Figure 1. Catecholamines bind the βARs on adipocytes to activate the Gs and increase cAMP. cAMP activates PKA, which can phosphorylate proteins to allow lipolysis of stored triglycerides. βARs and PKA can also activate a protein kinase cascade, culminating in the activation of p38α MAPK, which phosphorylates key transcription factors to promote transcription of the UCP1 and PGC-1α genes, mitochondrial biogenesis and thermogenic energy expenditure.