High Dietary Iron Research Articles

Effects of iron overload in human joint tissue explant cultures and animal models.

Osteoarthritis (OA) is a prevalent degenerative joint disease affecting over 530 million individuals worldwide. Recent studies suggest a potential link between iron overload, a condition characterised by the excessive accumulation of iron in the body, and the onset of OA. Iron is essential for various biological processes, and any disruption in its homeostasis can trigger significant health effects, including OA. This study aimed to elucidate the effects of excess iron on joint tissue and the underlying mechanisms associated with excess iron and OA development. Human articular cartilage (n = 6) and synovium (n = 4) were collected from patients who underwent total knee arthroplasty. Cartilage and synovium explants were incubated with a gradually increasing concentration of ferric ammonium citrate for 3days respectively. The effects of iron homeostasis in tissue explants were analysed using a Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). To further study the effects of iron excess on OA initiation and development, male 3-week-old Hfe-/- and 5-week-old Tfr2-/- mice, animal models of hereditary haemochromatosis were established. Littermate wild-type mice were fed a high-iron diet to induce dietary overload. All animals were sacrificed at 8weeks of age, and knee joints were harvested for histological analysis. The LA-ICP-MS analysis unveiled changes in the elemental composition related to iron metabolism, which included alterations in FTH1, FPN1, and HAMP within iron(III)-treated cartilage explants. While chondrocyte viability remained stable under different iron concentrations, ex vivo treatment with a high concentration of Fe3+ increased the catabolic gene expression of MMP13. Similar alterations were observed in the synovium, with added increases in GAG content and inflammation markers. In vivo studies further supported the role of iron overload in OA development as evidenced by spontaneous OA symptoms, proteoglycan loss, increased Mankin scores, synovial thickening, and enhanced immunohistochemical expression of MMP13, ADAMTS5, and P21 in Hfe-/-, Tfr2-/-, and diet-induced iron overload mouse models. Our findings elucidate the specific pathways through which excess iron accelerates OA progression and highlights potential targets for therapeutic intervention aimed at modulating iron levels to mitigate OA symptoms. KEY MESSAGES: Iron overload alters joint iron metabolism, increasing OA markers in cartilage and synovium. High iron levels in mice accelerate OA, highlighting genetic and dietary impacts. Excess iron prompts chondrocyte iron storage response, signalling potential OA pathways. Iron dysregulation linked to increased cartilage degradation and synovial inflammation. Our findings support targeted therapies for OA based on iron modulation strategies.

The effects of iron deficient and high iron diets on SARS-CoV-2 lung infection and disease.

The severity of Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is often dictated by a range of comorbidities. A considerable literature suggests iron deficiency and iron overload may contribute to increased infection, inflammation and disease severity, although direct causal relationships have been difficult to establish. Here we generate iron deficient and iron loaded C57BL/6 J mice by feeding standard low and high iron diets, with mice on a normal iron diet representing controls. All mice were infected with a primary SARS-CoV-2 omicron XBB isolate and lung inflammatory responses were analyzed by histology, immunohistochemistry and RNA-Seq. Compared with controls, iron deficient mice showed no significant changes in lung viral loads or histopathology, whereas, iron loaded mice showed slightly, but significantly, reduced lung viral loads and histopathology. Transcriptional changes were modest, but illustrated widespread dysregulation of inflammation signatures for both iron deficient vs. controls, and iron loaded vs. controls. Some of these changes could be associated with detrimental outcomes, whereas others would be viewed as beneficial. Diet-associated iron deficiency or overload thus induced modest modulations of inflammatory signatures, but no significant histopathologically detectable disease exacerbations.

Effect of Different Dietary Iron Contents on Liver Transcriptome Characteristics in Wujin Pigs.

