Influence of insulin on beta-endorphin plasma levels in obese and normal weight subjects.
OBJECTIVE
To establish the possible role of hyperinsulinemia in the elevation of plasma beta-endorphin (beta-EP) levels observed in obese patients after an oral glucose load.


METHODS
Oral glucose tolerance test (OGTT) and euglycemic-hyperinsulinemic clamp.


METHODS
Two groups of six (age: 22-39 y, BMI: 30-48 kg/m2) and eight obese men (age: 18-37 y, BMI: 35-45 kg/m2), respectively, and five normal weight healthy men (age: 22-30 y, BMI 22-23 kg/m2).


METHODS
Glucose, insulin and beta-EP levels at baseline and every 30 min until 180 min during the OGTT; glucose, insulin, C-peptide and beta-EP concentrations at baseline and in steady state condition (i.e. during the last 30 min of insulin infusion) in the euglycemic-hyperinsulinemic clamp studies.


RESULTS
In the six obese patients undergoing the OGTT a significant elevation of beta-EP plasma levels was observed between 60 and 90 min after glucose ingestion. In the clamp studies no significant differences in beta-EP plasma levels, blood glucose and serum insulin were observed between obese and normal weight subjects both at baseline and at steady state. A markedly diminished insulin sensitivity along with a lower inhibition of C-peptide during insulin infusion was observed in obese patients compared to control subjects.


CONCLUSIONS
A rise in serum insulin levels unaccompanied by a concomitant increase in blood glucose concentration is unable to elicit a beta-EP response in obese patients.
Brunani
A
A
IRCCS Ospedale San Giuseppe, Piancavallo (Verbania), Italy.
Pincelli
A I
AI
Pasqualinotto
L
L
Tibaldi
A
A
Baldi
G
G
Scacchi
M
M
Fatti
L M
LM
Cavagnini
F
F
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000097:blood; D005947:Glucose / Q000494:pharmacology; D005951:Glucose Tolerance Test; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood / Q000503:physiopathology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009765:Obesity / Q000097:blood*; D001615:beta-Endorphin / Q000097:blood*
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D001615:beta-Endorphin; D005947:Glucose