Identification of Muscle-Specific Biomarkers of Fatty Acid beta-Oxidation

Summary

Principal Investigator: Sean Adams
Affiliation: Agricultural Research Service
Country: USA
Abstract: DESCRIPTION (provided by applicant): Elevated fat levels within tissues and reduced capacity/inefficiencies in long-chain fatty acid (LCFA) oxidative catabolism are highly correlated with muscle, liver, adipose, and whole-body insulin resistance. Specific metabolites whose intra- or extra-cellular concentrations shift in response to changes in capacity or efficiency of mitochondrial LCFA combustion may act as bioactive molecules that impact insulin signaling. Our parent project is leveraging multiple metabolomics analysis platforms to discover new metabolites that correlate with muscle mitochondrial FA combustion and T2DM generally, and one interesting outcome to date has been the identification of medium-chain fatty acylcarnitines (MCFA-carnitines [C6-C14-carns], reflective of incomplete LCFA [unreadable]-oxidation) as entities increased in T2DM plasma. Proof-of-principle studies demonstrated activation by MCFA-carnitines of NF?B-related pro-inflammatory pathways in a murine macrophage cell line. Might the mechanism underlying the pro-inflammatory effect of MCFA-carnitines, acting locally or systemically, be via activation of upstream Toll-like receptors (TLRs), previously shown to be triggered by saturated FAs including C12:0 and C14:0 but not previously linked to acylcarnitines? Could such a mechanism underlie part of the insulin resistance associated with dysfunctional FA metabolism, as seen in many pre-diabetics and T2DM patients? Our novel preliminary results point to specific activation of the upstream cell-surface receptor Toll-like receptor 2 (TLR2) by MCFA-carnitines, and we anticipate that this in turn elicits insulin resistance phenotypes in target cells. If true, this would be a major step forward in understanding the etiology of T2DM, and in identifying the specific links between dysfunctional fatty acid metabolism and insulin resistance. The proposed project, which complements our parent project, has two primary Aims that will definitively answer if acylcarnitines evoke inflammation via TLR2 (and specifically, TLR2-TLR1 dimerization), and whether acylcarnitines can attenuate insulin action in vivo and in vitro through TLR2-dependent mechanisms. Specific Aim 1--Confirm that MCFA-Carnitines Specifically Activate TLR2-TLR1 Leading to Impaired Insulin Signaling. Studies to date using murine cell systems and murine TLR gene constructs suggest that C12-carn treatment increases NF?B-based pro-inflammatory gene expression through activation of TLR2-TLR1 heterodimerization but not other TLR systems. This aim will confirm and extend those results by: (a) evaluating if knockdown of TLR2 or its immediate downstream adaptor MyD88 reduces or abolishes the activation of inflammatory pathways by MCFA-carnitine, (b) testing if a TLR2 dominant-negative mutant (but not other TLR mutants) reduces the effects of MCFA-carnitine, (c) determining whether MCFA-carnitine induces TLR2-TLR1 heterodimerization, and (d) determining if MCFA-acylcarnitine can impair insulin signaling through TLR2-mediated pathways. Specific Aim 2--Determine if MCFA-Carnitine Administration Activates Pro-Inflammatory Pathways and Induces Insulin Resistance in vivo, Mediated Through TLR2-Dependent Mechanisms. No studies have examined effects of acylcarnitines on inflammation and insulin action in vivo. We predict that the inflammatory phenotype observed in cultured cells in response to C12-carn (Aim 1 &Preliminary Results) will be recapitulated in vivo, which would support our working hypothesis that local and/or systemic accumulation of acylcarnitines in T2DM exacerbates chronic inflammation and hence plays a role in the insulin resistance phenotype. These proof-of-concept studies will: (a) examine if acute i.v. injection of C12-carn in mice triggers TLR2/NF?B-dependent gene pro-inflammatory pathways in target tissues (muscle, liver, fat, blood leukocytes), and will determine if these outcomes are abolished or dampened in TLR2-KO mice, and (b) test if longer-term exposure to high systemic C12-carn increases tissue inflammatory markers and whole-body insulin resistance, with effects abolished or reduced in TLR2-KO mice. 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). Relatively poor fat combustion by fasting muscle is often correlated with insulin resistance, even in the pre-diabetic state, and altered fat metabolism also appears to diminish insulin action in liver, fat tissue, and the insulin-producing cells of the pancreas. Thus, the overarching aim of our research is to identify clinically-relevant metabolite biomarkers of dysfunctional fat metabolism, and to understand if at least some of these factors not only mark disease susceptibility but also participate in diabetes causation or exacerbation. Specific to this project is the goal to follow-up on initial results indicating that naturally-occurring acylcarnitine metabolites (fatty acids of differing chain-lengths, bound to an amino-acid-like molecule), which are elevated in the T2DM blood as byproducts of inefficient fat metabolism, activate pro-inflammatory/insulin-resistance pathways through the specific cell-surface receptor Toll-like receptor 2 (TLR2). If true, this will have a profound influence on our understanding of diabetes pathophysiology and may provide new targets for preventive and therapeutic modalities.
Funding Period: 2009-09-20 - 2011-08-31
more information: NIH RePORT

