- Email: [email protected]
Serum ferritin levels adversely affect cardiac function in patients with ST-elevation myocardial infarction who underwent successful percutaneous coronary intervention
286
Letters to the Editor
Table 2 Weight of evidence approach using the Bradford Hill criteria for the association between diagnosis as myocardial infarction and presenting toxoplasmosis. Hill's criterion Constant Strength Consistency Specificity Temporality Dose–response Plausibility Coherence Experimental evidence Analogy Sum Final probability
Evidence
Probability (%)
Probability×weight for category 1
Probability×weight for category 2A
Strong OR detected Studies reveal that toxoplasmic myocarditis mimics AMI. Studies report that many infectious agents can mimic AMI. Toxoplasmic myocarditis is one of the confounding situations in the diagnosis of AMI. Only one study showed a clear dose–response. T. gondii and Neospora caninum were distinguished in cardiac problems of cat and dog [5]. T. gondii affects myocardium. No information for this criterion. Some infective agents may contribute to myocarditis and mimic AMI.
80 75 40 100 50 80 80 0 80
− 14.7799 4.9784 3.04575 − 1.1148 7.657 − 1.764 18.42 0.076968 0 − 1.0352 15.484218
− 10.08346 1.5384 1.35225 − 1.5508 8.281 − 1.767 17.3512 − 0.2672 0 − 0.8088 14.04559
e15.484218 / e15.484218 + e14.04559 = 80.82%
0167-5273/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2012.09.206
Serum ferritin levels adversely affect cardiac function in patients with ST-elevation myocardial infarction who underwent successful percutaneous coronary intervention Tomoyasu Suzuki a, Ken Toba a,⁎, Kiminori Kato a, Takuya Ozawa a, Masutaka Higasimura a, Toshiki Kitajima a, Hirotaka Oda b, Keiichi Tsuchida b, Naohisa Tomosugi c, Hideki Saitoh d, Yoshifusa Aizawa a a
First Department of Internal Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan Niigata City General Hospital, Niigata, Japan Proteomics Research Unit, Kanazawa Medical University, Kanazawa, Japan d Chugai Pharmaceutical Co., Ltd, Tokyo, Japan b c
a r t i c l e
i n f o
Article history: Received 4 September 2012 Accepted 26 September 2012 Available online 15 October 2012 Keywords: Ferritin Interleukin-6 Erythropoietin Hepcidin STEMI
Several cohort studies have revealed that increased body iron stores raise the risk of ischemic heart disease [1,2]. The characteristics of iron status in patients with ST-segment elevation myocardial infarction (STEMI) are also well known. A decline in serum iron, followed by a decrease in the iron saturation rate of transferrin as a result, and a rise in ferritin levels immediately appear after STEMI [3,4]. However, these biomarkers do not correlate with the amount of ischemic tissue damage as estimated by creatine-kinase levels. Moreover, there have been no reports on the clinical significance or direct evidence of the role of iron metabolism in patients with STEMI.
⁎ Corresponding author at: Division of Hematology, Niigata University Graduate School of Medical and Dental Sciences, 1-754 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan. Tel.: +81 25 227 2185; fax: +81 25 227 0774. E-mail address: [email protected] (K. Toba).
