Associations of total osteocalcin with all-cause and cardiovascular mortality in older men. The Health In Men Study.

SUMMARY: In older men, both lower and higher total osteocalcin levels predict increased all-cause mortality, with comparable associations for cardiovascular and non-cardiovascular deaths. Differences in osteocalcin levels might influence glucose metabolism and thereby cardiovascular risk, or reflect changes in bone turnover thus representing a marker for poorer health outcomes. INTRODUCTION: Reduced levels of total osteocalcin (TOC) are associated with adiposity, insulin resistance and type 2 diabetes, implying this bone-derived peptide might modulate cardiovascular risk. However, there are few longitudinal data relating TOC levels to survival. We examined associations of TOC level with all-cause and cardiovascular mortality in older men. METHODS: We conducted a prospective cohort study of community-dwelling men aged 70-89 years. Aliquots of plasma collected at baseline (2001-2004) were assayed for TOC. Incidence and causes of death to 31 December 2008 were ascertained using data linkage. Cox regression analyses were performed with adjustment for conventional cardiovascular risk factors. RESULTS: From 3,542 men followed for median 5.2 years there were 572 deaths (16.1%). Mortality was lowest in men with TOC levels in the second quintile (12.6%). In multivariate analyses, men with TOC in the lowest and highest quintiles of values had increased all-cause mortality (Q1 vs Q2: hazard ratio [HR], 1.36; 95% confidence interval 1.02-1.80 and Q5 vs Q2: HR, 1.53, 95% CI 1.18-1.98). Men with low TOC levels had similar HR for cardiovascular and non-cardiovascular deaths (Q1 vs Q2: HR, 1.35 and 1.30 respectively). Higher TOC levels predicted cardiovascular disease (CVD)-related mortality (Q5 vs Q2, HR, 1.69, 95% CI 1.09-2.64). CONCLUSIONS: TOC predicts all-cause and CVD-related mortality in community-dwelling older men. However, the relationship is U shaped with men at both ends of the distribution at increased risk. Further investigation is required to clarify whether the underlying mechanisms involve altered bone turnover or relate specifically to the biological activity of osteocalcin.

The PHF11 gene is not associated with asthma or asthma phenotypes in two independent populations.

BACKGROUND: Numerous areas of the human genome have previously been associated with asthma and asthma-related phenotypes, but few positive findings have been successfully replicated in independent populations. Initial studies have reported strong associations of variants in the plant homeodomain zinc finger protein 11 (PHF11) gene with serum IgE levels, asthma, airway hyper-responsiveness and childhood atopic dermatitis. OBJECTIVES: To investigate the association of variants in the PHF11 gene with asthma and associated intermediate phenotypes in two independent Western Australian population-based samples. METHODS: A linkage-disequilibrium (LD)-tagging set of 20 single nucleotide polymorphisms (SNPs) was genotyped in PHF11 in two separate populations (total n = 2315), a family-based twin study consisting of 230 families (n = 992 subjects) and a population-based nested case-control study consisting of 617 asthma cases and 706 controls. Information regarding asthma, respiratory physiology, atopy and environmental exposures was collected. Transmission disequilibrium tests, variance components models and generalised linear models were used to test for association between PHF11 SNPs and selected asthma outcomes (including longitudinal change in lung function). RESULTS: After correction for multiple testing, no statistically significant (p < 0.05) associations were found between PHF11 and either asthma or total serum IgE levels in either population. No statistically significant associations were found with any other asthma-associated phenotypes in either population. CONCLUSIONS: Previously reported associations of PHF11 with asthma outcomes were not replicated in this study. This study suggests that PHF11 is unlikely to contain polymorphic loci that have a major impact on asthma susceptibility in our populations.

The association of common genetic variants in the APOA5, LPL and GCK genes with longitudinal changes in metabolic and cardiovascular traits.

