Published online before print May 24, 2004, doi: 10.1161/01.CIR.0000129304.98566.D8
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Circulation. 2004;109:2885-2889.)
© 2004 American Heart Association, Inc.
Clinical Investigation and Reports |
Determinants of Arterial Nitrate-Mediated Dilatation in Children
Role of Oxidized Low-Density Lipoprotein, Endothelial Function, and Carotid Intima-Media Thickness
From the Department of Clinical Physiology and Turku PET Centre (M.J.J., O.T.R.), Turku University Hospital, and the Research Centre of Applied and Preventive Cardiovascular Medicine (M.J.J.), University of Turku, and the Laboratory of Atherosclerosis Genetics (T.L.), Department of Clinical Chemistry, Centre for Laboratory Medicine, Tampere University Hospital and University of Tampere, Finland.
Correspondence to Mikko J Järvisalo, Turku PET Centre, Turku University Hospital, Kiinamyllynkatu 4-8, FIN-20520 Turku, Finland. E-mail mikko.jarvisalo{at}utu.fi
Received December 8, 2003; revision received February 27, 2004; accepted March 4, 2004.
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Background— Impaired arterial dilatation response to nitroglycerin has been observed in adults with risk factors for atherosclerosis and in patients with established atherosclerotic disease. This defect parallels changes in vascular endothelial function and may be attributed to increased oxidative stress. Because atherosclerosis begins in childhood, we examined the correlates of nitrate-mediated dilatation (NMD) in children, including brachial artery endothelial function, oxidized LDL, and carotid artery intima-media thickness (IMT).
Methods and Results— Brachial artery flow-mediated endothelium-dependent dilatation (FMD) and nitrate-mediated smooth muscle function, IMT of the carotid bulb, and brachial artery and oxidized LDL were measured in 142 children (mean age, 11 years; range, 8 to 17 years), including 87 healthy children, 41 diabetic children, and 14 children with familial hypercholesterolemia. NMD correlated directly with FMD (r=0.46, P<0.001) and inversely with brachial artery baseline diameter (r=–0.36, P<0.001), age (r=–0.25, P=0.003), body mass index (r=–0.31, P<0.001), diabetes (r=–0.22, P=0.008), oxidized LDL (r=–0.18, P=0.045), and IMT (r=–0.33, P<0.001). In a multivariate regression model, the significant correlates for NMD were FMD response (ß=0.003, P<0.001), brachial artery diameter (ß=–0.03, P=0.01), oxidized LDL (ß=–0.07, P=0.02), and IMT (ß=–0.15, P=0.03).
Conclusions— Reduced endothelial function, increased oxidative stress, and preclinical carotid atherosclerosis are independent determinants of impaired NMD in children. These data thus suggest that primary nitrate tolerance occurs in children at risk for atherosclerosis.
Key Words: arteries • diabetes mellitus • endothelium • nitroglycerin • pediatrics
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Endothelial dysfunction is currently considered a key early event in the atherosclerotic process already evident in children with cardiovascular risk factors, such as hypercholesterolemia1 and diabetes.2 The brachial artery ultrasound test for flow-mediated endothelial-dependent vasodilatory function (FMD), described by Celermajer et al,1 includes administration of sublingual nitrates to examine the vasodilating effect of an exogenous source of nitric oxide (NO). NO acts directly at the level of the arterial smooth muscle cells and produces an endothelium-independent dilatation response. Nitrate-mediated dilatation (NMD) has therefore been used as a control test for the FMD measurement to ensure that a decreased FMD capacity observed is truly a consequence of endothelial dysfunction and not a reflection of underlying smooth muscle dysfunction.
Recent evidence indicates that in addition to influencing endothelial function, atherosclerosis may also induce changes in arterial dilatation responses to exogenous NO.3,4 Adult patients with coronary artery disease show impaired brachial NMD compared with healthy control subjects.4 Attenuated NMD is associated with serum cholesterol concentration independently of endothelial function in apparently healthy adults.3 In most previous studies in children, the NMD responses have actually been mildly reduced in high-risk individuals, although the difference has not reached statistical significance, possibly because of limited sample size.1,2,5
Increased oxidative stress and oxidized LDL have been implicated as risk factors for atherosclerosis6 and shown to potently quench NO7 and decrease its production8 in experimental studies. Recent studies have associated oxidative stress with nitrate tolerance.9 Because the atherosclerotic process begins in childhood,10 we examined the correlates of NMD in children, including brachial artery endothelial function, oxidized LDL, and carotid artery intima-media thickness (IMT).
