Trace glucose fluxes in individuals with prediabetes using stable isotopes

The glucose fluxes of individuals with prediabetes in Chinese population are not clear. This study was to determine whether the endogenous glucose production (EGP), oral glucose rate of appearance (Ra) and glucose rate of disappearance (Rd) were different in Chinese individuals with prediabetes under fasting conditions and following an oral glucose challenge.

Five subjects with type 2 diabetes, 5 subjects with prediabetes and 5 non-diabetic subjects matched for age, weight, fat free mass and body mass index underwent a 180 minute stable glucose isotope tracing ([6, 6-(2)H2] glucose, [1-(13)C] glucose, and [U-(13)C] glucose) study under fasting and after ingestion of a 75 g oral glucose load. Isotope glucose enrichment was measured by gas chromatography-mass spectrometry. Insulin sensitivity was estimated using the oral glucose tolerance test (OGTT)-derived insulin sensitivity index, β cell function was determined by the insulinogenic index (δI30/δG30).

The insulin sensitivity index (P = 0.043) and insulinogenic index (P = 0.021) were decreased in subjects with prediabetes compared with non-diabetes. Fasting EGP was slightly higher (P = 0.29) and postprandial EGP was comparable in subjects with prediabetes and non-diabetes during 120 minutes after glucose ingestion, but nadir EGP occurred later in prediabetic than non-diabetic subjects. Ra did not differ among the three groups. Rd was substantially lower in subjects with prediabetes than non-diabetes after glucose intake (P = 0.013).

The mild hyperglycemia observed among individuals with prediabetes may result from decreased Rd during the postprandial state.