DGAT1-Mediated Lipid Droplet Accumulation Promotes M. Bovis BCG Persistence on Dendritic Cells by Acting as an Immunoinflammatory Platform Through PGE₂ Signaling

Why It Matters

Targeting DGAT1 disrupts a critical lipid‑driven survival pathway for TB bacteria, offering a novel adjunctive strategy to boost current antimicrobial regimens. The findings also clarify how PGE₂ signaling intertwines metabolism and inflammation in TB pathogenesis.

Key Takeaways

• DGAT1 inhibition cuts BCG load in dendritic cells
• Reduced lipid droplets lower pro‑inflammatory cytokine release
• PGE₂ supplementation restores bacterial persistence despite DGAT1 blockade
• DGAT1 activity links host lipid metabolism to TB immune evasion
• Targeting DGAT1 offers potential adjunct TB therapy

Pulse Analysis

Tuberculosis remains a leading cause of infectious mortality, in part because Mycobacterium tuberculosis can hijack host lipid pathways to create a protective niche. Dendritic cells, as early antigen‑presenting cells in the lung, are prime targets for infection; their ability to process and present antigens is compromised when they become laden with lipid droplets. Recent work underscores that these droplets are not passive storage sites but active platforms that modulate immune signaling, especially during the latent phase when bacteria rely on host‑derived triacylglycerols for carbon.

The enzyme diacylglycerol acyltransferase‑1 (DGAT1) catalyzes the final step of triacylglycerol synthesis, and its activity spikes in BCG‑infected bone‑marrow‑derived dendritic cells. Inhibiting DGAT1 with the small‑molecule A922500 dramatically curbed lipid droplet formation, dampened expression of Nos2, Il1b, and Il6, and reduced secretion of IL‑1β, IL‑6, IL‑10, IL‑23, and TNF‑α. Crucially, the blockade also lowered prostaglandin E₂ output, a lipid mediator known to skew T‑cell differentiation and suppress effective antimycobacterial immunity. Adding back PGE₂ reversed these benefits, confirming a feed‑forward loop where DGAT1‑generated lipids fuel PGE₂ production, which in turn sustains bacterial survival.

These insights open a translational avenue: combining DGAT1 inhibitors with standard anti‑TB drugs could weaken the bacterial stronghold by dismantling its metabolic armor. Moreover, modulating PGE₂ signaling may recalibrate the inflammatory milieu to favor protective immunity rather than chronic inflammation. Future studies must assess safety, optimal dosing, and potential synergy with host‑directed therapies, but the metabolic‑immune nexus illuminated here promises a fresh lever in the fight against drug‑resistant and latent TB.