Amanda Oakie1,2, Zhi-Chao Feng1, Jinming Li1,3, Jenna Silverstein1, Siu-Pok Yee4,5, Rennian Wang6,7,8. 1. Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada. 2. Department of Pathology and Laboratory Medicine, University of Western Ontario, London, ON, Canada. 3. Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada. 4. Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA. 5. Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA. 6. Children's Health Research Institute, University of Western Ontario, Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, ON, N6C 2V5, Canada. rwang@uwo.ca. 7. Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada. rwang@uwo.ca. 8. Department of Medicine, University of Western Ontario, London, ON, Canada. rwang@uwo.ca.
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.
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.
Authors: R Aikin; S Hanley; D Maysinger; M Lipsett; M Castellarin; S Paraskevas; L Rosenberg Journal: Diabetologia Date: 2006-10-20 Impact factor: 10.122
Authors: Cristina Aguayo-Mazzucato; Mark van Haaren; Magdalena Mruk; Terence B Lee; Caitlin Crawford; Jennifer Hollister-Lock; Brooke A Sullivan; James W Johnson; Aref Ebrahimi; Jonathan M Dreyfuss; Jan Van Deursen; Gordon C Weir; Susan Bonner-Weir Journal: Cell Metab Date: 2017-04-04 Impact factor: 27.287