Hypertension
Asymmetric Dimethylarginine and Augmentation Index in Newly Diagnosed Patients With Hypertension
Angiology 2015, Vol. 66(1) 43-48 ª The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0003319713513145 ang.sagepub.com
Mustafa C ¸ akar, MD1, Fatih Bulucu, MD1, Murat Karaman, MD1, ¨ mer Kurt, MD1, S¸ evket Balta, MD2, Seyit Ahmet Ay, MD1, O 2 Sait Demirkol, MD , Hakan S¸ arlak, MD1, Muharrem Akhan, MD1, Battal Altun, MD3, Halil Yaman, MD4, Erol Arslan, MD1, S¸ eref Demirbas¸ , MD1, and Kenan Sag˘lam, MD1
Abstract Pulse wave velocity (PWV), augmentation index (Aix), and central aortic pressure (CAP) are arterial stiffness markers of endothelial dysfunction (ED). We investigated the relationship between arterial stiffness parameters and asymmetric dimethylarginine (ADMA; a marker of ED), in newly diagnosed patients with hypertension (n ¼ 101; 61 females). These patients were investigated in accordance with the recommendations of hypertension guidelines. Arterial stiffness was measured, and serum ADMA and C-reactive protein (CRP; a marker of inflammation) levels were determined. In both women and men, there was no difference in terms of age, body mass index, systolic and diastolic blood pressures, PWV, CAP and the levels of ADMA, while Aix and CRP levels were significantly higher in women (P ¼ .004, P ¼ .046, respectively). In the whole group, ADMA levels correlated with Aix (Pearson r ¼ .237, P ¼ .024). Our findings provide further evidence of a link between arterial stiffness and ED in newly diagnosed patients with hypertension. Keywords arterial stiffness, pulse wave velocity, central aortic pressure, augmentation index, ADMA, CRP
Introduction Hypertension (HT) is a serious health problem with increasing prevalence worldwide.1 Its prevalence is 29% in the United States, 44% in developed countries of Europe, and 30.3% in Turkey.2,3 Hypertension increases the risk of several cardiovascular diseases (CVDs),4 particularly playing an important role in the pathogenesis of end organ damage. Hypertension is responsible for nearly 55% of myocardial infarctions and congestive heart failure cases, 50% to 75% of strokes and is blamed for approximately 27% of end-stage renal disease in patients on dialysis.5,6 End organ damage worsens with increasing levels and duration of the HT.7 Therefore, improvement in the blood pressure (BP) significantly reduces morbidity and mortality.7 Endothelial dysfunction (ED), a precursor of atherosclerosis,8 is present in patients with essential HT.9 Investigators have focused on noninvasive methods to assess ED and atherosclerosis, such as serum levels of markers as well as measurements of arterial stiffness, ankle brachial index, and flow-mediated dilatation.10 Asymmetrical dimethylarginine (ADMA) is a competitive endogenous nitric oxide (NO) synthase inhibitor that occurs as a natural cellular product.11 Increased synthesis of ADMA is a marker of ED,12 and this makes it a useful marker
of ED.13,14 Additionally, several markers have been used to assess systemic inflammation. A positive association between serum C-reactive protein (CRP) levels and high BP has been reported.15,16 Arterial stiffness is associated with known atherosclerotic risk factors such as HT, smoking, hypercholesterolemia, diabetes mellitus (DM), or aging17 and is an indicator of coronary artery disease, cerebrovascular disease, and peripheral arterial disease (PAD).18,19 Hypertension is related to ED, increased arterial stiffness, and mortality rates.20 The measures of arterial stiffness, that is, pulse wave velocity (PWV), augmentation index (Aix), and central aortic pressure (CAP) are used as
1
Department of Internal Medicine, Gulhane Medical Faculty, Ankara, Turkey Department of Cardiology, Gulhane Medical Faculty, Ankara, Turkey 3 Department of Internal Medicine, Kasımpas¸ a Hospital, Istanbul, Turkey 4 Department of Clinical Biochemistry, Gulhane Medical Faculty, Ankara, Turkey 2
Corresponding Author: Sevket Balta, Department of Cardiology, Gulhane School of Medicine, Tevfik Saglam St, 06018 Etlik, Ankara, Turkey. Email: [email protected]
Downloaded from ang.sagepub.com at Gebze Yuksek Teknoloji Enstitu on December 23, 2014
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Angiology 66(1)
indicators of ED.21 These indices are useful because they can detect CVD at early stages.22 Furthermore, noninvasive devices to measure arterial stiffness are becoming widely available. In this study, we investigated the relationships between arterial stiffness parameters and biochemical markers, reflecting ED and inflammation in newly diagnosed patients with hypertension.
