Performance of the enhanced Sampson-NIH equation for VLDL-C and LDL-C in a population with familial combined hyperlipidemia

INTRODUCTION

Low-density cholesterol (LDL-C) has long been estimated by the Friedewald formula (F-LDL-C); however, this method underestimates LDL-C in patients with hypertriglyceridemia (HTG) or low LDL-C levels. The Martin (M-LDL-C) and Sampson (S-LDL-C) formulas partially resolve these limitations. Recently, Sampson et al. developed a new equation (eS-VLDL-C) that includes ApoB. This new equation could be particularly useful in FCHL, which is characterized by the predominance of triglyceride-rich VLDL and a discordance between LDL-C and ApoB.

METHODS

Very low-density lipoproteins (VLDL-C) was measured in 336 patients with FCHL by sequential ultracentrifugation. LDL-C was estimated by subtracting VLDL-C, estimated by the different equations, from non-HDL cholesterol. Spearman correlations, R2, mean squared error (RMSE), and bias were used to compare the accuracy of the different equations. Concordance of the estimated LDL-C values with LDL-C thresholds and ApoB was also assessed by their kappa coefficients and ROC analysis.

RESULTS

Overall population had a mean age of 47 years, and 61.5% were women. 19.5% had type 2 diabetes, hypertension was present in 20.8%, and only 12.2% were on statin treatment. Both S-LDL-C and eS-LDL-C performed similarly, and better than M-LDL-C and F-LDL-C. In Bland-Altman analysis, eS-LDL-C showed the lowest bias, better performance in HTG, and better concordance with LDL-C treatment goals compared to other formulas (e.g. ρ: 0.87, 95% CI 0.84-0.89).

CONCLUSIONS

LDL-S and LDL-eS equations estimate the concentration of LDL-C with greater accuracy than other formulas. The LDL-eS has best performance in estimating LDL-C with lower RMSE than other formulas.

Familial hypercholesterolemia and young patients' thoughts on own condition and treatment

OBJECTIVES

Familial hypercholesterolemia (FH) is a hereditary and usually asymptomatic condition characterized by elevated blood cholesterol and increased risk of premature cardiovascular disease. It is treated with dietary modifications and lipid lowering drugs. The objective was to learn about young FH patients' perceptions and choices regarding treatment.

METHODS

Data were collected through in-depth interviews with 24 patients (ages 16-35), and analysed according to Grounded Theory.

RESULTS

The findings are presented as theoretical concepts describing the participants' way of handling their condition. The core category was identified as "Thoughts of consequences vs. Postponing thoughts of consequences", which could be described through the following subcategories: 1. Normalising the condition, 2. Belittling of treatment vs. Committed to treatment and 3. Trust in advice vs. Avoid unnecessary interference. The participants' position regarding these categories was described to affect motivation and challenges with treatment.

CONCLUSIONS

Participants who postpone the thoughts of consequences, belittle the treatment and avoid unnecessary interference represent a challenge to health care practitioners.

PRACTICAL IMPLICATIONS

Practitioners should explore aspects such as thoughts of consequences, view of treatment and the feeling of interference to be able to better understand illness behaviour, adjust their communication and hopefully improve adherence.

[Familial combined hyperlipidemia: consensus document]

Familial combined hyperlipidemia (FCH) is a frequent disorder associated with premature coronary artery disease. It is transmitted in an autosomal dominant manner, although there is not a unique gene involved. The diagnosis is performed using clinical criteria, and variability in lipid phenotype and family history of hyperlipidemia are necessaries. Frequently, the disorder is associated with type2 diabetes mellitus, arterial hypertension and central obesity. Patients with FCH are considered as high cardiovascular risk and the lipid target is an LDL-cholesterol <100mg/dL, and <70mg/dL if cardiovascular disease or type 2 diabetes are present. Patients with FCH require lipid lowering treatment using potent statins and sometimes, combined lipid-lowering treatment. Identification and management of other cardiovascular risk factors as type 2 diabetes and hypertension are fundamental to reduce cardiovascular disease burden. This document gives recommendations for the diagnosis and global treatment of patients with FCH directed to specialists and general practitioners.

Rosuvastatin: a highly potent statin for the prevention and management of coronary artery disease

Since the identification of a fungal metabolite that inhibits HMG-CoA reductase in 1976, statins have emerged rapidly as the global leader in pharmacotherapeutics designed to lower low-density lipoprotein cholesterol (LDL-C). In conjunction, practice guidelines have recommended increasingly aggressive measures to improve coronary heart disease (CHD) outcomes by lowering LDL-C. By virtue of unique chemical characteristics, enhanced binding thermodynamics and limited cytochrome P450 3A4 metabolism, rosuvastatin calcium has a safety profile in line with currently marketed statins, but a different efficacy profile. Mirroring this chemical profile, the GALAXY program represents a comprehensive evaluation of the efficacy, safety and cost-effectiveness of rosuvastatin in individuals representing various clinical diagnoses, pathophysiological states and ethnicities. Also results from the Justification for the Use of statins in Primary prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) study could provide further evidence for the use of rosuvastatin in individuals with traditional and emerging CHD risk factors, such as an elevated high sensitivity C-reactive protein level. This review will provide a comprehensive evaluation of the chemistry, clinical efficacy, safety and tolerability of rosuvastatin, and discuss the future role in the management of CHD and atherosclerosis.

[Dyslipidemia - when are lipid lowering medications useful in clinical practice?]

