Biomedical subjects

G Assmann

Publications and source records attributed to G Assmann.

At least 253 records · Page 14Linked to original sources

PubMed1994

Fibrinogen and factor VII in the prediction of coronary risk. Results from the PROCAM study in healthy men.

Coronary thrombosis is regarded as the final occlusive event in the progress of coronary heart disease (CHD). Disturbances of the hemostatic system may favor this process and thus may indicate increased risk of myocardial infarction. Coagulation and lipid factors were measured in 2116 healthy male participants of the Prospective Cardiovascular Münster (PROCAM) study. After 6 years of follow-up, 82 coronary events (9 sudden cardiac deaths and 14 fatal and 59 nonfatal myocardial infarctions) were observed. The mean plasma fibrinogen levels of the event and nonevent groups differed by 0.25 g/L (2.88 [SD, 0.68] versus 2.63 [SD, 0.63] g/L, respectively; P = .001). The incidence of coronary events in the upper tertile of the plasma fibrinogen distribution was 2.4-fold higher than in the lower tertile. By multiple logistic function analysis, plasma fibrinogen was found to be an independent risk indicator for CHD (P < .05). Individuals in the high serum low-density lipoprotein (LDL) cholesterol tertile who also showed high plasma fibrinogen concentrations had a 6.1-fold increase in coronary risk. Unexpectedly, individuals with low plasma fibrinogen had a low incidence of coronary events even when serum LDL cholesterol was high. The mean factor VIIc activities in the event and nonevent groups did not differ significantly (112.3% [SD, 19.9] versus 108.4% [SD, 21.6]; P = .09). There was, however, a trend toward higher factor VIIc values when only fatal events were taken into account. Thus, higher levels of plasma fibrinogen markedly increased the predictive power of high serum LDL cholesterol. Low plasma fibrinogen is associated with low coronary risk even when LDL is raised.

Adult↗

PubMed1994

Plasma Lp(a) levels correlate with number, severity, and length-extension of coronary lesions in male patients undergoing coronary arteriography for clinically suspected coronary atherosclerosis.

The relation between lipoprotein(a) [Lp(a)] as an independent risk factor for coronary atherosclerosis and the severity and extension of angiographically detectable coronary atherosclerotic lesions has not been systematically evaluated. In 118 male patients (54.3 +/- 7.4 years) with suspected coronary artery disease and without a history of myocardial infarction undergoing coronary angiography, the relation between plasma Lp(a) levels and other lipoproteins and the severity and extension of coronary lesions was studied. The coronary angiograms were evaluated in a blinded manner according to three scores: vessel score (0 to 3 points for 0 to 3 vessels with stenoses > or = 70%), stenosis score (0 to 32 points; number and severity of coronary stenoses or lesions), and extent score (0 to 100 points; length-extension of all coronary lesions in relation to the total coronary vessel length). The score values obtained were analyzed for correlations with age and levels of total cholesterol (6.08 +/- 1.26 mmol/L; mean +/- SD), high-density lipoprotein cholesterol (1.04 +/- 0.33 mmol/L), low-density lipoprotein cholesterol (4.18 +/- 1.15 mmol/L), triglycerides (1.88 +/- 1.37 mmol/L), and Lp(a) in plasma (19.5 +/- 22.6 mg/dL). Bivariate correlation analysis resulted in positive correlations between Lp(a) and vessel score (P < .01), stenosis score (P < .01), and extent score (P < .05). With multivariate analyses, besides Lp(a) plasma level (nl), only patient age showed a significant correlation to all three scores used, whereas none of the lipid parameters correlated significantly with all three scores.

Adult↗

PubMed1994

A nonsense mutation in the apolipoprotein A-I gene is associated with high-density lipoprotein deficiency and periorbital xanthelasmas.

Conflicting data from epidemiological trials, genetic family studies, transgenic animal models, and in vitro experiments have created controversy regarding the importance of HDL and apolipoprotein (apo) A-I for reverse cholesterol transport and protection from atherosclerosis. In this study we identified a homozygous nonsense mutation in codon 32 (Q32X) of the apoA-I gene as the molecular basis of apoA-I deficiency in a 31-year-old woman who did not present with clinical signs of atherosclerosis. Despite half-normal plasma concentrations of HDL cholesterol and apoA-I in subjects heterozygous for this mutation, the history of the patient's large family did not indicate any increased prevalence of myocardial infarction.

