Kurt Oette

The gene encoding ATP-binding cassette transporter 1 is mutated in Tangier disease.

Tangier disease (TD) is an autosomal recessive disorder of lipid metabolism. It is characterized by absence of plasma high-density lipoprotein (HDL) and deposition of cholesteryl esters in the reticulo-endothelial system with splenomegaly and enlargement of tonsils and lymph nodes. Although low HDL cholesterol is associated with an increased risk for coronary artery disease, this condition is not consistently found in TD pedigrees. Metabolic studies in TD patients have revealed a rapid catabolism of HDL and its precursors. In contrast to normal mononuclear phagocytes (MNP), MNP from TD individuals degrade internalized HDL in unusual lysosomes, indicating a defect in cellular lipid metabolism. HDL-mediated cholesterol efflux and intracellular lipid trafficking and turnover are abnormal in TD fibroblasts, which have a reduced in vitro growth rate. The TD locus has been mapped to chromosome 9q31 (ref. 9). Here we present evidence that TD is caused by mutations in ABC1, encoding a member of the ATP-binding cassette (ABC) transporter family, located on chromosome 9q22–31 (ref. 10). We have analysed five kindreds with TD and identified seven different mutations, including three that are expected to impair the function of the gene product. The identification of ABC1 as the TD locus has implications for the understanding of cellular HDL metabolism and reverse cholesterol transport, and its association with premature cardiovascular disease.

Change in Hemorrheological and Biochemical Parameters following Membrane Differential Filtration

Introduction: The elimination of high molecular weight proteins may have a positive influence on disorders of the microcirculation due to an improvement in rheological parameters. We therefore attempted to evaluate the rheological efficacy of membrane differential filtration (MDF). Patients and methods: Ten patients suffering from macular disease underwent MDF. Rheological and biochemical parameters as well as visual acuity were determined one day before and after therapy: The study aimed at a reduction in plasma viscosity, standardized whole blood viscosity at hematocrit 0.45 and erythrocyte aggregation at hematocrit 0.3. Results: Severe side-effects were not observed. The rheological parameters were significantly reduced. In detail the posttreatment values were reduced as compared to the pretreatment values as follows: plasma viscosity 85%, standardised whole blood viscosity 86% (hematocrit 0.45), erythrocyte aggregation 59% (hematocrit 0.3), total protein 81%, IgG 66%, IgA 59%, IgM 33%, alpha-2-macroglobulin 30%, triglycerides 102%, total cholesterol 47%, VLDL cholesterol 94%, LDL cholesterol 33%, HDL cholesterol 62%. Visual acuity was improved in 7/10 patients. Conclusions: MDF is a safe and highly effective method for lowering biochemical and improving rheological parameters which led to improvement in visual acuity. We have already replaced plasma exchange with MDF in our clinical practice of hemorrheological therapy.

Screening for mutations in exon 4 of the LDL receptor gene in a German population with severe hypercholesterolemia

A group of 218 patients with severe hypercholesterolemia (LDL cholesterol >260 mg/dl) living in the Cologne area were screened for mutations in the 3′ half of exon 4 of the low density lipoprotein (LDL) receptor gene by the single-strand conformation polymorphism (SSCP) method. The analysed fragment was 242 bp in length and comprised approximately 6% of the coding region. In 11 patients an abnormal SSCP pattern was observed. Two of the abnormal fragment patterns were identical. The results of the SSCP screening could be confirmed by direct DNA sequencing. Three of the ten different mutations were previously described (3 bp deletion: codon 197; Asp200→Gly; Glu207→stop). Of the newly identified mutations there were two deletions, two insertions, one combined insertion and deletion mutation and two single base pair substitutions [1 bp deletion: G in codon 197; 37 bp deletion: T in codon 196–208 or AT in 196–207 and GA in codon 208; 18 bp insertion: codon 201–206; 8 bp insertion: codon 155–156 and GA in codon 157; 6 bp insertion (codon 196–197) and 5 bp deletion (codon 199, C in codon 198 and G in codon 198 or 200); Asp200→Tyr; Asp203→Val]. The 8-bp insertion was detected in a second unrelated individual. The analysis of the functional consequences of the mutations indicates that all mutations were causative of the LDL cholesterol elevation.

Apolipoprotein E2/E2 genotype in combination with mutations in the LDL receptor gene causes type III hyperlipoproteinemia.

