| 1. |
- Mancina, Rosellina Margherita, et al.
(author)
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PSD3 downregulation confers protection against fatty liver disease.
- 2022
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In: Nature metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 4:1, s. 60-75
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Journal article (peer-reviewed)abstract
- Fatty liver disease (FLD) is a growing health issue with burdening unmet clinical needs. FLD has a genetic component but, despite the common variants already identified, there is still a missing heritability component. Using a candidate gene approach, we identify a locus (rs71519934) at the Pleckstrin and Sec7 domain-containing 3 (PSD3) gene resulting in a leucine to threonine substitution at position 186 of the protein (L186T) that reduces susceptibility to the entire spectrum of FLD in individuals at risk. PSD3 downregulation by short interfering RNA reduces intracellular lipid content in primary human hepatocytes cultured in two and three dimensions, and in human and rodent hepatoma cells. Consistent with this, Psd3 downregulation by antisense oligonucleotides in vivo protects against FLD in mice fed a non-alcoholic steatohepatitis-inducing diet. Thus, translating these results to humans, PSD3 downregulation might be a future therapeutic option for treating FLD.
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| 2. |
- Marini, Ester, et al.
(author)
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Discovery of Stars Surrounded by Iron Dust in the Large Magellanic Cloud
- 2019
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In: Astrophysical Journal Letters. - : IOP PUBLISHING LTD. - 2041-8205 .- 2041-8213. ; 871:1
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Journal article (peer-reviewed)abstract
- We consider a small sample of oxygen-rich, asymptotic giant branch stars in the Large Magellanic Cloud, observed by the Spitzer Space Telescope, exhibiting a peculiar spectral energy distribution, which can hardly be explained by the common assumption that dust around Asymptotic Giant Branch stars is primarily composed of silicate grains. We suggest that this uncommon class of objects is the progeny of a metal-poor generation of stars, with metallicity Z similar to 1-2 x 10(-3), formed similar to 100 Myr ago. The main dust component in the circumstellar envelope is solid iron. In these stars the poor formation of silicates is set by the strong nucleosynthesis experienced at the base of the envelope, which provokes a scarcity of magnesium atoms and water molecules, required for the silicate formation. The importance of the present results to interpret the data from the incoming James Webb Space Telescope is also discussed.
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| 3. |
- Ventura, P., et al.
(author)
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Gas and dust from extremely metal-poor AGB stars
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 655
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Journal article (peer-reviewed)abstract
- Context. The study of stars that evolve through the asymptotic giant branch (AGB) proves crucial in several astrophysical contexts because these objects provide important feedback to the host system in terms of the gas that is poured into the interstellar medium after being exposed to contamination from nucleosynthesis processes, and in terms of the dust that forms in their wind. Most of the studies conducted so far have been focused on AGB stars with solar and sub-solar chemical composition, whereas the extremely metal-poor domain has been poorly explored. Aims. We study the evolution of extremely metal-poor AGB stars with metallicities down to [Fe/H] = -5 to understand the main evolutionary properties and the efficiency of the processes able to alter their surface chemical composition, and to determine the gas and dust yields. Methods. We calculated two sets of evolutionary sequences of stars in the 1-7.5M(circle dot) mass range that evolved from the pre-main sequence to the end of the AGB phase. To explore the extremely metal-poor chemistries, we adopted the metallicities Z= 3 x 10(-5) and Z= 3 x 10(-7), which correspond to [Fe/H]= -3 and [Fe/H]= -5, respectively. The results from stellar evolution modelling were used to calculate the yields of the individual chemical species. We also modelled dust formation in the wind to determine the dust produced by these objects. Results. The evolution of AGB stars in the extremely metal-poor domain we explored proves highly sensitive to the initial mass of the star. M <= 2 M-circle dot stars experience several third-dredge-up events, which favour the gradual surface enrichment of C-12 and the formation of significant quantities of carbonaceous dust, similar to 0.01 M-circle dot. The C-13 and nitrogen yields are found to be significantly smaller than in previous explorations of low-mass metal-poor AGB stars because the proton ingestion episodes experienced during the initial AGB phases are weaker. M >= 5 M-circle dot stars experience hot bottom burning, and their surface chemistry reflects the equilibria of a very advanced proton-capture nucleosynthesis; little dust production takes place in their wind. Intermediate-mass stars experience both third dredge-up and hot bottom burning: they prove efficient producers of nitrogen, which is formed by proton captures on C-12 nuclei of primary origin dredged up from the internal regions.
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| 4. |
- Ventura, Paolo, et al.
(author)
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Nucleosynthesis, Mixing Processes, and Gas Pollution from AGB Stars
- 2022
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In: Universe. - : MDPI AG. - 2218-1997. ; 8:1, s. 45-
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Journal article (peer-reviewed)abstract
- We discuss the evolution of stars through the asymptotic giant branch, focusing on the physical mechanisms potentially able to alter the surface chemical composition and on how changes in the chemistry of the external regions affect the physical properties of the star and the duration of this evolutionary phase. We focus on the differences between the evolution of low-mass stars, driven by the growth of the core mass and by the surface carbon enrichment, and that of their higher mass counterparts, which experience hot bottom burning. In the latter sources, the variation of the surface chemical composition reflects the equilibria of the proton capture nucleosynthesis experienced at the base of the convective envelope. The pollution expected from this class of stars is discussed, outlining the role of mass and metallicity on the chemical composition of the ejecta. To this aim, we considered evolutionary models of 0.7-8 M & ODOT; stars in a wide range of metallicities, extending from the ultra-metal-poor domain to super-solar chemistries.
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