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U Beisiegel

Publications and source records attributed to U Beisiegel.

At least 19 recordsLinked to original sources
PubMed2004

A sensitive noninvasive method for monitoring successful liver-directed gene transfer of the low-density lipoprotein receptor in Watanabe hyperlipidemic rabbits in vivo.

Noninvasive tools to quantitate transgene expression directly are a prerequisite for clinical gene therapy. We established a method to determine location, magnitude, and duration of low-density lipoprotein (LDL) receptor (LDLR) transgene expression after adenoviral gene transfer into LDLR-deficient Watanabe hypercholesterolemic rabbits by following tissue uptake of intravenously injected (111)In-labeled LDL using a scintillation camera. Liver-specific tracer uptake was calculated by normalizing the counts measured over the liver to counts measured over the heart that represent the circulating blood pool of the tracer (liver/heart (L/H) ratio). Our results indicate that the optimal time point for transgene imaging is 4 h after the tracer injection. Compared with control virus-injected rabbits, animals treated with the LDLR-expressing adenovirus showed seven-fold higher L/H ratios on day 6 after gene transfer, and had still 4.5-fold higher L/H ratios on day 30. This imaging method might be a useful strategy to obtain reliable data on functional transgene expression in clinical gene therapy trials of familial hypercholesterolemia.

Adenoviridae↗
PubMed2003

CSF-tau, CSF-Abeta1-42, ApoE-genotype and clinical parameters in the diagnosis of Alzheimer's disease: combination of CSF-tau and MMSE yields highest sensitivity and specificity.

This study evaluated the sensitivity and specificity of the cerebrospinal fluid (CSF) levels of tau-protein, amyloid-beta-peptide 1-42 (Abeta1-42), ApoE-genotype and the degree of cognitive decline as diagnostic markers for Alzheimer's disease (AD). Data was obtained from 105 AD patients and 68 controls. Median CSF-tau levels were increased (512 pg/ml vs. 145 pg/ml, p<0.001) and Abeta1-42-levels were decreased (238.5 pg/ml vs. 310 pg/ml, p<0.001) in AD patients compared to controls. A weak correlation was found between CSF-Abeta1-42 and MMSE score (r=.245). Within all subjects, a correlation of CSF-Abeta1-42 (r=-.337) and CSF-tau (r=.384) with age was found. The combination of CSF-tau levels and MMSE revealed the highest sensitivity (92%) and specificity (87%). In summary, CSF-tau was a useful biological marker to discriminate AD from normal aging, neurological and psychiatric disorders. CSF-Abeta1-42 showed no additional benefit in discriminating patients from controls but might be useful for tracking the severity of the disease.

Adolescent↗
PubMed2003

Therapeutic dose of HIV-1 protease inhibitor saquinavir does not permanently influence early insulin signaling.

UNLABELLED: The introduction of HIV-1 protease inhibitor therapy has significantly improved the expectancy and quality of life for HIV-infected patients. Recent reports have highlighted the development of metabolic complications in patients taking protease inhibitors, including abnormalities in glucose metabolism such as impaired glucose tolerance and type 2 diabetes. The mechanisms by which protease inhibitors induce these metabolic syndromes are not well understood. The aim of this study was to determine whether treatment with the HIV-1 protease inhibitor, saquinavir, influences the early insulin signaling cascade in insulin-sensitive cell lines. METHODS: Insulin-stimulated phosphorylation of insulin receptor (IR-beta), insulin receptor substrates (IRS-1 and IRS-2), association of phosphatidylinositol 3-kinase (PI 3-kinase), Ser 473-phosphorylation of Akt and Thr202/Tyr204-phosphorylated p44/42 MAP kinase in 3T3L1 adipocytes and FAO hepatoma cells incubated with increasing concentrations of saquinavir for 24, 36 hours, 2, 3 and 6 days were measured. Results. Phosphorylation of IR-beta, IRS-1 and IRS-2 was not permanently affected by incubation with therapeutic doses (2.5 microM) of saquinavir for 36 hours. After 24 hours we observed an increase of IR-beta and IRS-1 phosphorylation. However, this initial stimulation of IR-beta and IRS-1 phosphorylation was not permanent and did not result in an increased PI 3-kinase association. Phosphorylation of IRS-2 and MAP kinase as well as glucose transport activity was not altered by therapeutic doses. Doses of 10, 25 and 50 microM of saquinavir altered the early insulin signaling events in a dose-dependent manner. However, this effect was primarily due to the cytotoxic effect of higher saquinavir doses. Glucose transport activity was not significantly reduced in 3T3L1 cells treated with 2.5 microM saquinavir in comparison to the control cells stimulated with insulin. CONCLUSION: Early insulin signaling cascade, essential for normal glucose metabolism, is not affected by therapeutic doses of saquinavir. The reduction of insulin-induced phosphorylation in higher concentrations is primarily related to cytotoxic effects. Other mechanisms than early insulin signaling must be primarily responsible for the metabolic alterations during saquinavir therapy.

