolic syndrome patients and in a large cohort from the general population. Moreover, ghrelin acylation is regulated by a nutrient sensor mechanism, specifically set on fatty acids availability. These recent findings consistently point towards a novel independent role of UnAG as a regulator of muscle metabolic pathways maintaining energy status and tissue anabolism. While a specific receptor for UnAG still needs to be identified, recent evidence strongly supports the hypothesis that the modulation of ghrelin-related molecular pathways, including those involved in its acylation, may be a potential novel target in the treatment of metabolic derangements in disease states characterized by metabolic and nutritional complications.Level of evidence Level V, narrative review.

OR-035 Effect of Aerobic Training on the Exercise Capacity of Apelin Knock-out Mice

Objective Aerobic training is considered to be an effective way to enhance the body’s exercise capacity which is closely related to the improvement of skeletal muscle energy metabolism. And as a new myokine, apelin has been found to play a key role in regulating the energy metabolism of skeletal muscle. However, whether the loss of apelin gene affects exercise capacity and what role aerobic training play in it remains unknown. This study was designed to investigate the effect of apelin on exercise capacity during aerobic training and to provide a theoretical basis for the mechanism of aerobic exercise affecting exercise capacity.&#x0D; Methods Male C57BL/6J wild type mouse(n=20) and apelin knock-out mouse(n=20) were assigned by random allocation to four groups(n=10): wild type control(WC), wild type exercised(WE), apelin knock-out control(KC) and apelin knock-out exercised(KE). Exercise training consisted of treadmill running 60 minutes/day ×6 days/week for 4 weeks. The training intensity corresponded to the 70-75% maximum oxygen uptake of mice. The running speed was 15m/min with an incline of +5° in the first 2 weeks and subsequently adjusted to 20m/min according to the maximum oxygen uptake in the last 2 weeks. On the day after training, all groups were forced to perform a incremental exercise test to exhaustion. This test was started with an incline of +5°and a speed of 10 m/min for 5 min. After this initial phase, the speed was progressively increased by 3m/min every 3 min until animal exhausted. The maximum running speed, movement time and distance were recorded during the test.&#x0D; Results Compared with group WC, the maximum running speed, movement time and distance of group KC were significantly decreased(P&lt;0.01). And the maximum running speed, movement time and distance of group KE were clearly higher than those of group KC(P&lt;0.01). There is no significant difference between group WE and group WC, and between group KE and group WE.&#x0D; Conclusions The exercise capacity of mice was significantly decreased because of knocking out the apelin gene, and the exercise ability of apelin knock-out mice can be clearly enhanced by aerobic training.

OR-025 Association study between Chinese excellent long-distance female athletes’ PGC-1β genetic polymorphism and aerobic capacity