Dyslipidemia is one of the main modifiable cardiovascular risk factors. There is strong evidence for the efficacy of lipid-lowering drugs in secondary prevention, as well as in primary prevention for patients at high cardiovascular risk. In primary prevention, indication for lipid-lowering interventions should be based on an individual assessment of the cardiovascular risk and on the LDL cholesterol level, despite less strong evidence for the efficacy of drug-based interventions in low risk patients. Treatment consists of statins, as well as lifestyle modifications such as body weight control and increased physical exercise. The latter constitute the primary intervention in patients at low cardiovascular risk. Secondary dyslipidemias due to an underlying medical condition and familial dyslipidemias such as Familial Hypercholesterolemia and Familial Combined Hyperlipidemia should be identified and treated accordingly, taking into account that the risk scoring systems are not appropriate in these situations.

[Dyslipidemia: news in diagnosis and drug therapy]

Plasma lipid levels are to a large extent determined by genetic factors. In its more extreme forms this is manifested as familial hyperlipidemias, which are an important cause of premature coronary heart disease. It has been demonstrated that rigorous treatment of familial forms reduces the burden of ischemic heart disease. Statins are among the most studied drugs in cardiovascular prevention; a number of large-scale clinical trials have demonstrated that statins substantially reduce cardiovascular morbidity and mortality in both primary and secondary prevention. The currently available evidence suggests that the clinical benefit is largely independent of the type of statin, but depends on the extent of LDL-C lowering. When the most potent statins are insufficient, LDL-C apheresis should be used.

[Fifty years studying hiperlipidemias: the case of familial combined hyperlipidemia]

Familial combined hyperlipidemia (FCHL) is the most frequent primary dyslipidemia. Its manifestations include hypercholesterolemia, hypertriglyceridemia or the combination of both abnormalities. In spite of its high frequency, the proper diagnosis is rarely done. For this purpose, the measurement of a lipid profile is required in at least three first-degree relatives. A critical review of the current literature in this field is presented in this paper. Prospective studies have confirmed the atherogenicity of the disease. It is possible to identify the FCHL causal genes with the current methodology because it is an oligogenic disease. Based on the use of new technologies, several loci that regulate apolipoprotein B concentrations have been identified. In addition it was demostrated that variations of the activity or the expression of various nuclear factors (USF1, TCF7L2, HNF4alfa) have a major role in the pathophysiology of FCHL. These nuclear factors regulate the expression of multiple genes involved in the metabolism of lipids or carbohydrates.

Combined hyperlipidaemia as a presenting sign of cholesteryl ester storage disease

Lysosomal acid lipase (LAL) deficiency results in Wolman disease and cholesteryl ester storage disease (CESD), a more benign form. CESD is a recessive disorder characterized by hypercholesterolaemia, hypertriglyceridaemia, low blood HDL and variable phenotype, while hepatomegaly is usually evident during childhood or adolescence. An 11-year-old girl was referred to our department for combined hyperlipidaemia (total cholesterol 323, triglycerides 259 mg/dl). All family members had normal lipid profile and liver function tests. At 8 years she was admitted for acute Epstein-Barr virus infection, with hepatosplenomegaly and elevation of liver enzymes. Liver-spleen enlargement resolved, but serum alanine aminotransferase and aspartate aminotransferase were persistently twice the upper limits, with other liver function tests within the normal range. Ultrasonography showed normal liver and spleen size and minimal hepatic steatosis. Infectious, autoimmune and metabolic causes of elevated liver enzymes were ruled out, including glycogen storage disease. Dysbetalipoproteinaemia was also ruled out (ApoE phenotype: E3E3). In the following 2 years the girl was symptom-free, BMI was at the 50th-75th centile for age and lipid profile was unchanged despite a low-fat diet. At 13 years of age, low acid lipase activity was demonstrated in leukocytes (10 nmol/h/ per mg protein, normal 140-380) and cultured skin fibroblasts (181 nmol/h per mg protein, normal 1100-2400), leading to diagnosis of CESD. CESD usually progresses to hepatic fibrosis, with high risk of premature atherosclerosis. CESD prevalence may be underestimated in the general population. The diagnosis may be considered in all subjects with atypical combined hyperlipidaemia (usually dominant in transmission or related to metabolic syndrome) and atypical 'fatty liver disease', in the absence of overweight.

Tissue-specific stable isotope measurements of postprandial lipid metabolism in familial combined hyperlipidaemia

OBJECTIVE

The metabolic defects underlying familial combined hyperlipidaemia (FCHL) are not clearly understood. We used stable isotope techniques combined with tissue-specific measurements in adipose tissue and forearm muscle to investigate fatty acid handling by these tissues in the fasting and postprandial states.

RESULTS

Patients were insulin resistant as shown by higher glucose and insulin concentrations and lower muscle glucose extraction than controls. Plasma triacylglycerol (TAG) concentrations were higher in patients. Adipose tissue TAG extraction was not lower in patients than controls, although TAG clearance was lower, probably representing saturation. Following a test meal, patients showed a greater increase in chylomicron-TAG concentrations. There were no differences between FCHL patients and controls in postprandial suppression of non-esterified fatty acid (NEFA) concentrations or postprandial NEFA release, but patients had greater trapping of exogenous fatty acids in adipose tissue. 3-Hydroxybutyrate concentrations were lower in patients indicative of decreased hepatic fatty acid oxidation.

