Influence of Iron on the Gut Microbiota in Colorectal Cancer

Current iron therapy in the light of regulation, intestinal microbiome, and toxicity: are we prescribing too much iron?

Iron deficiency is a widespread global health concern with varying prevalence rates across different regions. In developing countries, scarcity of food and chronic infections contribute to iron deficiency, while in industrialized nations, reduced food intake and dietary preferences affect iron status. Other causes that can lead to iron deficiency are conditions and diseases that result in reduced intestinal iron absorption and blood loss. In addition, iron absorption and its bioavailability are influenced by the composition of the diet. Individuals with increased iron needs, including infants, adolescents, and athletes, are particularly vulnerable to deficiency. Severe iron deficiency can lead to anemia with performance intolerance or shortness of breath. In addition, even without anemia, iron deficiency leads to mental and physical fatigue, which points to the fundamental biological importance of iron, especially in mitochondrial function and the respiratory chain. Standard oral iron supplementation often results in gastrointestinal side effects and poor compliance. Low-dose iron therapy seems to be a valid and reasonable therapeutic option due to reduced hepatic hepcidin formation, facilitating efficient iron resorption, replenishment of iron storage, and causing significantly fewer side effects. Elevated iron levels influence gut microbiota composition, favoring pathogenic bacteria and potentially disrupting metabolic and immune functions. Protective bacteria, such as bifidobacteria and lactobacilli, are particularly susceptible to increased iron levels. Dysbiosis resulting from iron supplementation may contribute to gastrointestinal disorders, inflammatory bowel disease, and metabolic disturbances. Furthermore, gut microbiota alterations have been linked to mental health issues. Future iron therapy should consider low-dose supplementation to mitigate adverse effects and the impact on the gut microbiome. A comprehensive understanding of the interplay between iron intake, gut microbiota, and human health is crucial for optimizing therapeutic approaches and minimizing potential risks associated with iron supplementation.

Therapeutic and antioxidant potential of bionanofactory Ochrobactrum sp.-mediated magnetite and zerovalent iron nanoparticles against acute experimental toxoplasmosis

The control of toxoplasmosis, a rampant one health disease, has been focussed on conventional antitoxoplasmic agents with their adverse outcomes, including serious side effects, treatment failure and emergence of drug resistant strains. Nanobiotechnology may provide a strong impetus for versatile alternative therapies against toxoplasmosis. Bionanofactory Ochrobactrum sp. strain CNE2 was recruited for the biosynthesis of functionalized magnetite iron nanoparticles (MNPs) and nanozerovalent iron (nZVI) under aerobic and anaerobic conditions and their therapeutic efficacy was evaluated against acute toxoplasmosis in murine model. The formation of self-functionalized spherical nanoparticles varied in size, identity and surface properties were substantiated. Mice were orally administered 20 mg/kg of each formulation on the initial day of infection and continued for seven consecutive days post infection (PI). Parasitological, ultrastructural, immunological, and biochemical studies were performed for assessment of therapeutic activity of biogenic iron nanoparticles (INPs). Parasitologically, MNPs showed the highest antitoxoplasmic efficacy in terms of 96.82% and 91.87% reduction in mean tachyzoite count in peritoneal fluid and liver impression smears, respectively. Lesser percentage reductions were recorded in nZVI-treated infected subgroup (75.44% and 69.04%). In addition, scanning electron microscopy (SEM) examination revealed remarkable reduction in size and extensive damage to the surface of MNPs-treated tachyzoites. MNPs-treated infected mice revealed a statistically significant increase in the serum levels of both interferon gamma (IFN-γ) to 346.2 ± 4.6 pg/ml and reduced glutathione (GSH) to 8.83 ± 0.30 mg/dl that subsequently exerted malondialdehyde (MDA) quenching action. MNPs showed a superior promising antitoxoplasmic activity with respect to both spiramycin (SPI) and nZVI. To best of our knowledge, this is the first study of a bio-safe oral iron nanotherapeutic agent fabricated via an eco-friendly approach that offers promising potential against acute experimental toxoplasmosis.