Top Publications

  1. ncbi Associations between dairy foods, diabetes, and metabolic health: potential mechanisms and future directions
    Kristin M Hirahatake
    Obesity and Metabolism Research Unit, USDA ARS Western Human Nutrition Research Center, Davis, CA
    Metabolism 63:618-27. 2014
  2. pmc Improved metabolic health alters host metabolism in parallel with changes in systemic xeno-metabolites of gut origin
    Caitlin Campbell
    USDA ARS Western Human Nutrition Research Center, Davis, California, United States of America
    PLoS ONE 9:e84260. 2014
  3. pmc Muscle uncoupling protein 3 overexpression mimics endurance training and reduces circulating biomarkers of incomplete β-oxidation
    Celine Aguer
    2M E H, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON K1H 8M5, Canada
    FASEB J 27:4213-25. 2013
  4. pmc Leucine and protein metabolism in obese Zucker rats
    Pengxiang She
    Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
    PLoS ONE 8:e59443. 2013
  5. pmc Regulation of adipose branched-chain amino acid catabolism enzyme expression and cross-adipose amino acid flux in human obesity
    Denise E Lackey
    Obesity and Metabolism Research Unit, United States Department of Agriculture Agricultural Research Service Western Human Nutrition Research Center, Davis, CA 95616, USA
    Am J Physiol Endocrinol Metab 304:E1175-87. 2013
  6. pmc Type 2 diabetes associated changes in the plasma non-esterified fatty acids, oxylipins and endocannabinoids
    Dmitry Grapov
    Department of Nutrition, University of California Davis, Davis, California, USA
    PLoS ONE 7:e48852. 2012
  7. pmc Induced pluripotent stem cells show metabolomic differences to embryonic stem cells in polyunsaturated phosphatidylcholines and primary metabolism
    John K Meissen
    University of California Davis Genome Center, University of California Davis, Davis, California, USA
    PLoS ONE 7:e46770. 2012
  8. pmc imDEV: a graphical user interface to R multivariate analysis tools in Microsoft Excel
    Dmitry Grapov
    Department of Nutrition, University of California, Davis, CA 95616, USA
    Bioinformatics 28:2288-90. 2012
  9. pmc Decreased expression of adipose CD36 and FATP1 are associated with increased plasma non-esterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris)
    Jose Abraham Viscarra
    School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
    J Exp Biol 215:2455-64. 2012
  10. pmc Qualitative analysis of algal secretions with multiple mass spectrometric platforms
    Tobias Kind
    UC Davis Genome Center Metabolomics, University of California, Davis, CA 95616, USA
    J Chromatogr A 1244:139-47. 2012

Scientific Experts

  • Sean H Adams
  • Oliver Fiehn
  • John K Meissen
  • Dmitry Grapov
  • John W Newman
  • Charles L Hoppel
  • Mary Ellen Harper
  • W Timothy Garvey
  • Tobias Kind
  • Erin L Seifert
  • Caitlin Campbell
  • Kristin M Hirahatake
  • Denise E Lackey
  • Kristine C Olson
  • Celine Aguer
  • Christopher J Lynch
  • Pengxiang She
  • Jose Abraham Viscarra
  • David R Bickel
  • Veronic Bezaire
  • Nancy L Keim
  • Kevin C Maki
  • Gary R Hunter
  • Jose R Fernandez
  • Elaine C Souza
  • Kohei Take
  • Gretchen A Casazza
  • Joanne L Slavin
  • Mary B Gustafson
  • Carol J Chandler
  • Dustin J Burnett
  • Marta Padilla
  • Ayami Inukai
  • Mohamed Ali
  • Yoshiharu Shimomura
  • Tracy G Anthony
  • Ryosei Sakai
  • Hideki Matsumoto
  • Pieter J Oort
  • Rajesh Amin
  • Yasuko Kawamata
  • Amanda Daniels
  • Tamara N Dunn
  • Fawaz G Haj
  • Sandy Humphreys
  • Daniel H Bedinger
  • Charles H Lang
  • William H Smith
  • Dorothy A Kieffer
  • Michael Dysart
  • Ahmed Bettaieb
  • Fredrik Karpe
  • Yoshihiro Kadota
  • Kyle Scott
  • Jean Marc Renaud
  • Anthony P Thomas
  • Paska Permana
  • Rouzbeh Mostaedi
  • Jean S VanderGheynst
  • Cory D Champagne
  • Paul S Knoepfler
  • Benjamin T K Yuen
  • Dawei Yang
  • Daniel E Crocker
  • John W Riggs
  • Ruben Rodriguez
  • Arpana Vaniya
  • Dinesh K Barupal
  • José Pablo Vázquez-Medina
  • Rudy M Ortiz
  • Yu Shen Cheng
  • Fernando Nocito
  • Theresa L Pedersen
  • Gert Wohlgemuth
  • Kerry H Lok

