Oleanolic acid ameliorates high glucose-induced endothelial dysfunction via PPARδ activation

Abstract

Oleanolic acid (3β-hydroxyolean-12-en-28-oic acid, OA) is a pentacyclic triterpenes widely distributed in food, medicinal plants and nutritional supplements. OA exhibits various pharmacological properties, such as hepatoprotective and anti-tumor effects. In this study, we analyzed the effect of OA on endothelial dysfunction induced by high glucose in human vascular endothelial cells (ECs). Western blotting showed that OA attenuated high glucose-reduced nitric production oxide (NO) as well as Akt-Ser473 and eNOS-Ser1177 phosphorylation in cultured human umbilical vein ECs (HUVECs). Next, luciferase reporter assay showed that OA activated peroxisome proliferators-activated receptor δ (PPARδ) activity. Quantitative reverse transcriptase PCR (qRT-PCR) demonstrated that OA increased the expressions of PPARδ target genes (PDK4, ADRP and ANGPTL4) in ECs. Meanwhile, the induced expressions of PDK4, ADRP and ANGPTL4 by OA were inhibited by GSK0660, a specific antagonist of PPARδ. In addition, inhibition of PPARδ abolished OA-induced the Akt-Ser473 and eNOS-Ser1177 phosphorylation, and NO production. Finally, by using Multi Myograph System, we showed that OA prevented high glucose-impaired vasodilation. This protective effect on vasodilation was inhibited in aortic rings pretreated with GSK0660. Collectively, we demonstrated that OA improved high glucose-impaired endothelial function via a PPARδ-mediated mechanism and through eNOS/Akt/NO pathway.

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“…Altered endothelial phenotype is a prominent feature of metabolic disturbance in DM. In cultured human umbilical vein endothelial cells (HUVECs), high glucose (HG) reduces nitric oxide (NO) production and eNOS-Ser 1177 phosphorylation [5]. In animal models relevant to T1DM, hyperglycemia-mediated endothelial sloughing and apoptosis contributes to atherosclerosis [3,6].…”

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“…The NO production is also stimulated by PPARγ and leads to endothelial vasodilation. OA was able to restore the endothelial function impaired by high glucose levels due to the activation of the PPARγ-mediated Akt/eNOS signaling pathway [ 162 ].…”