Anemia and Its Connections to Inflammation in Older Adults: A Review.

Anemia is a common hematological disorder that affects 12% of the community-dwelling population, 40% of hospitalized patients, and 47% of nursing home residents. Our understanding of the impact of inflammation on iron metabolism and erythropoiesis is still lacking. In older adults, anemia can be divided into nutritional deficiency anemia, bleeding anemia, and unexplained anemia. The last type of anemia might be caused by reduced erythropoietin (EPO) activity, progressive EPO resistance of bone marrow erythroid progenitors, and the chronic subclinical pro-inflammatory state. Overall, one-third of older patients with anemia demonstrate a nutritional deficiency, one-third have a chronic subclinical pro-inflammatory state and chronic kidney disease, and one-third suffer from anemia of unknown etiology. Understanding anemia's pathophysiology in people aged 65 and over is crucial because it contributes to frailty, falls, cognitive decline, decreased functional ability, and higher mortality risk. Inflammation produces adverse effects on the cells of the hematological system. These effects include iron deficiency (hypoferremia), reduced EPO production, and the elevated phagocytosis of erythrocytes by hepatic and splenic macrophages. Additionally, inflammation causes enhanced eryptosis due to oxidative stress in the circulation. Identifying mechanisms behind age-related inflammation is essential for a better understanding and preventing anemia in older adults.

Iron Related Biomarkers Predict Disease Severity in a Cohort of Portuguese Adult Patients during COVID-19 Acute Infection.

Large variability in COVID-19 clinical progression urges the need to find the most relevant biomarkers to predict patients' outcomes. We evaluated iron metabolism and immune response in 303 patients admitted to the main hospital of the northern region of Portugal with variable clinical pictures, from September to November 2020. One hundred and twenty-seven tested positive for SARS-CoV-2 and 176 tested negative. Iron-related laboratory parameters and cytokines were determined in blood samples collected soon after admission. Demographic data, comorbidities and clinical outcomes were recorded. Patients were assigned into five groups according to severity. Serum iron and transferrin levels at admission were lower in COVID-19-positive than in COVID-19-negative patients. The levels of interleukin (IL)-6 and monocyte chemoattractant protein 1 (MCP-1) were increased in COVID-19-positive patients. The lowest serum iron and transferrin levels at diagnosis were associated with the worst outcomes. Iron levels negatively correlated with IL-6 and higher levels of this cytokine were associated with a worse prognosis. Serum ferritin levels at diagnosis were higher in COVID-19-positive than in COVID-19-negative patients. Serum iron is the simplest laboratory test to be implemented as a predictor of disease progression in COVID-19-positive patients.

Hepcidin-Mediated Hypoferremia Disrupts Immune Responses to Vaccination and Infection.

BACKGROUND: How specific nutrients influence adaptive immunity is of broad interest. Iron deficiency is the most common micronutrient deficiency worldwide and imparts a significant burden of global disease; however, its effects on immunity remain unclear. METHODS: We used a hepcidin mimetic and several genetic models to examine the effect of low iron availability on T cells in vitro and on immune responses to vaccines and viral infection in mice. We examined humoral immunity in human patients with raised hepcidin and low serum iron caused by mutant TMPRSS6. We tested the effect of iron supplementation on vaccination-induced humoral immunity in piglets, a natural model of iron deficiency. FINDINGS: We show that low serum iron (hypoferremia), caused by increased hepcidin, severely impairs effector and memory responses to immunizations. The intensified metabolism of activated lymphocytes requires the support of enhanced iron acquisition, which is facilitated by IRP1/2 and TFRC. Accordingly, providing extra iron improved the response to vaccination in hypoferremic mice and piglets, while conversely, hypoferremic humans with chronically increased hepcidin have reduced concentrations of antibodies specific for certain pathogens. Imposing hypoferremia blunted the T cell, B cell, and neutralizing antibody responses to influenza virus infection in mice, allowing the virus to persist and exacerbating lung inflammation and morbidity. CONCLUSIONS: Hypoferremia, a well-conserved physiological innate response to infection, can counteract the development of adaptive immunity. This nutrient trade-off is relevant for understanding and improving immune responses to infections and vaccines in the globally common contexts of iron deficiency and inflammatory disorders. FUNDING: Medical Research Council, UK.

Hepcidin, Serum Iron, and Transferrin Saturation in Full-Term and Premature Infants during the First Month of Life: A State-of-the-Art Review of Existing Evidence in Humans.

