Expression of the stress proteins, ubiquitin, heat shock protein 72, and myofibrillar protein content after 12 weeks of leg cycling in persons with spinal cord injury.

Abstract

To determine the effects of leg cycling exercise on ubiquitin (UBI), heat shock protein 72 (HSP-72) mRNA, protein expression, and myofibrillar protein content in individuals with spinal cord injury (SCI). Case series. Motor behavior laboratory. Seven subjects with motor-complete SCI (4 men, 3 women). A 12-week exercise program involving an electromagnetically braked recumbent bicycle ergometer, which allowed for passive exercise of the legs. Training occurred 2 days a week at approximately 75% of each subject's maximum heart rate. Total body mass (TBM) and muscle biopsies were obtained pre- and posttraining. The mRNA and protein expression of UBI, HSP-72, and myofibrillar protein content were determined. Nonsignificant increases (P > .05) of 2.45% were observed for TBM. There were significant increases (P < .05) in the expression of both HSP-72 mRNA (33.71%) and protein (30.23%). For UBI, there were also significant decreases (P < .05) in the expression of both mRNA (26.86%) and protein (69.43%). Myofibrillar protein content increased significantly (P < .05, 41.86%). Leg cycling exercise in SCI increases myofibrillar protein content, possibly because of up-regulation in the expression of HSP-72 with concomitant down-regulation in the expression of UBI.