Iron Metabolism Contributes to Prognosis in Coronary Artery Disease: Prognostic Value of the Soluble Transferrin Receptor Within the AtheroGene Study

Iron deficiency and all-cause mortality after myocardial infarction

BACKGROUND

Data on the clinical significance of iron deficiency (ID) in patients with myocardial infarction (MI) are conflicting. This may be related to the use of various ID criteria. We aimed to compare the association of different ID criteria with all-cause mortality after MI.

METHODS

Consecutive patients hospitalized for their first MI at a large tertiary heart center were included. We evaluated the association of different iron metabolism parameters measured on the first day after hospital admission with all-cause mortality.

RESULTS

From the 1,156 patients included (aged 64±12 years, 25 % women), 194 (16.8 %) patients died during the median follow-up of 3.4 years. After multivariate adjustment, iron level ≤13 µmol/L (HR 1.67, 95 % CI 1.19-2.34) and the combination of iron level ≤12.8 µmol/L and soluble transferrin receptor (sTfR) ≥3 mg/L (HR 2.56, 95 % CI 1.64-3.99) termed as PragueID criteria were associated with increased mortality risk and had additional predictive value to the GRACE score. Compared to the model including iron level, the addition of sTfR improved risk stratification (net reclassification improvement 0.61, 95 % CI 0.52-0.69) by reclassifying patients into a higher-risk group. No association between ferritin level and mortality was found. 51 % of patients had low iron levels, and 58 % fulfilled the PragueID criteria.

CONCLUSION

Iron deficiency is common among patients with the first MI. The PragueID criteria based on iron and soluble transferrin receptor levels provide the best prediction of mortality and should be evaluated in future interventional studies for the identification of patients potentially benefiting from intravenous iron therapy.

Iron deficiency and supplementation in heart failure

Non-anaemic iron deficiency (NAID) is a strategic target in cardiovascular medicine because of its association with a range of adverse effects in various conditions. Endeavours to tackle NAID in heart failure have yielded mixed results, exposing knowledge gaps in how best to define 'iron deficiency' and the handling of iron therapies by the body. To address these gaps, we harness the latest understanding of the mechanisms of iron homeostasis outside the erythron and integrate clinical and preclinical lines of evidence. The emerging picture is that current definitions of iron deficiency do not assimilate the multiple influences at play in patients with heart failure and, consequently, fail to identify those with a truly unmet need for iron. Additionally, current iron supplementation therapies benefit only certain patients with heart failure, reflecting differences in the nature of the unmet need for iron and the modifying effects of anaemia and inflammation on the handling of iron therapies by the body. Building on these insights, we identify untapped opportunities in the management of NAID, including the refinement of current approaches and the development of novel strategies. Lessons learned from NAID in cardiovascular disease could ultimately translate into benefits for patients with other chronic conditions such as chronic kidney disease, chronic obstructive pulmonary disease and cancer.

A Comprehensive Review on Serum Ferritin as a Prognostic Marker in Intensive Care Units: Insights Into Ischemic Heart Disease

Serum ferritin has garnered considerable attention as a prognostic marker in intensive care units (ICUs), offering valuable insights into patient outcomes and clinical management strategies. This comprehensive review examines the role of serum ferritin in predicting outcomes among critically ill patients, with a particular focus on its implications for ischemic heart disease (IHD). Elevated serum ferritin levels have consistently been associated with adverse outcomes in ICU settings, including increased mortality, prolonged hospital stays, and higher morbidity rates. Furthermore, the relationship between serum ferritin levels and IHD underscores its potential as a biomarker for cardiovascular risk assessment in critically ill populations. The review synthesizes existing literature to highlight the predictive value of serum ferritin in assessing illness severity and guiding clinical decision-making in the ICUs. It also explores potential mechanisms linking serum ferritin to adverse outcomes and discusses implications for clinical practice. Integrating serum ferritin measurements into routine assessments could enhance prognostication and risk stratification in ICU patients, while further research is needed to elucidate optimal management strategies and therapeutic targets. Collaborative efforts between clinicians and researchers are essential to advance our understanding of serum ferritin's prognostic value in the ICUs and translate this knowledge into improved patient care and outcomes.

Association of soluble transferrin receptor/log ferritin index with all-cause and cause-specific mortality: National Health and Nutrition Examination Survey

Background

Soluble transferrin receptor (sTfR)/log ferritin index (sTfR Index) can be used to assess the entire spectrum of iron status, and is valuable in evaluating iron status in population studies. There is still a lack of evidence on the association between sTfR index and all-cause mortality.

Object

To explore the association between sTfR index and all-cause mortality, as well as mortality due to cardiovascular disease (CVD) and cancer.

