Cytokines d’origine adipocytaire, obésité et développement du diabète

La régulation et le maintien d’un état métabolique normal dépend d’un système d’homéostasie complexe incluant de nombreux organes et tissus. Des défauts acquis dans ce système associés à des facteurs environnementaux mènent au développement d’anomalies métaboliques comme le syndrome X, qui est devenu un syndrome fréquent dans les pays industrialisés. Ce syndrome se caractérise par l’association d’anomalies incluant une résistance à l’insuline, un hyper-insulinisme, une intolérance au glucose ou un diabète de type 2, une hypertension artérielle et des troubles du métabolisme lipidique et de la coagulation. Sa gravité résulte de la fréquence des complications cardiovasculaires associées à ces altérations. La résistance à l’insuline du tissu adipeux (en particulier viscéral) et du muscle, qui se répercute sur le métabolisme hépatique, et les altérations des flux de substrats métaboliques entre ces tissus jouent un rôle majeur dans sa physiopathologie. De nouvelles classes pharmacologiques viennent enrichir l’arsenal thérapeutique et semblent prometteuses pour traiter l’insulinorésistance. À cet égard, le tissu adipeux n’est plus simplement considéré comme un simple tissu de stockage des réserves graisseuses, mais comme un organe jouant un rôle actif dans la régulation métabolique. Le tissu adipeux sécrète, en effet, une grande variété de molécules biologiquement actives agissant pour prévenir l’accumulation délétère de lipides et la modulation de l’insulinorésistance. Cet article a pour objectif de mieux comprendre les mécanismes menant à l’insulinorésistance et au diabète de type 2, selon les plus récentes avancées dans la connaissance du rôle et des interactions d’hormones spécifiquement issues de l’adipocyte, récemment identifiées, et appelées adipocytokines ou adipokines.Normal metabolic balance is maintained by a complex homeostatic system involving multiple tissues and organs. Acquired or inherited defects associated to environmental factors in any part of this system can lead to metabolic disorders such as the syndrome X which is presently a frequent syndrome in industrialized countries. It is characterized by a cluster of risk factors of atherosclerosis including insulin resistance, hyperinsulinemia, impaired glucose tolerance or type 2 diabetes, hypertension, dyslipidemia, and coagulation abnormalities. Its pathophysiology is likely to involve insulin resistance at the level of both skeletal muscle and visceral adipose tissue and altered fluxes of metabolic substrates between these tissues that in turn impair liver metabolism. Therapeutic intervention favours at present diet and exercise prescriptions. In addition, if necessary, specific treatment of the metabolic disorders is required. In the treatment of insulin resistance, new promising drugs are likely to be used in the next future. In this regard, adipose tissue, once thought to function primarily as a passive depot for the storage of excess lipid, is now understood to play a much more active role in metabolic regulation, secreting a variety of metabolic hormones and actively functioning to prevent deleterious lipid accumulation in other tissues and to modulate the insulin resistance. Here, we review new advances in our understanding of mechanisms leading to insulin resistance and type 2 diabetes from the perspective of the role and interactions of recently identified adipocyte-specific chemical messengers, the adipocytokines, such as adiponectin, tumor necrosis factor-alpha, interleukin 6, and resistin

Combined effect of injected interstitials and He implantation, and cavities inside dislocation loops in high purity Fe-Cr alloys

International audienceHigh purity Fe-Cr alloys with Cr content ranging from 3 to 14 wt% were irradiated by self-ions at 500 °C in dual-beam mode up to 157 displacements per atom (dpa), 17 appm He/dpa. Transmission electron microscopy (TEM) on focused ion beam foils revealed the depth distribution of irradiation induced cavities and dislocation loops. A detailed quantitative analysis of cavity microstructure was performed on Fe14%Cr, while Fe(3, 5, 10, 12)%Cr were analysed qualitatively. A homogeneous distribution of small cavities were observed up to the damage peak. From surface to the damage peak, cavity number density increased almost linearly. The cavity microstructure changed drastically at and after the damage peak, where the size increased and number density decreased. Most notably, the microstructure consisted of a striking mixture of heterogeneously nucleated cavities inside dislocation loops and freely nucleated cavities in the matrix. Further, the depth-dependent void swelling increased continuously along the damage depth. This contrasts with most ion irradiation results where suppression of void swelling occurs adjacent to the damage peak due the injected interstitial effect. We hypothesize a plausible mechanism of the observed swelling variation based on a combined effect of the injected interstitials and helium implantation near the damage peak by comparing the results with those in pure iron irradiated under same conditions. This synergistic effect may develop cavity microstructures which do not necessarily reflect microstructures expected due to injected interstitial effect and can be easily wrongly interpreted. The depth dependent dislocation loop microstructure was studied qualitatively in Fe14%Cr sample. Up to the damage peak, a complex dense network of dislocations formed due to the interaction/impingement of the dislocation loops. Individually resolvable loops were only observed after the damage peak, where their association with cavities was noted. Helium also induced heterogeneous cavity nucleation on dislocations constituting a grain boundary and on pre-existing dislocation lines

