A review on the diagnosis, natural history, and treatment of familial hypercholesterolaemia

Molecular genetic testing for familial hypercholesterolemia in the Netherlands: a stepwise screening strategy enhances the mutation detection rate

Familial hypercholesterolemia (FH) has been identified as a major risk factor for coronary vascular disease and is associated with mutations in the low-density liporotein receptor (LDLR) and apolipoprotein B (APOB) gene. The molecular basis of FH in the Dutch population is well understood. Approximately 160 different LDLR and APOB gene defects have been identified with a panel of 9 LDLR gene and 1 APOB gene frequently occurring mutations accounting for approximately 30% of all clinically diagnosed FH cases. As molecular diagnosis of FH is becoming increasingly widely applied, a variety of mutation detection rates is reported, ranging from as low as 30% and up to 80%. This variability appears to depend on the clinical criteria applied to identify patients with FH and on the strategies and methodologies used for mutation screening. In this study we describe the application of a stepwise screening approach, combining different methodologies, to detect mutations of the LDLR gene and APOB gene in 1465 patients with FH. A mutation was found in approximately 44% of the patients, which demonstrates that this is an effective strategy for the molecular diagnosis of FH.

Premature cardiovascular disease in young women with heterozygous familial hypercholesterolemia

Heterozygous familial hypercholesterolemia is associated with elevated low-density lipoprotein cholesterol levels and the development of premature cardiovascular disease. Despite this general statement, data regarding the incidence of cardiovascular disease in young women with familial hypercholesterolemia are lacking. In this review, information of age-specific incidence, risk factors and therapeutic avenues in women with heterozygous familial hypercholesterolemia are discussed.

Perceived vulnerability to heart disease in patients with familial hypercholesterolemia: a qualitative interview study

PURPOSE

Knowledge about the ways patients perceive their vulnerability to disease is important for communication with patients about risk and preventive health measures. This interview study aimed to explore how patients with a diagnosis of heterozygous familial hypercholesterolemia understand and perceive their vulnerability to coronary heart disease.

METHODS

We did a qualitative study of 40 patients with familial hypercholesterolemia who were recruited through a lipid clinic in Norway. We elicited participants' perceptions about their vulnerability to heart disease in semistructured interviews. Data were analyzed by systematic text condensation inspired by Giorgi's phenomenological method.

RESULTS

We found that participants negotiated a personal and dynamic sense of vulnerability to coronary heart disease that was grounded in notions of their genetic and inherited risk. Participants developed a sense of their vulnerability in a 2-step process. First, they consulted their family history to assess their genetic and inherited risk, and for many a certain age determined when they could expect to develop symptoms of coronary heart disease. Second, they negotiated a personal sense of vulnerability by comparing themselves with their family members. In these comparisons, they accounted for individual factors, such as sex, cholesterol levels, use of lipid-lowering medications, and lifestyle. Participants' personal sense of vulnerability to heart disease could shift dynamically as a result of changes in situational factors, such as cardiac events in the family, illness experiences, or becoming a parent.

CONCLUSIONS

Patients with a diagnosis of familial hypercholesterolemia negotiate a personal and dynamic sense of vulnerability to coronary heart disease that is grounded in their understanding of their genetic and inherited risk. Doctors should elicit patients' understanding of their family history and their personal vulnerability to individualize clinical management.

Heterozygous familial hypercholesterolemia: an underrecognized cause of early cardiovascular disease

Heterozygous familial hypercholesterolemia (HeFH) is a monogenic disorder that affects about 1 in 500 people, with a higher prevalence in certain subpopulations such as people of Quebecois, Christian Lebanese and Dutch South Afrikaner extraction. HeFH is characterized by cholesterol deposits affecting the corneas, eyelids and extensor tendons; elevated plasma concentrations of low-density lipoprotein (LDL) cholesterol; and accelerated vascular disease, especially coronary artery disease (CAD). Although HeFH is genetically heterogeneous, it is most often caused by heterozygous mutations in the LDLR gene encoding the LDL receptor. We describe a man who was diagnosed with HeFH after he had a myocardial infarction at 33 years of age. By DNA sequence analysis, he was found to have a heterozygous splicing mutation in his LDLR gene. This discovery expanded the growing mutational spectrum in patients with HeFH in Ontario. Given that HeFH is a treatable cause of early vascular disease, it is important that this condition be recognized, diagnosed and treated in affected patients; but as yet, there is no consensus on the best approach. Diagnostic criteria based on family history and clinical presentation have been proposed for patients with suspected HeFH. Biochemical or molecular screening might be considered to detect new cases of HeFH in populations with a relatively high HeFH prevalence and a relatively small number of possible causative mutations. So far, however, the most cost-effective and efficient systematic strategy to detect previously undiagnosed cases of HeFH is still cascade testing: clinical and biochemical screening of close relatives of the proband patient diagnosed with HeFH. Pharmacologic treatment of HeFH is cost-effective.

Genetic heterogeneity of autosomal dominant hypercholesterolemia in Mexico

BACKGROUND

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) are relatively common lipid disorders caused by mutations of the low-density lipoprotein receptor (LDLR) and apolipoprotein B (apoB) genes, respectively. A third locus on chromosome 1p34.1-p32 was recently linked to FH and the responsible gene has been identified [protein convertase subtilisin/kexin type 9 (PCSK9)].

