Aim: Leptin, a hormone which regulates food intake and energy expenditure, is excessively expressed in obese patients. Leptin signaling is regulated by a negative feedback regulator, suppressor of cytokine signaling 3 (SOCS3) that competitively binds to the leptin receptor (ObR) and promotes leptin resistance. We hypothesized that an exogenously delivered SOCS3 binding domain (SH2) would compete with SOCS3 for binding to p-Tyr985ObR, and thereby maintain leptin-initiated JAK/STAT signaling.

Method: Cell-permeable, dominant-interfering ΔSOCS3 protein consists of the SOCS3 SH2 domain, a sequence optimized-advanced macromolecule transduction domain to deliver the protein into cells and tissues to facilitate soluble purification, biologically active proteins. Intracellular delivery of ΔSOCS3 was tested for the ability to enhance leptin signaling and sensitivity in diet-induced obese (DIO) mice.

Result: The cell-permeable ΔSOCS3 was delivered efficiently into cell types and tissues examined including the hypothalamus; thus, the protein appeared to cross the blood-brain barrier. CP-ΔSOCS3 competitively bound p-Tyr985ObR and blocked negative regulation by endogenous SOCS3 as assessed by increased levels of phospho-STAT3. DIO mice treated with CP-ΔSOCS3 showed 12.1% body weight loss in 14 days. In addition, fat volume (53.5%), food intake (29.2%), serum leptin (93.1%) and expression of SOCS3 mRNA were also decreased in CP-ΔSOCS3-treated compared to mice treated with diluent. In addition, treatment group showed a significant increase in STAT3 phosphorylation and pro-opiomelanocortin in the hypothalamus.

Conclusion: CP-ΔSOCS3 appeared to competitively suppress feedback inhibition of JAK/STAT signaling by endogenous SOCS3 thereby enhancing leptin sensitivity. This establishes the importance of SOCS3 in the biology of leptin signaling and resistance and suggests CP-ΔSOCS3 might be used as a mechanism-specific weight-loss therapy.


K. Lee: None. J. Jeon: None. S. Kim: None. H. Kang: None. J. Kwak: None. Y. Choi: None. D. Jo: None.

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