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Insulin and alpha-Lipoic Acid Improve Decreased Regeneration Capacity of Diabetic Fast Skeletal Muscle

Introduction. Skeletal muscle is composed of different fiber types (type I, IIA, IIX and IIB). 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, ageing, etc. Skeletal muscle has the remarkable ability to complete a rapid and extensive regeneration process in response to pathological stimulus. The aim of this study was to investigate the influence of insulin and alpha-lipoic acid (LA) on the process of fast skeletal muscle regeneration. Materials and Methods. Two-month old male Wistar rats were randomly assigned to control group, diabetic group, diabetic group treated with insulin, and diabetic group treated with insulin and alpha-lipoic acid (50 mg/kg once daily). Rats in diabetic groups were made diabetic by a single intraperitoneal injection of streptozotocin (STZ - 50 mg/kg). In all groups, regeneration process was induced in fast skeletal muscle (m. extensor digitorum longus, EDL) by injection of local anesthetic (bupivacain). Fibre cross area of skeletal muscle fibers was analyzed 28 days and 56 days after bupivacaine injection. Results. In EDL diabetic muscle, the cross areas of all fibre types were significantly smaller than in control group after 28 and 56 days. In diabetic EDL treated with insulin, the fibre cross areas were significantly higher, compared to diabetic EDL during the all experimental periods. The cross areas of muscle fibres in diabetic EDL treated with insulin and alpha lipoic acid were higher for all fibre types in both tested periods versus diabetic EDL treated with insulin only (except for fibre type IIB after 28 days) and it is statistically significant for fibre types I and IIX after 28 days and for fibre types IIA and IIB after 56 days. Discussion. In the process of the regeneration of fast diabetic skeletal muscle, joint treatment with insulin and antioxidant, alpha lipoic acid, can significantly better restore cross sectional areas of EDL muscle fibers regarding to insulin treatment only.

alpha lipoic acid; muscle regeneration; diabetes

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