METHODS

We assessed the contribution of the LDLR, apoB, and PCSK9 genes as cause of FH in Mexico. Forty six unrelated probands, as well as 68 affected and 60 healthy relatives, were included.

RESULTS

All index cases were diagnosed as having heterozygous autosomal dominant FH. Seventeen of the 46 index cases had LDLR gene mutations, four of which were novel (Fs92ter108, C268R, Q718X, and Fs736ter743); and only one patient had an apoB mutation (R3500Q). We sequenced the PCSK9 gene in the remainder of the 28 probands with no identified LDLR or APOB gene defects; however, no PCSK9 mutations were found, including one large kindred with positive linkage to the 1p34.1-32 locus (multipoint LOD score of 3.3) and two small pedigrees. Linkage was excluded from these three loci in at least four kindreds suggesting that other yet uncharacterized genes are involved.

CONCLUSIONS

Our results underline substantial genetic heterogeneity for FH in the Mexican population.

Management of Dyslipidemia in Special Populations

Dyslipidemia is a significant contributor to morbidity and mortality in the industrialized world. Because it is often intertwined with other medical conditions, its management is becoming progressively more complex. Populations that pose a particular challenge to clinicians include diabetic patients, children and adolescents, elderly persons, transplant patients, patients with the human immunodeficiency virus, and patients with chronic kidney disease. When establishing lipid goals, it is imperative to have a thorough understanding of the evidence, or lack thereof, supporting the use of lipid-lowering agents among these patients. To maximize the benefits and minimize the risks of pharmacological intervention, clinicians must consider not only the unique alterations in the lipid profile of the aforementioned populations but also individual changes in patients' pharmacokinetic and pharmacodynamic parameters, as well as the potential for drug-drug and drug-disease interactions.

Postprandial lipemia in postmenopausal women with high fasting high-density lipoprotein cholesterol

BACKGROUND

Several groups of patients at high risk for cardiovascular disease have been found to show an exaggerated postprandial hypertriglyceridemia. Postprandial lipemia (PPL) therefore has been implicated as a potential additional risk factor that has been evading us. The purpose of this study was to test the effect of high fasting high-density lipoprotein cholesterol (HDL-C) levels on PPL in postmenopausal females.

METHODS

Oral fat tolerance test, as quantified by the areas under the curve (AUC) of triglyceride (TG) levels, was given to 3 groups: normal postmenopausal females (control), postmenopausal females with exceptionally high HDL-C and a familial history of longevity (longevity syndrome), and postmenopausal females that were heterozygotes of familial hypercholesterolemia (hFH) with exceptionally high HDL-C.

RESULTS

The PPL was not different between the control and longevity syndrome groups but was significantly higher in the hFH group; AUC (SD), in mg/dl/h; 749 (195), 882 (278) and 1244 (497) respectively, p=0.002. In linear regression analysis only fasting TG levels were a significant predictor of the AUC (Coefficient B = 11.779, p < 0.001).

CONCLUSIONS

In subjects with longevity syndrome the PPL is similar to controls, which means that high fasting HDL-C has not any beneficial influence on PPL. The fasting TG concentration is the main determinant of PPL. Furthermore, postmenopausal females with hFH have higher TG response postprandially, even in the case of high fasting HDL-C. Whether there is a threshold below or above, where HDL-C becomes a significant independent determinant of PPL is a question to be answered by future research.

Women at risk of coronary heart disease experience barriers to diagnosis and treatment: a qualitative interview study

OBJECTIVE

To explore barriers in the health service to diagnosis and treatment experienced by women at increased risk of coronary heart disease (CHD).

DESIGN

Qualitative study using semi-structured interviews.

SETTING

Norway.

SUBJECTS

Twenty women diagnosed with heterozygous familial hypercholesterolemia (FH) recruited through a lipid clinic.

RESULTS

Women reported three specific barriers related to diagnosis and treatment of CHD. They had to struggle to take a cholesterol test; they experienced that their risk was being downplayed by doctors; and that their symptoms of CHD were misinterpreted when they consulted doctors for evaluation and treatment.

CONCLUSION

Stereotyping CHD as a man's disease may result in barriers to diagnosis and treatment for women. Doctors should ask the patient about the family history of CHD if a concern about heart disease is on the patient's agenda.

Severe supravalvar aortic stenosis in familial homozygous hypercholesterolemia

Familial homozygous hypercholesterolemia is a rare disease with diverse clinical presentations. Patients often present with cutaneous xanthomas, particularly in the Achilles' tendon. They may have significant cardiovascular involvement, including premature atherosclerotic coronary artery disease and valvar and supravalvar aortic stenosis. Standard therapy includes diet modulation, pharmacotherapy, and lipid apheresis. Rarely, patients require surgical intervention for coronary artery bypass grafting and/or relief of the aortic stenosis. We present the case of a patient with severe progressive supravalvar aortic stenosis that ultimately required surgical resection despite aggressive medical therapy.

Increased inflammatory markers in children with familial hypercholesterolaemia

BACKGROUND

While data are abundant on increased levels of inflammatory markers in adult patients with hypercholesterolaemia, such data in children are limited. Therefore, we sought to investigate the degree and character of inflammation in children with heterozygous familial hypercholesterolaemia (FH) by measuring levels of neopterin, high-sensitivity C-reactive protein (hsCRP), and soluble CD40 ligand (sCD40L).

