APPL1 Counteracts Obesity-Induced Vascular Insulin Resistance and Endothelial Dysfunction by Modulating the Endothelial Production of Nitric Oxide and Endothelin-1 in Mice
- Yi Wang1,2,
- Kenneth K.Y. Cheng2,
- Karen S.L. Lam2,
- Donghai Wu3,
- Yu Wang4,
- Yu Huang5,
- Paul M. Vanhoutte4,
- Gary Sweeney6,
- Yiming Li1 and
- Aimin Xu2,4⇓
- 1Department of Medicine, Division of Endocrinology and Metabolism, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
- 2Department of Medicine, the University of Hong Kong, Hong Kong
- 3Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
- 4Department of Pharmacology and Pharmacy, the University of Hong Kong, Hong Kong
- 5Institute of Vascular Medicine, Li Ka Shing Institute of Health Sciences and School Of Biomedical Sciences, Chinese University of Hong Kong, Hong Kong
- 6Department of Biology, York University, Toronto, Ontario, Canada
- Corresponding authors: Aimin Xu, , and Yiming Li, .
Y.W. and K.K.Y.C. contributed equally to this study.
OBJECTIVE Insulin stimulates both nitric oxide (NO)-dependent vasodilation and endothelin-1 (ET-1)–dependent vasoconstriction. However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear. This study aimed to investigate the roles of the multidomain adaptor protein APPL1 in modulating vascular actions of insulin in mice and in endothelial cells.
RESEARCH DESIGN AND METHODS Both APPL1 knockout mice and APPL1 transgenic mice were generated to evaluate APPL1’s physiological roles in regulating vascular reactivity and insulin signaling in endothelial cells.
RESULTS Insulin potently induced NO-dependent relaxations in mesenteric arteries of 8-week-old mice, whereas this effect of insulin was progressively impaired with ageing or upon development of obesity induced by high-fat diet. Transgenic expression of APPL1 prevented age- and obesity-induced impairment in insulin-induced vasodilation and reversed obesity-induced augmentation in insulin-evoked ET-1–dependent vasoconstriction. By contrast, genetic disruption of APPL1 shifted the effects of insulin from vasodilation to vasoconstriction. At the molecular level, insulin-elicited activation of protein kinase B (Akt) and endothelial NO synthase and production of NO were enhanced in APPL1 transgenic mice but were abrogated in APPL1 knockout mice. Conversely, insulin-induced extracellular signal–related kinase (ERK)1/2 phosphorylation and ET-1 expression was augmented in APPL1 knockout mice but was diminished in APPL1 transgenic mice. In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.
CONCLUSIONS APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.
This article contains Supplementary Data online at http://diabetes.diabetesjournals.org/lookup/suppl/doi:10.2337/db11-0666/-/DC1.
- Received May 17, 2011.
- Accepted August 22, 2011.
- © 2011 by the American Diabetes Association.
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