| 1. |
- Molinaro, Angela, et al.
(författare)
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Insulin-Driven PI3K-AKT Signaling in the Hepatocyte Is Mediated by Redundant PI3Kα and PI3Kβ Activities and Is Promoted by RAS.
- 2019
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 29:6
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Tidskriftsartikel (refereegranskat)abstract
- Phosphatidylinositol-3-kinase (PI3K) activity is aberrant in tumors, and PI3K inhibitors are investigated as cancer therapeutics. PI3K signaling mediates insulin action in metabolism, but the role of PI3K isoforms in insulin signaling remains unresolved. Defining the role of PI3K isoforms in insulin signaling is necessary for a mechanistic understanding of insulin action and to develop PI3K inhibitors with optimal therapeutic index. We show that insulin-driven PI3K-AKT signaling depends on redundant PI3Kα and PI3Kβ activities, whereas PI3Kδ and PI3Kγ are largely dispensable. We have also found that RAS activity promotes AKT phosphorylation in insulin-stimulated hepatocytes and that promotion of insulin-driven AKT phosphorylation by RAS depends on PI3Kα. These findings reveal the detailed mechanism by which insulin activates AKT, providing an improved mechanistic understanding of insulin signaling. This improved model for insulin signaling predicts that isoform-selective PI3K inhibitors discriminating between PI3Kα and PI3Kβ should bedosed below their hyperglycemic threshold to achieve isoform selectivity.
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| 2. |
- van Leeuwen, F., et al.
(författare)
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Gaia Data Release 1 : Open cluster astrometry: Performance, limitations, and future prospects
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 601
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Tidskriftsartikel (refereegranskat)abstract
- Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.
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| 3. |
- Becattini, Barbara, et al.
(författare)
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Adipocyte PI3K links adipostasis with baseline insulin secretion at fasting through an adipoincretin effect.
- 2024
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Ingår i: Cell reports. - 2211-1247. ; 43:5
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-PI3K signaling controls insulin secretion. Understanding this feedback mechanism is crucial for comprehending how insulin functions. However, the role of adipocyte insulin-PI3K signaling in controlling insulin secretion invivo remains unclear. Using adipocyte-specific PI3Kα knockout mice (PI3KαAdQ) and a panel of isoform-selective PI3K inhibitors, we show that PI3Kα and PI3Kβ activities are functionally redundant in adipocyte insulin signaling. PI3Kβ-selective inhibitors have no effect on adipocyte AKT phosphorylation in control mice but blunt it in adipocytes of PI3KαAdQ mice, demonstrating adipocyte-selective pharmacological PI3K inhibition in the latter. Acute adipocyte-selective PI3K inhibition increases serum free fatty acid (FFA) and potently induces insulin secretion. We name this phenomenon the adipoincretin effect. The adipoincretin effect operates in fasted mice with increasing FFA and decreasing glycemia, indicating that it is not primarily a control system for blood glucose. This feedback control system defines the rates of adipose tissue lipolysis and chiefly controls basal insulin secretion during fasting.
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| 4. |
- Breasson, Ludovic, et al.
(författare)
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PI3Kγ activity in leukocytes promotes adipose tissue inflammation and early-onset insulin resistance during obesity.
- 2017
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Ingår i: Science signaling. - : American Association for the Advancement of Science (AAAS). - 1937-9145 .- 1945-0877. ; 10:488
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Tidskriftsartikel (refereegranskat)abstract
- The phosphoinositide 3-kinase γ (PI3Kγ) plays a major role in leukocyte recruitment during acute inflammation and has been proposed to inhibit classical macrophage activation by driving immunosuppressive gene expression. PI3Kγ plays an important role in diet-induced obesity and insulin resistance. In seeking to determine the underlying molecular mechanisms, we showed that PI3Kγ action in high-fat diet-induced inflammation and insulin resistance depended largely on its role in the control of adiposity, which was due to PI3Kγ activity in a nonhematopoietic cell type. However, PI3Kγ activity in leukocytes was required for efficient neutrophil recruitment to adipose tissue. Neutrophil recruitment was correlated with proinflammatory gene expression in macrophages in adipose tissue, which triggered insulin resistance early during the development of obesity. Our data challenge the concept that PI3Kγ is a general suppressor of classical macrophage activation and indicate that PI3Kγ controls macrophage gene expression by non-cell-autonomous mechanisms, the outcome of which is context-dependent.
