engleski

Insulin restores changes of skeletal muscles induced by diabetes mellitus

Diabetic neuromyopathy is charactized with muscle weakness and muscle wasting. Skeletal muscle requires insulin for normal growth and development. It is composed of district fiber types with unique metabolic characteristics and heterogenity of insulin action (slow-contracting fibers, called type I, and three different types of fast-contracting fibers, called IIA, IIX and IIB muscle fibers). It has been shown that progression of diabetes mellitus is concomitant with decrease of the regenerative capacity of skeletal muscle. The aim of present study was to investigate the influence of insulin during the long term diabetes on the process of slow and fast skeletal muscle regeneration. Two-months-old male Wistar rats were randomised to control group, untreated diabetic group and diabetic group treated with insulin. We used a single streptozotocin (STZ) 65 mg/kg with i.p. injection for inducing experimental diabetes. Muscle regeneration was induced by injection of local anesthetic, bupivacain in slow (m.soleus, SOL) and fast (m.extensor digitorum longus, EDL) skeletal muscles. Morphometric analysis (fibre cross areas and fibre type distribution) of skeletal muscles was performed at intervals of 10 days, 4 weeks and 8 weeks. Soleus muscle. Four weeks after the process of regeneration started, in control group fiber type distribution was similar to normal SOL without the regeneration. In contrast, in diabetic muscles after eight weeks of regeneration, the percentage of fiber types did not reach values of control group and normal SOL without the process of regeneration. In the diabetic group treated with insulin fiber type distribution after four weeks was similar to these in control group. In diabetic soleus muscles, during all investigated intervals, the fibre cross areas of type I and IIA were significantly smaller than in normal muscle. In diabetic soleus muscle treated with insulin, the fibre cross areas of type I and type IIA were significantly higher than in diabetic muscles after 10 days of treatment, but this effect was diminished after 8 weeks. Extensor digitorum longus After 8 weeks of experiment control muscles were completely regenerated. In diabetic untreated muscles in all observed subgroups, fibers type distribution was changed. After 8 weeks of diabetes the percentage of type I and IIA fibers, which have predominant oxidative metabolism, was greater. The treatment with insulin prevented changes in fiber type distribution during all investigated periods. In diabetic EDL muscle, the cross areas of all fibre types were significantly smaller than in control muscles with an exception of fibre type I after 10 days. In diabetic group treated with insulin the fibre cross areas were significantly higher, than in diabetic group during the all experimental periods. Diabetes mellitus is associated with evident decrease of the regenerative capacity of skeletal muscle. Treatment with insulin in long-term diabetes mellitus can prevent atrophy of regenerative slow and fast skeletal muscles.

muscle regeneration; diabetes mellitus; insulin

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