Red meat intake-induced increases in fecal water genotoxicity correlate with pro-carcinogenic gene expression changes in the human colon

Adding a Leafy Vegetable Fraction to Diets Decreases the Risk of Red Meat Mortality in MASLD Subjects: Results from the MICOL Cohort

BACKGROUND

Dietary guidelines recommend limiting red meat intake because it has been amply associated with increased cancer mortality, particularly in patients with liver conditions, such as metabolic dysfunction-associated fatty liver disease (MASLD). MASLD is the leading cause of liver dysfunction in the world today, and no specific treatment other than lifestyle correction has yet been established. The aim of this study was to explore the protective role of leafy vegetables when associated with high red meat consumption.

METHODS

The study cohort included 1646 participants assessed during the fourth recall of the MICOL study, subdivided into two groups based on red meat intake (≤50 g/die vs. >50 g/die), in order to conduct a cancer mortality analysis. The prevalence of subjects that consumed >50 g/die was only 15.73%. Leafy vegetable intake was categorized based on median g/die consumption, and it was combined with red meat intake.

CONCLUSIONS

This is the first study to demonstrate that the consumption of about 30 g/die of leafy vegetables reduces the risk of mortality. A strong association with mortality was observed in subjects with MASLD, and the protective role of vegetables was demonstrated.

Genetic Variability Impacts Genotoxic and Transcriptome Responses in the Human Colon after the Consumption of Processed Red Meat Products and Those with Added Phytochemical Extracts

The PHYTOME study investigated the effect of consuming processed meat products on outcomes related to colorectal cancer risk without testing the impact of genetic variability on these responses. This research aims to elucidate the genetic impact on apparent total N-nitroso compound (ATNC) excretion, colonic DNA adduct formation, ex vivo-induced DNA damage, and gene expression changes in colon biopsies of healthy participants. Through a systematic literature review, candidate polymorphisms were selected and then detected using TaqMan and PCR analysis. The effect of genotype on study outcomes was determined via a linear mixed model and analysis of variance. Machine learning was used to evaluate relative allele importance concerning genotoxic responses, which established a ranking of the most protective alleles and a combination of genotypes (gene scores). Participants were grouped by GSTM1 genotype and differentially expressed genes (DEGs), and overrepresented biological pathways were compared between groups. Stratifying participants by ten relevant genes revealed significant variations in outcome responses. After consumption of processed red meat, variations in NQO1 and COMT impacted responses in ATNC levels (µmol/L) (+9.56 for wildtype vs. heterozygous) and DNA adduct levels (pg/µg DNA) (+1.26 for variant vs. wildtype and +0.43 for variant vs. heterozygous), respectively. After phytochemicals were added to the meat, GSTM1 variation impacted changes in DNA adduct levels (-6.12 for deletion vs. wildtype). The gene scores correlated with these responses and DEGs were identified by GSTM1 genotype. The altered pathways specific to the GSTM1 wildtype group included 'metabolism', 'cell cycle', 'vitamin D receptor', and 'metabolism of water-soluble vitamins and co-factors'. Genotype impacted both the potential genotoxicity of processed red meat and the efficacy of protective phytochemical extracts.

Substituting meat for mycoprotein reduces genotoxicity and increases the abundance of beneficial microbes in the gut: Mycomeat, a randomised crossover control trial

PURPOSE

The high-meat, low-fibre Western diet is strongly associated with colorectal cancer risk. Mycoprotein, produced from Fusarium venanatum, has been sold as a high-fibre alternative to meat for decades. Hitherto, the effects of mycoprotein in the human bowel have not been well considered. Here, we explored the effects of replacing a high red and processed meat intake with mycoprotein on markers of intestinal genotoxicity and gut health.

METHODS

Mycomeat (clinicaltrials.gov NCT03944421) was an investigator-blind, randomised, crossover dietary intervention trial. Twenty healthy male adults were randomised to consume 240 g day^-1 red and processed meat for 2 weeks, with crossover to 2 weeks 240 g day^-1 mycoprotein, separated by a 4-week washout period. Primary end points were faecal genotoxicity and genotoxins, while secondary end points comprised changes in gut microbiome composition and activity.

RESULTS

The meat diet increased faecal genotoxicity and nitroso compound excretion, whereas the weight-matched consumption of mycoprotein decreased faecal genotoxicity and nitroso compounds. In addition, meat intake increased the abundance of Oscillobacter and Alistipes, whereas mycoprotein consumption increased Lactobacilli, Roseburia and Akkermansia, as well as the excretion of short chain fatty acids.

CONCLUSION

Replacing red and processed meat with the Fusarium-based meat alternative, mycoprotein, significantly reduces faecal genotoxicity and genotoxin excretion and increases the abundance of microbial genera with putative health benefits in the gut. This work demonstrates that mycoprotein may be a beneficial alternative to meat within the context of gut health and colorectal cancer prevention.

