The dual PPAR-alpha/gamma agonist aleglitazar increases number and function of endothelial progenitor cells: implications for vascular function and atherogenesis

Abstract

Background: Endothelial progenitor cells (EPC) improve endothelial function and promote vascular repair. Aleglitazar combines lipid-modifying effects of PPAR-α agonists (fibrates) and insulin-sensitizing effects of PPAR-γ agonists (thiazolidinediones). We studied the effects of the novel dual peroxisome proliferator-activated receptor (PPAR)-α/γ agonist aleglitazar on glucose tolerance, EPC, endothelial function, neoangiogenesis and atherosclerosis in mice. Methods and results: C57Bl/6 wild-type (WT, normal chow), ApoE-/- mice (Western-type diet) and eNOS-/- mice were treated with aleglitazar (10 mg/kg/d, i.p.) or vehicle. Aleglitazar enhanced the expression of both the PPAR-α and PPAR-γ target genes and normalized glucose tolerance in cholesterol-fed ApoE-/- mice. In WT mice, aleglitazar treatment upregulated sca-1/VEGFR-2-positive EPC in the blood (153±10%) and bone marrow (197±22%), and upregulated spleen-derived diLDL/lectin-positive EPC (182±8%). Furthermore, aleglitazar augmented EPC migration (186±6% vs. controls) and enhanced neoangiogenesis (vascularized disk area 178±18% vs. controls). The effects of the dual PPAR-α/γ agonist on EPC number and function were abolished in eNOS knock-out mice. In ApoE-/- mice, aleglitazar upregulated EPC number and function, potently improved endothelium-dependent vasodilation and markedly reduced the formation of atherosclerotic plaques (plaque area/total lumen area 2.3±0.8% vs. 10.1±1.9% after 6 weeks and 22±2.2% vs. 36±2.1% after 8 weeks treatment). OilRed staining of hepatic sections showed a profound reduction of liver steatosis in ApoE-/- mice. In cultured human EPC, aleglitazar increased migration and colony forming units in a concentration-dependent manner. Furthermore, oxidative stress-induced EPC apoptosis and protein expression of p53 were reduced, while telomerase activity and expression of phospho-eNOS (S1177) and phospho-Akt were elevated. Comparative and inhibitor experiments revealed that aleglitazar's effects on EPC migration and colony forming units (CFU) were mediated by both PPAR-α and -γ signaling. E.g., aleglitazar treatment (10nM/l) induced EPC migration (304±21% vs. controls) and CFU (300±67% vs. controls) comparably to a co-stimulation of EPC with pioglitazone 10μM/l+fenofibric acid (150μM/l) (Migration: 332±28%; CFU: 289±72%). Conclusions: The dual PPAR-α/γ agonist aleglitazar augments number, function and survival of endothelial progenitor cells in an Akt- and eNOS-dependent fashion. The effects on EPC correlate with improved neoangiogenesis, restored endothelial function and prevention of atherosclerosis.