Glucocorticoids suppress brown adipose tissue function in humans: a double-blind placebo-controlled study

Aim: To investigate the effect of glucocorticoids on brown adipose tissue (BAT) function in humans. Materials and methods: In a randomized double-blind cross-over design, 13 healthy adults underwent 1 week of oral prednisolone treatment (15mg/d) and placebo with an intervening 2-week wash-out period. BAT function was assessed in response to cooling (19°C) and to a standardized meal, by measuring fluoro-deoxyglucose (FDG) uptake using positron emission tomography-computed tomography and skin temperatures overlying the supraclavicular (SCL) BAT depots using infrared thermography. Postprandial energy and substrate metabolism was assessed by indirect calorimetry. Results: During cooling, prednisolone significantly reduced BAT FDG uptake (standardized uptake value, SUV 6.1±2.2 vs 3.7±1.2; P<.05) and SCL temperature (-0.45±0.1 vs -1.0±0.1°C; P<.01) compared to placebo. Postprandially, prednisolone significantly blunted the rise in SCL temperature (+0.2±0.1 vs -0.3±0.1°C; P<.05), enhanced energy production (+221±17 vs +283±27kcal/d; P<.01) and lipid synthesis (+16.3±3.2 vs +23.6±4.9 mg/min; P<.05). The prednisolone-induced reduction in SCL temperature significantly correlated with the reduction in FDG uptake (r=0.65, P<.05), while the increase in energy production significantly correlated with the increase in lipogenesis (r=0.6, P<.05). Conclusion: Prolonged exposure to glucocorticoid suppresses the function of human BAT. The enhancement of energy production and lipogenesis in the face of reduced dissipation of energy as heat suggests that glucocorticoids channel energy towards fat storage after nutrient intake. This is a novel mechanism of glucocorticoid-induced obesity.