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BACKGROUND Isolated postchallenge diabetes (IPD), a subtype of type 2 diabetes mellitus (T2DM) defined as 2-h postprandial plasma glucose ≥200 mg/dL (≥11.1 mmol/L) and fasting plasma glucose (FPG) METHODS We applied a nontargeted metabolomic approach using ultra-high-performance liquid chromatography–quadrupole TOF–mass spectrometry (UPLC-QTOF-MS) to analyze serum samples from 51 patients with IPD, 52 with newly diagnosed T2DM, and 49 healthy individuals. We processed metabolite profiles by multivariate analysis to identify potential metabolites, which were further confirmed by tandem MS (MS/MS). We also used GC-MS and ELISA methods to detect potentially important metabolites. A number of independent samples were selected to validate the identified candidates. RESULTS We selected 15 metabolites with a view to distinguishing patients with IPD, whereas 11 were identified with an authentic standard. The selected metabolites included linoleic acid, oleic acid, phospholipids, and dehydroepiandrosterone sulfate (DHEA-S). In IPD samples, significantly higher linoleic and oleic acid (P < 0.001) and lower DHEA-S (P < 0.001) concentrations were observed, compared with controls. The area under the curve from a combination of linoleic acid, oleic acid, and DHEA-S in the validation study was 0.849 for the IPD group. CONCLUSIONS The current study provides useful information to bridge the gaps in our understanding of the metabolic alterations associated with IPD and might facilitate the characterization of patients with IPD by the use of fasting serum.

A procedure was evaluated for the extraction of 16 free fatty acids (FFAs) from liver. Ultrasonic energy was used for the extraction and the variables affecting the extraction efficiency were investigated. The best conditions for extraction were: 2 mL isopropanol‐ n-hexane (3:2, v/v), 20 min and 80 w. Recoveries ranging from 87.00 to 120.00% were obtained under the optimum conditions, and the linearity as correlation coefficient was higher than 0.9914. Analytical results for the 16 FFAs in the same liver sample, analyzed by ultrasound-assisted and conventional extraction, showed acceptable agreement, thus suggesting the possibility of using ultrasound-assisted extraction instead of the conventional procedure. Moreover, the ultrasound-assisted extraction was successfully applied to the determination of FFAs in the liver of mice with hyperlipidemia and normal mice.