The loss of postprandial glycemic control precedes stepwise deterioration of fasting with worsening diabetes.

OBJECTIVE: The aim of the study was to determine whether the loss of fasting and postprandial glycemic control occurs in parallel or sequentially in the evolution of type 2 diabetes. RESEARCH DESIGN AND METHODS: In 130 type 2 diabetic patients, 24-h glucose profiles were obtained using a continuous glucose monitoring system. The individuals with type 2 diabetes were divided into five groups according to A1C levels: 1 (<6.5%, n = 30), 2 (6.5-6.9%, n = 17), 3 (7-7.9%, n = 32), 4 (8-8.9%, n = 25), and 5 (> or =9%, n = 26). The glucose profiles between the groups were compared. The overall glucose concentrations for the diurnal, nocturnal, and morning periods, which represent the postprandial, fasting, and the dawn phenomenon states, respectively, were also compared.
RESULTS: Glucose concentrations increased steadily from group 1 to 5 in a stepwise manner. The initial differences in mean glucose concentrations reaching statistical significance occurred 1) between groups 1 and 2 (6.4 vs. 7.7 mmol/l, P = 0.0004) for daytime postprandial periods, followed by differences; 2) between groups 2 and 3 (7.5 vs. 9.3 mmol/l, P = 0.0003) for the morning periods (dawn phenomenon); and finally 3) between groups 3 and 4 (6.3 vs. 8.4 mmol/l, P < 0.0001) for nocturnal fasting periods.
CONCLUSIONS: The deterioration of glucose homeostasis in individuals with type 2 diabetes progressed from postprandial to fasting hyperglycemia following a three-step process. The first step related to the three diurnal postmeal periods considered as a whole, the second step occurred during the morning period, and the third and final step corresponded to sustained hyperglycemia over the nocturnal fasting periods. Such a description of the key stages in the evolution of type 2 diabetes may be of interest for implementing antidiabetes treatment.