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Birol Ay, Erdal Karaoz, Cumhur C Kesemenli, Halime Kenar
The reconstruction of skeletal muscle tissue is currently performed by transplanting a muscle tissue graft from local or distant sites of the patient`s body, but this practice leads to donor site morbidity in case of large defects. With the aim of providing an alternative treatment approach, skeletal muscle tissue formation potential of human myoblasts and human menstrual blood derived mesenchymal stem cells (hMB-MSCs) on synthetic (poly(L-lactide-co-caprolactone), 70:30) scaffolds with oriented microfibers, human muscle extracellular matrix (ECM), and their hybrids was investigated in this study...
October 22, 2016: Journal of Biomedical Materials Research. Part A
Min Joo Kim, Young Do Koo, Min Kim, Soo Lim, Young Joo Park, Sung Soo Chung, Hak C Jang, Kyong Soo Park
BACKGROUND: Panax ginseng has glucose-lowering effects, some of which are associated with the improvement in insulin resistance in skeletal muscle. Because mitochondria play a pivotal role in the insulin resistance of skeletal muscle, we investigated the effects of the ginsenoside Rg3, one of the active components of P. ginseng, on mitochondrial function and biogenesis in C2C12 myotubes. METHODS: C2C12 myotubes were treated with Rg3 for 24 hours. Insulin signaling pathway proteins were examined by Western blot...
October 2016: Diabetes & Metabolism Journal
Rajeev B Tajhya, Xueyou Hu, Mark R Tanner, Redwan Huq, Natee Kongchan, Joel R Neilson, George G Rodney, Frank T Horrigan, Lubov T Timchenko, Christine Beeton
Myoblasts are mononucleated precursors of myofibers; they persist in mature skeletal muscles for growth and regeneration post injury. During myotonic dystrophy type 1 (DM1), a complex autosomal-dominant neuromuscular disease, the differentiation of skeletal myoblasts into functional myotubes is impaired, resulting in muscle wasting and weakness. The mechanisms leading to this altered differentiation are not fully understood. Here, we demonstrate that the calcium- and voltage-dependent potassium channel, KCa1...
October 20, 2016: Cell Death & Disease
Jan Hansen, Silvie Timmers, Esther Moonen-Kornips, Helene Duez, Bart Staels, Matthijs K C Hesselink, Patrick Schrauwen
Cell and animal studies have demonstrated that circadian rhythm is governed by autonomous rhythmicity of clock genes. Although disturbances in circadian rhythm have been implicated in metabolic disease development, it remains unknown whether muscle circadian rhythm is altered in human models of type 2 diabetes. Here we used human primary myotubes (HPM) to investigate if rhythmicity of clock- and metabolic gene expression is altered in donors with obesity or type 2 diabetes compared to metabolically healthy donors...
October 19, 2016: Scientific Reports
Renjing Liu, Kun-Yong Kim, Yong-Wook Jung, In-Hyun Park
DNA methylation is an important epigenetic mark that regulates gene expression. Dnmt1 plays an important role in maintaining DNA methylation patterns on daughter DNA strands. Studies have shed light into the functional role of Dnmt1 regulation in the hematopoietic and epidermal systems. Here we show that Dnmt1 is required for myogenesis. Loss of Dnmt1 results in reduced expression of myogenic genes and defects in myogenic differentiation. We have utilized a conditional knockout mouse approach to examine the functional consequences of Dnmt1 depletion specifically in the developing muscle...
October 18, 2016: Scientific Reports
Nagendra Yaluri, Shalem Modi, Tarja Kokkola
Simvastatin is a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor widely used for the treatment of hypercholesterolemia. Recent data indicates that simvastatin increases the risk of new-onset diabetes by impairing both insulin secretion and insulin sensitivity. However, systematic evaluation of mechanistic pathways is lacking. We aimed to explore the effects of simvastatin on glucose uptake and underlying mechanisms using L6 skeletal muscle myotubes. We performed our experiments at basal and insulin-stimulated conditions, at normal (5...
October 12, 2016: Biochemical and Biophysical Research Communications
Shinichiro Hayashi, Ichiro Manabe, Yumi Suzuki, Frédéric Relaix, Yumiko Oishi
Krüppel-like factor 5 (Klf5) is a zinc-finger transcription factor that controls various biological processes, including cell proliferation and differentiation. We show that Klf5 is also an essential mediator of skeletal muscle regeneration and myogenic differentiation. During muscle regeneration after injury (cardiotoxin injection), Klf5 was induced in the nuclei of differentiating myoblasts and newly formed myofibers expressing myogenin in vivo. Satellite cell-specific Klf5 deletion severely impaired muscle regeneration, and myotube formation was suppressed in Klf5-deleted cultured C2C12 myoblasts and satellite cells...
