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      Insulin treatment before resuscitation following hemorrhagic shock improves cardiac contractility and protects the myocardium in the isolated rat heart

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          Abstract

          Background:

          Insulin has been shown to exert positive inotropic effects in several in vivo ex vivo models and in human hearts. Resuscitation following hemorrhagic shock results in myocardial contractile dysfunction. However, the optimal timing for treatment with insulin for the cardioprotection effects is unclear.

          Objectives:

          The objective of this study was to test the hypothesis that treatment with insulin before resuscitation provides better cardioprotection than treatment with insulin after resuscitation.

          Materials and Methods:

          Rats were assigned to 3 experimental groups ( n = 6 per group): (1) Hemorrhagic shock and resuscitation, (2) hemorrhagic shock resuscitated then treated with insulin and (3) hemorrhagic shock treated with insulin before resuscitation. Rats were hemorrhaged for 60 min to rach mean arterial blood pressure of 40 mmHg. Rats were resuscitated in vivo by reinfusion of the shedded blood to restore normotension and monitored for 60 min. Rats were treated or not with insulin 200 μU/g body weight intramuscularly either before or after resuscitation. The maximum of the left ventricular developed pressure (+dP/dt) was measured for 60 min in the isolated perfused hearts using the Langendorff method. Blood samples were obtained for measurements of tumor necrosis factor-alpha (TNF-α).

          Results:

          Treatment with insulin before resuscitation following hemorrhagic shock significantly elevated max dP/dt compared with insulin treatment after resuscitation and the untreated group. TNF-α levels were lower in the insulin treatment before resuscitation compared to the treatment after resuscitation and the untreated group.

          Conclusion:

          Insulin treatment before resuscitation following hemorrhagic shock provides better cardiac protection than treatment with insulin after resuscitation, as evidenced by the improved myocardial contractility, preservation of myocardial structure. The mechanism of cardiac protection involves decrease in the inflammatory response to shock by lowering the levels of TNF.

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          Most cited references36

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          Akt activation preserves cardiac function and prevents injury after transient cardiac ischemia in vivo.

          The serine-threonine kinase Akt is activated by several ligand-receptor systems previously shown to be cardioprotective. Akt activation reduces cardiomyocyte apoptosis in models of transient ischemia. Its role in cardiac dysfunction or infarction, however, remains unclear. We examined the effects of a constitutively active Akt mutant (myr-Akt) in a rat model of cardiac ischemia-reperfusion injury. In vivo gene transfer of myr-Akt reduced infarct size by 64% and the number of apoptotic cells by 84% (P<0.005 for each). Ischemia-reperfusion injury decreased regional cardiac wall thickening as well as the maximal rate of left ventricular pressure rise and fall (+dP/dt and -dP/dt). Akt activation restored regional wall thickening and +dP/dt and -dP/dt to levels seen in sham-operated rats. To better understand this benefit, we examined the effects of myr-Akt on hypoxic cardiomyocyte dysfunction in vitro. myr-Akt prevented hypoxia-induced abnormalities in cardiomyocyte calcium transients and shortening. Akt activation also enhanced sarcolemmal expression of Glut-4 in vivo and increased glucose uptake in vitro to the level seen with insulin treatment. Akt activation exerts a powerful cardioprotective effect after transient ischemia that probably reflects its ability to both inhibit cardiomyocyte death and improve function of surviving cardiomyocytes. Akt may represent an important nodal target for therapy in ischemic and other heart disease.
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            Prospective randomised study of intensive insulin treatment on long term survival after acute myocardial infarction in patients with diabetes mellitus. DIGAMI (Diabetes Mellitus, Insulin Glucose Infusion in Acute Myocardial Infarction) Study Group.

