Received September 10, 2007
Revised October 17, 2007
Accepted after revision November 2, 2007

¹ Syracuse University
² LeMoyne College
³ University of Florida

^* To whom correspondence should be addressed. E-mail: kcderuis{at}syr.edu.

	Abstract

Increased free radical production and oxidative damage in ageing muscle may be a contributing factor to the development of sarcopenia. It has been suggested that the accumulation of iron may be an underlying factor in the development of oxidative stress in ageing tissues, including skeletal muscle. At present, however, the mechanisms responsible for ageing-associated muscle iron accumulation are unknown. These experiments tested the hypothesis that ageing-associated elevations in skeletal muscle iron are accompanied by altered expression of key regulators of intracellular iron status. We determined non-haem iron, oxidative injury, and expression levels of iron regulation proteins in plantaris muscles harvested from 6 and 24-26 month old Fisher 344 rats (n = 10/group). Ageing resulted in a 62% elevation in skeletal muscle non-haem iron (p < 0.05) and higher protein oxidative damage (p < 0.05). Notably, ageing was associated with elevated expression of ferritin (heavy (H) chain, +56.2 fold; light (L) chain, +7.3 fold), an important iron storage protein. Conversely, the iron transport protein transferrin receptor-1 demonstrated dramatic downregulation (-10.8 fold; p < 0.05) in old muscle whereas the level of divalent metal transporter-1 protein expression was unaltered. No change in protein level of iron regulatory protein-1 was observed. In summary, these results demonstrate the occurrence of altered iron regulation concomitant with iron accumulation and oxidative stress in aged skeletal muscle. Importantly, the maintenance of divalent metal transporter-1 protein expression into old age could play a role in the accumulation of skeletal muscle iron.

Key Words: Ageing, Iron, Skeletal muscle