Method

Data were from the National Health and Nutrition Examination Survey (NHANES) between 2003 to 2020. Participants aged 16 years and older who had complete data of serum ferritin and sTfR were included. Pregnant individuals or those with ineligible data on death or follow-up were excluded from the analysis. Baseline sTfR index was calculated by baseline sTfR/log (ferritin) and classified as three tertile. We performed the Cox proportional hazard regression to assess the association of sTfR index (both continuous and categorical scale) with all-cause and cause-specific mortality and further assess the non-linear relationship between sTfR index and the outcomes with restricted cubic spline.

Result

In this study, 11,525 participants, a total of 231 (2.0%) all-cause deaths occurred during a median follow-up of 51 months. The risk of all-cause mortality, CVD-related mortality, and cancer-related mortality was higher in participants with highest tertile of sTfR index. After confounding factors adjustment, participants with highest tertile of sTfR index were associated with an increased risk of all-cause mortality (HR: 1.71, 95% CI: 1.14-2.57) as compared with lowest tertile. Additionally, sTfR index per SD increment was associated with a 25% increasing risk of all-cause mortality (HR: 1.25, 95% CI: 1.08-1.45, p = 0.003) and a 38% cancer-related mortality (HR: 1.38, 95% CI: 1.07-1.77, p = 0.018). These associations remained robust after adjusting for the serum ferritin as well as in various subgroups stratified by age, sex, smoking statue, hypertension, diabetes, and CVD. Spline analysis showed that there is approximately linear relationship between sTfR index with all-cause mortality (p for non-linear = 0.481). Moreover, ferritin was not a predictor of all-cause death after adjustment for confounding factors.

Significance

This cohort study demonstrated a significant association between sTfR index increment and an increased risk of all-cause and cancer-related mortality, independent of ferritin levels.

A comprehensive proteomic profiling of urinary exosomes and the identification of early non-invasive biomarker in patients with coronary artery disease

Urinary small extracellular vesicles or exosomes (uEVs) source could be an emerging trove of biomarkers in coronary artery disease (CAD). It is a chronic inflammatory disease having a long asymptomatic phase of fatty-fibrous development in arteries leading to angina, myocardial infarction, and death. Our study was aimed at identifying differential protein expression profiling of uEVs in CAD. We collected urine samples of CAD patients (n = 41) age 18-65 years and gender matched healthy controls (n = 41). We isolated uEVs using differential ultracentrifugation. Further, uEV samples were characterized by western blotting exosome markers (Flotillin, TSG, CD63, and CD9), nano tracking analysis, and transmission and scanning electron microscopy. A total of 508 proteins were identified by iTRAQ-based mass spectrometry. We observed protein expression levels of AZGP1, SEMG1/2, ORM1, IGL, SERPINA5, HSPG2, prosaposin, gelsolin, and CD59 were upregulated, and UMOD, KNG1, AMBP, prothrombin, and TF were downregulated. Protein-protein interactions, gene ontology and pathway analysis were performed to functionally annotate identified uEVs proteins. A novel uEVs differential protein signature is shown. On validating UMOD protein by ELISA in two clinically different CAD, stable-CAD patients had lower levels than healthy controls whereas recent myocardial infarction patients had lowest. Our findings suggest UMOD importance as early diagnostic biomarker. SIGNIFICANCE: Coronary artery disease is a chronic inflammatory disease caused by gradual deposition of cholesterol and fat along with other proteins to develop plaque inside arteries. This further leads to blockage of artery, heart attack and death. There are no identifiable early biomarkers to diagnose this. For the first time, we have identified the differentially expressed proteins isolated from non-invasive uEV of CAD patients compared to healthy controls by using MS Orbitrap and iTRAQ labelling of peptides. We have identified decreased levels of UMOD protein in CAD. These findings have been confirmed by ELISA. Furthermore, the levels of UMOD were observed as more highly decreased in recent myocardial infarction CAD patients, indicating the importance of this protein as an early diagnostic biomarker. Conclusively, our study represents a non-invasive urinary EVs trove of differentially expressed proteins in CAD. This will form a groundwork for understanding the pathophysiology of CAD and will help in future translational research utilizing uEVs.