Neonates regulate iron at birth and in early postnatal life. We reviewed literature from PubMed and Ovid Medline containing data on umbilical cord and venous blood concentrations of hepcidin and iron, and transferrin saturation (TSAT), in human neonates from 0 to 1 mo of age. Data from 59 studies were used to create reference ranges for hepcidin, iron, and TSAT for full-term-birth (FTB) neonates over the first month of life. In FTB neonates, venous hepcidin increases 100% over the first month of life (to reach 61.1 ng/mL; 95% CI: 20.1, 102.0 ng/mL) compared with umbilical cord blood (29.7 ng/mL; 95% CI: 21.1, 38.3 ng/mL). Cord blood has a high concentration of serum iron (28.4 µmol/L; 95% CI: 26.0, 31.1 µmol/L) and levels of TSAT (51.7%; 95% CI: 46.5%, 56.9%). After a short-lived immediate postnatal hypoferremia, iron and TSAT rebounded to approximately half the levels in the cord by the end of the first month. There were insufficient data to formulate reference ranges for preterm neonates.

Distinct iron homeostasis in C57BL/6 and Balb/c mouse strains.

C57BL/6 (BL6) and Balb/c mice exhibit prototypical Th1- and Th2-dominant immune predispositions, respectively. Iron is a proinflammatory metal ion; however, limited information is documented on the differences in iron homeostasis between BL6 and Balb/c strains. The objective of this study was to investigate the extent to which strain-level differences in these mice dictates the regulation of iron homeostasis during physiologic and inflammatory conditions. At basal levels, Balb/c mice displayed significantly higher levels of iron in systemic circulation and tissue compared to BL6 mice. Moreover, Balb/c mice had greater iron absorption as indicated by higher gene expressions of duodenal DcytB, DMT1, Fpn, SFT, and Heph. Similarly, hepatic Tf, TfR1, TfR2, and DMT1 expressions were augmented in Balb/c mice. Interestingly, there was no change in hepatic Hamp expression between the two strains, suggesting that the disparity in their maintenance of iron is independent of hepcidin. Additionally, the basal levels of intracellular labile iron pool in Balb/c intestinal epithelial cells, and bone marrow-derived macrophages and neutrophils, were higher compared to BL6 mice. When mice were challenged with lipopolysaccharide, the acute inflammatory response in BL6 mice was more pronounced than in Balb/c mice, as indicated by the more rapid development of hypoferremia and upregulation of serum IL-6 and TNF-α levels in BL6 mice. In conclusion, this study underscores that iron homeostasis is distinct between BL6 and Balb/c strains under both physiologic and inflammatory conditions.

Neonatal iron distribution and infection susceptibility in full term, preterm and low birthweight babies in urban Gambia: study protocol for an observational study.

Background: Neonatal infection is the third largest cause of death in children under five worldwide.  Nutritional immunity is the process by which the host innate immune system limits nutrient availability to invading organisms. Iron is an essential micronutrient for both microbial pathogens and their mammalian hosts. Changes in iron availability and distribution have significant effects on pathogen virulence and on the immune response to infection. Our previously published data shows that, during the first 24 hours of life, full-term neonates have reduced overall serum iron. Transferrin saturation decreases rapidly from 45% in cord blood to ~20% by six hours post-delivery. Methods: To study neonatal nutritional immunity and its role in neonatal susceptibility to infection, we will conduct an observational study on 300 full-term normal birth weight (FTB+NBW), 50 preterm normal birth weight (PTB+NBW), 50 preterm low birth weight (PTB+LBW) and 50 full-term low birth weight (FTB+LBW), vaginally-delivered neonates born at Kanifing General Hospital, The Gambia. We will characterize and quantify iron-related nutritional immunity during the early neonatal period and use ex vivo sentinel bacterial growth assays to assess how differences in serum iron affect bacterial growth. Blood samples will be collected from the umbilical cord (arterial and venous) and at serial time points from the neonates over the first week of life. Discussion: Currently, little is known about nutritional immunity in neonates. In this study, we will increase understanding of how nutritional immunity may protect neonates from infection during the first critical days of life by limiting the pathogenicity and virulence of neonatal sepsis causing organisms by reducing the availability of iron. Additionally, we will investigate the hypothesis that this protective mechanism may not be activated in preterm and low birth weight neonates, potentially putting these babies at an enhanced risk of neonatal infection. Trial registration: clinicaltrials.gov ( NCT03353051) 27/11/2017.

Salmonella effector SpvB interferes with intracellular iron homeostasis via regulation of transcription factor NRF2.

