- Email: [email protected]
Paraoxonase-1 activity determination via paraoxon substrate yields no significant difference in mild hyperhomocysteinemia
42
Letters to the Editor
References [1] Johnston BT, Carre IJ, Thomas PS, Collins BJ. Twenty to 40 year follow up of infantile hiatal hernia. Gut 1995;36:809–12. [2] Ruigomez A, Garcia Rodriguez LA, Wallander MA, Johansson S, Eklund S. Esophageal stricture incidence, treatment patterns, and recurrence rate. Am J Gastroenterol 2006;101(2685):92. [3] Gibson DG, Francis DP. Clinical assessment of left ventricular diastolic function. Heart 2003;89:231–8. [4] Van Tellingen C. Suspension of disbelief, — or the Bumetanide paradox. Neth Heart J 2007;15:31–2. [5] Hunt I, Siva M, Southon R, Treasure T. Does lung cancer screening with chest X-ray improve disease-free survival? Interac Cardiovasc Thorac Surg 2006;5:483–7. [6] Ak G, Metintas M, Yildirim H, Erginel S, Alatas F. Lung cancer in individuals less than 50 years of age. Lung 2007;185:279–86. [7] Coats AJ. Ethical authorship and publishing. Int J Cardiol 2009;131:149–50.
Fig. 2. CT-thorax, longitudinal, showing a large herniation of stomach and colon.
0167-5273/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2009.03.121
Paraoxonase-1 activity determination via paraoxon substrate yields no significant difference in mild hyperhomocysteinemia Hatice Türkeli a, Tuncer Çaycı a, Emin Özgür Akgül a,⁎, Enis Macit b, Halil Yaman a, Ibrahim Aydın a, Hilmi Demirin a, Hasan Alacam c, Esin Özkan a, Erdinç Çakır a, Özgür Deren d, Mehmet Kemal Erbil a, Z. Ilker Kunak e, Kutlay Burat a, Şerif Akman a a
Gülhane Military School of Medicine, Department of Biochemistry, Ankara, Turkey Gülhane Military School of Medicine, Department of Toxicology, Ankara, Turkey Hacettepe University, School of Medicine, Department of Biochemistry, Ankara, Turkey d Hacettepe University, School of Medicine, Department of Obstetrics and Gynecology, Ankara, Turkey e Department of Medical CBRN, Gulhane Military Medical Academy, Ankara, Turkey b c
a r t i c l e
i n f o
Article history: Received 25 March 2009 Accepted 26 March 2009 Available online 5 23May June2009 2009 Keywords: Homocysteine Hyperhomocysteinemia Paraoxonase
Dear Sir, Elevated plasma homocystein (Hcy) level has been recognized as an important risk factor for a number of cardiovascular diseases [1], peripheral arterial occlusive disease [2] and venous thrombosis [3]. ⁎ Corresponding author. Department of Biochemistry, Gülhane Military School of Medicine, Etlik, Keciören, 06018, Ankara, Turkey. Tel.: +90 312 3043314; fax: +90 312 3043300. E-mail address: [email protected] (E.Ö. Akgül).
A part of Hcy in the organism is turned to homocysteine thiolactone (HcyT) via a ring closure reaction, which gains rate in hyperhomocysteinemia [4,5]. HcyT is believed to account for the Hcy toxicity, via binding to protein lysine residues, which impairs or alters protein's function. Protein targets for the modification by HcyT include fibrinogen, low-density lipoprotein (LDL), high-density lipoprotein (HDL), albumin, hemoglobin, and ferritin. HcyT undergoes a second hydrolysis reaction back to Hcy by a thiolactonase, previously identified as paraoxonase (PON) possibly a protective reflex of the organism [6]. PON is an HDL-bound enzyme, which plays a key role in the protection of LDL and HDL from oxidation by hydrolyzing activated phospholipids and lipid peroxide products. PON is synthesized by the liver, and is secreted into the serum as a HDL-associated protein. Some chronic diseases seem to associate with alterations in the activity of this enzyme. Although serum PON appears to be mainly under genetic control, studies suggest that environmental factors also contribute modulation of its activity. Research on interactions between genetic and nutritional components is particularly of interest, and attempts are being made to find modulators of serum PON activity for therapeutic purposes. Nevertheless, it still remains unclear how nutritional or other environmental agents affect PON1
Letters to the Editor
Fig. 1. Plasma total homocysteine (tHcy) levels (μmol/L). Hcy1: fasting plasma tHcy levels Hcy2: post-methionine plasma tHcy levels.
