Identification of a common variant in the lipoprotein lipase gene in a large Utah kindred ascertained for coronary heart disease: the -93G/D9N variant predisposes to low HDL-C/high triglycerides

Defects in the lipoprotein lipase (LPL) gene are associated with dyslipidemia in the general population. Several rare mutations in the gene, as well as two common coding region polymorphisms, D9N and N291S, exhibit deleterious effects on circulating lipid levels. Using a linkage-based approach, we have identified a large Utah kindred segregating the D9N variant in the LPL gene. The kindred was ascertained for premature coronary heart disease and was expanded based on familial dyslipidemia. A genomic scan identified a region of linkage including LPL, and mutation screening identified the segregating variant. In the kindred, the variant shows high penetrance for a hypoalphalipoproteinemia phenotype, but is also associated with hypertriglyceridemia and elevated insulin levels. The strength of linkage was dependent on the combination of phenotype definition and model parameters, favoring the use of a MOD score approach. Most other studies of LPL have proceeded by mutation screening of randomly chosen individuals or selected affected probands; this is the first example identifying a segregating LPL mutation using direct linkage.     

The gene for apolipoprotein C-ll is closely linked to the gene for apolipoprotein E on chromosome 19

We have used a common TaqI restriction fragment length polymorphism (RFLP) near the human apolipoprotein C-II (apoC-II) gene to study linkage with apolipoprotein E (apoE). The inheritance of the apoC-II RFLP was followed in seven families that were segregating for apoE protein variants. No recombinants were observed in 20 informative meioses, giving an overall lod score of > 4.0 at recombination fraction 0. We have also observed apparent linkage disequilibrium between apoE and the apoC-II RFLP. Taken together these results demonstrate that these two apolipoprotein genes are closely linked and confirm that the gene for apoC-II is on human chromosome 19.     

DNA polymorphisms of human apolipoprotein A-IV gene: frequency and effects on lipid, lipoprotein and apolipoprotein levels in a French population

Genetic polymorphisms of apolipoprotein (apo) A-IV have been shown to influence lipoprotein metabolism in some human populations. In this study, we have evaluated the physiological effect of three apo A-IV polymorphisms (Gln_{360- < His}, Thr_{347- < Ser} and XbaI within the second intron of the apo A-IV gene), in a French population, on seven quantitative traits: total cholesterol and triglycerides, cholesterol of HDL, apo A-IV, apo B, apo A-I and glucose. The polymorphism at amino-acid 360 was determined by direct analysis of polymerase chain reaction products. The allele frequencies were 0.92 for the A-IV¹ and 0.08 for the A-IV² allele. The genetic polymorphism at codon 347 was investigated by allele-specific oligonucleotide hybridization. The allele frequencies of the two alleles, A-IV^347Thr and A-IV^347Ser, were 0.78 and 0.22, respectively. The XbaI polymorphism was investigated by polymerase chain reaction followed by XbaI restriction enzyme digestion of the amplified products. The frequencies of the two apo A-IV alleles, XbaI-1 and XbaI-2, were 0.79 and 0.21, respectively. None of the three apo A-IV polymorphisms had a significant effect on lipoprotein, apolipoprotein and glucose levels.     

Apolipoprotein E polymorphism and lipid levels differ by gender and family history of diabetes: the Rancho Bernardo Study

Association between apolipoprotein E (apoE) gene polymorphism and lipid levels was studied in 164 nondiabetic first-degree relatives of persons with diabetes and 962 nondiabetic persons with no family history of diabetes. Sex-specific genotypic distribution of apoE polymorphism did not differ between persons with and without a family history of diabetes. In first-degree relatives, lipid levels did not differ among persons with apoE2 (E2/2, E2/3), apoE3/3, and apoE4 (E4/4, E3/4) after adjusting for age, waist circumference, smoking, and alcohol and estrogen use. In persons without a family history of diabetes, both men (p<0.01) and women (p<0.001) with apoE2 showed lower levels of total and low density lipoprotein cholesterol compared with persons with apoE3/3 and apoE4. In women with a family history of diabetes, persons with apoE4 had larger waist circumference (p<0.05). ApoE2 allele is associated with more favorable levels of total and low density lipoprotein cholesterol in men and women without a family history of diabetes. ApoE4 allele is associated with obesity independent of dyslipidemia in women but not men with a family history of diabetes. ApoE polymorphism is not associated with lipids in men or women with a family history of diabetes.     

