Regulation of hepcidin through GDF-15 in cancer-related anemia

Growth differentiation factor-15 serum concentrations reflect disease severity and anemia in patients with inflammatory bowel disease

BACKGROUND

Population of patients with inflammatory bowel disease (IBD) is burdened by various extraintestinal manifestations which substantially contribute to greater morbidity and mortality. Growth-differentiation factor-15 (GDF-15) is often over-expressed under stress conditions, such as inflammation, malignancies, heart failure, myocardial ischemia, and many others.

AIM

To explore the association between GDF-15 and IBD as serum concentrations of GDF-15 were shown to be an independent predictor of poor outcomes in multiple diseases. An additional aim was to determine possible associations between GDF-15 and multiple clinical, anthropometric and laboratory parameters in patients with IBD.

METHODS

This cross-sectional study included 90 adult patients diagnosed with IBD, encompassing both Crohn's disease (CD) and ulcerative colitis (UC), and 67 healthy age- and sex-matched controls. All patients underwent an extensive workup, including colonoscopy with subsequent histopathological analysis. Disease activity was assessed by two independent gastroenterology consultants specialized in IBD, employing well-established clinical and endoscopic scoring systems. GDF-15 serum concentrations were determined following an overnight fasting, using electrochemiluminescence immunoassay.

RESULTS

In patients with IBD, serum GDF-15 concentrations were significantly higher in comparison to the healthy controls [800 (512-1154) pg/mL vs 412 (407-424) pg/mL, P < 0.001], whereas no difference in GDF-15 was found between patients with CD and UC [807 (554-1451) pg/mL vs 790 (509-956) pg/mL, P = 0.324]. Moreover, multiple linear regression analysis showed that GDF-15 levels predict CD and UC severity independent of age, sex, and C-reactive protein levels (P = 0.016 and P = 0.049, respectively). Finally, an association between GDF-15 and indices of anemia was established. Specifically, negative correlations were found between GDF-15 and serum iron levels (r = -0.248, P = 0.021), as well as GDF-15 and hemoglobin (r = -0.351, P = 0.021). Accordingly, in comparison to IBD patients with normal hemoglobin levels, GDF-15 serum levels were higher in patients with anemia (1256 (502-2100) pg/mL vs 444 (412-795) pg/mL, P < 0.001).

CONCLUSION

For the first time, we demonstrated that serum concentrations of GDF-15 are elevated in patients with IBD in comparison to healthy controls, and the results imply that GDF-15 might be involved in IBD pathophysiology. Yet, it remains elusive whether GDF-15 could serve as a prognostic indicator in these patients.

Mitochondrial dysfunction decreases cisplatin sensitivity in gastric cancer cells through upregulation of integrated stress response and mitokine GDF15

Gastric neoplasm is a high-mortality cancer worldwide. Chemoresistance is the obstacle against gastric cancer treatment. Mitochondrial dysfunction has been observed to promote malignant progression. However, the underlying mechanism is still unclear. The mitokine growth differentiation factor 15 (GDF15) is a significant biomarker for mitochondrial disorder and is activated by the integrated stress response (ISR) pathway. The serum level of GDF15 was found to be correlated with the poor prognosis of gastric cancer patients. In this study, we found that high GDF15 protein expression might increase disease recurrence in adjuvant chemotherapy-treated gastric cancer patients. Moreover, treatment with mitochondrial inhibitors, especially oligomycin (a complex V inhibitor) and salubrinal (an ISR activator), respectively, was found to upregulate GDF15 and enhance cisplatin insensitivity of human gastric cancer cells. Mechanistically, it was found that the activating transcription factor 4-C/EBP homologous protein pathway has a crucial function in the heightened manifestation of GDF15. In addition, reactive oxygen species-activated general control nonderepressible 2 mediates the oligomycin-induced ISR, and upregulates GDF15. The GDF15-glial cell-derived neurotrophic factor family receptor a-like-ISR-cystine/glutamate transporter-enhanced glutathione production was found to be involved in cisplatin resistance. These results suggest that mitochondrial dysfunction might enhance cisplatin insensitivity through GDF15 upregulation, and targeting mitokine GDF15-ISR regulation might be a strategy against cisplatin resistance of gastric cancer.

