Palmitic acid induces macrophage sialylation via TLR4/MyD88/TRAF6/NF-κB signaling

Globalization has spread Western diets and lifestyles beyond traditional boundaries. These patterns increase the risk of metabolic disorders and promote low-grade inflammation. However, the role of macrophage glycosylation in this context is still not fully elucidated. In this study, we examined the impact of PA-induced macrophage inflammation on cellular sialylation and its functional consequences.

In vitro, immunofluorescence, flow cytometry, and Western blot analyses showed that TLR4/MyD88/TRAF6/NF-κB signaling activation promotes macrophage polarization 24 h after PA treatment. Metabolomics, Neu5Ac tracing, immunofluorescence, transwell assays, and Western blot demonstrated that PA upregulates Cytidine monophosphate N-acetylneuraminic acid synthetase (CMAS) and ST3 beta-galactoside alpha-2, 3-sialyltransferase III (ST3Gal-III) expression, promoting CMP-Neu5Ac and Neu5Ac metabolism, macrophage sialylation, and migration. TLR4-in-C34 blockade reversed these effects. In vivo, blood biochemical analysis, ELISA, flow cytometry, and liver tissue sectioning showed that a high-fat diet increases serum and hepatic lipid levels, promotes sialylation, and increases peritoneal and hepatic macrophage numbers. Immunofluorescence, flow cytometry, and Western blot confirmed that a high-fat diet activates TLR4 signaling in macrophages, driving M1 polarization and CMAS/ST3Gal-III upregulation.

A high-fat diet increases PA levels and activates the TLR4/MyD88/TRAF6/NF-κB signaling pathway in macrophages, thereby upregulating CMAS and ST3Gal-III expression. Thus, it not only induces the M1 polarization of macrophages, thereby augmenting the inflammatory response, but also modulates sialylation, facilitating the recruitment of macrophages to tissues.