Dietary iron regulates intestinal goblet cell function and alleviates Salmonella typhimurium invasion in mice

Iron is an important micronutrient that plays a vital role in host defenses and bacterial pathogenicity. As iron treatments increase the risk of infection by stimulating the growth and virulence of bacterial pathogens, their roles in anti-infection immunity have frequently been underestimated. To estimate whether adequate dietary iron intake would help defend against pathogenic bacterial infection, mice were fed iron-deficient (2 mg kg-1 feed), iron-sufficient (35 mg kg-1 feed), or iron-enriched diet (350 mg kg-1 feed) for 12 weeks, followed by oral infection with Salmonella typhimurium. Our results revealed that dietary iron intake improved mucus layer function and decelerated the invasion of the pathogenic bacteria, Salmonella typhimurium. Positive correlations between serum iron and the number of goblet cells and mucin2 were found in response to total iron intake in mice. Unabsorbed iron in the intestinal tract affected the gut microbiota composition, and the abundance of Bacteroidales, family Muribaculaceae, was positively correlated with their mucin2 expression. However, the results from antibiotic-treated mice showed that the dietary iron-regulated mucin layer function was not microbial-dependent. Furthermore, in vitro studies revealed that ferric citrate directly induced mucin2 expression and promoted the proliferation of goblet cells in both ileal and colonic organoids. Thus, dietary iron intake improves serum iron levels, regulates goblet cell regeneration and mucin layer function, and plays a positive role in the prevention of pathogenic bacteria.

Preoperative Identification and Management of Anemia in the Colorectal Surgery Patient

Preoperative anemia is a common finding in patients undergoing colorectal surgery, particularly those with cancer. While often multifactorial, iron deficiency anemia remains the most common cause of anemia in this patient population. Although seemingly innocuous, preoperative anemia is associated with an increased risk of perioperative complications and need for allogenic blood transfusions, both of which may worsen cancer-specific survival. Preoperative correction of anemia and iron deficiency is thus necessary to diminish these risks. Current literature supports preoperative screening for anemia and iron deficiency in patients slated to undergo colorectal surgery for malignancy or for benign conditions with associated patient- or procedure-related risk factors. Accepted treatment regimens include iron supplementation-either oral or intravenous-as well as erythropoietin therapy. Autologous blood transfusion should not be utilized as a treatment for preoperative anemia when there is time to implement other corrective strategies. Additional study is still needed to better standardize preoperative screening and optimize treatment regimens.

Ferric carboxymaltose infusion versus oral iron supplementation for preoperative iron deficiency anaemia in patients with colorectal cancer (FIT): a multicentre, open-label, randomised, controlled trial

BACKGROUND

A third of patients with colorectal cancer who are eligible for surgery in high-income countries have concomitant anaemia associated with adverse outcomes. We aimed to compare the efficacy of preoperative intravenous and oral iron supplementation in patients with colorectal cancer and iron deficiency anaemia.

METHODS

In the FIT multicentre, open-label, randomised, controlled trial, adult patients (aged 18 years or older) with M0 stage colorectal cancer scheduled for elective curative resection and iron deficiency anaemia (defined as haemoglobin level of less than 7·5 mmol/L (12 g/dL) for women and less than 8 mmol/L (13 g/dL) for men, and a transferrin saturation of less than 20%) were randomly assigned to either 1-2 g of ferric carboxymaltose intravenously or three tablets of 200 mg of oral ferrous fumarate daily. The primary endpoint was the proportion of patients with normalised haemoglobin levels before surgery (≥12 g/dL for women and ≥13 g/dL for men). An intention-to-treat analysis was done for the primary analysis. Safety was analysed in all patients who received treatment. The trial was registered at ClincalTrials.gov, NCT02243735, and has completed recruitment.

