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[Endothelial dysfunction in a family with familial combined hyperlipidemia].

Familial Combined Hyperlipidemia is the most frequent familial hyperlipidemia with a high risk a early manifestation of arteriosclerosis. Endothelial dysfunction is the first step in the development of arteriosclerosis. The aim of our investigation was to examine selected markers of endothelial dysfunction in hyperlipidemic members of families with familial combined hyperlipidemia and their normolipidemia first-line relatives and to compare them with healthy individuals. The study includes non-smoking members of the affected families (probands and first-line relatives), who have not suffered from clinical manifestations of arteriosclerosis and/or hypertension during the start of the study. The cohort was divided into hyperlipidemic individuals (N = 25) and normolipidemic individuals (N = 21). Both groups were compared with control groups of healthy individuals (two groups, N = 17 each), who were adjusted by age and sex. The following markers of endothelial dysfunction were examined: 1. ultrasound--flow mediated dilatation of brachial artery and 2. humoral--serum levels of von Willebrand factor, inhibitor of activator of plasminogen-1 and vasoadhesive molecules (vascular cell adhesion molecule-1, intercellular adhesion molecule-1). The members of families with familial combined hyperlipidemia displayed symptoms of endothelial dysfunction. In comparison with healthy controls the endothelial dysfunction was more expressed in hyperlipidemic individuals. They displayed a significantly lower flow-mediated dilatation of brachial artery (3.6 +/- 3.3% versus 6.6 +/- 2.8%, P < 0.01), higher levels of von Willebrand factor (152.8% +/- 79.1% versus 110.4% +/- 24.8%, P < 0.05), inhibitor of activator of plasminogen-1 (94.6 +/- 30.8 ng/ml versus 60.4 +/- 38.0 ng/ml, P < 0.01) and vasoadhesive molecules: vascular cell adhesion molecule-1 (927.0 +/- 167.7 ng/ml versus 814.7 +/- 171.1 ng/ml, P < 0.05), intercellular adhesion molecule-1 (601.7 +/- 89.5 ng/ml versus 544.8 +/- 59.8 ng/ml, P < 0.05). The normolipidemic individuals displayed only a significantly lower flow-mediated dilatation of brachial artery (5.6 +/- 2.6% versus 7.5 +/- 2.8%, P < 0.05) and higher levels of von Willebrand factor (136.8 +/- 40.32% versus 104.1 +/- 24.9%, P < 0.05). No significant difference was found in the levels of inhibitor of activator of plasminogen-1 and vasoadhesive molecules. The results indicated that members of families with familial combined hyperlipidemia represent a high-risk group from the standpoint of early manifestation of arteriosclerosis.

Adult↗

Apolipoprotein B is associated with metabolic syndrome in Chinese families with familial combined hyperlipidemia, familial hypertriglyceridemia and familial hypercholesterolemia.

There is a paucity of data concerning the metabolic syndrome (MetS) in families with familial combined hyperlipidemia (FCHL), familial hypertriglyceridemia (FHTG), familial hypercholesterolemia (FH) and normolipidemic families in China. This study investigated the prevalence of MetS in these families and explored potential factors relevant to MetS. We recruited 70 families with 560 individuals > or = 20 years of age, including 43 FCHL families with 379 individuals, 3 FHTG families with 30 individuals, 16 FH families with 102 individuals and 8 normolipidemic families with 49 individuals. The definition of MetS is determined using modified criteria of National Cholesterol Education Program substituting body mass index for waist circumference. MetS is identified in 60.7% of FCHL patients and 71.4% of FHTG patients. The prevalence of MetS in family members is 36.7% for FCHL, 33.3% for FHTG, 17.6% for FH and 16.3% for normolipidemic families, with an odds ratio (OR) of 2.97 (95% CI 1.29-7.07, P=0.007) in FCHL families compared with normolipidemic families. Apolipoprotein B (apoB) is associated with MetS by multiple logistic analysis with an OR of 1.05 (1.03-1.07, P<0.001) in FCHL families, OR of 1.26 (1.03-1.55, P=0.026) in FHTG and OR of 1.07 (1.01-1.12, P=0.014) in FH families, independent of variables including age, gender, apolipoprotein A1, and low density lipoprotein cholesterol. Apolipoprotein A1 provided an OR of 0.95 (0.94-0.97, P<0.001) in FCHL families and OR of 0.94 (0.90-0.97, P=0.011) in FH families, but neither in FHTG nor in normolipidemic families (both P>0.05). Thus, apoB may be regarded as a relevant factor in the assessment of MetS in FCHL, FHTG and FH families. However, this finding needs to be verified by prospective studies in diverse ethnicities and warrants additional studies to elucidate possible mechanisms linking apoB to MetS.

