dnRas stimulates autocrine-paracrine growth of regenerating muscle via calcineurin-NFAT-IL-4 pathway

Eugenol mimics exercise to promote skeletal muscle fiber remodeling and myokine IL-15 expression by activating TRPV1 channel

Metabolic disorders are highly prevalent in modern society. Exercise mimetics are defined as pharmacological compounds that can produce the beneficial effects of fitness. Recently, there has been increased interest in the role of eugenol and transient receptor potential vanilloid 1 (TRPV1) in improving metabolic health. The aim of this study was to investigate whether eugenol acts as an exercise mimetic by activating TRPV1. Here, we showed that eugenol improved endurance capacity, caused the conversion of fast-to-slow muscle fibers, and promoted white fat browning and lipolysis in mice. Mechanistically, eugenol promoted muscle fiber-type transformation by activating TRPV1-mediated CaN signaling pathway. Subsequently, we identified IL-15 as a myokine that is regulated by the CaN/nuclear factor of activated T cells cytoplasmic 1 (NFATc1) signaling pathway. Moreover, we found that TRPV1-mediated CaN/NFATc1 signaling, activated by eugenol, controlled IL-15 levels in C2C12 myotubes. Our results suggest that eugenol may act as an exercise mimetic to improve metabolic health via activating the TRPV1-mediated CaN signaling pathway.

A Short Overview of Changes in Inflammatory Cytokines and Oxidative Stress in Response to Physical Activity and Antioxidant Supplementation

Excessive release of inflammatory cytokines and oxidative stress (OS) are triggering factors in the onset of chronic diseases. One of the factors that can ensure health in humans is regular physical activity. This type of activity can enhance immune function and dramatically prevent the spread of the cytokine response and OS. However, if physical activity is done intensely at irregular intervals, it is not only unhealthy but can also lead to muscle damage, OS, and inflammation. In this review, the response of cytokines and OS to exercise is described. In addition, it is focused predominantly on the role of reactive oxygen and nitrogen species (RONS) generated from muscle metabolism and damage during exercise and on the modulatory effects of antioxidant supplements. Furthermore, the influence of factors such as age, sex, and type of exercise protocol (volume, duration, and intensity of training) is analyzed. The effect of antioxidant supplements on improving OS and inflammatory cytokines is somewhat ambiguous. More research is needed to understand this issue, considering in greater detail factors such as level of training, health status, age, sex, disease, and type of exercise protocol.

Follistatin treatment suppresses SERCA1b levels independently of other players of calcium homeostasis in C2C12 myotubes

Follistatin (FS) is a high affinity activin-binding protein, neutralizing the effects of the Transforming Growth Factor-beta (TGF-β) superfamily members, as myostatin (MSTN). Since MSTN emerged as a negative regulator, FS has been considered as a stimulator of skeletal muscle growth and differentiation. Here, we studied the effect of FS administration on the Ca²⁺-homeostasis of differentiating C2C12 skeletal muscle cells. FS-treatment increased the fusion index, the size of terminally differentiated myotubes, and transiently elevated the expression of the calcium-dependent protein phosphatase, calcineurin, at the beginning of differentiation. Functional experiments did not detect any alterations in the Ca²⁺ transients following the stimulation by KCl or caffeine in myotubes. On the other hand, decreased Ca²⁺-uptake capability was determined by calculating the maximal pump rate (332 ± 17 vs. 279 ± 11 µM/s, in control and FS-treated myotubes, respectively; p < 0.05). In the same way, the expression and ATPase activity of the neonatal sarcoplasmic/endoplasmic reticulum Ca²⁺ATPase (SERCA1b) were decreased (0.59 ± 0.01 vs. 0.19 ± 0.01 mM ATP/min, in control and FS-treated myotubes, respectively; p < 0.05). However, the expression level of other proteins involved in Ca²⁺-homeostasis and differentiation (calsequestrin, STIM1, MyoD) were not affected. Our results suggest that the FS controlled myotube growth is paralleled with the tight regulation of cytosolic calcium concentration, and the decline of SERCA1b appears to be one of the key components in this process.

Transfection efficiency along the regenerating soleus muscle of the rat

We investigated the efficiency of a single plasmid transfection along the longitudinal axis of the regenerating soleus of young rats. This also reflected transfection efficiency along the fibers because the soleus is a nearly fusiform muscle in young animals. The complete regeneration was induced by notexin and the transfection was made by intramuscular injection of enhanced green fluorescent protein- or Discosoma red-coding plasmids after 4 days. One week after transfection the number of transfected fibers was higher at the place of injection (i.e., in the muscle belly) and lower or absent at the ends of the muscle. The inspection of longitudinal sections and neuromuscular endplates indicated that one of the reasons of uneven transfection might be the shortness of transfected myotubes and the other reason might be the limit of diffusion of transgenic proteins from the expressing nuclei. As a result, the efficiency of transfection in the whole regenerating muscle was much lower than it could be estimated from the most successfully transfected part.