3T3 Cells↗
PubMed2001

Recycling of apolipoprotein E and lipoprotein lipase through endosomal compartments in vivo.

We have recently described a novel recycling pathway of triglyceride-rich lipoprotein (TRL)-associated apolipoprotein (apo) E in human hepatoma cells. We now demonstrate that not only TRL-derived apoE but also lipoprotein lipase (LPL) is efficiently recycled in vitro and in vivo. Similar recycling kinetics of apoE and LPL in normal and low density lipoprotein receptor-negative human fibroblasts also indicate that the low density lipoprotein receptor-related protein seems to be involved. Intracellular sorting mechanisms are responsible for reduced lysosomal degradation of both ligands after receptor-mediated internalization. Immediately after internalization in rat liver, TRLs are disintegrated, and apoE and LPL are found in endosomal compartments, whereas TRL-derived phospholipids accumulate in the perinuclear region of hepatocytes. Subsequently, substantial amounts of both proteins can be found in purified recycling endosomes, indicating a potential resecretion of these TRL components. Pulse-chase experiments of perfused rat livers with radiolabeled TRLs demonstrated a serum-induced release of internalized apoE and LPL into the perfusate. Analysis of the secreted proteins identified approximately 80% of the recycled TRL-derived proteins in the high density lipoprotein fractions. These results provide the first evidence that recycling of TRL-derived apoE and LPL could play an important role in the modulation of lipoproteins in vivo.

Animals↗
PubMed2001

Influence of vitamin E and C supplementation on lipoprotein oxidation in patients with Alzheimer's disease.

Because increased oxidation is an important feature of Alzheimer's disease (AD) and low concentrations of antioxidant vitamins C and E have been observed in cerebrospinal fluid (CSF) of AD patients, supplementation with these antioxidants might delay the development of AD. Major targets for oxidation in brain are lipids and lipoproteins. We studied whether supplementation with antioxidative vitamins E and C can increase their concentrations not only in plasma but also in CSF, and as a consequence decrease the susceptibility of lipoproteins to in vitro oxidation. Two groups, each consisting of 10 patients with AD, were for 1 month supplemented daily with either a combination of 400 IU vitamin E and 1000 mg vitamin C, or 400 IU vitamin E alone. We found that supplementation with vitamin E and C significantly increased the concentrations of both vitamins in plasma and CSF. Importantly, the abnormally low concentrations of vitamin C were returned to normal level following treatment. As a consequence, susceptibility of CSF and plasma lipoproteins to in vitro oxidation was significantly decreased. In contrast, the supplementation with vitamin E alone significantly increased its CSF and plasma concentrations, but was unable to decrease the lipoprotein oxidizability. These findings document a superiority of a combined vitamin E + C supplementation over a vitamin E supplementation alone in AD and provide a biochemical basis for its use.

Age of Onset↗
PubMed2001

The effect of pharmacological doses of different antioxidants on oxidation parameters and atherogenesis in hyperlipidaemic rabbits.

