Clinical, diagnostic, and therapeutic aspects of familial hypercholesterolemia

Heterozygous familial hypercholesterolemia (FH) is a common inherited disorder of lipoprotein metabolism. FH is characterized by elevated levels of low-density lipoprotein cholesterol, the presence of tendon xanthomas, and premature cardiovascular disease. The underlying molecular defect of FH consists of mutations in the gene coding for the low-density-lipoprotein-receptor protein, detection of which provides the only unequivocal diagnosis. Although the cause of FH is monogenic, there is wide variation in the onset and severity of atherosclerotic disease in these patients. Additional atherogenic risk factors of environmental, metabolic, and genetic origin are presumed to influence the clinical phenotype in FH. Criteria used to identify individuals with FH include a combination of clinical characteristics, personal and family history of early coronary artery disease, and biochemical parameters. Since the introduction in 1989 of statins, which have been shown to be effective and to delay or prevent the onset of cardiovascular disease, drug treatment of FH has greatly improved. New lipid-lowering agents are presently being developed for clinical use. This review provides an update on the clinical, diagnostic, and therapeutic aspects of heterozygous familial hypercholesterolemia.

Toll-like receptor-4 Asp299Gly polymorphism does not influence progression of atherosclerosis in patients with familial hypercholesterolaemia

BACKGROUND

Toll-like receptor-4 (TLR4) is a major receptor for inflammatory stimuli potentially involved in the pathogenesis of atherosclerosis, such as lipopolysaccharide (LPS) and heat-shock proteins. The Asp299Gly polymorphism of the TLR4 gene has been associated with a reduced intima-media thickness (IMT) of the common carotid artery in healthy individuals. We have investigated whether the presence of the Asp299Gly polymorphism in patients with familial hypercholesterolaemia (FH) has a similar protective effect, and whether it influences the effects of HMG-CoA reductase treatment.

MATERIALS AND METHODS

A cohort of 293 FH patients and 200 healthy volunteers were genotyped for the presence of the Asp299Gly allele using polymerase chain reaction followed by restriction fragment length polymorphism analysis. Intima-media thickness measurements, inflammatory parameters and the effect of HMG-CoA reductase inhibitors were compared between the patients with and without Asp299Gly allele.

RESULTS

The Asp299Gly allele was present in 10.6% of the FH patients and 11.0% of the healthy individuals. Whereas the FH patients carrying the Asp299Gly allele displayed a reduced absolute IMT value compared with the FH patients carrying the wild-type allelle, the difference did not reach statistical significance. In addition, the effect of treatment with HMG-CoA reductase inhibitors was not influenced by the presence of Asp299Gly allele.

CONCLUSION

The presence of the Asp299Gly allele of the TLR4 gene does not seem to exert a major influence on the progression of atherosclerosis in patients with FH.

Arterial intima-media thickness in children heterozygous for familial hypercholesterolaemia

Patients with familial hypercholesterolaemia have severe coronary-artery disease early in adult life. Whether lipid-lowering treatment should be started in childhood remains to be established. We therefore assessed 201 children heterozygous for familial hypercholesterolaemia and 80 unaffected siblings (both age ranges 8-18 years) with B-mode ultrasound to measure carotid wall intima-media thickness. Mean combined carotid intima-media thickness of heterozygotes was significantly greater than that of unaffected siblings (0.494 mm [SD 0.051] vs 0.472 [SD 0.049], p=0.002). A significant deviation in intima-media thickness was noted from age 12 years in children with familial hypercholesterolaemia. Findings on multivariate analysis showed LDL cholesterol, age, and sex to be strong and independent predictors of intima-media thickness. Since raised LDL cholesterol concentrations can be lowered efficiently, clinical studies are needed to investigate long-term safety and effectiveness of statin treatment in children with familial hypercholesterolaemia.

Steady-State Pharmacokinetics of Pravastatin in Children with Familial Hypercholesterolaemia

OBJECTIVE

To determine pharmacokinetic data for pravastatin in children, since current data are insufficient in this age group.

SUBJECTS AND METHODS

A 2-week, multiple-dose, steady-state pharmacokinetic study was carried out with pravastatin 20mg daily in 24 children with familial hypercholesterolaemia (aged 8-16 years; 12 prepubertal, 12 pubertal). A plasma concentration-time curve was performed on day 14. Pharmacokinetic curves for each individual were constructed using nonparametric methods, yielding area under the plasma concentration-time curve (AUC), maximum plasma concentration (C(max)) and half-life (t((1/2))). Clearance values and volumes of distribution were calculated from these parameters. Cholesterol lowering was observed on day 14 and 6 weeks after the start of pravastatin.

RESULTS

The C(max) in prepubertal (group A) children (52.1 +/- 27.0 mug/L [mean +/- SD]) differed, although not significantly (p = 0.09, unpaired two-tailed t-test), from the C(max) in adolescents (group B) [31.7 +/- 29.2 mug/L]. There was a moderate negative correlation between C(max) and age (Spearman correlation r = -0.42; p = 0.04). The AUC in prepubertal children (91.3 +/- 39.7 mug . h/L) did not differ significantly from the AUC in adolescents (69.3 +/- 57.0 mug . h/L). The t((1/2)) was the same for the two groups: 2.5 +/- 1.1h. Clearance values (CL/f) varied widely between the two groups (group A: 4.3 +/- 1.8 L/min; group B: 11.0 +/- 11.9 L/min; p = 0.08). A moderate positive correlation was found between clearance and age (Spearman correlation r = 0.36; p = 0.09). A large variation was found in the volumes of distribution within the two groups (group A: 31.2 mL/kg [SD 26.7], group B:37.0 mL/kg [SD 29.6]; p = 0.12). A very weak positive correlation was found between age and volume of distribution (Spearman correlation r = 0.11; p = 0.61). A 27% low-density lipoprotein-cholesterol reduction from baseline was achieved at day 14.

CONCLUSIONS

Body surface area and gender did not influence the pharmacokinetics of pravastatin in children aged 8-16 years. On the basis of our findings there are no reasons to use pravastatin at a dosage according to bodyweight or to use different dosage regimens from those in adults. However, for prepubertal children half the advised starting dose for adults may be sufficient.

Interaction between a genetic variant of the platelet fibrinogen receptor and fibrinogen levels in determining the risk of cardiovascular events

BACKGROUND

The PlA1A2 polymorphism of glycoprotein IIIa (GPIIIa), which affects postoccupancy signaling by the platelet fibrinogen receptor IIbIIIa, has been investigated as a potential genetic risk factor for cardiovascular events in numerous studies, without consistent results. We investigated whether the effect of this genetic variant of the platelet fibrinogen receptor on the risk of cardiovascular events is affected by fibrinogen plasma levels.

METHODS

The GPIIIa PlA1A2 polymorphism and fibrinogen levels were determined in 455 men with angiographically documented coronary atherosclerosis.

RESULTS

Neither carriership of the rare PlA2 allele nor fibrinogen plasma levels affected the time to cardiovascular event, as assessed in a proportional hazards model. However, there was a significant interaction between PlA2 carriership and fibrinogen plasma levels (P =.002). Carriership of the variant PlA2 allele significantly affected event-free survival only in individuals within the highest fibrinogen quartile (hazard ratio, 2.7; 95% CI, 1.1 to 7.1; P =.03).

CONCLUSIONS

We observed a statistically significant interaction between a genetic variant of the platelet fibrinogen receptor and fibrinogen levels in determining the risk of cardiovascular events. This interaction may account for the inconsistent results of genetic association studies investigating this genotype as a genetic risk factor in thrombotic cardiovascular events.

Cholesteryl ester transfer protein concentration is associated with progression of atherosclerosis and response to pravastatin in men with coronary artery disease (REGRESS)

BACKGROUND

The TaqIB polymorphism in the cholesteryl ester transfer protein (CETP) gene is associated with HDL-C, progression of coronary artery disease (CAD) and response to pravastatin treatment in men with angiographically proven CAD (REGRESS). We hypothesized that differences in CETP concentration could explain these associations and now investigated whether CETP concentration is an independent determinant of these parameters.

MATERIALS AND METHODS

Plasma CETP concentrations at baseline and after 2 years' treatment with pravastatin or placebo were measured (n=674), and correlations with lipid and angiographic parameters (mean segment- and obstruction-diameter; MSD and MOD), and TaqIB genotype were studied.

