title: Contribution of insulin and Akt1 signaling to endothelial nitric oxide synthase in the regulation of endothelial function and blood pressure.
abstract: Impaired insulin signaling via phosphatidylinositol 3-kinase/Akt to endothelial nitric oxide synthase (eNOS) in the vasculature has been postulated to lead to arterial dysfunction and hypertension in obesity and other insulin resistant states. To investigate this, we compared insulin signaling in the vasculature, endothelial function, and systemic blood pressure in mice fed a high-fat (HF) diet to mice with genetic ablation of insulin receptors in all vascular tissues (TTr-IR(-/-)) or mice with genetic ablation of Akt1 (Akt1-/-). HF mice developed obesity, impaired glucose tolerance, and elevated free fatty acids that was associated with endothelial dysfunction and hypertension. Basal and insulin-mediated phosphorylation of extracellular signal-regulated kinase 1/2 and Akt in the vasculature was preserved, but basal and insulin-stimulated eNOS phosphorylation was abolished in vessels from HF versus lean mice. In contrast, basal vascular eNOS phosphorylation, endothelial function, and blood pressure were normal despite absent insulin-mediated eNOS phosphorylation in TTr-IR(-/-) mice and absent insulin-mediated eNOS phosphorylation via Akt1 in Akt1-/- mice. In cultured endothelial cells, 6 hours of incubation with palmitate attenuated basal and insulin-stimulated eNOS phosphorylation and NO production despite normal activation of extracellular signal-regulated kinase 1/2 and Akt. Moreover, incubation of isolated arteries with palmitate impaired endothelium-dependent but not vascular smooth muscle function. Collectively, these results indicate that lower arterial eNOS phosphorylation, hypertension, and vascular dysfunction following HF feeding do not result from defective upstream signaling via Akt, but from free fatty acid-mediated impairment of eNOS phosphorylation.
authors.affiliation: College of Health, University of Utah School of Medicine, 30 N 2030 E, Salt Lake City, UT 84132, USA. j.david.symons@hsc.utah.edu
authors.forename: J David
authors.initials: JD
authors.lastname: Symons
authors.forename: Shawna L
authors.initials: SL
authors.lastname: McMillin
authors.forename: Christian
authors.initials: C
authors.lastname: Riehle
authors.forename: Jason
authors.initials: J
authors.lastname: Tanner
authors.forename: Milda
authors.initials: M
authors.lastname: Palionyte
authors.forename: Elaine
authors.initials: E
authors.lastname: Hillas
authors.forename: Deborah
authors.initials: D
authors.lastname: Jones
authors.forename: Robert C
authors.initials: RC
authors.lastname: Cooksey
authors.forename: Morris J
authors.initials: MJ
authors.lastname: Birnbaum
authors.forename: Donald A
authors.initials: DA
authors.lastname: McClain
authors.forename: Quan-Jiang
authors.initials: QJ
authors.lastname: Zhang
authors.forename: Derrick
authors.initials: D
authors.lastname: Gale
authors.forename: Lloyd J
authors.initials: LJ
authors.lastname: Wilson
authors.forename: E Dale
authors.initials: ED
authors.lastname: Abel