MATERIALS AND METHODS

In the present study, we compared the concentration of inflammatory markers in children suffering from heterozygous FH (n = 207) with those in unaffected siblings (n = 84). Furthermore, we investigated the effect of 2-year treatment with pravastatin (20-40 mg qd) or placebo on plasma levels of those markers.

RESULTS

Our main finding was that serum levels of neopterin and hsCRP were significantly higher in FH children compared with healthy siblings, whereas sCD40L was not. Body mass index and high-density lipoprotein cholesterol levels were significant independent predictors of hsCRP and neopterin. Furthermore, pravastatin therapy decreased neopterin, but not hsCRP and sCD40L, in the FH children, but these changes were not different from the placebo group.

CONCLUSION

These findings indicate low-grade monocyte/macrophage hyperactivity in the early stages of atherogenesis, but our findings also suggest that inflammation as well as anti-inflammatory effects of statins are less prominent features of atherosclerosis in FH children than in FH adults.

Chemokines in Children With Heterozygous Familiar Hypercholesterolemia

OBJECTIVE

Increasing data support the involvement of chemokines in atherogenesis. However, although several studies have shown increased chemokine levels in adult patients, the literature is virtually devoid of data on chemokines in children with hypercholesterolemia.

METHODS AND RESULTS

We examined the gene expression of chemokines in peripheral blood mononuclear cells (PBMCs) from clinically healthy children with and without heterozygous familial hypercholesterolemia (FH). Our main findings were: (1) compared with healthy controls, PBMCs from FH children showed significantly higher mRNA levels of RANTES, but not of the other examined chemokines; (2) an opposite pattern was seen in adult FH subjects, with markedly enhanced expression of macrophage inflammatory peptide-1alpha, but not of RANTES; (3) this increased gene expression of RANTES in PBMCs from FH children seemed to reflect enhanced RANTES expression in monocytes but not in T cells; (4) FH children also had raised serum levels of neopterin, additionally suggesting monocyte/macrophage activation in these children; and (5) PBMCs from both FH children and controls showed enhanced release of interleukin 8 on RANTES stimulation in vitro.

CONCLUSIONS

Our findings support a role of inflammation also in the early stages of atherogenesis possibly involving monocyte-derived RANTES as an important mediator.

Direct Adsorption of Lipoproteins from Whole Blood by Direct Adsorption of Lipoprotein Apheresis: First Experience in Two Hypercholesterolemic Children

Low density lipoprotein (LDL) cholesterol apheresis, combined with lipid lowering drugs, provides a safe and effective means of improving the prognosis of patients with homozygote familial hypercholesterolemia, especially if started before the age of seven. The direct adsorption of lipoprotein (DALI) is the first extracorporeal low density lipoprotein removing system compatible with whole blood. The purpose of the present study was to clarify the efficacy and safety of DALI in children with homozygous familial hypercholesterolemia. Two boys, aged 9 and 15 years, with familial hypercholesterolemia, who were highly resistant to dietary regimes and to drug therapy, were treated with the low density lipoprotein adsorber DALI apheresis once every 2 weeks for 24 weeks. The treated blood volumes for each procedure were 2911 mL (493 +/- SD) and 5982 mL (1129 +/- SD), respectively. In our patients, the acute mean LDL cholesterol reductions were 44.7 +/- 8.9% and 58.8 +/- 4.5%. The corresponding reductions were 42.5 +/- 7.2% and 56 +/- 4.3% for total cholesterol, and 46.5 +/- 17.1% and 55 +/- 7.5% for very low density lipoprotein cholesterol (VLDL-C). There were insignificant losses of high density lipoprotein (12.2 +/- 5.7%, 8.3 +/- 5.5%). Treatment was well tolerated in general, and neither patient suffered from irreversible or long-lasting adverse effects. Our experience with DALI apheresis is encouraging. The present report is the first on the use of DALI in children. Based on this short-term evaluation we think that DALI might be safe and effective in children with homozygote familial hypercholesterolemia, however further evaluation of long-term effects is needed.

Familial hypercholesterolaemia commonly presents with Achilles tenosynovitis

BACKGROUND

Patients with heterozygous familial hypercholesterolaemia (HeFH) develop tendon xanthomata (TX), most commonly in their Achilles tendons. Even before tendons are chronically enlarged, tenosynovitis may occur and medical advice be sought. Untreated HeFH carries a high risk of premature coronary heart disease, which can be ameliorated by early diagnosis.

OBJECTIVE

To determine the prevalence of episodes of Achilles tendon pain in HeFH before its diagnosis.

METHODS

Patients with definite HeFH (Simon Broome criteria) attending a lipid clinic were identified. They completed a questionnaire asking about symptoms relating to their Achilles tendons. Unaffected spouses or cohabiting partners served as controls.

RESULTS

133 patients (47% men) and 87 controls (51% men) participated. TX had been recognised by the referring physicians in <5% of cases. However, 62 (46.6% (95% confidence interval (CI) 38.1 to 55.1)) patients had experienced one or more episodes of pain in one or both Achilles tendons lasting >3 days, whereas only 6 (6.9% (1.6 to 12.2)) controls had done so (difference p<0.001; likelihood ratio 6.75). Typically, in the patients with HeFH the pain lasted 4 days (median). It was described as severe or very severe in 24/62 (38.7% (30.4 to 47.0)) patients with HeFH, but never more than moderate in controls. 35 (26.3% (18.8 to 33.8)) patients with HeFH had consulted a doctor about Achilles tendon pain, but in no case had this led to a diagnosis of HeFH. None of the controls had consulted a doctor.

