Green Tea Polyphenol Epigallocatechin Gallate Promotes Autophagy and Lipid Droplet Degradation in HepG2 Cells

Abstract Epigallocatechin gallate (EGCG), a major polyphenol in green tea, exerts beneficial effects on lipid metabolism and liver health. However, its underlying action mechanisms remain unclear. Therefore, in this study, we investigated the effects of EGCG on autophagy and lipid metabolism using HepG2 cells. Autophagy induction was evaluated based on light chain (LC)-3B-II protein expression and green fluorescent protein-LC3 puncta formation. Autophagic flux was assessed using tandem red fluorescent protein-green fluorescent protein-LC3. Lipophagy was examined by analyzing the co-localization of lipid droplets with the lysosomal marker, lysosomal-associated membrane protein-1. Oil red O staining was used to quantify intracellular lipid accumulation. EGCG treatment increased LC3B-II levels in a concentration-dependent manner and induced LC3 puncta formation, indicating enhanced autophagosome formation. Tandem red fluorescent protein-green fluorescent protein-LC3 analysis revealed that EGCG enhanced the autophagic flux, as evidenced by the increased proportions of autolysosomes. Furthermore, EGCG enhanced the co-localization of lipid droplets with lysosomes, suggesting the activation of lipophagy. Oil Red O staining revealed that EGCG significantly reduced intracellular lipid accumulation in HepG2 cells. These findings suggest that EGCG activates autophagy and lipophagy, leading to reduced lipid accumulation in HepG2 cells. Overall, our results provide mechanistic insights into the lipid-lowering effects of EGCG and highlight its potential as a dietary compound to prevent steatotic liver disease. Keywords EGCG; Obesity; Autophagy; Lipophagy