Study On The Preventive And Therapeutic Effects Of Kaempferol On Insulin Resistance And ITS Mechanism

Objective Using high glucose and high fat combined with small dose of streptozotocin to rat establish type 2 diabetes model with insulin resistance, observation the influence of kaempferol (Kaempferol, KPF) on the blood lipid level of rats, insulin resistance index, and hepatic IRS-1 protein expression, and explore the mechanism of KPF on type 2 diabetes with insulin resistance.Methods Male Sprague-Dawley (SD) rats were fed with high fat and sugar diet for 6 weeks and given 30mg/kg injection of streptozotocin to establish type 2 diabetic rats. SD rats were randomly divided into:normal control group, model group, low-dose KPF group (50 mg/kg), high-dose KPF group (150 mg/kg), positive control group (aspirin,100 mg/kg), which were given the high fat diet or normal feeding for 10 weeks, respectively. At 3 week and 9 weekend, fasting blood glucose, insulin release content immunosorbent assay fasting, calculating insulin sensitivity index。Glucose tolerance test (IPGTT) and hyperinsulinemic euglycemic clamp (HECT) detect the improvement of kaempferol on insulin sensitivity. The content of serum triglyceride (TG), cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), free fatty acid (FFA) were Detected. Effect of kaempferol on the key proteins expression which is related to insulin resistance in rats was detected by Western Blotting Technology:Insulin receptor substrate (IRS-1);inflammation related proteins expression: hepatic I kappa B kinase (IKK) and I kappa B kinase (IKK beta) protein expression and phosphorylation, nucleic acid and cytoplasmic nuclear factor kappa B (NF-κB); proinflammatory cytokines:tumor necrosis factor (TNF-a) and interleukin -6 (IL-6).Results 1. High glucose and high fat diet for 6 weeks combined with intraperitoneal injection of streptozotocin to establish 30mg/kg with type 2 diabetes rat model of insulin resistance, impaired fasting glucose in rat model>11.1mmol/L, success rate of the model is about 55%。2. At 10 weekend, serum lipid in model group increased significantly, kaempferol significantly decreased serum lipids group compared with model group; At the same time, the model group insulin levels and FFA significantly higher than normal group, and compared with model group, kaempferol group had a significantly lower insulin levels and FFA.3. Through the clamp test, The average glucose infusion rate (GIR) of diabetic model group (5.89±0.75 ml/kg/min) was significantly lower than that in normal control group (12.35±2.25 ml/kg/min), and high-dose kaempferol group (9.7±0.84 ml/kg/min) and small-dose kaempferol group (9.25±1.55 ml/kg/min) was significantly increased as compared with model group. Through insulin intolerance test and insulin resistance index, the insulin sensitivity in the model group was decreased significantly compared with the normal group, while that in kaempferol group was increased significantly as compared with model group.4. The phosphorylation protein expression of IKKa, IKKp and IRS-1 in the liver of diabetic group were significantly elevated, nucleic acid and cytoplasm of nuclear factor kappa B (NF-κB) increased, the proinflammatory cytokines tumor necrosis factor (TNF-a) and interleukin-6 (IL-6) level also increased. Compared with model group, kaempferol administered for 10 weeks can significantly reduce the phosphorylation protein expression of IKKa, IKKβ and IRS-1, decrease nucleic acid and cytoplasm of nuclear factor kappa B (NF-κB) expression, decrease tumor necrosis factor (TNF-a) and interleukin -6 (IL-6) protein expression.Conclusion 1、Using high glucose and high fat combined with small dose of streptozotocin to rat establish rat model of type 2 diabetes characterized by insulin resistance successfully.2、Kaempferol has good effect on biochemical indicators such as serum lipids in model rats.3、Kaempferol can significantly improve insulin sensitivity in model rats, has good preventive and therapeutic effects on insulin resistance.4、Kaempferol improving insulin sensitivity in model rats may be through the regulation of insulin receptor substrate-1 (IRS-1) protein, its mechanism may be related to the regulation of IKK/NF-κB signaling pathway.