Hepcidin, the master regulator of iron homeostasis in humans, has been found to shift transferrin-bound iron to storage [5]. Hepcidin is produced in the liver as well as in ischemic cardiomyocytes in response to interleukin-6 (IL-6) [6,7]. Iron metabolism-related factors such as the IL-6/hepcidin axis, its resulting iron storage system in tissue macrophages, and reactive oxygen species produced via the Fenton reaction of iron, overall should play an important role in cardiac protection and injury. We undertook a cohort study to observe the status of iron and its regulators in patients with STEMI. Serum samples were collected from 53 patients with STEMI (age: 36 to 82, median 66, 47 males and 6 females) on arrival within emergency visits at a general hospital. We prospectively enrolled patients with STsegment elevations. Patients were eligible if they were admitted within 24 h after onset of STEMI and had undergone successful percutaneous coronary intervention (PCI). Complete blood count and blood chemistry were analyzed and serum samples initially collected during the emergency visit before urgent PCI were stored for the study of iron status. Left ventricular ejection fraction (LVEF) was estimated by left ventriculography just after PCI. One of the 53 patients died of cardiac tamponade during the time of the first hospitalization, five patients were treated at other clinics after discharge, and finally 47 patients were evaluated for the 6-month follow-up study by left ventriculography. The observational cohort studies were deliberated and approved by its Institutional Ethics Committees. Serum levels of IL-6 (pg/ml) and EPO (mIU/ml) were measured using an enzyme linked immunosorbent assay (ELISA) method distributed by R&D Systems (Minneapolis, MN) and eBioscience (Vienna, Austria),
Letters to the Editor
respectively. Serum levels of hepcidin-25 were measured by a proteomic method using a liquid chromatography-mass spectrometry (LC-MS/MS) assay system (Applied Biosystems) as described previously [8]. Normal ranges of serum IL-6, EPO, and hepcidin-25 are less than 35 pg/ml, 2.7 to 40.7 mIU/ml, and 9.9 to 34.5 ng/ml, respectively. An increase in hepcidin-25 levels was observed in 14 of the 53 patients (26%). A decrease in serum iron levels and an increase in ferritin levels were observed in 48/53 (91%) and 7/53 (13%), respectively. Only one of the 53 patients showed microcytic anemia, while the other 52 patients did not demonstrate such anemia. Two patients who expressed an increase in EPO levels showed normocytic anemia, low levels of hepcidin-25, and an increase in blood urea nitrogen levels, and thus may have been complicated with anemia due to gastrointestinal bleeding. Taken overall, low iron levels did not represent iron deficiency in most cases. The expected influences of hepcidin-25 on serum levels of iron and ferritin were not observed. The relationship between cardiac function and serum biomarkers was analyzed and only serum levels of IL-6 and ferritin revealed a significant correlation with LVEF as shown in Fig. 1. Serum IL-6 expressed a significant correlation with baseline LVEF that may have resulted in low 6-month follow-up LVEF. IL-6 positively related with maximum serum creatine-kinase (R= 0.3102, p b 0.05) (data not shown). Serum iron levels did not affect LVEF. On the other hand, serum ferritin levels significantly affected ΔLVEF, but not baseline LVEF. No difference in LVEF was observed in three groups categorized according to levels of hepcidin-25 (b10, 10 to 34.5, and N34.5, ng/ml), transferrin saturation
287
Fig. 2. Correlation of serum levels of ferritin and the size of red blood cells.Correlations between ferritin levels and mean corpuscular volume (A, B) and that of ferritin levels and mean corpuscular hemoglobin (C, D) are shown. To confirm the significance of these relationships, two cases with extraordinary high levels of ferritin were eliminated and the remaining 51 patients were analyzed again (B, D). R: correlation coefficient (goodness of fit), p: p-value in linear regression analysis.
Fig. 1. Effects of serum levels of interleukin-6, iron, and ferritin on left ventricular ejection fraction.Left ventricular ejection fraction (LVEF) just after coronary intervention (A-1 to C-1), at 6month follow-up (A-2 to C-2), and increments of LVEF during 6-month follow-up (A-3 to C-3) are shown.
288
Letters to the Editor
rates (b20%, 20 to 30%, and N30%), or serum EPO (b2.7, 2.7 to 40.7, and N40.7). The baseline characteristics of two groups, relatively high ferritin levels (≥120 ng/ml, n =27) and low ferritin levels (n =26), were compared (data not shown). No bias of culprit lesion or background such as age, smoking, diabetes mellitus, hypertension, dyslipidemia etc. was observed in the two groups. Surprisingly, significant differences in mean corpuscular volume of red blood cells were observed in the two groups. Therefore, we analyzed the correlation between ferritin levels and red blood cell size and a significant correlation was observed (Fig. 2). Because red cell life span is 120 days, this correlation meant that the ferritin levels measured after STEMI reflected iron stores before a heart attack. In the current study, two mechanisms to influence the iron status of patients with STEMI were estimated, i.e., the extent of iron