Abstract
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 Eisoforms, in physiological concentrations, on asthma and allergic airway disease.