FINDINGS

Between Oct 31, 2014, and Feb 23, 2021, 202 patients were included and assigned to intravenous (n=96) or oral (n=106) iron treatment. Treatment began a median of 14 days (IQR 11-22) before surgery for intravenous iron and 19 days (IQR 13-27) for oral iron. Normalisation of haemoglobin at day of admission was reached in 14 (17%) of 84 patients treated intravenously and 15 (16%) of 97 patients treated orally (relative risk [RR] 1·08 [95% CI 0·55-2·10]; p=0·83), but the proportion of patients with normalised haemoglobin significantly increased for the intravenous treatment group at later timepoints (49 [60%] of 82 vs 18 [21%] of 88 at 30 days; RR 2·92 [95% CI 1·87-4·58]; p<0·0001). The most prevalent treatment-related adverse event was discoloured faeces (grade 1) after oral iron treatment (14 [13%] of 105), and no treatment-related serious adverse events or deaths were observed in either group. No differences in other safety outcomes were seen, and the most common serious adverse events were anastomotic leakage (11 [5%] of 202), aspiration pneumonia (5 [2%] of 202), and intra-abdominal abscess (5 [2%] 202).

INTERPRETATION

Normalisation of haemoglobin before surgery was infrequent with both treatment regimens, but significantly improved at all other timepoints following intravenous iron treatment. Restoration of iron stores was feasible only with intravenous iron. In selected patients, surgery might be delayed to augment the effect of intravenous iron on haemoglobin normalisation.

FUNDING

Vifor Pharma.

Urbanisation and its Associated Factors Affecting Human Gut Microbiota: Where are we Heading to?

ContextThe continuous rise in urbanisation and its associated factors have been reflected in the structure of the human gut ecosystem.ObjectiveThe main focus of the review is to discuss and summarise the major risk factors associated with urbanisation that affects human gut microbiota thus affecting human health.MethodsMultiple medical literature databases, namely PubMed, Google, Google Scholar, and Web of Science were used to find relevant materials for urbanization and its major factors affecting human gut microbiota/microbiome. Both layman and Medical Subject Headings (MeSH) terms were used in the search. Due to the scarcity of the data, no limitation was set on the publication date. Relevant material in the English language which includes case reports, chapters of books, journal articles, online news reports and medical records was included in this review.ResultsBased on the data discussed in the review, it is quite clear that urbanisation and its associated factors have long-standing effects on the human gut microbiota that result in alterations of gut microbial diversity and composition. This is a matter of serious concern as chronic inflammatory diseases are on the rise in urbanised societies.ConclusionA better understanding of the factors associated with urbanisation will help us to identify and implement new biological and social approaches to prevent and treat diseases and improve health globally by deepening our understanding of these relationships and increasing studies across urbanisation gradients.HIGHLIGHTSHuman gut microbiota has been linked to almost every important function, including metabolism, intestinal homeostasis, immune system, biosynthesis of vitamins, brain processes, and its behaviour.However, dysbiosis i.e., alteration in the composition and diversity of gut microbiota is associated with the pathogenesis of many chronic conditions.In the 21st century, urbanisation represents a major demographic shift in developed and developing countries.During this period of urbanisation, humans have been exposed to many environmental exposures, all of which have led to the dysbiosis of human gut microbiota.The main focus of the review is to discuss and summarize the major risk factors associated with urbanisation and how it affects the diversity and composition of gut microbiota which ultimately affects human health.

Characterizing the microbiota of cleft lip and palate patients: a comprehensive review

Orofacial cleft disorders, including cleft lip and/or palate (CL/P), are one of the most frequently-occurring congenital disorders worldwide. The health issues of patients with CL/P encompass far more than just their anatomic anomaly, as patients with CL/P are prone to having a high incidence of infectious diseases. While it has been previously established that the oral microbiome of patients with CL/P differs from that of unaffected patients, the exact nature of this variance, including the relevant bacterial species, has not been fully elucidated; likewise, examination of anatomic locations besides the cleft site has been neglected. Here, we intended to provide a comprehensive review to highlight the significant microbiota differences between CL/P patients and healthy subjects in various anatomic locations, including the teeth inside and adjacent to the cleft, oral cavity, nasal cavity, pharynx, and ear, as well as bodily fluids, secretions, and excretions. A number of bacterial and fungal species that have been proven to be pathogenic were found to be prevalently and/or specifically detected in CL/P patients, which can benefit the development of CL/P-specific microbiota management strategies.

