"Nerve-associated macrophages control adipose homeostasis across lifespan and restrain age-related inflammation."

Age-related inflammation or 'inflammaging' increases disease burden and controls lifespan. Adipose tissue macrophages (ATMs) are critical regulators of inflammaging; however, the mechanisms involved are not well understood in part because the molecular identities of niche-specific ATMs are unknown. Using intravascular labeling to exclude circulating myeloid cells followed by single-cell sequencing with orthogonal validation via multiparametric flow cytometry, we define sex-specific changes and diverse populations of resident ATMs through lifespan in mice. Aging led to depletion of vessel-associated macrophages, expansion of lipid-associated macrophages and emergence of a unique subset of CD38⁺ age-associated macrophages in visceral adipose tissue with inflammatory phenotype. Notably, CD169⁺CD11c^- ATMs are enriched in a subpopulation of nerve-associated macrophages (NAMs) that declines with age. Depletion of CD169⁺ NAMs in aged mice increases inflammaging and impairs lipolysis suggesting catecholamine resistance in visceral adipose tissue. Our findings reveal NAMs are a specialized ATM subset that control adipose homeostasis and link inflammation to tissue dysfunction during aging.