Reserpine: effect on structure of heart muscle

We examined the ultrastructure of hearts from dogs given reserpine intramuscularly for 4 days, and from untreated dogs. Sections of the myocardium from treated dogs invariably revealed mitochondrial abnormalities at the 5th and 14th days. These included fragmentation and loss of structure of the cristae, and cyst formation. The appearance at 25 days in the treated as well as in all the untreated dogs was normal. We concluded that reserpine in the dose used produces marked structural changes in the mitochondria of heart muscle, and that these changes are reversible. These changes may account for the myocardial depression sometimes seen after administration of reserpine.

Vascular outcome in patients with homocystinuria due to cystathionine beta-synthase deficiency treated chronically: a multicenter observational study

An inborn error of metabolism, homocystinuria due to cystathionine beta-synthase deficiency, results in markedly elevated levels of circulating homocysteine. Premature vascular events are the main life-threatening complication. Half of all untreated patients have a vascular event by 30 years of age. We performed a multicenter observational study to assess the effectiveness of long-term homocysteine-lowering treatment in reducing vascular risk in 158 patients. Vascular outcomes were analyzed and effectiveness of treatment in reducing vascular risk was evaluated by comparison of actual to predicted number of vascular events, with the use of historical controls from a landmark study of 629 untreated patients with cystathionine beta-synthase deficiency. The 158 patients had a mean (range) age of 29.4 (4.5 to 70) years; 57 (36%) were more than 30 years old, and 10 (6%) were older than 50 years. There were 2822 patient-years of treatment, with an average of 17.9 years per patient. Plasma homocysteine levels were markedly reduced from pretreatment levels but usually remained moderately elevated. There were 17 vascular events in 12 patients at a mean (range) age of 42.5 (18 to 67) years: pulmonary embolism (n=3), myocardial infarction (n=2), deep venous thrombosis (n=5), cerebrovascular accident (n=3), transient ischemic attack (n=1), sagittal sinus thrombosis (n=1), and abdominal aortic aneurysm (n=2). Without treatment, 112 vascular events would have been expected, for a relative risk of 0.09 (95% CI 0.036 to 0.228; P<0.0001). Treatment regimens designed to lower plasma homocysteine significantly reduce cardiovascular risk in cystathionine beta-synthase deficiency despite imperfect biochemical control. These findings may be relevant to the significance of mild hyperhomocysteinemia that is commonly found in patients with vascular disease.

Cytomegalovirus inhibits p53 nuclear localization signal function

Endothelial cells (EC) infected with the VHL strain of cytomegalovirus (CMV) are resistant to p53-mediated apoptosis, which may be relevant to EC dysfunction and atherogenesis. This resistance to apoptosis may be mediated by cytoplasmic sequestration of p53, which functions only in the nucleus. We explored the hypothesis that CMV sequesters p53 in the cytoplasm by blocking p53 nuclear localization signal (NLS) function. We transfected VHL CMV infected EC with recombinant p53 NLSI conjugated with chicken muscle pyruvate kinase (PK) plasmid. NLSI is responsible for 90% of p53 nuclear localization, and PK is not normally translocated to the nucleus after cytoplasmic production. Thus it cannot be localized in the nucleus without the assistance of the artificial NLSI. A double-labeling immunofluorescence staining method was used to identify the localization of p53 NLSI-conjugated PK in CMV-infected EC. We found that CMV infection sequesters PK and p53 in the cytoplasm by blocking NLSI function. This inactivation of NLSI function is dependent upon infection stage; it occurs only in the early and late phases and not the immediate early phase of infection. These findings may be relevant to endothelial dysfunction and initiation of atherogenesis. Our study also suggests a novel mechanism of the p53 inactivation by virus, which may be important for atherogenesis and tumorgenesis.

Influence of an inducible nitric oxide synthase promoter variant on clinical variables in patients with coronary artery disease

Pathophysiological processes in coronary artery disease (CAD) are influenced by genetic factors. Since (i) inducible nitric oxide synthase (iNOS) has important cardiovascular effects, and (ii) the promoter of the iNOS gene (NOS2A) is genetically modulated by a 4 bp insertion/deletion (+/-) polymorphism located 0.7 kb upstream, we decided to examine the influence of this variant on clinical variables in 856 CAD patients of Anglo-Celtic/Northern European extraction. We found that 2% of CAD patients were homozygous for the + allele, and 19% were heterozygous. Males made up 74% of the patient group, and in these the + allele was associated with 38% higher plasma glucose levels (P=0.005), a 4.8% elevation in the waist/hip ratio (P=0.009) and a 48% greater frequency of unstable angina (P=0.014). The + allele, by influencing iNOS expression, could thus contribute to indices of insulin resistance and angina severity in male CAD patients.

Vascular complications of severe hyperhomocysteinemia in patients with homocystinuria due to cystathionine beta-synthase deficiency: effects of homocysteine-lowering therapy

Homocystinuria (HCU) due to cystathionine beta-synthase (CBS) deficiency leads to severe hyperhomocysteinemia (HHcy). Vascular events (VE) remain the major cause of morbidity and mortality in the untreated patients with HCU. The study on the natural history of untreated HCU disclosed that, at the time of maximal risk, in other words beyond 10 years old, there was one event per 25 years. Recent studies from Australia (n = 32), The Netherlands (n = 28), and Ireland (n = 24) have documented the effects of long-term treatment on the vascular outcome of a total of 84 patients with 1314 patient-years of treatment for HCU. The mean (range) age was 27.8 (2.5 to 70) years. Five VE were recorded during treatment; one pulmonary embolism, two myocardial infarctions, and two abdominal aneurysms. All five VE occurred in B6-responsive patients at a mean (range) age of 48.8 (30 to 60) years. In 1314 patient-years of treatment, 53 VE would have been expected if they remained untreated; instead only 5 were documented, relative risk = 0.091 (95% confidence interval [CI] 0.043 to 0.190; p < 0.001). Appropriate homocysteine-lowering therapy for severe HHcy significantly reduced the vascular risk in patients with HCU. VE were rare with treatment despite the fact that the post-treatment homocysteine levels were several times higher than the cutoff point for homocysteine in the normal population. The present findings may have relevance to the current concept of "mild HHcy" as a risk factor for vascular disease, with elevated plasma homocysteine levels considerably lower than that of the post-treatment levels in this group of reported patients.

Cigarette smoke activates caspase-3 to induce apoptosis of human umbilical venous endothelial cells

We explored an hypothesis that cigarette smoking-induced endothelial injury is mediated by accelerated apoptosis by treating human endothelial cells with cigarette smoke extracts (CSE). In cells treated with an increasing doses of CSE (0.005-0.03 cigarette equivalents/mL), we found a dose-dependent increase in the proportion of endothelial cells stained positive for apoptotic changes (8.3 +/- 0.7 to 50.7 +/- 2.2%, P < 0.01), accompanied by changes in caspase-3 activities and p53 protein levels. We suggest that excessive endothelial apoptosis may contribute to cigarette smoke-induced endothelial dysfunction and hence atherogenesis.

Homocysteine and cardiovascular disease: cause or effect?

Both markedly and mildly elevated circulating homocysteine concentrations are associated with increased risk of vascular occlusion. Here we review possible mechanisms that mediate these effects. Inborn errors of homocysteine metabolism result in markedly elevated plasma homocysteine (200-300 micromol/L) and thromboembolic (mainly venous) disease: treatment to lower but not to normalize these concentrations prevents vascular events. Mild homocysteine elevation (>15 micromol/L) occurs in approximately 20-30% of patients with atherosclerotic disease. Usually, this is easily normalized with oral folate and ongoing trials are assessing the effect of folate treatment on outcomes. Although there is evidence of endothelial dysfunction with both markedly and mildly elevated homocysteine concentrations, the elevated homocysteine concentration in atherosclerotic patients is also associated with most standard vascular risk factors, and importantly, with early decline in renal function, which is common in atherosclerosis. Decline in renal function alone causes elevated plasma homocysteine (and cysteine). These observations suggest that mild hyperhomocysteinemia could often be an effect rather than a cause of atherosclerotic disease. Data on the common C677T methylenetetrahydrofolate reductase polymorphism supports this, in that, although homozygosity is a frequent cause of mild hyperhomocysteinemia when plasma folate is below median population concentrations, it appears not to increase cardiovascular risk. Indeed, there is recent evidence suggesting an acute antioxidant effect of folic acid independent of its effect on homocysteine concentrations. This antioxidant mechanism may oppose an oxidant effect of homocysteine and be relevant to treatment of patients with vascular disease, especially those with chronic renal insufficiency. Such patients have moderately elevated plasma homocysteine and greatly increased cardiovascular risk that is largely unexplained.