stores before a heart attack and transfer of iron from the circulation to stores caused by cardiac ischemia. Although cardiac ischemia triggers an activation of the intrinsic IL-6/hepcidin system in the heart [6], and it temporarily transfers transferrin-bound iron to ferritin-bound iron in the reticuloendothelial system, the serum iron pool is only 3 to 4 mg (ferritinbound iron: 1,000 mg), and thus the effect of iron stores before a heart attack is estimated to be much stronger than the effect of hepcidin. In fact, in the present study, serum ferritin levels correlated with the red blood cell size, but not with the hepcidin-25 levels. IL-6 levels affected baseline LVEF as well as follow-up LVEF, thus the production of IL-6 may reflect the degree of heart damage. In contrast, levels of ferritin did not
0167-5273/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2012.09.205
affect baseline LVEF, but inhibited the recovery of LVEF during the six months after STEMI. In conclusion, relatively high levels of body iron stores are not only a risk factor for ischemic heart disease, but also the factor to deteriorate cardiac function after PCI. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology. References [1] Tuomainen TP, Punnonen K, Nyyssönen K, Salonen JT. Association between body iron stores and the risk of acute myocardial infarction in men. Circulation 1998;97:1461–6. [2] Klipstein-Grobusch K, Koster JF, Grobbee DE, et al. Serum ferritin and risk of myocardial infarction in the elderly: the Rotterdam Study. Am J Clin Nutr 1999;69:1231–6. [3] Griffiths JD, Campbell LJ, Woodruff IW, et al. Acute changes in iron metabolism following myocardial infarction. Am J Clin Pathol 1985;84:649–54. [4] van der Schouw YT, van der Veeken PM, Kok FJ, Koster JF, Schouten EG, Hofman A. Iron status in the acute phase and six weeks after myocardial infarction. Free Radic Biol Med 1990;8:47–53. [5] Rivera S, Nemeth E, Gabayan V, Lopez MA, Farshidi D, Ganz T. Synthetic hepcidin causes rapid dose-dependent hypoferremia and is concentrated in ferroportin-containing organs. Blood 2005;106:2196–9. [6] Isoda M, Hanawa H, Watanabe R, et al. Expression of the peptide hormone hepcidin increases in cardiomyocytes under myocarditis and myocardial infarction. J Nutr Biochem 2010;21:749–56. [7] Suzuki H, Toba K, Kato K, et al. Serum hepcidin-20 is elevated during the acute phase of myocardial infarction. Tohoku J Exp Med 2009;218:93–8. [8] Tomosugi N, Kawabata H, Wakatabe R, et al. Detection of serum hepcidin in renal failure and inflammation by using ProteinChip System. Blood 2006;108:1381–7.
Letters to the Editor
Table 2 Weight of evidence approach using the Bradford Hill criteria for the association between diagnosis as myocardial infarction and presenting toxoplasmosis. Hill's criterion Constant Strength Consistency Specificity Temporality Dose–response Plausibility Coherence Experimental evidence Analogy Sum Final probability
Evidence
Probability (%)
Probability×weight for category 1
Probability×weight for category 2A
Strong OR detected Studies reveal that toxoplasmic myocarditis mimics AMI. Studies report that many infectious agents can mimic AMI. Toxoplasmic myocarditis is one of the confounding situations in the diagnosis of AMI. Only one study showed a clear dose–response. T. gondii and Neospora caninum were distinguished in cardiac problems of cat and dog [5]. T. gondii affects myocardium. No information for this criterion. Some infective agents may contribute to myocarditis and mimic AMI.
80 75 40 100 50 80 80 0 80
− 14.7799 4.9784 3.04575 − 1.1148 7.657 − 1.764 18.42 0.076968 0 − 1.0352 15.484218
− 10.08346 1.5384 1.35225 − 1.5508 8.281 − 1.767 17.3512 − 0.2672 0 − 0.8088 14.04559
e15.484218 / e15.484218 + e14.04559 = 80.82%
0167-5273/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2012.09.206
Serum ferritin levels adversely affect cardiac function in patients with ST-elevation myocardial infarction who underwent successful percutaneous coronary intervention Tomoyasu Suzuki a, Ken Toba a,⁎, Kiminori Kato a, Takuya Ozawa a, Masutaka Higasimura a, Toshiki Kitajima a, Hirotaka Oda b, Keiichi Tsuchida b, Naohisa Tomosugi c, Hideki Saitoh d, Yoshifusa Aizawa a a
First Department of Internal Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan Niigata City General Hospital, Niigata, Japan Proteomics Research Unit, Kanazawa Medical University, Kanazawa, Japan d Chugai Pharmaceutical Co., Ltd, Tokyo, Japan b c
a r t i c l e
i n f o
Article history: Received 4 September 2012 Accepted 26 September 2012 Available online 15 October 2012 Keywords: Ferritin Interleukin-6 Erythropoietin Hepcidin STEMI
Several cohort studies have revealed that increased body iron stores raise the risk of ischemic heart disease [1,2]. The characteristics of iron status in patients with ST-segment elevation myocardial infarction (STEMI) are also well known. A decline in serum iron, followed by a decrease in the iron saturation rate of transferrin as a result, and a rise in ferritin levels immediately appear after STEMI [3,4]. However, these biomarkers do not correlate with the amount of ischemic tissue damage as estimated by creatine-kinase levels. Moreover, there have been no reports on the clinical significance or direct evidence of the role of iron metabolism in patients with STEMI.
