Resveratrol initiates differentiation of mouse skeletal muscle-derived C2C12 myoblasts

RNA Sequencing Reveals the Inhibitory Effect of High Levels of Arachidonic Acid and Linoleic Acid on C2C12 Differentiation and Myogenic Biomarkers

Over the past three decades, studies have shown that consuming polyunsaturated fatty acids (PUFAs) can enhance animal and human health and welfare through biological, biochemical, pathological, and pharmacological impacts. Furthermore, omega-6 plays key roles in the cardiopulmonary system, including promoting airway relaxation and inhibiting atherosclerosis and hypertension. However, findings from investigations of the effects of omega-6 fatty acids on molecular and cellular activity and discussions on their influence on biomarkers are still unclear. Therefore, the present study aimed to evaluate omega-6 fatty acids, the arachidonic acid (AA), and linoleic acid (LA) effects on C2C12 proliferation, myogenesis morphology, and relative myogenic biomarker expression through the Wnt pathway. C2C12 cells were cultured with and without 25, 50, 100, and 150 µM of LA and AA and then subjected to CCK8, Giemsa staining, RT qPCR, Western blotting, and RNA Sequencing. The CCK8 Assay results showed that 25, 50, 100, and 150 µM LA significantly decreased the viability after 72 h for 25, 50, 100, and 150 µM concentrations. Also, AA supplementation decreased cell viability after 24 h for 150 µM, 48 h for 150 µM, and 72 h for 50, 100, and 150 µM concentrations. Moreover, the LA and AA inhibitory effects noticed through Gimesa staining were morphological changes during myoblast differentiation. Both LA and AA showed inhibiting IGF1, Cola1, Col6a2, Col6a1, Itga10, Itga11, SFRP2, DAAM2, and NKD2 effects; however, the depressing effect was higher for AA compared to LA. The previous results were confirmed through Western blotting, which showed that 50 µM LA and AA significantly reduced DAAM2 and SFRP2 protein levels compared to the control. Regarding RNA sequencing results, LA and AA increased the number of differentially expressed (DE) Mt-rRNA and snoRNA; however, the numbers of lncRNA detected decreased compared to the control. Our findings demonstrate that high and moderate LA and AA concentrations reduce primary myoblast proliferation and differentiation. Also, they highlight novel biomarkers and regulatory factors to improve our understanding of how the nutrition of fatty acids can control and modulate the myogenesis and differentiation process through different biomarker families.

Moracin E and M isolated from Morus alba Linné induced the skeletal muscle cell proliferation via PI3K-Akt-mTOR signaling pathway

Twigs of Morus alba have been used in traditional medicine to treat muscle-related symptoms such as aches, numbness, and stiffness. Despite its clinical use in traditional medicine, its active compounds and mode of action have not yet been investigated. Therefore, we aimed to isolate the compounds from the twigs of M. alba and deduce active compounds, key gene targets, and mechanism of action against sarcopenia using network pharmacology analysis. Using various isolation techniques and spectroscopic methods, 43 phytochemicals, including 3 new flavonoids, were isolated and performed network pharmacology analysis. According to the computational-assistant analysis, 28 compounds, 9 genes, and the PI3K-Akt-mTOR signaling pathway were deduced as expected active compounds (EAC), key targets, and the main signaling pathway. To verify the predicted results, the cell proliferation activities of the EAC were evaluated. Especially, moracin E and M significantly increased by 130% (p < 0.001) and 57% (p < 0.05), respectively, which have more than 2- and 1.5-fold stronger effects compared to the control. Furthermore, both increased the expression level of proteins involved in the PI3K-Akt-mTOR signaling pathway and myogenic proteins, including myogenin and MyoD. This study demonstrated that moracin E and M exhibit cell proliferative effects on skeletal muscle cells through the PI3K-Akt-mTOR signaling pathway.

7β-Hydroxycholesterol and 7-ketocholesterol: New oxidative stress biomarkers of sarcopenia inducing cytotoxic effects on myoblasts and myotubes

Aging is a complex biological process which can be associated with skeletal muscle degradation leading to sarcopenia. The aim of this study consisted i) to determine the oxidative and inflammatory status of sarcopenic patients and ii) to clarify the impact of oxidative stress on myoblasts and myotubes. To this end, various biomarkers of inflammation (C-reactive protein (CRP), TNF-α, IL-6, IL-8, leukotriene B4 (LTB4)) and oxidative stress (malondialdehyde, conjugated dienes, carbonylated proteins and antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase) as well as oxidized derivatives of cholesterol formed by cholesterol autoxidation (7-ketocholesterol, 7β-hydroxycholesterol), were analyzed. Apelin, a myokine which contributes to muscle strength, was also quantified. To this end, a case-control study was conducted to evaluate the RedOx and inflammatory status in 45 elderly subjects (23 non-sarcopenic; 22 sarcopenic) from 65 years old and higher. SARCopenia-Formular (SARC-F) and Timed Up and Go (TUG) tests were used to distinguish between sarcopenic and non-sarcopenic subjects. By using red blood cells, plasma and/or serum, we observed in sarcopenic patients an increased activity of major antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase) associated with lipid peroxidation and protein carbonylation (increased level of malondialdehyde, conjugated dienes and carbonylated proteins). Higher levels of 7-ketocholesterol and 7β-hydroxycholesterol were also observed in the plasma of sarcopenic patients. Significant differences were only observed with 7β-hydroxycholesterol. In sarcopenic patients comparatively to non-sarcopenic subjects, significant increase of CRP, LTB4 and apelin were observed whereas similar levels of TNF-α, IL-6 and IL-8 were found. The increased plasma level of 7-ketocholesterol and 7β-hydroxycholesterol in sarcopenic patients led us to study the cytotoxic effect of these oxysterols on undifferentiated (myoblasts) and differentiated (myotubes) murine C2C12 cells. With the fluorescein diacetate and sulforhodamine 101 assays, an induction of cell death was observed both on undifferentiated and differentiated cells: the cytotoxic effects were less pronounced with 7-ketocholesterol. In addition, IL-6 secretion was never detected whatever the culture conditions, TNF-α secretion was significantly increased on undifferentiated and differentiated C2C12 cells treated with 7-ketocholesterol- and 7β-hydroxycholesterol, and IL-8 secretion was increased on differentiated cells. 7-ketocholesterol- and 7β-hydroxycholesterol-induced cell death was strongly attenuated by α-tocopherol and Pistacia lentiscus L. seed oil both on myoblasts and/or myotubes. TNF-α and/or IL-8 secretions were reduced by α-tocopherol and Pistacia lentiscus L. seed oil. Our data support the hypothesis that the enhancement of oxidative stress observed in sarcopenic patients could contribute, especially via 7β-hydroxycholesterol, to skeletal muscle atrophy and inflammation via cytotoxic effects on myoblasts and myotubes. These data bring new elements to understand the pathophysiology of sarcopenia and open new perspectives for the treatment of this frequent age-related disease.

Effects of Protein Hydrolysate from Silkworm (Bombyx mori) pupae on the C2C12 Myogenic Differentiation

This study investigated the effects and active compounds of silkworm pupae, an edible insect, on C2C12 muscle differentiation. The protein of silkworm pupae was extracted using sonication after defatting with hexane. Subsequently, the extract was rehydrated using Alcalase to obtain a protein hydrolysate. The silkworm pupae protein hydrolysate effectively promoted C2C12 myogenic differentiation without cytotoxicity. Subsequently, the hydrolysate was fractionated into four subfractions using preparative high-performance liquid chromatography (Prep-HPLC). Subfraction 1 was the most effective in promoting C2C12 myogenic differentiation and significantly upregulated the expression of myoblast transcription factors, 1.5-fold of myoblast determination protein 1 (MyoD), 2-fold of myogenin, and 3-fold of myosin heavy chain (MyHC). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and multivariate statistical analysis were used to identify the active peptides in silkworm pupae responsible for the observed effects; then, dipeptides and essential amino acids, such as isoleucine (Ile), valine (Val), and methionine (Met), were identified. In addition, Val, Ile, and two dipeptides underwent quantification to determine the potential bioactive peptides that enhanced C2C12 myogenic differentiation. This study suggests that the peptides from silkworm pupae could be used as a nutraceutical to enhance muscle growth.

