Evaluation of immunologic and intestinal effects in rats administered an E 171-containing diet, a food grade titanium dioxide (TiO2)

The toxicity of dietary E 171, a food grade titanium dioxide was evaluated. A recent study reported rats receiving E 171 in water developed inflammation and aberrant crypt foci (ACF) in the gastrointestinal tract. Here, rats received food containing E 171 (7 or 100 days). The 100-day study included feeding E 171 after dimethylhydrazine (DMH) or vehicle only pretreatment. Food consumption was similar between treatment groups with maximum total cumulative E 171 exposure being 2617 mg/kg in 7 days and 29,400 mg/kg in 100 days. No differences were observed due to E 171 in the percentage of dendritic, CD4+ T or Treg cells within Peyer's patches or the periphery, or in cytokine production in plasma, sections of jejunum, and colon in 7- or 100-day E 171 alone fed rats. Differences were observed for IL-17A in colon (400 ppm E 171 + DMH) and IL-12p70 in plasma (40 ppm E 171 + DMH). E 171 had no effect on histopathologic evaluations of small and large intestines, liver, spleen, lungs, or testes, and no effects on ACF, goblet cell numbers, or colonic gland length. Dietary E 171 administration (7- or 100-day), even at high doses, produced no effect on the immune parameters or tissue morphology.

Colorectal Carcinogenesis in the A/J Min/+ Mouse Model is Inhibited by Hemin, Independently of Dietary Fat Content and Fecal Lipid Peroxidation Rate

Background

Intake of red meat is considered a risk factor for colorectal cancer (CRC) development, and heme, the prosthetic group of myoglobin, has been suggested as a potential cause. One of the proposed molecular mechanisms of heme-induced CRC is based on an increase in the rate of lipid peroxidation catalysed by heme.

Methods

In the present work, the novel A/J Min/+ mouse model for Apc-driven colorectal cancer was used to investigate the effect of dietary heme (0.5 μmol/g), combined with high (40 energy %) or low (10 energy %) dietary fat levels, on intestinal carcinogenesis. At the end of the dietary intervention period (week 3–11), spontaneously developed lesions in the colon (flat aberrant crypt foci (flat ACF) and tumors) and small intestine (tumors) were scored and thiobarbituric reactive substances (TBARS), a biomarker for lipid peroxidation was analysed in feces.

Results

Dietary hemin significantly reduced colonic carcinogenesis. The inhibitory effect of hemin was not dependent on the dietary fat level, and no association could be established between colonic carcinogenesis and the lipid oxidation rate measured as fecal TBARS. Small intestinal carcinogenesis was not affected by hemin. Fat tended to stimulate intestinal carcinogenesis.

Conclusions

Contradicting the hypothesis, dietary hemin did inhibit colonic carcinogenesis in the present study. The results indicate that fecal TBARS concentration is not directly related to intestinal lesions and is therefore not a suitable biomarker for CRC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2874-0) contains supplementary material, which is available to authorized users.