Abstract Body (Do not enter title and authors here): Background: Beige adipocytes, express UCP1 and have thermogenic capability, making them a promising target for obesity treatments. However, beige adipocytes quickly transition into white adipocytes upon removal of stimuli. Our research identifies the cyclin-dependent kinase inhibitor 2A (Cdkn2a) as a crucial regulator of this transition. Ablation of Cdkn2a prolongs beige adipocyte lifespan, enhances energy expenditure, and improves glucose tolerance by inhibiting BECN1-mediated autophagy. These findings offer a potential therapeutic strategy to maintain beige adipocytes and combat obesity and related diseases.

Methods: We used Ucp1-Cre^ERT2 mice with a Rosa26R^RFP indelible labeling reporter and Cdkn2a floxed mice. All mice were maintained on a mixed C57BL6/J-129SV background. To induce Cre recombination, mice received tamoxifen for 2 days. For in vitro induction, cells were treated with 2 µM 4-hydroxy-tamoxifen. In our in vitro study, we isolated stromal vascular fraction (SVF) cells from the inguinal white adipose tissue (IGW) or brown adipose tissue (BAT) of 6-week-old male mice for seeding. For the in vivo study, we used cold exposure, metabolic cages, and glucose tolerance tests.

Results: Cdkn2a plays a pivotal role in the beige-to-white transition. Its absence prolongs the lifespan of beige adipocytes and in male mice, confers long-term metabolic protection against diet-induced obesity, along with enhanced energy expenditure and improved glucose tolerance. Mechanistically, Cdkn2a promotes the expression and activity of beclin 1 (BECN1) by directly binding to its mRNA and its negative regulator BCL2 like 1 (BCL2L1), activating autophagy and accelerating the beige-to-white transition. Reactivating autophagy by pharmacological or genetic methods abolishes beige adipocyte maintenance induced by Cdkn2a ablation. Furthermore, hyperactive BECN1 alone accelerates the beige-to-white transition in mice and human. Hence, blocking Cdkn2a-mediated BECN1 activity holds therapeutic potential in treating obesity and related metabolic diseases.

Conclusion: Cdkn2a depletion extends beige adipocyte lifespan, providing long-term metabolic benefits against diet-induced obesity in male mice. Cdkn2a boosts BECN1 expression, triggering the beige-to-white transition by directly interacting with BECN1 mRNA and its negative regulator BCL2L1, activating autophagy. Targeting Cdkn2a-mediated BECN1 activity holds promise as a therapeutic approach for treating obesity.