Changes of genetic apolipoprotein phenotypes caused by liver transplantation. Implications for apolipoprotein synthesis.

Liver transplantation provides a unique opportunity to investigate the contribution in vivo of the liver to the synthesis and degradation of genetically polymorphic plasma proteins. We have determined the genetic polymorphisms plasma proteins. We have determined the genetic polymorphisms of apo A-IV, apo E, and of the Lp(a) glycoprotein (apo (a] in the plasma of subjects undergoing liver transplantation and in respective organ donors. The results show that in humans, greater than 90% of the plasma apo E and virtually all apo (a) are liver derived, whereas this organ does not significantly contribute to plasma apo A-IV levels.

A variant primary structure of apolipoprotein C-II in individuals of African descent.

We have isolated an isoform of the protein activator of lipoprotein lipase, apolipoprotein C-II, from the very low density lipoproteins of four patients of African ancestry with hypertriglyceridemia and eruptive or pedunculated xanthomata. This protein, which we designate apolipoprotein C-II2, differs from the previously recognized species, which we denote apolipoprotein C-II1, by substitution of glutamine for lysine at residue 55, a mutation which would require only a single-base substitution in the structural gene for apolipoprotein C-II1. Each of the patients in whom apolipoprotein C-II2 was found had approximately equal amounts of apolipoprotein C-II1 and apolipoprotein C-II2 among the apoproteins of the very low density lipoproteins, suggesting that the structural genes for these proteins are allelic. Two additional apparent heterozygotes were found among the first-degree relatives of each of two of the patients in patterns compatible with monogenic autosomal transmission. Approximately equal amounts of apolipoproteins C-II2 and C-II1 were also found by isoelectric focusing in 6 of a casual series of 50 normolipidemic blacks, but none or only trace amounts of apolipoprotein C-II2 were found in 500 samples from Caucasian subjects with hyperlipidemia. These findings suggest that this polymorphism is distributed primarily among blacks, possibly reflecting some positive Darwinian selection pressure. Whether this polymorphism has a modifying effect upon the development of hyperlipemia remains to be determined.

Lp(a) glycoprotein phenotypes. Inheritance and relation to Lp(a)-lipoprotein concentrations in plasma.

The Lp(a) lipoprotein represents a quantitative genetic trait. It contains two different polypeptide chains, the Lp(a) glycoprotein and apo B-100. We have demonstrated the Lp(a) glycoprotein directly in human sera by sodium dodecyl sulfate-gel electrophoresis under reducing conditions after immunoblotting using anti-Lp(a) serum and have observed inter- and intraindividual size heterogeneity of the glycoprotein with apparent molecular weights ranging from approximately 400,000-700,000 D. According to their relative mobilities compared with apo B-100 Lp(a) patterns were categorized into phenotypes F (faster than apo B-100), B (similar to apo B-100), S1, S2, S3, and S4 (all slower than apo B-100), and into the respective double-band phenotypes. Results from neuraminidase treatment of isolated Lp(a) glycoprotein indicate that the phenotypic differences do not reside in the sialic acid moiety of the glycoprotein. Family studies are compatible with the concept that Lp(a) glycoprotein phenotypes are controlled by a series of autosomal alleles (Lp[a]F, Lp[a]B, Lp[a]S1, Lp[a]S2, Lp[a]S3, Lp[a]S4, and Lp[a]0) at a single locus. Comparison of Lp(a) plasma concentrations in different phenotypes revealed a highly significant association of phenotype with concentration. Phenotypes B, S1, and S2 are associated with high and phenotypes S3 and S4 with low Lp(a) concentrations. This suggests that the same gene locus is involved in determining Lp(a) glycoprotein phenotypes and Lp(a) lipoprotein concentrations in plasma and is the first indication for structural differences underlying the quantitative genetic Lp(a)-trait.

Dopamine D4 receptor polymorphism and idiopathic Parkinson's disease.

Patients with idiopathic Parkinson's disease (IPD) are described as having markedly decreased novelty seeking characteristics. Since recent publications suggest an association between the dopamine D4 receptor polymorphism and novelty seeking, we investigated this polymorphism in a group of 122 patients with IPD and 127 healthy control subjects. We found similar allele and genotype frequencies in both groups and no association with the age of onset of symptoms. Therefore, the dopamine D4 receptor polymorphism does not confer genetic susceptibility to IPD and cannot explain the decreased novelty seeking in IPD patients.

