- Email: [email protected]
Effects of the C-344T aldosterone synthase gene variant on preclinical vascular alterations in essential hypertension
Letters to the Editor [42] Goette A, Staack T, Rocken C, et al. Increased expression of extracellular signalregulated kinase and angiotensin-converting enzyme in human atria during atrial fibrillation. J Am Coll Cardiol 2000;35:1669–77. [43] Kumagai K, Nakashima H, Urata H, et al. Effects of angiotensin II type 1 receptor antagonist on electrical and structural remodeling in atrial fibrillation. J Am Coll Cardiol 2003;41:2197–204.
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[44] Shimano M, Tsuji Y, Inden Y, et al. Pioglitazone, a peroxisome proliferators-activated receptor-gamma activator, attenuates atrial fibrosis and atrial fibrillation promotion in rabbits with congestive heart failure. Heart Rhythm 2008;5:451–9.
0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.01.037
Effects of the C-344T aldosterone synthase gene variant on preclinical vascular alterations in essential hypertension Emmanuel Androulakis 1, Dimitris Tousoulis ⁎,1, Nikolaos Papageorgiou, Antigoni Miliou, Evaggelos Chatzistamatiou, George Moustakas, Stavroula Papaoikonomou, Ioannis Kallikazaros, Christodoulos Stefanadis 1st Cardiology Department, Athens University Medical School, Greece
a r t i c l e
i n f o
Article history: Received 22 November 2012 Accepted 18 January 2013 Available online 11 March 2013 Keywords: Renin–angiotensin–aldosterone Genes Polymorphisms Vascular damage Atherosclerosis Renal function
The role of the renin–angiotensin–aldosterone system (RAAS) in the pathophysiology of essential hypertension (EH) and subclinical atherosclerosis remains unclear, while an increase in the local production of angiotensin II (Ang-II) and aldosterone may be implicated in the hypertension-associated vascular disease through several mechanisms [1,2]. Scarce and inconsistent data suggest that M235T polymorphism of the angiotensinogen (AGT) gene may be a genetic marker for endothelial dysfunction and arterial stiffness [3–5]. Moreover, it has been suggested that C-344T, a genetic variant of the aldosterone synthase (CYP11B2) gene, might be associated with subclinical atherosclerosis, assessed by intima–media thickness (IMT) [6]. However, its effects on endothelial and vascular function remain unknown. Thus, in the present study we investigated the potential associations between the C-344T aldosterone synthase gene variant with vascular damage in essential hypertension. The study population consisted of 318 untreated, newly diagnosed essential hypertensives, and a control group of 193 matched, normotensive individuals. All subjects underwent the routine work-up in order to exclude secondary forms of hypertension. The study was approved by the Institutional Ethics Committees, and an informed consent was given by all the participants. Carotid–femoral pulse wave velocity (cf-PWV) measurements were obtained using a validated non-invasive automatic device (Complior SP; Artech Medical, Pantin, France). Augmentation index (AIx) was ⁎ Corresponding author at: Athens University Medical School, Hippokration Hospital, Vasilisis Sofias 114, 115 28, Athens, Greece. Tel.: +30 2132088099; fax: +30 2132088676. E-mail address: [email protected] (D. Tousoulis). 1 Equally contributed.
estimated by applanation tonometry of the left radial artery by using the SphygmoCor device. Flow mediated dilation (FMD) was assessed in the brachial artery, which was scanned in longitudinal section, using a 7–12 MHz linear array transducer (baseline) (Vivid 7, General Electric, USA), as described previously [7]. In all patients, ankle-brachial index (ABI) values were determined in our vascular laborator by Doppler measurements. The IMT was measured by echocardiography as described previously. Levels of fibrinogen and high sensitivity Creactive protein (hsCRP) were measured by immunonephelometry (Dade Behring, Marburg, Germany). Polymorphism analysis of the CYP11B2 gene (rs1799998) was performed using the primers rs1799998F: 5′-CAGGGGGTACGTGGAC ATTT-3′ and rs1799998R: 5′-CAGGGCTGAGAGGAGTAAAA-3′ and PCR products were digested with HaeIII endonuclease. Allele frequencies were compared between groups by Chi-square analysis and differences in continuous variables between 2 groups were assessed by the Student t-test for parametric data. On variables found to deviate from normality, nonparametric tests (Kruskal–Wallis/Mann–Whitney) were applied. Relationships among variables were assessed using linear regression analysis and Pearson's correlation coefficient. All tests were two sided, and a p value of b0.05 was considered to indicate statistical significance. SPSS version 18.0 (SPSS, Chicago, IL) software was used for all the statistical calculations. The demographic characteristics of the study population are shown in Table 1. Notably, we have observed higher values of IMT in −344TT homozygosity compared to C-carriers, in the group of hypertensives Table 1 Demographic characteristics of subjects.
Number of subjects Age (years) Smokers N (%) Dyslipidemia N (%) Body mass index (kg/m2) Average heart rate** (bpm) Ejection fraction (%) Glucose (mg/dl) Creatinine (mg/dl) Uric acid (mg/dl) Total cholesterol (mg/dl) Fibrinogen (mg/dl) C-reactive protein (mg/l)
Controls
Hypertensives*
p value
193 51.5 ± 0.9 68 (35.6%) 81 (42.1%) 27.1 ± 0.3 72.9 ± 0.7 64.4 ± 0.3 96.5 ± 0.9 0.93 ± 0.06 4.8 ± 0.13 211.7 ± 3.6 355.6 ± 7.8 2.09 ± 0.2
318 52.3 ± 0.7 130 (41.0%) 120 (38.1%) 28.6 ± 0.3 75.3 ± 0.6 63.4 ± 0.3 99.1 ± 0.8 0.94 ± 0.01 5.2 ± 0.11 215.2 ± 2.5 365.7 ± 6.2 2.54 ± 0.2
p = NS p = NS p = NS p = NS p = 0.027 p = 0.06 p = NS p = 0.039 p = 0.041 p = NS p = NS p = 0.054
*Untreated hypertensives; **measurements obtained by ambulatory blood pressure monitoring; values expressed as means ± SEM; p by chi-square analysis; NS: non significant.
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Letters to the Editor
Fig. 1. Intima–media thickness (IMT) values in relation to the CYP11B2 promoter genotype in healthy and hypertensive subjects.
Table 2 Vascular measurements of the C-344T variant in the hypertensive and control subjects. CT + CT
TT
p value
4.2 ± 0.2 8.9 ± 0.2 26.6 ± 1.7 1.16 ± 0.009 781.6 ± 33.5
0.066 0.083 0.879 0.735 0.039
EH FMD (%) c-fPWV (m/s) AIx ABI IMT (μm)
5.0 ± 0.3 8.6 ± 0.1 27.6 ± 1.3 1.16 ± 0.008 712.5 ± 16.2
CC + CT
TT
p value
6.1 ± 0.4 7.7 ± 0.2 26.6 ± 1.5 1.14 ± 0.02 693.2 ± 27.7
0.137 0.348 0.225 0.697 0.163
Controls 7.3 ± 0.4 7.4 ± 0.1 23.8 ± 1.6 1.15 ± 0.008 655.1 ± 23.4
EH: essential hypertension; FMD: flow mediated dilation; c-fPWV: carotid-femoral pulse wave velocity; AIx: augmentation index; ABI: ankle brachial index; p values are from oneway ANOVA; IMT: carotid intima media thickness; values expressed as means ± SEM.
(781.6 ± 33.5 vs 712.5 ± 16.2 μm, p = 0.039) but not in the control group (693.2 ± 27.7 vs 655.1 ± 23.4 μm, p = 0.163) (Fig. 1). No significant differences were observed between C-allele carriers and TT homozygotes regarding PWV, FMD and ABI in untreated hypertension (p= 0.083, p = 0.066, and p = 0.735 respectively) (Table 2). In conclusion in the present study, we examined the potential association of C-344T, a genetic variant of the aldosterone synthase gene, with indices of preclinical vascular damage. Interestingly, our results support a significant main effect of the promoter genotype on IMT in untreated hypertension. This finding is novel and may have important clinical implications. However further studies are needed to further elucidate the association between the genetic variant of aldosterone synthase with vascular alterations in essential hypertension. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.
0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.01.035
References [1] Tousoulis D, Kampoli AM, Papageorgiou N, et al. Pathophysiology of atherosclerosis: the role of inflammation. Curr Pharm Des 2011;17:4089–110. [2] Androulakis ES, Tousoulis D, Papageorgiou N, Tsioufis C, Kallikazaros I, Stefanadis C. Essential hypertension: is there a role for inflammatory mechanisms? Cardiol Rev 2009;17:216–21. [3] Bozec E, Lacolley P, Bergaya S, et al. Arterial stiffness and angiotensinogen gene in hypertensive patients and mutant mice. J Hypertens 2004;22:1299–307. [4] Méthot J, Hamelin BA, Arsenault M, Bogaty P, Plante S, Poirier P. The ACE-DD genotype is associated with endothelial dysfunction in postmenopausal women. Menopause 2006;13:959–66. [5] Tousoulis D, Androulakis E, Papageorgiou N, et al. Genetic polymorphism M235T of angiotensinogen: effects on endothelial function and arterial stiffness in hypertensives. Int J Cardiol 2012;155:501–3. [6] Balkestein EJ, Wang JG, Struijker-Boudier HA, et al. Carotid and femoral intima–media thickness in relation to three candidate genes in a Caucasian population. J Hypertens 2002;20:1551–61. [7] Tousoulis D, Antoniades C, Stefanadis C. Evaluating endothelial function in humans: a guide to invasive and non-invasive techniques. Heart 2005;91:553–8.
