Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) tract disorder characterized by recurrent abdominal pain and changes in stool frequency and form, which are often comorbid with anxiety and depression. It affects up to 14% of the middle-aged population, is twice as prevalent in women as men and places a large cost on both the individual and the healthcare system. IBS results from a combination of genetic, psychosocial and physiological factors that make treatment difficult, creating a need for novel therapies that address the whole spectrum of symptoms. Probiotics have recently emerged as a new treatment option for people suffering from gastrointestinal diseases and numerous studies have shown that probiotics can help alleviate symptoms in IBS patients. Currently, very little is known about the probiotic mechanism of action. Alterations in gut serotonin signaling have been implicated in abnormalities of gut motility and visceral sensitivity seen in IBS patients. In the gut, serotonin (5-hydroxytryptamine, 5-HT) is an important paracrine signaling molecule released by enterochromaffin cells in the mucosa. This 5-HT regulates gut motility, secretion and visceral sensation (pain). Probiotics are ingested with food and directly interact with the gut mucosa so we explored the interactions between a common probiotic and the 5-HT system in the gut to help elucidate possible mechanisms of action.In this work, we studied the beneficial effects of a probiotic, Lactobacillus reuteri 6475, in an animal model of IBS: the serotonin transporter knockout (SERT KO) rat. We showed that SERT KO rats recapitulate some of the human symptoms of IBS such as increased visceral hypersensitivity and decreased fecal output. Alterations in gut 5-HT availability did not fully account for the increased visceral hypersensitivity seen in SERT KO rats nor did SERT KO rats exhibit a sub-clinical level of inflammation. L.reuteri treatment decreased visceral hypersensitivity in both male and female SERT KO rats and increased fecal output in male SERT KO rats only, but did not alter gut 5-HT availability. L.reuteri shows promise as a probiotic that may help alleviate symptoms of IBS.
Read
