Amino Acid Dysregulation in the Mother-Fetus Unit: Multi-Compartment Metabolomic Signatures of Gestational Diabetes Mellitus and Fetal Macrosomia

Despite numerous studies on carbohydrate metabolism in gestational diabetes mellitus (GDM), the role of amino acid metabolic disturbances in the mother-fetus system remains insufficiently characterized, even though amino acids play a critical role in the develop-ment of fetal macrosomia (FM) and the programming of offspring metabolic health. This study included 62 mother–newborn dyads, stratified into clinical groups based on the presence of GDM and FM. Quantitative amino acid analysis was performed in maternal serum, umbilical cord serum, and amniotic fluid samples. Statistical analysis included Kruskal–Wallis, Mann–Whitney, chi-square tests, Spearman's correlation, and machine learning methods (Random Forest) with SHAP value calculation. Metabolic pathway analysis was conducted using MetaboAnalyst. Specific amino acid markers were identi-fied for each biological compartment. In maternal serum, GDM markers included glycine, 1-methylhistidine, γ-aminobutyric acid, lysine, and tryptophan, all showing significantly decreased levels. In cord blood, 11 amino acids exhibited reduced concentrations in GDM, including glutamine, glycine, asparagine, methionine, and proline. In amniotic fluid, GDM was associated with increased levels of lysine and 1-methylhistidine. In GDM complicated by FM, cord blood showed elevated lysine, proline, leucine, and al-lo-isoleucine, whereas amniotic fluid in this group was characterized by low homocitrul-line, asparagine, and lysine alongside high histidine levels. Correlation analysis revealed multiple associations between amino acids and clinical parameters, including an inverse correlation of fetal weight with homocitrulline and positive correlations with lysine and isoleucine. Metabolic pathway analysis indicated that GDM markers in maternal serum are associated with disturbances in biotin, glutamate, and carnitine metabolism, whereas cord blood markers implicated a broader spectrum of processes, including amino acid and purine metabolism. In amniotic fluid from GDM with FM, the methylhistidine me-tabolism pathway was additionally enriched, potentially reflecting specific alterations in neonatal muscle metabolism. GDM is accompanied by differential alterations in the amino acid profile across all investigated biological compartments, with the combination of GDM and FM characterized by unique metabolic signatures. The identified amino ac-ids may serve as potential biomarkers for early prediction of GDM and its complications, and offer prospects for targeted correction of metabolic disturbances.