Dissertation/Thesis Abstract

Obesity Alters Global Response to Ischemia and GLP-1 Agonism
by Sassoon, Daniel Jay, Ph.D., Indiana University - Purdue University Indianapolis, 2016, 165; 10159843
Abstract (Summary)

Glucagon-like peptide 1 (GLP-1) receptor agonists are a class of incretin based therapeutics which aid in blood glucose management in Type II diabetes mellitus (T2DM). Recent studies have demonstrated direct cardiovascular benefits conferred by these agents including protection in ischemia and heart failure. Despite these observations, human clinical trials fail to support improvements in cardiovascular outcomes independent of glucose lowering effects in the T2DM populations. Prior data from our lab demonstrate that obesity impairs GLP-1 associated increases in myocardial glucose uptake. However, the reasons for this impairment/resistance to cardiac effects of GLP-1 in the setting of obesity remain ill defined. This investigation tested the hypothesis that underlying differences in the cardiac proteome and microRNA (miR) transcriptome could contribute to distinct cardiac responses to ischemia and activation of GLP-1 signaling in the setting of obesity.

To identify whether obesity modulated cardiac functional responses to GLP-1 related drugs, we first examined the effects of obesity on cardiac function, miR transcriptome, and proteome in response to short duration ischemia-reperfusion (I/R). We observed divergent physiologic responses (e.g. increased diastolic volume and systolic pressure in lean, decreased diastolic volumes in obese) to regional I/R in obese vs lean hearts that were associated with significant molecular changes as detected by protein mass spectrometry and miR microarray. Molecular changes were related to myocardial calcium handling (SERCA2a, histidine-rich Ca2+ binding protein), myocardial structure and function (titin), and miRs relating to cardiac metabolism, hypertrophy, and cell death, including miR-15, miR-30, miR-199a, miR-214. Importantly, these effects were modified differently by GLP-1 agonism in lean vs obese swine.

Additional studies investigated the functional effects of 30 days of treatment with the GLP-1 analogue liraglutide on a model of slowly-developing, unrelieved coronary ischemia. Liraglutide failed to reduce infarct size or collagen deposition. However, analysis of left ventricular pressure-volume relationships support that liraglutide improved diastolic relaxation/filling, load-dependent indices of cardiac function, and cardiac efficiency in response to sympathetic stimulation in obese swine. Taken together, these findings support that miR and proteomic differences underlie distinct changes in functional cardiac responses to I/R and pharmacologic activation of GLP-1 signaling in the setting of obesity.

Indexing (document details)
Advisor: Tune, Johnathan D.
Commitee: Elmendorf, Jeffrey, Herring, B. P., Mather, Kieren J., Sturek, Michael
School: Indiana University - Purdue University Indianapolis
Department: Cellular and Integrative Physiology
School Location: United States -- Indiana
Source: DAI-B 78/02(E), Dissertation Abstracts International
Subjects: Biology, Physiology
Keywords: Cardiac, Incretin, Infarction, Microrna, Obesity, Proteome
Publication Number: 10159843
ISBN: 978-1-369-14771-1
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