Red Pepper (Capsicum annuumL.) Seed Extract Decreased Hepatic Gluconeogenesis and Increased Muscle Glucose UptakeIn Vitro

Red pepper seed, a by-product of red pepper, has been reported to have antioxidant and antiobesity activities. However, its role in diabetes has not yet been highly investigated. Glucose homeostasis is mainly maintained by insulin, which suppresses glucose production in the liver and enhances glucose uptake in peripheral tissues. In this study, we investigated the underlying mechanisms through which red pepper seed extract (RPSE) affects glucose production in AML12 hepatocytes and glucose uptake in C2C12 myotubes. RPSE reduced glucose production in a dose-dependent manner in AML12 cells. The levels of glucose 6 phosphatase, phosphoenolpyruvate carboxykinase, and critical enzymes for hepatic gluconeogenesis were decreased by RPSE. Gluconeogenesis regulating proteins, Akt and forkhead box protein O1, were also activated by RPSE. In addition, RPSE increased glucose uptake in C2C12 via inducing translocation of glucose transporter type 4 from cytosol to plasma membrane. Analysis of the insulin-dependent pathway showed that the activities of insulin receptor substrate 1, phosphatidylinositol 3-kinase, and Akt were significantly stimulated by RPSE. In conclusion, RPSE might improve glucose homeostasis by reducing hepatic gluconeogenesis and increasing peripheral glucose uptake. Results obtained also suggest that RPSE can be a compelling antidiabetic nutraceutical.