Suggestive evidence for the induction of colonic aberrant crypts in mice fed sodium nitrite

Two intertwined compartments coexisting in sporadic conventional colon adenomas

Sporadic conventional colon adenomas are microscopically built of 2 intertwined compartments: one on top, harboring the dysplastic tissue that defines their histo-biomolecular attributes, and the other below, composed of non-dysplastic crypts with corrupted shapes (CCS). The CCS of 306 colon adenomas revealed asymmetric, haphazardly-distributed proliferating cell-domains (PC). In contrast, the PC-domains in normal controls were symmetric, being limited to the lower thirds of the crypts. In 28% out of 501 sporadic conventional adenomas, foci of p53-upregulated dysplastic tissue were found. The CCS in 30% of 108 sporadic adenomas showed p53-upregulated single cells, suggesting mounting somatic mutations. No p53-upregulated cells were found in the crypts of controls. In polypoid adenomas, the mucosa of the stalk without dysplastic tissue on top disclosed CCS with asymmetrical PC-domains and single p53-upregulated cells. The latter observations suggested that CCS had developed prior to and not after the growth of the dysplastic tissue on top. CCS were also found below colon adenomas in carcinogen-treated rats. It is concluded that the 2 intertwined histo-biological compartments of sporadic conventional colon adenomas are probably interdependent components. These findings may open new directions aimed to uncover the link between the normal colonic mucosa and the histogenesis of, conventional adenomas.

Mechanism underlying nephroprotective property of curcumin against sodium nitrite-induced nephrotoxicity in male Wistar rat

The current work examined the outcome of curcumin (20 mg/kg body weight/day) administration on arginase and adenosine deaminase (ADA) activities and other kidney markers, as well as markers of oxidative stress, in Wistar rats exposed to sodium nitrite (NaNO₂ ) (60 mg/kg of body weight, single dose) for 28 days. The results revealed that the NaNO₂ exposed rats had significantly altered the ADA activities, arginase activities alongside other biomarkers of kidney function, and oxidative stress. However, pretreatment with curcumin significantly mitigated the altered activities ADA and arginase as well as other parameters. This was supported by the histopathological examination of the kidney tissues. Our findings suggest that the alteration in the activities of ADA and arginase could be involved in the mechanism of action employed by NaNO₂ and curcumin in the respective induction and prevention of nephrotoxicity. PRACTICAL APPLICATIONS: These results suggest that moderate exposure to the acceptable daily dose of curcumin can improve food-related kidney damage through regulations of ADA and arginase activities, enhancement in the antioxidant system, and suppression of lipid peroxidation.

A Review of the In Vivo Evidence Investigating the Role of Nitrite Exposure from Processed Meat Consumption in the Development of Colorectal Cancer

The World Cancer Research Fund (WCRF) 2007 stated that the consumption of processed meat is a convincing cause of colorectal cancer (CRC), and therefore, the public should avoid it entirely. Sodium nitrite has emerged as a putative candidate responsible for the CRC-inducing effects of processed meats. Sodium nitrite is purported to prevent the growth of Clostridium botulinum and other food-spoiling bacteria, but recent, contradictory peer-reviewed evidence has emerged, leading to media reports questioning the necessity of nitrite addition. To date, eleven preclinical studies have investigated the effect of consuming nitrite/nitrite-containing meat on the development of CRC, but the results do not provide an overall consensus. A sizable number of human clinical studies have investigated the relationship between processed meat consumption and CRC risk with widely varying results. The unique approach of the present literature review was to include analysis that limited the human studies to those involving only nitrite-containing meat. The majority of these studies reported that nitrite-containing processed meat was associated with increased CRC risk. Nitrite consumption can lead to the formation of N-nitroso compounds (NOC), some of which are carcinogenic. Therefore, this focused perspective based on the current body of evidence links the consumption of meat containing nitrites and CRC risk.

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.

Prevalence of pre-cancerous colon lesions in referred patients under patronage of a local relief foundation in Guilan province

Colon cancer is the most commonly diagnosed gastrointestinal cancers in developed countries with varied incidence and the onset age of disease worldwide. Overall, 161 participants who were under patronage of a local relief foundation and referred to the endoscopy ward of Razi Hospital affiliated to the Guilan University of Medical Sciences. These patients have been aged more than 50 or more than 40 years with history of colorectal cancer in their first-degree family were enrolled from March 2016–March 2017. Demographic information were collected. Colonoscopy was performed and histopathological evaluation of observed lesions and polyps was done. Most of participants were female (113 individuals, 70.2%) and aged 50–60 years (83 individuals, 51.6%). Seventy-four (46%) had certain lesions. Most of colonoscopy findings were observed in the ascending colon in which depressed polyps and diverticulum were most frequent. However, rectum showed the most histological findings. All polyps of descending and ascending colons were neoplastic, while most of rectal polyps were non-neoplastic. Male patients, who were aged more than 60 years and smokers had significant higher percentage of both lesions and polyps in their colon (p<0.05). Moreover, significant positive association was detected between exposure to harmful industries and having polyps (p=0.01). We found male gender, higher age, smoking, and exposure to harmful industries as important risk factors for having colorectal lesions, which must be confirmed in further studies.

