Search PubMed⌕ Search

Biomedical subjects

G Utermann

Publications and source records attributed to G Utermann.

At least 181 records · Page 10Linked to original sources
PubMed1982

Apolipoprotein AIMarburg: studies on two kindreds with a mutant of human apolipoprotein AI.

Three probands heterozygous for a mutant of apolipoprotein AI (apo AIMarburg, Utermann et al. 1982a) were detected by screening of 2282 unrelated individuals resulting an a frequency estimate of about 1/750 in the German population. All three probands with apo AIMarburg had hypertriglyceridemia (triglyceride above 250 mg/dl) and subnormal HDL-cholesterol (below 30 mg/dl), but no other lipoprotein abnormalities. The kindreds of two probands with AIMarburg were studied. The family data are consistent with an autosomal codominant inheritance of the trait. A total of 16 heterozygous blood relatives with the mutant AIMarburg were detected in these kindreds. Analysis of the plasma lipid and lipoprotein levels in relation to the apo AI phenotype was complicated by the high prevalence of diabetes mellitus and thyroid disease in one kindred and of hyperlipidemia in both kindreds. No consistent relationship between plasma lipid and lipoprotein levels, and the mutant apo AI could be demonstrated. Instead the mutant apo AI and the dyslipoproteinemia seem to co-exist independently in these kindreds. Three sibs with the homozygous apo E-2/2 phenotype were detected in one kindred, and all three sibs had subnormal LDL-cholesterol and beta-VLDL, e.g., the lipoprotein abnormality characterizing primary dysbetalipoproteinemia. Genetic apo E phenotypes and the apo AI mutant segregated independently, indicating that the structural gene loci for apo E and apo AI are not closely linked.

Adult↗
PubMed1981

Genetic transmission of isoapolipoprotein E phenotypes in a large kindred: relationship to dysbetalipoproteinemia and hyperlipidemia.

The largest reported kindred of a proband with type III hyperlipoproteinemia was investigated by assessment of lipid and lipoprotein levels and very low density lipoprotein (VLDL) isoapolipoprotein E distributions in all accessible family members (56% of the 124 living blood relatives and 59% of the 37 spouses). The results confirm in this kindred a trimodal distribution of apoE3/E2 ratios, and segregation analysis of 16 informative matings classified according to E3/E2 ratio demonstrated classical Mendelian inheritance of the autosomal codominant type: the E3/E2 ratio is determined by two alleles, apoE3d and apoE3n, which produce three phenotypes apoE3-D, apoE3-ND, and apoE3-N, corresponding to the low, intermediate, and high modes, respectively. Vertical transmission of the apoE3-D phenotype occurred in two branches of the second generation. In both instances this represented pseudodominance; i.e., products of heterozygous (apoE3-ND) x homozygous (apoE3-D) matings. Hyperlipidemia (defined as a low density lipoprotein cholesterol and/or plasma triglyceride level exceeding the respective age-, sex-, and sex-steroid-specific 95th percentiles derived from Lipid Research Clinics population studies) was present in 15 blood relatives in multiple lipoprotein patterns, consistent with the presence of familial combined hyperlipidemia in this kindred. Eight of nine members with the apoE3-D phenotype had either type III hyperlipoproteinemia or, in the absence of hyperlipidemia, beta-VLDL and at least marginally cholesterol-rich VLDL (VLDL-cholesterol/plasma triglyceride greater than 0.25) (defined as dysbetalipoproteinemia). The ninth such member, the only child with this phenotype, was normal. beta-VLDL and marginally cholesterol-rich VLDL was seen in but one of six hyperlipidemic family members of phenotype apoE3-ND, in none of seven hyperlipidemic blood relatives of phenotype apoE3-N, in no normolipidemic family members of phenotype apoE3-ND or apoE3-N, and in no spouses (three of whom were hyperlipidemic and nine of phenotype apoE3-ND). Thus, among adult members of the O'D kindred the apo3-D phenotype was nearly specifically associated with dysbetalipoproteinemia or, when hyperlipidemia was present, type III hyperlipoproteinemia.

Adolescent↗
PubMed1981

Lecithin-cholesterol-acyltransferase deficiency: autosomal recessive transmission in a large kindred.