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Subjects
We studied 142 children (83 boys; mean age, 11 years; range, 8 to 17 years), including 41 children with diabetes and 14 children with familial hypercholesterolemia (FH). All subjects were nonsmokers.
Children with diabetes were consecutively recruited from the outpatient clinic of the Department of Pediatrics, Turku University Central Hospital. They met inclusion criteria if they were between 7 and 14 years of age, had a duration of diabetes >6 months, were normotensive, and had no chronic diseases other than type 1 diabetes. The mean duration of diabetes was 4.4±2.9 years. None of the children with diabetes were taking regular medications other than daily insulin. The daily insulin dose was 0.97±0.26 IU/kg (range, 0.62 to 1.53 IU/kg). None of the patients with diabetes had evidence of microvascular complications, such as diabetic retinopathy, neuropathy, or microalbuminuria. In the group with diabetes, the mean glycosylated hemoglobin (HbA1c) level was 8.9±1.4% (range, 6.2% to 12.8%; reference range, 4.2% to 6.0%) and ratio of urinary albumin to urinary creatinine was 0.80±0.53 mg/mmol. Participants did not differ in any clinical characteristics from the whole eligible diabetic clinic population of the same age.
The children with FH were consecutively recruited from the outpatient clinic of the Department of Pediatrics, Turku University Central Hospital. Every child with FH had a serum total cholesterol level >6.0 mmol/L or LDL cholesterol level >4.5 mmol/L, but none of the children had tendon xanthoma, arcus lipoids, or xanthelasma. FH had been confirmed by lymphocyte testing. Ten of the children with FH were taking lipid-lowering medication, including 7 taking statins (simvastatin 40 mg, 1; simvastatin 5 mg, 1; lovastatin 40 mg, 2; lovastatin 20 mg, 3) and 3 undergoing bile acid sequestrant treatment with cholestyramine 4 to 8 g/d. Four of the children were undergoing diet therapy only.
The healthy control children included in the study were friends of the diabetic children studied, children of Turku University or Turku University Central Hospital staff members, or children participating in an ongoing trial aimed at decreasing children’s exposure to known environmental atherosclerotic risk factors.11 Written informed consent was acquired from the legal guardians of the children. The study was conducted according to the Declaration of Helsinki, and the Joint Commission on Ethics of Turku University and Turku University Central Hospital approved the study protocol.
Ultrasound Studies
All studies were undertaken in the morning, with fasting subjects, using an Acuson Sequoia 512 mainframe (Acuson) and a 13.0-MHz linear-array transducer.
Brachial artery diameter was measured from ultrasound images, as described earlier.12 For the measurement of FMD, scans of the left brachial artery 5 cm above the elbow were obtained at rest and during reactive hyperemia induced by inflating and deflating a forearm blood pressure cuff (250 mm Hg, 4.5 minutes). Scans were recorded on super-VHS tapes for offline analysis. Vessel diameter was measured by a blinded reader using ultrasonic calipers at a fixed distance from an anatomic marker. Measurements were taken at end-diastole, coincident with R-wave on ECG, every 10 seconds between 40 and 120 seconds and every 15 seconds between 120 and 180 seconds after cuff release (a total of 13 measurement points). The maximal dilatation from baseline (peak FMD, %) and area under the FMD curve (FMDAUC, percent multiplied by seconds) were calculated. NMD capacity was tested by administering 4 consecutive sublingual 50-µg doses of glyceryl trinitrate (GTN), all 5 minutes apart (cumulative dose, 200 µg). Brachial artery diameter was measured 5 minutes after each dose to acquire a dose-response curve. Maximal proportional increase in diameter from the baseline value during the test was calculated, as well as the area under the dose-response curve. In our laboratory, the interobserver and intraobserver variations of FMD measurements were 8.6% and 6.2%, respectively.13
For the measurement of the IMT of the left carotid bulb, the bulb region was first scanned carefully in many interrogation angles to identify the beginning of the bulb and the location of the maximal IMT. The scan was focused on the posterior (far) wall, and resolution box function was used to magnify the arterial far wall. Several images of carotid bulb far wall were acquired. All scans were digitally stored on the ultrasound system internal hard disk for subsequent offline analysis. Two end-diastolic frames with the greatest IMT were selected and analyzed for mean IMT, and the average reading from these 2 frames was calculated. Six to 12 measurements of IMT were taken by 2 independent and experienced readers blinded to the subject’s clinical details. Average values of the 2 readers were used in the analyses.
