Bacterial lipopolysaccharide (LPS) inhibits colonic uptake of the microbiota-generated forms of vitamin B1 [thiamin pyrophosphate (TPP), and free thiamin] via different mechanisms

LPS is a major component of the outer membrane of Gram-negative bacteria. The gut is exposed to high levels of this endotoxin in conditions such as IBD, necrotizing enterocolitis, and sepsis. LPS affects different aspects of cell physiology including transport at the cell membrane. Effects on the latter, however, are differential; and both induction and inhibition in substrate uptake have been observed. Nothing is currently known about the effect of LPS on colonic uptake of the microbiota-generated forms of vitamin B1, i.e., TPP and free thiamine. We investigated this issue in the current study using human-derived colonic epithelial NCM460 cells, human native differentiated and polarized colonoid monolayers, and mouse intact colonic tissue preparation together with appropriate cellular and molecular approaches. The results showed that exposure of colonic epithelial cells to LPS leads to a significant inhibition in carrier-mediated [3H]-TPP uptake. This inhibition was associated with: (i) a significant reduction in level of expression of the colonic TPPT transporter (cTPPT; SLC44A4) protein and mRNA; (ii) a significant inhibition in SLC44A4 promoter activity (associated with suppression in level of expression of the transcription factor Elf-3, which is need for promoter activity); the inhibition also appeared to be mediated via NF-κB, p38 and JNK (MAPK) mediated pathways. Similarly, LPS treatment of colonic epithelial cells was found to lead to a significant inhibition in colonic carrier-mediated uptake of free [3H]-thiamin. This inhibition, however, was not associated with changes in level of protein and mRNA expression of the involved transporters, i.e., THTR-1 & -2. These results demonstrate for the first time that exposure of colonic epithelial to LPS leads to significant inhibition in colonic uptake of the microbiota-generated TPP as well as free thiamin. The inhibition, however, appears to be mediated via different cellular mechanisms. This study was supported by NIH grant DK-56061, and VA grants 101BX001142 & IK6BX006189 to HMS; NIH grant AI089894 and AI126887 and VA grant 5I01BX001469-05 to JMF. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.