Thirty-four members of a single Sardinian kindred with lecithin-cholesterol-acyltransferase deficiency have been studied. The kindred spans four generations and the parents of the two affected siblings are blood relatives. Segregation of the acyltransferase deficiency gene in the family clearly demonstrated an autosomal recessive mode of inheritance. Thirteen family members, including all obligate heterozygotes, had roughly half-normal acyltransferase activities (mean +/- S.D. = 0.39 +/- 0.06 mU/ml) when compared to 17 intrafamilial controls and spouses (mean +/- S.D. = 0.72 +/- 0.09 mU/ml) and 40 blood donors from Marburg/Lahn (mean +/- S.D. =0.76 +/- 0.1 mU/ml). Characterization of the heterozygotes did not reveal abnormalities in their plasma lipoproteins. LCAT deficiency and the beta-thalassaemia trait coexisting in this kindred segregated independently.

Consanguinity↗
PubMed1981

Familial dysbetalipoproteinemia. Abnormal binding of mutant apoprotein E to low density lipoprotein receptors of human fibroblasts and membranes from liver and adrenal of rats, rabbits, and cows.

Patients with familial dysbetalipoproteinemia (F. Dys.), also called familial type 3 hyperlipoproteinemia, are homozygous for a mutant allele, Ed, that specifies an abnormal form of apoprotein (apo) E, a prominent constituent of remnant lipoproteins derived from very low density lipoproteins (VLDL) and chylomicrons. Apo E is thought to mediate the removal of remnant lipoproteins from the plasma by virtue of its ability to bind to hepatic lipoprotein receptors. In F. Dys. patients, remnant-like lipoproteins accumulate, apparently because of delayed clearance by the liver. In the current studies, we show that the abnormal protein specified by the Ed allele (apo E-D) from some, but not all, patients with F. Dys. has a markedly deficient ability to bind to low density lipoprotein (LDL) receptors. Apo E was isolated from eight control subjects and nine patients with F. Dys. and incorporated into phospholipid complexes. The complexes were tested for their ability to compete with human 125I-LDL or rabbit 125I-beta-VLDL fo binding to LDL receptors in four assay systems: cultured human fibroblasts, solubilized receptors from bovine adrenal cortex, liver membranes from rats treated with 17 alpha-ethinyl estradiol, and liver membranes from normal rabbits. The apo E-D from six of the nine patients with F. Dys. showed binding affinities for LDL receptors that were reduced by greater than 98% in all receptor assays (group 1 patients). All of these group 1 patients were unequivocally of phenotype apo E-D/D by the criterion of isoelectric focussing. The apo E from the three other F. Dys. patients showed a near normal binding ability in all four of the receptor assays (group 2 patients). One of these group 2 patients appeared to have the apo E-D/D phenotype by isoelectric focussing. In the other two patients in group 2, apo E-D was the predominant protein (phenotype, apo E-D/D), but traces of protein in the region corresponding to normal apo E (apo E-N) were also present. The difference between group 1 and group 2 patients was also apparent when the apo E was iodinated and tested directly for binding to liver membranes from rats treated with 17 alpha-ethinyl estradiol. The 125I-labeled apo E from a group 2 patient, but not a group 1 patient, showed enhanced uptake when perfused through the liver of an estradiol-treated rate, indicating that the receptor binding ability of apo E correlated with uptake in the intact liver. The current studies allow the subdivision of patients with F. Dys. into two groups. In group 1, the elevated plasma level of remnants appears to be due to a diminished receptor binding activity of the abnormal protein specified by the Ed allele; in group 2 patients, the cause of the elevated plasma level of remnants remains to be explained.

Adrenal Glands↗
PubMed1981

Genetic control of lecithin-cholesterol acyltransferase (LCAT): measurement of LCAT mass in a large kindred with LCAT deficiency.

Lecithin-cholesterol acyltransferase (LCAT) mass was measured by radioimmunoassay in a large Sardinian kindred with LCAT deficiency. The frequency distribution of LCAT levels in the M-kindred demonstrated a trimodal distribution, one more corresponding to the normal controls and containing the normal relatives, a second mode completely separate from the controls and containing subjects with LCAT levels approximately one-half normal, and a third mode distinct from the other modes containing the two subjects with LCAT deficiency. Fifteen kindred members, including all six spouses, had enzyme levels of 4.92 +/- 0.49 microgram/ml (mean +/- SD), slightly lower but in the same range as controls (6.13 +/- 0.98; no. = 66). Twelve family members, including the two obligate heterozygotes, had enzyme levels of 2.68 +/- 0.32 microgram/ml, roughly one-half that of control levels. The LCAT-deficient subjects had enzyme levels of 0.30 and 0.37 microgram/ml, respectively. Segregation of the acyltransferase deficiency gene (LCATd) provided clear evidence of an autosomal recessive mode of inheritance of LCAT deficiency. Furthermore, the data strongly suggest that family members with half-normal enzyme levels are heterozygous carriers of the LCATd gene.