Low Serum Hepcidin Levels in Patients with Ulcerative Colitis - Implications for Treatment of Co-existent Iron-Deficiency Anemia

Ulcerative colitis (UC) is often associated with anemia. Hepcidin, the central regulator of iron homeostasis, is known to be induced by inflammation and suppressed by anemia. It is not clear how hepcidin is affected in those with UC, when both inflammation and anemia may co-exist.Such knowledge may hold implications for treatment. Hematological and iron-related parameters, C-reactive protein (CRP), growth differentiation factor 15 (GDF-15) and erythroferrone (ERFE) (erythroid regulators of hepcidin) levels were estimated in blood from those with UC and in control subjects. Values for hematological and iron-related parameters showed evidence of iron-deficiency and resultant anemia, in patients with UC. The presence of UC was significantly associated with inflammation. Serum levels of ERFE, but not of GDF-15, were significantly higher in patients with UC than in control patients, while hepcidin levels were significantly lower. Serum hepcidin concentrations in patients with UC correlated positively with serum iron, ferritin and GDF-15, and negatively with serum ERFE. The iron status and serum hepcidin levels in UC patients with co-existent anemia were significantly lower and serum ERFE values significantly higher than in those with UC without anemia. The effect of anemia on hepcidin predominated over that of inflammation in patients with UC, resulting in suppressed hepcidin levels. This effect is possibly mediated through erythroferrone. We suggest that a serum hepcidin-guided approach may be useful to guide use of oral iron supplements to treat co-existent iron-deficiency anemia in patients with UC and other chronic inflammatory diseases.

Role of growth differentiation factor 15 in cancer cachexia (Review)

Growth differentiation factor 15 (GDF15), a member of the transforming growth factor-β family, is a stress-induced cytokine. Under normal circumstances, the expression of GDF15 is low in most tissues. It is highly expressed during tissue injury, inflammation, oxidative stress and cancer. GDF15 has been established as a biomarker in patients with cancer, and is associated with cancer cachexia (CC) and poor survival. CC is a multifactorial metabolic disorder characterized by severe muscle and adipose tissue atrophy, loss of appetite, anemia and bone loss. Cachexia leads to reductions in quality of life and tolerance to anticancer therapy, and results in a poor prognosis in cancer patients. Dysregulated GDF15 levels have been discovered in patients with CC and animal models, where they have been found to be involved in anorexia and weight loss. Although studies have suggested that GDF15 mediates anorexia and weight loss in CC through its neuroreceptor, glial cell-lineage neurotrophic factor family receptor α-like, the effects of GDF15 on CC and the potential regulatory mechanisms require further elucidation. In the present review, the characteristics of GDF15 and its roles and molecular mechanisms in CC are elaborated. The targeting of GDF15 as a potential therapeutic strategy for CC is also discussed.

Synergistic immunotherapy targeting cancer-associated anemia: prospects of a combination strategy

Cancer-associated anemia promotes tumor progression, leads to poor quality of life in patients with cancer, and even obstructs the efficacy of immune checkpoint inhibitors therapy. However, the precise mechanism for cancer-associated anemia remains unknown and the feasible strategy to target cancer-associated anemia synergizing immunotherapy needs to be clarified. Here, we review the possible mechanisms of cancer-induced anemia regarding decreased erythropoiesis and increased erythrocyte destruction, and cancer treatment-induced anemia. Moreover, we summarize the current paradigm for cancer-associated anemia treatment. Finally, we propose some prospective paradigms to slow down cancer-associated anemia and synergistic the efficacy of immunotherapy. Video Abstract.

Growth differentiation factor 15 as an emerging novel biomarker in SARS-CoV-2 infection

BACKGROUND

Growth differentiation factor (GDF)-15 is a member of a transforming growth factor-β cytokine superfamily that regulates metabolism and is released in response to inflammation, hypoxia and tissue injury. It has evolved as one of the most potent cytokines for predicting the severity of infections and inflammatory conditions, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

AIM

To investigate the utility of GDF-15 in predicting the severity of SARS-CoV-2 infection.

METHODS

PubMed, Reference Citation Analysis, CNKI, and Goggle Scholar were explored by using related MeSH keywords and data such as the first author’s name, study duration, type and place of study, sample size and subgroups of participants if any, serum/plasma GDF- 15 level in pg/mL, area under the curve and cut-off value in receiver operating characteristic analysis, method of measurement of GDF-15, and the main conclusion were extracted.

