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Artifactual FA dimers mimic FAHFA signals in untargeted metabolomics pipelines. | LitMetric

Artifactual FA dimers mimic FAHFA signals in untargeted metabolomics pipelines.

J Lipid Res

Division of Molecular Medicine; Department of Medicine, University of Minnesota, Minneapolis, MN, USA. Electronic address:

Published: May 2022

AI Article Synopsis

  • FA esters of hydroxy FAs (FAHFAs) are important lipids that affect insulin sensitivity and glucose levels, but they are typically found in low amounts and require sensitive methods for detection.
  • In our analysis of human serum using advanced LC-MS techniques, we discovered that what were thought to be FAHFAs were often actually FA dimers, which can be confused with FAHFAs due to their similar mass and fragmentation patterns.
  • To prevent misidentification, we created a database specifically for FA dimers, which helps distinguish these nonbiological compounds from true FAHFAs in metabolomics research.

Article Abstract

FA esters of hydroxy FAs (FAHFAs) are lipokines with extensive structural and regional isomeric diversity that impact multiple physiological functions, including insulin sensitivity and glucose homeostasis. Because of their low molar abundance, FAHFAs are typically quantified using highly sensitive LC-MS/MS methods. Numerous relevant MS databases house in silico-spectra that allow identification and speciation of FAHFAs. These provisional chemical feature assignments provide a useful starting point but could lead to misidentification. To address this possibility, we analyzed human serum with a commonly applied high-resolution LC-MS untargeted metabolomics platform. We found that many chemical features are putatively assigned to the FAHFA lipid class based on exact mass and fragmentation patterns matching spectral databases. Careful validation using authentic standards revealed that many investigated signals provisionally assigned as FAHFAs are in fact FA dimers formed in the LC-MS pipeline. These isobaric FA dimers differ structurally only by the presence of an olefinic bond. Furthermore, stable isotope-labeled oleic acid spiked into human serum at subphysiological concentrations showed concentration-dependent formation of a diverse repertoire of FA dimers that analytically mimicked FAHFAs. Conversely, validated FAHFA species did not form spontaneously in the LC-MS pipeline. Together, these findings underscore that FAHFAs are endogenous lipid species.  However, nonbiological FA dimers forming in the setting of high concentrations of FFAs can be misidentified as FAHFAs. Based on these results, we assembled a FA dimer database to identify nonbiological FA dimers in untargeted metabolomics datasets.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9034316PMC
http://dx.doi.org/10.1016/j.jlr.2022.100201DOI Listing

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