Sensorineural hearing loss and the incidence of Cx26 mutations in Austria.

A clinical evaluation and Cx26 mutation analysis was performed in 92 consecutive patients with sensorineural hearing loss in order to delineate the spectrum of genetically caused hearing loss. Among patients of Austrian origin, 53% were classified with hereditary hearing loss. Cx26 mutations were found in 26% of NSHL patients (40% of familial vs 18% of sporadic cases). The mutation 35delG accounted for 52.8% of all presumed GJB2 disease alleles. The second most frequent mutation was L90P (16.7%) having been reported with a prevalence of 0.7-3.5% in other populations. Three novel mutations were found. The novel mutation, R143Q, was associated with dominant high-frequency hearing loss. Pseudodominant transmission of NSHL was seen in four families with Cx26 mutations. A mutation 35delG carrier rate of 0.9% was observed among 672 controls from West-Austria. Cx26 mutations were found associated with mild to profound, and with asymmetric hearing impairment.

Frequency gradients of DHCR7 mutations in patients with Smith-Lemli-Opitz syndrome in Europe: evidence for different origins of common mutations.

Smith-Lemli-Opitz syndrome/RSH (SLOS) is a multiple congenital anomaly syndrome caused by mutations in the gene for Delta7-sterol reductase (DHCR7) which catalyses the last step in the biosynthesis of cholesterol. SLOS is among the common recessive disorders in Europeans but almost absent in most other populations. More than 40 mutations in the DHCR7 gene some of which are frequent have been described in SLOS patients of various origins. Here we report mutation analysis of the DHCR7 gene in SLOS patients from Poland (n = 15), Germany/Austria (n = 22) and Great Britain (n = 22). Altogether 35 different mutations were identified and the two null mutations IVS8-1G > C and W151X were the most frequent in the total sample. In all three populations three mutations accounted for >0.5 of SLOS chromosomes. The mutational spectra were, however, significantly different across these populations with each of the common mutations showing an east-west gradient (W151X, V326L) or vice versa (IVS8-1G > C). W151X is the most frequent (0.33) mutation in Polish SLOS patients. It has an intermediate frequency in German/Austrian patients (0.18) and is rare among British patients (0.02). V326L shows the same distribution pattern (Poland 0.23, Germany/Austria 0.18, Britain 0.02). In contrast IVS8-1G > C is most frequent in Britain (0.34) intermediate in Germany/Austria (0.20) and rare in Poland (0.03). All analysed IVS8-1G > C and V326L alleles shared the same DHCR7 haplotype, whereas the W151X mutation occurred on different haplotypes. There is evidence for both recurrent mutations and founder effects. Together this suggests that the common SLOS mutations in Europe have different geographic and historic origins and spread across the continent in opposite directions.

Genetic polymorphism of apolipoprotein A-IV in five different regions of Europe. Relations to plasma lipoproteins and to history of myocardial infarction: the EARS study. European Atherosclerosis Research Study.

As a part of the EARS study we assessed the role of the common apo A-IV polymorphism in determining the hereditary predisposition to cardiovascular disease. The study population consisted of 1261 controls and 629 cases (students whose father had MI before 55 years) from five different European regions. The apo A-IV 1-1 phenotype accounted for 85% of the individuals. One per cent of subjects were homozygous for the apo A-IV2 allele. There was significant regional variation in the apo A-IV allele frequencies from North to South in Europe, with the lowest A-IV2 frequency in Finland. The distribution of the apo A-IV phenotypes was similar in cases and controls, as was the regional variation. The apo A-IV polymorphism did not affect HDL cholesterol. There was no correlation between apo A-IV alleles and the plasma concentration of apo A-IV. The plasma concentration of apo A-IV was lower in females than in males; furthermore, there was a significant difference in apo A-IV concentrations between oral contraceptive users and nonusers: users had the lowest values. As no strongly significant genetic difference could be demonstrated between plasma lipid concentration in cases and controls, and as the apo A-IV polymorphism did not significantly influence plasma lipid concentration, we conclude that the apo A-IV gene is not a major determinant of the risk for MI and/or CHD.

