Triglyceride metabolism controls inflammation and microglial phenotypes associated with APOE4

Area of Science:

• Neuroimmunology
• Cellular Metabolism
• Lipid Biology

Background:

• Microglial cell states are associated with cellular lipid changes, but their functional role is unclear.
• Lipid droplets accumulate in microglia under activation and with the Alzheimer's disease-associated APOE4 genotype.

Purpose of the Study:

• To investigate the functional significance of lipid metabolism in microglial activation and APOE4-associated Alzheimer's disease.
• To determine if modulating triglyceride metabolism affects microglial immune activity.

Main Methods:

• Utilized human induced pluripotent stem cell-derived microglia.
• Examined the effects of lipopolysaccharide treatment and the APOE4 genotype.
• Inhibited triglyceride biosynthesis and assessed microglial functions like cytokine secretion and phagocytosis.
• Analyzed microglial surveillance in APOE4 humanized transgenic mouse models.

Main Results:

• Both extrinsic activation and the APOE4 genotype induce triglyceride-rich lipid droplet accumulation in microglia.
• Triglyceride biosynthesis and catabolism are essential for activation-induced inflammatory responses and phagocytosis.
• Inhibiting triglyceride biosynthesis reduces disease-associated transcriptional states in APOE4 microglia.
• Triglyceride biosynthesis inhibition ameliorates microglial surveillance defects in APOE4 mouse models.

Conclusions:

• Triglyceride metabolism plays a critical, non-concomitant role in regulating microglial immune activity.
• Targeting triglyceride biosynthesis can modulate microglial responses to activation and in APOE4-associated Alzheimer's disease.
• Modulating lipid metabolism presents a potential therapeutic strategy for neuroinflammatory diseases.