            To test the hypothesis that intensive metabolic treatment with insulin-glucose infusion followed by multidose insulin treatment in patients with diabetes mellitus and acute myocardial infarction improves the prognosis. Patients with diabetes mellitus and acute myocardial infarction were randomly allocated standard treatment plus insulin-glucose infusion for at least 24 hours followed by multidose insulin treatment or standard treatment (controls). 620 patients were recruited, of whom 306 received intensive insulin treatment and 314 served as controls. Long term all cause mortality. The mean (range) follow up was 3.4 (1.6-5.6) years. There were 102 (33%) deaths in the treatment group compared with 138 (44%) deaths in the control group (relative risk (95% confidence interval) 0.72 (0.55 to 0.92); P = 0.011). The effect was most pronounced among the predefined group that included 272 patients without previous insulin treatment and at a low cardiovascular risk (0.49 (0.30 to 0.80); P = 0.004). Insulin-glucose infusion followed by intensive subcutaneous insulin in diabetic patients with acute myocardial infarction improves long term survival, and the effect seen at one year continues for at least 3.5 years, with an absolute reduction in mortality of 11%. This means that one life was saved for nine treated patients. The effect was most apparent in patients who had not previously received insulin treatment and who were at a low cardiovascular risk.
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              Nitric oxide mediates the antiapoptotic effect of insulin in myocardial ischemia-reperfusion: the roles of PI3-kinase, Akt, and endothelial nitric oxide synthase phosphorylation.

              Recent evidence from cultured endothelial cell studies suggests that phosphorylation of endothelial nitric oxide synthase (eNOS) through the PI3-kinase-Akt pathway increases NO production. This study was designed to elucidate the signaling pathway involved in the antiapoptotic effect of insulin in vivo and to test the hypothesis that phosphorylation of eNOS by insulin may participate in the cardioprotective effect of insulin after myocardial ischemia and reperfusion. Male Sprague-Dawley rats were subjected to 30 minutes of myocardial ischemia and 4 hours of reperfusion. Rats were randomized to receive vehicle, insulin, insulin plus wortmannin, or insulin plus L-NAME. Treatment with insulin resulted in 2.6-fold and 4.3-fold increases in Akt and eNOS phosphorylation and a significant increase in NO production in ischemic/reperfused myocardial tissue. Phosphorylation of Akt and eNOS and increase of NO production by insulin were completely blocked by wortmannin, a PI3-kinase inhibitor. Pretreatment with L-NAME, a nonselective NOS inhibitor, had no effect on Akt and eNOS phosphorylation but significantly reduced NO production. Moreover, treatment with insulin markedly reduced myocardial apoptotic death (P<0.01 versus vehicle). Pretreatment with wortmannin abolished the antiapoptotic effect of insulin. Most importantly, pretreatment with L-NAME also significantly reduced the antiapoptotic effect of insulin (P<0.01 versus insulin). These results demonstrated that in vivo administration of insulin activated Akt through the PI3-kinase-dependent mechanism and reduced postischemic myocardial apoptotic death. Phosphorylation of eNOS and the concurrent increase of NO production contribute significantly to the antiapoptotic effect of insulin.
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                Author and article information

                Journal
                J Emerg Trauma Shock
                J Emerg Trauma Shock
                JETS
                Journal of Emergencies, Trauma, and Shock
                Medknow Publications & Media Pvt Ltd (India )
                0974-2700
                0974-519X
                Jul-Sep 2015
                : 8
                : 3
                : 144-148
                Affiliations
                [1]Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
                Author notes
                Address for correspondence: Dr. Mona Soliman, E-mail: monaslmn@ 123456yahoo.com
                Article
                JETS-8-144
                10.4103/0974-2700.160714
                4520027
                b9a691c7-e18f-473c-8add-4da853c368d5
                Copyright: © Journal of Emergencies, Trauma, and Shock

                This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 21 August 2014
                : 06 January 2015
                Categories
                Original Article

                Emergency medicine & Trauma
                contractility,hemorrhage,insulin,resuscitation,shock
                Emergency medicine & Trauma
                contractility, hemorrhage, insulin, resuscitation, shock

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