The role of diet in genotoxicity of fecal water derived from IBD patients and healthy controls

Certain dietary factors with anti-inflammatory and/or anti-cancer properties would be a promising preventive strategy for inflammatory bowel disease (IBD) patients against developing colitis-associated colorectal cancer (CAC). In this study, fecal water (FW) was obtained from 80 IBD patients and 20 healthy controls (HCs). The comet assay was applied to determine the DNA damage induced by FW, and the protective potential of FW against hydrogen peroxide (H₂O₂) induced DNA damage in Caco-2 cells. Information on diet was obtained via food frequency questionnaires. The results showed that FW from IBD patients, especially patients with flares, induced higher levels of direct DNA damage in Caco-2 cells and showed less protection against H₂O₂-induced DNA damage, when compared to HCs. The DNA damage induced by FW was positively associated with consumption of processed meat and sugary foods, and nutrient intakes including heme iron and added sugars, whereas negatively correlated to intakes of soy products, and a dietary pattern characterized by high consumption of potatoes, white meat, nuts and seeds, eggs, legumes and soy products. FW from subjects with high coffee consumption protected against H₂O₂-induced DNA damage. These results can help to develop potential preventive strategies for IBD patients to reduce the CAC risk.

The comet assay for the evaluation of gut content genotoxicity: Use in human studies as an early biomarker of colon cancer risk

This short narrative review describes the use of the comet assay to evaluate the formation of genotoxic compounds in the gut lumen in human studies. The fecal water genotoxicity assay is based on ability of the gut content to induce genotoxicity in a cellular model, employing the aqueous component of the feces (fecal water) as this is supposed to contain most of the reactive species and to convey them to the intestinal epithelium. This non-invasive and low-cost assay has been demonstrated to be associated with colon cancer risk in animal models, and although the final validation against human tumors is lacking, it is widely used as a colo-rectal cancer risk biomarker in human nutritional intervention studies. The contribution given to the field of nutrition and cancer by the FW genotoxicity assay is highlighted, particularly in conjunction with other risk biomarkers, to shed light on the complex relationship among diet, microbiota, individual subject characteristics and the formation of genotoxic compounds in the gut.

Replacement of Nitrite in Meat Products by Natural Bioactive Compounds Results in Reduced Exposure to N-Nitroso Compounds: The PHYTOME Project

SCOPE

It has been proposed that endogenously form N-nitroso compounds (NOCs) are partly responsible for the link between red meat consumption and colorectal cancer (CRC) risk. As nitrite has been indicated as critical factor in the formation of NOCs, the impact of replacing the additive sodium nitrite (E250) by botanical extracts in the PHYTOME project is evaluated.

METHOD AND RESULTS

A human dietary intervention study is conducted in which healthy subjects consume 300 g of meat for 2 weeks, in subsequent order: conventional processed red meat, white meat, and processed red meat with standard or reduced levels of nitrite and added phytochemicals. Consumption of red meat products enriched with phytochemicals leads to a significant reduction in the faecal excretion of NOCs, as compared to traditionally processed red meat products. Gene expression changes identify cell proliferation as main affects molecular mechanism. High nitrate levels in drinking water in combination with processed red meat intake further stimulates NOC formation, an effect that could be mitigated by replacement of E250 by natural plant extracts.

CONCLUSION

These findings suggest that addition of natural extracts to conventionally processed red meat products may help to reduce CRC risk, which is mechanistically support by gene expression analyses.

Effects of processed meat and drinking water nitrate on oral and fecal microbial populations in a controlled feeding study

BACKGROUND

One mechanism that can explain the link between processed meat consumption and colorectal cancer (CRC) is the production of carcinogenic N-nitroso compounds (NOCs) in the gastrointestinal tract. Oral and gut microbes metabolize ingested proteins (a source of secondary and tertiary amines and amides) and can reduce nitrate to nitrite, generating potentially carcinogenic NOCs.

OBJECTIVE

We evaluated whether nitrate/nitrite in processed meat or water influences the fecal or salivary microbiota.

DESIGN

In this dietary intervention study, 63 volunteers consumed diets high in conventional processed meats for two weeks, switched to diets high in poultry for two weeks, and then consumed phytochemical-enriched conventional processed or low-nitrite processed meat diets for two weeks. During the intervention, they drank water with low nitrate concentrations and consumed a healthy diet with low antioxidants. Then the volunteers drank nitrate-enriched water for 1 week, in combination with one of the four different diets. We measured creatinine-adjusted urinary nitrate levels and characterized the oral and fecal microbiota using 16S rRNA amplicon sequencing.

RESULTS

Using linear mixed models, we found that, compared to baseline, urinary nitrate levels were reduced during the phytochemical-enriched low-nitrite meat diet (p-value = 0.009) and modestly during the poultry diet (p-value = 0.048). In contrast, urinary nitrate increased after 1-week of drinking nitrate-enriched water (p-value<10^-5). Nitrate-enriched water, but not processed meats with or without phytochemicals, altered the saliva microbial population (p-value ≤0.001), and significantly increased abundance of 8 bacterial taxa, especially genus Neisseria and other nitrate-reducing taxa. Meats, phytochemicals and nitrate-enriched water had no significant effects on saliva alpha diversity or any diversity parameter measured for the fecal microbiota.

CONCLUSION

These findings support the hypothesis that drinking high nitrate water increases oral nitrate-reducing bacteria, which likely results in increased NOC. However, meat nitrate/nitrite at the levels tested had no effect on either the gut or oral bacteria. CLINICALTRIALS.

GOV IDENTIFIER

NCT04138654.

Dietary Factors Modulating Colorectal Carcinogenesis

The development of colorectal cancer, responsible for 9% of cancer-related deaths, is favored by a combination of genetic and environmental factors. The modification of diet and lifestyle may modify the risk of colorectal cancer (CRC) and prevent neoplasia in up to 50% of cases. The Western diet, characterized by a high intake of fat, red meat and processed meat has emerged as an important contributor. Conversely, a high intake of dietary fiber partially counteracts the unfavorable effects of meat through multiple mechanisms, including reduced intestinal transit time and dilution of carcinogenic compounds. Providing antioxidants (e.g., vitamins C and E) and leading to increased intraluminal production of protective fermentation products, like butyrate, represent other beneficial and useful effects of a fiber-rich diet. Protective effects on the risk of developing colorectal cancer have been also advocated for some specific micronutrients like vitamin D, selenium, and calcium. Diet-induced modifications of the gut microbiota modulate colonic epithelial cell homeostasis and carcinogenesis. This can have, under different conditions, opposite effects on the risk of CRC, through the production of mutagenic and carcinogenic agents or, conversely, of protective compounds. The aim of this review is to summarize the most recent evidence on the role of diet as a potential risk factor for the development of colorectal malignancies, as well as providing possible prevention dietary strategies.

The benefits and risks of beetroot juice consumption: a systematic review

Beetroot juice (BRJ) has become increasingly popular amongst athletes aiming to improve sport performances. BRJ contains high concentrations of nitrate, which can be converted into nitric oxide (NO) after consumption. NO has various functions in the human body, including a vasodilatory effect, which reduces blood pressure and increases oxygen- and nutrient delivery to various organs. These effects indicate that BRJ may have relevant applications in prevention and treatment of cardiovascular disease. Furthermore, the consumption of BRJ also has an impact on oxygen delivery to skeletal muscles, muscle efficiency, tolerance and endurance and may thus have a positive impact on sports performances. Aside from the beneficial aspects of BRJ consumption, there may also be potential health risks. Drinking BRJ may easily increase nitrate intake above the acceptable daily intake, which is known to stimulate the endogenous formation of N-nitroso compounds (NOC's), a class of compounds that is known to be carcinogenic and that may also induce several other adverse effects. Compared to studies on the beneficial effects, the amount of data and literature on the negative effects of BRJ is rather limited, and should be increased in order to perform a balanced risk assessment.

Impact of high drinking water nitrate levels on the endogenous formation of apparent N-nitroso compounds in combination with meat intake in healthy volunteers

BACKGROUND

Nitrate is converted to nitrite in the human body and subsequently can react with amines and amides in the gastrointestinal tract to form N-nitroso compounds (NOCs), which are known to be carcinogenic in animals. Humans can be exposed to nitrate via consumption of drinking water and diet, especially green leafy vegetables and cured meat. The contribution of nitrate from drinking water in combination with meat intake has not been investigated thoroughly. Therefore, in the present pilot study, we examined the effect of nitrate from drinking water, and its interaction with the consumption of white and processed red meat, on the endogenous formation of NOCs, taking into account the intake of vitamin C, a nitrosation inhibitor.

METHODS

Twenty healthy subjects were randomly assigned to two groups consuming either 3.75 g/kg body weight (maximum 300 g per day) processed red meat or unprocessed white meat per day for two weeks. Drinking water nitrate levels were kept low during the first week (< 1.5 mg/L), whereas in week 2, nitrate levels in drinking water were adjusted to the acceptable daily intake level of 3.7 mg/kg bodyweight. At baseline, after 1 and 2 weeks, faeces and 24 h urine samples were collected for analyses of nitrate, apparent total N-nitroso compounds (ATNC), compliance markers, and genotoxic potential in human colonic Caco-2 cells.

RESULTS

Urinary nitrate excretion was significantly increased during the high drinking water nitrate period for both meat types. Furthermore, levels of compliance markers for meat intake were significantly increased in urine from subjects consuming processed red meat (i.e. 1-Methylhistidine levels), or unprocessed white meat (i.e. 3-Methylhistidine). ATNC levels significantly increased during the high drinking water nitrate period, which was more pronounced in the processed red meat group. Genotoxicity in Caco-2 cells exposed to faecal water resulted in increased genotoxicity after the interventions, but results were only significant in the low drinking water nitrate period in subjects consuming processed red meat. Furthermore, a positive correlation was found between the ratio of nitrate/vitamin C intake (including drinking water) and the level of ATNC in faecal water of subjects in the processed red meat group, but this was not statistically significant.

