Genetics of Ultrasonographic Carotid Atherosclerosis

From the Division of Epidemiology and Clinical Applications (T.A.M., C.J.O.), National Heart, Lung, and Blood Institute, Bethesda, Md; the Human Genetics Center (E.B.), University of Texas Health Science Center at Houston, Houston, Tex; the National Heart, Lung, and Blood Institute Framingham Heart Study (C.J.O.), Framingham, Mass; and the Inherited Disease Research Branch (A.F.W.), National Human Genome Research Institute, Baltimore, Md.

ABSTRACT

The search for genes related to the cause of common complex disorders such as cardiovascular disease has been frustrating, partly because of the many factors known to contribute to cardiovascular disease and the potential "distance" of cardiovascular disease as a phenotype from genes and gene products. Linkage and association studies for phenotypes more proximal in the pathway from DNA sequence variation to overt clinical disease, such as ultrasound-defined carotid atherosclerosis, may potentially be more enlightening. Only one genetic variant previously reported to be associated with atherosclerosis or clinically evident cardiovascular disease, matrix metalloproteinase (MMP) 3, has shown consistently positive associations with carotid disease, although it has not been studied widely. Another, PON1 L55M, is weakly associated in subgroups only, and 2, ApoE and MTHFR, are equivocal. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis. This may reflect the known inconsistency in associations of genetic variants with clinical cardiovascular disease itself. Alternatively, genetic determinants of ultrasound-defined carotid atherosclerosis may differ from those of clinically manifest cardiovascular disease and may require pursuit through large-scale genomic studies of carotid atherosclerosis as a distinct phenotype.

Only 1 genetic variant, MMP 3, has shown consistently positive associations with ultrasonographic carotid disease, although it has not been studied widely. Another, PON1 L55 mol/L, is weakly associated in subgroups only. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis.

Key Words: atherosclerosis ? genes ? human ? carotid artery ? cardiovascular disease

Introduction

Identification of genes influencing complex clinically manifest traits such as myocardial infarction and stroke has been difficult, in part because of the many interacting factors known to contribute to these traits and the large conceptual, physiological, and temporal distance between gene variation and clinical manifestation of adult disease.1,2 In addition, genetic analysis of a disease end point is complicated by vagaries in disease diagnosis, including variations in presentation, access to care, and acumen of care providers. Studies of phenotypes further upstream in the pathway from DNA sequence variation to overt clinical disease, such as ultrasonographic carotid atherosclerosis, may thus yield valuable information not obtainable by studying clinical conditions alone.

Intimal-medial thickening (IMT) of the carotid artery determined by B-mode ultrasonography is a quantitative measure of atherosclerosis that has a graded, predictive relationship to overt clinical disease.3 Carotid IMT can be measured noninvasively in population-based samples free of many of the biases of clinically identified cases and controls.3–5 Focal carotid wall thickening (plaque) and lumen narrowing (stenosis) can also be imaged and also predict cardiovascular events.6

Ultrasonographic measures of the carotid artery may thus provide a useful intermediate phenotype for the identification of atherosclerosis-related genes. In this review, we describe the most commonly reported ultrasound-defined carotid phenotypes and estimates of their heritability, genetic variants examined for linkage or association with these phenotypes in human studies, and the strength of the evidence for or against a causative role of the variants.

Carotid Phenotypes and Their Heritability

Intimal-Medial Thickness

IMT is the most commonly assessed ultrasonographic carotid measurement because of its high measurement precision7 and its strong predictive value for subsequent cardiovascular events.3,4 Measurements are typically performed in the common carotid artery, usually in the 1 to 3 cm proximal to the origin of the carotid bulb (where the near and far walls cease to be parallel; Figure 1). The carotid bulb, or bifurcation, includes the segment from the initial outward curving of the walls to the proximal tip of the flow divider between the external and internal carotid arteries. The internal carotid artery is more difficult to image as it proceeds beneath the angle of the jaw, and rarely can more than the most proximal centimeter be measured. Measurement variability of the internal carotid can be up to 3 times greater than in the common carotid, and missing data are more frequent.8

Figure 1. Normal carotid bifurcation showing the common carotid (I), origin of the bulb (O), and flow divider (D). Reproduced with modification and permission from Ebrahim S, Papacosta O, Whincup P, Wannamethee G, Walker M, Nicolaides AN, Dhanjil S, Griffin M, Belcaro G, Rumley A, Lowe GD. Carotid plaque, intima media thickness, cardiovascular risk factors, and prevalent cardiovascular disease in men and women: the British Regional Heart Study. Stroke. 1999;30:841–850.

Variability of carotid IMT has been suggested to be higher for the near wall (that is, nearest the skin and the ultrasound transducer) than the far wall, because of physical characteristics of transmission and reflection of the ultrasound beam.9,10 Risk factor associations are at least as strong in the near wall as the far wall, however, and atherosclerosis progression rates are similar, with the most precise measure probably being combined near and far wall thickness.11

Reported differences in relationships of risk factors and disease incidence with IMT measured at different carotid sites have raised the possibility of site-specific differences in their cause and, possibly, their genetic determinants.12 Development and progression of atherosclerotic lesions of the internal carotid, where flow is turbulent, have been suggested to be related primarily to lipid accumulation and plaque hemorrhage, whereas the laminar flow typical of the common carotid may lead to more diffuse medial thickening indistinguishable ultrasonographically from atherosclerosis.3,12,13 This may explain why internal carotid IMT has been more strongly related to increased risk of incident disease, particularly incident coronary heart disease (CHD), than has IMT in the common carotid.3

One of the earliest reports of the potential familial nature of carotid artery structure demonstrated parental history of myocardial infarction to be associated with higher pressure-strain elastic modulus (Ep, a measure of stiffness) in 10- to 17-year-old adolescents.14 Although Ep is infrequently assessed, subsequent studies confirmed associations of carotid IMT with an estimated CHD family risk score,15 early-onset parental CHD death,16 and early-onset parental CHD incidence.17–19 Adjustment for measured CHD risk factors had little impact on any of these associations. Similar to the site-specific differences in subsequent clinical cardiovascular disease reported, internal carotid IMT has been more strongly related to early parental history of stroke, whereas common carotid IMT may be more strongly related to early parental history of myocardial infarction.20

The metric commonly used to summarize the familial and genetic nature of a trait is heritability (H, h2, or 2G/2P). The heritability of a trait is the proportion of interindividual variation in the trait (2P) attributable to genetic variation (2G). Heritability of a trait is a population- and environment-specific parameter, and its value, high or low, does not indicate the role of genes in any specific individual or patient. Heritability does, however, allow one to predict the expected degree of familial aggregation of a trait, and traits with a high heritability should prove fruitful in identifying trait-related genes.

One of the first formal assessments of heritability of carotid atherosclerosis was reported for carotid IMT in 46 sibships in Mexico City.21 The estimate of heritability was high, 92%, for the common carotid, and 82% for the internal carotid, after adjustment for standard CHD risk factors (Table 1). These high estimates have been questioned and subsequent reports have consistently estimated heritabilities in the range of 20% to 40% in unselected subjects,22,23 twins,24,25 and subjects with type II diabetes,26 although they are somewhat higher in families ascertained through a hypertensive parent27 and in randomly ascertained families.12

TABLE 1. Heritability of Various Carotid Artery Phenotypes.

Carotid Plaque and Stenosis

Carotid plaque is focal thickening of the carotid wall caused by atherosclerosis (Figure 2). Like definitions of IMT, plaque definitions vary and include focal thickening >50% of the surrounding wall;22,28 focal widening with protrusion into the lumen;29 localized IMT more than or equal to the cutpoints in the range of 0.75 mm to 1.5 mm;24,30–35 and focal acceleration of flow as measured by Doppler spectral analysis.7,36 Reference may also be made to "carotid atherosclerosis," also typically defined as thickening greater than a given threshold, whether focal or not.37,38 A plaque score or "B" score developed for the Asymptomatic Carotid Artery Plaque Study39 based on increasing categories of IMT has also been used,40–42 whereas other studies have calculated plaque scores by summing the maximal thickness of each plaque in the carotid arteries bilaterally.43

Figure 2. Common carotid artery and bulb with plaque (P). Reproduced with modification and permission from Ebrahim S, Papacosta O, Whincup P, Wannamethee G, Walker M, Nicolaides AN, Dhanjil S, Griffin M, Belcaro G, Rumley A, Lowe GD. Carotid plaque, intima media thickness, cardiovascular risk factors, and prevalent cardiovascular disease in men and women: the British Regional Heart Study. Stroke. 1999;30:841–850.

Plaque as a carotid atherosclerosis phenotype is not studied as frequently as carotid IMT. The heritability of plaque determined by localized IMT 1.5 mm was recently estimated at 23% to 28%.35 Carotid plaque has also been reported to be more strongly related to early parental CHD death than is IMT.44 Whereas one would anticipate that genes influencing plaque overlap with those influencing IMT, there are likely to be unique sets of genes related to both.45

Other Carotid Phenotypes

Other phenotypes related to carotid atherosclerosis include plaque echogenicity (consistent pathologically with more organized and fibrotic plaques) or echolucency (consistent with greater lipid deposition, intraplaque hemorrhage, and vulnerability to rupture),46 lumen diameter, distensibility, and stiffness. Lumen diameter is not widely reported because it correlates relatively poorly with atherosclerosis in its early stages, probably because the vessel dilates to preserve the lumen from encroachment until fairly late in the disease.10 Distensibility and stiffness are related to the elasticity measures described14 and are often calculated as the difference between minimum and maximum luminal diameter during the cardiac cycle multiplied by some index of blood pressure.47 Few reports of heritability of these measures are available, although one study did demonstrate higher heritability of lumen diameter (0.44) than IMT (0.21) and similar heritability of arterial stiffness (0.23).22

Genetic Variants Related to Carotid Phenotypes

Several genetic variants have been examined in relation to carotid atherosclerosis, more commonly by association than linkage analysis. Most have related genetic variants to IMT as a continuous trait, although many have reported dichotomous carotid plaque measures derived from arbitrary threshold levels of IMT as described. Findings from the most widely studied variants are summarized, followed by a listing of variants only beginning to be explored in relation to carotid disease.

