Preventive Effect of Apple Polyphenol Extract on High-Fat Diet-Induced Hepatic Steatosis in Mice through Alleviating Endoplasmic Reticulum Stress

In this work, the protective effect of apple polyphenol extract (APE) on hepatic steatosis was investigated. Thirty-two C57BL/6J mice were assigned randomly to control group, hepatic steatosis group, lovastatin group, and APE group. After 8 weeks of intervention, APE supplementation markedly decreased the body weight gain, liver weight, liver index, epididymal adipose weight, epididymal adipose index, serum, and hepatic lipid levels. Hematoxylin and eosin staining revealed that APE supplementation alleviated histopathological changes of hepatic steatosis. Western blot revealed that APE downregulated the protein levels of GRP78, IRE1 alpha, p-IRE1 alpha, XBP1, PERK, p-PERK, p-eIF2 alpha, ATF6, PPAR-gamma, SREBP-1c, FAS, and ACC1. In conclusion, this study found that APE inhibited IRE1 alpha-XBP1, PERK-eIF2 alpha, and ATF6 signaling pathways to alleviate endoplasmic reticulum stress, thereby improving HFD-induced hepatic steatosis.