Effects of Mepiquat Exposure on Rat Urine Based on Metabolomics

Mepiquat (Mep) is a food contaminant produced usually during heat processing. It is formed by Maillard reaction with free lysine, reducing sugar and alkylating agent under typical roasting conditions. It was found that Mep exposure could cause kidney vacuolization, liver and spleen damage, but its metabolic mechanism in vivo was still not clear, which made it difficult to assess its exposure risk. Untargeted metabolomics was used to reveal effects of Mep on the metabolic profile of urine in rats based on gas chromatography-mass spectrometry. Differential metabolites and histopathological changes of rat kidneys were analyzed. The result showed that 24 differential metabolites were screened out from rat urine before and after Mep exposure. Among them, 5 metabolites were upregulated, 19 metabolites were down-regulated. Metabolic pathway analysis of the differential metabolites revealed that 5 major perturbed metabolic pathways were found with response values greater than 0.1 before and after the exposure of Mep, which were glycine, serine and threonine metabolism, glycerolipid metabolism, pentose and glucuronate interconversions, inositol phosphate metabolism, and glyoxylate and dicarboxylic acid metabolism. These pathways were mainly related to amino acid metabolism, energy metabolism, carbohydrate metabolism and lipid metabolism. Glycine, serine and threonine metabolism was the metabolic pathway with the largest response value. It was hoped that this study could provide theoretical reference for elucidating the toxic mechanism of Mep.