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.

Moxibustion attenuates liver metastasis of colorectal cancer by regulating gut microbial dysbiosis

The liver metastasis is the primary factor attributing to the poor prognosis of colorectal cancer (CRC). Moxibustion has been used clinically against multiple malignancies. In this study, we explored the safety, efficacy, and the potential functional mechanisms of moxibustion in modulating the liver metastasis of CRC by using GFP-HCT116 cells-derived CRC liver metastasis model in Balb/c nude mice. The tumor bearing mice were randomly divided into model control and treatment groups. Moxibustion was applied to the BL18 and ST36 acupoints. CRC liver metastasis was measured by fluorescence imaging. Furthermore, feces from all mice were collected, and 16S rRNA analysis was used to assess their microbial diversity, which was analyzed for its correlation with liver metastasis. Our results indicated that the liver metastasis rate was decreased significantly by moxibustion treatment. Moxibustion treatment also caused statistically significant changes in the gut microbe population, suggesting that moxibustion reshaped the imbalanced gut microbiota in the CRC liver metastasis mice. Therefore, our findings provide new insights into the host-microbe crosstalk during CRC liver metastasis and suggest moxibustion could inhibit CRC liver metastasis by remolding the structure of destructed gut microbiota community. Moxibustion may serve as a complementary and alternative therapy for the treatment of patients with CRC liver metastasis.

Pharmacological Mechanism of Pingxiao Formula against Colorectal Cancer

Colorectal cancer (CRC) is the most common cancer worldwide and develops due to a broad range of causative factors. Pingxiao (PX) formula and Xihuang (XH) formula are two commonly used drugs to treat CRC, especially as an alternative therapy for those patients who could not suffer surgery, chemotherapy, or immunotherapy, namely, elder or advanced CRC patients. However, the pertinent pharmacological mechanisms are still elusive. The investigation was designed to explain the pharmacological mechanisms of the PX formula. A murine model of CRC was established by injecting CT26.WT cells into the caecum of 4-week-old male Balb/c mice, following PX or XH treatment for 30 days. Network pharmacology analysis combined with weighted gene coexpression network analysis (WGCNA) predicted the pharmacological mechanisms and therapeutic value. High-throughput 16S rRNA sequencing determined the alterations in the gut microbiota communities. Western blotting, immunofluorescence, and flow cytometry examined the influence of PX on the tumor microenvironment (TME). Injection of CT26.WT-induced CRC in Balb/c mice was markedly attenuated by PX treatment. Compared with XH administration, PX exhibited a stronger antitumor effect, such as smaller tumor volume, lower interleukin 17 (IL-17), IL-6 and tumor necrosis factor-alpha (TNFα) serum levels, and higher interferon-gamma (IFN-γ) concentration. Network pharmacology analysis demonstrated that both PX and XH targets were enriched in cancers and inflammatory responses. RNA sequencing confirmed that PX treatment induced cancer cell apoptosis and inhibited inflammatory reactions within the tumor. Moreover, the PX formula considerably restored homeostasis of the gut microbiota, which was not observed in the XH group. PX targets, those associated with the survival probability of CRC patients, correlated with macrophage (Mφ) infiltration, which presented an independent risk factor for the CRC outcome. PX treatment promoted the transition of alternatively activated Mφs (M2 Mφs) to classically activated Mφs (M1 Mφs). Moreover, the peritoneal Mφs from the PX group inhibited the migration of CW26.WT cells, as evidenced by the wound healing experiment and transwell assay, which was consistent with the decreased expression of the vascular endothelial growth factor (VEGF). Furthermore, the coculturing system confirmed that PX-treated Mφs suppressed colorectal tumor-derived organoid proliferation. PX formula exhibits a potential antitumor effect against CRC by suppressing the colonization of pathological microorganisms, reshaping Mφ effector functions and hence inhibiting cancer cell proliferation.

