Assessment of Digestion and Absorption Properties of 1,3-Dipalmitoyl-2-Oleoyl Glycerol-Rich Lipids Using an In Vitro Gastrointestinal Digestion and Caco-2 Cell-Mediated Coupled Model

The digestion and absorption properties of 1,3-dipalmitoyl-2-oleoyl glycerol (POP)-rich lipids was evaluated using in vitro gastrointestinal digestion and a Caco-2 cell-mediated coupled model. Caco-2 cell viability and monolayer integrity were assessed by an MTT assay and transepithelial electrical resistance. The IC50 for bile salts, pancreatin, and free fatty acid (FFA) were 0.22 mM, 0.22 mg/mL, and 1.47 mM, respectively, and no cytotoxicity was observed for bovine serum albumin (0.01-0.20 mM) or triacylglycerol (1.00-10.00 mM). The in vitro-digested POP-rich lipid containing FFA > 2.95 mM caused the disruption of monolayer tight junctions in Caco-2 cells. The major triacylglycerols (TAG) of POP-rich lipids were POP (50.8%), POO (17.8%), POL/OPL/PLO (7.6%), PPO (7.1%), and PLP (6.8%). Following digestion and uptake into Caco-2 cells, the resynthesized TAGs included PPO (20.6%), PPP (15.9%), POO (14.0%), POL/OPL/PLO (12.2%), POP (10.9%), OOO (7.5%), OPO (7.0%), OOL/OLO (6.7%), PLP (3.1%), and PPL (2.2%). The secreted major TAGs were POL/OPL/PLO (50.8%), PPP (11.1%), and OOL/OLO (8.4%), indicating a diverse TAG profile in newly synthesized lipids. This study provides a coupled model for lowering cytotoxicity and maintaining the monolayer in Caco-2 cells, and for evaluating the digestion and absorption properties of functional lipids containing specific fatty acids incorporated into TAG.