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 beta-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 (Aims 1 &2). Pilot validation studies in Aim 3 will test whether plasma metabolites and/or metabolite signatures that track muscular FA beta-oxidation (as identified in Aims 1 and 2) can be experimentally increased in obese, insulin-resistant subjects via a diet-exercise regimen designed to improve muscle fitness and FA combustion.
Aim 1 --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 FA 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.
Aim 2 --Identify Metabolite Biomarkers of Muscle Fat Combustion in Humans Harboring a UCP3 Missense Polymorphic Allele. We predict that subjects with this polymorphism (which yields a truncated UCP3 and 50% decreased whole-body fat combustion) will display a distinctive plasma metabolite profile indicative of reduced muscle FA oxidation, when compared to subjects without the polymorphism.
Aim 3 --Determine Whether Metabolomic Profiles Reflective of Muscle Fat Combustion Predict Metabolic Health Changes Following Diet &Exercise Intervention in Obese Subjects. We hypothesize that biomarkers reflective of normal to increased muscle beta-oxidation will be increased, and markers indicative of poor muscle fat combustion reduced, in a cohort of sedentary obese subjects undergoing a 4 month diet- exercise protocol which will increase muscle fitness and improve insulin action.

Public Health Relevance

A reduced ability of the pancreatic hormone insulin to trigger tissue uptake of blood sugar is an early event in the course of development of type 2 diabetes mellitus (T2DM), and the muscle beds are important sites for this phenomenon in many people. Relatively poor fat combustion by fasting muscle is often correlated with insulin resistance, even in the pre-diabetic state. Thus, the overarching aim of our research-- identification of clinically-relevant biomarkers of muscle fat metabolism--is critical to help identify at-risk persons, determine etiology of disease, and ultimately thwart development of T2DM through nutritional, physical activity, and pharmacological interventions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK078328-03
Application #
7903969
Study Section
Clinical and Integrative Diabetes and Obesity Study Section (CIDO)
Program Officer
Castle, Arthur
Project Start
2008-09-30
Project End
2013-07-31
Budget Start
2010-08-01
Budget End
2011-07-31
Support Year
3
Fiscal Year
2010
Total Cost
$262,561
Indirect Cost
Name
U.S. Agricultural Research Service
Department
Type
DUNS #
136650657
City
Albany
State
CA
Country
United States
Zip Code
94710
Chintapalli, Sree V; Anishkin, Andriy; Adams, Sean H (2018) Binding energies and the entry route of palmitic acid and palmitoylcarnitine into myoglobin. Data Brief 21:1106-1110
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Piccolo, Brian D; Graham, James L; Stanhope, Kimber L et al. (2016) Plasma amino acid and metabolite signatures tracking diabetes progression in the UCD-T2DM rat model. Am J Physiol Endocrinol Metab 310:E958-69
Chintapalli, Sree V; Jayanthi, Srinivas; Mallipeddi, Prema L et al. (2016) Novel Molecular Interactions of Acylcarnitines and Fatty Acids with Myoglobin. J Biol Chem 291:25133-25143
Chintapalli, Sree V; Bhardwaj, Gaurav; Patel, Reema et al. (2015) Molecular dynamic simulations reveal the structural determinants of Fatty Acid binding to oxy-myoglobin. PLoS One 10:e0128496
McCoin, Colin S; Knotts, Trina A; Adams, Sean H (2015) Acylcarnitines--old actors auditioning for new roles in metabolic physiology. Nat Rev Endocrinol 11:617-25
Meissen, John K; Hirahatake, Kristin M; Adams, Sean H et al. (2015) Temporal metabolomic responses of cultured HepG2 liver cells to high fructose and high glucose exposures. Metabolomics 11:707-721

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