A central role for heme iron in colon carcinogenesis associated with red meat intake

Spatial metabolomics using mass-spectrometry imaging to decipher the impact of high red meat diet on the colon metabolome in rat

Colorectal cancer (CRC) is the third most common cancer in the world with a higher prevalence in the developed countries, mainly caused by environmental and lifestyle factors such as diet, particularly red meat consumption. The metabolic impact of high red meat consumption on the epithelial part of the colon was investigated using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MSI), to specifically analyze the epithelial substructure. Ten colons from rats fed for 100 days high red or white meat diet were subjected to untargeted MSI analyses using two spatial resolutions (100 μm and 10 μm) to evaluate metabolite changes in the epithelial part and to visualize the distribution of metabolites of interest within the epithelium crypts. Our results suggest a specific effect of red meat diet on the colonic epithelium metabolism, as evidenced by an increase of purine catabolism products or depletion in glutathione pool, reinforcing the hypothesis of increased oxidative stress with red meat diet. This study also highlighted cholesterol sulfate as another up-regulated metabolite, interestingly localized at the top of the crypts. Altogether, this study demonstrates the feasibility and the added value of using MSI to decipher the effect of high red meat diet on the colonic epithelium.

Epithelial-mesenchymal interaction protects normal colonocytes from 4-HNE-induced phenotypic transformation

INTRODUCTION

Recent studies have shown that epithelial-stromal interactions could play a role in the development of colorectal cancer. Here, we investigated the role of fibroblasts in the transformation of normal colonocytes induced by 4-HNE.

METHODS

Normal Co colonocytes and nF fibroblasts from the same mouse colon were exposed, in monoculture (m) or coculture (c), to 4-HNE (5 μM) twice weekly for 3 weeks. Gene expression was then analysed and the ability of Co colonocytes to grow in anchorage-independent conditions was tested in soft agar. Fibroblasts previously treated or not with 4-HNE were also seeded in culture inserts positioned above the agar layers to allow paracrine exchanges with colonocytes.

RESULTS

First, 60% of the genes studied were modulated by coculture in Co colonocytes, with notably increased expression of BMP receptors. Furthermore, while 4-HNE increased the ability of monoculture-treated Co colonocytes to form colonies, this effect was not observed in coculture-treated Co colonocytes. Adding a selective BMPR1 inhibitor during the treatment phase abolished the protective effect of coculture. Conversely, addition of a BMP4 agonist to the medium of monoculture-treated Co colonocytes prevented phenotypic transformation by 4-HNE. Second, the presence of nF(m)-HNE fibroblasts during the soft agar assay increased the number and size of Co(m) colonocyte colonies, regardless of whether these cells had been previously treated with 4-HNE in monoculture. For soft agar assays performed with nF(c) and Co(c) cells initially treated in coculture, only the reassociation between Co(c)-HNE and nF(c)-HNE resulted in a small increase in the number of colonies.

CONCLUSIONS

During the exposure phase, the epithelial-mesenchymal interaction protected colonocytes from 4-HNE-induced phenotypic transformation via activation of the BMP pathway. This intercellular dialogue also limited the ability of fibroblasts to subsequently promote colonocyte-anchorage-independent growth. In contrast, fibroblasts pre-exposed to 4-HNE in monoculture strongly increased the ability of Co(m) colonocytes to form colonies.

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.

Association between adherence to a dietary approach to stop hypertension and the Mediterranean diets and risk of colorectal cancer: A matched case-control study

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers and is currently the third leading cause of cancer-related deaths worldwide. This study aimed to evaluate whether the dietary approach to stop hypertension (DASH) and Mediterranean (MED) diets are associated with CRC in Iranian adults.

METHODS

This hospital-based case-control study was conducted on 71 cases and 142 controls (40-75 years old) in three general hospitals in Tehran, Iran. The dietary intakes of individuals were collected through face-to-face interviews using a semi-quantitative food frequency questionnaire (FFQ) that included 125 food items. The DASH and MED diet scores were calculated according to food items based on guidelines. Two logistic regression models were applied to evaluate the association between DASH and MED score adherence.

RESULTS

After adjusting for confounding factors, a negative association between DASH diet adherence and CRC risk was observed in the second and last tertile compared to the first tertile (T) (T2: odds ratio (OR) = 0.33; 95% confidence interval (CI): 0.14-0.77 - T3: OR = 0.09; 95% CI: 0.03-0.27). There was no significant association between the MED diet and the risk of CRC.

CONCLUSIONS

In conclusion, the current study's findings presented that adherence to a DASH diet could reduce the odds of CRC.

C-Nitrosation, C-Nitration, and Coupling of Flavonoids with N-Acetyltryptophan Limit This Amine N-Nitrosation in a Simulated Cured and Cooked Meat

Nitrite is a common additive in cured meat formulation that provides microbiological safety, lipid oxidation management, and typical organoleptic properties. However, it is associated with the formation of carcinogenic N-nitrosamines. In this context, the antinitrosating capacity of selected flavonoids and ascorbate was evaluated in a simulated cooked and cured meat under formulation and digestion conditions. N-Acetyltryptophan was used as a secondary amine target. (-)-Epicatechin, rutin, and quercetin were all able to limit the formation of N-acetyl-N-nitrosotryptophan (NO-AcTrp) at pH 2.5 and pH 5 although (-)-epicatechin was 2 to 3-fold more efficient. Kinetics for the newly identified compounds allowed us to unravel common mechanistic pathways, which are flavonoid oxidation by nitrite followed by C-nitration and an original covalent coupling between NO-AcTrp and flavonoids or their nitro and nitroso counterparts. C-nitrosation of the A-ring was evidenced only for (-)-epicatechin. These major findings suggest that flavonoids could help to manage N-nitrosamine formation during cured meat processing, storage, and digestion.

Iron metabolism in colorectal cancer: a balancing act

BACKGROUND

Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second deadliest malignancy worldwide. Current dietary habits are associated with increased levels of iron and heme, both of which increase the risk of developing CRC. The harmful effects of iron overload are related to the induction of iron-mediated pro-tumorigenic pathways, including carcinogenesis and hyperproliferation. On the other hand, iron deficiency may also promote CRC development and progression by contributing to genome instability, therapy resistance, and diminished immune responses. In addition to the relevance of systemic iron levels, iron-regulatory mechanisms in the tumor microenvironment are also believed to play a significant role in CRC and to influence disease outcome. Furthermore, CRC cells are more prone to escape iron-dependent cell death (ferroptosis) than non-malignant cells due to the constitutive activation of antioxidant genes expression. There is wide evidence that inhibition of ferroptosis may contribute to the resistance of CRC to established chemotherapeutic regimens. As such, ferroptosis inducers represent promising therapeutic drugs for CRC.

CONCLUSIONS AND PERSPECTIVES

This review addresses the complex role of iron in CRC, particularly in what concerns the consequences of iron excess or deprivation in tumor development and progression. We also dissect the regulation of cellular iron metabolism in the CRC microenvironment and emphasize the role of hypoxia and of oxidative stress (e.g. ferroptosis) in CRC. Finally, we underline some iron-related players as potential therapeutic targets against CRC malignancy.