apoE/LDLR双基因突变小鼠肝脏脂代谢相关基因的表达研究

目的探讨载脂蛋白E和低密度脂蛋白受体双基因缺失（apoE^-/-/LDLR^-/-）小鼠肝脏脂代谢相关基因表达特征与动脉粥样硬化早期病变的关系及发生机制。方法应用RT-PCR技术检测apoE^-/-／LDLR^-/-与野生型小鼠肝脏脂代谢相关基因表达差异,并进行血生化指标检测及主动脉形态学观察。结果所检测的11个脂代谢相关基因中,apoE^-/-／LDLR^-/-小鼠与野生型小鼠相比,载脂蛋白B100和脂肪酸转运体（FAT／CD36）的mRNA水平从14天龄至3月龄均升高。载脂蛋白AⅣ、载脂蛋白AⅤmRNA水平分别于14天龄和3月龄时明显降低。载脂蛋白AⅠ、载脂蛋白F、过氧化物增殖物激活型受体α、肝X受体α、血管生成素样蛋白3、酰基辅酶A氧化酶1及肉碱棕榈酰转移酶ImRNA表达水平无明显差异。血清总胆固醇、总甘油三酯和低密度脂蛋白胆固醇水平分别高于同龄野生型小鼠约7、2和30倍。随年龄增长apoE^-/-／LDLR^-/-小鼠主动脉内膜出现典型的动脉粥样硬化早期病变。结论上述脂代谢相关基因表达变化表明它们在动脉粥样硬化发生发展过程中起重要作用。     

Molecular cloning and characteristics of a new apolipoprotein C-II mutant identified in three unrelated individuals with hypercholesterolemia and hypertriglyceridemia

A new rare mutant form of apolipoprotein C-II (apoC-II), designatedapoC-II_SF, was identified in three unrelated hyperlipidemicpatients. The first was a Caucasian male with a total cholesterol(TC) of 313 mg/dl and total triglyceride (TG) of 282 mg/dl,the second an African-American female (TC 345 mg/dl, TG 203mg/dl) and the third, an African—American male (TC 345mg/dl, TG 1000 mg/dl). Each subject was found to be heterozygousfor a G to A substitution in the codon for residue 38, resultingin a Lys for Glu exchange. This accounts for the increased plvalue of 5.3. The third patient, in addition to apoC-II_SF, hadapoC-II₂, another charge variant. This was determined by DNAsequencing, confirming the Gln for Lys change at residue 55previously predicted by analysis of peptide fragments in thislaboratory. Similar Michaelis constants of activation and activationenergies were observed when the ability of apoC-II_SF to activatelipoprotein lipase was compared to normal apoC-II. This indicatesthat major changes in charge around residue 38 lack effect onthe activation properties. The variant may be altered in someother property, such as lipid binding, but since the distributionof apoC-II_SF revealed no simple co-inheritance with lipid levels,it is unclear to what extent it plays a role in the observedhyperlipidemia. The presence of other factors acting togetherwith the variant may predispose to elevated lipid levels.     

Co-segregation of elevated LDL with a novel mutation (D92K) of the LDL receptor in a kindred with multiple lipoprotein abnormalities

Factors predisposing to the phenotypic features of familial combined hyperlipidemia have not been clearly defined. In the course of investigating familial coronary artery disease in Utah, we identified a three-generation family in which multiple members were affected with type IIa hyperlipoproteinemia (HLP IIa), type IIb hyperlipoproteinemia (HLP IIb), or type IV hyperlipoproteinemia (HLP IV). Because several family members had relatively severe low-density lipoprotein (LDL) cholesterol elevation, in order to dissect the possible contribution to the plasma lipoprotein abnormalities in this pedigree, we identified a novel point mutation in the low-density lipoprotein receptor (LDLR) gene, a G-to-A transition at nucleotide position 337 in exon 4. This change substituted lysine for glutamic acid at codon 92 (D92K) of the LDL receptor. By means of mutant allele-specific amplification we determined that the mutation co-segregated with elevated cholesterol and LDL cholesterol in the plasma of family members with HLP IIa and HLP IIb, but not with the elevated plasma triglycerides seen in HLP IIb and HLP IV patients. Thus, in families with apparent familial combined hyperlipidemia, a defective LDLR allele and other genetic or environmental factors that elevate plasma triglycerides may account for the multiple lipid phenotypes observed in this kindred. Received: November 5, 1999 / Accepted: January 8, 2000     

