Department of Nutrition, Dietetics, and Food Science, Brigham Young University, Provo, Utah, USA.
Medical Education Program, Des Moines University, Des Moines, IA, 50312, USA.
Biol Cell. 2021 Dec;113(12):507-521. doi: 10.1111/boc.202100035. Epub 2021 Sep 27.
Over 400 million people are diabetic. Type 1 and type 2 diabetes are characterized by decreased functional β-cell mass and, consequently, decreased glucose-stimulated insulin secretion. A potential intervention is transplantation of β-cell containing islets from cadaveric donors. A major impediment to greater application of this treatment is the scarcity of transplant-ready β-cells. Therefore, inducing β-cell proliferation ex vivo could be used to expand functional β-cell mass prior to transplantation. Various molecular pathways are sufficient to induce proliferation of young β-cells; however, aged β-cells are refractory to these proliferative signals. Given that the majority of cadaveric donors fit an aged demographic, defining the mechanisms that impede aged β-cell proliferation is imperative.
We demonstrate that aged rat (5-month-old) β-cells are refractory to mitogenic stimuli that otherwise induce young rat (5-week-old) β-cell proliferation. We hypothesized that this change in proliferative capacity could be due to differences in cyclin-dependent kinase inhibitor expression. We measured levels of p16 , p15 , p18 , p19 , p21 , p27 and p57 by immunofluorescence analysis. Our data demonstrates an age-dependent increase of p27 in rat β-cells by immunofluorescence and was validated by increased p27 protein levels by western blot analysis. Interestingly, HDAC1, which modulates the p27 promoter acetylation state, is downregulated in aged rat islets. These data demonstrate increased p27 protein levels at 5 months of age, which may be due to decreased HDAC1 mediated repression of p27 expression.
As the majority of transplant-ready β-cells come from aged donors, it is imperative that we understand why aged β-cells are refractory to mitogenic stimuli. Our findings demonstrate that increased p27 expression occurs early in β-cell aging, which corresponds with impaired β-cell proliferation. Furthermore, the correlation between HDAC1 and p27 levels suggests that pathways that activate HDAC1 in aged β-cells could be leveraged to decrease p27 levels and enhance β-cell proliferation.
全球有超过 4 亿人患有糖尿病。1 型和 2 型糖尿病的特征是功能性β细胞数量减少，因此葡萄糖刺激的胰岛素分泌减少。一种潜在的干预措施是从尸体供体移植含有β细胞的胰岛。这种治疗方法应用受限的一个主要障碍是移植准备好的β细胞稀缺。因此，在移植前体外诱导β细胞增殖可以扩大功能性β细胞数量。各种分子途径足以诱导年轻β细胞增殖；然而，衰老的β细胞对这些增殖信号无反应。鉴于大多数尸体供体都属于老年人群，确定阻碍衰老β细胞增殖的机制至关重要。
我们证明，衰老的大鼠（5 月龄）β细胞对有丝分裂刺激无反应，而这些刺激会诱导年轻的大鼠（5 周龄）β细胞增殖。我们假设这种增殖能力的变化可能是由于细胞周期蛋白依赖性激酶抑制剂表达的差异。我们通过免疫荧光分析测量了 p16、p15、p18、p19、p21、p27 和 p57 的水平。我们的数据通过免疫荧光显示，大鼠β细胞中 p27 随年龄的增长呈依赖性增加，并通过 Western blot 分析证实了 p27 蛋白水平的增加。有趣的是，调节 p27 启动子乙酰化状态的 HDAC1 在衰老的大鼠胰岛中下调。这些数据表明，5 月龄时 p27 蛋白水平增加，这可能是由于 HDAC1 介导的 p27 表达抑制减少所致。
由于大多数可移植的β细胞来自老年供体，因此我们必须了解为什么衰老的β细胞对有丝分裂刺激无反应。我们的研究结果表明，p27 表达增加发生在β细胞衰老的早期，这与β细胞增殖受损相对应。此外，HDAC1 与 p27 水平之间的相关性表明，在衰老的β细胞中激活 HDAC1 的途径可以用来降低 p27 水平并增强β细胞增殖。