CONCLUSIONS

In this group of patients with FCHL, the major defect appeared to be overproduction of TAG by the liver due to decreased fatty acid oxidation, with fatty acids directed to TAG synthesis. We found no evidence of decreased lipoprotein lipase action or impaired fatty acid re-esterification in adipose tissue.

Vascular and metabolic effects of treatment of combined hyperlipidemia: focus on statins and fibrates

Combined hyperlipidemia results from overproduction of hepatically synthesized apolipoprotein B in very low-density lipoproteins in association with reduced lipoprotein lipase activity. Thus, this condition is typically characterized by concurrent elevations in total cholesterol and triglycerides with decreased high-density lipoprotein cholesterol. High levels of apolipoprotein B-containing lipoproteins, most prominently carried by low-density lipoprotein (LDL) particles, are an important risk factor for coronary heart disease. Statin therapy is highly effective at lowering LDL cholesterol. Despite the benefits of statin treatment for lowering total and LDL cholesterol, many statin-treated patients still have initial or recurrent coronary heart disease events. In this regard, combined therapy with statins and fibrates is more effective in controlling atherogenic dyslipidemia in patients with combined hyperlipidemia than either drug alone. Furthermore, statins and fibrates activate PPARalpha in a synergistic manner providing a molecular rationale for combination treatment in coronary heart disease. Endothelial dysfunction associated with cardiovascular diseases may contribute to insulin resistance so that there may also be additional beneficial metabolic effects of combined statin/fibrates therapy. However, there has been little published evidence that combined therapy is synergistic or even better than monotherapy alone in clinical studies. Therefore, there is a great need to study the effects of combination therapy in patients. When statins are combined with gemfibrozil therapy, this is more likely to be accompanied by myopathy. However, this limitation is not observed when fenofibrate, bezafibrate, or ciprofibrate are used in combination therapy.

Associations of apolipoprotein B with pulse pressure and glucose in Chinese families with familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL), with a marked elevation of apolipoprotein B (apoB), is estimated to cause 10-20% of premature coronary artery disease. However, little data are available to demonstrate the associations of apoB with pulse pressure and glucose levels in FCHL families in China. This study was to investigate the potential influence factors for blood pressure and glucose phenotypes in FCHL families by multiple linear regression analysis. We recruited 147 FCHL relatives and 90 spouses, aged 30 to 60 years, from 42 Chinese families with FCHL. Our results showed that triglyceride and low density lipoprotein cholesterol were associated with fasting glucose levels (all P<0.05). Body mass index and glucose significantly correlated to systolic blood pressure, diastolic blood pressure, and mean arterial pressure, respectively (all P<0.05). Furthermore, apoB was significantly related to pulse pressure and glucose in FCHL families (all P<0.05). Thus, this study demonstrates that apoB is significantly associated with pulse pressure and glucose levels in FCHL families. Accordingly, our data suggest that apoB may be a candidate risk marker for pulse pressure and glucose in FCHL populations.

Haplotype analyses of the APOA5 gene in patients with familial combined hyperlipidemia

BACKGROUND

Familial combined hyperlipidemia (FCH) is the most common genetic lipid disorder with an undefined genetic etiology. Apolipoprotein A5 gene (APOA5) variants were previously shown to contribute to FCH. The aim of the present study was to evaluate the association of APOA5 variants with FCH and its related phenotypes in Dutch FCH patients. Furthermore, the effects of variants in the APOA5 gene on carotid intima-media thickness (IMT) and cardiovascular disease (CVD) were examined.

MATERIALS AND METHODS

The study population consisted of 36 Dutch families, including 157 FCH patients. Two polymorphisms in the APOA5 gene (-1131T>C and S19W) were genotyped.

RESULTS

Haplotype analysis of APOA5 showed an association with FCH (p=0.029), total cholesterol (p=0.031), triglycerides (p<0.001), apolipoprotein B (p=0.011), HDL-cholesterol (p=0.013), small dense LDL (p=0.010) and remnant-like particle cholesterol (p=0.001). Compared to S19 homozygotes, 19W carriers had an increased risk of FCH (OR=1.6 [1.0-2.6]; p=0.026) and a more atherogenic lipid profile, reflected by higher triglyceride (+22%) and apolipoprotein B levels (+5%), decreased HDL-cholesterol levels (-7%) and an increased prevalence of small dense LDL (16% vs. 26%). In carriers of the -1131C allele, small dense LDL was more prevalent than in -1131T homozygotes (29% vs. 16%). No association of the APOA5 gene with IMT and CVD was evident.

CONCLUSION

In Dutch FCH families, variants in the APOA5 gene are associated with FCH and an atherogenic lipid profile.

Clinical inquiries. When should we screen children for hyperlipidemia?

Children should be screened for hyperlipidemia when there is a history of familial hypercholesterolemia (strength of recommendation [SOR]: C). No clear evidence supports screening all children or just those with family history of cardiovascular disease (CVD) or hyperlipidemia (SOR: C).

Combined hyperlipidemia in a single subject with tetraplegia: ineffective risk reduction after atorvastatin monotherapy

BACKGROUND/OBJECTIVE

Effects of atorvastatin (Lipitor) drug monotherapy (10 mg daily) on fasting blood lipid profiles and cardiovascular disease (CVD) risks were examined for a single subject with C5-C6 tetraplegia. Routine fasting lipid profiles were analyzed by standard biochemistry techniques for total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C). Lipid profiles were analyzed on 3 occasions before drug therapy was initiated and 3 months after therapy commenced. The TC:HDL and LDL:HDL ratios were computed for all sampling times and used to assess pretreatment and post-treatment CVD risk.

