Effect of Resistance Training on Extracellular Matrix Adaptations in Skeletal Muscle of Older Rats

Abstract

Accumulation of connective tissue, particularly extracellular matrix (ECM) proteins, has been observed in skeletal muscles with advancing age. Resistance training (RT) has been widely recommended to attenuate age-induced sarcopenia, even though its effects on the components that control ECM turnover in skeletal muscles remain to be elucidated. Thus, the aim of this study was to determine the effects of RT on connective tissue content and gene expression of key components of ECM in the skeletal muscles of aged rats. Young (3 mo.) and older (21 mo.) adult male Wistar rats were submitted to a RT protocol (ladder climbing with 65, 85, 95, and 100% load), 3 times a week for 12 weeks. Forty-eight hours post-training, the soleus (SOL) and gastrocnemius (GAS) muscles were dissected for histological and mRNA analysis. RT mitigated the age-associated increase of connective tissue content in both muscles, even though mRNA levels of COL-1 and−3 were elevated in older trained rats. Overall, RT significantly elevated the gene expression of key components of connective tissue deposition (TGFβ and CTGF; MMP-2 and-9; TIMP-1 and−2) in the GAS and SOL muscles of older rats. In conclusion, RT blunted the age-induced accumulation of connective tissue concomitant to the upregulation of genes related to synthesis and degradation of the ECM network in the SOL and GAS muscles of older rats. Although our findings indicate that RT plays a crucial role reducing connective tissue accumulation in aged hindlimb muscles, key components of ECM turnover were paradoxically elevated. The phenotypic responses induced by RT were not accompanied by the gene expression of those components related to ECM turnover.

Aging‐associated skeletal muscle defects in HER2/Neu transgenic mammary tumour model

“…Advancing age is associated with accumulation of ECM proteins in the skeletal muscle, 38 and we had previously reported excessive ECM deposition in the skeletal muscle of PyMT+ compared with wild-type mice. 16 Interestingly, similar increase in ECM deposition in the skeletal muscle was observed in Neu+ mice ( Figure 6C; bottom row).…”

Skeletal Muscle Extracellular Matrix – What Do We Know About Its Composition, Regulation, and Physiological Roles? A Narrative Review

“…de Sousa Neto et al (2018) reported that 12 weeks of resistance training consisting of ladder climbs with progressive, additional loads equivalent to 65-100% of each individual's maximum carrying capacity upregulated MMP-2 activity in the plantarflexor muscles of old rats, while down-regulating MMP-2 and MMP-9 in blood circulation. The authors' conclusion that resistance training might, therefore, be a useful tool to maintain ECM remodeling at older age has recently received empirical support by another training study in rats that used the same training protocol and showed a reduced deposition of connective tissue in trained older muscles (Guzzoni et al, 2018).…”

Comparative Transcriptome and Methylome Analysis in Human Skeletal Muscle Anabolism, Hypertrophy and Epigenetic Memory

“…File 8). Importantly, some of these ECM/actin structural and remodelling genes have been shown to demonstrate increases after aerobic or resistance exercise at the gene expression, protein abundance or activity level such as; TIMP3 25 , FLNB 26 , COL4A1 27,28 , or are involved in satellite/muscle cell regulation (ITGB3 29 , CTTN 30 , LAMA5 31 , CRK 32,33 ). However, to the authors knowledge there is no evidence to suggest that any of these genes are differentially methylated at the DNA level in skeletal muscle anabolism or hypertrophy.…”