Elevated circulating homocyst(e)ine levels in placental vascular disease and associated pre-eclampsia

We examined the hypothesis that hyperhomocyst(e)inaemia in the maternal or fetal circulation is associated with placental vascular disease with either the maternal syndrome of pre-eclampsia and/or fetal syndrome of growth restriction. Maternal plasma homocyst(e)ine levels were significantly higher in pregnancies complicated by pre-eclampsia, pregnancies with evidence of umbilical placental vascular disease, and pregnancies with both complications compared with the normal pregnancy group. In the fetal circulation mean plasma homocyst(e)ine concentration was significantly higher in the pre-eclampsia group compared with the normal group. The results suggest that hyperhomocyst(e)inaemia may be a risk marker for placental vascular disease and maternal pre-eclampsia. The elevated fetal plasma homocyst(e)ine concentrations, found only in the group of pregnancies with pre-eclampsia in the absence of umbilical placental vascular disease, may be due to an effect of placental vascular disease on homocyst(e)ine transfer from the maternal to fetal circulation.

Human cytomegalovirus immediate early proteins upregulate endothelial p53 function

Infected endothelial cells are found to be resistant to apoptosis possibly mediated by p53 cytoplasmic sequestration. We explored whether the immediate early 84 kDa protein (IE84) of cytomegalovirus (CMV) is responsible for p53 cytoplasmic sequestration. The endothelial cells were transfected with plasmids containing IE1 and 2 coding regions which are known to synthesize IE84 and 72 proteins. Our study found that p53 expression was significantly elevated in endothelial cells transfected with IE1 and 2 plasmids. However, p53 was only found in the nucleus rather than sequestered in the cytoplasm. We have demonstrated that IE84 and 72 are not responsible for p53 dysfunction caused by CMV infection, rather they upregulate p53 function and promote endothelial apoptosis.

Lp(a) and conventional risk profiles predict the severity of coronary stenosis in high-risk hospital-based patients

AIMS

To explore predictive power of Lp(a), of conventional lipoprotein profiles and their carrier proteins, and of biometric measurements, for the presence and severity of angiographically documented coronary disease in high-risk patients, and to compare risk profiles in men and women.

METHODS

We determined coronary artery disease (CAD) risk factors in 1308 Australian Caucasian patients (313 women and 995 men) aged < or =65 years who consecutively underwent coronary angiography.

RESULTS

In univariate analyses of the risk factors, lipid profiles, Lp(a), cigarette smoking, diabetes, hypertension and obesity were all higher in men and women with CAD and changed significantly with the number of significantly diseased vessels (> or =50% luminal obstruction). When stepwise logistic regression analysis was applied, age (OR 1.06, 95% CI: 1.04-1.09), TC/HDL-C (OR 1.29, 95% CI: 1.15-1.45), male gender (OR 2.64, 95% CI: 1.67-4.16), hyperLp(a) (> or =300 mg/L) (OR 2.09, 95% CI: 1.42-3.07), lifetime smoking dose (OR 1.02, 95% CI: 1.01-1.03), diabetes (OR 2.19, 95% CI: 1.14-4.18) and waist/hip ratio (OR 14.53, 95% CI: 1.21-174.90) were predictive of the disease. Both Lp(a) levels and percentage of hyperLp(a) increased linearly with the number of significantly diseased vessels. When the analyses were conducted in men and women separately, hyperLp(a), TC/HDL-C, lifetime smoking dose and age remained as significant predictors in both groups but the waist/hip ratio was only predictive in women.

CONCLUSIONS

As Lp(a) is an independent predictor of the occurrence and extent of coronary stenosis and relevant to treatment options, we suggest that it should be measured routinely in the coronary risk profile assessment of high-risk patients.

Relationship between homocysteine and superoxide dismutase in homocystinuria: possible relevance to cardiovascular risk

A modest homocysteine elevation is associated with an increased cardiovascular risk. Marked circulating homocysteine elevations occur in homocystinuria due to cystathionine beta-synthase (CbetaS) deficiency, a disorder associated with a greatly enhanced cardiovascular risk. Lowering homocysteine levels reduces this risk significantly. Because homocysteine-induced oxidative damage may contribute to vascular changes and extracellular superoxide dismutase (EC-SOD) is an important antioxidant in vascular tissue, we assessed EC-SOD and homocysteine in patients with homocystinuria. We measured circulating EC-SOD, total homocysteine (free plus bound), and methionine levels during the treatment of 21 patients with homocystinuria, 18 due to CbetaS deficiency, aged 8 to 59 years, and 3 with remethylating defects. We measured total homocysteine by immunoassay, EC-SOD by ELISA, and methionine by amino acid analysis and assessed interindividual and intraindividual relationships. There was a significant, positive relationship between EC-SOD and total homocysteine. For the interindividual assessment, levels were highly correlated, r=0.746, N=21, P<0.0001. This relationship was maintained after taking into account intraindividual patient variation (r=0.607, N=62, P<0.0001). In 2 newly diagnosed CbetaS-deficient patients, treatment that lowered the markedly elevated pretreatment homocysteine level (from 337 to 72 and from 298 to 50 micromol/L) reduced the associated elevated EC-SOD in each by 50%. EC-SOD and methionine levels were unrelated (r=0.148, n=39, P=0.368). The positive relationship between circulating EC-SOD and homocysteine could represent a protective antioxidant response to homocysteine-induced oxidative damage and contribute to reducing cardiovascular risk in homocystinuric patients. EC-SOD levels may be relevant to the pathogenesis of vascular disease in other patient groups.

Plasma levels of extracellular superoxide dismutase in an Australian population: genetic contribution to normal variation and correlations with plasma nitric oxide and apolipoprotein A-I levels

Extracellular superoxide dismutase (EC-SOD) is a major superoxide scavenger and may be important to normal vascular function and cardiovascular health. We analyzed family data from 610 healthy Australians to detect and quantify the effects of genes on normal variation in plasma levels of EC-SOD and to test for pleiotropy with plasma nitric oxide (NO) and apolipoprotein A-I (apoA-I). Using maximum-likelihood-based variance decomposition methods, we determined that sex, age, and plasma levels of HDL cholesterol, apoA-I, and creatinine accounted for 38.6% of the variance in plasma EC-SOD levels and that additive genes accounted for 35% (P<0.00002). Multivariate analyses of plasma levels of EC-SOD, NO(x) (a measure of basal NO production), and apoA-I detected significant genetic correlations, indicating pleiotropy between EC-SOD and apoA-I (genetic correlation [rho(G)]=-0.45) and between NO(x) and apoA-I (rho(G)=0.58) but not between EC-SOD and NO(x). Genes shared by EC-SOD and apoA-I account for 20% of the genetic variance and, respectively, 7% and 9% of the phenotypic variance in both traits. Shared genes also account for >33% of the genetic variance and 5% and 15% of the respective phenotypic variance in NO(x) and apoA-I. In healthy individuals, over a third of the variance in EC-SOD plasma levels is due to the additive effects of genes. Some genes influence EC-SOD and apoA-I levels. The same is true of NO(x) and apoA-I but not of EC-SOD and NO(x). These patterns of pleiotropy can guide subsequent attempts to identify the genes and physiological mechanisms underlying them.

