Increased desmin expression in hindlimb muscles of aging rats

BACKGROUND: Aging skeletal muscle frequently exhibits a reduction in force produced per unit muscle tissue, variously termed muscle quality, specific tension or dynapenia. Muscles from animals in which desmin expression is reduced exhibit similar properties, raising the possibility that reduced desmin expression contributes to impaired force production in aging muscles. METHODS: We examined expression of desmin and synemin, both intermediate filament proteins, in the plantarflexor muscles of adult (6-8 months) and older (24 months) rats. We have previously reported age-related reductions in muscle quality and sarcoplasmic reticulum function in these animals. RESULTS: Significant effects of age and muscle were found for the expression of desmin (P = 0.040 and <0.001 respectively), but not synemin. Desmin expression was increased in the aging muscles, with the greatest changes observed in the gastrocnemius muscles. Muscle quality, but not muscle mass, was reduced in the aging plantarflexor muscles. CONCLUSIONS: Loss of desmin does not account for reduced force production in aging muscles. The potential effects of the age-related increase in desmin on muscle function remain unclear, but may include dissipation of contractile force.