Plasma Proprotein Convertase Subtilisin Kexin Type 9 as a Predictor of Carotid Atherosclerosis in Asymptomatic Adults.

BACKGROUND: Atherosclerosis is a lipid-driven inflammatory disease of the arterial wall involving complex and multifactorial processes. Proprotein convertase subtilisin kexin type 9 (PCSK9) may play a role in the development of atherosclerosis. METHODS: We investigated the associations between serum PCSK9 and carotid intima-medial wall thickness (IMT), a measure of subclinical atherosclerosis that predicts cardiovascular events, in 295 asymptomatic subjects from community. Carotid IMT was determined by high-resolution B-mode carotid ultrasonography and serum PCSK9 was measured by immunoassay. RESULTS: In univariate analysis, serum PCSK9 concentration was positively (P<0.05 in all) associated with age (r=0.204), BMI (r=0.149), waist circumference (r=0.139), systolic blood pressures (r=0.116), glucose (r=0.211), insulin (r=0.178), HOMA score (r=0.195), plasma triglyceride (r=0.285), total cholesterol (r=0.241) and LDL-cholesterol concentrations (r=0.172). In multivariate regression including male gender, hypertension, smoking status, HOMA score, obesity, LDL-cholesterol, lipoprotein (a) or markers of inflammation, serum PCSK9 remained an independent predictor of mean carotid IMT (P<0.001). CONCLUSIONS: These data suggest that serum levels of PCSK9 may contribute to increased risk of subclinical carotid atherosclerosis independent of conventional risk factors. Whether PCSK9 inhibition improves cardiovascular outcomes remains to be demonstrated in large, ongoing clinical trials.

Circulating adiponectin levels associate with inflammatory markers, insulin resistance and metabolic syndrome independent of obesity.

BACKGROUND: Adiponectin is an abundantly expressed adipocyte-specific protein, whose level is decreased in obesity, and which appears to be a key participant in developing inflammation, insulin resistance and metabolic syndrome (MetS). We examined whether the relationship between adiponectin and inflammatory markers, insulin resistance and MetS was independent of obesity. METHODS AND RESULTS: The study was performed in 1094 men and women, aged 27-77 years, from a representative community population. We measured serum inflammatory markers, homoeostasis model assessment of insulin resistance (HOMA-IR) and prevalent MetS using National Cholesterol Education Program ATPIII criteria. Sex- and age-adjusted plasma adiponectin concentration was inversely correlated with body mass index (BMI), waist-hip ratio, diastolic blood pressure, triglycerides, glucose and fasting insulin, and positively correlated with HDL cholesterol (all P<0.005). Log plasma adiponectin was a significant negative correlate of the levels of C-reactive protein, interleukin-6, interleukin-18, fibrinogen and white cell count independent of level of obesity. Log plasma adiponectin was also an inverse associate of log HOMA-IR (P<0.001) independent of obesity. Subjects in the top compared to bottom sex-specific plasma adiponectin quartile had a multivariate-adjusted odds ratio (OR) of 0.21 (95% CI, 0.11-0.42; P<0.001) for prevalent MetS, and the association was independent of age, sex, BMI, log insulin and log interleukin-18 levels. CONCLUSION: Our findings suggest that higher circulating adiponectin levels may mitigate against adipose-related inflammation, insulin resistance and MetS as much in lean as obese persons. At any rate circulating adiponectin level is a strong risk marker for MetS, which is independent of measures of adiposity, insulin resistance and inflammatory markers.

Clinical correlates and reference intervals for pulmonary artery systolic pressure among echocardiographically normal subjects.

