Extracellular Vesicles From <i>Limosilactobacillus johnsonii</i> Enhance Milk Fat Synthesis by Inducing CD36 Dynamic Palmitoylation and Activating PPARγ Signalling

Mammals support offspring survival through efficient milk production, ensuring the transfer of essential nutrients and energy. Extracellular vesicles (EVs) released by gut microorganisms function as signalling molecules that influence host physiology. In this study, we observed an association between gut microbiota and lactation performance, with Limosilactobacillus johnsonii showing potential in promoting milk fat synthesis. Using a mouse model, we demonstrated that L. johnsonii-derived EVs enhance mammary gland function, leading to increased milk fat content and improved pup growth. Mechanistically, palmitic acid (C16:0) from L. Johnsonii EVs was found to induce the dynamic changes in CD36 palmitoylation in mammary epithelial cells, thereby facilitating fatty acid uptake as substrates for milk fat synthesis. Additionally, the increased availability of fatty acids further promotes the activation of peroxisome proliferator-activated receptor-γ (PPARγ), reinforcing its role in regulating milk fat synthesis. These findings provide new insights into the gut-mammary gland axis and its role in lactation regulation.