载脂蛋白E基因多态性与早发冠心病的关系及其对血脂的影响

目的 研究载脂蛋白E（apolipoprotein E,apoE)基因多态性与早发冠心病（coronary heart disease,CHD)的相关关系及其对血脂水平的影响。方法 应用聚合酶链反应－限制性片段长度多态性（polymerase chain reaction-restricted fragment hength polymorphism,PCR-RFLP)基因分析方法,测定52例早发CHD、161例迟发CHD患者和180名对照者的apoE基因型;血脂水平按常规方法测定。结果 发现的5种apoE基因型,分别为E3／3、E4／4、E3／2、E4／3及E4／2。早发CHD组和迟发CHD组apoE4/3基因型和ε4等位基因频率均高于对照组（P＜0．01）;进一步对两组CHD患者的apoE多态性进行分析,发现早发组ε4等位基因频率较迟发组为高（P＜0．05）。apoE各等位基因型之间,TC和LDL－C水平之间存在统计学差异（P＜0．05）。结论 apoE基因多态性与早发CHD的发生发展有关并影响血脂的水平。     

Apolipoprotein CII-Padova (Tyr37-->stop) as a cause of chylomicronaemia in an Italian kindred from Siculiana.

In this paper we report on the molecular defect underlying apolipoprotein CII (apoCII) deficiency in an Italian kindred. ApoCII serves as cofactor for lipoprotein lipase (LPL) in triglyceride hydrolysis of chylomicrons and very low density lipoproteins. Homozygous apoCII deficiency manifests with type I hyperlipoproteinaemia and is a rare disorder of lipoprotein metabolism. Until now, only 10 kindreds with apoCII deficiency have been published and all underlying mutations were unique. The proband was the offspring of a consanguineous mating. Sequencing of cloned DNA from the proband presented in this report showed homozygosity for a C-->A substitution at position 3002 in the apoCII gene, resulting in the introduction of a premature stop codon at residue 37 of the mature apoCII protein. Therefore, a truncated apoCII is synthesised, lacking the part of the apolipoprotein that activates LPL. This mutation has previously been described in another Italian family and is known as apoCIIPadova. We propose that apoCIIPadova is a frequent cause of apoCII deficiency in persons of Italian descent.     

Clinical manifestations in a large hereditary hemorrhagic telangiectasia (HHT) type 2 kindred

HHT type 2 (HHT 2) is a multi-system vascular dysplasia caused by a mutation in the ALK-1 gene, but the phenotype has not been well defined. We report on 51 members of an HHT 2 kindred with an ALK-1 gene mutation shown to be associated with the disorder. This ALK-1 mutation was detected in 38 kindred members who were evaluated systematically for associated vascular abnormalities. Pulmonary arteriovenous malformations (AVMs) were found in 6% of those screened, cerebral AVM in 7%, hepatic AVM in 17%, and spinal AVM in 3%. We discuss these and other findings in the 38 affected kindred members, as well as findings in the 13 kindred members in whom the mutation was not detected. This study shows that pulmonary, cerebral, spinal, and hepatic AVMs can all occur in HHT 2. It also adds to the evidence suggesting that pulmonary AVMs are more common in HHT 1 than in HHT 2. We identify a higher prevalence of hepatic AVMs than previously reported in either HHT 1 or 2. This may be specific to the mutation in this kindred, but probably reflects the lack of routine screening for this manifestation. Even in this family in which all affected individuals have the same mutation, the clinical manifestations of HHT and their severity varied tremendously. Intrafamilial variation in expression of HHT is clearly significant, emphasizing the difficulty in establishing the diagnosis in individuals and in sub-typing families when DNA testing is not available.     

Apolipoprotein E Isoforms Increase Intracellular Ca2+ Differentially Through a ω-Agatoxin IVa-Sensitive Ca2+-Channel

Apolipoprotein E (apoE) is the major apolipoprotein in the brain and is known for its important role in plasticity and neurodegeneration. We show that apoE dose-dependently increases intracellular free Ca²⁺ in rat hippocampal astrocytes and neurons. This effect varies with isoforms in the order E4>E3>E2. It is insensitive to blockade of action potentials by tetrodotoxin or inhibition of binding of apoE by heparinase, by the LRP ligand lactoferrin and by low density lipoprotein. ApoE evoked Ca²⁺-increases are blocked in zero [Ca]o and by the Ca-channel antagonists nickel and ω-Agatoxin-IVa but not by nifedipine and ω-Conotoxin-GVIa, demonstrating an isoform-specific activation of P/Q type Ca²⁺-channels. This novel mechanism is discussed with respect to Alzheimer's disease, that is linked for most cases to the apoE ε-allelic variation (ε4 > ε3 > ε2).     

