School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
China National Institute of Standardization, 4 Zhichun Road, Beijing, 100191, China.
BMC Complement Med Ther. 2024 Aug 2;24(1):296. doi: 10.1186/s12906-024-04592-1.
The fruit of Phyllanthus emblica L., a traditional medicine in China and India, is used to treat diabetes mellitus. Its water extract (WEPE) has demonstrated hypoglycemic effects in diabetic rats, but its mechanisms on glucose utilization and insulin resistance in skeletal muscle remain unclear. Therefore, this study aims to investigate the effects and underlying mechanisms of WEPE on glucose utilization and insulin resistance using C2C12 myotubes.
Effects of WEPE on glucose uptake, GLUT4 translocation, and AMPK and AKT phosphorylation were investigated in C2C12 myotubes and palmitate-treated myotubes. An AMPK inhibitor and siRNA were used to explore the mechanisms of WEPE. Glucose uptake was determined using a 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino)-2-deoxyglucose (2-NBDG) uptake assay, and protein expression and GLUT4 translocation were assessed via western blotting.
In normal myotubes, WEPE significantly stimulated glucose uptake and GLUT4 translocation to the plasma membrane at concentrations of 125 and 250 µg/mL. This was accompanied by an increase in the phosphorylation of AMPK and its downstream targets. However, both compound C and AMPK siRNA blocked the WEPE-induced GLUT4 translocation and glucose uptake. Moreover, pretreatment with STO-609, a calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ) inhibitor, inhibited WEPE-induced AMPK phosphorylation and attenuated the WEPE-stimulated glucose uptake and GLUT4 translocation. In myotubes treated with palmitate, WEPE prevented palmitate-induced insulin resistance by enhancing insulin-mediated glucose uptake and AKT phosphorylation. It also restored the insulin-mediated translocation of GLUT4 from cytoplasm to membrane. However, these effects of WEPE on glucose uptake and GLUT4 translocation were blocked by pretreatment with compound C.
WEPE significantly stimulated basal glucose uptake though CaMKKβ/AMPK pathway and markedly ameliorated palmitate-induced insulin resistance by activating the AMPK pathway in C2C12 myotubes.
中国和印度传统医学中使用的余甘子的果实可用于治疗糖尿病。其水提取物（WEPE）在糖尿病大鼠中表现出降血糖作用，但它在骨骼肌葡萄糖利用和胰岛素抵抗方面的机制尚不清楚。因此，本研究旨在使用 C2C12 肌管研究 WEPE 对葡萄糖利用和胰岛素抵抗的影响及其潜在机制。
在 C2C12 肌管和棕榈酸处理的肌管中，研究了 WEPE 对葡萄糖摄取、GLUT4 易位以及 AMPK 和 AKT 磷酸化的影响。使用 AMPK 抑制剂和 siRNA 探讨 WEPE 的作用机制。通过 2-（N-（7-硝基苯并-2-氧代-1,3-二唑-4-基）氨基）-2-脱氧葡萄糖（2-NBDG）摄取测定法测定葡萄糖摄取，通过 Western blot 评估蛋白质表达和 GLUT4 易位。
在正常肌管中，WEPE 在 125 和 250μg/mL 浓度下显著刺激葡萄糖摄取和 GLUT4 向质膜易位。这伴随着 AMPK 及其下游靶标的磷酸化增加。然而，化合物 C 和 AMPK siRNA 均阻断了 WEPE 诱导的 GLUT4 易位和葡萄糖摄取。此外，钙/钙调蛋白依赖性蛋白激酶激酶β（CaMKKβ）抑制剂 STO-609 的预处理抑制了 WEPE 诱导的 AMPK 磷酸化，并减弱了 WEPE 刺激的葡萄糖摄取和 GLUT4 易位。在棕榈酸处理的肌管中，WEPE 通过增强胰岛素介导的葡萄糖摄取和 AKT 磷酸化来预防棕榈酸诱导的胰岛素抵抗，同时还恢复了胰岛素介导的 GLUT4 从细胞质向膜的易位。然而，WEPE 对葡萄糖摄取和 GLUT4 易位的这些作用被化合物 C 的预处理所阻断。
WEPE 通过 CaMKKβ/AMPK 通路显著刺激基础葡萄糖摄取，并通过激活 C2C12 肌管中的 AMPK 通路，显著改善棕榈酸诱导的胰岛素抵抗。
