Insulin deficiency in non-insulin-dependent diabetes.
A highly specific two-site immunoradiometric assay for insulin was used to measure the plasma insulin response to 75 g glucose administered orally to 49 patients with non-insulin-dependent diabetes (NIDDM). The plasma insulin concentration 30 min after glucose ingestion was lower in the diabetic patients than in matched controls for both non-obese (11-83 pmol/l vs 136-297 pmol/l, p less than 0.01) and obese subjects (23-119 pmol/l vs 137-378 pmol/l, p less than 0.01). By means of another two-site immunoradiometric assay, the basal intact proinsulin level was found to be higher in the NIDDM patients than in the controls for both non-obese (7.1 [SEM 1.2] pmol/l vs 2.4 [0.4] pmol/l, p less than 0.01) and obese subjects (14.4 [2.2] pmol/l vs 5.9 [1.9] pmol/l, p less than 0.01). The basal level of 32-33 split proinsulin was also raised in NIDDM. Previous failure to show clear separation between normal and NIDDM insulin responses was probably due to the high concentrations of proinsulin-like molecules in the plasma of NIDDM patients. These substances cross-react as insulin in most, if not all, insulin radioimmunoassays but have very little biological insulin-like activity. It is therefore now possible and necessary to designate most NIDDM patients as insulin deficient.
Temple
R C
RC
Department of Clinical Biochemistry, Addenbrooke's Hospital, Cambridge.
Carrington
C A
CA
Luzio
S D
SD
Owens
D R
DR
Schneider
A E
AE
Sobey
W J
WJ
Hales
C N
CN
D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005069:Evaluation Studies as Topic; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000172:deficiency*; D007333:Insulin Resistance; D008875:Middle Aged; D009765:Obesity / Q000097:blood; D011384:Proinsulin / Q000097:blood; D011863:Radioimmunoassay; D013997:Time Factors
D007328:Insulin; D011384:Proinsulin