Elevated Serum Levels of Soluble Transferrin Receptor Are Associated with an Increased Risk of Cardiovascular, Pulmonary, and Hematological Manifestations and a Decreased Risk of Neuropsychiatric Manifestations in Systemic Lupus Erythematosus Patients

The aim of this study was to analyze the relationship between the serum levels of soluble transferrin receptor (sTfR) and interleukin 4 (IL-4), and the disease activity and organ manifestations in SLE patients. We studied 200 SLE patients and 50 controls. We analyzed disease activity, organ involvement, serum sTfR, IL-4 and interleukin-6 (IL-6) levels, and antinuclear and antiphospholipid antibody profiles. The median serum levels of sTfR (p > 0.000001) and IL-4 (p < 0.00001) were higher in the study group than in the controls. SLE patients, compared to the controls, had significantly lower HGB levels (p < 0.0001), a lower iron concentration (p = 0.008), a lower value of total iron-binding capacity (TIBC) (p = 0.03), and lower counts of RBC (p = 0.004), HCT (p = 0.0004), PLT (p = 0.04), neutrophil (p = 0.04), and lymphocyte (p < 0.0001). Serum sTfR levels were negatively correlated with lymphocyte (p = 0.0005), HGB (p = 0.0001) and HCT (p = 0.008), and positively correlated with IL-4 (p = 0.01). Elevated serum sTfR > 2.14 mg/dL was associated with an increased risk of myocardial infarction (OR: 10.6 95 CI 2.71-464.78; p = 0.001), ischemic heart disease (OR: 3.25 95 CI 1.02-10.40; p = 0.04), lung manifestations (OR: 4.48 95 CI 1.44-13.94; p = 0.01), and hematological manifestations (OR: 2.07 95 CI 1.13-3.79; p = 0.01), and with a reduced risk of neuropsychiatric manifestations (OR: 0.42 95 CI 0.22-0.80; p = 0.008). Serum IL-4 was negatively correlated with CRP (p = 0.003), and elevated serum IL-4 levels > 0.17 mg/L were associated with a reduced risk of mucocutaneous manifestations (OR: 0.48 95 CI 0.26-0.90; p = 0.02). In SLE patients, elevated serum levels of sTfR were associated with an increased risk of cardiovascular, pulmonary, and hematological manifestations, and with a decreased risk of neuropsychiatric manifestations. In contrast, elevated serum IL-4 levels were associated with a decreased risk of mucocutaneous manifestations.

Effect of roxadustat on iron metabolism in patients with peritoneal dialysis: a real-world 24-week study

BACKGROUND

Roxadustat is an oral hypoxia inducing factor-prolyl hydroxylase inhibitor (HIF-PHI) that regulates iron metabolism in patients with chronic kidney disease (CKD) primarily by reducing hepcidin levels and mobilizing internal iron stores. More data are needed to demonstrate the efficacy of roxadustat in regulating iron metabolism in patients with peritoneal dialysis (PD) compared with erythropoiesis stimulating agents (ESAs).

METHODS

This prospective cohort study enrolled PD patients with a mean hemoglobin level of 60-100 g/L. All subjects were randomized into two groups at a ratio of 2:1 the roxadustat group (106 cases), and the ESA group (53 cases). The primary endpoint was the change in the iron biomarker levels and the proportion of patients with absolute iron deficiency and functional iron deficiency.

RESULTS

Compared with ESAs, roxadustat significantly decreased hepcidin level (difference, - 20.09 ng/mL; 95% CI, - 30.26 to - 9.92), attenuated the increase in serum soluble transferrin receptor (sTFR) level (difference, - 7.87 nmol/L; 95% CI, - 12.11 to - 3.64), and reduced the proportion of patients with functional iron deficiency (roxadustat, 11.43%; ESA, 33.33%). There was no significant difference in safety of the two groups over the duration of the study.

CONCLUSIONS

Compared with ESA group, roxadustat group showed significant differences in all iron biomarker levels except serum ferritin (sFt) and transferrin saturation (TSAT). These results suggest that roxadustat was superior to ESAs as a therapy for iron metabolism in PD patients.

TRIAL REGISTRATION

This study completed Chinese Clinical Trial Registration on March 4, 2022 (registration number: ChiCTR2200057231).

Soluble Transferrin Receptor as Iron Deficiency Biomarker: Impact on Exercise Capacity in Heart Failure Patients

The soluble transferrin receptor (sTfR) is a marker of tissue iron status, which could indicate an increased iron demand at the tissue level. The impact of sTfR levels on functional capacity and quality of life (QoL) in non-anemic heart failure (HF) patients with otherwise normal systemic iron status has not been evaluated. We conducted an observational, prospective, cohort study of 1236 patients with chronic HF. We selected patients with normal hemoglobin levels and normal systemic iron status. Tissue iron deficiency (ID) was defined as levels of sTfR > 75th percentile (1.63 mg per L). The primary endpoints were the distance walked in the 6 min walking test (6MWT) and the overall summary score (OSS) of the Minnesota Living with Heart Failure Questionnaire (MLHFQ). The final study cohort consisted of 215 patients. Overall QoL was significantly worse (51 ± 27 vs. 39 ± 20, p-value = 0.006, respectively), and the 6 MWT distance was significantly worse in patients with tissue ID when compared to patients without tissue ID (206 ± 179 m vs. 314 ± 155, p-value < 0.0001, respectively). Higher sTfR levels, indicating increased iron demand, were associated with a shorter distance in the 6 MWT (standardized β = -0.249, p < 0.001) and a higher MLHFQ OSS (standardized β = 0.183, p-value = 0.008). In this study, we show that in patients with normal systemic iron parameters, higher levels of sTfR are strongly associated with an impaired submaximal exercise capacity and with worse QoL.

