Lipid cargo of exosomes derived from pancreatic stellate cells and cancer cells: Role in pancreatic cancer-related diabetes.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy often accompanied by pancreatic cancer related diabetes (PCRD), a paraneoplastic condition characterised by early metabolic dysfunction. Emerging evidence suggests that factors carried by exosomes, small extracellular vesicles secreted by tumour cells and pancreatic stellate cells (PSCs), play a pivotal role in mediating intercellular communication and metabolic reprogramming associated with PCRD. While protein and RNA contents of exosomes have been studied as potential mediators of PCRD, their lipid cargo remains underexplored. In this study, we employed targeted liquid chromatography triple quadrupole mass spectrometry (LC-QQQ-MS) to profile lipids in exosomes derived from mouse PSCs (PSC-Ex), pancreatic cancer KPC cells (KPC-Ex), and their co-cultures (PSC + KPC-Ex), along with their parent cell pellets. A total of 451 lipid species were identified, encompassing phospholipids, sphingolipids, triglycerides, and cholesteryl esters. Principal component analysis revealed distinct lipid signatures between exosomes and their parent cells, indicating selective lipid loading. Notably, PSC-Ex were enriched in lysophosphatidylcholines (e.g., LPC 16:0, LPC 22:5), which have been implicated in enhancing insulin secretion and modulating inflammation. Conversely, KPC-Ex exhibited higher levels of ganglioside GM3(d18:1_24:0), sphingomyelin SM(d18:1_16:1), and phosphatidylethanolamine PE(16:0_20:3), lipids associated with insulin receptor inhibition and membrane remodelling in cancer. Co-culture exosomes demonstrated a shift toward glycosphingolipids, with an enrichment of lactosylceramide (Hex2Cer(d18:1_16:0), a lipid linked to insulin resistance and tumour progression. These findings suggest that exosomal lipid composition is modulated by tumour-stromal interactions and may contribute to systemic glucose dysregulation in PDAC. Identifying specific bioactive lipids within exosomes offers potential for developing biomarkers for early detection of PCRD and understanding the metabolic crosstalk in pancreatic cancer.