Creatine transporter and mitochondrial creatine kinase protein content in myopathies

Total creatine or phosphocreatine, or both, are reduced in the skeletal mus cle of patients with inflammatory myopathy, mitochondrial myopathy, and mus cular dystrophy/congenital myopathy. We used Western blotting techniques to measure skeletal muscle creatine transporter protein and sarcomeric mitoch ondrial creatine kinase (mtCK) protein content in patients with inflammator y myopathy (N = 8), mitochondrial myopathy (N = 5), muscular dystrophy (N = 7), and congenital myopathy (N = 3), as compared to a control group withou t a neuromuscular diagnosis (N = 8). Creatine transporter protein content w as lower for all groups compared to control subjects (P < 0.05; P < 0.01 fo r congenital myopathy). Mitochondrial CK (mtCK) was lower for inflammatory myopathy (P < 0.05), higher for mitochondrial myopathy (P < 0.05), not diff erent for muscular dystrophy, and markedly lower for the congenital myopath y group (P < 0.01), compared to control subjects. Together, these data sugg est that the reduction in total creatine or phosphocreatine in patients wit h certain myopathies is correlated with creatine transporter and not mtCK p rotein content. This further supports the belief that creatine monohydrate supplementation may benefit patients with low muscle creatine stores, altho ugh the reduction in creatine transporter protein may have implications for dosing. (C) 2001 John Wiley & Sons, Inc.