Abstract:
Objective To investigate the effect of growth differentiation factor 11 (GDF11) on free fatty acid (FFA)-induced hepatocyte steatosis and the role of autophagy in this process. Methods A model of nonalcoholic fatty liver disease was established invitro, and recombinant GDF11 was added to observe its effect on hepatocyte steatosis and apoptosis. Chloroquine was added to inhibit autophagy, and the change in hepatocyte autophagy flow induced by GDF11 and its association with steatosis were explored. AM-12 cells were divided into control group, control+GDF11 group, model group, GDF11 group, and GDF11+chloroquine group. The cells in the control group were cultured with DMEM complete culture medium; the cells in the control+GDF11 group were cultured with GDF11 (100 ng/mL) added to the complete culture medium; the cells in the model group were treated with 1 mmol/L FFA (with an oleic acid/palmitic acid ratio of 2∶1) to induce hepatocyte steatosis; the cells in the GDF11 group were co-cultured with FFA and GDF11; the cells in the GDF11+chloroquine group were co-cultured with FFA, GDF11, and 20 μmol/L chloroquine (an autophagy inhibitor). Lipid droplet fluorescence staining and an automatic biochemical analyzer were used to observe lipid deposition in hepatocytes; Western blotting and protein immunofluorescence assay were used to measure the levels of autophagy-related proteins (p62 and LC3B) and the level of autophagy; JC-1 staining was used to measure mitochondrial membrane potential. A one-way analysis of variance was used for comparison of continuous data between multiple groups, and the least significant difference t-test was used for further comparison between two groups. Results Compared with the model group, the GDF11 group and the control group had significant reductions in the accumulation and volume of lipid droplets in hepatocytes (all P<0.05). The model group had a significantly higher level of triglyceride in hepatocytes than the GDF11 group and the control group (P<0.000 1). Compared with the control group, the model group had a significantly lower level of LC3B (P<0.05) and a significantly higher level of p62 (P<0.05); compared with the GDF11 group, the GDF11+chloroquine group had a significant increase in the level of triglyceride in hepatocytes (P<0.001); compared with the model group, the GDF11 group had a significant reduction in the content of ROS (P<0.05). After FFA induction, there was a significant increase in green fluorescence in cytoplasma, and compared with the control group, the model group had a significant increase in JC-1 monomers/aggregates (P<0.000 1) and a reduction in mitochondrial membrane potential; there was a reduction in the intensity of green fluorescence after the addition of GDF11, and compared with the model group, the GDF11 group had a significant reduction in JC-1 monomers/aggregates (P<0.05) and an increase in mitochondrial membrane potential. Conclusion GDF11 can alleviate FFA-induced lipotoxic liver injury and improve hepatocyte steatosis in nonalcoholic fatty liver disease by promoting autophagy.
ZHANG T, YIN XC, REN FF, et al. Mechanism of growth differentiation factor 11 regulating nonalcoholic fatty liver disease[J]. J Clin Hepatol, 2023, 39(9): 2103-2109.. doi: 10.3969/j.issn.1001-5256.2023.09.011.