To investigate the effect of fibroblast growth factor 21 (FGF21) on hepatic fibrosis in mice and the mechanism of its action.Methods Male ICR mice were randomly divided three groups : control group, model group (treated with CCl4 ), and treatment group (treated with CCl4 +1.0 mg/kg FGF21).All mice were sacrificed to collect serum and liver tissues after 36 consecutive days of treatment.Serum levels of alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total bilirubin (TBil), interleukin -6 (IL -6), interleukin -1β(IL -1β), and tumor necrosis factor -α(TNF -α) were measured.Liver pathological changes were analyzed by Masson staining .The hepatic 4 -hydroxyproline (4 -Hyp) level was measured using a hydroxyproline detection kit.The mRNA levels of hepatic collagen I, α-smooth muscle actin (α-SMA), transforming growth factor -β(TGF -β), IL -6, IL - 1β, and TNF -αwere determined by quantitative real -time PCR.Comparison between multiple groups was made by one -way analysis of variance, and comparison between any two groups weas made using the LSD -t test.Results The Masson staining showed that the model group had a significantly higher degree of hepatic fibrosis than the control group , and the treatment group had a significantly lower degree of hepatic fibrosis than the model group.The model group had significantly higher serum levels of ALT , AST, ALP, and TBil (all P <0.05),and the treatment group showed significant reductions in the above parameters compared with the model group (all P <0.05).Enzyme - linked immunosorbent assay indicated that the model group had significantly higher serum levels of IL -1β, IL -6, and TNF -αthan the control group (all P <0.05), and the treatment group showed significant reductions in the above parameters compared with the model group (all P <0.05).The hepatic 4 -Hyp level and mRNA levels of collagen I and α-SMA were significantly higher in the model group than in the control group (P =0.04, <0.001, and <0.001), and they were significantly lower in the treatment group than in the model group (P =0.005, <0.001, and <0.001).The hepatic mRNA levels of TGF -β, IL -6, IL -1β, and TNF -αwere significantly higher in the model group than in the control group(all P <0.001), and they were significantly lower in the treatment group than in the control group (all P <0.001).Conclusion FGF21 attenuates hepatic fibrogenesis in mice, possibly by inhibiting the expression of TGF -β, IL -6, IL - 1β, and TNF -αin the liver.

Objective To investigate the optimal adaptation period for mice at different developmental stages during metabolic cage experiments, aiming to provide a reference for conducting metabolic research using mice. Methods A total of 80 male C57BL/6J mice at three developmental stages (weaning period M1, adolescent M2, and adulthood M3) were subjected to a 7-day metabolic cage experiment. Data on food intake, water intake, energy expenditure, respiratory quotient, body weight, and activity levels were recorded every five minutes. The collected data were processed using time series decomposition and comprehensive cluster analysis. Statistical differences were compared using repeated measures ANOVA combined with t-test to determine the optimal adaptation period. Results Significant differences in metabolism were observed among mice in different developmental stages (P<0.01). Compared with adolescent (M2) and adult (M3) mice, weaned mice (M1) exhibited lower activity level (P<0.01) and less distinct circadian rhythm. M1 mice had higher oxygen consumption, carbon dioxide production, and energy expenditure, as well as a lower respiratory quotient (all P<0.001), indicating that they mainly relied on fat as an energy source. Analysis of food intake, water intake, and energy expenditure revealed significant differences between the first light cycle (0-12 h) and the second light cycle (24-36 h) across all developmental stages (all P<0.05) . However, there was no significant difference in daily food intake or water intake after 24 hours (both P>0.05). Comprehensive cluster analysis of multiple indicators showed that the overall indicators of mice during the first 24 hours in the metabolic cages did not cluster with those of the subsequent 6 days, demonstrating significant differences. Conclusion Metabolic cage experiment can be used to detect continuous physiological changes in mice. The results suggest that mice can adapt to new metabolic cages environment within 24 hours, providing a theoretical basis for the design of metabolic experiments using mice.