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[44] Shimano M, Tsuji Y, Inden Y, et al. Pioglitazone, a peroxisome proliferators-activated receptor-gamma activator, attenuates atrial fibrosis and atrial fibrillation promotion in rabbits with congestive heart failure. Heart Rhythm 2008;5:451–9.
0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.01.037
Effects of the C-344T aldosterone synthase gene variant on preclinical vascular alterations in essential hypertension Emmanuel Androulakis 1, Dimitris Tousoulis ⁎,1, Nikolaos Papageorgiou, Antigoni Miliou, Evaggelos Chatzistamatiou, George Moustakas, Stavroula Papaoikonomou, Ioannis Kallikazaros, Christodoulos Stefanadis 1st Cardiology Department, Athens University Medical School, Greece
a r t i c l e
i n f o
Article history: Received 22 November 2012 Accepted 18 January 2013 Available online 11 March 2013 Keywords: Renin–angiotensin–aldosterone Genes Polymorphisms Vascular damage Atherosclerosis Renal function
The role of the renin–angiotensin–aldosterone system (RAAS) in the pathophysiology of essential hypertension (EH) and subclinical atherosclerosis remains unclear, while an increase in the local production of angiotensin II (Ang-II) and aldosterone may be implicated in the hypertension-associated vascular disease through several mechanisms [1,2]. Scarce and inconsistent data suggest that M235T polymorphism of the angiotensinogen (AGT) gene may be a genetic marker for endothelial dysfunction and arterial stiffness [3–5]. Moreover, it has been suggested that C-344T, a genetic variant of the aldosterone synthase (CYP11B2) gene, might be associated with subclinical atherosclerosis, assessed by intima–media thickness (IMT) [6]. However, its effects on endothelial and vascular function remain unknown. Thus, in the present study we investigated the potential associations between the C-344T aldosterone synthase gene variant with vascular damage in essential hypertension. The study population consisted of 318 untreated, newly diagnosed essential hypertensives, and a control group of 193 matched, normotensive individuals. All subjects underwent the routine work-up in order to exclude secondary forms of hypertension. The study was approved by the Institutional Ethics Committees, and an informed consent was given by all the participants. Carotid–femoral pulse wave velocity (cf-PWV) measurements were obtained using a validated non-invasive automatic device (Complior SP; Artech Medical, Pantin, France). Augmentation index (AIx) was ⁎ Corresponding author at: Athens University Medical School, Hippokration Hospital, Vasilisis Sofias 114, 115 28, Athens, Greece. Tel.: +30 2132088099; fax: +30 2132088676. E-mail address: [email protected] (D. Tousoulis). 1 Equally contributed.
estimated by applanation tonometry of the left radial artery by using the SphygmoCor device. Flow mediated dilation (FMD) was assessed in the brachial artery, which was scanned in longitudinal section, using a 7–12 MHz linear array transducer (baseline) (Vivid 7, General Electric, USA), as described previously [7]. In all patients, ankle-brachial index (ABI) values were determined in our vascular laborator by Doppler measurements. The IMT was measured by echocardiography as described previously. Levels of fibrinogen and high sensitivity Creactive protein (hsCRP) were measured by immunonephelometry (Dade Behring, Marburg, Germany). Polymorphism analysis of the CYP11B2 gene (rs1799998) was performed using the primers rs1799998F: 5′-CAGGGGGTACGTGGAC ATTT-3′ and rs1799998R: 5′-CAGGGCTGAGAGGAGTAAAA-3′ and PCR products were digested with HaeIII endonuclease. Allele frequencies were compared between groups by Chi-square analysis and differences in continuous variables between 2 groups were assessed by the Student t-test for parametric data. On variables found to deviate from normality, nonparametric tests (Kruskal–Wallis/Mann–Whitney) were applied. Relationships among variables were assessed using linear regression analysis and Pearson's correlation coefficient. All tests were two sided, and a p value of b0.05 was considered to indicate statistical significance. SPSS version 18.0 (SPSS, Chicago, IL) software was used for all the statistical calculations. The demographic characteristics of the study population are shown in Table 1. Notably, we have observed higher values of IMT in −344TT homozygosity compared to C-carriers, in the group of hypertensives Table 1 Demographic characteristics of subjects.