Adult↗

PubMed1994

Effects of age, lipoproteins, and hemostatic parameters on the role of homocyst(e)inemia as a cardiovascular risk factor in men.

Previous studies have identified moderately elevated plasma concentrations of homocyst(e)ine as an independent risk factor for coronary heart disease (CHD). The atherogenicity of homocyst(e)ine has mostly been attributed to its effects on endothelial cells, platelets, and the hemostatic system. In this case-control study of 199 male CHD patients and 156 age-matched control subjects, we analyzed the role of homocyst(e)ine as a cardiovascular risk marker in the context of traditional risk factors as well as of plasma fibrinogen, plasminogen, and viscosity. Both univariate and multivariate regression analyses revealed that homocyst(e)ine levels were significantly correlated with age, fibrinogen, and plasma viscosity in both study groups. Geometric mean homocyst(e)ine levels by univariate analysis were significantly higher in patients than in control subjects (8.9 versus 7.8 mumol/L, P < .001). This difference remained significant on multiple logistic function analysis after being adjusted for body mass index, systolic blood pressure, serum cholesterol, and high-density lipoprotein cholesterol but not after additional adjustment for fibrinogen. By contrast, geometric mean fibrinogen levels after adjustment for homocyst(e)ine levels were significantly different between patients and control subjects (296.4 versus 230.8 mg/dL, P < .001). Within the group of CHD patients, both fibrinogen and homocyst(e)ine significantly increased in parallel with the number of stenosed coronary vessels. We conclude that hyperhomocyst(e)inemia is an independent coronary risk factor and that its interrelation with fibrinogen levels merits further study.

Adult↗

PubMed1994

Sex-specific effects of the glutamine/histidine polymorphism in apo A-IV on HDL metabolism.

In Caucasians, a histidine for glutamine substitution (Gln-->His) at residue 360 in apolipoprotein (apo) A-IV leads to an electrophoretically detectable polymorphism whose contribution to lipid metabolism regulation is controversial. In this study of 426 male and 188 female coronary heart disease patients, we analyzed the impact of this polymorphism on lipid metabolism, particularly high-density lipoprotein (HDL). The frequency of the rarer apo A-IV (360:His) allele was .069. This polymorphism exerted opposite effects in men and women in terms of serum concentrations of total cholesterol; triglycerides; HDL cholesterol; LDL cholesterol; lipoprotein (Lp) A-I; and apo A-I, A-II, and B. Only the difference in Lp A-I levels between male apo A-IV (360:Gln/Gln) homozygotes and apo A-IV (360:Gln/His) heterozygotes was significant (P < .05). In randomly selected subgroups of 38 male and 15 female apo A-IV (360:Gln/His) heterozygotes and 104 male and 15 female apo A-IV (360:Gln) homozygotes, heterozygosity for apo A-IV (360:Gln/His) in both sexes was associated with lower plasma cholesteryl ester transfer protein (CETP) activity (P < .05) and higher serum apo A-IV concentrations (P < .01 in men). Moreover, only men had significantly higher mean plasma activity levels of lecithin:cholesterol acyltransferase (LCAT) (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1994

Electrophoretic screening for genetic variation in apolipoprotein C-III: identification of a novel apoC-III variant, apoC-III(Asp45-->Asn), in a Turkish patient.

