Distinct β-Cell Defects in Impaired Fasting Glucose and Impaired Glucose Tolerance

Abstract

To characterize the defects in β-cell function in subjects with impaired fasting glucose (IFG) and compare the results to impaired glucose tolerance (IGT) and normal glucose tolerance (NGT) subjects, β-cell glucose sensitivity and rate sensitivity during the oral glucose tolerance test were measured with the model by Mari in 172 Mexican Americans. A subgroup (n = 70) received a 2-h hyperglycemic clamp (+125 mg/dL), and first- and second-phase insulin secretion were quantitated. Compared with NGT, subjects with IFG and IGT manifested a decrease in β-cell glucose sensitivity; IFG subjects, but not IGT subjects, had decreased β-cell rate sensitivity. In IFG subjects, the defect in β-cell glucose sensitivity was time dependent, began to improve after 60 min, and was comparable to NGT after 90 min. The incremental area under the plasma C-peptide concentration curve during the first 12 min of the hyperglycemic clamp (ΔC-pep[AUC]0–12) was inversely related with the increase in FPG concentration (r = −36, r = 0.001), whereas ΔC-pep[AUC]15–120 positively correlated with FPG concentration (r = 0.29, r < 0.05). When adjusted for the prevailing level of insulin resistance, first-phase insulin secretion was markedly decreased in both IFG and IGT, whereas second-phase insulin secretion was decreased only in IGT. These results demonstrate distinct defects in β-cell function in IFG and IGT.

The impact of ethnicity on glucose homeostasis after gestational diabetes mellitus

“…When adjusting the insulinogenic index for HOMA-IR in the disposition index, beta cell function was similarly affected in women with IFG and IGT. These findings are consistent with previously published results [23,24]. DeFronzo and colleagues compared the presence of impaired insulin secretion and insulin resistance in individuals with IFG and IGT, as defined by the ADA criteria, using the OGTT and the hyperinsulinemic clamp [23].…”

Failure to increase insulin secretory capacity during pregnancy-induced insulin resistance is associated with ethnicity and gestational diabetes

“…Severe hepatic insulin resistance, which is linked to elevated FPG (29), is reported to deteriorate b-cell function in the first year post partum after gestational dysglycaemia (31). Recent reports indicate that subjects with elevated FPG have impaired first-phase insulin secretion and therefore b-cell failure (32).…”

No Effect of High-Dose Vitamin D Treatment on β-Cell Function, Insulin Sensitivity, or Glucose Homeostasis in Subjects With Abnormal Glucose Tolerance: A Randomized Clinical Trial

“…The result was adjusted for relative random fluctuation in glucose increase minutes 0-12, calculated as area under the curve in p-glucose above the basal level, between the baseline and study-end investigations (23). ISec was calculated accordingly during minutes 12-120 but was not adjusted for glucose stimuli as the glucose levels were very stable during this period.…”