A lipase-independent pathway of lipid release and immune modulation by adipocytes

Exosomes that fatten immune cells Adipose tissue in mammals contains not only adipocytes (fat cells) but also a variety of immune cells—most notably, macrophages. Proper communication between these cell types is thought to be important for metabolic health. Flaherty et al. found that adipocytes release lipid-filled vesicles (AdExos) that serve as the primary source of lipid for adipose-resident macrophages (see the Perspective by Antonyak et al. ). AdExos were present at low levels in the circulation of mice and were produced at twice the rate in obese versus lean animals. In vitro, AdExos induced differentiation of bone marrow precursor cells into cells resembling adipose-resident macrophages. Science , this issue p. 989 ; see also p. 931