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Biomedical subjects

Gerd Assmann

Publications and source records attributed to Gerd Assmann.

At least 55 records · Page 3Linked to original sources
PubMed2003

High density lipoprotein-associated lysosphingolipids reduce E-selectin expression in human endothelial cells.

Adhesion and recruitment of blood monocytes, processes mediated by cell adhesion molecules including E-selectin, represent an early event in atherogenesis. High density lipoproteins (HDLs) were shown to inhibit cytokine-induced expression of adhesion molecules, but mechanisms underlying this effect are not fully understood. We here investigated the effects of sphingosylphosphorylcholine (SPC) and lysosulfatide (LSF), two lysosphingolipids associated with HDL, on TNF-alpha-induced E-selectin expression in human umbilical endothelial cells. We found that HDL, SPC, and LSF inhibited E-selectin expression both on mRNA and protein level. In addition, all three agents reduced the number of E-selectin molecules present on endothelial cell surface. The inhibitory effects of HDL, SPC, and LSF on TNF-alpha-induced E-selectin expression were partially reverted in the presence of suramin, an antagonist of lysosphingolipid receptor EDG-3, or pertussis toxin, an inhibitor of trimeric G proteins. In addition, inhibition of activation of protein kinase Akt with LY294002 but not inhibition of phosphatidylinositol-specific phospholipase C (PI-PLC) with U73122 abolished the restrictive effects of HDL-, SPC-, or LSF on E-selectin expression. We conclude that HDL-associated lysosphingolipids may at least partially account for the inhibitory effects of HDL on cytokine-induced expression of adhesion molecules, and that activations of G-protein-coupled receptors and protein kinase Akt are involved in this process.

Cells, Cultured↗
PubMed2003

From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: Part I.

Atherosclerotic cardiovascular disease results in >19 million deaths annually, and coronary heart disease accounts for the majority of this toll. Despite major advances in treatment of coronary heart disease patients, a large number of victims of the disease who are apparently healthy die suddenly without prior symptoms. Available screening and diagnostic methods are insufficient to identify the victims before the event occurs. The recognition of the role of the vulnerable plaque has opened new avenues of opportunity in the field of cardiovascular medicine. This consensus document concludes the following. (1) Rupture-prone plaques are not the only vulnerable plaques. All types of atherosclerotic plaques with high likelihood of thrombotic complications and rapid progression should be considered as vulnerable plaques. We propose a classification for clinical as well as pathological evaluation of vulnerable plaques. (2) Vulnerable plaques are not the only culprit factors for the development of acute coronary syndromes, myocardial infarction, and sudden cardiac death. Vulnerable blood (prone to thrombosis) and vulnerable myocardium (prone to fatal arrhythmia) play an important role in the outcome. Therefore, the term "vulnerable patient" may be more appropriate and is proposed now for the identification of subjects with high likelihood of developing cardiac events in the near future. (3) A quantitative method for cumulative risk assessment of vulnerable patients needs to be developed that may include variables based on plaque, blood, and myocardial vulnerability. In Part I of this consensus document, we cover the new definition of vulnerable plaque and its relationship with vulnerable patients. Part II of this consensus document focuses on vulnerable blood and vulnerable myocardium and provide an outline of overall risk assessment of vulnerable patients. Parts I and II are meant to provide a general consensus and overviews the new field of vulnerable patient. Recently developed assays (eg, C-reactive protein), imaging techniques (eg, CT and MRI), noninvasive electrophysiological tests (for vulnerable myocardium), and emerging catheters (to localize and characterize vulnerable plaque) in combination with future genomic and proteomic techniques will guide us in the search for vulnerable patients. It will also lead to the development and deployment of new therapies and ultimately to reduce the incidence of acute coronary syndromes and sudden cardiac death. We encourage healthcare policy makers to promote translational research for screening and treatment of vulnerable patients.

Acute Disease↗
PubMed2003

Apolipoprotein C-III, a strong discriminant of coronary risk in men and a determinant of the metabolic syndrome in both genders.

