Metabolic, microbial, and pharmacological stimuli elicit distinct lipidomic and cytokine responses in the human placenta

Abstract

The placenta integrates metabolic and immune functions essential for fetal development, and disruptions in lipid metabolism and inflammatory signaling have been implicated in pregnancy complications such as gestational diabetes mellitus (GDM), infection-associated inflammation, and preterm birth. To examine how distinct clinically relevant stressors shape these processes, we investigated placental explant responses to three representative exposures. These included high glucose (metabolic stress relevant to diabetes/GDM), lipopolysaccharide (LPS; microbial-inflammatory stress relevant to infection/chorioamnionitis), and metformin (pharmacological exposure in treated pregnancies). Human term placental explants were cultured under controlled ex vivo conditions and exposed to these stimuli. Lipidomic profiling was performed using supercritical fluid chromatography-mass spectrometry (SFC-MS), and inflammatory responses were assessed at gene, protein, and cytokine levels by qRT-PCR, western blotting, and ELISA. Explants preserved the lipid complexity of intact placenta and secreted defined lipid species, including free fatty acids, phospholipids, and sterols, indicating selective export. High glucose induced only modest cytokine responses, suggesting that acute exposure alone is insufficient for robust inflammasome activation. In contrast, LPS triggered pronounced lipid remodeling with consistent ceramide accumulation, alongside strong upregulation of interleukin 1 beta (IL1B), interleukin 6 (IL6), and tumor necrosis factor alpha (TNF) transcripts and protein release, supporting a role for ceramides in innate immune activation. Metformin displayed modest downregulation of inflammatory transcripts and lipid remodeling under basal conditions but paradoxical potentiation of LPS-induced cytokine release. These findings show that human placental explants retain key metabolic and immune functions and reveal distinct stimulus-specific signatures, offering insight into placental adaptation to metabolic, microbial, and pharmacological stressors relevant to pregnancy complications.