Vasculoprotective effect of insulin in the ischemic/reperfused canine heart: role of Akt-stimulated NO production.
OBJECTIVE
The objectives of this study were to investigate the vasculoprotective effects of glucose-insulin-potassium (GIK) on ischemia/reperfusion-induced coronary endothelial functional injury and to elucidate the mechanism involved.


METHODS
Dogs were subjected to 50 min of coronary occlusion and 4 h of reperfusion. Vehicle, GIK, or GK were intravenously infused 5 min before reperfusion, and the coronary vascular dysfunction and endothelial apoptosis were determined. In a separate study, cultured endothelial cells were subjected to simulated ischemia/reperfusion, and the signaling pathway involved in insulin's anti-apoptotic effect was investigated.


RESULTS
In vivo ischemia/reperfusion caused significant coronary vascular endothelial dysfunction as evidenced by reduced endothelium-dependent vasorelaxation, decreased nitric oxide (NO) production, and endothelial cell apoptosis as determined by caspase 3 activation and TUNEL staining. Treatment with GIK, but not GK, markedly improved the endothelium-dependent coronary vasorelaxation (P<0.01 versus vehicle), increased total NO production (P<0.01), and attenuated endothelial apoptosis. In cultured endothelial cells, treatment with insulin also markedly increased NO production and reduced simulated ischemia/reperfusion-induced apoptosis. Moreover, pre-treatment with either Akt inhibitor or NO synthase inhibitor almost abolished the anti-apoptotic effect exerted by insulin but not by SNAP, an NO donor.


CONCLUSIONS
These results demonstrate that in vivo treatment with GIK at reperfusion attenuates ischemia/reperfusion-induced coronary endothelial dysfunction and endothelial apoptosis in an Akt-dependent and NO-mediated fashion. The coronary vasculoprotective effect elicited by insulin may contribute to the previously observed cardiac protective effect of GIK.
Ma
Heng
H
Department of Physiology, Fourth Military Medical University, Xi'an, 710032, China.
Zhang
Hai-Feng
HF
Yu
Lu
L
Zhang
Quan-Jiang
QJ
Li
Jia
J
Huo
Jian-Hua
JH
Li
Xue
X
Guo
Wen-Yi
WY
Wang
Hai-Chang
HC
Gao
Feng
F
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004285:Dogs; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D019332:Endothelin-1 / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D009566:Nitrates / Q000494:pharmacology; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011188:Potassium / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology
D019332:Endothelin-1; D007328:Insulin; D009566:Nitrates; D014665:Vasodilator Agents; D009569:Nitric Oxide; C031618:sodium nitrate; D019001:Nitric Oxide Synthase; D051057:Proto-Oncogene Proteins c-akt; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D005947:Glucose; D000109:Acetylcholine; D011188:Potassium