OBJECTIVE

Cardiovascular peptides such as angiotensin II (Ang II) and atrial natriuretic peptide (ANP) have metabolic effects on adipose cells. These peptides might also regulate adipocyte proliferation and visceral adipose tissue (VAT) expansion. Well-differentiated and stabilized primary cultures of human visceral mature adipocytes (MA) and in vitro-differentiated preadipocytes (DPA) were used as a model to study regulation of VAT expansion.

METHODS

Adipocyte differentiation was evaluated by Oil Red O staining and antiperilipin antibodies. MA and DPA from intra- and retro-peritoneal depots were treated with increasing Ang II (with or without valsartan, a highly selective, competitive, 'surmountable' AT1 antagonist devoid of peroxisome proliferator-activated receptor gamma agonistic activity) or ANP concentrations. Cell counts and bromodeoxyuridine incorporation were used to evaluate proliferation. Apoptosis was evaluated by Hoechst 33342 staining. 8-Bromo cyclic guanosine monophosphate (8Br-cGMP) was used to investigate ANP effects, and real-time PCR to evaluate Ang II and ANP receptors' expression.

RESULTS

Cell proliferation was progressively stimulated by increasing Ang II concentrations (starting at 10-11 M) and inhibited by ANP (already at 10-13 M) in both MA and DPA. Co-incubation with increasing Ang II concentrations and valsartan indicated that Ang II effects were AT1-mediated. Indeed, AT2 receptors were not expressed. Valsartan alone slightly inhibited basal proliferation indicating an autocrine/paracrine growth factor-like effect of endogenous, adipocyte-derived Ang II. 8Br-cGMP experiments indicated that the effects of ANP were mediated by the guanylyl cyclase type A receptor.

CONCLUSION

A cell-culture model to study VAT growth showed stimulation by Ang II and inhibition by ANP at physiological concentrations. Because similar effects are likely to occur in vivo, Ang II and ANP might be important modulators of VAT expansion and associated metabolic and cardiovascular consequences.