ZnO Nanowires as a Promotor of High Photo-Induced Efficiency and Voltage Gain for Cathode Battery Recharging

International audienceIn recent years, intensive efforts have been focused on the conversion and storage of solar energy in a single device. In this work, we report the use of ZnO-based electrodes in the form of monolayer or nanowires as a light inducer for battery recharging. Two transition metal complexes of ruthenium(II) and iron(II) are grafted onto the ZnO-based electrode to tune the efficiency of the system. We explore the influence of both the ZnO morphology and nature of the transition metal complex on the light induced voltage and faradaic efficiency toward electrochemical storage. The resulting ZnO-based electrodes have all been found to be electrochemically photoactive and their functionalized ZnO nanowire counterpart has shown the best results. Once the ruthenium complex has been grafted, a high potential gain between dark and illumination conditions of 1.3 V is reached, which is associated with a modest faradaic efficiency of 50%. However, in the presence of the iron complex, a favorable potential gain of 700 mV is obtained and advantageously combined with a faradic efficiency of 100%. These results undoubtedly highlight the remarkable synergy between photoactive ZnO, especially in the form of nanowires, and a redox center allowing it to be applied for a photorechargeable battery device

RuII tris-bipyridine-modified electrode as a sensor for battery electrolyte

International audienceFunctionalization of a carbon electrode through the electrochemical reduction of ruthenium tris-bipyridine diazonium salts prepared in situ allows determination of the nature of the anions often present in commonly used lithium and sodium battery electrolyte (i.e. PF6− and ClO4−) and also the presence of fluoride anions arising from PF6− degradation. Surprisingly, although these “battery” anions are supposed to exhibit poor coordination ability, their interaction with the electrogenerated RuIII complex is sufficiently strong and reversible to selectively discriminate between the anions ClO4− and PF6− through the observed shift in E°. This study examined the impact of any fluoride present and found a linear relationship between the current response and the F− concentration. This has been applied to ageing LP30 battery electrolyte, confirming the low solubility of LiF in battery electrolyte. This overall behavior could help in the analysis of electrolytes from the recycling sector

Photo-Assisted ITO Systems for Li-ion Batteries

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Photo-assisted rechargeable battery using photosensitive cathode material

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Raman spectra analysis of ZrO 2 thermally grown on Zircaloy substrates irradiated with heavy ion: Effects of oxygen isotopic substitution

International audienceRecently, unusual Raman signals were observed in different works conducted on thin zirconia layers grown on zirconium alloys simulating in‐reactor materials after high fluence ion irradiation or for samples cut from fuel rods irradiated in nuclear plants. As such, these spectra clearly do not correspond to any known spectrum of a pure standard zirconia phase. Therefore, the analysis conducted in this paper aims to provide a better understanding of these peculiar Raman features. For that purpose, specific ion‐irradiated samples were analysed. In situ Raman spectroscopy was first used to follow the irradiation process. Then, samples were characterized using different excitation wavelengths. Finally, the effects of oxygen isotopic substitution were examined in details. Results are discussed in terms of disorder and size‐related effects

Scintillating Screens Investigations with Proton Beams at 30 keV and 3 MeV

International audienceLuminescent screens hit by accelerated charged particle beams are commonly used as beam diagnostics to produce a visible emitted light, which can be sensed by a camera. In order to investigate the characteristics of the luminescence response of several scintillators, the beam shape and the observation of the transverse position, experiments were done with different low intensity proton beams produced by two different test benches. This study is motivated by the need to identify scintilla-tor materials for the development of a 4-dimensional emittancemeter which will allow the characterization of the beams, in particular the emittance measurement (size, angular divergence). This paper describes the experimental setups and our investigations of the optical properties of various scintillating materials at two different proton beam energies respectively about 30 keV and 3 MeV. The light produced by these screens is characterized by yield, flux of the emitted light versus the beam intensity, time response, and long life-time and they are compared