Dissertation Defense Announcement

Herff College of Engineering announces the Final Dissertation Defense 

Hayden Johnson

for the Degree of Doctor of Philosophy

March 15, 2022 at 11:30 AM in Engineering Administration Building, Room-203

Advisor: – Dr. Aaryani Tipirneni-Sajja

Multi-tissue Time-domain NMR Metabolomics for Robust and Accurate Assessment of Dietary Effects

ABSTRACT: "Nuclear magnetic resonance (NMR) spectroscopy is a highly quantitative, non-destructive analytical technique for quantifying metabolites. Conventional NMR analysis for quantification of metabolites involves processing the recorded time-domain signal into a frequency-domain spectrum along with several user-dependent processing and resonance characterization steps which may introduce bias and error. In this study, we implement a Bayesian approach for NMR data analysis directly in the time-domain to bypass these drawbacks and increase automation in metabolite quantification. The time-domain NMR workflow was first assessed using metabolite reference standards to validate accurate resonance identification and quantification before profiling metabolites in tissue samples. Biofluids are commonly profiled in metabolomics research; however, organ-level metabolite profiling can provide valuable information regarding local, tissue-specific metabolism. This study uses a multi-organ metabolomics approach to determine differences in metabolite levels in metabolically active organs such as the liver, heart, and white adipose tissue in animals fed with different dietary regimens. High-fat ad libitum and time-restricted feeding (TRF) regimens are investigated in males and females of a diurnal animal model, the Nile grass rat. Compared to a standard chow diet, rats on an ad-libitum high fat diet exhibited lipid remodeling in all three tissues and accumulation of lipids in the heart and liver. TRF was associated with decreased cardiac and hepatic lipid levels, but no significant differences were noted in adipose tissue. Regardless of diet, females harbored greater amounts of lipids and lower levels of aqueous metabolites than males. In conclusion, this study demonstrates the validity of systematic Bayesian time-domain NMR data analysis and its application to understanding the tissue-level responses to TRF in multiple metabolically active tissues."