BACKGROUND: Data in normal human subjects on the factors affecting pulmonary artery systolic pressure (PASP) are limited. We determined the correlates of and established a reference range for PASP as determined by Doppler transthoracic echocardiography (TTE) from a clinical echocardiographic database of 102 818 patients, of whom 15 596 (15%) had a normal Doppler TTE study. METHODS AND RESULTS: A normal TTE was based on normal cardiac structure and function during complete Doppler TTE studies. The PASP was calculated by use of the modified Bernoulli equation, with right atrial pressure assumed to be 10 mm Hg. Among TTE normal subjects, 3790 subjects (2432 women, 1358 men) from 1 to 89 years old had a measured PASP. The mean PASP was 28.3+/-4.9 mm Hg (range 15 to 57 mm Hg). PASP was independently associated with age, body mass index (BMI), male sex, left ventricular posterior wall thickness, and left ventricular ejection fraction (P<0.001). The estimated upper 95% limit for PASP among lower-risk subjects was 37.2 mm Hg. A PASP >40 mm Hg was found in 6% of those >50 years old and 5% of those with a BMI >30 kg/m(2). CONCLUSIONS: Among 3790 echocardiographically normal subjects, PASP was associated with age, BMI, sex, wall thickness, and ejection fraction. Of these subjects, 28% had a PASP >30 mm Hg, and the expected upper limit of PASP may include 40 mm Hg in older or obese subjects. These findings support the use of age- and BMI-corrected values in establishing the expected normal range for PASP.

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)

BACKGROUND: Hyperhomocysteinemia has been identified as a potential risk factor for atherosclerosis. This study examined whether a modest elevation of plasma total homocysteine (tHcy) was an independent risk factor for increased carotid artery intimal-medial wall thickness (IMT) and focal plaque formation in a large, randomly selected community population. We also examined whether vitamin cofactors and the C677T genetic mutation of the methylenetetrahydrofolate reductase (MTHFR) enzyme were major contributors to elevated plasma tHcy and carotid vascular disease. METHODS AND RESULTS: In 1111 subjects (558 men, 553 women) 52+/-13 years old (mean+/-SD; range, 27 to 77 years) recruited from a random electoral roll survey, we measured fasting tHcy and performed bilateral carotid B-mode ultrasound. For the total population, mean tHcy was 12.1+/-4.0 micromol/L. Plasma tHcy levels were correlated with IMT (Spearman rank rs=0.31, P=0.0001). After adjustment for age, sex, and other conventional risk factors, subjects in the highest versus the lowest quartile of tHcy had an odds ratio of 2.60 (95% CI, 1.51 to 4.45) for increased IMT and 1.76 (95% CI, 1.10 to 2.82) for plaque. Serum and dietary folate levels and the C677T mutation in MTHFR were independent determinants of tHcy (all P=0.0001). The mutant homozygotes (10% of the population) had higher mean tHcy than heterozygotes or those without the mutation (14.2 versus 12.3 versus 11.6 micromol/L, respectively, P=0.0001). The inverse association of folate levels with tHcy was steeper in the mutant homozygotes. Despite this, the C677T MTHFR mutation was not independently predictive of increased carotid IMT or plaque formation. CONCLUSIONS: Mild hyperhomocysteinemia is an independent risk factor for increased carotid artery wall thickness and plaque formation in a general population. Lower levels of dietary folate intake and the C677T mutation in MTHFR are important causes of mild hyperhomocysteinemia and may therefore contribute to vascular disease in the community.

Antioxidant vitamins and the risk of carotid atherosclerosis. The Perth Carotid Ultrasound Disease Assessment study (CUDAS).

