Zhan Shuo, Huang Jiaqiang, Liu Yiqun, Han Feng, Wang Jianrong, Wang Qin, Huang Zhenwu
Department of Nutrition and Metabolism, Chinese Center for Disease Control and Prevention, National Institute for Nutrition and Health, Beijing, 100050, China.
Beijing Advanced Innovation Center for Food Nutrition and Human Health, Department of Nutrition and Health, China Agricultural University, Beijing, 100193, China.
Biol Trace Elem Res. 2025 Jan 10. doi: 10.1007/s12011-024-04492-y.
Selenium (Se) intake or selenoprotein overexpression can cause abnormal glucose metabolism and increase the risk of type 2 diabetes (T2D). The purpose of this study is to observe whether glycolysis bypass in the de novo serine synthesis pathway (SSP) is activated under high-Se stress in vitro. Initially, HCT-116, L02, HepG2, and differentiated C2C12 cells were exposed to five selenomethionine (SeMet) concentrations (0.001 to 10 µmol/L) for 48 h. The expressions of glutathione peroxidase 1 (GPX1), selenoprotein P (SELENOP), 3-phosphoglycerate dehydrogenase (PHGDH), and serine hydroxy-methyltransferases 1 (SHMT1) were assessed by western blotting (WB). Then, corresponding to the peak expressions of GPX1, SELENOP, and PHGDH, 0.1 µmol/L SeMet was identified as the highest intervention concentration. With more detailed levels of SeMet (0.001 to 0.1 µmol/L) given, the differentiated C2C12 cells were treated for 48 h to analyze the expressions of selenoproteins, enzymes related with serine metabolism and insulin signaling pathway. Among the four cell lines, the expressions of selenoproteins and metabolic enzymes of serine in C2C12 cells were more sensitive to changes in Se concentrations, which was similar to that in L02 cells. In C2C12 cells, the expressions of GPX1, SELENOP, selenoprotein N (SELENON), PHGDH, and SHMT1 exhibited a parabolic inflection point at SeMet concentrations of 0.05 µmol/L or 0.075 µmol/L, while 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) showed no such trend. After 15 min of insulin stimulation, glucose retained more in the culture medium due to the decreased uptake by C2C12 cells. The expressions of key enzymes (AKT, AKT (Ser-473), AKT (Thr-308), mTOR, and PI3K) in the PI3K-AKT-mTOR signaling pathway decreased with the increased level of SeMet. This study demonstrated that excessive Se intake could induce abnormal glucose metabolism via SSP and impair the normal signaling of insulin in the differentiated C2C12 cells.
摄入硒（Se）或硒蛋白过表达会导致葡萄糖代谢异常，并增加2型糖尿病（T2D）的发病风险。本研究旨在观察在体外高硒胁迫下，从头丝氨酸合成途径（SSP）中的糖酵解旁路是否被激活。首先，将HCT-116、L02、HepG2和分化的C2C12细胞暴露于5种硒代蛋氨酸（SeMet）浓度（0.001至10 μmol/L）下48小时。通过蛋白质免疫印迹法（WB）评估谷胱甘肽过氧化物酶1（GPX1）、硒蛋白P（SELENOP）、3-磷酸甘油酸脱氢酶（PHGDH）和丝氨酸羟甲基转移酶1（SHMT1）的表达。然后，对应于GPX1、SELENOP和PHGDH的峰值表达，确定0.1 μmol/L SeMet为最高干预浓度。给予更详细水平的SeMet（0.001至0.1 μmol/L），对分化的C2C12细胞进行48小时处理，以分析硒蛋白、与丝氨酸代谢相关的酶和胰岛素信号通路的表达。在这四种细胞系中，C2C12细胞中硒蛋白和丝氨酸代谢酶的表达对硒浓度变化更敏感，这与L02细胞相似。在C2C12细胞中，GPX1、SELENOP、硒蛋白N（SELENON）、PHGDH和SHMT1的表达在SeMet浓度为0.05 μmol/L或0.075 μmol/L时呈现抛物线型拐点，而5,10-亚甲基四氢叶酸还原酶（MTHFR）和甲硫氨酸合酶（MS）则无此趋势。胰岛素刺激15分钟后，由于C2C12细胞摄取减少，葡萄糖在培养基中保留更多。PI3K-AKT-mTOR信号通路中关键酶（AKT、AKT（Ser-473）、AKT（Thr-308）、mTOR和PI3K）的表达随SeMet水平升高而降低。本研究表明，过量摄入硒可通过SSP诱导葡萄糖代谢异常，并损害分化的C2C12细胞中胰岛素的正常信号传导。
