Effect of dietary creatine on skeletal muscle myosin heavy chain isoform expression in an animal model of uremia.

ABSTRACT

BACKGROUND: Chronic renal failure is accompanied with muscle dysfunction and myopathy, characterized by muscle weakness and increased fatigue. Myosin heavy chain (MHC) is the principal structural protein that controls the intrinsic contractile properties of striated muscle. Creatine is widely used as an ergogenic nutritional supplement in sportsmen. This study investigates the effect of creatine supplementation on MHC expression in the setting of uremic myopathy. METHODS: Male Wistar rats were either sham operated or subtotally nephrectomized and received a control diet or creatine (2% w/w)-supplemented diet. After 4 weeks of treatment, serum creatinine, creatine, urea and creatinine clearances were determined. MHC isoforms were determined electrophoretically in the extensor digitorum longus and soleus muscles. RESULTS: Creatinine clearances were lower in nephrectomized animals, but similar in creatine-supplemented and control diet animals. Nephrectomized animals had significantly higher MHC IIb and lower MHC IIx isoform expression in the extensor digitorum longus muscle compared to sham-operated animals. In the soleus muscle, MHC IIb expression was increased in nephrectomized animals. Creatine supplementation reversed the MHC transitions observed in uremia in the soleus muscle, but not in the extensor digitorum longus muscle. CONCLUSION: We observed altered expression of MHC isoforms in uremia. In uremic animals, fast MHC IIb isoforms were increased, whereas MHC I and IIx isoforms predominate in control animals. Dietary creatine supplementation reversed the altered MHC expression during uremia in slow-twitch, but not in fast-twitch muscles.