**5. Conclusions**

In summary, the present study showed that the WY dipeptide improves pharmacologicallyinduced and age-related memory impairment in mice. Effective intake of the WY dipeptide and other dipeptides with N-terminal tryptophan via supplements or nutraceutical foods including certain whey peptide preparations might be beneficial for improving cognitive function in older age.

**Author Contributions:** Y.A., T.A., and R.O. conducted the experiments and analyzed the results. Y.A., S.K., and T.F. wrote the paper, and K.K. supervised this research.

**Funding:** This study was supported by Kirin Company, Ltd. and in part by a CREST grant from AMED (JP18gm0910012 to T.F.); Grants-in-Aids for Scientific Research (16H05132 and 17K19457 to T.F. and 17K08593 to S.K.) from the Japan Society for the Promotion of Science; and Grants-in-Aids for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology in Japan (18H05429 to T.F.)

**Conflicts of Interest:** Ano, Y., Ayabe, T., Ohya, R., and Kondo, K. are employed by Kirin Co. Ltd. All other authors declare no competing interests.

## **References**


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