Submitted to: Developmental and Comparative Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/20/2004
Publication Date: 3/1/2005
Citation: Chang, W.P., Combs, G.F., Scanes, C.G., Marsh, J.A. 2005. The effects of dietary vitamin E and selenium deficiencies on plasma thyroid and thymic hormone concentrations in the chicken. Developmental and Comparative Immunology 29:265-273. Interpretive Summary: The paper describes the effects of two antioxidant nutrients, vitamin E and selenium, on hormone status in an animal model, the chick. Selenium (Se), an essential constituent of the enzymes that convert the pre-hormone, tetraiodothyronine (T4), to the active form of thyroid hormone (T3), reduced circulating levels of the latter while increasing plasma T4 levels. These effects were accompanied by decreases in plasma thymic hormone levels, but no changes in those of growth hormone. Because the thymic hormone and T3 levels were correlated, it was concluded that both deficiencies could contribute to immune impairment due to Se deprivation.
Technical Abstract: Beginning at hatching, male Cornell K strain single comb white leghorn chickens were fed a basal diet, with or without vitamin E (100 IU/kg) and/or selenium (Se, 0.2 ppm). After 3 weeks of treatment, animals fed either the Se-deficient or basal diet had significantly reduced plasma Se-dependent glutathione peroxidase activities when compared to those fed a vitamin E and Se-supplemented diet. Similarly, animals fed the vitamin E-deficient or basal diet had significantly reduced plasma alpha-tocopherol levels. The effect of these treatments on plasma concentrations of thyroid hormones (T3/T4), growth hormone (GH), and thymic hormone (thymulin) was determined using radioimmunoassay and ELISA. A deficiency in Se, but not in vitamin E, resulted in an increase in plasma T4 concentrations while plasma T3 concentrations were decreased. Plasma GH levels showed some fluctuation as a result of the dietary treatments but there was no significant correlation between plasma GH levels and any of the other variables. A significant decrease in plasma thymulin levels was observed in Se-deficient birds compared to those receiving adequate Se in the diet. A vitamin E deficiency had no measurable effect on plasma thymulin levels. From these studies, we conclude that plasma thymulin concentrations directly correlate with plasma T3 concentrations which are negatively affected by a Se deficiency.