A novel point mutation (Pro84 ← Ser) of the low density lipoprotein receptor gene in a family with moderate hypercholesterolemia

To obtain insight into the possibility that genetic variation of the structure of the low density lipoprotein (LDL) receptor protein could result in subtle changes of serum cholesterol levels, we used single-strand conformation polymorphism (SSCP) to screen all 18 exons of the LDL receptor gene in a panel of subjects with moderate hypercholesterolemia. One novel mutation, replacing C to T at nucleotide 313 and predicted to cause a substitution of serine for proline at codon 84, was identified in a single proband. A convenient PCR assay based on the use of primer-introduced restriction fragment length polymorphism was set up for the detection of this mutation. However, the pathophysiologic significance of the Pro84 → Ser replacement remains to be clarified, as serum LDL cholesterol levels were not significantly higher in mutation carriers vs. non-carriers in the affected family, and no other proband was identified, on screening of DNA samples from 350 Finns. The Pro84 → Ser mutation represents the second single-amino acid change of the LDL receptor protein so far reported which is not associated with the clinical phenotype of familial hypercholesterolemia.     

Characterization of an apolipoprotein E3 variant (Arg 145-->His) associated with mild hypertriglyceridemia

In a proband (21-yr-old female), we previously identified an apolipoprotein (apo) E variant, apoE3 (Arg 145-->His), with an isoelectric point midway between apoE3 and apoE2. ApoE gene analysis of 4 of the proband's kin indicated that 3 possess the same variant. All 4 had a high concentration of apoE in plasma, while 3 of 4 had hypertriglyceridemia. In the proband (who had no hypertriglyceridemia), most apoE was distributed in slow-alpha lipoproteins (predominantly in the form of apoE-AII heterodimer) and in larger molecules with apparent molecular weights of 80 and 100 kDa. In the proband's brother (with hypertriglyceridemia), however, most apoE was distributed in slow pre-beta lipoproteins, predominantly in the form of monomeric apoE. In each subject, the concentration of apoE3 variant was significantly higher than that of normal apoE3 in the predominant apoE-rich lipoprotein. The apoE3 variant, which displayed a slightly reduced binding ability to LDL-receptor and heparin, may induce an accumulation of apoE-rich lipoproteins. These observations suggest that the difference in distribution of apoE3 variant in plasma lipoproteins between the proband and her brother (combined with its reduced affinity for the LDL receptor) may provide key insights into the pathogenesis of hypertriglyceridemia.     

Interaction between low density lipoprotein receptor (LDLR) and apolipoprotein E (apoE) alleles contributes to normal variation in lipid level

Subjects drawn from a population-based register were studied with respect to lipid level association. The association of isoforms of apolipoprotein E (apoE) with lipid level in the general population was found to be limited to people with one particular genotype at the low density lipoprotein receptor (LDLR) locus. The results presented in this paper suggest that functional LDLR variants enhance or limit the effect of isoforms of apoE. The association between apoE4 and serum total and LDL cholesterol level may be mediated through the LDL (apoB100, apoE) receptor to a greater extent than previously thought.     

Growth hormone receptor variant (L526I) modifies plasma HDL cholesterol phenotype in familial hypercholesterolemia: intra-familial association study in an eight-generation hyperlipidemic kindred

Defect of growth hormone receptor (GHR) is classically known to cause Laron syndrome, characterized by short stature, specific facial appearance, elevated serum growth hormone levels, and decreased insulin-like growth factor I levels. In addition, an increased cardiovascular risk due to elevated plasma total and LDL cholesterol levels marks another feature of the disease. Growth hormone (GH) plays an important role in the regulation of lipoprotein metabolism. GH status was found to be an independent determinant of plasma total cholesterol and triglyceride levels in humans. We studied a total of 207 members of eight-generation extended family of familial hypercholesterolemia (FH) in which affected members presented with various lipoprotein phenotypes. Intra-familial correlation analysis of a modifier effect of a Leu526Ile substitution in GHR gene was carried out among 95 carriers for LDL receptor gene (LDLR) mutation and 112 non-carriers. When plasma high-density lipoprotein cholesterol (HDL-c) levels in the LDLR-mutation carriers were compared, a significant lowering effect of HDL-c was observed with the Leu allele; the values were lowest among Leu/Leu homozygotes (mean +/- SD = 37 +/- 2 mg/dl), highest in Ile/Ile homozygotes (50 +/- 4 mg/dl), and intermediate among Leu/Ile heterozygotes (41 +/- 2 mg/dl) (P = 0.0021). The results indicate a significant modification of the phenotype of FH with the defective LDLR allele, by GHR Leu variation in the kindred studied.     

