Biochemical Characteristics of Urine Metabolomics in Female Giant Pandas at Different Estrous Stages

The composition of urinary metabolites can reflect the physiological state of animals. Investigating the alterations in urine metabolomics during the estrus stage can provide valuable insights for enhancing the efficacy of estrus monitoring. This study aimed to perform an analysis of urinary metabolomics in female giant pandas, specifically examining the variations in specific metabolites across different estrous stages, namely, diestrus, proestrus, estrus, and metestrus. A total of 1234 metabolites were identified in positive ion mode from 76 samples of 19 individuals, with 643 metabolites identified in negative ion mode. The content of urine metabolites exhibited significant variation throughout different stages of estrus. During the peak of estrus, the metabolic pathways primarily enriched by significantly differential metabolites were the AMPK signaling pathway, vitamin digestion and absorption, galactose metabolism, and cysteine and methionine metabolism, as well as taurine and hypotaurine metabolism. By comparing the content of specific metabolites in distinct pathways across the four distinct estrous stages, higher levels of acetylcholine, D-fructose1,6-bisphosphate, L-homocystine, dulcitol, inositol, and S-sulfo-L-cysteine and lower levels of phosphoethanolamine, vitamin A, vitamin B12, and maleic acid were detected at estrus. This study offers a novel comparative analysis of urine metabolomics across different estrus stages in female giant pandas, identifying several potential perspectives for estrus monitoring and contributing to the breeding management of captive giant panda populations.