Impact of hydroxytyrosol and EVOO INFOGEST digesta on tight junction modulation and chylomicron assembly in Caco-2 cells.

Abstract

Extra virgin olive oil (EVOO) and hydroxytyrosol (HT), an amphipathic phenol, are both recognized for their health benefits; however, their direct effects on the gastrointestinal tract, particularly on intestinal barrier function and lipid metabolism, remain to be fully elucidated. This study aimed to describe the effects of complete EVOO digesta (obtained via the standardized INFOGEST protocol) and HT on chylomicron production and intestinal integrity. Differentiated Caco-2 cell monolayers were exposed to these treatments, followed by evaluations of trans-epithelial electrical resistance (TEER), global transcriptomic profiling (RNAseq), and apolipoprotein B (apoB) protein quantification. Results indicate that both EVOO digesta and HT significantly modulate tight junction (TJ) proteins and chylomicron assembly pathways. Notably, exposure to a high dose of HT (1 mM) decreased TEER without compromising cell viability. Transcriptomic analysis revealed that this shift was driven by a reorganization of TJ proteins (including upregulation of claudin-19 and ZO-3) and increased myosin light chain kinase (MYLK) expression, suggesting potential activation of the paracellular leak pathway. Furthermore, both EVOO and HT upregulated microsomal triglyceride transfer protein (MTTP) expression. Crucially, HT exposure led to a significant increase in intracellular apoB protein mass, a modulation that dot blot analysis confirmed is effectively coupled to active apoB secretion into the basolateral medium. These findings suggest that EVOO digesta and HT can selectively modulate gene expression associated with intestinal permeability and chylomicron assembly in Caco-2 cells, highlighting the need for further functional in vivo studies to elucidate their gastrointestinal bioactivity fully.