Iron Deficiency Might Impair the Recovery of Left Ventricular Function after Surgical Revascularization in Diabetic Patients: A Retrospective Study

Background

Iron deficiency (ID) is one of the most common micronutrient deficiencies affecting public health. Studies show that ID affects the prognosis of patients with heart disease, including heart failure, coronary artery disease and myocardial infarction. However, there is limited information regarding the impact of ID on patients undergoing cardiac surgery. This study aimed to evaluate the influence of preoperative ID on the prognosis of type 2 diabetes mellitus (T2DM) patients undergoing coronary artery bypass grafting (CABG).

Methods

In the Glycemic control using mobile-based intervention in patients with diabetes undergoing coronary artery bypass to promote self-management (GUIDEME) study, patients with T2DM undergoing CABG were prospectively recruited. In this study, only those patients with preoperative iron metabolism results were enrolled. Patients were grouped based on the presence of preoperative ID. The primary endpoint was defined as the significant improvement of follow-up ejection fraction (EF) compared to postoperative levels (classified according to the 75th percentile of the change, and defined as an improvement of greater than or equal to 5%). Univariable logistic regression was performed to explore the potential confounders, followed by multiple adjustment.

Results

A total of 302 patients were enrolled. No deaths were observed during the study period. A higher incidence of the primary endpoint was observed in the ID group (25.4% vs 12.9%, p = 0.015). The postoperative and follow-up EF were similar beween the two groups. In the regression analysis, ID was noticed to be a strong predictor against the significant improvement of EF in both univariable (odds ratio [OR]: 0.44, 95% confidence interval [CI]: 0.22-0.86, p = 0.017) and multivariable (OR: 0.43, 95% CI: 0.24-0.98, p = 0.043) logistic regression. In the subgroup analysis, ID was a predictor of significant improvement of EF in age ≤ 60 years, male, EF ≤ 60%, and on-pump CABG patients.

Conclusions

In T2DM patients undergoing CABG, ID might negatively affect the early recovery of left ventricular systolic function in terms of recovery of EF 3-6 months after surgery, especially in patients age ≤ 60 years, males, EF ≤ 60% and in those undergoing on-pump CABG.

Iron deficiency and cardiovascular disease

Iron deficiency (ID) is common in patients with cardiovascular disease. Up to 60% of patients with coronary artery disease, and an even higher proportion of those with heart failure (HF) or pulmonary hypertension have ID; the evidence for cerebrovascular disease, aortic stenosis and atrial fibrillation is less robust. The prevalence of ID increases with the severity of cardiac and renal dysfunction and is probably more common amongst women. Insufficient dietary iron, reduced iron absorption due to increases in hepcidin secondary to the low-grade inflammation associated with atherosclerosis and congestion or reduced gastric acidity, and increased blood loss due to anti-thrombotic therapy or gastro-intestinal or renal disease may all cause ID. For older people in the general population and patients with HF with reduced ejection fraction (HFrEF), both anaemia and ID are associated with a poor prognosis; each may confer independent risk. There is growing evidence that ID is an important therapeutic target for patients with HFrEF, even if they do not have anaemia. Whether this is also true for other HF phenotypes or patients with cardiovascular disease in general is currently unknown. Randomized trials showed that intravenous ferric carboxymaltose improved symptoms, health-related quality of life and exercise capacity and reduced hospitalizations for worsening HF in patients with HFrEF and mildly reduced ejection fraction (<50%). Since ID is easy to treat and is effective for patients with HFrEF, such patients should be investigated for possible ID. This recommendation may extend to other populations in the light of evidence from future trials.

Iron metabolism and cardiovascular disease: Basic to translational purviews and therapeutical approach

Iron interactions with the cardiovascular system were proposed about half a century ago, yet a clear-cut understanding of this micronutrient and its intricacies with acute and chronic events is still lacking. In chronic heart failure, patients with decreased iron stores appear to benefit from intravenous administration of metallic formulations, whereas acute diseases (e.g., myocardial infarction, stroke) are barely studied in randomized controlled trials in humans. However, proof-of-concept studies have indicated that the dual redox characteristics of iron could be involved in atherosclerosis, necrosis, and ferroptosis. To this end, we sought to review the currently available body of literature pertaining to these temporal profiles of heart diseases, as well as the pathophysiologic mechanism by which iron enacts, underlining key points related to treatment options.