43
given orally to the subjects in order to achieve an acute hyperhomocysteinemic condition. Second blood samples were taken four hours later. Both the samples were analyzed for plasma total Hcy (tHcy) levels and PON activities. tHcy levels were analyzed by a liquid chromatographic method by means of a commercial kit; PON analyses were done by means of a spectrophotometrical method mentioned elsewhere [7]. Such a diet led to a mild hyperhomocysteinemia in the subjects after 4 h (23.6 ± 1.8 μmol/L; p b 0.0001) (Fig. 1), and decreased serum PON activity (687.3 ± 47.4 U/mL) compared to fasting levels (657.8 ± 45.3 U/mL) (Fig. 2). This decrease was in concordance with the literature [1,8]. However, in our opinion, the difference detected via enzymatic activity using the paraoxon substrate was statistically nonsignificant (p = 0.19). Jakubowski et al. reported that the hydrolytic activities of the serum PON protein towards HcyT and paraoxon substrates were strongly correlated [4]. Turnover numbers for HTase and paraoxonase are 848- and 833-fold higher, respectively, with phenyl acetate than with paraoxon. There are several studies reporting that phenyl acetate gives upto ~ 1000 fold reaction with PON, suggesting a 3–1000 fold better representation of the enzymatic activity [9–11]. Thus, the substrate used in our human model of mild hyperhomocysteinemia might have a defective performance to reflect the expected significance. In summary it may be concluded that serum PON activity determination via paraoxon substrate yielded no significant difference in an acute mild hyperhomocysteinemic diet model in humans. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [12]. References
Fig. 2. Serum PON1 activities (U/mL). PON1: fasting serum PON 1 activities, PON2: postmethionine serum PON1 activities.
activity in general population since most of the conclusions reported to date have been the result of experimental investigations or intervention studies with patients. Thus we aimed in present study to investigate how a mild hyperhomocysteinemic nutritional habit affect serum PON activity in a population-based study. We, hereby, declare that our study complies with the principles of ethical authorship and publishing in the International Journal of Cardiology [12]. 32 (ages between 18 and 35, 16–16 female/male) volunteer defined as healthy via questionnaire and routine biochemical analysis were informed about and involved in the study. They were normohomocysteinemic (7.9 ± 0.6 μmol/L) with one exception. Bloods were taken after overnight fasting and 100 mg/kg L-methionine was
0167-5273/$ – see front matter © 2009 Published by Elsevier Ireland Ltd. doi:10.1016/j.ijcard.2009.03.138
[1] Janel N, Robert K, Chabert C, Ledru A, Gouédard C, Barouki R, Delabar JM, Chassé JF. Mouse liver paraoxonase-1 gene expression is downregulated in hyperhomocysteinemia. Thromb Haemost 2004;92:221–2. [2] Kang SS, Wong PW, Malinow MR. Hyperhomocyst(e)inemia as a risk factor for occlusive vascular disease. Annu Rev Nutr 1992;12:279–98. [3] Den Heijer M, Koster T, Blom HJ, Bos GM, Briet E, Reitsma PH, Vandenbroucke JP, Rosendaal FR. Hyperhomocysteinemia as a risk factor for deep-vein thrombosis. N Engl J Med 1996;334:759–62. [4] Jakubowskı H. Calcium-dependent human serum homocysteine thiolactone hydrolase—a protective mechanism against protein N-homocysteinylation. J Biol Chem 2000;275(6):3957–62. [5] Langman LJ, Cole DEC. Cholesterol of the 90's? Clin Chim 1999;286:63–80. [6] Perla-Kajan J, Twardowski T, Jakubowski H. Mechanisms of homocysteine toxicity in humans. Amino Acids 2007;32:561–72. [7] Eckerson HW, Wyte CM, LA DU, BN. The human serum paraoxonase/arylesterase polymorphism. Am J Hum Genet 1983;35(6):1126–38. [8] Kerkeni M, Addad F, Chauffert M, Chuniaud L, Miled A, Trivin F, Maaroufi K. Hyperhomocysteinemia, paraoxonase activity and risk of coronary artery disease. Clinical Biochemistry 2006;39:821–5. [9] Aharoni A, Gaidukov L, Yagur S, Toker L, Silman I, Tawfik DS. Directed evolution of mammalian paraoxonases PON1 and PON3 for bacterial expression and catalytic specialization. PNAS Jan 13 2004;101(2):482–7. [10] Zech R, Severin RM, Chemnitius JM, Nebendahl K. Paraoxonase polymorphism in rabbits. Chemico-Biological Interactions 1999;119–120:283–8. [11] Costa LG, Furlong CE. Paraoxonase (PON1) in health and disease: Basic and Clinical Aspects. Kluwer Academic Publishers. [12] Coats AJ. Ethical authorship and publishing. Int J Cardiol 2009;131:149–50.
