基于PTP1B研究树豆酮酸A对2型糖尿病胰岛素与瘦素抵抗的作用

Blood-stasis is one of major pathogensis in type 2 diabetes. Drugs for invigorating blood circulation and eliminating stasis can improve insulin resistance, leptin resistance and glycolipid metabolism disorder. In our previous work, a new stilbene compound, cajanonic acid A, was isolated and identificated from Canjanus cajan (L.) Millsp with efficacy in activating blood cirulation to disspate blood stasis. Enzyme assay revealed that cajanonic acid A strongly inhibited the activity of potien tyrosine phosphatase 1B (PTP1B) which is a negative regulator of both the insulin and leptin signal transduction. And it was showed that cajanonic acid A significantly reduced blood glucose and lipid, and elevated insulin sensitivity in diabetic rats and insulin resistance cell type. In this study, we will investigate the effects of cajanonic acid A on insulin and leptin resistance with high fat diet-induced type 2 diabetes rats model and 3T3-L1 adipocyte or HepG2 hepatocyte tranduced with PTP1B gene. The expression and activity of PTP1B, the activation of insulin and leptin signaling pathways, the glucose and lipid metabolism will be analyzed. The results will provide experimental basis for the application of cajanonic acid A, and also make contribution to researching on molecular mechanism and material basis of drugs for invigorating blood circulation and eliminating stasis in the treatment of diabetes.

血瘀是2型糖尿病的重要病机，活血化瘀药物可改善胰岛素和瘦素抵抗，起到调节糖脂代谢平衡的作用。课题组从临床上具有活血化瘀功效的木豆叶中分离出一种新的化合物树豆酮酸A，体外实验证明对胰岛素和瘦素信号传导通路的共同负性调节因子- - 蛋白酪氨酸磷酸酶1B（PTP1B）活性有显著的抑制作用，并且动物和细胞试验证实其具有降糖、降脂、增强胰岛素敏感性的作用。本研究采用高脂饮食诱导的2型糖尿病大鼠模型以及PTP1B基因转化的3T3-L1和HepG2细胞模型评价树豆酮酸A对PTP1B的表达和活性的抑制作用，对胰岛素和瘦素信号传导通路的调控作用，以及对改善胰岛素和瘦素抵抗、调节糖脂代谢平衡的作用。为树豆酮酸A用于治疗2型糖尿病的开发应用提供实验依据，同时也为活血化瘀药物治疗2型糖尿病的分子机制和物质基础研究提供参考依据。

本研究采用高脂饮食＋STZ诱导的2型糖尿病SD大鼠模型、蛋白酪氨酸磷酸酶1B（PTP1B）基因转化的PTP1B过表达HepG2细胞模型以及地塞米松诱导的胰岛素抵抗HepG2肝细胞、3T3-L1脂肪细胞模型评价树豆酮酸A对胰岛素和瘦素信号传导通路的调控作用，以及改善胰岛素抵抗、调节糖脂代谢平衡的作用。研究发现：PTP1B过度表达抑制胰岛素转导通路导致胰岛素抵抗。树豆酮酸A （CAA）可通过下调PTP1B表达，增加胰岛素信号转导通路相关蛋白IR、IRS1、PI3K、Akt、GLUT1/4表达及磷酸化水平，提高细胞胰岛素敏感性。另一方面，树豆酮酸A （CAA）可通过下调过氧化物酶体增殖物活化受体γ( PPARγ)以及相应的脂肪合成基因（乙酰辅酶A羧化酶基因ACC、脂肪酸合成酶基因FAS、脂蛋白脂酶基因LPL)表达, 下调脂肪分解限速酶（激素敏感性脂肪酶HSL和脂肪甘油三酯脂酶ATGL）基因mRNA水平，促进脂肪酸氧化关键酶（乙酰辅酶A氧化酶ACOX和肉碱棕榈酰转移酶-1CPT-1）基因的表达，明显降低动物与细胞的脂肪合成、减少游离脂肪酸的释放，改善脂肪细胞的脂质代谢平衡。因此，我们推测，树豆酮酸A可能是PTP1B和PPARγ的双重拮抗剂，通过抑制PTP1B和PPARγ表达，激活胰岛素信号转导通路，改善体内脂质水平，达到同时改善糖脂代谢的作用。