| 1. |
- 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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| 2. |
- Becattini, Barbara, et al.
(författare)
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PI3K gamma promotes obesity-associated hepatocellular carcinoma by regulating metabolism and inflammation
- 2021
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Ingår i: Jhep Reports. - : Elsevier BV. - 2589-5559. ; 3:6
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Phosphatidylinositides-3 kinases (PI3Ks) are promising drug targets for cancer therapy, but blockage of PI3K-AKT signalling causes hyperglycaemia, hyperinsulinaemia, and liver damage in patients, and hepatocellular carcinoma (HCC) in mice. There are 4 PI3K alpha: PI3K beta, PI3K delta, PI3K gamma, and PI3K gamma. The role of PI3K gamma in HCC is unknown. Methods: We performed histopathological, metabolic, and molecular phenotyping of mice with genetic ablation of PI3K gamma using models where HCC was initiated by the carcinogen diethylnitrosamine (DEN) and promoted by dietary or genetic obesity (ob/ob). The role of PI3K gamma in leucocytes was investigated in mice lacking PI3K gamma in haematopoietic and endothelial cells. Results: Loss of PI3K gamma had no effects on the development of DEN-induced HCC in lean mice. However, in mice injected with DEN and placed on an obesogenic diet, PI3K gamma ablation reduced tumour growth, which was associated with reduced insulinaemia, steatosis, and expression of inflammatory cytokines. ob/ob mice lacking PI3K gamma, and mice with diet-induced obesity lacking PI3K gamma in leucocytes and endothelial cells did not display improved insulin sensitivity, steatosis, metabolic inflammation, or reduced tumour growth. However, these mice showed a reduced number of tumours, reduced liver infiltration by neutrophils, and reduced hepatocyte proliferation acutely induced by DEN. Conclusions: Loss of PI3K gamma reduces tumour development in obesity-promoted HCC through multiple cell types and mechanisms that include improved insulinaemia, steatosis, and metabolic inflammation as well as the regulation of acute neutrophil infiltration and compensatory hepatocyte proliferation. PI3K gamma-selective inhibition may represent a novel therapeutic approach to reduce HCC initiation and slow HCC progression. Lay summary: Class-1 phosphatidylinositides-3 kinases (PI3K gamma) are critical targets in cancer therapy, but complete inhibition of all isoforms causes liver damage, hyperglycaemia, and insulinaemia. Here we show that selective ablation of the PI3K gamma isoform dampens tumour initiation and growth in a mouse model of carcinogen-initiated and obesity-promoted hepatocellular carcinoma (HCC). The effect of PI3K gamma ablation on reduced tumour growth was explained by reduced tumour cell proliferation, which was associated with reduced insulin levels, liver lipids, and reduced expression of tumour-promoting cytokines. PI3K gamma ablation in leucocytes of obese mice had no effects on tumour size. However, it reduced tumour number in association with reduced carcinogen-induced neutrophil infiltration and hepatocyte proliferation in livers of obese mice. Inhibition of PI3K gamma may thus reduce HCC initiation and growth in obese subjects by a mechanism involving reduced metabolic stress and insulinaemia and reduced carcinogen-induced neutrophil infiltration to the fatty liver. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL).
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| 3. |
- Becattini, Barbara, et al.
(författare)
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PI3Kγ within a Nonhematopoietic Cell Type Negatively Regulates Diet-Induced Thermogenesis and Promotes Obesity and Insulin Resistance.