Adult↗

Association between carotid intima-media thickness and low-density lipoprotein size and susceptibility of low-density lipoprotein to oxidation in asymptomatic members of familial combined hyperlipidemia families.

BACKGROUND AND PURPOSE: In addition to low-density lipoprotein (LDL) cholesterol, small, dense LDL particles and oxidative modification of LDL have been linked to the pathogenesis of atherosclerosis. The present study was aimed at investigating the association between carotid artery intima-media thickness (IMT) and LDL particle size and susceptibility of LDL to oxidation in vitro in asymptomatic members of familial combined hyperlipidemia (FCHL) families. METHODS: LDL particle size, susceptibility of LDL to oxidation in vitro, and carotid IMT were measured in 148 asymptomatic FCHL family members. RESULTS: LDL particle size and lag time for LDL oxidation were reduced in hyperlipidemic compared with normolipidemic family members. LDL particle size, serum total cholesterol, and alpha-tocopherol in LDL were independently associated with lag time for LDL oxidation in multivariate analysis. LDL particle size was associated with carotid mean IMT independently of clinical, lipid, and antioxidant variables in multivariate analysis. Although the susceptibility of LDL to oxidation in vitro was correlated with mean IMT, it did not have a significant independent contribution to variation in mean IMT in the multivariate model. CONCLUSIONS: We conclude that LDL particle size but not susceptibility of LDL to oxidation in vitro is independently associated with carotid IMT in asymptomatic FCHL family members. These results imply that small, dense LDL as an inherent feature of FCHL is an important diagnostic indicator for coronary artery disease risk in FCHL.

Adult↗

[Familial combined hyperlipidemia].

Familial combined hyperlipidemia is a common inherited disorder characterized by a hepatic overproduction of apo B particles and an elevated risk for the development of atherosclerosis. LDL particles are smaller and denser and are more prone to oxidation. The exact pathogenesis of familial combined hyperlipidemia is unclear at present. Treatment should aim to reduce the synthesis of atherogenic lipoproteins and to increase the clearance of triglyceride-rich lipoproteins.

Apolipoproteins B↗

Codon 54 polymorphism of the human intestinal fatty acid binding protein 2 gene is associated with dyslipidemias but not with insulin resistance in patients with familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is associated with variable expression of dyslipidemias and insulin resistance. In nondiabetic Pima Indians an A to G substitution in codon 54 of the fatty acid binding protein 2 (FABP2) gene has been shown to be associated with insulin resistance. We screened the entire coding region of this gene by single-strand conformation polymorphism analysis in 24 probands (17 men and 7 women; age, 63.0 +/- 7.4 years [mean +/- SD]; body mass index [BMI], 27.7 +/- 4.2 kg/m2) who had FCHL and in 40 healthy men from a random population sample of 82 men (age, 54.0 +/- 5.0 years; BMI, 26.3 +/- 3.2 kg/m2). Insulin resistance was assessed with the euglycemic clamp in 58 subjects from FCHL families (14 probands with FCHL and 44 first-degree relatives of probands; 38 men and 20 women; age, 51.5 +/- 12.6 years; BMI, 25.5 +/- 3.9 kg/m2). We found three nucleotide substitution in the FABP2 gene: GCT to ACT (Ala-->Thr) in codon 54, GTA to GTG in codon 118, and GCGCA to GCACA in the 3'-noncoding region. Frequencies of these variants did not differ between the patients and control subjects. The Ala to Thr substitution in codon 54 was associated with a high lipid oxidation rate (P = .011 after adjustment for sex and family relationship), high HDL triglycerides (P = .042), and high LDL triglycerides (P = .013) but not with insulin resistance in subjects from FCHL families. The FABP2 gene is unlikely to be a major gene for FCHL, but it might affect lipid metabolism in subjects with FCHL.