Linoleic acid-induced ANGPTL4 inhibits C2C12 skeletal muscle differentiation by suppressing Wnt/β-catenin

Skeletal muscle differentiation is an essential process in embryonic development as well as regeneration and repair throughout the lifespan. It is well-known that dietary fat intake impacts biological and physiological function in skeletal muscle, however, understanding of the contribution of nutritional factors in skeletal muscle differentiation is limited. Therefore, the objective of the current study was to evaluate the effects of free fatty acids (FFAs) on skeletal muscle differentiation in vitro. We used C2C12 murine myoblasts and treated them with various FFAs, which revealed a unique response of angiopoietin-like protein-4 (ANGPTL4) with linoleic acid (LA) treatment that was associated with reduced differentiation. LA significantly inhibited myotube formation and lowered the protein expression of myogenic regulatory factors, including MyoD and MyoG and increased Pax7 during cell differentiation. Next, recombinant ANGPTL4 protein or siRNA knockdown of ANGPTL4 was employed to examine its role in skeletal muscle differentiation, and we confirmed that ANGPTL4 knockdown at day 2 and -6 of differentiation restored myotube formation in the presence of LA. RNA-sequencing analysis revealed that ANGPTL4-mediated inhibition of skeletal muscle differentiation at day 2 as well as LA at day 2 or -6 led to a reduction in Wnt/β-catenin signaling pathways. We confirmed that LA reduced Wnt11 and Axin2 while increasing expression of the Wnt inhibitor, Dkk2. ANGPTL4 knockdown increased β-catenin protein in the nucleus in response to LA and increased Axin2 and Wnt11 expression. Taken together, these results demonstrate that LA induced ANGPTL4 inhibits C2C12 differentiation by suppressing Wnt/β-catenin signaling.

Ripretinib induced skeletal muscle toxicity through mitochondrial impairment in C2C12 myotubes

Ripretinib is a multikinase inhibitor drug approved in 2020 by the FDA and in 2021 by EMA for use in the treatment of advanced gastrointestinal stromal tumors (GIST) which have not adequately responded to previous treatments with kinase inhibitors. The most common side effects of the drug are myalgia and fatigue, which likely causes interruption of the treatment or reduction of the dose. Skeletal muscle cells highly depend on ATP to perform their functions and mitochondrial damage may play a role in skeletal muscle toxicity induced by kinase inhibitors. However, the molecular mechanism has not been clearly identified in the literature yet. In this study, it has been aimed to elucidate the role of mitochondria in the toxic effect of ripretinib on skeletal muscle using the mouse C2C12 myoblast-derived myotubes. The myotubes were exposed to ripretinib at the range of 1-20 μM concentrations for 24 h. To determine the potential role of mitochondrial impairment in ripretinib-induced skeletal muscle toxicity, intracellular ATP level, mitochondrial membrane potential (MMP), mitochondrial ROS production (mtROS), mitochondrial DNA (mtDNA) copy number, and mitochondrial mass were examined after ripretinib treatment. Furthermore, changes in PGC 1α/NRF 1/NRF 2 expression levels that play a role in mitochondrial biogenesis and mitophagy were investigated. Additionally, the mitochondrial electron transport chain (ETC) enzyme activities were evaluated. Lastly, a molecular docking study was done to see ripretinib's possible interaction with DNA polymerase gamma (POLG) which is important for DNA replication in the mitochondria. According to the findings, ripretinib decreases the ATP level and mtDNA copy number, induces loss of MMP, and reduces mitochondrial mass. The activities of the ETC complexes were inhibited with ripretinib exposure which is in line with the observed ATP depletion and MMP loss. The molecular docking study revealed that ripretinib has inhibitory potential against POLG which supports the observed inhibition of mtDNA. The expression of PGC 1α was reduced in the nuclear fraction indicating that PGC-1α was not activated since the NRF 1 expression was reduced and NRF 2 level did not show significant change. Consequently, mtROS production increased in all treatment groups and mitophagy-related gene expressions and Parkin protein expression level were up-regulated at high doses. In conclusion, mitochondrial damage/loss can be one of the underlying causes of ripretinib-induced skeletal muscle toxicity. However, further studies are needed to confirm the results in vivo.

A Review of free fatty acid-induced cell signaling, angiopoietin-like protein 4, and skeletal muscle differentiation

Postnatal skeletal muscle differentiation from quiescent satellite cells is a highly regulated process, although our understanding of the contribution of nutritional factors in myogenesis is limited. Free fatty acids (FFAs) are known to cause detrimental effects to differentiated skeletal muscle cells by increasing oxidative stress which leads to muscle wasting and insulin resistance in skeletal muscle. In addition, FFAs are thought to act as inhibitors of skeletal muscle differentiation. However, the precise molecular mechanisms underlying the effects of FFAs on skeletal muscle differentiation remains to be elucidated. There is a clear relationship between dietary FFAs and their ability to suppress myogenesis and we propose the hypothesis that the FFA-mediated increase in angiopoietin-like protein 4 (ANGPTL4) may play a role in the inhibition of differentiation. This review discusses the role of FFAs in skeletal muscle differentiation to-date and proposes potential mechanisms of FFA-induced ANGPTL4 mediated inhibition of skeletal muscle differentiation.

Cytotoxic and Antioxidant Activities of Imine Analogs of Trans-Resveratrol towards Murine Neuronal N2a Cells

Trans-resveratrol is a natural polyphenol showing numerous biological properties, especially anti-tumoral and antioxidant activity. Among numerous resveratrol derivatives, aza-stilbenes, which bear an imine bound, show interesting biological activities. In the present study, we synthesized a series of imine analogs of trans-resveratrol (seven aza-stilbenes) following an easy and low-cost procedure of green chemistry. The toxicity of synthesized aza-stilbenes, which is currently unknown, was evaluated on murine neuronal N2a cells, comparatively to trans-resveratrol, by considering: cell density evaluated by staining with sulforhodamine 101; esterase activity, which is a criteria of cell viability, by staining with fluorescein diacetate; and transmembrane mitochondrial potential, which is known to decrease during cell death, by staining with DiOC₆(3) using flow cytometry. In addition, the antioxidant activity was quantified with the KRL (Kit Radicaux Libres) assay, the DPPH (2,2′-diphenyl-1-picrylhydrazyl radical) assay and the FRAP (ferric reducing antioxidant power) assay. The PAOT (Pouvoir Antioxidant Total) score was also used. The aza-stilbenes provide different cytotoxic and antioxidant activities, which are either higher or lower than those of trans-resveratrol. Based on their cytotoxic and antioxidant characteristics, all synthesized aza-stilbenes are distinguished from trans-resveratrol.

Natural products: Potential therapeutic agents to prevent skeletal muscle atrophy

The skeletal muscle (SkM) is the largest organ, which plays a vital role in controlling musculature, locomotion, body heat regulation, physical strength, and metabolism of the body. A sedentary lifestyle, aging, cachexia, denervation, immobilization, etc. Can lead to an imbalance between protein synthesis and degradation, which is further responsible for SkM atrophy (SmA). To date, the understanding of the mechanism of SkM mass loss is limited which also restricted the number of drugs to treat SmA. Thus, there is an urgent need to develop novel approaches to regulate muscle homeostasis. Presently, some natural products attained immense attraction to regulate SkM homeostasis. The natural products, i.e., polyphenols (resveratrol, curcumin), terpenoids (ursolic acid, tanshinone IIA, celastrol), flavonoids, alkaloids (tomatidine, magnoflorine), vitamin D, etc. exhibit strong potential against SmA. Some of these natural products have been reported to have equivalent potential to standard treatments to prevent body lean mass loss. Indeed, owing to the large complexity, diversity, and slow absorption rate of bioactive compounds made their usage quite challenging. Moreover, the use of natural products is controversial due to their partially known or elusive mechanism of action. Therefore, the present review summarizes various experimental and clinical evidence of some important bioactive compounds that shall help in the development of novel strategies to counteract SmA elicited by various causes.

