Nutrition-Metabolism Unit, San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy.
Nutr Metab Cardiovasc Dis. 2011 Mar;21(3):197-205. doi: 10.1016/j.numecd.2009.09.004. Epub 2010 Jan 21.
Lupin seed is referred to as an antidiabetic product in traditional medicine. Conglutin-γ, a lupin seed glycoprotein, was found to cause a significant plasma glucose reduction when orally administered to rats in glucose overload trials. Conglutin-γ was identified as being responsible for the claimed biological activity, and the aim of this work was to envisage its hypothetical insulin-mimetic cellular mechanism of action. Insulin is responsible for proteosynthesis control through IRS/AKT/P70S6k/PHAS1 pathways modulation, glucose homeostasis through PKC/Flotillin-2/caveolin-3/Cbl activation and muscle differentiation/hypertrophy via muscle-specific MHC gene transcription control.
To assess whether conglutin-γ modulates the same insulin-activated kinases, myoblastic C2C12 cells were incubated after 72 h of differentiation with 100 nM insulin or 0.5 mg/mL (∼10 μM) conglutin-γ. Metformin-stimulated cells were used as a positive control. The effect on the above mentioned pathways was evaluated after 5, 10, 20 and 30 min. In the control cells medium insulin, conglutin-γ and metformin were not added. We demonstrated that insulin or conglutin-γ cell stimulation resulted in the persistent activation of protein synthetic pathway kinases and increased glucose transport, glut4 translocation and muscle-specific gene transcription regulation.
Our results indicate that conglutin-γ may regulate muscle energy metabolism, protein synthesis and MHC gene transcription through the modulation of the same insulin signalling pathway, suggesting the potential therapeutic use of this natural legume protein in the treatment of diabetes and other insulin-resistant conditions, as well as the potential conglutin-γ influence on muscle cells differentiation and regulation of muscle growth.
卢宾种子在传统医学中被称为抗糖尿病产品。在葡萄糖过载试验中，给大鼠口服凝集素-γ（卢宾种子糖蛋白），发现其能显著降低血浆葡萄糖水平。凝集素-γ被认为是具有生物活性的物质，本工作旨在推测其假定的胰岛素模拟细胞作用机制。胰岛素通过 IRS/AKT/P70S6k/PHAS1 途径调节控制蛋白质合成，通过 PKC/Flotillin-2/caveolin-3/Cbl 激活和肌肉分化/肥大来调节葡萄糖稳态，通过肌肉特异性 MHC 基因转录控制来调节肌肉分化/肥大。
为了评估凝集素-γ是否调节相同的胰岛素激活激酶，在分化 72 小时后，用 100 nM 胰岛素或 0.5 mg/mL（约 10 μM）凝集素-γ孵育肌母细胞 C2C12。用二甲双胍刺激的细胞作为阳性对照。在 5、10、20 和 30 分钟后评估对上述途径的影响。在对照细胞培养基中，未添加胰岛素、凝集素-γ和二甲双胍。我们证明，胰岛素或凝集素-γ刺激细胞导致蛋白质合成途径激酶持续激活，并增加葡萄糖转运、Glut4 易位和肌肉特异性基因转录调控。
我们的结果表明，凝集素-γ可能通过调节相同的胰岛素信号通路来调节肌肉能量代谢、蛋白质合成和 MHC 基因转录，这表明这种天然豆科蛋白在治疗糖尿病和其他胰岛素抵抗疾病以及潜在的凝集素-γ对肌肉细胞分化和肌肉生长的调节方面具有潜在的治疗用途。