CONCLUSIONS

Drinking water nitrate significantly contributed to the endogenous formation of NOC, independent of the meat type consumed. This implies that drinking water nitrate levels should be taken into account when evaluating the effect of meat consumption on endogenous formation of NOC.

TRIAL REGISTRATION

Dutch Trialregister: 29707 . Registered 19th of October 2018. Retrospectively registered.

Dietary protein sources and tumoral overexpression of RhoA, VEGF-A and VEGFR2 genes among breast cancer patients

BACKGROUND

High protein intake may promote angiogenesis giving support to the development of metastasis according to the experimental data. However, nutritional epidemiologic evidence is inconsistent with metastasis. Therefore, we aimed to study the association between dietary intake of protein and tumoral expression levels of Ras homologous gene family member A (RhoA), vascular endothelial growth factor-A (VEGF-A), and VEGF receptor-2 (VEGFR2) in primary breast cancer (BC) patients.

METHODS

Over this consecutive case series, 177 women primary diagnosed with histopathologically confirmed BC in Tabriz (Iran) were enrolled between May 2011 and November 2016. A validated food frequency questionnaire was completed for eligible participants. Fold change in gene expression was measured using quantitative real-time PCR. Principal component factor analysis (PCA) was used to express dietary groups of proteins.

RESULTS

Total protein intake was associated with the expression level of VEGF-A in progesterone receptor-positive (PR+: β = 0.296, p < 0.01) and VEGFR2 in patients with involvement of axillary lymph node metastasis (ALNM+: β = 0.295, p < 0.01) when covariates were adjusted. High animal protein intake was correlated with overexpression of RhoA in tumors with estrogen receptor-positive (ER+: β = 0.230, p < 0.05), ALNM+ (β = 0.238, p < 0.05), and vascular invasion (VI+: β = 0.313, p < 0.01). Animal protein intake was correlated with the overexpression of VEGFR2 when tumors were positive for hormonal receptors (ER+: β = 0.299, p < 0.01; PR+: β = 0.296, p < 0.01). Based on the PCA outputs, protein provided by whole meat (white and red meat) was associated inversely with RhoA expression in ALNM+ (β = - 0.253, p < 0.05) and premenopausal women (β = - 0.285, p < 0.01) in adjusted models. Whole meat was correlated with VEGFR2 overexpression in VI+ (β = 0.288, p < 0.05) and premenopausal status (β = 0.300, p < 0.05) in adjusted models. A group composed of dairy products and legumes was correlated with the overexpression of RhoA (β = 0.249, p < 0.05) and VEGF-A (β = 0.297, p < 0.05) in VI+.

CONCLUSIONS

Based on the multivariate findings, the dietary protein could associate with the overexpression of RhoA and VEGF-VEGFR2 in favor of lymphatic and vascular metastasis in BC patients.

Haem iron reshapes colonic luminal environment: impact on mucosal homeostasis and microbiome through aldehyde formation

BACKGROUND

The World Health Organization classified processed and red meat consumption as "carcinogenic" and "probably carcinogenic", respectively, to humans. Haem iron from meat plays a role in the promotion of colorectal cancer in rodent models, in association with enhanced luminal lipoperoxidation and subsequent formation of aldehydes. Here, we investigated the short-term effects of this haem-induced lipoperoxidation on mucosal and luminal gut homeostasis including microbiome in F344 male rats fed with a haem-enriched diet (1.5 μmol/g) 14-21 days.

RESULTS

Changes in permeability, inflammation, and genotoxicity observed in the mucosal colonic barrier correlated with luminal haem and lipoperoxidation markers. Trapping of luminal haem-induced aldehydes normalised cellular genotoxicity, permeability, and ROS formation on a colon epithelial cell line. Addition of calcium carbonate (2%) to the haem-enriched diet allowed the luminal haem to be trapped in vivo and counteracted these haem-induced physiological traits. Similar covariations of faecal metabolites and bacterial taxa according to haem-induced lipoperoxidation were identified.

CONCLUSIONS

This integrated approach provides an overview of haem-induced modulations of the main actors in the colonic barrier. All alterations were closely linked to haem-induced lipoperoxidation, which is associated with red meat-induced colorectal cancer risk.

Dietary intake alters gene expression in colon tissue: possible underlying mechanism for the influence of diet on disease

Supplemental Digital Content is available in the text.

Background

Although the association between diet and disease is well documented, the biologic mechanisms involved have not been entirely elucidated. In this study, we evaluate how dietary intake influences gene expression to better understand the underlying mechanisms through which diet operates.

Methods

We used data from 144 individuals who had comprehensive dietary intake and gene expression data from RNAseq using normal colonic mucosa. Using the DESeq2 statistical package, we identified genes that showed statistically significant differences in expression between individuals in high-intake and low-intake categories for several dietary variables of interest adjusting for age and sex. We examined total calories, total fats, vegetable protein, animal protein, carbohydrates, trans-fatty acids, mutagen index, red meat, processed meat, whole grains, vegetables, fruits, fiber, folate, dairy products, calcium, and prudent and western dietary patterns.