Brachial IMT was measured offline from digitized B-mode ultrasound images acquired 5 cm proximal to the antecubital fossa. Resolution box function was used to magnify a brachial artery far-wall segment of 1 cm in width. The images were captured at end-diastole, incident with the R-wave on a continuously recorded ECG, and digitally stored for offline analyses. Six to 8 measurements were taken, covering the entire segment of arterial wall, by a single blinded observer. The average of these measurements was used as a measure of mean brachial IMT in the analyses.
Serum Lipids and Oxidized LDL
Venous blood samples were taken in the morning, after an overnight fast (10 to 12 hours). Serum total cholesterol, HDL cholesterol, and triglyceride concentrations were measured using standard enzymatic methods with the use of Boehringer Mannheim GmbH reagents, with a fully automated analyzer (Hitachi 917; Hitachi Ltd). LDL cholesterol concentration was calculated using the Friedewald equation.14 Serum apolipoprotein B was measured using immunophelometry (Behring Nephelometer II, Dade Behring Inc). HbA1c was measured with high-performance liquid chromatography (Variant Analyser, Bio-Rad). Thawed samples were used for the determination of oxidized LDL by a capture ELISA (also known as a sandwich ELISA) according to manufacturer’s instructions (Mercodia AB). Shortly thereafter, microtiter plates were coated with the specific murine monoclonal antibody, mAb-4E6.6 During incubation, oxidized LDL in the sample reacted with the mAb-4E6 antibodies bound to the wells. After washing steps, a peroxidase-conjugated antiapolipoprotein B antibody was used to recognize the oxidized LDL. Finally, the bound conjugate was detected by reaction with 3,3',5,5'-tetramethylbenzidine, and the reaction was stopped by adding acid to give a colorimetric end point that was read spectrophotometrically at 450 nm. The detection limit of the method is <1 mU/L according to the manufacturer.
Statistical Methods
Results are expressed as mean±SD. Univariate associations between the study variables were analyzed by calculating the Spearman’s correlation coefficients. Multivariate analyses were done using the linear regression technique. To examine whether disease group (healthy versus diabetes mellitus versus FH) modifies the associations between risk factors and NMD, we included group x risk factor interaction terms in the regression models. The associations between risk factors and NMD were not different between the groups (all interaction terms, P>0.4). All statistical analyses were performed using the statistical analysis system SAS.15
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The characteristics of the study children are shown in Table 1. Mean maximal NMD in all subjects was 10.9±4.6, and mean peak FMD was 6.7±4.0%. Mean NMD was 11.6±4.4 in healthy children and 9.8±4.7% in children at risk (diabetes mellitus or FH) (P=0.02). Mean brachial artery IMT was higher in high-risk children (0.17±0.02 versus 0.19±0.02 mm, P<0.001). On univariate analysis, a reduced NMD response was significantly and inversely associated with diabetes, increasing age, body mass index, oxidized LDL, IMT, brachial IMT, and brachial artery baseline diameter (Table 2). FMDAUC showed similar associations with risk factors apart from oxidized LDL (Table 2). Associations between NMD and risk factors did not differ between healthy, diabetic, and FH children (risk factor x disease group interaction terms; P>0.4). When subjects with diabetes or FH were excluded from the analyses, the association between NMD and age (r=–0.35, P=0.001), body mass index (r=–0.32, P<0.001), and IMT (r=–0.24, P=0.028) persisted, but the association between NMD and oxidized LDL was abolished (r=–0.17, P=0.16). In all subjects pooled together, FMD and NMD were directly correlated (Table 2, Figure).
