AIM:This study investigates the effect of fibroblast growth factor 21(FGF21)long-acting ana-logue PF-05231023 on promoting the"browning"of white adipose tissue(WAT)by inhibiting mitophagy in WAT and the molecular mechanisms involved.METHODS:Using a high-fat diet(HFD)to replicate an obesity model in mice,18 C57BL/6J mice were divided into three groups:normal control(NC)group,HFD group,and PF-05231023 intervention(PF+HFD)group,each consisting of 6 mice.After 12 weeks of feeding,the mice were anaesthetized,their eyeballs were removed to collect blood samples,and serum was separated to measure levels of total cholesterol(TC),triglycerides(TG),low-density lipoprotein cholesterol(LDL-C)、alanine aminotransferase(ALT),and aspartate aminotransferase(AST)in mouse serum.The inguinal WAT(iWAT),epididymal WAT(eWAT)and liver were collected.Part of the tis-sues were used for Western blot experiments to measure the protein levels of"browning"related markers uncoupling pro-tein-1(Ucp-1)and peroxisome proliferator-activated receptor γ coactivator-1α(PGC-1α),as well as mitophagy-related markers PTEN-induced kinase 1(Pink1),parkin,beclin-1 and microtubule-associated protein 1 light chain 3-Ⅱ(LC3-Ⅱ).Another part of the tissues was fixed in paraformaldehyde for subsequent HE and immunohistochemical staining.3T3-L1 cells were induced to mature adipocytes using the classic"cocktail"method.The CCK-8 assay was used to assess the impact of different concentrations of PF-05231023 intervention on cell viability.After 48 h of PF-05231023 intervention,the 3T3-L1 cell clumps were collected for Western blot experiments to measure the expression levels of"browning"related markers Ucp-1 and PGC-1α,as well as mitochondrial autophagy-related markers Pink1,parkin,beclin-1,and LC3-Ⅱ proteins.Oil red O staining was performed to detect cell accumulation,and immunofluorescence staining was used to mea-sure Ucp-1 protein content.Subsequently,3T3-L1 cells were divided into the normal group,PF-05231023 intervention group,Pink1 agonist MTK458 intervention group,and MTK458+PF-05231023 intervention group.Cell clumps were col-lected for Western blot experiments to measure the markers as mentioned above.RESULTS:The key findings of our study indicate that the PF-05231023 intervention did not affect energy intake in mice but significantly reduced the weight,liver weight,and fat weight of mice induced by a high-fat diet(P<0.05).The intervention also decreased lipid accumula-tion(TC,TG、LDL-C)and liver damage(ALT,AST)and alleviated hepatocyte vacuolization and adipocyte size(P<0.05).Compared with the HFD group,the PF-05231023 intervention increased the levels of Ucp-1 and PGC-1α protein expression in iWAT and eWAT(P<0.01).Immunohistochemical staining showed higher Ucp-1 protein content in the PF-05231023 intervention group than in the HFD group.The PF-05231023 intervention dose-dependently increased Ucp-1 and PGC-1α protein expression levels in mature 3T3-L1 cells(P<0.01),reduced cellular lipid accumulation,and immu-nofluorescence staining showed increased Ucp-1 protein content in mature 3T3-L1 cells after PF-05231023 intervention.The PF-05231023 intervention inhibited mitochondrial autophagy-related indicators Pink1,parkin,beclin-1,and LC3-Ⅱ protein expression levels in iWAT,eWAT,and induced mature 3T3-L1 cells(P<0.05).The MTK intervention increased Pink1,parkin,beclin-1,and LC3-Ⅱ protein expression levels,increased Ucp-1 protein expression level,compared with the MTK intervention group,after MTK and PF-05231023 co-intervention,partially decreased Pink1,parkin,beclin-1,and LC3-Ⅱ protein expression levels,and partially restored Ucp-1 protein expression level(P<0.01).CONCLUSION:(1)Intervention with PF-05231023 can improve obesity and related metabolic disorders induced by a high-fat diet in mice;(2)PF-05231023 intervention can inhibit white adipose tissue(WAT)and induce mature 3T3-L1 cell mitochondria autophagy,promoting"browning"by inhibiting mitochondrial autophagy;(3)Its mechanism may be related to the inhibi-tion of the Pink1-parkin signalling pathway.