Virginia Via Research Day Book 2026

Undergraduate Student Research Biomedical

07 ORGANIC CATION TRANSPORTER-3 AND TRIMETHYLAMINE N-OXIDE-INDUCED HEART FAILURE

Alyssa Morrison, Claudia Ramos-Lopez, Junting Zhou, Austin Mason, Sam Castellani, Claire Cho, Alina Xie, Allyson Meador, Reece Girdharry, Ian Jeong, Braxton McDaniel, Hanna Allouch, and Jia-Qiang He, PhD Corresponding author: alyssam0223@vt.edu

Department of Biomedical Sciences and Pathobiology, College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia

Trimethylamine N-oxide (TMAO) is a gut microbiota dependent metabolite derived from trimethylamine, containing nutrient precursors that are rich in meat and dairy products. An increasing number of animal and clinical studies have confirmed a strong association between elevated plasma level of TMAO and cardiovascular diseases. Although it is well established that TMAO promotes vasculopathy (i.e., atherosclerosis), little is known regarding its direct effects on the heart and cardiomyocytes. This study aims to investigate whether and how TMAO modulates cardiac structure and function using a mouse model. Briefly, C57BL6J/wild type (WT) and organic cation transporter-3 knockout (OCT3-KO) mice with the same genetic background were treated with TMAO drinking water for 13 weeks, while the control mice were supplied with regular drinking water without TMAO. At the end of the treatments, echocardiography (Echo) and electrocardiograms (ECG) were utilized to determine the cardiac structure and functional changes. In the Echo anameter, posterior wall thickness, and anterior wall thickness in both diastole and systole. Changes in function were determined by changes

in ejection fraction (EF%) and fractional shortening (FS%), wave amplitude or period changes in ECG, and contraction strength. To evaluate single cellular responses, the heart was first perfused with anti clotting and collagenase IV buffer, followed by gentle pipetting and filtering. The isolated cardiomyocytes were wither used for contraction analysis under electrical stimulation or gene/protein expression with qPCR, Western blot, and biochemical assays. All data were expressed as mean+/-SD with p. Our preliminary study found that long-term feeding of TMAO to WT male mice induced hypertrophic cardiomyopathy and heart failure, evidenced by increased wall thickness, decreased EF, and abnormal ECG compared to the control mice (CTRL). However, the same TMAO treatment did not alter the structural parameters in OCT3-KO male mice. Interestingly, in the female mouse groups, TMAO treatment appeared to increase EF% and FS% compared to non-treated OCT3-KO mice. Although the contraction peak and 50% peak time showed no differences between CTRL and TMAO group in single cell contraction assay, there seemed to be an increasing trend following TMAO treatment.

Furthermore, ECG analysis identified reduced amplitudes of P and R waves of WT mice treated with TMAO. Ongoing experiments are using isolated and cultured single cardiomyocytes to determine cellular and molecular mechanisms associated with TMAO-induced cardiomyopathy, especially the role of OCT3. Our results partially supported our hypothesis that OCT3 might facilitate the influx of TMAO into cardiomyocytes, leading to disorders of the cardiomyocyte electrical and/or contraction components, although we could not exclude another pathway beyond OCT3 that may be involved in this regard.

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128 Edward Via College of Osteopathic Medicine (VCOM)