Results

Using a false discovery rate of less than 0.1, meat-related foods were statistically associated with 68 dysregulated genes, calcium with three dysregulated genes, folate with four dysregulated genes, and nonmeat-related foods with 65 dysregulated genes. With a more stringent false discovery rate of less than 0.05, there were nine meat-related dysregulated genes and 23 nonmeat-related genes. Ingenuity pathway analysis identified three major networks among genes identified as dysregulated with respect to meat-related dietary variables and three networks among genes identified as dysregulated with respect to nonmeat-related variables. The top networks (Ingenuity Pathway Analysis network score >30) associated with meat-related genes were (i) cancer, organismal injury, and abnormalities, tumor morphology, and (ii) cellular function and maintenance, cellular movement, cell death, and survival. Among genes related to nonmeat consumption variables, the top networks were (i) hematological system development and function, nervous system development and function, tissue morphology and (ii) connective tissue disorders, organismal injury, and abnormalities.

Conclusion

Several dietary factors were associated with gene expression in our data. These findings provide insight into the possible mechanisms by which diet may influence disease processes.

Potential health hazards of eating red meat

Red meat (beef, veal, pork, lamb and mutton) consumption contributes several important nutrients to the diet, for example essential amino acids, vitamins (including B12) and minerals (including iron and zinc). Processed red meat (ham, sausages, bacon, frankfurters, salami, etc.) undergoes treatment (curing, smoking, salting or the use of chemical preservatives and additives) to improve its shelf life and/or taste. During recent decades, consumption of red meat has been increasing globally, especially in developing countries. At the same time, there has been growing evidence that high consumption of red meat, especially of processed meat, may be associated with an increased risk of several major chronic diseases. Here, a comprehensive summary is provided of the accumulated evidence based on prospective cohort studies regarding the potential adverse health effects of red meat consumption on major chronic diseases, such as diabetes, coronary heart disease, heart failure, stroke and cancer at several sites, and mortality. Risk estimates from pooled analyses and meta-analyses are presented together with recently published findings. Based on at least six cohorts, summary results for the consumption of unprocessed red meat of 100 g day^-1 varied from nonsignificant to statistically significantly increased risk (11% for stroke and for breast cancer, 15% for cardiovascular mortality, 17% for colorectal and 19% for advanced prostate cancer); for the consumption of 50 g day^-1 processed meat, the risks were statistically significantly increased for most of the studied diseases (4% for total prostate cancer, 8% for cancer mortality, 9% for breast, 18% for colorectal and 19% for pancreatic cancer, 13% for stroke, 22% for total and 24% for cardiovascular mortality and 32% for diabetes). Potential biological mechanisms underlying the observed risks and the environmental impact of red meat production are also discussed. The evidence-based integrated message is that it is plausible to conclude that high consumption of red meat, and especially processed meat, is associated with an increased risk of several major chronic diseases and preterm mortality. Production of red meat involves an environmental burden. Therefore, some European countries have already integrated these two issues, human health and the 'health of the planet', into new dietary guidelines and recommended limiting consumption of red meat.

Consumption of Red/Processed Meat and Colorectal Carcinoma: Possible Mechanisms Underlying the Significant Association

Epidemiology and experimental studies provide an overwhelming support of the notion that diets high in red or processed meat accompany an elevated risk of developing pre-neoplastic colorectal adenoma and frank colorectal carcinoma (CRC). The underlying mechanisms are disputed; thus several hypotheses have been proposed. A large body of reports converges, however, on haem and nitrosyl haem as major contributors to the CRC development, presumably acting through various mechanisms. Apart from a potentially higher intestinal mutagenic load among consumers on a diet rich in red/processed meat, other mechanisms involving subtle interference with colorectal stem/progenitor cell survival or maturation are likewise at play. From an overarching perspective, suggested candidate mechanisms for red/processed meat-induced CRC appear as three partly overlapping tenets: (i) increased N-nitrosation/oxidative load leading to DNA adducts and lipid peroxidation in the intestinal epithelium, (ii) proliferative stimulation of the epithelium through haem or food-derived metabolites that either act directly or subsequent to conversion, and (iii) higher inflammatory response, which may trigger a wide cascade of pro-malignant processes. In this review, we summarize and discuss major findings of the area in the context of potentially pertinent mechanisms underlying the above-mentioned association between consumption of red/processed meat and increased risk of developing CRC.

The Joint Effects of Lifestyle Factors and Comorbidities on the Risk of Colorectal Cancer: A Large Chinese Retrospective Case-Control Study

Background

Colorectal cancer (CRC) is a major cause of cancer morbidity and mortality. In previous epidemiologic studies, the respective correlation between lifestyle factors and comorbidity and CRC has been extensively studied. However, little is known about their joint effects on CRC.

Methods

We conducted a retrospective case-control study of 1,144 diagnosed CRC patients and 60,549 community controls. A structured questionnaire was administered to the participants about their socio-demographic factors, anthropometric measures, comorbidity history and lifestyle factors. Logistic regression model was used to calculate the odds ratio (ORs) and 95% confidence intervals (95%CIs) for each factor. According to the results from logistic regression model, we further developed healthy lifestyle index (HLI) and comorbidity history index (CHI) to investigate their independent and joint effects on CRC risk.