AIMS: Apolipoprotein C-III (apoC-III) has been recognized as a useful marker of triglyceride-rich lipoproteins (TRLs) metabolism and proposed as an indicator of prognosis for coronary risk in healthy subjects. We studied cross-sectionally in a population having low cholesterol levels, but a high prevalence of the metabolic syndrome, whether serum levels of total apoC-III or its sub-fractions were independent markers of prevalent coronary heart disease (CHD) or were related to variables reflecting the metabolic syndrome. METHODS AND RESULTS: In 857 unselected participants of the representative population sample of the Turkish Adult Risk Factor Survey in 2001, apoC-III as well as other risk variables were evaluated, and CHD was diagnosed based on clinical findings and Minnesota coding of resting electrocardiograms. The sample consisted of men and women, aged 33-82 years, having a mean waist circumference of 89.4 and 92.9 cm, respectively, 42% of whom had the metabolic syndrome identified by criteria of the ATP III. ApoC-III values were measured by turbidimetric immunoassay. Mean concentrations for non-high-density lipoprotein (nonHDL) apoC-III in men and women were 6.4 and 6.2 mg/dl, respectively, and for apoC-III in HDL were 6.2 and 6.3 mg/dl, respectively. NonHDL apoC-III was similar to, and apoC-III in HDL was higher than that in Western populations. Both fractions of apoC-III were significantly correlated with lipids, lipoproteins, apoB, anthropometric measures, and blood pressures in both genders. Correlations for both were high with serum triglycerides (r(s)=around 0.70) and apoB (r(p)=around 0.37). Total apoC-III as well as both fractions were significantly correlated in women also with levels of inflammatory risk markers: strongly (r=0.40-0.45, P<0.001) with complement C3, and weakly (r(s)=around 0.20, P<0.001) with C-reactive protein. A cutoff of >7.0 mg/dl as opposed to lower levels of nonHDL apoC-III indicated the presence of hypertriglyceridemic hyperapo B with an age-adjusted odds ratio (OR) of 13.8; it indicated the presence of metabolic syndrome with 4.66-fold likelihood. Total apoC-III and nonHDL apoC-III proved to be significantly (P-trend <0.05 and 0.002) and strongly associated with prevalent CHD in men even after adjustment for age, low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C): OR gradients across upper and lower quartiles were 3.88-fold (CI: 1.3; 11.4) and 8.8-fold (CI: 2.6; 29.8), respectively. CONCLUSIONS: In a population among whom the metabolic syndrome prevails, total- and nonHDL apoC-III are each a determinant in both genders of the metabolic syndrome and of hypertriglyceridemic hyperapo B. Each is a powerful significant marker of prevalent CHD in men independent of LDL- and HDL-C levels. In women, despite being correlated with inflammatory risk markers, the significant association of elevated levels of apoC-III with CHD did not prove to be independent of age.

Adult↗
PubMed2003

Framingham risk function overestimates risk of coronary heart disease in men and women from Germany--results from the MONICA Augsburg and the PROCAM cohorts.

BACKGROUND: The prediction of the absolute risk of coronary heart disease (CHD) is commonly based on risk prediction equations that originate from the Framingham Heart Study. However, differences in population risk levels compromise the external validity of these risk functions. SETTING AND STUDY POPULATION: Participants aged 35-64 years from the MONICA Augsburg (2861 men and 2925 women) and the PROCAM (5527 men and 3155 women) cohorts were followed-up with regard to incident non-fatal myocardial infarction (MI) and fatal coronary events. For each participant, the predicted absolute risk of fatal plus non-fatal events was derived using Framingham risk equations. Predicted and actually observed risks were compared. RESULTS: The two cohorts were similar in their baseline characteristics. Coronary risk predicted by the Framingham risk function substantially exceeded the risk actually observed in the German cohorts, irrespective of gender. The difference between predicted and observed absolute CHD risk increased with age while the ratio of predicted over observed risk remained constant at about a value of 2. Taking potentials for underascertainment in the German cohorts due to unrecognised MI and sudden deaths into account, the residual magnitude of risk overestimation by the Framingham risk function is probably at least 50%. CONCLUSIONS: Local guidelines for the management of patients with risk factors need to correct for this overestimation to avoid inadequate initiation of treatment and inflation of costs in primary prevention. Similar studies should be conducted in other populations with the aim of defining appropriate factors that calibrate absolute risk predictions to local population levels of CHD risk.

