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Biomedical subjects

G Assmann

Publications and source records attributed to G Assmann.

At least 145 records · Page 8Linked to original sources
PubMed1997

Treatment goals for low-density lipoprotein cholesterol in the secondary prevention of coronary heart disease: absolute levels or extent of lowering?

The results of the Scandinavian Simvastatin Survival Study (4S) and the Cholesterol and Recurrent Events (CARE) study make abundantly clear the benefits of lowering low-density lipoprotein (LDL) cholesterol in patients with a history of coronary artery disease. Current guidelines in the United States and Germany recommend a treatment goal for LDL cholesterol of 100 mg/dl. However, the evidence for setting such a goal is not consistent among trials. It has even been argued that setting an absolute LDL goal may be unhelpful, per se, because the higher the patient's pretreatment LDL cholesterol, the more difficult achieving this goal becomes. It has also been recognized that measures to lower LDL cholesterol, and medications in particular, produce a relative rather than an absolute degree of reduction in circulating levels. For example, most statins produce a similar proportional decrease in LDL cholesterol irrespective of baseline LDL. Thus, if the baseline LDL is 180 mg/dl, the decrease in LDL with a particular statin dose may be 60 to 120 mg/dl, whereas if the baseline LDL is 120 mg/dl, the expected decrease in LDL with the same statin dose would be only 40 to 80 mg/dl (i.e., a 30% reduction in each case). These points have led some investigators to suggest that it may be more practicable to recommend the amount by which LDL should be lowered rather than by specifying an absolute level of LDL cholesterol which should be achieved. This report summarizes the proceedings of an international symposium held on this topic on October 4, 1996, in Berlin by the International Task Force for Prevention of Coronary Heart Disease and the Institute of Arteriosclerosis Research at the University of Münster.

Adult↗
PubMed1997

Translational research studies of erbB oncogenes: selection strategies for breast cancer treatment.

Specific gene families, e.g. encoding members of signal transduction pathways, show a gene dosage sensitivity. We report on the determination of the gene dosages of egfr and c-erbB-2 in relation to the intratumoral concentration of the tyrosine kinase receptor protein EGFR and p185c-erbB-2 and the clinical outcome of breast cancer patients in a retrospective study. Prognostic unfavorable subgroups were determined in a life-table analysis by (a) an average gene copy number of egfr of less than 0.4 and greater than 1.6 and an intratumoral EGFR concentration of more than 56 fmol/mg, (b) an intratumoral p185c-erbB-2 concentration above 26 HNU/mg and (c) a quotient of egfr and c-erbB-2 average gene copy numbers of less than 0.15 and greater than 4.35.

Breast Neoplasms↗
PubMed1997

The Münster Heart Study (PROCAM): total mortality in middle-aged men is increased at low total and LDL cholesterol concentrations in smokers but not in nonsmokers.

BACKGROUND: Some large epidemiological studies have shown an increase in mortality at low levels of total and LDL cholesterol. It has been speculated that low cholesterol levels may play a causative role in this association. To investigate this question, we analyzed all deaths occurring among middle-aged men in the Münster Heart Study (PROCAM), one of the largest prospective epidemiological studies of coronary heart disease risk markers in Europe. METHODS AND RESULTS: In the Münster Heart Study, 10,856 men aged 36 to 65 years at study entry (46.8+/-7.3 years [mean+/-SD]) were followed for 4 to 14 years (7.1+/-2.4 years). During this period, 313 deaths occurred--46 from myocardial infarction, 48 from suspected or definite sudden cardiac death, 14 from cerebrovascular disease, and 10 from other diseases of the circulatory system. There were 121 deaths from cancer and 33 deaths from violent causes (injuries in 16, suicide in 14, and homicide in 3 cases). Death in 29 cases occurred from other causes and was unexplained in 12 cases. Total cholesterol, LDL cholesterol, and the LDL/HDL ratio showed a J-shaped relationship with total mortality. At high total and LDL cholesterol concentrations, increased mortality was due to increased coronary deaths. At low total and LDL cholesterol concentrations, increased mortality was seen in smokers only and was explained by an increase in smoking-related cancer deaths. CONCLUSIONS: The increase in mortality at low levels of total and LDL cholesterol among middle-aged men in the Münster Heart Study is explained by an increase in smoking-related cancer deaths among smokers.