RESULTS

After segregation into three groups (baseline CETP<1.58, 1.58-2.21, >2.21 mg L(-1)), subjects with the highest CETP had significantly higher baseline total cholesterol, LDL-C and triglycerides (P<0.01), while HDL-C, MSD and MOD were not different among these groups. After 2 years of placebo, the MSD decreased threefold (P<0.001) and the MOD decreased 2.4-fold (P=0.042) more in the highest compared with the lowest CETP quartile. Pravastatin treatment reduced total cholesterol LDL-C and triglycerides significantly more in the highest CETP quartile. Moreover, only in the highest CETP quartile, pravastatin significantly reduced the MSD- (P=0.003) and MOD-decrease (P=0.014) compared with placebo, and, notably, this was independent of baseline lipids and differential lipid changes in these quartiles. Strikingly, baseline associations and treatment responses according to baseline CETP were independent of TaqIB genotype.

CONCLUSIONS

High CETP concentration is associated with faster progression of coronary atherosclerosis in men with proven CAD. Second, pravastatin yielded the highest improvement of lipid and angiographic parameters in patients with high baseline CETP independent of baseline lipids, lipid changes and TaqIB genotype, indicating that the plasma CETP level itself is an important determinant of the response to statins.

Pharmacoeconomic evaluation of testing for angiotensin-converting enzyme genotype before starting ??-hydroxy-??-methylglutaryl coenzyme A reductase inhibitor therapy in men

This study aimed to assess the potential cost-effectiveness of screening men for their angiotensin-converting enzyme (ACE)-genotype before starting statin therapy. We used a combination of decision-analytic and Markov modelling techniques to evaluate the long-term incremental clinical and economic effects associated with genetic testing of men with hypercholesterolemia before starting treatment with statins. The study was performed from a health care payer perspective. We used data from the Rotterdam study, a prospective population-based cohort study in the Netherlands, which was started in 1990 and included 7983 subjects aged 55 years and older. Men treated with cholesterol-lowering drugs at baseline or with a baseline total cholesterol > or = 6.5 mmol/l were included. The ratio of difference in lifelong costs between the screening strategy and the no screening strategy to difference in life expectancy between these strategies was calculated. We also performed a cost-utility analysis. The base case was a 55-year-old man with hypercholesterolemia who was initially untreated. Several univariate sensitivity analyses were performed. All costs were discounted with an annual rate of 5%. Screening men for their ACE-genotype was the dominant strategy for the base case analysis, because the screening strategy saved money (851 Euro), but life expectancy was not changed. Screening was the dominant strategy for all age-groups in our cohort. Even in 80-year-old subjects, with the shortest life-expectancy, it was cheaper to screen than to give lifelong treatment to men with a DD genotype without success. Even if all DD subjects were treated with other (non-statin) cholesterol-lowering drugs, screening remained the cost-effective strategy. The results of the cost-utility analysis were similar. Discounting the effects with 5% per year also had no major impact on the conclusions. If other studies confirm that men with the DD genotype do not benefit from treatment with statins, screening for ACE genotype in men most likely will be a cost-effective strategy before initiating statin therapy.

Molecular variation at the apolipoprotein B gene locus in relation to lipids and cardiovascular disease: a systematic meta-analysis

Apolipoprotein B (apoB) is the sole protein component of low-density lipoprotein (LDL) and is thought to play an important role in atherogenesis. We performed a meta-analysis of the associations between the three most frequently investigated polymorphisms (XbaI, signal peptide insertion/deletion, EcoRI) in the apolipoprotein B (APOB) gene, lipid parameters, and the risk of ischemic heart disease (IHD). We restricted our analysis to Caucasians. Homozygotes for the XbaI X+ allele had significantly elevated levels of LDL cholesterol (LDL-C) and apoB, but a decreased risk (OR=0.80; 95%CI: 0.66-0.96) of IHD. Homozygosity for the signal peptide deletion allele was associated with similarly increased levels of LDL-C and apoB, and with an increased risk of IHD (OR=1.30; 95%CI: 1.08-1.58). Subjects homozygous for the rare EcoRI allele had significantly decreased levels of total and LDL cholesterol, but unaltered risk of IHD. We conclude that all three polymorphic apoB sites are associated with altered lipid levels, but not necessarily with a consistently altered risk of IHD. These data suggest that the relationship between apoB levels, hypercholesterolemia and IHD risk cannot have a simple molecular basis in the apoB gene.

Regression of carotid and femoral artery intima-media thickness in familial hypercholesterolemia: treatment with simvastatin

OBJECTIVE

To investigate whether high-dose simvastatin therapy could reduce carotid and femoral artery intima-media thickness (IMT) in patients with familial hypercholesterolemia (FH) to prevent cardiovascular disease.

BACKGROUND

Imaging of arterial walls with B-mode ultrasonography is increasingly used as a noninvasive surrogate marker of cardiovascular disease. Intervention trials using this modality have shown that by reducing risk factors, progression of atherosclerosis was inhibited.

METHODS

After a washout period of 6 weeks, all patients with FH started monotherapy with simvastatin, 80 mg/d, for 2 years. The primary end point was the change (in millimeters) of the mean combined far-wall IMT of predefined carotid and femoral arterial segments at 2 years.

RESULTS

We included a total of 153 patients with FH. Mean +/- SD combined baseline IMT was 1.07 +/- 0.23 mm. After treatment with simvastatin for 2 years, this IMT decreased by a mean of 0.081 mm (95% confidence interval, -0.109 to -0.053; P<.001), with its largest reduction in the femoral artery (-0.283 mm; P<.001). An actual decrease of combined IMT was seen in 69.8% of all patients.

CONCLUSIONS

High-dose simvastatin therapy reduces arterial wall IMT in more than two thirds of the patients, with its largest effect on the femoral artery. Furthermore, patients with FH who were treated with both statin and antihypertensive medication experienced a significantly greater benefit in terms of IMT reduction.

Long term statin treatment reduces lipoprotein(a) concentrations in heterozygous familial hypercholesterolaemia

BACKGROUND

Raised plasma lipoprotein(a) (Lp(a)) is associated with increased risk of cardiovascular disease. It is unknown whether increased Lp(a) is an additional risk factor for coronary artery disease in familial hypercholesterolaemia (FH) or whether statin treatment can reduce Lp(a) concentrations in the long term.

OBJECTIVE

To investigate Lp(a) concentrations in relation to statin treatment and the progression of atherosclerosis in a large cohort of FH patients.

DESIGN

A two year, randomised, double blind trial (the ASAP trial).

PATIENTS

325 heterozygous FH patients.

INTERVENTION

Treatment with 80 mg atorvastatin or 40 mg simvastatin.

MAIN OUTCOME MEASURE

Change in Lp(a) concentrations and intima-media thickness of carotid artery segments at one year and two years.

RESULTS

At baseline, median Lp(a) concentrations were 327 mg/l and 531 mg/l in the atorvastatin and simvastatin arms, respectively (p = 0.03). In the atorvastatin arm, Lp(a) concentrations decreased to 243 mg/l after one year (p < 0.001) and to 263 mg/l after two years (p < 0.001). In the simvastatin arm, Lp(a) concentrations decreased to 437 mg/l after one year (p < 0.001) and to 417 mg/l after two years (p < 0.001). The difference in Lp(a) reduction between the two treatment arms was significant after one year (p = 0.004), but not after two years (p = 0.086). Lp(a) concentrations at baseline were not related to cardiovascular events at baseline. There was no correlation between baseline Lp(a) concentrations and low density lipoprotein cholesterol concentrations or intima-media thickness at baseline. Change in Lp(a) concentrations was not correlated with change in intima-media thickness after one or two years.

CONCLUSIONS

Long term statin treatment significantly lowers Lp(a) in FH patients. However, this reduction was unrelated to changes in intima-media thickness and casts doubt on the importance of Lp(a) in the progression of atherosclerotic disease in these patients.

Allelic variation in the promoter region of the LDL receptor gene: analysis of an African-specific variant in the FP2 cis-acting regulatory element

DNA samples of 2303 individuals from nine different population groups were screened for variant -175g-->t in the promoter region of the low-density lipoprotein receptor (LDLR) gene. The -175g-->t variant detected at carrier frequencies of 3-10% in different African population groups was absent in the Caucasian and Asian (Chinese) individuals studied. In contrast to previous findings in Black South Africans where this polymorphism predominated in patients with familial hypercholesterolaemia (FH), it occurred at a significantly lower frequency in hypercholesterolaemics from the recently admixed Coloured population of South Africa compared with population-matched controls (P<0.0001). Haplotype and mutation analysis excluded the likelihood that this finding is due to association with a specific disease-related mutation in FH patients, although reversal of the positive association with FH observed in the Black population may, at least in part, be due to admixture linkage disequilibrium. Transient transfection studies in HepG2 cells demonstrated that the -175t allele is associated with a non-significant decrease ( approximately 7%) of LDLR transcription in the absence of sterols. The data presented in this study raise the possibility that the -175g-->t polymorphism may have subtle effects that become clinically important within certain genetic and/or environmental contexts.

