Mitochondrial mRNA Translation is Required for Maintenance of Oxidative Capacity

<p>Oxidative metabolism is required to produce adequate energy to sustain human life. A primary example of deteriorating oxidative capacity is seen in the cardiac musculature during chronic heart failure. This suggests that by improving oxidative potential, chronic heart disease could be mitigated and one approach to accomplish this may be through targeting the mt-mRNA translation system. Purpose: This investigation’s purpose was to characterize disruptions in mt-mRNA translation machinery in multiple forms of cardiomyopathy and to determine if mitochondrial mRNA translation initiation factor (mtIF2) is necessary to maintain oxidative capacity in cardiomyocytes. Methods Using a combination of animal and cell culture experiments, we first analyzed the oxidative detriments of the myocardium using an LLC tumor implantation model and followed by assessing how antioxidant protection against LLC-conditioned culture media. Additionally, we used a model of concurrent aging and high fat-diet induced cardiac hypertrophy. After identifying mtIF2 as a potential contributor to oxidative detriments in the heart, we used genetic alterations of H9c2 cardiomyocytes to characterize its necessity. Analyses performed in animal and culture experiments include optical metabolic imaging, immunoblot of mitochondrial quality controllers, bioenergetics flux analysis and hypoxic resistance, Results: LLC-implanted animal hearts demonstrated ~15% lower optical redox ratio (FAD/FAD+NADH), a marker for greater glycolytic reliance compared to controls. mt-mRNA translation machinery was unchanged between groups relative to amount of mitochondria. Mitochondrial DNA-encoded CytB was ~30% lower in LLC hearts suggesting impairments in outcomes of mitochondrial mRNA translation. Aged mouse hearts were larger and contained less mtIF2 protein alongside reduced content of CytB. Reducing the content of mtIF2 is associated with reduced oxidative characteristics such as OXPHOS complex I and IV content, optical redox ratio, oxygen consumption, and viability following hypoxia. Conclusion: In conclusion, the research investigations presented within this dissertation are the first to establish mitochondrial mRNA translation as a process that is dysregulated during cardiometablic disease and as a potential therapeutic target to enhance oxidative characteristics of the myocardium. mtIF2 presents as a key regulator for the process of mt-mRNA translation and is necessary for maintain oxidative capacity in cardiac muscle. </p>

Name thesis:degree_name

Doctor of Philosophy in Kinesiology (PhD)

Level thesis:degree_level

Dissertation

Year dc:date.available

2018

Author dc:creator

• Lee, David

Advisor dc:contributor.advisor

• Greene, Nicholas P.

Contributors dc:contributor

• Washington, Tyrone A.
• Rajaram, Narasimhan

• Cardiomyopathy
• Heart Disease
• Mitochondria
• Mitochondrial mRNA Translation
• mtIF2
• Cell Biology
• Molecular Biology
• Molecular, Cellular, and Tissue Engineering

Repository record dc:identifier

https://scholarworks.uark.edu/etd/2626

OAI identifier oai:identifier

oai:scholarworks.uark.edu:etd-4175