CONCLUSIONS

Measurement of serum cholesterol in patients presenting with painful Achilles tendon could lead to early diagnosis of HeFH.

Risks and benefits of population-based genetic testing for Mendelian subsets of common diseases were examined using the example of colorectal cancer risk

OBJECTIVE

Genetic testing for adult-onset, common diseases is becoming more commonplace in clinical medicine. We modeled the proportions of hypothetic populations that would potentially benefit or suffer harm from widespread predisposition testing.

METHODS

Using the traditional two-by-two table from the discipline of epidemiology, we modeled three hypothetic populations using the example of genetic testing for hereditary colorectal cancer in three groups: the general population, a genetically increased-risk population, and a population at increased risk due to nongenetic factors.

RESULTS

We demonstrate that the potential benefits are increased and risks are reduced when testing is limited to those at increased genetic risk when compared with testing in the general population. Where disease incidence is increased due to nongenetic factors, genetic testing has the potential to detract from the detection and reduction of other potentially important risk factors.

CONCLUSION

While targeted testing can benefit those truly at increased risk, broadly applied genetic testing can do more harm than good.

Tendon Xanthomas in Familial Hypercholesterolemia Are Associated With Cardiovascular Risk Independently of the Low-Density Lipoprotein Receptor Gene Mutation

OBJECTIVE

To investigate the significance of tendon xanthomas (TX) in heterozygous subjects with familial hypercholesterolemia (hFH).

METHODS AND RESULTS

951 men and women with genetic diagnosis of hFH were studied, of whom 278 (29.2%) presented TX. TX frequency increased with age from 6.9% in subjects 20 to 30 years to 38.3% at 51 to 60 years, with a decrease in those older than 60 years. Total and low-density lipoprotein (LDL) cholesterol were higher in TX+ than in TX- subjects (439.0+/-78.5 mg/dL and 363.1+/-76.5 mg/dL versus 400.6+/-73.4 and 323.3+/-71.0, respectively; P=0.001). High-density lipoprotein (HDL) cholesterol was lower in TX+ than in TX- subjects (50.4+/-15.0 mg/dL versus 53.1+/-14.8 mg/dL; P=0.005). Lp(a), apolipoprotein E genotype, and type of LDL receptor gene mutation showed no differences between groups. 102 TX+ reported premature cardiovascular disease (CVD) (36.7%) versus 93 TX- (13.8%) (P=0.001). The relative odds for premature CVD were higher in women (4.49 versus 2.26), and increased in hFH younger than 51 years to 3.60 (95% CI, 1.703 to 7.608) in men and to 17.1 (95% CI, 2.697 to 108.920) in women. In the multivariate analysis, age, male sex, LDL cholesterol, and hypertension showed significant positive association with TX, whereas body mass index showed negative association with TX.

CONCLUSIONS

TX are associated with cardiovascular risk factors and higher CVD, indicating that their detection indicates the need for more aggressive lipid-lowering intervention.

The use of Achilles tendon sonography to distinguish familial hypercholesterolemia from other genetic dyslipidemias

OBJECTIVE

Achilles tendon (AT) xanthomas, specific for familial hypercholesterolemia (FH), may be clinically undetectable. We assessed the usefulness of AT sonography in the diagnosis of FH.

METHODS AND RESULTS

Sonographic AT characteristics were evaluated in 127 subjects with FH (81 genetically ascertained), 84 familial combined hyperlipidemia, 79 polygenic hypercholesterolemia, and 88 normolipidemic controls. Abnormal echostructure (sonographic xanthoma) was noted only in FH. AT thickness was higher (P<0.001) in FH men and women compared with all of the other groups and, in FH mutation carriers but not in others, correlated positively with low-density lipoprotein cholesterol (r=0.345; P<0.001) and negatively with high-density lipoprotein cholesterol (r=-0.265, P=0.015). Thickness thresholds for the diagnosis of FH with specificity >80%, as were derived from receiver operating curves, were 5.3 and 5.7 mm in men < and >45 years, and 4.8 and 4.9 mm in women < and >50 years, respectively. In FH mutation carriers, sonographic findings increased the clinical diagnosis of xanthomas from 35 (43%) to 55 (68%). Using thresholds in validation sets of 70 genetically identified FH and 54 dyslipidemic non-FH correctly classified 80% and 88%, respectively.

CONCLUSIONS

Sonographic AT characteristics are normal in non-FH dyslipidemias. Identification of suspected FH by ultrasound using sex- and age-specific AT thickness thresholds is recommended.

Implementation of cascade testing for the detection of familial hypercholesterolaemia

PURPOSE OF REVIEW

Cascade testing is an important method for identifying individuals at risk of a genetic condition. Recent advances in its application to familial hypercholesterolaemia are reviewed to identify potential problems impeding its application and the extent to which current data address these concerns.

RECENT FINDINGS

Different paradigms for cascade testing are being applied in national programmes. Current data demonstrates cost-effectiveness, and an increased uptake of preventive measures. The relationship between molecular and clinical diagnostic methods is discussed. Psychological impacts of a diagnosis of familial hypercholesterolaemia are in line with the risks associated with the disorder. The efficacy of statins in improving vascular function of children with familial hypercholesterolaemia has been demonstrated, but extensive safety data are lacking. Ethical arguments support that it is equally acceptable for relatives of familial hypercholesterolaemia patients to be contacted by healthcare workers as by family members, but the former is likely to be more efficient. Concerns about increased life insurance premiums are valid but insurance companies are assessing risk realistically, so this should not be a barrier to cascade testing.

