The down‐regulation of hepatic GPR55 ameliorates NAFL induced by a vHFD (60%‐kcal fat content) in mice. C57BL/6J mice fed a vHFD diet for 6 weeks randomly received a TVI with Lentiv‐sh scrambled or Lentiv‐shGPR55, maintaining the vHFD for 4 weeks more. (A) GPR55 mRNA levels in the liver. (B) Body‐weight change and food intake. (C) Serum levels of AST, triglycerides, NEFAs, and cholesterol. (D) H&E staining (upper panel), Oil Red O staining (middle panel), and F4/80‐immunohistochemistry staining (lower panel) of liver sections. Lipids were quantified in the Oil Red O staining sections, and the F4/80‐positive area was quantified in the F4/80‐immunohistochemistry staining sections. Hepatic triglyceride content was also directly measured. (E) Hepatic levels of proteins involved in lipid metabolism and hepatic levels of malonyl‐CoA. (F) Protein levels of ER stress markers, gene expression of inflammatory markers, and cleaved isoforms of apoptotic markers caspase 3 and caspase 7 in the liver. HPRT and GAPDH were used to normalize mRNA and protein levels, respectively. Dividing lines indicate splicing in the same gel. Data are presented as mean ± SEM (n = 7). Statistical differences are denoted by *P < 0.05, **P < 0.01, and ***P < 0.001. Abbreviations: AST, aspartate aminotransferase; CoA, coenzyme A; CPT1a, carnitine palmitoyl transferase 1a; ER, endoplasmic reticulum; FAS, fatty acid synthase; GAPDH, glyceraldehyde 3‐phosphate dehydrogenase; GPR55, G protein–coupled receptor 55; H&E, hematoxylin and eosin; HPRT, hypoxanthine‐guanine phosphoribosyltransferase; i.p., intraperitoneally; Lentiv‐shGPR55, lentiviral vector encoding short hairpin RNA against GPR55; Lentiv‐sh scrambled, lentiviral vector encoding scrambled short hairpin RNA; NAFL, nonalcoholic fatty liver; NEFA, nonesterified fatty acid; pEIF2α, phosphorylated eukaryotic initiation factor 2α; pIRE, phosphorylated iron‐responsive element; pPERK, phosphorylated protein kinase R‐like ER kinase; shCTL, short hairpin RNA control; shGPR55, short hairpin RNA against GPR55; TVI, tail‐vein injection; vHFD, very high‐fat diet; XBP1S, X‐box binding protein 1S.