Screening of 6,840 plasma samples by isoelectric focusing (IEF) led to the identification of a novel apolipoprotein C-III variant. The underlying molecular defect was established by sequencing of exons 3 and 4 of the apoC-III gene subsequent to their amplification by the polymerase chain reaction (PCR). A G-->A transition in the first nucleotide of codon 45 results in a replacement of aspartic acid by asparagine. ApoC-III(Asp45-->Asn) was detected in a Turkish patient who previously had undergone coronary bypass surgery. Family studies identified two of the three children of the index patient as heterozygous variant carriers. The family was too small to demonstrate a significant effect of the variant on lipid metabolism. However, as judged by two-dimensional immunoelectrophoresis as well as IEF and subsequent scanning densitometry, the concentrations of the variant allele products were increased twofold in very low density lipoproteins (VLDL) and slightly decreased both in low density lipoproteins (LDL) and in high density lipoproteins (HDL) relative to the concentrations of the normal allele products. The disproportional distribution of the variant apoC-III isoproteins may indicate differences in the metabolism of variant and normal apoC-III. We conclude that genetically determined structural variants of apoC-III with changes in complete net charges are very rare and, hence, do not significantly contribute to the formation of dyslipidemia in the German population. Although heterozygosity for apoC-III(Asp45-->Asn) is not associated with severe dyslipidemia, the disproportional distribution of the allele products among plasma lipoproteins indirectly indicates some impact on lipoprotein metabolism.

Alleles↗

PubMed1994

[Coronary angiography and intravascular ultrasound examination of a 60-year-old patient with familial HDL deficiency (Tangier disease)].

A 60-year-old homozygous patient with familial high density lipoprotein deficiency (Tangier disease) was examined by coronary angiography and intravascular ultrasound because of typical angina pectoris. We found a normal left ventricular function, moderately diffuse coronary sclerosis without stenosis, and no critical stenosis of peripheral arteries. Intravascular ultrasound revealed normal thickness and the three-layer appearance of the arterial intima, media, and adventitia within the peripheral arteries, and showed a single, discrete arteriosclerotic lesion in one iliac artery segment. The lack of severe atherosclerosis was remarkable insofar as massive foam cell formation in reticuloendothelial tissues and the virtually complete absence of circulating HDL is characteristic of Tangier disease and had been previously demonstrated in this patient.

Arteriosclerosis↗

PubMed1994

Effects of two kinds of decaffeinated coffee on serum lipid profiles in healthy young adults.

OBJECTIVE: To investigate the effects of two kinds of decaffeinated coffee on serum lipid profiles in healthy young adults. DESIGN: Randomized controlled study with three study groups and a parallel design, consisting of two consecutive periods. SETTING: Outpatient clinical research center in a university clinic. SUBJECTS: 119 healthy students (60 male, 59 female) who were selected after a screening. All completed the study. Blood samples of three subjects (1 male, 2 female) were excluded from evaluation due to later diagnosed genetic anomalies of lipid metabolism. INTERVENTIONS: All subjects consumed 750-1000 ml of caffeinated filtered coffee per day for a 2 week wash-in period. During the 6 week test period one group continued drinking the caffeinated coffee, while the two other groups consumed different kinds of decaffeinated coffee. RESULTS: Consumption of both types of decaffeinated coffee did not lead to any significant changes in serum total and LDL cholesterol, triglycerides and apolipoprotein B. Furthermore, there were no significant differences in the reactions between the three groups. The diet did not change during the study. CONCLUSIONS: Switch from regular to decaffeinated coffee had no cholesterol-elevating effects, irrespective of the type of coffee.

Adult↗

PubMed1993

NMR determination of the secondary structure and the three-dimensional polypeptide backbone fold of the human sterol carrier protein 2.

Nuclear magnetic resonance (NMR) spectroscopy was used to determine the secondary structure and the three-dimensional polypeptide backbone fold of the human sterol carrier protein 2 (hSCP2), which is a basic protein with 123 residues believed to participate in the intracellular transport of cholesterol and various other lipids. Sequence-specific assignments were obtained for nearly all backbone 1H and 15N resonances, as well as for about two-thirds of the side-chain 1H resonances, using uniform 15N-labeling of the protein combined with homonuclear two-dimensional 1H NMR and three-dimensional 15N-correlated 1H NMR. Three alpha-helices comprising the polypeptide segments of residues 9-22, 25-30 and 78-84 were identified by sequential and medium-range nuclear Overhauser effects (NOE). The analysis of long-range backbone-backbone NOEs showed that hSCP2 further contains a five-stranded beta-sheet including the residues 33-41, 47-54, 60-62, 71-76 and 100-102, which is a central feature of the molecular architecture. The first three strands are arranged in an antiparallel fashion, the polypeptide chain then crosses over this three-stranded sheet in a right-handed sense so that the fourth strand is added parallel to the first one. The fifth strand runs antiparallel to the fourth one, so that the overall topology is +1, +1, -3x, -1. The three-dimensional arrangement of the beta-sheet and the first two helices was determined using an input of 625 NOE upper distance constraints and 95 scalar coupling constants for a preliminary structure calculation with the distance geometry program DIANA.

