Differentiation of obese and healthy mice by analyzing the carboxylic acids in the TCA cycle in their feces

Abstract

The tricarboxylic acid cycle is an important metabolic route in almost all living bodies, yet current analytical methods for the detection of the relevant tricarboxylic acids (TCAs) in biological samples are still unsatisfactory due to their complex matrix and physicochemical properties. In this work, a sample method based on solid phase extraction (SPE) in conjunction with liquid chromatography-mass spectrometry (LC-MS) analysis has been developed for the simultaneous determination of 7 TCAs, including α-ketoglutaric acid, malic acid, malonic acid, aconitic acid, citric acid, succinic acid and fumaric acid, in mice faeces. By treatment with macroporous styrene chelate resin and solid phase extraction, the matrix in mice feces was selectively and efficiently removed. Under optimized parameters, the limit of quantitation for the TCAs was in the range of 1-50 ng/mL, and the content of the TCAs in mice feces was determined with a recovery range of 76.2 % to 128.4 %. Interestingly, the content of malic acid, malonic acid, succinic acid and fumaric acid in the normal mice's feces was found to be 2-10 times higher than that of obese mice, indicating a new potential method for the diagnosis of obesity.