Angiotensin 1-Converting Enzyme

Perhaps the most studied locus in relation to carotid atherosclerosis, and cardiovascular disease in general, is the insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene.48 Presence (insertion, I) or absence (deletion, D) of a 287-bp alu-repeat sequence in reverse orientation in intron 16 of this gene is associated with substantially different levels of plasma ACE activity in a codominant fashion, with DD homozygotes having the highest levels.48 ACE converts inactive angiotensin I to the vasoconstrictor angiotensin II and also inactivates the vasodilator bradykinin, leading to increased vascular tone, vascular smooth muscle cell growth, neointimal proliferation, and extracellular matrix deposition.34,49 Variants associated with higher ACE activity might thus be expected to be related to increased carotid wall thickness and plaque formation.

Evidence for such an association is inconsistent, however, with the majority of studies showing no association23,31,33,46,49–62 whereas several show higher IMT and plaque frequency in DD homozygotes or D allele carriers34,36,63–73 (Table I, available online at http://atvb.ahajournals.org). In only one was higher IMT associated with the II genotype, but this was in a small number of patients with symptomatic carotid territory cerebral ischemia.64 Most studies of the ACE genotype and carotid atherosclerosis, regardless of findings, include <500 subjects, with the 2 largest (100054 and 400031 subjects) showing no association. Only 2 studies reported possible interactions of the D allele with other factors in relation to IMT, in that IMT increased more steeply with increasing systolic blood pressure61 and age58 in D allele carriers than in II homozygotes.61 Another showed an association of the DD genotype with echolucent (high-risk) plaques despite lack of association with IMT or stenosis.46

Apolipoprotein E

Another widely studied gene in relation to carotid atherosclerosis is apolipoprotein E (APOE), whose role in cardiovascular disease has been reviewed by Eichner et al.74 Three common alleles (designated 2, 3, and 4) produce 3 protein isoforms differing at amino acid positions 112 and 158. The most common allele, APOE*3, produces the Apo E3 isoform with cysteine at position 112 and arginine at 158, whereas the least common, APOE*2, produces the Apo E2 protein with cysteine at both positions, and Apo E4 has arginine at both positions. Apolipoprotein levels vary by polymorphism, with APOE*2 associated with higher and APOE*4 associated with lower plasma apo E levels.75 Apo E2 in turn is associated with lower low-density lipoprotein (LDL) cholesterol levels, and Apo E4 with higher levels, than is the Apo E3 isoform.76 Carrying an APOE*4 allele has generally been associated with modestly increased risk of coronary heart disease (and strongly increased risk of Alzheimer disease), and carrying an APOE*2 allele has been associated with lower risk of coronary disease, compared with the 3/3 genotype,75 although the APOE*2 allele has also been related to increased risk of coronary disease.74,77

Most studies of the APOE 2/3/4 polymorphism have shown carotid IMT to be lower in carriers of the 2 allele and higher in carriers of the 4 allele, compared with 3/3 homozygotes76,78–84 (Table II, available online at http://atvb.ahajournals.org). These associations have not been totally consistent, however, with de Andrade38 and Hanon85 showing higher IMT in 2 carriers, Zannad23 showing higher IMT in 3/3 homozygotes compared with 2 or 4 carriers but on the right side only, and several studies30,37,49,58,62,68,86–89showing no association. Both studies reporting higher IMT in 2 carriers excluded persons with prevalent cardiovascular disease, which excludes proportionately more persons with carotid thickening,38 although relationships of APOE and IMT have been suggested to be similar regardless of prevalent disease.78 Most positive findings have remained after adjustment for multiple cardiovascular disease (CVD) risk factors and particularly for lipoprotein levels, through which the apo E polymorphism might be expected to exert some of its effect.75 Associations in diabetics68,80 and dialysis patients30,79 have tended to be less consistent than those in unselected populations. Interactions with environmental or context-dependent factors have been infrequently examined, although 2 studies suggested an interaction of the 4 allele with smoking to produce increased carotid atherosclerosis,37,88 and 1 formally tested and demonstrated a greater increase in IMT with increasing body mass index in 4 carriers.58 Another demonstrated a greater increase in plaque frequency per "unit change" in genotype in women than in men.84

Angiotensinogen and Angiotensin II Type 1 Receptor

Polymorphisms in the genes for angiotensinogen (AGT) and angiotensin II type 1 receptor (AGTR1) have been associated with increased cardiovascular disease risk.90,91 AGT is the precursor peptide of angiotensin II, a potent vasoconstrictor involved in regulation of blood pressure and fluid and electrolyte balance.92 AGT is cleaved by renin and ACE (discussed previously) to form angiotensin II, which then interacts with the AGTR1 to initiate a signal transduction cascade resulting in vasoconstriction.92 Angiotensin II stimulates proliferation and migration of vascular smooth muscle cells, causing intimal thickening; it also upregulates monocyte chemoattractant factor-1 to attract monocytes to the vessel wall and increases oxidation and uptake of LDL by macrophages, thus promoting foam cell formation.93–95

The most widely studied AGT polymorphism, a methionine to threonine substitution at position 235 in exon 2 of the gene, appears to be nonfunctional, but is in strong linkage disequilibrium with a guanine for adenine substitution 6 nucleotides upstream of the transcription initiation site (G-6A), which leads to increased gene transcription.96 It is also in strong linkage disequilibrium with a threonine to methionine substitution at position 174 (T174M), also in exon 2. Both the T allele of the M235T variant and M allele of the T174M variant have been associated with increased angiotensinogen levels, hypertension, and/or coronary disease.96,97 A second polymorphism in the promoter region, an adenine for cytosine substitution (A-20C), is also in nearly complete linkage disequilibrium with the G-6A polymorphism and has been related to increased plasma AGT levels and risk of hypertension. Lastly, an A-to-C transversion in the AGTR1 at nucleotide 1166 (AGTR1 A1166C) in the 3' untranslated region has been associated with increased risk of essential hypertension and higher prevalence of coronary disease.92

Studies of the AGT M235T polymorphism have fairly consistently shown no association with IMT in a variety of population samples,50,56,58,73,97–100 although 1 study of 98 previously untreated hypertensive patients showed higher IMT at entry and greater reduction in IMT after treatment in TT homozygotes101 (Table III, available online at http://atvb.ahajournals.org). Losito et al73 also examined the T174M polymorphism, with no association demonstrated. Similarly, no associations were detected with the AGTR1 A1166C polymorphism.52,56,58,73,92,100,102 Only one study to date has examined the promoter region polymorphisms, with no overall association detected, but women carrying the AGT-6A and AGT-20C alleles were shown to have higher IMT after adjustment.92 Only 1 possible gene–environment interaction was reported, for the AGT M235T polymorphism, with TT homozygotes shown to have a steeper increase in IMT with increasing systolic blood pressure compared with M allele carriers.58 Two studies examined possible gene–gene interactions, with one suggesting that the ACE I allele is associated with increased IMT in AGT G-6A GG homozygotes only,92 and another showing carriers of the ACE D allele, AGT M235T T allele, and AGT1R A1166C C allele together to have the highest carotid IMT.56

Methylene Tetrahydrofolate Reductase

Genetic variation in the enzyme methylene tetrahydrofolate reductase has been associated with increased levels of homocysteine and increased risk of coronary disease. methylene tetrahydrofolate reductase reduces 5,10-methylenetetrahydrofolate to produce 5-methyltetrahydrofolate, which acts as a carbon donor in the conversion of homocysteine to methionine.103 C-to-T transition at position 677 produces an alanine to valine substitution, increasing the thermolability of the enzyme and reducing its activity.104 Homocysteine levels tend to be higher in persons homozygous for the thermolabile variant, particularly in the setting of dietary folate deficiency.105 Homocysteine may promote atherosclerosis and thrombosis by enhancing vascular cell proliferation and promoting prothrombotic activity in the vessel wall.103

Associations with carotid atherosclerosis have been inconsistent, with 8 studies showing no association,100,104,106–111 7 showing higher IMT or more frequent stenosis in T allele carriers or TT homozygotes, although often only in subgroups,100,103,112–116 and 1 showing less frequent atherosclerosis in TT homozygotes62 (Table IV, available online at http://atvb.ahajournals.org). Although 1 study of hemodialysis patients showed a graded relationship of IMT to number of T alleles,113 others showed increased atherosclerosis only in those without cardiovascular disease,103 or in men only,100 or in women only.116 This last analysis also suggested an interaction with cigarette smoking and alcohol consumption in that TT homozygous women who smoked or consumed alcohol had higher IMTs than those who did not; this difference was not seen for the other genotypes.116

Paraoxonase

Three paraoxonase genes (PON 1, PON 2, PON 3) have been mapped to chromosome 7 and a number of polymorphisms have been identified.32 PON prevents lipid peroxidation of LDLs and PON 1 has been shown to hydrolyze lipid peroxides in human atherosclerotic lesions.32 Oxidative modification of LDL cholesterol renders it particularly atherogenic, making identification of factors protecting against oxidative modification potentially important in the prevention of atherosclerosis.117 Two frequent PON 1 polymorphisms at positions 192 (glutamine to arginine) and 55 (methionine to leucine) are in linkage disequilibrium and are associated with variations in PON activity to different substrates.117 Associations between PON 1 and PON 2 polymorphisms and a variety of CVD phenotypes, however, have been inconsistent,32 with some studies showing the 55L allele and/or the 192R allele to be associated with increased risk118 and others showing no association.32 Both cigarette smoking and diabetes are associated with increased lipid peroxidation, leading to examination of associations with CVD in subgroups defined by these traits, which have also been inconsistent.118