Adult↗

Haplotypes of the ApoA-I/C-III/A-IV gene cluster and familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is the most frequent familial lipoprotein disorder associated with premature coronary heart disease. However, no genetic defect(s) underlying FCHL has been identified. A linkage between FCHL and the apoA-I/C-III/A-IV gene cluster has been reported but not verified in other populations. A recent study identified FCHL susceptibility haplotypes at this gene cluster. To study whether such haplotypes are also associated with FCHL susceptibility in Finns, we studied 600 well-defined Finnish FCHL patients and their relatives belonging to 28 extended FCHL families by using haplotype, linkage, sib-pair, and linkage disequilibrium analyses. The genotypes of the MspI polymorphisms were associated with total serum cholesterol (P<0.01) and apoB (P<0.05) levels in spouses, which represent the general Finnish population. However, no evidence of direct involvement of any of these loci or their specific haplotypes in the expression of FCHL in the Finnish FCHL families was found.

Adolescent↗

Soluble cell adhesion molecules s-VCAM-1 and s-ICAM-1 in subjects with familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCH) is the most common familial hyperlipidemia with a high risk for early atherosclerosis. The aim of this study was to compare levels of soluble intercellular cell adhesion molecule 1 (s-ICAM-1) and soluble vascular cell adhesion molecule 1 (s-VCAM-1) in asymptomatic members of FCH families with healthy controls and to determine the relation between s-ICAM-1, s-VCAM-1 and risk factors accompanying FCH. We also investigated the association between adhesion molecules and the intima-media thickness (IMT) of the common carotid artery, a recognized morphological marker of early atherosclerosis. 82 members of 29 FCH families were divided into the 2 groups: HL (probands and hyperlipidemic first-degree relatives, n = 47) and NL (normolipidemic first-degree relatives, n = 35). The control groups--HL-C (n = 20) and NL-C (n = 20)--consisted of sex- and age-matched healthy individuals. Hyperlipidemic members had significantly higher concentration of s-ICAM-1 (633.7 +/- 169.6 ng/ml versus 546.2 +/- 155.9 ng/ml, p < 0.05). The elevation of s-VCAM-1 was not significant (880.8 +/- 202.9 ng/ml versus 826.5 +/- 174.6 ng/ml, N.S.). Levels of s-ICAM-1 and of s-VCAM-1 in normolipidemic relatives were not significantly different from the control group (530.8 +/- 113.9 ng/ml versus 530.0 +/- 101.0 ng/ml and 860.2 +/- 265.7 ng/ml versus 822.1 +/- 197.0 ng/ml respectively). There was a significant correlation between s-ICAM-1 and apoB (r = 0.42; p < 0.01) in hyperlipidemic subjects and between s-ICAM-1 and proinsulin (r = 0.54; p < 0.01) in normolipidemic subjects. S-ICAM-1 correlated with IMT (r = 0.32; p < 0.05) in all members of FCH families. The increase of s-ICAM-1 in asymptomatic hyperlipidemic members of FCH families reflects their high cardiovascular risk. The positive association between s-ICAM-1 and IMT could indicate s-ICAM-1 as a potential predictor of atherosclerosis manifestation.

Adult↗

The level and species of plasma non-esterified fatty acids are not related to elevated plasma apolipoprotein B levels in familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL), the leading cause of familial hyperlipidemia with premature coronary artery disease, has been associated with insulin resistance and elevated plasma levels of apolipoproten B (apoB) and non-esterified fatty acids (NEFA). Becaus dietary fats affect plasma cholesterol levels, and specific saturated fatty acids (FA) are particularly potent stimulators in vitro of apoB secretio from hepatocytes, we hypothesized that FCHL patients would exhibit elevations in plasma levels of total FA or specific saturated species. Five families containing 12 FCHL subjects (5 adults, 7 children and 8 normals (5 adults, 3 children) were assessed by dietary, anthropometric, and plasma measurements (glucose, insulin, lipoproteins, total NEFA, and specific FA types). After adjustment of the data for age, gender, and family affiliation, multivariate ANOVA indicated that FCHL was significantly associated with elevated plasma levels of apoB (p = 0.001) and insulin (p< 0.001) and increased body weight (p=0.043). Nevertheless, dietary intakes of total and saturated fat were comparable in the two groups, as were plasma levels of total NEFA and the major saturated species. In a study population possessing the salient features of FCHL, circulating total NEFA were not elevated, nor were specific saturated NEFA that had been associated with apoB oversecretion in vitro. Despite the speculated link between plasma FA and apoB overproduction in FCHL, our data suggest that other metabolic factors underlie this disease.

Adult↗

[Familial combined hyperlipidemia].

Familial combined hyperlipidemia (FCHL) is the most common genetic hyperlipidemia of unknown etiology. FCHL is characterized by a variable phenotype of both hypercholesterolemia and hypertriglyceridemia in proband and family members. While, the genetic basis for FCHL has not been characterized, recently, linkage analysis of Finnish FCHL family indicated major gene locus on chromosome 1q21-23. We review recent progress of genetics of FCHL.

