N-Glycan profile of the cell membrane as a probe for lipopolysaccharide-induced microglial neuroinflammation uncovers the effects of common fatty acid supplementation

Altered N-glycosylation of proteins on the cell membrane is associated with several neurodegenerative diseases. Microglia are an ideal model for studying glycosylation and neuroinflammation, but whether aberrant N-glycosylation in microglia can be restored by diet remains unknown. Herein, we profiled the N-glycome, proteome, and glycoproteome of the human microglia following lipopolysaccharide (LPS) induction to probe the impact of dietary and gut microbe-derived fatty acids-oleic acid, lauric acid, palmitic acid, valeric acid, butyric acid, isobutyric acid, and propionic acid-on neuroinflammation using liquid chromatography-tandem mass spectrometry. LPS changed N-glycosylation in the microglial glycocalyx altering high mannose and sialofucosylated N-glycans, suggesting the dysregulation of mannosidases, fucosyltransferases, and sialyltransferases. The results were consistent as we observed the restoration effect of the fatty acids, especially oleic acid, on the LPS-treated microglia, specifically on the high mannose and sialofucosylated glycoforms of translocon-associated proteins, SSRA and SSRB along with the cell surface proteins, CD63 and CD166. In addition, proteomic analysis and in silico modeling substantiated the potential of fatty acids in reverting the effects of LPS on microglial N-glycosylation. Our results showed that N-glycosylation is likely affected by diet by restoring alterations following LPS challenge, which may then influence the disease state.