OBJECTIVES: This study examined whether dietary intake or plasma levels of antioxidant vitamins were independently associated with common carotid artery intima-media (wall) thickness (IMT) or focal plaque, or both, in a large, randomly selected community population. BACKGROUND: Oxidation of low-density lipoprotein (LDL) cholesterol is thought to be important in early atherogenesis. Antioxidant micronutrients may therefore protect against lipid peroxidation and atherosclerotic vascular disease. METHODS: We studied 1,111 subjects (558 men and 553 women; age 52 +/- 13 years [mean +/- SD], range 27 to 77). We measured dietary vitamin intake and fasting plasma levels of vitamins A, C and E, lycopene and alpha- and beta-carotene and performed bilateral carotid artery B-mode ultrasound imaging. RESULTS; After adjustment for age and conventional risk factors, there was a progressive decrease in mean IMT, with increasing quartiles of dietary vitamin E intake in men (p = 0.02) and a nonsignificant trend in women (p = 0.10). Dietary vitamin E levels accounted for 1% of the variance in measured IMT in men. For plasma antioxidant vitamins, there was an inverse association between carotid artery mean IMT and plasma lycopene in women (p = 0.047), but not in men. None of the other dietary or plasma antioxidant vitamins, nor antioxidant vitamin supplements, were associated with carotid artery IMT or focal carotid artery plaque. CONCLUSIONS: This study provides limited support for the hypothesis that increased dietary intake of vitamin E and increased plasma lycopene may decrease the risk of atherosclerosis. No benefit was demonstrated for supplemental antioxidant vitamin use.

Serum ferritin and C282Y mutation of the hemochromatosis gene as predictors of asymptomatic carotid atherosclerosis in a community population.

BACKGROUND AND PURPOSE: Serum ferritin and heterozygosity for the C282Y mutation of the hemochromatosis gene have both been associated with an increased risk of cardiovascular events. The purpose of the study was to test whether either is a risk predictor for asymptomatic carotid atherosclerosis. METHODS: We assessed carotid intima-media wall thickness (IMT) and focal plaque formation by high-resolution B-mode ultrasound, conventional risk factors, serum ferritin levels, and the C282Y mutation of the hemochromatosis gene in a randomly selected community population of 1098 subjects (545 women and 553 men) aged 27 to 77 years. RESULTS: After adjustment for conventional risk factors, serum ferritin was not associated with carotid mean IMT. Women with ferritin values over the first quartile (>34 microg/L) had an adjusted odds ratio of 2.1 (95% CI, 1. 3 to 3.4; P:=0.0016) for carotid plaque compared with the first quartile. Ferritin was not associated with carotid plaque in men. Subjects who were heterozygous for the C282Y mutation constituted 11. 4% of the population, and there was no independent association of this genotype with either carotid IMT or focal plaque formation. CONCLUSIONS: We conclude that in our community population, C282Y genotype status was not a risk predictor for either carotid mean IMT or plaque formation. Serum ferritin values in women were independently associated with carotid plaque.

Polymorphisms in the angiotensinogen gene are associated with carotid intimal-medial thickening in females from a community-based population.

BACKGROUND: Polymorphisms within genes of the renin-angiotensin system have been associated with an increased risk of cardiovascular disease. We investigated the association of polymorphisms in the angiotensinogen (AGT) and angiotensin II receptor type 1 (AGTR1) genes with increased intima-media thickness (IMT) and the presence of plaques in carotid arteries. METHODS: Subjects (1111) from the Perth Carotid Ultrasound Disease Assessment Study (CUDAS) were genotyped for three polymorphisms: two in the promoter of the AGT gene, G-6A and A-20C; and one in the AGTR1 gene, A1166C. RESULTS: Using multivariate generalised linear models, the AGT-6A allele (P<0.001) and the AGT-20C allele (P<0.03) were significantly associated with increased mean carotid IMT in females but not in males when adjusted for conventional risk factors. The AGTR1 A1166C polymorphism did not show any significant relationship to mean IMT. Results suggest that the I allele of the angiotensin converting enzyme insertion/deletion polymorphism may interact with the AGT-6G allele to increase mean carotid IMT in the population as a whole. None of the polymorphisms investigated were significantly associated with the presence of carotid plaques. CONCLUSION: This study shows that polymorphisms in the angiotensinogen gene are associated with an increased risk of carotid intimal-medial wall thickening in females.

Lack of association between seropositivity to Chlamydia pneumoniae and carotid atherosclerosis.

