The Effects of Diabetes Mellitus Type 1 on Regeneration Capacity of Rat Skeletal Muscle

Muscle fibers are dynamic structures capable of altering their phenotype under altered hormonal profiles. Skeletal muscle is able to complete a rapid and extensive regeneration process in response to various pathological conditions. The aim of our study was to explore the effects of experimentaly induced diabetes mellitus type 1 on muscle regeneration process in fast and slow rat skeletal muscle. Two-months-old male Wistar rats were randomly assigned to control and diabetic group. Regeneration process was induced in slow (m.soleus, SOL) and fast (m.extensor digitorum longus, EDL) skeletal muscles by injection of local anaesthetic, bupivacain. Morphometric analysis was performed 10 days, 4 and 8 weeks after bupivacaine treatment. Ten days after bupivacaine treatment control SOL muscle is composed of 89% of type I fibers and 11% of type II A fibers. In diabetic SOL muscles type I fibers became predominant after 8 weeks of regeneration. Ten days after bupivacaine treatment control EDL muscle is composed of 9% of type I fibers, 24% of type II A, 10% of type II X, and of 57% of type II B fibers. After 8 weeks of regeneration diabetic EDL muscles were composed of fibers with mainly oxidative metabolism i.e. type I and type IIA fibers. Diabetic muscles, both SOL and EDL, showed a considerable degree of muscle atrophy at all time-point of muscle regeneration comparing to normal muscles. After 8 weeks of diabetes type I fibers showed statistically significant reduction in cross-sectional areas, while type IIA fibers completely disappeared. In diabetic EDL muscles the cross areas of all fiber types were significant smaller than in normal muscles in all investigated periods of regeneration with exception of type I fibers after 10 days of diabetes. Diabetes mellitus type 1 have changed the morphological properties in slow (SOL) and fast (EDL) muscles during the process of regeneration. These changes are evident in redistribution of muscle fibers and significant level of muscle atrophy. The changes of redistribution of muscle fibers depend on duration of diabetes.