October 15, 2016: ELife
Xijun Liang, Lin Liu, Tingting Fu, Qian Zhou, Danxia Zhou, Liwei Xiao, Jing Liu, Yan Kong, Hui Xie, Fanchao Yi, Ling Lai, Rick B Vega, Daniel P Kelly, Steven R Smith, Zhenji Gan
Lactate dehydrogenase (LDH) catalyzes the interconversion of pyruvate and lactate, which are critical fuel metabolites of skeletal muscle particularly during exercise. However, the physiological relevance of LDH remains poorly understood. Here we show that Ldhb expression is induced by exercise in human muscle and negatively correlated with changes in intramuscular pH levels, a marker of lactate production, during isometric exercise. We found that the expression of Ldhb is regulated by exercise-induced peroxisome proliferator-activated receptor-g coactivator 1α (PGC-1α)...
October 13, 2016: Journal of Biological Chemistry
Annalisa Bonifacio, Gerda M Sanvee, Karin Brecht, Denise V Kratschmar, Alex Odermatt, Jamal Bouitbir, Stephan Krähenbühl
Statins are generally well tolerated, but treatment with these drugs may be associated with myopathy. The mechanisms of statin-associated myopathy are not completely understood. Statins inhibit AKT phosphorylation by an unclear mechanism, whereas insulin-like growth factor (IGF-1) activates the IGF-1/AKT signaling pathway and promotes muscle growth. The aims of the study were to investigate mechanisms of impaired AKT phosphorylation by simvastatin and to assess effects of IGF-1 on simvastatin-induced myotoxicity in C2C12 myotubes...
October 12, 2016: Archives of Toxicology
Carrie E McCurdy, Simon Schenk, Byron Hetrick, Julie Houck, Brian G Drew, Spencer Kaye, Melanie Lashbrook, Bryan C Bergman, Diana L Takahashi, Tyler A Dean, Travis Nemkov, Ilya Gertsman, Kirk C Hansen, Andrew Philp, Andrea L Hevener, Adam J Chicco, Kjersti M Aagaard, Kevin L Grove, Jacob E Friedman
Maternal obesity is proposed to alter the programming of metabolic systems in the offspring, increasing the risk for developing metabolic diseases; however, the cellular mechanisms remain poorly understood. Here, we used a nonhuman primate model to examine the impact of a maternal Western-style diet (WSD) alone, or in combination with obesity (Ob/WSD), on fetal skeletal muscle metabolism studied in the early third trimester. We find that fetal muscle responds to Ob/WSD by upregulating fatty acid metabolism, mitochondrial complex activity, and metabolic switches (CPT-1, PDK4) that promote lipid utilization over glucose oxidation...
October 6, 2016: JCI Insight
Yuanfei Zhou, Jiao Ren, Tongxing Song, Jian Peng, Hongkui Wei
The mammalian target of rapamycin complex 1 (mTORC1) integrates amino acid (AA) availability to support protein synthesis and cell growth. Taste receptor type 1 member (T1R) is a G protein-coupled receptor that functions as a direct sensor of extracellular AA availability to regulate mTORC1 through Ca(2+) stimulation and extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation. However, the roles of specific AAs in T1R1/T1R3-regulated mTORC1 are poorly defined. In this study, T1R1 and T1R3 subunits were expressed in C2C12 myotubes, and l-AA sensing was accomplished by T1R1/T1R3 to activate mTORC1...
October 11, 2016: International Journal of Molecular Sciences
Olivera Evrova, Vahid Hosseini, Vincent Milleret, Gemma Palazzolo, Marcy Zenobi-Wong, Tullio Sulser, Johanna Buschmann, Daniel Eberli
Cellular responses are regulated by their microenvironments and engineered synthetic scaffolds can offer control over different microenvironment properties. This important relationship can be used as a tool to manipulate cell fate and cell responses for different biomedical applications. We showed for the first time in this study how blending of poly(ethylene oxide) (PEO) to poly(lactic-co-glycolic acid) (PLGA) fibers to yield hybrid scaffolds changes physical and mechanical properties of PLGA fibrous scaffolds and in turn affects cellular response...
October 11, 2016: ACS Applied Materials & Interfaces
Frédéric Capel, Naoufel Cheraiti, Cécile Acquaviva, Carole Hénique, Justine Bertrand-Michel, Christine Vianey-Saban, Carina Prip-Buus, Béatrice Morio
Because the protective effect of oleate against palmitate-induced insulin resistance may be lessened in skeletal muscle once cell metabolism is overloaded by fatty acids (FAs), we examined the impact of varying amounts of oleate on palmitate metabolic channeling and insulin signaling in C2C12 myotubes. Cells were exposed to 0.5mM of palmitate and to increasing doses of oleate (0.05, 0.25 and 0.5mM). Impacts of FA treatments on radio-labelled FA fluxes, on cellular content in diacylglycerols (DAG), triacylglycerols (TAG), ceramides, acylcarnitines, on PKCθ, MAPKs (ERK1/2, p38) and NF-ΚB activation, and on insulin-dependent Akt phosphorylation were examined...
October 8, 2016: Biochimica et Biophysica Acta
R M Downs, M A Hughes, S T Kinsey, M C Johnson, B L Baumgarner
Caffeine is a widely consumed stimulant that has previously been shown to promote cytotoxic stress and even cell death in numerous mammalian cell lines. Thus far there is little information available regarding the toxicity of caffeine in skeletal muscle cells. Our preliminary data revealed that treating C2C12 myotubes with 5 mM caffeine for 6 h increased nuclear fragmentation and reduced basal and maximal oxygen consumption rate (OCR) in skeletal myotubes. The purpose of this study was to further elucidate the pathways by which caffeine increased cell death and reduced mitochondrial respiration...