Since the Chlamydia pneumoniae (C. pneumoniae)-specific antibody was shown to be associated with acute myocardial infarction and chronic coronary heart disease, the role of C. pneumoniae in the etiology of cardiovascular disease has been studied by a number of groups. We investigated the association between the C. pneumoniae-specific antibody, measured by microimmunofluorescence, risk factors for cardiovascular disease, and atherosclerosis in a randomly selected urban population. Overall, immunoglobulin-G (IgG) seroprevalence to C. pneumoniae in this sample of 1,034 subjects was 58%, whereas IgA seroprevalence was 32%. There was a decline in seropositivity with age for IgG but not IgA. Men were more likely than women to be IgG (66% vs 51%, chi-square p = 0.001) and IgA seropositive (36% vs 28%, chi-square p = 0.005). Current smokers had higher IgA seropositivity than nonsmokers (43% vs 30%). Those patients with a family history of cerebrovascular disease were more likely to have IgG antibody than those without (75% vs 57%, chi-square p= 0.007). Neither IgG nor IgA seropositivity was associated with the standard risk factors of hypertension, hyperlipidemia, or family history of ischemic heart disease, nor was seropositivity associated with carotid intima medial thickening (IMT) or atherosclerotic plaque as measured by carotid B-mode ultrasound. There was no difference between those participants who were IgG or IgA seropositive and seronegative in measurements of mean IMT, prevalence of abnormal IMT, and percentage with atherosclerotic plaque. In conclusion, although C. pneumoniae was associated with several risk factors for cardiovascular disease in a large cross-sectional population, we found no independent association between seroprevalence to C. pneumoniae and carotid atherosclerosis as measured by carotid IMT.

A Pro12Ala polymorphism in the human peroxisome proliferator-activated receptor-gamma 2 is associated with combined hyperlipidaemia in obesity.

OBJECTIVE: Peroxisome proliferator-activated receptor-gamma 2 (PPAR gamma 2) is an important regulator of adipose tissue metabolism and insulin sensitivity. The aim of this investigation was to determine whether a PPAR gamma 2 Pro12Ala polymorphism was associated with cardiovascular risk factors (obesity, blood pressure, diabetes and blood lipids) in Western Australian Caucasians (n=663). DESIGN: Subjects were selected from two population studies (the Carotid Ultrasound Disease Assessment Study (CUDAS) and Busselton Population Health Survey) on the basis of body mass index (BMI). 292 obese (BMI > or =30 kg/m) and 371 lean (BMI <25 kg /m) subjects were studied. METHODS: Blood pressure and anthropometric measurements were collected from all participants, as well as a fasting venous blood sample. Biochemical measurements (high-density lipoprotein (HDL)- and low-density lipoprotein-cholesterol, triglycerides) and PPAR gamma 2 Pro12Ala genotype were also determined. RESULTS: Obese Pro/Ala and Ala/Ala subjects had lower levels of HDL-cholesterol (P=0.032) and a trend towards higher levels of triglycerides (P=0.055) compared with obese Pro/Pro subjects. In the obese group, the Ala allele was significantly associated with the presence of combined hyperlipidaemia (odds ratio = 2.33, P=0.042). There was no significant difference in the frequency of the polymorphism between lean and obese groups (P=0.069). No association was observed between Pro12Ala genotype and obesity, blood pressure or diabetes in either group. CONCLUSIONS: Obese carriers of the Pro12Ala polymorphism have a greater risk of developing combined hyperlipidaemia, possibly due to impaired activation of PPAR gamma target genes. The Pro12Ala polymorphism is not directly associated with obesity, hypertension or diabetes in this population.

Severe mitral regurgitation secondary to partial papillary muscle rupture following myocardial infarction.

The scenario is not new--elderly patient, myocardial infarction, cardiac shock, new systolic murmur, rising enzymes--but the cause may not be common. Mechanical problems are probably at the root of the complications, but transthoracic echocardiography is not pinpointing the cause. Where to turn next? This patient's diagnosis of partial papillary muscle rupture is facilitated by multiplane transesophageal echocardiography.

