PPARgamma Agonist Beyond Glucose Lowering Effect

The nuclear hormone receptor PPARgamma is activated by several agonists, including members of the thiazolidinedione group of insulin sensitizers. Pleiotropic beneficial effects of these agonists, independent of their blood glucose-lowering effects, have recently been demonstrated in the vasculature. PPARgamma agonists have been shown to lower blood pressure in animals and humans, perhaps by suppressing the renin-angiotensin (Ang)-aldosterone system (RAAS), including the inhibition of Ang II type 1 receptor expression, Ang-II-mediated signaling pathways, and Ang-II-induced adrenal aldosterone synthesis/secretion. PPARgamma agonists also inhibit the progression of atherosclerosis in animals and humans, possibly through a pathway involving the suppression of RAAS and the thromboxane A2 system, as well as the protection of endothelial function. Moreover, PPARgamma-agonist-mediated renal protection, especially the reduction of albuminuria, has been observed in diabetic nephropathy, including animal models of the disease, and in non-diabetic renal dysfunction. The renal protective activities may reflect, at least in part, the ability of PPARgamma agonists to lower blood pressure, protect endothelial function, and cause vasodilation of the glomerular efferent arterioles. Additionally, anti-neoplastic effects of PPARgamma agonists have recently been described. Based on the multiple therapeutic actions of PPARgamma agonists, they will no doubt lead to novel approaches in the treatment of lifestyle-related and other diseases.

Induction of PPAR Gamma mRNA and Protein Expression by Rosiglitazone in Chronic Cyclosporine Nephropathy in the Rat

PURPOSE: We recently reported that rosiglitazone (RGTZ), a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, has a protective effect against cyclosporine (CsA)- induced renal injury. Here we report the effect of RGTZ on peroxisome proliferator-activated receptor gamma (PPARgamma) expression in an experimental model of chronic cyclosporine (CsA) nephropathy. MATERIALS AND METHODS: Chronic CsA nephropathy was induced in Sprague-Dawley rats by administering CsA (15mg/kg per day) for 28 days, and control rats were treated with vehicle (VH group, olive oil 1mL/kg per day) for 28 days. RGTZ (3mg/kg) was concurrently administered via gavage to the CsA and VH groups. Expression of PPARgamma mRNA and protein was evaluated with RT-PCR, immunohistochemistry, and immunoblotting. RESULTS: PPARgamma mRNA expression was similar to the level of PPARgamma protein constitutively expressed in the kidneys of the VH treated rats, with expression in the glomerular epithelial, distal tubular cells, and collecting tubular cells. PPARgamma protein expression in CsA-treated rat kidneys was significantly less than in the VH group. However, concomitant administration of RGTZ restored PPARgamma protein expression in the kidneys of the CsA- reated rats. CONCLUSION: Exogenous administration of RGTZ treatment upregulates PPARgamma expression and that this mechanism may play a role in protecting against CsA-induced renal injury.