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Objective: During muscle development or regeneration, myocytes produce nerve growth factor (NGF) as well as its tyrosine-kinase and p75-neurotrophin (p75NTR) receptors. It has been published that the p75NTR receptor could represent a key regulator of NGF-mediated myoprotective effect on satellite cells, but the precise function of NGF/p75 signaling pathway on myogenic cell proliferation, survival and differentiation remains fragmented and controversial. Here, we verified the role of NGF in the growth, survival and differentiation of p75NTR- expressing L6C5 myogenic cells, specifically inquiring for the putative involvement of the nuclear factor δB (NFδB) and the small heat shock proteins (sHSPs) αB-crystallin and Hsp27 in these processes. Results: Although NGF was not effective in modulating myogenic cell growth or survival in both standard or stress conditions, we demonstrated for the first time that, under serum deprivation, NGF sustained the activity of some key enzymes involved in energy metabolism. Moreover, we confirmed that NGF promotes myogenic fusion and expression of the structural protein myosin heavy chain while modulating NFδB activation and the content of sHSPs correlated with the differentiation process. We conclude that p75NTR is sufficient to mediate the modulation of L6C5 myogenic differentiation by NGF in term of structural, metabolic and functional changes. [ABSTRACT FROM AUTHOR]

The low-carbohydrate ketogenic diet (LCKD) is a dietary approach characterized by the intake of high amounts of fat, a balanced amount of protein, and low carbohydrates, which is insufficient for metabolic demands. Previous studies have shown that an LCKD alone may contribute to fatty acid oxidation capacity, along with endurance. In the present study, we combined a 10-week LCKD with an 8-week forced treadmill running program to determine whether training in conjunction with LCKD enhanced fatty acid oxidation capacity, as well as whether the maximal exercise capacity would be affected by an LCKD or training in a mice model. We found that the lipid pool and fatty acid oxidation capacity were both enhanced following the 10-week LCKD. Further, key fatty acid oxidation related genes were upregulated. In contrast, the 8-week training regimen had no effect on fatty acid and ketone body oxidation. Key genes involved in carbohydrate utilization were downregulated in the LCKD groups. However, the improved fatty acid oxidation capacity did not translate into an enhanced maximal exercise capacity. In summary, while favoring the fatty acid oxidation system, an LCKD, alone or combined with training, had no beneficial effects in our intensive exercise-evaluation model. Therefore, an LCKD may be promising to improve endurance in low- to moderate-intensity exercise, and may not be an optimal choice for those partaking in high-intensity exercise. [ABSTRACT FROM AUTHOR]

Epidermal keratinocytes undergo differentiation in response to several stimuli to form the cornified envelope, a structure that contributes to the barrier function of skin. Although differentiation has been extensively analyzed, the precise role of vitamin C during this process is still not defined. Ascorbic acid, besides acting as a radical scavenger, has been shown to promote mesenchymal differentiation. In this study, we found that keratinocytes grown in ascorbate-supplemented medium developed a differentiated phenotype, as demonstrated by enhanced expression of marker genes and increase in cornified envelope content. The pro-differentiating effects of ascorbate were mediated by the protein-kinase-C-dependent induction of activating protein 1 DNA binding activity; indeed, down-modulation of protein kinase C activity abolished differentiation triggered by ascorbic acid. Although vitamin C appeared to regulate the same signaling pathway modulated by calcium, a classical in vitro inducer of epidermal differentiation, nonetheless terminally differentiated keratinocytes exhibited different ascorbate homeostasis and cellular antioxidant status. Indeed, we found that, unlike calcium, differentiation promoted by ascorbate was accompanied by (i) an enhanced ascorbate transport, due to overexpression of specific transporters, (ii) a great efficiency of dehydroascorbate uptake, and (iii) an increase in glutathione content with respect to proliferating cells. Ascorbic acid may be useful to promote epidermal differentiation, avoiding depletion of hydrophilic antioxidant stores. [ABSTRACT FROM AUTHOR]

Sirtuins are NAD+ dependent deacetylases that play a key role in the regulation of many processes related to homeostasis, such as the regulation of metabolism, apoptosis, DNA repair and inflammatory response. Studies on humans reported a relation between the alteration of their expression and the incidence of various diseases such as metabolic, cardiovascular, cancer and neurodegenerative diseases. According with these findings the maintenance of their optimal level of activity is considered important to ensure a low risk of pathologies related with the aging process. Indeed, SIRT1 has been correlated with the redox homeostasis maintenance and with the levels of oxidative damage, such as those affecting telomeric sequences of DNA. The aim of this study is to verify the correlation between sirtuins’ expression, histone deacetylation and redox status in young and old monozygotic twins. For this study we took advantage from blood samples of young (20-40 years old) and old (70-80 years old) monozygotic twins couple, where we analysed the expression of SIRT1 and SIRT2, Lysine acetylation proteins and Histone H4 acetylation, the protein oxidation through the detection of carbonyl groups have been analysed in PBMCs, plasma level of oxidized and reduced glutathione. The putative increase of SIRT1 and SIRT2 levels that should also lead to an improvement in redox and inflammatory homeostasis, hormonal response to stress, and in the maintenance of telomeric DNA sequences could open an interesting view in this field. Particularly the twin model can help to better understand the interaction between genetic and epigenetic effects in the age-related mechanisms. [ABSTRACT FROM AUTHOR]

The imbalance between reactive oxygen species (ROS) production and antioxidant defense systems leads to macromolecule and tissue damage as a result of cellular oxidative stress. This phenomenon is considered a key factor in fatigue and muscle damage following chronic or high-intensity physical exercise. In the present study, the antioxidant effect of Moringa oleifera leaf extract (MOLE) was evaluated in C2C12 myotubes exposed to an elevated hydrogen peroxide (H 2 O 2 ) insult. The capacity of the extract to influence the myotube redox status was evaluated through an analysis of the total antioxidant capacity (TAC), glutathione homeostasis (GSH and GSSG), total free thiols (TFT), and thioredoxin (Trx) activity, as well as the enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and transferase (GST). Moreover, the ability of MOLE to mitigate the stress-induced peroxidation of lipids and oxidative damage (TBARS and protein carbonyls) was also evaluated. Our data demonstrate that MOLE pre-treatment mitigates the highly stressful effects of H 2 O 2 in myotubes (1 mM) by restoring the redox status (TFT, Trx, and GSH/GSSG ratio) and increasing the antioxidant enzymatic system (CAT, SOD, GPx, GST), thereby significantly reducing the TBARs and PrCAR levels. Our study provides evidence that MOLE supplementation has antioxidant potential, allowing myotubes better able to cope with an oxidative insult and, therefore, could represent a useful nutritional strategy for the preservation of muscle well-being.

Objective: During muscle development or regeneration, myocytes produce nerve growth factor (NGF) as well as its tyrosine-kinase and p75-neurotrophin (p75 NTR ) receptors. It has been published that the p75 NTR receptor could represent a key regulator of NGF-mediated myoprotective effect on satellite cells, but the precise function of NGF/p75 signaling pathway on myogenic cell proliferation, survival and differentiation remains fragmented and controversial. Here, we verified the role of NGF in the growth, survival and differentiation of p75 NTR -expressing L6C5 myogenic cells, specifically inquiring for the putative involvement of the nuclear factor κB (NFκB) and the small heat shock proteins (sHSPs) αB-crystallin and Hsp27 in these processes., Results: Although NGF was not effective in modulating myogenic cell growth or survival in both standard or stress conditions, we demonstrated for the first time that, under serum deprivation, NGF sustained the activity of some key enzymes involved in energy metabolism. Moreover, we confirmed that NGF promotes myogenic fusion and expression of the structural protein myosin heavy chain while modulating NFκB activation and the content of sHSPs correlated with the differentiation process. We conclude that p75 NTR is sufficient to mediate the modulation of L6C5 myogenic differentiation by NGF in term of structural, metabolic and functional changes.

Skeletal muscle cells are continuously exposed to oxidative stress. Thus, they compensate environmental challenges by increasing adaptive responses, characterized by activating protein 1 (AP-1)- and nuclear factor kappaB (NF-kappaB)-mediated transcriptional upregulation of endogenous enzymatic and nonenzymatic antioxidants. We investigated the crosstalk of molecules involved in redox signaling in muscle cells, by using the rat L6C5 and mouse C2C12 cell lines, which represent a useful experimental model for studying muscle metabolism. We analyzed specific antioxidant systems, including glutathione, thioredoxin reductase, and antioxidant enzymes, and the redox-sensitive transcription factors AP-1 and NF-kappaB, in both myoblasts and myotubes. We found that the high levels of NF-kappaB DNA binding activity and thioredoxin reductase, together with inhibitory AP-1 complexes, allowed increased expression of antioxidant enzymes and survival of C2C12 cells after oxidant exposure. On the contrary, L6C5 myoblasts had a sensitive phenotype, correlated with lower levels of thioredoxin reductase, catalase, and NF-kappaB activity and higher levels of GSSG and activating AP-1 complexes. Interestingly, this cell line acquired an apoptosis-resistant phenotype, accompanied by drastic changes in the oxidant/antioxidant balance, when induced to differentiate. In conclusion, the two cell lines, although similar in terms of growth and differentiation, displayed significant heterogeneity in terms of redox homeostasis.