SUMMARY

Current data support the implementation of cascade testing for familial hypercholesterolaemia as being feasible and cost-effective, but national implementation is limited to a small number of countries. Funding and the infrastructure to support it may be the major stumbling blocks in implementing this technique in many countries. Concerns about the ethics of carrying out cascade testing, and the potential psychological damage of DNA testing, appear to have been largely addressed for familial hypercholesterolaemia.

The relationship of molecular genetic to clinical diagnosis of familial hypercholesterolemia in a Danish population

The genes encoding the LDL receptor and apoB were screened for mutations associated with familial hypercholesterolemia (FH) in 408 patients referred to the Lipid Clinic in 1995-2003. The study aimed at testing the ability of three different sets of clinical criteria to predict the results of molecular genetic analysis, and secondly test whether population-based age- and sex-specific percentiles of LDL-cholesterol offer useful supplemental information in the selection of patients for molecular genetic analysis. The patients were retrospectively categorised according to Simon Broome Register Group criteria, Make Early Diagnosis to Prevent Early Death criteria (MEDPED) and the Dutch Lipid Clinic Network criteria, and the distribution of patients was compared to the results of the molecular genetic analysis. The study illustrates a classical dilemma. Mutation detection rates (and specificities) are high only if sensitivity is very low and vice versa: to find most mutation carriers, even patients with only possible FH must be examined by molecular genetic testing leading to mutation detection rates as low as 30-40%.

The influence of natural menopause on postprandial lipemia in heterozygotes for familial hypercholesterolemia

BACKGROUND

Heterozygous familial hypercholesterolemia (hFH) is a genetic disease that leads to premature atherosclerosis. Natural menopause leads to an adverse lipid profile and an enhanced risk of coronary heart disease (CHD). Raised plasma triglyceride (TG) levels also contribute to the risk of vascular events. The aim of this study was to evaluate the postprandial TG levels (after a standardized fatty meal) in premenopausal and postmenopausal women with hFH.

METHODS

Thirty-three Greek women with hFH were divided into the premenopausal group--n = 16, mean age 34(SD = 7), mean total cholesterol = 330(30) mg/dl--and the postmenopausal group--n = 17, mean age 62(5), mean total cholesterol = 346(63) mg/dl. Plasma TG concentrations were measured before and 2, 4, 6, and 8 hours after a standardized fat load. A value of >219 mg/dl (2.5 mmol/L) was taken as an abnormal response to the fat load, according to our previous studies.

RESULTS

Postmenopausal women had higher TG levels at 2 (p = 0.001), 4 (p = 0.003), 6 (p = 0.003), and 8 hours (p = 0.005) after the fatty meal compared to premenopausal women. Forty-one percent of postmenopausal hFH women had abnormal TG response (hFH-A) after a fatty meal, and such women had higher fasting TG levels than postmenopausal hFH women with a normal response to the fatty meal (hFH-N) (p = 0.0014).

CONCLUSIONS

Women with hFH tend to have an abnormal TG response to a fatty meal after the menopause. Fasting TG levels may be able to predict the abnormal response to a fatty meal.

Non-high density lipoprotein cholesterol is the best discriminator of myocardial infarction in young individuals

BACKGROUND

Several studies have shown that non-high density lipoprotein (HDL) cholesterol is a strong and independent predictor of cardiovascular events. We investigated whether non-HDL cholesterol can discriminate young individuals with myocardial infarction (MI) from age- and sex-matched controls.

METHODS

We conducted a case-control study which included 100 consecutive patients who had survived their first MI before the age of 36 years and 100 age- and sex-matched healthy controls without a history of cardiovascular disease. Cardiovascular risk factors were reported and fasting lipids and apolipoproteins were measured.

RESULTS

Patients with premature MI had significantly higher levels of total cholesterol, low density lipoprotein cholesterol, triglycerides, apolipoprotein B, lipoprotein (a) and non-HDL cholesterol and significantly lower levels of HDL cholesterol and apolipoprotein A. Multivariate logistic regression analysis showed that for every 10mg/dl increase in non-HDL cholesterol levels, the odds of having a MI were increased by 34% after controlling for age, sex, body mass index, presence of hypertension, diabetes and smoking habits. Moreover, participants in the highest tertile of non-HDL cholesterol levels had 28-fold higher odds for having a MI (95% confidence interval, 7.5-104.1), compared to those in the lowest tertile. Finally, discriminant analysis showed that non-HDL cholesterol (lambda-Wilks=0.68) was the strongest discriminator for MI among all studied risk factors while smoking (lambda-Wilks=0.80) was the strongest discriminator for MI among the non-lipid risk factors.

CONCLUSIONS

Our study suggests that among conventional lipid and non-lipid risk factors non-HDL cholesterol is the best discriminator to predict the presence of MI in individuals under the age of 36 years.

