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K J Lackner

Publications and source records attributed to K J Lackner.

At least 55 records · Page 3Linked to original sources
PubMed1994

Genomic organization of the human lysosomal acid lipase gene (LIPA).

Defects in the human lysosomal acid lipase gene are responsible for cholesteryl ester storage disease (CESD) and Wolman disease. Exon skipping as the cause for CESD has been demonstrated. We present here a summary of the exon structure of the entire human lysosomal acid lipase gene consisting of 10 exons, together with the sizes of genomic EcoRI and SacI fragments hybridizing to each exon. In addition, the DNA sequence of the putative promoter region is presented. The EMBL accession numbers for adjacent intron sequences are given.

Base Sequence↗
PubMed1994

Lipid-lowering therapy--implications for the prevention of atherosclerosis.

Lipid-lowering therapy has been advocated as a means to decrease the incidence of cardiovascular disease. The basis for this are results of animal studies, epidemiologic surveys, and intervention studies in man. There have been recommendations by national and international advisory boards regarding the aims and means of such interventional strategies. These have not been unanimously accepted, however. The present article will review the evidence on which intervention strategies may be based and the current status of the scientific discussion. The implications for future strategies to prevent atherosclerosis are discussed.

Adult↗
PubMed1994

Purification, cloning, and expression of a human enzyme with acyl coenzyme A: cholesterol acyltransferase activity, which is identical to liver carboxylesterase.

An enzyme with acyl coenzyme A:cholesterol acyltransferase (ACAT) activity was isolated from porcine liver, and sequences derived from trypsinized peptides indicated homology to liver carboxylesterase. By use of degenerate primers, human cDNA clones were identified, which were identical to human liver carboxylesterase. Expression of the full-length cDNA in Chinese hamster ovary (CHO) cells led to an approximately threefold increase in cellular ACAT activity. This was accompanied by an approximately 20-fold increase of cellular cholesteryl ester content. By light and electron microscopy, recombinant CHO cells contained numerous lipid droplets that were not present in control CHO cells. Expression of an antisense cDNA in HepG2 cells reduced cellular ACAT activity by 35% compared with control. To further investigate the role of the enzyme in cellular cholesterol homeostasis, regulation of the mRNA was investigated in 7-day cultured human mononuclear phagocytes (MNPs). When these cells were incubated in lipoprotein-deficient serum for 18 hours, the mRNA for ACAT/carboxylesterase was almost not detectable on Northern blots, whereas after incubation with acetylated low-density lipoproteins, a strong hybridization signal was obtained. This is evidence that the mRNA of ACAT/carboxylesterase is induced by cholesterol loading. It is concluded from the data presented that ACAT/carboxylesterase is relevant for cellular cholesterol esterification in vivo. The regulation in MNPs indicates that the enzyme is also involved in foam cell formation during early atherogenesis.

Amino Acid Sequence↗
PubMed1994

[Classification of hyperlipoproteinemias and interpretation of laboratory parameters].

Hyperlipidemias are grouped according to their lipid levels in hypercholesterolemia, hypertriglyceridemias, and mixed hyperlipidemias. Among these, hypercholesterolemia has the strongest correlation to the risk for coronary heart disease. Based on the results from epidemiologic studies and intervention trials several expert panels have defined cholesterol values with low and high cardiovascular risk and cholesterol target levels for treatment. In the presence of hyperlipidemia additional parameters like LDL cholesterol, HDL cholesterol, and Lp(a) may be determined depending on the individual patient's risk profile. For classification of familial lipid disorders, analysis of relatives and the determination of special parameters may be necessary. These include apolipoproteins (concentration, isoforms, mutants), enzyme activities (lipases, LCAT), LDL receptor activity, oratypical lipoproteins.

Apolipoproteins↗
PubMed1993

Effects of purinergic agents on human mononuclear phagocytes are differentiation dependent. Implications for atherogenesis.

