Factors Responsible for Combined Glucose Intolerance Developing into Isolated Post-challenge Hyperglycemia in Subjects with Impaired Fasting Glucose

We hypothesized that isolated post-challenge hyperglycemia (IPH) is the earliest stage of Type 2 diabetes. We conducted this study to determine factors responsible for combined glucose intolerance (CGI) developing into IPH in subjects with impaired fasting glucose. Materials and Methods: One hundred subjects with impaired fasting glucose were screened and 77 were enrolled. These subjects were divided into 3 groups: CGI, IPH -(IPH with HbA1c < 6.5%), and IPH+ (IPH with HbA1c 6.5%). The insulin secretion and insulin sensitivity index during the oral glucose tolerance test were compared among the CGI, IPH - and IPH + groups. Results: There were 27 subjects in the CGI group, 34 in the IPH -group, and 16 in the IPH + group. Compared with the CGI group, the subjects with IPH -had a higher glucose AUC and lower insulinogenic index. The subjects with IPH + had a higher glucose AUC, lower insulinogenic index, lower HOMA-, lower insulin AUC, lower total insulin secretion, and lower deposition index. Compared with the IPH -group, subjects with IPH + were younger, and had lower body mass index, higher cholesterol, higher HbA1c, lower mean HOMA-, lower insulin AUC, and lower total insulin secretion. Conclusions: The factor responsible for CGI developing into IPH with HbA1c < 6.5% was decreased early-phase insulin secretion, but both decreased early and total insulin secretion were responsible for the development of CGI into IPH with HbA1c 6.5%.