title: Medium chain acylcarnitines dominate the metabolite pattern in humans under moderate intensity exercise and support lipid oxidation.
abstract: BACKGROUND
  Exercise is an extreme physiological challenge for skeletal muscle energy metabolism and has notable health benefits. We aimed to identify and characterize metabolites, which are components of the regulatory network mediating the beneficial metabolic adaptation to exercise.
  
  
  RESULTS
  First, we investigated plasma from healthy human subjects who completed two independent running studies under moderate, predominantly aerobic conditions. Samples obtained prior to and immediately after running and then 3 and 24 h into the recovery phase were analyzed by a non-targeted (NT-) metabolomics approach applying liquid chromatography-qTOF-mass spectrometry. Under these conditions medium and long chain acylcarnitines were found to be the most discriminant plasma biomarkers of moderately intense exercise. Immediately after a 60 min (at 93% V(IAT)) or a 120 min run (at 70% V(IAT)) a pronounced, transient increase dominated by octanoyl-, decanoyl-, and dodecanoyl-carnitine was observed. The release of acylcarnitines as intermediates of partial beta-oxidation was verified in skeletal muscle cell culture experiments by probing (13)C-palmitate metabolism. Further investigations in primary human myotubes and mouse muscle tissue revealed that octanoyl-, decanoyl-, and dodecanoyl-carnitine were able to support the oxidation of palmitate, proving more effective than L-carnitine.
  
  
  CONCLUSIONS
  Medium chain acylcarnitines were identified and characterized by a functional metabolomics approach as the dominating biomarkers during a moderately intense exercise bout possessing the power to support fat oxidation. This physiological production and efflux of acylcarnitines might exert beneficial biological functions in muscle tissue.
authors.affiliation: Central Laboratory, Division of Clinical Chemistry and Pathobiochemistry, University Hospital Tuebingen, Tuebingen, Germany. Rainer.Lehmann@med.uni-tuebingen.de
authors.forename: Rainer
authors.initials: R
authors.lastname: Lehmann
authors.forename: Xinjie
authors.initials: X
authors.lastname: Zhao
authors.forename: Cora
authors.initials: C
authors.lastname: Weigert
authors.forename: Perikles
authors.initials: P
authors.lastname: Simon
authors.forename: Elvira
authors.initials: E
authors.lastname: Fehrenbach
authors.forename: Jens
authors.initials: J
authors.lastname: Fritsche
authors.forename: Jürgen
authors.initials: J
authors.lastname: Machann
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Jiangshan
authors.initials: J
authors.lastname: Wang
authors.forename: Miriam
authors.initials: M
authors.lastname: Hoene
authors.forename: Erwin D
authors.initials: ED
authors.lastname: Schleicher
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Häring
authors.forename: Guowang
authors.initials: G
authors.lastname: Xu
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Niess
mesh_terms: D000328:Adult; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D015444:Exercise / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D050356:Lipid Metabolism / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C116917:acylcarnitine; D002331:Carnitine