The differentiation-dependent expression of purinergic receptors for metabolically stable analogues of adenosine and ATP was studied in human mononuclear phagocytes (MNPs). Ligands of these receptors are able to modulate cellular cholesterol metabolism. In addition, the intracellular signal transduction pathways of the purinergic receptor system were examined. ATP gamma S, the metabolic stable analogue of ATP, was used as a P2 ligand, and 2-p-(2-carboxyethyl)phenylethylamino-5'-N-ethylcarboxamido adenosine (CGS 21680) and 5'-(N-ethylcarboxamido)adenosine (NECA) were used as P1 ligands in binding studies. Binding of [35S]ATP gamma S to MNPs at 4 degrees C revealed saturable low-affinity binding sites with a Kd of 868 +/- 52 nmol/L and Bmax of 7.3 +/- 0.4 pmol per 10(6) cells in 1-day cultured human MNPs and a Kd of 780 +/- 30 nmol/L and Bmax of 14.0 +/- 0.8 pmol per 10(6) cells in 7-day cultured human MNPs. The characterization of the P1 receptors on 1- and 7-day cultured human MNPs showed that they are expressed only on 7-day cultured human MNPs. The specific binding curve of the adenosine A2 receptor agonist [3H]CGS 21680 was biphasic, with a Kd1 of 33 +/- 15 nmol/L and a Kd2 of 90 +/- 10 nmol/L and with Bmax1 of 0.19 +/- 0.06 pmol per 10(6) cells and Bmax2 of 0.41 +/- 0.09 pmol per 10(6) cells, whereas NECA did not exhibit specific binding. The typical agonists for probing A1 receptor subtypes did not bind to 1- and 7-day cultured human MNPs, indicating that only A2 receptors are expressed on 7-day cultured human MNPs. ATP gamma S enhanced [Ca2+]i in 1- and 7-day cultured human MNPs in a concentration-dependent manner, whereas the P1 ligands, adenosine and CGS 21680, induced Ca2+ flux only in 7-day cultured MNPs. All three drugs increased intracellular cAMP levels in 7-day cultured human MNPs at a concentration of 10(-5) mol/L, whereas no effect was observed in 1-day cultured human MNPs. The uptake of fluorescently labeled acetylated low-density lipoprotein (LDL) in 7-day cultured human MNPs was inhibited by adenosine, CGS 21680, ATP, and ATP gamma S. No significant influence of these compounds was measured on the uptake of LDL, acetylated LDL, and high-density lipoprotein, in 1-day cultured MNPs. Our investigations indicate that the expression of P2y and A2 receptors is increased during differentiation of blood monocytes to macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1993

High density lipoprotein deficiency with xanthomas. A defect in reverse cholesterol transport caused by a point mutation in the apolipoprotein A-I gene.

A 7-yr-old girl with high density lipoprotein (HDL) deficiency and xanthomas has been identified in a Turkish kindred with repetitive consanguinity. She has severely reduced HDL-cholesterol and no apolipoprotein (apo) A-I. ApoA-II is reduced, whereas apoA-IV and apoC-III are normal. ApoB and low density lipoprotein (LDL)-cholesterol are increased. This is reflected in hypercholesterolemia. VLDL and IDL particles are low, and serum triglycerides are normal. The genetic defect could be identified as a base insertion into the third exon of the apoA-I gene. This leads to a nonsense peptide sequence beginning at amino acid 5 of the mature plasma protein and early termination of translation. The patient is homozygous for this mutation. Pedigree analysis indicated an autosomal dominant inheritance with no evidence of another genetic defect of lipoprotein metabolism in the kindred. In HDL deficiency, HDL binding to leukocytes was increased compared to normal. In the postprandial state, binding of labeled HDL3 to leukocytes is unchanged. This is in contrast to results with postprandially isolated leukocytes from controls or Tangier patients, which have a reduced binding capacity for HDL3. These results indicate that postprandial HDL precursors may compete the binding of labeled HDL3. The metabolic consequences of HDL deficiency were analyzed. There is only a small number of HDL-like particles containing apoA-II, apoA-IV, apoE, and lecithin/cholesteryl acyl transferase. The C-apolipoproteins were normal in the proband. Due to the lack of HDL they can only associate with apoB-containing particles, where they may interfere with cellular uptake. Thus, pure apoA-I deficiency leads to a complex metabolic derangement.

Amino Acid Sequence↗
PubMed1993

A splice junction mutation causes deletion of a 72-base exon from the mRNA for lysosomal acid lipase in a patient with cholesteryl ester storage disease.

