积雪草酸改善小鼠脂肪细胞胰岛素抵抗的机制研究

 目的： 观察番石榴叶三萜化合物积雪草酸对小鼠3T3-L1前脂肪细胞增殖、分化以及胰岛素抵抗脂肪细胞糖脂代谢的影响并探讨其作用机制。方法：MTT法检测药物对3T3-L1前脂肪细胞增殖的影响；油红O染色法观察药物对其分化的影响。地塞米松诱导建立脂肪细胞胰岛素抵抗模型，药物干预后采用葡萄糖氧化酶法检测培养液中葡萄糖消耗量；比色法检测游离脂肪酸浓度；ELISA法检测脂联素水平；Western blotting法检测过氧化物酶体增殖物激活受体γ（PPARγ）和蛋白酪氨酸磷酸酶1B(PTP1B)蛋白表达的变化。结果：与溶媒对照组相比，积雪草酸在10~100 μmol/L时能显著促进3T3-L1前脂肪细胞增殖，但明显抑制其分化（P<0.05或P<0.01）；在30和100 μmol/L时，无论是基础状态还是胰岛素刺激状态，均能显著增加胰岛素抵抗脂肪细胞葡萄糖的消耗，减少游离脂肪酸的产生（P<0.05）；其对胰岛素抵抗脂肪细胞的脂联素分泌和PPARγ蛋白表达无明显影响（P>0.05），但能显著下调PTP1B蛋白的表达（P<0.05或P<0.01）。结论：积雪草酸能显著改善脂肪细胞胰岛素抵抗，增加胰岛素抵抗脂肪细胞葡萄糖的消耗和减少游离脂肪酸的产生，其机制可能是其下调胰岛素信号转导的负性调节因子PTP1B的表达，增强胰岛素信号转导，从而改善胰岛素抵抗。

Role of asiatic acid in treatment of insulin resistance in mouse adipocytes

AIM：To investigate the effects of asiatic acid, one of triterpenoids from Psidium guajava leaves, on the proliferation and differentiation of 3T3-L1 preadipocytes, and glucose and lipid metabolism of insulin-resistant adipocytes. METHODS：The proliferation of 3T3-L1 preadipocytes was tested by MTT assay, and the accumulation of lipid droplets in differentiated preadipocytes was measured by oil red O staining. The insulin-resistant cell model was established by exposure of the cells to dexamethasone. The cellular glucose uptake was determined by glucose oxidase-peroxidase assay. The free fat acid (FFA) concentration was detected by colorimetric method. Secreted adiponectin were measured by ELISA. The protein levels of peroxisome proliferator-activated receptor γ (PPARγ) and protein tyrosine phosphatase 1B (PTP1B) in insulin-resistant adipocytes were analyzed by Western blotting. RESULTS：Compared with medium group, asiatic acid increased the proliferation of 3T3-L1 preadipocytes and inhibited their differentiation at a concentration range of 10~100 μmol/L (P<0.05 or P<0.01). At concentrations of 30 μmol/L and 100 μmol/L, asiatic acid enhanced cellular glucose uptake in the insulin-resistant adipocytes both in basic and insulin-stimulation states. Asiatic acid decreased FFA production (P<0.05), and down-regulated the protein expression of PTP1B (P<0.05, or P<0.01). However, no effect on the secretion of adiponectin and the protein expression of PPARγ was observed (P>0.05). CONCLUSION：Asiatic acid enhances glucose uptake and inhibits FFA production in insulin-resistant adipocytes via down-regulating the protein expression of PTP1B, all of which play the roles of increasing insulin signaling sensitivity to improve insulin resistance.