Erythroid Growth Differentiation Factor 15 and Ferroportin Expression During Gestational Iron Deficiency Anemia

Abstract 5286

Iron homeostasis during pregnancy is modulated to meet the increased iron needs but how this is achieved is not very clear. Growth Differentiation Factor (GDF15) produced by the expanded erythroid compartment in β thalassemia has been shown to increase iron absorption by suppressing hepcidin. GDF15 is also highly expressed in the placenta and increasing levels of GDF15 are seen with advancing gestational age of pregnancy. But the role of GDF15 in iron homeostasis in pregnancy has not been elucidated till date. Ferroportin (FPN) is the only known protein involved in iron export and it is the target of hepcidin, the central regulator of iron homeostasis. In this study we analyzed the expression of GDF15 and FPN in pregnant women with iron deficiency anemia.

Fourteen pregnant women with proven iron deficiency anemia (IDAP) [Hb<11g/dL and Ferritin <12ng/ul] and thirteen healthy subjects as controls (NC) were enrolled as part of an ongoing study. Serum GDF15 and hepcidin levels were measured by ELISA kits from R&D systems and Bachem, UK respectively. Reticulocytes were isolated and total RNA was purified using Trizol. GDF15 and FPN transcripts were quantified using Taqman Gene expression assays using GAPDH as an internal control. Gene expression values were calculated on the basis of the 2-^ΔΔCt method.

The mean age of the pregnant women was 22.5±2.5 years. The median ferritin in IDAP was 1.4 and ranged from 0.2 to 8.3 ng/ml. The hepcidin levels were very low [<2ng/ml] in IDAP. Serum GDF15 levels in IDAP was significantly higher as compared to controls [IDAP-3333.71±409 pg/ml vs. NC-309.7±127.0 pg/ml; p=0.000]. Reticulocyte GDF15 mRNA expression was significantly lower [IDAP-25.09 (1.28–239.8) vs. NC-910.4 (0.28–1962); p=0.004] and FPN expression was significantly higher in pregnancy [IDAP-209.8 (48.33–1201) vs. NC-77.96(17.21–281.3); p=0.001] than in the controls. GDF15 mRNA as well as serum GDF15 levels significantly correlated with FPN expression in IDAP [RNA r=0.895; p=0.000; Protein r=0.555, p=0.049] Eight patients were followed up after 8 weeks of supplementation and there was no significant change in the serum GDF15 concentration (3235±468.26pg/ml; p=1.000). However their serum ferritin and hepcidin levels were significantly higher [Ferritin-11.60 (9.80–21.30), p=0.0021; Hepcidin-17.86(0.29–38.50), p=0.015]. There was no significant correlation between GDF15 protein levels and hepcidin (r=0.429, p=0.354).

Molecular mechanisms of iron homeostasis in pregnancy are poorly understood. IDAP had very low hepcidin levels which normalized after iron stores were replenished. Elevated GDF15 protein levels in IDAP inspite of low reticulocyte expression indicate that erythroid contribution is minimal and placenta is the main source of GDF15. The significant correlation between GDF15 (mRNA and protein) with FPN expression and absence of correlation with hepcidin levels indicate a possible role for GDF15 in iron homeostasis in pregnancy. These findings has to be validated and the role of GDF15 in modulating FPN and there by iron absorption has to be further elucidated.