Voelcker Academy

Research Symposium 2011


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Catherine Arcos

Role of maternal obesity in regulating fetal cardiac microRNA (miRNA) expression

Catherine Arcos

Mentor(s): Alina Maloyan, PhD

Introduction: Maternal obesity has been shown to be an independent risk factor for offspring to develop cardiovascular disease in later life (so-called the 'developmental programming' phenomenon). Maternal obesity creates a state of chronic inflammation and dyslipidemia (high levels of free fatty acids), which affect normal fetal development. Recent studies have demonstrated that gene regulators called microRNAs (miRNAs) play powerful roles in diverse aspects of cardiac development and function. The expression of miRNAs is dynamic and largely dependent on tissue or cell types; as in any other tissue, cardiac tissue also displays a 'signature expression' pattern for miRNAs. However, a particular pathological process is often associated with a particular gene expression pattern that can aid in the diagnosis and prognosis of human diseases. The implication of several miRNAs in cardiovascular diseases has been well documented such as miR-21 and miR-18a in cardiac fibrosis, miR-193 and miR-378 in myocardial infarction. Our preliminary data in baboon model of maternal obesity have shown significant aberrations in the expression of cardiac miRNAs in fetuses carried by obese mothers, which may suggest a role in fetal development in the evolution of heart disease in humans. For example, the expression of cardiac miR-21 and miR-193 was increased in baboon fetuses born to obese mothers, while the expression of miR-18a and miR-378 was decreased.

Objectives: The overall goal of this study is to determine the mechanism by which maternal obesity can affect cardiovascular health in her offspring. We hypothesize that abnormal fetal cardiac miRNA expression is caused by an exposure to excessive in utero inflammation or high levels of free fatty acids.

Methods: All experiments were done in human primary cardiomyocyte cell cultures. In order to mimic the obesogenic in utero environment, human primary cardiomyocyte cell cultures were either non-treated (control) or incubated at 37°C for 24 hours with 2 ng, 10 ng, and 20 ng of TNF-α, a cytokine involved in systemic inflammation. The effect of high free fatty acids was measured by incubating human primary cardiomyocyte cell cultures at 37°C for 24 hours with 2% BSA [control], 100 μM, 200 μM, and 400 μM palmitic acid, which is the most common fatty acid found in animals. miRNA was then extracted, cDNA was made, and then RT-PCR was run testing for expression levels of miR-193a, miR-378, miR-18, and miR-21. This experiment was repeated for a total of 4 times, and data was then analyzed.

Results: After incubation with TNF-α of varying concentrations, the expression of miR-193a and miR-21 were found to be upregulated compared to controls. No changes were detected in the expression of miR-18a and miR-378. In contrast, an incubation with palmitic acid of varying concentrations caused a downregulation of miR-193a, miR-378, and miR-18 compared to controls. No changes were detected in miR-21 expression. Conclusions. Changes in the expression of fetal cardiac miRNAs might be a result of fetal exposure to adverse intrauterine environment as seen in pregnancies complicated by maternal obesity. (This study was supported by CTSA UL1RR025767).

Collaborators: Arcos C, Koythong T, Muralimanoharan S, Myatt L, and Maloyan A