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Ivovic A, Oprescu AI, Koulajian K, Mori Y, Eversley JA, Zhang L, Nino-Fong R, Lewis GF, Donath MY, Karin M, Wheeler MB, Ehses J, Volchuk A, Chan CB, Giacca A. IKKβ inhibition prevents fat-induced beta cell dysfunction in vitro and in vivo in rodents. Diabetologia 2017; 60:2021-2032. [PMID: 28725915 DOI: 10.1007/s00125-017-4345-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/16/2017] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS We have previously shown that oxidative stress plays a causal role in beta cell dysfunction induced by fat. Here, we address whether the proinflammatory kinase inhibitor of (nuclear factor) κB kinase β (IKKβ), which is activated by oxidative stress, is also implicated. METHODS Fat (oleate or olive oil) was infused intravenously in Wistar rats for 48 h with or without the IKKβ inhibitor salicylate. Thereafter, beta cell function was evaluated in vivo using hyperglycaemic clamps or ex vivo in islets isolated from fat-treated rats. We also exposed rat islets to oleate in culture, with or without salicylate and 4(2'-aminoethyl)amino-1,8-dimethylimidazo(1,2-a)quinoxaline; BMS-345541 (BMS, another inhibitor of IKKβ) and evaluated beta cell function in vitro. Furthermore, oleate was infused in mice treated with BMS and in beta cell-specific Ikkb-null mice. RESULTS 48 h infusion of fat impaired beta-cell function in vivo, assessed using the disposition index (DI), in rats (saline: 1.41 ± 0.13; oleate: 0.95 ± 0.11; olive oil [OLO]: 0.87 ± 0.15; p < 0.01 for both fats vs saline) and in mice (saline: 2.51 ± 0.39; oleate: 1.20 ± 0.19; p < 0.01 vs saline) and ex vivo (i.e., insulin secretion, units are pmol insulin islet-1 h-1) in rat islets (saline: 1.51 ± 0.13; oleate: 1.03 ± 0.10; OLO: 0.91 ± 0.13; p < 0.001 for both fats vs saline) and the dysfunction was prevented by co-infusion of salicylate in rats (oleate + salicylate: 1.30 ± 0.09; OLO + salicylate: 1.33 ± 0.23) or BMS in mice (oleate + BMS: 2.25 ± 0.42) in vivo and by salicylate in rat islets ex vivo (oleate + salicylate: 1.74 ± 0.31; OLO + salicylate: 1.54 ± 0.29). In cultured islets, 48 h exposure to oleate impaired beta-cell function ([in pmol insulin islet-1 h-1] control: 0.66 ± 0.12; oleate: 0.23 ± 0.03; p < 0.01 vs saline), an effect prevented by both inhibitors (oleate + salicylate: 0.98 ± 0.08; oleate + BMS: 0.50 ± 0.02). Genetic inhibition of IKKβ also prevented fat-induced beta-cell dysfunction ex vivo ([in pmol insulin islet-1 h-1] control saline: 0.16 ± 0.02; control oleate: 0.10 ± 0.02; knockout oleate: 0.17 ± 0.04; p < 0.05 control saline vs. control oleate) and in vivo (DI: control saline: 3.86 ± 0.40; control oleate: 1.95 ± 0.29; knockout oleate: 2.96 ± 0.24; p < 0.01 control saline vs control oleate). CONCLUSIONS/INTERPRETATION Our results demonstrate a causal role for IKKβ in fat-induced beta cell dysfunction in vitro, ex vivo and in vivo.
