Planta Med 2006; 72(1): 9-13
DOI: 10.1055/s-2005-916177
Original Paper
Pharmacology
© Georg Thieme Verlag KG Stuttgart · New York

Mediation of β-Endorphin by Ginsenoside Rh2 to Lower Plasma Glucose in Streptozotocin-Induced Diabetic Rats

Dar-Ming Lai1 , Yong-Kwang Tu1 , I-Min Liu2 , Pei-Feng Chen3 , Juei-Tang Cheng3
  • 1Neurosurgical Division, Department of Surgery, National Taiwan University Hospital, Taipei City, Taiwan, R.O.C.
  • 2Department of Pharmacy, Tajen University, Yen-Pou, Ping Tung Shien, Taiwan, R.O.C.
  • 3Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan, R.O.C.
Further Information

Publication History

Received: April 1, 2005

Accepted: May 27, 2005

Publication Date:
25 October 2005 (online)

Abstract

We investigated the plasma glucose-lowering mechanism(s) of Rh2, a ginsenoside derived from Panax ginseng, in rats with streptozotocin-induced diabetes (STZ-diabetic rats). After intravenous injection over 120 min into fasting STZ-diabetic rats, Rh2 decreased plasma glucose in a dose-dependent manner. In parallel to the lowering of plasma glucose, an increase of plasma β-endorphin-like immunoreactivity was observed. In addition, naloxone and naloxonazine at doses sufficient to block opioid μ-receptors inhibited the plasma glucose-lowering action of Rh2 in genetically wild-type, diabetic mice. In contrast, Rh2 failed to lower plasma glucose in opioid μ-receptor knockout diabetic mice. An increase in gene expression at both the mRNA and protein levels of glucose transporter subtype 4 (GLUT 4) was observed in soleus muscle obtained from STZ-diabetic rats treated with Rh2 three times daily for one day; this increase in expression was absent when opioid μ-receptors were blocked. In conclusion, our results suggest that ginsenoside Rh2 may lower plasma glucose in STZ-diabetic rats based on an increase in β-endorphin secretion that activates opioid μ-receptors thereby resulting in an increased expression of GLUT 4.

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Professor Juei-Tang Cheng

Department of Pharmacology

College of Medicine

National Cheng Kung University

Tainan City

Taiwan 70101

R.O.C.

Fax: +886-6-238-6548

Email: jtcheng@mail.ncku.edu.tw