RESULTS

Fasting TC, TG, and LDL-C were all significantly reduced by therapy. The pretreatment HDL-C of 35 mg/dL was lowered to 21 mg/dL. As a result, the TC:HDL risk ratio was only marginally reduced from 6.6 to 6.4, whereas the LDL:HDL risk ratio remained unchanged by treatment.

CONCLUSIONS

In this man with tetraplegia, atorvastatin drug monotherapy rapidly lowered TC, TG, LDL-C, and HDL-C. However, the TC:HDL ratio, considered the best predictor of CVD risk, was unchanged.

Familial combined hyperlipidemia: controversial aspects of its diagnosis and pathogenesis

Familial combined hyperlipidemia is the most frequent cause of primary dyslipidemia in Mexico. Its manifestations include hypercholesterolemia, hypertriglyceridemia, or a combination of both. Despite its high frequency, a proper diagnosis is rarely made. Assessment of the lipid profiles of at least three first-degree relatives is necessary. The diagnosis of familial combined hyperlipidemia in a family not only leads to the identification of other affected family members but, more important, allows cardiovascular risk stratification of those affected. Prospective studies have confirmed the atherogenicity of the disease. A critical review of the current literature in this field is presented in this article. Although three screenings of the genome have been completed, the genes responsible for this disorder have not been identified. Limitations with respect to the characterization of affected subjects and the heterogeneity of the disease are among possible explanations. However, familial combined hyperlipidemia, because of its high prevalence, must be given greater priority. It represents a great challenge for physicians involved in the treatment of dyslipidemic patients.

Diagnostic Criteria in Relation to the Pathogenesis of Familial Combined Hyperlipidemia

Familial combined hyperlipidemia (FCH) is the most common inherited hyperlipidemia in humans, affecting 1 to 3% of the adult population and up to 20% of patients with premature myocardial infarction. FCH is traditionally diagnosed by total plasma cholesterol and/or triglyceride levels above the 90th percentile adjusted for age and gender; however, the diagnosis of FCH based on these diagnostic criteria is inconsistent in 26% of the subjects over a five-year period, emphasizing the need for re-evaluation of the diagnostic criteria for FCH. Recently, a nomogram was developed based on absolute apolipoprotein B levels in combination with triglyceride and total cholesterol levels adjusted for both age and gender to simply and accurately diagnose FCH. When percentiles of triglyceride and total cholesterol adjusted for age and gender are not available in a population, the definition of FCH can be established based on hypertriglyceridemia (> 1.5 mmol/l) and hyperapoB (> 1200 mg/l). Standardized and simple diagnostic criteria are necessary to further delineate the pathogenesis of FCH. Several metabolic pathways have been suggested to be important in causing the FCH phenotype including hepatic VLDL overproduction either with or without impaired clearance of triglyceride-rich lipoproteins from plasma. The presence of insulin resistance and obesity in FCH patients further contribute to the expression of the lipidphenotype. A disturbed adipose tissue metabolism that results in an increased plasma free fatty acid pool may be the culprit in the pathogenesis of FCH.

Nomogram to Diagnose Familial Combined Hyperlipidemia on the Basis of Results of a 5-Year Follow-Up Study

Background— Familial combined hyperlipidemia (FCH) is traditionally diagnosed by total plasma cholesterol and/or triglyceride levels above the 90th percentile adjusted for age and gender. In a recent study, we showed that the diagnosis of FCH on the basis of these diagnostic criteria was inconsistent in 26% of the subjects over a 5-year period. This result emphasizes the need for reevaluation of the diagnostic criteria for FCH.

Methods and Results— A total of 32 families (299 subjects) were studied in 1994 and 1999. A subject was defined “truly” FCH when diagnosed FCH in 1994 and/or 1999 on the basis of traditional plasma lipid criteria. Additional lipid and lipoprotein parameters, including apolipoprotein B (apoB) and small, dense LDL, were measured at both time points. In total, 121 subjects (40%) were defined as truly FCH. Multivariate analysis revealed that absolute apoB values combined with triglyceride and total cholesterol levels adjusted for age and gender best predicted truly FCH. A nomogram including these parameters is provided to simply and accurately calculate the probability to be affected by FCH. Furthermore, it is shown that when percentiles of triglyceride and total cholesterol adjusted for age and gender are not available in a population, the definition of FCH can be established on the basis of hypertriglyceridemia (>1.5 mmol/L) and hyper-apoB (>1200 mg/L).

Conclusions— The diagnosis of FCH is best predicted by absolute apoB levels combined with triglyceride and total cholesterol levels adjusted for age and gender and can accurately be calculated by a nomogram. This definition is also a good predictor of cardiovascular risk in FCH.

[Schnyder's crystalline corneal dystrophy. Further narrowing of the linkage interval at chromosome 1p34.1-p36?]

BACKGROUND

Schnyder's crystalline corneal dystrophy (SCCD) is a rare autosomal dominant disease and can occur in association with hyperlipoproteinemia. The disease has been mapped to chromosome 1p34.1-p36.

CASE REPORT

We report on a 66-year-old woman and her son with Schnyder's crystalline corneal dystrophy. The mother had type IV hyperlipoproteinemia and hypercholesterolemia while her son had hypercholesterolemia with elevated LDL-cholesterol. Analysis of microsatellite markers within the candidate interval of 1p34.1-p36 showed that the affected son and his unaffected brother had inherited different alleles only for the proximal marker D1S228 from their affected mother.

