Fat cell invasion in long‐term denervated skeletal muscle

Abstract

There are several differences between red and white muscles submitted to different experimental conditions, especially following denervation: a) denervation atrophy is more pronounced in red than white muscles; b) the size of the fibers in the red muscles does not vary between different parts of the muscle before and after denervation, when compared to white muscles; c) the regional difference in the white muscles initially more pronounced after denervation than red muscle; d) red muscle fibers and fibers of the deep white muscle present degenerative changes such as disordered myofibrils and sarcolemmal folds after long-term denervation; e) myotube-like fibers with central nuclei occur in the red muscle more rapidly than white after denervation. Denervation of skeletal muscles causes, in addition to fibers atrophy, loss of fibers with subsequent regeneration, but the extent of fat cell percentage invasion is currently unknown. The present article describes a quantitative study on fat cell invasion percentage in red m. soleus and white m. extensor digitorum longus (EDL) rat muscles at 7 weeks for up to 32 weeks postdenervation. The results indicate that the percentage of fat cells increase after denervation and it is steeper than the age-related fat invasion in normal muscles. The fat percentage invasion is more pronounced in red compared with white muscle. All experimental groups present a statistically significant difference as regard fat cell percentage invasion.

Age- and Stroke-Related Skeletal Muscle Changes

“…In summary, clinicians must be cognizant that post-stroke there may be an acceleration of negative skeletal muscle changes typically associated with aging, 31, 37, 38, 76 resulting in a greater disadvantage for optimal muscle performance when compared to younger individuals post-stroke. Further, post-stroke skeletal muscle changes may occur in both limbs, 40, 41, 43 warranting caution when comparing the paretic limb to the non-paretic limb.…”

“…37 More recently, using a rat model, de Castro Rodrigues et al reported that the intramuscular fat increase after denervation is greater than the age-related increase observed in healthy muscle, with greater fat invasion in slow-twitch muscles. 76 The functional implications of increased intramuscular fat in individuals post-stroke remain unexplored.…”

Apoptosis in Denervated Skeletal Muscle

“…Continuing the study of this phenomenon, already developed by our group (Rodrigues & Schmalbruch, 1995;Rodrigues et al, 2005), through other techniques, we decided by means of the TUNEL technique which is the most accepted technique for marking this phenomenon (Gavrieli et al, 1992;Knaapen et al, 2001;Van Cruchten & Van Den Broeck, 2002), to confirm the occurrence of apoptosis in two muscles (red and white), submitted to experimental denervations.…”

Células satélites e fusos neuromusculares em músculos estriados de ratos desnervados por longo período

“…Várias pesquisas foram realizadas, tais como analise morfológica e morfométrica de músculos esqueléticos em diversos períodos pós-desnervação, observações da proliferação das células satélites e mionúcleos e apoptose de fibras musculares (RODRIGUES e SCHMALBRUCH, 1995;RODRIGUES et al, 2002;RODRIGUES et al, 2006a;RODRIGUES et al, 2006b;RODRIGUES et al, 2007;DAVATZ et al, 2007;MORGUETE et al, 2007).…”

“…A desnervação promove alterações no músculo esquelético, fato que pode ser observado pela diminuição do trofismo, aumento do tecido gorduroso e do tecido conjuntivo no músculo acometido (MINAMOTO, 2007;RODRIGUES et al, 2007 Quando o músculo esta em repouso, a tropomiosina esta em íntimo contato com a actina, cobrindo esta molécula e impedindo o contato entre a actina e miosina. Contudo, quando o músculo é estimulado, o aumento da permeabilidade induzido pelo estimulo na membrana celular se transmite ao reticulo endoplasmático liso, que libera no citosol íons de cálcio no seu interior (GEEVES e HOLMES, 1999).…”