Iron is an important trace element that affects the growth and development of animals and regulates oxygen transport, hematopoiesis, and hypoxia adaptations. Wujin pig has unique hypoxic adaptability and iron homeostasis; however, the specific regulatory mechanisms have rarely been reported. This study randomly divided 18 healthy Wujin piglets into three groups: the control group, supplemented with 100 mg/kg iron (as iron glycinate); the low-iron group, no iron supplementation; and the high-iron group, supplemented with 200 mg/kg iron (as iron glycinate). The pre-feeding period was 5 days, and the formal period was 30 days. Serum was collected from empty stomachs before slaughter and at slaughter to detect changes in the serum iron metabolism parameters. Gene expression in the liver was analyzed via transcriptome analysis to determine the effects of low- and high-iron diets on transcriptome levels. Correlation analysis was performed for apparent serum parameters, and transcriptome sequencing was performed using weighted gene co-expression network analysis to reveal the key pathways underlying hypoxia regulation and iron metabolism. The main results are as follows. (1) Except for the hypoxia-inducible factor 1 (HIF-1) content (between the low- and high-iron groups), significant differences were not observed among the serum iron metabolic parameters. The serum HIF-1 content of the low-iron group was significantly higher than that of the high-iron group (p < 0.05). (2) Sequencing analysis of the liver transcriptome revealed 155 differentially expressed genes (DEGs) between the low-iron and control groups, 229 DEGs between the high-iron and control groups, and 279 DEGs between the low- and high-iron groups. Bioinformatics analysis showed that the HIF-1 and transforming growth factor-beta (TGF-β) signaling pathways were the key pathways for hypoxia regulation and iron metabolism. Four genes were selected for qPCR validation, and the results were consistent with the transcriptome sequencing data. In summary, the serum iron metabolism parameter results showed that under the influence of low- and high-iron diets, Wujin piglets maintain a steady state of physiological and biochemical indices via complex metabolic regulation of the body, which reflects their stress resistance and adaptability. The transcriptome results revealed the effects of low-iron and high-iron diets on the gene expression level in the liver and showed that the HIF-1 and TGF-β signaling pathways were key for regulating hypoxia adaptability and iron metabolism homeostasis under low-iron and high-iron diets. Moreover, HIF-1α and HEPC were the key genes. The findings provide a theoretical foundation for exploring the regulatory pathways and characteristics of iron metabolism in Wujin pigs.

Effect of High Dietary Iron on Fat Deposition and Gut Microbiota in Chickens.

To meet the demand of consumers for chicken products, poultry breeders have made improvements to chickens. However, this has led to a new problem in the modern poultry industry, namely excessive fat deposition. This study aims to understand the effects of dietary iron supplementation on fat deposition and gut microbiota in chickens. In this study, we investigated the effects of iron on the growth performance, fat deposition, and gut microbiota of silky fowl black-bone chickens. A total of 75 7-week-old silky fowl black-bone chickens were randomly divided into three groups (five replicates per group, five chickens per replicate) and fed them for 28 days using a growing diet (control group), a growing diet + 10% tallow (high-fat diet group, HFD group), and a growing diet + 10% tallow + 500 mg/kg iron (HFDFe500 group), respectively. We detected the effects of iron on the growth performance, fat deposition, and gut microbiota of silky fowl black-bone chickens using the growth performance index test, oil red O staining, and HE staining, and found that the high-fat diet significantly increased liver and serum fat deposition and liver injury, while the addition of iron to the diet could reduce the fat deposition caused by the high-fat diet and alleviate liver injury. In addition, 16S rDNA sequencing was used to compare the relative abundance of gut microbiota in the cecal contents in different feeding groups. The results showed that the high-fat diet could induce gut microbiota imbalance in chickens, while the high-iron diet reversed the gut microbiota imbalance. PICRUSt functional prediction analysis showed that dietary iron supplementation affected amino acid metabolism, energy metabolism, cofactors, and vitamin metabolism pathways. In addition, correlation analysis showed that TG was significantly associated with Firmicutes and Actinobacteriota (p < 0.05). Overall, these results revealed high dietary iron (500 mg/kg) could reduce fat deposition and affect the gut microbiota of silky fowl black-bone chickens, suggesting that iron may regulate fat deposition by influencing the gut microbiota of chickens and provides a potential avenue that prevents excessive fat deposition in chickens by adding iron to the diet.

Iron Regulates Cellular Proliferation by Enhancing the Expression of Glucose Transporter GLUT3 in the Liver.

Iron is often accumulated in the liver during pathological conditions such as cirrhosis and cancer. Elevated expression of glucose transporters GLUT1 and GLUT3 is associated with reduced overall survival in patients with hepatocellular carcinoma. However, it is not known whether iron can regulate glucose transporters and contribute to tumor proliferation. In the present study, we found that treatment of human liver cell line HepG2 with ferric ammonium citrate (FAC) resulted in a significant upregulation of GLUT3 mRNA and protein in a dose-dependent manner. Similarly, iron accumulation in mice fed with high dietary iron as well as in mice injected intraperitoneally with iron dextran enhanced the GLUT3 expression drastically in the liver. We demonstrated that iron-induced hepatic GLUT3 upregulation is mediated by the LKB1/AMPK/CREB1 pathway, and this activation was reversed when treated with iron chelator deferiprone. In addition, inhibition of GLUT3 using siRNA prevented iron-mediated increase in the expression of cell cycle markers and cellular hyperproliferation. Furthermore, exogenous sodium beta-hydroxybutyrate treatment prevented iron-mediated hepatic GLUT3 activation both in vitro and in vivo. Together, these results underscore the importance of iron, AMPK, CREB1 and GLUT3 pathways in cell proliferation and highlight the therapeutic potential of sodium beta-hydroxybutyrate in hepatocellular carcinoma with high GLUT3 expression.

