[Effects of different swimming exercises on alcoholic fatty liver formation in mice].

Objective

To investigate the effects of 7-week swimming exercise with different loads on the improvement of liver lipid metabolism in mice with alcoholic fatty liver disease (AFLD) and its relationship with the regulation of miR-34a/PPARα.

Methods

Fifty male KM mice were randomly divided into control group (K, n=10) and alcoholic fatty liver group (AFLD, n=40). The AFLD model was constructed after feeding with 50% alcohol for 7 weeks with 1 d rest per week. After successful model construction, the mice were divided into a model group (M), a 30-min swimming exercise group (LE), a 60-min swimming exercise group (ME), and a 90-min loaded swimming exercise group (HE, 5% of body mass as tail lead load), with 10 mice in each group, for a total of 7 weeks of intervention. After completion, the serum and liver tissues were collected, the liver index, visceral fat ratio, hepatocyte injury indicators, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transpeptidase (γ-GT), total cholesterol (TC), triglyceride (TG), and high/low density lipoprotein cholesterol (H/LDL-C) content were measured; HE staining was used to observe the changes in liver structure, Western blot was used to detect the protein levels of PPARα, FAS and TNF-α in liver tissues, and mRNA expression profiles were analyzed by sequencing After RT-PCR, the mRNA expressions of miR-34a, PPARα, FAS, TNF-α and CPT-1 were verified.

Results

Compared with K group, the hepatic cord disorder, focal lipid vacuum, obvious lipid droplet vacuolation, abnormal ectopic nucleus were observed in AFLD group ; liver function was decreased significantly. Compared with the M group, the liver functions of the ME and HE groups were improved significantly, the serum levels of TG, TC and LDL-C were decreased, while the HDL-C level was increased (P<0.01 or P<0.05), and the liver index and visceral fat ratio were decreased (P< 0.01 or P<0.05), the focal lipid droplet degeneration of hepatocytes was decreased, and the structure of the hepatic cord was clearer; and the ME group showed a more significant intervention effect. Compared with the M group, the expression levels of PPARα protein in the liver tissues of the LE, ME, and HE groups were increased, while the protein expression levels of FAS and TNF-α were decreased (P<0.01 or P<0.05). Based on Illumina high-throughput sequencing and mRNA differential expression analysis, there are 38 differentially expressed genes in the PPARα pathway, including 9 up-regulated genes and 29 down-regulated genes, which are involved in liver fatty acid oxidation, lipid metabolism, and apoptosis inhibition. Compared with group M, the gene levels of miR-34a, FAS, and TNF-α in LE, ME, and HE groups were decreased, and the gene levels of PPARα and CPT-1 were increased (P<0.01 or P<0.05).

Conclusion

Swimming with different loads can improve liver functions in AFLD mice, promote lipid droplet degradation, and regulate liver lipid metabolism. The mechanism may be related to the activation of miR-34a/PPARα, and the intervention effect of moderate-load swimming is better.