We examined the
glucose response curves (biphasic [BPh], monophasic [MPh], incessant increase [IIn]) during an oral
glucose tolerance test (OGTT) and their relationship to
insulin sensitivity (IS) and β-cell function (βCF) in youth versus adults with
impaired glucose tolerance or recently diagnosed
type 2 diabetes.RESEARCH DESIGN AND METHODSThis was both a cross-sectional and a longitudinal evaluation of participants in the RISE study randomized to
metformin alone for 12 months or
glargine for 3 months followed by
metformin for 9 months. At baseline/randomization, OGTTs (85 youth, 353 adults) were categorized as BPh, MPh, or IIn. The relationship of the
glucose response curves to hyperglycemic clamp-measured IS and βCF at baseline and the change in
glucose response curves 12 months after randomization were assessed.RESULTSAt randomization, the prevalence of the BPh curve was significantly higher in youth than adults (18.8% vs. 8.2%), with no differences in MPh or IIn. IS did not differ across
glucose response curves in youth or adults. However, irrespective of curve type, youth had lower IS than adults (P < 0.05). βCF was lowest in IIn versus MPh and BPh in youth and adults (P < 0.05), yet compared with adults, youth had higher βCF in BPh and MPh (P < 0.005) but not IIn. At month 12, the change in
glucose response curves did not differ between youth and adults, and there was no treatment effect.CONCLUSIONSDespite a twofold higher prevalence of the more favorable BPh curve in youth at randomization, RISE interventions did not result in beneficial changes in
glucose response curves in youth compared with adults. Moreover, the typical β-cell hypersecretion in youth was not present in the IIn curve, emphasizing the severity of β-cell dysfunction in youth with this least favorable
glucose response curve.