Prospective epidemiological studies, observational cross-sectional studies and some randomised prevention trials have demonstrated inconsistent findings of the impact of vitamin E on asthma risk. The goals of this study were to explore whether this differing association of vitamin E on asthma risk is due to an interaction of vitamin E isoforms. To address this question, in a population-based asthma incidence study we assessed the interaction between the plasma concentrations of vitamin E isoforms α-tocopherol and γ-tocopherol on asthma risk. Second, to understand the mechanisms of any interaction of these isoforms, we conducted experimental supplementation of α-tocopherol and γ-tocopherol isoforms in mice on the outcome of allergic airway inflammation. We found that in the highest γ-tocopherol tertile, low levels of α-tocopherol were associated with increased asthma risk, while highest tertile α-tocopherol levels trended to be protective. Similarly, in a mouse model of asthma, diet supplementation with α-tocopherol decreased lung inflammation in response to house dust mite (HDM) challenge. In contrast, diet supplementation with γ-tocopherol increased lung inflammation in response to HDM. These human and animal studies provide evidence for the competing effects of the vitamin E isoforms, in physiological concentrations, on asthma and allergic airway disease.
Bibliographical noteFunding Information:
This study was funded by National Institute of Allergy and Infectious Diseases RO1 AI 50884 (TH), K24 AI 77930 (TH), National Institute of Complementary and Alternative Medicine R01 AT004837 (JC-M) and National Institute of Heart, Lung, and Blood R01HL111624 (JC-M). The project described was also supported by the U.S. National Cancer Institute R37 (Dr Wei Zheng) and NO2-CP11010-66 (XOS).