The genetic defect leading to cholesteryl ester storage disease (CESD) has been determined in a 12-yr-old patient. Lysosomal acid lipase (LAL) activity in cultured skin fibroblasts was reduced to approximately 9% of control fibroblasts. Plasma cholesterol (255 mg/dl) and LDL-cholesterol (215 mg/dl) were elevated whereas HDL-cholesterol was reduced (19 mg/dl). Triglycerides were moderately elevated (141 mg/dl). There were no clinical abnormalities with the exception of hepatosplenomegaly. Both parents have reduced LAL activity in white blood cells. PCR analysis of the LAL mRNA from the propositus revealed a single slightly smaller mRNA species in skin fibroblasts as well as in leukocytes. The mother of the patient and his older brother had two mRNA species: one of normal size and one of the same size as the propositus. The father has a LAL mRNA of normal size only. Sequence analysis of a PCR-amplified cDNA fragment showed a 72-bp in-frame deletion resulting in the loss of the codons for amino acids 254-277. Analysis of genomic DNA revealed that the 72 bp represent an exon, indicating that the deletion in the mRNA is caused by defective splicing. Sequence analysis of the patient's genomic DNA revealed a G-->A substitution in the last nucleotide of the 72-bp exon in one of his alleles. The mutant allele was shown to cosegregate with the truncated mRNA in the pedigree, providing further evidence that the G-->A substitution causes aberrant splicing and exon skipping. No normal-sized mRNA is detectable in the propositus even though he is not homozygous for the splice site mutation. This can be only accounted for by assuming that he is a compound heterozygote with a null allele inherited from his father. In summary, the data presented provide evidence that deletion of the codons for amino acids 254-277 in the LAL mRNA in combination with a null allele cause the clinical expression of CESD in our patient.

Adolescent↗
PubMed1992

Severe type III hyperlipoproteinemia associated with unusual apolipoprotein E1 phenotype and epsilon 1/'null' genotype.

A 60-year-old white male (KH) was diagnosed to suffer from severe type III hyperlipoproteinemia (HLP) and premature cardiovascular disease. Biochemical analysis revealed an unusual apolipoprotein (apo) E phenotype and genotype. All clinical characteristics of type III HLP were present in the patient. His very low density lipoprotein (VLDL) cholesterol to plasma triglyceride (TG) ratio was elevated at 0.97 without therapy which is unusually high (normal ratio about 0.18). By contrast his plasma apo E level was only moderately elevated (6.8 mg dl-1). The patient's apo E migrated in the apo E1 position on isoelectric focusing gels. Chemical modification with cysteamine and treatment with neuraminidase confirmed the presence of two cysteine residues in the patient's apo E and a normal sialylation pattern. Pedigree analysis suggested that the patient was a compound heterozygote with one apo epsilon 1 allele and another allele whose product did not appear in the plasma compartment ('null' allele). Direct sequencing of polymerase chain reaction (PCR) amplified segments of the apo E gene as well as restriction fragment length polymorphism (RFLP) analysis with the endonuclease Taq I identified an adenosine for guanosine (G-->A) exchange in the second base of codon 127 that is predictive for an Asp for Gly substitution in the encoded apo E amino acid sequence. This mutation is the structural basis for the apo E1 isoform identified upon isoelectric focusing. Five other family members are also carriers of the mutant apo epsilon 1 allele. Two of those were hyperlipidemic and exhibited biochemical characteristics of type III HLP. A second mutation, a deletion of a G in codon 31, is predictive for a reading frameshift that encodes for a premature stop in codon 60. Our inability to identify the product of a second apo E allele in the plasma of the patient and two other members of the KH family corresponds with the heterozygous presence of this mutation in the affected individuals. Both relatives (like the index case) had an increased VLDL cholesterol to plasma TG ratio, which indicates the presence of cholesterol-enriched VLDL particles. We propose that the single base deletion in the apo E gene which is the cause of a non-functional 'null' allele in addition to a probably dominant apo E1 (Gly127-->Asp, Arg158-->Cys) variant of late or incomplete penetrance are the primary genetic defects in this kindred leading to severe dysbetalipoproteinemia.

Adolescent↗
PubMed1990

Impaired response to intrarenal administered atrial natriuretic peptide in ischemic acute renal failure of a transplanted patient.

A 30-year-old male patient suffering from membrano-proliferative glomerulonephritis was transplanted a cadaveric kidney 3 years ago. Five days later the transplant was removed because of fresh thrombosis in larger arteries. Three years after first transplantation a second graft was transplanted. Repeated perfusion scintigraphies of persistent anuric patient showed a delayed perfusion of renal parenchyma, no intrarenal bolus was obtained. Urgently, an arterial angiography was performed. It demonstrated that calibers of renal parenchymal vasculature were narrowed. Suggesting ischemic nature of acute renal failure, 50 micrograms human atrial natriuretic peptide (hANP) was injected intrarenally as bolus. Five minutes after hANP injection in a second angiography a significant improvement of renal blood flow was demonstrated but no amelioration of urine production or electrolyte excretion was observed. Histologically an ischemic lesion of transplant was proven. This finding indicates a blunted excretory response of acute renal failure after kidney transplantation despite of significantly ameliorated renal blood flow visualized radiologically.