Effects of sodium nitrite reduction, removal or replacement on cured and cooked meat for microbiological growth, food safety, colon ecosystem, and colorectal carcinogenesis in Fischer 344 rats

Epidemiological and experimental evidence indicated that processed meat consumption is associated with colorectal cancer risks. Several studies suggest the involvement of nitrite or nitrate additives via N-nitroso-compound formation (NOCs). Compared to the reference level (120 mg/kg of ham), sodium nitrite removal and reduction (90 mg/kg) similarly decreased preneoplastic lesions in F344 rats, but only reduction had an inhibitory effect on Listeria monocytogenes growth comparable to that obtained using the reference nitrite level and an effective lipid peroxidation control. Among the three nitrite salt alternatives tested, none of them led to a significant gain when compared to the reference level: vegetable stock, due to nitrate presence, was very similar to this reference nitrite level, yeast extract induced a strong luminal peroxidation and no decrease in preneoplastic lesions in rats despite the absence of NOCs, and polyphenol rich extract induced the clearest downward trend on preneoplastic lesions in rats but the concomitant presence of nitrosyl iron in feces. Except the vegetable stock, other alternatives were less efficient than sodium nitrite in reducing L. monocytogenes growth.

Targeting beta-catenin signaling for prevention of colorectal cancer - Nutraceutical, drug, and dietary options

Progressive up-regulation of β-catenin signaling is very common in the transformation of colorectal epithelium to colorectal cancer (CRC). Practical measures for opposing such signaling hence have potential for preventing or slowing such transformation. cAMP/PKA activity in colon epithelium, as stimulated by COX-2-generated prostaglandins and β2-adrenergic signaling, boosts β-catenin activity, whereas cGMP/PKG signaling has the opposite effect. Bacterial generation of short-chain fatty acids (as supported by unrefined high-carbohydrate diets, berberine, and probiotics), dietary calcium, daily aspirin, antioxidants opposing cox-2 induction, and nicotine avoidance, can suppress cAMP production in colonic epithelium, whereas cGMP can be boosted via linaclotides, PDE5 inhibitors such as sildenafil or icariin, and likely high-dose biotin. Selective activation of estrogen receptor-β by soy isoflavones, support of adequate vitamin D receptor activity with UV exposure or supplemental vitamin D, and inhibition of CK2 activity with flavanols such as quercetin, can also oppose β-catenin signaling in colorectal epithelium. Secondary bile acids, the colonic production of which can be diminished by low-fat diets and berberine, can up-regulate β-catenin activity by down-regulating farnesoid X receptor expression. Stimulation of PI3K/Akt via insulin, IGF-I, TLR4, and EGFR receptors boosts β-catenin levels via inhibition of glycogen synthase-3β; plant-based diets can down-regulate insulin and IGF-I levels, exercise training and leanness can keep insulin low, anthocyanins and their key metabolite ferulic acid have potential for opposing TLR4 signaling, and silibinin is a direct antagonist for EGFR. Partially hydrolyzed phytate can oppose growth factor-mediated down-regulation of β-catenin by inhibiting Akt activation. Multifactorial strategies for safely opposing β-catenin signaling can be complemented with measures that diminish colonic mutagenesis and DNA hypomethylation - such as avoidance of heme-rich meat and charred or processed meats, consumption of phase II-inductive foods and nutraceuticals (e.g., Crucifera), and assurance of adequate folate status.

Therapeutic effect of trace elements on multiple myeloma and mechanisms of cancer process

In the human body, trace elements and other micronutrients play a vital role in growth, health and immune system function. The trace elements are Iron, Manganese, Copper, Iodine, Zinc, Cobalt, Fluoride, and Selenium. Estimating the serum levels of trace elements in hematologic malignancy patients can determine the severity of the tumor. Multiple myeloma (MM) is a hematopoietic malignancy and is characterized by plasma cell clonal expansion in bone marrow. Despite the advances in treatment methods, myeloma remains largely incurable. In addition to conventional medicine, treatment is moving toward less expensive noninvasive alternatives. One of the alternative treatments is the use of dietary supplements. In this review, we focused on the effect of three trace elements including iron, zinc and selenium on important mechanisms such as the immune system, oxidative and antioxidant factors and cell cycle. Using some trace minerals in combination with approved drugs can increase patients' recovery speed. Trace elements can be used as not only a preventive but also a therapeutic tool, especially in reducing inflammation in hematological cancers such as multiple myeloma. We hope that the prospect of the correct use of trace element supplements in the future could be promising for the treatment of diseases.

Heme: The Lord of the Iron Ring

Heme is an iron-protoporphyrin complex with an essential physiologic function for all cells, especially for those in which heme is a key prosthetic group of proteins such as hemoglobin, myoglobin, and cytochromes of the mitochondria. However, it is also known that heme can participate in pro-oxidant and pro-inflammatory responses, leading to cytotoxicity in various tissues and organs such as the kidney, brain, heart, liver, and in immune cells. Indeed, heme, released as a result of tissue damage, can stimulate local and remote inflammatory reactions. These can initiate innate immune responses that, if left uncontrolled, can compound primary injuries and promote organ failure. In contrast, a cadre of heme receptors are arrayed on the plasma membrane that is designed either for heme import into the cell, or for the purpose of activating specific signaling pathways. Thus, free heme can serve either as a deleterious molecule, or one that can traffic and initiate highly specific cellular responses that are teleologically important for survival. Herein, we review heme metabolism and signaling pathways, including heme synthesis, degradation, and scavenging. We will focus on trauma and inflammatory diseases, including traumatic brain injury, trauma-related sepsis, cancer, and cardiovascular diseases where current work suggests that heme may be most important.

Transferrin Receptor-Mediated Iron Uptake Promotes Colon Tumorigenesis

Transferrin receptor (TFRC) is the major mediator for iron entry into a cell. Under excessive iron conditions, TFRC is expected to be reduced to lower iron uptake and toxicity. However, the mechanism whereby TFRC expression is maintained at high levels in iron-enriched cancer cells and the contribution of TFRC to cancer development are enigmatic. Here the work shows TFRC is induced by adenomatous polyposis coli (APC) gene loss-driven β-catenin activation in colorectal cancer, whereas TFRC-mediated intratumoral iron accumulation potentiates β-catenin signaling by directly enhancing the activity of tankyrase. Disruption of TFRC leads to a reduction of colonic iron levels and iron-dependent tankyrase activity, which caused stabilization of axis inhibition protein 2 (AXIN2) and subsequent repression of the β-catenin/c-Myc/E2F Transcription Factor 1/DNA polymerase delta1 (POLD1) axis. POLD1 knockdown, iron chelation, and TFRC disruption increase DNA replication stress, DNA damage response, apoptosis, and reduce colon tumor growth. Importantly, a combination of iron chelators and DNA damaging agents increases DNA damage response and reduces colon tumor cell growth. TFRC-mediated iron import is at the center of a novel feed-forward loop that facilitates colonic epithelial cell survival. This discovery may provide novel strategies for colorectal cancer therapy.

Urinary Metabolome Analysis Reveals Potential Microbiota Alteration and Electrophilic Burden Induced by High Red Meat Diet: Results from the French NutriNet-Santé Cohort and an In Vivo Intervention Study in Rats

SCOPE

High red and processed meat consumption is associated with several adverse outcomes such as colorectal cancer and overall global mortality. However, the underlying mechanisms remain debated and need to be elucidated.

METHODS AND RESULTS

Urinary untargeted Liquid Chromatography-Mass Spectrometry (LC-MS) metabolomics data from 240 subjects from the French cohort NutriNet-Santé are analyzed. Individuals are matched and divided into three groups according to their consumption of red and processed meat: high red and processed meat consumers, non-red and processed meat consumers, and at random group. Results are supported by a preclinical experiment where rats are fed either a high red meat or a control diet. Microbiota derived metabolites, in particular indoxyl sulfate and cinnamoylglycine, are found impacted by the high red meat diet in both studies, suggesting a modification of microbiota by the high red/processed meat diet. Rat microbiota sequencing analysis strengthens this observation. Although not evidenced in the human study, rat mercapturic acid profile concomitantly reveals an increased lipid peroxidation induced by high red meat diet.

