Phablo Abreu

Satellite cell activation induced by aerobic muscle adaptation in response to endurance exercise in humans and rodents.

Abstract Although the requirement of satellite cells activation and expansion following injury, mechanical load or growth stimulus provoked by resistance exercise has been well established, their function in response to aerobic exercise adaptation remains unclear. A clear relationship between satellite cell expansion in fiber‐type specific myosin heavy chain and aerobic performance has been related, independent of myonuclear accretion or muscle growth. However, the trigger for this activation process is not fully understood yet and it seems to be a multi‐faceted and well‐orchestrated process. Emerging in vitro studies suggest a role for metabolic pathways and oxygen availability for satellite cell activation, modulating the self‐renewal potential and cell fate control. The goal of this review is to describe and discuss the current knowledge about the satellite cell activation and expansion in response to aerobic exercise adaptation in human and rodent models. Additionally, findings about the in vitro metabolic control, which seems be involved in the satellite cell activation and cell fate control, are presented and discussed.

Effects of high EPA and high DHA fish oils on changes in signaling associated with protein metabolism induced by hindlimb suspension in rats

The effects of either eicosapentaenoic (EPA)‐ or docosahexaenoic (DHA)‐rich fish oils on hindlimb suspension (HS)‐induced muscle disuse atrophy were compared. Daily oral supplementations (0.3 mL/100 g b.w.) with mineral oil (MO) or high EPA or high DHA fish oils were performed in adult rats. After 2 weeks, the animals were subjected to HS for further 2 weeks. The treatments were maintained alongside HS. At the end of 4 weeks, we evaluated: body weight gain, muscle mass and fat depots, composition of fatty acids, cross‐sectional areas (CSA) of the soleus muscle and soleus muscle fibers, activities of cathepsin L and 26S proteasome, and content of carbonylated proteins in the soleus muscle. Signaling pathway activities associated with protein synthesis (Akt, p70S6K, S6, 4EBP1, and GSK3‐beta) and protein degradation (atrogin‐1/MAFbx, and MuRF1) were evaluated. HS decreased muscle mass, CSA of soleus muscle and soleus muscle fibers, and altered signaling associated with protein synthesis (decreased) and protein degradation (increased). The treatment with either fish oil decreased the ratio of omega‐6/omega‐3 fatty acids and changed protein synthesis‐associated signaling. EPA‐rich fish oil attenuated the changes induced by HS on 26S proteasome activity, CSA of soleus muscle fibers, and levels of p‐Akt, total p70S6K, p‐p70S6K/total p70S6K, p‐4EBP1, p‐GSK3‐beta, p‐ERK2, and total ERK 1/2 proteins. DHA‐rich fish oil attenuated the changes induced by HS on p‐4EBP1 and total ERK1 levels. The effects of EPA‐rich fish oil on protein synthesis signaling were more pronounced. Both EPA‐ and DHA‐rich fish oils did not impact skeletal muscle mass loss induced by non‐inflammatory HS.

Contractile function recovery in severely injured gastrocnemius muscle of rats treated with either oleic or linoleic acid

What is the central question of this study? Oleic and linoleic acids modulate fibroblast proliferation and myogenic differentiation in vitro. However, their in vivo effects on muscle regeneration have not yet been examined. We investigated the effects of either oleic or linoleic acid on a well‐established model of muscle regeneration after severe laceration. What is the main finding and its importance? We found that linoleic acid increases fibrous tissue deposition and impairs muscle regeneration and recovery of contractile function, whereas oleic acid has the opposite effects in severely injured gastrocnemius muscle, suggesting that linoleic acid has a harmful effect and oleic acid a potential therapeutic effect on muscle regeneration.

Anaerobic threshold employed on exercise training prescription and performance assessment for laboratory rodents: A short review.

Several studies have generated numerous terms in the field of exercise training prescription and performance assessment that often do not match the information previously demonstrated by many other works, generating much debate and resulting in an immense pool of scientific results. Several protocols in exercise training prescription and performance assessment have been proposed for these purposes by many reasons. In the field of exercise science, the protocol must be thoroughly investigated and provide real tools to be reproducible. Many laboratories have been adapting and developing evaluation protocols and testing on physical training of rodents in different experimental conditions. In this context, mice, rats and rabbits are preferentially chosen due to easy manipulation and good response to exercise, and comparable at results obtained with humans in compatible effort intensities. But, the exercise training programs and aerobic-anaerobic transition assessment proposed for animal models vary extensively, depending on the species, gender, age, type of stimulus, type of exercise, type of method and also on the specific objectives of the program. This short review demonstrates the need in offering tools performed by invasive measurement to assess the anaerobic threshold by blood lactate employed on evolution of aerobic-anaerobic parameters of rodents. The objective of this short review was to present and to discuss physical evaluation protocols applications to rodents. The table submitted may give a basis for anaerobic threshold employed on exercise training prescription and performance assessment for laboratory rodents in future research.

Experimental Model of Skeletal Muscle Laceration in Rats

This is a modified experimental model previously developed in mouse to study skeletal muscle laceration in rats. All experimental procedures are performed during the light period, including anesthesia and surgery. The animals are randomly distributed into control and injured groups prior to the procedure. This experimental model can be used to investigate skeletal muscle laceration repair.