Integrated Analysis of mRNA and MicroRNA Co-expressed Network for the Differentiation of Bovine Skeletal Muscle Cells After Polyphenol Resveratrol Treatment

Resveratrol (RSV) has been confirmed to benefit human health. Resveratrol supplemented in the feeds of animals improved pork, chicken, and duck meat qualities. In this study, we identified differentially expressed (DE) messenger RNAs (mRNAs) (n = 3,856) and microRNAs (miRNAs) (n = 93) for the weighted gene co-expression network analysis (WGCNA) to investigate the co-expressed DE mRNAs and DE miRNAs in the primary bovine myoblasts after RSV treatment. The mRNA results indicated that RSV treatments had high correlations with turquoise module (0.91, P-value = 0.01) and blue module (0.93, P-value < 0.01), while only the turquoise module (0.96, P-value < 0.01) was highly correlated with the treatment status using miRNA data. After biological enrichment analysis, the 2,579 DE genes in the turquoise module were significantly enriched in the Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The top two GO terms were actin filament-based process (GO:0030029) and actin cytoskeleton organization (GO:0030036). The top two KEGG pathways were regulation of actin cytoskeleton (bta04810) and tight junction (bta04530). Then, we constructed the DE mRNA co-expression and DE miRNA co-expression networks in the turquoise module and the mRNA–miRNA targeting networks based on their co-expressions in the key module. In summary, the RSV-induced miRNAs participated in the co-expression networks that could affect mRNA expressions to regulate the primary myoblast differentiation. Our study provided a better understanding of the roles of RSV in inducing miRNA and of the characteristics of DE miRNAs in the key co-expressed module in regulation of mRNAs and revealed new candidate regulatory miRNAs and genes for the beef quality traits.

Resveratrol improves muscle regeneration in obese mice through enhancing mitochondrial biogenesis

Obesity is increasing rapidly worldwide and is accompanied by many complications, including impaired muscle regeneration. Obesity is known to inhibit AMP-activated protein kinase (AMPK) activity, which impedes mitochondrial biogenesis, myogenic differentiation and muscle regeneration. Resveratrol has an effective anti-obesity effect, but its effect on regeneration of muscle in obese mice remains to be tested. We hypothesized that resveratrol activates AMPK and mitochondrial biogenesis to improve muscle regeneration. Male C57BL/6J mice were fed a control diet or a 60% high-fat diet with or without resveratrol supplementation for 8 weeks and, then, the tibialis anterior muscle was subjected to cardiotoxin-induced muscle injury. Muscle tissue was collected at 3 and 7 d after injury. We found that resveratrol enhanced both proliferation and differentiation of satellite cells following injury in obese mice. Markers of mitochondrial biogenesis were upregulated in resveratrol-treated mice. In C2C12 myogenic cells, resveratrol activated AMPK and stimulated the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, which were associated with enhanced myogenic differentiation. Such effects of resveratrol were abolished by AMPKα1 ablation, showing the mediatory roles of AMPK. In summary, dietary resveratrol activates AMPK/ proliferator-activated receptor gamma coactivator 1-alpha axis to facilitate mitochondrial biogenesis and muscle regeneration impaired due to obesity.

Towards resolving the enigma of the dichotomy of resveratrol: cis- and trans-resveratrol have opposite effects on TyrRS-regulated PARP1 activation

Unlike widely perceived, resveratrol (RSV) decreased the average lifespan and extended only the replicative lifespan in yeast. Similarly, although not widely discussed, RSV is also known to evoke neurite degeneration, kidney toxicity, atherosclerosis, premature senescence, and genotoxicity through yet unknown mechanisms. Nevertheless, in vivo animal models of diseases and human clinical trials demonstrate inconsistent protective and beneficial effects. Therefore, the mechanism of action of RSV that elicits beneficial effects remains an enigma. In a previously published work, we demonstrated structural similarities between RSV and tyrosine amino acid. RSV acts as a tyrosine antagonist and competes with it to bind to human tyrosyl-tRNA synthetase (TyrRS). Interestingly, although both isomers of RSV bind to TyrRS, only the cis-isomer evokes a unique structural change at the active site to promote its interaction with poly-ADP-ribose polymerase 1 (PARP1), a major determinant of cellular NAD+-dependent stress response. However, retention of trans-RSV in the active site of TyrRS mimics its tyrosine-bound conformation that inhibits the auto-poly-ADP-ribos(PAR)ylation of PARP1. Therefore, we proposed that cis-RSV-induced TyrRS-regulated auto-PARylation of PARP1 would contribute, at least in part, to the reported health benefits of RSV through the induction of protective stress response. This observation suggested that trans-RSV would inhibit TyrRS/PARP1-mediated protective stress response and would instead elicit an opposite effect compared to cis-RSV. Interestingly, most recent studies also confirmed the conversion of trans-RSV and its metabolites to cis-RSV in the physiological context. Therefore, the finding that cis-RSV and trans-RSV induce two distinct conformations of TyrRS with opposite effects on the auto-PARylation of PARP1 provides a potential molecular basis for the observed dichotomic effects of RSV under different experimental paradigms. However, the fact that natural RSV exists as a diastereomeric mixture of its cis and trans isomers and cis-RSV is also a physiologically relevant isoform has not yet gained much scientific attention.

Effects of resveratrol on the proliferation and osteogenic differentiation of deciduous dental pulp stem cells from neurofibromatosis type 1 patient

PURPOSE

We aimed at verifying whether resveratrol can decrease cell proliferation and change osteogenic differentiation of cells obtained from patients with type 1 neurofibromatosis (NF1).

METHODS

Deciduous dental pulp derived stem cells were isolated from NF1 patient and healthy volunteer. These cells were subjected to increasing concentrations of resveratrol and evaluated for proliferation and mineralization of osteogenic differentiation.

RESULTS

The results showed that resveratrol reduced the difference in proliferation between CNT and NF1 cells in a dose-dependent manner and this property was more prominent in affected cells than in healthy cells. Resveratrol showed no statistically significant changes in mineralization in osteogenic differentiation of NF1 cells, at low doses tested.

CONCLUSIONS

In conclusion, in a dose-dependent manner, resveratrol displays interesting properties that could be applied in a possible treatment aimed at decreasing cellular proliferation in neurofibromatosis. Furthermore, it is selective concerning healthy cells and not affecting cell differentiation. Further research to cell selectivity, differentiation to other tissue types, and cell cytotoxicity are needed.

Resveratrol Promotes Hypertrophy in Wildtype Skeletal Muscle and Reduces Muscle Necrosis and Gene Expression of Inflammatory Markers in Mdx Mice

Duchenne muscular dystrophy (DMD) is a progressive fatal neuromuscular disorder with no cure. Therapies to restore dystrophin deficiency have been approved in some jurisdictions but long-term effectiveness is yet to be established. There is a need to develop alternative strategies to treat DMD. Resveratrol is a nutraceutical with anti-inflammatory properties. Previous studies have shown high doses (100–400 mg/kg bodyweight/day) benefit mdx mice. We treated 4-week-old mdx and wildtype mice with a lower dose of resveratrol (5 mg/kg bodyweight/day) for 15 weeks. Voluntary exercise was used to test if a lower dosage than previously tested could reduce exercise-induced damage where a greater inflammatory infiltrate is present. We found resveratrol promoted skeletal muscle hypertrophy in wildtype mice. In dystrophic muscle, resveratrol reduced exercise-induced muscle necrosis. Gene expression of immune cell markers, CD86 and CD163 were reduced; however, signalling targets associated with resveratrol’s mechanism of action including Sirt1 and NF-κB were unchanged. In conclusion, a lower dose of resveratrol compared to the dosage used by other studies reduced necrosis and gene expression of inflammatory cell markers in dystrophic muscle suggesting it as a therapeutic candidate for treating DMD.