The oxidation hypothesis of atherosclerosis implies that antioxidants are able to inhibit lipoprotein oxidation in the arterial wall and thereby retard atherogenesis. Since most of the animal studies performed have used very high doses of antioxidants, it is to date unknown whether antioxidants are effective antiatherosclerotic agents when given in pharmacological doses. Here we addressed this question using homozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits as an animal model of atherosclerosis. The rabbits were divided into four groups, each consisting of ten animals. They received either a standard diet or a diet containing 4.3 mg ubiquinone-10, or 4.3 mg vitamin E or 15 mg probucol/kg body weight daily. After 12 months, the extent of aortic atherosclerosis was assessed as the intima thickness, media thickness and intima-to-media ratio in 14 cross sections equally distributed over the whole aorta. To evaluate the antioxidant effects of the diet, lipophilic and hydrophilic antioxidants, lipids, fatty acids and plasma oxidizability were measured after 0, 3 and 6 months of feeding. We found that supplementation with probucol significantly decreased aortic intima-to-media ratio compared to controls. The antiatherosclerotic action of probucol was accompanied by its beneficial action on plasma oxidizability and some plasma antioxidants. No decrease in aortic atherosclerosis was measured in ubiquinone-10- and vitamin E-supplemented rabbits, despite the fact that both antioxidants decreased plasma oxidizability and ubiquinone-10 increased the plasma levels of antioxidants. Taken together, these data suggest that pharmacological doses of probucol retard atherogenesis in WHHL rabbits by an antioxidant mechanism, while ubiquinone-10 and vitamin E at these dosages are ineffective in this highly hyperlipidaemic model. The measurement of some oxidation-related parameters in plasma, such as lipophilic antioxidants, polyunsaturated fatty acids and lipoprotein oxidizability, may be useful in assessing the risk of atherogenesis in humans.

Administration, Oral↗
PubMed2001

Amyloid-beta is an antioxidant for lipoproteins in cerebrospinal fluid and plasma.

Amyloid-beta (Abeta) peptide, a major constituent of senile plaques and a hallmark of Alzheimer's disease (AD), is normally secreted by neurons and can be found in low concentrations in cerebrospinal fluid (CSF) and plasma, where it is associated with lipoproteins. However, the physiological role of Abeta secretion remains unknown. Here we show that at the concentrations measured in biological fluids (0.1-1.0 nM), Abeta(1-40) strongly inhibits autooxidation of CSF lipoproteins and plasma low density lipoprotein (LDL). At higher concentrations of the peptide its antioxidant action was abolished. Abeta(1-40) also inhibited copper-catalyzed LDL oxidation when added in molar excess of copper, but did not influence oxidation induced by an azo-initiator. Other Abeta peptides also possessed antioxidant activity in the order Abeta(1-40) > Abeta(1-42) > Abeta(25-35), whereas Abeta(35-25) was inactive. These data suggest that Abeta(1-40) may act as a physiological antioxidant in CSF and plasma lipoproteins, functioning by chelating transition metal ions.

Adult↗
PubMed2001

A polymorphism, L162V, in the peroxisome proliferator-activated receptor alpha (PPARalpha) gene is associated with lower body mass index in patients with non-insulin-dependent diabetes mellitus.

This study examined the effect a polymorphism (L162V) in the gene for peroxisome proliferator activated receptor (PPAR) alpha in the development of non-insulin-dependent diabetes mellitus (type 2 DM), obesity and hyperlipidaemia. The frequency of the L162V polymorphism in the PPARalpha gene was determined in 370 morbidly obese patients who underwent gastric banding surgery, 154 patients attending a type 2 DM clinic, 188 patients attending a lipid clinic and 199 healthy blood donors. The overall frequency of the V allele of the L162V polymorphism was 0.06. There were no significant differences in the allele frequency between patients with morbid obesity, hyperlipidaemia, type 2 DM and healthy controls, suggesting that it does not play a major role in the development of these conditions. The polymorphism was associated with a lower body mass index (BMI) in two independently recruited groups of patients with type 2 DM. There was no effect of the polymorphism on subjects without type 2 DM. Thus a polymorphism in PPARalpha protects type 2 DM patients from the overweight which is frequently associated with their condition.

