Abstract
The main objective of the study was to examine whether crocetin, a natural product from Gardenia jaminoides Ellis, has beneficial effects on the state of insulin resistance induced by dexamethasone in a rat model. Measured using the oral glucose tolerance tests (OGTT), male Wistar rats treated with subcutaneous dexamethasone (0.08 mg/kg/d) for 6 weeks exhibited reduced insulin sensitivity at weeks 2 and 4 and impaired glucose tolerance at week 4. In the dexamethasone-treated group, serum insulin, free fatty acids (FFA), triglyceride (TG) and tumor necrosis factor (TNF)-α levels were significantly increased at the end of the study. In addition, the hepatic glycogen content was reduced as indicated by periodic acid-Schiff (PAS) staining, and pancreatic islet β cells showed compensatory hyperactivity suggested by immunohistochemical (IHC) staining using an antibody against insulin. Treatment with crocetin (40 mg/kg/d) significantly attenuated all the described effects of dexamethasone. These results suggest that crocetin might prevent the development of dexamethasone-induced insulin resistance and related abnormalities in rats.
Abbreviations
AUC:area under the curve
CON:control
CRO(H):high-dose crocetin
CRO(L):low-dose crocetin
CRO:crocetin
DEX:dexamethasone
FFA:free fatty acids
GAUC:area under the glucose curve
HE:hematoxylin-eosin
IAUC:area under the insulin curve
IHC:immunohistochemical
ISI:insulin sensitivity index
MET:metformin
OGTT:oral glucose tolerance test
PAS:periodic acid-Schiff
TG:triglyceride
TNF:tumor necrosis factor
Key words
Crocetin - glucocorticoids - insulin resistance - impaired glucose tolerance - rats
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Zhiyu Qian
Department of Pharmacology
China Pharmaceutical University
P.O. Box 46
24 Tongjia Xiang
Nanjing 210009
People’s Republic of China
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Fax: +86-25-8327-1355
eMail: trueqianzhiyu@yahoo.com.cn