|
|
|
In the multivariate analysis including all study subjects, the independent predictors of a reduced NMD response included oxidized LDL, FMDAUC, IMT, and brachial baseline diameter (Table 3). Multivariate results remained essentially the same when brachial IMT was included in the model instead of IMT. Brachial IMT was not independently associated with NMD in the multivariate model (ß=10.11, P=0.58). Similar results were obtained when girls and boys were examined separately (data not shown).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The present study demonstrates that NMD, the vasodilatory response to an exogenous source of NO, is closely associated with endothelial function in children. The independent determinants of impaired NMD response included low FMD, increased oxidized LDL, and higher IMT. These novel findings suggest that decreased dilatation response to exogenous NO donors occurs in children at increased risk for atherosclerosis.
Endothelial dysfunction is an early event in atherosclerosis. It is generally thought that in the early stages of atherosclerosis, the endothelium-independent NMD responses remain unaltered. In most previous small-scale studies in children and in adults, however, the NMD responses have actually been mildly reduced in high-risk individuals, although this result has not always reached statistical significance.1,2,5 Adams et al3 have previously shown in a large population-based sample of adults that an attenuated response to GTN associates with cardiovascular risk factors independently of endothelial dysfunction. In addition, Raitakari et al4 have recently demonstrated that patients with coronary artery disease have impaired NMD response compared with healthy controls. In that study, the difference in NMD between the groups was evident with subplateau doses of GTN. Therefore, it is likely that small sample sizes and the use of full antianginal doses of nitrates that induce a plateau arterial dilatation have led to the misinterpretation that NMD would not be compromised in individuals at increased risk for atherosclerosis. In the present study, we administered 4 consecutive 50-µg doses of GTN to acquire a dose-response curve. This approach seems to be a more sensitive means to observe subtle impairments in endothelium-independent vasodilatation. Because the NMD responses in the present study were lower compared with previous studies in children,1,2,5 it can be assumed that the response plateau, which reflects the maximum arterial endothelium-independent vasodilatory capacity, was not reached.
An impaired dilator response to GTN might be attributable to mechanical forces limiting the artery’s ability to relax, to decreased GTN bioconversion to NO inside the smooth muscle cells, or to decreased bioavailability of NO to the smooth muscle. Although up to 75% of adults show atherosclerotic lesions of any grade in the brachial artery,16 this arterial site does not develop occlusive plaques. It seems therefore unlikely that our present findings in children would be explained by vasodilatation-limiting mechanical forces attributable to atherosclerotic plaque formation. However, diffuse intima-medial thickening also occurs in the brachial artery in response to risk factors,17 as shown in the high-risk children of the present study. It is not known whether such morphological changes may mechanically influence smooth muscle function, but in the present study, brachial IMT was not associated with NMD in the multivariate model. Exogenous organic nitrates enter the smooth muscle cells and react with sulfhydryl groups, most probably from cysteine and glutathione, to facilitate the generation of NO and s-nitrothiols, which leads to vasodilatation.18 It has been shown that cellular glutathione levels are decreased in children with increased oxidative stress and diabetes,19 suggesting that the impaired NMD observed in children with risk factors might result from attenuated bioconversion of GTN to NO. However, it has been shown that even during nitrate tolerance caused by long-term GTN administration, the bioconversion of GTN to NO may remain unaltered.20
Given the subtle nature of the impairment in NMD observed in the present study, it is unlikely that this defect would significantly influence the measurement of FMD. Our present results demonstrate a close relationship between NMD and FMD, but causality of this association cannot be proven in this cross-sectional study setting, and it is possible that the correlation is merely a result of colinearity attributable to similar risk factor influences on these measures of arterial function.
