Protein tyrosine phosphatase 1B (PTP1B) is an established therapeutic target for type 2 diabetes mellitus (T2DM) and obesity. The aim of this study was to investigate the inhibitory activity of Magnolia officinalis extract (ME) on PTP1B and its anti-T2DM effects. Inhibition assays and inhibition kinetics of ME were performed in vitro. 3T3-L1 adipocytes and C2C12 myotubes were stimulated with ME to explore its bioavailability in cell level. The in vivo studies were performed on db/db mice to probe its anti-T2DM effects. In the present study, ME inhibited PTP1B in a reversible competitive manner and displayed good selectivity against PTPs in vitro. Furthermore, ME enhanced tyrosine phosphorylation levels of cellular proteins, especially the insulin-induced tyrosine phosphorylations of insulin receptor β-subunit (IRβ) and ERK1/2 in a dose-dependent manner in stimulated 3T3-L1 adipocytes and C2C12 myotubes. Meanwhile, ME enhanced insulin-stimulated GLUT4 translocation. More importantly,... See full list on Diabetes mellitus (DM) is a chronic disease accompanied by a series of metabolic disorders due to insulin deficiency or impaired insulin aceasing globally. According to the latest data from the International Diabetes Federation (IDF), 382 million people are living with diabetes in 2013, and this figure will rise up to 592 million by 2035 [1 1. International Diabetes Federation, IDF Diabetes Atlas, IDF, 6th edition, 2013, http:///diabetesatlas. See in References ]. Type 2 diabetes mellitus (T2DM) is the most common form, which accounts for around 90% of all diabetes worldwide. It is characterized by hyperglycemia and dyslipidaemia, due to a dysfunction of insulin to activate signaling pathways (insulin resistance) in metabolic target tissues [2 1. World Health Organization, 10 Facts about Diabetes, 2014, http:///features/factfiles/diabetes/en/. See in References , 3 1. B. J. Goldstein, “Protein-tyrosine phosphatases: emerging ta... See full list on All the dried magnolia barks were purchased from the Grand Pharmacy and were identified by Academy of Traditional Chinese Medicine and Chinese Med, China, asMagnolia officinalis Rehder & E. H. Wilson. Recombit proteins containing the catalytic domains of protein tyrosine phosphatase 1B (PTP1B), T cell protein tyrosine phosphatase (TCPTP), Src homology 2 (SH2) domain-containing tyrosine phosphatase 1 (SHP1), Src homology 2 (SH2) domain-containing tyrosine phosphatase 2 (SHP2), and hematopoietic protein tyrosine phosphatase (HePTP) were purified as previously described [15 1. X. Liang, W. Meng, T. Niu, Z. Zhao, and G. W. Zhou, “Expression, purification, and crystallization of the catalytic domain of protein tyrosine phosphatase SHP-1,” Journal of Structural Biology, vol. 120, no. 2, pp. 201–203, 1997. View at: Publisher Site| Google Scholar See in References –18 1. Z.-C. Zhu, M. Sun, X.-Y. Zhang et al., “Expression and characterization of cat... See full list on The inhibitory potency of ME on the PTP1B was evaluated according to the concentration-dependent inhibition curves as shown in Figure 1. ME was identified as a PTP1B inhibitor, with an IC50 of 55.96 μg/mL. Our results also demonstrated selectivity of ME towards PTPs (Table 1). We determined the content of magnolol and honokiol in ME by using HPLC-MS/MS. The content of magnolol and honokiol in ME is about 50% and 5%, respectively (Figure S1 available online in Supplementary Material at http:///10.1155/2015/139451). In order to further determine the inhibition mode of the ME on PTP1B, Lineweaver-Burk analysis was conducted. As shown in Figure 2, a common intercept of four Lineweaver-Burk lines on the -axis can beeases, suggesting that ME was a typical competitive inhibitor against PTP1B. The inhibitor constant (Ki) was a complex dissociation constant of enzyme with inhibitor. From Figure 2, −1/Ki value was determined from the -axis intercept... See full list on PTP1B has been identified as the main negative regulator of insulin signaling. Normally, insulin evokes a cascade of phosphorylation events, starting with the autophosphorylation of IR on multiple tyrosyl residues, which enhances IR kinase activity and leads to recruitment of IRS-1, followed by activation of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB also known as AKT), and finally glucose transporter 4 (GLUT4). Activated GLUT4 could translocate to membrane and thus improve the glucose uptake [21 1. N. J. Bryant, R. Govers, and D. E. James, “Regulated transport of the glucose transporter GLUT4,” Nature Reviews Molecular Cell Biology, vol. 3, no. 4, pp. 267–277, 2002. View at: Publisher Site| Google Scholar See in References , 22 1. M. F. White and C. R. Kahn, “The insulin signaling system,” Journal of Biological Chemistry, vol. 269, no. 1, pp. 1–4, 1994. View at: Google Scholar See in References ]. Current evidence indicates that PTP1B could dephosphorylate IR with... See full list on ME potently inhibits PTP1Bin vitroand greatly facilitates GLUT4 translocation from cytoplasm to cell membrane by activating insulin signaling pathway in both 3T3-L1 adipocytes and C2C12 myotubes. More importantly, ME can lower blood glucose in db/db mice. See full list on This work was supported ficially by the National Natural Science Foundation of China ) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (2013M541323). See full list on
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