Materials and Methods Patients We recruited 101 newly diagnosed patients (61 females) with HT between January 2012 and May 2012. The diagnosis was made in our outpatient clinics according to European Society of Cardiology/European Society of Hypertension (ESC/ESH) 2007 guidelines. All patients were investigated in accordance with these guidelines. Informed consent was obtained from all patients. The Local Ethics Committee approved the study. Age, HT duration, gender, family history and medications, and biochemical data (serum lipid profile, glycemia, and creatinine taken in the last 3 months for diagnosis or follow-up) of the participants were recorded. The patients were not taking any antihypertensive medication. Arterial stiffness parameters, PWV, Aix, and CAP were measured. In addition, serum markers of ED and inflammation, ADMA and CRP levels were determined. The correlations between these markers and those of arterial stiffness were investigated.
Exclusion Criteria Patients with a secondary cause of HT, DM (fasting glucose > 126 mg/dL), chronic kidney disease, any CVD, cerebrovascular disease, malignancy, morbid obesity, PAD, heart failure, 10 mm Hg difference between both arms, additional measurements were performed from both arms, and the measurement of the arm with the higher value was used.
Measurement of Arterial Stiffness A device for arterial stiffness measurement (TensoMed Ltd, Budapest, Hungary) was used. Systolic BP, diastolic BP, pulse pressure, PWV, Aix, and CAP were recorded.
Pulse Wave Velocity, Aix, and CAP Analysis The arterial stiffness measurements were made after 5 minutes rest in the sitting position and away from external stimuli and in a quiet room. The patients did not smoke or take caffeinated beverages for at least the previous 30 minutes. The distance between the jugular notch and the symphysis pubis was measured, and the data were recorded on the device. At the measurement period, brachial artery occlusion was performed for about 8 to 20 seconds, and the blood flow was blocked as a part of the measurement process. Then, the systolic and diastolic BP, mean arterial BP, pulse rate, pulse pressure, PWV, Aix, and CAP were calculated by the device. The pressure waves were derived from the Aix, PWV, and CAP values.
Demographic Measurements Weight (in kg) and height (in cm) were measured, and body mass index (BMI) was calculated as body weight/height2 (kg/m2).
Laboratory Studies All blood samples were drawn in the morning at least after 10 hours of fasting. Routine laboratory tests and biochemistry, including a full blood count, serum glucose, urea, creatinine, sodium, potassium, and liver enzymes, were performed during the outpatient visit. Serum samples for ADMA and CRP were run in the same assay. These samples were promptly centrifuged, the plasma and serum were separated and stored at 80 C. Fasting plasma glucose, total cholesterol, triglyceride, and high-density lipoprotein cholesterol (HDL-C) levels were measured by an enzymatic colorimetric method with an Olympus AU2700 auto analyzer using reagents from Olympus Diagnostics (GmbH, Hamburg, Germany). Low-density lipoprotein cholesterol was calculated by Friedewald formula.23 Asymmetric dimethylarginine was measured in serum using an ADMA (human) enzyme-linked immunosorbent assay (ELISA) kit (Enzo Life Sciences, Farmingdale, New York, USA; minimum detectable concentration ¼ 0.05 mmol/L). The intensity of the color reaction was inversely proportional to ADMA level in the sample, measured by reading the optical density at 450 nm with a microplate reader (QS-500; Leica Company, Germany). C-reactive protein was measured in serum with a sensitive CRP ELISA kit with rabbit anti-CRP (Dako, Copenhagen, Denmark) as a catching and a tagging antibody.
