No abstract

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial metabolic disorder that poses health challenges worldwide and is expected to continue to rise dramatically. NAFLD is associated with metabolic syndrome, type 2 diabetes mellitus, and impaired gut health. Increased gut permeability, caused by disturbance of tight junction proteins, allows passage of damaging microbial components that, upon reaching the liver, have been proposed to trigger the release of inflammatory cytokines and generate cellular stress. A growing body of research has suggested the utilization of targeted probiotic supplements as a preventive therapy to improve gut barrier function and tight junctions. Furthermore, specific microbial interactions and metabolites induce the secretion of hormones such as GLP-1, resulting in beneficial effects on liver health. To increase the likelihood of finding beneficial probiotic strains, we set up a novel screening platform consisting of multiple in vitro and ex vivo assays for the screening of 42 bacterial strains. Analysis of transepithelial electrical resistance response via co-incubation of the 42 bacterial strains with human colonic cells (Caco-2) revealed improved barrier integrity. Then, strain-individual metabolome profiling was performed revealing species-specific clusters. GLP-1 secretion assay with intestinal secretin tumor cell line (STC-1) found at least seven of the strains tested capable of enhancing GLP-1 secretion in vitro. Gene expression profiling in human biopsy-derived intestinal organoids was performed using next generation sequencing transcriptomics post bacterial co-incubation. Here, different degrees of immunomodulation by the increase in certain cytokine and chemokine transcripts were found. Treatment of mouse primary hepatocytes with selected highly produced bacterial metabolites revealed that indole metabolites robustly inhibited de novo lipogenesis. Collectively, through our comprehensive bacterial screening pipeline, not previously ascribed strains from both Lactobacillus and Bifidobacterium genera were proposed as potential probiotics based on their ability to increase epithelial barrier integrity and immunity, promote GLP-1 secretion, and produce metabolites relevant to liver health.

Clostridioides difficile infection (CDI) is frequently associated with intestinal injury and mucosal barrier dysfunction, leading to an inflammatory response involving neutrophil localization and upregulation of pro-inflammatory cytokines. The severity of clinical manifestations is associated with the extent of the immune response, which requires mitigation for better clinical management. Probiotics could play a protective role in this disorder due to their immunomodulatory ability in gastrointestinal disorders. We assessed five single-strain and three multi-strain probiotics for their ability to modulate CDI fecal water (FW)-induced effects on T84 cells. The CDI-FW significantly (p < 0.05) decreased T84 cell viability. The CDI-FW-exposed cells also exhibited increased pro-inflammatory cytokine production as characterized by interleukin (IL)-8, C-X-C motif chemokine 5, macrophage inhibitory factor (MIF), IL-32, and tumor necrosis factor (TNF) ligand superfamily member 8. Probiotics were associated with strain-specific attenuation of the CDI-FW mediated effects, whereby Saccharomyces boulardii CNCM I-1079 and Lacticaseibacillus rhamnosus R0011 were most effective in reducing pro-inflammatory cytokine production and in increasing T84 cell viability. ProtecFlor™, Lactobacillus helveticus R0052, and Bifidobacterium longum R0175 showed moderate effectiveness, and L. rhamnosus GG R0343 along with the two other multi-strain combinations were the least effective. Overall, the findings showed that probiotic strains possess the capability to modulate the CDI-mediated inflammatory response in the gut lumen.