Atractylodes macrocephala Koidz. and Cuscuta chinensis Lam. extract relieves insulin resistance via PI3K/Akt signalling in diabetic Drosophila

Type-2 diabetes mellitus (T2DM) is mainly characterized by insulin resistance (IR) induced by hyperglycaemia and insufficient insulin secretion. We employed a diabetic fly model to examine the effect and molecular mechanism of Atractylodes macrocephala Koidz. and Cuscuta chinensis Lam. (AMK–CCL) extract as traditional Chinese medicine in treating IR and T2DM. The contents of the active ingredients (rhamnose, xylose, mannose, and hyperoside) in AMK–CCL extract were determined by high-performance liquid chromatography. Wild-type (Cg-GAL4/+) or diabetic (Cg > InRK1409A) Drosophila flies were divided into the control group or metformin group and AMK–CCL (0.0125, 0.025, 0.05, 0.1 g/ml) groups. Food intake, haemolymph glucose and trehalose, protein, weight, triglycerides (TAG), and glycogen were measured to assess glycolipid metabolism. Phosphatidylinositol-3-kinase (PI3K)/Akt signalling was detected using fluorescent reporters [tGPH, Drosophila forkhead box O (dFoxO)–green fluorescent protein (GFP), Glut1–GFP, 2-NBDG] in vivo. Glut1/3 mRNA levels and Akt phosphorylation levels were detected by quantitative polymerase chain reaction and western blotting, respectively, in vitro. AMK–CCL extract contained 0.038 % rhamnose, 0.017 % xylose, 0.69 % mannose, and 0.039 % hyperoside. AMK–CCL at 0.0125 g/mL significantly suppressed the increase in circulating glucose, and the decrease in body weight, TAG, and glycogen contents of diabetic flies. AMK–CCL improved PI3K activity, Akt phosphorylation, Glut1/3 expression, and glucose uptake in diabetic flies, and also rescued diabetes-induced dFoxO nuclear localisation. These findings indicate that AMK–CCL extract ameliorates IR-induced diabetes via the PI3K/Akt signalling pathway, providing an experimental basis for clinical treatment.