Walnut Peptide KG-7 Alleviates Scopolamine-Induced Memory Deficits and Enhances Paracellular Transport via Tight Junction Modulation in a Mouse Model

Walnut peptide Lys-Gly-His-Leu-Phe-Pro-Asn (KG-7) is a food-derived bioactive peptide with a high antioxidant capacity. We systematically evaluated the ameliorative effects of KG-7 on scopolamine-induced memory deficits in mice and its intestinal absorption mechanisms through integrating motion behavior analysis, molecular biochemistry research, and fluorescence imaging technology. Morris water maze tests revealed that KG-7 significantly improved the behavioral performance of these mice. Further mechanistic investigations demonstrated that KG-7 restored cholinergic function by reducing acetylcholinesterase activity and increasing acetylcholine levels. Hematoxylin-eosin staining and hippocampal immunohistochemistry confirmed that KG-7 alleviated neuronal damage by downregulating Hes1 overexpression, clarifying its behavioral improvement mechanism. In vitro fluorescence imaging showed that KG-7 reached peak accumulation in brain tissue 8 h post-administration, confirming its brain delivery. To elucidate the absorption mechanism, immunohistochemistry and immunofluorescence revealed that KG-7 markedly reduced the expression of efflux transporter P-gp in the small intestine, thereby diminishing efflux activity, while weakened tight junction (Occludin, ZO-1) fluorescence indicated activation of the paracellular pathway. Western blot analysis confirmed that KG-7 enhanced paracellular absorption efficiency and reduced intestinal efflux by downregulating ZO-1, Occludin, and efflux transporters (P-gp, BCRP, and LRP1) alongside upregulating Claudin-2 expression. These findings provide a foundation for exploring walnut peptides that enhance memory and optimize absorption.