Foxo1 is an iron-responsive transcriptional factor regulating systemic iron homeostasis

AbstractThe liver plays a crucial role in maintaining systemic iron homeostasis by secreting hepcidin, which is essential for coordinating iron levels in the body. Imbalances in iron homeostasis are associated with various clinical disorders related to iron deficiency or iron overload. Despite the clinical significance, the mechanisms underlying how hepatocytes sense extracellular iron levels to regulate hepcidin synthesis and iron storage are not fully understood. In this study, we identified Foxo1, a well-known regulator of macronutrient metabolism, which translocates to the nucleus of hepatocytes in response to high-iron feeding, holo-transferrin, and bone morphogenetic protein 6 (BMP6) treatment. Furthermore, Foxo1 plays a crucial role in mediating hepcidin induction in response to both iron and BMP signals by directly interacting with evolutionally conserved Foxo binding sites within the hepcidin promoter region. These binding sites were found to colocalize with Smad-binding sites. To investigate the physiological relevance of Foxo1 in iron metabolism, we generated mice with hepatocyte-specific deletion of Foxo1. These mice exhibited reduced hepatic hepcidin expression and serum hepcidin levels, accompanied by elevated serum iron and liver nonheme iron concentrations. Moreover, high-iron diet further exacerbated these abnormalities in iron metabolism in mice lacking hepatic Foxo1. Conversely, hepatocyte-specific Foxo1 overexpression increased hepatic hepcidin expression and serum hepcidin levels, thereby ameliorating iron overload in a murine model of hereditary hemochromatosis (Hfe−/− mice). In summary, our study identifies Foxo1 as a critical regulator of hepcidin and systemic iron homeostasis. Targeting Foxo1 may offer therapeutic opportunities for managing conditions associated with aberrant iron metabolism.

A novel circPIK3C2A/miR‐31‐5p/TFRC axis drives ferroptosis and accelerates myocardial injury

Iron overload is common in cardiovascular disease, it is also the factor that drives ferroptosis. Noncoding RNAs play an important role in heart disease; however, their regulatory role in iron overload-mediated ferroptosis remains much unknown. In our study, the iron overload model in mice was constructed through a high-iron diet, and ammonium iron citrate treatment was used to mimic iron overload in vitro. We found iron overload induced ferroptosis incardiomyocytes, which was dependent on the high expression of transferrin receptor (TFRC). MiR-31-5p was downregulated during iron overload; it inhibitedcardiomyocyte ferroptosis by targeting TFRC. CircPIK3C2A, a highly expressed circRNA in the heart, was upregulated when iron was overloaded. CircPIK3C2A enhanced the expression of TFRC by sponging miR-31-5p and promoted ferroptosis during iron overload. Our results reveal a novel mechanistic insight into noncoding RNA-based ferroptosis and identify the circPIK3C2A/miR-31-5p/TFRC axis as a promising therapeutic target for myocardial damage.

Plasma and tissue transferrin and ferritin, and gene expression of ferritin, transferrin, and transferrin receptors I and II in channel catfish Ictalurus punctatus fed diets with different concentrations of inorganic or organic iron.

Ferritin, transferrin, and transferrin receptors I and II play a vital role in iron metabolism, health, and indication of iron deficiency anaemia in fish. To evaluate the use of high-iron diets to prevent or reverse channel catfish (Ictalurus punctatus) anaemia of unknown causes, we investigated the expression of these iron-regulatory genes and proteins in channel catfish fed plant-based diets. Catfish fingerlings were fed five diets supplemented with 0 (basal), 125, and 250 mg/kg of either inorganic iron or organic iron for 2 weeks. Ferritin, transferrin, and transferrin receptor I and II mRNA and protein expression levels in fish tissues (liver, intestine, trunk kidney, and head kidney) and plasma were determined. Transferrin (iron transporter) and TfR (I and II) genes were generally highly expressed in fish fed the basal diet compared to those fed the iron-supplemented diets. In contrast, ferritin (iron storage) genes were more expressed in the trunk kidney of fish fed the iron-supplemented diets than in those fed the basal diet. Our results demonstrate that supplementing channel catfish plant-based diets with iron from either organic or inorganic iron sources affected the expression of the iron-regulatory genes and increased body iron status in the fish.