Amino Acid Sequence↗

PubMed1993

Mutagenically separated PCR (MS-PCR): a highly specific one step procedure for easy mutation detection.

With increasing knowledge about the causal role of genetic defects in clinical diseases the necessity is apparent to have procedures for rapid diagnosis of point mutations. We developed a PCR-based technique, whereby both normal and mutant alleles can be amplified in the same reaction tube, using different length allele-specific primers. Furthermore the allele-specific primers introduce additional deliberate differences into the allelic PCR-products that drastically reduce crossreactions in subsequent cycles. This mutagenesis separates the amplification reactions of the alleles performed in the same tube. Subsequent identification of the PCR-products is done by gel electrophoresis and shows at least one of the two allelic products. Therefore, in addition to simple handling, MS-PCR provides a within-assay quality control for the exclusion of false negative results. The feasibility of this technique has been tested using six different mutations. The high sensitivity of MS-PCR also allows screening for mutation carriers in pooled DNA samples.

Apolipoproteins B↗

PubMed1993

Structural and functional properties of natural and chemical variants of apolipoprotein A-I.

Four isoforms of human apolipoprotein A-I (apo A-I): the normal allele product and the corresponding Lys-107 deletion mutant, and apo A-I with sulfoxidized Met-112 and Met-148 residues and the corresponding reduced form, were investigated in their lipid binding properties, structures, and abilities to activate lecithin-cholesterol acyltransferase. All apo A-I isoforms reacted completely with palmitoyloleoylphosphatidylcholine to give reconstituted high density lipoprotein (rHDL) particles with diameters of 96 A. These particles reacted with low density lipoprotein (LDL) and lecithin-cholesterol acyltransferase (LCAT) equally well, except that the Lys-107 deletion mutant was resistant to structural rearrangements in the presence of LDL. The spectral measurements revealed only minor structural differences among the free apo A-I forms or among their rHDL products, but showed a decreased stability of the Lys-107 deletion mutant and the isoform with reduced Met towards denaturation by guanidine hydrochloride. The results demonstrate that these specific alterations of the apo A-I sequence, which change the helix orientation and hydrophobic moment in one or two putative lipid binding regions, are not sufficient to disrupt the overall properties of the apo A-I complexes with lipid nor to impair significantly their ability to activate LCAT.

Amino Acid Sequence↗

PubMed1993

Interaction of reconstituted high density lipoprotein discs containing human apolipoprotein A-I (ApoA-I) variants with murine adipocytes and macrophages. Evidence for reduced cholesterol efflux promotion by apoA-I(Pro165-->Arg).

