ABSTRACT
Summary 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.
Resumo O tecido muscular esquelético possui a notável capacidade plástica de alterar suas propriedades estruturais e funcionais após um estímulo lesivo, regulando a expressão de proteínas durante eventos complexos como a regeneração muscular. Nesse contexto, considerando que possíveis agentes terapêuticos vêm sendo amplamente estudados, estratégias nutricionais têm sido investigadas na perspectiva de melhorar a capacidade regenerativa do músculo esquelético. Há evidências da ação modulatória dos ácidos graxos, como os ácidos oleico e linoleico, que são abundantes nas dietas ocidentais, sobre a função muscular e o trofismo. Nesse sentido, os ácidos graxos parecem ser potenciais candidatos para promover ou prejudicar a recuperação da massa e a função muscular durante a regeneração, uma vez que modulam vias intracelulares reguladoras da miogênese. Este trabalho é o primeiro a descrever e discutir o efeito dos ácidos graxos sobre a plasticidade e o trofismo muscular, com ênfase na regeneração do músculo esquelético e na diferenciação de células musculares in vitro.
Subject(s)
Humans , Regeneration/physiology , Muscle, Skeletal/physiology , Fatty Acids/metabolism , Cell Differentiation/drug effects , Muscle, Skeletal/cytology , Muscle, Skeletal/metabolism , Muscle Fibers, Skeletal/cytology , Muscle Fibers, Skeletal/metabolism , Myoblasts, Skeletal/cytologyABSTRACT
Satellite cells of adult skeletal muscle fibres are myogenic monoculeated cells that are closely attached to muscle fibres. These cells provide new myonuclei during growth and regeneration; myonuclei are postmiotic. Three to 11 of myonuclei seen by lght microscopy in reality are satellite cell nuclei. Developing muscles contain up to 35% satellite cells. Their incidence decreases after denervation and possibly also with age. They are more numerous in slow-twitch than in fast-twitch muscles. The turnover rate of myonuclei in normal muscles is at most 1% per week, and satellite cells are quiescent. Injury, excessive muscle activity, mechanical stretching and also androgens induce proliferation and eventually fusion into myotubes. Myostatin keeps the satellite cells quiescent, and hepatocyte growth factor (HGF) induces activation. Myoblasts during muscle development express Pax3 while satellite cells express Pax7. Pax3 is upregulated in activated satellite cells. Satellie cells form a self-sustaining population, and when labelled satellite cells are grafted into a necrotic muscle, the label occurs not only in the new myonuclei but also in the satellite cells of the new fibres. Satllite cells are stem cells that may form haematopoetic colonies, and bone-marrow-and endothelium-derived cells may become myogenic. Nevertheless, the capability of these cells to replace each other is apparently limited. Satellite celss from aged individuals are activated with delay, possibly also their number declines. The delay is due to impaired Notch signaling and becomes normal in parabiotic old-young animals. The length of the telomeric DNA decreases with the number of mitotic cycles and therefore is shorter in aged individuals, in overworked muscles and in children with muscular dystrophy. The number of miotic cycles is 50 to 60 when human staellite cells are harvested at birth, but it is only 15 to 20 beyond the age of 20 years. Satellite cells have gained much interest during...