Number of subjects Age (years) Smokers N (%) Dyslipidemia N (%) Body mass index (kg/m2) Average heart rate** (bpm) Ejection fraction (%) Glucose (mg/dl) Creatinine (mg/dl) Uric acid (mg/dl) Total cholesterol (mg/dl) Fibrinogen (mg/dl) C-reactive protein (mg/l)
Controls
Hypertensives*
p value
193 51.5 ± 0.9 68 (35.6%) 81 (42.1%) 27.1 ± 0.3 72.9 ± 0.7 64.4 ± 0.3 96.5 ± 0.9 0.93 ± 0.06 4.8 ± 0.13 211.7 ± 3.6 355.6 ± 7.8 2.09 ± 0.2
318 52.3 ± 0.7 130 (41.0%) 120 (38.1%) 28.6 ± 0.3 75.3 ± 0.6 63.4 ± 0.3 99.1 ± 0.8 0.94 ± 0.01 5.2 ± 0.11 215.2 ± 2.5 365.7 ± 6.2 2.54 ± 0.2
p = NS p = NS p = NS p = NS p = 0.027 p = 0.06 p = NS p = 0.039 p = 0.041 p = NS p = NS p = 0.054
*Untreated hypertensives; **measurements obtained by ambulatory blood pressure monitoring; values expressed as means ± SEM; p by chi-square analysis; NS: non significant.
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Letters to the Editor
Fig. 1. Intima–media thickness (IMT) values in relation to the CYP11B2 promoter genotype in healthy and hypertensive subjects.
Table 2 Vascular measurements of the C-344T variant in the hypertensive and control subjects. CT + CT
TT
p value
4.2 ± 0.2 8.9 ± 0.2 26.6 ± 1.7 1.16 ± 0.009 781.6 ± 33.5
0.066 0.083 0.879 0.735 0.039
EH FMD (%) c-fPWV (m/s) AIx ABI IMT (μm)
5.0 ± 0.3 8.6 ± 0.1 27.6 ± 1.3 1.16 ± 0.008 712.5 ± 16.2
CC + CT
TT
p value
6.1 ± 0.4 7.7 ± 0.2 26.6 ± 1.5 1.14 ± 0.02 693.2 ± 27.7
0.137 0.348 0.225 0.697 0.163
Controls 7.3 ± 0.4 7.4 ± 0.1 23.8 ± 1.6 1.15 ± 0.008 655.1 ± 23.4
EH: essential hypertension; FMD: flow mediated dilation; c-fPWV: carotid-femoral pulse wave velocity; AIx: augmentation index; ABI: ankle brachial index; p values are from oneway ANOVA; IMT: carotid intima media thickness; values expressed as means ± SEM.
(781.6 ± 33.5 vs 712.5 ± 16.2 μm, p = 0.039) but not in the control group (693.2 ± 27.7 vs 655.1 ± 23.4 μm, p = 0.163) (Fig. 1). No significant differences were observed between C-allele carriers and TT homozygotes regarding PWV, FMD and ABI in untreated hypertension (p= 0.083, p = 0.066, and p = 0.735 respectively) (Table 2). In conclusion in the present study, we examined the potential association of C-344T, a genetic variant of the aldosterone synthase gene, with indices of preclinical vascular damage. Interestingly, our results support a significant main effect of the promoter genotype on IMT in untreated hypertension. This finding is novel and may have important clinical implications. However further studies are needed to further elucidate the association between the genetic variant of aldosterone synthase with vascular alterations in essential hypertension. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.
0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.01.035
References [1] Tousoulis D, Kampoli AM, Papageorgiou N, et al. Pathophysiology of atherosclerosis: the role of inflammation. Curr Pharm Des 2011;17:4089–110. [2] Androulakis ES, Tousoulis D, Papageorgiou N, Tsioufis C, Kallikazaros I, Stefanadis C. Essential hypertension: is there a role for inflammatory mechanisms? Cardiol Rev 2009;17:216–21. [3] Bozec E, Lacolley P, Bergaya S, et al. Arterial stiffness and angiotensinogen gene in hypertensive patients and mutant mice. J Hypertens 2004;22:1299–307. [4] Méthot J, Hamelin BA, Arsenault M, Bogaty P, Plante S, Poirier P. The ACE-DD genotype is associated with endothelial dysfunction in postmenopausal women. Menopause 2006;13:959–66. [5] Tousoulis D, Androulakis E, Papageorgiou N, et al. Genetic polymorphism M235T of angiotensinogen: effects on endothelial function and arterial stiffness in hypertensives. Int J Cardiol 2012;155:501–3. [6] Balkestein EJ, Wang JG, Struijker-Boudier HA, et al. Carotid and femoral intima–media thickness in relation to three candidate genes in a Caucasian population. J Hypertens 2002;20:1551–61. [7] Tousoulis D, Antoniades C, Stefanadis C. Evaluating endothelial function in humans: a guide to invasive and non-invasive techniques. Heart 2005;91:553–8.