Curcumin protects sodium nitrite-induced hepatotoxicity in Wistar rats

In this study, the protective effect of curcumin on sodium nitrite (NaNO2) induced hepatotoxicity was assessed in male Wistar rats. Wistar rats were administered orally daily with 20 mg/kg of curcumin for 28 days and NaNO2 was administered as a single dose of 60 mg/kg on day 28. Lipid profile, liver function biomarkers and C-reactive protein were assessed in the serum; lipid peroxidation, non-enzymatic and enzymatic antioxidants were assessed in the liver. Alanine amino transferases (94.67 U/L), aspartate amino transferases (194.33 U/L), alkaline phosphatases, C-reactive proteins (19.56 ng/L) and lipid peroxidation (8.03 × 10-6 μmol/mg protein) were significantly elevated (P < 0.05), while a significant decrease in lipid profiles (total cholesterol, HDL,LDL, and triglycerides): (0.61,0.37, 0.4 and 0.47 mg/dl respectively), reduced glutathione level (4.16 μmol/mg protein), and decreased catalase, superoxide dismutase and glutathione peroxidase activities with severe histological alterations were observed in the livers of rats exposed to NaNO2. Pre-treatment with curcumin significantly (P < 0.05) prevented these alterations by adjusting the lipid profile, liver function markers, and C-reactive proteins and abrogating the elevated markers of oxidative stress as supported by the liver histology. This suggests that dietary consumption of curcumin is beneficial against NaNO2 induced oxidative stress of the liver via its antioxidant potential.

Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project

Objective

As part of the World Cancer Research Fund International Continuous Update Project, we updated the systematic review and meta-analysis of prospective studies to quantify the dose-response between foods and beverages intake and colorectal cancer risk.

Data sources

PubMed and several databases up to 31 May 2015.

Study selection

Prospective studies reporting adjusted relative risk estimates for the association of specific food groups and beverages and risk of colorectal, colon and rectal cancer.

Data synthesis

Dose-response meta-analyses using random effect models to estimate summary relative risks (RRs).

Results

About 400 individual study estimates from 111 unique cohort studies were included. Overall, the risk increase of colorectal cancer is 12% for each 100 g/day increase of red and processed meat intake (95% CI = 4-21%, I2=70%, pheterogeneity (ph)<0.01) and 7% for 10 g/day increase of ethanol intake in alcoholic drinks (95% CI = 5-9%, I2=25%, ph = 0.21). Colorectal cancer risk decrease in 17% for each 90g/day increase of whole grains (95% CI = 11-21%, I2 = 0%, ph = 0.30, 6 studies) and 13% for each 400 g/day increase of dairy products intake (95% CI = 10-17%, I2 = 18%, ph = 0.27, 10 studies). Inverse associations were also observed for vegetables intake (RR per 100 g/day =0.98 (95% CI = 0.96-0.99, I2=0%, ph = 0.48, 11 studies) and for fish intake (RR for 100 g/day = 0.89 (95% CI = 0.80-0.99, I2=0%, ph = 0.52, 11 studies), that were weak for vegetables and driven by one study for fish. Intakes of fruits, coffee, tea, cheese, poultry and legumes were not associated with colorectal cancer risk.

Conclusions

Our results reinforce the evidence that high intake of red and processed meat and alcohol increase the risk of colorectal cancer. Milk and whole grains may have a protective role against colorectal cancer. The evidence for vegetables and fish was less convincing.

Taurine mitigates nitrite-induced methemoglobin formation and oxidative damage in human erythrocytes

Nitrite is present as a noxious contaminant in drinking water and causes oxidative damage in various tissues of humans and animals. It is a well-known methemoglobin-forming agent that has been shown to damage blood cells. The protective effect of taurine, a semi-essential sulfur-containing amino acid, was studied on sodium nitrite (NaNO₂)-induced oxidative damage in human erythrocytes. Erythrocytes were incubated with NaNO₂, in the presence and absence of taurine, and changes in oxidative stress parameters determined. Pretreatment with taurine significantly ameliorated NaNO₂-induced oxidative damage to lipids, proteins, and plasma membrane. It also reduced the NaNO₂-induced increase in methemoglobin levels and ROS production. Taurine improved the antioxidant capacity of cells, restored the alterations in the activities of various metabolic enzymes, and prevented morphological changes in erythrocytes. Thus, taurine can be potentially used as a protective agent against the damaging effects of nitrite.

