2009 Annual Report
1a.Objectives (from AD-416)
Elevated fat levels within skeletal muscle cells (intramyocellular lipids) are highly correlated with muscle and whole-body insulin resistance, and more prevalent in obesity. The molecular links and metabolic shifts driving this association remain open to debate, but notably, reduced muscle mitochondrial fatty acid (FA) beta-oxidation is more prevalent among insulin-resistant/diabetic persons. Therefore, discovery of biomarkers reflective of the status of an individual’s muscle FA beta-oxidation activity or capacity would have tremendous prognostic and diagnostic value in terms of diabetes. Furthermore, characterization of metabolites associated with muscle mitochondrial fat metabolism should uncover candidate signaling factors which tie FA ß-oxidation to insulin signaling. We propose to identify, for the first time, specific biomarkers of muscle FA beta-oxidation using multiple metabolomic analytical platforms to compare metabolite profiles in samples derived from biological systems displaying disparate muscle fat combustion, including: isolated mitochondrial organelles and muscle cells catabolizing FA at different rates, a UCP3 transgenic animal model, and human subjects harboring a UCP3 truncation polymorphism. Pilot validation studies will test whether plasma metabolites and/or metabolite signatures identified in cell, animal, and human studies that track muscular FA beta-oxidation can be experimentally increased in obese, insulin-resistant subjects via a diet-exercise regimen designed to improve muscle fitness and FA combustion.
1b.Approach (from AD-416)
Identify Metabolite Biomarkers of Muscle Fat Combustion in Organelle, Cell, and Animal Models Displaying Significantly Altered Fatty Acid Beta-Oxidation. We will determine how metabolite profiles shift in models displaying increased muscle beta-oxidation (uncoupling protein 3-overexpressing muscle cell line and muscle UCP3-transgenic mice), and hypothesize that profiles in UCP3-overexpressing systems will reflect increased fatty acid beta-oxidation. Complementary studies will identify tissue-specific metabolites generated by mitochondria in the course of palmitate catabolism in vitro, comparing muscle to liver and kidney preparations. Documents Grant with University of Ottowa.
Significant progress has been made toward several of the objectives in the parent project (5306-51530-016-09R), which examines broad metabolite patterns reflective of metabolic status in muscle in order to identify biomarkers of muscle fat combustion. This overarching aim is driven by the fact that poor insulin sensitivity and frank type 2 diabetes typically occur in the setting of reduced or inefficient muscle long chain fatty acid (LCFA) catabolism in mitochondria. One aspect of the project being conducted at the University of Ottawa is evaluation of plasma metabolite patterns (metabolomics) in genetically-modified mice with altered muscle LCFA metabolism. These studies have been planned and exercise regimens designed to challenge the muscle tissue of the animals, with concurrent assessment of metabolomics in the blood. Other studies are underway that will determine the metabolite patterns of effluxed moieties from muscle cells burning LCFA at different rates. Finally, experiments have been completed to determine unique metabolites effluxed from and changing within mitochondrial during active LCFA combustion. Those studies are under consideration at a peer-reviewed journal, and were conducted in collaboration with a UC, Davis scientist. The ADODR monitors the annual financial report from cooperating institutions, and conducts in-person or teleconference discussion sessions relating to the project.