Bioenergetics mechanisms regulating muscle stem cell self-renewal commitment and function

Muscle stem cells or satellite cells are crucial for muscle maintenance and repair. These cells are mitotically quiescent and uniformly express the transcription factor Pax7, intermittently entering the cell cycle to give rise to daughter myogenic precursors cells and fuse with neighboring myofibers or self-renew, replenishing the stem cell pool in adult skeletal muscle. Pivotal roles of muscle stem cells in muscle repair have been uncovered, but it still remains unclear how muscle stem cell self-renewal is molecularly regulated and how muscle stem cells maintain muscle tissue homeostasis. Defects in muscle stem cell regulation to maintain/return to quiescence and self-renew are observed in degenerative conditions such as aging and neuromuscular disease. Recent works has suggested the existence of metabolic regulation and mitochondrial alterations in muscle stem cells, influencing the self-renewal commitment and function. Here I present a brief overview of recent understanding of how metabolic reprogramming governs self-renewal commitment, which is essential for conservation of muscle satellite cell pools throughout life, as well as the implications for regenerative medicine.

Regulation of muscle plasticity and trophism by fatty acids: A short review

The skeletal muscle tissue has a remarkable ability to alter its plastic structural and functional properties after a harmful stimulus, regulating the expression of proteins in complex events such as muscle regeneration. In this context, considering that potential therapeutic agents have been widely studied, nutritional strategies have been investigated in order to improve the regenerative capacity of skeletal muscle. There is evidence of the modulatory action of fatty acids, such that oleic and linoleic acids, that are abundant in Western diets, on muscle function and trophism. Thus, fatty acids appear to be potential candidates to promote or impair the recovery of muscle mass and function during regeneration, since they modulate intracellular pathways that regulate myogenesis. This study is the first to describe and discuss the effect of fatty acids on muscle plasticity and trophism, with emphasis on skeletal muscle regeneration and in vitro differentiation of muscle cells.

ADAPTATION OF SKELETAL MUSCLE TO PHYSICAL EXERCISE: MOLECULAR AND ENERGY CONSIDERATIONS

The health benefits and physiological adaptations to regular physical exercise are widely known, and with the advent of the omic and molecular sciences, a complex network of signaling pathways and regulatory molecules that coordinate the adaptive response of skeletal muscle to exercise has been revealed. Transient organic changes, however, are cumulative in the post-exercise period. They mainly include transcription of genes related to regulatory factors of myogenesis, carbohydrate metabolism, fat mobilization, transport and oxidation of substrates, mitochondrial metabolism through oxidative phosphorylation, and finally, the transcriptional regulation of genes involved in mitochondrial biogenesis. Given their great scientific impact, in addition to some of the main molecular responses experienced by the skeletal muscle to exercise, factors that coordinate muscle plasticity for performance gain were summarized in this work. This review mentioned dozens of biomarkers linked to some molecular aspects of skeletal muscle adaptations to physical exercise, some major signaling pathways and the role of mitochondria, revealing some new paradigms for the understanding of this field of science.

ADAPTAÇÃO DO MÚSCULO ESQUELÉTICO AO EXERCÍCIO FÍSICO: CONSIDERAÇÕES MOLECULARES E ENERGÉTICAS

The health benefits and physiological adaptations to regular physical exercise are widely known, and with the advent of the omic and molecular sciences, a complex network of signaling pathways and regulatory molecules that coordinate the adaptive response of skeletal muscle to exercise has been revealed. Transient organic changes, however, are cumulative in the post-exercise period. They mainly include transcription of genes related to regulatory factors of myogenesis, carbohydrate metabolism, fat mobilization, transport and oxidation of substrates, mitochondrial metabolism through oxidative phosphorylation, and finally, the transcriptional regulation of genes involved in mitochondrial biogenesis. Given their great scientific impact, in addition to some of the main molecular responses experienced by the skeletal muscle to exercise, factors that coordinate muscle plasticity for performance gain were summarized in this work. This review mentioned dozens of biomarkers linked to some molecular aspects of skeletal muscle adaptations to physical exercise, some major signaling pathways and the role of mitochondria, revealing some new paradigms for the understanding of this field of science.

ADAPTACIÓN DEL MÚSCULO ESQUELÉTICO AL EJERCICIO FÍSICO: CONSIDERACIONES MOLECULARES Y ENERGÉTICAS

The health benefits and physiological adaptations to regular physical exercise are widely known, and with the advent of the omic and molecular sciences, a complex network of signaling pathways and regulatory molecules that coordinate the adaptive response of skeletal muscle to exercise has been revealed. Transient organic changes, however, are cumulative in the post-exercise period. They mainly include transcription of genes related to regulatory factors of myogenesis, carbohydrate metabolism, fat mobilization, transport and oxidation of substrates, mitochondrial metabolism through oxidative phosphorylation, and finally, the transcriptional regulation of genes involved in mitochondrial biogenesis. Given their great scientific impact, in addition to some of the main molecular responses experienced by the skeletal muscle to exercise, factors that coordinate muscle plasticity for performance gain were summarized in this work. This review mentioned dozens of biomarkers linked to some molecular aspects of skeletal muscle adaptations to physical exercise, some major signaling pathways and the role of mitochondria, revealing some new paradigms for the understanding of this field of science.