Results

Four lifestyle factors (including physical activities, sleep, red meat and vegetable consumption) and four types of comorbidity (including diabetes, hyperlipidemia, history of inflammatory bowel disease and polyps) were found to be independently associated with the risk of CRC in multivariant logistic regression model. Intriguingly, their combined pattern- HLI and CHI demonstrated significant correlation with CRC risk independently (OR_HLI: 3.91, 95%CI: 3.13–4.88; OR_CHI: 2.49, 95%CI: 2.11–2.93) and jointly (OR: 10.33, 95%CI: 6.59–16.18).

Conclusions

There are synergistic effects of lifestyle factors and comorbidity on the risk of colorectal cancer in the Chinese population.

Nitrate and nitrite in the diet: how to assess their benefit and risk for human health

Nitrate is a natural constituent of the human diet and an approved food additive. It can be partially converted to nitrogen monoxide, which induces vasodilation and thereby decreases blood pressure. This effect is associated with a reduced risk regarding cardiovascular disease, myocardial infarction, and stroke. Moreover, dietary nitrate has been associated with beneficial effects in patients with gastric ulcer, renal failure, or metabolic syndrome. Recent studies indicate that such beneficial health effects due to dietary nitrate may be achievable at intake levels resulting from the daily consumption of nitrate-rich vegetables. N-nitroso compounds are endogenously formed in humans. However, their relevance for human health has not been adequately explored up to now. Nitrate and nitrite are per se not carcinogenic, but under conditions that result in endogenous nitrosation, it cannot be excluded that ingested nitrate and nitrite may lead to an increased cancer risk and may probably be carcinogenic to humans. In this review, the known beneficial and detrimental health effects related to dietary nitrate/nitrite intake are described and the identified gaps in knowledge as well as the research needs required to perform a reliable benefit/risk assessment in terms of long-term human health consequences due to dietary nitrate/nitrite intake are presented.

Heme-related gene expression signatures of meat intakes in lung cancer tissues

Lung cancer causes more deaths worldwide than any other cancer. In addition to cigarette smoking, dietary factors may contribute to lung carcinogenesis. Epidemiologic studies, including the environment and genetics in lung cancer etiology (EAGLE), have reported increased consumption of red/processed meats to be associated with higher risk of lung cancer. Heme-iron toxicity may link meat intake with cancer. We investigated this hypothesis in meat-related lung carcinogenesis using whole genome expression. We measured genome-wide expression (HG-U133A) in 49 tumor and 42 non-involved fresh frozen lung tissues of 64 adenocarcinoma EAGLE patients. We studied gene expression profiles by high-versus-low meat consumption, with and without adjustment by sex, age, and smoking. Threshold for significance was a false discovery rate (FDR) ≤ 0.15. We studied whether the identified genes played a role in heme-iron related processes by means of manually curated literature search and gene ontology-based pathway analysis. We found that gene expression of 232 annotated genes in tumor tissue significantly distinguished lung adenocarcinoma cases who consumed above/below the median intake of fresh red meats (FDR = 0.12). Sixty-three (∼ 28%) of the 232 identified genes (12 expected by chance, P-value < 0.001) were involved in heme binding, absorption, transport, and Wnt signaling pathway (e.g., CYPs, TPO, HPX, HFE, SLCs, and WNTs). We also identified several genes involved in lipid metabolism (e.g., NCR1, TNF, and UCP3) and oxidative stress (e.g., TPO, SGK2, and MTHFR) that may be indirectly related to heme-toxicity. The study's results provide preliminary evidence that heme-iron toxicity might be one underlying mechanism linking fresh red meat intake and lung cancer.

Gut microbes, diet, and cancer

An expanding body of evidence supports a role for gut microbes in the etiology of cancer. Previously, the focus was on identifying individual bacterial species that directly initiate or promote gastrointestinal malignancies; however, the capacity of gut microbes to influence systemic inflammation and other downstream pathways suggests that the gut microbial community may also affect risk of cancer in tissues outside of the gastrointestinal tract. Functional contributions of the gut microbiota that may influence cancer susceptibility in the broad sense include (1) harvesting otherwise inaccessible nutrients and/or sources of energy from the diet (i.e., fermentation of dietary fibers and resistant starch); (2) metabolism of xenobiotics, both potentially beneficial or detrimental (i.e., dietary constituents, drugs, carcinogens, etc.); (3) renewal of gut epithelial cells and maintenance of mucosal integrity; and (4) affecting immune system development and activity. Understanding the complex and dynamic interplay between the gut microbiome, host immune system, and dietary exposures may help elucidate mechanisms for carcinogenesis and guide future cancer prevention and treatment strategies.

