Proteomic changes in skeletal muscle of aged rats in response to resistance training.

Sarcopenia is a multifactorial process defined by loss of strength and skeletal muscle mass, which leads to a reduction in muscle cross-sectional area (CSA). Although resistance training (RT) has been indicated as a tool to counteract sarcopenia, the protein profile associated with skeletal muscle adaptations remains to be determined. We investigated the effects of 12 weeks of RT on the skeletal muscle proteome profile and CSA of young and older rats. Twenty-four animals were divided into four groups: young sedentary or trained and older sedentary or trained (six animals per group). A 12-week RT protocol was performed, which consisted of climbing a vertical ladder. The proteins from the gastrocnemius were analysed by LC-ESI-MS/MS. One-hundred and thirty-one proteins were identified, of which 28 were assessed between the groups. Ageing induced an increase in proteins associated with the glycolytic pathway, transport and stress response, which represent crucial mechanisms for muscle adaptation. RT upregulated metabolic enzymes, anti-oxidant activity and transport proteins, besides increasing hypertrophy, regardless of age, suggesting a beneficial adaptation to mitigate age-related sarcopenia. RT reduced muscle atrophy through the regulation of stress response and by increasing proteins related to energy production and transport, which in turn might protect tissue damage arising from exercise and ageing. SIGNIFICANCE OF THE STUDY: Protein abundance levels related to the metabolic process and stress response were increased in the aged muscle. RT proved to be an important intervention capable of inducing significant effects on muscle proteome regardless of ageing, due to upregulation of glycolytic enzymes, and anti-oxidant and transport proteins. This effect could lead to a beneficial adaptation in muscle structure, cellular function and overall homeostasis maintenance. This study contributes to better understanding of the basic biology of ageing and clarifies more profoundly the molecular networks behind physiological adaptations promoted by exercise training. Therefore, the results open new perspectives and insights for studies based on transcriptomics, metabolomics and functional assays.

Beneficial effects of resistance training on the protein profile of the calcaneal tendon during aging.

The calcaneal tendon (CT) is the most commonly injured tendon in the human body. Moreover, with advancing age, the amount of damage increases further. Resistance training (RT) could be used to minimize such damages. The aim of the present study was to obtain the identification, detailed protein cataloging and biochemical characterization based on the effects of the aging process and the RT in CT of rats. The analysis by liquid chromatography tandem-mass spectrometry showed 142 distinct proteins, however, only 29 proteins met the inclusion criteria and were analyzed. Aging causes a reduction in the abundance of seven proteins related to extracellular matrix organization, biological regulation and cellular processes. However, RT promoted the positive regulation of proteins important for the maintenance of healthy tendons: seven proteins in young trained and two in older trained group. This study contributes to a better understanding of molecular aspects of the tendon. The down regulation of proteins linked to mechanical function and extracellular matrix remodeling of the tendon during aging can contribute to the increase of injury and weakness in the tendon. Nevertheless, RT proved to be a tool to prevent these adverse effects during aging by increasing proteins involved in the functionality of the tendon.