Sex-Specific Plasma Metabolomic Signatures in COPD Reveal Creatine, Purine/Urate, and Bile-Acid Axes

Metabolomic studies in COPD reveal systemic metabolic perturbations, yet sex is often treated as a covariate rather than a biological driver. We aimed to identify plasma metabolites differentiating COPD from controls and to define sex-specific metabolic signatures in both groups. Methods: In this controlled observational study (BIOMEPOC cohort), untargeted plasma metabolomics was performed by LC-MS/MS. Differential abundance was tested across four contrasts (COPD vs. controls; men vs. women within controls; men vs. women within COPD; sex-by-disease interaction) with a false discovery rate (FDR) correction. Because smoking history differed between COPD and controls, a post hoc ever-smokers analysis was conducted. Results: COPD differed from controls in nine metabolites (all decreased): DL-stachydrine, 3-methyl-L-histidine, fructose, pipecolinic and nipecotic acids, 5-nitro-o-toluidine, conjugated linoleic acid, aminoadipate, and creatinine. This pattern is compatible with metabolic depletion, remodeling, and/or altered flux across multiple compartments rather than simple substrate deficiency, spanning muscle-related pools, amino acid handling, carbohydrate-associated metabolism, and exposome-linked inputs. In ever-smokers, results were directionally consistent, with five metabolites remaining nominally significant. Among controls, five metabolites were higher in men after FDR correction (PABA, cis-4-hydroxy-D-proline, N-acetylasparagine, deoxycarnitine, and creatinine), consistent with physiological sex dimorphism in energy pathways, connective-tissue remodeling, and diet/microbiome-related metabolism. Within COPD, six metabolites differed by sex after FDR correction, defining three axes: creatine energy buffering (men: higher GAA/creatinine, lower creatine), purine/urate handling (men: higher urate), and conjugated bile acids (men: higher GCDCA), implicating muscle bioenergetics, redox/inflammatory tone, and gut-liver crosstalk. Conclusions: Plasma metabolomics identifies a pattern compatible with systemic remodeling in COPD and sex-associated divergences in creatine, purine/urate, and bile-acid pathways, supporting a sex-influenced view of systemic COPD heterogeneity and highlighting targets for mechanistic validation.