Heme-induced biomarkers associated with red meat promotion of colon cancer are not modulated by the intake of nitrite

Red and processed meat consumption is associated with the risk of colorectal cancer. Three hypotheses are proposed to explain this association, via heme-induced oxidation of fat, heterocyclic amines, or N-nitroso compounds. Rats have often been used to study these hypotheses, but the lack of enterosalivary cycle of nitrate in rats casts doubt on the relevance of this animal model to predict nitroso- and heme-associated human colon carcinogenesis. The present study was thus designed to clarify whether a nitrite intake that mimics the enterosalivary cycle can modulate heme-induced nitrosation and fat peroxidation. This study shows that, in contrast with the starting hypothesis, drinking water added with nitrite to mimic the salivary nitrite content did not change the effect of hemoglobin on biochemical markers linked to colon carcinogenesis, notably lipid peroxidation and cytotoxic activity in the colon of rat. However, ingested sodium nitrite increased fecal nitroso-compounds level, but their fecal concentration and their nature (iron-nitrosyl) would probably not be associated with an increased risk of cancer. We thus suggest that the rat model could be relevant for study the effect of red meat on colon carcinogenesis, in spite of the lack of nitrite in the saliva of rats.

Fecal water genotoxicity in healthy free-living young Italian people

Dietary habit affects the composition of human feces thus determining intestinal environment and exposure of colon mucosa to risk factors. Fecal water (FW) citotoxicity and genotoxicity were investigated in 33 healthy young Italian people, as well as the relationship between genotoxicity and nutrient intake or microflora composition. Two fecal samples were collected at 2 weeks apart and 3-d dietary diary was recorded for each volunteer. Cytotoxicity was measured using the Trypan Blue Dye Exclusion assay and genotoxicity using the Comet Assay (alkaline single-cell electrophoresis). Fecal bifidobacteria, total microbial count and nutrient intakes were also assessed. High intra- and inter-variability in genotoxicity data and in bacteria counts were found. None of the FW samples were citotoxic, but 90% of FW samples were genotoxic. Seventy five percent indicated intermediate and 15% were highly genotoxic. There was a different sex-related distribution. Genotoxicity was positively correlated to the total lipid intake in females and to the bifidobacteria/total bacteria count ratio in male volunteers. These results demonstrate that the majority of FW samples isolated from free-living Italian people show intermediate level of genotoxicity and sustain a relation between this possible non-invasive marker of colorectal cancer risk with both dietary habits and colonic ecosystem.

Calcium and α-tocopherol suppress cured-meat promotion of chemically induced colon carcinogenesis in rats and reduce associated biomarkers in human volunteers

BACKGROUND

Processed meat intake has been associated with increased colorectal cancer risk. We have shown that cured meat promotes carcinogen-induced preneoplastic lesions and increases specific biomarkers in the colon of rats.

OBJECTIVES

We investigated whether cured meat modulates biomarkers of cancer risk in human volunteers and whether specific agents can suppress cured meat-induced preneoplastic lesions in rats and associated biomarkers in rats and humans.

DESIGN

Six additives (calcium carbonate, inulin, rutin, carnosol, α-tocopherol, and trisodium pyrophosphate) were added to cured meat given to groups of rats for 14 d, and fecal biomarkers were measured. On the basis of these results, calcium and tocopherol were kept for the following additional experiments: cured meat, with or without calcium or tocopherol, was given to dimethylhydrazine-initiated rats (47% meat diet for 100 d) and to human volunteers in a crossover study (180 g/d for 4 d). Rat colons were scored for mucin-depleted foci, putative precancer lesions. Biomarkers of nitrosation, lipoperoxidation, and cytotoxicity were measured in the urine and feces of rats and volunteers.

RESULTS

Cured meat increased nitroso compounds and lipoperoxidation in human stools (both P < 0.05). Calcium normalized both biomarkers in rats and human feces, whereas tocopherol only decreased nitro compounds in rats and lipoperoxidation in feces of volunteers (all P < 0.05). Last, calcium and tocopherol reduced the number of mucin-depleted foci per colon in rats compared with nonsupplemented cured meat (P = 0.01).

CONCLUSION

Data suggest that the addition of calcium carbonate to the diet or α-tocopherol to cured meat may reduce colorectal cancer risk associated with cured-meat intake. This trial was registered at clinicaltrials.gov as NCT00994526.

Diet and nutrition in cancer survivorship and palliative care

The primary goal of palliative cancer care is typically to relieve suffering and improve quality of life. Most approaches to diet in this setting have focused only on eating as many calories as possible to avoid cachexia. However, as the concept of palliative care has evolved to include all aspects of cancer survivorship and not just end of life care, there is an increasing need to thoughtfully consider diet and nutrition approaches that can impact not only quality of life but overall health outcomes and perhaps even positively affect cancer recurrence and progression. In this regard, there has been a recent emphasis in the literature on nutrition and cancer as an important factor in both quality of life and in the pathophysiology of cancer. Hence, the primary purpose of this paper is to review the current data on diet and nutrition as it pertains to a wide range of cancer patients in the palliative care setting.

