Influence of selenised dairy proteins on biomarkers of colon cancer risk

Abstract

Selenium is an essential trace element for mammals, and a component of at least 25 selenoproteins which incorporate the amino acid selenocysteine (Sec). These proteins include a number with oxidoreductase functions. An examination of the selenoproteins and their influence on carcinogenesis in an animal model may assist in determining their relevance in chemoprevention.Food sources offer a number of organic forms of selenium, with selenomethionine a common component, as in selenised yeasts. A selenium-rich dairy protein product has been developed (TaturaBioSe, Tatura Milk Industries, Tatura, Victoria) which could improve selenium status in populations considered marginal or deficient. It could also provide higher intakes (e.g. several fold above recommended dietary intake recommendations) of potential benefit as chemopreventive to those at greater risk of some selenium-responsive diseases, such as some sporadic colorectal cancers. Clinical studies are showing it to be a safe, palatable product for consumption in the form provided.Dairy protein selenium at 1 ppm in diet had a significant chemopreventive effect compared with control (0.05 ppm Se) in an azoxymethane model of colon cancer. Colon tumour incidence in rats was down by 29%, and tumour burden (colon tumours/rat) was halved, effects not observed when an equivalent Se concentration was provided as yeast selenium. When assessed by plasma Se concentration, this dairy protein form of selenium showed greater bioavailability (as assessed by plasma selenium) as well as efficacy in chemoprevention. Programmed cell death (apoptosis) was increased in colonic crypts and crypt height significantly diminished. The influence on early changes in carcinogenesis provides an insight into possible mechanism(s) of action. Histological and biochemical assays (e.g. monitoring oxidoreductase enzymes) could potentially provide early biomarkers with clinical relevance.

Proteins are potent biomarkers to detect colon cancer progression

“…Some of the potent serum protein biomarkers identified are proteinglutamine gamma-glutamyltransferase 2 (TGM2), insulin-like growth factor-binding protein 7 (IGFBP7) and calcyclin binding protein (CacyBP) as involving in colorectal metastasis (Pan et al, 2009, Katayama et al, 2006, Zhao et al, 2007, Ghosh et al, 2011). Other tumorigenic factors such as cyclooxygenase 2 (COX2), selenoproteins and inducible nitric oxide synthase (iNOS/NOS2) have often been involved in colon tumorigenesis (Mcintosh et al, 2008). These protein biomarkers have an influence to detect the early changes in carcinogenesis (Xuezhi et al, 2006).…”