Iron is a necessary nutrient for humans and nearly all bacterial species. During Salmonella infection, macrophages limit the availability of iron to intracellular pathogens in one of the central components of nutritional immunity. However, Salmonella also have mechanisms to interfere with the antimicrobial effect of host iron withdrawal and meet their own nutrient requirements by scavenging iron from the host. Here, we provide what is, to our knowledge, the first report that SpvB, a pSLT-encoded cytotoxic protein whose function is associated with the intracellular stage of salmonellosis, perturbs macrophage iron metabolism, thereby facilitating Salmonella survival and intracellular replication. In investigating the underlying mechanism, we observed that the Salmonella effector SpvB down-regulated nuclear factor erythroid-derived 2-related factor 2 (NRF2), and its C-terminal domain was necessary and sufficient for NRF2 degradation via the proteasome pathway. Decreased NRF2 expression in the nucleus resulted in a decrease in its transcriptional target ferroportin, encoding the sole macrophage iron exporter, thus ultimately decreasing iron efflux and increasing the intracellular iron content. Additionally, SpvB contributes to the pathogenesis of Salmonella including severe serum hypoferremia, increased splenic and hepatic bacterial burden, and inflammatory injury in vivo. Together, our observations uncovered a novel contribution of SpvB to Salmonella pathology via interference with host intracellular iron metabolism.-Yang, S., Deng, Q., Sun, L., Dong, K., Li, Y., Wu, S., Huang, R. Salmonella effector SpvB interferes with intracellular iron homeostasis via regulation of transcription factor NRF2.

Lipocalin 2: An Emerging Player in Iron Homeostasis and Inflammation.

Lipocalin 2 (Lcn2), an innate immune protein, has emerged as a critical iron regulatory protein during physiological and inflammatory conditions. As a bacteriostatic factor, Lcn2 obstructs the siderophore iron-acquiring strategy of bacteria and thus inhibits bacterial growth. As part of host nutritional immunity, Lcn2 facilitates systemic, cellular, and mucosal hypoferremia during inflammation, in addition to stabilizing the siderophore-bound labile iron pool. In this review, we summarize recent advances in understanding the interaction between Lcn2 and iron, and its effects in various inflammatory diseases. Lcn2 exerts mostly a protective role in infectious and inflammatory bowel diseases, whereas both beneficial and detrimental functions have been documented in neurodegenerative diseases, metabolic syndrome, renal disorders, skin disorders, and cancer. Further animal and clinical studies are necessary to unveil the multifaceted roles of Lcn2 in iron dysregulation during inflammation and to explore its therapeutic potential for treating inflammatory diseases.

Diagnóstico de la deficiencia de hierro: aspectos esenciales / Diagnosis of iron deficiency: essencial features

Se estima que un tercio de la población mundial es anémica, la mayoría por deficiencia de hierro. La anemia por deficiencia de hierro es la etapa final de un prolongado periodo de balance negativo del mineral. Aunque es raro que esta anemia sea causa de muerte, su impacto sobre la salud es significativo. En los adultos, se asocia con fatiga, síndrome de las piernas inquietas, pica, etc; en los neonatos, con retraso del crecimiento y desarrollo y; en los adolescentes, con disminución del aprendizaje y alteraciones conductuales. No existe una prueba única para diagnosticar la deficiencia de hierro; aunque la disminución de la ferritina sérica o de la saturación de la transferrina, con una capacidad total de fijación de hierro elevada, son elementos sugestivos. Se revisan las características clínicas y de laboratorio de esta entidad(AU)

It is estimated that one-third of the world's population is anemic, the majority being due to iron deficiency. Iron deficiency anemia is the result of a large negative iron balance period. Iron deficiency anemia rarely causes death, but the impact on human health is significant. In adults, it is associated with fatigue, restless legs syndrome, pica; in neonates, delayed growth and development and, in adolescents, decrements in learning and behavioral abnormalities. No single test is diagnostic of ID unless the serum ferritin is low or the percent transferring saturation is low with an elevated total iron binding capacity are suggestive. Clinical and laboratory features of the disease are discussed(AU)

Modulation of urinary siderophores by the diet, gut microbiota and inflammation in mice.

Mammalian siderophores are believed to play a critical role in maintaining iron homeostasis. However, the properties and functions of mammalian siderophores have not been fully clarified. In this study, we have employed Chrome Azurol S (CAS) assay which is a well-established method for bacterial siderophores study, to detect and quantify mammalian siderophores in urine samples. Our study demonstrates that siderophores in urine can be altered by diet, gut microbiota and inflammation. C57BL/6 mice, fed on plant-based chow diets which contain numerous phytochemicals, have more siderophores in the urine compared to those fed on purified diets. Urinary siderophores were up-regulated in iron overload conditions, but not altered by other tested nutrients status. Further, germ-free mice displayed 50% reduced urinary siderophores, in comparison to conventional mice, indicating microbiota biotransformation is critical in generating or stimulating host metabolism to create more siderophores. Altered urinary siderophores levels during inflammation suggest that host health conditions influence systemic siderophores level. This is the first report to measure urinary siderophores as a whole, describing how siderophores levels are modulated under different physiological conditions. We believe that our study opens up a new field in mammalian siderophores research and the technique we used in a novel manner has the potential to be applied to clinical purpose.