CONCLUSIONS

The haplotype analysis suggests that either recombination has occurred, which would allow the candidate interval to be narrowed down, or alternatively, the SCCD in the reported family is not linked to chromosome 1, which would be a first indication of genetic heterogeneity in this disease. To reduce the risk of cardiovascular disease, hyperlipidemia should always be excluded in patients with Schnyder's crystalline corneal dystrophy.

Chylomicron remnants of various sizes are lowered more effectively by fenofibrate than by atorvastatin in patients with combined hyperlipidemia

Both atorvastatin and fenofibrate are known to lower postprandial chylomicrons and chylomicron remnants. However, until now it has not been investigated which of the two drugs is more effective in one and the same patient and, secondly, whether these drugs exert different effects on chylomicron remnants of different sizes. To this end 12 patients with mixed hyperlipidemia were treated in a crossover study with 40 mg atorvastatin or with 200 mg micronized fenofibrate once daily for 6 weeks. Oral fat loading was given before and after each treatment. Chylomicron remnants of various sizes were determined by fluorometric determinations of retinyl palmitate after lipoprotein separation by size-exclusion chromatography. As expected, atorvastatin was more effective than fenofibrate on total and LDL-cholesterol (P < 0.05). Fenofibrate, in contrast, was more effective on all triglyceride-rich lipoproteins in both the fasting and the postprandial state. The stronger effect of fenofibrate affected not only chylomicrons and VLDL but also chylomicron remnants. It reduced large chylomicron remnants by 66% at 6h and by 74% at 8 h. The action of atorvastatin was less pronounced, with corresponding reductions of 42 and 65% (P < 0.05 only after 8 h). Fenofibrate was even more effective on small chylomicron remnants, yielding reductions of 47, 74, and 66% at 4, 6, and 8 h. Atorvastatin, in contrast, gave reductions of 30 and 26% after 6 and 8 h, the effect reaching statistical significance only after 6h. Fenofibrate is therefore more effective than atorvastatin in lowering all triglyceride-rich lipoproteins, including large and small chylomicron remnants.

Biochemical and genetic association of plasma apolipoprotein A-II levels with familial combined hyperlipidemia

Apolipoprotein A-II (apoA-II) is a major protein on high-density lipoprotein (HDL) particles, and in mice, its levels are associated with triglyceride and glucose metabolism. In particular, transgenic mice overexpressing apoA-II exhibit hypertriglyceridemia, increased body fat, and insulin resistance, whereas apoA-II-null mice have decreased triglycerides and increased insulin sensitivity. Given the phenotypic overlap between familial combined hyperlipidemia (FCH) and apoA-II transgenic mice, we investigated the relationship of apoA-II to this disorder. Despite having lower HDL-cholesterol (HDL-C), FCH subjects had higher apoA-II levels compared with unaffected relatives (P<0.00016). Triglyceride and HDL-C levels were significant predictors of apoA-II, demonstrating that apoA-II variation is associated with several FCH-related traits. After adjustment for multiple covariates, there was evidence for the heritability of apoA-II levels (h2=0.15; P<0.02) in this sample. A genome scan for apoA-II levels identified significant evidence (LOD=3.1) for linkage to a locus on chromosome 1q41, coincident with a suggestive linkage for triglycerides (LOD score=1.4). Thus, this locus may have pleiotropic effects on apoA-II and FCH traits. Our results demonstrate that apoA-II is biochemically and genetically associated with FCH and may serve as a useful marker for understanding the mechanism by which FCH develops.

Screening for Familial Combined Hyperlipidemia in Children Using Lipid Phenotypes

The purpose of this study was to screen for FCHL in children using serum lipid phenotypes. The subjects were 1190 (599 male, 591 female) children who participated in a screening and care program for life style-related diseases in school children. Total cholesterol, high-density lipoprotein cholesterol and triglyceride were determined, and information on the family history of parents was obtained by questionnaire. Candidates for FCHL were screened by the following criteria; type IIb hyperlipidemia, type IIa hyperlipidemia with positive family history of CHD, hyperlipidemia or both. We informed them of the results by mail. A second series of examinations to diagnose FCHL was performed on volunteer participants, including their parents. The candidates consisted of 9 children with type IIb and 27 with type IIa hyperlipidemia, 11 of whom participated, in the second series of examinations, in which 5 children were diagnosed with FCHL. The prevalence was 0.4%, suggesting that at least half of all individuals with FCHL already demonstrate hyperlipidemia in childhood.

Diagnosis of familial combined hyperlipidemia based on lipid phenotype expression in 32 families: results of a 5-year follow-up study

