Effect of hyperinsulinemia on myocardial fluorine-18-FDG uptake.
This study was performed to evaluate the effect of insulin on myocardial kinetics of 18F-fluorodeoxyglucose (FDG) and glucose in patients with ischemic heart disease. Twelve male patients (age range 54-79 yr; mean age 69 +/- 8 yr) were studied during the fasting awake state. Patients with diabetes and previous myocardial infarction of the left anterior descending vascular bed were excluded from the study. Patients were injected with a 185-MBq (5-mCi) bolus of FDG during arterial and coronary sinus catheterization. Thirty minutes after FDG injection, paired basal arterial and coronary sinus blood samples were taken for the measurement of FDG and glucose uptake. Thereafter, a primed (100 mU x m(-2) x min(-1) for 10 min) continuous (50 mU x m(-2) x min(-1) infusion of insulin was administered for 60 min using the euglycemic clamp technique, and blood samples were repeated. Blood samples also were taken periodically for the measurement of arterial free fatty acids and insulin. Euglycemic insulin infusion lowered arterial concentrations of free fatty acids, reducing myocardial extraction of free fatty acids by 85% and stimulated uptake of glucose and FDG. Myocardial glucose and FDG extraction fractions (%) increased from 1 +/- 1 and 2 +/- 2 at baseline to 8 +/- 2 and 10 +/- 3 during insulin infusion, respectively. The lumped constant value was estimated to be 1.44 +/- 0.14 (r = 0.87) for the fasted state, 0.99 +/- 0.07 (r = 0.74) during insulin infusion and 1.00 +/- 0.05 (r = 0.92) when both groups of data were pooled together. The data obtained in this study show that FDG uptake quantitatively traces glucose uptake during physiological hyperinsulinemia in patients with ischemic heart disease.