Raw potato starch alters the microbiome, colon and cecal gene expression, and resistance to citrobacter rodentium infection in mice fed a western diet

Authors: Smith, Allen; Chen, Celine; Cheung, Lumei; Dawson, Harry

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2022
Publication Date: 1/10/2023
Citation: Smith, A.D., Chen, C.T., Cheung, L., Dawson, H.D. 2023. Raw potato starch alters the microbiome, colon and cecal gene expression, and resistance to citrobacter rodentium infection in mice fed a western diet. Frontiers in Nutrition. 9:2022. https://doi.org//10.3389/fnut.2022.1057318.
DOI: https://doi.org/10.3389/fnut.2022.1057318

Interpretive Summary: Resistant starches (RS) consumed in the diet are digested in the large intestine to produce short-chain fatty acids and other bacterial metabolites that can change host physiology and the composition of the gut bacteria. We previously showed that mice fed a Total Western Diet (TWD) that mimics a typical American diet that contained resistant potato starch (RPS), produced changes in the amount of short-chain fatty acids produced in the large intestine, altered the bacterial composition and produced changes in gene expression in the large intestine that were most prevalent in mice fed the 10% RPS diet. We were then interested in whether feeding TWD/RPS would alter the resistance to bacterial-induced colitis caused by Citrobacter rodentium (Cr), a mouse pathogen that shares 66.7% of encoded genes with Enteropathogenic Escherichia coli that cause food-borne illnesses in people. Mice were fed the TWD for 6 weeks followed by a 3-weeks on the RPS diets before infecting with Cr. The amount of Cr present in the feces was followed over time and fecal samples were collected to determine what types of bacteria were present. Mice were euthanized on day 12 post-infection and cecal contents collected o determine what types of bacteria were present. Cecum and colon tissues were obtained for gene expression analysis, histology and to determine the level of mucosa-associated Cr. Feeding RPS increased the percentage of mice infected by Cr and fecal Cr excretion on day 4 post-infection was higher in mice fed the RPS diets. Mice fed the TWD/10% RPS diet also had greater number of Cr attached to the colon at day 12 post-infection and had increased damage to the colon tissue. Both diet and infection altered the types of bacteria found on the large intestine with increased levels of RPS resulting in decreased bacterial diversity that was partially reversed by Cr infection. Studies to determine which genes were changing in the large intestine were undertaken to find out why feeding RPS made the bacterial infection worse. In the large intestine we found less genes associated with T cells, B cells, genes associated with the synthesis of DHA-derived SPMs and vitamin A metabolism/retinoic acid signaling. These results suggest that high-level consumption of RPS in the context of a typical American diet, may increase susceptibility to gastrointestinal bacterial infections.

Technical Abstract: Resistant starches (RS) are fermented in the cecum and colon to produce short-chain fatty acids and other microbial metabolites that can alter host physiology and the composition of the microbiome. We previously showed that mice fed a Total Western Diet (TWD) based on NHANES data that mimics the composition of a typical American diet, containing resistant potato starch (RPS), produced concentration dependent changes to the cecal short-chain fatty acids, the microbiome composition as well as gene expression changes in the cecum and colon that were most prevalent in mice fed the 10% RPS diet. We were then interested in whether feeding TWD/RPS would alter the resistance to bacterial-induced colitis caused by Citrobacter rodentium (Cr), a mouse pathogen that shares 66.7% of encoded genes with Enteropathogenic Escherichia coli. Mice were fed the TWD for 6 weeks followed by a 3-weeks on the RPS diets before infecting with Cr. Fecal Cr excretion was monitored over time and fecal samples were collected for 16S sequencing. Mice were euthanized on day 12 post-infection and cecal contents collected for 16S sequencing. Cecum and colon tissues were obtained for gene expression analysis, histology and to determine the level of mucosa-associated Cr. Feeding RPS increased the percentage of mice productively infected by Cr and fecal Cr excretion on day 4 post-infection. Mice fed the TWD/10% RPS diet also had greater colonization of colonic tissue at day 12 post-infection and colonic pathology. Both diet and infection altered the fecal and cecal microbiome composition with increased levels of RPS resulting in decreased a-diversity that was partially reversed by Cr infection. RNASeq analysis identified several mechanistic pathways that could be associated with the increased colonization of Cr-infected mice fed 10% RPS. In the distal colon we found a decrease in enrichment for genes associated with T cells, B cells, genes associated with the synthesis of DHA-derived SPMs and VA metabolism/retinoic acid signaling. We also found an increase in the expression of the potentially immunosuppressive gene, Ido1. These results suggest that high-level consumption of RPS in the context of a typical American diet, may increase susceptibility to gastrointestinal bacterial infections.