Ionic Silicon Protects Oxidative Damage and Promotes Skeletal Muscle Cell Regeneration

Volumetric muscle loss injuries overwhelm the endogenous regenerative capacity of skeletal muscle, and the associated oxidative damage can delay regeneration and prolong recovery. This study aimed to investigate the effect of silicon-ions on C2C12 skeletal muscle cells under normal and excessive oxidative stress conditions to gain insights into its role on myogenesis during the early stages of muscle regeneration. In vitro studies indicated that 0.1 mM Si-ions into cell culture media significantly increased cell viability, proliferation, migration, and myotube formation compared to control. Additionally, MyoG, MyoD, Neurturin, and GABA expression were significantly increased with addition of 0.1, 0.5, and 1.0 mM of Si-ion for 1 and 5 days of C2C12 myoblast differentiation. Furthermore, 0.1-2.0 mM Si-ions attenuated the toxic effects of H2O2 within 24 h resulting in increased cell viability and differentiation. Addition of 1.0 mM of Si-ions significantly aid cell recovery and protected from the toxic effect of 0.4 mM H2O2 on cell migration. These results suggest that ionic silicon may have a potential effect in unfavorable situations where reactive oxygen species is predominant affecting cell viability, proliferation, migration, and differentiation. Furthermore, this study provides a guide for designing Si-containing biomaterials with desirable Si-ion release for skeletal muscle regeneration.

Synthesis and Biological Evaluation of Halogenated E-Stilbenols as Promising Antiaging Agents

The increased risk of illness and disability is related to the age inevitable biological changes. Oxidative stress is a proposed mechanism for many age-related diseases. The crucial importance of polyphenol pharmacophore for aging process is largely described thanks to its effects on concentrations of reactive oxygen species. Resveratrol (3,5,4'-trihydroxy-trans-stilbene, RSV) plays a critical role in slowing the aging process but has a poor bioavailabity after oral intake. In this present work, a series of RSV derivatives was designed, synthesized, and evaluated as potential antioxidant agents. These derivatives contain substituents with different electronic and steric properties in different positions of aromatic rings. This kind of substituents affects the activity and the bioavailability of these compounds compared with RSV used as reference compound. Studies of Log P values demonstrated that the introduction of halogens gives the optimum lipophilicity to be considered promising active agents. Among them, compound 6 showed the higher antioxidant activity than RSV. The presence of trifluoromethyl group together with a chlorine atom increased the antioxidant activity compared to RSV.

Prevention by Dietary Polyphenols (Resveratrol, Quercetin, Apigenin) Against 7-Ketocholesterol-Induced Oxiapoptophagy in Neuronal N2a Cells: Potential Interest for the Treatment of Neurodegenerative and Age-Related Diseases

The Mediterranean diet is associated with health benefits due to bioactive compounds such as polyphenols. The biological activities of three polyphenols (quercetin (QCT), resveratrol (RSV), apigenin (API)) were evaluated in mouse neuronal N2a cells in the presence of 7-ketocholesterol (7KC), a major cholesterol oxidation product increased in patients with age-related diseases, including neurodegenerative disorders. In N2a cells, 7KC (50 µM; 48 h) induces cytotoxic effects characterized by an induction of cell death. When associated with RSV, QCT and API (3.125; 6.25 µM), 7KC-induced toxicity was reduced. The ability of QCT, RSV and API to prevent 7KC-induced oxidative stress was characterized by a decrease in reactive oxygen species (ROS) production in whole cells and at the mitochondrial level; by an attenuation of the increase in the level and activity of catalase; by attenuating the decrease in the expression, level and activity of glutathione peroxidase 1 (GPx1); by normalizing the expression, level and activity of superoxide dismutases 1 and 2 (SOD1, SOD2); and by reducing the decrease in the expression of nuclear erythroid 2-like factor 2 (Nrf2) which regulates antioxidant genes. QCT, RSV and API also prevented mitochondrial dysfunction in 7KC-treated cells by counteracting the loss of mitochondrial membrane potential (ΨΔm) and attenuating the decreased gene expression and/or protein level of AMP-activated protein kinase α (AMPKα), sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) implicated in mitochondrial biogenesis. At the peroxisomal level, QCT, RSV and API prevented the impact of 7KC by counteracting the decrease in ATP binding cassette subfamily D member (ABCD)3 (a peroxisomal mass marker) at the protein and mRNA levels, as well as the decreased expresssion of genes associated with peroxisomal biogenesis (Pex13, Pex14) and peroxisomal β-oxidation (Abcd1, Acox1, Mfp2, Thiolase A). The 7KC-induced decrease in ABCD1 and multifunctional enzyme type 2 (MFP2), two proteins involved in peroxisomal β-oxidation, was also attenuated by RSV, QCT and API. 7KC-induced cell death, which has characteristics of apoptosis (cells with fragmented and/or condensed nuclei; cleaved caspase-3; Poly(ADP-ribose) polymerase (PARP) fragmentation) and autophagy (cells with monodansyl cadaverine positive vacuoles; activation of microtubule associated protein 1 light chain 3–I (LC3-I) to LC3-II, was also strongly attenuated by RSV, QCT and API. Thus, in N2a cells, 7KC induces a mode of cell death by oxiapoptophagy, including criteria of OXIdative stress, APOPTOsis and autoPHAGY, associated with mitochondrial and peroxisomal dysfunction, which is counteracted by RSV, QCT, and API reinforcing the interest for these polyphenols in prevention of diseases associated with increased 7KC levels.

Nutrition and microRNAs: Novel Insights to Fight Sarcopenia

Sarcopenia is a progressive age-related loss of skeletal muscle mass and strength, which may result in increased physical frailty and a higher risk of adverse events. Low-grade systemic inflammation, loss of muscle protein homeostasis, mitochondrial dysfunction, and reduced number and function of satellite cells seem to be the key points for the induction of muscle wasting, contributing to the pathophysiological mechanisms of sarcopenia. While a range of genetic, hormonal, and environmental factors has been reported to contribute to the onset of sarcopenia, dietary interventions targeting protein or antioxidant intake may have a positive effect in increasing muscle mass and strength, regulating protein homeostasis, oxidative reaction, and cell autophagy, thus providing a cellular lifespan extension. MicroRNAs (miRNAs) are endogenous small non-coding RNAs, which control gene expression in different tissues. In skeletal muscle, a range of miRNAs, named myomiRNAs, are involved in many physiological processes, such as growth, development, and maintenance of muscle mass and function. This review aims to present and to discuss some of the most relevant molecular mechanisms related to the pathophysiological effect of sarcopenia. Besides, we explored the role of nutrition as a possible way to counteract the loss of muscle mass and function associated with ageing, with special attention paid to nutrient-dependent miRNAs regulation. This review will provide important information to better understand sarcopenia and, thus, to facilitate research and therapeutic strategies to counteract the pathophysiological effect of ageing.

The calmodulin redox sensor controls myogenesis

Muscle aging is accompanied by blunted muscle regeneration in response to injury and disuse. Oxidative stress likely underlies this diminished response, but muscle redox sensors that act in regeneration have not yet been characterized. Calmodulin contains multiple redox sensitive methionines whose oxidation alters the regulation of numerous cellular targets. We have used the CRISPR-Cas9 system to introduce a single amino acid substitution M109Q that mimics oxidation of methionine to methionine sulfoxide in one or both alleles of the CALM1 gene, one of three genes encoding the muscle regulatory protein calmodulin, in C2C12 mouse myoblasts. When signaled to undergo myogenesis, mutated myoblasts failed to differentiate into myotubes. Although early myogenic regulatory factors were present, cells with the CALM1 M109Q mutation in one or both alleles were unable to withdraw from the cell cycle and failed to express late myogenic factors. We have shown that a single oxidative modification to a redox-sensitive muscle regulatory protein can halt myogenesis, suggesting a molecular target for mitigating the impact of oxidative stress in age-related muscle degeneration.

