Intestinal absorption of DHA microcapsules with different formulations based on ex vivo rat intestine and in vitro dialysis models

Mechanism of Intestinal Epithelial Absorption and Electrophysiological Regulation of the Shrimp Peptide QMDDQ

We investigated the absorption mechanism of the shrimp peptide QMDDQ in small intestines, explored its physiological function in inhibiting neuronal hyperactivity, and verified its entry into the brain in vivo to display functional activity. The everted rat sac model and a Caco-2 paracellular absorption monolayer model were used, indicating that QMDDQ has a good absorption capacity with an apparent permeability coefficient (Papp) > 1 × 10-6 cm/s and the absorption of QMDDQ was concentration-dependent. When the concentration of QMDDQ was 1 mM and the transport time was 180 min, the highest absorption concentration of QMDDQ was 41.17 ± 3.48 μM (P < 0.05). The myosin light-chain kinase (MLCK)-specific inhibitor ML-7 and activator MPA, Western blotting, and immunofluorescence results showed that QMDDQ absorption takes place by mediating the MLCK-p-MLCK-MLC signaling pathway, reversibly opening the zonula occludens-1 (ZO-1), occludin in tight junctions (TJs), upregulating claudin-2 expression, and reaching targets through blood to inhibit neuronal overactivity. Results of fluorescence imaging in vivo verified that QMDDQ could enter the brain 4 h after oral administration. The results provide a theoretical foundation for the mechanism of paracellular absorption of active peptides and a starting point for the development of functional foods for Alzheimer's disease intervention.

Study on the transport and internalisation mechanism of dietary supplement nattokinase in the small intestine using animal and Caco-2 cell monolayer models

Maintaining proper blood flow is critical to promoting good health. Nattokinase is a serine protease from Bacillus subtilis that has significant in vitro thrombolytic activity, but its mechanism as a dietary supplement to prevent thrombosis through intestinal absorption and transport is still unclear.The purpose of this study is to study the transport and internalisation mechanism of NK in the small intestine using animal models and Caco-2 cell monolayer models.This study first evaluated the preventive effect of supplementing low dose (4000 FU (Fibrin Unit)/kg, n = 6), medium dose (8000 FU/kg, n = 6), and high dose (12000 FU/kg, n = 6) of nattokinase on carrageenan induced thrombosis in mice. Subsequently, we used the rat gut sac model, ligated intestinal loop model, and Caco-2 cell uptake model to study the intestinal transport mechanism of NK.Results indicate that NK is a moderately absorbed biomolecule whose transport through enterocytes is energy- and time-dependent. Chlorpromazine, nystatin and EIPA all inhibited the endocytosis of NK to varying degrees, indicating that the endocytosis of NK in Caco-2 cells involves macropinocytosis, clathrin-mediated and caveolae-mediated pathway. These findings offer a theoretical basis for investigating the mechanism of oral NK supplementation in greater depth.