Periadventitial adipose tissue impairs coronary endothelial function via PKC-β-dependent phosphorylation of nitric oxide synthase

Endogenous periadventitial adipose-derived factors have been shown to contribute to coronary vascular regulation by impairing endothelial function through a direct inhibition of endothelial nitric oxide synthase (eNOS). However, our understanding of the underlying mechanisms remains uncertain. Accordingly, this study was designed to test the hypothesis that periadventitial adipose tissue releases agents that attenuate coronary endothelial nitric oxide production via a protein kinase C (PKC)-β-dependent mechanism. Isometric tension studies were conducted on isolated canine circumflex coronary arteries with and without natural amounts of periadventitial adipose tissue. Adipose tissue significantly diminished coronary endothelial-dependent vasodilation and nitric oxide production in response to bradykinin and acetylcholine. The selective inhibition of endothelial PKC-β with ruboxistaurin (1 μM) abolished the adipose-induced impairment of bradykinin-mediated coronary vasodilation and the endothelial production of nitric oxide. Western blot analysis revealed a significant increase in eNOS phosphorylation at the inhibitory residue Thr495 in arteries exposed to periadventitial adipose tissue. This site-specific phosphorylation of eNOS was prevented by the inhibition of PKC-β. These data demonstrate that periadventitial adipose-derived factors impair coronary endothelial nitric oxide production via a PKC-β-dependent, site-specific phosphorylation of eNOS at Thr495

Metabolic syndrome reduces the contribution of K+ channels to ischemic coronary vasodilation

This investigation tested the hypothesis that metabolic syndrome decreases the relative contribution of specific K+ channels to coronary reactive hyperemia. Ca2+-activated (BKCa), voltage-activated (KV), and ATP-dependent (KATP) K+ channels were investigated. Studies were conducted in anesthetized miniature Ossabaw swine fed a normal maintenance diet (11% kcal from fat) or an excess calorie atherogenic diet (43% kcal from fat, 2% cholesterol, 20% kcal from fructose) for 20 wk. The latter diet induces metabolic syndrome, increasing body weight, fasting glucose, total cholesterol, and triglyceride levels. Ischemic vasodilation was determined by the coronary flow response to a 15-s occlusion before and after cumulative administration of antagonists for BKCa (penitrem A; 10 μg/kg iv), KV (4-aminopyridine; 0.3 mg/kg iv) and KATP (glibenclamide; 1 mg/kg iv) channels. Coronary reactive hyperemia was diminished by metabolic syndrome as the repayment of flow debt was reduced ∼30% compared with lean swine. Inhibition of BKCa channels had no effect on reactive hyperemia in either lean or metabolic syndrome swine. Subsequent inhibition of KV channels significantly reduced the repayment of flow debt (∼25%) in both lean and metabolic syndrome swine. Additional blockade of KATP channels further diminished (∼45%) the repayment of flow debt in lean but not metabolic syndrome swine. These data indicate that the metabolic syndrome impairs coronary vasodilation in response to cardiac ischemia via reductions in the contribution of K+ channels to reactive hyperemia

channels to ischemic coronary vasodilation + Metabolic syndrome reduces the contribution of K

intact animal to the cellular, subcellular, and molecular levels. It is published 12 times a year (monthly) by the American lymphatics, including experimental and theoretical studies of cardiovascular function at all levels of organization ranging from the publishes original investigations on the physiology of the heart, blood vessels, and AJP -Heart and Circulatory Physiology on December 12, 2011 ajpheart.physiology.org Downloaded fro

Impaired function of coronary BKCa channels in metabolic syndrome

The role of large-conductance Ca2+-activated K+ (BKCa) channels in regulation of coronary microvascular function is widely appreciated, but molecular and functional changes underlying the deleterious influence of metabolic syndrome (MetS) have not been determined. Male Ossabaw miniature swine consumed for 3–6 mo a normal diet (11% kcal from fat) or an excess-calorie atherogenic diet that induces MetS (45% kcal from fat, 2% cholesterol, 20% kcal from fructose). MetS significantly impaired coronary vasodilation to the BKCa opener NS-1619 in vivo (30–100 μg) and reduced the contribution of these channels to adenosine-induced microvascular vasodilation in vitro (1–100 μM). MetS reduced whole cell penitrem A (1 μM)-sensitive K+ current and NS-1619-activated (10 μM) current in isolated coronary vascular smooth muscle cells. MetS increased the concentration of free intracellular Ca2+ and augmented coronary vasoconstriction to the L-type Ca2+ channel agonist BAY K 8644 (10 pM–10 nM). BKCa channel α and β1 protein expression was increased in coronary arteries from MetS swine. Coronary vascular dysfunction in MetS is related to impaired BKCa channel function and is accompanied by significant increases in L-type Ca2+ channel-mediated coronary vasoconstriction