Effects of dietary iron deficiency or overload on bone: Dietary details matter

PurposeBone is susceptible to fluctuations in iron homeostasis, as both iron deficiency and overload are linked to poor bone strength in humans. In mice, however, inconsistent results have been reported, likely due to different diet setups or genetic backgrounds. Here, we assessed the effect of different high and low iron diets on bone in six inbred mouse strains (C57BL/6J, A/J, BALB/cJ, AKR/J, C3H/HeJ, and DBA/2J). MethodsMice received a high (20,000 ppm) or low-iron diet (∼10 ppm) after weaning for 6–8 weeks. For C57BL/6J males, we used two dietary setups with similar amounts of iron, yet different nutritional compositions that were either richer (“TUD study”) or poorer (“UCLA study”) in minerals and vitamins. After sacrifice, liver, blood and bone parameters as well as bone turnover markers in the serum were analyzed. ResultsAlmost all mice on the UCLA study high iron diet had a significant decrease of cortical and trabecular bone mass accompanied by high bone resorption. Iron deficiency did not change bone microarchitecture or turnover in C57BL/6J, A/J, and DBA/2J mice, but increased trabecular bone mass in BALB/cJ, C3H/HeJ and AKR/J mice. In contrast to the UCLA study, male C57BL/6J mice in the TUD study did not display any changes in trabecular bone mass or turnover on high or low iron diet. However, cortical bone parameters were also decreased in TUD mice on the high iron diet. ConclusionThus, these data show that cortical bone is more susceptible to iron overload than trabecular bone and highlight the importance of a nutrient-rich diet to potentially mitigate the negative effects of iron overload on bone.

Difference in the Mechanism of Iron Overload-Enhanced Acute Hepatotoxicity Induced by Thioacetamide and Carbon Tetrachloride in Rats.

Iron overload has been recognized as a risk factor for liver disease; however, little is known about its pathological role in the modification of liver injury. The purpose of this study is to investigate the influence of iron overload on liver injury induced by two hepatotoxicants with different pathogenesis in rats. Rats were fed a control (Cont), 0.8% high-iron (0.8% Fe), or 1% high-iron diet (1% Fe) for 4 weeks and were then administered with saline, thioacetamide (TAA), or carbon tetrachloride (CCl4). Hepatic and systemic iron overload were seen in the 0.8% and 1% Fe groups. Twenty-four hours after administration, hepatocellular necrosis induced by TAA and hepatocellular necrosis, degeneration, and vacuolation induced by CCl4, as well as serum transaminase values, were exacerbated in the 0.8% and 1% Fe groups compared to the Cont group. On the other hand, microvesicular vacuolation induced by CCl4 was decreased in 0.8% and 1% Fe groups. Hepatocellular DNA damage was increased by iron overload in both models, whereas a synergistic effect of oxidative stress by excess iron and hepatotoxicant was only present in the CCl4 model. The data showed that dietary iron overload exacerbates TAA- and CCl4-induced acute liver injury with different mechanisms.

Iron Fortification and Inulin Supplementation in Early Infancy: Evaluating the Impact on Iron Metabolism and Trace Mineral Status in a Piglet Model

BackgroundInfant formula in the United States contains abundant iron, raising health concerns about excess iron intake in early infancy. ObjectivesUsing a piglet model, we explored the impact of high iron fortification and prebiotic or synbiotic supplementation on iron homeostasis and trace mineral bioavailability. MethodsTwenty-four piglets were stratified and randomly assigned to treatments on postnatal day 2. Piglets were individually housed and received an iron-adequate milk diet (AI), a high-iron milk diet (HI), HI supplemented with 5% inulin (HI with a prebiotic [HIP]), or HIP with an oral gavage of Ligilactobacillus agilis YZ050, an inulin-fermenting strain, every third day (HI with synbiotic [HIS]). Milk was provided in 14 meals daily, mimicking formula feeding in infants. Fecal consistency score and body weight were recorded daily or every other day. Blood and feces were sampled weekly, and tissues collected on postnatal day 29. Data were analyzed using mixed model analysis of variance with repeated measures whenever necessary. ResultsDiet did not affect growth. HI increased hemoglobin, hematocrit, and serum iron compared to AI. Despite marginal adequacy, AI upregulated iron transporter genes and maintained satisfactory iron status in most pigs. HI upregulated hepcidin gene expression in liver, caused pronounced tissue iron deposition, and markedly increased colonic and fecal iron. Inulin supplementation, regardless of L. agilis YZ050, not only attenuated hepatic iron overload but also decreased colonic and fecal iron without altering pH or the expression of iron regulatory genes. HI lowered zinc (Zn) and copper (Cu) in the duodenum and liver compared to AI, whereas HIP and HIS further decreased Zn and Cu in the liver and diminished colonic and fecal trace minerals. ConclusionsEarly-infancy excessive iron fortification causes iron overload and compromises Zn and Cu absorption. Inulin decreases trace mineral absorption likely by enhancing gut peristalsis and stool frequency.

