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OBESITY ALTERS MOLECULAR AND FUNCTIONAL CARDIAC RESPONSES TO ISCHEMIA-REPERFUSION AND GLUCAGON-LIKE PEPTIDE-1 RECEPTOR AGONISM

ABSTRACT: Diet induced obesity in swine was associated with altered cardiovascular functional, miR transcriptome, and proteomic response to ischemia-reperfusion. Furthermore, the GLP-1 mimetic exendin-4 altered functional, miR and protein responses differently in obese versus lean swine, demonstrating the pervasive effect of obesity on modulating cardiac response to pathophysiologies and therapeutics. This study tested the hypothesis that obesity alters the left ventricular microRNA (miR) transcriptome, proteome and functional cardiac response to ischemia-reperfusion (I/R) injury and to glucagon like peptide-1 (GLP-1) receptor activation. Ossabaw swine were fed normal chow or obesogenic diet for 6 months followed by IV infusion of either saline (vehicle) or the GLP-1 mimetic exendin-4 (Ex-4). Left ventricular pressure volume relationships were assessed under baseline conditions, during a 30-minute occlusion of the circumflex artery and during a 2 hour reperfusion period. Cardiac biopsies were obtained from normally-perfused and ischemia-reperfusion territories, and analyzed using Affymetrix 3.0 miR microarray and protein mass spectrometry. I/R was found to depress global cardiac function in lean swine (systolic pressure, end-diastolic volume). In contrast, Ex-4 therapies did not affect blood pressure in obese animals, but significantly reduced end-diastolic volume following the reperfusion period. These divergent physiologic response to regional I/R in obese vs lean hearts were associated with significantly different protein and miRNA changes. Obesity was associated with altered abundance of proteins associated with calcium handling and contractility, and with changes in miRs relating to metabolism, hypertrophy, and cell death, including the miR-15 and miR-30 families, miR-199a, and miR-214. These effects were modified differently by EX-4 treatment in lean vs obese swine. These findings suggest specific miR and proteomic differences contribute to differences in functional cardiac responses to ischemia-reperfusion injury and pharmacologic activation of GLP-1 signaling in the setting of obesity, volume, stroke volume and ejection fraction) with partial amelioration seen in Ex-4 treated animals.

ORGANISM(S): synthetic construct Sus scrofa

PROVIDER: GSE77378 | GEO | 2017/01/06

SECONDARY ACCESSION(S): PRJNA310187

REPOSITORIES: GEO

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Project description:Disruption of peripheral circadian rhyme pathways dominantly leads to metabolic disorders. Studies on circadian rhythm proteins in the heart indicated a role for Clock or Per2 in cardiac metabolism. In fact, Per2-/- mice have larger infarct sizes with a deficient lactate production during myocardial ischemia. To test the hypothesis that cardiac Per2 represents an important regulator of cardiac metabolism during myocardial ischemia, we performed lactate measurements during reperfusion in Per1-/-, Per2-/- or wildtype mice followed by gene array studies using various ischemia-reperfusion protocols comparing wildtype and Per2-/- mice. Lactate measurements in whole blood confirmed a dominant role of Per2 for lactate production during myocardial ischemia. Surprisingly, high-throughput gene array analysis of eight different conditions on one 24-microarray plate revealed dominantly lipid metabolism as differentially regulated pathway in wildtype mice when compared to Per2-/-. In all treatment groups, the enzyme enoyl-CoA hydratase, which is essential in fatty acid beta-oxidation, was regulated in wildtype animals only. Studies using nuclear magnet resonance imaging (NMRI) confirmed altered fatty acid populations with higher mono-unsaturated fatty acid levels in hearts from Per2-/- mice. Unexpectedly, studies on gene regulation during reperfusion revealed solely pro inflammatory genes as differentially regulated 'Per2-genes'. Subsequent studies on inflammatory markers showed increasing IL6 or TNFa levels during reperfusion in Per2-/- mice. In summary, these studies reveal a novel role of cardiac Per2 for fatty acid metabolism or inflammation during myocardial ischemia and reperfusion. We pursued studies on Per2 dependent gene expression during myocardial ischemia or reperfusion to understand its impact on cardiac metabolism. We designed different ischemia and reperfusion protocols and performed a high-throughput expression profiling of 24 samples at a time using an industry-standard whole mouse gene array (Affymetrix, Mouse Gene 2.1 ST 24-Array). To understand differential gene regulation during different conditions we performed 1) 30 minutes of ischemia without reperfusion, 2) ischemic preconditioning (IP, 4 x 5 minutes ischemia and reperfusion), as known cardioprotective mechanism, and 3) 30 minutes of ischemia followed by 60 minutes of reperfusion. Based on three arrays per condition the total number of arrays was 24, which we analyzed at the same time on a multi plate array to avoid inter-array variations. Quality analysis using Partek Genomics Suite 6.6 revealed high confidence in the quality of the microarray data and all samples met 'Quality Assurance/Quality Control' (QA/QC) criteria.

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OBESITY ALTERS MOLECULAR AND FUNCTIONAL CARDIAC RESPONSES TO ISCHEMIA-REPERFUSION AND GLUCAGON-LIKE PEPTIDE-1 RECEPTOR AGONISM

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