RESPONSE OF SWINE TO VITAMIN E-DEFICIENT RATIONS

A vitamin E-deficient diet affects nerve regeneration in rats

Degenerative changes in the neuromuscular system have been found in animals and humans with vitamin E (E) deficiency. This morphologic study examined the effect of dietary E on the regeneration of peripheral nerves in male Sprague-Dawley rats. After feeding an E-sufficient diet (dl-alpha-tocopheryl acetate 50 mg/kg diet) for 6 d, 24 rats were randomly and equally assigned to one of three groups: control (CTRL) fed an E-sufficient diet for 43 d without surgery, normal (NE) fed an E-sufficient diet, or low (LE) fed an E-deficient diet (dl-alpha-tocopheryl acetate 0 mg/kg diet). After 22 d of feeding, NE and LE had surgical compression of the right sciatic nerve and continued eating for 15 d. On day 43, the right triceps surae muscles and a segment of the right sciatic nerve were removed, then all rats were euthanized. The nerve and muscles were processed for morphologic analyses. Presurgery and postsurgery LE ate less food (P < 0.048 and P < 0.001, respectively), which resulted in a lower body weight gain (P < 0.0002). LE had irregularly shaped and less myelinated axons than NE (P < 0.0001) and CTRL (P < 0.0001). The LE plantaris muscle had less type II fibers when compared with NE (P < 0.007) and CTRL (P < 0.03). The results suggest that an E-deficient diet affects food intake, impairs nerve regeneration, and decreases type II fibers, whereas an E-sufficient diet contributes to normal axon regeneration.

Do vitamin E supplements in diets for laboratory animals jeopardize findings in animal models of disease?

Vitamin E has been supplemented to the diets of farm animals to improve fertility, health, growth rates and quality of animal products. Because of the positive experience obtained in farm animals, vitamin E has been added in increasing amounts to the diets of laboratory animals. Today, vitamin E levels in standard rodent maintenance diets range from 30 mg/kg (France, United States), 90-120 mg/kg (Netherlands, United Kingdom) to as much as 200 mg/kg (Germany). While increasing fertility and health of laboratory animals, these vitamin E supplements affect diverse pathophysiological conditions and thus the outcome of animal models of disease. Because of the large variability of vitamin E levels between laboratories within and between different countries, results obtained in established animal models may no longer be comparable and/or reproducible. Researchers should be aware of these vitamin E supplements and carefully control for potential effects in their respective animal models that involve--or may involve--the generation of reactive oxygen species.