A simple method to assess the oxidative susceptibility of low density lipoproteins

BACKGROUND: Oxidative modification of low density lipoproteins (LDL) is recognized as one of the major processes involved in atherogenesis. The in vitro standardized measurement of LDL oxidative susceptibility could thus be of clinical significance. The aim of the present study was to establish a method which would allow the evaluation of oxidative susceptibility of LDL in the general clinical laboratory. RESULTS: LDL was isolated from human plasma by selective precipitation with amphipathic polymers. The ability of LDL to form peroxides was assessed by measuring thiobarbituric acid reactive substances (TBARS) after incubation with Cu(2+) and H(2)O(2). Reaction kinetics showed a three-phase pattern (latency, propagation and decomposition phases) which allowed us to select 150 min as the time point to stop the incubation by cooling and EDTA addition. The mixture Cu(2+)/H(2)O(2) yielded more lipoperoxides than each one on its own at the same time end-point. Induced peroxidation was measured in normal subjects and in type 2 diabetic patients. In the control group, results were 21.7 ± 1.5 nmol MDA/mg LDL protein, while in the diabetic group results were significantly increased (39.0 ± 3.0 nmol MDA/mg LDL protein; p < 0.001). CONCLUSION: a simple and useful method is presented for the routine determination of LDL susceptibility to peroxidation in a clinical laboratory

Feedback on Shopping Receipt Data Through a Mobile App: A Pilot Study

Mobile applications have become popular tools for supporting healthy nutrition behavior. Current tools are primarily based on the detailed tracking of a user’s direct consumption, thus intervening only during or even after a user has eaten something. With increasing home office hours (especially during the COVID-19 pandemic), people are eating more often at home, which has also led to a decrease in fruit and vegetable consumption. Therefore, we aim to support people in the food-shopping process. We suggest a mobile application that helps people reflect on their purchases and tries to nudge users toward healthier product choices. We conducted a pilot study with 31 participants who used the application for two consecutive weeks. During this time, we observed a decrease in the caloric values per 100 g of purchases. Furthermore, we collected positive feedback on the app regarding acceptance, usability, and user experience

Einflussfaktoren und soziale Räume für Solidarität in Zeiten der Individualisierung

Der vorliegende Beitrag untersucht, wie inklusive Solidarität als zentraler Motor für die Organisationsmacht von Gewerkschaften in Zeiten der Individualisierung aufgebaut werden kann. Angelehnt an die Theorie der soziologischen Phänomenologie werden fünf qualitative Interviews mit Absolventinnen und Absolventen der Wiener Gewerkschaftsschule hinsichtlich wesentlicher Faktoren für Solidarität und der Rolle sozialer Räume dafür ausgewertet. Die wesentlichen Ergebnisse sind: Solidarität kann in einem Prozess der primären und sekundären Sozialisation gelernt werden. Solidarität braucht soziale Räume, die den Austausch und die Begegnung ermöglichen. Die Gewerkschaftsschule ist ein solcher sozialer Raum, der wesentlich zur Förderung von Solidarität beiträgt. Auch in Zeiten der Individualisierung und der Digitalisierung ist es möglich, Solidarität auszubauen. Die Faktoren, Räume und Unterstützungsnetzwerke müssen dafür weitergedacht werden.The present study explores how inclusive solidarity, a vital stimulus for the associational power of trade unions, can be strengthened in times of individualization. Based on the theory of sociological phenomenology, five qualitative interviews with graduates of the trade union school in Vienna are analyzed in terms of key factors for solidarity and the role of suitable social spaces. The main results are: Solidarity can be learned in a process of primary and secondary socialization. Solidarity requires social spaces where exchange and encounter can take place. The trade union school is one example of such social spaces, and contributes significantly to promoting solidarity. Even in times of individualization and digitalization, solidarity can be strengthened. It is necessary to expand ideas regarding factors, spaces and support networks contributing to it

Natural Antioxidants for the Prevention of Atherosclerosis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90387/1/j.1875-9114.1995.tb02875.x.pd

Antioxidants inhibit low density lipoprotein oxidation less at lysosomal pH: a possible explanation as to why the clinical trials of antioxidants might have failed

Oxidised low density lipoprotein (LDL) was considered to be important in the pathogenesis of atherosclerosis, but the large clinical trials of antioxidants, including the first one using probucol (the PQRST Trial), failed to show benefit and have cast doubt on the importance of oxidised LDL. We have shown previously that LDL oxidation can be catalysed by iron in the lysosomes of macrophages. The aim of this study was therefore to investigate the effectiveness of antioxidants in preventing LDL oxidation at lysosomal pH and also establish the possible mechanism of oxidation. Probucol did not effectively inhibit the oxidation of LDL at lysosomal pH, as measured by conjugated dienes or oxidised cholesteryl esters or tryptophan residues in isolated LDL or by ceroid formation in the lysosomes of macrophage-like cells, in marked contrast to its highly effective inhibition of LDL oxidation at pH 7.4. LDL oxidation at lysosomal pH was inhibited very effectively for long periods by N,N'-diphenyl-1,4-phenylenediamine, which is more hydrophobic than probucol and has been shown by others to inhibit atherosclerosis in rabbits, and by cysteamine, which is a hydrophilic antioxidant that accumulates in lysosomes. Iron-induced LDL oxidation might be due to the formation of the superoxide radical, which protonates at lysosomal pH to form the much more reactive, hydrophobic hydroperoxyl radical, which can enter LDL and reach its core. Probucol resides mainly in the surface monolayer of LDL and would not effectively scavenge hydroperoxyl radicals in the core of LDL. This might explain why probucol failed to protect against atherosclerosis in various clinical trials. The oxidised LDL hypothesis of atherosclerosis now needs to be re-evaluated using different and more effective antioxidants that protect against the lysosomal oxidation of LDL