Letters to the Editor
References [1] Johnston BT, Carre IJ, Thomas PS, Collins BJ. Twenty to 40 year follow up of infantile hiatal hernia. Gut 1995;36:809–12. [2] Ruigomez A, Garcia Rodriguez LA, Wallander MA, Johansson S, Eklund S. Esophageal stricture incidence, treatment patterns, and recurrence rate. Am J Gastroenterol 2006;101(2685):92. [3] Gibson DG, Francis DP. Clinical assessment of left ventricular diastolic function. Heart 2003;89:231–8. [4] Van Tellingen C. Suspension of disbelief, — or the Bumetanide paradox. Neth Heart J 2007;15:31–2. [5] Hunt I, Siva M, Southon R, Treasure T. Does lung cancer screening with chest X-ray improve disease-free survival? Interac Cardiovasc Thorac Surg 2006;5:483–7. [6] Ak G, Metintas M, Yildirim H, Erginel S, Alatas F. Lung cancer in individuals less than 50 years of age. Lung 2007;185:279–86. [7] Coats AJ. Ethical authorship and publishing. Int J Cardiol 2009;131:149–50.
Fig. 2. CT-thorax, longitudinal, showing a large herniation of stomach and colon.
0167-5273/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2009.03.121
Paraoxonase-1 activity determination via paraoxon substrate yields no significant difference in mild hyperhomocysteinemia Hatice Türkeli a, Tuncer Çaycı a, Emin Özgür Akgül a,⁎, Enis Macit b, Halil Yaman a, Ibrahim Aydın a, Hilmi Demirin a, Hasan Alacam c, Esin Özkan a, Erdinç Çakır a, Özgür Deren d, Mehmet Kemal Erbil a, Z. Ilker Kunak e, Kutlay Burat a, Şerif Akman a a
Gülhane Military School of Medicine, Department of Biochemistry, Ankara, Turkey Gülhane Military School of Medicine, Department of Toxicology, Ankara, Turkey Hacettepe University, School of Medicine, Department of Biochemistry, Ankara, Turkey d Hacettepe University, School of Medicine, Department of Obstetrics and Gynecology, Ankara, Turkey e Department of Medical CBRN, Gulhane Military Medical Academy, Ankara, Turkey b c
a r t i c l e
i n f o
Article history: Received 25 March 2009 Accepted 26 March 2009 Available online 5 23May June2009 2009 Keywords: Homocysteine Hyperhomocysteinemia Paraoxonase
Dear Sir, Elevated plasma homocystein (Hcy) level has been recognized as an important risk factor for a number of cardiovascular diseases [1], peripheral arterial occlusive disease [2] and venous thrombosis [3]. ⁎ Corresponding author. Department of Biochemistry, Gülhane Military School of Medicine, Etlik, Keciören, 06018, Ankara, Turkey. Tel.: +90 312 3043314; fax: +90 312 3043300. E-mail address: [email protected] (E.Ö. Akgül).
A part of Hcy in the organism is turned to homocysteine thiolactone (HcyT) via a ring closure reaction, which gains rate in hyperhomocysteinemia [4,5]. HcyT is believed to account for the Hcy toxicity, via binding to protein lysine residues, which impairs or alters protein's function. Protein targets for the modification by HcyT include fibrinogen, low-density lipoprotein (LDL), high-density lipoprotein (HDL), albumin, hemoglobin, and ferritin. HcyT undergoes a second hydrolysis reaction back to Hcy by a thiolactonase, previously identified as paraoxonase (PON) possibly a protective reflex of the organism [6]. PON is an HDL-bound enzyme, which plays a key role in the protection of LDL and HDL from oxidation by hydrolyzing activated phospholipids and lipid peroxide products. PON is synthesized by the liver, and is secreted into the serum as a HDL-associated protein. Some chronic diseases seem to associate with alterations in the activity of this enzyme. Although serum PON appears to be mainly under genetic control, studies suggest that environmental factors also contribute modulation of its activity. Research on interactions between genetic and nutritional components is particularly of interest, and attempts are being made to find modulators of serum PON activity for therapeutic purposes. Nevertheless, it still remains unclear how nutritional or other environmental agents affect PON1
Letters to the Editor
Fig. 1. Plasma total homocysteine (tHcy) levels (μmol/L). Hcy1: fasting plasma tHcy levels Hcy2: post-methionine plasma tHcy levels.
