Combined α- and β-adrenergic receptor activation triggers thermogenesis by the futile creatine cycle

Noradrenaline is the primary physiological regulator of adipocyte thermogenesis in response to decreased environmental temperature¹. However, the molecular factors and effector pathways that lie downstream of noradrenaline-stimulated thermogenesis are still not fully understood but are purportedly driven by cAMP downstream of β-adrenergic receptor (βAR) activation. Furthermore, while the transcriptional mechanisms regulating Ucp1 are well-characterized², the transcriptional regulation of UCP1-independent thermogenesis is largely unknown. Here, we show that brown adipose tissue (BAT) is primed to respond to environmental cold by triggering coordinated α-adrenergic receptor (αAR) and βAR signaling to induce the expression of thermogenic genes of the futile creatine cycle^3,4. Using fat-specific loss-of-function models, we reveal that EBFs, ERRs, and PGC1α are required for the cold-stimulated transcriptional induction of the futile creatine cycle in vivo. Through the application of chemogenetics, we demonstrate that combined fat-selective Gαs (activated by βARs) and Gαq (activated by αARs) signaling elevates whole-body energy expenditure to a greater extent than either signaling pathway alone in a manner that is dependent on the key effector protein of the futile creatine cycle, CKB³. Moreover, genetic and pharmacological studies reveal that CKB is necessary for nearly all of the α₁AR-stimulated component of brown adipocyte-intrinsic respiration and is thus critical for the full activation of noradrenaline-stimulated thermogenesis. Thus, the futile creatine cycle is integrated into facultative and adaptive thermogenesis through coordinated α₁AR and β₃AR signaling.