SUMMARY Increasing energy expenditure through activation of endogenous brown adipose tissue (BAT) is a potential approach to treat obesity and diabetes. The class of β3-adrenergic receptor (AR) agonists stimulates rodent BAT, but this activity has never been demonstrated in humans. Here we determined the ability of 200 mg oral mirabegron (Myrbetriq, Astellas Pharma, Inc.), a β3-AR agonist currently approved to treat overactive bladder, to stimulate BAT as compared to placebo. Mirabegron led to higher BAT metabolic activity as measured via 18F-fluorodeoxyglucose (18F-FDG) using positron emission tomography (PET) combined with computed tomography (CT) in all twelve healthy male subjects (p = 0.001), and it increased resting metabolic rate (RMR) by 203 ± 40 kcal/day (+13%; p = 0.001). BAT metabolic activity was also a significant predictor of the changes in RMR (p = 0.006). Therefore, a β3-AR agonist can stimulate human BAT thermogenesis and may be a promising treatment for metabolic disease.

No abstract

Objective Diet-induced obesity (DIO) causes several pathophysiological changes in adipose tissue. Increased inflammation reduces white adipose tissue (WAT) insulin sensitivity and contributes to the development of diabetes. However, little is known about how DIO alters the function of brown adipose tissue (BAT), an organ that consumes calories by β3-adrenergic receptor (AR)-mediated thermogenesis and helps regulate energy balance. Methods To test the effects of DIO on BAT, we fed 6 week-old C57BL/6 mice either a normal chow diet (NCD) or a high-fat diet (HFD). After 16 additional weeks, we measured body fat, WAT and BAT mRNA expression, glucose tolerance, and rates of glucose uptake in response to insulin and the β3-AR agonist mirabegron. Results Compared with NCD, HFD increased body fat and impaired glucose tolerance. Both WAT and BAT had higher mRNA levels of markers of inflammation, including TNFα and F4/80. Insulin signaling in BAT and WAT was reduced, with decreased Akt phosphorylation. Diet-normalized BAT glucose uptake rates were lower in response to mirabegron. Conclusions These results support a model in which DIO leads to BAT inflammation and insulin resistance, leading to a broader impairment of BAT function.