Acute Kidney Injury↗
PubMed1989

Plasma cholesterol, lipid lowering, and risk for cancer. An update of the results from epidemiologic studies and intervention trials.

Plasma cholesterol has been shown to be correlated to the incidence of cardiovascular events. This observation and experimental data on the pathogenesis of atherosclerosis have led to a number of recommendations for the treatment of elevated plasma lipids by national and international consensus panels and organizations. However, the issue whether lowering cholesterol might increase the risk for other diseases including cancer is still controversial. In this article, an attempt is made to review the currently available data on the relation between plasma cholesterol and cancer. Special emphasis is given to the results of intervention trials aimed at lowering cholesterol by diet and/or drugs, because they apply best to the human situation and are particularly relevant for the clinician. Data from animal experiments are only briefly discussed.

Cholesterol↗
PubMed1987

Adrenocortical function in type II hyperlipoproteinemic patients treated with lovastatin (mevinolin).

Lovastatin (Mevinolin), a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase, has been used effectively as a hypocholesterolemic agent in man. As an inhibitor of endogenous cholesterol synthesis, a potentially serious side effect of therapy with this drug is interference with adrenocortical function. The effect of lovastatin on adrenal function was evaluated in a 6-month, randomized, double blinded, placebo-controlled, crossover study involving 24 type II hyperlipoproteinemic patients. Despite significant lowering of total and low density lipoprotein (LDL) cholesterol by lovastatin, no statistically or clinically significant differences were seen in free cortisol excretion or in plasma cortisol response to intravenous ACTH infusion between baseline, placebo, and lovastatin-treated patients. We conclude that lovastatin does not adversely affect adrenocortical reserve in patients with heterozygous familial hypercholesterolemia (FH) or non-FH type II hyperlipoproteinemia.

Adrenal Cortex↗
PubMed1986

Effectiveness of mevinolin on plasma lipoprotein concentrations in type II hyperlipoproteinemia.

Patients with low-density lipoprotein (LDL) concentrations in the top 10th percentile of the population (type II hyperlipoproteinemia [HLP]) are at increased risk for premature cardiovascular disease; however, the incidence of myocardial infarction and death can be decreased by LDL cholesterol reduction. Mevinolin, an inhibitor of endogenous cholesterol synthesis, has been shown to reduce LDL cholesterol concentrations in a subset of type II patients with heterozygous familial hypercholesterolemia (FH). Using a double-blind, randomized, crossover, placebo-controlled trial, the safety and efficacy of mevinolin were compared in 24 patients with type II HLP with heterozygous FH (n = 6) or without FH type II HLP (n = 18). Compared with placebo treatment, both apolipoprotein B and LDL cholesterol levels were reduced (p less than 0.01) in both FH and non-FH patients by 28 to 34% with mevinolin treatment. In addition, high-density lipoprotein cholesterol levels were significantly increased (p less than 0.001) in both patients with FH (16%) and those with non-FH type II HLP (14%). Patients had no serious or clinically significant adverse effects. Thus, mevinolin is a useful drug for treatment of most patients with elevated plasma LDL cholesterol concentrations.

Adult↗
PubMed1986

The expressed human hepatic receptor for low-density lipoproteins differs from the fibroblast low-density lipoprotein receptor.

