Gas chromatographic determination of oxo- and hydroxycarboxylic acids in serum and urine of diabetic and normal subjects.

Oxo- and hydroxycarboxylic acids in serum and urine are metabolites of valine, leucine and isoleucine and products of ketogenesis. They are simultaneously determined in the form of their methyl esters and methyl esters-O-methyloximes by gas chromatography, using internal and external standards. Normal values for the urinary excretion of these amino acid metabolites are between 3 +/- 2 mumole per 24 h (mean +/- standard deviation) for 2-oxoisocaproic acid and 122 +/- 58 mumole per 24 h for 3-hydroxyisobutyric acid. In diabetic ketoacidosis the values are increased by a factor of 2-10. In the urine of diabetic patients under fasting conditions all metabolites are elevated and reach a maximum on about the seventh day of fasting. In the serum only 2-oxoisocaproic acid, 3-oxobutyric acid and 3-hydroxybutyric acid reach elevated levels under fasting conditions.