Consumption of a Western type diet is a known risk factor for colorectal cancer. Our group previously developed the total Western diet (TWD) for rodents with energy and nutrient profiles that emulate a typical Western diet. In this study, we tested the hypothesis that consumption of the TWD would enhance colitis, delay recovery from gut injury and promote colon tumorigenesis.In multiple experiments using the azoxymethane + dextran sodium sulfate or Apc Min/+ mouse models of colitis-associated colorectal carcinogenesis (CAC), we determined that mice fed TWD experienced more severe and more prolonged colitis compared to their counterparts fed the standard AIN93G diet, ultimately leading to markedly enhanced colon tumorigenesis. Additionally, this increased tumor response was attributed to the micronutrient fraction of the TWD, and restoration of calcium and vitamin D to standard amounts ameliorated the tumor-promoting effects of TWD. Finally, exposure to the TWD elicited large scale, dynamic changes in mRNA signatures of colon mucosa associated with interferon (IFN) response, inflammation, innate immunity, adaptive immunity, and antigen processing pathways, among others. Taken together, these observations indicate that consumption of the TWD markedly enhanced colitis, delayed recovery from gut injury, and enhanced colon tumorigenesis likely via extensive changes in expression of immune-related genes in the colon mucosa.Nutrients 2020, 12, 544 2 of 35 characterizes these conditions is now recognized as an important factor in CRC due to its involvement in the disruption of the same oncogenic pathways that are disrupted in CRC [5]. The mutation of genes involved in the maintenance of the intestinal mucosal barrier that protects the intestinal wall from bacterial invasion contributes to both Crohn's and UC [6,7].Dysfunction of the intestinal mucosal barrier leads to sustained damage of gut epithelial cells. This chronic injury to the gut triggers a compensatory immune response characterized by the up-regulation of cell proliferation and anti-apoptotic pathways that promote cell survival [8]. Various molecules are involved in the activation of such pathways, including transcription factors (e.g., NF-κB, and STAT3) and various inflammatory cytokines (e.g., IL-6 and TNF-α), which are normally secreted during an inflammatory response. The resulting compensatory cell regeneration results in increased rates of mitosis that, when chronically active, increase DNA mutation rates [8,9]. Not only can this process promote the disruption of oncogenic pathways, but it can also provide cancerous cells with a nurturing environment due to the increased availability of proliferative and survival signals. This notion is supported by an animal study by Tanaka et al. [10], in which a combined treatment of the chemical carcinogen azoxymethane (AOM) with the inflammatory agent dextran sodium sulfate (DSS) significantly increased intestinal tumorigenesis in CD-1 mice. The AOM + DSS model yields a consistent, reproducible colon cancer outcome ...

The Western dietary pattern can alter the gut microbiome and cause obesity and metabolic disorders. To examine the interactions between diet, the microbiome, and obesity, we transplanted gut microbiota from lean or obese human donors into mice fed one of three diets for 22 weeks: (1) a control AIN93G diet; (2) the total Western diet (TWD), which mimics the American diet; or (3) a 45% high-fat diet-induced obesity (DIO) diet. We hypothesized that a fecal microbiome transfer (FMT) from obese donors would lead to an obese phenotype and aberrant glucose metabolism in recipient mice that would be exacerbated by consumption of the TWD or DIO diets. Prior to the FMT, the native microbiome was depleted using an established broad-spectrum antibiotic protocol. Interestingly, the human donor body type microbiome did not significantly affect final body weight or body composition in mice fed any of the experimental diets. Beta diversity analysis and linear discriminant analysis with effect size (LEfSe) showed that mice that received an FMT from obese donors had a significantly different microbiome compared to mice that received an FMT from lean donors. However, after 22 weeks, diet influenced the microbiome composition irrespective of donor body type, suggesting that diet is a key variable in the shaping of the gut microbiome after FMT.