October 4, 2016: Biochemical and Biophysical Research Communications
Madina Naimi, Filip Vlavcheski, Brennan Murphy, Tomas Hudlicky, Evangelia Tsiani
Compounds that increase the activity of the energy sensor AMP-activated kinase (AMPK) have the potential to regulate blood glucose levels. Although rosemary extract (RE) has been reported to activate AMPK and reduce blood glucose levels in vivo, the chemical components responsible for these effects are not known. In the present study, we measured the levels of the polyphenol carnosic acid (CA) in RE and examined the effects and the mechanism of action of CA on glucose transport system in muscle cells. High performance liquid chromatography (HPLC) was used to measure the levels of CA in RE...
September 22, 2016: Clinical and Experimental Pharmacology & Physiology
Agnieszka Mikłosz, Bartłomiej Łukaszuk, Małgorzata Żendzian-Piotrowska, Justyna Brańska-Januszewska, Halina Ostrowska, Adrian Chabowski
The Akt substrate of 160 kDa (AS160) is a key regulator of GLUT4 translocation from intracellular depots to the plasma membrane in myocytes. Likely, AS160 also controls LCFAs transport, which requires relocation of fatty acid transporters. The aim of the present study was to determine the impact of AS160 knockdown on lipid milieu in L6 myotubes incubated with palmitate (PA). Therefore, we compared two different settings, namely: 1) AS160 knockdown prior to palmitate incubation (pre-PA-silencing, AS160(-) /PA); 2) palmitate incubation with subsequent AS160 knockdown (post-PA-silencing, PA/AS160(-) )...
October 7, 2016: Journal of Cellular Physiology
Min Park, Vincent Kaddai, Jianhong Ching, Kevin T Fridianto, Ryan J Sieli, Shigeki Sugii, Scott A Summers
The accumulation of sphingolipids in obesity leads to impairments in insulin sensitivity and mitochondrial metabolism, but the precise species driving these defects is unclear. We have modelled these obesity-induced effects in cultured C2C12 myotubes, using BSA-conjugated palmitate to increase synthesis of endogenous sphingolipids and inhibit insulin signaling and oxidative phosphorylation. Palmitate (a) induced the accumulation of SM precursors such as sphinganine, dihydroceramide, and ceramide, (b) inhibited insulin-stimulation of a central modulator of anabolic metabolism, Akt/PKB, (c) inhibited insulin-stimulated glycogen synthesis, and (d) decreased oxygen consumption and ATP synthesis...
October 4, 2016: Journal of Biological Chemistry
Kelsey A Thomas, Michael C Gibbons, John G Lane, Anshuman Singh, Samuel R Ward, Adam J Engler
Full thickness rotator cuff tendon (RCT) tears have long-term effects on RC muscle atrophy and fatty infiltration, with lasting damage even after surgical tendon repair. Skeletal muscle progenitor cells (SMPs) are critical for muscle repair in response to injury, but the inability of RC muscles to recover from chronic RCT tear indicates possible deficits in repair mechanisms. Here we investigated if muscle injury state was a crucial factor during human SMP expansion and differentiation ex vivo. SMPs were isolated from muscles in patients with no, partial-thickness (PT), or full-thickness (FT) RCT tears...
October 4, 2016: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
Mei Hua Gao, Dimosthenis Giamouridis, N Chin Lai, Evelyn Walenta, Vivian Almeida Paschoal, Young Chul Kim, Atsushi Miyanohara, Tracy Guo, Min Liao, Li Liu, Zhen Tan, Theodore P Ciaraldi, Simon Schenk, Aditi Bhargava, Da Young Oh, H Kirk Hammond
Using mice rendered insulin resistant with high fat diets (HFD), we examined blood glucose levels and insulin resistance after i.v. delivery of an adeno-associated virus type 8 encoding murine urocortin 2 (AAV8.UCn2). A single i.v. injection of AAV8.UCn2-normalized blood glucose and glucose disposal within weeks, an effect that lasted for months. Hyperinsulinemic-euglycemic clamps showed reduced plasma insulin, increased glucose disposal rates, and increased insulin sensitivity following UCn2 gene transfer...
September 22, 2016: JCI Insight
Alexander P Nesmith, Matthew A Wagner, Francesco S Pasqualini, Blakely B O'Connor, Mark J Pincus, Paul R August, Kevin Kit Parker
Tongue weakness, like all weakness in Duchenne muscular dystrophy (DMD), occurs as a result of contraction-induced muscle damage and deficient muscular repair. Although membrane fragility is known to potentiate injury in DMD, whether muscle stem cells are implicated in deficient muscular repair remains unclear. We hypothesized that DMD myoblasts are less sensitive to cues in the extracellular matrix designed to potentiate structure-function relationships of healthy muscle. To test this hypothesis, we drew inspiration from the tongue and engineered contractile human muscle tissues on thin films...
October 10, 2016: Journal of Cell Biology
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