Lumped constant for [¹⁸F]fluorodeoxyglucose in skeletal muscles of obese and nonobese humans

Abstract

Quantitative 2-[(18)F]fluoro-2-deoxy-D-glucose ([(18)F]FDG) positron emission tomography (PET) has been widely used to calculate glucose utilization in skeletal muscle. FDG-PET results depend partly on the lumped constant (LC), which accounts for the differences in the transport and phosphorylation between [(18)F]FDG and glucose. In this study, we estimated the LC for [(18)F]FDG directly in normal and in insulin-resistant obese subjects by combining FDG PET with the microdialysis technique. Eight obese [age 29.4 +/- 1.0 yr, body mass index (BMI) 33.6 +/- 1.0 kg/m(2)] and eight nonobese (age 25.0 +/- 1.0 yr, BMI 23.1 +/- 1.0 kg/m(2)) males were studied during euglycemic hyperinsulinemia (1 mU. kg(-1).min(-1) for 150 min). Muscle blood flow was measured using (15)O-labeled water and PET. Muscle [(18)F]FDG uptake (rGU(FDG)) was calculated with Patlak graphic analysis. Interstitial glucose concentration of the quadriceps femoris muscle was measured simultaneously with [(18)F]FDG scanning using microdialysis. Muscle glucose uptake (by microdialysis, rGU(MD)) was calculated by multiplying glucose extraction by regional muscle blood flow. A significant correlation was found between rGU(MD) and rGU(FDG) (r = 0.78, P < 0.01). The LC was determined as the ratio of the rGU(FDG) to the rGU(MD). The LC averaged 1.16 +/- 0.16 and was similar in the obese and nonobese subjects (1.15 +/- 0.11 vs. 1.16 +/- 0.07, respectively, not significant). In conclusion, the microdialysis technique can be reliably combined with FDG PET to measure glucose uptake in skeletal muscle. Direct measurements with these two independent techniques suggest an LC value of 1.2 for [(18)F]FDG in human skeletal muscle during insulin stimulation, and the LC appears not to be sensitive to insulin resistance.

Rosiglitazone but Not Metformin Enhances Insulin- and Exercise-Stimulated Skeletal Muscle Glucose Uptake in Patients With Newly Diagnosed Type 2 Diabetes

“…18 F]FDG method used for the measurement of femoral glucose uptake (38), applying a lumped constant of 1.2, has been validated repeatedly for human skeletal muscle (30,47,48). Hepatic glucose output was assumed to be suppressed during hyperinsulinemia (40).…”

“…A 5-min transmission scan for the correction of photon attenuation with a removable ring source containing 68 Ge was performed before the emission scan. For image processing, we used a recently developed Bayesian iterative reconstruction algorithm, using median root prior with iterations and applying a Bayesian coefficient of 0.3 (30,35). Measurement of muscle blood flow and oxygen consumption.…”

Effect of Bariatric Surgery on Adipose Tissue Glucose Metabolism in Different Depots in Patients With or Without Type 2 Diabetes

“…The fractional uptake rate, like the influx constant (K i ), was calculated for each voxel drawn using the tissue and plasma input time activity curves (17). GU for adipose tissue and skeletal muscle were calculated at the voxel level by multiplying the K i by the plasma glucose concentration and dividing this by a lumped constant of 1.14 for adipose tissue (10) and 1.2 for skeletal muscle (18). The depotspecific GU was calculated by multiplying tissue-specific GU (mmol z L 21 z min…”

Differential contributions of ankle plantarflexors during submaximal isometric muscle action: A PET and EMG study

“…Lumped constant is the value that takes into account differences in the uptake of glucose and 18 F-FDG from the blood and it has been shown to be 1.2 for skeletal muscle (Kelley et al 1999, Peltoniemi et al 2000.…”