Interaction of cells with both native and reconstituted high density lipoproteins (rHDL) containing apolipoprotein (apo) A-I mediates efflux of cellular cholesterol. To characterize structural requirements for this activity in apoA-I, six different genetic apoA-I variants and the corresponding normal allele products were isolated from heterozygous carriers, reconstituted with dimyristoylphosphatidylcholine (DMPC) into discoidal HDL and compared with regard to their ability to release intracellular cholesterol from murine adipocytes and peritoneal macrophages. In previous studies we determined the amino acid changes of these variants: Pro3-->Arg, Pro4-->Arg, Lys107-->0, Lys107-->Met, Pro165-->Arg, and Glu198-->Lys (von Eckardstein, A., Funke, H., Walter, M., Altland, K., Benninghoven, A., and Assmann, G. (1990) J. Biol. Chem. 265, 8610-8617) and demonstrated that all apoA-I variants except apoA-I(Lys107-->0) form discoidal HDL particles with phosphatidylcholine analogues indistinguishable from normal apoA-I (Jonas, A., von Eckardstein, A., Kezdy, K. E., Steinmetz, A., and Assmann, G. (1991) J. Lipid Res. 32, 95-106). In the present study, all apoA-I.DMPC complexes except those containing apoA-I(Pro165-->Arg) promoted cholesterol efflux as effectively as those containing normal apoA-I. Cholesterol efflux from adipocytes obtained after 180 min of incubation with apoA-I(Pro165-->Arg).DMPC complexes was decreased by 30% although this variant was bound to adipocytes with normal affinity. By contrast, apoA-I(Lys107-->Met).DMPC complexes were decreased in their binding affinity compared to normal apoA-I.DMPC complexes but normally promoted cholesterol efflux. Incubation of mouse peritoneal macrophages with apoA-I(Pro165-->Arg).DMPC complexes did also result in a 30% decreased efflux of radiolabeled cholesterol if compared to rHDL with the normal allele product from the same donor. Together the observations suggest that the substitution of proline at residue 165 interferes with the formation of a structural domain in apoA-I that is crucial for cellular cholesterol efflux stimulation. Furthermore, our results suggest that binding of HDL to adipocytes and cholesterol efflux promotion by HDL requires different structural domains.

Adipose Tissue↗

PubMed1993

Cloning, expression and sequences of mouse sterol-carrier protein-x-encoding cDNAs and a related pseudogene.

The expression of the sterol-carrier protein 2 (SCP-2)-encoding gene (SCP-2) is unusually complex. At least four SCP-2-related transcripts are detected in mouse liver: two, of 1.6 and 3.0 kb, are expressed to high levels while the other two, of 0.9 and 2.2 kb, reveal relatively low expression. Hybridization with a probe which specifically hybridizes with the rat SCP-2-related cDNA encoding rat SCP-x reveals that the 2.2- and 3.0-kb transcripts encode mouse SCP-x. SCP-x transcripts are expressed predominantly in the liver, but low-level expression can be demonstrated in all tissues analyzed. Isolation and characterization of two overlapping SCP-x cDNAs indicate that the cDNAs are derived from alternatively polyadenylated transcripts spanning approx. 2.2 and approx. 2.9 kb. Nucleotide sequencing reveals that the predicted ORF, which consists of 547 codons, is composed of 143 C-terminal amino acids which are essentially identical with mouse pre-SCP-2 and 404 N-terminal residues which are specific for SCP-x. To date, it is not clear if all SCP-2-related transcripts are transcribed from a single gene. We have isolated a genomic clone containing an SCP-2-related pseudogene which has some of the characteristics expected for a truncated processed pseudogene. Therefore, our results indicate that at least some of the multiple restriction fragments which are detected by Southern hybridization analyses with SCP-x cDNA-derived probes can be explained by cross-hybridization with a pseudogene.

Acetyl-CoA C-Acetyltransferase↗

PubMed1993

Glutamine/histidine polymorphism in apo A-IV affects plasma concentrations of lipoprotein(a) and fibrin split products in coronary heart disease patients.

A glutamine/histidine polymorphism at residue 360 in apolipoprotein (apo) A-IV that generates two electrophoretically detectable isoforms, apo A-IV-1 and apo A-IV-2, affects the plasma concentration of lipoprotein(a) (Lp[a]) in a healthy population. To verify this unexpected association we analyzed the effect of the apo A-IV polymorphism on Lp(a) serum concentrations in 275 male coronary heart disease patients. Allele frequencies of apo A-IV-1 and apo A-IV-2 were 0.917 and 0.083, respectively. In addition, apo A-IV-1/2 heterozygotes showed a 30% lower geometric mean concentration of Lp(a) than apo A-IV-1/1 homozygotes in this study. The relative frequency of Lp(a) concentrations > 20 mg/dl was significantly increased by a factor of 2.25 in apo A-IV-1/1 homozygotes. Other lipid parameters were not significantly affected by this apo A-IV polymorphism. Because of the relations between Lp(a) and the fibrinolytic system, we also analyzed the effect of the apo A-IV polymorphism on hemostatic variables. Apo A-IV-1/2 heterozygosity was associated with a 70% higher geometric mean plasma concentration of D-dimer, i.e., proteolytic fragments of cross-linked fibrin. Plasma concentrations of prothrombin fragments F1 + F2, fibrinogen, plasminogen, and plasminogen activator inhibitor-1 were unaffected. In conclusion, our results indicate a hitherto unappreciated role of the apo A-IV gene or a closely linked locus for the regulation of Lp(a) metabolism and hemostasis and also possibly for atherosclerosis and thrombosis.

