| Abstract |
The Maillard reaction, a nonenzymatic browning reaction that occurs between amines and carbonyl groups during food processing and cooking, generates products with antioxidant activity. Dipeptides composed of leucine and lysine (Leu-Lys and Lys-Leu) are frequent sequences in a variety of food proteins. Previously, we demonstrated that these dipeptides exhibit antioxidant activity and extend the lifespan of the nematode Caenorhabditis elegans (C. elegans). Although the Maillard reaction can improve peptide bioactivity, its effects on Leu-Lys and Lys-Leu remain unclear. Therefore, we investigated the antioxidant activity of Maillard reaction products (MRPs) derived from these dipeptides in vitro and their effects on the aging process in C. elegans. The antioxidant activity of Leu-Lys was unaffected by the Maillard reaction. By contrast, MRPs generated from Lys-Leu exhibited the highest antioxidant activity after 2 h of heat treatment with glucose. In wild-type C. elegans, the administration of Lys-Leu MRPs extended lifespan under both normal and oxidative stress conditions and improved motility with aging. In addition, Lys-Leu MRPs reduced the accumulation of reactive oxygen species and increased the mRNA expression of an antioxidant-related gene (sod-3). However, lifespan extension by Lys-Leu MRPs was not observed in sod-3 and daf-16 mutants. These findings suggest that Lys-Leu MRPs extend the lifespan of C. elegans via the insulin/insulin-like growth factor signaling pathway.
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