Angiotensin type 1 receptor blockers induce peroxisome proliferator-activated receptor-gamma activity.

Angiotensin type 1 receptor (AT(1)R) blockers (ARB) have been shown to reduce the incidence of type 2 diabetes mellitus by an unknown molecular mechanism. The peroxisome proliferator-activated receptor-gamma (PPARgamma) is the central regulator of insulin and glucose metabolism improving insulin sensitivity. We investigated the regulation of PPARgamma function by ARBs. The ARBs irbesartan and telmisartan (10 micromol/L) potently enhanced PPARgamma-dependent 3T3-L1 adipocyte differentiation associated with a significant increase in mRNA expression of the adipogenic marker gene adipose protein 2 (aP2), as measured by quantitative real-time polymerase chain reaction (irbesartan: 3.3+/-0.1-fold induction; telmisartan: 3.1+/-0.3-fold induction; both P<0.01). Telmisartan showed a more pronounced induction of aP2 expression in lower, pharmacologically relevant concentrations compared with the other ARBs. The ARB losartan enhanced aP2 expression only at high concentrations (losartan 100 micromol/L: 3.6+/-0.3-fold induction; P<0.01), whereas eprosartan up to 100 micromol/L had no significant effects. In transcription reporter assays, irbesartan and telmisartan (10 micromol/L) markedly induced transcriptional activity of PPARgamma by 3.4+/-0.9-fold and 2.6+/-0.6-fold (P<0.05), respectively, compared with 5.2+/-1.1-fold stimulation by the PPARgamma ligand pioglitazone (10 micromol/L). Irbesartan and telmisartan also induced PPARgamma activity in an AT1R-deficient cell model (PC12W), demonstrating that these ARBs stimulate PPARgamma activity independent of their AT(1)R blocking actions. The present study demonstrates that a specific subset of ARBs induces PPARgamma activity, thereby promoting PPARgamma-dependent differentiation in adipocytes. The activation of PPARgamma demonstrates new pleiotropic actions of certain ARBs, providing a potential mechanism for their insulin-sensitizing/antidiabetic effects.