Of 13 studies considering the PON 1 192 polymorphism separately or jointly with PON 1 55 (Table V, available online at http://atvb.ahajournals.org), 10 showed no association with PON 1 192 considered alone,32,57,100,117–123 although 1 of these showed IMT to be higher in subjects homozygous for the PON 1 55 L and PON 1 192Q alleles compared with LL/RR and MM/QQ subjects,122 and another showed the PON 1 192RR genotype to be more common than QQ in stenosis cases but only after adjustment for PON activity level.121 This report was subsequently refuted in an expanded sample from the same authors, who found no association regardless of adjustment for PON activity.123 An eleventh study showed higher IMT in RR homozygotes than Q allele carriers;124 the twelfth showed plaque to be more frequent in PON 1 192R carriers with high levels of high-density lipoprotein, but no difference in plaque by genotype in subjects with low levels of high-density lipoprotein.125 The thirteenth showed the R allele to be more frequent in older persons with moderate versus no atherosclerosis.62

Association studies of the PON 1 55 polymorphism have suggested that IMT and plaque are increased in L allele carriers, but relationships are complex. Of 5 studies examining the PON 1 55 allele, 1 showed plaque score to be higher in LL homozygotes,117 1 showed the L allele to be more frequent in stenosis cases but only after adjustment for PON activity level,121 another showed the aforementioned higher IMT in LL/QQ subjects,122 a fourth showed higher IMT in nonsmoking LL homozygotes but no association in smokers,126 and the fifth showed plaque to be more frequent in L allele carriers but only in nonsmokers, with a reversal of this relationship in smokers.32 Subsequent expansion of the sample showing increased L allele frequency in stenosis cases after adjustment for PON activity failed to confirm this association.123 Only 2 studies examined the PON 2 S311C polymorphism and found no relationship with carotid atherosclerosis.32,57 Examination of 2 additional promoter polymorphisms, as well as a haplotype comprising polymorphisms at –162/–108/55/192, failed to detect any association with stenosis cases.123

Nitric Oxide Synthase

Nitric oxide is a potent vasodilator produced by the action of nitric oxide synthase (NOS) on L-arginine.127 NO also inhibits platelet aggregation and adhesion, leukocyte chemotaxis and adhesion, adhesion molecule and chemokine expression, smooth muscle cell proliferation and migration, and LDL oxidation.127,128 For these reasons, endothelial NO may have a prominent role in protection against atherosclerosis.

NOS exists in 3 forms: endothelial, neuronal, and inducible. Endothelial NOS (eNOS or NOS 3) is presumed responsible for most of the endothelial and vascular effects of NO. Several polymorphisms of the NOS 3 gene have been identified, one of which, a G-to-T transversion at nucleotide 894 of exon 7, produces a glutamic acid to aspartic acid substitution at amino acid 298.129 This induces a conformational change that may reduce NOS 3 activity.127 This variant has been associated with enhanced vasoconstrictive response to phenylephrine; with enhanced blood pressure response to endurance training; and with hypertension, coronary disease, and myocardial infarction.127,128 A second polymorphism in the 5' flanking region (T-786C) reduces NOS 3 gene promoter activity and has been associated with coronary spasm.130 Multiple intronic polymorphisms of unknown significance have also been identified.127

No association of the G894T variant with carotid atherosclerosis was found in 4 studies,89,128–130,148 although a fifth demonstrated T homozygosity to be more frequent in subjects with plaque127 (Table VI, available online at http://atvb.ahajournals.org). The T-786C polymorphism was more frequent in stenosis cases in the 1 study that examined it.130 The intronic polymorphisms have not been widely studied,127 although loss of heterozygosity for the intron 13 CA repeat has been detected in excised carotid plaques.131 One study of epistasis in hemodialysis patients reported increased plaque frequency in subjects with the T-786C polymorphism in combination with APOE*4; the same interaction was found for a NOS 3 intron 4 polymorphism tightly linked to the T-786C locus.89

Genes Related to Lipid and Lipoprotein Levels

Multiple genes in pathways of production or metabolism of lipids and lipoproteins have been examined in relation to carotid atherosclerosis100,139,149–165 (Table VII, available online at http://atvb.ahajournals.org). IMT is consistently higher and plaque more frequent in familial hypercholesterolemia patients, but specific mutations have not consistently been implicated. Associations with other mutations have either been inconsistent, not yet replicated (that is, single reports), or not detected.

Other Polymorphisms

Genetic variants related to hemostatic and inflammatory factors, interleukins and immune response,41,137,139–141,168–171 platelet receptors,100,134,136–139,166,167 and oxidative pathways,172–174 have also been studied sporadically (Table VIII, available online at http://atvb.ahajournals.org). Associations with hemostasis-related variants have generally been absent132–134 or present only in subgroups.28,100 The Marburg I variant of factor VII activating protease and factor V Leiden, however, have been shown to be more frequent in those with plaque progression,135 whereas the ?-fibrinogen C148T polymorphism in the homozygous TT form was associated with higher plaque score,135 although none of these associations was replicated in a large sample from the Framingham Heart Study.134

Of the other variants studied, the 6A allele of the MMP3 5A/6A promoter polymorphism has been associated with higher IMT and stenosis in all 4 studies examining it.136–139 Four studies assessed the IL-6 G-174C polymorphisms but with inconsistent or negative results.137,139–141 Two studies examined the Leu7Pro variant in pre-pro-neuropeptide Y and both showed higher IMT in 7Pro allele carriers.142,143 Scattered reports of other polymorphisms are difficult to interpret but are included for completeness.42,43,100,175–180

Summary

A wide variety of genetic variants previously reported to be associated with atherosclerosis or clinically evident cardiovascular disease has been examined for associations with carotid atherosclerosis. Only 1 of these, MMP3, has been consistently positive (although not widely studied); 1 (PON1 L55M) has weak associations in subgroups, and 2 (ApoE and methylene tetrahydrofolate reductase) are equivocal (Table 2).

TABLE 2. Number of Reports For and Against Associations of Genetic Variants With Carotid Atherosclerosis

Several factors may account for the discordance among these studies, including: (1) sampling error or random type I errors in positive studies; (2) lack of power in negative studies; (3) genetic heterogeneity; (4) population stratification or confounding; (5) gene–environment interactions modulating expression of an associated genotype; or (6) differences in measurement methods and reproducibility across studies.

Despite its high heritability, high measurement precision, and strong relation to subsequent CVD, all of which making ultrasonographic carotid atherosclerosis an attractive intermediate phenotype, genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis. This may reflect inconsistency in associations with clinical cardiovascular disease itself, as many initial reports of candidate gene associations are not replicated in further investigation.144–146 An alternative hypothesis suitable for investigation is that genetic determinants of ultrasound-defined carotid atherosclerosis differ from those of overt cardiovascular disease. Because of its association with multiple cardiovascular diseases, discovery of the gene(s) for carotid atherosclerosis should be pursued through large-scale genomic studies as distinct studies unto themselves. In addition, sequence variants may not adequately capture the totality of heritable variation in this or other traits; epigenetic and posttranslational protein modifications should also be investigated for relationships to carotid atherosclerosis.

References

Kannel WB, Abbott RD. Incidence and prognosis of unrecognized myocardial infarction. An update on the Framingham study. N Engl J Med. 1984; 311: 1144–1147.

Price TR, Manolio TA, Kronmal RA, Kittner SJ, Yue NC, Robbins J, Anton-Culver H, O’Leary DH. Silent brain infarction on magnetic resonance imaging and neurological abnormalities in community-dwelling older adults. The Cardiovascular Health Study. CHS Collaborative Research Group. Stroke. 1997; 28: 1158–1164.

O’Leary DH, Polak JF, Kronmal RA, Manolio TA, Burke GL, Wolfson SK, Jr. Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults. Cardiovascular Health Study Collaborative Research Group. N Engl J Med. 1999; 340: 14–22.

Bots ML, Hoes AW, Koudstaal PJ, Hofman A, Grobbee DE. Common carotid intima-media thickness and risk of stroke and myocardial infarction: the Rotterdam Study. Circulation. 1997; 96: 1432–1437.

Hodis HN, Mack WJ, LaBree L, Selzer RH, Liu CR, Liu CH, Azen SP. The role of carotid arterial intima-media thickness in predicting clinical coronary events. Ann Intern Med. 1998; 128: 262–269.

Salonen JT, Salonen R. Ultrasonographically assessed carotid morphology and the risk of coronary heart disease. Arterioscler Thromb. 1991; 11: 1245–1249.

O’Leary DH, Polak JF, Wolfson SK, Jr, Bond MG, Bommer W, Sheth S, Psaty BM, Sharrett AR, Manolio TA. Use of sonography to evaluate carotid atherosclerosis in the elderly. The Cardiovascular Health Study. CHS Collaborative Research Group. Stroke. 1991; 22: 1155–1163.

O’Leary DH, Polak JF, Kronmal RA, Savage PJ, Borhani NO, Kittner SJ, Tracy R, Gardin JM, Price TR, Furberg CD. Thickening of the carotid wall. A marker for atherosclerosis in the elderly? Cardiovascular Health Study Collaborative Research Group. Stroke. 1996; 27: 224–231.

Wendelhag I, Gustavsson T, Suurkula M, Berglund G, Wikstrand J. Ultrasound measurement of wall thickness in the carotid artery: fundamental principles and description of a computerized analysing system. Clin Physiol. 1991; 11: 565–577.

Wikstrand J, Wiklund O. Frontiers in cardiovascular science. Quantitative measurements of atherosclerotic manifestations in humans. Arterioscler Thromb. 1992; 12: 114–119.

Bots ML, De Jong PT, Hofman A, Grobbee DE. Left, right, near or far wall common carotid intima-media thickness measurements: associations with cardiovascular disease and lower extremity arterial atherosclerosis. J Clin Epidemiol. 1997; 50: 801–807.

