Introduction: Renin-Angiotensin System (RAS) induces oxidative stress and contributes to various pathological conditions including insulin resistance and the metabolic syndrome. Recent studies have shown the role of PPARδ-agonist in attenuation of Angiotensin II induced oxidative stress.The aim of this study was to explore the effectiveness of a PPARδ-agonist in the prevention of Ang II-induced vascular and adipocyte dysfunction and the possible interaction between PPARδ and HO-1 system in a model of enhanced oxidative stress, the Goldblatt 2K1C model.
Methods: We first established a direct stimulatory effect of the PPARδ-agonist (GW 501516) on the HO-1 gene by demonstrating increased luciferase activity in COS-7 cells transfected with a luciferase-HO-1 promoter construct. SD rats were divided in 4 groups: sham operated animals, 2K1C rats and 2K1C rats treated with GW 501516, in the absence or presence of the HO activity inhibitor, stannous mesoporphyrin (SnMP).
Results: 2K1C animals had increased blood pressure, visceral adiposity, adipocyte hypertrophy, increased inflamatory cytokines, increased circulatory and adipose tisssue levels of renin and Ang II along with increased adipose tissue gp91 phox expression (p<0.05) when compared to sham operated animals. Treatment with GW 501516 increased adipose tissue HO-1 and adiponectin levels (p<0.01) along with enhancement of Wnt10b and β-catenin expression. HO-1 induction was accompanied by the decreased expression of Wnt 5b, Mest and C/EBPα levels and an increased number of small adipocytes (p<0.05). These effects of GW501516 were reversed in 2K1C animals exposed to SnMP (p<0.05).
Conclusion: This novel study corroborates the existence of a PPARδ-HO-1 axis whose direct stimulation via the administration of an exogenous PPARδ-agonist induces HO-1 expression, abates RAS associated adipocyte and vascular dysfunction and induces adipocyte remodeling with smaller adipocytes while decreasing inflammation and increasing adiponectin secretion.