Objective Peroxisome proliferator-activated receptor-γ coactivator-1β (PGC-1β) is mainly expressed in mitochondria-rich tissues, which involved in skeletal muscle mitochondrial biosynthesis and energy metabolism processes such as fatty acid transport and oxidation, hepatic gluconeogenesis. PGC-1β is Previous studies have shown that this genetic polymorphism is associated with the athletic ability of elite endurance athletes. Therefore, based on the previous research, the relationship between PGC-1β gene polymorphism and aerobic exercise ability of elite female long-distance runners was discussed to provide new effective indicators for athletes' selection of materials, and improve the accuracy and advancement of athletes' selection of materials.&#x0D; Methods 56 Chinese elite female long-distance runners were selected, and venous blood was extracted to analyze the gene polymorphism of specific gene locus. The subjects were tested for aerobic endurance index and lung function index, wherein the aerobic endurance index included maximum oxygen uptake, relative maximal oxygen uptake relative value, anaerobic threshold and anaerobic threshold relative value, and lung function indicators including vital capacity, Time lung capacity, minute ventilation and maximum ventilation . Subsequently, the cross-sectional association study method was used to analyze the association between four genotypes locus of PGC-1β including rs32579, rs2161257, rs1544744 and rs10783180 in 56 subjects.&#x0D; Results 1) All four polymorphic locus were tested by H-W balance, indicating that the subjects were representative of the population. 2) rs32579 locus: There were no significant differences in lung function indicators and aerobic exercise capacity between different genotype athletes. 3) rs2161257 locus: There were no significant differences in lung function indicators and aerobic exercise capacity between different genotype athletes. 4) rs1544744 locus: There were no significant differences in lung function indicators and aerobic exercise capacity between different genotype athletes. 5) rs10783180 locus: There is a significant difference in the relative values of anaerobic threshold and anaerobic threshold between different genotype athletes. The anaerobic threshold of AG genotype athletes was 2156.35±227.69 ml/min and the anaerobic threshold of athletes with GG genotype was 2143.41±217.30 ml/min. So the anaerobic threshold of AG genotype athletes was significantly greater than the anaerobic threshold of GG genotype athletes. The Anaerobic threshold relative value for AG genotype athletes was 50.99±3.99 ml/kg/min, while the anaerobic threshold relative value for athletes with GG genotype was 48.12±4.25 ml/kg/min. The anaerobic threshold relative value of AG genotype athletes was significantly greater than that of GG genotype athletes&#x0D; Other indicators showed no significant difference.&#x0D; Conclusions The rs10783180 polymorphism is associated with the athletic ability of elite endurance athletes. The population carrying AG genotype may have higher anaerobic threshold value and relative value of anaerobic threshold, which may become more excellent endurance athletes. Rs10783180 polymorphic locus AG genotype can be used as a molecular genetic marker to predict the relative value of anaerobic threshold and anaerobic threshold of Chinese Han women's long-distance runners in northern China.

PGC-1α and PGC-1β Increase Protein Synthesis via ERRα in C2C12 Myotubes.

The transcriptional coactivators peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and PGC-1β are positive regulators of skeletal muscle mass and energy metabolism; however, whether they influence muscle growth and metabolic adaptations via increased protein synthesis is not clear. This study revealed PGC-1α or PGC-1β overexpression in C2C12 myotubes increased protein synthesis and myotube diameter under basal conditions and attenuated the loss in protein synthesis following the treatment with the catabolic agent, dexamethasone. To investigate whether PGC-1α or PGC-1β signal through the Akt/mTOR pathway to increase protein synthesis, treatment with the PI3K and mTOR inhibitors, LY294002 and rapamycin, respectively, was undertaken but found unable to block PGC-1α or PGC-1β’s promotion of protein synthesis. Furthermore, PGC-1α and PGC-1β decreased phosphorylation of Akt and the Akt/mTOR substrate, p70S6K. In contrast to Akt/mTOR inhibition, the suppression of ERRα, a major effector of PGC-1α and PGC-1β activity, attenuated the increase in protein synthesis and myotube diameter in the presence of PGC-1α or PGC-1β overexpression. To characterize further the biological processes occurring, gene set enrichment analysis of genes commonly regulated by both PGC-1α and PGC-1β was performed following a microarray screen. Genes were found enriched in metabolic and mitochondrial oxidative processes, in addition to protein translation and muscle development categories. This suggests concurrent responses involving both increased metabolism and myotube protein synthesis. Finally, based on their known function or unbiased identification through statistical selection, two sets of genes were investigated in a human exercise model of stimulated protein synthesis to characterize further the genes influenced by PGC-1α and PGC-1β during physiological adaptive changes in skeletal muscle.

