Glucose-Mediated Glucose Disposal at Baseline Insulin is Impaired in IFG.

Objective: To quantitate glucose-mediated glucose disposal with and without basal insulin replacement and insulin-mediated glucose disposal in impaired fasting glucose (IFG) subjects.

Research Design and Methods: We utilized the hyperglycemic/ pancreatic clamp and stepped euglycemic clamp techniques to quantitate glucose disposal and suppression of EGP in normal glucose tolerant (NGT) (n=14) and IFG (n=14) subjects.

Results: Total body glucose-mediated glucose uptake, measured with the hyperglycemic/pancreatic clamp, was not significantly affected by basal plasma insulin levels in both IFG and NGT subjects. Compared to subjects with NGT, IFG subjects had significantly lower glucose-mediated glucose uptake (by 15%) during the hyperglycemic clamp performed with and without basal insulin replacement. Conversely, insulin-mediated glucose disposal was comparable in both groups. The suppression of EGP by hyperglycemia was similar in both groups. However, the suppression of EGP by insulin was attenuated in IFG compared to NGT subjects.

Conclusions: The results of the present study demonstrate that: (i) glucose-mediated glucose disposal is impaired in IFG subjects; (ii) insulin-mediated glucose uptake in IFG is normal, and (iii) insulin action to suppress endogenous glucose production is impaired.