Dietary heme iron and the risk of colorectal cancer with specific mutations in KRAS and APC

Red meat intake has been linked to increased colorectal cancer (CRC) risk. Although the underlying mechanisms remain unclear, experimental studies suggest a role for dietary heme iron. Because heme iron was shown to promote specific mutations, it would be insightful to link heme iron data to CRC with mutations in key genes in an observational, population-based study. We investigated the association between dietary heme iron intake and risk of CRC with mutations in APC (adenomatous polyposis coli) and KRAS (Kirsten ras) and P53 overexpression in the Netherlands Cohort Study. After 7.3 years of follow-up, excluding the first 2.3 years due to incomplete coverage of the pathology registry and to avoid preclinical disease, adjusted hazard ratios (including adjustment for total meat) and 95% confidence intervals were calculated, using 4026 subcohort members (aged 55-69 years at baseline), 435 colon and 140 rectal cancer patients. When comparing the highest with the lowest tertile of intake, heme iron intake was associated with an increased risk of CRC harboring activating mutations in KRAS (hazard ratio = 1.71, 95% confidence interval: 1.15-2.57; P for trend = 0.03) and CRC without truncating mutations in APC (hazard ratio = 1.79, 95% confidence interval: 1.23-2.60; P for trend = 0.003). We observed a positive association between heme iron intake and the risk of CRC with activating G>A mutations in KRAS (P for trend = 0.01) and overall G>A mutations in APC (P for trend = 0.005). No associations were found with CRC harboring G>T mutations in KRAS/APC. Heme iron intake was positively associated with the risk of P53 overexpressed tumors but not with tumors without P53 overexpression (Pheterogeneity = 0.12). Heme iron intake was associated with an increased risk of colorectal tumors harboring G>A transitions in KRAS and APC and overexpression of P53. These novel findings suggest that alkylating rather than oxidative DNA-damaging mechanisms are involved in heme-induced colorectal carcinogenesis.

A comparison of the anticancer properties of isoxanthohumol and 8-prenylnaringenin using in vitro models of colon cancer

The hops plant (Humulus lupulus L.) is an essential ingredient in beer and contains a number of potentially bioactive prenylflavonoids, the predominant being the weakly estrogenic isoxanthohumol (Ix), which can be converted to the more strongly estrogenic 8-PN by the colonic microbiota. The aim of this study was to investigate the biological activity of 8-PN and Ix using in vitro models representing key stages of colorectal carcinogenesis, namely cell growth and viability (MTT assay), cell-cycle progression (DNA content assay), DNA damage (Comet assay), and invasion (Matrigel assay). A significant decrease in Caco-2 cell viability was noted after both 8-PN and Ix treatments at the higher doses (40 and 50 μM, respectively) although the impact on cell cycle differed between the two compounds. The decreased cell viability observed after Ix treatment was associated with a concentration-dependent increase in G2/M and an increased sub-G1 cell-cycle fraction, whereas treatment with 8-PN was associated with an elevated G0/G1 and an increased sub-G1 cell-cycle fraction. Significant antigenotoxic activity was noted at all 8-PN concentrations tested (5-40 μM). Although significant antigenotoxic activity was also noted with Ix treatment at ≤25 μM, at a higher dose, Ix itself exerted genotoxic activity. In a dose-dependent manner, both compounds inhibited HT115 cell invasion with reductions up to 52 and 46% for Ix and 8-PN, respectively, in comparison to untreated cells. This study demonstrated that both Ix and its gut microbial metabolite 8-PN exert anticancer effects on models of key stages of colon tumourigenesis.

Identifying molecular targets of lifestyle modifications in colon cancer prevention

One in four deaths in the United States is cancer-related, and colorectal cancer (CRC) is the second leading cause of cancer-associated deaths. Screening strategies are utilized but have not reduced disease incidence or mortality. In this regard, there is an interest in cancer preventive strategies focusing on lifestyle intervention, where specific etiologic factors involved in cancer initiation, promotion, and progression could be targeted. For example, exposure to dietary carcinogens, such as nitrosamines and polycyclic aromatic hydrocarbons influences colon carcinogenesis. Furthermore, dietary deficiencies could alter sensitivity to genetic damage and influence carcinogen metabolism contributing to CRC. High alcohol consumption increases the risk of mutations including the fact that acetaldehyde, an ethanol metabolite, is classified as a group 1 carcinogen. Tobacco smoke exposure is also a risk factor for cancer development; approximately 20% of CRCs are associated with smoking. Additionally, obese patients have a higher risk of cancer development, which is further supported by the fact that physical activity decreases CRC risk by 55%. Similarly, chronic inflammatory conditions also increase the risk of CRC development. Moreover, the circadian clock alters digestion and regulates other biochemical, physiological, and behavioral processes that could influence CRC. Taken together, colon carcinogenesis involves a number of etiological factors, and therefore, to create effective preventive strategies, molecular targets need to be identified and beleaguered prior to disease progression. With this in mind, the following is a comprehensive review identifying downstream target proteins of the above lifestyle risk factors, which are modulated during colon carcinogenesis and could be targeted for CRC prevention by novel agents including phytochemicals.