Adult↗
PubMed2001

[Lipid peroxidation as a common pathomechanism in coronary heart disease and Alzheimer disease].

Oxidative processes are involved in aging as well as the pathogenesis of different degenerative diseases. In the last few years the role of low density lipoprotein oxidation in the development of artherosclerosis and coronary heart disease has become evident. Lipoprotein oxidation in plasma is used as a marker for disease progression. We were interested in the role of lipoprotein oxidation in Alzheimer's disease. For this purpose we developed methods to determine the in vitro oxidizability of cerebrospinal fluid and plasma lipoproteins of Alzheimer patients. In addition we measured the lipophilic and hydrophillic antioxidants, alpha-tocopherol (vitamin E) and ascorbate (vitamin C). Cerebrospinal fluid and plasma lipoprotein oxidation was found to be increased in Alzheimer's patients compared to controls and a corresponding decrease of antioxidant vitamins was found. In a pilot study, in vitro lipoprotein oxidation in cerebrospinal fluid of Alzheimer patients could be delayed by vitamin E and C supplementation. In conclusion these data show that increased lipoprotein oxidation could play an important role in Alzheimer's disease and possibly provide a rationale for the treatment of this disease with antioxidant drugs. The clinical effect of this therapeutical approach remains to be proved in long-term studies.

Aged↗
PubMed2001

Association between polymorphisms in candidate genes and morbid obesity.

Polymorphisms in a number of candidate genes have been reported to be associated with obesity. We have determined the incidence of the following polymorphisms in the following candidate genes in a group of 388 morbid obese patients (mean body mass index (BMI) 52+/-8.01) who underwent gastric banding surgery: lipoprotein lipase (LpL) t-93 g and N291S; peroxisome proliferator receptor gamma (PPARgamma), P12A, P115Q and c1431t; peroxisome proliferator receptor alpha (PPARalpha) L162V; beta-adrenergic receptor 2 (beta-AR 2), Q27E; beta-adrenergic receptor 3 (beta-AR 3) W64R; uncoupling protein 1 (ucp-1), a-3826g, ucp-2, 45 bp insertion. Only for the ucp2 polymorphism did we find a statistically significant association with obesity. The beta-AR 3 W64R and ucp-1 a-3826g polymorphisms influenced the rate of the development of obesity and may act synergistically.

Adult↗
PubMed2001

Renal handling of human apolipoprotein(a) and its fragments in the rat.

The sites and mechanisms of the catabolism of atherogenic lipoprotein(a) (Lp(a)) are not well understood. Lp(a) is increased in patients with end-stage renal disease, suggesting a renal catabolism of Lp(a). To gain a better insight into renal handling of Lp(a), we established a heterologous rat model to study the renal catabolism of human Lp(a). Pure human Lp(a) was injected into Wistar rats, and animals were sacrificed at different time points (30 minutes to 24 hours). Intact Lp(a) was cleared from the circulation of injected rats with a half-life time of 14.5 hours. Strong intracellular immunostaining for apolipoprotein(a) (apo(a)) was observed in the cytoplasm of proximal tubular cells after 4, 8, and 24 hours. Apolipoprotein B (apoB) was colocalized with glomerular apo(a) 1 to 8 hours after Lp(a) injection, but renal capillaries and tubules remained negative. No relevant amounts of apo(a) fragments were found in the plasma of rats after injection of Lp(a). During all urine collection periods, apo(a) fragments with molecular weights of 50 to 160 kd were detected in the urine, however. Our results show that human Lp(a) injected into rats accumulates intracellularly in the rat kidney, and apo(a) fragments are excreted in the urine. The kidney apparently plays a major role in fragmentation of Lp(a). Despite the fact that rodents lack endogenous Lp(a), rats injected with human Lp(a) may provide a useful heterologous animal model to study the renal metabolism of Lp(a) further.

