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Fatty Acids Differentially Modulate Insulin-Stimulated Endothelial Nitric Oxide Production by an Akt-Independent Pathway
  1. Matthew A. Lynn,
  2. Heidi L. Rupnow,
  3. Dean J. Kleinhenz,
  4. William A. Kanner,
  5. Samuel C. Dudley,
  6. Michael C. Hart
  1. From the Department of Medicine, Veterans Affairs, and Emory University Medical Centers, Decatur, GA.
  1. Address correspondence to: C. Michael Hart, Veterans Affairs Medical Center 151-P, 1670 Clairmont Rd, Decatur, GA 30033; tel: 404-321-6111 ext. 7278; fax: 404-728-7750; e-mail: michael.hart3{at}med.va.gov.
  2. Supported by grants from the American Diabetes Association (to C.M.H.), the National Institutes of Health (DK61274 to C.M.H. and HL64828 to S.C.D.), and the Veterans Affairs Research Service (to S.C.D. and C.M.H.).
  3. Presented in abstract form at the Experimental Biology meeting San Diego, CA, April 2003.

Abstract

Background Insulin increases endothelial nitric oxide (NO) production by activating endothelial nitric oxide synthase (eNOS) through protein kinase B (Akt)-mediated phosphorylation of serine residue 1179 (p-eNOS serine 1179). Because fatty acids modulate insulinstimulated Akt signaling cascades in smooth muscle cells, we hypothesized that fatty acids would differentially regulate endothelial Akt signaling, eNOS phosphorylation, and NO production.

Methods Porcine pulmonary artery endothelial cells (PAECs) were treated for 3 hours with 100 μM oleic (18:1) or eicosapentaenoic (20:5) acids or with an equivalent volume of ethanol vehicle (0.1%). PAECs were then treated with graded concentrations (10−9-10−5 M) of insulin or incubated overnight (24 hours) in culture medium without fatty acids before insulin treatment. Activation and phosphorylation of Akt and eNOS were determined by immunoblotting. NO production was measured with a chemiluminescence NO analyzer or with a NO-selective carbon fiber microelectrode.

Results Insulin-stimulated Akt phosphorylation, eNOS phosphorylation, and NO production. The phosphatidylinositol-3 kinase inhibitor wortmannin attenuated insulin-stimulated Akt activation and NO production. Treatment with the ω-3 fatty acid 20:5, but not 18:1, enhanced insulin-stimulated NO production but failed to alter insulin-stimulated Akt activation or eNOS serine 1179 phosphorylation.

Conclusion Individual fatty acyl species have distinct effects on insulin-stimulated endothelial NO production. Although fatty acids alter Akt signaling in muscle cells, the current results indicate that fatty acids do not modulate endothelial NO production through alterations in insulin-stimulated, Akt-mediated eNOS phosphorylation.

Key Words
  • fatty acid
  • endothelial cell
  • nitric oxide

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