ObjectiveTo investigate the effects of hepatic fatty acid transporter 5 (FATP5) gene expression on the levels of free long-chain fatty acid (LCFA) in mice with metabolic associated fatty liver disease (MAFLD).

MethodsFrom June to December 2022, a prospective study was conducted with three experimental groups: wild-type (WT) group, FATP5 gene expression negative (FATP5 ^-) group, and human FATP5 gene expression positive (hFATP5 ⁺) group, with 10 mice in each group. Each group of mice was fed a high-fat diet for 16 weeks to establish a model of MAFLD. Hepatic tissue changes were observed using hematoxylin-eosin staining. The liver mass and liver coefficient of the mice were measured. Total cholesterol (TC), triglycerides (TG), aspartate aminotransferase (AST), alanine aminotransferase (ALT), uric acid (UA), and LCFA levels were determined using an automatic biochemical analyzer. Blood glucose (Glu) levels were measured using a blood glucose analyzer. The liver mass and liver coefficient, TC and TG levels, AST and ALT levels, Glu and UA levels, and LCFA levels were compared among the three groups.

ResultsIn the WT group, there was significant inflammatory cell infiltration within the hepatocytes and a large amount of fat accumulation. In the FATP5 ^- group, the inflammatory cell infiltration in the hepatocytes was mild with slight fat accumulation. In the hFATP5 ⁺ group, the inflammatory cell infiltration in the hepatocytes was severe, with great fat accumulation. The liver mass [(1.27 ± 0.25) g], liver coefficient (2.38 ± 0.19), TC [(1.82 ± 0.26) mmol/L], TG [(0.93 ± 0.24) mmol/L], AST [(169.95 ± 37.73) U/L], ALT [(95.36 ± 21.49) U/L], Glu [(8.34 ± 1.52) mmol/L], and UA [(74.32 ± 15.52) μmol/L] in the FATP5 ^- group were all significantly lower than those in the WT group [(1.61 ± 0.23) g, (2.71 ± 0.20), (2.31 ± 0.28) mmol/L, (1.34 ± 0.21) mmol/L, (278.31 ± 43.24) U/L, (147.32 ± 28.81) U/L, (10.52 ± 1.24) mmol/L, (96.28 ± 17.43) μmol/L], while the LCFA level [(3.57 ± 0.48) mg/L] in the FATP5 ^- group was significantly higher than that in the WT group [(2.63 ± 0.56) mg/L] ( t = 3.17, 3.78, 4.06, 4.07, 5.97, 4.57, 3.51, 2.98, 4.03, all P < 0.05). In the hFATP5 ⁺ group, the liver mass [(1.92 ± 0.30) g], liver coefficient (2.95 ± 0.23), TC [(2.59 ± 0.24) mmol/L], TG [(1.76 ± 0.35) mmol/L], AST [(341.22 ± 48.98) U/L], ALT [(189.45 ± 17.97) U/L], Glu [(13.21 ± 1.98) mmol/L], and UA [(117.74 ± 18.38) μmol/L] were all significantly higher than those in the WT group, while the LCFA level [(3.57 ± 0.48) mg/L] in the FATP5 ⁺ group was significantly lower than that in the WT group ( t = 2.59, 2.49, 2.40, 3.25, 3.04, 3.92, 3.64, 2.68, 3.19, all P < 0.05).

ConclusionsThe absence of FATP5 in the liver can elevate blood levels of LCFA in mice with MAFLD, reduce food intake, and help alleviate the symptoms of MAFLD.