Measurement of lumbar muscle glucose utilization rate can be as useful in estimating skeletal muscle insulin resistance as that of thigh muscle

Background: Skeletal muscle glucose utilization (SMGU) can be accessed by positron emission tomography (PET) and 18F-FDG to characterize insulin resistance. The quantity of skeletal muscle in the lumbar is sufficient to indicate that SMGU in the lumbar (SMGUlumbar) can be measured with 18F-FDG PET of the chest instead of obtaining thigh muscle SMGU (SMGU-thigh). This would reduce PET scan time to avoid thigh muscle PET scan. This study was aimed to compare SMGU-lumbar and thigh muscle SMGU under insulin clamping to identify the validity of measurements of SMGU in the lumbar for studies of insulin resistance. Methods: Thirty-three patients underwent sequential dynamic 18F-FDG PET of both the thoracic (37 min) and thigh region (22 min) during hyperinsulinemic euglycemic insulin clamping. Both SMGU-lumbar and SMGU-thigh were calculated by Patlak graphical analysis. Whole body insulin resistance was assessed by a whole body glucose disposal rate during hyperinsulinemic euglycemic insulin clamping. Input function was obtained from the time activity curve of the descending aorta and venous blood sampling as previously validated. Results: SMGU-thigh (0.0506 ± 0.0334 μmol/min/g) was comparable to SMGU-lumbar (0.0497 ± 0.0255 μmol/min/g). The Bland-Altman method of difference plot analysis showed a significant correlationship between SMGUthigh and SMGU-lumbar (r = 0.506, p = 0.0028). There were seen very good significant correlationship between whole body glucose utilization rate in both thigh (r = 0.737, p = 0.0001) and lumbar (r = 0.772, p = 0.0001). Conclusion: These results support the validity of measuring SMGU-lumbar to estimate insulin resistance during PET imaging of the chest.