P3191Alterations in skeletal muscle energy and protein metabolism of patients with HFpEF and HFrEF compared to control subjects

P3191Alterations in skeletal muscle energy and protein metabolism of patients with HFpEF and HFrEF compared to control subjects

L-tyrosine supplementation does not ameliorate skeletal muscle dysfunction in zebrafish and mouse models of dominant skeletal muscle \u03b1-actin nemaline myopathy

L-tyrosine supplementation may provide benefit to nemaline myopathy (NM) patients, however previous studies are inconclusive, with no elevation of L-tyrosine levels in blood or tissue reported. We evaluated the ability of L-tyrosine treatments to improve skeletal muscle function in all three published animal models of NM caused by dominant skeletal muscle α-actin (ACTA1) mutations. Highest safe L-tyrosine concentrations were determined for dosing water and feed of wildtype zebrafish and mice respectively. NM TgACTA1D286G-eGFP zebrafish treated with 10 μM L-tyrosine from 24 hours to 6 days post fertilization displayed no improvement in swimming distance. NM TgACTA1D286G mice consuming 2% L-tyrosine supplemented feed from preconception had significant elevations in free L-tyrosine levels in sera (57%) and quadriceps muscle (45%) when examined at 6–7 weeks old. However indicators of skeletal muscle integrity (voluntary exercise, bodyweight, rotarod performance) were not improved. Additionally no benefit on the mechanical properties, energy metabolism, or atrophy of skeletal muscles of 6–7 month old TgACTA1D286G and KIActa1H40Y mice eventuated from consuming a 2% L-tyrosine supplemented diet for 4 weeks. Therefore this study yields important information on aspects of the clinical utility of L-tyrosine for ACTA1 NM.

Combination of Canagliflozin and Exercise Training Leads to Lipid-Dependent Energy Expenditure in Skeletal Muscle in Obese Diabetic Mice

Background and Aim: Sodium-glucose cotransporter 2 (SGLT2) inhibitors exert multiple metabolic effects. Exercise training is a robust treatment of obesity and diabetes, but the effect of SGLT2 inhibitors on exercise training is unclear. We investigated the association between canagliflozin (CAN) and training effects on skeletal muscle and liver in obese diabetic mice. Method: Male mice loaded with a high-fat diet for 4 weeks were housed in a normal cage (sedentary; sed) or wheel cage (WCR). A total of 0.03%w/w CAN was administrated for 2 weeks. Glucose and lipid metabolism of skeletal muscle (gastrocnemius) was analyzed and compared among 4 groups (control/sed, control/WCR, CAN/sed, and CAN/WCR). Results: Body weight in control/WCR and CAN/sed mice was significantly lower compared with that in control/sed mice, and further weight loss was observed in CAN/WCR mice. There was no difference in running distance between control/WCR and CAN/WCR mice. Control/WCR mice showed lower blood glucose levels than did control/sed mice (200.0±4.2 vs. 231.9±8.7 mg/dL, p=0.01). CAN decreased glucose levels, but there was no difference between CAN/sed (118.9±6.29 mg/dL) and CAN/WCR mice (113.6±4.48 mg/dL). GLUT1 and GLUT4 mRNA levels in skeletal muscle in CAN/sed and CAN/WCR mice were significantly lower than those in control/sed mice. Levels of mRNA of CD36 (× 1.26 in CAN/sed and × 1.31 in CAN/WCR mice, both p&amp;lt;0.05) and CPT1b (× 1.09 in CAN/sed and × 1.21 in CAN/WCR mice, both p&amp;lt;0.05) were significantly higher than those in control/sed mice. CPT1b mRNA levels in CAN/WCR mice were significantly higher than those in CAN/sed mice (p&amp;lt;0.05). Discussion: CAN promoted transition from glucose to lipid-dependent energy metabolism in skeletal muscle and this effect might have been enhanced by concomitant exercise. Conclusion: The combination of CAN and exercise may be effective for weight loss in obesity by an increase in lipid energy expenditure. Disclosure K. Tanaka: Research Support; Self; Mitsubishi Tanabe Pharma Corporation. H. Takahashi: Research Support; Self; Mitsubishi Tanabe Pharma Corporation. K. Sasaki: Employee; Self; Mitsubishi Tanabe Pharma Corporation. K. Inoue: None. Y. Matsuda: None. Y. Eguchi: None. K. Anzai: Research Support; Self; Mitsubishi Tanabe Pharma Corporation, Sysmex Corporation.