AIMS/HYPOTHESIS: Common genetic variants influence plasma triacylglycerol, HDL-cholesterol (HDL-C) and glucose levels in cross-sectional studies. However, the longitudinal effects of these established variants have not been studied. Our aim was to examine the longitudinal associations of four such variants in the apolipoprotein A-V (APOA5), lipoprotein lipase (LPL), and glucokinase (GCK) genes with fasting glucose or lipid levels. METHODS: The individuals analysed were participants in the Busselton Health Survey (n = 4,554). Cross-sectional analyses of family data used the total association test. Longitudinal association analyses of unrelated participant data (n = 2,864) used linear mixed-effects models. RESULTS: The findings of cross-sectional association analyses replicated those of previous studies. We observed associations of the G and C alleles at the APOA5 single nucleotide polymorphisms (SNPs) rs662799 and rs3135506 with raised triacylglycerol levels (p = 0.0003 and p < 0.0001, respectively), the 447X allele at the LPL SNP rs328 with reduced triacylglycerol levels (p = 0.0004) and raised HDL-C levels (p = 0.0004), and the A allele of the GCK SNP rs1799884 with raised fasting glucose level (p = 0.015). Longitudinal association analyses showed that most of these associations did not change in the same individuals over an average follow-up time of 17.4 years, though there was some evidence that the association of the 447X allele of rs328 with raised HDL-C level significantly increased with age (p = 0.01), and that the association of the C allele of rs3135506 with raised triacylglycerol level significantly increased over time (p = 0.0007). CONCLUSIONS/INTERPRETATION: The current study suggests that the effects of established gene variants on lipid and glucose traits do not tend to alter with age during adulthood or over time.

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.

The relationship between ACE genotype and risk of severe hypoglycaemia in a large population-based cohort of children and adolescents with type 1 diabetes.

AIMS/HYPOTHESIS: Genetic factors may account for familial clustering related to diabetes complications. Studies have shown a significant relationship between the presence of the deletion (D) allele of the gene encoding ACE and risk of severe hypoglycaemia. This large prospective cohort study assesses this relationship in a large sample of children and adolescents with type 1 diabetes. SUBJECTS AND METHODS: We studied 585 children and adolescents (mean age 11.9 +/- 4 years, 48.4% males). The frequency of severe hypoglycaemia (an event leading to loss of consciousness or seizure) was prospectively assessed over the 13-year period 1992-2004. Patients were seen with their parents every 3 months and data recorded at each visit. The ACE gene was detected using PCR. RESULTS: In our cohort of 585 children, 186 (31.8%) had at least one episode of severe hypoglycaemia, and of these 28.0% had the II genotype, 48.9% had the ID genotype and 23.1% had the DD genotype. This was in agreement with the Hardy-Weinberg proportion. A total of 477 severe hypoglycaemic episodes was recorded with a total of 3,404 person-years of follow-up, giving a total incidence of 14 per 100 patient-years. No significant increase in risk for DD genotype (incidence rate ratio = 0.97, 95% CI 0.61-1.55) relative to II genotype was observed. CONCLUSIONS/INTERPRETATION: This large prospective study concludes that the presence of the D allele of the ACE gene does not predict a significantly higher risk of severe hypoglycaemia in type 1 diabetic children and adolescents.

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.

AluyMICB dimorphism within the class I region of the major histocompatibility complex is associated with asthma and airflow obstruction in the Busselton population.

AIM: To examine the association between the Alu dimorphism within the first intron of the MICB gene and asthma and airflow obstruction. Background The highly polymorphic non-classical MHC class I polypeptide-related (MIC) genes, MICA and MICB, encode stress inducible glycoproteins, which are expressed on a variety of epithelial cells, including those of the lungs. METHODS: AluyMICB genotyping was performed on 1109 subjects from the Busselton Health Study. From a standard questionnaire, 359 individuals indicated that they had been diagnosed by a doctor with asthma. Lung function was assessed by the forced expired volume in 1 second (FEV1) and expressed as a percent of the predicted value. Airflow obstruction was defined as FEV1<80% predicted. RESULTS: In men, a dominant relationship was found between the AluyMICB DD genotype and asthma (P=0.006; chi2(2)=7.65). Furthermore, multivariate analysis adjusted for age, height, weight and body mass index (BMI) showed a relationship between DD genotype and asthma in men in a dominant model (odds ratio (OR)=1.97; 95% confidence interval (CI)=1.11-3.51; P=0.021). In women, an association was found between the AluyMICB II genotype and FEV1 percent predicted as a continuous variable (P=0.001). When adjusted for age and BMI, it showed a significant relationship between AluyMICB and airflow obstruction in a dominant model (OR=14.11%, 95% CI 3.29-60.57, P<0.001). However, no association was found between the AluyMICB II genotypes and airflow obstruction in men. CONCLUSION: These findings suggest the possible involvement of a MHC class I gene in abnormal airway structure in women and airway function in men.

Variegate porphyria in Western Australian Aboriginal patients.

