Our VA-funded research team has identified deployed veterans with chronic GI symptoms who have increased intestinal permeability. Although the pathophysiology of chronic GI symptoms is unknown, increased intestinal permeability could be a major contributing factor. The increased intestinal permeability itself may be due to several factors including stress, inflammation, allergc disorders and/or through decreased glutamine synthetase activity, resulting in decreased intestinal glutamine levels. Our recent study demonstrated that increased expression of miR-29a leads to decreased glutamine synthetase levels and increased intestinal permeability through glutamine dependent mechanisms (Zhou et al., 2010). These data strongly suggest that glutamine may serve as a potential therapeutic agent for veterans with IBS and increased intestinal permeability and the signaling pathway of miRNA-modulated targets could lead to new therapeutic approaches. We now have preliminary data for veterans with chronic GI symptoms and increased intestinal permeability indicating increased colonic expression of miR-124 and miR-373. The mechanisms by which miR-124 and miR-373 modulates intestinal permeability may be through glutamine synthetase pathways. Interestingly, miR- 124 and miR-373 expression is increased in deployed veterans with GI symptoms but not in asymptomatic deployed veterans. Thus, our studies will provide a novel model that explains the mechanism underlying increased permeability and GI symptoms in deployed veterans and suggest new ways to treat these veterans.
The first aim of our study is to determine if the mechanisms of interaction between (a) miR-124 and miR- 373 expression and (b) if chronic GI symptoms/increased intestinal permeability in veterans occurs through glutamine-dependent or glutamine-independent signaling pathways.
Our second aim i s to characterize key pathways involved in miR-124 and miR-373 mediated mucosal barrier defects by using cell culture techniques.
This aim will be accomplished using in vitro cell and/or tissue culture to determine if (1) miR-124 and miR-373 over expression directly inhibits glutamine synthetase expression, which leads to increased intestinal permeability;and/or (2) if miR-124 and miR-373 expression directly alters intestinal permeability through a glutamine independent signaling pathway.
Chronic GI symptoms are common (abdominal pain, bloating, diarrhea, constipation) amoung deployed veterans. Veterans with these chronic GI symptoms have hypersenstivity of the gut and body which may be attributed to a leaky gut in which bacteria and toxins may penetrate the gut wall, termed increased intestinal permeability. A major goal of the proposed studies is to determine the mechanisms that lead to increased intestinal permeability that may subsequently lead to chronic GI symptoms, including abdominal pain and diarrhea, in deployed veterans. A better understanding of these mechanisms may lead to new potential therapies to treat veterans with chronic GI symptoms.