Stability towards the gastrointestinal simulated digestion and bioactivity of PAYCS and its digestive product PAY with cognitive improving properties

The peptide derived from Anchovy hydrolysates, Pro-Ala-Tyr-Cys-Ser (PAYCS), was reported to display a neuroprotective effect in vitro in our previous study. The in vivo memory improving effects of PAYCS were investigated in this study. Prior to the scopolamine-induced amnesia mice trial, the stability of PAYCS during digestion was detected and the digestive products were identified. The results showed that PAYCS was susceptible to proteolytic degradation after incubation with pepsin and pancreatin and Pro-Ala-Tyr (PAY) was released and survived during the simulated GI digestion. The results of scopolamine-induced amnesia model trials showed that PAYCS and PAY treatment exhibited cognitive improvement effects in the behavioral tests and different pathways were determined. The results indicated that only PAYCS facilitated cholinergic activity by up-regulating the amount of acetylcholine (Ach) and acetylcholine receptor (AChR). Additionally, both PAYCS and PAY enhanced the superoxide dismutase (SOD) activity. Furthermore, PAYCS was found to be beneficial for the expression of the nuclear factor (erythroid-derived2)-like 2 protein (Nrf2), brain-derived neurotrophic factor (BDNF) and cAMP response element binding protein (CREB). This indicated that PAYCS could regulate the oxidative stress by activating the Nrf2/antioxidant response elements (Nrf2/ARE) pathway. In our study, we demonstrated that the memory improving effects conferred by PAYCS on amnesia mice were linked to the attenuation of the cholinergic system and the activation of Nrf2/ARE and BDNF/CREB signaling.