Genetic polymorphism of heparan sulfate proteoglycan (perlecan, HSPG2), lipid profiles and coronary artery disease in the Australian population

Perlecan is one of the three major classes of heparan sulfate proteoglycans (HSPGs) within the cardiovascular system; it interacts with lipid metabolism by binding to lipoprotein lipase (LpL) and apolipoprotein B (apo B) and may be related to vascular disease. We explored interactions between an HSPG2 polymorphism (BamHI marker), and apo B and coronary artery disease (CAD) in patients undergoing coronary angiography. The frequencies of the HSPG2 BamHI +/+, +/-, and -/- genotypes were 4.7, 31.7 and 63.6%, respectively, with a '+' allele frequency of 20.6%. The genotype distribution was in Hardy-Weinberg equilibrium (chi(2)=0.669, P0.05). The +/+homozygotes had the lowest apo B levels (0.74+/-0.06 g/l, n=36) compared to +/- (0.89+/-0.03 g/l, n=241) and -/- (0.93+/-0.02 g/l, n=480) genotypes. Although plasma apo B concentration was the strongest lipid risk factor for significant CAD, the HSPG2 genotypes were not independently associated with the presence of CAD (P=0.640 in males; P=0.224 in females), with significant CAD (P=0.764; P=0.110) or with the number of significantly stenosed coronary arteries (P=0.945; P=0. 335). In Australian Caucasians undergoing coronary angiography the HSPG2 BamHI polymorphism is associated with lower circulating apo B but not with the occurrence or severity of CAD. This may be due to HSPG2-mediated alterations in the HSPG2-apo B-LpL system and requires further exploration.

Body mass index in Australian children: recent changes and relevance of ethnicity

AIM

To determine changes over time in the body mass index (BMI) profile of Australian primary schoolchildren and to assess the effects of sex and ethnicity.

METHODS

Height and weight were measured in 3645 children (1869 girls and 1596 boys), aged 5-12 years from 39 schools in southeastern Sydney during 1994-7. Levels in the four largest ethnic groups of the population were compared with those measured by the 1985 Australian Council on Health, Physical Education, and Recreation (ACHPER) survey.

RESULTS

The study population was 59.9% white (north European), 8.5% Mediterranean white, 7.7% Asian, 7.7% other, and 16.2% mixed (mainly Asian-white (36%) and Arab-white (24.7%)). There were sufficient numbers in four groups for analysis and comparison with the ACHPER survey: Mediterranean white, other white, mixed ethnicity, and Asian children. The age and sex adjusted BMI was highest in Mediterranean white, then white, mixed race, and Asian children. There were minimal differences between sexes within each group. However, boys had an age and sex adjusted BMI 1.5-6.5% higher (mean, 3.9%) than in ACHPER in 1985, as did white girls (mean increase, 2.4%).

CONCLUSIONS

BMI in southeastern Sydney schoolchildren is related strongly to ethnicity and age; in boys and white girls it is on average 3.9% and 2.4% greater, respectively, than that recorded in the 1985 ACHPER survey. We suggest that this 10 year increase reflects a general trend in developed countries. Because increased BMI in childhood tracks to adulthood and is then associated with adverse effects on health, these findings signal a need for prevention.

Relationship between total plasma homocysteine, polymorphisms of homocysteine metabolism related enzymes, risk factors and coronary artery disease in the Australian hospital-based population

Modest elevations of circulating homocysteine are common in patients with vascular disease. We explored interrelations between total plasma homocysteine levels and mutations in genes for three key enzymes in methionine-homocysteine metabolism. Methyltetrahydrofolate reductase (MTHFR) 677C-->T, cystathionine beta synthase (CBS) 68-bp insertion at exon 8, and methionine synthase (MS) 2756A-->G were typed in 685 Australian caucasian patients aged < or =65 years with and without angiographically documented coronary artery disease (CAD). We also assessed associations between homocysteine levels and extracellular superoxide dismutase (EC-SOD) and other CAD risk factors. There were significant correlations between plasma total homocysteine, and EC-SOD (r = 0.170, p = 0.001 for men; r = 0.241, p = 0.003 for women) and LDL (r = 0.153, p = 0.001 for men; r = 0.132, p = 0.081 for women). Levels were also significantly higher among patients with unstable angina (15.30+/-0.44 micromol/l for men, 14.44+/-0.74 micromol/l for women) than those without angina (13.98+/-0.38 micromol/l for men, 13.41+/-0.98 micromol/l for women) or with stable angina (14.00+/-0.37 micromol/l for men, 12.88+/-0.71 micromol/l for women). There were no significant associations between the levels and the presence or severity of CAD. The mutant MTHFR homozygotes tended to have higher levels and those with the MS and CBS mutations tended to have lower levels. We conclude that there is a significant correlation between plasma homocysteine levels and EC-SOD suggesting that elevated homocysteine may exert oxidative stress and that levels are associated with unstable angina, but not the occurrence or extent of coronary stenosis. The contributions to total plasma homocysteine levels of the common mutations of genes coding for the enzymes controlling homocysteine metabolism are modest.

NADH/NADPH oxidase p22 phox C242T polymorphism and coronary artery disease in the Australian population

BACKGROUND

Oxidative stress induced by the superoxide anion (.O2-) has been implicated in atherogenesis. The NADH/NADPH oxidase system is involved in.O2- production and p22 phox is an essential component of that system.

MATERIAL AND METHODS

We analysed the p22 phox C242T polymorphism in 689 consecutive Australian Caucasians aged </= 65 years with and without angiographically documented coronary artery disease (CAD) RESULTS: We report the rare T allele frequency of 0.33, which is 3 fold higher than that reported in the Japanese population by Inoue et al. [7]. The genotype distributions were not different among patients with CAD (CC:0.422, CT:0.459 and TT: 0.119 in men; 0.447, 0.439 and 0.114 in women) and without CAD (0.479, 0. 420 and 0.101%, chi2 = 0.794, P = 0.672 in men; 0.443, 0.471 and 0. 86, chi2 = 0.442, P = 0.802 in women). The frequencies of the rare TT homozygotes or of the 'T' allele frequency were also not associated with the number of significantly stenosed vessels (chi2 = 4.466, P = 0.614 in men; chi2 = 4.736, P = 0.578 in women) or with a myocardial infarction (MI) history (chi2 = 2.310, P = 0.315 in men; chi2 = 1.178, P = 0.555 in women). However, when the analysis was conducted in young male patients aged </= 45 years (n = 44), TT + TC patients tended to have an increased risk for CAD (odds ratio: 5.71 95% CI: 1.22-26.75, P = 0.0271).

CONCLUSION

The p22 phox C242T polymorphism is not associated with the occurrence or severity of CAD or with a history of MI in Australian Caucasian patients aged </= 65 years. However, the polymorphism could be associated with an increased CAD risk in young patients, which requires confirmation in large populations.

The Glu-298-->Asp (894G-->T) mutation at exon 7 of the endothelial nitric oxide synthase gene and coronary artery disease

We examined associations between the endothelial nitric oxide synthase (eNOS) gene Glu-298-->Asp (894G-->T) mutation and the occurrence and severity of angiographically defined coronary artery disease (CAD). eNOS mediates basal vascular wall nitric oxide production, and altered nitric oxide production has been implicated in atherosclerosis. The newly identified eNOS Glu-298-->Asp mutation in exon 7 is common and likely to be functional. It was found to be associated with myocardial infarction (MI) in Japanese but not in whites. We genotyped 763 white Australians undergoing coronary angiography for the eNOS Glu-298-->Asp mutation. The frequencies of the eNOS GG, TG and TT genotypes were 47.8%, 41.2% and 11.0% in men and 45.2%, 41.1% and 13.7% in women with CAD, and were not significantly different from those without CAD (43.2%, 40.7% and 16.0%, P=0.423 in men; 40.2%, 48.1% and 11.7%, P=0.582 in women). The mutation was also not associated with MI (P=0.469 in males; P=0.389 in females) or with the number of significantly stenosed vessels (P=0.954; P=0.734). The "T" allele frequency (32.5%) was much greater than that reported for the Japanese population (7.8% in controls and 10.0% in MI patients). In conclusion, the eNOS Glu-298-->Asp mutation is common, occurring with an allele frequency of 32.5%, but is not associated with either the occurrence or severity of CAD in the Australian population or with other established coronary risk factors assessed in our study. The mutation is significantly more frequent in the Australian than in the Japanese.