⁎ Corresponding author at: Division of Hematology, Niigata University Graduate School of Medical and Dental Sciences, 1-754 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan. Tel.: +81 25 227 2185; fax: +81 25 227 0774. E-mail address: [email protected] (K. Toba).
Hepcidin, the master regulator of iron homeostasis in humans, has been found to shift transferrin-bound iron to storage [5]. Hepcidin is produced in the liver as well as in ischemic cardiomyocytes in response to interleukin-6 (IL-6) [6,7]. Iron metabolism-related factors such as the IL-6/hepcidin axis, its resulting iron storage system in tissue macrophages, and reactive oxygen species produced via the Fenton reaction of iron, overall should play an important role in cardiac protection and injury. We undertook a cohort study to observe the status of iron and its regulators in patients with STEMI. Serum samples were collected from 53 patients with STEMI (age: 36 to 82, median 66, 47 males and 6 females) on arrival within emergency visits at a general hospital. We prospectively enrolled patients with STsegment elevations. Patients were eligible if they were admitted within 24 h after onset of STEMI and had undergone successful percutaneous coronary intervention (PCI). Complete blood count and blood chemistry were analyzed and serum samples initially collected during the emergency visit before urgent PCI were stored for the study of iron status. Left ventricular ejection fraction (LVEF) was estimated by left ventriculography just after PCI. One of the 53 patients died of cardiac tamponade during the time of the first hospitalization, five patients were treated at other clinics after discharge, and finally 47 patients were evaluated for the 6-month follow-up study by left ventriculography. The observational cohort studies were deliberated and approved by its Institutional Ethics Committees. Serum levels of IL-6 (pg/ml) and EPO (mIU/ml) were measured using an enzyme linked immunosorbent assay (ELISA) method distributed by R&D Systems (Minneapolis, MN) and eBioscience (Vienna, Austria),
Letters to the Editor
respectively. Serum levels of hepcidin-25 were measured by a proteomic method using a liquid chromatography-mass spectrometry (LC-MS/MS) assay system (Applied Biosystems) as described previously [8]. Normal ranges of serum IL-6, EPO, and hepcidin-25 are less than 35 pg/ml, 2.7 to 40.7 mIU/ml, and 9.9 to 34.5 ng/ml, respectively. An increase in hepcidin-25 levels was observed in 14 of the 53 patients (26%). A decrease in serum iron levels and an increase in ferritin levels were observed in 48/53 (91%) and 7/53 (13%), respectively. Only one of the 53 patients showed microcytic anemia, while the other 52 patients did not demonstrate such anemia. Two patients who expressed an increase in EPO levels showed normocytic anemia, low levels of hepcidin-25, and an increase in blood urea nitrogen levels, and thus may have been complicated with anemia due to gastrointestinal bleeding. Taken overall, low iron levels did not represent iron deficiency in most cases. The expected influences of hepcidin-25 on serum levels of iron and ferritin were not observed. The relationship between cardiac function and serum biomarkers was analyzed and only serum levels of IL-6 and ferritin revealed a significant correlation with LVEF as shown in Fig. 1. Serum IL-6 expressed a significant correlation with baseline LVEF that may have resulted in low 6-month follow-up LVEF. IL-6 positively related with maximum serum creatine-kinase (R= 0.3102, p b 0.05) (data not shown). Serum iron levels did not affect LVEF. On the other hand, serum ferritin levels significantly affected ΔLVEF, but not baseline LVEF. No difference in LVEF was observed in three groups categorized according to levels of hepcidin-25 (b10, 10 to 34.5, and N34.5, ng/ml), transferrin saturation
287
Fig. 2. Correlation of serum levels of ferritin and the size of red blood cells.Correlations between ferritin levels and mean corpuscular volume (A, B) and that of ferritin levels and mean corpuscular hemoglobin (C, D) are shown. To confirm the significance of these relationships, two cases with extraordinary high levels of ferritin were eliminated and the remaining 51 patients were analyzed again (B, D). R: correlation coefficient (goodness of fit), p: p-value in linear regression analysis.
