Akebia Saponin D Targeting Ubiquitin Carboxyl‐Terminal Hydrolase 4 Promotes Peroxisome Proliferator‐Activated Receptor Gamma Deubiquitination and Activation of Brown Adipose Tissue Thermogenesis in Obesity

Promoting thermogenesis in adipose tissue to enhance energy expenditure is widely regarded as a promising strategy for obesity treatment. However, the development of effective thermogenic drugs remains challenging. Our screenings identified the natural compound Akebia Saponin D (ASD) as a potent brown fat thermogenesis activator in mice, showing effects through mitochondrial brown fat uncoupling protein 1 (UCP1)-dependent pathways. ASD was found to significantly mitigate high-fat diet-induced obesity and enhance the mitochondrial quality of brown adipocytes to promote thermogenesis. Utilizing human protein microarrays, cellular thermal shift assay, and drug affinity responsive target stability, along with microscale thermophoresis and molecular docking analysis, we identified ubiquitin carboxyl-terminal hydrolase 4 (USP4) as a direct target of ASD. ASD interacts with USP4 and promotes the deubiquitination of peroxisome proliferator-activated receptor gamma, thus inhibiting its proteasomal degradation and enhancing the transcriptional activation of UCP1 in brown adipocytes. Additionally, USP4 knockdown was shown to attenuate brown fat thermogenesis induced by ASD. In summary, our findings demonstrate that ASD promotes brown fat thermogenesis by targeting USP4, highlighting its potential as a promising natural small molecule for obesity treatment.