Hepatocyte Nuclear Factor 4α Controls Iron Metabolism and Regulates Transferrin Receptor 2 in Mouse Liver.

Iron is an essential element in biological systems, but excess iron promotes the formation of reactive oxygen species, resulting in cellular toxicity. Several iron-related genes are highly expressed in the liver, a tissue in which hepatocyte nuclear factor 4α (HNF4α) plays a critical role in controlling gene expression. Therefore, the role of hepatic HNF4α in iron homeostasis was examined using liver-specific HNF4α-null mice (Hnf4a(ΔH) mice). Hnf4a(ΔH) mice exhibit hypoferremia and a significant change in hepatic gene expression. Notably, the expression of transferrin receptor 2 (Tfr2) mRNA was markedly decreased in Hnf4a(ΔH) mice. Promoter analysis of the Tfr2 gene showed that the basal promoter was located at a GC-rich region upstream of the transcription start site, a region that can be transactivated in an HNF4α-independent manner. HNF4α-dependent expression of Tfr2 was mediated by a proximal promoter containing two HNF4α-binding sites located between the transcription start site and the translation start site. Both the GC-rich region of the basal promoter and the HNF4α-binding sites were required for maximal transactivation. Moreover, siRNA knockdown of HNF4α suppressed TFR2 expression in human HCC cells. These results suggest that Tfr2 is a novel target gene for HNF4α, and hepatic HNF4α plays a critical role in iron homeostasis.

Plasma iron, C-reactive protein, albumin, and plasma fibrinogen concentrations in dogs with systemic inflammatory response syndrome.

OBJECTIVE: To investigate the diagnostic and prognostic value over time of plasma iron compared with the inflammatory markers albumin, C-reactive protein (CRP), and fibrinogen in dogs with systemic inflammatory response syndrome (SIRS). DESIGN: Prospective observational study of sequentially enrolled dogs. SETTING: ICU of a veterinary teaching hospital. ANIMALS: One hundred and sixteen client-owned dogs: 54 dogs with SIRS or sepsis, 42 with focal inflammation, and 20 clinically healthy dogs. MEASUREMENTS AND MAIN RESULTS: Blood samples were obtained on admission in all study groups, and then on alternate days until discharge or death in both inflammation groups. On admission, dogs with SIRS had significantly lower plasma iron (65 ± 5.8 µg/dL, P = 0.001) concentrations than dogs with focal inflammation (89.5 ± 6.2 µg/dL, P = 0.001). Plasma iron, albumin, and CRP effectively discriminated the SIRS/sepsis group from those presenting with focal inflammation with areas under the curve for the receiver operating curves of 0.679, 0.834, and 0.704, respectively. The admission values for these variables did not discriminate survivors from nonsurvivors within the SIRS/sepsis group. However, the magnitude of increase in iron concentration and the decrease in CRP concentration from admission to hospital discharge was higher in survivors than in nonsurvivors within the SIRS/septic group (22.8 vs. 2.51 µg/dL, respectively, P = 0.021 for iron; -67.1 vs. -4.1 mg/L, respectively, P = 0.002 for CRP), resulting in iron and CRP concentrations at hospital discharge for survivors similar to those in the focal inflammation group. CONCLUSION: Hypoferremia is a sensitive marker of systemic inflammation in dogs. In this study, the increase in iron concentrations during the hospitalization period of SIRS/septic dogs was associated with a better prognosis, suggesting that plasma iron in combination with CRP and albumin concentrations might be used to monitor dogs with inflammatory disease processes.

Mutual interaction between iron homeostasis and obesity pathogenesis.