The role of the cellular receptor for the low-density lipoproteins (LDL) in cholesterol transport was initially defined through the study of nonhepatic cells in vitro. Since the liver is central in plasma lipoprotein metabolism, an investigation of hepatic lipoprotein receptors is important for understanding normal lipoprotein transport. Utilizing human hepatic and fibroblast membranes, the characteristics of receptors for LDL from hepatic and nonhepatic tissues were directly compared. Human hepatic membranes reversibly bound LDL within 5 min. Although both fibroblast and hepatic membranes saturably bound LDL at 37 degrees C, the fibroblast LDL receptor affinity (Kd = 2.5 X 10(-8) M) and number (5.5 X 10(12) sites/mg membrane protein) were greater than the hepatic receptor affinity (Kd = 10.8 X 10(-8) M) and number (0.5 X 10(12) sites/mg membrane protein). In contrast to the fibroblast LDL receptor which was unable to bind LDL in the presence of EDTA, the hepatic LDL receptor binding of LDL was only partially blocked by EDTA. The binding of LDL to its hepatic receptor is highly temperature-dependent, and studies utilizing both radiolabeled LDL and colloidal gold-labeled LDL indicate that little, if any, binding of LDL hepatic membranes occur at 0-4 degrees C. The hepatic membrane receptor(s) (Mr approximately equal to 270 000 and 330 000) differ from that of the fibroblast LDL receptor (Mr approximately equal to 130 000) and these proteins are present in hepatic membranes from a patient lacking the fibroblast LDL receptor. These data indicate that an expressed hepatic LDL receptor has unique properties different from those of the fibroblast LDL receptor and that the expressed protein(s) is genetically distinct from the fibroblast receptor.

Biological Transport, Active↗
PubMed1986

The molecular biology of human apoA-I, apoA-II, apoC-II and apoB.

The application of molecular biology techniques has enabled us to determine the gene sequence, organization, transcription and processing of apolipoprotein genes. Consequently, new insights have been gained in the biosynthesis and processing of these proteins. In addition to apoA-I, apoA-II and apoC-III reported here, other apolipoprotein genes such as apoC-II and apoE genes were found to share common intron-exon organizations. The results suggest that these genes most probably arise from a common ancestral gene. Utilizing cDNA as hybridization probes, we have localized apoA-I, apoA-II, apoC-II, apoC-III, apoE and apoB to specific locations of individual chromosomes (for review, see ref. 6). There is no clear relationship between currently known physiological function and the organization of the apolipoproteins in the chromosomes with the exception of the LDL receptor and its ligand, apoE which are localized to chromosome 19. However, apoB-100, the major ligand for the LDL receptor is on chromosome 2 and not in synteny with the apoE and the LDL receptor genes. The cloning of the major human apolipoprotein genes have also allowed us to initiate studies on the molecular defects leading to various dyslipoproteinemias including Tangier disease and abetalipoproteinemia. Undoubtedly, information derived from these studies will provide the basis for future in vitro and in vivo studies on patients with dyslipoproteinemia and premature atherosclerosis.

Amino Acid Sequence↗
PubMed1986

Analysis of the apolipoprotein B gene and messenger ribonucleic acid in abetalipoproteinemia.

The apolipoprotein B-100 (apoB-100) gene in leukocytes and the apoB-100 messenger RNA (mRNA) and translated apolipoprotein in the livers from normal and abetalipoproteinemic individuals were evaluated. Four complementary DNA probes for apoB-100 covering the 5', middle, and 3' regions of the apoB-100 mRNA were utilized and Southern blot analysis indicated that the apoB-100 gene is present in abetalipoproteinemia without major insertions or deletions. Polyadenylated hepatic apoB-100 mRNA from two abetalipoproteinemic patients was normal in size, and the concentration of apoB-100 mRNA was increased sixfold compared with control hepatic apoB-100 mRNA levels. ApoB-100 was detected in hepatocytes of abetalipoproteinemic patients by immunohistochemical techniques. These results indicate that the biochemical defect in abetalipoproteinemic patients studied is most consistent with a posttranslational defect in apoB-100 processing or secretion with an up-regulation of the apoB-100 mRNA.

Abetalipoproteinemia↗
PubMed1985

The human apolipoprotein A-II gene: complete nucleic acid sequence and genomic organization.

The gene for human apolipoprotein (apo) A-II has been isolated from a human genomic DNA library. The cloned fragment was approximately 14 kilobase-pair (kb) long, and extended about 9.0 kb upstream as well as 3.5 kb downstream from the apoA-II gene, which was contained within a 3.1 kb HindIII fragment of human DNA. The complete nucleic acid sequence of the apoA-II gene has been determined, establishing that the apoA-II gene is interrupted by three intervening sequences of 182, 293, and 395 bp. The second intron is of particular interest, because it contains a 33 bp sequence of alternating G and T residues very close to the 3' splice site which has the potential to form a left handed Z-helix structure in vivo. A restriction fragment length polymorphism 3' from the apoA-II gene has been detected which may serve as a marker for the long arm of chromosome 1 in linkage analyses.

Apolipoprotein A-II↗