Adult↗
PubMed1997

Measuring cholesterol in macrophages: comparison of high-performance liquid chromatography and gas-liquid chromatography with enzymatic fluorometry.

Cholesterol and cholesteryl esters in human macrophages were analyzed by three different methods. Values obtained by high-performance liquid chromatography and by gas-liquid chromatography were compared with those obtained using enzymatic fluorometry. We also assessed fractional lipid recovery from these cells using radiolabeled cholesterol and cholesteryl ester. Enzymatic fluorometry substantially underestimated cellular cholesterol content. Two reasons for this were found. First, recovery into a variety of solvents was incomplete, particularly when extracted lipids were dried and redissolved in a second solvent. Second, the cells appeared to contain an intrinsic inhibitor of the enzymatic fluorometric method.

Cells, Cultured↗
PubMed1997

New and classical risk factors--the Münster heart study (PROCAM).

A total of 4,849 male participants of the prospective cardiovascular Münster Study (PROCAM), aged 40 - 65 years underwent extensive screening for cardiovascular risk factors before 1986 and were subsequently followed up for at least 8 years. During this time 189 non-fatal and 49 fatal myocardial infarctions occurred, 28 men suffered a sudden cardiac death and 169 persons died of other causes. Using multivariate statistical methods we confirmed that age, increased LDL cholesterol levels, decreased HDL cholesterol levels, high blood pressure, cigarette smoking, diabetes mellitus, angina pectoris and a positive family history are important risk factors for a myocardial infarction or cardiac death. The results of the PROCAM Study demonstrate that elevated triglycerides are an independent risk factor for an early myocardial infarction or cardiac death. Using a multiple logistic function analysis an algorithm for the assessment of the global risk was derived from the data. The observed incidence of coronary heart disease rises sharply as the global risk increases, thus permitting the use of this algorithm in clinical practice for the assessment of the individual risk of myocardial infarction. Risk factors such as lipoprotein(a) and coagulation factors may improve the predictive value of this algorithm. Furthermore it is expected that the exploration of genetic defects will strongly increase the predictive value and precise determination of individual risk.

Adult↗
PubMed1997

Low-density lipoproteins inhibit the Na+/H+ antiport in human platelets. A novel mechanism enhancing platelet activity in hypercholesterolemia.

BACKGROUND: LDL have been reported to augment platelet activation, and increased platelet reactivity has been observed in familial hypercholesterolemia. However, the underlying mechanisms of this putatively atherogenic effect is unknown. Because intracellular pH (pHi) may play an important role in platelet function, we examined the influence of LDL on pHi and Na+/H+ antiport activity in human platelets and compared it with the effect of [3-methylsulfonyl-4-piperidinobenzoyl] guanidine hydrochloride (HOE 694), a selective Na+/H+ antiport inhibitor. METHODS AND RESULTS: Using a fluorescent dye technique, we demonstrated that incubation of platelets with physiological concentrations of LDL or with HOE 694 decreased pHi. In addition, both LDL and HOE 694 inhibited the Na+/H+ antiport in platelets treated with sodium propionate or thrombin. The inhibitory effect of LDL was observed both in normal and in glycoprotein (GP)IIb/IIIa-as well as in GPIIIb (CD36)-deficient platelets and was not influenced by the covalent modification of apolipoprotein B lysine residues, suggesting that specific LDL binding sites were not involved. Thrombin-induced phosphoinositide breakdown, diacylglycerol formation, and Ca2+ mobilization, as well as platelet aggregation and granule secretion, were potentiated by both LDL and HOE 694. pHi and Na+/H+ antiport activity were significantly reduced in platelets from patients with familial hypercholesterolemia. Both parameters were normalized after normalization of LDL levels by apheresis treatment. CONCLUSIONS: LDL inhibits the Na+/H+ antiport most likely via receptor-independent mechanisms, thereby augmenting platelet reactivity. This novel mechanisms explains increased platelet reactivity in patients with familial hypercholesterolemia and may contribute to the atherogenic potential of LDL.

