ALTERATIONS IN THE PATTERNS OF INSULIN-SECRETION BEFORE AND AFTER DIAGNOSIS OF IDDM

OBJECTIVE-To study the natural history of beta-cell dysfunction in an individual who developed insulin-dependent diabetes mellitus (IDDM) ov er a 13-month period while under observation. RESEARCH DESIGN AND METH ODS-Insulin secretion rates (ISR) in response to intravenous glucose a nd mixed meals were estimated by deconvolution of C-peptide levels. RE SULTS-When fasting glucose and glycosylated hemoglobin concentrations were still within the normal range, insulin secretory responses to int ravenous glucose infusion were reduced, but 80- to 100-min secretory o scillations could still be detected. Sequential glucose infusion studi es over a 3-month period demonstrated a progressive reduction in insul in secretion. The light temporal coupling between ultradian oscillatio ns in ISR and glucose observed in nondiabetic subjects was lost. In re sponse to mixed meals, the oscillatory pattern of secretion was preser ved, but the magnitude of the secretory responses was reduced.CONCLUSI ONS-Our results indicate that despite the lower absolute secretory rat es, ultradian ISR oscillations persist in the period before and immedi ately after the onset of IDDM in this subject, but they are less tight ly coupled to glucose than in nondiabetic subjects.