Hole-transfer induced energy transfer in perylene diimide dyads with a donor–spacer–acceptor motif

We investigate the photoinduced dynamics of perylene diimide dyads based on a donor–spacer–acceptor motif with polyyne spacers of varying length by pump–probe spectroscopy, time resolved fluorescence, chemical variation and quantum chemistry. While the dyads with pyridine based polyyne spacers undergo energy transfer with near-unity quantum efficiency, in the dyads with phenyl based polyyne spacers the energy transfer efficiency drops below 50%. This suggests the presence of a competing electron transfer process from the spacer to the energy donor as the excitation sink. Transient absorption spectra, however, reveal that the spacer actually mediates the energy transfer dynamics. The ground state bleach features of the polyyne spacers appear due to the electron transfer decay with the same time constant present in the rise of the ground state bleach and stimulated emission of the perylene energy acceptor. Although the electron transfer process initially quenches the fluorescence of the donor it does not inhibit energy transfer to the perylene energy acceptor. The transient signatures reveal that electron and energy transfer processes are sequential and indicate that the donor–spacer electron transfer state itself is responsible for the energy transfer. Through the introduction of a Dexter blocker unit into the spacer we can clearly exclude any through bond Dexter-type energy transfer. Ab initio calculations on the donor–spacer and the donor–spacer–acceptor systems reveal the existence of a bright charge transfer state that is close in energy to the locally excited state of the acceptor. Multipole–multipole interactions between the bright charge transfer state and the acceptor state enable the energy transfer. We term this mechanism coupled hole-transfer FRET. These dyads represent a first example that shows how electron transfer can be connected to energy transfer for use in novel photovoltaic and optoelectronic devices

Structural identification of oxidized acyl-phosphatidylcholines that induce platelet activation

Oxidation of low-density lipoprotein (LDL) generates proinflammatory and prothrombotic mediators that may play a crucial role in cardiovascular and inflammatory diseases. In order to study platelet-activating components of oxidized LDL 1-stearoyl-2-arachidonoyl-sn-glycero-3- phosphocholine, a representative of the major phospholipid species in LDL, the 1-acyl-phosphatidylcholines (PC), was oxidized by CuCl2 and H2O2. After separation by high-performance liquid chromatography, three compounds were detected which induced platelet shape change at low micromolar concentrations. Platelet activation by these compounds was distinct from the pathways stimulated by platelet-activating factor, lysophosphatidic acid, lyso-PC and thromboxane A(2), as evidenced by the use of specific receptor antagonists. Further analyses of the oxidized phospholipids by electrospray ionization mass spectrometry structurally identified them as 1-stearoyl-2-azelaoyl-sn-glycero-3-phosphocholine (m/z 694; SAzPC), 1-stearoyl-2-glutaroyl-snglycero-3- phosphocholine (m/z 638; SGPC), and 1-stearoyl-2-( 5-oxovaleroyl)-sn-glycero-3-phosphocholine (m/z 622; SOVPC). These observations demonstrate that novel 1-acyl-PC which had previously been found to stimulate interaction of monocytes with endothelial cells also induce platelet activation, a central step in acute thrombogenic and atherogenic processes. Copyright (C) 2005 S. Karger AG, Basel

Oxidation of Low-Density Lipoprotein by Iron at Lysosomal pH: Implications for Atherosclerosis

Low density lipoprotein (LDL) has recently been shown to be oxidised by iron within the lysosomes of macrophages and this is a novel potential mechanism for LDL oxidation in atherosclerosis. Our aim was to characterise the chemical and physical changes induced in LDL by iron at lysosomal pH and to investigate the effects of iron chelators and α-tocopherol on this process. LDL was oxidised by iron at pH 4.5 and 37°C and its oxidation monitored by spectrophotometry and HPLC. LDL was oxidised effectively by FeSO4 (5-50 µM) and became highly aggregated at pH 4.5, but not at pH 7.4. Cholesteryl esters decreased and after a pronounced lag 7-ketocholesterol increased greatly. Total hydroperoxides (measured by tri-iodide assay) increased up to 24 h and then decreased only slowly. The lipid composition after 12 h at pH 4.5 and 37°C was similar to that of LDL oxidised by copper at pH 7.4 and 4°C, i.e. rich in hydroperoxides but low in oxysterols. Previously oxidised LDL aggregated rapidly and spontaneously at pH 4.5, but not at pH 7.4. Ferrous was much more effective than ferric iron at oxidising LDL when added after the oxidation was already underway. The iron chelators diethylenetriaminepentaacetic acid and, to a lesser extent, desferrioxamine inhibited LDL oxidation when added during its initial stages, but were unable to prevent LDL aggregating after it had been partially oxidised. Surprisingly, desferrioxamine increased the rate of LDL modification when added late in the oxidation process. α-Tocopherol enrichment of LDL initially increased the oxidation of LDL, but inhibited it later. The presence of oxidised and highly aggregated lipid within lysosomes has the potential to perturb the function of these organelles and to promote atherosclerosis