CD40-TRAF6 pathway as a therapeutic target in obesity-associated metabolic dysfunction

Objective: Inflammation contributes to the pathogenesis of obesity-associated metabolic dysregulation and co-stimulatory molecules, including CD40, are important mediators of this process. This study aimed to reveal the role of CD40 and its signaling intermediates, TNF-Receptor-Associated-Factors (TRAFs), in diet-induced obesity (DIO).

Methods: The DIO model was performed in CD40-deficient or -sufficient mice as well as in mice with deficient CD40-TRAF2/3/5- or CD40-TRAF6-signaling in MHCII⁺ cells. Several metabolic parameters were measured and subcutaneous and gonadal adipose tissues (AT) and liver were isolated. FACS analysis of the stromal vascular fraction from AT as well as qPCR-analysis and histochemistry of the isolated tissues were performed. Virtual Ligand Screening, TRAF6 C-domain expression, purification and binding analyses were also performed to construct a CD40-TRAF6 signalling inhibitor that was used as therapy in DIO mice.

Results: CD40ko mice were characterized by worsened insulin resistance linked to excessive AT inflammation, increased accumulation of CD8⁺ T-cells and M1 macrophages in AT, and enhanced hepatosteatosis. In contrast, mice with deficient CD40-TRAF6 signaling in MHCII⁺ cells displayed no insulin resistance and showed a reduction in both AT inflammation and hepatosteatosis in DIO, whereas the mice with deficient CD40-TRAF2/3/5 signaling excibited a phenotype similar to the CD40ko mice. Treatment of DIO mice with a small-compound that blocks CD40-TRAF6 interactions displayed improved insulin sensitivity, reduced AT inflammation and decreased hepatosteatosis.

Conclusions: The CD40-TRAF6 pathway contributes whereas the CD40-TRAF2/3/5 pathway protects from obesity-associated metabolic dysfunction. Improvement of metabolic dysregulation by a newly-developed CD40-TRAF6-pathway inhibitor may represent a therapeutic innovation in the field of immunometabolism.