White adipose tissue (WAT) serves primarily as energy storage; however, in response to cold or β-adrenergic agonists, WAT develops characteristics of brown adipose tissue (BAT), which expends energy in the form of heat. WAT beiging has proposed as potential strategy for treating obesity. In this episode, Philip Kern and colleagues exposed lean and obese subjects to cold or treatment with the β3 agonist mirabegron and evaluated markers of adipose beiging. Both treatments induced beiging, regardless of obesity status or age. The results of this study support further evaluation of the long-term effects of induced adipose beiging for treatment of obesity and associated metabolic dysfunction.
BACKGROUND. The induction of beige adipocytes in s.c. white adipose tissue (WAT) depots of humans is postulated to improve glucose and lipid metabolism in obesity. The ability of obese, insulin-resistant humans to induce beige adipose tissue is unknown. METHODS. We exposed lean and obese research participants to cold (30-minute ice pack application each day for 10 days of the upper thigh) or treated them with the β3 agonist mirabegron. We determined beige adipose marker expression by IHC and quantitative PCR, and we analyzed mitochondrial bioenergetics and UCP activity with an Oxytherm system. RESULTS. Cold significantly induced UCP1 and TMEM26 protein in both lean and obese subjects, and this response was not associated with age. Interestingly, these proteins increased to the same extent in s.c. WAT of the noniced contralateral leg, indicating a crossover effect. We further analyzed the bioenergetics of purified mitochondria from the abdominal s.c. WAT of cold-treated subjects and determined that repeat ice application significantly increased uncoupled respiration, consistent with the UCP1 protein induction and subsequent activation. Cold also increased State 3 and maximal respiration, and this effect on mitochondrial bioenergetics was stronger in summer than winter. Chronic treatment (10 weeks; 50 mg/day) with the β3 receptor agonist mirabegron induces UCP1, TMEM26, CIDEA, and phosphorylation of HSL on serine660 in obese subjects. CONCLUSION. Cold or β3 agonists cause the induction of beige adipose tissue in human s.c. WAT; this phenomenon may be exploited to increase beige adipose in older, insulin-resistant, obese individuals. TRIAL REGISTRATION. Clinicaltrials.gov NCT02596776, NCT02919176. FUNDING. NIH (DK107646, DK112282, P20GM103527, and by CTSA grant UL1TR001998).
Brian S. Finlin, Hasiyet Memetimin, Amy L. Confides, Ildiko Kasza, Beibei Zhu, Hemendra J. Vekaria, Brianna Harfmann, Kelly A. Jones, Zachary R. Johnson, Philip M. Westgate, Caroline M. Alexander, Patrick G. Sullivan, Esther E. Dupont-Versteegden, Philip A. Kern