Provided are a carnosine dipeptidase 1 inhibitor composition, a use for said composition in order to inhibit carnosine dipeptidase 1, and a method for inhibiting carnosine dipeptidase 1. The present invention demonstrates the discovery of a specific ring-shaped dipeptide or salt thereof exhibiting an inhibitory activity against carnosine dipeptidase 1, and thus, provides a novel and effective means that contributes to the prevention or amelioration of a cognitive function decline or the like.本發明為提供一種使用於阻礙肉鹼二肽酶1阻礙用組成物、肉鹼二肽酶1的該組成物之用途及阻礙肉鹼二肽酶1之方法。本發明發現特定環狀二肽或其鹽具有肉鹼二肽酶1阻礙作用。本發明亦提供一種使用於認知功能降低等預防或改善的有效且新穎的方法。