Familial combined hyperlipidemia (FCH) is characterized by a variable expression of hypercholesterolemia and/or hypertriglyceridemia. We evaluated the variability in lipid phenotype expression over a 5-year period and studied factors affecting the lipid phenotype expression. A total of 32 families (299 subjects) were studied in 1994 and in 1999. Subjects were classified as having FCH when total cholesterol and/or triglyceride levels exceeded the 90th percentile adjusted for age and sex. In 1994, 93 (31%) of the 299 subjects were affected, whereas 206 (69%) of the subjects were unaffected relatives. In 1999, a diagnosis of FCH was consistent in 69 (74%) of the 93 subjects. So, 26% of the FCH subjects in 1994 showed a sporadic normolipidemic pattern (ie, total cholesterol and/or triglycerides <90th percentile) in 1999. Among the 206 unaffected relatives in 1994, 178 (86%) remained unaffected in 1999, and 28 (14%) developed an FCH lipid phenotype. Multiple regression analysis showed that sex (odds ratio 2.03, 95% CI 1.09 to 3.87; P=0.03) and body mass index (odds ratio 1.14, 95% CI 1.05 to 1.24; P<0.01) significantly contributed to the variability in lipid phenotype expression. Thus, a diagnosis of FCH, based on plasma total cholesterol and/or triglyceride levels, is consistent in only 74% of the subjects over a 5-year period. Two other major characteristics of our FCH group, compared with the unaffected relatives, included elevated apolipoprotein B (apoB) levels and the presence of small dense low density lipoprotein (LDL), as reflected by a low value of the parameter K (apoB 1461 +/- 305 versus 997 +/- 249 mg/L, respectively [P < 0.001]; K value -0.22 +/- 0.19 versus -0.02 +/- 0.19, respectively [P < 0.001]). We now report that the apoB concentration and the K value show less variability in time and are more consistently associated with FCH, inasmuch as affected FCH subjects, compared with the unaffected relatives, persistently show a higher apoB level and a lower value of parameter K, reflecting small dense LDL, even when they present a sporadic normolipidemic pattern. In conclusion, our results emphasize the need for reevaluation of the diagnostic criteria for FCH. We demonstrate that apoB and small dense LDL are attractive new candidates for defining FCH. Further studies are indicated to evaluate the role of apoB and small dense LDL as diagnostic criteria for FCH.

Lack of agreement between the plasma lipid-based criteria and apoprotein B for the diagnosis of familial combined hyperlipidemia in members of familial combined hyperlipidemia kindreds

Our objective was to analyze the concordance between abnormally high-cholesterol and triglyceride concentrations and increased apoliprotein B (apoB) concentrations for considering subjects as affected in familial combined hyperlipidemia (FCHL) kindreds. Twenty-two FCHL families (n = 217) were included. There was a lack of agreement in the identification of the abnormal subjects when several cholesterol- and triglyceride-based criteria were compared against various apoprotein B-based criteria. The agreement, measured as kappa coefficients, between 14 lipid-based criteria and 8 apoB concentrations is reported. For the most frequently used criterion (> or = 90th percentile for cholesterol or triglyceride concentrations), the agreement was low for all apoB levels (kappa, 0.42 to 0.49). A concentration of triglycerides > or = 150 mg/dL and cholesterol > or = 200 mg/dL was the only criterion with a kappa value above 0.6; the acceptable agreement was found with an apoB concentration > or = 120 mg/dL (kappa = 0.604). In conclusion, the data reported here clearly show that a large degree of diagnostic uncertainty exists in the categorization as normal or abnormal of members of FCHL kindred. Different diagnostic criteria would result in conflicting results. This is a critical issue, depending on the diagnostic criteria used, completely different conclusions could result from the linkage analysis in the FCHL studies.

Recognition of familial dyslipidemias in 5-year-old children using the lipid phenotypes of parents. The STRIP project

Adult dyslipidemias may reveal familial and, therefore, offspring dyslipidemias. We evaluated the prevalences of the adult-offspring dyslipidemias in 441 general population families composed of both parents and one 5-year-old child. Family members were classified using the 90th or 10th percentiles for hypercholesterolemia (IIA), hypertriglyceridemia (IV), combined hyperlipidemia (IIB), and low high density lipoprotein cholesterol concentration without hyperlipidemia (hypoHDL). In familial combined hyperlipidemia (FCHL), the IIB-phenotype was in one generation and one of the three hyperlipidemias in the other generation. Finally, the parental dyslipidemia phenotypes and elevated lipids (>80th percentile) that reveal offspring dyslipidemia were selected by stepwise logistic regression. Either the IIA-, IV- or hypoHDL phenotype was found in both generations in 2.8, 2.0 and 1.4% of the families, respectively. FCHL was seen in 1.8% of the families, which confirms the earlier views. The predictive values of the elevated parental cholesterol, type IV or hypoHDL parents to find type IIA, IV and hypoHDL children were low for systematic screening: 16, 13 and 15%, respectively. However, 44% of the children of IIB parents expressed hyperlipidemia (odds ratio 4.7, P=0.006). The IIB phenotype of the parent is a good predictor of the child's hyperlipidemia, and when encountered, it indicates that the lipids of the child should be studied. This would be as important as selective screening of familial hypercholesterolemia.

Lipoprotein(a) as a risk factor for maternal cardiovascular disease mortality in kindreds with familial combined hyperlipidemia or familial hypertriglyceridemia

Most but not all epidemiologic studies have shown that lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease (CVD). Lp(a) levels are also strongly genetically influenced. The purpose of this study was to evaluate the association between Lp(a) levels in adult offspring and parental CVD mortality in 61 kindreds with familial forms of hyperlipidemia. The study sample consisted of offspring-parent pairs in which offspring had fasting Lp(a) measurements and parents had 20-year vital status data and standardized cause-of-death classification if deceased. Linear regression analyses, using a robust variance estimator, were performed separately for 241 offspring with known maternal history (114 mothers) and 194 offspring with known paternal history (93 fathers). Maternal history of CVD mortality was significantly (p=0.004) associated with 2.4-fold higher median Lp(a) levels in offspring compared with those with no maternal history, independent of diabetes, lipid-lowering medications and hormone use. No association was observed between paternal CVD mortality and offspring Lp(a) levels (p=0.505). Adjusting for apolipoprotein(a) kringle 4 number did not alter these parent-specific associations. In conclusion, Lp(a) levels in offspring may be associated with maternal but not paternal history of CVD mortality. This parent-specific finding needs to be confirmed in other samples of high-risk families.