Comparison of ezetimibe plus simvastatin versus simvastatin monotherapy on atherosclerosis progression in familial hypercholesterolemia. Design and rationale of the Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression (ENHANCE) trial

BACKGROUND

Lipid lowering through statin therapy significantly reduces the risk of cardiovascular events. The ENHANCE study is an international 2-year, randomized, double-blind, controlled trial designed to test the hypothesis that treatment of hypercholesterolemia by use of 2 complementary agents, ezetimibe (a specific cholesterol absorption inhibitor) and simvastatin (a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor), will result in larger beneficial effects on carotid artery intima-media thickness (CA IMT) than simvastatin monotherapy.

METHODS

The study will recruit 725 men and women with heterozygous familial hypercholesterolemia. After a placebo washout period, participants are randomized to receive daily administration of either simvastatin 80 mg and ezetimibe 10 mg or simvastatin 80 mg and placebo. The ENHANCE trial uses novel state-of-the-art single-frame digital image acquisition and rigorous quality assurance and control.

RESULTS

The primary end point is mean change from baseline to 2 years in CA IMT, using composite measures from the right and left far wall common carotid artery, carotid bulb, and internal carotid artery. Secondary end points include (1) the proportion of participants who exhibit reductions in CA IMT, (2) the change in maximum far wall IMT, (3) the proportion of participants who develop new carotid artery plaques, and (4) the changes in carotid plus common femoral artery IMT.

CONCLUSIONS

This study addresses the question of whether a regimen that uses drugs with different mechanisms of action will be of further benefit in terms of atherosclerosis reduction compared to statin monotherapy.

Multiplex ligation-dependent probe amplification of LDLR enhances molecular diagnosis of familial hypercholesterolemia

Autosomal dominant (AD) familial hypercholesterolemia [FH; Mendelian Inheritance in Man (MIM) 143890] typically results from mutations in the LDL receptor gene (LDLR), which are now commonly diagnosed using exon-by-exon screening methods, such as exon-by-exon sequence analysis (EBESA) of genomic DNA (gDNA). However, many patients with FH have no LDLR mutation identified by this method. Part of the diagnostic gap is attributable to the genetic heterogeneity of AD FH, but another possible explanation is inadequate sensitivity of EBESA to detect certain mutation types, such as large deletions or insertions in LDLR. Multiplex ligation-dependent probe amplification (MLPA) is a new method that detects larger gDNA alterations that are overlooked by EBESA. We hypothesized that some FH patients with no LDLR mutation detectable by EBESA would have an abnormal LDLR MLPA pattern. In 70 unrelated FH patients, 44 had LDLR mutations detected by EBESA, including missense, RNA splicing, nonsense, or small deletion mutations, and 5 had the APOB R3500Q mutation. Among the remaining 21 AD FH patients with no apparent LDLR mutation, we found abnormal LDLR MLPA patterns in 12 and then demonstrated the deleted sequence in 5 of these. These findings indicate that MLPA may be a useful new adjunctive tool for the molecular diagnosis of FH.

The Effect of HMG-CoA Reductase Inhibitors on Coenzyme Q10

The HMG-CoA reductase inhibitors, also known as statins, have an enviable safety profile; however, myotoxicity and to a lesser extent hepatotoxicity have been noted in some patients following treatment. Statins target several tissues, depending upon their lipophilicity, where they competitively inhibit HMG-CoA reductase, the rate-limiting enzyme for mevalonic acid synthesis and subsequently cholesterol biosynthesis. HMG-CoA reductase is also the first committed rate-limiting step for the synthesis of a range of other compounds including steroid hormones and ubidecarenone (ubiquinone), otherwise known as coenzyme Q(10) (CoQ(10)). Recent interest has focused on the possible role CoQ(10) deficiency may have in the pathophysiology of the rare adverse effects of statin treatment. Currently, there is insufficient evidence from human studies to link statin therapy unequivocally to pathologically significantly decreased tissue CoQ(10) levels. Although statin treatment has been reported to lower plasma/serum CoQ(10) status, few human studies have assessed tissue CoQ(10) status. The plasma/serum CoQ(10) level is influenced by a number of physiological factors and, therefore, has limited value as a means of assessing intracellular CoQ(10) status. In those limited studies that have assessed the effect of statin treatment upon tissue CoQ(10) levels, none have shown evidence of a fall in CoQ(10) levels. This may reflect the doses of statins used, since many appear to have been used at doses below those recommended for their maximum therapeutic effects. Moreover, the poor bioavailability in those peripheral tissues tested may not reflect the effects the agents are having in liver and muscle, the tissues commonly affected in those patients who do not tolerate statins. This article reviews the biochemistry of CoQ(10), its role in cellular metabolism and the available evidence linking possible CoQ(10) deficiency to statin therapy.

Low Density Lipoprotein - Receptor (LDL-R) Gene Mutations among Filipinos with Familial Hypercholesterolemia

BACKGROUND

Familial Hypercholesterolemia (FH) is an autosomal dominant disease resulting from mutations of the LDL (LDLR) receptor gene leading to a diminished catabolism and elevated level of LDL cholesterol (LDL-C). It is associated with an increased risk for cardiovascular disease (CVD). The MEDPED (Make Early Diagnosis-Prevent Early Death) program, an initiative cited by the WHO Human Genetics Programme in their report on FH, initiated international collaboration to identify and follow-up patients with FH globally. From Asia-Pacific, only 6 countries are participating and no data among Filipinos particularly on genetic profiles is available at present. This study attempts to initiate data collection and participation in the global initiative.

