摘要Background Sphingolipids(SL)are key regulators of inflammatory processes,yet their roles in dairy cows remain poorly understood.This study investigated the effects of inflammation(plasma haptoglobin concentration),ketosis,and mastitis on plasma SL profiles in Holstein cows sampled seven days postpartum.From a cohort of 427 cows across 25 farms,80 animals were classified into four groups:inflammation(n=20),ketosis(n=19),mastitis(n=21),and healthy controls(n=20).Plasma SL were quantified by targeted HPLC-MS/MS,while cytokines were quantified with a 15-plex bead-based assay.Both univariate and multivariate analyses were applied to assess pathological effects,along with SL ratios and correlations between SL and cytokines.Results Systemic inflammation detected through the haptoglobin measure induced the most pronounced altera-tions in SL metabolism,characterized by elevated dihydrosphingomyelins(DHSM)and lactosylceramides(LacCer),higher C22-24:C16 ratios,and lower unsaturated:saturated ratios in ceramides(Cer)and sphingomyelins(SM).Although total Cer,SM,and the Cer:SM ratio remained unchanged,specific reductions were observed in both Cer and SM in C14,Cer C18:1,SM C16:1,and SM C23:1,whereas SM C25:0 and C26:0 increased.Sphingosine-1-phosphate(So1P)was positively correlated with IL-10 as well as IL-1α and TNFα,while C1 8-20 Cer correlated positively with mul-tiple pro-inflammatory cytokines and chemokines such as CXCL8 and CCL2.Ketosis induced subtler changes,primarily an increase in plasma DHSM and DHSM:SM ratio(driven by C1 6:0),an increase in C22-24:C16 DHCer ratio,and a decrease in both LacSo:LacCer and unsaturated:saturated ratios in C23-SM.In this group,So1 P correlated positively with CXCL8 and CCL2.Moreover C1 8-20 Cer and DHCer were positively associated with CXCL8,CCL2,CCL3,and CCL4,which also showed correlations with most LacCer species.Analysis of chronic mastitis cases yielded a clear separation from controls in multivariate analysis but only minimal changes in SL concentrations and ratios,maybe due to the localized nature of the inflammatory response.Conclusions In summary,heightened inflammatory response in early post-partum is associated with the strongest systemic effects on SL metabolism,followed by ketosis,while mastitis induced only modest alterations.These findings highlight condition-specific patterns of SL regulation postpartum and suggest potential immunometabolic biomark-ers of disease.