Co-Director, Translational Center for Metabolic Imaging
Research Assistant Professor, Radiology; Adjunct, Bioengineering
University of Washington
Seattle, WA 98195-7115
The goal of Dr.
PRIMARY AIMS OF RESEARCH PROGRAM
Mitochondria play multiple roles in the cell, including maintaining energy homeostasis in response to environmental and cellular stress. Therefore, a key aspect of normal cellular function is the ability of the cell to respond to stress by stimulating mitochondrial biogenesis and turnover. Impairment of this ability can lead to mitochondrial dysfunction and disruption of cell energetics. My research focuses on understanding the regulation of mitochondrial metabolism and how this changes with age. My primary research goals are to identify how:
1) biochemical events affect in vivo mitochondrial function
2) the ability of the cell to respond to metabolic stress changes with age.
I believe that in order to understand how the body regulates mitochondrial function in response to stress it is necessary to integrate research on molecular, biochemical, and organismal levels. However, due to the lack of necessary tools to measure mitochondrial function in vivo, approaches have typically focused on in vitro measurements, particularly of the electron transport chain (ETC). However, mitochondria are sensitive to many systemic and cellular factors making it difficult to extrapolate results from isolated mitochondria to function in the intact organism. To bridge this gap we have developed state of the art molecular imaging/spectroscopy tools to study oxidative phosphorylation in skeletal muscle of intact organisms. We use optical and magnetic resonance spectroscopies to provide independent measures of O2 and ATP fluxes in vivo. By independently measuring these fluxes we determine several parameters of mitochondrial energetics in intact skeletal muscle, including the coupling of oxidative phosphorylation (P/O), phosphorylation capacity, and the sensitivity of respiration to oxygen content.
My research program uses transgenic models and pharmacological treatment to induce energetic and oxidative stress in mouse modes to address the cellular and molecular mechanisms responsible for changes in the regulation of energy metabolism with age. The combination of transgenic models and drug manipulations allows us to apply both chronic and acute challenges to determine how changes at the molecular and biochemical levels affect mitochondrial function and cellular energetics in vivo.
The focus of my current research is to understand how changes in the ability of the cell to stimulate mitochondrial biogenesis in response to cellular stress affect in vivo mitochondrial function. My research addresses these issues at multiple levels of biological organization. The strategy is to pair in vivo functional measures with studies of isolated muscles to address cellular mechanisms of the stress response. Our lab applies a combination of in vivo spectroscopy, Western blotting, quantitative PCr, and microarray analysis to determine if the responses of the signaling pathways regulating antioxidant and mitochondrial biogenesis are altered with age. The ability to integrate modern molecular genetic approaches with the physiological relevance of studying the intact organism combines two of the most exciting areas in physiology and is the necessary next step to understanding both normal and pathological physiological function.
- Diagnosis – Combine state-of-the-art non-invasive technology coupled with basic science studies of the physiology of disease to guide development of novel diagnostic tools. The tools are designed to 1) diagnose presymptomatic disease changes, 2) reveal the degree of disease progression, and 3) show the effectiveness of a intervention designed to treat the disease. This tools are currently focused on aging, post-cancer fatigue and Huntington’s disease. Future studies include post-stroke fatigue, kidney failure and HIV.
- Development – In vivo diagnostic innovations provide an unprecedented window into human tissue that – for the first time – shows mitochondrial functional and adaptive variation as key to cell homeostasis. These new molecular imaging methods for direct measurement of cell metabolism, oxygenation and blood flow in vivo are developed by a multidisciplinary team composed of physicists, physiologists and physician-scientist. A new research program focused on Mitochondrial Medicine has resulted from the insights gained from quantifying dynamic energetic fluxes and tissue blood flow. New tools in the works include functional measurement of reactive oxygen species in brain and muscle and brain oxidative phosphorylation measures.
- Discovery – Identifying and quantifying key signaling molecules that regulate tissue function and underlie disease at the cellular level in vivo using high-sensitivity imaging measurements. A current project is measurement of low concentration signaling molecules in brain centers regulating food intake, body weight and satiety.
- Dissemination – A major goal is to establish the experimental procedures and spectroscopic tools sites involved in human muscle aging studies both nationally and internationally. This dissemination provides what is currently lacking in human muscle studies - a standardized approach for characterizing mitochondrial and cell energetic properties. We currently have a highly successful collaboration with Dr. Steve Smith and colleagues at the Pennington Biomedical Research Center in Baton Rouge, which is supported by an independent NIH R01 that was awarded based on the success of our collaboration. We are in the process of expanding to 3 new sites: University of Pittsburgh, University of Florida, and the National Institutes of Aging/Baltimore Longitudinal Study. The University of Washington Team’s efforts involve installation of our procedures and training in our approach, ongoing quality control monitoring of data collected offsite, and data analysis. Data interpretation and manuscript preparation are collaborative efforts of the UW and each site.