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Planta Med 2007; 73(10): 1054-1060
DOI: 10.1055/s-2007-981577
Pharmacology
Original Paper
© Georg Thieme Verlag KG Stuttgart · New York

Improvement of Insulin Sensitivity in Obese Zucker Rats by Myricetin Extracted from Abelmoschus moschatus

I-Min Liu1 , Thing-Fong Tzeng2 , Shorong-Shii Liou1 , Ting-Wei Lan1
  • 1Department of Pharmacy, Tajen University, Yanpu Shiang, Ping Tung Shien, Taiwan, R.O.C.
  • 2Department of Internal Medicine, Pao Chien Hospital, Ping Tung City, Taiwan, R.O.C.
Further Information

Publication History

Received: December 11, 2006 Revised: June 17, 2007

Accepted: June 22, 2007

Publication Date:
13 August 2007 (online)

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Abstract

In an attempt to develop new substances for treating insulin resistance, obese Zucker rats were employed to screen the effect of myricetin, an active principle of Abelmoschus moschatus (Malvaceae), on insulin resistance. Myricetin purified from the aerial portion of the plant was administered intravenously (i. v.) into animals. A dose-dependent decrease in the plasma glucose concentration of obese Zucker rats was observed 30 min following an i. v. injection. Moreover, repeated i. v. injection of myricetin (1 mg/kg) into obese Zucker rats 3 times daily for 1 week reduced the value of the glucose-insulin index, an index of insulin resistance calculated from the areas under the curve of glucose and insulin during the intraperitoneal glucose tolerance test. Additionally, repeated myricetin treatments overturned the inability of insulin to increase the expression of glucose transporter subtype 4 (GLUT 4) and to increase the protein levels and phosphorylation of insulin receptor substrate-1 (IRS-1) in soleus muscle of these obese rats. The inability of insulin to increase expression of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3-kinase) and to promote Akt serine phosphorylation in soleus muscle of these rats were also overturned by repeated myricetin treatments. These findings indicate that myricetin improves insulin sensitivity through increased post-receptor insulin signaling mediated by enhancements in IRS-1-associated PI3-kinase and GLUT 4 activity in muscles of obese Zucker rats. Myricetin might be used as a model substance for the development of antidiabetic compounds.

Key words

Akt - glucose transporter subtype 4 - insulin receptor - insulin receptor substrate-1 - myricetin - phosphatidylinositol 3-kinase - obese Zucker rat - Abelmoschus moschatus - Malvaceae

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I-Min Liu, Ph. D.

Department of Pharmacy

Tajen University

Yanpu Shiang

Ping Tung Shien

Taiwan

R.O.C.

Fax: +886-8-762-5308

Email: iml@mail.tajen.edu.tw

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