CONCLUSION

Novel microbiota metabolites are identified as red meat consumption potential biomarkers, suggesting a deleterious effect, which could partly explain the adverse effects associated with high red and processed meat consumption.

Processed meat, red meat, white meat, and digestive tract cancers: A two-sample Mendelian randomization study

Background

Previous observational studies suggested inconsistent insights on the associations between meat intake and the risk of digestive tract cancers (DCTs). The causal effect of meat intake on DCTs is unclear.

Methods

Two-sample Mendelian randomization (MR) was performed based on genome-wide association studies (GWAS) summary data from UK Biobank and FinnGen to evaluate the causal effect of meat intake [processed meat, red meat (pork, beef, and lamb), and white meat (poultry)] on DCTs (esophageal, stomach, liver, biliary tract, pancreatic, and colorectal cancers). The causal effects were estimated using a primary analysis that employed inverse-variance weighting (IVW) and complementary analysis that utilized MR-Egger weighted by the median. A sensitivity analysis was conducted using the Cochran Q statistic, a funnel plot, the MR-Egger intercept, and a leave-one-out approach. MR-PRESSO and Radial MR were performed to identify and remove outliers. To demonstrate direct causal effects, multivariable MR (MVMR) was applied. In addition, risk factors were introduced to explore potential mediators of the relationship between exposure and outcome.

Results

The results of the univariable MR analysis indicated that genetically proxied processed meat intake was associated with an increased risk of colorectal cancer [IVW: odds ratio (OR) = 2.12, 95% confidence interval (CI) 1.07-4.19; P = 0.031]. The causal effect is consistent in MVMR (OR = 3.85, 95% CI 1.14-13.04; P = 0.030) after controlling for the influence of other types of exposure. The body mass index and total cholesterol did not mediate the causal effects described above. There was no evidence to support the causal effects of processed meat intake on other cancers, except for colorectal cancer. Similarly, there is no causal association between red meat, white meat intake, and DCTs.

Conclusions

Our study reported that processed meat intake increases the risk of colorectal cancer rather than other DCTs. No causal relationship was observed between red and white meat intake and DCTs.

The Role of the Gut Microbiota in the Relationship Between Diet and Human Health

The interplay between diet, the gut microbiome, and host health is complex. Diets associated with health have many similarities: high fiber, unsaturated fatty acids, and polyphenols while being low in saturated fats, sodium, and refined carbohydrates. Over the past several decades, dietary patterns have changed significantly in Westernized nations with the increased consumption of calorically dense ultraprocessed foods low in fiber and high in saturated fats, salt, and refined carbohydrates, leading to numerous negative health consequences including obesity, metabolic syndrome, and cardiovascular disease. The gut microbiota is an environmental factor that interacts with diet and may also have an impact on health outcomes, many of which involve metabolites produced by the microbiota from dietary components that can impact the host. This review focuses on our current understanding of the complex relationship between diet, the gut microbiota, and host health, with examples of how diet can support health, increase an individual's risk for disease, and be used as a therapy for specific diseases.

β-catenin-IRP2-primed iron availability to mitochondrial metabolism is druggable for active β-catenin-mediated cancer

BACKGROUND

Although β-catenin signaling cascade is frequently altered in human cancers, targeting this pathway has not been approved for cancer treatment.

METHODS

High-throughput screening of an FDA-approved drug library was conducted to identify therapeutics that selectively inhibited the cells with activated β-catenin. Efficacy of iron chelator and mitochondrial inhibitor was evaluated for suppression of cell proliferation and tumorigenesis. Cellular chelatable iron levels were measured to gain insight into the potential vulnerability of β-catenin-activated cells to iron deprivation. Extracellular flux analysis of mitochondrial function was conducted to evaluate the downstream events of iron deprivation. Chromatin immunoprecipitation, real-time quantitative PCR and immunoblotting were performed to identify β-catenin targets. Depletion of iron-regulatory protein 2 (IRP2), a key regulator of cellular iron homeostasis, was carried out to elucidate its significance in β-catenin-activated cells. Online databases were analyzed for correlation between β-catenin activity and IRP2-TfR1 axis in human cancers.

RESULTS

Iron chelators were identified as selective inhibitors against β-catenin-activated cells. Deferoxamine mesylate, an iron chelator, preferentially repressed β-catenin-activated cell proliferation and tumor formation in mice. Mechanically, β-catenin stimulated the transcription of IRP2 to increase labile iron level. Depletion of IRP2-sequered iron impaired β-catenin-invigorated mitochondrial function. Moreover, mitochondrial inhibitor S-Gboxin selectively reduced β-catenin-associated cell viability and tumor formation.

CONCLUSIONS

β-catenin/IRP2/iron stimulation of mitochondrial energetics is targetable vulnerability of β-catenin-potentiated cancer.

Iron metabolism in colorectal cancer

Iron, as one of the essential trace elements in the human body, is involved in a wide range of critical biochemical reactions and physiological processes, including the maintenance of the normal cell cycle, mitochondrial function, nucleotide metabolism, and immune response. In this context, iron is naturally associated with cancer occurrence. Cellular iron deficiency can induce apoptosis, however, iron can also engage in potentially harmful reactions that produce free radicals because of its capacity to gain and lose electrons. Studies suggest that dietary iron, particularly heme iron, may be one of the leading causes of colorectal cancer (CRC). Moreover, patients with CRC have abnormal iron absorption, storage, utilization, and exportation. Therefore, iron is crucial for the development and progression of CRC. Elaborating on the alterations in iron metabolism during the onset and advancement of CRC would help to further explain the role and mechanism of iron inside the body. Thus, we reviewed the alterations in numerous iron metabolism-related molecules and their roles in CRC, which may provide new clues between iron metabolism and CRC.

Dietary inclusion of nitrite-containing frankfurter exacerbates colorectal cancer pathology and alters metabolism in APCmin mice

Colorectal cancer (CRC) is the second most prevelant malignancy in Europe and diet is an important modifiable risk factor. Processed meat consumption, including meats with preservative salts such as sodium nitrite, have been implicated in CRC pathogenesis. This study investigated how the CRC pathology and metabolic status of adenomatous polyposis coli (APC) multiple intestinal neoplasia (min) mice was perturbed following 8 weeks of pork meat consumption. Dietary inclusions (15%) of either nitrite-free pork, nitrite-free sausage, or nitrite-containing sausage (frankfurter) were compared against a parallel control group (100% chow). Comprehensive studies investigated: gastrointestinal tract histology (tumours), aberrant crypt foci (ACF), mucin deplin foci (MDF), lipid peroxidation (urine and serum), faecal microbiota, and serum metabolomics (599 metabolites). After 8 weeks mice consuming the frankfurter diet had 53% more (P = 0.014) gastrointestinal tumours than control, although ACF and MDF did not differ. Urine and serum lipid peroxidation markers were 59% (P = 0.001) and 108% (P = 0.001) higher, respectively in the frankfurter group. Gut dysbiosis was evident in these mice with comparably fewer Bacteriodes and more Firmicutes. Fasting serum levels of trimethylamine N-oxide (TMAO) and numerous triglycerides were elevated. Various serum phosphotidylcholine species were decreased. These results demonstrate that nitrite-containing sausages may exaccerbate the development of CRC pathology in APC^Min mice to a greater extent than nitrite-free sausages, and this is associated with greater lipid peroxidation, wide-ranging metabolic alternation and gut dysbiosis.