Theaflavin Promotes Myogenic Differentiation by Regulating the Cell Cycle and Surface Mechanical Properties of C2C12 Cells

Aging and muscle diseases often lead to a decline in the differentiation capacity of myoblasts, which in turn results in the deterioration of skeletal muscle (SkM) function and impairment of regeneration ability after injury. Theaflavins, the "gold molecules" found in black tea, have been reported to possess various biological activities and have a positive effect on maintaining human health. In this study, we found that among the four theaflavins (theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3,3'-digallate (TF3) monomers), TF1 (20 μM) significantly promoted the fusion index of myoblasts, number of mature myotubes, and degree of myotube development. By combining transcriptomics, bioinformatics, and molecular biology experiments, we showed that TF1 may promote myoblast differentiation by (1) regulating the withdrawal of myoblasts from the cell cycle, inducing the release of myogenic factors (MyoD, MyoG, and MyHC) and accelerating myogenic differentiation and (2) regulating the adhesion force of myoblasts and mechanical properties of mature myotubes and promoting the migration, fusion, and development of myoblasts. In conclusion, our study outcomes show that TF1 can promote myoblast differentiation and regulate myotube mechanical properties. It is a potential dietary supplement for the elderly. Our findings provide a new scientific basis for the relationship between tea drinking and aging.

Transcriptomic changes in bovine skeletal muscle cells after resveratrol treatment

Skeletal muscles constitute a high proportion of the cellular mass that is essential for the growth traits in cattle. Resveratrol (RSV) is a natural polyphenol compound involved in pleiotropic biological activities of muscle. Therefore, the aim of our study was to investigate the transcriptome-level effects of RSV on bovine primary myoblast to reveal differentially expressed genes (DEGs). We treated three replicates of primary myoblasts with 20 μM mother solution containing RSV, whereas three other replicates without RSV were used as control group. Then, we conducted genome-wide transcriptome analysis for the two groups. The results of expression analysis identified 3856 DEGs of which 1805 genes were up-regulated and 2051 genes were down-regulated (adjusted P < 0.05). In addition, qRT-PCR analysis of 19 selected DEGs were consistent with the expression levels observed in the transcriptome data. Gene Ontology (GO) and pathway enrichment analysis showed 72 and 66 significant GO terms and KEGG pathways, respectively (adjusted P < 0.05). The most significant GO term was actin cytoskeleton organization (GO:0030036). The top significant KEGG pathway was focal adhesion (bta04510). Predicted protein-protein interactions (PPIs) showed that CDKN1A encoding cyclindependent kinase inhibitor 1A connects several larger protein complexes. In conclusion, our results found a list of DEGs, significant GO terms and pathways, and provided an improved and expanded understanding of the impact of RSV on cattle muscle cells at the transcriptomic level. The study elucidates the potential of using the genes enriched in pathways mediating resveratrol effects as targets in genomic selection for muscle development and growth in beef cattle.

Aza- and Azo-Stilbenes: Bio-Isosteric Analogs of Resveratrol

Several series of natural polyphenols are described for their biological and therapeutic potential. Natural stilbenoid polyphenols, such as trans-resveratrol, pterostilbene and piceatannol are well-known for their numerous biological activities. However, their moderate bio-availabilities, especially for trans-resveratrol, prompted numerous research groups to investigate innovative and relevant synthetic resveratrol derivatives. This review is focused on isosteric resveratrol analogs aza-stilbenes and azo-stilbenes in which the C=C bond between both aromatic rings was replaced with C=N or N=N bonds, respectively. In each series, synthetic ways will be displayed, and structural sights will be highlighted and compared with those of resveratrol. The biological activities of some of these molecules will be presented as well as their potential therapeutic applications. In some cases, structure-activity relationships will be discussed.

The Putative Caloric Restriction Mimetic Resveratrol has Moderate Impact on Insulin Sensitivity, Body Composition, and the Metabolome in Mice

SCOPE

Data on resveratrol-(trans-3,5,4'-trihydroxystilbene)-induced caloric-restriction-(CR)-mimicking effects in mice receiving a high-fat diet (HFD) are contradictory. It is hypothesized that this can possibly stem from different bioactivities of resveratrol (RSV) microbial metabolites.

METHODS AND RESULTS

C57BL/6Rj mice are fed an ad-libitum HFD supplemented with RSV or its metabolites, dihydroresveratrol (DHR) and lunularin (LUN) (≈28 mg (dihydro)stilbene kg^-1 mouse per day). A 40% CR group was included in the study. While CR mice show robust changes in bodyweight and composition, hormone levels and mRNA expression, slight changes are found (more muscle, less adipose tissue) in body composition, leptin, and insulin levels in RSV-supplemented mice compared to ad libitum controls. LUN hardly and DHR does not change the hormone levels measured. Metabolome analysis of serum shows changes in CR mice but only slight, if any, changes in RSV-, DHR-, or LUN-supplemented mice compared to the controls. Evaluating the capability of RSV and its metabolites to inhibit carbohydrate-hydrolyzing enzymes in vitro, it is found that RSV reduced α-glucosidase activity to a stronger extent than DHR and LUN.

CONCLUSION

Decelerated carbohydrate breakdown by RSV may have contributed to the moderate impact of dietary RSV on mouse insulin sensitivity (lowered fasting and post-glucose-bolus insulin levels).

The Potential Use of Resveratrol for Cancer Prevention

In addition to the traditional treatments of cancer and cancer prevention, the use of natural compounds, especially those found in food, should be considered. To clarify if resveratrol has the potential for cancer prevention and the possibility of use in therapy, the following must be taken into account: data from epidemiology, clinical protocol (case and control), preclinical studies (lab animals), use of established cell lines as models of cancer cells, test tube assays (enzymes activities), and requirements of nanotechnologies in order to discover new drugs to fight cancer. From this perspective and future expected advances, more information is needed such as improved efficacy, methods of application, and the synergistic sensitization of resveratrol as an adjuvant. In addition, resveratrol nanoformulation is considered to overcome its weak bioavailability.

Promotion of myotube differentiation and attenuation of muscle atrophy in murine C2C12 myoblast cells treated with teaghrelin

This study aimed to investigate the effects of teaghrelin, an active ingredient of Chin-shin oolong tea, on murine C2C12 myoblast cells. Under high serum conditions, teaghrelin inhibited C2C12 cell proliferation, indicating a cell cycle arrest and cessation of proliferative progression. Teaghrelin promoted pro-differentiation of C2C12 cells as evidenced by a progressively elongated morphology, as well as the induction of muscle specific myogenin, myosin heavy chain (MHC), and MyoD. The formation of multinucleated myotubes, and the increase of MHC-positive immunoreactivity within the myotubes, further reflected a complete differentiation and maturation of the contractile skeletal muscle cells induced by teaghrelin. Like ghrelin, teaghrelin attenuated dexamethasone-decreased myotube diameter, indicating its protective effects against skeletal muscle atrophy. Additionally, the expressions of Atrogin-1 and MuRF-1 ubiquitin E3 ligase were reduced. In conclusion, the results highlight a possibility of developing teaghrelin as a functional food for the prevention or therapeutic treatment of disease-associated skeletal muscle atrophy.

Natural constituents from food sources: potential therapeutic agents against muscle wasting

Skeletal muscle wasting is highly correlated with not only reduced quality of life but also higher morbidity and mortality. Although an increasing number of patients are suffering from various kinds of muscle atrophy and weakness, there is still no effective therapy available, and skeletal muscle is considered as an under-medicated organ. Food provided not only essential macronutrients but also functional substances involved in the modulation of the physiological systems of our body. Natural constituents from commonly consumed dietary plants, either extracts or compounds, have attracted more and more attention to be developed as agents for preventing and treating muscle wasting due to their safety and effectiveness, as well as structural diversity. This review provides an overview of the mechanistic aspects of muscle wasting, and summarizes the extracts and compounds from food sources as potential therapeutic agents against muscle wasting.

