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Lipoprotein Lipase Regulates Microglial Lipid Droplet Accumulation
Bailey A Loving1, Maoping Tang2, Mikaela C Neal2
1Department of Radiation Oncology, Oakland University William Beaumont School of Medicine, Royal Oak, MI 48309, USA.
Abstract:
Microglia become increasingly dysfunctional with aging and contribute to the onset of neurodegenerative disease (NDs) through defective phagocytosis, attenuated cholesterol efflux, and excessive secretion of pro-inflammatory cytokines. Dysfunctional microglia also accumulate lipid droplets (LDs); however, the mechanism underlying increased LD load is unknown. We have previously shown that microglia lacking lipoprotein lipase (LPL KD) are polarized to a pro-inflammatory state and have impaired lipid uptake and reduced fatty acid oxidation (FAO). Here, we also show that LPL KD microglia show excessive accumulation of LD-like structures. Moreover, LPL KD microglia display a pro-inflammatory lipidomic profile, increased cholesterol ester (CE) content, and reduced cholesterol efflux at baseline. We also show reduced expression of genes within the canonical cholesterol efflux pathway. Importantly, PPAR agonists (rosiglitazone and bezafibrate) rescued the LD-associated phenotype in LPL KD microglia. These data suggest that microglial-LPL is associated with lipid uptake, which may drive PPAR signaling and cholesterol efflux to prevent inflammatory lipid distribution and LD accumulation. Moreover, PPAR agonists can reverse LD accumulation, and therefore may be beneficial in aging and in the treatment of NDs.
Insights
Microglia dysfunction in aging and neurodegenerative diseases involves lipid droplets. Lipoprotein lipase deficiency in microglia increases these droplets, but PPAR agonists can reverse this, offering potential therapeutic benefits.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia, the brain's immune cells, become dysfunctional with age, contributing to neurodegenerative diseases (NDs).
- Dysfunctional microglia exhibit impaired phagocytosis, reduced cholesterol efflux, and increased pro-inflammatory cytokine secretion.
- Accumulation of lipid droplets (LDs) is observed in dysfunctional microglia, but the underlying mechanisms remain unclear.
Purpose of the Study:
- To investigate the role of lipoprotein lipase (LPL) in microglial lipid droplet accumulation and inflammatory status.
- To explore the potential of peroxisome proliferator-activated receptor (PPAR) agonists in reversing microglial lipid dysregulation.
Main Methods:
- Utilized microglia lacking lipoprotein lipase (LPL KD) to study lipid metabolism and inflammatory profiles.
- Analyzed lipid droplet accumulation, cholesterol ester content, and gene expression related to cholesterol efflux.
- Assessed the effects of PPAR agonists (rosiglitazone and bezafibrate) on LPL KD microglia.
Main Results:
- LPL KD microglia exhibited excessive accumulation of LD-like structures and a pro-inflammatory lipidomic profile.
- These cells showed increased cholesterol ester content and reduced cholesterol efflux, with downregulated genes in the cholesterol efflux pathway.
- PPAR agonists significantly rescued the LD-associated phenotype in LPL KD microglia.
Conclusions:
- Microglial LPL is crucial for lipid uptake, PPAR signaling, and cholesterol efflux, preventing inflammatory lipid distribution and LD accumulation.
- PPAR agonists demonstrate potential therapeutic value by reversing microglial LD accumulation in aging and neurodegenerative conditions.
