Introduction: Macrophage infiltration into adipose tissue and their polarization from an anti-inflammatory M2 to pro-inflammatory M1 phenotype contributes to adipose tissue inflammation and the development of insulin resistance. Androgen-dependent tissue factor pathway inhibitor-regulating protein (ADTRP) is a recently discovered enzyme that breaks down a class of anti-inflammatory and anti-diabetic lipids in adipose tissues. Our study aims to investigate the effect of ADTRP on macrophage polarization and migration to adipocytes.
Methods: Mouse 3T3-L1 mature adipocytes were either transduced with AAV-ADTRP viral vectors or transfected with ADTRP siRNA to overexpress or knockdown ADTRP respectively. Conditioned media from the ADTRP-overexpressed and ADTRP-knockdown adipocytes were collected and treated to mouse RAW 264.7 macrophages. Lipopolysaccharide (LPS) was used to induce a pro-inflammatory state in the macrophages. Gene expression of macrophage M1 and M2 markers, including IL-1β, IL-6, TNF-α, iNOS, CD206 and IL-10 were measured using RT-qPCR. Macrophage migration assay was performed by co-culturing RAW 264.7 macrophages and 3T3-L1 adipocytes in a transwell system.
Results: Conditioned media from ADTRP-overexpressed adipocytes reduced the expression of anti-inflammatory M2 macrophage markers, CD206 and IL-10. On the contrary, conditioned media from ADTRP-knockdown adipocytes increased M2 markers in basal-state macrophages and decreased pro-inflammatory M1 markers, including IL-1β, TNF-α and iNOS, in LPS-stimulated macrophages. We also observed reduced macrophage migration towards ADTRP-knockdown adipocytes.
Conclusion: ADTRP regulates macrophage polarization and migration to adipocytes. Inhibition of ADTRP can be further studied as a possible strategy to reduce adipose tissue inflammation.
S. Ong: None. C. Heng: None. Y. Lee: None. D. Ooi: None.
Khoo Teck Puat - National University Children's Medical Institute research grant