Adult↗
PubMed2003

Tibolone lowers high density lipoprotein cholesterol by increasing hepatic lipase activity but does not impair cholesterol efflux.

OBJECTIVE: Androgens and other drugs that reduce plasma concentrations of high density lipoprotein (HDL) cholesterol are often considered to be pro-atherogenic. Tibolone lowers HDL-cholesterol by 20% but the clinical significance of this effect is unknown. METHODS: In a randomized, double-blind study, 34 women received 2.5 mg tibolone daily and 34 women received placebo. Serum concentrations of lipids, lipoprotein subclasses and apolipoproteins, together with plasma activities of lipid transfer proteins and lipolytic enzymes and the capacity of plasma to induce cholesterol efflux from cultured cells, were measured. RESULTS: Compared to placebo, tibolone reduced serum concentrations of HDL-cholesterol (-14%), HDL phosphatidylcholine (-14%), apolipoprotein (apo)A-I (-12%), HDL subclasses lipoprotein (Lp)A-I (-20%), HDL-apoE (-16%), pre beta-LpA-I (-10%) and alpha-LpA-I (-12%) and increased hepatic lipase activity (+25%) and HDL sphingomyelin : phosphatidylcholine ratio (10.5%), but did not alter serum concentrations of HDL sphingomyelin, apoA-IV and LpA-I/A-II, lipoprotein lipase, the plasma activities of lecithin : cholesterol acyl transferase, cholesteryl ester transfer protein, phospholipid transfer protein or the plasma capacity to release cholesterol from cultured fibroblasts or Fu5AH hepatocytes. CONCLUSIONS: Tibolone lowers HDL-cholesterol in part by increasing hepatic lipase activity. Conservation of sphingomyelin and apoA-II in HDL, as well as cholesteryl ester transfer protein activity, preserves the capacity of plasma to release cholesterol, despite the lower concentrations of HDL-cholesterol. This may have important implications for the use of steroid effects on HDL concentrations as surrogates for atherosclerosis.

Carrier Proteins↗
PubMed2003

Dietary mono- and polyunsaturated fatty acids similarly increase plasma apolipoprotein A-IV concentrations in healthy men and women.

We investigated the effect of dietary fatty acid composition on plasma apolipoprotein (apo) A-IV concentrations. Plasma apo A-IV concentrations were measured by ELISA in plasma of 48 healthy men and women in a controlled dietary study. First, all participants consumed a 2-wk baseline diet rich in saturated fatty acids (SFA). Then, they were randomly assigned to one of three dietary treatments, which contained refined olive oil [rich in monounsaturated fatty acids (MUFA), n = 17], rapeseed oil [rich in MUFA and alpha-linolenic acid [18:3(n-3)], n = 13], or sunflower oil [rich in (n-6) PUFA, n = 18] as the principal source of fat for 4 wk. The plasma concentrations of apo A-IV increased when subjects consumed the diets rich in unsaturated fatty acids, by 16% or 13.0 mg/L [F((2,76)) = 12.874, P < 0.001 by repeated-measures ANOVA]. The increase was not affected by diet group affiliation, gender or apo A-IV genotype. In conclusion, diets rich in unsaturated fatty acids, independent of the degree of unsaturation, gender and apo A-IV genotype, increase plasma apo A-IV concentrations compared with a baseline diet rich in SFA in healthy men and women.

Adult↗
PubMed2002

Branched chain fatty acids induce nitric oxide-dependent apoptosis in vascular smooth muscle cells.

Clinical observations in patients with peroxisomal disorders and studies employing corresponding mouse models have shown that supraphysiological concentrations of dietary branched chain fatty acids (BCFAs) are associated with a high level of toxicity, which is poorly understood at present. Here we show that phytanic and pristanic acid, two BCFAs that are metabolized in peroxisomes, promote apoptosis in cultured vascular smooth muscle cells of human, rat, and porcine origin. Under the conditions used, the apoptosis-promoting effect of BCFAs was neither shared by saturated or unsaturated straight chain fatty acids nor by artificial peroxisome proliferators, which, like phytanic and pristanic acid, have been shown to activate the peroxisome proliferator-activated receptor alpha (PPARalpha). We could demonstrate, however, that BCFA induced tumor necrosis factor alpha (TNFalpha) activation and secretion, which is an obligatory step required for induction of apoptosis by BCFAs. Furthermore, incubation of VSMCs with BCFA increased inducible nitric-oxide synthase (iNOS) mRNA and protein concentrations markedly within 2 h of treatment. Correspondingly, apoptosis was significantly reduced when the cells were co-treated with the competitive NOS inhibitors monomethyl-L-arginine monoacetate and aminoguanidine. Moreover, co-incubation with TGFbeta1, previously shown to destabilize iNOS mRNA, also abolished apoptosis. These results establish a new signaling cascade in which natural BCFA induced NO-dependent apoptosis, which is apparently triggered by autocrine secretion of TNFalpha in cultured VSMCs.

Animals↗
PubMed2002

Testosterone up-regulates scavenger receptor BI and stimulates cholesterol efflux from macrophages.

By lowering high density lipoprotein (HDL) cholesterol, testosterone contributes to the gender difference in HDL cholesterol and has been accused to be pro-atherogenic. The mechanism by which testosterone influences HDL cholesterol is little understood. We therefore investigated the effect of testosterone on the gene expression of apolipoprotein A-I (apoA-I), hepatic lipase (HL), scavenger receptor B1 (SR-BI), and the ATP binding cassette transporter A1 (ABCA1), all of which are important regulators of HDL metabolism. In both cultivated HepG2 hepatocytes and primary human monocyte-derived macrophages, testosterone led to a dose-dependent up-regulation of SR-BI, which was assessed on both the mRNA and the protein levels. As a functional consequence, we observed an increased HDL(3)-induced cholesterol efflux from macrophages. At supraphysiological dosages, testosterone also increased the expression of HL in HepG2 cells. Testosterone had no effect on the expression of apoA-I in HepG2 cells and ABCA1 in either HepG2 cells or macrophages. These data suggest that testosterone, despite lowering HDL cholesterol, intensifies reverse cholesterol transport and thereby exerts an anti-atherogenic rather than a pro-atherogenic effect.

ATP Binding Cassette Transporter 1↗
PubMed2002

Relation of serum levels of sex hormone binding globulin to coronary heart disease in postmenopausal women.

Hyperandrogenemia and low levels of sex hormone binding globulin (SHBG) are frequently found in women with metabolic syndrome, which is characterized by low high-density lipoprotein cholesterol, hypertriglyceridemia, obesity, and hyperinsulinemia. The specific contribution of these various factors to coronary heart disease (CHD) is controversial. The coronary angiograms of 87 consecutive postmenopausal women were evaluated using 2 semiquantitative scoring systems to estimate the extent of focal and diffuse vessel wall alterations. Fasting sera were analyzed for levels of glucose, lipids, insulin, leptin, dehydroepiandrosterone sulfate, testosterone, and SHBG. Obesity was assessed by measuring body mass index, waist-to-hip ratio, skinfold thicknesses, and body impedance. After adjusting for age, there were significant differences in 55 women with CHD compared with 32 women without CHD: higher levels of low-density lipoprotein cholesterol (159 +/- 51 vs 132 +/- 39 mg/dl), apolipoprotein B (121 +/- 33 vs 102 +/- 29 mg/dl), triglycerides (115 vs 91 mg/dl), and basal insulin (7.5 vs 4.6 mU/L), as well as lower levels of high-density lipoprotein cholesterol (59.9 +/- 18.0 vs 69.0 +/- 17.1 mg/dl), SHBG (44.6 vs 68.1 nmol/L) and the quantitative insulin sensitivity check index (0.66 +/- 0.41 vs 0.93 +/- 0.73). Multivariate analysis by logistic regression identified age (odds ratio [OR] 1.22, 95% confidence intervals [CI] 1.09 to 1.37), smoking (OR 11.46, 95% CI 2.56 to 51.39), SHBG (OR 0.98, 95% CI 0.96 to 0.99), and apolipoprotein B (OR 1.02, 95% CI 1.01 to 1.04) as independently associated with the presence of CHD. Thus, low plasma levels of SHBG are associated with CHD in women independently of insulin, obesity markers, and dyslipidemia.