Efflux and atherosclerosis: the clinical and biochemical impact of variations in the ABCA1 gene

Approximately 50 mutations and many single nucleotide polymorphisms have been described in the ABCA1 gene, with mutations leading to Tangier disease and familial hypoalphalipoproteinemia. Homozygotes and heterozygotes for mutations in ABCA1 display a wide range of phenotypes. Identification of ABCA1 as the molecular defect in these diseases has allowed for ascertainment based on genetic status and determination of genotype-phenotype correlations and has permitted us to identify mutations conferring a range of severity of cellular, biochemical, and clinical phenotypes. In this study we review how genetic variation at the ABCA1 locus affects its role in the maintenance of lipid homeostasis and the natural progression of atherosclerosis.

Rapid, arteriovenous graft failure due to intimal hyperplasia: a porcine, bilateral, carotid arteriovenous graft model

BACKGROUND

The loss of patency constitutes the major complication of arteriovenous (AV) polytetrafluoroethylene hemodialysis grafts. In most cases, this graft failure is due to intimal hyperplasia at the venous outflow tract, including proliferation of vascular, smooth muscle cells and fibroblasts with deposition of extracellular matrix proteins. Thus far, procedures developed for improving patency have proven unsuccessful, which can be partly explained by the lack of relevant animal models. For this purpose, we developed a porcine model for AV graft failure that will allow the assessment of promising therapeutic strategies in the near future.

MATERIALS AND METHODS

In 14 pigs, AV grafts were created bilaterally between the carotid artery and the jugular vein using expanded polytetrafluoroethylene. Two, 4 or 8 weeks after AV shunting, the grafts and adjacent vessels were excised and underwent histologic analysis.

RESULTS

From 2 weeks onwards, a thick neo-intima developed at the venous anastomosis, predominantly consisting of alpha-actin-positive vascular smooth muscle cells (VSMC). Intimal area increased over time, coinciding with a decreased graft flow. Grafts remained patent for at least 4 weeks. At 8 weeks, patency rates declined to less than 50% due to thrombus formation superimposed on progressive neo-intima formation.

CONCLUSIONS

Implantation of an AV graft between the carotid artery and jugular vein in pigs causes a rapid neo-intimal response, accompanied by a loss of patency of 50% at 8 weeks after surgery. This model offers a suitable tool to study local interventions aimed at the improvement of AV graft patency rates.

Restoration of endothelial function by increasing high-density lipoprotein in subjects with isolated low high-density lipoprotein

BACKGROUND

Loss-of-function mutations in the ATP-binding cassette (ABCA)-1 gene locus are the underlying cause for familial hypoalphalipoproteinemia, providing a human isolated low-HDL model. In these familial hypoalphalipoproteinemia subjects, we evaluated the impact of isolated low HDL on endothelial function and the vascular effects of an acute increase in HDL.

METHODS AND RESULTS

In 9 ABCA1 heterozygotes and 9 control subjects, vascular function was assessed by venous occlusion plethysmography. Forearm blood flow responses to the endothelium-dependent and -independent vasodilators serotonin (5HT) and sodium nitroprusside, respectively, and the inhibitor of nitric oxide synthase NG-monomethyl-l-arginine (L-NMMA) were measured. Dose-response curves were repeated after systemic infusion of apolipoprotein A-I/phosphatidylcholine (apoA-I/PC) disks. At baseline, ABCA1 heterozygotes had decreased HDL levels (0.4+/-0.2 mmol/L; P<0.05), and their forearm blood flow responses to both 5HT (maximum, 49.0+/-10.4%) and L-NMMA (maximum, -22.8+/-22.9%) were blunted compared with control subjects (both P< or =0.005). Infusion of apoA-I/PC disks increased plasma HDL to 1.3+/-0.4 mmol/L in ABCA1 heterozygotes, which resulted in complete restoration of vasomotor responses to both 5HT and L-NMMA (both P</=0.001). Endothelium-independent vasodilation remained unaltered throughout the protocol.

CONCLUSIONS

In ABCA1 heterozygotes, isolated low HDL is associated with endothelial dysfunction, attested to by impaired basal and stimulated NO bioactivity. Strikingly, both parameters were completely restored after a single, rapid infusion of apoA-I/PC. These findings indicate that in addition to its long-term role within reverse cholesterol transport, HDL per se also exerts direct beneficial effects on the arterial wall.

The apolipoprotein epsilon4 allele confers additional risk in children with familial hypercholesterolemia

Children with familial hypercholesterolemia (FH) exhibit substantial variance of LDL cholesterol. In previous studies, family members of children with FH were included, which may have influenced results. To avoid such bias, we studied phenotype in 450 unrelated children with FH and in 154 affected sib-pairs. In known families with classical FH, diagnosis was based on plasma LDL cholesterol above the age- and gender-specific 95th percentile. Girls had 0.47 +/- 0.15 mmol/L higher LDL cholesterol, compared with boys (p = 0.002). Also in girls, HDL cholesterol increased by 0.07 +/- 0.03 mmol/L per 5 y (pfor trend = 0.005); this age effect was not observed in boys. The distribution of apolipoprotein (apo) E genotypes was not significantly different between probands, their paired affected siblings, or a Dutch control population. Carriers with or without one epsilon4 allele had similar LDL and HDL cholesterol levels. Within the affected sib-pairs, the epsilon4 allele explained 72.4% of the variance of HDL cholesterol levels (-0.15 mmol/L, 95% confidence interval -0.24 to -0.05, p = 0.003). The effect of apoE4 on HDL cholesterol differed with an analysis based on probands or on affected sib-pairs. The affected sib-pair model used adjustment for shared environment, type of LDL receptor gene mutation, and a proportion of additional genetic factors and may, therefore, be more accurate in estimating effects of risk factors on complex traits. We conclude that the epsilon4 allele was associated with lower HDL cholesterol levels in an affected sib-pair analysis, which strongly suggests that apoE4 influences HDL cholesterol levels in FH children. Moreover, the strong association suggests that apoE4 carries an additional disadvantage for FH children.

The role of the ABCA1 transporter and cholesterol efflux in familial hypoalphalipoproteinemia

Defects in the gene encoding for the ATP binding cassette (ABC) transporter A1 (ABCA1) were shown to be one of the genetic causes for familial hypoalphalipoproteinemia (FHA). We investigated the role of ABCA1-mediated cholesterol efflux in Dutch subjects suffering from FHA. Eighty-eight subjects (mean HDL cholesterol levels 0.63 +/- 0.21 mmol/l) were enrolled. Fibroblasts were cultured and loaded with [3H]cholesterol. ABCA1 and non-ABCA1-mediated efflux was studied by using apolipoprotein A-I (apoA-I), HDL, and methyl-beta-cyclodextrin as acceptors. Efflux to apoA-I was decreased in four patients (4/88, 4.5%), and in all cases, a mutation in the ABCA1 gene was found. In the remaining 84 subjects, no correlation between efflux and apoA-I or HDL cholesterol was found. Efflux to both HDL and cyclodextrin, in contrast, did correlate with HDL cholesterol plasma levels (r = 0.34, P = 0.01; and r = 0.27, P = 0.008, respectively). The prevalence of defects in ABCA1-dependent cholesterol efflux in Dutch FHA patients is low. The significant correlation between plasma HDL cholesterol levels and methyl-beta-cyclodextrin-mediated efflux in the FHA patients with normal ABCA1 function suggests that non-ABCA1-mediated efflux might also be important for plasma HDL cholesterol levels in these individuals.

Variants of toll-like receptor 4 modify the efficacy of statin therapy and the risk of cardiovascular events

BACKGROUND

Atherosclerosis is increasingly considered to be a chronic inflammatory process. We examined whether genetic variants of the toll-like receptor 4 (TLR4), which are correlated with impaired innate immunity and with progression of carotid atherosclerosis, are also associated with coronary atherosclerosis and predict the risk of cardiovascular events.

