Metabolome analyses of mouse uteri two to four days post coitum

To elucidate the temporal and dynamic changes in uterine metabolites in mice, uterine samples were collected on Day 2 (D2; n = 8), Day 3 (D3; n = 6), and Day 4 (D4; n = 7) postcoitum and subjected to an untargeted metabolomic analysis. The results revealed significant metabolic alterations across the time points. Compared to D2, D3 showed 124 differentially expressed metabolites (95 upregulated and 29 downregulated), whereas D4 exhibited 377 (262 upregulated and 115 downregulated). Between D4 and D3, 370 metabolites were altered (242 upregulated and 128 downregulated). K-means clustering identified five metabolite clusters, with Clusters 3 and 5 displaying the most pronounced temporal variations. Metabolites in cluster 3 remained stable from D2 to D3 but sharply increased by D4, whereas those in cluster 5 were stable from D2 to D3 and markedly decreased by D4. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that metabolites in Cluster 3 were primarily enriched in the tricarboxylic acid (TCA) cycle, arachidonic acid metabolism, and cholesterol and linoleic acid metabolism pathways. Cluster 5 metabolites were primarily enriched in pathways related to unsaturated fatty acids (linoleic acid, arachidonic acid, and α-linolenic acid) and amino acid metabolism (vitamin B6, taurine, and hypotaurine). Cluster 3 mainly comprised prostaglandins and related compounds, whereas Cluster 5 consisted largely of long-chain fatty acids. Notably, most lipid and lipid-like metabolites in these clusters were associated with embryonic development. These findings elucidate the dynamic metabolic changes in the uterus during the preimplantation stage and highlight the critical roles of amino acids, unsaturated fatty acids, prostaglandins, and lipid-related metabolites in modulating the uterine environment to support embryo implantation and early development.