Histochemical and morphometrical analysis of skeletal muscle in spontaneous diabetic WBN/Kob rat

Spontaneous diabetic WBN/Kob rats develop diabetic peripheral neuropathy ch aracterized by primary segmental demyelination and secondary axonal degener ation. The objective of this study was to evaluate the histochemical and mo rphometric characteristics of the lesions of skeletal muscles innervated by the affected nerves in diabetic rats. The following groups of rats were in vestigated: 24-month-old males that had been diabetic for less than 12 mont hs, 10-month-old pre-diabetic males, 24-month-old non-diabetic females, and 10-month-old nondiabetic females. The soleus (SOL), extensor digitorum lon gus (EDL) and biceps femoris (BF) muscles were studied by light and electro n microscopy, including histochemical and morphometric analyses. Muscle wei ght was reduced with age to a remarkable degree in diabetic BF and EDL. Dis persed atrophy of muscle fiber was observed in type 2a fibers of BF and EDL , and type 2c fibers of SOL, and the incidence was higher in diabetic rats. Multi-core, myofibrillar disorientation and an increased number of central nucleus of SOL, along with connective tissue proliferation of BF perimysiu m were noted in diabetic rats. The fiber population and type of composition varied with age, but no remarkable changes attributable to diabetic condit ions were observed. Electron microscopically, an abnormal arrangement of my ofibrils, a number of myelin figures, mitochondrial swelling and lysis of m itochondrial cristae were seen in diabetic rats. However, the neuromuscular junction and capillaries were intact. These findings indicate that the dia betic skeletal muscle lesion in WBN/Kob rats was mainly myogenic in nature, and was aggravated by the age-related change.