Phosphatidylethanolamine/PKA signal axis mediated human milk extracellular vesicles enhance adipose thermogenesis and lipolysis via mitochondrial remodeling.

Background/objectives: Emerging evidence suggests that extracellular vesicles (EVs) in breast milk may serve as an abundant source of candidates for regulating metabolism. Our study aims to identify phospholipids derived from human milk EVs (mEVs) that can benefit people with obesity.

Methods: Infant mice were either fed with formula milk or breastfed to investigate whether mEVs affect adipose tissue physiology in infants. Human milk samples were collected from nursing mothers who had given birth at Shanghai Tongren Hospital. UPLC-MS/MS was used to characterize lipidomic profile of human colostrum and mature milk. Body weight changes, H&E staining, blood lipid test, GTT and ITT test were measured to evaluate physiology changes of phospholipid administrated high-fat-diet (HFD) mice. Infrared measurement, western blot, qPCR and IHC analysis were measured to evaluate thermogenesis. RNA-seq and qPCR were used to evaluate the cluster of genes and pathways. Seahorse, electron microscope observation and qPCR were measured to evaluate mitochondrial remodeling of adipocyte. PKA inhibitor (H89) was used to evaluate signal axis of mitochondrial coupling respiration in adipocyte.

Results: Lipidomic analyses of mEVs identified phosphatidylethanolamine (PE) as a signature molecule, whose abundance remains consistent between colostrum and mature milk. PE significantly enhanced brown adipocyte thermogenic respiration in vivo, activated mitochondrial biogenesis transcriptionally, and suppressed mitochondrial clearance. These results led to an increased number of mitochondria and promotes the beiging process. RNA sequencing revealed that PE potentially remodels mitochondria through the PKA signaling pathway, which may influence thermogenesis and lipolysis. The activation mechanism of PE in adipocytes was confirmed by a reduction in thermogenesis phenotype.

Conclusions: mEVs-derived PE serves as a universal cellular adjustor, regulating mitochondrial efficiency via PE/PKA signaling in response to shifts in demand of energy. mEVs serve as a tool for mother-to-child signaling bridge, which maintain a long-time health of adipose tissue.