Adult↗
PubMed1997

Heterozygous hepatic lipase deficiency, due to two missense mutations R186H and L334F, in the HL gene.

Hepatic lipase (HL) is an endothelial enzyme involved in the metabolism of intermediate density lipoproteins (IDL) and high density lipoproteins (HDL) in plasma. In a Finnish pedigree consisting of 18 members belonging to three generations two missense mutations RI86H and L334F in exons 5 and 7 of the HL gene co-segregated with low post-heparin HL activity. Haplotype analysis of the HL gene in family members revealed a high degree of genetic variation and demonstrated that the two missense mutations reside on the same chromosome. In vitro site-directed mutagenesis and expression of the cDNA constructs in COS-1 cells revealed that the R186H mutation leads to a protein that is not secreted while the L334F mutation results in the production of a HL protein that is secreted but has only about 30% of wild type HL activity. Carriers of the mutated HL gene exhibited clearly reduced HL activity and mass in post-heparin plasma. Probably due to their heterozygous carrier status they had only moderate elevation of total triglycerides, IDL, and LDL-triglycerides. The LDL-particles were enriched in triglycerides and depleted of cholesterol. Also their HDL2- and HDL3-particles were enriched in triglycerides.

Adolescent↗
PubMed1997

The replacement of arginine by cysteine at residue 151 in apolipoprotein A-I produces a phenotype similar to that of apolipoprotein A-IMilano.

Rare nonsynonymous mutations in the apolipoprotein A-I (apo A-I) gene are associated with low HDL-cholesterol levels. Despite the inverse correlation of high density lipoprotein (HDL)-cholesterol levels with the risk of coronary heart disease (CHD) in the population, reduced circulating concentrations of HDL do not necessarily predispose to premature CHD. One apo A-I defect was even reported to cause longevity. We describe a French patient who presented with very low serum HDL-cholesterol levels (10 mg/dl). Sequence analysis of the apo A-I gene identified a heterozygous mutation in the apo A-I gene which causes a cysteine for arginine replacement at residue 151. Family members with the mutation displayed 50% lower levels of plasma HDL-cholesterol and of apo A-I than unaffected members. Plasma activity of lecithin:cholesterol acyl transferase (LCAT) was significantly lower in apo A-I(R151C) heterozygotes than in controls. Furthermore, we found that as for apo A-IMilano (R173C), apo A-I(R151C) forms heterodimers with apo A-II. Moreover, HDL particles were abnormal in both lipid composition and size distribution. Despite these quantitative and qualitative differences in HDL, neither the history of the family over three generations nor the examination of the patient, gave any indication of premature occurrence of atherosclerosis or CHD. We conclude that apo A-I(R151C) causes a phenocopy of apo A-IMilano (R173C), an apo A-I variant which is assumed to cause longevity and which is considered as a potentially anti-atherogenic agent.

Adult↗
PubMed1997

Marked changes of lipid levels during puberty in a patient with lipoprotein lipase deficiency.

UNLABELLED: Clinical and biochemical characteristics of a female patient with familial lipoprotein lipase deficiency have been followed in short intervals before and during puberty. The proband is compound heterozygote for two missense mutations in the lipoprotein lipase gene. One mutation occurs in codon 250 (Asp250-->Asn), the other is in codon 410 (Glu410-->Lys). The residual lipoprotein lipase activity in the proband is less than 10% of controls. Before puberty the proband usually presented with moderate isolated hypertriglyceridaemia. During the initial phase of puberty a dramatic increase in the plasma concentration of both cholesterol and triglycerides was observed. During the second half of puberty a reduction of cholesterol but not of triglycerides was noticed. CONCLUSION: These findings show that the phenotypic expression of familial chylomicronaemia can be modified to a large extent by hormones. Furthermore they demonstrate the need for a closer clinical observation of type I patients during puberty.

