Cross talk between adipocytes and their precursors: relationships with adipose tissue development and blood pressure

Adipose tissue is an important source of angiotensinogen (AT). A possible involvement of increased plasma AT has been proposed in hypertension in obese patients, but growing evidence suggests also that the local renin-angiotensinogen system (RAS), giving rise to angiotensin II (AngII), may act as a distinct system from the plasma RAS. AngII stimulates in vitro the production and release of prostacyclin from adipocytes which in turn promotes the differentiation of precursor cells into new adipocytes (Darimont et al. 1994, Endocrinology 138: 1092-1096). Cross talk between adipocytes and precursor cells has been validated ex vivo and in vivo as (1) AngII stimulates specifically prostacyclin production, (2) both carbacyclin, a stable analogue of prostacyclin, and AngII promote the formation of new fat cells, and (3) AT (-/-) mice, which have decreased blood pressure (Tanimoto et al. 1994, J. Biol. Chem. 269: 31334-31336), exhibit both hypertrophy and hypoplasia of adipose tissue compared to wild-type mice (collaboration with Prof. A. Fukamizu, Tsukuba University, Japan). Altogether the data are consistent with an autocrine/paracrine mechanism implicating AT, AngII, and prostacyclin in adipose tissue development and suggest a new role for local AngII in addition to that of systemic AngII in blood pressure. Hormonal regulation of AT production from adipose tissue is also discussed.