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Rheb is a critical regulator of autophagy during myocardial ischemia: pathophysiological implications in obesity and metabolic syndrome.

ABSTRACT: BACKGROUND:Rheb is a GTP-binding protein that promotes cell survival and mediates the cellular response to energy deprivation (ED). The role of Rheb in the regulation of cell survival during ED has not been investigated in the heart. METHODS AND RESULTS:Rheb is inactivated during cardiomyocyte (CM) glucose deprivation (GD) in vitro, and during acute myocardial ischemia in vivo. Rheb inhibition causes mTORC1 inhibition, because forced activation of Rheb, through Rheb overexpression in vitro and through inducible cardiac-specific Rheb overexpression in vivo, restored mTORC1 activity. Restoration of mTORC1 activity reduced CM survival during GD and increased infarct size after ischemia, both of which were accompanied by inhibition of autophagy, whereas Rheb knockdown increased autophagy and CM survival. Rheb inhibits autophagy mostly through Atg7 depletion. Restoration of autophagy, through Atg7 reexpression and inhibition of mTORC1, increased cellular ATP content and reduced endoplasmic reticulum stress, thereby reducing CM death induced by Rheb activation. Mice with high-fat diet-induced obesity and metabolic syndrome (HFD mice) exhibited deregulated cardiac activation of Rheb and mTORC1, particularly during ischemia. HFD mice presented inhibition of cardiac autophagy and displayed increased ischemic injury. Pharmacological and genetic inhibition of mTORC1 restored autophagy and abrogated the increase in infarct size observed in HFD mice, but they failed to protect HFD mice in the presence of genetic disruption of autophagy. CONCLUSIONS:Inactivation of Rheb protects CMs during ED through activation of autophagy. Rheb and mTORC1 may represent therapeutic targets to reduce myocardial damage during ischemia, particularly in obese patients.

SUBMITTER: Sciarretta S

PROVIDER: S-EPMC3337789 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Rheb is a critical regulator of autophagy during myocardial ischemia: pathophysiological implications in obesity and metabolic syndrome.

Sciarretta Sebastiano S Zhai Peiyong P Shao Dan D Maejima Yasuhiro Y Robbins Jeffrey J Volpe Massimo M Condorelli Gianluigi G Sadoshima Junichi J

Circulation 20120131 9

<h4>Background</h4>Rheb is a GTP-binding protein that promotes cell survival and mediates the cellular response to energy deprivation (ED). The role of Rheb in the regulation of cell survival during ED has not been investigated in the heart.<h4>Methods and results</h4>Rheb is inactivated during cardiomyocyte (CM) glucose deprivation (GD) in vitro, and during acute myocardial ischemia in vivo. Rheb inhibition causes mTORC1 inhibition, because forced activation of Rheb, through Rheb overexpression ...[more]

PMID: 22294621

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Project description:The time course and relationships of myocardial hemorrhage and edema in patients after acute ST-segment elevation myocardial infarction (STEMI) are uncertain. Patients with ST-segment elevation myocardial infarction treated by primary percutaneous coronary intervention underwent cardiac magnetic resonance imaging on 4 occasions: at 4 to 12 hours, 3 days, 10 days, and 7 months after reperfusion. Myocardial edema (native T2) and hemorrhage (T2*) were measured in regions of interest in remote and injured myocardium. Myocardial hemorrhage was taken to represent a hypointense infarct core with a T2* value <20 ms. Thirty patients with ST-segment elevation myocardial infarction (mean age 54 years; 25 [83%] male) gave informed consent. Myocardial hemorrhage occurred in 7 (23%), 13 (43%), 11 (33%), and 4 (13%) patients at 4 to 12 hours, 3 days, 10 days, and 7 months, respectively, consistent with a unimodal pattern. The corresponding median amounts of myocardial hemorrhage (percentage of left ventricular mass) during the first 10 days after myocardial infarction were 2.7% (interquartile range [IQR] 0.0-5.6%), 7.0% (IQR 4.9-7.5%), and 4.1% (IQR 2.6-5.5%; P<0.001). Similar unimodal temporal patterns were observed for myocardial edema (percentage of left ventricular mass) in all patients (P=0.001) and for infarct zone edema (T2, in ms: 62.1 [SD 2.9], 64.4 [SD 4.9], 65.9 [SD 5.3]; P<0.001) in patients without myocardial hemorrhage. Alternatively, in patients with myocardial hemorrhage, infarct zone edema was reduced at day 3 (T2, in ms: 51.8 [SD 4.6]; P<0.001), depicting a bimodal pattern. Left ventricular end-diastolic volume increased from baseline to 7 months in patients with myocardial hemorrhage (P=0.001) but not in patients without hemorrhage (P=0.377). The temporal evolutions of myocardial hemorrhage and edema are unimodal, whereas infarct zone edema (T2 value) has a bimodal pattern. Myocardial hemorrhage is prognostically important and represents a target for therapeutic interventions that are designed to preserve vascular integrity following coronary reperfusion. URL: https://clinicaltrials.gov/. Unique identifier: NCT02072850.

Dataset Information

Rheb is a critical regulator of autophagy during myocardial ischemia: pathophysiological implications in obesity and metabolic syndrome.

Publications

Rheb is a critical regulator of autophagy during myocardial ischemia: pathophysiological implications in obesity and metabolic syndrome.

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