Association between soluble transferrin receptor and systolic hypertension in adults: National Health and Nutrition Examination Survey (2007-2010 and 2015-2018)

Background

Hypertension increases the global burden of disease and mortality. Iron metabolism is considered to be an important factor in hypertension. However, as an indicator of iron metabolism, little is known about the associations of soluble transferrin receptor (sTfR) with hypertension. We studied the relationship between sTfR and hypertension.

Materials and methods

We studied 7,416 adults aged 20 years old or above from the National Health and Nutrition Examination Survey (NHANES), a nationally representative, cross-sectional, population-based study. Weighted logistic regression was used to examine the association between markers of iron metabolism and hypertension. The restricted cubic spline (RCS) was used to characterize the association between sTfR and blood pressure.

Results

Weighted logistic regression showed that higher sTfR level was associated with higher odds of hypertension (OR = 1.05; 95% CI: 1.01-1.05; p = 0.001) after adjustment for all the potential confounding factors. Meanwhile, weighted logistic regression analyses indicated independent associations of high sTfR (p = 0.009) with systolic hypertension after adjusting for various different confounders. The result of restricted cubic splines showed a non-linear association between sTfR and systolic blood pressure among U.S. adults.

Conclusion

Soluble transferrin receptor was found to be an independent factor in systolic hypertension. And, a non-linear relationship between sTfR and systolic blood pressure was discovered.

Association between iron status and incident coronary artery disease: a population based-cohort study

Disorders of iron metabolism has been implicated in cardiovascular disease. However, the association of serum iron stores and coronary artery disease (CAD) remains inconsistent. Here, we investigated the associations of serum iron metabolism with the incidence of CAD, the severity of coronary artery stenosis, metabolic biomarkers, and the risk of major adverse cardiovascular event (MACE). A total of 643 CAD patients and 643 healthy controls were enrolled to assess the associations of serum iron status with the presence of CAD, the severity of CAD, and the risk of MACE. Serum iron metabolism and other metabolic markers were measured in all subjects. All statistical analyses were analyzed using SPSS22.0 software and STATA statistical package. Serum level of iron metabolism markers, including serum iron, unsaturated transferrin iron binding capacity (UIBC), Total iron binding capacity (TIBC) levels, in CAD groups was significantly lower than the control group (P < 0.001). UIBC and TIBC were negatively correlated with ferritin in both sexes. Each unit increase of serum iron and TIBC were found to have a protective role for CAD in women (iron: OR 0.794, 95% CI (0.647-0.973), TIBC: OR 0.891, 95% CI (0.795-0.999), P < 0.05). However, high ferritin level was significant associated the CAD incident in both sexes (OR 1.029, 95% CI (1.002-1.058) in men, OR 1.013, 95% CI (1.0-1.025) in women, P < 0.05). Serum iron metabolism markers exhibited no significant association with the severity of CAD. Increased serum level of iron and TIBC levels were found to have a protective role for CAD in women, but not in men. Elevated serum ferritin is independently and positively associated with CAD in men and women.

Soluble transferrin receptor can predict all-cause mortality regardless of anaemia and iron storage status

Despite interest in the clinical implications of soluble transferrin receptor (sTfR), previous studies on the association of sTfR with mortality in the general population are lacking. Therefore, we analysed the association between sTfR and all-cause mortality in the general United States adult population. We conducted a prospective cohort study using National Health and Nutrition Examination Survey data from 2003 to 2010. A total of 5403 premenopausal nonpregnant females were analysed in this study. The mean age was 34.2 years (range 20.0–49.9 years). Participants were divided into log(sTfR) tertiles. The primary outcome was all-cause mortality. The secondary outcome was chronic kidney disease (CKD) development (composite of estimated glomerular filtration rate < 60 ml/min/1.73 m² and/or random urine albumin-to-creatinine ratio ≥ 30 mg/g). During a median 8.7 years of follow-up, 103 (1.9%) participants died. Compared with the reference group (log(sTfR) 0.45–0.57), the highest tertile of log(sTfR) was associated with all-cause mortality (log(sTfR) > 0.57, hazard ratio [HR] 1.77 [95% CI 1.05–2.98]) in a multivariable hazards model including covariates such as haemoglobin and ferritin. Patients in the highest tertile of log(sTfR) also had an increased risk of CKD relative to those in the reference tertile. High sTfR was associated with all-cause mortality and CKD regardless of anaemia and iron storage status.