Dietary Iron Overload Triggers Hepatic Metabolic Disorders and Inflammation in Laying Hen.

Iron, an essential trace element, is involved in various physiological processes; however, consumption of excessive iron possesses detrimental effects. In practical feed production, the iron content added to feeds often far exceeds the actual demand, resulting in an excess of iron in the body. The liver as a central regulator of iron homeostasis is susceptible to damage caused by disorders in iron metabolism. A model of hepatic iron overload in laying hens was developed in this study by incorporating iron into their diet, and the specific mechanisms underlying iron overload-induced hepatic injury were investigated. Firstly, this study revealed that a high-iron diet resulted in hepatic iron overload, accompanied by impaired liver function. Next, assessment of oxidative stress markers indicated a decrease in activities of T-SOD and CAT, coupled with an increase in MDA content, pointing to the iron-overloaded liver oxidative stress. Thirdly, the impact of iron overload on hepatic glycolipid and bile acid metabolism-related gene expressions were explored, including PPAR-α, GLUT2, and CYP7A1, highlighting disruptions in hepatic metabolism. Subsequently, analyses of inflammation-related genes such as iNOS and IL-1β at both protein and mRNA levels demonstrated the presence of inflammation in the liver under conditions of dietary iron overload. Overall, this study provided comprehensive evidence that dietary iron overload contributed to disorders in glycolipid and bile acid metabolism, accompanied by inflammatory responses in laying hens. Further detailing the specific pathways involved and the implications of these findings could offer valuable insights for future research and practical applications in poultry nutrition.

Comparison of the effects of high dietary iron levels on bone microarchitecture responses in the mouse strains 129/Sv and C57BL/6J

Iron is an essential nutrient for all living organisms. Both iron deficiency and excess can be harmful. Bone, a highly metabolic active organ, is particularly sensitive to fluctuations in iron levels. In this study, we investigated the effects of dietary iron overload on bone homeostasis with a specific focus on two frequently utilized mouse strains: 129/Sv and C57BL/6J. Our findings revealed that after 6 weeks on an iron-rich diet, 129/Sv mice exhibited a decrease in trabecular and cortical bone density in both vertebral and femoral bones, which was linked to reduced bone turnover. In contrast, there was no evidence of bone changes associated with iron overload in age-matched C57BL/6J mice. Interestingly, 129/Sv mice exposed to an iron-rich diet during their prenatal development were protected from iron-induced bone loss, suggesting the presence of potential adaptive mechanisms. Overall, our study underscores the critical role of genetic background in modulating the effects of iron overload on bone health. This should be considered when studying effects of iron on bone.

High Dietary Intake of Iron Might Be Harmful to Atrial Fibrillation and Modified by Genetic Diversity: A Prospective Cohort Study.

Some studies suggest an association between iron overload and cardiovascular diseases (CVDs). However, the relationship between dietary iron intake and atrial fibrillation (AF) remains uncertain, as does the role of genetic loci on this association. The study involved 179,565 participants from UK Biobank, tracking incident atrial fibrillation (AF) cases. Iron intake was categorized into low, moderate, and high groups based on dietary surveys conducted from 2009 to 2012. The Cox regression model was used to estimate the risk of AF in relation to iron intake, assessing the hazard ratio (HR) and 95% confidence interval (95% CI). It also examined the impact of 165 AF-related and 20 iron-related genetic variants on this association. Pathway enrichment analyses were performed using Metascape and FUMA. During a median follow-up period of 11.6 years, 6693 (3.97%) incident AF cases were recorded. A total of 35,874 (20.0%) participants had high iron intake. High iron intake was associated with increased risk of AF [HR: 1.13 (95% CI: 1.05, 1.22)] in a fully adjusted model. Importantly, there were 83 SNPs (11 iron-related SNPs) that could enhance the observed associations. These genes are mainly involved in cardiac development and cell signal transduction pathways. High dietary iron intake increases the risk of atrial fibrillation, especially when iron intake exceeds 16.95 mg. The association was particularly significant among the 83 SNPs associated with AF and iron, the individuals with these risk genes. Gene enrichment analysis revealed that these genes are significantly involved in cardiac development and cell signal transduction processes.