RESULTS

In all studies, the baseline GDF-15 level was elevated in SARS-CoV-2-infected patients, and it was significantly associated with severity, hypoxemia, viral load, and worse clinical consequences. In addition, GDF-15 levels were correlated with C-reactive protein, D-dimer, ferritin and procalcitonin, and it had superior discriminatory ability to detect severity and in-hospital mortality of SARS-CoV-2 infection. Hence, GDF-15 might be used to predict the severity and prognosis of hospitalized patients with SARS-CoV-2.

CONCLUSION

Serial estimation of GDF-15 levels in hospitalized patients with SARS-CoV-2 infection appeared to have useful prognostic value and GDF-15 can be considered a clinically prominent sepsis biomarker for SARS-CoV-2 infection.

Growth Differentiation Factor 15 Regulates Oxidative Stress-Dependent Ferroptosis Post Spinal Cord Injury by Stabilizing the p62-Keap1-Nrf2 Signaling Pathway

Background

Spinal cord injury (SCI) is a severe traumatic disorder of the central nervous system (CNS) that causes irreversible damage to the nervous tissue. The consequent hemorrhage contributed by trauma induces neuronal ferroptosis post SCI, which is an important death mode to mediate neuronal loss. Growth differentiation factor 15 (GDF15) is a cytokine that regulates cell proliferation, differentiation, and death. However, the specific role of GDF15 in neuronal ferroptosis post SCI remains unknown.

Materials and Methods

Neuronal ferroptosis in vitro was measured by detection of lipid peroxidation, glutathione, iron content, and reactive oxidative stress. In vivo, western blotting and immunofluorescence (IF) staining was utilized to measure ferroptosis post SCI. IF staining, TUNEL staining, hematoxylin-eosin staining, and Nissl staining were used to measure neurological damage. Finally, locomotor function recovery was analyzed using the Basso Mouse Scale and Louisville Swim Scale.

Results

GDF15 was significantly increased in neuronal ferroptosis and silencing GDF15 aggravated ferroptosis both in vitro and in vivo. Besides, GDF15-mediated inhibition of neuronal ferroptosis is through p62-dependent Keap1-Nrf2 pathway. In SCI mice, knockdown of GDF15 significantly exacerbated neuronal death, interfered with axon regeneration and remyelination, aggravated ferroptosis-mediated neuroinflammation, and restrained locomotor recovery.

Conclusion

GDF15 effectively alleviated neuronal ferroptosis post SCI via the p62-Keap1-Nrf2 signaling pathway and promoted locomotor recovery of SCI mice, which is suggested as a potential target on SCI pathogenesis and treatment.

Targeting Stress Erythropoiesis Pathways in Cancer

Cancer-related anemia (CRA) is a common multifactorial disorder that adversely affects the quality of life and overall prognosis in patients with cancer. Safety concerns associated with the most common CRA treatment options, including intravenous iron therapy and erythropoietic-stimulating agents, have often resulted in no or suboptimal anemia management for many cancer patients. Chronic anemia creates a vital need to restore normal erythropoietic output and therefore activates the mechanisms of stress erythropoiesis (SE). A growing body of evidence demonstrates that bone morphogenetic protein 4 (BMP4) signaling, along with glucocorticoids, erythropoietin, stem cell factor, growth differentiation factor 15 (GDF15) and hypoxia-inducible factors, plays a pivotal role in SE. Nevertheless, a chronic state of SE may lead to ineffective erythropoiesis, characterized by the expansion of erythroid progenitor pool, that largely fails to differentiate and give rise to mature red blood cells, further aggravating CRA. In this review, we summarize the current state of knowledge on the emerging roles for stress erythroid progenitors and activated SE pathways in tumor progression, highlighting the urgent need to suppress ineffective erythropoiesis in cancer patients and develop an optimal treatment strategy as well as a personalized approach to CRA management.

