Antioxidant activity of selenium-enriched soybean proteins and the effect of selenomethionine on food allergy

Abstract

Selenium (Se) is an essential and one of the most important micronutrients for humans and animals. An adequate intake of Se is a pivotal key to good health and plays a crucial role in the development and physiological processes including immune responses. Se deficiency can cause immune damage, induces inflammation, and can affect a wide range of immune cells both directly and indirectly. In humans, Se is mainly obtained through the diet of animal products, vegetables, and fruits. The Se levels in animals and humans reflect the Se levels in their consumed diet, whereas the Se content of plants reflects the Se levels in the soil where they are grown. Thus, soil Se levels indirectly determine the Se levels of animals and humans. There are some geographical zones where Se levels in the soil are very low, which may be a causative factor in the development of certain diseases in livestock and humans. Therefore, Se supplementation is sometimes necessary for people to maintain health, especially for those who live in low Se regions which can result in an inadequate Se intake. Various plant species such as garlic, green tea, onion, and soy are known to effectively accumulate Se. Soy is one of the most important protein sources in the world and it has a strong ability to accumulate Se. SeMet is the predominant form of Se present in soybeans. Despite the importance of both Se and soy, information regarding the distribution of Se in different soybean protein fractions is scarce, and publications related to either the effects of Se on proteins or the potential application of Se-enriched protein components as a Se-supplement are very limited, especially for soy planted in natural Se-enriched soils. A better understanding of those Se-enriched foods can provide useful information regarding their potential for applications to ensure an adequate intake of Se. A wide variety of Se supplements, Se metabolites, and selenoproteins have been studied for their ability to prevent oxidative damage and disease. Se levels in the body may influence conditions associated with increased oxidative stress and inflammation. In addition, it has been reported that SeMet supplementation suppressed the development of atopic dermatitis-like skin lesions and suppressed ovalbumin-induced active cutaneous anaphylaxis reaction in ovalbumin-sensitized BALB/c mice. In patients suffering from allergic asthma, a pulmonary condition characterized by inflammation and oxidative stress, Se plasma levels were significantly lower compared to healthy individuals. More recently, serum Se levels in patients suffering from severe asthma were found to correlate with the severity of the disease. The rise in the prevalence of allergic diseases has persisted over the last decades, and because of the large impact these non-communicable diseases can have on the quality of life of the patient, it is important to look for ways to improve existing therapeutic strategies. Given the potential benefits of dietary Se-supplementation outlined above, this thesis aimed to contribute to expanding the knowledge on the Se-enrichment of soy protein and the role of dietary Se supplementation in the management of allergic diseases.