(M1030-03-14) Enhancing Glycyrrhizin Delivery to White Adipose Tissue: A Promising Approach for Safe and Effective Obesity Treatment

Purpose: Glycyrrhizin (GL), a saponin found in licorice root and commonly used as an anti-inflammatory agent, has the potential to be an effective obesity treatment. Nevertheless, the inadequate absorption of GL by adipose tissue has restricted its utilization. Thus, we conjugated GL with adipose homing peptide (AHP), a peptide that specifically attaches to membrane protein prohibitin (Phb) which is excessively expressed in mature adipocytes. The objective of this study is to investigate the therapeutic capacity of GPA as a safe and efficient treatment for obesity using an in vitro obesity model.

Methods: Polyethylene glycol (PEG) was utilized as a linker to achieve the conjugation of GL to AHP. The synthesis of GL-PEG was achieved using the EDC/NHS coupling technique, followed by conjugation to AHP using a Thiol-Michael addition process. The capacity of GPA to target adipocytes mediated by Phb was validated using fluorescence-activated cell sorting. The impact of GPA on the treatment of obesity was verified in both single culture of 3T3-L1 (a mouse fibroblast cell line) and in co-culture of 3T3-L1 with RAW 264.7 (a mouse macrophage cell line).

Results: GPA exhibited a higher affinity for mature adipocytes as opposed to pre-adipocytes. Leading to a more significant decrease in lipid accumulation in both normal physiological conditions and in an in vitro obesity model. When mature adipocytes were treated with GPA, it led to the reduction of the secretion and mRNA expression of pro-inflammatory cytokines and adipokines. The co-culture of Raw 264.7 cells with 3T3-L1 cells, which have been subjected to GPA treatment, led to a decrease in secretion and mRNA expression of pro-inflammatory cytokines and adipokines. It was found that GPA increased the expression of sirtuin-1, the primary transcription factor involved in thermogenesis signaling. This led to the activation of PPAR-γ coactivator 1 α and mitochondria biogenesis.

Conclusion: The GPA effectively enhanced the absorption of GL in mature adipocytes via binding to Phb. The therapeutic impact of GPA on an in vitro obesity model is achieved by the combined action of its anti-hypertrophic, anti-inflammatory, and browning actions, without causing any harm to cells. Additional research will be undertaken to investigate the therapeutic effect of GPA in diet-induced obesityanimal models

Acknowledgements: This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government Ministry of Science and ICT (MSIT) (NRF-2022R1A4A1030421, NRF-2020R1A2C3005834)


Figure 1. Prohibitin-mediated adipocyte targetability of GPA. FACS analysis of GL derivatives uptake in (a) preadipocytes and (b) mature adipocytes.


Figure 2. The therapeutic efficacy of GPA for the treatment of obesity. (a) Quantification of lipid accumulation of adipocytes after GL derivatives treatment in an in vitro obesity model. (b) mRNA expression of anti-inflammatory adipokine adiponectin in treated adipocytes and (c) TNF-α in macrophages relative to GAPDH after 24h of co-culture