Lipid Peroxidation Linking Diabetes and Cancer: The Importance of 4-Hydroxynonenal

Significance: It is commonly believed that diabetes mellitus may be associated with cancer. Hence, diabetic patients are at higher risk for hepatocellular carcinoma, pancreatic cancer, colorectal cancer, and breast cancer, but the mechanisms that may link these two severe diseases are not well understood. Recent Advances: A number of factors have been suggested to promote tumorigenesis in diabetic patients, including insulin resistance, hyperglycemia, dyslipidemia, inflammation, and elevated insulin-like growth factor-1 (IGF-1), which may also promote pro-oxidants, and thereby alter redox homeostasis. The consequent oxidative stress associated with lipid peroxidation appears to be a possible pathogenic link between cancer and diabetes. Critical Issues: Having summarized the above aspects of diabetes and cancer pathology, we propose that the major bioactive product of oxidative degradation of polyunsaturated fatty acids (PUFAs), the reactive aldehyde 4-hydroxynonenal (4-HNE), which is also considered a second messenger of free radicals, may be the key pathogenic factor linking diabetes and cancer. Future Directions: Because the bioactivities of 4-HNE are cell-type and concentration-dependent, are often associated with inflammation, and are involved in signaling processes that regulate antioxidant activities, proliferation, differentiation, and apoptosis, we believe that further research in this direction could reveal options for better control of diabetes and cancer. Controlling the production of 4-HNE to avoid its cytotoxicity to normal but not cancer cells while preventing its diabetogenic activities could be an important aspect of modern integrative biomedicine. Antioxid. Redox Signal. 37, 1222-1233.

4-Oxo-2-nonenal (4-ONE)-Induced Degradation of Bovine Skeletal Muscle Proteins

Lipids are an important component of meat, as they provide desirable sensory characteristics and nutritional benefits. However, lipids are susceptible to degradation through oxidation and produce toxic oxidative byproducts. 4-Oxo-2-nonenal (4-ONE) is an oxidative byproduct that is highly reactive and cytotoxic. In this study, we investigated the influence of 4-ONE-induced protein degradation on fresh and gastric digested bovine skeletal muscle proteins. The results indicated that 4-ONE naturally forms in fresh muscle proteins. We report here for the first time that 4-ONE causes severe degradation of bovine skeletal muscle proteins. An SDS-PAGE gel analysis showed evidence that the skeletal muscle proteins attenuated over the incubation time, as the density of the protein bands faded significantly after 120 h. Additionally, protein and band density analyses showed a significant decrease in protein abundance and band densities throughout the incubation time. This study revealed that the lipid oxidation byproduct, 4-oxo-2-nonenal (4-ONE) is responsible for causing skeletal muscle protein degradation. Future studies should assess the bioprotective role of antioxidants and other food ingredients for their potential to prevent the formation and/or detoxification of 4-ONE in meat.

Multi-DNA Adduct and Abasic Site Quantitation In Vivo by Nano-Liquid Chromatography/High-Resolution Orbitrap Tandem Mass Spectrometry: Methodology for Biomonitoring Colorectal DNA Damage

Epidemiological and mechanistic studies suggest that processed and red meat consumption and tobacco smoking are associated with colorectal cancer (CRC) risk. Several classes of carcinogens, including N-nitroso compounds (NOCs) in processed meats and heterocyclic aromatic amines (HAAs) and polycyclic aromatic hydrocarbons (PAHs) in grilled meats and tobacco smoke, undergo metabolism to reactive intermediates that may form mutation-inducing DNA adducts in the colorectum. Heme iron in red meat may contribute to oxidative DNA damage and endogenous NOC formation. However, the chemicals involved in colorectal DNA damage and the paradigms of CRC etiology remain unproven. There is a critical need to establish physicochemical methods for identifying and quantitating DNA damage induced by genotoxicants in the human colorectum. We established robust nano-liquid chromatography/high-resolution accurate mass Orbitrap tandem mass spectrometry (LC/HRAMS2) methods to measure DNA adducts of nine meat and tobacco-associated carcinogens and lipid peroxidation products in the liver, colon, and rectum of carcinogen-treated rats employing fresh-frozen and formalin-fixed paraffin-embedded (FFPE) tissues. Some NOCs form O6-carboxymethyl-2'-deoxyguanosine, O6-methyl-2'-deoxyguanosine, and unstable quaternary N-linked purine/pyrimidine adducts, which generate apurinic/apyrimidinic (AP) sites. AP sites were quantitated following derivatization with O-(pyridin-3-yl-methyl)hydroxylamine. DNA adduct quantitation was conducted with stable isotope-labeled internal standards, and method performance was validated for accuracy and reproducibility. Limits of quantitation ranged from 0.1 to 1.1 adducts per 108 bases using 3 μg of DNA. Adduct formation in animals ranged from ∼1 in 108 to ∼1 in 105 bases, occurring at comparable levels in fresh-frozen and FFPE specimens for most adducts. AP sites increased by 25- to 75-fold in the colorectum and liver, respectively. Endogenous lipid peroxide-derived 3-(2-deoxy-β-d-erythro-pentofuranosyl)pyrimido[1,2-α]purin-10(3H)-one (M1dG) and 6-oxo-M1dG adduct levels were not increased by carcinogen dosing but increased in FFPE tissues. Human biomonitoring studies can implement LC/HRAMS2 assays for DNA adducts and AP sites outlined in this work to advance our understanding of CRC etiology.

The Dark Side of Iron: The Relationship between Iron, Inflammation and Gut Microbiota in Selected Diseases Associated with Iron Deficiency Anaemia—A Narrative Review

Iron is an indispensable nutrient for life. A lack of it leads to iron deficiency anaemia (IDA), which currently affects about 1.2 billion people worldwide. The primary means of IDA treatment is oral or parenteral iron supplementation. This can be burdened with numerous side effects such as oxidative stress, systemic and local-intestinal inflammation, dysbiosis, carcinogenic processes and gastrointestinal adverse events. Therefore, this review aimed to provide insight into the physiological mechanisms of iron management and investigate the state of knowledge of the relationship between iron supplementation, inflammatory status and changes in gut microbiota milieu in diseases typically complicated with IDA and considered as having an inflammatory background such as in inflammatory bowel disease, colorectal cancer or obesity. Understanding the precise mechanisms critical to iron metabolism and the awareness of serious adverse effects associated with iron supplementation may lead to the provision of better IDA treatment. Well-planned research, specific to each patient category and disease, is needed to find measures and methods to optimise iron treatment and reduce adverse effects.

Maternal heme-enriched diet promotes a gut pro-oxidative status associated with microbiota alteration, gut leakiness and glucose intolerance in mice offspring

Maternal environment, including nutrition and microbiota, plays a critical role in determining offspring's risk of chronic diseases such as diabetes later in life. Heme iron requirement is amplified during pregnancy and lactation, while excessive dietary heme iron intake, compared to non-heme iron, has shown to trigger acute oxidative stress in the gut resulting from reactive aldehyde formation in conjunction with microbiota reshape. Given the immaturity of the antioxidant defense system in early life, we investigated the extent to which a maternal diet enriched with heme iron may have a lasting impact on gut homeostasis and glucose metabolism in 60-day-old C3H/HeN mice offspring.

