# USP25 deficiency suppresses diet-induced obesity via ubiquitination and degradation of PARP1 and Elovl3 downregulation

## TL;DR

This study shows that USP25 deficiency reduces obesity and improves insulin resistance by affecting fat cell development and lipid metabolism.

## Contribution

The study reveals a novel role of USP25 in adipocyte differentiation and obesity through its regulation of PARP1 and Elovl3.

## Key findings

- USP25-deficient mice showed reduced adipose tissue growth and better insulin resistance.
- USP25 stabilizes PARP1, which promotes preadipocyte differentiation via Elovl3 regulation.
- RNA sequencing revealed downregulation of lipid synthesis pathways in USP25-deficient mice.

## Abstract

Ubiquitin-specific protease 25 (USP25) is a key regulator of lipid metabolism and insulin-stimulated glucose transport. Nonetheless, its involvement in adipocyte maturation remains uncertain. In this study, we aimed to explore how the expression of USP25 contributes to obesity induced by a high-fat diet (HFD). Usp25-KO and WT mice, maintained on either a normal diet or an HFD, were evaluated for weight gain, insulin resistance status, adipose tissue development, energy metabolism, and systemic inflammation status. In vitro, 3T3-L1 cells were induced to mature adipocytes in a specific culture medium. We found that USP25 expression decreased in obese mice subjected to long-term HFD feeding and in mature adipocytes. Usp25-KO mice showed restrained adipose tissue development and improved insulin resistance, whereas USP25-deficient preadipocytes failed to differentiate. RNA sequencing analysis showed the downregulation of lipid synthesis-related pathways in Usp25-KO mice. Mechanistically, USP25 binds to and stabilizes poly (ADP-ribose) polymerase 1 through deubiquitination, whereas poly (ADP-ribose) polymerase 1 facilitates preadipocyte differentiation and maturation by regulating the elongation of very long-chain fatty acid protein 3. These findings show the essential role of USP25 in adipocyte differentiation and lipid metabolism, suggesting that targeting USP25 ablation in adipocytes could be a promising therapeutic strategy for obesity treatment.