PLIN1 (perilipin 1) is a lipid droplet-associated protein that serves as a critical modulator of lipid metabolism in adipocytes and other metabolic tissues. PLIN1 coats the surface of lipid droplets, functioning as a protective barrier that shields stored triglycerides from degradation by hormone-sensitive lipase (HSL) and regulates lipolysis through dynamic protein-protein interactions 1. At the molecular level, PLIN1 contains an amino-terminal PAT domain and an 11-mer repeat region that enables binding to lipid droplet surfaces with high avidity, particularly to droplets fully covered by phospholipids 2. PLIN1 works synergistically with CIDEC to promote unilocular lipid droplet formation and enlargement through directional neutral lipid transfer 3. PLIN1 expression correlates positively with mitochondrial biogenesis genes and increases following weight loss, suggesting metabolic adaptation 3. Clinically, PLIN1 mutations cause familial partial lipodystrophy-4 4, while pathogenic PLIN1 variants are associated with nonalcoholic fatty liver disease (NAFLD) and fibrosis 4. Beyond adipocytes, PLIN1 regulates macrophage polarization and atherosclerotic plaque stability by promoting stable lipid storage and anti-inflammatory phenotypes 5. Additionally, PLIN1 serves as a direct target of the farnesoid X receptor (FXR), stabilizing lipid droplets to prevent hepatic stellate cell activation and liver fibrosis 6. These findings establish PLIN1 as a multifunctional lipid droplet protein with therapeutic relevance in metabolic diseases.