Abstract The primary genetic cause of type III hyperlipoproteinemia is the homozygous presence of the apolipoprotein E2 allele. However, only approximately 1% of subjects with the apolipoprotein E2/E2 genotype develop type III hyperlipoproteinemia. Other factors are therefore necessary to express type III hyperlipoproteinemia. Two individuals were identified as having type III hyperlipoproteinemia (triglyceride to very low-density lipoprotein (VLDL) cholesterol ratio >0.3). However, in contrast to unchanged or slightly decreased low-density lipoprotein (LDL)-cholesterol levels typically observed in type III patients, elevated LDL-cholesterol levels were observed. The expected apolipoprotein E2/E2 isoform was confirmed by genetic analysis. To explain the elevated LDL-cholesterol level, single strand conformation polymorphism analysis was performed to screen for mutations in the LDL receptor gene. In both individuals, mutations causing an impaired LDL receptor function (2 bp insertion in exon 3 and Glu119→Gly mutation in exon 4) were identified. In six more unrelated individuals, these mutations combined with the common apolipoprotein E3/E3 genotype, resulted in an isolated, severe LDLcholesterol elevation. Our results indicate that the level of LDL receptors plays an important role in remnant clearance, and that the combination of the binding-defective apolipoprotein E2 with a defective LDL receptor precipitate type III hyperlipoproteinemia.

Changes of Hemorheological and Biochemical Parameters after Plasma Perfusion Using a Tryptophan-Polyvinyl Alcohol Adsorber Leading to Clinical Improvement in Patients Suffering from Maculopathy

Background: Selective adsorption is an extracorporeal treatment able to reduce high-molecular-weight proteins and lipids. We evaluated its efficacy in lowering hemorheological parameters to achieve a better microcirculation of the retina. Patients and Methods: Ten patients suffering from maculopathies of various origin underwent a selective plasma adsorption procedure using the TR-350. Plasma and whole blood viscosity, erythrocyte aggregation and proteins and lipids were determined before and 24 h after therapy. Results: Selective adsorption therapy reduced the high-molecular-weight proteins and lipids. Plasma viscosity, standardized whole blood viscosity and erythrocyte aggregation were significantly lowered to 87, 88 and 65%, respectively, of their values prior to treatment. An improvement of visual acuity was achieved in 6/10 patients. Minor side effects were noted in 2/10 patients. Conclusions: Selective adsorption using the TR-350 adsorber is a safe technique, showing a high impact on blood rheology. The changes of hemorheological parameters led to clinical improvement in 6/10 patients suffering from retinal disorders.

Biocompatibility studies on a clinically well-tolerated extracorporeal system

Summary A consistent repetitive change in the peripheral PMNL and monocyte counts during the clinically well-tolerated removal of LDL by SIA, using centrifugal BCS and antihuman apolipoprotein-B-antibody Sepharose 4B columns, has been observed. Also, a subsequent elevation of PMN-derived elastase-alpha 1 inhibitor-complex was found. Preliminary evidence and comparable laboratory data from other extracorporeal systems that are not biologically inert, suggest that plasma protein cascades may also be involved in the pathogenesis of these phenomena. The lack of potential clinical symptoms, in contrast to the laboratory observations, demonstrate that activation of plasma protein cascades that are not clinically relevant may occur. The long-term pathophysiologic consequences for patients treated regularly by SIA remain to be elucidated. Also, further systematic laboratory work is needed for a better understanding of the observations.

Mutation analysis of exon 3 of the LDL receptor gene in patients with severe hypercholesterolemia

Abstract Single-strand conformation polymorphism analysis was used to screen for mutations in exon 3 of the low density lipoprotein receptor gene in a group of 218 unrelated patients with severe hypercholesterolemia (low density lipoprotein cholesterol > 6.7 mmol/l) living in the Cologne area of Germany. Including the complementary primers the fragment studied had a length of 176 bp. An abnormal single-strand conformation polymorphism pattern was observed in eight patients, four of whom had an identical abnormal fragment pattern indicating that five different mutations were present. By direct DNA sequencing, the underlying mutations could be confirmed (Cys54→Tyr, Trp66→Gly, Glu80→Lys, 2 bp insertion (AT between codon 44 and 45, 9 bp deletion (codons 65 to 67)). The analysis of the pathogenicity indicates that all mutations were causative for the low density lipoprotein cholesterol elevation. The Trp66→Gly and Glu80→Lys mutations were previously described in a French-Canadian population and in an English population, respectively. The 2 bp insertion was detected in four unrelated patients and is one of the most frequent mutations detected up to now in the German population.