Coping With Stress: The Mitokine GDF-15 as a Biomarker of COVID-19 Severity

Growth differentiation factor 15 (GDF-15) is a transforming growth factor (TGF)-β superfamily cytokine that plays a central role in metabolism regulation. Produced in response to mitochondrial stress, tissue damage or hypoxia, this cytokine has emerged as one of the strongest predictors of disease severity during inflammatory conditions, cancers and infections. Reports suggest that GDF-15 plays a tissue protective role via sympathetic and metabolic adaptation in the context of mitochondrial damage, although the exact mechanisms involved remain uncertain. In this review, we discuss the emergence of GDF-15 as a distinctive marker of viral infection severity, especially in the context of COVID-19. We will critically review the role of GDF-15 as an inflammation-induced mediator of disease tolerance, through metabolic and immune reprogramming. Finally, we discuss potential mechanisms of GDF-15 elevation during COVID-19 cytokine storm and its limitations. Altogether, this cytokine seems to be involved in disease tolerance to viral infections including SARS-CoV-2, paving the way for novel therapeutic interventions.

Activation of STAT and SMAD Signaling Induces Hepcidin Re-Expression as a Therapeutic Target for β-Thalassemia Patients

Iron homeostasis is regulated by hepcidin, a hepatic hormone that controls dietary iron absorption and plasma iron concentration. Hepcidin binds to the only known iron export protein, ferroportin (FPN), which regulates its expression. The major factors that implicate hepcidin regulation include iron stores, hypoxia, inflammation, and erythropoiesis. When erythropoietic activity is suppressed, hepcidin expression is hampered, leading to deficiency, thus causing an iron overload in iron-loading anemia, such as β-thalassemia. Iron overload is the principal cause of mortality and morbidity in β-thalassemia patients with or without blood transfusion dependence. In the case of thalassemia major, the primary cause of iron overload is blood transfusion. In contrast, iron overload is attributed to hepcidin deficiency and hyperabsorption of dietary iron in non-transfusion thalassemia. Beta-thalassemia patients showed marked hepcidin suppression, anemia, iron overload, and ineffective erythropoiesis (IE). Recent molecular research has prompted the discovery of new diagnostic markers and therapeutic targets for several diseases, including β-thalassemia. In this review, signal transducers and activators of transcription (STAT) and SMAD (structurally similar to the small mothers against decapentaplegic in Drosophila) pathways and their effects on hepcidin expression have been discussed as a therapeutic target for β-thalassemia patients. Therefore, re-expression of hepcidin could be a therapeutic target in the management of thalassemia patients. Data from 65 relevant published experimental articles on hepcidin and β-thalassemia between January 2016 and May 2021 were retrieved by using PubMed and Google Scholar search engines. Published articles in any language other than English, review articles, books, or book chapters were excluded.

Growth differentiation factor-15 and lactoferrin immuno-expression in breast cancer: relationship with body iron-status and survival outcome

We aimed to evaluate the expression of growth differentiation factor-15 (GDF-15) and lactoferrin (Lf) in tumor and their relationship with the body iron-status and overall survival (OS) outcome of patients with breast cancer. A retrospective cohort study of female patients with primary breast cancer was performed. Clinical tumor samples from the Second Affiliated Hospital of Soochow University between December 2008 and June 2014 were collected. The immuno-expression of GDF-15 and Lf was stratified into positive or negative expression. Kaplan-Meier method and Cox proportional hazards regression model were used for data analysis. 74 breast cancer patients with a mean age of 52 years were included into our study. 14 (18.9%) patients were died by the end of August 1, 2019. The serum iron level of patients with GDF-15 (+)/Lf(-) expression was higher than that of patients with other expression patterns (18.2 ± 5.4 vs. 15.5 ± 5.0 μmol/L, P = 0.038), but was not associated with OS. In univariate Cox analyses, GDF-15(+) and GDF-15(+)/Lf(-) were significantly correlated with high mortality risk (HR = 3.75, 95%CI 1.05-13.48, P = 0.025; HR = 5.00, 95%CI 1.56-16.04, P = 0.004, respectively). After adjusted for age, menopause status and primary tumor grade, the association between GDF-15 and OS disappeared. However, the association between GDF-15/Lf and OS still existed in GDF-15(+)/Lf(-) (HR = 4.50, 95%CI 1.31-15.51, P = 0.017). The combined immuno-expression pattern of GDF-15 and Lf was significant associated with high serum iron level. GDF-15/Lf could be a powerful biomarker to predict survival outcome of patients with breast cancer but still needed to be confirmed by future studies.