Effects of N-Nitrosodiethylamine, a Potent Carcinogen, on Sexual Development, Gametogenesis, and Oocyte Maturation

N-Nitrosodiethylamine (DEN), a well-known hepatocarcinogen, is found in certain food products as such or as a metabolic byproduct. This study investigated the effects of DEN on sexual development, gametogenesis, and oocyte maturation in Japanese medaka (Oryzias latipes). DEN reduced the germ cell number dose-dependently during early stages of sexual differentiation in XX larvae, resulting in underdeveloped ovaries in adulthood at low doses. This effect was sex-specific as no such changes were seen in XY larvae. Furthermore, XX and XY larvae that were exposed at a low dose during early life showed a significant reduction in body weight in adulthood. Gonads in sexually immature adult medaka males and females exposed to DEN were in advanced stages in comparison to that of the controls. Gonado-somatic indices were significantly high in treated males and females. DEN induced oocyte maturation in vitro, which was inhibited by cordycepin, demonstrating that it stimulated oocyte maturation through polyadenylation of cyclin B mRNA as in the case of the endogenous maturation-inducing hormone. Altogether, our results have proven that DEN could disrupt or mimic the signaling pathways involved in germ cell development, proliferation, and maturation.

Acute oral dose of sodium nitrite induces redox imbalance, DNA damage, metabolic and histological changes in rat intestine

Industrialization and unchecked use of nitrate/nitrite salts for various purposes has increased human exposure to high levels of sodium nitrite (NaNO₂) which can act as a pro-oxidant and pro-carcinogen. Oral exposure makes the gastrointestinal tract particularly susceptible to nitrite toxicity. In this work, the effect of administration of a single acute oral dose of NaNO₂ on rat intestine was studied. Animals were randomly divided into four groups and given single doses of 20, 40, 60 and 75 mg NaNO₂/kg body weight. Untreated animals served as the control group. An NaNO₂ dose-dependent decline in the activities of brush border membrane enzymes, increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased thiol content was observed in all treated groups. The activities of various metabolic and antioxidant defense enzymes were also altered. NaNO₂ induced a dose-dependent increase in DNA damage and DNA-protein crosslinking. Histopathological studies showed marked morphological damage in intestinal cells. The intestinal damage might be due to nitrite-induced oxidative stress, direct action of nitrite anion or chemical modification by reaction intermediates.

Association between red meat consumption and colon cancer: A systematic review of experimental results

A role for red and processed meat in the development of colorectal cancer has been proposed based largely on evidence from observational studies in humans, especially in those populations consuming a westernized diet. Determination of causation specifically by red or processed meat is contingent upon identification of plausible mechanisms that lead to colorectal cancer. We conducted a systematic review of the available evidence to determine the availability of plausible mechanistic data linking red and processed meat consumption to colorectal cancer risk. Forty studies using animal models or cell cultures met specified inclusion criteria, most of which were designed to examine the role of heme iron or heterocyclic amines in relation to colon carcinogenesis. Most studies used levels of meat or meat components well in excess of those found in human diets. Although many of the experiments used semi-purified diets designed to mimic the nutrient loads in current westernized diets, most did not include potential biologically active protective compounds present in whole foods. Because of these limitations in the existing literature, there is currently insufficient evidence to confirm a mechanistic link between the intake of red meat as part of a healthy dietary pattern and colorectal cancer risk. Impact statement Current recommendations to reduce colon cancer include the reduction or elimination of red or processed meats. These recommendations are based on data from epidemiological studies conducted among cultures where meat consumption is elevated and consumption of fruits, vegetables, and whole grains are reduced. This review evaluated experimental data exploring the putative mechanisms whereby red or processed meats may contribute to colon cancer. Most studies used levels of meat or meat-derived compounds that were in excess of those in human diets, even in cultures where meat intake is elevated. Experiments where protective dietary compounds were used to mitigate the extreme levels of meat and meat-derived compounds showed protection against colon cancer, with some essentially negating the impact of meat in the diet. It is essential that better-designed studies be conducted that use relevant concentrations of meat or meat-derived compounds in complex diets representative of the foods consumed by humans.