Black raspberries (BRB) are rich in anthocyanins with purported anti-inflammatory properties. However, it is not known whether dietary supplementation would ameliorate Western-diet enhanced gut inflammation and colon tumorigenesis. We employed a mouse model of colitis-associated colorectal cancer (CAC) to determine the effects of dietary supplementation with 5 to 10% (w/w) whole, freeze-dried BRB in male C57BL/6J mice fed either a standard healthy diet (AIN93G) or the total Western diet (TWD). In a pilot study, BRB suppressed colitis and colon tumorigenesis while also shifting the composition of the fecal microbiome in favor of taxa with purported health benefits, including Bifidobacterium pseudolongum. In a follow-up experiment using a 2 ´ 2 factorial design with AIN and TWD basal diets with and without 10% (w/w) BRB, supplementation with BRB reduced tumor multiplicity and increased colon length, irrespective of the basal diet, but it did not apparently affect colitis symptoms, colon inflammation or mucosal injury based on histopathological findings. However, BRB intake increased alpha diversity, altered beta diversity and changed the relative abundance of Erysipelotrichaceae, Bifidobacteriaceae, Streptococcaceae, Rikenellaceae, Ruminococcaceae and Akkermansiaceae, among others, of the fecal microbiome. Notably, changes in microbiome profiles were inconsistent with respect to the basal diet consumed. Overall, these studies provide equivocal evidence for in vivo anti-inflammatory effects of BRB on colitis and colon tumorigenesis; yet, BRB supplementation led to dynamic changes in the fecal microbiome composition over the course of disease development.

Previous work by our group using a mouse model of inflammation-associated colorectal cancer (CAC) showed that the total Western diet (TWD) promoted colon tumor development. Others have also shown that vancomycin-mediated changes to the gut microbiome increased colorectal cancer (CRC). Therefore, the objective of this study was to determine the impact of vancomycin on colon tumorigenesis in the context of a standard mouse diet or the TWD. A 2 × 2 factorial design was used, in which C57Bl/6J mice were fed either the standard AIN93G diet or TWD and with vancomycin in the drinking water or not. While both the TWD and vancomycin treatments independently increased parameters associated with gut inflammation and tumorigenesis compared to AIN93G and plain water controls, mice fed the TWD and treated with vancomycin had significantly increased tumor multiplicity and burden relative to all other treatments. Vancomycin treatment significantly decreased alpha diversity and changed the abundance of several taxa at the phylum, family, and genus levels. Conversely, basal diet had relatively minor effects on the gut microbiome composition. These results support our previous research that the TWD promotes colon tumorigenesis and suggest that vancomycin-induced changes to the gut microbiome are associated with higher tumor rates.

Objectives The role of the gut microbiome in the etiology of colorectal cancer (CRC) and the therapeutic potential for modulation of gut microbiota is under intense investigation. Previously, we showed that consumption of the total Western diet (TWD) in mice increased gut inflammation, promoted colon tumorigenesis, and altered the microbiome composition compared to mice fed a healthy diet, AIN93G (AIN). However, it is unclear whether the gut microbiome contributes directly to colitis-associated CRC in this model. The objective of this study was to determine whether fecal microbiota transfer (FMT) from host mice fed either AIN or TWD basal diets would alter colitis symptoms or colitis-associated CRC in recipient mice, which were fed either AIN or TWD directly. Methods The resident microbiome of recipient mice was depleted using broad spectrum antibiotics and then replenished by FMT using fecal samples collected during a prior experiment from mice fed either AIN diet (resulting in modest colitis and low tumor burden) or TWD diet (extreme colitis and high tumor burden) in a time-matched fashion by week. Recipient mice were fed either AIN or TWD basal diets, such that four experiment groups were generated: 1) AIN-fed recipients with FMT from AIN-fed host, 2) AIN-fed recipients with FMT from TWD-fed host, 3) TWD-fed recipients with FMT from AIN-fed host, 2) TWD-fed recipients with FMT from TWD-fed host. In recipients, the standard azoxymethane + dextran sodium sulfate model of colitis-associated CRC was used. Results Preliminary results indicate that time-matched FMT from mice fed TWD did not significantly enhance symptoms of colitis, colon epithelial inflammation, mucosal injury, or colon tumor burden in recipient mice fed AIN diet. Conversely, FMT from AIN-fed mice did not impart a protective effect for recipient mice fed the TWD. Conclusions FMT from mice fed either basal diet with differing colitis or tumor outcomes did not shift colitis symptoms of colon tumorigenesis in recipient mice, regardless of the basal diet they consumed. These observations suggest that the gut microbiome may not contribute directly to the development of disease in this animal model. Gut microbiome 16s rRNA sequencing and analyses are pending. Funding Sources Funding support USDA NIFA grant no. 2018–67,017-27,516.