The effect on transcription efficiency of the apolipoprotein AI gene of DNA variants at the 5' untranslated region

Elevated circulating levels of high-density lipoprotein and apolipoprotein AI are associated with reduced coronary artery disease risk. We have shown that a C to T substitution at +83 bp and a G to A substitution at -75 bp of the apolipoprotein AI gene are both related to increased high-density lipoprotein levels in a healthy population but not in a coronary population, among whom the same mutations are associated with increased disease severity. In the present study, we explored the effects of these base changes on transcriptional efficiency in vitro. We directionally cloned (using polymerase chain reaction) the 5' region of the apolipoprotein AI gene (-281 to +330 bp) with GC, GT, and AC haplotypes into a pGL3-luciferase reporter gene basic vector, and transfected the constructed vectors into HepG2 cells. The cells carrying the T allele at the +83 bp site (GT 112.3 +/- 12.4) had the same transcriptional efficiency as those bearing the C allele (GC 126.3 +/- 9.6). However, for cells with the A allele at -75 bp there was a twofold decrease in transcription (AC 63.1 +/- 9.3) accompanied by similar changes in Luc+ mRNA levels; this reduced transcription was only present if the apolipoprotein AI leader sequence was included in the insert. While the findings are inconsistent with the T or A allele being associated with higher high-density lipoprotein levels, they are consistent with the finding that the alleles are associated with an increased coronary artery disease risk, and demonstrate that the 5' leader region of the apolipoprotein AI gene participates in regulating apolipoprotein AI transcription. They also suggest that other regions of the apolipoprotein AI gene may have an active role in such regulation, and that environmental effects may influence allele-specific expression.

Common methylenetetrahydrofolate reductase gene mutation leads to hyperhomocysteinemia but not to vascular disease: the result of a meta-analysis

BACKGROUND

The results of retrospective and prospective case-control studies have clearly established that mild elevations of the plasma homocysteine level are associated with increased risk of coronary, cerebral, and peripheral vascular disease. Recently, a mutation (677C-->T) was identified in the methylenetetrahydrofolate reductase (MTHFR) gene that results in reduced folate-dependent enzyme activity and reduced remethylation of homocysteine to methionine. Mutant homozygotes (TT genotype) constitute approximately 12% of the white population and frequently have mildly elevated circulating homocysteine. Therefore, it seems likely that they would also be at increased risk of vascular disease. A number of studies have investigated this during the past 3 years, and the present article evaluates the results in a meta-analysis.

METHODS AND RESULTS

We identified 13 studies in which there were measurements of plasma homocysteine in relation to the 3 genotypes (TT, CT, and CC) and 23 case-control studies comprising 5869 genotyped cardiovascular disease patients (mostly coronary artery disease) and 6644 genotyped control subjects. Those bearing the TT genotype had plasma homocysteine concentrations 2.6 micromol/L (25%) higher than those with the CC genotype. However, there was no difference between patients and control subjects either in the frequency of mutant alleles (T) (34.3% versus 33.8%) or the TT genotype (11.9% versus 11.7%). In the analysis of the 23 studies, the relative risk (OR) of vascular disease associated with the TT genotype was 1.12 (95% CI, 0.92 to 1.37).

CONCLUSIONS

We conclude that although the C677T/MTHFR mutation is a major cause of mild hyperhomocysteinemia, the mutation does not increase cardiovascular risk. Our findings suggest that the mild hyperhomocysteinemia found frequently in vascular disease patients is not causally related to the pathogenesis of the vascular disease.

Plasma extracellular superoxide dismutase levels in an Australian population with coronary artery disease

In vitro experiments suggest that free radicals may contribute importantly to atherogenesis. Superoxide dismutase (SOD), particularly extracellular SOD (EC-SOD), which accounts for the majority of SOD biological activity, is a major superoxide scavenger. We explored factors that may affect plasma EC-SOD levels measured by ELISA and assessed the association between plasma EC-SOD and coronary artery disease documented angiographically in 590 white Australian patients </=65 years old. Mean+/-SEM plasma EC-SOD in female patients (113.6+/-13.2 ng/mL) was significantly higher than in male patients (86.6+/-5.1 ng/mL, P<0.0001), and all 19 patients with levels >400 ng/mL were heterozygous for the Arg213-->Gly mutation at the EC-SOD gene; there was also a positive correlation with age (r=0.131, P=0.0016). Plasma EC-SOD in current smokers (75. 0+/-9.3 ng/mL) was much lower than in nonsmokers (111.7+/-8.2 ng/mL, P<0.01), and ex-smokers had intermediate levels (84.3+/-7.1 ng/mL). Levels were significantly lower in patients with than in those without a history of acute myocardial infarction (MI) (76.1+/-7.5 versus 110.1+/-6.0 ng/mL, P<0.05), and low plasma EC-SOD was independently associated with an increased likelihood of a history of MI (OR, 2.04; 95% CI, 1.10 to 3.82); higher EC-SOD levels also tended to be associated with delayed onset of MI. In conclusion, our study establishes that in patients assessed by coronary angiography, circulating EC-SOD is lower in men than in women and in smokers of each sex and that low levels are independently associated with a history of MI. These findings are consistent with EC-SOD's being protective and contributing to reduced coronary risk.

B vitamins and homocysteine in cardiovascular disease and aging

The sulfur-containing amino acid, homocysteine, is formed from the essential amino acid methionine, and a number of B vitamins are involved in methionine metabolism. Pyridoxine, vitamin B6, is a cofactor for cystathionine beta synthase, which mediates the transformation of homocysteine to cystathionine, the initial step in the transsulfuration pathway and the urinary excretion of sulfur. In a normal diet there is conservation of the carbon skeleton, and about 50% of the homocysteine formed is remethylated to methionine via steps that require folic acid and vitamin B12. A deficiency of any of these three vitamins leads to modest homocyst(e)ine elevation, as does diminished renal function, both of which are common in the elderly. It is also established that homocyst(e)ine elevation of this order is associated with increased cardiovascular risk but is also associated with most established risk factors, although it is thought to be an independent contributor. In the inborn error of metabolism homocystinuria due to cystathionine beta synthase deficiency there is greatly increased circulating homocyst(e)ine and a clear association with precocious vascular disease. In about 50% of these patients there is a vascular event before the age of 30 years. The homocysteine-induced adverse vascular changes appear to result from endothelial and smooth muscle cell effects and increased thrombogenesis. We have documented a highly significant reduction in the occurrence of vascular events during 539 patient years of treatment in 32 patients with cystathionine beta synthase deficiency (mean age 30 years, range 9-66 years) by aggressive homocyst(e)ine lowering with pyridoxine, folic acid, and B12 (p = 0.0001). The 15 pyridoxine nonresponsive patients also received oral betaine. Although a cause and effect relationship is postulated for the increased cardiovascular risk associated with mild homocysteine elevation, a common cause of this elevation is the methylenetetrahydrofolate reductase C677T mutation. Homozygotes occur in about 11% of Caucasian populations. However, the mutation is not associated with increased coronary risk. Since mild homocysteine elevation is easily normalized by B vitamin supplementation, usually with folic acid, it remains for controlled clinical trials of this inexpensive therapy to determine whether normalizing mild homocyst(e)ine elevation reduces cardiovascular risk.

The frequency of a common mutation of the methionine synthase gene in the Australian population and its relation to smoking and coronary artery disease

BACKGROUND

Modest elevations in levels of circulating homocysteine are common in patients with vascular disease. Methionine synthase is a vitamin B12-dependent enzyme catalysing the re-methylation of homocysteine to methionine; reduced methionine synthase activity results in elevated level of homocysteine.

DESIGN

A case-control study.

METHODS

We explored the frequency and distribution of a 2756A-->G (D919G) mutation of the methionine synthase gene, detected by polymerase chain reaction genotyping, in 745 Australian Caucasian patients aged < or = 65 years (550 men and 195 women) with and without angiographically documented coronary artery disease (CAD).

RESULTS

The frequency distributions of AA, AG and GG genotypes were 61.9%, 33.8% and 4.3%, respectively, and were in Hardy-Weinberg equilibrium. There was no correlation between the methionine synthase mutation and CAD from simple chi2 comparison. However, the interactive term of life-time smoking dose with methionine synthase genotypes was predictive of both the number of significantly diseased vessels (> or =50% luminal obstruction; chi2 = 12.518, P=0.0019), and the presence or absence of significant CAD (chi2=7.045, P=0.027). A stepwise logistic regression analysis showed that smokers who were also GG homozygotes had more severe CAD compared with smokers of other genotypes. The methionine synthase genotypes were not associated with any of the other established CAD risk factors assessed in our study.

