Palmitic Acid-Enriched Diet Induces Hepatic Steatosis and Injury in Adult Zebrafish

Palmitic acid (PA) is the most abundant saturated fatty acid in fast foods and is known to induce inflammation and cellular injury in various tissues. In this study, we investigated whether a PA-enriched diet can induce hepatic steatosis and injury in adult zebrafish. The adult zebrafish exhibited increased body weight, hyperlipidemia, hyperglycemia, and steatosis and a hepatic injury phenotype after being fed with a PA-enriched diet for 6 weeks. The quantitative polymerase chain reaction analysis demonstrated that genes associated with hepatic injury were all significantly increased in the liver. Furthermore, livers from the PA-fed group showed an increased messenger RNA (mRNA) expression associated with oxidative stress and endoplasmic reticulum (ER) stress responses. We also found significant upregulation of genes involved in lipid metabolism and triacylglyceride accumulation. Ultrastructural analysis revealed mitochondrial cristae injury and a dilated ER phenotype in the PA-fed hepatocytes, which can be causes of hepatic injury. PA-enriched diet induced hepatic steatosis and injury in adult zebrafish that recapitulated typical metabolic changes and pathophysiological changes as well as increased oxidative stress and ER stress observed in patients with nonalcoholic fatty liver disease.