Submitted on June 23, 2008
Revised on August 19, 2008
Accepted on September 16, 2008
Age-dependent increase in oxidative stress in gastrocnemius muscle with unloading
Parco M. Siu1*, Emidio Edward Pistilli2, and Stephen E. Alway3
1 Hong Kong Polytechnic University
2 University of Pennsylvania
3 West Virginia University School of Medicine
* To whom correspondence should be addressed. E-mail: htpsiu{at}inet.polyu.edu.hk.
Oxidative stress increases during unloading in muscle from young adult rats. The present study examined the markers of oxidative stress and antioxidant enzymes gene and protein expressions in medial gastrocnemius muscles of aged and young adult (30 and 6 mo of age) Fischer344xBrown Norway rats after 14 days of hindlimb suspension. Medial gastrocnemius muscle weight was decreased by ~30% in young adult and aged rats following suspension. When muscle weight was normalized to animal bodyweight, it was reduced by 12% and 22% in young adult and aged rats, respectively after suspension. Comparisons between young adult and aged control animals demonstrated a 25% and 51% decline in muscle mass when expressed as absolute muscle weight and muscle weight normalized to the animal bodyweight, respectively. H2O2 content was elevated by 43% while MnSOD protein content was reduced by 28% in suspended muscles when compared to control muscles exclusively in the aged animals. Suspended muscles had greater content of MDA/4-HAE (29% and 58% increase in young adult and aged rats, respectively), nitrotyrosine (76% and 65% increase in young adult and aged rats, respectively) and catalase activity (69% and 43% increase in young adult and aged rats, respectively) relative to control muscles. Changes in oxidative stress markers MDA/4-HAE, H2O2 and MnSOD protein contents in response to hindlimb unloading occurred in an age-dependent manner. These findings are consistent with the hypotheses that oxidative stress has a role in mediating disuse-induced and sarcopenia associated muscle losses. Our data suggest that aging may predispose skeletal muscle to increased levels of oxidative stress both at rest and during unloading.