Biological variability and reference intervals for total plasma homocysteine.

We determined the intra-individual biological variability of plasma homocysteine in 20 healthy subjects. The intra-individual coefficient of variation was relatively low (8.3%), indicating that a single measurement can be used to characterize the average homocysteine concentration. A population study measuring plasma homocysteine and serum folate levels was conducted on serum samples collected from 1109 randomly selected, fasting adults with a wide age range. We determined age- and gender-specific central 0.95 intervals and found that subjects in the highest quartile of serum folate had significantly lower (P = 0.0001) mean plasma homocysteine concentrations than did those in the lowest quartile of folate values. An 'ideal' homocysteine reference range, based on targeting those subjects who are likely to be folate replete, is preferable to the population-based range using the central 0.95 interval.

The C-480T hepatic lipase polymorphism is associated with HDL-C but not with risk of coronary heart disease.

High-density lipoprotein cholesterol (HDL-C) is a known predictor of coronary heart disease (CHD). Studies have shown that the C-480T polymorphism of the hepatic lipase (HL) gene is predictive of HDL-C; however, its observed relationship with the risk of CHD has been inconsistent. We analysed four biallelic polymorphisms in the HL gene in participants from three independent Western Australian populations. Samples were collected from two cross-sectional studies of 1111 and 4822 community-based subjects assessed for cardiovascular risk factors, and a third sample of 556 subjects with physician-diagnosed CHD. Genotypes were tested for association with plasma lipids and the risk of CHD. All polymorphisms were highly correlated (D' > 0.97, r(2) > 0.90); therefore, only C-480T was analysed. The -480T allele was significantly associated with an increase in HDL-C of between 0.08 and 0.16 mmol/l in all three populations (p < 0.001). No associations with other lipids were observed, nor was an association with CHD in a case-control study of males. The TT genotype was however associated with decreased risk of myocardial infarction among cases (odds ratio = 0.39, 95% confidence interval = 0.19-0.78, p = 0.008). These findings replicate those of previous studies in three independent populations and suggest that the genetic determinants of CHD are complex and cannot be entirely explained through intermediate phenotypes.

Angiotensin-converting enzyme gene polymorphism and carotid wall thickening in a community population.

The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with an increased risk of coronary heart disease, but whether it is a risk factor for underlying atherosclerosis remains unclear. Therefore, we examined to see whether the ACE gene deletion polymorphism was associated with carotid wall thickening and atherosclerotic plaque formation in a large randomly selected community population. A total of 1111 subjects, aged 27 to 77 years, with an equal male:female ratio and equal numbers in each age decile, were randomly selected from the Perth community population. Mean common carotid intima-medial wall thickness (IMT) and focal plaque formation were assessed by high-resolution B-mode ultrasound. The ACE gene I/D polymorphism was detected by PCR. The distribution of the ACE genotypes conformed to the Hardy-Weinberg equilibrium (DD, 31.0%; ID, 48.4%; and II, 20.6%). The D allele was strongly correlated in a codominant fashion with plasma ACE activity (r(s)=0.53, P<0.0001), and accounted for 33% of the total variance in circulating ACE activity. No significant differences among the ACE genotypes were found with respect to age, sex, and conventional risk variables, including a history of hypertension and vascular disease. The average mean IMT and prevalence of increased IMT and focal plaque were not significantly different among genotypes in the overall population or in the subset (n=852) who were conventionally low risk by Framingham coronary heart disease risk score. Logistic regression analysis selected age, systolic blood pressure, pack-years of smoking, LDL cholesterol level, waist/hip ratio, and history of hypertension, but not the D allele, as multivariate predictors of increased IMT and carotid plaque formation. We conclude that, although the ACE I/D polymorphism is strongly related to ACE activity, it is not a risk predictor of carotid wall thickening or focal plaque formation when examined in a large randomly selected community population.