Effects of HMG-CoA reductase inhibitors on growth and differentiation of cultured rat skeletal muscle cells

Abstract

HMG-CoA reductase inhibitors have been associated with skeletal muscle myopathy, ranging from asymptomatic elevations of serum creatine kinase (CK) activity to rhabdomyolysis. In this study, we assessed the effects of addition of different concentrations of simvastatin and pravastatin on growth and differentiation of cultured primary rat skeletal muscle cells. Protein concentration, CK activity and percentage CK-MM, which is a parameter for maturation, were determined. Effects were generally stronger if inhibitors were added to both growth and differentiation medium rather than only to differentiation medium. Addition of 25 μM pravastatin caused only a decrease of CK activity. Addition of 1–5 μM simvastatin resulted in a decrease of protein concentration, CK activity and percentage CK-MM, whereas 25 μM simvastatin resulted in cell death. Addition of mevalonic acid or cholesterol could not prevent the effects of 1 μM simvastatin. In addition, 1 μM simvastatin did not influence the cholesterol and phospholipid content of the cells. Superfusion of cultured cells with simvastatin concentrations of 10 μM and higher caused a transient increase of the cytoplasmic calcium concentration followed by an apparent second rise and cell puncture. The results indicate that HMG-CoA reductase inhibitors may affect skeletal muscle cell regeneration in vivo by a direct toxic effect on growth and differentiation.