(-)-Epicatechin Prevents High Fat Diet-Induced Bile-Associated Intestinal Permeabilization Both In Vivo and In Vitro. (29th May 2020) - Wang, Ziwei
Abstract: Objectives: This work investigated the capacity of (-)-epicatechin (EC) to prevent high fat diet (HFD)-induced intestinal permeabilization and the underlying mechanisms both in rodents and in Caco-2 cells. Methods: Male C57BL/6J mice (7 mice/group) (20–25 g) were fed for 15 w control or HFD, supplemented without or with 20 mg EC/kg body weight. Tissues and feces were collected and stored at −80 °C for further analysis. Caco-2 cells were differentiated into intestinal epithelial cells, which were incubated in the absence or the presence of deoxycholic acid (DCA), with or without EC, NADPH oxidase (NOX) inhibitors (apocynin and VAS-2870) and MEK inhibitor (U0126). After the corresponding incubations, monolayer permeability and the activation of signaling pathways and events involved in tight junction (TJ) opening/disruption were evaluated. Results: Consumption of a HFD caused intestinal permeabilization which was associated with decreased expression of ileal TJ proteins in mice. Supplementation with EC mitigated all these adverse effects. However, EC did not prevent neither the increase nor the altered profile of fecal bile acids caused by HFD consumption. DCA content was particularly elevated. In vitro, EC inhibited DCA-induced Caco-2 cell monolayer permeabilization. EC also prevented DCA-mediated increase in oxidant production and the parallel increase in NOX4 expression, which were both prevented by EC. Inhibition of the ERK1/2 pathway with U0126 prevented DCA-induced monolayer permeabilization, stressing the key involvement of NADPH oxidase and ERK1/2 in this process. DCA-mediated ERK1/2 activation was also inhibited by EC, apocynin and VAS-2870. DCA increased myosin light chain (MLC) phosphorylation levels, which was related to ERK1/2-mediated MLC phosphatase inactivation. DCA also decreased TJ protein levels, in part via Matrix Metallopeptidase-2 (MMP2) activation. Both events were prevented by EC, apocynin, VAS-2870 and U0126. Conclusions: EC protects the intestinal barrier from HFD-induced TJ alterations, and associated intestinal permeability both in vivo and in vitro . This is in part to mediated by EC's capacity to inhibit bile-induced NADPH oxidase, ERK1/2, and MMP2 activation, resulting in the preservation of TJ structure. Funding Sources: This work was supported by HE Jastro awards to ZW, and grant NIFA-USDA (CA-D-NTR-7244-H) to P.O.