Treatment of primary mixed hyperlipidemia with etophylline clofibrate: effects on lipoprotein-modifying enzymes, postprandial lipoprotein metabolism, and lipoprotein distribution and composition.

In 17 patients with primary mixed hyperlipidemia we studied levels and composition of lipoproteins in fasting plasma, lipoprotein-modifying enzymes, and postprandial lipoprotein metabolism after an oral fat-tolerance test supplemented with vitamin A before, and 12 weeks after treatment with etophylline clofibrate. With treatment, fasting plasma cholesterol, triglycerides, and the levels of very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), and low density lipoproteins (LDL) decreased significantly; high density lipoprotein (HDL) cholesterol increased significantly. Treatment caused also an increase in the protein content of IDL, a decrease in the triglyceride content of LDL, and an increase in the size of LDL as assessed by gradient gel electrophoresis. Concentrations of triglycerides, chylomicrons, and chylomicron remnants after an oral fat load supplemented with vitamin A decreased by 33%, 30% and 6%, respectively (P < 0.005; P < 0.01; and P < 0.05). The activity of lipoprotein lipase and hepatic lipase in postheparin plasma increased by 51% and 45%, respectively (P < 0.01; P < 0.05). We found a decrease in the mass concentration of cholesteryl ester transfer protein (P < 0.05). Stepwise multiple regression analysis showed that the triglyceride content of LDL is determined primarily by fasting triglycerides (r = + 0.53, P < 0.05;baseline) and cholesteryl ester transfer protein (r = + 0.49, P < 0.05; 12 weeks); in contrast, the triglyceride content of HDL3 is determined exclusively by accumulation of postprandial triglycerides (r = + 0.67; P < 0.05; baseline) and postprandial chylomicrons (r = +0.87; P < 0.005; 12 weeks). We conclude that hypolipidemic treatment with etophylline clofibrate favorably affects the cardiovascular risk factor profile in primary mixed hyperlipidemia.

Effects of pancreas transplantation on distribution and composition of plasma lipoproteins.

In type I (insulin-dependent) diabetic patients, peripheral hyperinsulinemia due to subcutaneous insulin treatment is associated with increased high-density lipoprotein (HDL) cholesterol, and also with an altered surface composition of HDL. Pancreas grafts also release insulin into the systemic rather than into the portal venous system, giving rise to pronounced peripheral hyperinsulinemia. We hypothesized that if peripheral hyperinsulinemia is responsible for high HDL cholesterol and/or altered surface composition of HDL in diabetic subjects, similar changes in the lipid profile should be present in pancreas-kidney transplant recipients (PKT-R). Using zonal ultracentrifugation, we isolated HDL2, HDL3, very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) from fasting plasma of 14 type I diabetic PKT-R, eight nondiabetic kidney transplant recipients (KT-R), and 14 healthy control subjects and determined the level and composition of the above lipoproteins. HDL2 cholesterol was increased in PKT-R as compared with KT-R and healthy controls (both P < .05), whereas HDL3 cholesterol was unchanged. However, an altered lipoprotein surface composition was evident in PKT-R: HDL2, HDL3, and LDL were enriched in unesterified cholesterol ([UC] PKT-R v KT-R, P=.13, P < .005, and P < .05, respectively; PKT-R v controls, all P < .005); HDL2 was enriched in phospholipids; and LDL was depleted of phospholipid. KT-R, in contrast, showed no changes in lipoprotein surface composition but a substantial triglyceride enrichment of HDL2 as compared with PKT-R and healthy controls (both P < .05). LDL size as determined by gradient gel electrophoresis was increased in PKT-R compared with controls (P < .005). The plasma concentration of cholesteryl ester (CE) transfer protein (CETP), involved also in phospholipid transfer, was increased in both transplant groups compared with healthy controls (both P < .05). Insulin concentrations in fasting plasma were directly related to CETP levels and to the weight-percentage of UC in HDL3, and inversely to the weight-percentage of phospholipids in LDL (all P < .05). We explain the increase in HDL2 cholesterol and LDL size in PKT-R by their high lipoprotein lipase (LPL) activity conferring an excellent capacity to clear chylomicron triglycerides. Effective handling of postprandial triglycerides, high HDL2 cholesterol, and predominance of LDL pattern A, respectively, are established indicators of a low risk of atherosclerosis. However, it is presently unclear what effects the compositional changes on the surface of HDL and LDL may have on cardiovascular risk in clinically stable PKT-R.

