Age and aerobic training status effects on plasma and skeletal muscle tPA and PAI-1

• Published in: European journal of applied physiology 2014-06, Vol.114 (6), p.1229-1238
• Main Authors: Francis, Ryan M., Romeyn, Christine L., Coughlin, Adam M., Nagelkirk, Paul R., Womack, Christopher J., Lemmer, Jeffrey T.
• Format: Article
• Language: English
• Subjects: Aerobics; Age; Age Factors; Aged; Aging; Biomedical and Life Sciences; Biomedicine; Cardiovascular disease; Case-Control Studies; Enzymes; Exercise; Human Physiology; Humans; Ischemia; Male; Maximum oxygen consumption; Middle Aged; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Musculoskeletal system; Occupational Medicine/Industrial Medicine; Older people; Original Article; Physical fitness; Plasma; Plasminogen Activator Inhibitor 1 - blood; Plasminogen Activator Inhibitor 1 - genetics; Plasminogen Activator Inhibitor 1 - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sports Medicine; Thrombosis; Tissue Plasminogen Activator - blood; Tissue Plasminogen Activator - genetics; Tissue Plasminogen Activator - metabolism; Young Adult
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-014-2857-2

Introduction Reductions in fibrinolytic potential occur with both aging and physical inactivity and are associated with an increased cardiovascular disease risk. Plasmin, the enzyme responsible for the enzymatic degradation of fibrin clots, is activated by tissue plasminogen activator (tPA), while plasminogen activator inhibitor-1 (PAI-1) inhibits its activation. Currently, fibrinolysis research focuses almost exclusively on changes within the plasma. However, tPA and PAI-1 are expressed by human skeletal muscle (SM). Currently, no studies have focused on changes in SM fibrinolytic activity with regard to aging and aerobic fitness. Purpose The purpose of this study was to cross-sectionally evaluate effects of age and aerobic fitness on tPA and PAI-1 expressions and activity in SM. Methods Twenty-six male subjects were categorized into the following groups: (1) young aerobically trained ( n  = 8); (2) older aerobically trained ( n  = 6); (3) young aerobically untrained ( n  = 7); and (4) older aerobically untrained ( n  = 5). Muscle biopsies were obtained from each subject. SM tPA activity was assessed using gel zymography and SM tPA and PAI-1 expressions were assessed using RT-PCR. Results Trained subjects had higher SM tPA activity compared to untrained (25.3 ± 2.4 × 10 3 vs. 21.5 ± 5.6 × 10 3  pixels, respectively; p  = 0.03) with no effect observed for age. VO 2 max and SM tPA activity were also significantly correlated ( r  = 0.42; p