Lipotoxicity and the development of heart failure: moving from mouse to man.

Intracardiac lipid accumulation can cause heart failure. A study in Journal of Clinical Investigation (Son et al., 2010) found that cardiac-specific PPARγ overexpression caused heart failure with intracardiac triglyceride accumulation. Overexpressing PPARγ on a PPARα−/− background improved cardiac function, suggesting that specific lipid metabolites and lipid packaging determine cardiac lipotoxicity

Omega-3 fatty acids for the prevention of myocardial infarction and arrhythmias.

In 1978, a report from the Chief Medical Officer in Greenland documented that coronary heart disease (CHD) was responsible for only 3.5% of all deaths in Greenland Eskimos [1], a strikingly small number compared to the typical figures found in the Western countries. Seeking potential explanations for such low frequency of cardiac events, investigators at the University of Aalborg, in Denmark, noted that the serum lipids of Eskimos was enriched in omega-3 fatty acids, that is, polyunsaturated fatty acids with the first double bond found in position 3 when the molecule is scanned from its methyl (-CH3) end (n-3 PUFA) [2,3]. They then identified fish oil as the primary source of n-3 PUFA in Eskimos’ diet [4], in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), whose abundance in plasma and platelets has antihemostatic, hence antithrombotic effects [5]. These molecules consequently became the target of a wealth of studies aimed at explaining their preventive effects against cardiovascular diseases

Giant cosmic ray halos around M31 and the Milky Way

International audienceRecently, a diffuse γ-rays emission in the energy range 1-100 GeV has been detected around M31, that extends up to 120-200 kpc from its center. Such extended emission is difficult to be explained in the typical scenario of cosmic rays produced in the galactic disk or in the galactic center (GC) and diffusing in the galactic halo. We show that a cosmic ray origin, either hadronic or leptonic, of the emission is viable if non-standard cosmic ray transport scenarios are considered, or if particles are accelerated directly in the galactic halo (in situ acceleration). The cosmic ray halo can be powered by the accretion of intergalactic gas or by the activity of galaxy’s central black hole. If giant cosmic ray halos are common around galaxies, the interactions of cosmic ray protons and nuclei with the circumgalactic gas surrounding Milky Way could explain the isotropic diffuse flux of neutrinos observed by Icecube

Giant cosmic ray halos around M31 and the Milky Way

International audienceRecently, a diffuse γ-rays emission in the energy range 1-100 GeV has been detected around M31, that extends up to 120-200 kpc from its center. Such extended emission is difficult to be explained in the typical scenario of cosmic rays produced in the galactic disk or in the galactic center (GC) and diffusing in the galactic halo. We show that a cosmic ray origin, either hadronic or leptonic, of the emission is viable if non-standard cosmic ray transport scenarios are considered, or if particles are accelerated directly in the galactic halo (in situ acceleration). The cosmic ray halo can be powered by the accretion of intergalactic gas or by the activity of galaxy’s central black hole. If giant cosmic ray halos are common around galaxies, the interactions of cosmic ray protons and nuclei with the circumgalactic gas surrounding Milky Way could explain the isotropic diffuse flux of neutrinos observed by Icecube

Local fading accelerator and the origin of TeV cosmic ray electrons

International audienceThe cosmic ray electron spectrum exhibits a break at a particle energy of ∼1  TeV and extends without any attenuation up to ∼20  TeV. Synchrotron and inverse Compton energy losses strongly constrain the time of emission of ∼20  TeV electrons to ≈2×104  yr and the distance of the potential source(s) to ≈100–500  pc, depending on the cosmic ray diffusion coefficient. This suggests that maybe one nearby discrete source may explain the observed spectrum of high energy electrons. Given the strong energy dependence (∝1/E) of the cooling time of TeV electrons, the spectral shape of the electron spectrum above the ∼1  TeV break strongly depends on the history of injection of these electrons from the source. In this paper we show that a local, continuous (on timescales of ∼105  yr) but fading electron accelerator, with a characteristic decay time of ∼104  yr, can naturally account for the entire spectrum of cosmic ray electrons in the TeV domain. Although the standard “nearby pulsar” scenario naturally meets this time condition, it is (almost) excluded by recent measurements of the positron fraction, which above ∼100  GeV saturates at a level well below 0.5 and drops above ∼400–500  GeV. The second potential source population, the supernova remnants, accelerate mostly electrons, rather than positrons. However, they hardly can provide an effective production of multi-TeV electrons via the standard diffusive shock acceleration scenario for ∼105  yr. A third possibility are stellar wind shocks, which however are likely to be continuous with nearly constant luminosity on timescales ≫10  kyr and probably cannot match the time requirement of our potential source. Therefore, we face a real challenge in the identification of the origin of the source of multi-TeV electrons. Thus, the link of this source with known particle accelerators would require a dramatic revision of the standard paradigms of acceleration and escape in such objects

Giant Cosmic-Ray Halos around M31 and the Milky Way

International audienc