Depletion of WWP1 increases Adrb3 expression and lipolysis in white adipose tissue of obese mice

Obesity is defined as abnormal or excessive fat accumulation of body fat and contributes to several metabolic disorders. White adipose tissue (WAT) stores energy in the form of triglycerides and releases energy as free fatty acids and glycerol through a process called lipolysis. People with obesity have impaired catecholamine-stimulated lipolysis, but comprehensive understanding of this lipolysis is still unclear. WW domain-containing E3 ubiquitin ligase 1 (WWP1) is a member of the HECT-type E3 family of ubiquitin ligases and is associated with several diseases. We previously showed that WWP1 expression was increased in WAT of obese mice. In this study, we investigated the function of WWP1 in WAT of obese mice by analyzing the phenotype of Wwp1 knockout (KO) mice fed a high-fat diet. The mRNA levels of beta-3 adrenergic receptor (Adrb3), which were decreased with a high-fat diet, were increased by Wwp1 KO in WAT. Moreover, Wwp1 KO mice showed increased phosphorylated hormone-sensitive lipase levels in WAT and plasma non-esterified fatty acid concentrations. In contrast, noradrenaline and its metabolism were not altered in WAT of obese Wwp1 KO mice. These findings indicate that WWP1, which is increased in adipocytes because of obesity, is a candidate for suppressing the Adrb3 signaling pathway and lipolysis independently of noradrenaline metabolism. Mice with global KO of Wwp1 (Wwp1-/-mice) and wild-type (WT) Wwp1+/+ mice were generated by mating Wwp1fl/fl/Wwp2+/+ (Wwp1fl/fl) mice, which were obtained by crossing Wwp1fl/+/Wwp2fl/+ mice with CAG-Cre mice. Wwp1fl/+/Wwp2fl/+ mice were obtained by crossing Wwp1fl/fl/Wwp2fl/fl and C57/BL6 (Wwp1 Knocuout (KO)) mice [Hoshino et al., FEBS Open Bio 2020]. At 5 weeks old, WT and Wwp1 KO mice were divided into two groups: the ND group or HFD group. The Charles River Formula-1 diet and High-Fat Diet 32 (25.5% crude protein, 32.0% crude lipid and 2.9% crude fiber; CREA, Tokyo, Japan) were fed as the ND and HFD, respectively. At 15 weeks old, mice were euthanized under isoflurane anesthesia (Mylan, Canonsburg, PA, USA) and epididymal white adipose tissue (eWAT) were collected. Then, we performed RNA-seq. using eWAT derived from ND-WT, ND-Wwp1 KO, HFD-WT and HFD-Wwp1 KO.