Familial hyperlipidaemia in Malaysian children

This paper highlights two cases of paediatric familial hyperlipidaemia (hypercholesterolaemia and hypertriglyceridaemia). The first case was an 11 year old Chinese boy, a "homozygous" (Type II) hypercholesterolaemic patient. He had extremely high blood cholesterol level (19.4 mmol/l), severe multiple xanthoma and abnormal resting electrocardiogram. He had repeated heart attacks and died at the age of 15 in spite of early intervention, treatment and follow up. The second case was a 2 1/2 years old girl who had severe hypertriglyceridaemia. She had raised cholesterol (6.2 mmol/l) and extremely high triglycerides (14.8 mmol/l). The patient did not resemble Type I lipoproteinaemia which is classically seen in childhood. On the contrary, the patient exhibited clinical and biochemical manifestations of a Type V lipoproteinaemia which often occurs in adults. Apart from a Type V lipoprotein pattern, the patient had low post hepatic lipase activity (PHLA), Apo C II and Apo E2/E3 phenotype. In addition, the lipid profile of her family members (both the parents and brothers) had raised triglycerides and thus ruled out the Type I lipoprotein inheritance pattern, which is an autosomal recessive condition. The issue of paediatric hyperlipidaemia, their management and treatments are discussed.

Familial combined hyperlipoproteinemia: experts panel position on diagnostic criteria for clinical practice. Committee of experts of the Atherosclerosis and Dysmetabolic Disorders Study Group

The Atherosclerosis and Dysmetabolic Disorders Study Group, headed by Prof. Rodolfo Paoletti, decided in 1994 to compose a committee of experts to formulate a clear description of familial combined hyperlipoproteinemia (FCH), a disorder illustrated in the literature, but still unknown to most physicians in spite of its severity and relative diffusion. The Committee consists of experts from the Lipid Clinics of the Universities of Ancona, Bari, Bologna, Ferrara, Genoa, Milan, Naples, Padua, Palermo, Perugia, Rome, Sassari, Turin, Verona and Venice. It has held several meetings coordinated by the national secretary at the "Giancarlo Descovich" Atherosclerosis Centre of the University of Bologna. This paper summarizes its conclusions.

Novel genes for familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is a complex genetic disorder of unknown etiology. Recently, 'modifier' genes of the FCHL phenotype, such as the apolipoprotein AI-CIII-AIV gene cluster and LPL, have been identified in several populations. A 'major' gene for FCHL has been identified in a Finnish isolate which maps to a region syntenic to murine chromosome 3 where a locus for combined hyperlipidemia has been identified. We review these and other recent studies which indicate that FCHL is genetically heterogeneous.

[Biochemical diagnosis of hereditary hyperlipoproteinemias]

AIM

To specify characteristics of lipoproteins (LPs) metabolism in patients with diverse forms of hereditary hyperlipoproteinemia (HLP) and determine biochemical tests for their differential diagnosis.

MATERIALS AND METHODS

According to the criteria of polygenic hypercholesterolemia (PHCE), family combined hyperlipidemia (FCHL), family hypertriglyceridemia (FHTG) and family hypercholesterolemia (FHCE), 157 patients were selected aged 7 to 70 years of 192 examinees (76 patients with primary HLP and 116 their close relatives). Lipids were measured by enzyme methods, apoproteins (apo)--by immunoturbidimetry and immune diffusion.

RESULTS

Compared to healthy subjects, PHCE patients were characterized by higher apoB level and proportion cholesterol (CS)/apoB in very low and low density lipoproteins (VLDL and LDL). In unchanged level of high density lipoprotein (HDL) CS and proportion HDLP CS/apoA1 there were reduced quantities of free HDLP CS, HDLP2 CS and apoA1. In FHCE and FCHL there were also low levels of HDL CS in elevated ones of apoE in (VLDL + LDL). However, in FCHL, contrary to FHCE, the proportion SC (VLDP + LDL)/apoB was as in control group. FHTG patients differed from healthy subjects by diminished HDL parameters: lower HDL CS due to free CS and its esters, apoA1 and proportion HDL Cs/apoA. There were no differences with controls by content of apoB and proportion CS (VLDL + LDL)/apoB, apoE levels in different class lipoproteins.

CONCLUSION

Biochemical parameters are proposed which can differentiate various forms of hereditary hyperlipoproteinemia.

[Screening and treatment of children and adolescents with hypercholesterolemias and dyslipidemias]

Evidence was provided that atherogenesis develops for several decades before pathological changes are manifested. It may thus be stated, that the "incubation period" of atherosclerotic pathological consequences is very long but it is reduced markedly already from childhood and adolescence in subjects with an atherogenic lipoprotein phenotype. Atherogenic lipoprotein phenotype comprises subjects suffering from one or more, frequently from a combination of several of the following metabolic indicators: hypercholesterolaemia, elevated levels of LDL-cholesterol, apolipoprotein B, lipoprotein (a), reduced levels of HDL-cholesterol and apolipoprotein A-1. The atherogenic lipoprotein phenotype is in 95% conditioned by inborn metabolic errors, i.e. familial hyperlipoproteinaemia and dyslipoproteinaemia. In the population the following are encountered most frequently: combined familial hyperlipidaemia, familial hypertriacylglycerolaemia and familial hypercholesterolaemia. Active screening and treatment of children and adolescents from these affected families is of great importance in primary prevention of atherosclerotic complications in adult age.

