title: 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.
authors.affiliation: Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Kanat
authors.forename: Andrea
authors.initials: A
authors.lastname: Mari
authors.forename: Luke
authors.initials: L
authors.lastname: Norton
authors.forename: Diedre
authors.initials: D
authors.lastname: Winnier
authors.forename: Ralph A
authors.initials: RA
authors.lastname: DeFronzo
authors.forename: Chris
authors.initials: C
authors.lastname: Jenkinson
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Abdul-Ghani
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001786:Blood Glucose / Q000032:analysis*; D005215:Fasting / Q000097:blood*; D005260:Female; D018149:Glucose Intolerance / Q000097:blood / Q000503:physiopathology*; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose