Defective insulin and acetylcholine induction of endothelial cell-nitric oxide synthase through insulin receptor substrate/Akt signaling pathway in aorta of obese rats.
The actions of acetylcholine (ACh) on endothelium mainly are mediated through muscarinic receptors, which are members of the G protein-coupled receptor family. In the present study, we show that ACh induces rapid tyrosine phosphorylation and activation of Janus kinase 2 (JAK2) in rat aorta. Upon JAK2 activation, tyrosine phosphorylation of insulin receptor substrate (IRS)-1 is detected. In addition, ACh induces JAK2/IRS-1 and IRS-1/phosphatidylinositol (PI) 3-kinase associations, downstream activation of Akt/protein kinase B, endothelial cell-nitric oxide synthase (eNOS), and extracellular signal-regulated kinase (ERK)-1/2. The pharmacological blockade of JAK2 or PI 3-kinase reduced ACh-stimulated eNOS phosphorylation, NOS activity, and aorta relaxation. These data indicate a new signal transduction pathway for IRS-1/PI 3-kinase/Akt/eNOS activation and ERK1/2 by means of JAK2 tyrosine phosphorylation stimulated by ACh in vessels. Moreover, we demonstrate that in aorta of obese rats (high-fat diet), there is an impairment in the insulin- and ACh-stimulated IRS-1/PI 3-kinase pathway, leading to reduced activation with lower protein levels of eNOS associated with a hyperactivated ERK/mitogen-activated protein kinase pathway. These results suggest that in aorta of obese rats, there not only is insulin resistance but also ACh resistance, probably mediated by a common signaling pathway that controls the activity and the protein levels of eNOS.
Zecchin
Henrique G
HG
Department of Internal Medicine, State University of Campinas, UNICAMP, Campinas 13083-970, Brazil.
Priviero
Fernanda B M
FB
Souza
Claudio T
CT
Zecchin
Karina G
KG
Prada
Patrícia O
PO
Carvalheira
José B C
JB
Velloso
Licio A
LA
Antunes
Edson
E
Saad
Mario J A
MJ
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D004041:Dietary Fats; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology*; D002149:Energy Intake; D004790:Enzyme Induction; D007328:Insulin / Q000494:pharmacology*; D053614:Janus Kinase 2 / Q000378:metabolism; D008297:Male; D052250:Nitric Oxide Synthase Type III / Q000096:biosynthesis*; D009765:Obesity / Q000201:enzymology / Q000503:physiopathology*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D051381:Rats; D011922:Rats, Mutant Strains; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000502:physiology*; D015398:Signal Transduction
D004041:Dietary Fats; D007328:Insulin; D052250:Nitric Oxide Synthase Type III; D011972:Receptor, Insulin; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D051057:Proto-Oncogene Proteins c-akt; D000109:Acetylcholine