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| 5. |
- Marco de La Cruz, Berta, 1990, et al.
(författare)
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Liprin-α proteins are master regulators of human presynapse assembly
- 2024
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Ingår i: NATURE NEUROSCIENCE. - 1097-6256 .- 1546-1726.
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Tidskriftsartikel (refereegranskat)abstract
- The formation of mammalian synapses entails the precise alignment of presynaptic release sites with postsynaptic receptors but how nascent cell-cell contacts translate into assembly of presynaptic specializations remains unclear. Guided by pioneering work in invertebrates, we hypothesized that in mammalian synapses, liprin-alpha proteins directly link trans-synaptic initial contacts to downstream steps. Here we show that, in human neurons lacking all four liprin-alpha isoforms, nascent synaptic contacts are formed but recruitment of active zone components and accumulation of synaptic vesicles is blocked, resulting in 'empty' boutons and loss of synaptic transmission. Interactions with presynaptic cell adhesion molecules of either the LAR-RPTP family or neurexins via CASK are required to localize liprin-alpha to nascent synaptic sites. Liprin-alpha subsequently recruits presynaptic components via a direct interaction with ELKS proteins. Thus, assembly of human presynaptic terminals is governed by a hierarchical sequence of events in which the recruitment of liprin-alpha proteins by presynaptic cell adhesion molecules is a critical initial step. This paper identifies the evolutionarily conserved liprin-alpha protein family as key mediators of presynaptic assembly in human neurons. Their recruitment to sites formed by contacting neurons is the critical initial step that triggers presynaptic differentiation.
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| 6. |
- Molinaro, Angela, et al.
(författare)
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Insulin signaling and glucose metabolism in different hepatoma cell lines deviate from hepatocyte physiology toward a convergent aberrant phenotype
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Hepatoma cell lines are widely used to model the hepatocyte for insulin signaling and fatty liver disease. However, a direct comparison of insulin action in primary hepatocytes and in hepatoma cell lines is needed to validate this model and to better understand liver cancer. Here we have investigated insulin signaling, gluconeogenic gene expression, glucose production, and fatty acid synthase abundance in primary hepatocytes and in HepG2, Hepa 1-6, and McARH7777 hepatoma cell lines. Differences in the electrophoretic profiles of protein extracts from human and mouse primary hepatocytes and the hepatoma cells lines are shown. Compared to primary hepatocytes, hepatoma cells showed high basal phosphorylation of AKT at Thr 308 and constitutively activated RAS-MAPK signaling, which were resistant to the dominant negative Ras mutant H-Ras17N. Hepatoma cell lines also showed defective expression of gluconeogenic enzymes, insulin unresponsive GSK phosphorylation, and marginal glucose production. Hepatoma cells also showed lower protein levels of fatty acid synthase and a largely distinct protein electrophoresis profile from hepatocytes but similar between different hepatoma lines. We conclude that hepatoma cell lines do not accurately model the hepatocyte for insulin action but may be valuable tools to investigate the proteomic changes conferring to hepatocellular carcinoma its peculiar metabolisms.