Our present results demonstrate that NMD is inversely associated with oxidized LDL, a marker of increased oxidative stress. Under physiological conditions, there is a balance between endothelial release of NO and vascular oxygen-derived free radicals. Various conditions associated with atherosclerosis and endothelial dysfunction (eg, hypertension, hypercholesterolemia, diabetes, and smoking) are characterized by increased oxidative stress and the formation of O2– and oxidized LDL.21–23 O2–9 and oxidized LDL7 potently quench NO, decrease its bioavailability, and therefore inhibit vasodilatation by both exogenous and endogenous sources of NO as they parallel a common final pathway during vasodilatation.24 In line with the hypothesis that increased oxidative stress is causally associated with decreased NMD, vitamin C has been shown to protect against nitrate tolerance, possibly by decreasing O2– formation.25 Oxidized LDL was not associated with FMD in the present study, although one would assume that if NO produced by GTN bioconversion is inactivated by oxidized LDL, the same would occur when NO is released from the endothelium. The reason for this controversy remains unclear, although it may be thought that other risk factors than oxidized LDL might be more potent in the development of endothelial dysfunction in children.
Our study has limitations. We examined the relationships between NMD, FMD, arterial IMT, and risk factors using a cross-sectional setting. Additional experimental studies are required to determine a causal relationship between impaired NMD, increased oxidative stress, and atherosclerosis. The study included a relatively small number of participants, which may have increased the risk of selection bias. However, the children with diabetes and the children with FH participating in the present study were representative of the total eligible clinic population of children with diabetes and children with FH, respectively. Increased oxidative stress was assessed by measuring oxidized LDL, which reflects only one aspect of increased oxidative burden.
In conclusion, the attenuated vasodilatation response to exogenous NO donor GTN is associated with endothelial dysfunction, oxidative stress, and increased arterial IMT in children. Thus, these data suggest primary nitrate tolerance in children at risk for atherosclerosis. Potential causes for this early impairment of NMD may include accelerated inactivation of NO by increased oxidative stress or a defect in smooth muscle function.
|
Acknowledgments |
|---|
This study was financially supported by the Academy of Finland (grants 77841 and 201888), Finnish Medical Foundation, Research Foundation of Orion Corporation, Turku University Foundation, Juho Vainio Foundation, Research Foundation of Instrumentarium, Finnish Cultural Foundation, Finnish Foundation for Cardiovascular Research, and Emil Aaltonen Foundation. The authors thank Pohl-Boskamp GmbH for providing the nitroglycerin preparation used in this study.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
- Celermajer DS, Sorensen KE, Gooch VM, et al. Non-invasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet. 1992; 340: 1111–1115.[CrossRef][Medline]
[Order article via Infotrieve]
- Singh TP, Groehn H, Kazmers A. Vascular function and carotid intimal-medial thickness in children with insulin-dependent diabetes mellitus. J Am Coll Cardiol. 2003; 41: 661–665.
[Abstract/Free Full Text]
- Adams MR, Robinson J, McCredie R, et al. Smooth muscle dysfunction occurs independently of impaired endothelium-dependent dilation in adults at risk of atherosclerosis. J Am Coll Cardiol. 1998; 32: 123–127.
[Abstract/Free Full Text]
- Raitakari OT, Seale JP, Celermajer DS. Impaired vascular responses to nitroglycerin in subjects with coronary atherosclerosis. Am J Cardiol. 2001; 87: 217–219.[CrossRef][Medline]
[Order article via Infotrieve]
- Celermajer DS, Sorensen K, Ryalls M, et al. Impaired endothelial function occurs in the systemic arteries of children with homozygous homocystinuria but not in their heterozygous parents. J Am Coll Cardiol. 1993; 22: 854–858.[Abstract]
- Holvoet P, Vanhaecke J, Janssens S, et al. Oxidized LDL and malondialdehyde-modified LDL in patients with acute coronary syndromes and stable coronary artery disease. Circulation. 1998; 98: 1487–1494.