Animals↗
PubMed2001

Association between the P12A and c1431t polymorphisms in the peroxisome proliferator activated receptor gamma (PPAR gamma) gene and type 2 diabetes.

Variation in the peroxisome proliferator-activated receptor gamma (PPAR gamma) gene may play a role in the development of type 2 diabetes mellitus. Therefore we investigated the association between the P12A and c1431t polymorphisms in the PPAR gamma gene and type 2 diabetes. The incidence of the P12A polymorphism was determined by PCR-RFLP and the c1431t by single-strand conformation polymorphism analysis in 219 patients with, and 429 without type 2 diabetes. The frequency of the A allele of P12A polymorphism was 0.16 and the t allele of c1431t polymorphism, 0.13 in patients with type 2 diabetes, and 0.13 and 0.12 respectively in subjects without diabetes 3.2% of patients with and 1.4% without type 2 diabetes were A12A. Since the polymorphisms are not linked the association of the 9 possible genotypes with type 2 diabetes was determined. All patients with genotype A12A/c1431c had type 2 diabetes (n = 3, p = 0.038). There was no association between A12A/t1431t and diabetes. DNA sequencing revealed no additional mutations in the coding region of the PPAR gamma gene in genotypes A12A/c1431c or A12A/t1431t. The associations found between polymorphisms in the PPAR gamma gene and type 2 diabetes suggest that either the A12 isofrom is functional leading to a predisposition to type 2 diabetes in homozygotes or that there is a third, unknown mutation linked to the A12/c1431 haplotype which is responsible.

Adult↗
PubMed2001

Resistance of human cerebrospinal fluid to in vitro oxidation is directly related to its amyloid-beta content.

Amyloid-beta (A beta) peptide, a major constituent of senile plaques and a hallmark of Alzheimer's disease (AD), is normally secreted by neurons and can be found in low concentrations in cerebrospinal fluid (CSF) and plasma where it is associated with lipoproteins. However, the physiological role of A beta secretion remains unknown. We measured the resistance to in vitro oxidation of CSF obtained from 20 control subjects and 30 patients with AD, and correlated it with CSF levels of antioxidants, lipids and A beta. We found that the oxidative resistance, expressed as a duration of the oxidation lag-phase, was directly related to CSF levels of A beta 1-40, A beta 1-42 and ascorbate and inversely to levels of fatty acids. These data suggest that, besides ascorbate, A beta is another major physiological antioxidant for CSF lipoproteins.

Adult↗
PubMed2001

Intracellular metabolism of triglyceride-rich lipoproteins.

Over the past 10 years, many advances have been made in our understanding of the intravascular metabolism of triglyceride-rich lipoproteins. It is now known that the complex extracellular interactions of triglyceride-rich lipoprotein-associated apolipoprotein E, lipoprotein lipase and hepatic lipase with heparan sulfate proteoglycans and lipoprotein receptors facilitate the hepatocellular uptake of triglyceride-rich lipoproteins. Recent studies have also revealed that the intracellular fate of internalized triglyceride-rich lipoproteins is highly complex. The dissociation of triglyceride-rich lipoprotein components within intracellular endosomal compartments involves the recycling of apolipoprotein E, whereas the remaining lipid core associated with apolipoprotein B is susceptible to lysosomal degradation. Apolipoprotein E recycling is an important newly discovered feature of lipoprotein metabolism, and will be discussed in the context of its intracellular transport mechanisms and cholesterol efflux. Current concepts concerning its potential relevance with regard to lipoprotein metabolism and atherosclerosis will also be discussed.

Animals↗
PubMed2001

Characterization of four lipoprotein classes in human cerebrospinal fluid.