As hypothesized, the form of iron added to the maternal diet differentially governed the offspring's microbiota establishment despite identical fecal iron status in the offspring. Importantly, despite female offspring was unaffected, oxidative stress markers were however higher in the gut of male offspring from heme enriched-fed mothers, and were accompanied by increases in fecal lipocalin-2, intestinal para-cellular permeability and TNF-α expression. In addition, male mice displayed blood glucose intolerance resulting from impaired insulin secretion following oral glucose challenge. Using an integrated approach including an aldehydomic analysis, this male-specific phenotype was further characterized and revealed close covariations between unidentified putative reactive aldehydes and bacterial communities belonging to Bacteroidales and Lachnospirales orders.

Our work highlights how the form of dietary iron in the maternal diet can dictate the oxidative status in gut offspring in a sex-dependent manner, and how a gut microbiota-driven oxidative challenge in early life can be associated with gut barrier defects and glucose metabolism disorders that may be predictive of diabetes development.

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Maternal heminic vs. non-heminic iron intake differentially and persistently imprints the offspring's fecal microbiota.

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Males from heme-fed dams exhibit increased gut lumen reactive aldehydes in absence of direct dietary exposure to heme iron.

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Some of the increased reactive aldehydes closely covariated with Orders belonging to Bacteroidales and Lachnospirales.

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Maternal exposure to dietary heme iron impairs gut barrier and glucose tolerance in male offspring.

Maternal oxidized soybean oil exposure in rats during lactation damages offspring kidneys via Nrf2/HO-1 and NF-κB signaling pathway

BACKGROUND

Cooking oil is an indispensable component of the human diet. However, oils usually undergo thermal oxidation. Oxidized soybean oil (OSO) has been shown to have detrimental effects on humans and has emerged as a root cause of many chronic diseases. The objective of this work was to evaluate the effects of puerpera exposure to OSO on kidney damage in the mother and offspring using lactating rats as an experimental model.

RESULTS

Pathological sections and ultrastructure showed that OSO exposure resulted in various levels of damage to lactating rats and their offspring. OSO induced oxidative stress in the kidneys of lactating rats, as evidenced by increased levels of hydrogen peroxide, interleukin (IL)-1β, and IL-8. OSO increased the activities of glutathione peroxidase and superoxide dismutase. OSO upregulated the expression of apoptosis-related genes, nuclear factor-erythroid 2-related factor 2 (Nrf2), and nuclear factor κB-related inflammatory factor genes. In the offspring of the OSO-exposed mothers, hydrogen peroxide, malondialdehyde, IL-6, and tumor necrosis factor-alpha contents were increased. Furthermore, OSO enhanced the levels of Nrf2, NAD(P)H quinone oxidoreductase 1, heme oxygenase 1, and p65 and decreased B-cell lymphoma 2.

CONCLUSION

These findings indicated that the kidneys of two generations of rats were compromised by oxidative damage when fed OSO during lactation. This study provides evidence for increasing the genes expression of the Nrf2/heme oxygenase 1 pathway to alleviate the kidney damage caused by OSO in the mother and offspring. © 2021 Society of Chemical Industry.

Pre-diagnosis meat intake and cooking method and ovarian cancer survival: results from the Ovarian Cancer Follow-Up Study (OOPS)

Objectives: The relationships between pre-diagnosis meat intake and ovarian cancer (OC) survival were limited and controversial. To date, no study has taken account of cooking methods. Thus, we aimed to firstly clarify these associations based on the Ovarian Cancer Follow-Up Study. Methods: This prospective cohort study, including 853 OC patients between 2015 and 2020, was conducted to examine the aforementioned associations. All women completed a food frequency questionnaire. Deaths were ascertained up to March 31, 2021 via medical records and active follow-up. We used the Cox proportional hazards model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results: During the median follow-up of 37.17 months, 130 women died. Pre-diagnosis fish and seafood intake was associated with better survival (HR_{T3 vs. T1} = 0.46, 95% CI = 0.26-0.82, p trend <0.05), whereas processed red meat (HR = 1.54, 95% CI = 1.04-2.26) and a high frequency of fried fish intake (HR = 1.49, 95% CI = 1.03-2.16) were associated with worse survival than consuming none. After considering the interaction of cooking methods, we found that compared with the lowest tertile of fish and seafood intake and almost no fried fish cooking, women with the highest tertile of intake and almost no fried fish cooking had better survival (HR = 0.35, 95% CI = 0.13-0.92). Additionally, compared with the lowest tertile of fish and seafood intake and almost no baked fish cooking, women with the lowest tertile of intake and consuming baked fish had worse survival (HR = 3.75, 95% CI = 1.53-9.15). Conclusions: Pre-diagnosis fish and seafood intake was associated with better OC survival, whereas processed red meat intake was associated with worse survival. Cooking methods, especially for fried or baked fish, may play interaction effects with fish intake on OC survival.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Epidemiology, Molecular Mechanisms, and Clinical Trials: an Update on Research on the Association Between Red Meat Consumption and Colorectal Cancer

PURPOSE OF THE REVIEW

Colorectal cancer is the second most common cause of cancer death in the world. The aim of this review is to provide an update on recent epidemiological studies, the molecular mechanisms involved, and ongoing clinical trials investigating the relationship between red meat consumption and colorectal cancer.

RECENT FINDINGS

Evidence in the literature proposes an association between red meat consumption and development of colorectal cancer, and there is some insight with regard to the mechanisms involved. Twenty studies of the IARC report (1990-2015) showed that red meat is positively associated with colorectal cancer whereas 14 studies either supported no positive association or no statistically significant association between red meat consumption and risk for CRC. More recent epidemiological studies conducted from 2016 and onwards provided further evidence that adherence to diets low in red and/or processed meat reduces the risk of colorectal cancer. Evidence from recent studies supports that quantity, doneness, and preparation of red meat play a role in colorectal carcinogenesis. Red meat's degradation products allow for the creation of a pro-inflammatory colonic microenvironment, and the gut microbiome plays a role in colorectal carcinogenesis. Heme, hydrogen sulfide, lipid peroxidation, nitroso compounds, and the bacterium Fusobacterium Nucleatum (as well as possibly other bacteria such as Akkermansia muciniphila, Eubacterium cylindroides, Eubacterium eligens 1 and 2, and Eubacterium rectale 1 and 2) also partake in the process of colorectal carcinogenesis. Several clinical trials are underway investigating the effects of different diets and red meat substitution products on colorectal cancer incidence as well as the underlying molecular mechanisms involved in the process.

Short-Term and Long-Term Carcinogenic Effects of Food Contaminants (4-Hydroxynonenal and Pesticides) on Colorectal Human Cells: Involvement of Genotoxic and Non-Genomic Mechanisms

Simple Summary

One’s environment, including diet, play a major role in the occurrence and the development of colorectal cancer (CRC). In this study, we are interested in two western diet associated food contaminants: 4-hydroxynonenal (HNE), a major lipid peroxidation product neoformed during digestion, and a mixture of pesticides to which we are commonly exposed to via fruit and vegetable consumption. The aim of this study was to analyse the impact of acute and long-term exposure to these contaminants, alone or in combination, on colorectal carcinogenesis. We used in vitro models of human colonic cells, either exhibiting or not different genetic susceptibilities to CRC. After acute exposure, we did not observe major alteration. However, long-term exposure to contaminants induce malignant transformation with different cellular mechanisms, depending on genetic susceptibility and contaminants alone or in mixtures.