Obesity is identified as an important medical problem. One of the pathologic conditions observed in obesity is systemic iron deficiency and hypoferremia. Along with a large number of studies indicating disturbed iron homeostasis in obesity, recent data indicate a cause-effect relationship between iron status and obesity-related pathologies. The primary objective of the article is to consider two aspects of the iron-obesity interplay: (1) the mechanisms leading to impaired iron balance, and (2) the pathways of iron participation in obesity-related pathogenesis. While considering disturbance of iron homeostasis in obesity, a number of potential mechanisms of hypoferremia are proposed. At the same time, the inflammation of obesity and obesity-related hepcidin and lipocalin 2 hyperproduction seem to be the most probable reasons of obesity-related hypoferremia. Oversecretion of these proteins leads to iron sequestration in reticuloendothelial system cells. The latter also leads to increased adipose tissue iron content, thus producing preconditions for adverse effects of local iron overload. Being a redox-active metal, iron is capable of inducing oxidative stress as well as endoplasmic reticulum stress, inflammation and adipose tissue endocrine dysfunction. Iron-mediated mechanisms of toxicity may influence aspects of obesity pathogenesis possibly even leading to obesity aggravation. Thus, a mutual interaction between disturbance in iron homeostasis and obesity pathogenesis is proposed. All sides of this interaction should be considered to design new therapeutic approaches to the treatment of disturbed iron homeostasis in obesity.

Heat stress stimulates hepcidin mRNA expression and C/EBPα protein expression in aged rodent liver.

Elevations in hepatic iron content occur with aging and physiological stressors, which may promote oxidative injury to the liver. Since dysregulation of the iron regulatory hormone, hepcidin, can cause iron accumulation, our goal was to characterize the regulation of hepcidin in young (6 mo) and old (24 mo) Fischer 344 rats exposed to environmental heat stress. Liver and blood samples were taken in the control condition and after heating. Hepcidin expression did not differ between young and old rats in the control condition, despite higher levels of hepatic iron and IL-6 mRNA in the latter. Following heat stress, pSTAT3 increased in both groups, but C/EBPα and hepcidin mRNA increased only in old rats. Despite this, serum iron decreased in both age groups 2 h after heat stress, suggesting hepcidin-independent hypoferremia in the young rats. The differential regulation of hepcidin between young and old rats after hyperthermia may be due to the enhanced expression of C/EBPα protein in old rats. These data support the concept of "inflammaging" and suggest that repeated exposures to stressors may contribute to the development of anemia in older individuals.

Iron supplementation does not worsen respiratory health or alter the sputum microbiome in cystic fibrosis.

BACKGROUND: Iron supplementation for hypoferremic anemia could potentiate bacterial growth in the cystic fibrosis (CF) lung, but clinical trials testing this hypothesis are lacking. METHODS: Twenty-two adults with CF and hypoferremic anemia participated in a randomized, double-blind, placebo-controlled, crossover trial of ferrous sulfate 325mg daily for 6weeks. Iron-related hematologic parameters, anthropometric data, sputum iron, Akron Pulmonary Exacerbation Score (PES), and the sputum microbiome were serially assessed. Fixed-effect models were used to describe how ferrous sulfate affected these variables. RESULTS: Ferrous sulfate increased serum iron by 22.3% and transferrin saturation (TSAT) by 26.8% from baseline (p<0.05) but did not affect hemoglobin, sputum iron, Akron PES, and the sputum microbiome. CONCLUSIONS: Low-dose ferrous sulfate improved hypoferremia without correcting anemia after 6weeks. We did not observe significant effects on sputum iron, Akron PES, and the sputum microbiome. Although we did not identify untoward health effects of iron supplementation, a larger blinded randomized controlled trial would be needed to fully demonstrate safety.

Evaluation of serum ceruloplasmin in aggressive and chronic periodontitis patients.

BACKGROUND: Pro-inflammatory markers are seen to increase in inflammatory diseases like periodontitis. Detecting an increase in these markers is one of the diagnostic modality. One such marker, which can be detected, is the ceruloplasmin. Ceruloplasmin induces hypoxia and generates oxygen radicals at the site of aggressive periodontitis. It also causes a state of hypoferremia leading to increase in the natural resistance of the body. The aim of this study was to evaluate the serum levels of cerruloplasmin in both aggressive and chronic periodontitis patients. MATERIALS AND METHODS: Blood samples were collected from aggressive periodontitis patients (n = 20), chronic periodontitis patients (n = 20) and periodontally healthy patients (n = 20). The serum was extracted from all the blood samples and ceruloplasmin levels were spectroscopically evaluated through a new kinetic method, which used a norfloxacin based reagent. RESULTS: Serum ceruloplasmin levels were found to be significantly higher in aggressive periodontitis patients (P > 0.05) than in chronic periodontitis patients (P > 0.05) even though increase in the level of ceruloplasmin was found in chronic periodontitis. Periodontally healthy patients did not show increase in the levels of serum ceruloplasmin. The levels of serum ceruloplasmin also increased with the disease severity whose manifestations were increased bleeding on probing, increased pocket depth and increased attachment loss. CONCLUSION: Serum ceruloplasmin levels increased in both aggressive and chronic periodontitis patients, but more in aggressive periodontitis patients making it a potential marker for diagnosis of periodontitis.