PROINSULIN SECRETION DURING THE FIRST 3 YEARS AFTER DIAGNOSIS IN DIABETIC-PATIENTS WITH AND WITHOUT ISLET-CELL ANTIBODIES

OBJECTIVE - To evaluate proinsulin secretion in different types of NID DM. RESEARCH DESIGN AND METHODS - Proinsulin and insulin were evaluate d at diagnosis of diabetes and 3 years later (fasting and after stimul ation with intravenous glucose and glucagon) in 10 NIDDM patients with out islet cell antibodies (ICAs) at diagnosis (age 52 +/- 4 years), 11 NIDDM patients with ICAs at diagnosis (age 50 +/- 5 years), and 21 he althy control subjects (age 53 +/- 4 years).RESULTS - At diagnosis, la sting proinsulin was higher in NIDDM patients without ICAs than in con trol subjects (39.6 +/- 10.0 vs. 12.8 +/- 1.6 pmol/l, P < 0.01). Proin sulin response to intravenous glucose decreased in NIDDM patients with ICAs (from 35.6 +/- 6.2 to 13.5 +/- 5.4 pmol/l, P < 0.05), but remain ed unchanged in those without ICAs. At 3 years after diagnosis, fastin g proinsulin (10.0 +/- 3.7 vs. 59.1 +/- 17.0 pmol/l) and proinsulin re sponses to intravenous glucose (13.5 +/- 5.4 vs. 103.9 +/- 35.1 pmol/l ) and to intravenous glucagon (7.4 +/- 3.9 vs. 36.0 +/- 7.7 pmol/l) we re much lower (P < 0.01) in NIDDM patients with ICAs than in those wit hout ICAs. CONCLUSIONS - After diagnosis of diabetes, proinsulin secre tion decreases significantly in NIDDM patients with ICAs and remains c onstant in those without.