OBJECTIVES

Primary: 1. To describe the phenotype of Filipino patients with FH. 2. To determine and characterize the LDL-R gene mutations among Filipino patients with clinical features of FH. Secondary: To determine the association of the clinical characteristics of FH with the presence of LDLR gene mutations.

DESIGN

Cross- Sectional Study.

SETTING

Multicenter, Outpatient Clinic.

PARTICIPANTS

60 unrelated patients, 18 y/o and above from UP-PGH, Manila Doctors Hospital and Cardinal Santos Medical Center. FH was diagnosed according to the Dutch Lipid Clinic Network Criteria cited by WHO which is based on a history of premature CVD, family history, tendon xanthoma, arcus cornealis, and LDL C levels.

METHODS

With informed consent, clinical history, physical examination and lipid profile data were determined. Blood samples were extracted, processed to isolate DNA specimens at the National Institutes of Health, Institute of Human Genetics, and sent to Canterbury Health Laboratories at Christchurch, New Zealand for DNA analysis.

ANALYSIS

Descriptive statistics, Fisher's exact test and Student's t-test using Stata version 6.0 software.

RESULTS

Sixty patients with a mean age of 55 y/o were included, including 39 (65%) females. The mean LDL level was 227 mg/dl. Cardiovascular Disease and a family history of dyslipidemia were present in 55 & 60% of the samples, respectively. Twenty percent had documented LDL-R gene mutations. Six of the mutations were considered novel. A family history of dyslipidemia, an elevated LDL-C level, and a high FH score exhibited a statistically significant association with mutations. The study population has a high prevalence of CVD at an average age of 55 years with a strong family history of dyslipidemia and very high average LDL-C levels. One out of every 5 patients had LDL-R gene mutations, 6 of which were considered novel. LDL-R gene mutation was significantly associated with family history of dyslipidemia, LDL-C Level and FH score.

CLINICAL AND RESEARCH IMPLICATION

This is the first international collaborative genetic study among Filipinos with FH. Data could allow the country to participate in the WHO/MEDPED global program. Collaborative efforts will lead to more effective detection, treatment and prevention of CV events. Novel mutations were discovered and further analysis of these genes will be done.

Genetic diagnosis of familial hypercholesterolaemia: a mutation and a rare non-pathogenic amino acid variant in the same family

Familial hypercholesterolaemia (FH), a relatively common inherited disorder, is caused by mutations in the gene for the low density lipoprotein (LDL) receptor (LDLR) that result in impaired clearance of LDL. Identification of mutations in patients with the clinical phenotype of FH allows unequivocal diagnosis in potentially affected relatives, but depends critically on distinguishing mutations that affect protein function from variants with no significant effect. A presumed functional mutation in LDLR (G198D in exon 4) was identified in two hypercholesterolaemic English brothers by high throughput screening and was not found in 550 controls. However, a second variant (L458P) was identified separately in their mother that co-segregated with hypercholesterolaemia in the entire pedigree. L458, but not G198, is strongly conserved between species and lies in a region important for beta-propeller stability. G198D was inherited from their normolipidaemic father by two of three siblings heterozygous for L458P; they appeared less severely hypercholesterolaemic and more responsive to statins than the third affected brother and their mother. This study emphasises that apparent co-segregation of an amino acid substitution in a critical region of the protein with hypercholesterolaemia and its absence from a large control population is insufficient evidence that a variant of the LDL receptor is necessarily deleterious to its function.

Clinical management of children and young adults with heterozygous familial hypercholesterolaemia in the UK

Life expectancy in familial hypercholesterolaemia (FH) has been greatly improved by the advent of statin therapy. In the UK, however, these agents are not licensed for use in children. We approached 169 physicians responsible for lipid clinics for information on their practice in young patients, and valid responses were received from 54%. A typical lipid clinic has only 3.5 patients aged under 16 with FH. In boys aged 10-15 years 65% of physicians were prepared to treat with bile acid sequestrants but only 23% with statins. There was greater reluctance to treat in girls of the same age, corresponding figures being 52% and 12%. Despite the efficacy of statins in reducing low-density-lipoprotein cholesterol, these agents are little used in children with FH. Their safety and clinical efficacy should be assessed by a randomized double-blind trial.

Genetically defined hyperlipidemia

The unraveling of genetic defects associated with disorders in lipid metabolism has contributed to the understanding of lipoprotein metabolism and the pathophysiological consequences of a particular mutation. The translation, however, of a single genetic defect into the individual's risk of cardiovascular disease and subsequent treatment strategies is an extremely complex issue that involves the identification of multiple additional determinants, including genetic, metabolic and environmental factors. The discovery of these factors, including genetic determinants of drug efficacy, provides insight into the interaction between regulatory systems traditionally thought to be unrelated and may, in the future, lead to a more complete diagnostic and therapeutic appreciation of the individual patient.