Catechins enhance skeletal muscle performance

Muscle-related disorders, such as sarcopenia and cachexia, caused by aging and chronic diseases can lead to the loss of muscle mass and strength to different degrees, severely affecting human health. Globally, tea is one of the three most popular beverages, and its major active ingredient catechins have been reported to delay muscular atrophy and enhance movement. However, currently, there is no systematic review to elaborate its roles and the associated mechanisms. This article reviews the (1) functions and mechanisms of catechins in the differentiation of myogenic stem cells, biogenesis of mitochondria, synthesis and degradation of proteins, regulation of glucose level, and metabolism of lipids in muscle cells; and (2) effect of catechins on the blood vessels, bones, and nerves that are closely related to the skeletal muscles. Catechins could prevent, mitigate, delay, and even treat muscle-related disorders caused by aging and diseases.

Strategic Syntheses of Vine and Wine Resveratrol Derivatives to Explore their Effects on Cell Functions and Dysfunctions

Trans-resveratrol, the most well-known polyphenolic stilbenoid, is found in grapes and accordingly in wine and it is considered to be beneficial for human health, especially towards the aging-linked cell alterations by providing numerous biological activities, such as anti-oxidant, antitumoral, antiviral, anti-inflammatory, neuroprotective, and platelet anti-aggregation properties. Although trans-resveratrol is a promising molecule, it cannot be considered as a drug, due to its weak bio-availability and fast metabolism. To overcome these weaknesses, several research teams have undertaken the synthesis of innovative trans-resveratrol derivatives, with the aim to increase its solubility in water and pharmacological activities towards cell targets. The aim of this review is to show the chronological evolution over the last 25 years of different strategies to develop more efficient trans-resveratrol derivatives towards organism physiology and, therefore, to enhance various pharmacological activities. While the literature on the development of new synthetic derivatives is impressive, this review will focus on selected strategies regarding the substitution of trans-resveratrol phenyl rings, first with hydroxy, methoxy, and halogen groups, and next with functionalized substituents. The effects on cell functions and dysfunctions of interesting resveratrol analogs will be addressed in this review.

Induction of Neuronal Differentiation of Murine N2a Cells by Two Polyphenols Present in the Mediterranean Diet Mimicking Neurotrophins Activities: Resveratrol and Apigenin

In the prevention of neurodegeneration associated with aging and neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease), neuronal differentiation is of interest. In this context, neurotrophic factors are a family of peptides capable of promoting the growth, survival, and/or differentiation of both developing and immature neurons. In contrast to these peptidyl compounds, polyphenols are not degraded in the intestinal tract and are able to cross the blood–brain barrier. Consequently, they could potentially be used as therapeutic agents in neurodegenerative pathologies associated with neuronal loss, thus requiring the stimulation of neurogenesis. We therefore studied the ability to induce neuronal differentiation of two major polyphenols present in the Mediterranean diet: resveratrol (RSV), a major compound found in grapes and red wine, and apigenin (API), present in parsley, rosemary, olive oil, and honey. The effects of these compounds (RSV and API: 6.25–50 µM) were studied on murine neuro-2a (N2a) cells after 48 h of treatment without or with 10% fetal bovine serum (FBS). Retinoic acid (RA: 6.25–50 µM) was used as positive control. Neuronal differentiation was morphologically evaluated through the presence of dendrites and axons. Cell growth was determined by cell counting and cell viability by staining with fluorescein diacetate (FDA). Neuronal differentiation was more efficient in the absence of serum than with 10% FBS or 10% delipidized FBS. At concentrations inducing neuronal differentiation, no or slight cytotoxicity was observed with RSV and API, whereas RA was cytotoxic. Without FBS, RSV and API, as well as RA, trigger the neuronal differentiation of N2a cells via signaling pathways simultaneously involving protein kinase A (PKA)/phospholipase C (PLC)/protein kinase C (PKC) and MEK/ERK. With 10% FBS, RSV and RA induce neuronal differentiation via PLC/PKC and PKA/PLC/PKC, respectively. With 10% FBS, PKA and PLC/PKC as well as MEK/ERK signaling pathways were not activated in API-induced neuronal differentiation. In addition, the differentiating effects of RSV and API were not inhibited by cyclo[DLeu⁵] OP, an antagonist of octadecaneuropeptide (ODN) which is a neurotrophic factor. Moreover, RSV and API do not stimulate the expression of the diazepam-binding inhibitor (DBI), the precursor of ODN. Thus, RSV and API are able to induce neuronal differentiation, ODN and its receptor are not involved in this process, and the activation of the (PLC/PKC) signaling pathway is required, except with apigenin in the presence of 10% FBS. These data show that RSV and API are able to induce neuronal differentiation and therefore mimic neurotrophin activity. Thus, RSV and API could be of interest in regenerative medicine to favor neurogenesis.

The role of resveratrol on skeletal muscle cell differentiation and myotube hypertrophy during glucose restriction

Glucose restriction (GR) impairs muscle cell differentiation and evokes myotube atrophy. Resveratrol treatment in skeletal muscle cells improves inflammatory-induced reductions in skeletal muscle cell differentiation. We therefore hypothesised that resveratrol treatment would improve muscle cell differentiation and myotube hypertrophy in differentiating C2C12 myoblasts and mature myotubes during GR. Glucose restriction at 0.6 g/L (3.3 mM) blocked differentiation and myotube hypertrophy versus high-glucose (4.5 g/L or 25 mM) differentiation media (DM) conditions universally used for myoblast culture. Resveratrol (10 µM) treatment increased SIRT1 phosphorylation in DM conditions, yet did not improve differentiation when administered to differentiating myoblasts in GR conditions. Resveratrol did evoke increases in hypertrophy of mature myotubes under DM conditions with corresponding elevated Igf-I and Myhc7 gene expression, coding for the ‘slow’ type I MYHC protein isoform. Inhibition of SIRT1 via EX-527 administration (100 nM) also reduced myotube diameter and area in DM conditions and resulted in lower gene expression of Myhc 1, 2 and 4 coding for ‘intermediate’ and ‘faster’ IIx, IIa and IIb protein isoforms, respectively. Resveratrol treatment did not appear to modulate phosphorylation of energy-sensing protein AMPK or protein translation initiator P70S6K. Importantly, in mature myotubes, resveratrol treatment was able to ameliorate reduced myotube growth in GR conditions over an acute 24-h period, but not over 48–72 h. Overall, resveratrol evoked myotube hypertrophy in DM conditions while favouring ‘slower’ Myhc gene expression and acutely ameliorated impaired myotube growth observed during glucose restriction.

Effect of polyphenols from coffee and grape on gene expression in myoblasts

Coffee and grape contain various bioactive compounds like polyphenols that may exert beneficial effects, especially antioxidant activity, on human health upon consumption. However, the molecular mechanisms through which these effects are achieved are not fully elucidated. Thus, in the present study in order to investigate these mechanisms, a whole genome expression DNA microarray analysis was carried out in myoblasts treated with polyphenols of coffee and grape pomace at concentrations that improved the redox status. Grape was composed of catechin, epicatechin, cyanidin, malvidin, delphinidin, petunidin, myrtillin, kuromanin, oenin, peonidin, quercetin, gallic acid and caftaric acid as LC-MS revealed, with a total polyphenolic content (TPC) of 648 mg of gallic acid equivalents/g of dry matter. Coffee had a TPC of 42.61 mg GAE/g coffee and was composed of 3-chlorogenic acid (16.61 mg/g), 4- and 5-chlorogenic acids (13.62 mg/g), as UHPLC-HRMS revealed. According to the results, grape polyphenols altered mainly the expression of cytoskeleton and differentiation-associated genes, while coffee compounds had a more profound effect, on the expression levels of many metabolic and antioxidant genes possibly through the nuclear factor (erythroid-derived 2) like-2 (Nrf2) pathway.

