Quantitative analysis of volatile organic compounds released and consumed by rat L6 skeletal muscle cells in vitro

Paweł Mochalski,Karl Unterkofler,Anton Amann,Andreas Niederwanger,Ramona Al-Zoairy

doi:10.1088/1752-7155/8/4/046003

Abstract

Knowledge of the release of volatile organic compounds (VOCs) by cells provides important information on the origin of VOCs in exhaled breath. Muscle cells are particularly important, since their release of volatiles during the exertion of an effort contributes considerably to breath concentration profiles. Presently, the cultivation of human skeletal muscle cells is encountering a number of obstacles, necessitating the use of animal muscle cells in in vitro studies. Rat L6 skeletal muscle cells are therefore commonly used as a model for studying the molecular mechanisms of human skeletal muscle differentiation and functions, and facilitate the study of the origin and metabolic fate of the endogenously produced compounds observed in breath and skin emanations. Within this study the production and uptake of VOCs by rat L6 skeletal muscle cells were investigated using gas chromatography with mass spectrometric detection, combined with head-space needle trap extraction as the pre-concentration technique (HS-NTE-GC-MS). Seven compounds were found to be produced, whereas sixteen species were consumed (Wilcoxon signed-rank test, p < 0.05) by the cells being studied. The set of released volatiles included two ketones (2-pentanone and 2-nonanone), two volatile sulphur compounds (dimethyl sulfide and methyl 5-methyl-2-furyl sulphide), and three hydrocarbons (2-methyl 1-propene, n-pentane and isoprene). Of the metabolized species there were thirteen aldehydes (2-propenal, 2-methyl 2-propenal, 2-methyl propanal, 2-butenal, 2-methyl butanal, 3-methyl butanal, n-pentanal, 2-methyl 2-butenal, n-hexanal, benzaldehyde, n-octanal, n-nonanal and n-decanal), two esters (n-propyl propionate and n-butyl acetate), and one volatile sulphur compound (dimethyl disulfide). The possible metabolic pathways leading to the uptake and release of these compounds by L6 cells are proposed and discussed. An analysis of the VOCs showed them to have huge potential for the identification and monitoring of some molecular mechanism and conditions.

Highlights

Over the last few decades, volatile organic compounds (VOCs) released by living organisms have provided invaluable information on the normal and disease processes occurring in an individual, as well as environmental exposure to pollutants/toxins, or microorganisms’ activity in the body [1,2,3,4,5,6,7,8,9,10]
The LOD values varied from 0.03 ppb for 2-methyl 2-propenal to 0.4 ppb for n-nonanal
The objective of this study was to identify volatile organic compounds metabolized and produced by rat L6 skeletal muscle cells—a cell line commonly used to explore the molecular mechanisms of muscle differentiation and function

Summary

Introduction

Over the last few decades, volatile organic compounds (VOCs) released by living organisms have provided invaluable information on the normal and disease processes occurring in an individual, as well as environmental exposure to pollutants/toxins, or microorganisms’ activity in the body [1,2,3,4,5,6,7,8,9,10]. The main unresolved issue limiting the use of this chemical fingerprint in biomedical applications is a poor understanding of the origin and metabolic fate of its constituents and the restricted knowledge on the partition of the volatile compounds into different compartments of the body [8, 11, 12]. This gap in our knowledge has stimulated extensive research in this exciting field. We expect that the compounds released by cells are of great importance for the exploration and understanding of endogenously produced compounds in exhaled breath and other body emanations

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Conclusion