Dual innervation of white adipose tissue: some evidence for parasympathetic nervous system involvement

The regulation of total body fat was first formally suggested in the lipostatic theory of Kennedy (1), and since that time, the mechanisms underlying the control of lipid energy stores have been sought. The waxing and waning of circulating factors that promote lipid storage or mobilization (e.g., insulin and adrenal medullary catecholamines, respectively) may be the method by which the brain adjusts metabolism as part of a feedback system regulating body fat levels. In other systems, fine and rapid control of biological responses requires direct neural involvement. For example, cardiac function is regulated in this manner through the opposing effects of its innervation by the two arms of the autonomic nervous system: the sympathetic (SNS) and parasympathetic (PSNS) nervous systems. Dual autonomic nervous system innervation of peripheral tissues is the rule, except for sweat glands, which are thought only to have SNS innervation, but until now, such dual innervation has not been shown for either brown adipose tissue or white adipose tissue (WAT). In this issue of the JCI, Kreier et al. (2) present neuroanatomical and functional evidence for the PSNS innervation of WAT, which complements the recent substantiation of the SNS innervation of this tissue (3, 4). Given the general lack of appreciation of the innervation of WAT until recently, despite many years of supportive functional and neuroanatomical evidence (for review see ref. 5), some discussion of WAT innervation seems warranted.