Adolescent↗
PubMed1980

Substitution in vitro of lecithin-cholesterol acyltransferase. Analysis of changes in plasma lipoproteins.

Lecithin-cholesterol acyltransferase (EC 2.3.1.43) was purified 15 000-fold from human plasma. The active material was homogeneous in different gel electrophoretic systems but separated into three major bands with apparent pI values of 4.28, 4.33 and 4.37 in isoelectrofocusing. The apparent Mr of the enzyme is 67 000 +/- 2000. An antiserum prepared against the purified enzyme specifically inhibited the activity of lecithin-cholesterol acyltransferase in whole serum. Serum from a patient with familial deficiency of lecithin-cholesterol acyltransferase was substituted in vitro with the highly purified enzyme. The serum from this patient did not contain immunochemically detectable enzyme protein. Substitution of enzyme resulted in the following major changes. 1. Cholesteryl ester content in serum increased by 36-89 mg/100 ml depending on the experimental conditions. The enzyme-mediated formation of cholesteryl ester led to an increase of cholesteryl ester content in high-density and very-low-density lipoproteins and in low-density lipoproteins containing apoprotein-B. No increase occurred in fractions containing very large flattened structures and the abnormal lipoprotein-X and in lipoprotein-E. Incubation of isolated fractions with lecithin-cholesterol acyltransferase led to significant cholesterol esterification only in high-density lipoproteins. 2. The characteristic disc-shaped rouleaux-forming high-density lipoproteins of enzyme-deficient serum disappeared. Instead a single homogeneous population of high-density lipoproteins formed. The particles generated were spherical and had the electrophoretic properties, density (1.080 g/ml), diameter (12.5 nm) and apoprotein composition of normal high-density lipoproteins-2. 3. The concentration of spherical particles containing apolipoprotein E (density 1.040-1.080 g/ml) and the lamellar lipoprotein-X-like structures in the low-density lipoprotein fraction were not affected by the enzyme substitution. 4. A single homogeneous population of spherical lipoprotein-B particles of 26.5-nm diameter occurred at density 1.029 g/ml. The data suggest that the discoidal high-density lipoproteins are the major site of cholesteryl ester formation that apolipoprotein-E is not involved in an undirectional transport of newly formed cholesteryl ester from high-density lipoproteins to other lipoproteins and that lipoprotein-X and lipoprotein-E are not preferential substrates for the acyltransferase.

Apolipoproteins↗
PubMed1980

Genetics of the apolipoprotein E system in man.

The polymorphism of apolipoprotein E (Apo E) in man is controlled by two codominant alleles, Apo E(n) and Apo E(d), at the Apo E-N/D locus and by two alleles, the dominant, Apo E4(+), and the recessive, Apo E4(o), at the Apo E4 locus. Frequency distribution analysis of Apo E phenotypes demonstrated a highly significant association between both systems (P approximately 1%). The Apo E4-(+) variant was about twice as frequent in phenotype Apo E-N (30.1%) than in phenotype Apo E-ND (16.4%). The phenotypic combination Apo E-D/-E4(+) was not observed. The segregation of Apo E phenotypes in informative matings is consistent with a close linkage of both loci. The results may be explained by different models. On the basis of the present data, these models cannot be distinguished by formal genetic criteria. (1) Haplotypes Apo E(n)/E4(+), Apo E(n)/E4(o), and Apo E(d)/E4(o) determine the different phenotypes, and a linkage disequilibrium exists of Delta = .0147 between the E-N/D and E4 loci. (2) The fourth haplotype, Apo E(d)/E4(+), exists, but the gene E4(+) is not expressed in coupling with Apo E(d). The four-haplotype model seems more attractive in view of Apo E-N/D polymorphism's quantitative character and of biochemical results, which show that phenotypes Apo E-N and Apo E-D differ in the apparent molecular weight (M(r)) of the respective major Apo E polymorphic form. Hence, the Apo E-N/D locus may control structural genes involved in the posttranslational modification of Apo E. (3) Finally, there may exist only one Apo E structural gene locus but with mutations at two sites susceptible to posttranslational modification.

Adult↗
PubMed1979

Apolipoprotein A-IV: a protein occurring in human mesenteric lymph chylomicrons and free in plasma. Isolation and quantification.

