Effect of postprandial hyperglycaemia in non-invasive measurement of cerebral metabolic rate of glucose in non-diabetic subjects

Abstract

The aim of this study was to determine the effect of postprandial hyperglycaemia (HG) on the non-invasive measurement of cerebral metabolic rate of glucose (CMRGlc). Five patients who had a meal within an hour before a fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) examination were recruited in this study. They underwent intermittent arterial blood sampling (measured input function), and, based on this sampling, CMRGlc was calculated using an autoradiographic method (CMRGlc_real). Simulated input functions were generated based on standardised input function, body surface area and net injected dose of FDG, and simulated CMRGlc (CMRGlc_sim) was also calculated. Percent error of the area under the curve (AUC) between measured (AUC_real) and simulated input function (AUC_IFsim) and percent error between CMRGlc_real and CMRGlc_sim were calculated. These values were compared with those obtained from a previous study conducted under fasting conditions (F). The serum glucose level in the HG group was significantly higher than that in the F group (165±69 vs 100±9 mg/dl, P=0.0007). Percent errors of AUC and CMRGlc in grey matter and white matter in HG were significantly higher than those in F (12.9%±1.3% vs 3.5%±2.2% in AUC, P=0.0015; 18.2%±2.2% vs 2.9%±1.9% in CMRGlc in grey matter, P=0.0028; 24.0%±4.6% vs 3.4%±2.2% in CMRGlc in white matter, P=0.0028). It is concluded that a non-invasive method of measuring CMRGlc should be applied only in non-diabetic subjects under fasting conditions.