CONCLUSIONS

We conclude that the methionine synthase 2756A-->G mutation is common, with homozygosity occurring in approximately 4% of white Australians, and that it has an interactive effect with life-time smoking dose to increase the severity of CAD. Smokers who are also GG homozygotes have additionally elevated CAD risk.

Nitric oxide induces and inhibits apoptosis through different pathways

Physiological levels of nitric oxide (NO) regulate vascular tone and protect the microvasculature from injury whereas excessive NO may be harmful. The present study explored the effects of NO on human endothelial cell apoptosis. We found that the NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited TNFalpha-induced endothelial apoptosis and that this was mediated partly through the cGMP pathway. In contrast, high SNAP concentration induced endothelial apoptosis via cGMP-independent pathways and the cGMP pathway protected against NO-induced apoptosis. These findings demonstrate that low NO concentrations contribute to human endothelial cell survival, whereas higher NO concentrations are pathological and promote destruction of endothelial cells.

Novel risk factors for vascular disease: the homocysteine hypothesis of cardiovascular disease

The possibility that modest elevations in the level of blood homocysteine (hyperhomocysteinaemia) could contribute to cardiovascular disease arose from investigation of patients with rare, severe homocysteine elevations caused by cystathionine beta-synthase deficiency. Such patients often had thromboembolic events before the age of 30 years. Since the established cardiovascular risk factors could only partly account for the occurrence and severity of vascular disease in the general population, other risk factors had to exist, and homocysteine elevation seemed to be a possible candidate. Australian case-control studies identified an association between mild homocysteine elevation and early-onset coronary disease, and also with chronic renal failure. Patients in the latter group have a high prevalence of unexplained vascular disease and particularly high homocysteine levels. Such elevations in levels of homocysteine in vascular patients could usually be normalised by daily supplementation with folic acid (1-5 mg) while in patients with chronic renal failure 5 mg of folic acid daily markedly reduced the increased concentrations of homocysteine. These initial observations have been confirmed by many investigators and biologically plausible mechanisms for homocysteine-induced vascular dysfunction, and particularly endothelial dysfunction, have been identified. However, associations between hyperhomocysteinaemia and other risk factors, such as smoking and hypertension, have also been documented and need to be controlled for when assessing any increase in risk that homocysteine may independently confer. Although it has been established that lowering the greatly elevated blood homocysteine levels in homocystinuria, due to cystathione beta-synthase deficiency, unquestionably reduces cardiovascular risk, it remains to be determined whether normalising mild homocysteine elevation could reduce cardiovascular risk. Trials to test this possibility have been initiated and others are planned.

Apolipoprotein screening in Australian children: feasibility and the effect of age, sex, and ethnicity

OBJECTIVE

(i) To evaluate the feasibility of detecting adverse lipid profiles in schoolchildren by measuring capillary dried blood spot apolipoprotein levels, and (ii) to assess the effect of age, sex and ethnicity on apolipoprotein levels.

DESIGN

We measured capillary dried blood spot apolipoproteins B and A-I (apo B and apo A-I); assessed levels in relation to age, sex and ethnicity; and recalled children with elevated levels for a full lipid profile measurement.

PARTICIPANTS AND SETTING

6992 children (3501 boys and 3491 girls), aged 5-13 years, from schools in eastern Sydney, 1991-1995.

MAIN OUTCOME MEASURES

Capillary blood levels of apolipoproteins B and A-I, and serum total cholesterol level.

RESULTS

Of the 6951 children who provided an adequate fingerprick blood sample, we recalled 1465 children (21.1%) (640 boys [43.7%] and 825 girls [56.3%]) with elevated apo B levels and/or apo B:apo A-I ratios for further testing, either by us or by their family doctor (overall estimated compliance rate up to 70%). Among the 458 children who returned to us, there was a 90% positive predictive value for a total cholesterol level of over 4.5 mmol/L in those with both elevated apo B levels and high apo B:apo A-I ratios. Girls had higher apo B levels and apo B:apo A-I ratios than boys (P < 0.00001 for both), and in both sexes there was a trend downwards for apo B and upwards for apo B:apo A-I ratio over the age range tested, but levels were relatively stable between the ages of 6 and 10 years. Indian children (1.5% of the screened population) had the highest apo B levels, followed by white children (71.1%); Asian children (9.2%) had the lowest (P < 0.00001 compared with Indian and white children).

CONCLUSIONS

The high positive predictive value of capillary blood apolipoprotein levels for an adverse lipid profile in children suggests that measuring apolipoprotein levels by this method is a useful initial approach to cardiovascular risk assessment.

Genetic contribution of the endothelial constitutive nitric oxide synthase gene to plasma nitric oxide levels

Nitric oxide (NO) has an important physiological role in regulating vascular tone and is also relevant to many pathological processes including hypertension and atherosclerosis. Endothelial constitutive nitric oxide synthase (ecNOS) is the key enzyme in determining basal vascular wall NO production. We used a combination of maximum-likelihood-based statistical genetic methods to explore the contributions of the ecNOS gene and other unmeasured genes to basal NO production measured by its metabolites (NOx: nitrite and nitrate) in 428 members of 108 nuclear families. Our initial quantitative genetic analysis estimated that approximately 30% of the variance in fasting NOx levels is due to genes (chi 2(1) = 16.04, P = .000062). Complex segregation analysis detected the effects of both a single locus and residual polygenes on NOx levels, and measured genotype analysis showed that plasma NOx levels in those homozygous for the rare allele (64.9 +/- 7.8 mumol/L) were significantly higher (P = .000242) than those homozygous for the common allele (30.2 +/- 3.1 mumol/L). The results of the variance component linkage analysis were consistent with linkage of a quantitative trait locus in or near the ecNOS gene to variation in plasma NOx levels (P = .0066). While many environmental factors have been shown to alter transiently plasma NOx levels, our study is the first to identify a substantial effect of the ecNOS locus on the variance of plasma NOx, i.e. basal NO production. This finding may be relevant to atherogenesis and NO-related disorders.

Interactive effect of the p53 gene and cigarette smoking on coronary artery disease

OBJECTIVE

p53 is a tumour suppressor protein involved in the control of cell growth and has an established role in carcinogenesis, particularly in relation to smoking. It may also be related to arteriosclerosis by affecting smooth muscle cell proliferation, a feature of atherogenesis.

METHODS

We explored a role for p53 in atherogenesis by assessing the association between two DNA polymorphisms of the p53 gene (MspI at intron 6 and HaeIII at intron 1) and angiographically documented coronary artery disease (CAD) in 654 Australian Caucasian patients.

RESULTS

There was a significant interactive effect of the two polymorphisms and cigarette smoking on CAD in a logistic regression analysis (P = 0.0039) but no association between CAD and either individual p53 polymorphic marker. CAD occurrence was more frequent in non-smoking patients with rare alleles at both sites (85.0%) compared to those homozygous for common alleles at both sites (70.4%). However, this was not seen in smokers (85.7 vs 82.8%). In all 654 patients cigarette smoking remained a significant predictor of CAD irrespective of p53 genotypes (P = 0.0065).

CONCLUSIONS

Our findings identify an interactive effect of both p53 polymorphisms and cigarette smoking on the occurrence of coronary artery disease in that non-smoking patients with rare alleles at both sites had increased incidence of CAD. They illustrate the relevance of genotype-specific and environment-dependent enhanced cardiovascular risk and foreshadow a need for further studies to establish functional changes.

