Normal inhibition by somatostatin of glucose-stimulated B cell secretion in the obese subjects.
Aim of the present study was to evaluate whether the inhibitory effect of somatostatin on pancreatic B-cell secretion is normal in nondiabetic obese subjects. For this purpose plasma C-peptide concentrations were measured in 10 nondiabetic obese subjects and 10 nonobese healthy controls during a 4-h hyperglycemic (11 mmol/l) glucose clamp. Somatostatin was infused (2.5 nmol/min) during the third hour of the study period in order to inhibit glucose-stimulated B-cell secretion. Fasting C-peptide averaged 0.46 +/- 0.04 nmol/l (mean +/- SEM) in nonobese subjects, and 0.85 +/- 0.08 nmol/l in obese patients (P less than 0.001). In the period 0-120 min the area under the plasma C-peptide curve was significantly higher in obese than in nonobese subjects (292 +/- 23 vs. 230 +/- 17 nmol/l x 120 min, P less than 0.05), however, in the last 20 min of the glucose infusion period without somatostatin (100-120 min) plasma C-peptide was not significantly different in the two groups (2.94 +/- 0.32 nmol/l in nonobese subjects and 3.21 +/- 0.19 nmol/l in obese patients, p = NS). During somatostatin infusion while maintaining hyperglycemia, plasma C-peptide decreased in both groups, and in the period 160-180 min it averaged 0.89 +/- 0.12 nmol/l in control subjects and 0.93 +/- 0.08 nmol/l in obese patients (P = NS), with a percent reduction similar in the two groups (70 +/- 2% in controls and 71 +/- 2% in obese patients). After discontinuing somatostatin infusion, plasma C-peptide increased to concentrations which were higher in obese than in nonobese subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Bonora
E
E
Cattedra di Malattie del Metabolismo, Università di Verona, Italy.
Moghetti
P
P
Zancanaro
C
C
Cigolini
M
M
Querena
M
M
Cacciatori
V
V
Zenere
M
M
Corgnati
A
A
Muggeo
M
M
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D013004:Somatostatin / Q000494:pharmacology*
D001786:Blood Glucose; D002096:C-Peptide; D013004:Somatostatin