Apolipoproteins A↗

PubMed1993

Cell-derived unesterified cholesterol cycles between different HDLs and LDL for its effective esterification in plasma.

Pulse-chase incubations of human plasma with [3H]cholesterol-laden skin fibroblasts or low density lipoproteins (LDL) and nondenaturing two-dimensional electrophoresis were used to study the transfer and esterification of cell-derived unesterified cholesterol (UC) in human plasma lipoproteins. Specific radioactivities ([3H]UC per microgram of UC) were calculated, and net cholesterol mass transfer was quantified using a fluoro-enzymatic assay to validate productive transfers of UC between high density lipoprotein (HDL) and LDL. Cellular UC was initially taken up by pre-beta 1-HDL and subsequently transferred in the sequence pre-beta 2-HDL-->pre-beta 3-HDL-->alpha-HDL-->LDL. During the first 5 minutes of this process, only 5% of cellular cholesterol was esterified in pre-beta 3-HDL and alpha-HDL; the remainder reached LDL as UC. Cellular UC accumulating in LDL was then redistributed to various HDL particles via two pathways: 1) the partially LDL receptor-mediated uptake and re-secretion of UC by cells and 2) the direct transfer of UC to HDL, mostly to alpha-HDL and a small amount to pre-beta-HDL. UC was not transferred from LDL to HDL after inhibition of lecithin:cholesterol acyltransferase (LCAT). The esterification of cellular [3H]cholesterol in plasma was competitively inhibited by the addition of excess unlabeled LDL but not of excess HDL. However, both excess LDL and excess HDL prevented the esterification of cell-derived cholesterol in apolipoprotein B-free plasma. This demonstrated that LDL is the major source of UC to the LCAT reaction and that the transfer of UC from LDL to HDL is LCAT dependent. In conclusion, the effective esterification of cell-derived cholesterol in plasma involves a rapid transfer of UC via HDL particles to LDL, from which it is distributed to pre-beta-HDL and alpha-HDL. Furthermore, we hypothesize that the transfer per se of cellular UC to LDL forms a cholesterol concentration gradient between cell membranes and HDL and thus a second, reverse cholesterol transport mechanism in addition to the esterification of cholesterol by LCAT.

Cells↗

PubMed1993

Multicenter evaluation of Reflotron direct dry-chemistry assay of high-density lipoprotein cholesterol in venous and fingerstick specimens.

The Reflotron HDL Cholesterol test (Boehringer Mannheim GmbH) directly separates and analyzes high-density lipoprotein (HDL) cholesterol in plasma collected with EDTA in an integrated dry-reagent system suitable for alternative site testing of lipoproteins. We describe a multicenter evaluation of this test by two US and six European laboratories experienced in lipid analysis. Each laboratory compared the Reflotron with the same conventional wet-chemistry method, Boehringer phosphotungstate-Mg2+ precipitation with enzymatic cholesterol assay. Imprecision was within accepted guidelines, with CVs of < or = 8% for fresh and frozen plasmas (median CV 1.7-3.9%) and for lyophilized sera (median CV 3.8-4.7%), similar to those of the conventional method. Results of linear-regression analysis were as follows: Reflotron HDL Cholesterol = 1.03 conventional - 3.9 mg/L, r = 0.987. The Reflotron results were somewhat low in the two US laboratories, demonstrating the need for general standardization of methods for measuring HDL cholesterol. Results from capillary fingerstick plasma agreed well with those from venous-derived plasma; capillary = 1.04 venous + 4.5 mg/L, r = 0.967. The system is relatively insensitive to interference from hemoglobin (< or = 0.75 g/L), ascorbic acid (< or = 0.3 g/L), bilirubin (< or = 50 mg/L), cholesterol (< or = 3.5 g/L), and triglycerides (< or = 4 g/L). The relative ease of operation and the rapid availability of results (within 90 s for plasma collected in EDTA) make the method appropriate for use by well-trained, but not necessarily technical, operators in the physician's office or other alternative sites.