Serum Concentration of Hepcidin as an Indicator of Iron Reserves in Children

Background

Anemia represents a significant cause of maternal and perinatal mortality, as well as child mortality. The aim of the research was to determine the serum concentration of hepcidin in children aged 6 months to 2 years and adolescents aged 11 to 19 years which suffer from iron deficiency anemia and compare it with the serum concentration of hepcidin in the control groups, as well as to determine its connection with the parameters of the iron metabolism.

Methods

The research included 173 examinees, 89 of them suffered from iron deficiency anemia and 84 did not suffer from iron deficiency anemia (the latter represented the control group). Blood samples were collected from all study participants. The samples were analyzed for complete blood count and parameters of iron metabolism. ELISA method was used for establishing serum hepcidin levels.

Results

The research showed that the concentration of hepcidin is statistically lower in children (4.4 ng/mL) and adolescents (4.1 ng/mL) who suffer from iron deficiency anemia in comparison with the control group (14 ng/mL, 10 ng/mL, respectively). The positive correlation between serum hepcidin level and iron in the serum, ferritin, the mean corpuscular volume and transferrin saturation was confirmed, but the negative one occurred in serum hepcidin level, transferrin and reticulocytes.

Conclusions

The age of the examinees does not influence the level of serum hepcidin which makes it a more sensitive indicator of the level of iron in the body. Besides this, serum hepcidin is a reliable biological marker for the assessment of iron deficiency anemia.

Hepcidin: Homeostasis and Diseases Related to Iron Metabolism

Iron is an essential metal for cell survival that is regulated by the peptide hormone hepcidin. However, its influence on certain diseases is directly related to iron metabolism or secondary to underlying diseases. Genetic alterations influence the serum hepcidin concentration, which can lead to an iron overload in tissues, as observed in haemochromatosis, in which serum hepcidin or defective hepcidin synthesis is observed. Another genetic imbalance of iron is iron-refractory anaemia, in which serum concentrations of hepcidin are increased, precluding the flow and efflux of extra- and intracellular iron. During the pathogenesis of certain diseases, the resulting oxidative stress, as well as the increase in inflammatory cytokines, influences the transcription of the HAMP gene to generate a secondary anaemia due to the increase in the serum concentration of hepcidin. To date, there is no available drug to inhibit or enhance hepcidin transcription, mostly due to the cytotoxicity described in the in vitro models. The proposed therapeutic targets are still in the early stages of clinical trials. Some candidates are promising, such as heparin derivatives and minihepcidins. This review describes the main pathways of systemic and genetic regulation of hepcidin, as well as its influence on the disorders related to iron metabolism.

Anaemia of Chronic Disease: An In-Depth Review

Anaemia is the most common haematological disorder affecting humanity and is usually observed in chronic disease states such as non-specific anaemia, which may cause diagnostic difficulties. In chronically ill patients with anaemia, this has a negative impact on quality of life as well as survival. This paper aims at reviewing the pathogenesis of this form of anaemia with a view to suggesting future targets for therapeutic intervention. The ability to diagnose this disorder depends on the ability of the physician to correlate the possible clinical pathways of the underlying disease with the patients' ferrokinetic state. It is important to rule out iron deficiency and other causes of anaemia as misdiagnosis will in most cases lead to refractoriness to standard therapy. The cytokines and acute-phase proteins play important roles in the pathogenesis of anaemia of chronic disease. Alterations in the metabolism of iron via the molecule hepcidin and ferritin are largely responsible for the consequent anaemia. Concomitant iron deficiency might be present and could affect the diagnosis and therapeutic protocol. Treatment options involve the use of erythropoiesis-stimulating agents, blood transfusion, and iron supplementation, in addition to treating the underlying disease.

GDF-15 and Hepcidin Levels in Nonanemic Patients with Impaired Glucose Tolerance

Aims. Growth Differentiation Factor-15 (GDF-15) has been suggested as one of the regulators of hepcidin, an important regulatory peptide for iron deposition. Current data is conflicting about the relationship between hepcidin and disorders of glucose metabolism. We aimed to investigate serum hepcidin and GDF-15 concentrations and their associations with each other, in nonanemic subjects with impaired glucose tolerance (IGT) in comparison with the nonanemic subjects with normal glucose tolerance (NGT). Methods. Thirty-seven subjects with IGT and 32 control subjects with NGT, who were age-, gender-, and body mass index- (BMI-) matched, were included in the study. Results. Serum GDF-15 levels were significantly higher in IGT compared to NGT. There were no differences in hepcidin, interleukin-6, and high sensitive C-reactive protein levels between the groups. We found a positive correlation between GDF-15 and hepcidin levels. There were also positive correlations between GDF-15 and age, uric acid, creatinine, and area under the curve for glucose (AUC-G). Hepcidin was correlated positively with ferritin levels. In the multiple regression analysis, GDF-15 concentrations were independently associated with age, uric acid, and AUC-G. Conclusions. Impaired glucose tolerance is associated with increased GDF-15 levels even in the absence of anemia, but the levels of hepcidin are not significantly altered in prediabetic state.

Modulation of hepcidin to treat iron deregulation: potential clinical applications

The secreted peptide hormone hepcidin regulates systemic and local iron homeostasis through degradation of the iron exporter ferroportin. Dysregulation of hepcidin leads to altered iron homeostasis and development of pathological disorders including hemochromatosis, and iron loading and iron restrictive anemias. Therapeutic modulation of hepcidin is a promising method to ameliorate these conditions. Several approaches have been taken to enhance or reduce the effects of hepcidin in vitro and in vivo. Based on these approaches, hepcidin modulating drugs have been developed and are undergoing clinical evaluation. In this article we review the rationale for development of these drugs, the data concerning their safety and efficacy, their therapeutic uses, and potential future prospects.

Relationship between hepcidin and GDF15 in anemic patients with type 2 diabetes without overt renal impairment

AIMS

Despite the absence of overt renal impairment and decreased erythropoietin (EPO) levels, patients are usually anemic. Hepcidin, which is induced by inflammatory stimuli, plays an important role in anemia in chronic disease. Growth differentiation factor 15 (GDF15) is a putative anti-inflammatory cytokine that is elevated in type 2 diabetes (T2DM). Hence, we investigated the relationship between hepcidin and GDF15 in anemic T2DM patients without overt renal impairment.

METHODS

Among 1150 patients who visited Kyungpook National University Hospital for T2DM between June 2006 and June 2014, we selected 55 anemic patients without overt renal impairment (serum creatinine <1.5 mg/dL or estimated glomerular filtration rate >60 mL/min/1.73 m(2)) and other co-morbid diseases, including malignancy, thyroid disease, rheumatic arthritis, liver disease, iron-deficiency anemia and other endocrine disease. We measured anthropometric and metabolic parameters, as well as measured the serum iron, ferritin, interleukin-6 (IL-6), erythropoietin, hepcidin-25 and GDF15 levels.

RESULTS

Anemic T2DM patients without overt renal impairment presented a greater inflammatory state, with increased serum hsCRP, ESR and IL-6 levels compared with non-anemic T2DM patients. Both hepcidin and GDF15 levels were increased and showed a positive correlation in anemic T2DM patients.

CONCLUSION

In the absence of overt renal impairment, anemia in T2DM is associated with chronic inflammation, inducing elevation of hepcidin and GDF15 levels independently of the erythropoietin level.

Can Serum Gdf-15 be Associated with Functional Iron Deficiency in Hemodialysis Patients?

Functional iron deficiency (FID) incidence is gradually increasing in hemodialysis (HD) patients. Recently, high levels of GDF-15 supressed the iron regulatory protein hepcidin and GDF-15 expression increased in iron-deficient patients. The relationship between FID, GDF-15, and hepcidin is currently unknown. The present study aimed to evaluate the association between GDF-15, hepcidin, and FID in chronic HD patients. Serum GDF-15 and hepcidin concentrations were measured in 105 HD patients and 40 controls. FID is defined as serum ferritin >800 ng/mL, TSAT <25 %, Hb levels <11 g/dL, and reticulocyte haemoglobin content (CHr) <29 pg. Serum GDF-15 and hepcidin levels were increased significantly in HD patients with FID, compared to HD patients without anemia and controls. GDF-15 correlated with ferritin, hepcidin, and CRP in the entire cohort. GDF-15 was related to ferritin and CRP in HD patients with FID. GDF-15 is better diagnostic marker than hepcidin for detection of FID [AUC = 0.982 (0.013) versus AUC = 0.921 (0.027); P = 0.0324]. GDF-15 appears to be a promising tool for detection of FID. High levels of ferritin and CRP correlated with GDF-15. Our results support GDF-15 as a new mediator of FID via hepcidin, chronic inflammation, or unknown pathways.