Androgens↗
PubMed2002

The ATP binding cassette transporter A1 contributes to the secretion of interleukin 1beta from macrophages but not from monocytes.

Deficiency of ABCA1 causes high density lipoprotein deficiency and macrophage foam cell formation in Tangier disease. ABCA1 was also postulated to mediate the secretion of IL-1beta from monocytes and macrophages. We investigated the contribution of ABCA1 to IL-1beta secretion from human monocytes and macrophages of normal donors and Tangier disease patients. Neither an anti-ABCA1 antisense oligonucleotide nor ABCA1 deficiency interfered with LPS-induced secretion of IL-1beta from full blood or freshly isolated monocytes. By contrast, anti-ABCA1 antisense oligonucleotides decreased the LPS-induced secretion of IL-beta from macrophages by 30-50%. The secretion of the precursor pro-IL-1beta and TNFalpha was not inhibited. Compared to normal macrophages, LPS-stimulated Tangier disease macrophages secreted less IL-1beta relative to TNFalpha. Also the spontaneous secretion of IL-1beta by Tangier macrophages was lower than by control cells. We conclude that IL-1beta is secreted from monocytes by an ABCA1-independent pathway and from macrophages by ABCA1-dependent and -independent pathways.

ATP Binding Cassette Transporter 1↗
PubMed2002

Simple scoring scheme for calculating the risk of acute coronary events based on the 10-year follow-up of the prospective cardiovascular Münster (PROCAM) study.

BACKGROUND: The absolute risk of an acute coronary event depends on the totality of risk factors exhibited by an individual, the so-called global risk profile. Although several scoring schemes have been suggested to calculate this profile, many omit information on important variables such as family history of coronary heart disease or LDL cholesterol. METHODS AND RESULTS: Based on 325 acute coronary events occurring within 10 years of follow-up among 5389 men 35 to 65 years of age at recruitment into the Prospective Cardiovascular Münster (PROCAM) study, we developed a Cox proportional hazards model using the following 8 independent risk variables, ranked in order of importance: age, LDL cholesterol, smoking, HDL cholesterol, systolic blood pressure, family history of premature myocardial infarction, diabetes mellitus, and triglycerides. We then derived a simple point scoring system based on the beta-coefficients of this model. The accuracy of this point scoring scheme was comparable to coronary event prediction when the continuous variables themselves were used. The scoring system accurately predicted observed coronary events with an area under the receiver-operating characteristics curve of 82.4% compared with 82.9% for the Cox model with continuous variables. CONCLUSIONS: Our scoring system is a simple and accurate way of predicting global risk of myocardial infarction in clinical practice and will therefore allow more accurate targeting of preventive therapy.

Acute Disease↗
PubMed2002

The mutagenically separated polymerase chain reaction is a rapid and reliable method for genotyping of the tumour necrosis factor-alpha promoter polymorphism (-308 G/A).