Statistical Analysis Statistical analysis was carried out using SPSS ver.15.0 (SPSS Inc, Chicago, Illinois). Independent samples t test, chi-square test, Mann-Whitney U statistical analysis, Pearson-r correlation, and linear regression analysis tests were used. Results of the analysis were expressed as percentage of qualitative variables and mean + standard deviation for continuous variables. Univariate analysis was used to calculate the isolated effects of dependent variables. A multivariate analysis was used to adjust
Downloaded from ang.sagepub.com at Gebze Yuksek Teknoloji Enstitu on December 23, 2014
C¸akar et al
45
Table 1. General Characteristics of Patients.a Male
Female
P
n (%) 40 (39.6) 61 (60.4) .791 Age, years 48.9 + 13.1 51.2 + 10.3 .341 28.8 + 4.0 28.9 + 4.6 .899 BMI, kg/m2 Height, cm 170.8 + 9.3 160.9 + 5.2
Asymmetric Dimethylarginine and Augmentation Index in Newly Diagnosed Patients With Hypertension
Angiology 2015, Vol. 66(1) 43-48 ª The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0003319713513145 ang.sagepub.com
Mustafa C ¸ akar, MD1, Fatih Bulucu, MD1, Murat Karaman, MD1, ¨ mer Kurt, MD1, S¸ evket Balta, MD2, Seyit Ahmet Ay, MD1, O 2 Sait Demirkol, MD , Hakan S¸ arlak, MD1, Muharrem Akhan, MD1, Battal Altun, MD3, Halil Yaman, MD4, Erol Arslan, MD1, S¸ eref Demirbas¸ , MD1, and Kenan Sag˘lam, MD1
Abstract Pulse wave velocity (PWV), augmentation index (Aix), and central aortic pressure (CAP) are arterial stiffness markers of endothelial dysfunction (ED). We investigated the relationship between arterial stiffness parameters and asymmetric dimethylarginine (ADMA; a marker of ED), in newly diagnosed patients with hypertension (n ¼ 101; 61 females). These patients were investigated in accordance with the recommendations of hypertension guidelines. Arterial stiffness was measured, and serum ADMA and C-reactive protein (CRP; a marker of inflammation) levels were determined. In both women and men, there was no difference in terms of age, body mass index, systolic and diastolic blood pressures, PWV, CAP and the levels of ADMA, while Aix and CRP levels were significantly higher in women (P ¼ .004, P ¼ .046, respectively). In the whole group, ADMA levels correlated with Aix (Pearson r ¼ .237, P ¼ .024). Our findings provide further evidence of a link between arterial stiffness and ED in newly diagnosed patients with hypertension. Keywords arterial stiffness, pulse wave velocity, central aortic pressure, augmentation index, ADMA, CRP
Introduction Hypertension (HT) is a serious health problem with increasing prevalence worldwide.1 Its prevalence is 29% in the United States, 44% in developed countries of Europe, and 30.3% in Turkey.2,3 Hypertension increases the risk of several cardiovascular diseases (CVDs),4 particularly playing an important role in the pathogenesis of end organ damage. Hypertension is responsible for nearly 55% of myocardial infarctions and congestive heart failure cases, 50% to 75% of strokes and is blamed for approximately 27% of end-stage renal disease in patients on dialysis.5,6 End organ damage worsens with increasing levels and duration of the HT.7 Therefore, improvement in the blood pressure (BP) significantly reduces morbidity and mortality.7 Endothelial dysfunction (ED), a precursor of atherosclerosis,8 is present in patients with essential HT.9 Investigators have focused on noninvasive methods to assess ED and atherosclerosis, such as serum levels of markers as well as measurements of arterial stiffness, ankle brachial index, and flow-mediated dilatation.10 Asymmetrical dimethylarginine (ADMA) is a competitive endogenous nitric oxide (NO) synthase inhibitor that occurs as a natural cellular product.11 Increased synthesis of ADMA is a marker of ED,12 and this makes it a useful marker
of ED.13,14 Additionally, several markers have been used to assess systemic inflammation. A positive association between serum C-reactive protein (CRP) levels and high BP has been reported.15,16 Arterial stiffness is associated with known atherosclerotic risk factors such as HT, smoking, hypercholesterolemia, diabetes mellitus (DM), or aging17 and is an indicator of coronary artery disease, cerebrovascular disease, and peripheral arterial disease (PAD).18,19 Hypertension is related to ED, increased arterial stiffness, and mortality rates.20 The measures of arterial stiffness, that is, pulse wave velocity (PWV), augmentation index (Aix), and central aortic pressure (CAP) are used as
1
Department of Internal Medicine, Gulhane Medical Faculty, Ankara, Turkey Department of Cardiology, Gulhane Medical Faculty, Ankara, Turkey 3 Department of Internal Medicine, Kasımpas¸ a Hospital, Istanbul, Turkey 4 Department of Clinical Biochemistry, Gulhane Medical Faculty, Ankara, Turkey 2
Corresponding Author: Sevket Balta, Department of Cardiology, Gulhane School of Medicine, Tevfik Saglam St, 06018 Etlik, Ankara, Turkey. Email: [email protected]
Downloaded from ang.sagepub.com at Gebze Yuksek Teknoloji Enstitu on December 23, 2014
44
Angiology 66(1)
indicators of ED.21 These indices are useful because they can detect CVD at early stages.22 Furthermore, noninvasive devices to measure arterial stiffness are becoming widely available. In this study, we investigated the relationships between arterial stiffness parameters and biochemical markers, reflecting ED and inflammation in newly diagnosed patients with hypertension.