Short-term treatment of iron deficiency anemia after cardiac surgery

Iron deficiency anemia (IDA) is frequent after cardiac surgery and is associated with increased morbidity and mortality. In a retrospective study, we analyzed 106 patients with IDA (hemoglobin [Hb] ≤ 12 g/dl in women and ≤ 13 g/dl in men, transferrin saturation [TSAT] ≤ 20%) on admission to a Cardiac Rehabilitation Unit after cardiac surgery. The patients were divided into two groups, one was treated with oral sucrosomial iron (SI) and the other with intravenous ferric carboxymaltose (FCM). Patients received a single 1000 mg dose of FCM from the day after admission to rehabilitation (T1), or a 120 mg/day dose of SI from T1 until discharge (T2); after discharge, SI was reduced to 30 mg/day until the end of follow-up (T3). Hb was evaluated at T1, T2 and T3; the other hematological parameters at T1 and T3; natriuretic peptides at T1, T2 and T3; 6-minute walk test (6MWT) at T1 and T2. Folate, vitamin B12 and reticulocytes were sampled on admission. Folate deficiency was documented in 60.4% of patients. Hb increased in both groups with no significant differences between the two treatments (p = 0.397). The other iron metabolism parameters (sideremia, transferrin, TSAT) displayed similar behavior, showing a significant increase at T3 (p < 0.001) with both therapies, although the increase was faster with FCM. Ferritin - high on admission - decreased at T3 in the SI group and rose significantly in the FCM group (SI 219.5 vs. FCM 689 ng/ml p < 0.0001). The 6MWT increased significantly at T2, with an overlap between SI and FCM. In conclusion, the results of this study show that SI and FCM exhibit the same effectiveness on IDA; the response time to therapy of both treatments is also equally fast. SI and FCM induce a similar increase in functional capacity. The study shows that SI can be a viable alternative to FCM after cardiac surgery in terms of effectiveness and tolerability.

Transferrin predicts trimethylamine-N-oxide levels and is a potential biomarker of cardiovascular disease

INTRODUCTION

Trimethylamine-N-oxide (TMAO) is a circulating biomarker associated with cardiovascular disease (CVD). Production of TMAO is facilitated by gut microbiota and dependent on micronutrients such as choline, betaine, and L-carnitine, present in foods such as red meat and eggs.

HYPOTHESIS

We sought to predict serum TMAO quartile levels among healthy individuals at increased risk of CVD using clinical data via an ordinal logistic model.

METHODS

Data from participants (n = 127) enrolled in a longitudinal observational study on CVD were used to build a predictive model for TMAO using ordinal logistic regression with demographic variables and 40 other variables considered related to CVD risk. First, univariate models for each covariate were tested (with serum TMAO quartiles as the dependent variable), and only variables with P < 0.30 were evaluated further. Second, demographic variables (age, gender, white vs. non-white race) were included in a multivariable model with each previously identified independent variable controlling for potential confounding. Last, the final model included fixed demographics and candidates from the confounder-adjusted model with P < 0.10.

RESULTS

Eight candidate variables were included in the final model, with only transferrin, high-density lipoprotein cholesterol (HDL-C) and race (white vs. non-white) showing significant associations with TMAO. Participants had 0.16 (Q2), 0.31 (Q3), and 0.20 (Q4) odds of being in a higher TMAO quartile compared with participants in the lowest transferrin quartile. Non-white participants had 2.92 times higher odds of being in the highest TMAO quartile compared to white individuals. Participants in the second quartile of HDL-C had 2.68 times higher odds of being in a higher TMAO quartile compared with participants in the lowest HDL-C quartile.

CONCLUSIONS

Transferrin demonstrated a significant predictive association with TMAO and may represent a novel potential biomarker of increased CVD risk worthy of further study. These results warrant further examination of iron, metabolism, homeostasis, and gut microbiome to better understand and mitigate known increased CVD risk.

Increased Serum Soluble Transferrin Receptor Levels Were Associated With High Prevalence of Cardiovascular Diseases: Insights From the National Health and Nutrition Examination Survey 2017–2018

Background: Iron deficiency is common in cardiovascular diseases (CVD), e.g., heart failure and coronary heart disease. Soluble transferrin receptor (sTfR) is a promising marker representing unmet cellular iron demands. However, whether higher serum sTfR is associated with increased risk of CVDs needs further investigation.

Methods: In the present cross-sectional study, we analyzed data of 4,867 adult participants of the National Health and Nutrition Examination Survey (NHANES) 2017–2018. Linear regression models were employed to identify possible correlations between sTfR and other characteristics. The association between sTfR and CVDs was assessed with univariable and multivariable logistics regression models.

