Proinsulin secretion during the first 3 years after diagnosis in diabetic patients with and without islet cell antibodies.

Abstract

To evaluate proinsulin secretion in different types of NIDDM. Proinsulin and insulin were evaluated at diagnosis of diabetes and 3 years later (fasting and after stimulation with intravenous glucose and glucagon) in 10 NIDDM patients without islet cell antibodies (ICAs) at diagnosis (age 52 +/- 4 years), 11 NIDDM patients with ICAs at diagnosis (age 50 +/- 5 years), and 21 healthy control subjects (age 53 +/- 4 years). At diagnosis, fasting proinsulin was higher in NIDDM patients without ICAs than in control subjects (39.6 +/- 10.0 vs. 12.8 +/- 1.6 pmol/l, P < 0.01). Proinsulin 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 remained unchanged in those without ICAs. At 3 years after diagnosis, fasting proinsulin (10.0 +/- 3.7 vs. 59.1 +/- 17.0 pmol/l) and proinsulin responses 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) were much lower (P < 0.01) in NIDDM patients with ICAs than in those without ICAs. After diagnosis of diabetes, proinsulin secretion decreases significantly in NIDDM patients with ICAs and remains constant in those without.