Mediation of beta-endorphin by the isoflavone puerarin to lower plasma glucose in streptozotocin-induced diabetic rats.
We investigate the mechanism(s) of plasma glucose lowering action of puerarin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Puerarin at the effective dosage to lower higher plasma glucose increased plasma beta-endorphin-like immunoreactivity (BER) in STZ-diabetic rats. Both effects of puerarin were abolished by the pretreatment with prazosin. Also, puerarin enhanced BER release from isolated rat adrenal medulla in a concentration-dependent manner that can be abolished by prazosin. Moreover, bilateral adrenalectomy in STZ-diabetic rats eliminated the actions of puerarin including the plasma glucose lowering effect and plasma BER elevating effect. In addition, naloxone and naloxonazine inhibited the plasma glucose lowering action of puerarin. Unlike in wild-type diabetic mice, puerarin failed to lower the plasma glucose in opioid micro-receptor knockout diabetic mice. In conclusion, our results suggest that puerarin may activate alpha (1)-adrenoceptors on the adrenal gland to enhance the secretion of beta-endorphin to result in a decrease of plasma glucose in STZ-diabetic rats.
Department of Obstetrics and Gynaecology, School of Medicine, Nihon University, Tokyo City, Japan. jtcheng@mail.ncku.edu.tw
Wang-Chuan
WC
Chen
Satoshi
S
Hayakawa
Tatsuo
T
Yamamoto
Hui-Chen
HC
Su
I-Min
IM
Liu
Juei-Tang
JT
Cheng
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D007529:Isoflavones / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D029908:Pueraria; D051381:Rats; D017208:Rats, Wistar; D013311:Streptozocin; D001615:beta-Endorphin / Q000187:drug effects
D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007529:Isoflavones; D010936:Plant Extracts; D013311:Streptozocin; D001615:beta-Endorphin; C033607:puerarin