- 2011
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Ingår i: Proceedings of the National Academy of Science of the United States of America. - 0027-8424 .- 1091-6490. ; 108:42
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is associated with a chronic low-grade inflammation, and specific antiinflammatory interventions may be beneficial for the treatment of type 2 diabetes and other obesity-related diseases. The lipid kinase PI3Kγ is a central proinflammatory signal transducer that plays a major role in leukocyte chemotaxis, mast cell degranulation, and endothelial cell activation. It was also reported that PI3Kγ activity within hematopoietic cells plays an important role in obesity-induced inflammation and insulin resistance. Here, we show that protection from insulin resistance, metabolic inflammation, and fatty liver in mice lacking functional PI3Kγ is largely consequent to their leaner phenotype. We also show that this phenotype is largely based on decreased fat gain, despite normal caloric intake, consequent to increased energy expenditure. Furthermore, our data show that PI3Kγ action on diet-induced obesity depends on PI3Kγ activity within a nonhematopoietic compartment, where it promotes energetic efficiency for fat mass gain. We also show that metabolic modulation by PI3Kγ depends on its lipid kinase activity and might involve kinase-independent signaling. Thus, PI3Kγ is an unexpected but promising drug target for the treatment of obesity and its complications.
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| 4. |
- Bousquenaud, M., et al.
(författare)
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Obesity promotes the expansion of metastasis-initiating cells in breast cancer
- 2018
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Ingår i: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-542X. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Background: Obesity is a strong predictor of poor prognosis in breast cancer, especially in postmenopausal women. In particular, tumors in obese patients tend to seed more distant metastases, although the biology behind this observation remains poorly understood. Methods: To elucidate the effects of the obese microenvironment on metastatic spread, we ovariectomized C57BL/6 J female mice and fed them either a regular diet (RD) or a high-fat diet (HFD) to generate a postmenopausal diet-induced obesity model. We then studied tumor progression to metastasis of Py230 and EO771 grafts. We analyzed and phenotyped the RD and HFD tumors and the surrounding adipose tissue by flow cytometry, qPCR, immunohistochemistry (IHC) and western blot. The influence of the microenvironment on tumor cells was assessed by performing cross-transplantation of RD and HFD tumor cells into other RD and HFD mice. The results were analyzed using the unpaired Student t test when comparing two variables, otherwise we used one-way or two-way analysis of variance. The relationship between two variables was calculated using correlation coefficients. Results: Our results show that tumors in obese mice grow faster, are also less vascularized, more hypoxic, of higher grade and enriched in CD11b(+)Ly6G(+) neutrophils. Collectively, this favors induction of the epithelial-to-mesenchymal transition and progression to claudin-low breast cancer, a subtype of triple-negative breast cancer that is enriched in cancer stem cells. Interestingly, transplanting HFD-derived tumor cells in RD mice transfers enhanced tumor growth and lung metastasis formation. Conclusions: These data indicate that a pro-metastatic effect of obesity is acquired by the tumor cells in the primary tumor independently of the microenvironment of the secondary site.
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| 5. |
- Breasson, Ludovic, et al.
(författare)
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PI3K gamma ablation does not promote diabetes in db/db mice, but improves insulin sensitivity and reduces pancreatic beta-cell apoptosis
- 2018
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Ingår i: Faseb Journal. - 0892-6638. ; 32:1
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Tidskriftsartikel (refereegranskat)abstract
- PI3K gamma has emerged as a promising target for the treatment of obesity and insulin resistance; however, previous studies have indicated that PI3K gamma activity in pancreatic beta cells is required for normal insulin secretion in response to glucose. Hence, a possible deterioration of insulin secretion capacity in patients who are predisposed to the failure of pancreatic beta-cell function is a major concern for the pharmacologic inhibition of PI3K gamma. To address this issue, we investigated the effects of PI3K gamma ablation in db/db diabetic mice, a genetic model of obesity-driven beta-cell failure and diabetes. Mice that lacked PI3K gamma were backcrossed into db/+ mice C57BL/KS (>10 generations) to obtain db/db-PI3K gamma(-/-) mice. db/db-PI3K gamma(-/-) mice and control db/db mice were phenotyped for glucose homeostasis, insulin sensitivity, insulin secretion, steatosis, metabolic inflammation, pancreatic islet morphometry, islet cellular composition, and inflammation. Pancreatic beta-cell apoptosis and proliferation were also evaluated. db/db-PI3K gamma(-/-) mice and control db/db mice developed similar body weight, steatosis, glycemia, and insulin levels after a glucose load; however, db/db-PI3K gamma(-/-) mice displayed improved insulin tolerance, higher levels of fasting seruminsulin, and lower pancreatic insulin content. In db/db-PI3K gamma(-/-) mice, the number of adipose tissue macrophages was similar to control, but displayed reduced adipose tissue neutrophils and M2-polarized adipose tissue gene expression. Finally, db/db-PI3K gamma(-/-) mice have more pancreatic beta cells and larger islets than db/db mice, despite displaying similar islet inflammation. This phenotype could be explained by reduced beta-cell apoptosis in db/db-PI3K gamma(-/-) mice compared with control db/db mice. Our results are consistent with the concept that the beneficial action of PI3K gamma ablation in obesity-driven glucose intolerance is largely a result of its leptin-dependent effects on adiposity and, to a lesser extent, the promotion of adipose tissue neutrophil recruitment and M1 polarization of gene expression. Of importance, our data challenge the concept that PI3K gamma is required for insulin secretion in response to glucose in vivo, and indicate that PI3K gamma ablation protects db/db mice from beta-cell apoptosis and improves fasting insulin levels. We conclude that PI3K gamma inhibition in obese patients who are predisposed to beta-cell failure is not expected to produce adverse effects on insulin secretion.
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| 6. |
- 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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| 7. |
- Caddeo, Andrea, et al.
(författare)
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MBOAT7 is anchored to endomembranes by six transmembrane domains.
- 2019
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Ingår i: Journal of structural biology. - : Elsevier BV. - 1095-8657 .- 1047-8477. ; 206:3, s. 349-360
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Tidskriftsartikel (refereegranskat)abstract
- Membrane bound O-acyltransferase domain- containing 7 (MBOAT7, also known as LPIAT1) is a protein involved in the acyl chain remodeling of phospholipids via the Lands' cycle. The MBOAT7 is a susceptibility risk genetic locus for non-alcoholic fatty liver disease (NAFLD) and mental retardation. Although it has been shown that MBOAT7 is associated to membranes, the MBOAT7 topology remains unknown. To solve the topological organization of MBOAT7, we performed: A) solubilization of the total membrane fraction of cells overexpressing the recombinant MBOAT7-V5, which revealed MBOAT7 is an integral protein strongly attached to endomembranes; B) in silico analysis by using 22 computational methods, which predicted the number and localization of transmembrane domains of MBOAT7 with a range between 5 and 12; C) in vitro analysis of living cells transfected with GFP-tagged MBOAT7 full length and truncated forms, using a combination of Western Blotting, co-immunofluorescence and Fluorescence Protease Protection (FPP) assay; D) in vitro analysis of living cells transfected with FLAG-tagged MBOAT7 full length forms, using a combination of Western Blotting, selective membrane permeabilization followed by indirect immunofluorescence. All together, these data revealed that MBOAT7 is a multispanning transmembrane protein with six transmembrane domains. Based on our model, the predicted catalytic dyad of the protein, composed of the conserved asparagine in position 321 (Asn-321) and the preserved histidine in position 356 (His-356), has a lumenal localization. These data are compatible with the role of MBOAT7 in remodeling the acyl chain composition of endomembranes.
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| 8. |
- Chang, Lufen, et al.
(författare)
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The E3 ubiquitin ligase itch couples JNK activation to TNFα-induced cell death by inducing c-FLIP L turnover
- 2006
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Ingår i: Cell. - 0092-8674 .- 1097-4172. ; 124:3, s. 601-613
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Tidskriftsartikel (refereegranskat)abstract
- The proinflammatory cytokine tumor necrosis factor (TNF) α signals both cell survival and death. The biological outcome of TNFα treatment is determined by the balance between NF-κB and Jun kinase (JNK) signaling; NF-κB promotes survival, whereas JNK enhances cell death. Critically, identity of a JNK substrate that promotes TNFα-induced apoptosis has been outstanding. Here we show that TNFα-mediated JNK activation accelerates turnover of the NF-κB-induced antiapoptotic protein c-FLIP, an inhibitor of caspase-8. This is not due to direct c-FLIP phosphorylation but depends on JNK-mediated phosphorylation and activation of the E3 ubiquitin ligase Itch, which specifically ubiquitinates c-FLIP and induces its proteasomal degradation. JNK1 or Itch deficiency or treatment with a JNK inhibitor renders mice resistant in three distinct models of TNFα-induced acute liver failure, and cells from these mice do not display inducible c-FLIPL ubiquitination and degradation. Thus, JNK antagonizes NF-κB during TNFα signaling by promoting the proteasomal elimination of c-FLIPL.
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| 9. |
- Cheon, Hwanju, et al.
(författare)
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Role of JNK activation in pancreatic β-cell death by streptozotocin
- 2010
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Ingår i: Molecular and Cellular Endocrinology. - 0303-7207. ; 321:2, s. 131-137
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Tidskriftsartikel (refereegranskat)abstract
- c-Jun N-terminal kinase (JNK) is activated by cellular stress and plays critical roles in diverse types of cell death. However, role of JNK in β-cell injury is obscure. We investigated the role for JNK in streptozotocin (STZ)-induced β-cell death. STZ induced JNK activation in insulinoma or islet cells. JNK inhibitors attenuated insulinoma or islet cell death by STZ. STZ-induced JNK activation was decreased by PARP inhibitors, suggesting that JNK activation is downstream of PARP-1. Phosphatase inhibitors induced activation of JNK and abrogated the suppression of STZ-induced JNK activation by PARP inhibitors, suggesting that the inhibition of phosphatases is involved in the activation of JNK by STZ. STZ induced production of reactive oxygen species (ROS) as potential inhibitors of phosphatases, which was suppressed by PARP inhibitors. PARP-1 siRNA attenuated insulinoma cell death and JNK activation after STZ treatment, which was reversed by MKP (MAP kinase phosphatase)-1 siRNA. These results suggest that JNK is activated by STZ downstream of PARP-1 through inactivation of phosphatases such as MKP, which plays important roles in STZ-induced β-cell death.
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| 10. |
- Dahlke, Eileen, et al.
(författare)
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Tubular IKKβ Deletion Alleviates Acute Ischemic Kidney Injury and Facilitates Tissue Regeneration.
- 2022
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Ingår i: International journal of molecular sciences. - : MDPI AG. - 1422-0067. ; 23:17
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Tidskriftsartikel (refereegranskat)abstract
- Acute kidney injury (AKI) is a common renal injury leading to relevant morbidity and mortality worldwide. Most of the clinical cases of AKI are caused by ischemia reperfusion (I/R) injury with renal ischemia injury followed by reperfusion injury and activation of the innate immune response converging to NF-ĸB pathway induction. Despite the clear role of NF-ĸB in inflammation, it has recently been acknowledged that NF-ĸB may impact other cell functions. To identify NF-ĸB function with respect to metabolism, vascular function and oxidative stress after I/R injury and to decipher in detail the underlying mechanism, we generated a transgenic mouse model with targeted deletion of IKKβ along the tubule and applied I/R injury followed by its analysis after 2 and 14 days after I/R injury. Tubular IKKβ deletion ameliorated renal function and reduced tissue damage. RNAseq data together with immunohistochemical, biochemical and morphometric analysis demonstrated an ameliorated vascular organization and mRNA expression profile for increased angiogenesis in mice with tubular IKKβ deletion at 2 days after I/R injury. RNAseq and protein analysis indicate an ameliorated metabolism, oxidative species handling and timely-adapted cell proliferation and apoptosis as well as reduced fibrosis in mice with tubular IKKβ deletion at 14 days after I/R injury. In conclusion, mice with tubular IKKβ deletion upon I/R injury display improved renal function and reduced tissue damage and fibrosis in association with improved vascularization, metabolism, reactive species disposal and fine-tuned cell proliferation.
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