Effect of alpha-tocopherol supplementation on the ultrastructural abnormalities of peripheral nerves in experimental diabetes

Ultrastructural observations were made on myelinated fibers in the tibial n erves in order to investigate the beneficial effects of alpha -tocopherol a dministration in streptozotocin-diabetic rats. Male Wistar rats, aged 12 we eks and weighing between 250 g to 300 g were studied. Six onset control rat s were used to obtain the baseline parameters for this strain and age. Furt her 3 groups-untreated diabetic animals, diabetic animals treated with alph a -tocopherol, and age-matched controls-were studied over a 3-month period. In the diabetic animal, administration of alpha -tocopherol resulted in a significant increase (p < 0.05) in total plasma vitamin E levels when compa red with other groups. Myelinated fiber cross-sectional area (p < 0.05), ax onal area (p < 0.01) and myelin sheath area (p < 0.05) were significantly l ess in the tibial nerve of diabetic animals than in age-matched controls, b ut not different from those of onset controls. In the alpha -tocopherol tre ated diabetic animals, the values for these parameters were intermediate wi thout showing significant difference when compared with age-matched control s and untreated diabetics. The "g" ratio (axon to fiber area) did not diffe r between any experimental groups. The number of large myelinated fibers we re less in the untreated diabetic animals, but in the alpha -tocopherol-tre ated diabetics, the values were significantly higher (p < 0.05) than with u ntreated diabetics and were similar to those of age-matched controls. In co nclusion, this ultrastructural study reiterated the fact that structural ab normalities of myelinated fibers occur in experimental diabetes and that <a lpha>-tocopherol administration may be useful in preventing the development of these abnormalities.