[The decalcification of teeth for histological studies by means of ultrasonics]. / Die Entkalkung von Zähnen für feingewebliche Untersuchungen unter der Einwirkung von Ultraschall

In order to accelerate decalcification of hard tissues for histological examinations, the additional application of ultrasonics is sometimes recommended. Comparative studies show that decalcification is not acclerated by ultrasonics.

Allele-specific competitive blocker PCR: a one-step method with applicability to pool screening.

We have developed a novel one-step pool screening PCR procedure which is based on the principles of amplification refractory mutation system (ARMS) and competitive oligonuleotide priming (COP) PCR. In addition to the usual primers, this approach uses two allele-specific competitive oligonucleotides, one of which is 3'-end labeled with a dideoxynucleotide and blocks amplification of the wild-type allele. An allele-specific product is generated only in the presence of the mutation. The introduction of an allele-specific competitive blocker oligonucleotide improves the specificity and robustness of ARMS-PCR. Further its sensitivity is dramatically increased, which allows detection of one mutant allele in a large excess of wild-type-bearing genomic DNA by electrophoresis in an ethidium bromide-stained agarose gel (up to 1 in 10(4) alleles). This makes the method ideal for nonradioactive pool screening. The successful application of the method has been demonstrated for four different point mutations, two in the apolipoprotein B gene (R3500Q, R3531C) which result in familial defective apolipoprotein B-100, one in the CFTR gene (R1162X), and one in the gene for lipoprotein lipase (G188E).

Genetics of the quantitative Lp(a) lipoprotein trait. II. Inheritance of Lp(a) glycoprotein phenotypes.

Lp(a) glycoprotein exhibits an apparent size polymorphism that is associated with genetically controlled Lp(a) lipoprotein concentrations in plasma (Utermann et al. 1988). We have tested the hypothesis that this polymorphism is genetically controlled by studying 15 matings with a total of 44 offspring. This confirmed our conclusion that Lp(a) types are controlled by a series of codominant alleles LpF, LpB, LpS1, LpS2, LpS3 and LpS4 and by a null allele LpO. Together with the data from the accompanying paper this indicates that the structural gene for the Lp(a) protein is the major gene locus determining Lp(a) lipoprotein concentrations in plasma.

One-step screening method for the polymorphism of apolipoproteins A-I, A-II, and A-IV.

Apolipoprotein A-I exhibits a polymorphism that can be easily investigated in native serum by a simple method involving incubation of serum in the presence of decylsulfate and beta-mercaptoethanol and subsequent isoelectric focusing. From six to eight proteins can be separated in a pH gradient from 4 to 6 and thus patients with apolipoprotein A-I variants can be distinguished from normal persons. This method also permits monitoring for polymorphic forms of apoA-II and apoA-IV as well as detection of C apolipoproteins. To verify the identity of the different apolipoproteins, a two-dimensional electrophoresis technique was applied, with an SDS system for the second dimension. In addition, monospecific antibodies for apolipoproteins A-I, A-II, and A-IV were used for the immunological identification. The method described here led to the discovery of three different familial apolipoprotein A-I variants.

Apolipoprotein E polymorphism and coronary artery disease.

