Forsythoside A Attenuates High-Fat Diet-Induced Obesity by Regulating Thermogenesis and Browning of White Adipose Tissue Through Activation of the AMPK Signaling Pathway.

Purpose: Obesity is a global public health issue, and natural products that promote white fat browning and enhance thermogenesis to consume energy represent promising strategy for addressing this problem. Forsythoside A (FTA) is key bioactive constituent isolated from the fruit of Forsythia suspensa. It has been reported that FTA can alleviate metabolic disorders such as hepatic lipid accumulation induced by high-fat diet (HFD). However, research on the role of FTA in alleviating obesity by promoting white fat browning remains scarce. Materials and Methods: We intervened in diet-induced obesity (DIO) mice and differentiated 3T3-L1 cells with FTA and detected thermogenic indices and the expression of thermogenesis-related genes under the guidance of network pharmacology. Mechanistically, molecular docking combined with molecular biology techniques was employed to verify the affinity of pathway-related proteins, and the AMPK inhibitor (BML-275) was used to intervene in 3T3-L1 cells to assist in demonstrating the main pathway through which FTA stimulates white fat browning. Results: FTA significantly attenuated lipid accumulation in both in vivo and in vitro models. Gene Ontology (GO) enrichment analysis revealed that FTA may promote white adipocyte browning and mitochondrial thermogenesis. Consistent with improved energy metabolism, FTA treatment increased oxygen consumption and carbon dioxide production in mice, while maintaining the respiratory exchange ratio (RER) at approximately 0.7. In vitro, FTA enhanced cellular oxygen consumption rate (OCR) and mitochondrial density. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis combined with molecular docking identified the AMPK signaling cascade as a key potential pathway mediating FTA action. Molecular biology assays further confirmed that FTA promotes AMPK phosphorylation and activates the canonical thermogenic downstream PGC-1α/UCP1 pathway. Consistently, inhibition of AMPK with BML-275 abolished the beneficial effects of FTA in 3T3-L1 adipocytes. Conclusions: This study reveals that FTA enhances white fat browning via the AMPK pathway while increasing thermogenesis in adipose tissue.