[Abstract/Free Full Text]
- Chin JH, Azhar S, Hoffman BB. Inactivation of endothelial derived relaxing factor by oxidized lipoproteins. J Clin Invest. 1992; 89: 10–18.[Medline]
[Order article via Infotrieve]
- Liao JK, Shin WS, Lee WY, et al. Oxidized low-density lipoprotein decreases the expression of endothelial nitric oxide synthase. J Biol Chem. 1995; 270: 319–324.
[Abstract/Free Full Text]
- Munzel T, Sayegh H, Freeman BA, et al. Evidence for enhanced vascular superoxide anion production in nitrate tolerance: a novel mechanism underlying tolerance and cross-tolerance. J Clin Invest. 1995; 95: 187–194.[Medline]
[Order article via Infotrieve]
- Ross R. The pathogenesis of atherosclerosis: an update. N Engl J Med. 1986; 314: 488–500.[Medline]
[Order article via Infotrieve]
- Niinikoski H, Viikari J, Ronnemaa T, et al. Prospective randomized trial of low-saturated-fat, low-cholesterol diet during the first 3 years of life: the STRIP baby project. Circulation. 1996; 94: 1386–1393.
[Abstract/Free Full Text]
- Jarvisalo MJ, Ronnemaa T, Volanen I, et al. Brachial artery dilatation responses in healthy children and adolescents. Am J Physiol Heart Circ Physiol. 2002; 282: H87–H92.
[Abstract/Free Full Text]
- Jarvisalo MJ, Toikka JO, Vasankari T, et al. HMG CoA reductase inhibitors are related to improved systemic endothelial function in coronary artery disease. Atherosclerosis. 1999; 147: 237–242.[CrossRef][Medline]
[Order article via Infotrieve]
- Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972; 18: 499–502.[Abstract]
- SAS/STAT User’s Guide. Cary, NC: SAS Institute Inc; 1998.
- Sorensen KE, Kristensen IB, Celermajer DS. Atherosclerosis in the human brachial artery. J Am Coll Cardiol. 1997; 29: 318–322.[Abstract]
- Toikka JO, Ahotupa M, Viikari JS, et al. Constantly low HDL-cholesterol concentration relates to endothelial dysfunction and increased in vivo LDL-oxidation in healthy young men. Atherosclerosis. 1999; 147: 133–138.[CrossRef][Medline]
[Order article via Infotrieve]
- Katsuki S, Arnold W, Mittal C, et al. Stimulation of guanylate cyclase by sodium nitroprusside, nitroglycerin and nitric oxide in various tissue preparations and comparison to the effects of sodium azide and hydroxylamine. J Cyclic Nucleotide Res. 1977; 3: 23–35.[Medline]
[Order article via Infotrieve]
- Dominguez C, Ruiz E, Gussinye M, et al. Oxidative stress at onset and in early stages of type 1 diabetes in children and adolescents. Diabetes Care. 1998; 21: 1736–1742.[Abstract]
- Laursen JB, Mulsch A, Boesgaard S, et al. In vivo nitrate tolerance is not associated with reduced bioconversion of nitroglycerin to nitric oxide. Circulation. 1996; 94: 2241–2247.
[Abstract/Free Full Text]
- Frostegard J, Wu R, Lemne C, et al. Circulating oxidized low density lipoprotein is increased in hypertension. Clin Sci (Lond). 2003; 105: 615–620.[Medline]
[Order article via Infotrieve]
- Ohara Y, Peterson TE, Harrison DG. Hypercholesterolemia increases endothelial superoxide anion production. J Clin Invest. 1993; 91: 2546–2551.[Medline]
[Order article via Infotrieve]
- Shinozaki K, Nishio Y, Okamura T, et al. Oral administration of tetrahydrobiopterin prevents endothelial dysfunction and vascular oxidative stress in the aortas of insulin-resistant rats. Circ Res. 2000; 87: 566–573.
[Abstract/Free Full Text]
- Laursen JB, Boesgaard S, Poulsen HE, et al. Nitrate tolerance impairs nitric oxide–mediated vasodilation in vivo. Cardiovasc Res. 1996; 31: 814–819.[CrossRef][Medline]
[Order article via Infotrieve]
- Mulsch A, Oelze M, Kloss S, et al. Effects of in vivo nitroglycerin treatment on activity and expression of the guanylyl cyclase and cGMP-dependent protein kinase and their downstream target vasodilator-stimulated phosphoprotein in aorta. Circulation. 2001; 103: 2188–2194.