Lipid status and apolipoprotein E phenotypes were tested in 1000 patients who underwent coronary angiography. The same number of factory employees was chosen as a control group. We distinguished between six different apolipoprotein E phenotypes and determined their frequencies in all groups. For the three homozygous phenotypes E3/3, E4/4, and E2/2, the percentage distribution in the group of factory employees was 62.7%, 2.3%, and 0.8%, respectively; for the three heterozygous phenotypes E4/3, E3/2, and E4/2, we determined frequencies of 20.3%, 11.0%, and 3.0%, respectively. In the group of patients with and without signs of coronary atherosclerosis, we observed almost the same frequencies except that heterozygotes (E3/2) occurred significantly more frequently in the group of coronary angiography patients unaffected by coronary sclerosis. Cholesterol and triglyceride values were significantly elevated in patients with coronary artery disease, whereas high density lipoprotein cholesterol levels were not significantly different. The data further suggest that apolipoprotein E2/2 homozygosity, despite the presence of beta-very low density lipoproteins in the plasma of these patients, cannot be considered a biochemical indicator of an increased risk of coronary atherosclerosis. On the other hand, apolipoprotein E3/2 heterozygosity may have a protective effect on the development of early atherosclerosis.

Plasma lipoprotein abnormalities in a case of primary high-density lipoprotein (HDL) deficiency.

A 53-year-old patient with primary HDL-deficiency is reported. About 2% of the normal concentration of alpha1 HDL was present in his plasma. The alpha1-high-density-lipoproteins separated into two fast-moving components in polyacrylamide gel electrophoresis. The Apo HDL contained both the main apolipoproteins, Apo A-I and Apo A-II, but in disproportionally reduced amounts, the concentration of Apo A-I being reduced about 360-fold, and that of Apo A-II about 14-fold. Concomitantly, the amount of the Apo C polypeptides in the HDL-fractions was decreased to about 5.5% and the activity of the enzyme lecithin cholesterol acyltransferase (EC 2.3.1.4.3) in plasma was found to be only 40% of normal. Apoprotein D was present in the LDL in association with Apo B, forming an abnormal, fast-moving LDL-complex. Apo A-I and Apo A-II were both of normal size as determined by SDS-PAGE, and reduction with thiols resulted in the shift of the M.W. of Apo A-II from 17,000 daltons to about 8,500 daltons. Both proteins were found in the same position as their normal counterparts in analytical isoelectric focusing. The most likely explanation for the multiple lipoprotein abnormalities seems to be that a defect in the regulation or structure of Apo A-I is the basis of the HDL-deficeincy.

Apolipoprotein E polymorphism and hyperlipidemia.

We tested apolipoprotein E phenotypes in 1557 normolipidemic factory workers and 822 hyperlipidemic hospital patients. We distinguished six different apolipoprotein E phenotypes and determined their frequencies in normolipidemia (factory workers), hypertriglyceridemia, hypercholesterolemia, and mixed hyperlipidemia. For the three homozygous phenotypes E3/3, E4/4, and E2/2, the percentage distribution in the normolipidemic group was 62.2%, 2.2%, and 0.9%, respectively; for the three heterozygous phenotypes E4/3, E3/2, and E4/2, we determined frequencies of 19.9%, 11.7%, and 2.9%, respectively. A higher prevalence of E2/2 homozygosity was observed in hypertriglyceridemic persons (2.5%) and persons affected by mixed hyperlipidemia (5.0%). E4/4 homozygosity occurred more often among hypercholesterolemic patients (5.0%) than normolipidemic persons (2.2%). These data suggest that E2/2 homozygosity and E4/4 homozygosity both predispose to hyperlipidemia. Patients affected by mixed hyperlipidemia should be investigated for their apolipoprotein E polymorphism because of the possible linkage of apolipoprotein E2/2 homozygosity, hyperlipidemia, and atherosclerosis.

Apolipoprotein A-IV polymorphism in man.

In man, apolipoprotein A-IV is characterized by a genetically determined polymorphism controlled by two codominant alleles. Two isoforms of this apolipoprotein, designated A-IV-1 and A-IV-2, can be identified by isoelectric focusing. Among 1000 healthy factory workers participating in an epidemiological study, A-IV-1 (genotype 1-1) was observed in 85%; A-IV-2 (genotype 2-2), in 0.5%; and A-IV-1 in combination with A-IV-2 (genotype 1-2), in 14%. In four nonrelated subjects, an apolipoprotein A-IV variant (A-IV-Münster), characterized by a slightly more basic isoelectric focusing behavior than A-IV-2, was detected in combination either with A-IV-1 or A-IV-2. Mendelian inheritance of this variant could be demonstrated.