Feedback inhibition of insulin secretion in type 2 diabetes.
1. The purpose of the present study was to examine the ability of insulin to inhibit its own secretion in type 2 diabetes independently of the prevailing plasma glucose concentration. 2. The responses of the plasma C-peptide concentration to sustained hyperinsulinaemia were assessed during a 200 min isoglycaemic clamp study in 14 patients with type 2 diabetes and seven age- and weight-matched control subjects. The arterialized venous plasma glucose concentration was clamped at approximately 0.3 mmol/l below each subject's own basal level and was not permitted to rise above the basal level. 3. In the fasting state, the plasma C-peptide concentration was slightly, but not significantly, higher in the diabetic patients than in the control subjects (667 versus 413 pmol/l, respectively, P = 0.07), but it remained significantly higher in the diabetic patients during the clamp studies in absolute terms (minimum plasma C-peptide concentration 400 pmol/l in diabetic patients versus 151 pmol/l in control subjects, P less than 0.05) and was suppressed to a lesser extent when expressed as a percentage change from basal (35.8% in diabetic patients versus 59.4% in control subjects, P less than 0.01). 4. In order to investigate whether a high plasma glucose concentration was maintaining the plasma C-peptide concentration in the diabetic patients, six of these patients underwent a second clamp study at euglycaemia (plasma glucose concentration 5.2 mmol/l). Under these conditions, the plasma C-peptide concentration was suppressed to the same extent as in the control subjects (from 623 to 195 pmol/l, a change of 62.7%).(ABSTRACT TRUNCATED AT 250 WORDS)
Baynes
C
C
Unit of Metabolic Medicine, St Mary's Hospital Medical School, London.
Anyaoku
V
V
Johnston
D G
DG
Elkeles
R S
RS
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000502:physiology; D002096:C-Peptide / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D005246:Feedback / Q000502:physiology; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin