Mechanistic Insights into Streptococcus thermophilus S131 Impact on Intestinal Health via in Vitro Fermentation Studies
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Abstract:
Using HT-29 cells in combination with a batch fermentation system that simulates human intestinal flora metabolism, the effects of Streptococcus thermophilus S131 on the intestinal barrier, including mitigation of pathogen-induced intestinal damage, and its role in promoting the growth of beneficial bacteria were assessed. Compared to control fermentations, cultures with S. thermophilus S131 increased mucin (MUC2) relative mRNA levels 1.34 fold, and respective tight junction protein (ZO-1, ZO-2, claudin-1, and occludin) levels 4.59, 2.17, 5.81, and 4.25 fold. Inclusion of S. thermophilus S131 also ameliorated downregulation of these genes by enterotoxigenic E. coli (ETEC), increasing respective expression levels 1.42, 6.28, 3.27, 5.03, and 4.79 fold relative to cultures exposed to ETEC alone. S. thermophilus S131 significantly suppressed ETEC-mediated increased inflammatory factor secretion by HT-29 cells, reducing IL-8 and IL-1β levels from 821.79 and 2.22 pg/mL to 573.92 and 0.29 pg/mL, respectively. It also ameliorated ETEC-induced epithelial cell damage, increasing the cell proliferation rate by 21.07%. S. thermophilus S131 also alleviated ETEC suppression of AQP-3 mRNA expression by 21%. qPCR assays revealed that S. thermophilus S131 increased the relative abundance of Faecalibacterium and Bacteroides thetaiotaomicron in our in vitro fermentation system, rescuing ETEC mediated suppression of Lactobacillus, Bifidobacterium, Bacteroides thetaiotaomicron, and Faecalibacterium. In conclusion, S. thermophilus S131 may promote intestinal health by strengthening the intestinal barrier, antagonizing pathogen-induced damage, and regulating the intestinal flora.