Abstract

To investigate environmental impacts upon colorectal carcinogenesis (CRC) by diet, we assessed two western diet food contaminants: 4-hydroxynonenal (HNE), a major lipid peroxidation product neoformed during digestion, and a mixture of pesticides. We used human colonic cell lines ectopically eliciting varied genetic susceptibilities to CRC: the non-transformed human epithelial colonic cells (HCECs) and their five isogenic cell lines with the loss of APC (Adenomatous polyposis coli) and TP53 (Tumor protein 53) and/or ectopic expression of mutated KRAS (Kristen-ras). These cell lines have been exposed for either for a short time (2–24 h) or for a long period (3 weeks) to 1 µM HNE and/or 10 µM pesticides. After acute exposure, we did not observe any cytotoxicity or major DNA damage. However, long-term exposure to pesticides alone and in mixture with HNE induced clonogenic transformation in normal HCECs, as well as in cells representing later stages of carcinogenesis. It was associated with genotoxic and non-genomic mechanisms (cell growth, metabolic reprogramming, cell mobility and epithelial-mesenchymal transition) depending on genetic susceptibility. This study demonstrated a potential initiating and promoting effect of food contaminants on CRC after long-term exposure. It supports that these contaminants can accelerate carcinogenesis when mutations in oncogenes or tumor suppressor genes occur.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Towards Aldehydomics: Untargeted Trapping and Analysis of Reactive Diet-Related Carbonyl Compounds Formed in the Intestinal Lumen

Lipid peroxidation and subsequent formation of toxic aldehydes, such as 4-hydroxynonenal, is known to be involved in numerous pathophysiological processes, possibly including the development of colorectal cancer. This work aimed at the development of an untargeted approach using high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) for tracking aldehydes in both suspect screening and untargeted methods in fecal water, representing the aqueous environment of colon epithelial cells. This original approach is based on the introduction of a characteristic isotopic labeling by selective derivatization of the carbonyl function using a brominated reagent. Following a metabolomics workflow, the developed methodology was applied to the characterization of aldehyde compounds formed by lipid peroxidation in rats fed two different diets differentially prone to lipoperoxidation. Derivatized aldehydes were first selectively detected on the basis of their isotopic pattern, then annotated and finally identified by tandem mass spectrometry. This original approach allowed us to evidence the occurrence of expected aldehydes according to their fatty acid precursors in the diet, and to characterize other aldehydes differentiating the different diets.

Targeting iron metabolism in cancer therapy

Iron is a critical component of many cellular functions including DNA replication and repair, and it is essential for cell vitality. As an essential element, iron is critical for maintaining human health. However, excess iron can be highly toxic, resulting in oxidative DNA damage. Many studies have observed significant associations between iron and cancer, and the association appears to be more than just coincidental. The chief characteristic of cancers, hyper-proliferation, makes them even more dependent on iron than normal cells. Cancer therapeutics are becoming as diverse as the disease itself. Targeting iron metabolism in cancer cells is an emerging, formidable field of therapeutics. It is a strategy that is highly diverse with regard to specific targets and the various ways to reach them. This review will discuss the importance of iron metabolism in cancer and highlight the ways in which it is being explored as the medicine of tomorrow.

Preoperative iron status is a prognosis factor for stage II and III colorectal cancer

BACKGROUND

Iron deficiency anemia is represented in colorectal cancer (CRC) patients. Iron surplus load to increase non-transferrin bound iron (NTBI), and NTBI promotes cancer progression and influences microbiota. This study investigated whether preoperative serum iron status was associated with prognosis after CRC resection.

METHODS

We evaluated preoperative iron and transferrin saturation (TSAT), which was calculated as iron divided by total iron-binding capacity, in 327 patients who underwent surgery for Stage II-III CRC. Fe < 60 μg/dl and TSAT > 40% were defined as low and high iron, respectively. The associations between iron status and overall survival (OS) were evaluated in univariate and multivariate Cox proportional hazards analysis.

RESULTS

Of the 327 patients, 179 (54.7%), 124 (37.9%) and 24 (7.3%) had low, normal and high iron, respectively. In univariate analysis, low iron was associated with shorter OS (hazard ratio [HR] 2.821, 95% confidence interval [CI] 1.451-5.485, P = 0.002). High iron was also associated with shorter OS (HR 3.396, 95% CI 1.359-8.489, P = 0.009). In multivariate analysis, high age (P = 0.002), depth of invasion pT4 (P = 0.012), lymph-node metastasis presence (P = 0.035), low albumin (P = 0.011), low iron (HR 2.282, 95% CI 1.163-4.478, P = 0.016) and high iron (HR 3.757, 95% CI 1.486-9.494 P = 0.005) were independently associated with shorter OS. High iron was associated with the amount of intratumoral Fusobacterium nucleatum compared with normal iron.

CONCLUSION

Both low and high preoperative iron in Stage II-III CRC patients were associated with unfavorable OS in univariate and multivariate analyses.

Roles of Lipid Peroxidation-Derived Electrophiles in Pathogenesis of Colonic Inflammation and Colon Cancer

Redox stress is a common feature of gut disorders such as colonic inflammation (inflammatory bowel disease or IBD) and colorectal cancer (CRC). This leads to increased colonic formation of lipid-derived electrophiles (LDEs) such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), trans, trans-2,4-decadienal (tt-DDE), and epoxyketooctadecenoic acid (EKODE). Recent research by us and others support that treatment with LDEs increases the severity of colitis and exacerbates the development of colon tumorigenesis in vitro and in vivo, supporting a critical role of these compounds in the pathogenesis of IBD and CRC. In this review, we will discuss the effects and mechanisms of LDEs on development of IBD and CRC and lifestyle factors, which could potentially affect tissue levels of LDEs to regulate IBD and CRC development.

Chronic intestinal inflammation drives colorectal tumor formation triggered by dietary heme iron in vivo

The consumption of red meat is associated with an increased risk for colorectal cancer (CRC). Multiple lines of evidence suggest that heme iron as abundant constituent of red meat is responsible for its carcinogenic potential. However, the underlying mechanisms are not fully understood and particularly the role of intestinal inflammation has not been investigated. To address this important issue, we analyzed the impact of heme iron (0.25 µmol/g diet) on the intestinal microbiota, gut inflammation and colorectal tumor formation in mice. An iron-balanced diet with ferric citrate (0.25 µmol/g diet) was used as reference. 16S rRNA sequencing revealed that dietary heme reduced α-diversity and caused a persistent intestinal dysbiosis, with a continuous increase in gram-negative Proteobacteria. This was linked to chronic gut inflammation and hyperproliferation of the intestinal epithelium as attested by mini-endoscopy, histopathology and immunohistochemistry. Dietary heme triggered the infiltration of myeloid cells into colorectal mucosa with an increased level of COX-2 positive cells. Furthermore, flow cytometry-based phenotyping demonstrated an increased number of T cells and B cells in the lamina propria following heme intake, while γδ-T cells were reduced in the intraepithelial compartment. Dietary heme iron catalyzed formation of fecal N-nitroso compounds and was genotoxic in intestinal epithelial cells, yet suppressed intestinal apoptosis as evidenced by confocal microscopy and western blot analysis. Finally, a chemically induced CRC mouse model showed persistent intestinal dysbiosis, chronic gut inflammation and increased colorectal tumorigenesis following heme iron intake. Altogether, this study unveiled intestinal inflammation as important driver in heme iron-associated colorectal carcinogenesis.

Red and processed meat consumption and cancer outcomes: Umbrella review

The purpose of this umbrella review was to evaluate the quality of evidence, validity and biases of the associations between red and processed meat consumption and multiple cancer outcomes according to existing systematic reviews and meta-analyses. The umbrella review identified 72 meta-analyses with 20 unique outcomes for red meat and 19 unique outcomes for processed meat. Red meat consumption was associated with increased risk of overall cancer mortality, non-Hodgkin lymphoma (NHL), bladder, breast, colorectal, endometrial, esophageal, gastric, lung and nasopharyngeal cancer. Processed meat consumption might increase the risk of overall cancer mortality, NHL, bladder, breast, colorectal, esophageal, gastric, nasopharyngeal, oral cavity and oropharynx and prostate cancer. Dose-response analyses revealed that 100 g/d increment of red meat and 50 g/d increment of processed meat consumption were associated with 11%-51% and 8%-72% higher risk of multiple cancer outcomes, respectively, and seemed to be not correlated with any benefit.