Therapeutic approaches to colorectal cancer via strategies based on modulation of gut microbiota

Colorectal cancer (CRC) ranks third in terms of global incidence and second in terms of death toll among malignant tumors. Gut microbiota are involved in the formation, development, and responses to different treatments of CRC. Under normal physiological conditions, intestinal microorganisms protect the intestinal mucosa, resist pathogen invasion, and regulate the proliferation of intestinal mucosal cells via a barrier effect and inhibition of DNA damage. The composition of gut microbiota and the influences of diet, drugs, and gender on the composition of the intestinal flora are important factors in the early detection of CRC and prediction of the results of CRC treatment. Regulation of gut microbiota is one of the most promising new strategies for CRC treatment, and it is essential to clarify the effect of gut microbiota on CRC and its possible mechanisms to facilitate the prevention and treatment of CRC. This review discusses the role of gut microbiota in the pathogenesis of CRC, the potential of gut microbiota as biomarkers for CRC, and therapeutic approaches to CRC based on the regulation of gut microbiota. It might provide new ideas for the use of gut microbiota in the prevention and treatment of CRC in the near future and thus reduce the incidence of CRC.

Biological Evaluation, Molecular Docking Analyses, and ADME Profiling of Certain New Quinazolinones as Anti-colorectal Agents

Colorectal carcinogenesis is a complex process, which is linked to dysregulation of human secretory phospholipases A₂ (hsPLA₂-G-IIA, hsPLA₂-G-V, and hsPLA₂-G-X), proteases (cathepsin-B, collagenase, thrombin, elastase, and trypsin), carbohydrate hydrolyzing enzymes (α-amylase and α-glucosidase), and free radical generating enzyme (xanthine oxidoreductase (XOR)). Therefore, some new quinazolinones were synthesized and evaluated as inhibitors against this array of enzymes as well as cytotoxic agents on LoVo and HCT-116 cells of colorectal cancer. Compounds 3g, 10, 8, 3c, and 1c exhibited promising cytotoxic effects with IC₅₀ values ranging from 206.07 to 459.79 μM. Nine compounds showed promising enzymatic inhibitory effects, 3b, 3d, 3f, 5, 1a, and 12 (α-amylase), 8 (thrombin, elastase and trypsin), 10 (hsPLA₂-G-IIA and hsPLA₂-G-V), and 3f (α-glucosidase and XOR). Therefore, the most active inhibitors, were subjected to validated molecular docking studies to identify their affinities and binding modes. The expected physicochemical and pharmacokinetic features of the active candidates, 1a, 1c, 3b, 3c, 3d, 3f, 3g, 5, 8, 10, and 12 were predicted using bioavailability radar charts and boiled-egg graphical representations along with the Lipinski rule of five filter. Collectively, these studies showed the significance of derivatives 1c, 3b, 3c, 3d, 8, 10, and 12 as lead scaffolds for further optimization to develop enzymes inhibitors and anti-colorectal agents.

Iron Supplementation at the Crossroads of Nutrition and Gut Microbiota: The State of the Art

Gut microbiota has received significant attention owing to its decisive role in human health and disease. Diet exerts a significant influence on the variety and number of bacteria residing in the intestinal epithelium. On the other hand, as iron is a key micronutrient for blood formation and oxygen supply, its deficiency is highly prevalent worldwide. In fact, it is the most common cause of anemia and thus, iron supplementation is widespread. However, there is concern due to some potential risks linked to iron supplementation. Therefore, we have reviewed the available evidence of the effects that iron supplementation exerts on the gut microbiota as well as its potential benefits and risks. The compiled information suggests that iron supplementation is potentially harmful for gut microbiota. Therefore, it should be performed with caution, and by principle, recommended only to individuals with proven iron deficiency or iron-deficiency anemia to avoid potential adverse effects. In any case, large and long-term population studies are urgently needed to confirm or refute these results, mainly focused on vulnerable populations.

Deciphering the involvement of iron targets in colorectal cancer: a network biology approach

Several studies suggested the role of heme iron, but not non-heme iron in colorectal cancer. A network and system biology-based approach was used to understand the role of heme and non-heme iron on colorectal cancer etiology. Heme and non-heme iron targets were screened in addition to CRC targets. The protein-protein interaction map of both iron targets was prepared with CRC targets. Moreover, functional enrichment analysis was performed in order to understand their role in cancer etiology. The heme iron is predicted to modulate several cancer-associated pathways. Our results indicate several targets and pathways, including IL-4/IL-13, ACE, and HIF-1 signaling, that may have an important role in heme iron-mediated CRC and must be given consideration for understanding their role in colorectal cancer.

Association between iron supplementation and the presence of diarrhoea in Peruvian children aged 6-59 months: analysis of the database of the Demographic and Family Health Survey in Peru (DHS, Peru), years 2009-2019

INTRODUCTION

According to the WHO, anaemia is a severe public health problem when the prevalence is ≥ 40 %. In 2019, in Peru, 40·1 % of children (aged 6 to 35 months) are diagnosed as anaemic. This is a concern since, despite the efforts of the governments to reduce the prevalence, the problem has stagnated since 2011. The treatment applied to deal with anaemia is Fe supplementation. Although Fe is essential for cell function, an excess can produce adverse responses, such as gut inflammation affecting microbiota and resulting in diarrhoeic episodes.

OBJECTIVE

To determine the association between diarrhoea and Fe supplementation in children with and without anaemia, controlling for different socio-demographic variables.

DESIGN

We conducted via logistic regression to obtain diarrhoea prevalence ratios (PR), adjusted by age, sex, geographic region, water and sanitation service, and rurality. The survey asked for recent episodes of diarrhoea during the last 7 d; similarly, after the consumption of Fe supplements during the last 12 months before the survey.

SETTING

Peru.

PARTICIPANTS

The Demographic and Family Health Survey (DHS) is conducted annually at home among 14 202 children on average (2009-2019).

RESULTS

Fe supplementation in the last 7 d (PR = 1·09) or the last 12 months (PR = 1·19) (P < 0·0001) was associated with an increased risk of diarrhoea. The same association was observed between Fe supplementation and the presence of anaemia.

CONCLUSIONS

Fe supplementation is associated with diarrhoea and overuse in children should be avoided.

Differences in the On- and Off-Tumor Microbiota between Right- and Left-Sided Colorectal Cancer

This study aims to determine differences in the on- and off-tumor microbiota between patients with right- and left-sided colorectal cancer. Microbiome profiling of tumor and tumor-adjacent biopsies from patients with right-sided (n = 17) and left-sided (n = 7) colorectal adenocarcinoma was performed using 16S ribosomal RNA sequencing. Off-tumor alpha and beta diversity were significantly different between right- and left-sided colorectal cancer patients. However, no differences in on-tumor diversity were observed between tumor locations. Comparing the off-tumor microbiota showed the right colon to be enriched with species of the Lachnoclostridium, Selenomonas, and Ruminococcus genera. Whereas the left colon is enriched with Epsilonbacteraeota phylum, Campylobacteria class, and Pasteurellales and Campylobacterales orders, in contrast, the on-tumor microbiota showed relatively fewer differences in bacterial taxonomy between tumor sites, with left tumors being enriched with Methylophilaceae and Vadin BE97 families and Alloprevotella, Intestinibacter, Romboutsia, and Ruminococcus 2 genera. Patients with left-sided colorectal cancer had large taxonomic differences between their paired on- and off-tumor microbiota, while patients with right-sided colorectal cancer showed relatively fewer taxonomic differences. Collectively, this suggests that the right and left colon show distinctive bacterial populations; however, the presence of a colonic tumor leads to a more consistent microbiota between locations.

Iron Reshapes the Gut Microbiome and Host Metabolism

Compelling studies have established that the gut microbiome is a modifier of metabolic health. Changes in the composition of the gut microbiome are influenced by genetics and the environment, including diet. Iron is a potential node of crosstalk between the host-microbe relationship and metabolic disease. Although iron is well characterized as a frequent traveling companion of metabolic disease, the role of iron is underappreciated because the mechanisms of iron's influence on host metabolism are poorly characterized. Both iron deficiency and excessive amounts leading to iron overload can have detrimental effects on cardiometabolic health. Optimal iron homeostasis is critical for regulation of host immunity and metabolism in addition to regulation of commensal and pathogenic enteric bacteria. In this article we review evidence to support the notion that altering composition of the gut microbiome may be an important route via which iron impacts cardiometabolic health. We discuss reshaping of the microbiome by iron, the physiological significance and the potential for therapeutic interventions.