Estradiol replacement increases the low-density lipoprotein receptor related protein (LRP) in the mouse brain

Numerous epidemiology studies have shown protective effects of hormone therapy (HT) on chronic neurological diseases. We have proposed that some of the neuroprotective effects of estrogen are mediated by apolipoprotein E (apoE). Polymorphisms of receptors for apoE modify the risk for dementia. To our knowledge, no reports exist showing CNS effects of estrogen replacement on members of the low-density lipoprotein receptor family. The current study focused on the effect of estradiol-17beta (E2) replacement on protein expression of two members of the receptor family, the low-density lipoprotein receptor (LDL-r) and low-density lipoprotein receptor related protein (LRP) in ovariectomized mice. Five days of E2 replacement significantly increased LRP expression in the hippocampus, olfactory bulb and neocortex but not in cerebellum. In contrast, E2 treatment decreased LDL-r protein expression in olfactory bulb. HT modification of both apoE and LRP could have wide-spread effects on cellular function given LRP's manifold signaling functions.     

Four novel mutations in APOB causing heterozygous and homozygous familial hypobetalipoproteinemia

Familial hypobetalipoproteinemia (FHBL) is a rare codominant disorder of lipoprotein metabolism characterized by low levels of low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B. Heterozygotes for FHBL have less-than-half normal LDL-cholesterol and apoB concentrations, whereas homozygotes have extremely low or undetectable LDL-cholesterol and apoB levels. These reductions in LDL-cholesterol and apoB have been suggested to provide FHBL subjects with resistance to atherosclerosis. FHBL can be caused by mutations in the APOB gene on chromosome 2. We present four novel mutations and one previously described mutation in APOB causing FHBL in five families. Immunoblotting and DNA sequencing were used to characterize the novel mutation apoB-40.3 (c.5564_5565insC) and the previously reported mutation apoB-80.5 (c.11040T>G). The apoB-6.9 (c.1018_1025del) and apoB-25.8 (c.3600T>A) mutations were identified by DNA sequence analysis, as variants shorter than apoB-31 are not detectable in plasma. A fifth mutation, the splice variant c.82+1G>A, was identified by sequencing and was found in a homozygous subject. In approximately 50% of the FHBL subjects, plasma alanine aminotransferase concentrations were mildly increased, suggestive of fatty liver. All affected FHBL subjects had low to low-normal serum vitamin E concentrations, highlighting the important and recognized relationship between lipid and vitamin E concentrations.     

Ethnic differences in lipid and lipoprotein metabolism in pregnant women of African and Caucasian origin.

AIMS--To investigate differences in serum lipid, lipoprotein and apolipoprotein concentrations in pregnant women of different ethnic origin. METHODS--Serum lipid, lipoprotein and apolipoprotein concentrations were measured in 232 women (114 Caucasians, 118 Africans/Afro-Caribbeans), who presented consecutively for screening for gestational diabetes in the third trimester of pregnancy. RESULTS--African/Afro-Caribbean pregnant women had lower serum concentrations of total cholesterol, low density lipoprotein cholesterol, triglycerides, and apolipoprotein B and higher high density lipoprotein cholesterol and Lp(a) lipoprotein concentrations compared with Caucasian women. Apolipoprotein A1 concentrations were similar in the two groups. The differences were not attributable to differences in weight, age, parity, or postload plasma glucose levels. CONCLUSION--Ethnic origin is an important determinant of serum lipid, lipoprotein and apolipoprotein concentrations during pregnancy.     

APOE/C1/C4/C2 hepatic control region polymorphism influences plasma apoE and LDL cholesterol levels

We characterized 102 kb of chromosome 19 containing the apolipoprotein (APO) E/C1/C4/C2 cluster and two flanking genes for common DNA variants associated with plasma low-density lipoprotein cholesterol (LDL-C) level. DNA variants were identified by comparing sequences of 48 haploid hybrid cell lines. We genotyped participants (1943 Whites and 2046 African-Americans) of the Coronary Artery Risk Development in Young Adults study for 115 variants. After controlling for the effects of the APOE epsilon2/3/4 polymorphism, a single nucleotide polymorphism, rs35136575, in the downstream hepatic control region 2 (HCR-2) was associated with LDL-C in Caucasians (P = 0.0004), accounting for 1% of variation. We genotyped rs35136575 in the Atherosclerosis Risk in Communities (ARIC) cohort (3679 African-Americans and 10 427 Whites) and in the Genetic Epidemiology Network of Arteriopathy (GENOA) sibships (1381 African-Americans in 592 sibships, 1116 Caucasians in 503 sibships and 1378 Mexican-Americans in 416 sibships), finding association with LDL-C level in ARIC Caucasians (P = 0.0064). Lower plasma LDL-C was observed with the rare allele. Plasma apoE level was strongly associated with HCR-2 variant genotype in all three GENOA samples (P 相似文献