Correlations of fasting and postprandial blood glucose increments to the overall diurnal hyperglycemic status in type 2 diabetic patients: variations with levels of HbA1c.

Studies from overseas have indicated that postprandial glucose excursions are predominant in subjects with moderate hyperglycemia, while fasting hyperglycemia become the predominant abnormality with worsening of hyperglycemia; however, few studies have yet investigated the correlation between HbA1c and fasting and/or postprandial hyperglycemia in Japanese subjects. We investigated the correlation between fasting and postprandial hyperglycemia and the overall diabetic status, as assessed by measurement of HbA1c, in Japanese patients with type 2 diabetes. Blood glucose (BG) concentrations were determined in the fasting state (8:00 A.M.), during the postprandial phases (at 10:30 A.M., 2:30 P.M. and 8:30 P.M.) and during the postabsorptive periods (at 11:30 A.M. and 17:30 P.M.) in 66 patients with type 2 diabetes who were not being treated with prandial/premixed insulins or alpha-glucosidase inhibitors. The areas under the curve above the fasting BG concentrations (AUC1) and over 110 mg/dl (AUC2) were calculated for further evaluation of the correlations of the postprandial (AUC1) and fasting (AUC2 - AUC1) BG increments to the overall diurnal hyperglycemic status. Subjects were separated into two groups using the HbA1c cutoff value of 8%. The fasting BG was not correlated with the HbA1c in the group with a HbA1c values of less than 8% (r = 0.125, p = 0.473). On the other hand, fasting hyperglycemia was strongly correlated with the HbA1c level in the group with HbA1c values of over 8.0% (r = 0.406, p = 0.023). Furthermore, postprandial hyperglycemia was strongly correlated with the HbA1c in the group with HbA1c levels less than 8.0% (r = 0.524, p = 0.001). Thus, there existed a progressive shift in the contribution of fasting and postprandial hyperglycemia to the overall hyperglycemic status with progression from moderate to severe diabetes mellitus in Japanese type 2 diabetic patients.