Oral and Intravenous Iron Therapy Differentially Alter the On- and Off-Tumor Microbiota in Anemic Colorectal Cancer Patients

Iron deficiency anemia is a common complication of colorectal cancer and may require iron therapy. Oral iron can increase the iron available to gut bacteria and may alter the colonic microbiota. We performed an intervention study to compare oral and intravenous iron therapy on the colonic tumor-associated (on-tumor) and paired non-tumor-associated adjacent (off-tumor) microbiota. Anemic patients with colorectal adenocarcinoma received either oral ferrous sulphate (n = 16) or intravenous ferric carboxymaltose (n = 24). On- and off-tumor biopsies were obtained post-surgery and microbial profiling was performed using 16S ribosomal RNA analysis. Off-tumor α- and β-diversity were significantly different between iron treatment groups. No differences in on-tumor diversity were observed. Off-tumor microbiota of oral iron-treated patients showed higher abundances of the orders Clostridiales, Cytophagales, and Anaeroplasmatales compared to intravenous iron-treated patients. The on-tumor microbiota was enriched with the orders Lactobacillales and Alteromonadales in the oral and intravenous iron groups, respectively. The on- and off-tumor microbiota associated with intravenous iron-treated patients infers increased abundances of enzymes involved in iron sequestration and anti-inflammatory/oncogenic metabolite production, compared to oral iron-treated patients. Collectively, this suggests that intravenous iron may be a more appropriate therapy to limit adverse microbial outcomes compared to oral iron.

Flipside of the Coin: Iron Deficiency and Colorectal Cancer

Iron deficiency, with or without anemia, is the most frequent hematological manifestation in individuals with cancer, and is especially common in patients with colorectal cancer. Iron is a vital micronutrient that plays an essential role in many biological functions, in the context of which it has been found to be intimately linked to cancer biology. To date, however, whereas a large number of studies have comprehensively investigated and reviewed the effects of excess iron on cancer initiation and progression, potential interrelations of iron deficiency with cancer have been largely neglected and are not well-defined. Emerging evidence indicates that reduced iron intake and low systemic iron levels are associated with the pathogenesis of colorectal cancer, suggesting that optimal iron intake must be carefully balanced to avoid both iron deficiency and iron excess. Since iron is vital in the maintenance of immunological functions, insufficient iron availability may enhance oncogenicity by impairing immunosurveillance for neoplastic changes and potentially altering the tumor immune microenvironment. Data from clinical studies support these concepts, showing that iron deficiency is associated with inferior outcomes and reduced response to therapy in patients with colorectal cancer. Here, we elucidate cancer-related effects of iron deficiency, examine preclinical and clinical evidence of its role in tumorigenesis, cancer progression and treatment response. and highlight the importance of adequate iron supplementation to limit these outcomes.

The Effects of Iron Supplementation and Fortification on the Gut Microbiota: A Review

Iron supplementation and fortification are used to treat iron deficiency, which is often associated with gastrointestinal conditions, such as inflammatory bowel disease and colorectal cancer. Within the gut, commensal bacteria contribute to maintaining systemic iron homeostasis. Disturbances that lead to excess iron promote the replication and virulence of enteric pathogens. Consequently, research has been interested in better understanding the effects of iron supplementation and fortification on gut bacterial composition and overall gut health. While animal and human trials have shown seemingly conflicting results, these studies emphasize how numerous factors influence gut microbial composition. Understanding how different iron formulations and doses impact specific bacteria will improve the outcomes of iron supplementation and fortification in humans. Furthermore, discerning the nuances of iron supplementation and fortification will benefit subpopulations that currently do not respond well to treatment.