Materials and Methods Patients We recruited 101 newly diagnosed patients (61 females) with HT between January 2012 and May 2012. The diagnosis was made in our outpatient clinics according to European Society of Cardiology/European Society of Hypertension (ESC/ESH) 2007 guidelines. All patients were investigated in accordance with these guidelines. Informed consent was obtained from all patients. The Local Ethics Committee approved the study. Age, HT duration, gender, family history and medications, and biochemical data (serum lipid profile, glycemia, and creatinine taken in the last 3 months for diagnosis or follow-up) of the participants were recorded. The patients were not taking any antihypertensive medication. Arterial stiffness parameters, PWV, Aix, and CAP were measured. In addition, serum markers of ED and inflammation, ADMA and CRP levels were determined. The correlations between these markers and those of arterial stiffness were investigated.
Exclusion Criteria Patients with a secondary cause of HT, DM (fasting glucose > 126 mg/dL), chronic kidney disease, any CVD, cerebrovascular disease, malignancy, morbid obesity, PAD, heart failure, 10 mm Hg difference between both arms, additional measurements were performed from both arms, and the measurement of the arm with the higher value was used.
Measurement of Arterial Stiffness A device for arterial stiffness measurement (TensoMed Ltd, Budapest, Hungary) was used. Systolic BP, diastolic BP, pulse pressure, PWV, Aix, and CAP were recorded.
Pulse Wave Velocity, Aix, and CAP Analysis The arterial stiffness measurements were made after 5 minutes rest in the sitting position and away from external stimuli and in a quiet room. The patients did not smoke or take caffeinated beverages for at least the previous 30 minutes. The distance between the jugular notch and the symphysis pubis was measured, and the data were recorded on the device. At the measurement period, brachial artery occlusion was performed for about 8 to 20 seconds, and the blood flow was blocked as a part of the measurement process. Then, the systolic and diastolic BP, mean arterial BP, pulse rate, pulse pressure, PWV, Aix, and CAP were calculated by the device. The pressure waves were derived from the Aix, PWV, and CAP values.
Demographic Measurements Weight (in kg) and height (in cm) were measured, and body mass index (BMI) was calculated as body weight/height2 (kg/m2).
Laboratory Studies All blood samples were drawn in the morning at least after 10 hours of fasting. Routine laboratory tests and biochemistry, including a full blood count, serum glucose, urea, creatinine, sodium, potassium, and liver enzymes, were performed during the outpatient visit. Serum samples for ADMA and CRP were run in the same assay. These samples were promptly centrifuged, the plasma and serum were separated and stored at 80 C. Fasting plasma glucose, total cholesterol, triglyceride, and high-density lipoprotein cholesterol (HDL-C) levels were measured by an enzymatic colorimetric method with an Olympus AU2700 auto analyzer using reagents from Olympus Diagnostics (GmbH, Hamburg, Germany). Low-density lipoprotein cholesterol was calculated by Friedewald formula.23 Asymmetric dimethylarginine was measured in serum using an ADMA (human) enzyme-linked immunosorbent assay (ELISA) kit (Enzo Life Sciences, Farmingdale, New York, USA; minimum detectable concentration ¼ 0.05 mmol/L). The intensity of the color reaction was inversely proportional to ADMA level in the sample, measured by reading the optical density at 450 nm with a microplate reader (QS-500; Leica Company, Germany). C-reactive protein was measured in serum with a sensitive CRP ELISA kit with rabbit anti-CRP (Dako, Copenhagen, Denmark) as a catching and a tagging antibody.
Statistical Analysis Statistical analysis was carried out using SPSS ver.15.0 (SPSS Inc, Chicago, Illinois). Independent samples t test, chi-square test, Mann-Whitney U statistical analysis, Pearson-r correlation, and linear regression analysis tests were used. Results of the analysis were expressed as percentage of qualitative variables and mean + standard deviation for continuous variables. Univariate analysis was used to calculate the isolated effects of dependent variables. A multivariate analysis was used to adjust
Downloaded from ang.sagepub.com at Gebze Yuksek Teknoloji Enstitu on December 23, 2014
C¸akar et al
45
Table 1. General Characteristics of Patients.a Male
Female
P
n (%) 40 (39.6) 61 (60.4) .791 Age, years 48.9 + 13.1 51.2 + 10.3 .341 28.8 + 4.0 28.9 + 4.6 .899 BMI, kg/m2 Height, cm 170.8 + 9.3 160.9 + 5.2
