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Open Access Research article

Peroxisome proliferator-activated receptor activating hypoglycemic effect of Gardenia jasminoides Ellis aqueous extract and improvement of insulin sensitivity in steroid induced insulin resistant rats

Ying-I Chen1, Yu-Wen Cheng23, Chung-Yuh Tzeng24, Yu-Chen Lee5, Yaw-Nan Chang6, Shih-Chieh Lee7, Chin-Chun Tsai89, Jaw-Chyun Chen10, Jason Tze-Cheng Tzen1* and Shih-Liang Chang105*

Author Affiliations

1 Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan

2 College of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan

3 Department of Internal Medicine, Lee’s General Hospital, Miaoli, Taiwan

4 Department of Orthopedics, Taichung Veterans General Hospital, Taichung City, Taiwan

5 Department of Acupuncture, China Medical University Hospital and School of Chinese Medicine, China Medical University, Taichung, Taiwan

6 Department of Biotechnology, National Formosa University, Yunlin County, Taiwan

7 Department of BioIndustry technology, Da-Yeh University, Changhua County, Taiwan

8 Chinese Medicine Department E-D Hospital, I-Shou University, Kaohsiung, Taiwan

9 School of Chinese Medicine for Post-Baccalaureate, I-Shou University, Kaohsiung, Taiwan

10 Department of Medicinal Botanicals and Health Applications, Da-Yeh University, Changhua, Taiwan

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BMC Complementary and Alternative Medicine 2014, 14:30  doi:10.1186/1472-6882-14-30

Published: 18 January 2014

Abstract

Background

The active components of Gardenia (Gardenia jasminoides Ellis, GJ) exhibit a hypoglycemic effect by improving insulin secretion and lowering plasma lipids. In the present study, we fed a water extract of gardenia to steroid-induced insulin-resistant (SIIR) rats and observed changes in signaling proteins in order to elucidate the mechanisms of the insulin-sensitizing effect of GJ and evaluate its possibility as an insulin-sensitizing agent.

Methods

Normal Wistar rats were randomly divided into a control group (i.e., saline) and experimental groups (GJ 100 and 200 mg/kg). Blood samples were taken at 0, 30, and 60 min for plasma glucose assay in order to determine the optimal dose to induce the hypoglycemic effect. SIIR rats were then randomly divided into a control group (i.e., saline) and an experimental group (optimal dose of gardenia extract) to observe the insulin-sensitizing effect of the extract. Finally, western blot analysis was performed to detect intracellular signaling proteins to elucidate the mechanisms of the insulin-sensitization effect of GJ.

Results

The normal Wistar rats in the GJ 200 mg/kg group exhibited significant hypoglycemic activity. Meanwhile, the SIIR rats had higher plasma glucose levels than normal rats. There was no obvious change in insulin level, but the insulin sensitivity index and homeostasis model assessment index were significantly elevated. Meanwhile, a significant hypoglycemic effect was observed with GJ 200 mg/kg. In addition, intracellular signaling proteins including insulin receptor substrate-1 (IRS-1) and peroxisome proliferator-activated receptor (PPARγ) were elevated in muscle cells.

Conclusions

The optimal dose of GJ aqueous extract of 200 mg/kg exerts a PPARγ-activating hypoglycemic effect and improves insulin resistance in SIIR rats. Therefore, it is a potential insulin-sensitizing agent in type 2 diabetes mellitus with insulin resistance.

Keywords:
Gardenia; Blood glucose; Insulin resistance; Peroxisome proliferator-activated receptor