Wheat Type (Class) Influences Development and Regression of Colon Cancer Risk Markers in Rats

Effect of red wheat, aleurone, and testa layers on colon cancer biomarkers, nitrosative stress, and gut microbiome composition in rats

We previously found greater reduction of colon cancer (CC) biomarkers for red wheat compared to white wheat regardless of refinement state. In the present study we examined whether the phenolic-rich aleurone and testa layers are drivers of chemoprevention by red wheat and their influence on gut microbiota composition using a 1,2-dimethylhydrazine-induced CC rat model. Rats were fed a low-fat diet (16% of energy as fat), high-fat diet (50% of energy as fat), or high-fat diet containing whole red wheat, refined red wheat, refined white wheat, or aleurone- or testa-enriched fractions for 12 weeks. Morphological markers (aberrant crypt foci, ACF) were assessed after methylene blue staining and biochemical markers (3-nitrotyrosine [3-NT], Dclk1) by immunohistochemical determination of staining positivity within aberrant crypts. Gut microbiota composition was evaluated from 16S rRNA gene sequencing of DNA extracted from cecal contents. Relative to the high-fat diet, the whole and refined red wheat, refined white wheat, and testa-enriched fraction decreased ACF, while only the refined red wheat and aleurone-enriched fraction decreased 3-NT. No significant differences were observed for Dclk1. An increase in microbial diversity was observed for the aleurone-enriched fraction (ACE index) and whole red wheat (Inverse Simpson Index). The diet groups significantly modified overall microbiome composition, including altered abundances of Lactobacillus, Mucispirillum, Phascolarctobacterium, and Blautia coccoides. These results suggest that red wheat may reduce CC risk through modifications to the gut microbiota and nitrosative stress, which may be due, in part, to the influence of dietary fiber and the phenolic-rich aleurone layer.

Lactobacillus acidophilus-Fermented Germinated Brown Rice Suppresses Preneoplastic Lesions of the Colon in Rats

Colorectal cancer (CRC) is a cancer associated with chronic inflammation. Whole grains and probiotics play a protective role against CRC. Fermented grains are receiving increased attention due to their anti-inflammatory and anti-cancer activities. Our previous study found that a combination of germinated brown rice (GBR) with probiotics suppressed colorectal carcinogenesis in rats. However, the cancer-preventive effect of probiotic-fermented GBR has not been reported. This study investigated the preventive effect and possible mechanism of GBR fermented by Lactobacillus acidophilus (FGBR) on colorectal carcinogenesis in rats induced by 1,2-dimethylhydrazine (DMH) and dextran sulfate sodium (DSS). DMH/DSS treatment induced preneoplastic aberrant crypt foci (ACF), elevated serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, as well as decreased pro-apoptotic Bax expression. GBR and FGBR reduced the primary ACF number and decreased TNF-α, IL-6 and IL-1β levels. GBR and FGBR at the 2.5% level increased pro-apoptotic cleaved caspase-3 and decreased anti-apoptotic B-cell lymphoma 2 (Bcl-2) expressions. FGBR at the 2.5% level further reduced the number of sialomucin-producing ACF (SIM-ACF) and increased Bax expression. These results suggest that FGBR may inhibit preneoplastic lesions of the colon via activating the apoptotic pathway. This fermented rice product may have the potential to be developed as a novel dietary supplement for CRC chemoprevention.

Apiaceous and Cruciferous Vegetables Fed During the Post-Initiation Stage Reduce Colon Cancer Risk Markers in Rats

BACKGROUND

Vegetable consumption reduces colon cancer risk when fed in the initiation stage of carcinogenesis; however, the effect of vegetable consumption during the post-initiation stage has rarely been examined.

OBJECTIVE

We investigated the chemopreventive effects of feeding apiaceous and cruciferous vegetables on colon cancer risk in the post-initiation stage.

METHODS

Thirty male Wistar rats (∼5 wk, 92 g) were subcutaneously injected with 1,2-dimethylhydrazine 1 time/wk for 2 wk. One week after the last dose, rats were randomly assigned to 3 groups: the basal diet, an apiaceous vegetable-containing diet (API; 21% fresh wt/wt), or a cruciferous vegetable-containing diet (CRU; 21% fresh wt/wt). All diets contained ∼20% protein, 7% fat, and 63% digestible carbohydrate. Experimental diets were fed for 10 wk, after which colons were harvested.

RESULTS

CRU reduced aberrant crypt foci (ACF) number compared to the basal group (P = 0.014) and API (P = 0.013), whereas API decreased the proportion of dysplastic ACF relative to the basal group (P < 0.05). Both CRU and API reduced doublecortin-like kinase 1-positive marker expression relative to basal by 57.9% (P = 0.009) and 51.4% (P < 0.02). The numbers of CD44-positive ACF did not differ between the groups. We identified 14 differentially expressed microRNAs (miRNAs). Of these, expression of 6 miRNAs were greater or tended to be greater (P ≤ 0.10) in one or both vegetable-containing groups compared to the basal group. Bioinformatic analysis of these expression changes in miRNA predicted a change in WNT/β-catenin signaling, indicating downregulation of β-catenin in the vegetable-fed groups. Consistent with this bioinformatics analysis, β-catenin-accumulated ACF were decreased in CRU (93.1%, P = 0.012), but not in API (54.4%, P = 0.125), compared to the basal group.

CONCLUSION

Both apiaceous and cruciferous vegetables, fed post-initiation, reduce colonic preneoplastic lesions as well as cancer stem cell marker expression in rats, possibly by suppressing oncogenic signaling through changes in miRNA expression.