Five pentacyclic triterpenoids isolated from Campsis grandiflora were tested for insulin-mimetic and insulin-sensitizing activity. The compounds enhanced the activity of insulin on tyrosine phosphorylation of the IR (insulin receptor) β-subunit in CHO/IR (Chinese-hamster ovary cells expressing human IR). Among the compounds tested, CG7 (ursolic acid) showed the greatest enhancement and CG11 (myrianthic acid) the least. We characterized the effect of CG7 further, and showed that it acted as an effective insulin-mimetic agent at doses above 50 μg/ml and as an insulin-sensitizer at doses as low as 1 μg/ml. Additional experiments showed that CG7 increased the number of IRs that were activated by insulin. This indicates that a major mechanism by which CG7 enhances total IR auto-phosphorylation is by promoting the tyrosine phosphorylation of additional IRs. CG7 not only potentiated insulin-mediated signalling (tyrosine phosphorylation of the IR β-subunit, phosphorylation of Akt and glycogen synthase kinase-3β), but also enhanced the effect of insulin on translocation of glucose transporter 4 in a classical insulin-sensitive cell line, 3T3-L1 adipocytes. The results of the present study demonstrate that a specific pentacyclic triterpenoid, CG7, exerts an insulin-sensitizing effect as an IR activator in CHO/IR cells and adipocytes. The enhancement of insulin activity by CG7 may be useful for developing a new class of specific IR activators for treatment of Type 1 and Type 2 diabetes.
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Research Article|
March 26 2007
Insulin-mimetic and insulin-sensitizing activities of a pentacyclic triterpenoid insulin receptor activator
Seung H. Jung;
Seung H. Jung
*Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Korea
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Yun J. Ha;
Yun J. Ha
*Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Korea
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Eun K. Shim;
Eun K. Shim
*Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Korea
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Soo Y. Choi;
Soo Y. Choi
*Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Korea
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Jing L. Jin;
Jing L. Jin
†Natural Product Research Institute, Seoul National University, Seoul 110-460, Korea
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Hye S. Yun-Choi;
Hye S. Yun-Choi
†Natural Product Research Institute, Seoul National University, Seoul 110-460, Korea
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Jong R. Lee
Jong R. Lee
1
*Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul 120-750, Korea
1To whom correspondence should be addressed (email jrlee@ewha.ac.kr).
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Publisher: Portland Press Ltd
Received:
July 25 2006
Revision Received:
December 19 2006
Accepted:
January 04 2007
Accepted Manuscript online:
January 04 2007
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2007
Biochem J (2007) 403 (2): 243–250.
Article history
Received:
July 25 2006
Revision Received:
December 19 2006
Accepted:
January 04 2007
Accepted Manuscript online:
January 04 2007
Citation
Seung H. Jung, Yun J. Ha, Eun K. Shim, Soo Y. Choi, Jing L. Jin, Hye S. Yun-Choi, Jong R. Lee; Insulin-mimetic and insulin-sensitizing activities of a pentacyclic triterpenoid insulin receptor activator. Biochem J 15 April 2007; 403 (2): 243–250. doi: https://doi.org/10.1042/BJ20061123
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