Redox Control of Skeletal Muscle Regeneration

Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

4-Phenyl butyric acid increases particulate hexokinase activity and protects against ROS injury in L6 myotubes

Hexokinase (HK) is the first enzyme in the glycolytic pathway and is responsible for glucose phosphorylation and fixation into the cell. HK (HK-II) is expressed in skeletal muscle and can be found in the cytosol or bound mitochondria, where it can protect cells against insults such as oxidative stress. 4-Phenyl butyric acid (4-PBA) is a chemical chaperone that inhibits endoplasmic reticulum stress and contributes to the restoring of glucose homeostasis.

AIMS

Here, we decided to investigate whether HK activity and its interaction with mitochondria could be a target of 4-PBA action.

MAIN METHODS

L6 myotubes were treated with 1mM 4-PBA for 24, 48 or 72h. We evaluated HK activity, glucose and oxygen consumption, gene and protein expression.

KEY FINDINGS

We found that L6 myotubes treated with 4-PBA presented more HK activity in the particulate fraction, increased glucose consumption and augmented Glut4, Hk2 and Vdac1 mRNA expression. Moreover, 4-PBA prevented the deleterious effect of antimycin-A on HK particulate activity.

SIGNIFICANCE

Together, these results suggest a new role of 4-PBA in glucose metabolism that includes HK as a potential target of beneficial effect of 4-PBA.

Nutraceuticals and Their Potential to Treat Duchenne Muscular Dystrophy: Separating the Credible from the Conjecture

In recent years, complementary and alternative medicine has become increasingly popular. This trend has not escaped the Duchenne Muscular Dystrophy community with one study showing that 80% of caregivers have provided their Duchenne patients with complementary and alternative medicine in conjunction with their traditional treatments. These statistics are concerning given that many supplements are taken based on purely "anecdotal" evidence. Many nutraceuticals are thought to have anti-inflammatory or anti-oxidant effects. Given that dystrophic pathology is exacerbated by inflammation and oxidative stress these nutraceuticals could have some therapeutic benefit for Duchenne Muscular Dystrophy (DMD). This review gathers and evaluates the peer-reviewed scientific studies that have used nutraceuticals in clinical or pre-clinical trials for DMD and thus separates the credible from the conjecture.

Resveratrol Enhances Cardiomyocyte Differentiation of Human Induced Pluripotent Stem Cells through Inhibiting Canonical WNT Signal Pathway and Enhancing Serum Response Factor-miR-1 Axis

Resveratrol (trans-3,5,4′-trihydroxystilbene) (RSV) is a natural polyphenol with protective effects over cardiac tissues and can affect cell survival and differentiation in cardiac stem cells transplantation. However, whether this agent can affect cardiomyocytes (CMs) differentiation of induced pluripotent stem cells (iPSCs) is not yet clear. This study explored whether RSV can affect CMs differentiation of human iPSCs. Under embryoid bodies (EBs) condition, the effect of RSV on the change of pluripotent markers, endoderm markers, mesoderm markers, and ectoderm markers was measured using qRT-PCR. Under CM differentiation culture, the effect of RSV on CM specific markers was also measured. The regulative role of RSV over canonical Wnt signal pathway and serum response factor- (SRF-) miR-1 axis and the functions of these two axes were further studied. Results showed that RSV had no effect on the self-renewal of human iPSCs but could promote mesoderm differentiation. Under CM differentiation culture, RSV could promote CM differentiation of human iPSCs through suppressing canonical Wnt signal pathway and enhancing SRF-miR-1 axis.

Exploring new ways of regulation by resveratrol involving miRNAs, with emphasis on inflammation

This review presents recent evidence implicating microRNAs (miRNAs) in the beneficial effects of resveratrol (trihydroxystilbene), a nonflavonoid plant polyphenol, with emphasis on its anti-inflammatory effects. Many diseases and pathologies have been linked, directly or indirectly, to inflammation. These include infections, injuries, atherosclerosis, diabetes mellitus, obesity, cancer, osteoarthritis, age-related macular degeneration, demyelination, and neurodegenerative diseases. Resveratrol can both decrease the secretion of proinflammatory cytokines (e.g., IL-6, IL-8, and TNF-α) and increase the production of anti-inflammatory cytokines; it also decreases the expression of adhesion proteins (e.g., ICAM-1) and leukocyte chemoattractants (e.g., MCP-1). Resveratrol's primary targets appear to be the transcription factors AP-1 and NF-κB, as well as the gene COX2. Although no mechanistic link between any particular miRNA and resveratrol has been identified, resveratrol effects depend at least in part upon the modification of the expression of a variety of miRNAs that can be anti-inflammatory (e.g., miR-663), proinflammatory (e.g., miR-155), tumor suppressing (e.g., miR-663), or oncogenic (e.g., miR-21).

Loquat leaf extract enhances myogenic differentiation, improves muscle function and attenuates muscle loss in aged rats

A main characteristic of aging is the debilitating, progressive and generalized impairment of biological functions, resulting in an increased vulnerability to disease and death. Skeletal muscle comprises approximately 40% of the human body; thus, it is the most abundant tissue. At the age of 30 onwards, 0.5‑1% of human muscle mass is lost each year, with a marked acceleration in the rate of decline after the age of 65. Thus, novel strategies that effectively attenuate skeletal muscle loss and enhance muscle function are required to improve the quality of life of older subjects. The aim of the present study was to determine whether loquat (Eriobotrya japonica) leaf extract (LE) can prevent the loss of skeletal muscle function in aged rats. Young (5-month-old) and aged (18‑19-month-old) rats were fed LE (50 mg/kg/day) for 35 days and the changes in muscle mass and strength were evaluated. The age‑associated loss of grip strength was attenuated, and muscle mass and muscle creatine kinase (CK) activity were enhanced following the administration of LE. Histochemical analysis also revealed that LE abrogated the age‑associated decrease in cross‑sectional area (CSA) and decreased the amount of connective tissue in the muscle of aged rats. To investigate the mode of action of LE, C2C12 murine myoblasts were used to evaluate the myogenic potential of LE. The expression levels of myogenic proteins (MyoD and myogenin) and functional myosin heavy chain (MyHC) were measured by western blot analysis. LE enhanced MyoD, myogenin and MyHC expression. The changes in the expression of myogenic genes corresponded with an increase in the activity of CK, a myogenic differentiation marker. Finally, LE activated the Akt/mammalian target of rapamycin (mTOR) signaling pathway, which is involved in muscle protein synthesis during myogenesis. These findings suggest that LE attenuates sarcopenia by promoting myogenic differentiation and subsequently promoting muscle protein synthesis.

The impact of resveratrol and hydrogen peroxide on muscle cell plasticity shows a dose-dependent interaction

While reactive oxygen species (ROS) play a role in muscle repair, excessive amounts of ROS for extended periods may lead to oxidative stress. Antioxidants, as resveratrol (RS), may reduce oxidative stress, restore mitochondrial function and promote myogenesis and hypertrophy. However, RS dose-effectiveness for muscle plasticity is unclear. Therefore, we investigated RS dose-response on C2C12 myoblast and myotube plasticity 1. in the presence and 2. absence of different degrees of oxidative stress. Low RS concentration (10 μM) stimulated myoblast cell cycle arrest, migration and sprouting, which were inhibited by higher doses (40–60 μM). RS did not increase oxidative capacity. In contrast, RS induced mitochondria loss, reduced cell viability and ROS production, and activated stress response pathways [Hsp70 and pSer36-p66(ShcA) proteins]. However, the deleterious effects of H₂O₂ (1000 µM) on cell migration were alleviated after preconditioning with 10 µM-RS. This dose also enhanced cell motility mediated by 100 µM-H₂O₂, while higher RS-doses augmented the H₂O₂-induced impaired myoblast regeneration and mitochondrial dehydrogenase activity. In conclusion, low resveratrol doses promoted in vitro muscle regeneration and attenuated the impact of ROS, while high doses augmented the reduced plasticity and metabolism induced by oxidative stress. Thus, the effects of resveratrol depend on its dose and degree of oxidative stress.