BACKGROUND: The tumour necrosis factor-alpha (TNF alpha) promoter polymorphism (-308 G/A) has been shown to be associated with the susceptibility to and/or the severity of diverse diseases such as infections, autoimmunity, and malignancies. We developed a genotyping technique based on the mutagenically separated polymerase chain reaction (MS-PCR) which may be useful in the clinical risk assessment. METHODS: Different length allele-specific primers and an unspecific complementary strand primer were used in a one-tube assay. At least one PCR product was generated in a single reaction obviating the need for an internal control amplification. Introduction of additional base substitutions into the allele-specific primers led to a clear-cut separation between the alleles through the reduction of cross-reactions during amplification. The only post-PCR step required was the separation of allelic PCR products by size upon agarose gel electrophoresis. RESULTS: The allele frequencies in 300 German healthy Caucasians were 0.84 for TNF1 (-308 G) and 0.16 for TNF2 (-308 A) in accordance with published data obtained with the conventional RFLP method. No significant deviation from Hardy-Weinberg equilibrium was observed. The specificity of MS-PCR was confirmed by sequence-based typing. CONCLUSIONS: MS-PCR is a rapid, reliable, and cost-effective technique for genotyping of the TNF alpha promoter polymorphism (-308 G/A).

Adult↗
PubMed2002

HDL and arteriosclerosis: beyond reverse cholesterol transport.

The inverse correlation between serum levels of high density lipoprotein (HDL) cholesterol and the risk of coronary heart disease, the protection of susceptible animals from atherosclerosis by transgenic manipulation of HDL metabolism, and several potentially anti-atherogenic in vitro-properties have made HDL metabolism an interesting target for pharmacological intervention in atheroslcerosis. We have previously reviewed the concept of reverse cholesterol transport, which describes both the metabolism and the classic anti-atherogenic function of HDL (Arterioscler. Thromb. Vasc. Biol. 20 2001 13). We here summarize the current understanding of additional biological, potentially anti-atherogenic properties of HDL. HDL inhibits the chemotaxis of monocytes, the adhesion of leukocytes to the endothelium, endothelial dysfunction and apoptosis, LDL oxidation, complement activation, platelet activation and factor X activation but also stimulates the proliferation of endothelial cells and smooth muscle cells, the synthesis of prostacyclin and natriuretic peptide C in endothelial cells, and the activation of proteins C and S. These anti-inflammatory, anti-oxidative, anti-aggregatory, anti-coagulant, and pro-fibrinolytic activities are exerted by different components of HDL, namley apolipoproteins, enzymes, and even specific phospholipids. This complexity further emphasizes that changes in the functionality of HDL rather than changes of plasma HDL-cholesterol levels determine the anti-atherogenicity of therapeutic alterations of HDL metabolism.

Animals↗
PubMed2002

Prediction of risk of coronary events in middle-aged men in the Prospective Cardiovascular Münster Study (PROCAM) using neural networks.

BACKGROUND: Logistic regression (LR) is commonly used to estimate risk of coronary heart disease. We investigated if neural networks improved on the risk estimate of LR by analysing data from the Prospective Cardiovascular Münster Study (PROCAM), a large prospective epidemiological study of risk factors for coronary heart disease among men and women at work in northern Germany. METHODS: We used a multi-layer perceptron (MLP) and probabilistic neural networks (PNN) to estimate the risk of myocardial infarction or acute coronary death (coronary events) during 10 years' follow-up among 5159 men aged 35-65 years at recruitment into PROCAM. In all, 325 coronary events occurred in this group. We assessed the performance of each procedure by measuring the area under the receiver-operating characteristics curve (AUROC). RESULTS: The AUROC of the MLP was greater than that of the PNN (0.897 versus 0.872), and both exceeded the AUROC for LR of 0.840. If 'high risk' is defined as an event risk >20% in 10 years, LR classified 8.4% of men as high risk, 36.7% of whom suffered an event in 10 years (45.8% of all events). The MLP classified 7.9% as high risk, 64.0% of whom suffered an event (74.5% of all events), while with the PNN, only 3.9% were at high risk, 58.6% of whom suffered an event (33.5% of all events). CONCLUSION: Intervention trials indicate that about one in three coronary events can be prevented by 5 years of lipid-lowering treatment. Our analysis suggests that use of the MLP to identify high-risk individuals as candidates for drug treatment would allow prevention of 25% of coronary events in middle-aged men, compared to 15% and 11% with LR and the PNN, respectively.

Adult↗