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Affiliation(s)
- Aleksandar Ivovic
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Andrei I Oprescu
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Khajag Koulajian
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Yusaku Mori
- Division of Diabetes, Metabolism, and Endocrinology, Showa University School of Medicine, Shinagawa, Tokyo, Japan
| | - Judith A Eversley
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Liling Zhang
- Division of Cellular and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, ON, Canada
| | - Rodolfo Nino-Fong
- Department of Biomedical Sciences, Ross University School of Veterinary Medicine, Basseterre, St Kitts and Nevis
| | - Gary F Lewis
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
- Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada
| | - Marc Y Donath
- Department of Endocrinology, Diabetes, and Metabolism, University Hospital Basel, Basel, Switzerland
| | - Michael Karin
- Department of Pharmacology, University of California, San Diego, School of Medicine, La Jolla, CA, USA
| | - Michael B Wheeler
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Jan Ehses
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- Child and Family Research Institute, Vancouver, BC, Canada
| | - Allen Volchuk
- Keenan Research Centre for Biomedical Science, St Michael's Hospital, Toronto, ON, Canada
| | - Catherine B Chan
- Department of Agriculture, Food and Nutritional Sciences, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Adria Giacca
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8.
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
- Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada.
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Westwell-Roper C, Ehses J, Verchere B. Distinct actions of oligomers and fibrils of islet amyloid polypeptide on Toll-like receptor 2 and NLRP3 inflammasome activation (INM7P.423). The Journal of Immunology 2014. [DOI: 10.4049/jimmunol.192.supp.123.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Aggregation of islet amyloid polypeptide (IAPP) to form amyloid contributes to beta cell dysfunction in type 2 diabetes. Human but not non-amyloidogenic rodent IAPP activates TLR2 and NLRP3 to induce IL-1β secretion by islet macrophages. It is unclear which form of IAPP aggregate induces IL-1β and whether this pathway is relevant to disease pathogenesis. We therefore evaluated the contributions of soluble and fibrillar IAPP to IL-1β secretion by bone marrow-derived macrophages (BMDMs) and assessed the effects of IL-1 receptor antagonist (IL-1Ra) on glucose homeostasis in transgenic mice with beta cell expression of human IAPP. BMDMs treated with soluble but not fibrillar IAPP provided a TLR2-dependent priming stimulus for ATP-induced IL-1β secretion, suggesting that pre-fibrillar species interact with TLR2. Fibrillar but not soluble IAPP aggregates were required for IL-1β secretion in LPS-primed BMDMs and are therefore likely the principal stimulus for NLRP3. Moreover, IL-1Ra (50 mg/kg/d for 8 weeks) improved glucose tolerance in obese human IAPP transgenic mice (AUC=1360±110 vs. 880±70; p<0.05) with no effect in wild-type littermates. These data provide the first in vivo evidence that IAPP-induced islet dysfunction in type 2 diabetes is mediated by IL-1, and suggest that both soluble and fibrillar IAPP aggregates participate in this process. Islet inflammation and amyloid formation are therefore important therapeutic targets to improve beta cell function in type 2 diabetes.
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Affiliation(s)
- Clara Westwell-Roper
- 1Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
- 3Child & Family Research Institute, Vancouver, BC, Canada
| | - Jan Ehses
- 2Surgery, University of British Columbia, Vancouver, BC, Canada
- 3Child & Family Research Institute, Vancouver, BC, Canada
| | - Bruce Verchere
- 1Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
- 2Surgery, University of British Columbia, Vancouver, BC, Canada
- 3Child & Family Research Institute, Vancouver, BC, Canada
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Han J, Patterson S, Ehses J, Levings M. Insulin impairs regulatory T cell function: implications for obesity (P1020). The Journal of Immunology 2013. [DOI: 10.4049/jimmunol.190.supp.65.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Chronic inflammation is known to drive metabolic dysregulation in obesity and type 2 diabetes. Although the precise origin of the unchecked inflammatory responses in obesity is unclear, it is known that over-production of pro-inflammatory cytokines such as TNF-α by innate immune cells has a key role in the development of metabolic dysfunction. One key hallmark of obesity is high levels of the pancreatic hormone insulin, and we hypothesized that there may be an unknown link between hyperinsulinemia and chronic inflammation. Here we show that high levels of insulin impair the ability of regulatory T cells to suppress inflammatory responses via effects on the AKT/mTOR signaling pathway. Insulin strongly activates AKT/mTOR signalling in regulatory T cells, leading to specific inhibition of the production of the anti-inflammatory cytokine IL-10. As a result, insulin hinders the ability of regulatory T cells to suppress the production of TNF-α by macrophages. Regulatory T cells from the visceral adipose tissue of hyperinsulinemic, obese mice also have a decrease in IL-10 production and a parallel increase in production of IFN-γ. These data suggest that the hyperinsulinemia associated with obesity may contribute to the development of obesity-associated inflammation via a previously unknown effect on regulatory T cells function.
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Affiliation(s)
- Jonathan Han
- 1Surgery, Univ. of British Columbia, Vancouver, BC, Canada
- 2Child & Family Research Institute, Vancouver, BC, Canada
| | - Scott Patterson
- 1Surgery, Univ. of British Columbia, Vancouver, BC, Canada
- 2Child & Family Research Institute, Vancouver, BC, Canada
| | - Jan Ehses
- 1Surgery, Univ. of British Columbia, Vancouver, BC, Canada
- 2Child & Family Research Institute, Vancouver, BC, Canada
| | - Megan Levings
- 1Surgery, Univ. of British Columbia, Vancouver, BC, Canada
- 2Child & Family Research Institute, Vancouver, BC, Canada
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Larsen CM, Faulenbach M, Vaag A, Vølund A, Ehses J, Seifert B, Mandrup-Poulsen T, Donath M. [Interleukin-1 receptor antagonist-treatment of patients with type 2 diabetes]. Ugeskr Laeger 2007; 169:3868-3871. [PMID: 18031661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Interleukin-1 receptor antagonist (IL-1Ra) expression is reduced in islets of patients with type 2 diabetes. 70 patients with type 2 diabetes were randomized to treatment with anakinra (IL-1Ra) or placebo for 13 weeks. Following treatment glycated hemoglobin was 0.46 percent lower, C-peptide secretion was enhanced, and systemic IL-6 and C-reactive protein levels were reduced in the anakinra group compared to the placebo group. Insulin resistance remained unchanged. Blocking IL-1 activity improved glycemia and b-cell secretory function and reduced markers of systemic inflammation.
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Affiliation(s)
- Claus Morten Larsen
- Steno Diabetes Center, Universitets Hospitalet, Zürich, Universitet i Lund, og Karolinska Institutet, Stockholm.
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Pamir N, Lynn FC, Buchan AMJ, Ehses J, Hinke SA, Pospisilik JA, Miyawaki K, Yamada Y, Seino Y, McIntosh CHS, Pederson RA. Glucose-dependent insulinotropic polypeptide receptor null mice exhibit compensatory changes in the enteroinsular axis. Am J Physiol Endocrinol Metab 2003; 284:E931-9. [PMID: 12540373 DOI: 10.1152/ajpendo.00270.2002] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that act via the enteroinsular axis to potentiate insulin secretion from the pancreas in a glucose-dependent manner. Both GLP-1 receptor and GIP receptor knockout mice (GLP-1R(-/-) and GIPR(-/-), respectively) have been generated to investigate the physiological importance of this axis. Although reduced GIP action is a component of type 2 diabetes, GIPR-deficient mice exhibit only moderately impaired glucose tolerance. The present study was directed at investigating possible compensatory mechanisms that take place within the enteroinsular axis in the absence of GIP action. Although serum total GLP-1 levels in GIPR knockout mice were unaltered, insulin responses to GLP-1 from pancreas perfusions and static islet incubations were significantly greater (40-60%) in GIPR(-/-) than in wild-type (GIPR(+/+)) mice. Furthermore, GLP-1-induced cAMP production was also elevated twofold in the islets of the knockout animals. Pancreatic insulin content and gene expression were reduced in GIPR(-/-) mice compared with GIPR(+/+) mice. Paradoxically, immunocytochemical studies showed a significant increase in beta-cell area in the GIPR-null mice but with less intense staining for insulin. In conclusion, GIPR(-/-) mice exhibit altered islet structure and topography and increased islet sensitivity to GLP-1 despite a decrease in pancreatic insulin content and gene expression.
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Affiliation(s)
- Nathalie Pamir
- Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia, Canada, V6T 1Z3
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Hinke SA, Pauly RP, Ehses J, Kerridge P, Demuth HU, McIntosh CH, Pederson RA. Role of glucose in chronic desensitization of isolated rat islets and mouse insulinoma (betaTC-3) cells to glucose-dependent insulinotropic polypeptide. J Endocrinol 2000; 165:281-91. [PMID: 10810292 DOI: 10.1677/joe.0.1650281] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It is well documented that the release of insulin from isolated perifused islets attenuates over time, despite a continued glucose stimulation. In the current study we have shown that potentiation of insulin release by the intestinal hormone glucose-dependent insulinotropic polypeptide (GIP) is also attenuated after its continuous application. In less than 20 h of maintained stimulus with either hyperglycaemia (11.0 mM glucose) or GIP (10 nM) under hyperglycaemic conditions, insulin release returned to basal values. This was not due to loss of islet viability or reduction in the releasable pool of insulin granules, as 1 mM isobutylmethylxanthine was able to stimulate equivalent insulin release under both conditions. Further examination of chronic GIP desensitization was examined in cultured mouse insulinoma (betaTC-3) cells. GIP-stimulated cAMP production was not greatly affected by the prevailing glucose conditions, suggesting that the glucose dependence of GIP-stimulated insulin release occurs distally to the increase in intracellular cAMP in betaTC-3 cells. The GIP-stimulated cAMP response curve after desensitization was of similar magnitude at all glucose concentrations, but GIP pretreatment did not affect forskolin-stimulated cAMP production. Desensitization of the cAMP response in betaTC-3 cells was shown not to involve induction of dipeptidyl peptidase IV or pertussis toxin-sensitive G-proteins, activation of protein kinase C or protein kinase A, or modulation of phosphodiesterase activity. Homologous desensitization of the insulin-potentiating activity of GIP was found to affect both GIP-stimulated and forskolin-stimulated insulin release, indicating desensitization of distal steps in the stimulus-exocytosis cascade.
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Affiliation(s)
- S A Hinke
- Department of Physiology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Wheeler MB, Gelling RW, Hinke SA, Tu B, Pederson RA, Lynn F, Ehses J, McIntosh CH. Characterization of the carboxyl-terminal domain of the rat glucose-dependent insulinotropic polypeptide (GIP) receptor. A role for serines 426 and 427 in regulating the rate of internalization. J Biol Chem 1999; 274:24593-601. [PMID: 10455124 DOI: 10.1074/jbc.274.35.24593] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone involved in the regulation of insulin secretion. In non-insulin-dependent diabetes mellitus insulin responses to GIP are blunted, possibly due to altered signal transduction or reduced receptor number. Site-directed mutagenesis was used to construct truncated GIP receptors to study the importance of the carboxyl-terminal tail (CT) in binding, signaling, and receptor internalization. Receptors truncated at amino acids 425, 418, and 405, expressed in COS-7 or CHO-K1 cells, exhibited similar binding to wild type receptors. GIP-dependent cAMP production with the 405 mutant was decreased in COS-7 cells. Maximal cAMP production in CHO-K1 cells was reduced with all truncated forms. Binding was undetectable with a receptor truncated at amino acid 400; increasing tail length by adding 5 alanines restored binding and signaling. Mutants produced by alanine scanning of residues 394-401, adjacent to transmembrane domain 7, were all functional. CT truncation by 30 or more amino acids, mutation of serines 426/427, singly or combined, or complete CT serine knockout all reduced receptor internalization rate. The majority of the GIP receptor CT is therefore not required for signaling, a minimum chain length of approximately 405 amino acids is needed for receptor expression, and serines 426 and 427 are important for regulating rate of receptor internalization.
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Affiliation(s)
- M B Wheeler
- Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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