Capsaicin Fights Fatty Liver by Activating a Key Cellular Cleanup Pathway

Capsaicin (CAP), the compound responsible for the heat in chili peppers, has long been associated with metabolic health benefits, but the precise cellular mechanisms behind its lipid-lowering effects have remained elusive. This study sheds light on how CAP targets liver fat metabolism at a molecular level, with implications for conditions like non-alcoholic fatty liver disease (NAFLD) and obesity.

Researchers used HepG2 human liver cells treated with oleic acid (OA) to create an in vitro model of lipid overload. Capsaicin was then applied to assess its ability to reduce this fat accumulation and to probe the underlying mechanisms driving any observed effects.

CAP significantly reduced levels of triglycerides (TG), total cholesterol (TC), and LDL cholesterol while increasing HDL cholesterol in the fat-loaded cells. It also modulated the expression of multiple lipid metabolism genes — including ACC, PPAR-α, PPAR-γ, Fasn, CPT-1, SREBP-1C, and SCD-1 — pushing the balance toward fat breakdown over synthesis. Most notably, CAP activated the PINK1/Parkin mitophagy pathway, which facilitates the selective removal of dysfunctional mitochondria, helping restore cellular energy homeostasis.

To confirm the pathway's necessity, researchers used two interventions: the mitophagy inhibitor Mdivi-1 and siRNA-mediated silencing of the PINK1 gene. Both approaches abolished CAP's lipid-lowering effects, providing strong mechanistic evidence that the PINK1/Parkin pathway is essential for CAP's action.

These findings lay a molecular foundation for developing capsaicin-based or mitophagy-targeting therapies for lipid metabolic disorders. However, this is a cell culture study only, and translation to human benefit requires in vivo validation.