[Diagnosis and treatment of severe hyperlipidemia]

Though severe hyperlipidaemia (total cholesterol level > or = 13 mmol/l in this study) is uncommon, it is important to make a precise diagnosis. We examined 57 patients with isolated severe hypercholesterolaemia. Of these, four were homozygotes for familial hypercholesterolaemia, 48 were heterozygotes for familial hypercholesterolacmia and one had sitosterolemia. The heterozygotes carried 15 different LDL receptor mutations, with no one mutation predominating. When the diagnosis is made, relatives should be given the opportunity to be tested. Combined severe hyperlipidaemia is usually due to a secondary cause, at our clinic, the most common cause is diabetes mellitus. The underlying disease should be treated first. However, many patients will require additional lipid-lowering drugs because the underlying disease may be associated with an increased risk of cardiovascular disease. With the exception of fish oil capsules, drugs that reduce serum triglyceride levels substantially are not registered in Norway at present.

Phenotype expression in familial combined hyperlipidemia

Familial combined hyperlipidaemia (FCHL) is one of the most common hereditary disorders predisposing to early coronary death. The affected family members have elevations of serum total cholesterol, triglycerides or both. Despite intensive research efforts the genetic and metabolic defects underlying this complex disorder are still unknown. To dissect the metabolism and genetics of FCHL the phenotype of an individual must be precisely defined. We assessed the influence of different diagnostic criteria on the phenotype definition and studied factors affecting the phenotype expression in 16 large Finnish families (n = 255) with FCHL. The fractile cut-points used to define abnormal lipid values had a profound influence on the diagnosis of FCHL. If the 90th percentile cut-point was used, approximately 45% of the family members were affected, in concord with the presumed dominant mode of transmission for FCHL. If the 95th percentile was used only 22% of study subjects were affected. To characterize the metabolic differences or similarities between the different lipid phenotypes, we determined very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) particles separated by ultracentrifugation. In linkage analysis no single ultracentrifugation variable could discriminate reliably affected family members from non-affected family members. Our data emphasizes the need for re-evaluation of FCHL diagnostic criteria. Preferably, the diagnosis should be based on a single, reliable metabolic marker.

Screening and identification of familial defective apolipoprotein B-100 in clinical samples by capillary gel electrophoresis

Familial defective apolipoprotein B-100 (FDB) is a dominantly inherited disorder. It is characterized by a decreased affinity of low density lipoprotein (LDL) for the LDL receptor, as a consequence of a substitution of adenine by guanine in exon 26 of the apolipoprotein B-100 gene, coding for the putative LDL receptor-binding domain of the mature protein. This disorder is associated with a strikingly high incidence of arteriosclerosis and tends to cause disease and premature death. In this communication we describe a rapid capillary gel electrophoretic method in combination with molecular biology techniques to facilitate the diagnosis of FDB. Mutation screening for FDB is performed by an allele-specific amplification followed by capillary gel electrophoresis (CGE). For the combined polymerase chain reaction (PCR)-CGE method, a total analysis time of only 3 h is needed, a period that is normally necessary for the run and for staining of the gel only, not including the time for PCR, gel casting, etc. In our pilot study 4 of 43 hypercholesterolemic patients were found to have the predominant apoB 3500 codon mutation. The verification is demonstrated by DNA-sequencing. This pilot study will be followed by a large cohort analysis of the south-west German population to determine the frequency of FDB in this area. The PCR-CGE method on the Dionex capillary electrophoresis system (CES I) allows rapid, fully automated detection of the mutation resulting in the unequivocal diagnosis of FDB.

Diagnosing heterozygous familial hypercholesterolemia using new practical criteria validated by molecular genetics

Heterozygous familial hypercholesterolemia (FH) is a serious disorder causing twice normal low-density lipoprotein cholesterol levels early in childhood and very early coronary disease in both men and women. Treatment with multiple medications and diet can normalize cholesterol levels in many persons with FH and prevent or delay the development of coronary atherosclerosis. Thus, there is a need for accurate and genetically validated criteria for the early diagnosis of heterozygous FH. Previously published blood cholesterol criteria greatly underdiagnosed new cases of FH among members of known families with FH in Utah and overdiagnosed FH among participants of general population screening, revealing the need for different cholesterol screening criteria in persons from these 2 different settings. The statistical concept of a priori probabilities was applied to derive 2 sets of practical screening criteria: one for persons participating in general population screening studies and another for close relatives of confirmed FH cases, showing dramatic differences. At a cholesterol level of 310 mg/dl, only 4% of persons in the general population would have FH but 95% of persons who were first-degree relatives of known cases would have FH. Detailed tables were derived to provide practical total and low-density lipoprotein blood cholesterol screening criteria for diagnosing FH in different screening settings and specific age groups. In population screening the new FH criteria require a total cholesterol > 360 mg/dl for age 40+ (or 270 mg/dl in youth). Among first-degree relatives of confirmed cases in families with FH, the new total cholesterol criteria are much lower (> 290 mg/dl for age 40+, > 220 mg/dl for youth).(ABSTRACT TRUNCATED AT 250 WORDS)