Long-Term Lowering of Plasma Cholesterol Levels in LDL-Receptor-Deficient WHHL Rabbits by Gene Therapy

Lentiviral vectors encoding rabbit low-density lipoprotein receptor (LDLR) or green fluorescent protein (GFP) under the control of a liver-specific promoter (LSP) were used for intraportal gene transfer into the liver of hypercholesterolemic LDLR-deficient Watanabe Heritable Hyperlipidemic rabbits. In vitro cell culture analysis demonstrated functionality of the LSP-LDLR vector in mediating increased degradation of LDL in transduced liver cells. Twenty-five rabbits were each injected with 1 x 10(9) infectious virus particles into the portal vein. Liver biopsy samples were collected 4 weeks after the gene transfer and the rabbits were followed up for 2 years. Histological and RT-PCR analyses showed the expression of GFP and LDLR transgenes in the biopsy samples. Clinical chemistry and histological analyses revealed normal liver function and morphology during the 2-year follow-up with no safety issues. LSP-LDLR-treated rabbits demonstrated an average of 14 +/- 7% decrease in serum cholesterol levels during the first 4 weeks, 44 +/- 8% decrease at 1 year, and 34 +/- 10% decrease at the 2-year time point compared to the control rabbits. This study demonstrates the safety and potential benefits of the third-generation liver-specific lentiviral vectors in the treatment of familial hypercholesterolemia using direct intraportal liver gene therapy without the need for liver resection.

Mutations in the PCSK9 gene in Norwegian subjects with autosomal dominant hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is at a locus for autosomal dominant hypercholesterolemia, and recent data indicate that the PCSK9 gene is involved in cholesterol biosynthesis. Mutations within this gene have previously been found to segregate with hypercholesterolemia. In this study, DNA sequencing of the 12 exons of the PCSK9 gene has been performed in 51 Norwegian subjects with a clinical diagnosis of familial hypercholesterolemia where mutations in the low-density lipoprotein receptor gene and mutation R3500Q in the apolipoprotein B-100 gene had been excluded. Two novel missense mutations were detected in the catalytic subdomain of the PCSK9 gene. Two patients were heterozygotes for D374Y, and one patient was a double heterozygote for D374Y and N157K. D374Y segregated with hypercholesterolemia in the two former families where family members were available for study. Our findings support the notion that mutations in the PCSK9 gene cause autosomal dominant hypercholesterolemia.

New promoter mutations in the low-density lipoprotein receptor gene which induce familial hypercholesterolaemia phenotype: molecular and functional analysis

Low-density lipoprotein receptor (LDLR) is a cell-surface glycoprotein that mediates specific uptake and catabolism of plasma LDL. Mutations located in the coding region of the LDLR gene affect the structure and function of the protein and cause familial hypercholesterolaemia (FH). Mutations in the regulatory regions of the gene are rare, but in some cases have been shown to alter the transcriptional activity of the gene and cause the FH phenotype as well. Adult heterozygous FH individuals have a markedly raised plasma cholesterol that is associated with accelerated atherosclerosis and premature coronary heart disease. The aim of this study was the functional characterization of a promoter mutation in the LDLR gene in one family from the register of Czech FH subjects. Molecular screening revealed that three members of this family carried a -27C > T nucleotide transition in the promoter sequence (calculated from the start of transcription). All three manifested a heterozygous FH phenotype. This new mutation is located between the TATA box and sterol-dependent regulatory element repeat 3. Using a luciferase reporter assay system, we analysed the transcriptional efficiency of the normal and mutant alleles. The mutation reduced promoter activity to background level. Another new promoter mutation -60C > T was identified in an unrelated patient in the conserved nucleotide sequence of the sterol-dependent regulation element repeat 2 which virtually abolished the promoter activity. We assume a causal effect of this -60C > T transition on the basis of its position in the promoter sequence.

Comparison of the risk of fatal coronary heart disease in treated xanthomatous and non-xanthomatous heterozygous familial hypercholesterolaemia: a prospective registry study

BACKGROUND

A clinical diagnosis of familial hypercholesterolaemia (FH) is often made in the absence of tendon xanthomata (TX), which are not usually present before the fourth decade of life. The prognosis of treated non-xanthomatous (TX-) FH is uncertain and the objective of this study was to compare mortality from coronary heart disease (CHD) in patients with treated TX+ (definite) and TX- (possible) heterozygous FH.

METHODS

A diagnosis of definite or possible FH was based on raised cholesterol levels (>7.5 mmol/l) and a family history of premature CHD or hypercholesterolaemia. Patients were recruited from 21 outpatient lipid clinics in the UK from 1980 to 1998. The cohort of 1569 patients with TX+ FH were followed for 12754 person years and the cohort of 1302 patients with TX- FH for 10238 person years. The standardised mortality ratio (SMR) was calculated from the ratio of the number of deaths observed to the number expected in the general population of England and Wales (SMR=100 for reference population).

FINDINGS AND DISCUSSION

CHD accounted for 64 (63%) of the 102 deaths in the TX+ cohort and 38 (57%) of the 67 deaths in the TX- cohort with the SMR for a fatal coronary event being, respectively, 294 (95% confidence interval 228, 380, P<0.00001) and 205 (95% CI 145, 282, P=0.0001). The similarly elevated CHD mortality risk suggests that, in adulthood, both groups of patients should be treated equally aggressively with HMG Co A reductase inhibitors (statins).

Dyslipidaemia

The lowering of serum cholesterol is increasingly recognised as essential in the prevention of coronary heart disease and other atherosclerotic disease. The success of statin trials and the need to deploy these drugs effectively in the population has led increasingly to the identification of many people whose serum cholesterol, triglycerides, and HDL-cholesterol require clinical assessment, and frequently treatment. Lipid disorders are mainly straightforward, but some are complex or resistant to simple treatment strategies. I have reviewed the clinical manifestations of disordered lipid metabolism (dyslipidaemia) and its management.