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| 7. |
- Molinaro, Angela
(författare)
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Investigating the role of Class-1 Phosphoinositide 3 Kinases (PI3Ks) in insulin signaling and obesity
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Obesity and obesity related diseases such as type 2 diabetes, cardiovascular disorders, and different types of cancer are leading causes of mortality and morbidity in modern society. However, the mechanism that links obesity to these diseases remains largely unresolved. Class 1 phosphatidylinositide 3 kinases (PI3Ka; PI3Kb; PI3Kd and PI3Kg) play a major role in several physiological processes such as the immune response, the metabolic insulin action, and tissues homeostasis. This thesis aims at a better understanding of the role of the different PI3K isoforms in obesity and insulin signaling. PI3Kg plays an important role in leukocyte recruitment during inflammation, in the inhibition of classical macrophage activation and in promoting diet-induced obesity and insulin resistance. In PAPER I we have investigated the PI3Kg mechanisms of action and we have found that the activity of PI3Kg in hematopoietic cells is dispensable in hepatic inflammation, liver steatosis, adiposity and macrophage recruitment in adipose tissue. However, PI3Kg activity promotes insulin resistance, the pro-inflammatory M1 macrophage phenotype and neutrophils recruitment in the adipose tissue of obese mice. This observation challenges the concept that PI3Kg activity is a general inhibitor of classical macrophage activation. In PAPER II, we aim to define the role of class-1 PI3K isoforms and RAS in insulin signaling in hepatocytes. Our data lead to a new and improved mechanism for insulin signaling where insulin-driven PI3K-AKT signaling is mediated by the activities of PI3Ka and PI3Kb, with RAS promoting PI3Ka-dependent insulin signaling. We conclude that PI3K inhibitors discriminating between PI3Ka and PI3Kb should be used at doses below their hyperglycemic threshold to preserve isoform specificity and achieve optimal therapeutic index. In PAPER III, we have found that compared to primary hepatocytes, three most commonly used hepatoma cell lines display aberrant insulin signaling, gluconeogenic genes expression, glucose production and different electrophoretic profiles, but similar among the hepatoma cell lines. We conclude that, because the hepatoma cell lines appear to converge to a common aberrant phenotype, these cells can be a valuable tool to study the metabolic aberrations in hepatocellular carcinoma. General conclusion: Altogether this thesis supports the concept that the therapeutic effects of PI3K inhibitors on obesity, insulin resistance and tumor promotion could be largely dissociated from their deleterious effects on glucose homeostasis by using isoform-selective inhibitors discriminating between PI3Ka and PI3Kb.
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| 8. |
- Rodrigues Silva, Vagner Ramon, 1985, et al.
(författare)
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Somatic ablation of IKKβ in liver and leukocytes is not tolerated in obese mice but hepatic IKKβ deletion improves fatty liver and insulin sensitivity.
- 2022
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - 1530-6860. ; 36:9
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Tidskriftsartikel (refereegranskat)abstract
- The kinase IKKβ controls pro-inflammatory gene expression, and its activity in the liver and leukocytes was shown to drive metabolic inflammation and insulin resistance in obesity. However, it was also proposed that liver IKKβ signaling protects obese mice from insulin resistance and endoplasmic reticulum (ER) stress by increasing XBP1s protein stability. Furthermore, mice lacking IKKβ in leukocytes display increased lethality to lipopolysaccharides. This study aims at improving our understanding of the role of IKKβ signaling in obesity. We induced IKKβ deletion in hematopoietic cells and liver of obese mice by Cre-LoxP recombination, using an INF-inducible system, or a liver-specific IKKβ deletion in obese mice by adenovirus delivery of the Cre recombinase. The histopathological, immune, and metabolic phenotype of the mice was characterized. IKKβ deletion in the liver and hematopoietic cells was not tolerated in mice with established obesity exposed to the TLR3 agonist poly(I:C) and exacerbated liver damage and ER-stress despite elevated XBP1s. By contrast, liver-specific ablation of IKKβ in obese mice reduced steatosis and improved insulin sensitivity in association with increased XBP1s protein abundance and reduced expression of de-novo lipogenesis genes. We conclude that IKKβ blockage in liver and leukocytes is not tolerated in obese mice exposed to TLR3 agonists. However, selective hepatic IKKβ ablation improves fatty liver and insulin sensitivity in association with increased XBP1s protein abundance and reduced expression of lipogenic genes.
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