[Abstract/Free Full Text]
This article has been cited by other articles:
 |
|
 |
|
  M. Juonala, M. Kahonen, T. Laitinen, N. Hutri-Kahonen, E. Jokinen, L. Taittonen, M. Pietikainen, H. Helenius, J. S.A. Viikari, and O. T. Raitakari Effect of age and sex on carotid intima-media thickness, elasticity and brachial endothelial function in healthy adults: The Cardiovascular Risk in Young Finns Study Eur. Heart J., May 1, 2008; 29(9): 1198 - 1206. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Fulop, E. Jebelovszki, N. Erdei, T. Szerafin, T. Forster, I. Edes, A. Koller, and Z. Bagi Adaptation of Vasomotor Function of Human Coronary Arterioles to the Simultaneous Presence of Obesity and Hypertension Arterioscler. Thromb. Vasc. Biol., November 1, 2007; 27(11): 2348 - 2354. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. M. Haney, L. H. Huffman, C. Bougatsos, M. Freeman, R. D. Steiner, and H. D. Nelson Screening and Treatment for Lipid Disorders in Children and Adolescents: Systematic Evidence Review for the US Preventive Services Task Force Pediatrics, July 1, 2007; 120(1): e189 - e214. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Kallio, E. Jokinen, O. T. Raitakari, M. Hamalainen, M. Siltala, I. Volanen, T. Kaitosaari, J. Viikari, T. Ronnemaa, and O. Simell Tobacco Smoke Exposure Is Associated With Attenuated Endothelial Function in 11-Year-Old Healthy Children Circulation, June 26, 2007; 115(25): 3205 - 3212. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Dalla Pozza, S. Bechtold, W. Bonfig, S. Putzker, R. Kozlik-Feldmann, H. Netz, and H.-P. Schwarz Age of Onset of Type 1 Diabetes in Children and Carotid Intima Medial Thickness J. Clin. Endocrinol. Metab., June 1, 2007; 92(6): 2053 - 2057. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. S. Pena, E. Wiltshire, K. MacKenzie, R. Gent, L. Piotto, C. Hirte, and J. Couper Vascular Endothelial and Smooth Muscle Function Relates to Body Mass Index and Glucose in Obese and Nonobese Children J. Clin. Endocrinol. Metab., November 1, 2006; 91(11): 4467 - 4471. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Juonala, J. S.A. Viikari, T. Ronnemaa, H. Helenius, L. Taittonen, and O. T. Raitakari Elevated Blood Pressure in Adolescent Boys Predicts Endothelial Dysfunction: The Cardiovascular Risk in Young Finns Study Hypertension, September 1, 2006; 48(3): 424 - 430. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Tsimikas, J. T. Willerson, and P. M. Ridker C-reactive protein and other emerging blood biomarkers to optimize risk stratification of vulnerable patients. J. Am. Coll. Cardiol., April 18, 2006; 47(8 Suppl): C19 - C31. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Kravariti, K. K. Naka, S. N. Kalantaridou, N. Kazakos, C. S. Katsouras, A. Makrigiannakis, E. A. Paraskevaidis, G. P. Chrousos, A. Tsatsoulis, and L. K. Michalis Predictors of Endothelial Dysfunction in Young Women with Polycystic Ovary Syndrome J. Clin. Endocrinol. Metab., September 1, 2005; 90(9): 5088 - 5095. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Juonala, J. S.A. Viikari, M. Kahonen, L. Taittonen, T. Ronnemaa, T. Laitinen, N. Maki-Torkko, V. Mikkila, L. Rasanen, H. K. Akerblom, et al. Geographic Origin as a Determinant of Carotid Artery Intima-Media Thickness and Brachial Artery Flow-Mediated Dilation: The Cardiovascular Risk in Young Finns Study Arterioscler. Thromb. Vasc. Biol., February 1, 2005; 25(2): 392 - 398. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||