43
given orally to the subjects in order to achieve an acute hyperhomocysteinemic condition. Second blood samples were taken four hours later. Both the samples were analyzed for plasma total Hcy (tHcy) levels and PON activities. tHcy levels were analyzed by a liquid chromatographic method by means of a commercial kit; PON analyses were done by means of a spectrophotometrical method mentioned elsewhere [7]. Such a diet led to a mild hyperhomocysteinemia in the subjects after 4 h (23.6 ± 1.8 μmol/L; p b 0.0001) (Fig. 1), and decreased serum PON activity (687.3 ± 47.4 U/mL) compared to fasting levels (657.8 ± 45.3 U/mL) (Fig. 2). This decrease was in concordance with the literature [1,8]. However, in our opinion, the difference detected via enzymatic activity using the paraoxon substrate was statistically nonsignificant (p = 0.19). Jakubowski et al. reported that the hydrolytic activities of the serum PON protein towards HcyT and paraoxon substrates were strongly correlated [4]. Turnover numbers for HTase and paraoxonase are 848- and 833-fold higher, respectively, with phenyl acetate than with paraoxon. There are several studies reporting that phenyl acetate gives upto ~ 1000 fold reaction with PON, suggesting a 3–1000 fold better representation of the enzymatic activity [9–11]. Thus, the substrate used in our human model of mild hyperhomocysteinemia might have a defective performance to reflect the expected significance. In summary it may be concluded that serum PON activity determination via paraoxon substrate yielded no significant difference in an acute mild hyperhomocysteinemic diet model in humans. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [12]. References
Fig. 2. Serum PON1 activities (U/mL). PON1: fasting serum PON 1 activities, PON2: postmethionine serum PON1 activities.
activity in general population since most of the conclusions reported to date have been the result of experimental investigations or intervention studies with patients. Thus we aimed in present study to investigate how a mild hyperhomocysteinemic nutritional habit affect serum PON activity in a population-based study. We, hereby, declare that our study complies with the principles of ethical authorship and publishing in the International Journal of Cardiology [12]. 32 (ages between 18 and 35, 16–16 female/male) volunteer defined as healthy via questionnaire and routine biochemical analysis were informed about and involved in the study. They were normohomocysteinemic (7.9 ± 0.6 μmol/L) with one exception. Bloods were taken after overnight fasting and 100 mg/kg L-methionine was
0167-5273/$ – see front matter © 2009 Published by Elsevier Ireland Ltd. doi:10.1016/j.ijcard.2009.03.138
[1] Janel N, Robert K, Chabert C, Ledru A, Gouédard C, Barouki R, Delabar JM, Chassé JF. Mouse liver paraoxonase-1 gene expression is downregulated in hyperhomocysteinemia. Thromb Haemost 2004;92:221–2. [2] Kang SS, Wong PW, Malinow MR. Hyperhomocyst(e)inemia as a risk factor for occlusive vascular disease. Annu Rev Nutr 1992;12:279–98. [3] Den Heijer M, Koster T, Blom HJ, Bos GM, Briet E, Reitsma PH, Vandenbroucke JP, Rosendaal FR. Hyperhomocysteinemia as a risk factor for deep-vein thrombosis. N Engl J Med 1996;334:759–62. [4] Jakubowskı H. Calcium-dependent human serum homocysteine thiolactone hydrolase—a protective mechanism against protein N-homocysteinylation. J Biol Chem 2000;275(6):3957–62. [5] Langman LJ, Cole DEC. Cholesterol of the 90's? Clin Chim 1999;286:63–80. [6] Perla-Kajan J, Twardowski T, Jakubowski H. Mechanisms of homocysteine toxicity in humans. Amino Acids 2007;32:561–72. [7] Eckerson HW, Wyte CM, LA DU, BN. The human serum paraoxonase/arylesterase polymorphism. Am J Hum Genet 1983;35(6):1126–38. [8] Kerkeni M, Addad F, Chauffert M, Chuniaud L, Miled A, Trivin F, Maaroufi K. Hyperhomocysteinemia, paraoxonase activity and risk of coronary artery disease. Clinical Biochemistry 2006;39:821–5. [9] Aharoni A, Gaidukov L, Yagur S, Toker L, Silman I, Tawfik DS. Directed evolution of mammalian paraoxonases PON1 and PON3 for bacterial expression and catalytic specialization. PNAS Jan 13 2004;101(2):482–7. [10] Zech R, Severin RM, Chemnitius JM, Nebendahl K. Paraoxonase polymorphism in rabbits. Chemico-Biological Interactions 1999;119–120:283–8. [11] Costa LG, Furlong CE. Paraoxonase (PON1) in health and disease: Basic and Clinical Aspects. Kluwer Academic Publishers. [12] Coats AJ. Ethical authorship and publishing. Int J Cardiol 2009;131:149–50.