Fox CS, Polak JF, Chazaro I, Cupples A, Wolf PA, D’Agostino RA, O’Donnell CJ. Genetic and environmental contributions to atherosclerosis phenotypes in men and women: heritability of carotid intima-media thickness in the Framingham Heart Study. Stroke. 2003; 34: 397–401.

Crouse JR, Goldbourt U, Evans G, Pinsky J, Sharrett AR, Sorlie P, Riley W, Heiss G. Risk factors and segment-specific carotid arterial enlargement in the Atherosclerosis Risk in Communities (ARIC) cohort. Stroke. 1996; 1927: 69–75.

Riley WA, Freedman DS, Higgs NA, Barnes RW, Zinkgraf SA, Berenson GS. Decreased arterial elasticity associated with cardiovascular disease risk factors in the young. Bogalusa Heart Study. Arteriosclerosis. 1986; 6: 378–386.

Bensen JT, Li R, Hutchinson RG, Province MA, Tyroler HA. Family history of coronary heart disease and pre-clinical carotid artery atherosclerosis in African-Americans and whites: the ARIC study: Atherosclerosis Risk in Communities. Genet Epidemiol. 1999; 16: 165–178.

Tonstad S, Joakimsen O, Leren TP, Ose L. Does maternal or paternal heredity affect carotid atherosclerosis in children with familial hypercholesterolaemia? Acta Paediatr. 2000; 89: 1490–1492.

Wang TJ, Nam BH, D’Agostino RB, Wolf PA, Lloyd-Jones DM, MacRae CA, Wilson PW, Polak JF, O’Donnell CJ. Carotid intima-media thickness is associated with premature parental coronary heart disease: the Framingham Heart Study. Circulation. 2003; 108: 572–576.

Cuomo S, Guarini P, Gaeta G, De Michele M, Boeri F, Dorn J, Bond M, Trevisan M. Increased carotid intima-media thickness in children-adolescents, and young adults with a parental history of premature myocardial infarction. Eur Heart J. 2002; 23: 1345–1350.

Gaeta G, De Michele M, Cuomo S, Guarini P, Foglia MC, Bond MG, Trevisan M. Arterial abnormalities in the offspring of patients with premature myocardial infarction. N Engl J Med. 2000; 343: 840–846.

Jerrard-Dunne P, Markus HS, Steckel DA, Buehler A, von Kegler S, Sitzer M. Early carotid atherosclerosis and family history of vascular disease: specific effects on arterial sites have implications for genetic studies. Arterioscler Thromb Vasc Biol. 2003; 23: 302–306.

Duggirala R, Gonzalez VC, O’Leary DH, Stern MP, Blangero J. Genetic basis of variation in carotid artery wall thickness. Stroke. 1996; 27: 833–837.

North KE, MacCluer JW, Devereux RB, Howard BV, Welty TK, Best LG, Lee ET, Fabsitz RR, Roman MJ. Heritability of carotid artery structure and function: the Strong Heart Family Study. Arterioscler Thromb Vasc Biol. 2002; 22: 1698–1703.

Zannad F, Visvikis S, Gueguen R, Sass C, Chapet O, Herbeth B, Siest G. Genetics strongly determines the wall thickness of the left and right carotid arteries. Hum Genet. 1998; 103: 183–188.

Jartti L, Ronnemaa T, Kaprio J, Jarvisalo MJ, Toikka JO, Marniemi J, Hammar N, Alfredsson L, Saraste M, Hartiala J, Koskenvuo M, Raitakari OT. Population-based twin study of the effects of migration from Finland to Sweden on endothelial function and intima-media thickness. Arterioscler Thromb Vasc Biol. 2002; 22: 832–837.

Swan L, Birnie DH, Inglis G, Connell JM, Hillis WS. The determination of carotid intima medial thickness in adults—a population-based twin study. Atherosclerosis. 2003; 166: 137–141.

Lange LA, Bowden DW, Langefeld CD, Wagenknecht LE, Carr JJ, Rich SS, Riley WA, Freedman BI. Heritability of carotid artery intima-medial thickness in type 2 diabetes. Stroke. 2002; 33: 1876–1881.

Xiang AH, Azen SP, Buchanan TA, Raffel LJ, Tan S, Cheng LS, Diaz J, Toscano E, Quinonnes M, Liu CR, Liu CH, Castellani LW, Hsueh WA, Rotter JI, Hodis HN. Heritability of subclinical atherosclerosis in Latino families ascertained through a hypertensive parent. Arterioscler Thromb Vasc Biol. 2002; 22: 843–848.

Li YH, Chen CH, Yeh PS, Lin HJ, Chang BI, Lin JC, Guo HR, Wu HL, Shi GY, Lai ML, Chen JH. Functional mutation in the promoter region of thrombomodulin gene in relation to carotid atherosclerosis. Atherosclerosis. 2001; 154: 713–719.

Bots ML, Hofman A, De Jong PT, Grobbee DE. Common carotid intima-media thickness as an indicator of atherosclerosis at other sites of the carotid artery. The Rotterdam Study. Ann Epidemiol. 1996; 6: 147–153.

Guz G, Nurhan OF, Sezer S, Isiklar I, Arat Z, Turan M, Haberal M. Effect of apolipoprotein E polymorphism on serum lipid, lipoproteins, and atherosclerosis in hemodialysis patients. Am J Kidney Dis. 2000; 36: 826–836.

Mannami T, Katsuya T, Baba S, Inamoto N, Ishikawa K, Higaki J, Ogihara T, Ogata J. Low potentiality of angiotensin-converting enzyme gene insertion/deletion polymorphism as a useful predictive marker for carotid atherogenesis in a large general population of a Japanese city: the Suita study. Stroke. 2001; 32: 1250–1256.

Fortunato G, Rubba P, Panico S, Trono D, Tinto N, Mazzaccara C, De Michele M, Iannuzzi A, Vitale DF, Salvatore F, Sacchetti L. A paraoxonase gene polymorphism, PON 1 (55), as an independent risk factor for increased carotid intima-media thickness in middle-aged women. Atherosclerosis. 2003; 167: 141–148.

Dessi-Fulgheri P, Catalini R, Sarzani R, Sturbini S, Siragusa N, Guazzarotti F, Offidani M, Tamburrini P, Zingaretti O, Rappelli A. Angiotensin converting enzyme gene polymorphism and carotid atherosclerosis in a low-risk population. J Hypertens. 1995; 13: 1593–1596.

Jeng JR. Carotid thickening, cardiac hypertrophy, and angiotensin converting enzyme gene polymorphism in patients with hypertension. Am J Hypertens. 2000; 13: 111–119.

Hunt KJ, Duggirala R, Goring HH, Williams JT, Almasy L, Blangero J, O’Leary DH, Stern MP. Genetic basis of variation in carotid artery plaque in the San Antonio Family Heart Study. Stroke. 2002; 33: 2775–2780.

Pfohl M, Fetter M, Koch M, Barth CM, Rudiger W, Haring HU. Association between angiotensin I-converting enzyme genotypes, extracranial artery stenosis, and stroke. Atherosclerosis. 1998; 140: 161–166.

Djousse L, Myers RH, Province MA, Hunt SC, Eckfeldt JH, Evans G, Peacock JM, Ellison RC. Influence of apolipoprotein E, smoking, and alcohol intake on carotid atherosclerosis: National Heart, Lung, and Blood Institute Family Heart Study. Stroke. 2002; 33: 1357–1361.

de Andrade M, Thandi I, Brown S, Gotto A, Jr., Patsch W, Boerwinkle E. Relationship of the apolipoprotein E polymorphism with carotid artery atherosclerosis. Am J Hum Genet. 1995; 56: 1379–1390.

Rationale and design for the Asymptomatic Carotid Artery Plaque Study (ACAPS). The ACAPS Group. Control Clin Trials. 1992; 13: 293–314.

Schmidt H, Schmidt R, Niederkorn K, Horner S, Becsagh P, Reinhart B, Schumacher M, Weinrauch V, Kostner GM. Beta-fibrinogen gene polymorphism (C148–>T) is associated with carotid atherosclerosis: results of the Austrian Stroke Prevention Study. Arterioscler Thromb Vasc Biol. 1998; 18: 487–492.

Kiechl S, Lorenz E, Reindl M, Wiedermann CJ, Oberhollenzer F, Bonora E, Willeit J, Schwartz DA. Toll-like receptor 4 polymorphisms and atherogenesis. N Engl J Med. 2002; 347: 185–192.

Wascher TC, Paulweber B, Malaimare L, Stadlmayr A, Iglseder B, Schmoelzer I, Renner W. Associations of a human G protein ?3 subunit dimorphism with insulin resistance and carotid atherosclerosis. Stroke. 2003; 34: 605–609.

Narita M, Kitagawa K, Nagai Y, Hougaku H, Hashimoto H, Sakaguchi M, Yang X, Takeshita T, Morimoto K, Matsumoto M, Hori M. Effects of aldehyde dehydrogenase genotypes on carotid atherosclerosis. Ultrasound Med Biol. 2003 Oct 1929: 1415–1419.

Zureik M, Touboul PJ, Bonithon-Kopp C, Courbon D, Ruelland I, Ducimetiere P. Differential association of common carotid intima-media thickness and carotid atherosclerotic plaques with parental history of premature death from coronary heart disease : the EVA study. Arterioscler Thromb Vasc Biol. 1999; 19: 366–371.

Spence JD, Hegele RA. Noninvasive phenotypes of atherosclerosis: similar windows but different views. Stroke. 2004; 1935: 649–653.

Diamantopoulos EJ, Andreadis E, Kakou M, Vlachonikolis I, Vassilopoulos C, Giannakopoulos N, Tarassi K, Papasteriades C, Nicolaides A, Raptis S. Atherosclerosis of carotid arteries and the ace insertion/deletion polymorphism in subjects with diabetes mellitus type 2. Int Angiol. 2002; 21: 63–69.