Adolescent↗
PubMed1997

Autosomal recessive long-QT syndrome (Jervell Lange-Nielsen syndrome) is genetically heterogeneous.

Jervell Lange-Nielsen syndrome (JLNS) is a recessive disorder with congenital deafness and long-QT syndrome (LQTS 1). Mutations in the potassium-channel gene KVLQT1 (LQTS 1) have been identified in JLNS and in autosomal-dominant LQTS as well. We performed haplotype analysis with microsatellite markers in a Lebanese family with JLNS, but failed to detect linkage at LQTS 1. Moreover, using this approach, we excluded two other ion-channel genes involved in autosomal-dominant LQTS, HERG (LQTS 2) and SCN5A (LQTS 3). Our findings indicate that JLNS is genetically heterogeneous and that, in this family, an unknown LQTS gene causes the disease.

Cation Transport Proteins↗
PubMed1997

Basal growth hormone levels are positively correlated with high-density lipoprotein cholesterol levels in women.

Previous studies in patients with either a deficiency or an excess of growth hormone (GH) yielded contradictory results on the regulation of lipoprotein metabolism by GH. In a cross-sectional study of 563 male and 126 female participants of the Prospective Cardiovascular Münster (PROCAM) Study, we determined biometric and demographic data, serum levels of total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein (apo)A-I, A-II, and B, and unstimulated GH levels. The median of basal GH levels was higher in women than in men. Moreover, 44.2% of men but only 8.7% of women had basal GH levels less than the detection limit of 0.05 microgram/L. The relationship between basal GH and lipoprotein metabolism was investigated by univariate and multivariate regression analysis of data from 315 men and 126 women with detectable basal GH levels. In men, GH correlated positively with HDL cholesterol and negatively with body mass index (BMI), age, and triglycerides. After multivariate analysis, the correlation with triglycerides remained independent of age and BMI. Among women, GH correlated positively with the use of hormonal contraception, HDL cholesterol, apoA-I, and apoA-II, and negatively with BMI, age, menopause, triglycerides, and apoB. With multivariate analysis, the positive correlations of GH with HDL cholesterol and apoA-I in women were independent of age. BMI, menopause, and oral contraception. We conclude that GH contributes to the regulation of HDL cholesterol levels. Moreover, in women the well-known effects of exogenous estrogen or estrogen loss on HDL metabolism may be partially mediated via GH.

Adult↗
PubMed1997

Effects of genotype and diet on cholesterol efflux into plasma and lipoproteins of normal, apolipoprotein A-I-, and apolipoprotein E-deficient mice.

We investigated the contribution of apoE to cholesterol efflux into plasmas of normal, apoA-I-, and apoE-deficient mice, which were fed with chow- and cholesterol-rich diets. Plasmas of normal and apoA-I-deficient mice contain apoE in pre-beta-migrating VLDL as well as in HDL-like lipoproteins, which have either electrophoretic alpha- or gamma-mobilities. The latter particle resembled gamma-LpE in human plasma also by its mobility on nondenaturing two-dimensional electrophoresis. No apoE-containing lipoproteins were found in plasmas of apoE-deficient mice. When apoA-I- and apoE-deficient mice received both chow- and fat-rich diets, their plasmas released significantly less 3H-cholesterol from radiolabeled fibroblasts than did plasma of normal mice. Removal of apoE from plasmas of normal and apoA-I-deficient mice by anti-apoE immunoaffinity chromatography decreased their cholesterol efflux capacities (per 1 minute/per 1 hour) by 26%/40% (P = 0.0092/0.0007) and 30%/26% (P = 0.0092/0.0003), respectively. Net cholesterol efflux from fibroblasts into apoA-I-deficient plasma was 45% lower compared with plasma of normal mice. Incubation of fibroblasts with apoE-deficient plasma caused net influx of cholesterol. Prior addition of human apoE to or removal of apoB-containing lipoproteins from apoE-deficient plasma restored its ability to cause net cholesterol efflux to 50% of normal plasma. Some of the differences between cholesterol efflux into normal and apoE-deficient plasmas were attributable to the failure of apoE-deficient plasmas to take up cell-derived 3H-cholesterol into gamma-LpE. Compared with normal plasma, both apoA-I-deficient and apoE-deficient plasmas were significantly decreased in their activity to esterify cell-derived 3H-cholesterol. Anti-apoE chromatography decreased significantly cholesterol esterification in normal plasma and apoA-I-deficient plasma but not in apoE-deficient plasma. Taken together, the data provide evidence that apoE is an important contributor to reverse cholesterol transport, partially because of initial uptake of cell-derived cholesterol by gamma-LpE and partially because of the contribution of apoE-containing lipoproteins to esterification of cholesterol in plasma.

