Department of Endocrine and Metabolic Diseases/ Shanghai institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
Center for Reproductive Medicine, Shandong University, Jinan 250000, China.
Theranostics. 2021 Mar 4;11(10):4825-4838. doi: 10.7150/thno.55330. eCollection 2021.
Sirtuins are NAD-dependent protein deacylases known to have protective effects against age-related diseases such as diabetes, cancer, and neurodegenerative disease. SIRT2 is the only primarily cytoplasmic isoform and its overall role in glucose homeostasis remains uncertain. SIRT2-knockout (KO) rats were constructed to evaluate the role of SIRT2 in glucose homeostasis. The effect of SIRT2 on β-cell function was detected by investigating the morphology, insulin secretion, and metabolomic state of islets. The deacetylation and stabilization of GKRP in β-cells by SIRT2 were determined by western blot, adenoviral infection, and immunoprecipitation. SIRT2-KO rats exhibited impaired glucose tolerance and glucose-stimulated insulin secretion (GSIS), without change in insulin sensitivity. SIRT2 deficiency or inhibition by AGK2 decreased GSIS in isolated rat islets, with lowered oxygen consumption rate. Adenovirus-mediated overexpression of SIRT2 enhanced insulin secretion from rat islets. Metabolomics analysis revealed a decrease in metabolites of glycolysis and tricarboxylic acid cycle in SIRT2-KO islets compared with control islets. Our study further demonstrated that glucokinase regulatory protein (GKRP), an endogenous inhibitor of glucokinase (GCK), was expressed in rat islets. SIRT2 overexpression deacetylated GKRP in INS-1 β-cells. SIRT2 knockout or inhibition elevated GKRP protein stability in islet β-cells, leading to an increase in the interaction of GKRP and GCK. On the contrary, SIRT2 inhibition promoted the protein degradation of ALDOA, a glycolytic enzyme. SIRT2 ablation inhibits GSIS through blocking GKRP protein degradation and promoting ALDOA protein degradation, resulting in a decrease in glycolytic flux.
沉默调节蛋白是一种 NAD 依赖性蛋白去乙酰化酶，已知其对与年龄相关的疾病（如糖尿病、癌症和神经退行性疾病）具有保护作用。SIRT2 是唯一主要存在于细胞质中的同工酶，其在葡萄糖稳态中的整体作用尚不确定。构建 SIRT2 敲除（KO）大鼠模型，以评估 SIRT2 在葡萄糖稳态中的作用。通过研究胰岛的形态、胰岛素分泌和代谢组状态来检测 SIRT2 对β细胞功能的影响。通过 Western blot、腺病毒感染和免疫沉淀确定 SIRT2 对β细胞中 GKRP 的去乙酰化和稳定作用。SIRT2-KO 大鼠表现出葡萄糖耐量受损和葡萄糖刺激的胰岛素分泌（GSIS）受损，而胰岛素敏感性没有变化。SIRT2 缺乏或通过 AGK2 抑制降低了分离的大鼠胰岛的 GSIS，同时降低了耗氧量。腺病毒介导的 SIRT2 过表达增强了大鼠胰岛的胰岛素分泌。代谢组学分析显示，与对照胰岛相比，SIRT2-KO 胰岛中的糖酵解和三羧酸循环代谢物减少。我们的研究进一步表明，葡萄糖激酶调节蛋白（GKRP），一种葡萄糖激酶（GCK）的内源性抑制剂，在大鼠胰岛中表达。SIRT2 过表达使 INS-1β细胞中的 GKRP 去乙酰化。SIRT2 敲除或抑制增加了胰岛β细胞中 GKRP 蛋白的稳定性，导致 GKRP 和 GCK 的相互作用增加。相反，SIRT2 抑制促进了糖酵解酶 ALDOA 的蛋白降解。SIRT2 缺失通过阻断 GKRP 蛋白降解和促进 ALDOA 蛋白降解来抑制 GSIS，导致糖酵解通量降低。
