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

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.

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.

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

An inpatient clinical research unit at an academic medical center.

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

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

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

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

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