engleski

Muscle regeneration capacity during the long-term experimental diabetes mellitus type 1

Background and Aims: Skeletal muscle is composed of different fiber types (type I, IIA, IIX and IIB) with unique metabolic and contractile characteristics. Muscle fibers are dynamic structures capable of altering their phenotype under various physiological and pathological conditions such as: altered hormonal profiles, increased or decreased neuromuscular activity, aging, etc. It is well known that skeletal muscle has the remarkable ability to complete a rapid and extensive regeneration process in response to pathological stimulus. The aim of the present time-course study was to investigate the influence of long-lasting diabetes mellitus type 1 on the process of muscle regeneration in fast and slow rat skeletal muscle. Material and Methods: Two-months-old male Wistar rats were randomly assigned to control and diabetic group. Rats were made diabetic by a single intraperitoneal injection of streptozotocin (STZ). Regeneration process was induced in slow (m.soleus, SOL) and fast (m.extensor digitorum longus, EDL) skeletal muscles by injection of local anaesthetic (bupivacain) in both groups. Fiber type distribution and fiber type areas were analysed after 10 days, 4 and 8 weeks of bupivacaine treatment in both SOL and EDL muscles. Results Changes in fiber type distribution Ten days after bupivacaine treatment control SOL muscle is composed of 89% of type I fibers and 11% of type II A fibers. In contrast, the percentage of type I fibers in diabetic SOL muscles was lower in respect to control group after 4 weeks of diabetes, while 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. Changes in fiber cross areas of diabetic muscles 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. Conclusions We have found that 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. In diabetic EDL muscles all fiber types showed stronger atrophy than muscle fibers in slow muscles which have more oxidative metabolism. The changes of redistribution of muscle fibers depend on duration of diabetes.

muscle regeneration; diabetes mellitus

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