BACKGROUND: Survivors of shipwrecks along the Western Australian coast may have introduced a mutation for variegate porphyria into the Aboriginal population prior to first settlement. AIMS: To assess the mutations responsible for variegate porphyria in Western Australian Aboriginal patients, particularly the R59W mutation, which is the most common cause of variegate porphyria in South Africa. METHODS: New cases of porphyria were diagnosed by biochemical separation of porphyrin subtypes. Single-stranded conformation polymorphism analysis and DNA sequencing of the protoporphyrinogen oxidase gene was performed on Aboriginal patients to define possible causative mutation sites. RESULTS: Of the 296 new cases of porphyria diagnosed in Western Australia from 1978 to 1998, six had biochemically proven variegate porphyria. Three of those cases occurred in Aboriginal patients. Evidence for a possible fourth Aboriginal case of variegate porphyria is described. The R59W founder mutation responsible for over 90% of variegate porphyria in South Africa was excluded. Two new mutations that predicted amino acid substitutions with significant effects on enzyme function were detected in conserved regions of the protoporphyrinogen oxidase gene in one Aboriginal variegate porphyria patient and the possible fourth case. CONCLUSION: Results suggest that the mutations causing variegate porphyria in the Western Australian Aboriginal population occur sporadically and were not inherited from shipwrecked sailors.

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.

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.

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.

Pharmacokinetics and pharmacodynamics of gliclazide in Caucasians and Australian Aborigines with type 2 diabetes.

AIMS: Gliclazide pharmacokinetics and pharmacodynamics were assessed in 9 Caucasians and 10 Australian Aborigines with uncomplicated type 2 diabetes. METHODS: Subjects were on a stable dose of 80 mg gliclazide twice daily, took 160 mg on the morning of study and had a standard breakfast. No further gliclazide was given over the next 48 h. Regular blood samples were drawn for serum glucose, insulin and gliclazide assay. Gliclazide was measured using h.p.l.c. Noncompartmental analysis was used to describe primary data. A multicompartment model incorporating entero-hepatic recirculation was fitted to group mean serum gliclazide profiles. RESULTS: The Caucasians were older than the Aborigines (mean +/- s.d. age 53.4 +/- 12.2 vs 40.3 +/- 6.9 years, P < 0.05) but had similar diabetes duration, body mass index and glycated haemoglobin. Noncompartmental analysis revealed no between-group differences in gliclazide kinetics. Post-breakfast serum glucose and insulin responses were also similar apart from a longer time to maximum concentration (tmax) for glucose amongst the Aborigines (2.6 +/- 0.4 vs 2.2 +/- 0. 3 h in Caucasians; P = 0.024). Gliclazide tmax exhibited a skewed unimodal distribution and was not associated with gliclazide maximum concentration, or glucose or insulin responses. Most patients had a serum gliclazide profile suggestive of enterohepatic recirculation and/or biphasic absorption. Model-derived estimates of the extent of putative enterohepatic recirculation were 30% and 20% of dose in Caucasians and Aborigines, respectively. CONCLUSIONS: Gliclazide is equally effective in Caucasian and Aboriginal diabetic patients. The pharmacokinetics of oral gliclazide appear more complex than previously thought. Gliclazide pharmacodynamics are unrelated to rate and extent of absorption, consistent with a threshold concentration for hypoglycaemic effect.

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.

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.

Genotyping as a diagnostic aid in genetic haemochromatosis.

BACKGROUND: Two mutations in a newly described gene, HFE, have been proposed as genetic markers for the inherited iron overload disease, genetic haemochromatosis. METHODS: We assessed the frequency of both mutations in a cohort of genetic haemochromatosis patients and compared these with a control population. The patients were genetic haemochromatosis patients from Western Australia whose diagnosis met strict criteria for phenotypic expression. Control patients had other liver disease where iron overload was excluded. RESULTS: Genomic DNA of 72 genetic haemochromatosis patients and 69 controls was examined for the C282Y and H63D mutations of the HFE gene using polymerase chain reaction amplification and restriction enzyme digestion. In genetic haemochromatosis patients, the C282Y mutation was homozygous in 64 of 72, giving a sensitivity of 89% (95% confidence interval 82-96%), heterozygous in five (7%) and absent in another three (4%), whereas none of the control subjects were homozygous. The H63D mutation was present in one genetic haemochromatosis patient and was not useful as a diagnostic marker. In this cohort of Western Australian patients with phenotypic expression of genetic haemochromatosis, the specificity of a homozygous C282Y mutation for genetic haemochromatosis was 100%. CONCLUSIONS: The results indicate that genotyping for the C282Y mutation is a useful test for the diagnosis of genetic haemochromatosis in clinical practice.

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.

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.