Results: The prevalence of CVDs was 9.5% among participants, and higher sTfR levels were found in participants with CVDs (p < 0.001). Linear regression models revealed positive associations between sTfR and age, body mass index, systolic blood pressure, glycated hemoglobulin A1c, and insulin resistance (all p < 0.001). In the multivariable logistics regression model, the adjusted odds ratio of sTfR for CVDs was 2.05 (per 1 log₂ mg/L, 95% confidence interval: 1.03∼4.05, p = 0.046). Further subgroup analysis identified the associations of sTfR and CVDs were only significant in participants ≥60 years old, or with hypertension (all p < 0.05).

Conclusion: Our study demonstrated that increased serum sTfR levels were associated with a high prevalence of cardiovascular diseases.

Relation of Iron Status to Prognosis After Acute Coronary Syndrome

Iron deficiency has been extensively researched and is associated with adverse outcomes in heart failure. However, to our knowledge, the temporal evolution of iron status has not been previously investigated in patients with acute coronary syndrome (ACS). Therefore, we aimed to explore the temporal pattern of repeatedly measured iron, ferritin, transferrin, and transferrin saturation (TSAT) in relation to prognosis post-ACS. BIOMArCS (BIOMarker study to identify the Acute risk of a Coronary Syndrome) is a prospective, multicenter, observational cohort study conducted in The Netherlands between 2008 and 2015. A total of 844 patients with post-ACS were enrolled and underwent high-frequency (median 17) blood sampling during 1 year follow-up. Biomarkers of iron status were measured batchwise in a central laboratory. We analyzed 3 patient subsets, including the case-cohort (n = 187). The primary endpoint (PE) was a composite of cardiovascular mortality and repeat nonfatal ACS, including unstable angina pectoris requiring revascularization. The association between iron status and the PE was analyzed using multivariable joint models. Mean age was 63 years; 78% were men, and >50% had iron deficiency at first sample in the case-cohort. After adjustment for a broad range of clinical variables, 1 SD decrease in log-iron was associated with a 2.2-fold greater risk of the PE (hazard ratio 2.19, 95% confidence interval 1.34 to 3.54, p = 0.002). Similarly, 1 SD decrease in log-TSAT was associated with a 78% increased risk of the PE (hazard ratio 1.78, 95% confidence interval 1.17 to 2.65, p = 0.006). Ferritin and transferrin were not associated with the PE. Repeated measurements of iron and TSAT predict risk of adverse outcomes in patients with post-ACS during 1 year follow-up. Trial Registration: The Netherlands Trial Register. Unique identifiers: NTR1698 and NTR1106. Registered at https://www.trialregister.nl/trial/1614 and https://www.trialregister.nl/trial/1073.

Triad role of hepcidin, ferroportin, and Nrf2 in cardiac iron metabolism: From health to disease

Iron is an essential trace element required for several vital physiological and developmental processes, including erythropoiesis, bone, and neuronal development. Iron metabolism and oxygen homeostasis are interlinked to perform a vital role in the functionality of the heart. The metabolic machinery of the heart utilizes almost 90 % of oxygen through the electron transport chain. To handle this tremendous level of oxygen, the iron metabolism in the heart is utmost crucial. Iron availability to the heart is therefore tightly regulated by (i) the hepcidin/ferroportin axis, which controls dietary iron absorption, storage, and recycling, and (ii) iron regulatory proteins 1 and 2 (IRP1/2) via hypoxia inducible factor 1 (HIF1) pathway. Despite iron being vital to the heart, recent investigations have demonstrated that iron imbalance is a common manifestation in conditions of heart failure (HF), since free iron readily transforms between Fe²⁺ and Fe³⁺via the Fenton reaction, leading to reactive oxygen species (ROS) production and oxidative damage. Therefore, to combat iron-mediated oxidative stress, targeting Nrf2/ARE antioxidant signaling is rational. The involvement of Nrf2 in regulating several genes engaged in heme synthesis, iron storage, and iron export is beginning to be uncovered. Consequently, it is possible that Nrf2/hepcidin/ferroportin might act as an epicenter connecting iron metabolism to redox alterations. However, the mechanism bridging the two remains obscure. In this review, we tried to summarize the contemporary insight of how cardiomyocytes regulate intracellular iron levels and discussed the mechanisms linking cardiac dysfunction with iron imbalance. Further, we emphasized the impact of Nrf2 on the interplay between systemic/cardiac iron control in the context of heart disease, particularly in myocardial ischemia and HF.

Anemia in Cardiovascular Disease: Marker of Disease Severity or Disease-modifying Therapeutic Target?

PURPOSE OF THE REVIEW

In this review paper, we examine the latest evidence regarding the use of iron supplementation, erythropoiesis-stimulating agents (ESAs), and blood transfusions as therapeutic targets for anemia to mitigate morbidity and mortality in patients with cardiovascular disease.