METHODS AND RESULTS

Two polymorphisms of the TLR4 gene (Asp299Gly and Thr399Ile) were determined in 655 men with angiographically documented coronary atherosclerosis. All patients participated in a prospective cholesterol-lowering trial evaluating the effect on coronary artery disease and were randomly assigned to either pravastatin or placebo for 2 years. There were no significant differences between genetically defined subgroups with respect to baseline risk factors, treatment, or in-trial changes of lipid, lipoprotein, or angiographic measurements. Genotype was not associated with progression of atherosclerosis. In the pravastatin group, 299Gly carriers had a lower risk of cardiovascular events during follow-up than noncarriers (2.0% versus 11.5%, P=0.045). Among noncarriers, pravastatin reduced the risk of cardiovascular events from 18.1% to 11.5% (P=0.03), whereas among 299Gly carriers this risk was strikingly reduced from 29.6% to 2.0% (P=0.0002, P=0.025 for interaction).

CONCLUSIONS

Among symptomatic men with documented coronary artery disease, the TLR4 Asp299Gly polymorphism was associated with the risk of cardiovascular events. This variant also modified the efficacy of pravastatin in preventing cardiovascular events, such that carriers of the variant allele had significantly more benefit from pravastatin treatment.

A novel functional polymorphism in the PECAM-1 gene (53G>A) is associated with progression of atherosclerosis in the LOCAT and REGRESS studies

A 53G>A polymorphism identified in the 5' untranslated region (5'UTR) of the platelet endothelial cell adhesion molecule-1 (PECAM-1) gene alters a putative shear stress responsive element (SSRE). PECAM-1 was shown to be responsive to shear stress and transient transfection of human umbilical vein endothelial cell (HUVECs) with two luciferase reporter constructs driven by the PECAM-1 promoter and 5'UTR showed a response of the 53G allele, not the 53A allele, to shear stress. Association between the 53G>A, and the previously published L125V polymorphism, and coronary atherosclerosis was examined in two angiographic studies. The frequencies of the rare alleles of the 53G>A and L125V polymorphisms were 0.01 and 0.49, respectively, in the Lopid Coronary Angiography Trial (LOCAT) study and 0.02 and 0.49, respectively, in the Regression Growth Evaluation Statin Study (REGRESS) study. Compared with 53G homozygotes, carriers of the 53A allele showed less focal progression of disease in the LOCAT study and a similar trend in the diffuse progression of disease in the REGRESS study, whereas no association between L125V and coronary atherosclerosis was observed in either study. These data demonstrate that the PECAM-1 gene is responsive to shear stress in vitro and that decreased PECAM-1 gene expression in 53A carriers may influence reduced progression of vessel stenosis in patients with coronary artery disease.

The future of lipid-lowering therapy: the big picture

Several lipid-lowering intervention studies published in 2002 shed light on the current status and the future of cardiovascular risk reduction by drug therapy. The Heart Protection Study has demonstrated that simvastatin reduces heart attack, stroke and revascularisation risk by about one-third irrespective of total cholesterol, LDL cholesterol, patient's age or sex, or the nature of pre-existing cardiovascular disease. Coronary heart disease death and myocardial infarction risk reduction in elderly patients by pravastatin in the PROSPER study was similar to the benefit of statins in middle-aged populations in other studies. The ALLHAT-LLT study has failed to demonstrate a benefit of pravastatin on all-cause mortality, CHD death or nonfatal myocardial infarction, illustrating that too modest cholesterol lowering does not result in clinical benefit under all circumstances. The cholesterol absorption inhibitor ezetimibe has demonstrated significant LDL and total cholesterol lowering, and induced an additional 21% LDL cholesterol lowering when added to ongoing statin therapy. The cholesteryl ester transfer protein inhibitor JJT-705 produced a dose-dependent increase in HDL cholesterol concentrations of up to 34% and improved the total cholesterol/HDL cholesterol ratio in healthy individuals while having very mild side effects. Cholesterol absorption inhibitors and HDL cholesterol enhancers may become useful tools to achieve further improvements in cardiovascular risk reduction in the future.

Adherence to and dosing of beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors in the general population differs according to apolipoprotein E-genotypes

Discontinuation and poor adherence to therapy are major problems during long-term treatment, particularly with cholesterol lowering drugs. Several studies have indicated that the cholesterol lowering effect of statins differs according to apolipoprotein (apo)E genotypes. Low-density lipoprotein-cholesterol lowering capacity appears to be smaller in subjects with the epsilon(4) allele. To assess whether the use of statins in daily practice differs according to apoE genotypes, we used data from the Rotterdam Study, a population-based prospective cohort study in the Netherlands, which started in 1990 and included 7983 subjects aged 55 years or more. During follow-up, there were 798 subjects who started to use statins. We used a Cox proportional hazard model to determine the rate of discontinuation in the first 3 years of statin use. Subjects on statin therapy with epsilon(2)epsilon(2) and epsilon(4)epsilon(4) genotypes showed a trend towards higher dosages than subjects with the other genotypes. Relative to subjects with the epsilon(2)epsilon(3) genotype, those with the epsilon(4)epsilon(4) genotype had a risk of 2.28 [95% confidence interval (CI) 1.02-5.12] to discontinue statins within 3 years. In women, this relative risk was 1.70 (CI 0.53-5.42) versus 3.18 (CI 1.01-10.03) in men. The apoE genotype is associated with discontinuation of statins. This suggests that subjects who are genetically prone to develop hypercholesterolemia show the highest risk of discontinuation of treatment.

Family history and cardiovascular risk in familial hypercholesterolemia: data in more than 1000 children

BACKGROUND

Elevated LDL cholesterol (LDL-C) levels in childhood predict cardiovascular disease (CVD) later in life. Familial hypercholesterolemia (FH) represents the paradigm of this relation.

METHODS AND RESULTS

The objectives of this study were to (1) establish the LDL-C level that provides the most accurate diagnosis of FH in children from families with known FH and (2) assess whether lipoprotein variation in these children is associated with premature CVD in relatives. Foremost, however, it was our objective to identify children with FH who are at high risk and in need of early intervention. A total of 1034 consecutive children from FH kindreds were investigated. First, LDL-C levels >3.50 mmol/L had a 0.98 post-test probability (95% CI, 0.96 to 0.99) of predicting the presence of an LDL receptor mutation. Second, children with FH in the highest LDL-C tertile (>6.23 mmol/L) had a 1.7-times higher incidence (95% CI, 1.24 to 2.36) of having a parent with FH suffering from premature CVD (P=0.001). In addition, such a parent was found 1.8 times more often (95% CI, 1.20 to 2.59) among children with FH who had HDL-C <1.00 mmol/L (P=0.004). Last, children with FH whose lipoprotein(a) was >300 mg/L had a 1.45-times higher incidence (95% CI, 0.99 to 2.13) of having a parent with FH suffering from premature CVD (P=0.05).

CONCLUSIONS

In FH families, LDL-C levels allow accurate diagnosis of FH in childhood. Moreover, increased LDL-C and lipoprotein(a) and decreased HDL-C levels in children identify FH kindreds with the highest CVD risk.

Surrogate markers of atherosclerosis: impact of statins

Carotid artery intima-media thickness (IMT) measured by ultrasound has been shown to be correlated with existing cardiovascular disease (CVD) and predictive of CVD in individuals without clinically evident disease. Carotid IMT is now widely used as a surrogate marker for atherosclerotic disease. A number of studies have shown that lipid-lowering therapy with a statin can reduce or reverse carotid IMT progression. The METEOR trial (Measuring Effects on Intima-Media Thickness: an Evaluation Of Rosuvastatin) will examine the effects of aggressive lipid-lowering treatment with rosuvastatin on IMT in mildly hypercholesterolemic low-risk subjects with relatively high IMT values. The results will provide important information on the ability to achieve regression of abnormal IMT with robust reductions in low-density lipoprotein (LDL) cholesterol levels to below current target levels. Another study will examine the effects of potent LDL cholesterol reduction with rosuvastatin in young patients with heterozygous familial hypercholesterolemia (FH). Patients with FH are at increased risk of premature coronary heart disease in association with marked LDL cholesterol elevations, exhibiting a rate of progression of IMT 5x greater than that of low-risk controls without the disorder and early intervention may be the optimal approach to modifying atherosclerosis progression in these patients.

