Ubc13 haploinsufficiency protects against age-related insulin resistance and high-fat diet-induced obesity.

Obesity is associated with low-grade inflammation that leads to insulin resistance and type 2 diabetes via Toll-like Receptor (TLR) and TNF-family cytokine receptor (TNFR) signaling pathways. Ubc13 is an ubiquitin-conjugating enzyme responsible for non-canonical K63-linked polyubiquitination of TNF receptor-associated factor (TRAF)-family adapter proteins involved in TLR and TNFR pathways. However, the relationship between Ubc13 and metabolic disease remains unclear. In this study, we investigated the role of Ubc13 in insulin resistance and high-fat diet (HFD)-induced obesity. We compared wild-type (WT) and Ubc13 haploinsufficient (ubc13+/- ) mice under normal diet (ND) and HFD, since homozygous knockout mice (ubc13-/- ) are embryonic lethal. Male and female ubc13+/- mice were protected against age-related insulin resistance under ND and HFD compared to WT mice. Interestingly, only female ubc13+/- mice were protected against HFD-induced obesity and hepatic steatosis. Moreover, only female HFD-fed ubc13+/- mice showed lower expression of inflammatory cytokines that was secondary to reduction in weight gain not present in the other groups. In summary, our results indicate that suppression of Ubc13 activity may play a metabolic role independent of its inflammatory function. Thus, Ubc13 could represent a therapeutic target for insulin resistance, diet-induced obesity, and associated metabolic dysfunctions.