Selective trophic effect of L-carnitine in type I and IIa skeletal muscle fibers.

Biopsies were taken from the vastus lateralis muscle of 26 chronic uremic patients before and after a 24-week treatment with L-carnitine given at the dose of 2 g i.v. at the end of hemodialysis, or in dialysis solution, or per os twice daily. The aim of the study was to evaluate both the muscle morphology in dialyzed subjects and the modification provoked by the therapy. All patients manifested a significant, even if variable, degree of muscular atrophy which involved all types of muscle fibers. After the treatment there was an increase of about 7% in the diameter of type I and type IIa fibers, which can utilize carnitine for fatty acid oxidation to produce energy, and a reduction in the atrophic fibers. No noteworthy changes were documented in type IIb fibers, which depend on glycolysis for energy production.