Methylselenocysteine

 

Se-methyl L-selenocysteine is a selenoamino acid found naturally in vegetables such as garlic and broccoli. It is a bioavailable and safe form of the essential trace mineral nutrient, selenium. Selenium in the form of Selenocysteine is an essential component of antioxidant enzymes such as glutathione peroxidase and is also found in several proteins in the body. Antioxidant enzymes containing selenium, protect cells against oxidative damage. Studies in animal models have shown that Se-methyl L-selenocysteine is effective in cancer chemoprevention. Its mechanism of action is reported to be through inhibiting reactive oxygen species.
Se-methyl L-selenocysteine is reported to be safer and more effective than other forms of supplemental selenium.

Selenium is an essential micronutrient for the well being of humans. Inadequate selenium intake results in various diseases and deficiencies. Selenium is present naturally in several plant and animal foods. Brazil nuts, walnuts, grains, meat and seafood are good sources of selenium. Dietary exposure from these sources varies with geographical location, depending upon the selenium content in the soil. Situations where adequate amounts of selenium cannot be obtained from natural resources warrant the use of selenium supplements. Research reveals that a monomethylated selenium metabolite is essential for cancer chemoprevention. Se-methyl L-selenocysteine fits this criterion, as it directly supplies a monomethylated metabolite.

Introduction

Methylselenocysteine
Se-Methyl L-selenocysteine

Se-methyl L-selenocysteine, commonly known as Methylselenocysteine (MSC), is a selenoamino acid found naturally in vegetables such as garlic and broccoli. It is a bioavailable and safe form of supplementing the essential trace mineral nutrient, selenium.

Selenium in the form of Selenocysteine is an essential component of antioxidant enzymes in the body, such as glutathione peroxidase, and is also found in several proteins in the body. Antioxidant enzymes containing selenium protect cells against oxidative damage1.

Selenium is an essential micronutrient for the well being of humans. Inadequate selenium intake results in various diseases and deficiencies. Selenium is present naturally in several plant and animal foods. Brazil nuts, walnuts, grains, meat and seafood are good sources of selenium. Dietary exposure from these sources varies with geographical location, depending upon the selenium content in the soil. Situations where adequate amounts of selenium cannot be obtained from natural resources warrant the use of selenium supplements.

Nutraceutical role of MSC

Studies in animal models have shown that MSC is effective in cancer prevention.  Researchers also reported that a monomethylated selenium metabolite is essential for cancer chemoprevention2. Selenium-enriched garlic is proven to be useful as a nutritional supplement in the prevention of cancer.  Plants such as garlic grown in selenium-rich media contain high amounts of MSC3, one of the most effective chemopreventive forms of selenium5. Studies indicate that MSC is not incorporated into proteins, thereby minimizing the possibility of excessive accumulation in tissues4. Figure shows the structure of Se-methyl L-selenocysteine.

Laboratory rats fed supplemental dietary Se-garlic at different levels showed consistently lower total tissue selenium accumu-lation than rats receiving Se-yeast.  However, Se-yeast was found to be only half as active as Se-garlic in mammary cancer prevention (Figure). The bulk of the selenium was found to be in the form of -L-glutamyl-Se-methyl-L-selenocysteine (73%) in selenium garlic and L-selenomethionine (85%) in selenium yeast6.


Figure: Effects of supplementation with Se-yeast and Se-garlic on mammary cancer in an animal model

The authors of this study postulated that differences in the metabolism of these two compounds and their subsequent disposition in tissues might account for their differences in cancer chemopreventive activity6.

A recent study hypothesizes that -L-glutamyl-Se-methyl-L-selenocysteine found in high selenium garlic serves primarily as a carrier of Se-Methyl-L-selenocysteine, which has been demonstrated to be a potent cancer chemopreventive agent in animal carcinogenesis bioassays10. Se-methyl L-selenocysteine was found to induce apoptosis (programmed cell death) in HL-60 cells by a mechanism mediated through reactive oxygen species9.

In rats challenged with a carcinogen, supplementation with either g-L-glutamyl-Se-methyl-L-selenocysteine or Se-methyl L-selenocysteine was associated with a lower prevalence of premalignant lesions in the mammary gland, and fewer malignant carcinomas when these lesions were allowed to progress 5,8.  A short term treatment schedule of 4 weeks with these compounds, immediately after carcinogen dosing was sufficient to provide significant cancer protection (even in the absence of a sustained exposure), after the initial 4 week period, through gene expression changes induced in the epithelial cells of the mammary gland 5,8.  

Therefore, Se-methyl L-selenocysteine is an efficient chemopreventive agent in animal models that are challenged with carcinogens

 


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