Epigallocatechin Gallate in Obesity and Depression: A Scoping Review of Shared and Distinct Molecular Pathways

Background: EGCG, a natural extract from green tea, has been demonstrated to possess multiple beneficial effects on the human body, including antioxidant, anticancer, and anti-inflammatory properties. Notably, its obesity-suppressing effects have garnered significant attention. However, in recent years, EGCG has also been extensively studied for its potential to inhibit neuroinflammation. Given the growing prevalence of both obesity and depression, comparative analysis and summarization of EGCG's action pathways in these two diseases remain scarce. Objective: This scoping review aims to summarize the molecular mechanisms of EGCG action in obese and depressed populations and identify overlapping pathways between these mechanisms. Methods: This study followed the PRISMA-ScR guideline. Data were retrieved from literature databases such as PubMed, Web of Science, and Scopus through two independent searches and screenings: one for literature on EGCG's effects on obesity and another for literature on EGCG's effects on depression. Suitable literature was then manually screened for analysis. Results: The inhibitory pathways of EGCG in obesity can be summarized as follows: suppression of adipocyte differentiation, inhibition of inflammatory progression, and regulation of gut microbiota imbalance. The inhibitory pathways of EGCG in depression are summarized in the following directions: neuroinflammation suppression, HPA axis regulation, GABAergic system regulation, and neuroplasticity modulation. Conclusion: The overlapping pathways in the mechanisms of action of EGCG in obesity and depression are the inflammatory suppression pathway and the gut-brain axis regulation pathway.