The natural history of vascular disease in homocystinuria and the effects of treatment

Among 40 patients with homocystinuria due to cystathionine beta-synthase deficiency diagnosed in the state of New South Wales, Australia (population 6 million) and followed long-term, there were 10 deaths at ages 2-30 years. Of these 8 were definite vascular deaths, one was a presumed vascular death, and the other was due to an accident and unrelated to homocystinuria. The vascular deaths were all early cases and only one patient, a pyridoxine-responsive 30-year-old woman, had been prescribed adequate treatment although it was uncertain that she was taking it. In 32 patients of mean age 30 years (range 9-66 years) there were 539 patient-years of treatment with pyridoxine, folic acid and hydroxocobalamin. There were 17 pyridoxine-responsive patients and all maintained plasma total free homocyst(e)ine levels < 20 mumol/L over an average treatment period of 16.6 years. The 15 nonresponsive patients received additionally 6-9 g of betaine daily. This resulted in a further 74% mean decline (+/-14% SD) in plasma total free homocyst(e)ine, persisting during an average (post-betaine) treatment period of 11 years; current mean +/- SD levels are 33 +/- 17 mumol/L (n = 15). There were two vascular events during treatment, one fatal pulmonary embolus (see above) and one myocardial infarction, whereas without treatment, 21 would have been expected, chi2 = 14.22, p = 0.0001, relative risk 0.09 (95% CI 0.02-0.38). There were no events during 258 patient-years of treatment in the 15 pyridoxine-nonresponsive patients (p < 0.005 versus expected untreated). Nineteen patients had a total of 19 major and 15 minor operations requiring anaesthetic, and three had successful pregnancies, one whilst receiving betaine. There were no thromboembolic complications. We conclude that treatment which effectively lowers circulating homocyst(e)ine, even to suboptimal levels, markedly reduces cardiovascular risk in patients with cystathionine beta-synthase deficiency, and that betaine therapy contributes importantly to this in pyridoxine-nonresponsive patients. Betaine as additional therapy is safe and effective for at least 16 years.

Circulating transforming growth factor beta 1 and coronary artery disease

OBJECTIVE

Transforming growth factor beta 1 (TGF-beta 1), a multifunctional cytokine, is involved in many physiological and pathological processes and possibly in atherogenesis.

METHODS

We explored the association between circulating plasma TGF-beta 1 measured by ELISA and coronary artery disease (CAD) assessed angiographically in 371 Caucasian patients (269 men and 102 women) aged < or = 65 years.

RESULTS

While mean +/- s.e.m total TGF-beta 1 was not different among patients with (56.9 +/- 1.5 ng/ml) or without (54.6 +/- 2.8 ng/ml) angiographically demonstrable CAD, naturally active TGF-beta 1 was significantly higher in CAD patients (1.74 +/- 0.18 vs 0.96 +/- 0.17 ng/ml, P < 0.01). Active TGF-beta 1 increased with the number of major coronary arteries with more than 50% luminal obstruction (P < 0.01) and patients with triple vessel disease had twice the level of those with no or mild vessel disease (2.15 +/- 0.46 vs 1.12 +/- 0.14 ng/ml, P < 0.001). We found no relationship between TGF-beta 1 and Lp(a), but TGF-beta 1 was significantly correlated with circulating fibrinogen (r = 0.178, P = 0.005) and fasting glucose (r = 0.177, P = 0.007) levels.

CONCLUSIONS

Our study identifies an increase in active TGF-beta 1 levels with both the occurrence and severity of CAD which is independent of standard CAD risk factors. This may reflect a 'double-edged sword' effect of TGF-beta 1 in that it may reduce atherogenesis by inhibiting smooth muscle cell proliferation but, when there is ongoing vessel wall injury, enhance it by promoting excessive extracellular matrix accumulation. The outcome could represent a complex balance between these two competing influences.

A twin study of polycystic ovary syndrome and lipids

Our objective was to assess the relative contribution of genetic and environmental factors (particularly androgens) on circulating levels of lipid fractions and to determine the effect, if any, of polycystic ovary syndrome (PCOS) on lipid fractions. The study was carried out in the outpatient clinic of the Royal Hospital for Women, Paddington, Sydney, Australia. A group of 19 monozygotic (MZ) and 15 dizygotic (DZ) twin pairs was identified from the National Twin Register. Ultrasound clinical and biochemical parameters were used to define polycystic ovaries. Serum androgen and lipid fractions were also measured. Eleven pairs of twins (five MZ, six DZ) were scan discordant (i.e. one twin had polycystic ovaries and the co-twin did not). Serum levels of the lipoprotein fractions in twins with polycystic ovaries were not significantly different from the levels found for their co-twins with normal ovaries. There were no significant correlations between androgen-related hormones and any of the lipid measurements. Body mass index (BMI) was positively correlated with triglycerides and lipoprotein (a), and negatively correlated with high-density lipoprotein cholesterol (HDL-C). Sex hormone-binding globulin (SHBG) levels were negatively correlated with triglycerides and lipoprotein (a) and positively associated with HDL-C. Fasting insulin levels were significantly correlated with triglycerides and negatively with HDL-C. The MZ intraclass correlation exceeded that of the DZ twin pairs for all the lipid variables measured. The heritability estimates for lipoprotein (a), apolipoprotein B, total cholesterol and HDL-C were 0.95, 0.56, 0.48 and 0.54, respectively. However, the intraclass correlation coefficient for triglycerides was not significantly different between MZ and DZ twins, but maximum likelihood analysis indicated that at least 10% of the variance of the circulating triglyceride concentration is determined by genetic factors. We conclude that twins discordant for the PCOS do not have significantly different lipid fractions.

Growth hormone increases and insulin-like growth factor-I decreases circulating lipoprotein(a)

BACKGROUND

Elevated serum lipoprotein(a) (Lp(a)) is a strong risk factor for coronary artery disease (CAD). Genetic factors appear to account for the major variance in Lp(a) levels but the contribution hormones make in modulating Lp(a) levels is not yet clear. In the present investigation we determined the effects of human growth hormone (hGH) and insulin-like growth factor-I (IGF-I) on circulating Lp(a).

METHODS

Four groups of patients were studied. Group a: adults with GH deficiency (n = 7) treated with hGH (0.05 U/kg/day, s.c.); group b: girls with Turner syndrome (n = 7) treated with hGH (0.1 U/kg/day, s.c.); group c: prepubertal boys with idiopathic short stature (n = 6) treated with the GH secretagogue (GHRP) hexarelin (60 micrograms t.i.d. intranasally); group d: Laron syndrome patients (n = 10) treated with IGF-I (100-200 micrograms/kg/day, s.c.). Following overnight fasting, serum was sampled before the initiation of treatment and during 6-9 months treatment.

RESULTS

Serum IGF-I rose significantly in all the subjects in all four groups. In the first three groups in which IGF-I was elevated by exogenous or endogenous GH stimulation, serum Lp(a) increased significantly (119 +/- 35%, P < 0.01; 126 +/- 44%, P < 0.05; 102 +/- 29%, P < 0.01 for groups a, b, and c respectively). By contrast, serum Lp(a) levels decreased in group d to whom exogenous IGF-I was administered (-66 +/- 5%, P < 0.001). The differential effect of endogenous vs exogenous IGF-I on serum Lp(a) paralleled the behaviour of serum insulin. Insulin was significantly increased in all the subjects receiving hGH or GHRP (65.2 +/- 31%, P = 0.109; 93.7 +/- 53%, P = 0.062; 353.8 +/- 52.7%, P < 0.01 for groups a, b, and c respectively) whereas insulin levels were reduced following exogenous administration of IGF-I (-34.1 +/- 9.1%, P < 0.01).

CONCLUSIONS

We conclude that long-term GH treatment increases and IGF-I decreases circulating levels of Lp(a). These findings may have clinical relevance in view of the increasing use of hGH in children and adults and the role of Lp(a) as a CAD risk factor.

Polymorphisms of factor V, factor VII, and fibrinogen genes. Relevance to severity of coronary artery disease

We explored the associations between G-->A mutations of factor V and factor VII genes and the Hae III polymorphism of the fibrinogen gene and the severity of coronary artery disease (CAD), as assessed angiographically in 545 white Australian patients (388 male and 157 female) aged < or = 65 years. We also assessed the relations with other potentially atherogenic variables. Elevated fibrinogen levels were associated with more severe CAD (P < .05), but none of the factor V, factor VII, and fibrinogen DNA variants were predictive of CAD severity, as assessed by the number of significantly diseased vessels (> 50% luminal obstruction). The rare allele frequencies of factor V (A allele), factor VII (M2 allele), and fibrinogen (H2 allele) were .025, .114, and .201 for men and .022, .077, and .169 for women, respectively, and were not different from those in healthy whites. In the patient population, there was a strong, positive association between lifetime smoking dose (in pack-years) and circulating fibrinogen levels (r = .184, P = .001). This association was stronger than that between current smoking habit and fibrinogen and is consistent with a dosage effect. However, there was no significant contribution of fibrinogen genotype to fibrinogen levels in this patient population. We conclude that elevated fibrinogen levels are associated not only with the occurrence of CAD but also with more severe CAD and that measurement of DNA variants of the factor V, factor VII, and fibrinogen genes that we assessed may not provide information in predicting CAD severity in addition to that obtained by measuring circulating levels of the relevant clotting factors. There is, moreover, a positive dosage effect (in pack-years) of smoking on circulating fibrinogen levels.

