Physiological elevations of plasma beta-endorphin alter glucose metabolism in obese, but not normal-weight, subjects.
The present study was undertaken to evaluate the metabolic and hormonal responses to physiologic elevations of plasma beta-endorphin concentrations in both normal-weight and obese healthy subjects. The infusion of synthetic human beta-endorphin (4.5 ng/kg/min) produced the following: (1) in normal-weight subjects, no significant change of plasma glucose and pancreatic hormones (insulin, C-peptide, and glucagon), a significant plasma free fatty acids (FFA) increase, and a suppression of glycerol plasma levels; (2) in obese subjects, significant increases of glucose, insulin, C-peptide, and glucagon, a progressive decline of circulating FFA, and no change in glycerol plasma levels. In obese subjects, the intravenous administration of naloxone, given as a bolus (5 mg injected in 5 minutes) before the start of beta-endorphin infusion, reduced the plasma glucose response to the opioid by approximately half, annulled the pancreatic hormonal responses, and also reduced the FFA, but not glycerol, response. In normal-weight subjects, naloxone pretreatment did not induce any change of the flat glucose and hormonal responses to beta-endorphin, but reversed its effects on circulating FFA and glycerol. These data suggest that physiological elevations of plasma beta-endorphin concentrations produce metabolic and hormonal effects in obese subjects significantly different from those occurring in normal-weight subjects; these effects are partially naloxone-sensitive, suggesting the mediation of endogenous opioid receptors.
Giugliano
D
D
Cattedra di Diabetologia, Prima Facoltà di Medicina, Università di Napoli, Italia.
Cozzolino
D
D
Salvatore
T
T
Ceriello
A
A
Torella
R
R
Franchimont
P
P
Lefebvre
P J
PJ
D'Onofrio
F
F
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight; D002096:C-Peptide / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood; D005951:Glucose Tolerance Test; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood; D007700:Kinetics; D008297:Male; D009765:Obesity / Q000097:blood*; D012016:Reference Values; D001615:beta-Endorphin / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology*
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D001615:beta-Endorphin; D005934:Glucagon