Alterations of intestinal lipoprotein metabolism in diabetes mellitus and metabolic syndrome

Diabetes and metabolic syndrome are associated with abnormal postprandial lipoprotein metabolism, with a significant delay in the clearance of many lipid parameters, including triglycerides and chylomicrons. Abnormal concentrations of plasma lipids can result from changes in the production, conversion, or catabolism of lipoprotein particles. Whereas the liver is involved in controlling serum lipid levels through synthesis of liver derived triglyceride-rich lipoproteins and low-density lipoprotein metabolism, the intestine also has a major role in lipoprotein production. Postprandial lipemia results from increases in apoB-48 availability, lipogenesis, and the synthesis and absorption of cholesterol in the enterocytes. Increased intestinal lipoprotein production prolongs postprandial lipemia in patients with diabetes and MetS, and may contribute directly to atherogenesis in these patients

The MEGaN project I. Missing formation of massive nuclear clusters and tidal disruption events by star clusters - massive black hole interactions

We investigated the evolution of a massive galactic nucleus hosting a super-massive black hole (SMBH) with mass $M_\mathrm{SMBH}=10^8 \mathrm{M}_\odot$ surrounded by a population of 42 heavy star clusters (GCs). Using direct $N$-body modelling, we show here that the assembly of an NSC through GCs orbital decay and merger is efficiently inhibited by the tidal forces exerted from the SMBH. The GCs mass loss induced by tidal forces causes a significant modification of their mass function, leading to a population of low-mass ($<10^4$) clusters. Nonetheless, the GCs debris accumulated around the SMBH give rise to well-defined kinematical and morphological properties, leading to the formation of a disk-like structure. Interestingly, the disk is similar to the one observed in the M31 galaxy nucleus, which has properties similar to our numerical model. The simulation produced a huge amount of data, which we used to investigate whether the GC debris deposited around the SMBH can enhance the rate of tidal disruption events (TDEs) in our galaxy inner density distribution. Our results suggest that the GCs disruption shapes the SMBH neighbourhoods leading to a TDE rate of $\sim 2 \times 10^{-4}$yr$^{-1}$, a value slightly larger than what expected in previous theoretical modelling of galaxies with similar density profiles and central SMBHs. The simulation presented here is the first of its kind, representing a massive galactic nucleus and its star cluster population on scales $\sim 100$ pc.Comment: 15 pages, 10 figures, 4 tables. Accepted for publication in MNRA

The Dense Stellar Systems Around Galactic Massive Black Holes

The central regions of galaxies show the presence of massive black holes and/or dense stellar systems. The question about their modes of formation is still under debate. A likely explanation of the formation of the central dense stellar systems in both spiral and elliptical galaxies is based on the orbital decay of massive globular clusters in the central region of galaxies due to kinetic energy dissipation by dynamical friction. Their merging leads to the formation of a nuclear star cluster, like that of the Milky Way, where a massive black hole (Sgr A*) is also present. Actually, high precision N-body simulations (Antonini, Capuzzo-Dolcetta et al. 2012, ApJ, 750, 111) show a good fit to the observational characteristics of the Milky Way nuclear cluster, giving further reliability to the cited `migratory' model for the formation of compact systems in the inner galaxy regions.Comment: Talk given at the Workshop on: Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation, November 6-8, 2012, Max-Planck-Insitut fuer Radioastronomie (MPIfR), Bonn, Germany. 6 pages, 4 figures, to be published in the Conference Proceedings, Proceedings of Science publishe