Lipoprotein Lipase Regulates Microglial Lipid Droplet Accumulation

Figure 1. AdipoRedTM staining of neutral lipid-containing lipid droplets in; (A,B). Control BV-2 microglial cells. (C,D). LPL KD BV-2 microglia. (E) Control primary microglia. (F). LPL KD primary microglia. White arrows indicate lipid droplets (LD). (G). Average number of LDs per cell in Control vs. LPL KD BV-2 microglia. N = 16 per group. (H). Average number of LDs per cell in Control vs. LPL KD primary microglia. N = 15 per group, * = p < 0.05, *** = p < 0.001.

Figure 2. Relative lipidomics between Control and LPL KD (BV-2) microglia. (A–I). Volcano plots representing lipidomic profiles of CE, TG, DAG, PA, PG, PC, PE, PI, and PS in BV-2 microglia. Significance was determined as a ≥1.5 or ≤−1.5-fold difference in the relative abundance of lipid species in LPL KD vs. control with a p-value ≤ 0.05. (J). Lipidomic profile by lipid class represents the difference in relative abundance of PUFA, MUFA, and SFA in control vs. LPL KD cells. (K). Lipidomic profile by saturation represents the degree of saturation in each lipid class in control vs. LPL KD cells. (L). Cholesterol efflux in control vs. LPL KD cells. where * = p < 0.05.

Figure 3. Altered expression of lipid metabolism and inflammatory genes in LPL KD BV-2 microglia, and microglia isolated from adult MiLPLKD mice. (A). Comparative gene expression between control and LPL KD BV-2 cells. B–F Comparative gene expression of CD11b+ microglia isolated from WT vs. MiLPLKD mice (B–F). Significance was determined as fold change ≥1.5 and p < 0.05.

Figure 4. PPAR agonists rescue LPL KD microglia from LDAM phenotype. (A–P) Confocal microscopy of BV-2 control and LPL KD cells, treated with either vehicle (DMSO), 100 µM rosiglitazone, or 500 µM bezafibrate. Green dye indicates AdipoRed staining of neutral lipids. Blue DAPI staining indicates nuclei. Scale bar: 10 µm. (A–D). Quantitative analysis of relative LD fraction and volume in Control (BV-2) microglia treated with vehicle or 100 µM rosiglitazone. (E–H). Quantitative analysis of relative LD fraction and volume in LPL KD (BV-2) microglia treated with vehicle or 100 µM rosiglitazone. (I–L). Quantitative analysis of relative LD fraction and volume in Control (BV-2) microglia treated with vehicle or 500 µM bezafibrate. (M–P). Quantitative analysis of relative LD fraction and volume in LPL KD (BV-2) microglia treated with vehicle or 500 µM bezafibrate. n = 10 per group. (Q). Western blot showing PPARγ protein expression in 60 μg of total protein from either control or LPL KD cells. (R–S). Quantification of PPAR target genes in control vs. LPL KD BV-2 microglia treated with vehicle 100 µM rosiglitazone or 500 µM bezafibrate. * = p < 0.05, *** = p < 0.001.