My disclaimer is that basic science research is not my area of expertise so I can’t comment on the methodological rigor, only the results and I only glanced at the article. We do know that intestinal permeability may play a role in the clinical expression of IBS. That is actually the basis for transmigration of bacterial products which sets the stage for submucosal inflammation and visceral sensitization. This is where all the work on bacterial flora and probiotics come in: to destabilize or stabilize the gut mucosal barrier. These authors have demonstrated an association in IBS patients who have increased intestinal membrane permeability with a genetic marker for glutamine synthetase expression. So there may a genetic linkage for a metabolic mechanism that leads to intestinal permeability which in turn may predispose to IBS development.
Hope that helps.