Catecholamine signaling is normal in the elderly; however, the catecholamine-induced generation of free fatty acids diminishes with age. In Nature, Camell et al. show that adipose tissue macrophages regulate the age-dependent decrease in adipocyte lipolysis in mice by lowering the availability of noradrenaline. Aged adipose tissue macrophages inhibit the release of free fatty acids from noradrenaline-stimulated young adipocytes and have high expression of enzymes that regulate catecholamine catabolism, such as monoamine oxidase A, as well as of genes encoding molecules linked to inflammasome activation. Aged Nlrp3−/− mice show restoration of expression of factors involved in catecholamine catabolism and in the release of free fatty acids after fasting, which are lower in old wild-type mice than in young wild-type mice. Inhibition of monoamine oxidase A in inflammasome-activated macrophages restores lipolysis in noradrenaline-induced adipocytes in vitro and fasting-induced lipolysis in old mice in vivo. Macrophages are present in association with sympathetic nerve fibers in the adipose tissue, which suggests that they might regulate the access of adipocytes to noradrenaline.

Nature (27 September 2017) doi:10.1038/nature23912