Original article Globular adiponectin improves high glucose-suppressed endothelial progenitor cell function through endothelial nitric oxide synthase dependent mechanisms Po-Hsun Huang a,d,e,1 , Jia-Shiong Chen f,1 , Hsiao-Ya Tsai d , Yung-Hsiang Chen g , Feng-Yen Lin h , Hsin-Bang Leu a,c,d,e , Tao-Cheng Wu a,e , Shing-Jong Lin a,b,d,e, ⁎, Jaw-Wen Chen a,b,e,f, ⁎ a Division of Cardiology, Department of Internal Medicine, Taipei Veterans General Hospital, Taipei, Taiwan b Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan c Healthcare and Management Center, Taipei Veterans General Hospital, Taipei, Taiwan d Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan e Cardiovascular Research Center, National Yang-Ming University, Taipei, Taiwan f Institute and Department of Pharmacology, National Yang-Ming University, Taiwan g Graduate Institute of Integrated Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan h Division of Internal Medicine, Taipei Medical University and Hospital, Taipei, Taiwan abstract article info Article history: Received 1 March 2011 Accepted 15 March 2011 Available online 31 March 2011 Keywords: Adiponectin Endothelial progenitor cell Nitric oxide Mitogen-activated protein kinase Hyperglycemia Plasma levels of adiponectin, an adipose-specific protein with putative anti-atherogenic properties, could be down-regulated in obese and diabetic subjects. Recent insights suggest that the injured endothelial monolayer is regenerated by circulating endothelial progenitor cells (EPCs), but high glucose reduces number and functions of EPCs. Here, we tested the hypothesis that globular adiponectin can improve high glucose- suppressed EPC functions by restoration of endothelial nitric oxide synthase (eNOS) activity. Late EPCs isolated from healthy subjects appeared with cobblestone shape at 2–4 weeks. EPCs were incubated with high glucose (25 mM) and treatment with globular adiponectin for functional study. Migration and tube formation assays were used to evaluate the vasculogenetic capacity of EPCs. The activities of eNOS, Akt and concentrations of nitric oxide (NO) were also determined. Administration of globular adiponectin at physiological concentrations promoted EPC migration and tube formation, and dose-dependently upregulated phosphorylation of eNOS, Akt and augmented NO production. Chronic incubation of EPCs in high-glucose medium significantly impaired EPC function and induced cellular senescence, but these suppression effects were reversed by treatment with globular adiponectin. Globular adiponectin reversed high glucose-impaired EPC functions through NO- and p38 MAPK-related mechanisms. In addition, nude mice that received EPCs treated with adiponectin in high glucose medium showed a significant improvement in blood flow than those received normal saline and EPCs incubated in high glucose conditions. The administration of globular adiponectin improved high glucose-impaired EPC functions in vasculogenesis by restoration of eNOS activity. These beneficial effects may provide some novel rational to the vascular protective properties of adiponectin. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Hyperglycemia is a key factor for the development of vascular complications in patients with type 2 diabetes [1]. However, the pathophysiology linking type 2 diabetes to atherosclerotic cardiovas- cular diseases is complex and still not fully clarified. Endothelial function has been shown to play an important role in the clinical manifestations of established atherosclerotic lesions [2]. Convincing evidence suggests that the injured endothelial monolayer is regen- erated by circulating bone marrow derived-endothelial progenitor cells (EPCs), which accelerate reendothelialization and protect against the initiation and progression of atherosclerosis [3,4]. Levels of circulating EPCs reflect vascular repair capacity and may be directly related to endothelial function [5]. In diabetic subjects, the reduced number and function of EPCs have been suggested as the pathogenesis of vascular complication [6,7]. A progressive reduction in circulating EPCs under long-term exposure to high glucose may contribute to a vicious cycle resulting in endothelial dysfunction and the rapid progression of atherosclerosis [8,9]. Our recent work further indicated that long term exposure to high glucose may impair the proliferation and functions of both early and late (outgrowth) human EPCs through Journal of Molecular and Cellular Cardiology 51 (2011) 109–119 ⁎ Corresponding authors at: Department of Medical Research and Education, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Road, Taipei, Taiwan. Tel.: + 886 2 2875 7229; fax: +886 2 2876 3336. E-mail addresses: sjlin@vghtpe.gov.tw (S.-J. Lin), jwchen@vghtpe.gov.tw (J.-W. Chen). 1 The first two authors contributed equally to this work. 0022-2828/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.yjmcc.2011.03.008 Contents lists available at ScienceDirect Journal of Molecular and Cellular Cardiology journal homepage: www.elsevier.com/locate/yjmcc