Protection against Gluten-mediated Tight Junction Injury with a Novel Lignite Extract Supplement

Background: Tight junctions are found in epithelial cells and function as selective gatekeepers to regulate absorption. PT-gliadin is the gluten protein segment that is known to impair the functioning of tight junctions. This study aimed to examine the effects of a lignite extract dietary supplement (RESTORE) on tight junction function in small intestine (IEC-6) and colon (Caco-2) epithelial cells. The study also evaluated the biologic safety of the same supplement as established by the rates of apoptosis in the intestinal and proximal renal tubule cell cultures treated with the supplement. Methods: IEC-6 and Caco-2 cells were incubated until a stable trans-epithelial electrical resistance (TEER) was measured. The dietary supplement at 20% concentration or a control were placed on the cells and left overnight. These cells were then treated with and without PT-gliadin. Tight junction expression was determined by immunofluorescent microscopy. The rate of apoptosis was established in cell culture with the lignite extract at 20% concentration in order to assess a toxic concentration in normal cell lines: IEC-6, Caco-2, and human renal proximal tubule cell (RPTC) lines. Results: The lignite extract supplement increased the TEER in IEC-6 (58%) and Caco-2 (15%) compared to control. PT-gliadin dramatically decreased the TEER in both control IEC-6 (49%) and control Caco-2 (27%) membranes. The lignite supplement prevented PT-gliadin-mediated decrease in TEER. The supplement reduced apoptosis in RPTC (44%), IEC-6 (13%), and Caco-2 (24%) cell cultures. Conclusion: The lignite supplement blocked a PT-gliadin dependent decrease in TEER in small intestine and colon cell line membranes. The lignite extract was not toxic on intestinal or renal cells at high concentration, and demonstrated a statistically significant reduction in apoptosis in RPTCs. Human clinical trials are needed to evaluate the use of RESTORE to support health in gluten-sensitive individuals.