1. Human mesenteric lymph chylomicrons were isolated from chylous ascites fluid by ultra-centrifugation and agarose/gel chromatography and their apoprotein composition was analysed by dodecylsulfate/polyacrylamide gel electrophoresis, analytical isoelectric focusing and immuno-chemically. Major components of mesenteric lymph chylomicrons were apoprotein A-I, proteins of Mr less than 15 000 including the C-group apoproteins and a protein of Mr 46 000. Minor components were apoprotein E and a protein of Mr approximately equal to 200 000 (B-like protein). This apoprotein composition was qualitatively identical with that of chylomicrons from intestinal lymph of the rat, but was distinctly different from plasma chylomicrons of humans with fasting chylomicronaemia. 2. The protein of Mr approximately equal to 46 000 has been isolated by preparative dodecylsulfate/polyacrylamide gel electrophoresis from human and rat lymph chylomicrons and was compared to a protein of identical Mr present in rat high-density lipoproteins (apoplipoprotein A-IV) and in the rho less than 1.006 g/ml serum lipoprotein fraction of individual humans with alimentary hypertriglyceridaemia. In both species the 46 000-Mr proteins isolated from lymph and serum were identical according to amino acid composition and isoelectric point in 6 M urea. The human proteins from both sources were also immunologically identical. The similarities in the molecular properties of the human apolipoprotein and rat apolipoprotein A-IV indicate that these proteins are homologous. 3. Plasma levels of human apolipoprotein A-IV determined by electroimmunodiffusion were 14.15 +/- 3.66 mg/100 ml (n = 59), but greater than 90% of the protein was unassociated with the major lipoprotein fractions. It is concluded, that apolipoprotein A-IV is a main protein component of human lymph chylomicrons, that is removed from the particles in the plasma compartment.

Animals↗
PubMed1979

Polymorphism of apolipoprotein E. II. Genetics of hyperlipoproteinemia type III.

Apolipoprotein E from human serum shows a genetic polymorphism determined by two autosomal codominant alleles, Apo En and Apo Ed. Homozygosity for the gene Apo Ed (phenotype Apo E-D) results in primary dysbetalipoproteinemia, but only some individuals with this phenotype develop gross hyperlipidemia (hyperlipoproteinemia type III). Vertical transmission of dysbetalipoproteinemia represents pseudodominance due to the high frequency of the gene Apo Ed. Dysbetalipoproteinemia is already expressed in childhood. To assess the influence of other genes on the expression of hyperlipidemia in phenotype Apo E-D, comparative studies were carried out in kindreds of hypercholesterolemic (group A) and normo- or hypocholesterolemic probands with dysbetalipoproteinemia (group B). This demonstrated the occurrence of familial (non-type III) forms of hyperlipidemia in group A but not in group B kindreds. Distribution of lipoprotein phenotypes in five of the group A kindreds was consistent with the occurrence of familial combined hyperlipidemia. Apo E phenotypes and hyperlipidemia segregated independently. It is concluded that primary dysbetalipoproteinemia is a frequent monogenic variant of lipoprotein metabolism, but not a disease. Coincidence in one individual of genes for this specific dyslipoproteinemia with any of the genes for monogenic or polygenic forms of familial hyperlipidemia results in hyperlipoproteinemia type III. Hence hyperlipoproteinemia type III is caused by at least two non-allelic genes and is a polygenic disorder.

Adolescent↗
PubMed1979

Polymorphism of apolipoprotein E. III. Effect of a single polymorphic gene locus on plasma lipid levels in man.

The two autosomal codominant alleles of the Apo E-N/D polymorphism, Apo En and Apo Ed, have a considerable influence on plasma lipid levels and distribution in man. Serum cholesterol levels are highest in phenotype Apo E-N, intermediate in phenotype Apo E-ND, and low in phenotype Apo E-D. Contrary VLDL-cholesterol is highest in phenotype Apo E-D, intermediate in heterozygotes, and lowest in phenotype Apo E-N. Serum-triglyceride, VLDL-triglyceride and the ratio of VLDL-cholesterol/serum-triglyceride are also intermediate in phenotype Apo E-ND between the two opposite homozygous groups. 10% of heterozygous Apo E-ND subjects exhibited a beta-VLDL subfraction compared to 0.8% in phenotype Apo E-N and 100% in Apo E-D. Hence the three phenotypic groups exhibit metabolic differences in vivo, and the gene Apo Ed has a mild dyslipoproteinemic effect even in a single dose. The Apo E-N/D polymorphism may therefore be a major influence on the occurrence of arteriosclerotic vascular disease in man.

Adult↗