Alan S, Ulgen MS, Ozturk O, Alan B, Ozdemir L, Toprak N. Relation between coronary artery disease, risk factors and intima-media thickness of carotid artery, arterial distensibility, and stiffness index. Angiology. 2003; 54: 261–267.

Rigat B, Hubert C, Alhenc-Gelas F, Cambien F, Corvol P, Soubrier F. An insertion/deletion polymorphism in the angiotensin I-converting enzyme gene accounting for half the variance of serum enzyme levels. J Clin Invest. 1990; 86: 1343–1346.

Sass C, Zannad F, Herbeth B, Salah D, Chapet O, Siest G, Visvikis S. Apolipoprotein E4, lipoprotein lipase C447 and angiotensin-I converting enzyme deletion alleles were not associated with increased wall thickness of carotid and femoral arteries in healthy subjects from the Stanislas cohort. Atherosclerosis. 1998; 140: 89–95.

Arnett DK, Borecki IB, Ludwig EH, Pankow JS, Myers R, Evans G, Folsom AR, Heiss G, Higgins M. Angiotensinogen and angiotensin converting enzyme genotypes and carotid atherosclerosis: the atherosclerosis risk in communities and the NHLBI family heart studies. Atherosclerosis. 1998; 138: 111–116.

Frost D, Pfohl M, Clemens P, Haring HU, Beischer W. Evaluation of the insertion/deletion ACE gene polymorphism as a risk factor for carotid artery intima-media thickening and hypertension in young type 1 diabetic patients. Diabetes Care. 1998; 21: 836–840.

Girerd X, Hanon O, Mourad JJ, Boutouyrie P, Laurent S, Jeunemaitre X. Lack of association between renin-angiotensin system, gene polymorphisms, and wall thickness of the radial and carotid arteries. Hypertension. 1998; 32: 579–583.

Huang XH, Loimaala A, Nenonen A, Mercuri M, Vuori I, Pasanen M, Oja P, Bond G, Koivula T, Hiltunen TP, Nikkari T, Lehtimaki T. Relationship of angiotensin-converting enzyme gene polymorphism to carotid wall thickness in middle-aged men. J Mol Med. 1999; 77: 853–858.

Hung J, McQuillan BM, Nidorf M, Thompson PL, Beilby JP. Angiotensin-converting enzyme gene polymorphism and carotid wall thickening in a community population. Arterioscler Thromb Vasc Biol. 1999; 19: 1969–1974.

Lin JJ, Yueh KC, Lin GY, Chang DC, Chang CY, Shieh HL, Harn HJ. Lack of association between angiotensin I-converting enzyme gene deletion polymorphism and cerebrovascular disease in Taiwanese. J Formos Med Assoc. 2000; 99: 895–901.

Pontremoli R, Ravera M, Viazzi F, Nicolella C, Berruti V, Leoncini G, Giacopelli F, Bezante GP, Sacchi G, Ravazzolo R, Deferrari G. Genetic polymorphism of the renin-angiotensin system and organ damage in essential hypertension. Kidney Int. 2000; 57: 561–569.

Markus H, Kapozsta Z, Ditrich R, Wolfe C, Ali N, Powell J, Mendell M, Cullinane M. Increased common carotid intima-media thickness in UK African Caribbeans and its relation to chronic inflammation and vascular candidate gene polymorphisms. Stroke. 2001; 32: 2465–2471.

Tabara Y, Kohara K, Nakura J, Miki T. Risk factor-gene interaction in carotid atherosclerosis: effect of gene polymorphisms of renin-angiotensin system. J Hum Genet. 2001; 46: 278–284.

Taute BM, Seifert H, Taute R, Glaser C, Podhaisky H. Angiotensin-converting enzyme gene insertion/deletion polymorphism and carotid artery wall thickness in patients with peripheral arterial occlusive disease. Int Angiol. 2000; 1919: 337–344.

Balkestein EJ, Wang JG, Struijker-Boudier HA, Barlassina C, Bianchi G, Birkenhager WH, Brand E, Den Hond E, Fagard R, Herrmann SM, Van Bortel LM, Staessen JA. Carotid and femoral intima-media thickness in relation to three candidate genes in a Caucasian population. J Hypertens. 2002; 20: 1551–1561.

Kawamoto R, Kohara K, Tabara Y, Miki T. An interaction between systolic blood pressure and angiotensin-converting enzyme gene polymorphism on carotid atherosclerosis. Hypertens Res. 2002; 25: 875–880.

Zuliani G, Cherubini A, Volpato S, Palmieri E, Mecocci P, De Rango P, Cao P, Costantini F, Mezzetti A, Mascoli F, Senin U, Fellin R. Genetic factors associated with the absence of atherosclerosis in octogenarians. J Gerontol A Biol Sci Med Sci. 2002; 57: M611–M615.

Castellano M, Muiesan ML, Rizzoni D, Beschi M, Pasini G, Cinelli A, Salvetti M, Porteri E, Bettoni G, Kreutz R. Angiotensin-converting enzyme I/D polymorphism and arterial wall thickness in a general population. The Vobarno Study. Circulation. 1995; 91: 2721–2724.

Markus HS, Barley J, Lunt R, Bland JM, Jeffery S, Carter ND, Brown MM. Angiotensin-converting enzyme gene deletion polymorphism. A new risk factor for lacunar stroke but not carotid atheroma. Stroke. 1995; 26: 1329–1333.

Hosoi M, Nishizawa Y, Kogawa K, Kawagishi T, Konishi T, Maekawa K, Emoto M, Fukumoto S, Shioi A, Shoji T, Inaba M, Okuno Y, Morii H. Angiotensin-converting enzyme gene polymorphism is associated with carotid arterial wall thickness in non-insulin-dependent diabetic patients. Circulation. 1996; 94: 704–707.

Kauma H, Paivansalo M, Savolainen MJ, Rantala AO, Kiema TR, Lilja M, Reunanen A, Kesaniemi YA. Association between angiotensin converting enzyme gene polymorphism and carotid atherosclerosis. J Hypertens. 1996; 14: 1183–1187.

Pujia A, Motti C, Irace C, Cortese C, Biagiotti L, Mattioli PL, Federici G, Gnasso A. Deletion polymorphism in angiotensin converting enzyme gene associated with carotid wall thickening in a healthy male population. Coron Artery Dis. 1996; 7: 51–55.

Kogawa K, Nishizawa Y, Hosoi M, Kawagishi T, Maekawa K, Shoji T, Okuno Y, Morii H. Effect of polymorphism of apolipoprotein E and angiotensin-converting enzyme genes on arterial wall thickness. Diabetes. 1997; 46: 682–687.

Watanabe Y, Ishigami T, Kawano Y, Umahara T, Nakamori A, Mizushima S, Hibi K, Kobayashi I, Tamura K, Ochiai H, Umemura S, Ishii M. Angiotensin-converting enzyme gene I/D polymorphism and carotid plaques in Japanese. Hypertension. 1997; 30: 569–573.

Kostulas K, Huang WX, Crisby M, Jin YP, He B, Lannfelt L, Eggertsen G, Kostulas V, Hillert J. An angiotensin-converting enzyme gene polymorphism suggests a genetic distinction between ischaemic stroke and carotid stenosis. Eur J Clin Invest. 1999; 29: 478–483.

Nergizoglu G, Keven K, Gurses MA, Aras O, Erturk S, Duman N, Ates K, Akar H, Akar N, Karatan O, Erbay B, Ertug AE. Carotid intima-media thickness and ACE-gene polymorphism in hemodialysis patients. J Nephrol. 1999; 12: 261–265.

Losito A, Selvi A, Jeffery S, Afzal AR, Parente B, Cao PG. Angiotensin-converting enzyme gene I/D polymorphism and carotid artery disease in renovascular hypertension. Am J Hypertens. 2000; 13: 128–133.

Losito A, Kalidas K, Santoni S, Ceccarelli L, Jeffery S. Polymorphism of renin-angiotensin system genes in dialysis patients–association with cerebrovascular disease. Nephrol Dial Transplant. 2002; 17: 2184–2188.

Eichner JE, Kuller LH, Orchard TJ, Grandits GA, McCallum LM, Ferrell RE, Neaton JD. Relation of apolipoprotein E phenotype to myocardial infarction and mortality from coronary artery disease. Am J Cardiol. 1993; 71: 160–165.

Eichner JE, Dunn ST, Perveen G, Thompson DM, Stewart KE, Stroehla BC. Apolipoprotein E polymorphism and cardiovascular disease: a HuGE review. Am J Epidemiol. 2002; 155: 487–495.

Cattin L, Fisicaro M, Tonizzo M, Valenti M, Danek GM, Fonda M, Da Col PG, Casagrande S, Pincetri E, Bovenzi M, Baralle F. Polymorphism of the apolipoprotein E gene and early carotid atherosclerosis defined by ultrasonography in asymptomatic adults. Arterioscler Thromb Vasc Biol. 1997; 17: 91–94.

Lahoz C, Schaefer EJ, Cupples LA, Wilson PW, Levy D, Osgood D, Parpos S, Pedro-Botet J, Daly JA, Ordovas JM. Apolipoprotein E genotype and cardiovascular disease in the Framingham Heart Study. Atherosclerosis. 2001; 154: 529–537.

Terry JG, Howard G, Mercuri M, Bond MG, Crouse JR, III. Apolipoprotein E polymorphism is associated with segment-specific extracranial carotid artery intima-media thickening. Stroke. 1996; 27: 1755–1759.

Olmer M, Renucci JE, Planells R, Bouchouareb D, Purgus R. Preliminary evidence for a role of apolipoprotein E alleles in identifying haemodialysis patients at high vascular risk. Nephrol Dial Transplant. 1997; 12: 691–693.

Vauhkonen I, Niskanen L, Ryynanen M, Voutilainen R, Partanen J, Toyry J, Mercuri M, Rauramaa R, Uusitupa M. Divergent association of apolipoprotein E polymorphism with vascular disease in patients with NIDDM and control subjects. Diabet Med. 1997; 14: 748–756.