The association between plant-based dietary patterns and risk of breast cancer: a case-control study

Limited data are available, linking the plant-based diets to breast cancer (BC). We examined the association of overall plant-based diet index (PDI), hypothesized healthful (hPDI) and unhealthful versions of a plant-based diet index (uPDI) with BC in Iranian women. This population-based case–control study included 350 cases with newly diagnosed BC and 700 age-matched apparently healthy controls. We collected dietary data using a validated, Willett-format semi-quantitative food frequency questionnaire. Using these data, we generated a PDI by dedicating positive scores to plant foods, and reverse scores to animal foods, hPDI by assigning positive scores to healthy plant foods and reverse scores to less healthy plant foods and animal foods, and finally uPDI in which positive scores were assigned to less healthy plant foods and reverse scores to healthy plant foods and animal foods. After controlling for potential confounders, individuals in the highest quartile of PDI had 67% lower odds of BC than those in the lowest quartile (OR 0.33; 95% CI 0.22–0.50). Individuals with the greatest adherence to hPDI were 36% less likely to have BC than those with the lowest adherence, in the fully adjusted model (OR 0.64; 95% CI 0.43–0.94). In terms of uPDI, women in the top quartile had a 2.23 times greater chance of BC than those in the bottom quartile (OR 2.23; 95% CI 1.48–3.36). Greater adherence to PDI and hPDI was inversely associated with the risk of BC, whereas uPDI was associated with an increased risk.

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.

Heme-Iron-Induced Production of 4-Hydroxynonenal in Intestinal Lumen May Have Extra-Intestinal Consequences through Protein-Adduct Formation

Some epidemiological studies show that heme iron consumption, in red meat, is associated to the development of several chronic diseases, including cancers and cardio-metabolic diseases. As heme iron intestinal absorption is finely regulated, we hypothesized that heme iron may act indirectly, through the peroxidation of dietary lipids, in food or in the intestinal lumen during digestion. This heme-iron-induced lipid peroxidation provokes the generation of toxic lipid oxidation products that could be absorbed, such as 4-hydroxynonenal (HNE). In a first experiment, heme iron given to rats by oral gavage together with the linoleic-acid-rich safflower oil induced the formation of HNE in the intestinal lumen. The HNE major urinary metabolite was elevated in the urine of the treated rats, indicating that this compound has been absorbed. In a second experiment, we showed that stable isotope-labeled HNE given orally to rats was able to reach non-intestinal tissues as a bioactive form and to make protein-adducts in heart, liver and skeletal muscle tissues. The presence of HNE-protein adducts in those tissues suggests a putative biological role of diet-originating HNE in extra-intestinal organs. This finding could have major consequences on the onset/development of chronic diseases associated with red meat over-consumption, and more largely to peroxidation-prone food consumption.

Iron: An Essential Element of Cancer Metabolism

Cancer cells undergo considerable metabolic changes to foster uncontrolled proliferation in a hostile environment characterized by nutrient deprivation, poor vascularization and immune infiltration. While metabolic reprogramming has been recognized as a hallmark of cancer, the role of micronutrients in shaping these adaptations remains scarcely investigated. In particular, the broad electron-transferring abilities of iron make it a versatile cofactor that is involved in a myriad of biochemical reactions vital to cellular homeostasis, including cell respiration and DNA replication. In cancer patients, systemic iron metabolism is commonly altered. Moreover, cancer cells deploy diverse mechanisms to increase iron bioavailability to fuel tumor growth. Although iron itself can readily participate in redox reactions enabling vital processes, its reactivity also gives rise to reactive oxygen species (ROS). Hence, cancer cells further rely on antioxidant mechanisms to withstand such stress. The present review provides an overview of the common alterations of iron metabolism occurring in cancer and the mechanisms through which iron promotes tumor growth.

Hemochromatosis risk genotype is not associated with colorectal cancer or age at its diagnosis

Homozygotes for the higher penetrance hemochromatosis risk allele, HFE c.845G>A (p.Cys282Tyr, or C282Y), have been reported to be at a 2- to 3-fold increased risk for colorectal cancer (CRC). These results have been reported for small sample size studies with no information about age at diagnosis for CRC. An association with age at diagnosis might alter CRC screening recommendations. We analyzed two large European ancestry datasets to assess the association of HFE genotype with CRC risk and age at CRC diagnosis. The first dataset included 59,733 CRC or advanced adenoma cases and 72,351 controls from a CRC epidemiological study consortium. The second dataset included 13,564 self-reported CRC cases and 2,880,218 controls from the personal genetics company, 23andMe. No association of the common hereditary hemochromatosis (HH) risk genotype and CRC was found in either dataset. The odds ratios (ORs) for the association of CRC and HFE C282Y homozygosity were 1.08 (95% confidence interval [CI], 0.91-1.29; p = 0.4) and 1.01 (95% CI, 0.78-1.31, p = 0.9) in the two cohorts, respectively. Age at CRC diagnosis also did not differ by HFE C282Y/C282Y genotype in either dataset. These results indicate no increased CRC risk in individuals with HH genotypes and suggest that persons with HH risk genotypes can follow population screening recommendations for CRC.

Heme oxygenase 1 protects human colonocytes against ROS formation, oxidative DNA damage and cytotoxicity induced by heme iron, but not inorganic iron

The consumption of red meat is probably carcinogenic to humans and is associated with an increased risk to develop colorectal cancer (CRC). Red meat contains high amounts of heme iron, which is thought to play a causal role in tumor formation. In this study, we investigated the genotoxic and cytotoxic effects of heme iron (i.e., hemin) versus inorganic iron in human colonic epithelial cells (HCEC), human CRC cell lines and murine intestinal organoids. Hemin catalyzed the formation of reactive oxygen species (ROS) and induced oxidative DNA damage as well as DNA strand breaks in both HCEC and CRC cells. In contrast, inorganic iron hardly affected ROS levels and only slightly increased DNA damage. Hemin, but not inorganic iron, caused cell death and reduced cell viability. This occurred preferentially in non-malignant HCEC, which was corroborated in intestinal organoids. Both hemin and inorganic iron were taken up into HCEC and CRC cells, however with differential kinetics and efficiency. Hemin caused stabilization and nuclear translocation of Nrf2, which induced heme oxygenase-1 (HO-1) and ferritin heavy chain (FtH). This was not observed after inorganic iron treatment. Chemical inhibition or genetic knockdown of HO-1 potentiated hemin-triggered ROS generation and oxidative DNA damage preferentially in HCEC. Furthermore, HO-1 abrogation strongly augmented the cytotoxic effects of hemin in HCEC, revealing its pivotal function in colonocytes and highlighting the toxicity of free intracellular heme iron. Taken together, this study demonstrated that hemin, but not inorganic iron, induces ROS and DNA damage, resulting in a preferential cytotoxicity in non-malignant intestinal epithelial cells. Importantly, HO-1 conferred protection against the detrimental effects of hemin.

