title: Differential regulation of the biosynthesis of glucose transporters by the PI3-K and MAPK pathways of insulin signaling by treatment with novel compounds from Liriope platyphylla.
abstract: The insulin signaling pathway, involving protein kinase B (PKB) and mitogen-activated protein kinase (MAPK), mediates the biological response to insulin and several growth factors and cytokines. To investigate the correlation between glucose transporter (Glut) biosynthesis and the insulin signaling pathway activated by novel compounds of Liriope platyphylla (LP9M80-H), alterations in Glut and key protein expression in the insulin signaling pathway were analyzed in the liver and brain of ICR mice treated with LP9M80-H. An in vitro assay showed that the highest level of insulin concentration was observed in the LP9M80-H-treated group, followed by the LP-H, LP-M, LP-E, and LP9M80-C-treated groups. Therefore, LP9M80-H was selected for use in studying the detailed mechanism of the insulin signaling pathway in animal systems. In an in vivo experiment, LP9M80-H induced a significant increase in glucose levels and a decrease of insulin concentration in the blood of mice, while their body weight remained constant over 5 days. The expression level of Glut-3 was down-regulated in the liver, or maintained at the same level in the brain of LP9MH80-H-treated mice. These changes corresponded to the phosphorylation of the p38 protein rather than to ERK and JNK in the MAPK signaling pathway. In addition, the expression level of Glut-1 increased significantly after LP9MH80-H treatment of both insulin target tissues in mice. Western blot analysis showed that Akt in the PI3-K pathway mainly participated in Glut-1 biosynthesis. Thus, these results suggest the possibility that the LP9M80-H-induced regulation of Glut-1 and Glut-3 biosynthesis may be mediated by the Akt and p38 MAPK signaling of the insulin signaling pathway in the liver and brain of mice.
authors.affiliation: College of Natural Resources and Life Science, Pusan National University, Miryang 627-706, Republic of Korea.
authors.forename: Yoen Kyung
authors.initials: YK
authors.lastname: Lee
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Kim
authors.forename: So Hee
authors.initials: SH
authors.lastname: Nam
authors.forename: Jun Seo
authors.initials: JS
authors.lastname: Goo
authors.forename: Sun Il
authors.initials: SI
authors.lastname: Choi
authors.forename: Young Hwan
authors.initials: YH
authors.lastname: Choi
authors.forename: Chang Jun
authors.initials: CJ
authors.lastname: Bae
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Woo
authors.forename: Jung Sik
authors.initials: JS
authors.lastname: Cho
authors.forename: Dae Youn
authors.initials: DY
authors.lastname: Hwang
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051274:Glucose Transporter Type 3 / Q000096:biosynthesis*; D006801:Humans; D007328:Insulin / Q000097:blood*; D031424:Liriope Plant / Q000737:chemistry*; D008099:Liver / Q000166:cytology / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D008813:Mice, Inbred ICR; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D004365:Drugs, Chinese Herbal; D051274:Glucose Transporter Type 3; D007328:Insulin; C495689:Slc2a3 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048670:MAP Kinase Kinase 4