Proinsulin, C-peptide, and insulin in normal subjects during an 8-h hyperglycemic clamp.
Increased concentrations of proinsulin immunoreactive material (PIM) absolutely or relative to insulin is a characteristic finding in patients with non-insulin-dependent diabetes mellitus (NIDDM). The aim of this study was to test if 8 h or mild hyperglycemia (7-9 mmol/l) in healthy subjects could induce a preferential secretion of PIM from B cells. Serum concentrations of insulin, C-peptide and PIM were measured every 10 min during the 8 h of continuous glucose infusion in nine normal-weight healthy subjects without diabetes among their first-degree relatives. After a gradual rise in B-cell peptides, a steady state was reached. From 4 to 8 h no further difference in insulin, C-peptide or PIM concentration was found. Fasting PIM/C-peptide and PIM/insulin ratios of 0.5% and 2.3% increased during the glucose clamp to levels of 1.4% and 7.6%, respectively. Neither testing the regression slope nor comparing individual time points showed any significant difference for the PIM/C-peptide ratio from 2 to 8 h and for the PIM/insulin ratio from 3 to 8 h. These results do not support the hypothesis that an increased glucose drive per se results in an altered B-cell function with increasing PIM/C-peptide ratio. At least 8 h of mild hyperglycemia in healthy subjects does not progressively alter B-cell function.
Hartling
S G
SG
Steno Diabetes Center, Gentofte, Denmark.
Røder
M E
ME
Dinesen
B
B
Binder
C
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002096:C-Peptide / Q000097:blood*; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000097:blood*; D007328:Insulin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011384:Proinsulin / Q000097:blood*
D002096:C-Peptide; D007328:Insulin; D011384:Proinsulin; D005947:Glucose