Abstract
Growth differentiation factor 15 (GDF15) is a member of the TGF-beta superfamily of cytokines previously found to suppress hepcidin in primary human hepatocytes. GDF15 is secreted from human erythroblasts, and extremely high serum levels are present in β-thalassemia patients (Tanno et al., Nat. Med. 2007, 13, 1096–1101). To determine if elevated GDF15 levels are unique for thalassemia or more generally associated with iron-loading related to ineffective erythropoiesis, we determined the GDF15 levels, as well as, serum hepcidin (Swinkels DW et al, PLoS ONE PLoS ONE. 2008;3:e2706), ferritin, erythropoietin (EPO) and soluble transferrin receptor (sTfR) in patients with the congenital dyserythropoietic anemia type I (CDA I). Seventeen Israeli Bedouins with CDA I were studied, all homozygous for the founder R1040W mutation in the CDAN1 gene. All of the patients studied were young adults with a mean age of 29 years. Two patients previously underwent splenectomy, and one patient is currently transfusion-dependent. For comparison, ten healthy volunteers (HV) were studied. The mean level of GDF15 in CDA I patients was significantly elevated [10,239 ± 3,049 pg/ml (range 5,530–17,008) compared to 269 ± 238 pg/ml in healthy controls; p = 1.5×10−10]. Consistent with a previous study of dyserythropoietic anemia patients, significantly higher levels of soluble transferrin receptor were detected among the CDA I population (sTfR; CDA I, 86.4 ± 14.0 nmol/L; HV, 21.4 ± 6.2 nmol/L, p = 7.4×10−15). Serum EPO levels were also elevated (EPO; CDA I, 118 ± 59 IU/dL; HV, 2.0 ± 1.5 IU/dL, p = 2.3×10−7). For iron analyses, three patients with extensive transfusion histories were excluded. Among the remaining 14 patients, iron overload was demonstrated by elevated serum ferritin (CDA I, 916 ± 507 ng/ml; HV, 72 ± 60 ng/ml, p = 1.4×10−5). Despite the significant elevation in iron stores, significantly elevated levels of hepcidin 25 (Hep25) were not detected in the CDA I patients. Instead, a minor decrease in serum Hep25 levels were detected (Hep25; CDA I, 3.3 ± 2.8 nM; HV, 4.1 ± 3.0 nM, p = 0.27). Correlation analyses were performed between the iron parameters (Ferritin and Hep25) and GDF15, sTfR, or EPO levels. Only GDF15 demonstrated a significant positive correlation with ferritin and significant inverse correlations with Hep25 and the Hep25/Ferritin ratio. Weaker correlations with EPO were identified. Unexpectedly, the correlation trends for sTfR were opposite those of GDF15 in this group. These results demonstrate that GDF15 is immensely over-expressed in CDA I, and further suggest this cytokine contributes to hepcidin dysregulation and secondary hemochromatosis in humans with ineffective erythropoiesis.
Clinical and Tumor Characteristics of Patients with High Serum Levels of Growth Differentiation Factor 15 in Advanced Pancreatic Cancer