Related Experiment Video
Updated: Jan 16, 2026
Isolation, Characterization, and Purification of Macrophages from Tissues Affected by Obesity-related Inflammation
Published on: April 3, 2017
Coordinated inhibition of M1 macrophage polarization by FIT2-mediated lipid droplet biosynthesis and FABP5
Yi-Han Liu1, Bei Li1, Yuan-Xing Zhang2,3
1State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
Abstract:
Lipid droplets (LDs) serve as dynamic organelles central to host immune response and bacterial infection resistance by recruiting multiple proteins and peptides with established antiviral and antibacterial properties. Although macrophage polarization is integral to both innate immunity and lipid homeostasis, the regulatory influence of LDs on this process remains unclear. In this study, augmentation of LDs via oleic acid (OA) treatment attenuated M1 polarization in RAW264.7 macrophages. Given that LD budding is mediated by fat storage-inducing transmembrane protein 2 (FIT2) encoded by FITM2, transcriptomic analysis following FITM2 knockdown revealed suppressed expression of fatty acid-binding protein 5 (FABP5), a lipid-binding protein that further modulated LD abundance. Both FIT2 and FABP5 were found to regulate LD content and collectively contributed to inhibition of M1 macrophage polarization. This shift impaired macrophage capacity to mount effective antibacterial responses. These findings identify a coordinated role for LDs and FABP5 in modulating M1 macrophage polarization, establishing a mechanistic link between lipid metabolism and innate host defense against bacterial infection.
Insights
Lipid droplets regulate macrophage immune responses. Increased lipid droplets, influenced by FIT2 and FABP5, inhibit M1 polarization, impairing antibacterial defense.
Area of Science:
- Cell Biology
- Immunology
- Metabolism
Background:
- Lipid droplets (LDs) are key organelles in immune responses and host defense against bacterial infections.
- Macrophage polarization is crucial for innate immunity and lipid homeostasis, but the role of LDs is not fully understood.
Purpose of the Study:
- To investigate the regulatory influence of lipid droplets on macrophage polarization.
- To elucidate the molecular mechanisms involving FIT2 and FABP5 in LD regulation and macrophage function.
Main Methods:
- RAW264.7 macrophages were treated with oleic acid to augment LDs.
- FITM2 knockdown was performed, followed by transcriptomic analysis.
- The roles of FIT2 and FABP5 in LD abundance and macrophage polarization were assessed.
Main Results:
- Oleic acid treatment augmented LDs and attenuated M1 polarization in macrophages.
- FITM2 knockdown suppressed fatty acid-binding protein 5 (FABP5) expression.
- Both FIT2 and FABP5 were found to regulate LD content and inhibit M1 macrophage polarization, impairing antibacterial responses.
Conclusions:
- Lipid droplets and FABP5 play a coordinated role in modulating M1 macrophage polarization.
- A mechanistic link between lipid metabolism and innate host defense against bacterial infection is established.
