Gas chromatographic--mass spectrometric determination of total 4-heptanone, a new marker in diabetes mellitus.

Total 4-heptanone is the sum of a beta-oxocarboxylic acid, 2-ethyl-3-oxohexanoic acid, and its decarboxylation product, 4-heptanone. The beta-oxocarboxylic acid is found in serum and in urine, and is detected by gas chromatography--mass spectrometry in the form of its methyl ester or its O-methyloximated acid methyl ester. The ketone is detected within the profile of volatile metabolites in serum and in urine. However, the analytical procedure includes some ketone coming from in vitro decarboxylation. Total 4-heptanone is measured by gas chromatography--mass fragmentography. The method includes a quantitative transformation of the beta-oxocarboxylic acid into the ketone. A comparative study with 270 patients with diabetes mellitus, 2 healthy individuals and 143 non-diabetic hospitalized patients showed that the urinary excretion of total 4-heptanone is increased in diabetes mellitus. The mean values are 1073 micrograms per 24 h for diabetics, compared with 207 micrograms per 24 h and 246 micrograms per 24 h for healthy individuals and Non-diabetic patients, respectively. Diabetic ketoacidosis and fasting conditions decrease the total 4-heptanone.