A Decrease in Cysteine Levels Causes the Glutathione Deficiency of Aging in the Mosquito

Abstract

Our previous results indicated that a glutathione (GSH) deficiency is a determinant of the aging process in many tissues and organisms. Correction of this deficiency in the aging mosquito by feeding the cysteine (Cys) precursor magnesium thiazolidine carboxylic acid (MgTc) suggested that the cause could be a lack of Cys. Adult mosquitoes (Aedes aegypti) were fed either a control diet or a diet supplemented with MgTC and then were analyzed for their Cys, cystine, GSH, and glutathione disulfide contents with our HPLC method. The life span profile of Cys levels paralleled that of GSH in the control group with high levels in the young that decreased during maturity and aging. Cystine and glutathione disulfide were undetectable. The causal relationship between the Cys and the GSH deficiencies was shown in the MgTC-supplemented group with an 83% increase in Cys and a 39% increase in GSH relative to control values. Further the conversion steps of MgTC to Cys and then to GSH were verified by use of buthionine sulfoximine. These results demonstrate that a Cys deficiency occurs in the aging mosquito and is the cause of the GSH deficiency.