Beneficial Impact of Zingiber zerumbet on Insulin Sensitivity in Fructose-Fed Rats

Zingiber zerumbet (L) Smith (Zingiberaceae), commonly known as the pinecone or shampoo ginger, is distributed in many parts of Asia. It has been demonstrated that the aqueous extract of Z. zerumbet exerted a potential blood glucose lowering effect in normoglycemic and streptozotocin-induced hyperglycemic rats. The present study was undertaken to clarify whether the ethanol extract of Zingiber zerumbet (EEZZ) is effective in improving insulin resistance. Insulin resistance was induced in rats by feeding a high-fructose diet for six weeks. Thereafter, rats were maintained on the same diet and treated with oral EEZZ or pioglitazone once daily for eight weeks. At the end of treatment, the degree of basal insulin resistance was measured by homeostasis model assessment (HOMA-IR). Insulin sensitivity was calculated using the composite whole body insulin sensitivity index (ISIcomp). Protein expression was evaluated by immunoblotting. Phytochemicals in EEZZ were determined through liquid chromatography-tandem mass. Not only curcumin but also quercetin and kaempferol were abundant in EEZZ. EEZZ (300 mg/kg/day) displayed similar characteristics to pioglitazone (20mg/kg/day) in reducing HOMA-IR and elevating ISIcomp aswell as enhancing hepatic glycogen accumulation. Elevated glycosylated hemoglobin levels and hyperinsulinemia were ameliorated by EEZZ. Further, EEZZ enhanced the action of insulin on muscle glucose transporter subtype 4 translocation and attenuated hepatic phosphoenolpyruvate carboxykinase expression. This study suggests that EEZZ may be an ethnomedicine for improving insulin sensitivity.