P.197Use of the D3-creatine dilution test as a non-invasive and accurate measurement of total body muscle mass in Duchenne muscular dystrophy

Abstract

Duchenne muscular dystrophy (DMD) results in progressive loss of functional capacities, which is a reflection of loss of muscle mass with contractile tissue being replaced by fat tissue. Currently, measurements of lean body mass (LBM) in DMD include dual energy x-ray absorptiometry (DEXA) and magnetic resonance imaging (MRI). Studies have shown that a decrease in LBM correlates with decreased quantitative strength measurements. However, DXA and MRI require cooperation from the subject and scanning can be uncomfortable for subjects in a more advanced stage of the disease with severe contractures or spine deformities. In addition, MRI requires specialized centers. Neither DEXA nor MRI provides an accurate assessment of functional skeletal muscle mass. In this on-going study we set the goal to investigate the D3-creatine dilution method in 10 DMD boys to determine total body muscle mass and lean mass and to compare these values with age-matched male control participants. This method uses a small oral dose of deuterated creatine to label the body pool of creatine, about 98% of which is found in skeletal muscle. Creatine is turned over through an irreversible conversion to creatinine and excreted in urine. The enriched urinary D3-creatinine reveals the endogenous whole body creatine pool size enabling determination of skeletal muscle mass. The method is not affected by renal function or changes in hydration status. The method has been validated in adults of all ages as well as infants and children. The advantage of this methodology is that it requires only a single dose of D3-creatine followed by a single spot urine sample 48-72 hours later. This method may provide an accurate, non-invasive tool to determine functional muscle mass in patients with neuromuscular disease. In this study, the total body D3-Cr muscle will be compared to LBM by DEXA in boys with DMD and age-matched healthy controls. Results will be presented.