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Oakie A, Feng ZC, Li J, Silverstein J, Yee SP, Wang R. Long-term c-Kit overexpression in beta cells compromises their function in ageing mice. Diabetologia 2019; 62:1430-1444. [PMID: 31154478 DOI: 10.1007/s00125-019-4890-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [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: 12/05/2018] [Accepted: 04/04/2019] [Indexed: 12/23/2022]
Abstract
AIMS/HYPOTHESIS c-Kit signalling regulates intracellular pathways that enhance beta cell proliferation, insulin secretion and islet vascularisation in mice up to 28 weeks of age and on short-term high-fat diet. However, long-term c-Kit activation in ageing mouse islets has yet to be examined. This study utilises beta cell-specific c-Kit-overexpressing transgenic (c-KitβTg) ageing mice (~60 weeks) to determine the effect of its activation on beta cell dysfunction and insulin secretion. METHODS Wild-type and c-KitβTg mice, aged 60 weeks, were examined using metabolic tests to determine glucose tolerance and insulin secretion. Pancreas histology and proteins in isolated islets were examined to determine the expression of beta cell transcription factors, proliferation and intracellular signalling. To determine the role of insulin receptor signalling in ageing c-KitβTg mice, we generated beta cell-specific inducible insulin receptor knockout in ageing c-KitβTg mice (c-KitβTg;βIRKO mice) and examined the ageing mice for glucose tolerance and islet histology. RESULTS Ageing c-KitβTg mice progressively developed glucose intolerance, compared with age-matched wild-type littermates, due to impaired insulin secretion. Increased beta cell mass, proliferation and nuclear forkhead box transcription factor O1 (FOXO1) expression and reduced exocytotic protein levels were detected in ageing c-KitβTg mouse islets. Protein analyses of isolated islets showed increased insulin receptor, phosphorylated IRS-1Ser612 and cleaved poly(ADP-ribose) polymerase levels in ageing c-KitβTg mice. Ageing c-KitβTg mouse islets treated ex vivo with insulin demonstrated reduced Akt phosphorylation, indicating that prolonged c-Kit induced beta cell insulin insensitivity. Ageing c-KitβTg;βIRKO mice displayed improved glucose tolerance and beta cell function compared with ageing c-KitβTg mice. CONCLUSIONS/INTERPRETATION These findings indicate that long-term c-Kit overexpression in beta cells has a negative impact on insulin exocytosis and that temporally dependent regulation of c-Kit-insulin receptor signalling is important for optimal beta cell function.
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Affiliation(s)
- Amanda Oakie
- Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada
- Department of Pathology and Laboratory Medicine, University of Western Ontario, London, ON, Canada
| | - Zhi-Chao Feng
- Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada
| | - Jinming Li
- Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Jenna Silverstein
- Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada
| | - Siu-Pok Yee
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
| | - Rennian Wang
- Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada.
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.
- Department of Medicine, University of Western Ontario, London, ON, Canada.
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Papaconstantinou J, Hsieh CC. IGF-1 mediated phosphorylation of specific IRS-1 serines in Ames dwarf fibroblasts is associated with longevity. Oncotarget 2015; 6:35315-23. [PMID: 26474286 DOI: 10.18632/oncotarget.6112] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 09/22/2015] [Indexed: 12/28/2022] Open
Abstract
Insulin/IGF-1 signaling involves phosphorylation/dephosphorylation of serine/threonine or tyrosine residues of the insulin receptor substrate (IRS) proteins and is associated with hormonal control of longevity determination of certain long-lived mice. The stimulation of serine phosphorylations by IGF-1 suggests there is insulin/IGF-1 crosstalk that involves the phosphorylation of the same serine residues. By this mechanism, insulin and IGF-1 mediated phosphorylation of specific IRS-1 serines could play a role in longevity determination. We used fibroblasts from WT and Ames dwarf mice to examine whether: (a) IGF-1 stimulates phosphorylation of IRS-1 serines targeted by insulin; (b) the levels of serine phosphorylation differ in WT vs. Ames fibroblasts; and (c) aging affects the levels of these serine phosphorylations which are altered in the Ames dwarf mutant. We have shown that IRS-1 is a substrate for IGF-1 induced phosphorylation of Ser307, Ser612, Ser636/639, and Ser1101; that the levels of phosphorylation of these serines are significantly lower in Ames vs. WT cells; that IGF-1 mediated phosphorylation of these serines increases with age in WT cells. We propose that insulin/IGF-1 cross talk and level of phosphorylation of specific IRS-1 serines may promote the Ames dwarf longevity phenotype.
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