title: Plasma acylcarnitines inadequately reflect tissue acylcarnitine metabolism.
abstract: Acylcarnitines have been linked to obesity-induced insulin resistance. However the majority of these studies have focused on acylcarnitines in plasma. It is currently unclear to what extent plasma levels of acylcarnitines reflect tissue acylcarnitine metabolism. We investigated the correlation of plasma acylcarnitine levels with selected tissue acylcarnitines as measured with tandem mass spectrometry, in both fed and fasted BALB/cJ (BALB) and C57BL/6N (Bl6) mice. Fasting affected acylcarnitine levels in all tissues. These changes varied substantially between the different tissue compartments. No significant correlations were found between plasma acylcarnitine species and their tissue counterparts in both mouse strains, with the exception of plasma C4OH-carnitine in BALB mice. We suggest that this lack of correlation is due to differences in acylcarnitine turnover rates between plasma and tissue compartments and the fact that the plasma acylcarnitine profile is a composition of acylcarnitines derived from different compartments. Therefore, plasma acylcarnitine levels do not reflect tissue levels and should be interpreted with caution. A focus on tissue acylcarnitine levels is warranted in metabolic studies.
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Marieke G
authors.initials: MG
authors.lastname: Schooneman
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Niki
authors.initials: N
authors.lastname: Achterkamp
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, NY, USA.
authors.forename: Carmen A
authors.initials: CA
authors.lastname: Argmann
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Soeters
authors.affiliation: Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Pediatrics, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, NY, USA. Electronic address: sander.houten@mssm.edu.
authors.forename: Sander M
authors.initials: SM
authors.lastname: Houten
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D052436:Adipose Tissue, White / Q000378:metabolism*; D000465:Algorithms; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood*; D016000:Cluster Analysis; D005215:Fasting; D005227:Fatty Acids / Q000378:metabolism; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011237:Predictive Value of Tests; D053719:Tandem Mass Spectrometry
chemical_list: D005227:Fatty Acids; C116917:acylcarnitine; D002331:Carnitine
keywords: Acylcarnitines; Fatty acid oxidation; Insulin resistance; Lipotoxicity