Ilveskoski E, Loimaala A, Mercuri MF, Lehtimaki T, Pasanen M, Nenonen A, Oja P, Bond MG, Koivula T, Karhunen PJ, Vuori I. Apolipoprotein E polymorphism and carotid artery intima-media thickness in a random sample of middle-aged men. Atherosclerosis. 2000; 153: 147–153.

Slooter AJ, Bots ML, Havekes LM, del Sol AI, Cruts M, Grobbee DE, Hofman A, Van Broeckhoven C, Witteman JC, van Duijn CM. Apolipoprotein E and carotid artery atherosclerosis: the Rotterdam study. Stroke. 2001; 32: 1947–1952.

Haraki T, Takegoshi T, Kitoh C, Wakasugi T, Saga T, Hirai JI, Aoyama T, Inazu A, Mabuchi H. Carotid artery intima-media thickness and brachial artery flow-mediated vasodilation in asymptomatic Japanese male subjects amongst apolipoprotein E phenotypes. J Intern Med. 2002; 252: 114–120.

Beilby JP, Hunt CC, Palmer LJ, Chapman CM, Burley JP, McQuillan BM, Thompson PL, Hung J. Apolipoprotein E gene polymorphisms are associated with carotid plaque formation but not with intima-media wall thickening: results from the Perth Carotid Ultrasound Disease Assessment Study (CUDAS). Stroke. 2003; 34: 869–874.

Hanon O, Girerd X, Luong V, Jeunemaitre X, Laurent S, Safar ME. Association between the apolipoprotein E polymorphism and arterial wall thickness in asymptomatic adults. J Hypertens. 2000; 18: 431–436.

Schmidt R, Schmidt H, Fazekas F, Schumacher M, Niederkorn K, Kapeller P, Weinrauch V, Kostner GM. Apolipoprotein E polymorphism and silent microangiopathy-related cerebral damage. Results of the Austrian Stroke Prevention Study. Stroke. 1997; 28: 951–956.

Horejsi B, Spacil J, Ceska R, Vrablik M, Haas T, Horinek A. The independent correlation of the impact of lipoprotein(a) levels and apolipoprotein E polymorphism on carotid artery intima thickness. Int Angiol. 2000; 1919: 331–336.

Karvonen J, Kauma H, Kervinen K, Ukkola O, Rantala M, Paivansalo M, Savolainen MJ, Kesaniemi YA. Apolipoprotein E polymorphism affects carotid artery atherosclerosis in smoking hypertensive men. J Hypertens. 2002; 20: 2371–2378.

Asakimori Y, Yorioka N, Tanaka J, Kohno N. Effect of polymorphism of the endothelial nitric oxide synthase and apolipoprotein E genes on carotid atherosclerosis in hemodialysis patients. Am J Kidney Dis. 2003; 1941: 822–832.

Gardemann A, Stricker J, Humme J, Nguyen QD, Katz N, Philipp M, Tillmanns H, Hehrlein FW, Haberbosch W. Angiotensinogen T174M and M235T gene polymorphisms are associated with the extent of coronary atherosclerosis. Atherosclerosis. 1999; 145: 309–314.

Fatini C, Abbate R, Pepe G, Battaglini B, Gensini F, Ruggiano G, Gensini GF, Guazzelli R. Searching for a better assessment of the individual coronary risk profile. The role of angiotensin-converting enzyme, angiotensin II type 1 receptor and angiotensinogen gene polymorphisms. Eur Heart J. 2000; 21: 633–638.

Chapman CM, Palmer LJ, McQuillan BM, Hung J, Burley J, Hunt C, Thompson PL, Beilby JP. Polymorphisms in the angiotensinogen gene are associated with carotid intimal-medial thickening in females from a community-based population. Atherosclerosis. 2001; 159: 209–217.

Daemen MJ, Lombardi DM, Bosman FT, Schwartz SM. Angiotensin II induces smooth muscle cell proliferation in the normal and injured rat arterial wall. Circ Res. 1991; 68: 450–456.

Hernandez-Presa M, Bustos C, Ortego M, Tunon J, Renedo G, Ruiz-Ortega M, Egido J. Angiotensin-converting enzyme inhibition prevents arterial nuclear factor-kappa B activation, monocyte chemoattractant protein-1 expression, and macrophage infiltration in a rabbit model of early accelerated atherosclerosis. Circulation. 1997; 95: 1532–1541.

Keidar S, Kaplan M, Aviram M. Angiotensin II-modified LDL is taken up by macrophages via the scavenger receptor, leading to cellular cholesterol accumulation. Arterioscler Thromb Vasc Biol. 1996; 16: 97–105.

Corvol P, Jeunemaitre X. Molecular genetics of human hypertension: role of angiotensinogen. Endocrinol Rev. 1997; 18: 662–677.

Schmidt R, Schmidt H, Fazekas F, Launer LJ, Niederkorn K, Kapeller P, Lechner A, Kostner GM. Angiotensinogen polymorphism M235T, carotid atherosclerosis, and small-vessel disease-related cerebral abnormalities. Hypertension. 2001; 38: 110–115.

Barley J, Markus H, Brown M, Carter N. Lack of association between angiotensinogen polymorphism (M235T) and cerebrovascular disease and carotid atheroma. J Hum Hypertens. 1995; 9: 681–683.

Jeng JR. Left ventricular mass, carotid wall thickness, and angiotensinogen gene polymorphism in patients with hypertension. Am J Hypertens. 1999; 12: 443–450.

Pallaud C, Sass C, Zannad F, Siest G, Visvikis S. APOC3, CETP, fibrinogen, and MTHFR are genetic determinants of carotid intima-media thickness in healthy men (the Stanislas cohort). Clin Genet. 2001; 59: 316–324.

Bozec E, Fassot C, Tropeano AI, Boutouyrie P, Jeunemaitre X, Lacolley P, Dabire H, Laurent S. Angiotensinogen gene M235T polymorphism and reduction in wall thickness in response to antihypertensive treatment. Clin Sci (Lond). 2003; 105: 637–644.

Castellano M, Muiesan ML, Beschi M, Rizzoni D, Cinelli A, Salvetti M, Pasini G, Porteri E, Bettoni G, Zulli R, Agabiti-Rosei E. Angiotensin II type 1 receptor A/C1166 polymorphism. Relationships with blood pressure and cardiovascular structure. Hypertension. 1996; 28: 1076–1080.

Bova I, Chapman J, Sylantiev C, Korczyn AD, Bornstein NM. The A677V methylenetetrahydrofolate reductase gene polymorphism and carotid atherosclerosis. Stroke. 1999; 30: 2180–2182.

Spence JD, Malinow MR, Barnett PA, Marian AJ, Freeman D, Hegele RA. Plasma homocyst(e)ine concentration, but not MTHFR genotype, is associated with variation in carotid plaque area. Stroke. 1999; 30: 969–973.

Jacques PF, Bostom AG, Williams RR, Ellison RC, Eckfeldt JH, Rosenberg IH, Selhub J, Rozen R. Relation between folate status, a common mutation in methylenetetrahydrofolate reductase, and plasma homocysteine concentrations. Circulation. 1996; 93: 7–9.

Demuth K, Moatti N, Hanon O, Benoit MO, Safar M, Girerd X. Opposite effects of plasma homocysteine and the methylenetetrahydrofolate reductase C677T mutation on carotid artery geometry in asymptomatic adults. Arterioscler Thromb Vasc Biol. 1998; 1918; 1838–1843.

Kostulas K, Crisby M, Huang WX, Lannfelt L, Hagenfeldt L, Eggertsen G, Kostulas V, Hillert J. A methylenetetrahydrofolate reductase gene polymorphism in ischaemic stroke and in carotid artery stenosis. Eur J Clin Invest. 1998; 28: 285–289.

McQuillan BM, Beilby JP, Nidorf M, Thompson PL, Hung J. Hyperhomocysteinemia but not the C677T mutation of methylenetetrahydrofolate reductase is an independent risk determinant of carotid wall thickening. The Perth Carotid Ultrasound Disease Assessment Study (CUDAS). Circulation. 1999; 99: 2383–2388.

Mazza A, Motti C, Nulli A, Marra G, Gnasso A, Pastore A, Federici G, Cortese C. Lack of association between carotid intima-media thickness and methylenetetrahydrofolate reductase gene polymorphism or serum homocysteine in non-insulin-dependent diabetes mellitus. Metabolism. 2000; 1949: 718–723.

Zuliani G, Volpato S, Mecocci P, Cherubini A. The A677V MTHFR allele is not associated with carotid atherosclerosis in octogenarians. Stroke. 2000; 31: 990–991.

Scaglione L, Gambino R, Rolfo E, Lillaz E, Gai M, Cassader M, Pagano G, Cavallo-Perin P. Plasma homocysteine, methylenetetrahydrofolate reductase gene polymorphism and carotid intima-media thickness in Italian type 2 diabetic patients. Eur J Clin Invest. 2002; 1932: 24–28.

Arai K, Yamasaki Y, Kajimoto Y, Watada H, Umayahara Y, Kodama M, Sakamoto K, Hori M. Association of methylenetetrahydrofolate reductase gene polymorphism with carotid arterial wall thickening and myocardial infarction risk in NIDDM. Diabetes. 1997; 46: 2102–2104.

Lim PS, Hung WR, Wei YH. Polymorphism in methylenetetrahydrofolate reductase gene: its impact on plasma homocysteine levels and carotid atherosclerosis in ESRD patients receiving hemodialysis. Nephron. 2001; 87: 249–256.

Passaro A, Vanini A, Calzoni F, Alberti L, Zamboni PF, Fellin R, Solini A. Plasma homocysteine, methylenetetrahydrofolate reductase mutation and carotid damage in elderly healthy women. Atherosclerosis. 2001; 157: 175–180.