Animals↗
PubMed1997

Coagulation factor VII and the risk of coronary heart disease in healthy men.

Numerous investigations have demonstrated the role of thrombus formation in the pathogenesis of coronary heart disease (CHD). A tendency to thrombosis may also be indicated by elevated levels of coagulation factor VII clotting activity (FVIIc). Significant associations of FVIIc with increased coronary risk, however, have been found only in the Northwick Park Heart Study. Here we present the results of the 8-year follow-up of FVIIc measurements in 2780 healthy men of the Prospective Cardiovascular Münster study. In the study population (age at entry, 49.3 +/- 6.1 years, mean +/- SD), 130 CHD events occurred during follow-up. FVIIc was significantly higher in subjects with coronary events than in those without (112.4 +/- 20.1% vs 108.7 +/- 21.4%, P = .023). Compared with individuals without coronary events, FVIIc was not significantly higher in men with nonfatal events (111.7 +/- 20.4%; P = .196, n = 93), but there was a tendency toward higher FVIIc activity in subjects with fatal events (114.6 +/- 19.5%; P = .076, n = 37). In the multiple logistic regression analysis, we did not find FVIIc to be an independent risk factor for CHD, and the significance of FVIIc disappeared after total cholesterol, LDL-cholesterol, and triglycerides were taken into account. The increase in the number of CHD events through higher levels of FVIIc was more pronounced in the presence of additional cardiovascular risk factors: smoking; myocardial infarction events in family; angina pectoris; high levels of fibrinogen, total cholesterol, LDL cholesterol, and triglycerides; and a low level of HDL cholesterol. We conclude that FVIIc is a risk factor for CHD, especially in the presence of additional risk factors, and must be taken into account when assessing cardiovascular risk in men.

Adult↗
PubMed1997

Downregulation of the selectin ligand-producing fucosyltransferases Fuc-TIV and Fuc-TVII during foam cell formation in monocyte-derived macrophages.

Identification of genes expressed during foam cell formation is important for understanding the molecular basis of atherosclerosis. We used polymerase chain reaction (PCR)-based differential display to isolate differentially expressed cDNA species in foam cells induced by incubation of human monocyte-derived macrophages in the presence of acetylated or oxidized LDL. This led to identification of a 306-bp cDNA with 100% homology to type IV fucosyltransferase (Fuc-TIV), which was downregulated by factors of 20 and 3 in acetylated LDL- and oxidized LDL-loaded macrophages, respectively. This enzyme is sufficient for the expression of Lewis X and sialyl Lewis X, carbohydrate adhesion molecules that bind to receptors of the selectin family. Expression of a second fucosyltransferase (Fuc-TVII) that synthesizes sialyl Lewis X but not Lewis X was shown by quantitative reverse transcription-PCR to also be reduced, by 40% and 20% in acetylated LDL- and oxidized LDL-loaded macrophages, respectively. alpha-(1,3)-Fucosyltransferase enzyme activity was reduced in lysates from both acetylated LDL- and oxidized LDL-loaded cells. Analysis by flow cytometry showed reduced expression of the CD15 (corresponding to Lewis X) and CD15s (sialyl Lewis X) antigens on the surface of cells loaded with either acetylated or oxidized LDL. Transformation of macrophages into foam cells results in reduced expression of selectin-binding ligands on the surface of such cells.

Acetylation↗