INTRODUCTION

Pro-hepcidin, synthesized primarily in hepatocytes is the pro-hormone of hepcidin which demonstrates antimicrobial activity and is the main regulator of iron homeo-
stasis. There are at least three major and distinct pathways of regulation of hepcidin: regulation by inflammation, dependent on IL-6, regulation by iron, dependent on some other factor, perhaps transferin saturation; and suppression of hepcidin production during hypoxia and anaemia. (1-4). Hepcidin binds to ferroportin and stimulates its proteolitic degradation. This resulted in reduction of iron absorption in the bowels and iron release from macrophages and liver. Ferroportin is also necessary for iron transfer in materno-faetal unit. In high concentration of hepcidin the supply of iron to erythropoesis becomes limited. Hepcidin concentration in serum would be expected to change in response to iron level. Iron deficiency during normal pregnancy, most apparent at 30-34 weeks of gestation, is a result of increase in intravascular volume compared to erythrocyte mass and is not related to haemoglobin values which remain within the physiological range. Limited data are available on link between hepcidin and iron status in pregnant women. In our previous studies we have shown that serum pro-hepcidin is not significantly changed during pregnancy but determination of this protein could be useful in the diagnosis of some pathological conditions. Studies in complicated pregnancies are not available. Premature rupture of membranes (PROM) and pregnancy induced hypertension (PIH) lead to 85% of obstetric complications and to 10% of premature delivery. In both pathologies iron metabolic imbalance could be observed (5-7). Preterm PROM is associated with low maternal haemoglobin and high levels of serum iron and ferritin. Elevated serum iron and concentration of ferritin were observed in PIH. Released iron species in preeclampsia and PROM may contribute to endothelial cell injury by decreasing antioxidant system and promotion of oxidative stress (7).

Therefore the aim of this study was the estimation of the serum pro-hepcidin concentrations in uncomplicated pregnancy and complicated by premature rupture of membranes and pregnancy induced hypertension.

MATERIAL AND METHODS

A total of 90 women with singleton pregnancies attending the Clinical Department of Obstetrics and Gynaecology Holy Family Hospital, Warsaw Medical University and the Institute of Mother and Child in Warsaw were enrolled in this study after providing written informed consent. The study was approved by the Institute’s Ethical Committee. We excluded pregnancies with gestational age less than 26 or more then 41 weeks, women with renal and cardiovascular diseases, diabetes mellitus, active hepatitis and rheumatoid arthritis. In the group of healthy pregnant women additional exclusion criteria were: PROM, PIH, chronic hypertension and preeclampsia. Gestational age was based on the last menstrual period and was confirmed by early second-trimester ultrasound examination. None of the foetuses showed any abnormalities and none of the women smoked cigarettes or drunk alcohol. All subjects were of similar socio-economic status and living in urban area.

The studied population was divided into three groups. Women with PROM (n=24) between 26 and 36 weeks of pregnancy with the presence/absence of uterine contractions constituted the first group. The second group consisted of 31 women with PIH between 30 and 41 weeks of gestation. In our study transient hypertension implies pregnancy induced hypertension without proteinuria with BP≥140/90 (one or both values exceeded) or rise in systolic BP≥30 mmHg or diastolic BP≥15 mmHg after 20 weeks of gestation. The third group consisted of 35 healthy women with uncomplicated pregnancy. The weeks of gestation in all groups of women were similar.

Fasting blood samples were obtained from mothers by venipuncture, centrifuged at 2500 x g, at 4o C for 10 minutes. The obtained serum was frozen (maximum 1 month) until markers of iron status and pro-hepcidin were determined.

Serum pro-hepcidin concentration was determined by immunoenzymatic method using a commercial pro-hepcidin assay (DRG, Germany). Serum levels of C-reactive protein (CRP) were measured by immunoturbidimetric method using commercially available kits on Cobas Integra analyser (Roche, Switzerland). White blood cell count (WBC), haemoglobin (Hb) and haematocrit (HCT) were determined using commercially available kits on Pentra 60 haematology analyzer (HORRIBA ABX, France).

The results were evaluated by ANOVA (STATISTICA 6.0, StatSoft, Poland). The significance level was set at p<0.05.

RESULTS

Data presented in Table I indicate that the serum levels of pro-hepcidin in studied groups of pregnant women were similar. The lowest value (93.7 µg/L) was observed in pregnancy complicated by PROM but the difference between groups was not statistically significant. In groups of PROM and PIH concentration of haemoglobin was significantly lower than in uncomplicated pregnancy group but remains in the physiological range which indicated that our patients were not anaemic. Concentrations of haemoglobin and pro-hepcidin levels were not related. Correct values of CRP and leucocytes count exclude acute inflammation. Correlation between the concentration of serum pro-hepcidin and iron status measurements was not observed.

DISCUSSION

In processes of haematological adaptation to the pregnancy the role of hepcidin as negative regulator of iron absorption in the bowels and iron release from macrophages should be taken into consideration. However, data on serum hepcidin concentration in the course of pregnancy are fragmentary and controversial. In rats reduction of iron maternal stores was accompanied by enhanced intestinal iron absorption and progressively reduced liver hepcidin expression (8, 9).

Limited data are available about link hepcidin/pro-hepcidin to iron status in pregnant women. Roe at al. (10) showed that fasting serum pro-hepcidin concentration was not significantly different at 16, 24 and 34 weeks of gestation and was not associated with iron status parameters or iron supplementation. These results are in agreement with Ervasti et al. (11) and also with our previous studies (12, 13). However, Rams et al. (14, 15) found higher serum pro-hepcidin in pregnant than in non pregnant healthy women not only in third trimester but also in early pregnancy. It was correlated negatively with soluble receptor of transferin and positively with ferritin. In non-anaemic pregnant women correlation between serum pro-hepcidin and ferritin was observed by Dallalio et al. (16) and Rams et al. (15). Moreover Rams et al. (15) reported that in anaemia complicated pregnancy serum pro-hepcidin concentration was higher than in non-anaemic group and was negatively correlated with haemoglobin, haematocrit and recepto
r of transferin.