Detail Information

Publications15

  1. ncbi Associations between dairy foods, diabetes, and metabolic health: potential mechanisms and future directions
    Kristin M Hirahatake
    Obesity and Metabolism Research Unit, USDA ARS Western Human Nutrition Research Center, Davis, CA
    Metabolism 63:618-27. 2014
    ..Such experiments would complement epidemiological studies and add to the evidence base for recommendations regarding consumption of dairy products and their individual components...
  2. pmc Improved metabolic health alters host metabolism in parallel with changes in systemic xeno-metabolites of gut origin
    Caitlin Campbell
    USDA ARS Western Human Nutrition Research Center, Davis, California, United States of America
    PLoS ONE 9:e84260. 2014
    ....
  3. pmc Muscle uncoupling protein 3 overexpression mimics endurance training and reduces circulating biomarkers of incomplete β-oxidation
    Celine Aguer
    2M E H, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON K1H 8M5, Canada
    FASEB J 27:4213-25. 2013
    ....
  4. pmc Leucine and protein metabolism in obese Zucker rats
    Pengxiang She
    Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
    PLoS ONE 8:e59443. 2013
    ..Elevated BCAAs/BCKAs may contribute to observed elevations in protein synthesis and BCAA oxidation...
  5. pmc Regulation of adipose branched-chain amino acid catabolism enzyme expression and cross-adipose amino acid flux in human obesity
    Denise E Lackey
    Obesity and Metabolism Research Unit, United States Department of Agriculture Agricultural Research Service Western Human Nutrition Research Center, Davis, CA 95616, USA
    Am J Physiol Endocrinol Metab 304:E1175-87. 2013
    ....
  6. pmc Type 2 diabetes associated changes in the plasma non-esterified fatty acids, oxylipins and endocannabinoids
    Dmitry Grapov
    Department of Nutrition, University of California Davis, Davis, California, USA
    PLoS ONE 7:e48852. 2012
    ....
  7. pmc Induced pluripotent stem cells show metabolomic differences to embryonic stem cells in polyunsaturated phosphatidylcholines and primary metabolism
    John K Meissen
    University of California Davis Genome Center, University of California Davis, Davis, California, USA
    PLoS ONE 7:e46770. 2012
    ..The identified metabolomics signatures of iPSCs and ESCs may have important implications for functional regulation of maintenance and induction of pluripotency...
  8. pmc imDEV: a graphical user interface to R multivariate analysis tools in Microsoft Excel
    Dmitry Grapov
    Department of Nutrition, University of California, Davis, CA 95616, USA
    Bioinformatics 28:2288-90. 2012
    ....
  9. pmc Decreased expression of adipose CD36 and FATP1 are associated with increased plasma non-esterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris)
    Jose Abraham Viscarra
    School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
    J Exp Biol 215:2455-64. 2012
    ..Delineation of the mechanisms responsible for this shift in regulation during fasting can contribute to a more thorough understanding of the changes in lipid metabolism associated with dyslipidemia and insulin resistance in mammals...
  10. pmc Qualitative analysis of algal secretions with multiple mass spectrometric platforms
    Tobias Kind
    UC Davis Genome Center Metabolomics, University of California, Davis, CA 95616, USA
    J Chromatogr A 1244:139-47. 2012
    ..We observed a series of triacylglycerols (TG), sulfoquinovosyldiacylglycerols (SQDG), phosphatidylinositols and phosphatidylglycerols, as well as betaine lipids diacylglyceryl-N,N,N-trimethylhomoserines (DGTS)...
  11. pmc Emerging perspectives on essential amino acid metabolism in obesity and the insulin-resistant state
    Sean H Adams
    Obesity and Metabolism Research Unit, USDA Agricultural Research Service Western Human Nutrition Research Center, and Department of Nutrition, University of California, Davis, CA, USA
    Adv Nutr 2:445-56. 2011
    ....
  12. pmc Plasma metabolomic profiles reflective of glucose homeostasis in non-diabetic and type 2 diabetic obese African-American women
    Oliver Fiehn
    Genome Center, University of California Davis, Davis, California, United States of America
    PLoS ONE 5:e15234. 2010
    ....
  13. pmc Long-chain fatty acid combustion rate is associated with unique metabolite profiles in skeletal muscle mitochondria
    Erin L Seifert
    Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
    PLoS ONE 5:e9834. 2010
    ..We have used unbiased metabolite profiling of mouse muscle mitochondria with the aim of identifying candidate metabolites within or effluxed from mitochondria and that are shifted with LCFA combustion rate...
  14. pmc Plasma acylcarnitine profiles suggest incomplete long-chain fatty acid beta-oxidation and altered tricarboxylic acid cycle activity in type 2 diabetic African-American women
    Sean H Adams
    USDA Agricultural Research Service Western Human Nutrition Research Center, USA
    J Nutr 139:1073-81. 2009
    ....