Insulin-like growth factor-I decreases serum lipoprotein (a) during long-term treatment of patients with Laron syndrome

An increased circulating level of lipoprotein(a) [Lp(a)] is a well-recognized risk factor for coronary artery disease. While much remains to be understood about its regulation and physiological functions, we explored the effect of recombinant insulin-like growth factor-I (IGF-I) administration on circulating Lp(a) levels in 10 Laron syndrome (LS) patients (five children and five adults) with inherited IGF-I deficiency. There was no relationship between pretreatment or posttreatment Lp(a) levels and age and sex of the patients. With IGF-I treatment for 6 to 12 months, there was a significant reduction in Lp(a) (65.7% +/- 15.5%, P < .0001) from the pretreatment level of 76 +/- 45 mg/L to the posttreatment level of 29 +/- 26 mg/L. This decrease was dosage-dependent on the IGF-I administered (r = .685, F = 0.708, P = .029) and correlated more strongly with the dosage ratio of the end to the beginning of treatment (r = .78, F = 12.23, P = .008). The higher the IGF-I dose and the higher the dose ratio, the greater the Lp(a) decrease and the lower the Lp(a) at the end of treatment. In conclusion, we observed a dose-dependent relationship between IGF-I administration and Lp(a) reduction in patients with LS. Further studies are needed to elucidate the mechanism of the effect, but our findings suggest a possible metabolic link between these two and shed more light on the regulation of apolipoprotein(a) [apo(a)] expression. It could also open an avenue for additional therapeutic usage of IGF-I.

Growth hormone treatment increases circulating lipoprotein(a) in children with chronic renal failure

Cardiovascular disease is the major cause of death in chronic renal failure (CRF) patients managed by dialysis or kidney transplantation. Whilst the use of human growth hormone (hGH) is of established benefit in CRF children particularly in those with short stature, in the present study we assessed in CRF children the effect of hGH treatment on circulating lipoprotein(a) [Lp(a)], a genetically determined cardiovascular risk factor. We studied 15 CRF children treated by dialysis or conventional therapy and after kidney transplantation. Overnight fasting blood samples were collected immediately before and after 6 months hGH treatment. In all but one of the children there was a significant increase in serum Lp(a) over the 6 month treatment period -(+)66.7% over the basal levels (range 14 to 180%). After the hGH treatment, in six children Lp(a) levels were elevated to above 300 mg/l, the cut-off level for increased coronary artery disease (CAD) risk. Concomitantly/children also had an increase in serum levels of IGF-I (+96.4%) and insulin (+85.8%). All children had an accelerated growth velocity during the treatment; there was no effect on serum creatinine. Our study shows that hGH treatment in CRF children, though beneficial in its growth promoting effects, increases the already characteristically high levels of serum Lp(a), a risk factor for CAD, and that serum Lp(a) monitoring during treatment with hGH may be useful in evaluating future cardiovascular risk.

Polymorphisms at the 5'-end of the apolipoprotein AI gene and severity of coronary artery disease

Elevated HDL-cholesterol (C) and apo AI are associated with decreased coronary artery disease (CAD) risk. We determined distributions of two MspI polymorphisms of the apo AI gene, associated in other studies with increased HDL-C, among 644 patients aged < or = 65 years in relation to circulating lipids and CAD severity assessed angiographically. The rare allele distributions at both sites were in Hardy-Weinberg equilibrium in these patients but the base changes were not associated with HDL-C and apo AI levels. However, patients homozygous for the -75 bp substitution were more likely to have one or more significantly diseased vessels (> 50% luminal obstruction)(OR: 4.75, 95%CI: 1.10- 20.46) as also were patients with the rare +83 bp alleles (OR: 2.56, 95%CI: 1.13-5.81). While there was an additive effect of the two polymorphisms to have severe CAD (OR: 6.33, 95%CI: 1.33-30.02), the polymorphism at +83 bp remained significant in predicting CAD severity after adjusting for other variables in a logistic regression analysis (OR: 2.95, 95%CI: 1.26-6.90), which was also strongly associated with the positive family CAD history (P = 0.009). We conclude that patients with these base changes in this Australian coronary population do not have increased HDL-C and apo AI levels but do have more severe CAD.

Distribution in healthy and coronary populations of the methylenetetrahydrofolate reductase (MTHFR) C677T mutation

Modest elevations of circulating homocyst(e)ine are common in patients with vascular disease. We explored in normal and coronary artery disease (CAD) populations the distribution of a mutation in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene that results in enzyme thermolability and reduced activity and in homocyst(e)ine elevation to assess its relevance to risk. We identified the C to T substitution at the MTHFR locus and compared the distributions of genotypes in 565 patients aged < or = 65 years without and with angiographically documented CAD and in 225 healthy subjects. In the patients, we also assessed interrelations between genotypes and CAD occurrence and severity, as well as standard risk factors. The frequency of homozygotes for the mutation was the same in patients with and without CAD and in healthy subjects (11.6%, 11.0%, and 10.7%, respectively: P > .5 for each). There was also no excess among the 419 patients with severe disease (ie, one or more vessels with > 50% luminal obstruction) compared with those with no or mild CAD (odds ratio: 1.004; 95% confidence interval: 0.59 to 1.70). Homozygosity for the mutation was also not associated with a history of myocardial infarction or the presence or severity of angina. However, body mass index increased linearly with the presence of the mutant allele (P = .005), and the mutation and hypertension were weakly associated (P = .036). We conclude that the MTHFR genotype is not a risk factor for coronary disease in this Australian population but that the strong association found with body mass index should be explored further.

Association between an angiotensinogen microsatellite marker in children and coronary events in their grandparents

BACKGROUND

Recently we found that the deletion (D) allele of the insertion/deletion (I/D) polymorphism of the ACE gene in 404 children was associated with a history of coronary artery disease (CAD) in their grandparents. This led us to explore polymorphisms in other genes of the renin-angiotensin system in this same population.

METHODS AND RESULTS

We determined the genotypes for three microsatellite markers located near or in the angiotensinogen, angiotensin II (type-1) receptor, and renin genes in the children and related the allele frequencies to grandparental CAD. We found a significant association between the angiotensinogen marker in children and grandparental CAD (chi2 = 42.2, P = .00001) with these children having an excess of the 125-bp and 129-bp alleles (odds ratio, 2.5; 95% confidence interval, 1.7 to 3.7). Greatest grandparental risk was when their grandchildren had the 125-bp/125-bp, 129-bp/129-bp, or 125-bp/129-bp genotypes (odds ratio, 7.75; 95% confidence interval, 2.2 to 27). There was no association between the microsatellites at either the angiotensin II (type-1) receptor (P = .8) or renin (P = .2) genes in children and grandparental CAD and none between the angiotensinogen and ACE polymorphisms in relation to CAD family history.

CONCLUSIONS

This study identifies a significant association between an angiotensinogen marker in children and grandparental CAD. There was no association between the microsatellites at either the angiotensin II (type-1) receptor or renin genes and CAD in this population. We conclude that the angiotensinogen polymorphism as well as the ACE polymorphism may explain a part of the risk related to a family history of CAD.

Common DNA polymorphisms at the lipoprotein lipase gene. Association with severity of coronary artery disease and diabetes

BACKGROUND

DNA variants of the lipoprotein lipase gene are associated with changes in lipid metabolism similar to those in diabetes and may relate to the development of atherosclerotic lesions, particularly premature lesions.

