Functional effects and mechanisms of Phyllanthus emblica fruit and gallic acid on metabolic diseases: Experimental evidence and clinical perspectives

Metabolic diseases have become a global health problem. In recent years, increasing attention has been paid to finding effective ways to prevent or improve metabolic diseases from functional foods. The fruit of Phyllanthus emblica (FPE) has been consumed worldwide as a reliable food source, often in the form of sauces, beverages, nutraceuticals, or extracts. Gallic acid (GA) is reported to be the main functional compound of FPE. Currently, FPE and GA have been shown to have multiple health benefits. In this review, we offer a comprehensive summary of the use of FPE and its functional compound GA in improving three metabolic diseases, namely type 2 diabetes mellitus (T2DM), obesity, and nonalcoholic fatty liver disease (NAFLD). The evidence suggests that FPE and GA hold significant potential in managing these three metabolic diseases. They can maintain glucose homeostasis by regulating the PI3K/p-Akt pathway and improve insulin resistance by regulating the PPARγ/AMPK/NF-κB pathway. They inhibit adipogenesis by down-regulating the expression of PPARγ, C/EBP α and FABP4 proteins, and increase energy expenditure by up-regulating the expression of UCP1 and CPT-1A proteins. The information can be utilized to assess the effectiveness and feasibility of FPE and GA as strategies for managing metabolic diseases. It should be noted that human clinical trials of FPE and GA for the three metabolic diseases, especially obesity and NAFLD, are still scarce. More large-scale, long-term, well-designed clinical trials are needed to further confirm the functional benefits and safety of FPE and GA in preventing and improving T2DM, obesity, and NAFLD.