The Sympathetic Innervation of Adipose Tissues: Regulation, Functions, and Plasticity.

The sympathetic nervous system (SNS) is a crucial arm of the peripheral nervous system (PNS) and includes catecholaminergic neurons that release norepinephrine (NE) onto numerous effector tissues and organs in the body. SNS innervation of both white (WAT) and brown adipose tissue (BAT) is clearly essential for proper tissue function and metabolic control, as decades of surgical, chemical, and genetic denervation studies have demonstrated. Despite our vast knowledge about adipose sympathetic innervation, especially in the context of cold-stimulated browning and thermogenesis that are under SNS control, newer data now provide a nuanced view of the SNS supply to adipose, including its regulation by local neuroimmune cells and neurotrophic factors, the co-release of modulatory neuropeptides along with NE, the importance of local SNS drive to adipose versus systemic increases in circulating catecholamines, and the long-overlooked interplay between adipose sympathetic and sensory nerves. This article brings a modern view to the regulation of sympathetic innervation patterns in WAT and BAT, how to image and quantify the nerve supply, contributions of adipose SNS to tissue functions, and how adipose tissue nerves respond to tissue remodeling and plasticity with changing energy demands. © 2023 American Physiological Society. Compr Physiol 13:4985-5021, 2023.