[Anti-apoptotic effect of insulin in myocardial ischemia-reperfusion and its principal signaling pathway].
OBJECTIVE
To investigate the signaling pathway involved in the insulin-elicited anti-apoptotic effect during myocardial ischemia and reperfusion (MI/R) in vivo.


METHODS
Male Sprague-Dawley rats were anesthetized and subjected to 30 min of myocardial ischemia followed by 4h-reperfusion. Rats were randomly treated with intravenous infusion of saline (vehicle, 4 ml.kg(-1).h(-1)), insulin (60 U/L), or insulin + wortmannin 5 min before reperfusion and continuing throughout the 4h-reperfusion period. Cardiac myocyte apoptosis was determined both qualitatively and quantitatively by DNA laddering and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) methods. Myocardial nitric oxide (NO) was measured by using NO-specific chemiluminescence detector. Activations of Akt and p38 mitogen-activated protein kinase (MAPK) were determined by kinase activity assays using corresponding kinase activity assay kits (Cell Signaling).


RESULTS
In the vehicle-treated rats, MI/R caused significant cardiac myocyte apoptotic death. Treatment with insulin produced a significant anti-apoptotic effect as evidenced by a marked reduction of apoptotic index [(8.0 +/- 2.9)% vs. (19.3 +/- 4.6)% of vehicle, P < 0.01] and decreased formation of myocardial DNA fragmentation. In addition, insulin treatment produced 2.7-fold increase (P < 0.01) of myocardial Akt activity and 28% increase of myocardial NO production (P < 0.05), while p38 MAPK activity changed insignificantly as compared with that of vehicle (P > 0.05). Both insulin-induced Akt activation and anti-apoptotic effect could be abrogated by wortmannin, a phosphatidylinositol (PI) 3-kinase inhibitor.


CONCLUSIONS
In vivo treatment with insulin at the initial of reperfusion significantly reduced postischemic apoptotic death via the PI3-kinase-Akt signaling pathway. Akt, but not p38 MAPK, activation plays a key role in the insulin-induced anti-apoptotic effect in MI/R.
Gao
Feng
F
Department of Physiology, The Fourth Military Medical University, Xi'an 710032, China. fgao@fmmu.du.cn
Yan
Wen-li
WL
Zhang
Hai-feng
HF
Shi
Dong-wei
DW
Mo
Qi-zhong
QZ
Ma
Xin-liang
XL
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000473:pathology* / Q000503:physiopathology* / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D009569:Nitric Oxide / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases
D007328:Insulin; D011518:Proto-Oncogene Proteins; D009569:Nitric Oxide; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases