ABSTRACT

　Many studies have attempted to determine the associations between blood and urinebiomarkers and muscle damage and atrophy. However, poor correlations between thechanges in biomarker levels and the magnitude of muscle damage and atrophy havebeen reported. Recently, the N-terminal fragment（ N-titin） of titin（ connectin）， a giantsarcomeric protein that is involved in muscular passive tension and viscoelasticity,has been reported to detect muscle damage in patients with skeletal muscle dystrophyand in healthy volunteers with endurance exercise. In the present study, we evaluatedwhether urinary N-titin is changed during a muscle atrophy period and whetherits increase reflects muscle atrophy. C57BL/6 mice （male, 10 weeks of age） wereused of this study. Urine samples were obtained after sciatic nerve removal surgery to induce muscle atrophy. We measured the urinary levels of N-titin with a highlysensitive ELISA system. 11 days after sciatic nerve removal surgery, dissection wasperformed and the limb muscle was removed and weighed. Unfortunately, althoughskeletal muscle weights were predominantly reduced and mRNA levels of Atrogin-1and MuRF-1 as markers of muscle atrophy, were increased, there was no significantchanges in urinary titin levels. These results suggest that it is difficult to identify themuscle atrophy with urinary titin levels.

DECENTE SPORTS SCIENCE Vol.40/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE