长期过表达 c-Kit 会损害衰老小鼠胰岛β细胞的功能。
Long-term c-Kit overexpression in beta cells compromises their function in ageing mice.
机构信息
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.
出版信息
Diabetologia. 2019 Aug;62(8):1430-1444. doi: 10.1007/s00125-019-4890-5. Epub 2019 Jun 1.
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-1 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.
目的/假设：c-Kit 信号调节细胞内途径，增强小鼠β细胞增殖、胰岛素分泌和胰岛血管生成，直至 28 周龄，并在短期高脂肪饮食下。然而，在衰老的胰岛中，长期的 c-Kit 激活尚未被研究。本研究利用β细胞特异性 c-Kit 过表达转基因（c-KitβTg）衰老小鼠（~60 周龄）来确定其激活对β细胞功能障碍和胰岛素分泌的影响。
方法
使用代谢试验检查 60 周龄的野生型和 c-KitβTg 小鼠，以确定葡萄糖耐量和胰岛素分泌情况。检查胰腺组织学和分离胰岛中的蛋白质，以确定β细胞转录因子、增殖和细胞内信号的表达。为了确定胰岛素受体信号在衰老的 c-KitβTg 小鼠中的作用，我们在衰老的 c-KitβTg 小鼠中生成了β细胞特异性诱导胰岛素受体敲除（c-KitβTg；βIRKO 小鼠），并检查了衰老小鼠的葡萄糖耐量和胰岛组织学。
结果
与年龄匹配的野生型同窝小鼠相比，衰老的 c-KitβTg 小鼠逐渐发展为葡萄糖不耐受，这是由于胰岛素分泌受损所致。在衰老的 c-KitβTg 小鼠胰岛中检测到β细胞质量增加、增殖和核叉头框转录因子 O1（FOXO1）表达增加，以及外显蛋白水平降低。分离胰岛的蛋白质分析显示，衰老的 c-KitβTg 小鼠中胰岛素受体、磷酸化 IRS-1 和切割多聚（ADP-核糖）聚合酶水平增加。衰老的 c-KitβTg 胰岛在体外用胰岛素处理后，Akt 磷酸化减少，表明 c-Kit 诱导的β细胞胰岛素不敏感持续存在。与衰老的 c-KitβTg 小鼠相比，衰老的 c-KitβTg；βIRKO 小鼠显示出改善的葡萄糖耐量和β细胞功能。
结论/解释：这些发现表明，β细胞中长期的 c-Kit 过表达对胰岛素胞吐作用有负面影响，并且 c-Kit-胰岛素受体信号的时间依赖性调节对于最佳β细胞功能很重要。
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