Serum Iron Overload Activates the SMAD Pathway and Hepcidin Expression of Hepatocytes via SMURF1.

Liver iron overload can induce hepatic expression of bone morphogenic protein (BMP) 6 and activate the BMP/SMAD pathway. However, serum iron overload can also activate SMAD but does not induce BMP6 expression. Therefore, the mechanisms through which serum iron overload activates the BMP/SMAD pathway remain unclear. This study aimed to clarify the role of SMURF1 in serum iron overload and the BMP/SMAD pathway. A cell model of serum iron overload was established by treating hepatocytes with 2 mg/mL of holo-transferrin (Holo-Tf). A serum iron overload mouse model and a liver iron overload mouse model were established by intraperitoneally injecting 10 mg of Holo-Tf into C57BL/6 mice and administering a high-iron diet for 1 week followed by a low-iron diet for 2 days. Western blotting and real-time PCR were performed to evaluate the activation of the BMP/SMAD pathway and the expression of hepcidin. Holo-Tf augmented the sensitivity and responsiveness of hepatocytes to BMP6. The E3 ubiquitin-protein ligase SMURF1 mediated Holo-Tf-induced SMAD1/5 activation and hepcidin expression; specifically, SMURF1 expression dramatically decreased when the serum iron concentration was increased. Additionally, the expression of SMURF1 substrates, which are important molecules involved in the transduction of BMP/SMAD signaling, was significantly upregulated. Furthermore, in vivo analyses confirmed that SMURF1 specifically regulated the BMP/SMAD pathway during serum iron overload. SMURF1 can specifically regulate the BMP/SMAD pathway by augmenting the responsiveness of hepatocytes to BMPs during serum iron overload.

High-iron consumption decreases copper accumulation and colon length, and alters serum lipids

In this study, we aimed to demonstrate that a significant increase in dietary iron intake disrupts the regulation of copper availability, ultimately leading to systemic copper deficiency. To investigate this, we conducted experiments using five-week-old male weanling Sprague–Dawley rats fed diets based on AIN-93G with some modifications. These diets featured varying iron content, offering choices of adequate iron (~ 120 μg/g, near the upper limit [UL]) or high iron (~ 7544 μg/g), along with low (~ 0.3 μg/g), adequate (~ 6 μg/g), or high (~ 153 μg/g) levels of dietary copper over a 5-week period. Rats consuming the high-iron diets displayed anemia, reduced copper levels in their organs and feces, and shortened colon lengths. Increased dietary iron intake resulted in an overall reduction in copper distribution within the body, likely leading to severe copper deficiency-related disorders in the experimental rats. However, the physiological disturbances caused by a high-iron diet were prevented when additional copper was included in the rodent diet. Furthermore, high iron intake led to copper deprivation, and high iron consumption resulted in elevated serum cholesterol levels. However, increasing dietary copper consumption led to a decrease in overall serum cholesterol levels. Additionally, serum alkaline phosphate and aspartate aminotransferase levels were increased by high-iron feeding, regardless of dietary copper concentration, while alanine aminotransferase levels decreased.

Iron and cancer: overview of the evidence from population-based studies.

Iron is an essential nutrient required for various physiological processes in the body. However, iron imbalance can potentially contribute to initiating and promoting cancer development. Epidemiological studies have investigated the relationship between dietary iron intake and the risk of different types of cancer, yet, not all studies have consistently shown a significant association between dietary iron and cancer risk. Also, studies have shown different effects of dietary heme and non-heme iron intake on cancer risk. While some epidemiological studies suggest a possible link between high dietary iron (mainly heme-iron) intake and increased cancer risk, the evidence remains inconsistent. Moreover, multiple iron biomarkers, which can mirror physiological iron status, have demonstrated varied correlations with the risk of cancer, contingent upon the specific biomarker analyzed and the type of cancer being investigated. Here, we have investigated the current evidence on the potential relationship between dietary iron intake on one hand, and iron biomarkers on the other hand, with the risk of developing different types of cancer, including breast, prostate, lung, pancreatic, colon, colorectal, and liver cancers. Further research is warranted to better understand the complex relationship between dietary iron, physiological iron and cancer development. Future research should account for factors that affect and interact with dietary iron and physiological iron levels, such as genetic susceptibility, overall diet quality, and lifestyle habits.