Fig. 1. Effects of serum levels of interleukin-6, iron, and ferritin on left ventricular ejection fraction.Left ventricular ejection fraction (LVEF) just after coronary intervention (A-1 to C-1), at 6month follow-up (A-2 to C-2), and increments of LVEF during 6-month follow-up (A-3 to C-3) are shown.
288
Letters to the Editor
rates (b20%, 20 to 30%, and N30%), or serum EPO (b2.7, 2.7 to 40.7, and N40.7). The baseline characteristics of two groups, relatively high ferritin levels (≥120 ng/ml, n =27) and low ferritin levels (n =26), were compared (data not shown). No bias of culprit lesion or background such as age, smoking, diabetes mellitus, hypertension, dyslipidemia etc. was observed in the two groups. Surprisingly, significant differences in mean corpuscular volume of red blood cells were observed in the two groups. Therefore, we analyzed the correlation between ferritin levels and red blood cell size and a significant correlation was observed (Fig. 2). Because red cell life span is 120 days, this correlation meant that the ferritin levels measured after STEMI reflected iron stores before a heart attack. In the current study, two mechanisms to influence the iron status of patients with STEMI were estimated, i.e., the extent of iron stores before a heart attack and transfer of iron from the circulation to stores caused by cardiac ischemia. Although cardiac ischemia triggers an activation of the intrinsic IL-6/hepcidin system in the heart [6], and it temporarily transfers transferrin-bound iron to ferritin-bound iron in the reticuloendothelial system, the serum iron pool is only 3 to 4 mg (ferritinbound iron: 1,000 mg), and thus the effect of iron stores before a heart attack is estimated to be much stronger than the effect of hepcidin. In fact, in the present study, serum ferritin levels correlated with the red blood cell size, but not with the hepcidin-25 levels. IL-6 levels affected baseline LVEF as well as follow-up LVEF, thus the production of IL-6 may reflect the degree of heart damage. In contrast, levels of ferritin did not
0167-5273/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2012.09.205
affect baseline LVEF, but inhibited the recovery of LVEF during the six months after STEMI. In conclusion, relatively high levels of body iron stores are not only a risk factor for ischemic heart disease, but also the factor to deteriorate cardiac function after PCI. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology. References [1] Tuomainen TP, Punnonen K, Nyyssönen K, Salonen JT. Association between body iron stores and the risk of acute myocardial infarction in men. Circulation 1998;97:1461–6. [2] Klipstein-Grobusch K, Koster JF, Grobbee DE, et al. Serum ferritin and risk of myocardial infarction in the elderly: the Rotterdam Study. Am J Clin Nutr 1999;69:1231–6. [3] Griffiths JD, Campbell LJ, Woodruff IW, et al. Acute changes in iron metabolism following myocardial infarction. Am J Clin Pathol 1985;84:649–54. [4] van der Schouw YT, van der Veeken PM, Kok FJ, Koster JF, Schouten EG, Hofman A. Iron status in the acute phase and six weeks after myocardial infarction. Free Radic Biol Med 1990;8:47–53. [5] Rivera S, Nemeth E, Gabayan V, Lopez MA, Farshidi D, Ganz T. Synthetic hepcidin causes rapid dose-dependent hypoferremia and is concentrated in ferroportin-containing organs. Blood 2005;106:2196–9. [6] Isoda M, Hanawa H, Watanabe R, et al. Expression of the peptide hormone hepcidin increases in cardiomyocytes under myocarditis and myocardial infarction. J Nutr Biochem 2010;21:749–56. [7] Suzuki H, Toba K, Kato K, et al. Serum hepcidin-20 is elevated during the acute phase of myocardial infarction. Tohoku J Exp Med 2009;218:93–8. [8] Tomosugi N, Kawabata H, Wakatabe R, et al. Detection of serum hepcidin in renal failure and inflammation by using ProteinChip System. Blood 2006;108:1381–7.