Estimation of multilocus haplotype effects using weighted penalised log-likelihood: analysis of five sequence variations at the cholesteryl ester transfer protein gene locus

Direct analyses of haplotype effects can be used to identify those specific combinations of alleles that are associated with a specific phenotype. We introduce a method for direct haplotype analysis that solves two problems that arise when haplotypes are analysed in populations of unrelated subjects. Instead of assigning a single, most likely, haplotype pair to multiple heterozygous subjects, all haplotype pairs compatible with their genotype were determined and the posterior probabilities of these pairs were calculated using Bayes' theorem and estimated haplotype frequencies. For the individual patients, all possible haplotype pairs were included in the statistical analysis using the posterior probabilities as weights, which were re-estimated in an iterative process together with the haplotype effects. The second problem of unstable haplotype effect estimates, due to the numerous haplotypes and the low frequency at which some occur, was solved by assuming that haplotypes sharing the same alleles show a similar effect and that the extent of this similarity relates to the number of alleles shared. These assumptions were incorporated in a weighted log-likelihood model by introducing a penalty, where differences in effects of similar haplotypes were penalised. Using CETP gene haplotypes, consisting of five closely linked polymorphisms, and baseline CETP and HDL-C concentrations from the REGRESS population, we demonstrated that the model resulted in more stable effects than estimates based on unambiguous patients only.

Prevalence and significance of cardiovascular risk factors in a large cohort of patients with familial hypercholesterolaemia

OBJECTIVE

Patients with familial hypercholesterolaemia (FH) vary widely in terms of onset of cardiovascular disease (CVD).

DESIGN

The association between cardiovascular risk factors and prevalent CVD was examined in a cross-sectional study in order to elucidate their contribution to atherogenesis.

SETTING AND SUBJECTS

Patients were recruited from 37 Dutch Lipid Clinics. The diagnosis of FH was based on a uniform diagnostic protocol, confirmed by DNA analysis in 62% of the cases. All patients were investigated free from any lipid-lowering drug for at least 6 weeks.

MAIN OUTCOME MEASURES

Differences in lipids, lipoproteins and other risk factors for CVD were analysed in FH patients with and without CVD.

RESULTS

A total of 526 patients were assessed and more than 37% had a history of CVD with a mean age of onset of 46.8 years. Mean LDL cholesterol (LDL-C) levels were severely elevated (8.38 +/- 2.13 mmol L-1). In univariate analysis, age, presence of hypertension or diabetes, body mass index, triglycerides (TG) and low HDL cholesterol (HDL-C) were all significantly associated with CVD. Also in multivariate analysis, all these risk factors, except TG and diabetes, were significantly linked to CVD.

CONCLUSION

A high CVD risk in this large well-documented characterized sample of FH patients is not only conferred by elevated LDL-C but also by low HDL-C.

Haplotype analysis of the CETP gene: not TaqIB, but the closely linked -629C-->A polymorphism and a novel promoter variant are independently associated with CETP concentration

The TaqIB polymorphism in intron 1 of the cholesteryl ester transfer protein (CETP) gene is associated with plasma CETP concentration, high-density lipoprotein cholesterol (HDL-C) and coronary artery disease (CAD). These associations are generally thought to arise from linkage disequilibrium between TaqIB and (an)other functional polymorphism(s). To identify putative functional sites, we investigated phenotypic associations of TaqIB and four tightly linked polymorphisms (novel -2708G-->A and +784CCC-->A, and previously identified -971G-->A and -629C-->A) in 709 males with CAD (REGRESS). In addition to genotype analyses, a novel method to estimate haplotype effects was used to examine the individual and joint effects of these DNA variants on CETP concentration and HDL-C. All polymorphisms were associated with CETP concentration and HDL-C, except for -971 with HDL-C. Stepwise regression and haplotype analyses indicated that only -629 was independently associated with HDL-C. Similar analyses additionally indicated that -2708 and -629 were independently associated with CETP concentration, whereby the most frequent alleles acted in a cumulative manner. Nonetheless, detailed haplotype analysis revealed that a 3-polymorphism haplotype model consisting of -2708, -629 and -971 explained the variation in CETP concentration best. The involvement of -971 could be due to interaction effects that were observed between -971 and both -629 (P<0.001) and -2708 (P=0.047). In conclusion, the TaqIB polymorphism is not instrumental in determining CETP or HDL-C levels, but is a marker for the -629 promoter variant. Our analyses, furthermore, indicate that the -2708 and -971 polymorphisms are likely to play a role in determining CETP concentration.

Raised serum levels of soluble CD40 ligand in patients with familial hypercholesterolemia: downregulatory effect of statin therapy

OBJECTIVES

In the present study, we investigated the effects of statins on serum levels of soluble CD40 ligand (sCD40L) in patients with familial hypercholesterolemia (FH).

BACKGROUND

Atherosclerotic disease seems to involve inflammatory and immunologic mechanisms, and sCD40L has recently been identified as one of the key players in the atherosclerotic process. HMG-Co A reductase inhibitors, statins, have been recognized as immunomodulators and reduce cardiovascular events and mortality, but the effects of statins on sCD40L has not been clarified.

METHODS

In a randomized, double-blind, clinical trial, as part of the Atorvastatin versus Simvastatin on Atherosclerosis Progression (ASAP) trial, 110 patients with FH were given atorvastatin 80 mg/daily (n = 57) or simvastatin 40 mg/daily (n = 53) for two years.

RESULTS

Our main findings were: 1) at baseline patients with FH had significantly higher (approximately 27-fold) serum levels of sCD40L than healthy controls; 2) statin therapy markedly decreased serum levels of sCD40L (approximately 40% reduction); 3) this decrease in sCD40L was found during both "aggressive" (i.e., atorvastatin) and "conventional" (i.e., simvastatin) statin therapy and was not correlated with the degree of reduction in cholesterol levels.

CONCLUSIONS

Our findings may suggest enhanced CD40L-CD40 interaction in FH and that this inflammatory response may be downregulated by statins.

Long-term compliance with lipid-lowering medication after genetic screening for familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia is a common lipid disorder that predisposes to premature cardiovascular disease. Lipid-lowering treatment of affected individuals is widely advocated, and maximum benefit can be obtained if medication is started early. A screening program for familial hypercholesterolemia is ongoing in the Netherlands since 1994. To assess the extent of treatment and therapy compliance, patients were followed up for 2 years after the diagnosis was established.

METHODS

Data were obtained by questionnaire. The 747 patients with familial hypercholesterolemia participating in the study were from the general community, and 62.4% were not receiving cholesterol-lowering medication.

RESULTS

The overall percentage of treated patients had risen from 37.6% at screening to 92.5% 1 year later and then decreased to 85.9% 2 years after screening. During follow-up, 6.4% of patients discontinued their medication and 12.0% of untreated patients never started medication for various reasons, but in the majority of cases as advised by their own physicians. The mean reduction in low-density lipoprotein cholesterol levels in previously untreated patients was 30.1% (from 219 to 153 mg/dL [5.7 to 4.0 mmol/L]). For those already receiving treatment, an additional reduction of 10.3% (from 195 to 175 mg/dL [5.0 to 4.5 mmol/L]) was obtained.

CONCLUSIONS

Most patients were receiving treatment 2 years after identification and had a positive attitude toward the screening program. However, the reduction of cholesterol levels still did not meet the internationally accepted goals of treatment. This underscores the fact that additional education is required to improve the treatment of individuals with familial hypercholesterolemia.

Plant sterols lower LDL cholesterol without improving endothelial function in prepubertal children with familial hypercholesterolaemia

In adults with familial hypercholesterolaemia (FH), cholesterol lowering with statins has been shown to improve the endothelial function, a hallmark of early atherogenesis. Currently, therapeutic options for treating high cholesterol levels in FH children are limited. Plant sterols safely and effectively reduce serum cholesterol concentrations by inhibiting cholesterol absorption. Therefore, we evaluated the effect of plant sterols on cholesterol and vascular function in prepubertal children with FH. We included 41 children (5-12 years old) with FH in a double-blind crossover trial using spreads containing 2.3 g of plant sterols (mainly sitosterol and campesterol) per 15 g spread and a placebo spread for a 4-week period, separated by a 6-week washout period. Lipid levels and endothelial function were assessed after both 4-week treatment periods. Endothelial function was assessed as flow-mediated dilation (FMD) of the brachial artery using a wall tracking system. Data were compared to those of 20 healthy controls. Intake of 2.3 g plant sterols per day decreased total cholesterol (-11%) and low-density cholesterol (-14%) as compared to placebo spread in FH children. FH children treated with placebo spread were characterized by an impaired FMD compared to healthy control children (7.2% +/- 3.4% versus 10.1% +/- 4.2%, p < 0.005). However, the reduction of LDL in FH children did not improve FMD (placebo: 7.2% +/- 3.4% versus plant sterols: 7.7% +/- 4.1%). In conclusion, the present study shows a clear reduction of LDL cholesterol by plant sterol treatment. However, short-term plant sterol treatment does not improve the endothelial function in FH children.

Atorvastatin and the dyslipidemia of early renal failure

Information about lipid abnormalities and the effect of lipid lowering therapy in the early stage of renal disease is limited, while preventive treatment in this stage might be much more beneficial. Lipid profiles and risk factors were assessed in 150 consecutive, non-diabetic patients. Preventive therapy consisted of cholesterol-reduced diet and atorvastatin 10 mg daily. Patients were considered at risk for cardiovascular disease if LDL-cholesterol was >2.6 mmol/l in the case of manifest cardiovascular disease (n=28) or when they had manifest cardiovascular risk factors (n=105) or if LDL was >3.5 mmol/l (n=17). A total of 128 patients (85%) had increased LDL. In men <60 years and women <40 years, total cholesterol was higher than in the general population. Linear regression analysis showed a decreased creatinine clearance to be significantly associated with the lipid profile. For a 10 ml/min decrease of creatinine clearance, a 0.085 increase of the total cholesterol to HDL ratio was observed (P=0.005). In similar analyses, proteinuria was strongly associated with cholesterol and triglycerides. An increase of 0.28 of the total cholesterol/HDL ratio was observed for each gram per 24 h proteinuria (P<0.001). On atorvastatin 10 mg daily, 30 of 60 treated patients had achieved their target LDL value. On average, LDL-cholesterol was reduced by 39% and triglycerides by 18%. No patient had to interrupt their treatment because of adverse side-effects. In conclusion, the majority of patients had an elevated LDL and other lipid abnormalities. Short-term therapy with atorvastatin and a cholesterol lowering diet appears to be safe and effective. It is probably useful to determine the lipid profile in patients with renal failure already in an early phase and to start lipid lowering treatment as soon as abnormalities are found.

Early statin therapy restores endothelial function in children with familial hypercholesterolemia

OBJECTIVES

This study was designed to determine whether simvastatin improves endothelial function in children with familial hypercholesterolemia (FH).

BACKGROUND

Endothelial function measured by flow-mediated dilation of the brachial artery (FMD) is used as a surrogate marker of cardiovascular disease (CVD). Adult studies have shown that statins reverse endothelial dysfunction and therefore reduce the risk for future CVD.

METHODS

The study included 50 children with FH (9 to 18 years) and 19 healthy, non-FH controls. Children with FH were randomized to receive simvastatin or placebo for 28 weeks. The FMD was performed at baseline and at 28 weeks of treatment.

RESULTS

At baseline, FMD was impaired in children with FH versus non-FH controls (p < 0.024). In the simvastatin FH group, FMD improved significantly, whereas the FMD remained unaltered in the placebo FH group throughout the study period (absolute increase 3.9% +/- 4.3% vs. 1.2% +/- 3.9%, p < 0.05). In the simvastatin FH group, FMD increased to a level similar to the non-FH controls (15.6% +/- 6.8% vs. 15.5% +/- 5.4%, p = 0.958). Upon treatment, the simvastatin FH group showed significant absolute reductions of total cholesterol (TC) (-2.16 +/- 1.04 mmol/l, 30.1%) and low-density lipoprotein cholesterol (LDL-C) (-2.13 +/- 0.99 mmol/l, 39.8%). The absolute change of FMD after 28 weeks of therapy was inversely correlated to changes of TC (r = -0.31, p < 0.05) and LDL-C (r = -0.31, p < 0.05).

CONCLUSIONS

Our data show significant improvement of endothelial dysfunction towards normal levels after short-term simvastatin therapy in children with FH. These results emphasize the relevance of statin therapy in patients with FH at an early stage, when the atherosclerotic process is still reversible.

Low-density lipoprotein receptor gene mutations and cardiovascular risk in a large genetic cascade screening population

BACKGROUND

A large cohort of patients with familial hypercholesterolemia (FH), free from selection for cardiovascular disease (CVD), and their unaffected relatives was collected by genetic cascade screening and examined for the influence of different mutations of the LDL receptor gene on lipoprotein levels and the risk of CVD. Multivariate analyses with adjustment for age, sex, and specific family ties were performed.

METHODS AND RESULTS

Significant variation of LDL levels was observed among 399 patients with FH with different mutations. Null alleles were associated with more severely elevated LDL cholesterol, whereas the frequent N543H/2393del9 mutation led to less elevated LDL cholesterol. The type of mutation did not influence HDL cholesterol levels. Patients with FH had CVD 8.5 times more often compared with their unaffected relatives (RR, 8.54; 95% CI, 5.29 to 13.80). The N543H/2393del9 mutation was associated with a smaller increase of risk compared with other mutations (P<0.0001). After exclusion of families with the N543H/2393del9 mutation, null alleles and other allele mutations no longer differed with regard to LDL cholesterol levels and CVD risk.

CONCLUSIONS

LDL receptor mutations only partly contributed to the variation of LDL cholesterol levels and cardiovascular burden in FH. Additional, so far unidentified, familial risk factors must underlie the differences of CVD risk, most likely independent of lipids and lipoproteins.

Measurement of subclinical atherosclerosis: beyond risk factor assessment

PURPOSE OF REVIEW

Assessment of subclinical atherosclerosis using the current available noninvasive imaging modalities holds promise for individual cardiovascular risk management and monitoring efficacy of therapeutic interventions (i.e. surrogate end-points). The present review addresses benefits and limitations of flow-mediated dilatation, intima-media thickness, electron-beam computed tomography and magnetic resonance coronary angiography.

RECENT FINDINGS

Both carotid intima-media thickness and peripheral flow-mediated dilatation correlate inversely with cardiovascular risk factors and coronary artery disease. They have been shown to carry predictive value for future cardiovascular events, but clinical application of both intima-media thickness and flow-mediated dilatation demands further methodological maturation of these techniques. Intima thickening has been successfully targeted in numerous intervention trials, but determination of an explicit threshold value beyond which cardiovascular risk significantly increases will facilitate its utility as a routine clinical tool. Electron-beam computed tomography can accurately detect and quantify coronary artery calcification (an established marker of the total coronary plaque burden). However, lack of evidence of its additional predictive power for future coronary events warrants for further research. Finally, magnetic resonance coronary angiography appears to be a promising technique, integrating both functional and anatomical aspects of coronary artery disease. Properly designed studies are needed to determine its value in clinical practice.

SUMMARY

Various noninvasive imaging techniques have recently emerged that may find applications in clinical research. However, before widespread clinical utilization, further technical refinement of all of the cited imaging modalities is mandatory. It will be a challenge over the coming few years to clarify whether improvements in surrogate end-points can directly be translated into improved outcomes.

Thrombospondin-2 polymorphism is associated with a reduced risk of premature myocardial infarction

OBJECTIVE

Recently, polymorphisms in thrombospondin (THBS) genes coding for THBS-1 (N700S), THBS-2 (T>G substitution in 3'-untranslated region), and THBS-4 (A387P) genes were proposed to modulate the risk of premature coronary artery disease (CAD) or myocardial infarction (MI). It was our objective to verify this hypothesis in an independent cohort.

METHODS AND RESULTS

We performed a case-control study among patients (n=503) referred to our institution for symptomatic CAD that occurred before the age of 50 years and a group of age- and sex-matched population-based controls free of CAD (n=1071). The THBS-1 variant allele was not associated with an altered risk of premature CAD or MI. Homozygosity for the THBS-2 variant allele and the THBS-4 variant (387P) allele was significantly associated with a reduced risk of premature MI compared with wild-type individuals (OR=0.44, 0.24 to 0.84 and OR=0.43, 0.22 to 0.85, respectively). The latter observation is in contrast with a previous report, although confidence intervals overlap.

CONCLUSIONS

We conclude that a relationship between the THBS-1 N700S polymorphism and premature CAD is unlikely. For the THBS-4 A387P polymorphism, additional studies are required to elucidate its role in premature CAD. Finally, we conclude that the THBS-2 polymorphism is associated with a reduced risk of premature MI.

Differential hs-CRP reduction in patients with familial hypercholesterolemia treated with aggressive or conventional statin therapy

BACKGROUND

High sensitivity C-reactive protein (hs-CRP) has emerged as the best studied and most promising marker of inflammation in atherosclerotic vascular disease.

MATERIALS AND METHODS

The ASAP (effects of Atorvastatin vs. Simvastatin on Atherosclerosis Progression) study was a 2-year randomised, double-blind trial with 325 familial hypercholesterolemia patients, treated with torvastatin 80 mg or imvastatin 40 mg. Intima media thickness (IMT) of carotid artery segments and hs-CRP levels were determined at baseline, 1 and 2 years.

RESULTS

Baseline median hs-CRP values were 2.1 mg/l (interquartile range (IQR) 0.9-5.2) and 2.0 mg/l (IQR 0.8-3.0) and after 2 years these levels decreased to 1.1 mg/l (IQR 0.6-2.4) and 1.5 mg/l (IQR 0.6-3.0) in the atorvastatin 80 mg and simvastatin 40 mg group, respectively. These changes were significant within as well as between the two groups. No correlations were observed between change in hs-CRP after 2 years and change in lipids. A significant correlation was found in univariate analysis between the decrease of hs-CRP and the reduction of IMT.

CONCLUSIONS

Our results show that atorvastatin 80 mg reduces hs-CRP levels to a greater extent than simvastatin 40 mg. Furthermore, we show that the extent of hs-CRP reduction is associated with the progression rate of the atherosclerotic process as measured by IMT.

Truncation mutations in ABCA1 suppress normal upregulation of full-length ABCA1 by 9-cis-retinoic acid and 22-R-hydroxycholesterol

Mutations in ABCA1 uniformly decrease plasma HDL-cholesterol (HDL-C) and reduce cholesterol efflux, yet different mutations in ABCA1 result in different phenotypic effects in heterozygotes. For example, truncation mutations result in significantly lower HDL-C and apoliprotein A-I (apoA-I) levels in heterozygotes compared with nontruncation mutations, suggesting that truncation mutations may negatively affect the wild-type allele. To specifically test this hypothesis, we examined ABCA1 protein expression in response to 9-cis-retinoic acid (9-cis-RA) and 22-R-hydroxycholesterol (22-R-OH-Chol) in a collection of human fibroblasts representing eight different mutations and observed that truncation mutations blunted the response to oxysterol stimulation and dominantly suppressed induction of the remaining full-length allele to 5-10% of wild-type levels. mRNA levels between truncation and nontruncation mutations were comparable, suggesting that ABCA1 expression was suppressed at the protein level. Dominant negative activity of truncated ABCA1 was recapitulated in an in vitro model using transfected Cos-7 cells. Our results suggest that the severe reduction of HDL-C in patients with truncation mutations may be at least partly explained by dominant negative suppression of expression and activity of the remaining full-length ABCA1 allele. These data suggest that ABCA1 requires a physical association with itself or other molecules for normal function and has important pharmacogenetic implications for individuals with truncation mutations.

Consumption of tall oil-derived phytosterols in a chocolate matrix significantly decreases plasma total and low-density lipoprotein-cholesterol levels

In a randomized, double-blind, placebo-controlled trial we evaluated the effect of dietary chocolates enriched with a wood-based phytosterol-phytostanol mixture, containing 18 % (w/w) sitostanol, compared with placebo dietary chocolates in seventy subjects with primary hypercholesterolaemia (total cholesterol levels below 8 mmol/l). For 4 weeks, participants consumed three servings of the phytosterol-enriched chocolate/d that provided 1.8 g unesterified phytosterols/d or a placebo chocolate in conjunction with a low-fat, low-cholesterol diet. Plasma total and LDL-cholesterol levels were statistically significantly reduced by 6.4 % (-0.44 mmol/l) and 10.3 % (-0.49 mmol/l), respectively, after 4 weeks of phytosterol-enriched-chocolate treatment. Plasma HDL-cholesterol and triacylglycerol levels were not affected. Consumption of phytosterol-enriched chocolates significantly increased plasma lathosterol concentration (+20.7 %), reflecting an increased endogenous cholesterol synthesis in response to phytosterol-induced decreased intestinal cholesterol absorption. Furthermore, the chocolates enriched with phytosterols significantly increased both plasma sitosterol (+95.8 %) and campesterol (+64.1 %) levels, compared with the placebo chocolate group. However, the absolute values of plasma sitosterol and campesterol remained within the normal range, that is, below 10 mg/l. The chocolates with phytosterols were palatable and induced no clinical or biochemical side effects. These findings indicate that dietary chocolate enriched with tall oil-derived phytosterols (1.8 g/d) is effective in lowering blood total and LDL-cholesterol levels in subjects with mild hypercholesterolaemia and thus may be helpful in reducing the risk of CHD in these individuals.

Efficacy and safety of statin therapy in children with familial hypercholesterolemia: a randomized, double-blind, placebo-controlled trial with simvastatin

BACKGROUND

A multicenter, randomized, double-blind, placebo-controlled study was conducted to evaluate LDL cholesterol-lowering efficacy, overall safety, and tolerability and the influence on growth and pubertal development of simvastatin in a large cohort of boys and girls with heterozygous familial hypercholesterolemia (heFH).

METHODS AND RESULTS

A total of 173 heFH children (98 boys and 75 girls) were included in this study. After a 4-week diet/placebo run-in period, children with heFH were randomized to either simvastatin or placebo in a ratio of 3:2. Simvastatin was started at 10 mg/d and titrated at 8-week intervals to 20 and then 40 mg/d. During a 24-week extension period, the patients continued to receive simvastatin (40 mg) or placebo according to their assignment. After 48 weeks of simvastatin therapy, there were significant reductions of LDL cholesterol (-41%), total cholesterol (-31%), apolipoprotein B (-34%), VLDL cholesterol (-21%), and triglyceride (-9%) levels. HDL cholesterol and apolipoprotein A-I levels were increased by 3.3% and 10.4%, respectively (not significant). No safety issues became evident. Except for small decreases in dehydroepiandrosterone sulfate compared with placebo, there were no significant changes from baseline in adrenal, gonadal, and pituitary hormones in either treatment group.

CONCLUSIONS

Simvastatin significantly reduced LDL cholesterol, total cholesterol, triglyceride, VLDL cholesterol, and apolipoprotein B levels and was well tolerated in children with heFH. There was no evidence of any adverse effect of simvastatin on growth and pubertal development. Therefore, simvastatin at doses up to 40 mg is a well-tolerated and effective therapy for heFH children.

Identification and functional analysis of a naturally occurring E89K mutation in the ABCA1 gene of the WHAM chicken

The Wisconsin hypoalpha mutant (WHAM) chicken has a >90% reduction in plasma HDL due to hypercatabolism by the kidney of lipid-poor apoA-I. The WHAM chickens have a recessive white skin phenotype caused by a single-gene mutation that maps to the chicken Z-chromosome. This corresponds to human 9q31.1, a chromosomal segment that contains the ATP-binding cassette protein-1 (ABCA1) gene, which is mutated in Tangier Disease and familial hypoalphalipoproteinemia. Complete sequencing of the WHAM ABCA1 cDNA identified a missense mutation near the N-terminus of the protein (E89K). The substitution of this evolutionary conserved glutamate residue for lysine in the mouse ABCA1 transporter leads to complete loss of function, resulting principally from defective intracellular trafficking and very little ABCA1 reaching the plasma membrane. The WHAM chicken is a naturally occurring animal model for Tangier Disease.

Baseline lipid values partly determine the response to high-dose simvastatin in patients with familial hypercholesterolemia. The examination of probands and relatives in Statin studies with familial hypercholesterolemia (ExPRESS FH)

Statins decrease low-density lipoprotein cholesterol (LDL-C), and additionally, reduce triglycerides (TG) and raise high-density lipoprotein cholesterol (HDL-C) levels. This study evaluated the frequency of abnormal TG and HDL-C levels in patients with classical familial hypercholesterolemia (FH) and assessed therapeutic response at different baseline levels of these lipoproteins after 1 year of statin therapy. A total of 508 FH patients were included and mean LDL-C levels (8.37+/-2.12 mmol l(-1)) were severely elevated. After a washout period of 6 weeks, all patients started monotherapy with 80 mg simvastatin. Remarkably, LDL-C reduction was dependent on baseline LDL-C levels ranging from 51.1 to 45.5% in the top versus the bottom third of the LDL-C distribution. Unexpected in FH, elevated baseline TG levels were seen in 30% and low HDL-C levels in 15% of all patients. Also, changes in these lipoproteins were dependent on baseline levels; TG reduction was 40.7 versus 22.2% in patients with elevated versus normal levels, while HDL-C increase was 29.1 versus 11.4% in patients with low versus normal HDL-C levels. In conclusion, FH patients with the worst lipoprotein profile showed the greatest benefit from high-dose simvastatin treatment, since changes in these parameters were partly determined by baseline lipid levels.

