Increased Rates of Meal Absorption Do Not Explain Elevated 1-Hour Glucose in Subjects With Normal Glucose Tolerance.

Context: In subjects with normal fasting glucose (NFG) and normal glucose tolerance (NGT), glucose concentrations >155 mg/dL 1 hour after 75 g of oral glucose predict increased risk of progression to diabetes. Recently, it has been suggested that the mechanism underlying this abnormality is increased gut absorption of glucose.

Objective: We sought to determine the rate of systemic appearance of meal-derived glucose in subjects classified by their 1-hour glucose after a 75-g oral glucose challenge.

Design: This was a cross-sectional study. Participating subjects underwent a 75-g oral glucose challenge and a labeled mixed meal test.

Setting: An inpatient clinical research unit at an academic medical center.

Participants: Thirty-six subjects with NFG/NGT participated in this study.

Interventions: Subjects underwent an oral glucose tolerance test. Subsequently, they underwent a labeled mixed meal to measure fasting and postprandial glucose metabolism.

Main Outcome Measures: We examined -cell function and the rate of meal appearance (Meal ) in NFG/NGT subjects. Subsequently, we examined the relationship of peak postchallenge glucose with Meal and indices of -cell function.

Results: Peak glucose concentrations correlated inversely with -cell function. No relationship of Meal with peak postchallenge glucose concentrations was observed.

Conclusion: In subjects with NFG/NGT, elevated 1-hour peak postchallenge glucose concentrations reflect impaired -cell function rather than increased systemic meal appearance.