The Iron Chaperone Poly C Binding Protein 1 Regulates Iron Efflux through Intestinal Ferroportin in Mice

Iron is an essential nutrient required by all cells but used primarily for red blood cell production. Because humans have no effective mechanism for ridding the body of excess iron, the absorption of dietary iron must be precisely regulated. The critical site of regulation is the transfer of iron from the absorptive enterocyte to the portal circulation via the sole iron efflux transporter, ferroportin (FPN). Here we report that poly(rC)-binding protein 1 (PCBP1), the major cytosolic iron chaperone, is necessary for the regulation of iron flux through FPN in the intestine of mice. PCBP1 binds iron-glutathione complexes in the cytosol of cells and delivers the iron to ferritin, the iron storage protein, to iron centers in enzymes, and to iron-sulfur cluster chaperones. PCBP1 also limits the chemical reactivity of iron, thereby limiting iron-catalyzed oxidative damage in cells. To explore the role of PCBP1 in dietary iron absorption, we developed mice with an inducible, enterocyte-specific deletion of PCBP1. Mice lacking PCBP1 in the intestinal epithelium exhibit low levels of enterocyte iron, poor retention of dietary iron in enterocyte ferritin, and excess efflux of iron through FPN. Kinetic studies of iron transport using a stable isotope ( 57Fe) coupled with a mini-hepcidin that blocks FPN activity demonstrated that PCBP1 deletion had no effect of intestinal iron uptake but caused high rates of iron efflux through FPN. Surprisingly, excess iron efflux occurred despite lower levels of FPN protein in enterocytes and upregulation of the iron regulatory hormone hepcidin. PCBP1 deletion and the resulting unregulated dietary iron absorption led to poor growth, severe anemia on a low iron diet and liver oxidative stress with iron loading on a high iron diet. To investigate the roles of PCBP1 more precisely in enterocytes, we developed 3-D organoid cultures from intestinal epithelium which functionally expressed the major iron trafficking proteins: divalent metal transporter 1, PCBP1, ferritin, transferrin receptor 1 and FPN. Ex vivo culture of wild-type and PCBP1-depleted enteroids demonstrated normal patterns of FPN expression and hepcidin-mediated turnover. However, fluorescence measurements of kinetically labile iron pools in enteroids competent or blocked for FPN iron efflux indicated that PCBP1 dramatically altered efflux activity. PCBP1 functioned as a cytosolic buffer for iron, binding and retaining iron and thereby keeping “free” iron at very low levels. This low concentration of free iron limited its availability for FPN-mediated efflux and allowed hepcidin-mediated changes in FPN levels to regulate the amount of iron exported from the enterocyte. Thus, by binding enterocyte iron, PCBP1 reduces the concentration of unchaperoned, “free” iron to a low level. This low level of cytosolic free iron is necessary for hepcidin-mediated regulation of FPN activity.

Caveolin-1 is critical for hepatic iron storage capacity in the development of nonalcoholic fatty liver disease

BackgroundNonalcoholic fatty liver disease (NAFLD) is associated with disordered lipid and iron metabolism. Our previous study has substantiated the pivotal role of Caveolin-1 (Cav-1) in protecting hepatocytes and mediating iron metabolism in the liver. This study aimed to explore the specific mechanisms underlying the regulation of iron metabolism by Cav-1 in NAFLD.MethodsHepatocyte-specific Cav-1 overexpression mice and knockout mice were used in this study. Cav-1-knockdown of RAW264.7 cells and mouse primary hepatocytes were performed to verify the changes in vitro. Moreover, a high-fat diet and palmitic acid plus oleic acid treatment were utilized to construct a NAFLD model in vivo and in vitro, respectively, while a high-iron diet was used to construct an in vivo iron overload model. Besides, iron concentration, the expression of Cav-1 and iron metabolism-related proteins in liver tissue or serum were detected using iron assay kit, Prussian blue staining, Western blotting, immunofluorescence staining, immunohistochemical staining and ELISA. The related indicators of lipid metabolism and oxidative stress were evaluated by the corresponding reagent kit and staining.ResultsSignificant disorder of lipid and iron metabolism occurred in NAFLD. The expression of Cav-1 was decreased in NAFLD hepatocytes (P < 0.05), accompanied by iron metabolism disorder. Cav-1 enhanced the iron storage capacity of hepatocytes by activating the ferritin light chain/ferritin heavy chain pathway in NAFLD, subsequently alleviating the oxidative stress induced by excess ferrous ions in the liver. Further, CD68+CD163+ macrophages expressing Cav-1 were found to accelerate iron accumulation in the liver, which was contrary to the effect of Cav-1 in hepatocytes. Positive correlations were also observed between the serum Cav-1 concentration and the serum iron-related protein levels in NAFLD patients and healthy volunteers (P < 0.05).ConclusionsThese findings confirm that Cav-1 is an essential target protein that regulates iron and lipid metabolic homeostasis. It is a pivotal molecule for predicting and protecting against the development of NAFLD.

Iron Dys-Homeostasis Contributed to Liver Gvhd after Allogeneic Hematopoietic Stem Cell Transplantation

Graft-versus-host disease (GVHD), which results from immunological attack to recipient organs or tissues (such as the skin, liver and gut) by donor allogeneic T cells, limits the success of allogeneic hematopoietic stem cell transplantation (allo-HSCT). A correlation of high serum ferritin levels with increased mortality after allo-HSCT has been suggested by several analyses. While the role of iron dys-homeostasis in the risk of GVHD remains unclear. Whether iron dys-homeostasis contributes to the development of GVHD or iron dys-homeostasis is only a result of severe GVHD remains unknown. To assess the status of iron metabolism during GVHD following allo-HSCT, we established aGVHD mouse model by transplantation of T cell-depleted bone marrow (TCD BM) with or without splenic T cells from C57BL/6 (B6) mice to BALB/c mice after being lethally irradiated. By 28 days post-transplantation, when aGVHD stable developed, the serum iron level was significantly higher in aGVHD group compared with control. Meanwhile, ferrous-ion load in aGVHD-involved liver was also increased, while the total iron load did not differ significantly in aGVHD-involved liver compared with control. The ferrous-ion load as well as the total iron load in intestine, lung and spleen were comparable between aGVHD group and control group. To further determine the dysregulation of iron metabolism during liver aGVHD, we detected the expression levels of pivotal iron regulatory genes in liver and duodenum. The expression levels of transferrin receptor 1 ( Tfr1) and divalent metal transporter 1 ( Dmt1) were significantly upregulated in aGVHD-involved liver, which contributed to ferrous-ion overload in the liver aGVHD. Besides, Ferroportin 1 was down-regulated in aGVHD-involved duodenum, which is the result of the upregulated hepcidin ( Hamp1) in liver. Our data suggested that the increased serum iron in aGVHD was not related to iron absorption by duodenum, but may be associated with ineffectively use of iron, which was caused by the impaired marrow function after myeloablative conditioning. To explore whether ferrous-ion overload in liver would lead to induction of reactive oxygen species (ROS) via the Fenton reaction, and eventually results in liver damage during aGVHD, we detected the activity of superoxide dismutase (SOD) and the load of thiol and lipid peroxidation product, malondialdehyde (MDA). The activity of SOD and thiol load both decreased significantly in aGVHD-involved liver, while the serum MDA level increased in aGVHD group, indicating that iron dys-homeostasis may aggravate liver GVHD damage by induction of lipid peroxidation injury. Finally, to explore how iron overload affect GVHD, we fed recipient mice with high-iron diet and low-iron diet since three weeks before transplantation, respectively. The survival rates and GVHD score were significantly worse in high-iron diet group compared with normal-iron diet group. Interestingly, low-iron diet didn't show survival benefit compared with the normal-iron diet. This suggests that excessive iron deficiency is not beneficial for preventing and treating GVHD. Thus, we applied apo-transferrin (apo-Tf) administration to receipt mice, which can render the poorly soluble non-transferrin bonding iron (NTBI) into a soluble transferrin-bound form, and prevent iron from being rapidly uptake by the liver. The administration of apo-Tf alleviated the organ damage during aGVHD, and reduced the infiltration of CD4 +IFN-γ +T cells, CD4 +IL17 +T cells and CD8 +IL17 +T cells in target organs such as intestine, liver and lung. These data suggested that ferrous-ion overload leads to the increase of NTBI, which aggravate GVHD tissue damage. Our findings reveal a novel mechanism of iron dys-homeostasis during the development of liver aGVHD, which may reveal promising therapeutic targeting in the prevention and treatment of liver aGVHD.