Author
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JAHOOR, FAROOK - Children'S Nutrition Research Center (CNRC) |
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Submitted to: Nutrition Reviews
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/18/2012 Publication Date: 3/1/2012 Citation: Jahoor, F. 2012. Effects of decreased availability of sulfur amino acids in severe childhood undernutrition. Nutrition Reviews. 70(3):176-187. Interpretive Summary: There are two main types of severe childhood malnutrition, kwashiorkor and marasmus. In kwashiorkor the child is not only severely malnourished, but also has edema (water retention in the tissues), his/her liver does not work very well, and he/she cannot fight off infections. Not surprisingly, whereas it is relatively easy to treat children with marasmus, it is very difficult to treat children with kwashiorkor, and worldwide about 25% of these children die. Despite extensive research it is still not known why a child develops kwashiorkor instead of marasmus during chronic food deprivation. We have found that children with kwashiorkor have evidence that their cells are being destroyed by compounds called oxidants and that they are not making sufficient quantities of glutathione, the most important anti-oxidant that destroys harmful oxidants in the body. The compound glutathione is made from another compound called cysteine which is part of the protein we eat in our meals. Our studies show that the children with kwashiorkor are not getting enough cysteine from the amount of protein normally fed during early treatment. When we provided the children with extra cysteine, they made more glutathione and they recovered faster. This finding suggest that extra cysteine should be added to the diet fed to the children during early treatment of kwashiorkor. We have made this recommendation in several published articles. Technical Abstract: In studies of glutathione (GSH) metabolism in children with severe childhood undernutrition (SCU), slower erythrocyte GSH synthesis in children with edema was associated with lower concentrations of cysteine, the rate-limiting precursor of GSH synthesis. This finding suggested a shortage of cysteine available for GSH synthesis in children with edematous SCU. The plasma concentration of methionine, the sulfur donor for cysteine synthesis, was also lower in children with edematous SCU, suggesting decreased availability of methionine for cysteine synthesis. It is also possible that reduced methionine availability will result in decreased synthesis of S-adenosylmethionine, which could lead to an overall defect in methylation reactions. This review focuses on the relationship between cysteine availability and GSH synthesis in children with SCU. It also examines whether there is an inadequate supply of cysteine in those with edematous SCU and, if so, whether this is due to a shortage of methionine due to a decreased release of methionine from protein breakdown. Finally, the review explores whether a shortage of methionine results in decreased synthesis of S-adenosylmethionine, the universal methyl donor. |