Role of microRNAs in the age-related changes in skeletal muscle and diet or exercise interventions to promote healthy aging in humans

Progressive age-related changes in skeletal muscle mass and composition, underpin decreases in muscle function, which can inturn lead to impaired mobility and quality of life in older adults. MicroRNAs (miRNAs) are important post-transcriptional regulators of gene expression in skeletal muscle and are associated with aging. Accumulating evidence suggests that miRNAs play an important role in the age-related changes in skeletal muscle mass, composition and function. At the cellular level, miRNAs have been demonstrated to regulate muscle cell proliferation and differentiation. Furthermore, miRNAs are involved in the transitioning of muscle stem cells from a quiescent, to either an activated or senescence state. Evidence from animal and human studies has shown miRNAs are modulated in muscle atrophy and hypertrophy. In addition, miRNAs have been implicated in changes in muscle fiber composition, fat infiltration and insulin resistance. Both exercise and dietary interventions can combat age-related changes in muscle mass, composition and function, which may be mediated by miRNA modulation in skeletal muscle. Circulating miRNA species derived from myogenic cell populations represent potential biomarkers of aging muscle and the molecular responses to exercise or diet interventions, but larger validation studies are required. In future therapeutic approaches targeting miRNAs, either through exercise, diet or drugs may be able to slow down or prevent the age-related changes in skeletal muscle mass, composition, function, hence help maintain mobility and quality of life in old age.

Naturally occurring plant polyphenols as potential therapies for inherited neuromuscular diseases

There are several lines of laboratory-based evidence emerging to suggest that purified polyphenol compounds such as resveratrol, found naturally in red grapes, epigallocatechin galate from green tea and curcumin from turmeric, might be useful for the treatment of various inherited neuromuscular diseases, including spinal muscular atrophy, Duchenne muscular dystrophy and Charcot-Marie-Tooth disease. Here, we critically examine the scientific evidence related to the known molecular effects that these polyphenols have on different models of inherited neuromuscular disease, with particular attention to problems with the validity of in vitro evidence. We also present proteomic evidence that polyphenols have in vitro effects on cells related to metal ion chelation in cell-culture media. Although their precise mechanisms of action remain somewhat elusive, polyphenols could be an attractive approach to therapy for inherited neuromuscular disease, especially since they may be safer to use on young children, compared with some of the other drug candidates.

Resveratrol inhibits the phosphatidylinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway in the human chronic myeloid leukemia K562 cell line

Resveratrol inhibits the initiation, promotion and progression of tumors, however, the mechanism by which resveratrol inhibits the proliferation of the human chronic myeloid leukemia K562 cell line remains unclear. The present study was conducted to investigate the effect of resveratrol on the activation of the phosphatidylinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling cascade in K562 cells. Resveratrol showed significant cytotoxic effects and induced apoptosis in K562 cells in a dose- and time-dependent manner. In addition, resveratrol attenuated the phosphorylation of PI3K, Akt and mTOR in the K562 cells. Furthermore, the selected inhibitors of PI3K (LY294002), Akt (SH-6) and mTOR (rapamycin) enhanced the effects of resveratrol in K562 cells. In addition, cyclin D1 levels were found to decrease and the activation of caspase-3 was observed. Resveratrol was also found to significantly attenuate the phosphorylation of the downstream molecules, p70S6K and 4EBP1. These results suggested that the downregulation of the PI3K/Akt/mTOR signaling cascades may be a crucial mediator in the inhibition of proliferation and induction of apoptosis by resveratrol in K562 cells.

Resveratrol: from basic studies to bedside

Plants produce a remarkable amount of low molecular mass natural products endowed with a large array of pivotal biological activities. Among these molecules, resveratrol (3,5,4'-trihydroxystilbene) has been identified as an important modulator of cell phenotype with a complex and pleiotropic mode of action. Extensive literature regarding its activity, mainly employing cellular models, suggests that this polyphenol controls cell proliferation, induces differentiation, and activates apoptosis and autophagy. The compound also modulates angiogenesis and inflammation. Similarly, studies on implanted cancers and chemical-induced tumors confirm the potential chemotherapeutical interest of the compound. Likewise, several reports clearly demonstrated, in animal models, that the compound might positively affect the development and evolution of chronic diseases including type 2 diabetes, obesity, coronary heart disease, metabolic syndrome, and neurogenerative pathologies. Finally, a number of investigations stated that the toxicity of the molecule is scarce. Despite these promising observations, few clinical trials have yet been performed to evaluate the effectiveness of the molecule both in prevention and treatment of human chronic disease. Preliminary findings therefore suggest the need for more extensive clinical investigations.

Resveratrol promotes myogenesis and hypertrophy in murine myoblasts

Background

Nutrigenomics elucidate the ability of bioactive food components to influence gene expression, protein synthesis, degradation and post-translational modifications.

Resveratrol (RSV), natural polyphenol found in grapes and in other fruits, has a plethora of health benefits in a variety of human diseases: cardio- and neuroprotection, immune regulation, cancer chemoprevention, DNA repair, prevention of mitochondrial disorder, avoidance of obesity-related diseases. In skeletal muscle, RSV acts on protein catabolism and muscle function, conferring resistance against oxidative stress, injury and cell death, but its action mechanisms and protein targets in myogenesis process are not completely known. Myogenesis is a dynamic multistep process regulated by Myogenic Regulator Factors (MRFs), responsible of the commitment of myogenic cell into skeletal muscle: mononucleated undifferentiated myoblasts break free from cell cycle, elongate and fuse to form multinucleated myotubes. Skeletal muscle hypertrophy can be defined as a result of an increase in the size of pre-existing skeletal muscle fibers accompanied by increased protein synthesis, mainly regulated by Insulin Like Growth Factor 1 (IGF-1), PI3-K/AKT signaling pathways.

Aim of this work was the study of RSV effects on proliferation, differentiation process and hypertrophy in C2C12 murine cells.

Methods

To study proliferative phase, cells were incubated in growth medium with/without RSV (0.1 or 25 μM) until reaching sub confluence condition (24, 48, 72 h). To examine differentiation, at 70% confluence, cells were transferred in differentiation medium both with/without RSV (0.1 or 25 μM) for 24, 48, 72, 96 hours. After 72 hours of differentiation, the genesis of hypertrophy in neo-formed myotubes was analyzed.

Results

Data showed that RSV regulates cell cycle exit and induces C2C12 muscle differentiation. Furthermore, RSV might control MRFs and muscle-specific proteins synthesis. In late differentiation, RSV has positive effects on hypertrophy: RSV stimulates IGF-1 signaling pathway, in particular AKT and ERK 1/2 protein activation, AMPK protein level and induces hypertrophic morphological changes in neo-formed myotubes modulating cytoskeletal proteins expression.

Conclusions

RSV might control cell cycle promoting myogenesis and hypertrophy in vitro, opening a novel field of application of RSV in clinical conditions characterized by chronic functional and morphological muscle impairment.

Role of reactive oxygen species in the defective regeneration seen in aging muscle

The ability of muscles to regenerate successfully following damage diminishes with age and this appears to be a major contributor to the development of muscle weakness and physical frailty. Successful muscle regeneration is dependent on appropriate reinnervation of regenerating muscle. Age-related changes in the interactions between nerve and muscle are poorly understood but may play a major role in the defective regeneration. During aging there is defective redox homeostasis and an accumulation of oxidative damage in nerve and muscle that may contribute to defective regeneration. The aim of this review is to summarise the evidence that abnormal reactive oxygen species (ROS) generation in nerve and/or muscle may be responsible for the defective regeneration that contributes to the degeneration of skeletal muscle observed during aging. Identifying the importance of ROS generation in skeletal muscle during aging could have fundamental implications for interventions to prevent muscle degeneration and treatments to reverse the age-related decline in muscle mass and function.