Extraction Captures Elusive Metabolites

In vivo solid-phase microextraction (SPME) captures metabolites that other sampling methods miss, giving researchers a more complete picture of the metabolome, according to Janusz Pawliszyn of the University of Waterloo, in Ontario, and coworkers (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201006715). Sampling methods that extract metabolites from drawn blood can lead to metabolite loss or degradation. Pawliszyn’s team avoids the need for blood draws by extracting metabolites with an SPME fiber inserted into a mouse via a hypodermic needle. The extraction takes two minutes, and then the metabolites are desorbed from the fiber and analyzed by LC/MS. The researchers detected more than 1,500 metabolites, including short-lived ones such as glutathione and retinol. They also detected adenosine monophosphate, which is too short-lived to be detected by any of the other extraction methods they tried. In the case of glutathione, extraction methods based on blood draws detected mostly the oxidized form, whereas in vivo SPME yielded ratios of glutathione to oxidized glutathione that agreed with expected values. “We show that in vivo SPME can capture an elusive portion of the metabolome,” the researchers write.