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Glycated proteins are the main source of dietary advanced glycation end products (AGEs). Glycated proteins are enzymatically hydrolyzed in the gastrointestinal tract, which releases more absorbable and smaller potentially harmful AGEs. This study investigated the inhibitory effect of catechin on AGE release from glycated bovine serum albumin (G-BSA) during gastrointestinal digestion. Catechin inhibited AGE release during gastrointestinal digestion, especially in the gastric digestion stage. Additionally, catechin altered these peptides in the small intestine by reducing G-BSA digestibility. The proposed mechanism involves interactions between catechin and G-BSA/digestive enzymes, inhibiting digestive enzyme activity and changing the conformation of G-BSA. Catechin reduced G-BSA β-sheet content and protected the helical conformation. Moreover, catechin enhanced the antioxidant capacity of G-BSA, which could attenuate postprandial oxidative stress in the gastrointestinal tract caused by the release of AGEs. This study improves our understanding of the nutritional and health effects of catechin on dietary AGEs during gastrointestinal digestion.

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Research on advanced glycation end product (AGEs) inhibition has generally focused on food processing, but many protein-AGEs will still be taken. Oligopeptide (OLP)-AGEs, as the main form after digestion, will damage human health once absorbed. Here, we investigated the ability of lotus seedpod oligomeric procyanidins (LSOPC) to inhibit the absorption of the OLP-AGEs and elucidated the underlying mechanism. Our results showed that the inhibition rate of LSOPC on the absorption of OLP-AGEs was about 50 ± 5.38%. 0.1, 0.2, and 0.3 mg/mL could upregulate the expression of ZO-1 and downregulate the expression of PepT1 and clathrin. Molecular docking showed that LSOPC could compete with the binding of OLP-AGEs to PepT1 and AP-2, thus inhibiting the absorption of OLP-AGEs. Furthermore, the interaction of LSOPC with the OLP-AGEs reduced the surface hydrophobicity of OLP-AGEs. It altered the secondary structure of the OLP-AGEs, thus weakening the affinity of the OLP-AGEs to the transporter protein to inhibit the absorption of OLP-AGEs. Together, our data revealed potential mechanisms by which LSOPC inhibit the absorption of OLP-AGEs and opened up new perspectives on the application of LSOPC in reducing the increasing health risks posed by OLP-AGEs.

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