Can Oral Tolerance Explain the Inconsistencies Associated with Total Dietary Diversity and Colon Cancer? A Mechanistic Systematic Review

Among the gastrointestinal tract cancers, the risk of colon cancer is strongly dependent on dietary factors. For the first time in the current review, all the original case-control studies, associated with the correlation between total dietary diversity score and colon cancer risk, were evaluated. In this regard, three databases, including PubMed/MEDLINE, Scopus, and Web of Sciences, were investigated to retrieve the related citations from 1990 until 2019. Among the included citations, three studies were finally included. In these included studies, the dietary diversity score was evaluated with 129-item and 800-item FFQs. Findings reveal that total dietary diversity can increase the risk of colon cancer in men, but not women; while, one study using 57-item FFQ reported the beneficial association of total dietary diversity with colon cancer among men. Significant demand for conducting more research to investigate the real mechanistic effects of dietary diversity on the risk of colon cancer development was demonstrated due to the inconsistent, questionable, and incomplete findings associated with the included studies.

Anxiety is a potential effect modifier of the association between red and processed meat consumption and cancer risk: findings from the NutriNet-Santé cohort

PURPOSE

Red and processed meats are recognized by the International Agency for Research on Cancer as probably carcinogenic and carcinogenic to humans, respectively. Heme iron has been proposed as a central factor responsible for this effect. Furthermore, anxiety affects the intestinal barrier function by increasing intestinal permeability. The objective of this work was to assess how anxiety modifies the association between red and processed meat consumption and cancer risk in the NutriNet-Santé prospective cohort (2009-2019).

METHODS

Using multi-adjusted Cox models in a sample of 101,269 subjects, we studied the associations between the consumption of red and processed meat, the amount of heme iron coming from these meats and overall, colorectal, prostate, and breast cancer risks, overall and separately among participants with and without anxiety.

RESULTS

An increase in red and processed meat consumption was associated with an increased risk of developing colorectal cancer in the total population (HR for an increase of 50 g/day = 1.18 (1.01-1.37), p = 0.03). After stratification on anxiety, the HR 50 g/day was 1.42 (1.03-1.94, p = 0.03) in anxious participants and 1.12 (0.94-1.33, p = 0.20) in other participants. Similar trends were observed for overall cancer risk. Analyses conducted with heme iron also provided similar results.

CONCLUSIONS

Our results strengthen the existing body of evidence supporting that red and processed meat consumption and heme iron intake are associated with an increased risk of overall and more specifically colorectal cancer, and suggest that anxiety modifies these associations, with an increased risk in anxious participants.

Commercial luncheon meat products and their in vitro gastrointestinal digests contain more protein carbonyl compounds but less lipid oxidation products compared to fresh pork

Because of the large diversity in processed meat products and the potential involvement of oxidation processes in the association between red and processed meat consumption and chronic diseases, the concentration of oxidation products after gastrointestinal digestion of commercial luncheon meat products was investigated. A broad spectrum of meat products (n = 24), displaying large variation in macro- and micronutrient composition and processing procedures, was digested in vitro by simulating digestion fluids of the human gastrointestinal tract. Lipid and protein oxidation was assessed in the meat products before digestion and in the corresponding digests by measurement of free malondialdehyde, 4-hydroxy-2-nonenal, hexanal and protein carbonyl compounds. Compared to an unprocessed cooked pork mince, that was included as a reference in the digestion experiment, levels of lipid oxidation products were low in the digests of most meat products. Only the digests of Parma ham had slightly higher or comparable levels as the reference pork. In contrast, protein carbonyl compounds were comparable or up to 6 times higher in the processed meat products compared to the reference pork. Particularly raw-cooked and precooked-cooked meat products and corresponding digests had higher protein carbonyl levels, but also lower protein contents and higher fat to protein ratios. In conclusion, most luncheon meat products and corresponding digests contained lower amounts of free lipid oxidation products, but more protein carbonyl compounds compared to the reference pork.

Synthesis and in vitro characterization of the genotoxic, mutagenic and cell-transforming potential of nitrosylated heme

Data from epidemiological studies suggest that consumption of red and processed meat is a factor contributing to colorectal carcinogenesis. Red meat contains high amounts of heme, which in turn can be converted to its nitrosylated form, NO-heme, when adding nitrite-containing curing salt to meat. NO-heme might contribute to colorectal cancer formation by causing gene mutations and could thereby be responsible for the association of (processed) red meat consumption with intestinal cancer. Up to now, neither in vitro nor in vivo studies characterizing the mutagenic and cell transforming potential of NO-heme have been published due to the fact that the pure compound is not readily available. Therefore, in the present study, an already existing synthesis protocol was modified to yield, for the first time, purified NO-heme. Thereafter, newly synthesized NO-heme was chemically characterized and used in various in vitro approaches at dietary concentrations to determine whether it can lead to DNA damage and malignant cell transformation. While NO-heme led to a significant dose-dependent increase in the number of DNA strand breaks in the comet assay and was mutagenic in the HPRT assay, this compound tested negative in the Ames test and failed to induce malignant cell transformation in the BALB/c 3T3 cell transformation assay. Interestingly, the non-nitrosylated heme control showed similar effects, but was additionally able to induce malignant transformation in BALB/c 3T3 murine fibroblasts. Taken together, these results suggest that it is the heme molecule rather than the NO moiety which is involved in driving red meat-associated carcinogenesis.

The Relation between Red Meat and Whole-Grain Intake and the Colonic Mucosal Barrier: A Cross-Sectional Study

The Colonic Mucosal Barrier (CMB) is the site of interaction between the human body and the colonic microbiota. The mucus is the outer part of the CMB and is considered as the front-line defense of the colon. It separates the host epithelial lining from the colonic content, and it has previously been linked to health and diseases. In this study, we assessed the relationship between red meat and whole-grain intake and (1) the thickness of the colonic mucus (2) the expression of the predominant mucin gene in the human colon (MUC2). Patients referred to colonoscopy at the University Hospital of Southern Denmark- Sonderjylland were enrolled between June 2017 and December 2018, and lifestyle data was collected in a cross-sectional study design. Colonic biopsies, blood, urine, and fecal samples were collected. The colonic mucus and bacteria were visualized by immunostaining and fluorescence in situ hybridization techniques. We found a thinner mucus was associated with high red meat intake. Similarly, the results suggested a thinner mucus was associated with high whole-grain intake, albeit to a lesser extent than red meat. This is the first study assessing the association between red meat and whole-grain intake and the colonic mucus in humans. This study is approved by the Danish Ethics Committee (S-20160124) and the Danish Data Protecting Agency (2008-58-035). A study protocol was registered at clinical trials.gov under NCT04235348.

Inulin and milk mineral fortification of a pork sausage exhibits distinct effects on the microbiome and biochemical activity in the gut of healthy rats

This study investigated inulin and calcium-rich milk mineral incorporation into a pork sausage in order to examine the effects on microbiome and biochemical activity in the gastrointestinal tract upon ingestion. Rats (n = 48) were fed one of four sausages; a pork sausage enriched with 1) inulin (6.0%) and milk mineral (3%), 2) inulin (6.0%), 3) milk mineral (3%) or 4) control sausages without enrichment. NMR-based metabolomics revealed that inulin-enrichment increased the fecal concentration of short-chain fatty acids (SCFAs). Milk mineral-enrichment also increased SCFA concentrations, although less pronounced. In addition, milk mineral reduced the concentration of nitroso compounds in feces and small intestinal content. Combined enrichment with both inulin and milk mineral showed no cumulative effect on SCFA formation and seemed to oppose the milk mineral-induced reduction of nitroso compound formation. 16S rRNA gene amplicon sequencing indicated that alterations of the gut microbiome contributed to the observed effects.