Effects And Action Mechanism Of Daidzin On Improving Insulin Resistance In3T3-L1Adipocytes

Objective: To investigate the effects of Daidzin on the proliferation anddifferentiation of3T3-L1preadipocytes, and glucose and lipid metabolism of insulinresistant (IR) adipocytes and its potential mechanism.Methods: The3T3-L1preadipocytes were differentiated into adipocytes with DMEMcontaining dexamethasonin, insulin and isobutyl-methylxanthine, and then dividedinto control group, medium group, drug groups and positive group. The proliferationof3T3-L1preadipocytes was tested by MTT assay and its differentiation wasdetermined by oil red O staining when cells were treated with Daidzin (0.1,0.3,1,3,10μM) for48h. The IR model was induced by1μM dexamethasonin. Cellularglucose consumption was determined by GOD-POD assay, the content of fatty acid(FFA) by colorimetric method and the adiponectin secretion by ELISA. Theexpression of PPARγ, adiponectin, IRS-1, GLUT4and PTP1B mRNA in IRadipocytes were analyzed by qPCR. The PPARγ-transactivation activity wasexamined by using a GAL4chimeric receptor assay and the activity of PTP1B bycolorimetric method.Results:1. Compared with medium group, Daidzin increased the proliferation of3T3-L1preadipocytes at3,10μM significantly (P<0.05or P<0.01), while inhibited itsdifferentiation significantly when cells were treated with0.1~1μM (P<0.05orP<0.01).2. Compared with medium group, the glucose consumption of model group wassignificantly reduced by42.5%when cells were treated with1μM dexamethasoninfor96h (P<0.01). The IR model was established successfully.3. Compared with the model group, Daidzin enhanced glucose consumption both inbasic and insulin stimulation states in a dose-dependent manner when cells weretreated at0.3~10μM (P<0.05or P<0.01) and decreased FFA production at0.1~10μM (P<0.05or P<0.01).4. Compared with medium group, Daidzin significantly inhibited PTP1B activity (P<0.05or P<0.01), in which could be up to37.67%in the presence of1μM(P<0.01).Also, it showed some effects on PPARγ, but their fold induction were muchlower than rosiglitazone (P<0.05or P<0.01).5. Compared with model group, Daidzin significantly increased the secretion ofadiponectin, up-regulated the expression of adiponectin, IRS-1, GLUT4mRNA anddown-regulated the expression of PTP1B mRNA (P<0.05or P<0.01), but had noobvious effect on the expression of PPARγ mRNA (P>0.05).Conclusion1. Daidzin could enhance glucose consumption and adiponectin secretion of IRadipocytes, but inhibit its differentiation and FFA production, all of which suggest thatit could improve IR.2. Daidzin may improve IR in3T3-L1adipocytes through inhibiting PTP1Bactivity and down-regulating the expression of PTP1B gene.