2012 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. (Formerly 5306-51530-016-12G (8/09).
This is the final report for the Identification of the sub-award entitled Muscle-Specific Biomarkers of Beta-Oxidation project 5306-51530-019-18G terminated in September 2011.
Significant progress was made toward several of the objectives. The goal of the project is 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. Dr. Mary-Ellen Harper’s laboratory at the University of Ottawa is evaluated plasma metabolite patterns (metabolomics) in genetically-modified mice with altered muscle LCFA metabolism, with or without a training regimen to improve muscle fitness and increase fat combustion. It was found that in trained animals, muscle tissue burns fat more efficiently and in turn the levels of certain metabolites called acylcarnitines are reduced in the bloodstream. Further studies in isolated tissues suggest that more efficient fat combustion and lower acylcarnitines are associated with less oxidative stress in the muscle, indicating that strategies such as increased physical activity and nutritional interventions that improve the efficiency of fat combustion will improve overall metabolic health. The PI and cooperator exchanged information and results via email regularly, and the cooperator provided edits on manuscripts and presentations, as well as assistance with results analysis. In addition, approximately quarterly teleconferences were utilized to exchange information and coordinate studies.