title: Dysfunction of endothelium-dependent relaxation to insulin via PKC-mediated GRK2/Akt activation in aortas of ob/ob mice.
abstract: In diabetic states, hyperinsulinemia may negatively regulate Akt/endothelial nitric oxide synthase (eNOS) activation. Our main aim was to investigate whether and how insulin might negatively regulate Akt/eNOS activities via G protein-coupled receptor kinase 2 (GRK2) in aortas from ob/ob mice. Endothelium-dependent relaxation was measured in aortic rings from ob/ob mice (a type 2 diabetes model). GRK2, β-arrestin2, and Akt/eNOS signaling-pathway protein levels and activities were mainly assayed by Western blotting. Plasma insulin was significantly elevated in ob/ob mice. Insulin-induced relaxation was significantly decreased in the ob/ob aortas [vs. age-matched control (lean) ones]. The response in ob/ob aortas was enhanced by PKC inhibitor or GRK2 inhibitor. Akt (at Thr(308)) phosphorylation and eNOS (at Ser(1177)) phosphorylation, and also the β-arrestin2 protein level, were markedly decreased in the membrane fraction of insulin-stimulated ob/ob aortas (vs. insulin-stimulated lean ones). These membrane-fraction expressions were enhanced by GRK2 inhibitor and by PKC inhibitor in the ob/ob group but not in the lean group. PKC activity was much greater in ob/ob than in lean aortas. GRK2 protein and activity levels were increased in ob/ob and were greatly reduced by GRK2 inhibitor or PKC inhibitor pretreatment. These results suggest that in the aorta in diabetic mice with hyperinsulinemia an upregulation of GRK2 and a decrease in β-arrestin2 inhibit insulin-induced stimulation of the Akt/eNOS pathway and that GRK2 overactivation may result from an increase in PKC activity.
authors.affiliation: Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Taguchi
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Katsuo
authors.initials: K
authors.lastname: Kamata
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D019390:Arrestins / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology* / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D004789:Enzyme Activation; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006946:Hyperinsulinism / Q000201:enzymology / Q000503:physiopathology; D007328:Insulin / Q000097:blood*; D051379:Mice; D008810:Mice, Inbred C57BL; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D001786:Blood Glucose; D007328:Insulin; D047428:Protein Kinase Inhibitors; D014665:Vasodilator Agents; D000071557:beta-Arrestins; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2