Activation of muscarinic M-1 cholinoceptors by curcumin to increase glucose uptake into skeletal muscle isolated from Wistar rats.
Curcumin, an active principle contained in rhizome of Curcuma longa, has been mentioned to show merit for diabetes through its anti-oxidative and anti-inflammatory properties. In the present study, we found that curcumin caused a concentration-dependent increase of glucose uptake into skeletal muscle isolated from Wistar rats. This action was inhibited by pirenzepine at concentration enough to block muscarinic M-1 cholinoceptor (M(1)-mAChR). In radioligand binding assay, the binding of [(3)H]-pirenzepine was also displaced by curcumin in a concentration-dependent manner. In the presence of inhibitors for PLC-PI3K pathway, either U73122 (phospholipase C inhibitor) or LY294002 (phosphoinositide 3-kinase inhibitor), curcumin-stimulated glucose uptake into skeletal muscle was markedly reduced. In Western blotting analysis, the membrane protein level of glucose transporter 4 (GLUT4) increased by curcumin was also reversed by blockade of M(1)-mAChR or PLC-PI3K pathway in a same manner. In conclusion, the obtained results suggest that curcumin can activate M(1)-mAChR at concentrations lower than to scavenge free radicals for increase of glucose uptake into skeletal muscle through PLC-PI3-kinase pathway.
Cheng
Tse-Chou
TC
Department of Urology, Chi-Mei Medical Center, Yong Kang, Taiwan, ROC.
Lin
Chian-Shiung
CS
Hsu
Chih-Chieh
CC
Chen
Li-Jen
LJ
Cheng
Kai-Chun
KC
Cheng
Juei-Tang
JT
D000818:Animals; D003474:Curcumin / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1 / Q000819:agonists* / Q000378:metabolism*
D043643:Receptor, Muscarinic M1; D003474:Curcumin; D005947:Glucose