The relationship between patients' serum glucose levels and metabolically active brown adipose tissue detected by PET/CT

Purpose: To compare blood glucose levels in patients with or without "detectable" brown adipose tissue (BAT) using 2-deoxy-2-[ ¹⁸F]fluoro-D-glucose positron emission tomography/ computed tomography (FDG PET/CT). Procedures: Nine hundred eight patients had PET/CT scans and were previously identified as having, or not having, FDG uptake in BAT. The original database was retrospectively reviewed for blood glucose level and body mass index (BMI) at the time of imaging. Blood glucose levels were compared between patients with or without FDG uptake in BAT, adjusting for age, sex, and BMI. Results: Fifty-six patients (6.2%) had FDG uptake in BAT. In the univariate analysis, patients without FDG uptake in BAT had a higher risk of glucose ≥100 mg/dL (odds ratio 3.4, 95% CI= 1.6-7.3; P=0.0007). After adjustment for age, sex, BMI, and significant interaction of sex and BMI, patients without BAT tended to have a higher risk of glucose =100 mg/dL, although not statistically significant (odds ratio=1.6, 95% CI=0.7-3.6; P=0.268). Conclusions: Although causal relationships are not specified, the data suggest that BAT uptake, glucose levels, BMI, sex, and age are inter-related and the possibility that presence of "detectable" BAT is protective against diabetes and obesity. FDG PET/CT may be a vital tool for further investigations of diabetes and obesity.