Long term efficacy and safety of atorvastatin in the treatment of severe type III and combined dyslipidaemia

BACKGROUND

Fibric acid derivatives and HMG-CoA reductase inhibitors are effective in combination for treating patients with familial dysbetalipoproteinaemia and severe combined dyslipidaemia, but combination therapy affects compliance and increases the risk of side effects.

AIM

To evaluate the efficacy and safety of monotherapy with atorvastatin, an HMG-CoA reductase inhibitor with superior efficacy in lowering low density lipoprotein cholesterol and triglyceride concentrations, in patients with dysbetalipoproteinaemia and severe combined dyslipidaemia.

METHODS

Atorvastatin was tested as single drug treatment in 36 patients with familial dysbetalipoproteinaemia and 23 patients with severe combined dyslipidaemia.

RESULTS

After 40 weeks of 40 mg atorvastatin treatment decreases in total cholesterol, triglycerides, and apolipoprotein B of 40%, 43%, and 41%, respectively, were observed in the combined dyslipidaemia group, and of 46%, 40%, and 43% in the dysbetalipoproteinaemic patients. Target concentrations of total cholesterol (< 5 mmol/l) were reached by 63% of the patients, and target concentrations of triglycerides (< 3.0 mmol/l) by 66%. Treatment with atorvastatin was well tolerated and no serious side effects were reported.

CONCLUSIONS

Atorvastatin is very effective as monotherapy in the treatment of familial dysbetalipoproteinaemia and severe combined dyslipidaemia.

Frequent mutation in the ABCC6 gene (R1141X) is associated with a strong increase in the prevalence of coronary artery disease

BACKGROUND

Pseudoxanthoma elasticum (PXE) is an inborn disorder of the connective tissue with specific skin, ocular, and cardiovascular disease (CVD) manifestations. Recently, we and others have identified mutations in the gene coding for the ABCC6 transporter in PXE patients with ocular and skin involvement. In the Netherlands, as in the rest of Europe, a particular premature truncation variant ABCC6 (R1141X) was found in a large cohort of PXE patients. Given the association between CVD and PXE, we hypothesized that heterozygosity of this ABCC6 mutation could also confer an increased risk for CVD.

METHODS AND RESULTS

To assess the relationship between the frequent R1141X mutation in the ABCC6 gene and the prevalence of premature coronary artery disease (CAD), we conducted a case-control study of 441 patients under the age of 50 years who had definite CAD and 1057 age- and sex-matched population-based controls who were free of coronary disease. Strikingly, the prevalence of the R1141X mutation was 4.2 times higher among patients than among controls (3.2% versus 0.8%; P<0.001). Consequently, among subjects with the R1141X mutation, the odds ratio for a coronary event was 4.23 (95% CI: 1.76 to 10.20, P= 0.001).

CONCLUSION

The presence of the R1141X mutation in the ABCC6 gene is associated with a sharply increased risk of premature CAD.

Elevated remnant-like particles in heterozygous familial hypercholesterolemia and response to statin therapy

BACKGROUND

Remnant lipoproteins (RLP-C) are considered important in atherogenesis. Hence, this study was designed to assess RLP-C levels and the effect of statin therapy in patients with familial hypercholesterolemia (FH). Elevated RLP-C levels have been associated with the presence and progression of atherosclerotic disease, and their presence in FH patients has been proposed but never established in a large cohort, nor has their response to statin therapy been confirmed.

METHODS AND RESULTS

FH patients were recruited from 36 lipid clinics. After a washout period of 6 weeks, all patients were started on monotherapy with 80 mg of simvastatin for 2 years. RLP-C levels were assessed by an immune-separation assay. In 327 FH patients, RLP-C measurements could be performed before and after treatment. Mean total cholesterol (10.55+/-2.17 mmol/L), mean LDL cholesterol (8.40+/-2.13 mmol/L), and median RLP-C (0.47 mmol/L) levels were all severely elevated at baseline. After treatment, RLP-C levels were reduced by 49% (0.24 mmol/L; P<0.0001). Even patients with normal triglyceride levels had elevated RLP-C levels at baseline, and those with high RLP-C levels were generally characterized by a very atherogenic lipoprotein profile.

CONCLUSIONS

Baseline RLP-C levels are severely elevated in FH patients and are reduced by simvastatin but do not return to normal. These elevated RLP-C levels could be the consequence of impaired function of the LDL receptor in FH. RLP-C levels in FH contribute to an atherogenic lipoprotein profile and could identify patients who require additional treatment.

Genetic polymorphisms: importance for response to HMG-CoA reductase inhibitors

Coronary artery disease is among the leading causes of death worldwide. Clinical trials show a protective effect of statins against the sequelae of coronary artery disease. The mean risk reductions for subjects using statins compared with placebo found in these trials is about 30%. These are average reductions for all patients included in the trials. Important factors in interpreting the variability in the outcome of drug therapy include the patient's health profile, prognosis, disease severity, quality of drug prescribing, compliance with prescribed pharmacotherapy and the genetic profile of the patient. This review aims to give an overview of the known polymorphisms (Cholesteryl Ester Transfer Protein polymorphism, Stromelysin-1 polymorphism, -455G/A and TaqI polymorphisms of the beta-fibrinogen gene, apoE4, Asp(9)Asn mutation in the lipoprotein lipase gene, the -514 CT polymorphism in the hepatic lipase gene and the ACE deletion type gene) that have an influence on the effects of statins in the general population. The expectation is that in the future a subject's genotype may determine whether he will be treated with statins or not. Determining the genotype will not deny therapy to a subject, but will help in deciding the therapy that will suit the patient best.

Lipoprotein lipase deficiency--rare or common?

Cardiovascular disease is the number one killer in the world. Prevention is the most promising treatment. However, predicting an individual's risk for cardiovascular disease is quite complicated, involving the complex interaction of a plethora of environmental and genetic factors. Many of the environmental factors can be suppressed by adopting a healthier lifestyle; dietary modifications, increasing exercise, not smoking, etc. Understanding the role of many genetic factors remains somewhat elusive. Genes involved in lipid metabolism are a focus of this ongoing genetic research. There is substantial evidence to suggest that one such gene, lipoprotein lipase (LPL), has a profound influence on triglyceride and high-density lipoprotein (HDL) cholesterol levels in the blood; both independent risk factors for cardiovascular disease. Although a direct association has not be found, mutations resulting in LPL deficiencies have been linked to unfavorable lipid profiles. Although homozygous or compound heterozygous mutations in LPL resulting in complete loss of catalytically activity are rare, heterozygous mutations are quite common worldwide. It is when these moderate mutations are compounded by other risk factors, that a significant increase in risk of cardiovascular disease is observed. Therefore, it may be that these common deficiencies in LPL are an underlying cause for many incidents of cardiovascular disease.

Family history of cardiovascular events and endothelial dysfunction in children with familial hypercholesterolemia

OBJECTIVES

in patients with familial hypercholesterolemia (FH), the propensity towards atherosclerosis may vary considerably. In the general population, a positive family history is associated with an increased risk for cardiovascular events. Since endothelial dysfunction is predictive for future cardiovascular events, we evaluated whether FH-children with a positive family history of premature cardiovascular disease have more pronounced endothelial dysfunction compared to children with a negative family history.

STUDY DESIGN

50 FH children, 10-18 years, participated in this study. Thirty-one children had a positive family history for cardiovascular events (fh(+)) and 19 children had no events in the family (fh(-)). Nineteen matched siblings participated as controls. Endothelial function was assessed by testing the flow mediated dilatation (FMD) of the brachial artery.

RESULTS

baseline characteristics were comparable for fh(+), fh(-) and controls. Lipid levels were significantly higher in FH children. In FH, FMD was impaired compared to controls (11.7+/-4.4 vs. 15.6+/-6.8%, P<0.03). In addition, FMD was significantly lower in fh(+) compared to fh(-) (10.7+/-9.9 vs. 13.3+/-4.6%, P<0.05).

CONCLUSION

In FH-children, endothelial function is impaired compared to matched controls. This impairment is most pronounced in FH children with a positive family history of premature cardiovascular disease.