Increase of beta-endorphin secretion by syringin, an active principle of Eleutherococcus senticosus, to produce antihyperglycemic action in type 1-like diabetic rats.
We employed streptozotocin-induced diabetic rats (STZ-diabetic rats) as type 1 diabetes-like animal models to investigate the mechanism(s) of antihyperglycemic action produced by syringin, an active principle purified from the rhizome and root part S of ELEUTHEROCOCCUS SENTICOSUS (Araliaceae). Bolus intravenous (i. v.) injection of syringin dose-dependently decreased the plasma glucose of STZ-diabetic rats in 30 minutes in a way parallel to the increase of plasma beta-endorphin-like immunoreactivity (BER). Syringin enhanced BER release from the isolated adrenal medulla of STZ-diabetic rats in a concentration-dependent manner from 0.001 to 10 micromol/l. Bilateral adrenalectomy in STZ-diabetic rats eliminated the activities of syringin (1 mg/kg, i. v.) including the plasma glucose-lowering effect and the plasma BER-elevating effect. Also, syringin failed to lower plasma glucose in the presence of micro-opioid receptor antagonists and/or in the micro-opioid receptor knockout diabetic mice. In conclusion, the obtained results suggest that syringin can enhance the secretion of beta-endorphin from adrenal medulla to stimulate peripheral micro-opioid receptors resulting in a decrease of plasma glucose in diabetic rats lacking insulin.
Niu
H-S
HS
Graduate Institute of Pharmacognosy, College of Pharmacy, Taipei Medical University, Taipei City, Taiwan, ROC.
Hsu
F-L
FL
Liu
I-M
IM
Cheng
J-T
JT
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000315:Adrenalectomy; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy*; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy*; D028001:Eleutherococcus / Q000737:chemistry*; D005960:Glucosides / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D006943:Hyperglycemia / Q000188:drug therapy*; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D007275:Injections, Intravenous; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010666:Phenylpropionates / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D008517:Phytotherapy; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000172:deficiency; D013311:Streptozocin; D014020:Tissue Extracts; D001615:beta-Endorphin / Q000378:metabolism*
D001786:Blood Glucose; D005960:Glucosides; D007004:Hypoglycemic Agents; D010666:Phenylpropionates; D017450:Receptors, Opioid, mu; D014020:Tissue Extracts; D013311:Streptozocin; D001615:beta-Endorphin; C028305:syringin