Aminopyrine↗

PubMed1993

High density lipoproteins, reverse transport of cholesterol, and coronary artery disease. Insights from mutations.

BACKGROUND: The reverse cholesterol transport model is most widely used to explain both the role of high density lipoproteins (HDL) in lipid metabolism and the inverse association between HDL cholesterol plasma concentration and the risk for coronary artery disease (CAD). As familial HDL cholesterol deficiency is frequently paralleled with a family history of premature CAD, much interest has been directed toward the molecular defects in apolipoproteins and lipid-transfer enzymes involved in the formation and metabolism of HDL. Knowledge of the basic defects in rare HDL-deficiency syndromes and apolipoprotein variants provides genetic markers of whether the presence of these molecular defects accounts for low HDL cholesterol levels and the accompanying coronary risk. METHODS AND RESULTS: Sequence analysis of proteins or DNA from patients with HDL deficiency or hyperalphalipoproteinemia as well as from randomly screened probands has helped to identify a series of molecular defects in the genes of apolipoprotein (apo) A-I, apo A-II, apo A-IV, apo C-III, lecithin cholesterol acyltransferase, and cholesterol ester-transfer protein. Some of these mutations were associated with absent and low levels of HDL cholesterol in homozygous and heterozygous carries, respectively, but only a few homozygotes were at an increased risk of CAD. These mutations were invaluable for gaining insight into structural-functional relations in HDL metabolism. CONCLUSIONS: Mutations in the genes of apo A-I, apo A-II, apo A-IV, apo C-III, lecithin cholesterol acyltransferase, and cholesterol ester-transfer protein can influence HDL cholesterol plasma concentrations but do not account for the coronary risk associated with low HDL cholesterol levels. In general, these observations suggest that the low HDL concentrations in CAD patients are not a reflection of impaired reverse cholesterol transport but rather of some other metabolic disturbances, such as catabolism of triglyceride-rich particles.

Apolipoprotein A-I↗

PubMed1993

Characterization of five new mutants in the carboxyl-terminal domain of human apolipoprotein E: no cosegregation with severe hyperlipidemia.

Assessment of the apolipoprotein E (apoE) phenotype by isoelectric focusing of both hyperlipidemic and normolipidemic individuals identified five new variants. All mutations were confined to the downstream part of the APOE gene by using denaturing gradient gel electrophoresis (DGGE). Sequence analysis revealed five new mutations causing unique amino acid substitutions in the carboxyl-terminal part of the protein containing the putative lipid-binding domain. Three hyperlipoproteinemic probands were carriers of the APOE*2(Val236-->Glu) allele, the APOE*3(Cys112-->Arg; Arg251-->Gly) allele, or the APOE*1(Arg158-->Cys; Leu252-->Glu) allele. DGGE of the region encoding the receptor-binding domain was useful for haplotyping the mutations at codons 112 and 158. Family studies failed to demonstrate cosegregation between the new mutations and severe hyperlipoproteinemia, although a number of carriers for the APOE*3(Cys112-->Arg; Arg251-->Gly) allele and the APOE*1(Arg158-->Cys; Leu252-->Glu) allele expressed hypertriglyceridemia and/or hypercholesterolemia. Two other mutant alleles, APOE*4-(Cys112-->Arg; Arg274-->His) and APOE*4+(Ser296-->Arg), were found in normolipidemic probands. The lack of cosegregation of these new mutations with severe hyperlipoproteinemia suggests that these mutations do not exert a dominant effect on the functioning of apoE.

Adult↗