Ravera M, Viazzi F, Berruti V, Leoncini G, Zagami P, Bezante GP, Rosatto N, Ravazzolo R, Pontremoli R, Deferrari G. 5,10-Methylenetetrahydrofolate reductase polymorphism and early organ damage in primary hypertension. Am J Hypertens. 2001; 1914: 371–376.

Inamoto N, Katsuya T, Kokubo Y, Mannami T, Asai T, Baba S, Ogata J, Tomoike H, Ogihara T. Association of methylenetetrahydrofolate reductase gene polymorphism with carotid atherosclerosis depending on smoking status in a Japanese general population. Stroke. 2003; 34: 1628–1633.

Schmidt H, Schmidt R, Niederkorn K, Gradert A, Schumacher M, Watzinger N, Hartung HP, Kostner GM. Paraoxonase PON1 polymorphism leu-Met54 is associated with carotid atherosclerosis: results of the Austrian Stroke Prevention Study. Stroke. 1998; 29: 2043–2048.

Koch M, Hering S, Barth C, Ehren M, Enderle MD, Pfohl M. Paraoxonase 1 192 Gln/Arg gene polymorphism and cerebrovascular disease: interaction with type 2 diabetes. Exp Clin Endocrinol Diabetes. 2001; 109: 141–145.

Cao H, Girard-Globa A, Serusclat A, Bernard S, Bondon P, Picard S, Berthezene F, Moulin P. Lack of association between carotid intima-media thickness and paraoxonase gene polymorphism in non-insulin dependent diabetes mellitus. Atherosclerosis. 1998; 138: 361–366.

Dessi M, Gnasso A, Motti C, Pujia A, Irace C, Casciani S, Staffa F, Federici G, Cortese C. Influence of the human paraoxonase polymorphism (PON1 192) on the carotid-wall thickening in a healthy population. Coron Artery Dis. 1999; 10: 595–599.

Jarvik GP, Rozek LS, Brophy VH, Hatsukami TS, Richter RJ, Schellenberg GD, Furlong CE. Paraoxonase (PON1) phenotype is a better predictor of vascular disease than is PON1(192) or PON1(55) genotype. Arterioscler Thromb Vasc Biol. 2000; 20: 2441–2447.

Leus FR, Wittekoek ME, Prins J, Kastelein JJ, Voorbij HA. Paraoxonase gene polymorphisms are associated with carotid arterial wall thickness in subjects with familial hypercholesterolemia. Atherosclerosis. 2000; 149: 371–377.

Jarvik GP, Hatsukami TS, Carlson C, Richter RJ, Jampsa R, Brophy VH, Margolin S, Rieder M, Nickerson D, Schellenberg GD, Heagerty PJ, Furlong CE. Paraoxonase activity, but not haplotype utilizing the linkage disequilibrium structure, predicts vascular disease. Arterioscler Thromb Vasc Biol. 2003; 1923: 1465–1471.

Sakai T, Matsuura B, Onji M. Serum paraoxonase activity and genotype distribution in Japanese patients with diabetes mellitus. Intern Med. 1998; 37: 581–584.

Gnasso A, Motti C, Irace C, Di G, I, Pujia A, Leto E, Ciamei M, Crivaro A, Bernardini S, Federici G, Cortese C. The Arg allele in position 192 of PON1 is associated with carotid atherosclerosis in subjects with elevated HDLs. Atherosclerosis. 2002; 164: 289–295.

Malin R, Loimaala A, Nenonen A, Mercuri M, Vuori I, Pasanen M, Oja P, Bond G, Koivula T, Lehtimaki T. Relationship between high-density lipoprotein paraoxonase gene M/L55 polymorphism and carotid atherosclerosis differs in smoking and nonsmoking men. Metabolism. 2001; 50: 1095–1101.

Lembo G, De Luca N, Battagli C, Iovino G, Aretini A, Musicco M, Frati G, Pompeo F, Vecchione C, Trimarco B. A common variant of endothelial nitric oxide synthase (Glu298Asp) is an independent risk factor for carotid atherosclerosis. Stroke. 2001; 32: 735–740.

Karvonen J, Kauma H, Kervinen K, Rantala M, Ikaheimo M, Paivansalo M, Savolainen MJ, Kesaniemi YA. Endothelial nitric oxide synthase gene Glu298Asp polymorphism and blood pressure, left ventricular mass and carotid artery atherosclerosis in a population-based cohort. J Intern Med. 2002; 251: 102–110.

Markus HS, Ruigrok Y, Ali N, Powell JF. Endothelial nitric oxide synthase exon 7 polymorphism, ischemic cerebrovascular disease, and carotid atheroma. Stroke. 1998; 29: 1908–1911.

Ghilardi G, Biondi ML, DeMonti M, Bernini M, Turri O, Massaro F, Guagnellini E, Scorza R. Independent risk factor for moderate to severe internal carotid artery stenosis: T786C mutation of the endothelial nitric oxide synthase gene. Clin Chem. 2002; 48: 989–993.

Grati FR, Ghilardi G, Sirchia SM, Massaro F, Cassani B, Scorza R, De Andreis C, Sironi E, Simoni G. Loss of heterozygosity of the NOS3 dinucleotide repeat marker in atherosclerotic plaques of human carotid arteries. Atherosclerosis. 2001; 159: 261–267.

Garg UC, Arnett DK, Evans G, Eckfeldt JH. No association between factor V Leiden mutation and coronary heart disease or carotid intima media thickness: the NHLBI Family Heart Study. Thromb Res. 1998; 89: 289–293.

Ghaddar HM, Folsom AR, Aleksic N, Hearne LB, Chambless LE, Morrissey JH, Wu KK. Correlation of factor VIIa values with factor VII gene polymorphism, fasting and postprandial triglyceride levels, and subclinical carotid atherosclerosis. Circulation. 1998; 98: 2815–2821.

Fox CS, Larson MG, Corey D, Feng D, Lindpaintner K, Polak JF, Wolf PA, D’Agostino RB, Tofler GH, O’Donnell CJ. Absence of association between polymorphisms in the hemostatic factor pathway genes and carotid intimal medial thickness: the Framingham Heart Study. Stroke. 2004; 1935: e65–e67.

Willeit J, Kiechl S, Weimer T, Mair A, Santer P, Wiedermann CJ, Roemisch J. Marburg I polymorphism of factor VII–activating protease: a prominent risk predictor of carotid stenosis. Circulation. 2003; 107: 667–670.

Gnasso A, Motti C, Irace C, Carallo C, Liberatoscioli L, Bernardini S, Massoud R, Mattioli PL, Federici G, Cortese C. Genetic variation in human stromelysin gene promoter and common carotid geometry in healthy male subjects. Arterioscler Thromb Vasc Biol. 2000; 20: 1600–1605.

Rauramaa R, Vaisanen SB, Luong LA, Schmidt-Trucksass A, Penttila IM, Bouchard C, Toyry J, Humphries SE. Stromelysin-1 and interleukin-6 gene promoter polymorphisms are determinants of asymptomatic carotid artery atherosclerosis. Arterioscler Thromb Vasc Biol. 2000; 20: 2657–2662.

Ghilardi G, Biondi ML, DeMonti M, Turri O, Guagnellini E, Scorza R. Matrix metalloproteinase-1 and matrix metalloproteinase-3 gene promoter polymorphisms are associated with carotid artery stenosis. Stroke. 2002; 33: 2408–2412.

Rundek T, Elkind MS, Pittman J, Boden-Albala B, Martin S, Humphries SE, Juo SH, Sacco RL. Carotid intima-media thickness is associated with allelic variants of stromelysin-1, interleukin-6, and hepatic lipase genes: the Northern Manhattan Prospective Cohort Study. Stroke. 2002; 33: 1420–1423.

Chapman CM, Beilby JP, Humphries SE, Palmer LJ, Thompson PL, Hung J. Association of an allelic variant of interleukin-6 with subclinical carotid atherosclerosis in an Australian community population. Eur Heart J. 2003; 24: 1494–1499.

Jerrard-Dunne P, Sitzer M, Risley P, Steckel DA, Buehler A, von Kegler S, Markus HS. Interleukin-6 promoter polymorphism modulates the effects of heavy alcohol consumption on early carotid artery atherosclerosis: the Carotid Atherosclerosis Progression Study (CAPS). Stroke. 2003; 34: 402–407.

Karvonen MK, Valkonen VP, Lakka TA, Salonen R, Koulu M, Pesonen U, Tuomainen TP, Kauhanen J, Nyyssonen K, Lakka HM, Uusitupa MI, Salonen JT. Leucine7 to proline7 polymorphism in the preproneuropeptide Y is associated with the progression of carotid atherosclerosis, blood pressure and serum lipids in Finnish men. Atherosclerosis. 2001; 159: 145–151.

Niskanen L, Karvonen MK, Valve R, Koulu M, Pesonen U, Mercuri M, Rauramaa R, Toyry J, Laakso M, Uusitupa MI. Leucine 7 to proline 7 polymorphism in the neuropeptide Y gene is associated with enhanced carotid atherosclerosis in elderly patients with type 2 diabetes and control subjects. J Clin Endocrinol Metab. 2000; 85: 2266–2269.

Staessen JA, Wang JG, Ginocchio G, Petrov V, Saavedra AP, Soubrier F, Vlietinck R, Fagard R. The deletion/insertion polymorphism of the angiotensin converting enzyme gene and cardiovascular-renal risk. J Hypertens. 1997; 19;15: 1579–1592.

Keavney B, McKenzie C, Parish S, Palmer A, Clark S, Youngman L, Delepine M, Lathrop M, Peto R, Collins R. Large-scale test of hypothesised associations between the angiotensin-converting-enzyme insertion/deletion polymorphism and myocardial infarction in about 5000 cases and 6000 controls. International Studies of Infarct Survival (ISIS) Collaborators. Lancet. 2000; 355: 434–442.

Agerholm-Larsen B, Nordestgaard BG, Tybjaerg-Hansen A. ACE gene polymorphism in cardiovascular disease: meta-analyses of small and large studies in whites. Arterioscler Thromb Vasc Biol. 2000; 1920: 484–492.