RECENT FINDINGS

Intravenous ferric carboxymaltose (FC) injections in heart failure (HF) have resulted in improved self-reported patient symptoms; higher exercise capacity, as measured by 6-min walk test distance in anemic patients; and lower re-hospitalization rates in iron deficient patients. Darbepoetin alfa has shown evidence of improved Kansas City Cardiomyopathy Questionnaire scores. No mortality benefits have been noted thus far with FC injections or darbepoetin in HF, with an increase in adverse events with darbepoetin. Aggressive transfusions (Hg < 10 g/dL) are not associated with improved outcomes in cardiovascular disease. Quality of life metrics, rather than mortality, appear to improve with IV FC and ESA use in HF. More studies are required to see if these treatments have a role in coronary artery disease. Current evidence suggests that anemia is a marker of underlying disease severity, with a limited role in disease modification. Further studies are required to solidify our understanding of this topic.

High soluble transferrin receptor in patients with heart failure: a measure of iron deficiency and a strong predictor of mortality

AIMS

Iron deficiency (ID) is frequent in heart failure (HF), linked with exercise intolerance and poor prognosis. Intravenous iron repletion improves clinical status in HF patients with left ventricular ejection fraction (LVEF) ≤45%. However, uncertainty exists about the accuracy of serum biomarkers in diagnosing ID. The aims of this study were (i) to identify the iron biomarker with the greatest accuracy for the diagnosis of ID in bone marrow in patients with ischaemic HF, and (ii) to establish the prevalence of ID using this biomarker and its prognostic value in HF patients.

METHODS AND RESULTS

Bone marrow was stained for iron in 30 patients with ischaemic HF with LVEF ≤45% and 10 healthy controls, and ID was diagnosed for 0-1 grades (Gale scale). A total of 791 patients with HF with LVEF ≤45% were prospectively followed up for 3 years. Serum ferritin, transferrin saturation, soluble transferrin receptor (sTfR) were assessed as iron biomarkers. Most patients with HF (n = 25, 83%) had ID in bone marrow, but none of the controls (P < 0.001). Serum sTfR had the best accuracy in predicting ID in bone marrow (area under the curve 0.920, 95% confidence interval 0.761-0.987, for cut-off 1.25 mg/L sensitivity 84%, specificity 100%). Serum sTfR was ≥1.25 mg/L in 47% of HF patients, in 56% and 46% of anaemics and non-anaemics, respectively (P < 0.05). The reclassification methods revealed that serum sTfR significantly added the prognostic value to the baseline prognostic model, and to the greater extent than plasma N-terminal pro B-type natriuretic peptide. Based on internal derivation and validation procedures, serum sTfR ≥1.41 mg/L was the optimal threshold for predicting 3-year mortality, independent of other established variables.

CONCLUSIONS

High serum sTfR accurately reflects depleted iron stores in bone marrow in patients with HF, and identifies those with a high 3-year mortality.

Iron Metabolism Contributes to Prognosis in Coronary Artery Disease: Prognostic Value of the Soluble Transferrin Receptor Within the AtheroGene Study

Background

Coronary heart disease is a leading cause of mortality worldwide. Iron deficiency, a frequent comorbidity of coronary heart disease, causes an increased expression of transferrin receptor and soluble transferrin receptor levels (sTfR) levels, while iron repletion returns sTfR levels to the normal physiological range. Recently, sTfR levels were proposed as a potential new marker of iron metabolism in cardiovascular diseases. Therefore, we aimed to evaluate the prognostic value of circulating sTfR levels in a large cohort of patients with coronary heart disease.

Methods and Results

The disease cohort comprised 3423 subjects who had angiographically documented coronary heart disease and who participated in the AtheroGene study. Serum levels of sTfR were determined at baseline using an automated immunoassay (Roche Cobas Integra 400). Two main outcomes were considered: a combined end point of myocardial infarction and cardiovascular death and cardiovascular death alone. During a median follow‐up of 4.0 years, 10.3% of the patients experienced an end point. In Cox regression analyses for sTfR levels, the hazard ratio (HR) for future cardiovascular death and/or myocardial infarction was 1.27 (95% CI, 1.11–1.44, P<0.001) after adjustment for sex and age. This association remained significant (HR, 1.23; 95% CI, 1.03–1.46, P=0.02) after additional adjustment for body mass index, smoking status, hypertension, diabetes mellitus, dyslipidemia, C‐reactive protein, and surrogates of cardiac function, size of myocardial necrosis (hs‐Tnl), and hemoglobin levels.

Conclusions

In this large cohort study, sTfR levels were strongly associated with future myocardial infarction and cardiovascular death. This implicates a role for sTfR in secondary cardiovascular risk prediction.