Lipoprotein metabolism in brain has not yet been fully elucidated, although there are a few reports concerning lipids in the brain and lipoproteins and apolipoproteins in the cerebrospinal fluid (CSF). To establish normal levels of lipoproteins in human CSF, total cholesterol, phospholipids, and fatty acids as well as apolipoprotein E (apoE) and apoA-I levels were determined in CSF samples from 216 individuals. For particle characterization, lipoproteins from human CSF were isolated by affinity chromatography and analyzed for size, lipid and apolipoprotein composition. Two consecutive immunoaffinity columns with antibodies, first against apoE and subsequently against apoA-I, were used to define four distinct lipoprotein classes. The major lipoprotein fraction consisted of particles of 13;-20 nm containing apoE and apoA-I as well as apoA-IV, apoD, apoH, and apoJ. In the second particle class (13;-18 nm) mainly apoA-I and apoA-II but no apoE was detected. Third, there was a small number of large particles (18;-22 nm) containing no apoA-I but apoE associated with apoA-IV, apoD, and apoJ. In the unbound fraction we detected small particles (10;-12 nm) with low lipid content containing apoA-IV, apoD, apoH, and apoJ. In summary, we established lipid and apolipoprotein levels in CSF in a large group of individuals and described four distinct lipoprotein classes in human CSF, differing in their apolipoprotein pattern, lipid composition, and size. On the basis of our own data and previous findings from other groups, we propose a classification of CSF lipoproteins.

Apolipoprotein A-I↗
PubMed2000

Annexin VI stimulates endocytosis and is involved in the trafficking of low density lipoprotein to the prelysosomal compartment.

Annexins are calcium-binding proteins with a wide distribution in most polarized and nonpolarized cells that participate in a variety of membrane-membrane interactions. At the cell surface, annexin VI is thought to remodel the spectrin cytoskeleton to facilitate budding of coated pits. However, annexin VI is also found in late endocytic compartments in a number of cell types, indicating an additional important role at later stages of the endocytic pathway. Therefore overexpression of annexin VI in Chinese hamster ovary cells was used to investigate its possible role in endocytosis and intracellular trafficking of low density lipoprotein (LDL) and transferrin. While overexpression of annexin VI alone did not alter endocytosis and degradation of LDL, coexpression of annexin VI and LDL receptor resulted in an increase in LDL uptake with a concomitant increase of its degradation. Whereas annexin VI showed a wide intracellular distribution in resting Chinese hamster ovary cells, it was mainly found in the endocytic compartment and remained associated with LDL-containing vesicles even at later stages of the endocytic pathway. Thus, data presented in this study suggest that after stimulating endocytosis at the cell surface, annexin VI remains bound to endocytic vesicles to regulate entry of ligands into the prelysosomal compartment.

Animals↗
PubMed2000

Increased lipoprotein oxidation in Alzheimer's disease.

Oxidation has been proposed to be an important factor in the pathogenesis of Alzheimer's disease (AD) and amyloid beta is considered to induce oxidation. In biological fluids, including cerebrospinal fluid (CSF), amyloid beta is found complexed to lipoproteins. On the basis of these observations, we investigated the potential role of lipoprotein oxidation in the pathology of AD. Lipoprotein oxidizability was measured in vitro in CSF and plasma from 29 AD patients and found to be significantly increased in comparison to 29 nondemented controls. The levels of the hydrophilic antioxidant ascorbate were significantly lower in CSF and plasma from AD patients. In plasma, alpha-carotene was significantly lower in AD patients compared to controls while alpha-tocopherol levels were indistinguishable between patients and controls. In CSF, a nonsignificant trend to lower alpha-tocopherol levels among AD patients was found. Polyunsaturated fatty acids, the lipid substrate for oxidation, were significantly lower in the CSF of AD patients. Our findings suggest that (i) lipoprotein oxidation may be important in the development of AD and (ii) the in vitro measurement of lipid peroxidation in CSF might become a useful additional marker for diagnosis of AD.

Age Factors↗