Gegen Qinlian decoction activates PPARγ to ameliorate adipocytic insulin resistance in diabetic SD rats and IR-3T3-L1 adipocytes

Abstract

To investigate the effects of Gegen Qinlian decoction(GQD) in improving adipocytic insulin resistance(IR) and explore its related molecular mechanism. Diabetic rats models were induced by high glucose and high-fat diet with a small dose of streptozotocin, and after GQD treatment for 3 months, blood biochemical indexes such as fasting blood-glucose(FBG), insulin, glycosylated serum protein(GSP) and HOMA-IRI were detected and assessed. After the total RNA was extracted from the adipose tissue of diabetic SD rats, PPARγ, ADPN, GLUT4, GLUT2, ACACA and ACACB mRNA expression levels were separately detected by qPCR. Then, stable IR-3T3-L1 adipocyte model was built with 1 μmol•L⁻¹ dexamethasone. After the cell viability was detected by CCK-8 assay, 5%, 10% and 15% GQD-containing serum(GQD-CS) were respectively used to treat IR-3T-L1 adipocytes for 24 h. The contents of glucose, nonesterified fatty acid(NEFA) and adiponectin in cell culture supernatants were separately detected whereas the intracellular triglyceride(TG) contents of IR-3T3-L1 adipocytes were also measured. The ADPN, PPARγ and GLUT4 mRNA and protein expression levels were respectively detected by qPCR and Western blot in IR-3T3-L1 adipocytes. Results showed that GQD significantly decreased fasting blood glucose, insulin and GSP(P<0.01), and down-regulated HOMA-IRI(P<0.05) after the high-fat diet/streptozotocin-induced diabetic SD rats were treated for three months, with a good hypoglycemic effect. Moreover, PPARγ, ADPN, GLUT4, GLUT2, ACACA and ACACB mRNA expression levels were significantly elevated in the adipose tissue of GQD-treated diabetic SD rats. The 5%, 10% and 15% GQD-CS significantly increased glucose consumption of IR-3T3-L1 adipocytes at 24 h treatment(P<0.01), significantly decreased the intracellular TG content (P<0.01), and down-regulated NEFA to a certain extent but not significantly. Moreover, GQD-CS significantly up-regulated GLUT4 and ADPN expression. The results indicated that GQD could activate PPARγ to ameliorate adipocytic insulin resistance in the diabetic SD rats and IR-3T3-L1 adipocytes.