Ebrahim S, Papacosta O, Whincup P, Wannamethee G, Walker M, Nicolaides AN, Dhanjil S, Griffin M, Belcaro G, Rumley A, Lowe GD. Carotid plaque, intima media thickness, cardiovascular risk factors, and prevalent cardiovascular disease in men and women: the British Regional Heart Study. Stroke. 1999; 30: 841–850.

Schmoelzer I, Renner W. Paulweber B, Malaimare L, Iglseder B, Schmid P, Schallmoser K, Wascher TC. Lack of association of the Glu298Asp polymorphism of endothelial nitric oxide synthase with manifest coronary artery disease, carotid atherosclerosis and forearm vascular reactivity in two Austrian populations. Eur J Clin Invest. 2003; 33: 191–198.

Wendelhag I, Wiklund O, Wikstrnad J. Arterial wall thickness in familial hypercholesterolemia. Ultrasound measurement of intima-media thickness in the common carotid artery. Arterioscler Thromb. 1992; 12: 70–77.

Tonstad S, Joakimsen O, Stensland-Bugge E, Leren TP, Ose L, Russell D, Bonaa KH. Risk factors related to carotid intima-media thickness and plaque in children with familial hypercholesterolemia and control subjects. Arterioscler Thromb Vasc Biol. 1996; 16: 984–991.

Tonstad S, Joakimsen O, Stensland-Bugge E, Ose L, Bonaa KH, Leren TP. Carotid intima-media thickness and plaque in patients with familial hypercholesterolaemia mutations and control subjects. Eur J Clin Invest. 1998; 28: 971–979.

Descamps OS, Gilbeau JP, Leysen X, Van Leuven F, Heller FR. Impact of genetic defects on atherosclerosis in patients suspected of familial hypercholesterolaemia. Eur J Clin Invest. 2001; 31: 958–965.

Brorholt-Petersen JU, Jensen HK, Jensen JM, Refsgaard J, Christiansen T, Hansen LB, Gregersen N, Faergeman O. LDL receptor mutation genotype and vascular disease phenotype in heterozygous familial hypercholesterolaemia. Clin Genet. 2002; 61: 408–415.

Chen L, Patsch W, Bowerwinkle E. HindIII DNA polymorphism in the lipoprotein lipase gene and plasma lipid phenotypes and carotid artery atherosclerosis. Hum Genet. 1996; 98: 551–556.

Huang P, Kostulas K, Huang WX, Crisby M, Kostulas V, Hillert J. Lipoprotein lipase gene polymorphisms in ischaemic stroke and carotid stenosis. Eur J Clin Invest. 1997; 27: 740–742.

Spence JD, Ban MR, Hegele RA. Lipoprotein lipase (LPL) gene variation and progression of carotid artery plaque. Stroke. 2003; 34: 1176–1180.

Patsch W, Sharrett AR, Chen IY, Lin-Lee YC, Brown SA, Gotto AM Jr, Boerwinkle E. Associations of allelic differences at the A-1/C-III/A-IV gene cluster with carotid artery intima-media thickness and plasma lipid transport in hypercholesterolemic-hypertriglyceridemic humans. Arterioscler Thromb. 1994; 14: 874–883.

Sirtori CR, Calabresi L, Franceschini G, Baldassarre D, Amato M, Johansson J, Salvetti M, Monteduro C, Zulli R, Muiesan ML, Agabiti-Rosei E. Cardiovascular status of carriers of the apolipoprotein A-I(Milano) mutant: the Limone sul Garda study. Circulation. 2001; 103: 1949–1954.

Kasturi R, Yatsu FM, Alam R, Rogers S. Restriction fragment length polymorphism of the apoprotein A-I-C-III gene cluster in control and stroke-prone white and black subjects: racial differences. Stroke. 1992; 23: 1257–1264.

Brown SA, Morrisett JD, Boerwinkle E, Hutchinson R, Ratsch W. The relation of lipoprotein concentrations and apolipoprotein phenotypes with asymptomatic atherosclerosis in subjects of the Atherosclerosis Risk in Communities (ARIC) Study. Arterioscler Thromb. 1993; 13: 1558–1566.

Monsalve MV, Young R, Jobsis J, Wiseman SA, Dhamu S, Powell JT, Greenhalgh RM, Humphries SE. DNA polymorphisms of the gene for apolipoprotein B in patients with peripheral arterial disease. Atherosclerosis. 1988; 70: 123–129.

Tybjaerg-Hansen A, Nordestgaard BG, Gerdes LU, Humphries SE. Variation of apoliprotein B gene is association with myocardial infarction and lipoprotein levels in Danes. Atherosclerosis. 1991; 89: 69–81.

Kakko S, Tamminen M, Paivansalo M, Kauma H, Rantala AO, Lilja M, Reunanen A, Kesaniemi YA, Savolainen MJ. Cholesteryl ester transfer protein gene polymorphisms are associated with carotid atherosclerosis in men. Eur J Clin Invest. 2000; 30: 18–25.

Attie AD, Kastelein JP, Hayden MR. Pivotal role of ABCA1 in reverse cholesterol transport influencing HDL levels and susceptibility to atherosclerosis. J Lipid Res. 2001 Nov 1942; 1717–1726.

Fox CS, Cupples LA, Chazaro I, Polak JF, Wolf PA, D-Agostino RB, Ordovas JM, O’Donnell CJ. Genomewide linkage analysis for internal carotid artery intimal medial thickness: evidence for linkage to chromosome 12. Am J Hum Genet. 2004; 74: 253–261.

Garg UC, Arnett DK, Folsom AR, Province MA, Williams RR, Eckfeldt JH. Lack of association between platelet glycoprotein IIb/IIIa receptor P1A polymorphism and coronary artery disease or carotid intima-media thickness. Thromb Res. 1998; 89: 85–89.

Maeno T, Koyama H, Tahara H, Komatsu M, Emoto M, Shoji T, Inaba M, Miki T, Okuno Y, Nishizawa Y. The 807T allele in alpha2 integrin is protective against atherosclerotic arterial wall thickening and the occurrence of plaque in patients with type 2 diabetes. Diabetes. 2002; 51: 1523–1528.

Hegele RA, Ban MR, Anderson CM, Spence JD. Infection-susceptibility alleles of mannose-binding lectin are associated with increased carotid plaque area. J Investig Med. 2000; 48: 198–202.

Risley P, Jerrard-Dunne P, Sitzer M, Buchler A, von Kegler S, Markus HS. Promoter polymorphism in the endotoxin receptor (CD14) is associated with increased carotid atherosclerosis only in smokers: the Carotid Atherosclerosis Progression Study (CAPS). Stroke. 2003; 34: 600–604.

Worrall BB, Azhar S, Nyquist PA, Ackerman RH, Hamm TL, DeGraba TJ. Interleukin-1 receptor antagonist gene polymorphisms in carotid atherosclerosis. Stroke. 2003; 34: 790–793.

Dwyer JH, Allayee H, Dwyer KM, Fan J, Wu H, Mar R, Lusis AJ, Mehrabian M. Arachidonate 5-lipoxygenase promoter genotype, dietary arachidonic acid, and atherosclerosis. N Engl J Med. 2004; 350: 29–37.

de Waart FG, Kok FJ, Smilde TJ, Hijmans A, Wollersheim H, Stalenhoef AF. Effect of glutathione S-transferase M1 genotype on progression of atherosclerosis in lifelong male smokers. Atherosclerosis. 2001; 158: 227–231.

Hayaishi-Okano R, Yamasaki Y, Kajimoto Y, Sakamoto K, Ohtoshi K, Katakami N, Kawamori D, Miyatsuka T, Hatazaki M, Hazama Y, Hori M. Association of NAD(P)H oxidase p22 phox gene variation with advanced carotid atherosclerosis in Japanese type 2 diabetes. Diabetes Care. 2003; 26: 458–463.

Kakko S, Paivansalo M, Koistinen P, Kesaniemi YA, Kinnula VL, Savolainen MJ. The signal sequence polymorphism of the MnSOD gene is associated with the degree of carotid atherosclerosis. Atherosclerosis. 2003; 168: 147–152.

Boerma M, Forsberg L, Van Zeijl L, Morgenstern R, De Faire U, Lemne C, Erlinge D, Thulin T, Hong Y, Cotgreave IA. A genetic polymorphism in connexin 37 as a prognostic marker for atherosclerotic plaque development. J Intern Med. 1999; 246: 211–218.

Rossi E, McQuillan BM, Hung J, Thompson PL, Kuek C, Beilby JP. Serum ferritin and C282Y mutation of the hemochromatosis gene as predictors of asymptomatic carotid atherosclerosis in a community population. Stroke. 2000; 31: 3015–3020.

Hanon O, Luong V, Mourad JJ, Bortolotto LA, Jeunemaitre X, Girerd X. Aging, carotid artery distensibility, and the Ser422Gly elastin gene polymorphism in humans. Hypertension. 2001; 38: 1185–1189.

Vedie B, Jeunemaitre X, Megnien JL, Atger V, Simon A, Moatti N. A new DNA polymorphism in the 5' untranslated region of the human SREBP-1a is related to development of atherosclerosis in high cardiovascular risk population. Atherosclerosis. 2001; 154: 589–597.

Brandstrom H, Stiger F, Lind L, Kahan T, Melhus H, Kindmark A. A single nucleotide polymorphism in the promoter region of the human gene for osteoprotegerin is related to vascular morphology and function. Biochem Biophys Res Commun. 2002; 293: 13–17.

Cakir B, Heiss G, Pankow JS, Salomaa V, Sharrett AR, Couper D, Weston BW. Association of the Lewis genotype with cardiovascular risk factors and subclinical carotid atherosclerosis: the Atherosclerosis Risk in Communities (ARIC) Study. J Intern Med. 2004; 255: 40–51.