Animals↗

Identification of TNFRSF1B as a novel modifier gene in familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is the most commonly inherited hyperlipidemia in man, with a frequency of +/-1% in the general population and approximately 10% in myocardial infarction survivors. A genomic scan in 18 Dutch FCHL families resulted in the identification of several loci with evidence for linkage. One of these regions, 1p36.2, contains TNFRSF1B which encodes one of the tumor necrosis factor receptors. An intron 4 polymorphic CA-repeat was used to confirm linkage to FCHL. Linear regression analysis using 79 independent sib pairs showed linkage with a quantitative FCHL discriminant function (P = 0.032), and, borderline, with apolipoprotein B levels (P = 0.064). Furthermore, in a case-control study, association was demonstrated since the overall CA-repeat genotype distribution was significantly different among 40 unrelated FCHL patients and 48 unrelated healthy spouse controls (P = 0.029). This difference was due to a significant increase in allele CA271 homozygotes in the FCHL patients (P = 0.019). Mutation analysis of exon 6 in 73 FCHL family members demonstrated the presence of a single nucleotide polymorphism with two alleles, coding for methionine (196M) and arginine (196R). Complete linkage disequilibrium between CA267, CA271 and CA273 and this polymorphism was detected. In 85 hyperlipidemic FCHL subjects, an association was demonstrated between soluble TNFRSF1B plasma concentrations and the CA271-196M haplotype. In conclusion, TNFRSF1B was found to be associated with susceptibility to FCHL. Our data suggest that an as yet unknown disease-associated mutation, linked to alleles 196M and CA271, plays a role in the pathophysiology of FCHL.

Adult↗

LDL physical and chemical properties in familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is characterized by elevations of triglyceride and/or cholesterol within families and an elevation in apoB. Although small dense LDL has been consistently associated with hypertriglyceridemia, small dense LDL persists despite reductions in triglyceride after treatment with gemfibrozil in FCHL. The current study evaluated potential differences in the distribution and chemical composition of LDL species in patients with FCHL and normolipidemic control subjects. LDL from FCHL patients was characterized by a relative abundance of a discrete LDL species with a mean peak analytic ultracentrifuge flotation rate (S0f) of 4.7 +/- 0.5 (SEM), a density of 1.041 +/- 0.001 g/mL, and a particle diameter of 250 +/- 1 A as assessed by gradient gel electrophoresis. The major LDL species in the control subjects had a higher mean S0f rate (6.3 +/- 0.4), was more buoyant (density, 1.037 +/- 0.001 g/mL), and was larger (diameter, 262 +/- 2 A). In addition, in a series of six LDL fractions separated by equilibrium density gradient ultracentrifugation, particle diameters were significantly smaller in all fractions from FCHL patients compared with those from control subjects. LDL particles from patients contained less free cholesterol, cholesteryl ester, and phospholipid than LDL from control subjects. The amount of triglyceride per LDL particle, however, did not differ between FCHL patients and control subjects. Differences in flotation rate and mass of the major LDL species between patients and control subjects could not be fully accounted for by differences in plasma triglyceride levels. Thus, LDL particles from FCHL patients are smaller and more dense with less cholesterol and phospholipid. Many of these differences appear to be independent of plasma triglyceride.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

The V73M mutation in the hepatic lipase gene is associated with elevated cholesterol levels in four Dutch pedigrees with familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is a heritable lipid disorder characterized by multiple lipoprotein phenotypes within a single family. Previously, we have shown an increased incidence of mutations in the LPL gene which was associated with elevated levels of very low density lipoprotein (VLDL) and decreased levels of high density lipoprotein among the families studied. Now, we report the results of our study on the hepatic lipase gene. We found the HL V73M variant to be present in four FCHL families. By means of a pedigree-based maximum log-likelihood method we analyzed the effect of this variant on the lipid levels in these families. Carriers of the HL V73M variant revealed significantly higher levels of total cholesterol (P < 0.01) and apoB (P <0.01). These findings show that the HL V73M mutant explains another part of the variability in the phenotype observed among FCHL family members, compared with mutations in the LPL gene. Family analysis shows that in these FCHL families, carriers of mutations in the LPL or HL genes have an increased risk for FCHL compared with their non-carrier relatives.

Adult↗

Genetic evidence from 7 families that the apolipoprotein B gene is not involved in familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is the most common genetic form of hyperlipidemia in which affected individuals manifest multiple lipoprotein phenotypes. Although the molecular defect is still unknown, several kinetic studies have demonstrated increased turnover rates of apolipoprotein B (apo B) in patients with FCHL, irrespective of their lipoprotein phenotype. Using 3 restriction fragment length polymorphisms (RFLPs) of the apo B gene (XbaI, MspI and EcoRI) we have investigated 33 families which fulfill the diagnostic criteria of FCHL. No significant difference in allele frequency was found between 33 unrelated individuals with FCHL and 107 normolipidemic controls. 3-RFLP haplotypes were constructed in each pedigree. A co-segregation analysis was performed in 7 informative families. In no family was co-segregation observed between the haplotype of the apo B gene and the phenotype of FCHL. These data are not compatible with the hypothesis that FCHL is caused by mutations of the apo B gene acting as a simple mendelian trait.

Adult↗

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.

Age Factors↗

Genetic dissection of familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is the most common genetic hyperlipidemia in man. FCHL is characterized by familial clustering of hyperlipidemia and clinical manifestations of premature coronary heart disease, i.e., before the age of 60. Although FCHL was delineated about 25 years ago, at present the FCHL phenotype and its complex genetics are not fully understood. Initially, the familial aggregation of high plasma total cholesterol and triglyceride levels, with a bimodal distribution of triglycerides, was taken as evidence of a dominant mode of inheritance. However, it is now clear that the genetics of FCHL is more complex, and it has been suggested that FCHL is heterogeneous. Several approaches can be taken to identify genes contributing to the disease phenotype in complex genetic disorders either by studying the disease in the human situation or by using animal models. Recent reports have shown that a combination of genetic linkage studies, association studies, and differential gene expression studies provides a useful tool for the genetic dissection of complex diseases. Therefore, the genetic strategies that will be used to dissect the genetic background of FCHL are reviewed.

Animals↗

Analysis of DNA changes in the LPL gene in patients with familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCHL) is a common lipid disorder characterized by an increase in cholesterol and/or triglyceride levels in multiple individuals of the same family. Prior reports document a decreased activity of lipoprotein lipase (LPL) in FCHL, and studies of the role of LPL in the remodeling of nascent lipoproteins suggest that disturbances in LPL function could underlie FCHL. We studied the LPL gene in 31 unrelated individuals with FCHL. A total of 25 DNA changes (13 "silent" substitutions and 12 DNA changes resulting in amino acid substitutions) were detected in 16 patients. Three new exonic polymorphisms as well as a previously described Ser447-->stop and an Asp9-->Asn substitution were seen with similar frequency on control and FCHL chromosomes. Two novel DNA changes resulting in an Asp21-->Val and an His44-->Tyr substitution were seen in only two FCHL individuals. In vitro studies showed no effect of these mutations on LPL catalytic activity. LPL mutations impairing catalytic activity did not represent a significant factor leading to FCHL in this population. Variations in any portion of the coding region of the LPL gene affecting other functions besides catalysis are not a frequent cause of FCHL.

Adult↗

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.

Adult↗

A common genetic mechanism determines plasma apolipoprotein B levels and dense LDL subfraction distribution in familial combined hyperlipidemia.

Familial combined hyperlipidemia (FCH) is a common lipid disorder characterized by elevations of plasma cholesterol and/or triglyceride in first-degree relatives. A predominance of small, dense LDL particles and elevated apolipoprotein B (apoB) levels is commonly found in members of FCH families. Many studies have investigated the genetic mechanisms determining individuals' lipid levels, in FCH families. Previously, we demonstrated a major gene effect on LDL particle size and codominant Mendelian inheritance involved in determination of apoB levels in a sample of 40 well-defined FCH families. An elevation of apoB levels is associated metabolically with a predominance of small, dense LDL particles in FCH. To establish whether a common gene regulates both traits, we conducted a bivariate genetic analysis to test the hypothesis of a common genetic mechanism. In this study, we found that 66% of the total phenotypic correlation is due to shared genetic components. Further bivariate segregation analysis suggested that both traits share a common major gene plus individual polygenic components. This common major gene explains 37% of the variance of adjusted LDL particle size and 23% of the variance of adjusted apoB levels. Our study suggests that a major gene that has pleiotropic effects on LDL particle size and apoB levels may be the gene underlying FCH in the families we studied.

Apolipoproteins B↗