Selenium-enriched Bifidobacterium longum DD98 relieves irritable bowel syndrome induced by chronic unpredictable mild stress in mice.

Irritable bowel syndrome (IBS) is a functional intestinal disorder without clear pathological mechanisms. Classical treatments for IBS are not always effective and are usually accompanied by side effects. Selenium-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) is a selenized probiotic strain which has shown many beneficial effects on the gastrointestinal tract, but its effects on IBS and the underlying mechanism are unclear. This study aims to investigate the relieving effects of Se-B. longum DD98 on chronic unpredictable mild stress (CUMS)-induced IBS in mice. The model mice were treated with saline, B. longum DD98, or Se-B. longum DD98 while receiving CUMS. The results suggest that Se-B. longum DD98 significantly relieved the intestinal symptoms of IBS mice and reduced intestinal permeability and inflammation. The depression and anxiety-like behaviors of IBS mice were also improved by Se-B. longum DD98. In addition, the expression of serotonin (5-HT), γ-aminobutyric acid (GABA), neuropeptide Y (NPY), and brain-derived neurotrophic factor (BDNF), which are indicators closely related to mood and brain-gut axis, were up-regulated in mice treated with Se-B. longum DD98. Furthermore, the 16S rRNA sequencing study showed that Se-B. longum DD98 effectively restored the relative abundance of intestinal microbes (e.g., Lactobacillus, Desulfovibrio, Akkermansia) and regulated the impaired diversity of gut microbiota in IBS mice. These results suggest that Se-B. longum DD98 positively acts on the brain-gut axis by improving intestinal functions and regulating mood-associated behaviors and indicators of IBS mice. Therefore, this Se-enriched probiotic strain could be considered a promising candidate for the alleviation of CUMS-induced IBS.