Our results indicated that concentration of pro-hepcidin was not statistically significant different in the groups of pregnant women with PIH and PROM but without anaemia. Up to date studies concerning the role of hepcidin in the course of pregnancy were based on serum measurement of inactive pro-form of this hormone (10-15). Active hepcidin was investigated only by Shulze et al. (17) in urine of anaemic pregnant women. Their results indicated that the relation between this hormone and the iron status might exist also during pregnancy, the same as in anaemia of chronic disease and haemochromatosis (18, 19). To characterize the role of pro-hepcidin and active hepcidin in physiological and complicated pregnancy further longitudinal studies on larger population are needed.

CONCLUSION

In pregnancies complicated by premature rupture of membranes and in pregnancy induced hypertension with normal values of haemoglobin and haematocrite the serum pro-hepcidin concentrations are similar to those observed in healthy pregnant women.

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REFERENCES

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5.     Saha C.K., Jain V., Gupta I., Varma N.: Serum ferritin levels as a marker of preterm labor. Int. J. Gynaecol. Obstst., 2000, 71, 107-111.

6.     Ferguson S.E., Smith G.N., Salenieks M.E., Windrim R., Walker M.C.: Preterm premature rupture of membranes. Nutricional and socioeconomic factors. Obstet. Gynecol., 2002, 100, 1250-1256.

7.     Hubel C.A., Kozlov A.V., Kagan V.E., Evans R.W., Davidge S.T., McLaughlin M.K., Roberts J.M.: Decreased transferring and increased transferring saturation in sera of women with preeclampsia: Implications for oxidative stress. Am. J. Obstet. Gynecol., 1996, 175, 692-700.

8.     Millard K.N., Frazer D.M., Wilkins S.J., Anderson G.J.: Changes in the expression of intestinal iron transport and hepatic regulatory molecules explain the enhanced iron absorption associated with pregnancy in the rat. Gut, 2004, 53, 655-660.

9.     Gambling L., Czopek A., Andersen H.S., Holtrop G., Srai S.K., Krejpcio Z., McArdle H.J.: Fetal iron status regulates maternal iron metabolism during pregnancy in the rat. Am. J. Physiol. Regul. Integr. Comp. Physiol,. 2009, 296, R1063-1070.

10.     Laskowska-Klita T., Chełchowska M., Ambroszkiewicz J., Świątek E., Leibschang J.: Serum pro-hepcidin and iron markers during uncomplicated pregnancy. Eur. J. Obstet. Gynecol. Rep. Biol., 2007, 130, 273-274.

11.     Chełchowska M., Świątek E., Ambroszkiewicz J., Gajewska J., Laskowska-Klita T., Leibschang J.: Concentrations of pro-hepcidin in serum of pregnant women and in umbilical cord blood. Ginekol. Pol., 2008, 79,754-757.

12.     Roe M.A., Spinks C., Heath A.M., Harvey L.J., Foxall R., Wimperis J., Wolf Ch., Fairweather-Tait S.J.: Serum pro-hepcidin concentration: no association with iron absorption in healthy men; and no relationship with iron status in man carrying HFE mutations, hereditary haemochromatosis patients undergoing phlebotomy treatment, or pregnant women. Br. J. Nutr., 2007, 97, 544-549.

13.     Ervasti M., Sankilampi U., Luukkonen S., Heinonen S., Punnonen K.: Maternal pro-hepcidin at term correlates with cord blood pro-hepcidin at birth. Eur. J. Obstet. Gynecol. Rep. Biol., 2009, 147, 161-165.

14.     Rams L., Drozdowska-Rams L., Małyszko J., Pawlak K., Małyszko J.: Prohepcidin in pregnancy: Acute phase protein, marker of iron metabolism, or both? Eur. J. Obstet. Gynecol. Rep. Biol., 2008, 140, 293-294.

15.     Rams L., Drozdowska-Rams L., Małyszko J. Pawlak K., Małyszko J.: Prohepcidin and its possible role in anemia of pregnancy. Arch. Med. Sci., 2008, 3, 305-309.

16.     Dallalio G., Fleury T., Means T.: Serum hepcidin in clinical specimens. Br. J. Haematol., 2003, 122, 996-1000.

17.     Schulze K.J., Christian P., Ruczinski I., Ray A.L., Nath A., Wu L.S-F., Semba R.D.: Hepcidin and iron status among pregnant women in Bangladesh. Asia Pac. J. Clin. Nutr. 2008, 17,451-456.

18.     Kulaksiz H., Gehrke S.G., Janetzko A., Rost D., Bruckner T., Kallinowski B., Stremmel W.: Pro-hepcidin: expression and cell specific localisation in the liver and its regulation in hereditary haemochromatosis, chronic renal insufficiency, and renal anaemia. Gut, 2004, 53, 735-743.

19.     Małyszko J., Małyszko J.S., Mysliwiec M.: A possible role of hepcidin in the pathogenesis of anemia among kidney allograft recipients. Transplant. Proc., 2009, 41, 3056-3059.

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Corresponding address:

Teresa Laskowska-Klita
Screening Test Department,
Institute of Mother and Child
ul. Kasprzaka 17a, 01-211 Warsaw, Poland
tel. (+48 22) 32-77-260
fax (+48 22) 32-77-280
lipidy.imid@imid.med.pl