METHODS AND RESULTS

To determine whether lipoprotein lipase gene variants are relevant to ongoing atherogenesis, we explored relationships between two common lipoprotein lipase gene polymorphic markers, Pvu II at intron 6 and HindIII at intron 8; the severity of coronary artery disease (CAD); and lipid variables in 475 white patients 65 years of age or younger. We assessed CAD severity as the number of significantly stenosed (> 50% luminal obstruction) major coronary arteries at angiography and by the Green Lane coronary score. We found a significant association between the Pvu II polymorphism and the number of significantly diseased vessels (P = .0099) and coronary score (P = .028), with the Pvu II(-) alleles associated with less severe disease. The HindIII polymorphism was not associated with severity but had an additive effect with the Pvu II polymorphism. There was a close relationship between the Pvu II(+/+) genotype and the presence of diabetes (P = .0025), with an OR of 3.12 (95% CI, 1.30 to 7.49) compared with the Pvu II(-/-) genotype. The interaction between these polymorphisms and CAD severity (rather than occurrence) was independent of the levels of triglycerides and HDL cholesterol and of other lipid variables. There was also a dosage-dependent relationship between the Pvu II polymorphism and levels of triglyceride. The Pvu II(-) allele was associated with low levels and variances of triglycerides.

CONCLUSIONS

We conclude that the lipoprotein lipase Pvu II polymorphism is significantly associated with CAD severity and with type II diabetes in CAD patients, independent of changes in circulating lipid levels. These findings may be relevant to mechanisms mediating atherogenesis.

Human homocysteine catabolism: three major pathways and their relevance to development of arterial occlusive disease

Two separate metabolic pathways that methylate homocysteine to methionine are known in humans, utilizing, respectively, 5-methyltetrahydrofolate and betaine as methyl donors. Deficiency of the folate-dependent methylation system is linked to hyperhomocysteinemia. Our data suggest that this deficiency leads to concurrent metabolic down-regulation of homocysteine transsulfuration that may contribute to hyperhomocysteinemia. By contrast, no instances have been reported of hyperhomocysteinemia resulting from deficiencies of betaine-dependent homocysteine methylation. Long-term betaine supplementation of 10 patients, who had pyridoxine-resistant homocystinuria and gross hyperhomocysteinemia due to deficiency of cystathionine beta-synthase activity, caused a substantial lowering of plasma homocysteine, which has now been maintained for periods of up to 13 years. Betaine had to be taken regularly because the effect soon disappeared when treatment was stopped. In conclusion, depressed activity of the transsulfuration pathway may contribute to hyperhomocysteinemia because of primary deficiencies of enzymes of either the transsulfuration or of the folate-dependent methylation pathways. Stimulation of betaine-dependent homocysteine remethylation causes a commensurate decrease in plasma homocysteine that can be maintained as long as betaine is taken.

Relevance of body weight to apolipoprotein levels in Australian children

OBJECTIVES

To assess weight and apolipoprotein profiles in a representative sample of primary school children.

PARTICIPANTS AND SETTING

1543 children (936 girls and 607 boys) aged 6-11 years from schools in the Eastern Sydney Area Health Service region in 1994.

METHODS

We measured body mass index (BMI) and capillary blood apolipoprotein (apo) B and A-I levels (the carrier proteins for low and high density lipoprotein cholesterol, respectively) as well as lipoprotein (Lp) (a). We related BMI levels to those documented in the 1985 Australian Council on Health, Physical Education and Recreation (ACHPER) survey of school children.

RESULTS

Compared with the ACHPER distribution, BMI was increased in the boys but not in the girls; 16.8% of boys were above the 90th percentile of the ACHPER distribution (P = 0.003) and only 6.5% were below the 10th percentile (P = 0.046). There were 45 boys (7.4%) and 53 girls (5.7%) with BMIs above the 95th percentile who were, by definition, obese. They had highly significant increases in apo B (P = 0.003) and apo B: apo A-I ratio (P = 0.0001) compared with children in the normal BMI range (10th-90th percentiles); and 20% of the population, including the obese group, also had Lp(a) levels greater than 300 mg/L. The results in children aged 10 and 11 years were not different from those of the whole group, consistent with an absence of possible confounding effects due to early puberty or smoking.

CONCLUSIONS

There was an increase in weight relative to height in boys aged 6-11 years in eastern Sydney, compared with the 1985 ACHPER survey. In both boys and girls with the highest BMI category, levels of apo B and the apo B: apo A-I ratio were significantly increased. As these apolipoprotein changes are correlated closely with early onset atherogenesis and are correctable, their identification offers prospects for prevention.

New MspI polymorphism at +83 bp of the human apolipoprotein AI gene: association with increased circulating high density lipoprotein cholesterol levels

We recently showed that loss of a MspI restriction site in the 5'-end (intron 1) of the apolipoprotein (apo) AI gene is due to a C to T transition (+83 bp) and/or a G to A transition (+84 bp). Since this region may be relevant to the regulation of apo AI gene expression and therefore to plasma high density lipoprotein cholesterol (HDL-C), we explored the association between this MspI polymorphic site and circulating HDL-C levels in 243 healthy Caucasians. There were 143 aged 18-67 years (60 males and 83 females) and 100 aged 6-12 years (58 males and 42 females). We also compared this association with a known MspI polymorphic site, a G to A transition at -75 bp of the apo AI gene. The rare allele (-) frequency for the polymorphism at +83 bp was 4.1% and 22.1% for the polymorphism at -75 bp. Subjects heterozygous for the loss of the MspI restriction site at +83 bp (genotype: M2+-, n = 20) had higher HDL-C levels than M2+2 subjects (mean +/- SD: 1.73 +/- 0.31 vs. 1.41 +/- 0.39 mmol/l, P < 0.05 for adults; 1.71 +/- 0.33 vs. 1.34 +/- 0.29 mmol/l, P < 0.01 for children). Adults with the G to A substitution at -75 bp also had higher HDL-C levels (1.56 +/- 0.36 mmol/l for AA, 1.53 +/- 0.38 mmol/l for GA, and 1.36 +/- 0.38 mmol/l for GG, P < 0.05); this difference was not observed in the children. The MspI polymorphisms at both sites were in linkage disequilibrium. Their joint effect on the HDL-C levels was also significant and individuals with rare alleles (-) at both sites had the highest HDL-C levels. In an analysis of variance, the MspI polymorphism at +83 bp, and at -75 bp and gender independently accounted for 6.5%, 1.7%, and 5.9%, respectively, of the variance in circulating HDL-C levels when age was controlled as a covariate. We conclude that loss of the MspI site by the C to T (+83 bp) and/or the G to A (+84 bp) transitions is highly associated with increased HDL-C levels. The association appears to be more significant than that of the G to A transition at -75 bp.

Genotype distribution of angiotensin-converting enzyme polymorphism in Australian healthy and coronary populations and relevance to myocardial infarction and coronary artery disease

Angiotensin-converting enzyme is a key component of the renin-angiotensin system that plays an important role in cardiovascular regulation. An association between the angiotensin-converting enzyme insertion/deletion (I/D) polymorphism and increased coronary risk has been found in some studies but not in others. To explore this further in an Australian white population, we compared the ACE genotype distribution in 550 patients aged 37 to 65 years with coronary artery disease documented by angiography with the genotype distribution in 404 healthy school children aged 6 to 13 years. We also explored associations in the patients between the angiotensin-converting enzyme I/D polymorphism and a history of myocardial infarction and coronary artery disease severity assessed by the number of major coronary arteries with more than 50% luminal obstructions and by the Green Lane coronary score. The frequencies of the angiotensin-converting enzyme genotype in the coronary artery disease patients were 0.236 for I/I, 0.395 for I/D, and 0.369 for D/D genotypes. This distribution with an excess of the D/D genotype was significantly different (chi 2 = 23.69, P < .0001) from that in the school children, in whom the genotype distribution was in Hardy-Weinberg equilibrium (I/I, 0.21; I/D, 0.54; D/D, 0.25). There was also a significant excess of D/D genotype among patients with a history of myocardial infarction (chi 2 = 9.42, P = .009), and there was the same D/D excess in the subgroup of children (n = 60) with two or more grandparents who had had coronary artery disease. We found no associations between the angiotensin-converting enzyme polymorphism and the number of significantly stenosed coronary arteries (chi 2 = 2.069, P = .91). We conclude that the D/D genotype is a significant predictor for coronary artery disease events in the Australian white population but is not a marker for angiographically assessed coronary artery disease severity. The angiotensin-converting enzyme genotype-associated increased risk for coronary events may be mediated more by angiotensin II-induced coronary vasoconstriction than by an increase in injury-related smooth muscle cell proliferation in the coronary vasculature.