The Mitochondrial Biogenesis Injury Of Alcoholic Fatty Liver In Mice

Alcoholic liver disease is rising year by year in China, and alcohol becomes the second cause of liver damage following the virus. Researches on alcoholic liver disease were increased in the world, but these researches mostly concentrated on the alcohol itself or its metabolites, the direct toxic effects of liver cells as well as nutritional imbalance, lipid metabolism and lipid peroxidation in alcoholic liver disease, and the changes in the role of pathogenesis of alcohol liver disease. Liver mitochondria are the main site of alcohol metabolism, which is the direct injury subcellular of alcoholism. Mitochondrial biosynthesis is an important step in mitochondrial damage and repair, but there are rare reports about the biosynthesis of mitochondria in alcoholic fatty liver. The mechanism of mitochondrial biogenesis injury in alcoholic fatty liver is unclear.ObjectiveOn the basis of constructing a mice model of alcoholic fatty liver, to detect the mitochondrial ultrastructure and the expression levels of the genes related to mitochondrial biosynthesis. Research the changes in the ability of mitochondrial biosynthesis, thus to further clarify the mechanism of mitochondrial damage in alcoholic liver disease and to find new ways for the treatment of alcoholic liver disease.Materials and methodsThirty male C57BL/6 mice weighting between 22g and 24g were divided into two groups randomly:control group and model group, according to Liber-Decarli model to set up a mice model of alcoholic fatty liver. The mice in model group were given alcohol liquid diet, and mice in the control group were given equal liquid diet without alcohol. At the end of the experiment, we collected the heart blood after anesthesia, and detected the levels of AST, ALT and TG. We made HE stained paraffin sections and frozen sections by oil red staining to observe the degree of fatty degeneration and morphological changes in liver cells. We also observed the changes of mitochondria, endoplasmic reticulum, lipid droplets and other ultrastructural changes produced in liver cell by electron microscope and measured the expression levels of mitochondria DNA, PGC-1a, NRF-1, TFAM, PPAR-a and CPT-I in mice liver by real-time fluorescence quantified PCR.All statistical analyses were performed using the program SPSS12.0 for Windows, Measurement data were expressed with x±s. Comparisons between two groups were analyzed by t test, and correlation analysis by Pearson test. All results were considered statistically significant at a=0.05.Results1. Compared with the control group:The levels of ALT, TG, hepatic TG in mice serum of alcoholic fatty liver model were significantly higher (P<0.01, P<0.05, P<0.01), no significant difference in AST changes; and liver index increased (P <0.01). Macroscopic observation:the volume of liver increased, the brim blunted, and lustre gray. HE staining showed that more than 30% of the liver cells had fatty degeneration, and oil red staining of liver tissue showed a large number of lipid droplets. All the results showed that the mice model of alcoholic fatty liver had been established successfully.2. Compared with the control group:the mitochondrial ultrastructure of mice liver in model group were changed. Mitochondria were significant swelling. Mitochondrial membrane fusion, electron density of matrix decreased, cristae mitochondriales ruptured or disappeared. The number of mitochondrias decreased (P<0.01). Fatty acid B-oxidation reduced (P<0.01). The expression level of mitochondrial DNA reduced (P<0.05). The mRNA expression levels of PGC-la, NRF-1 and TFAM which regulated the mitochondrial generation reduced (P<0.05, P<0.05, P<0.01). The mRNA expression level of PPAR-a, CPT-I which regulated fatty acid oxidation also reduced (P<0.01, P<0.05).3. Negative correlations were found between the expression level of mitochondrial DNA and hepatic TG, liver mass, fatty acidβ-oxidation respectively (P<0.01).Conclusions1. In the mice model of alcoholic fatty liver, the liver mitochondrial morphology and function were injured by alcohol.2. In the mice model of alcoholic fatty liver, the mRNA expression levels of PGC-1a, NRF-1 and TFAM which regulated the mitochondrial generation reduced, then caused the reduction of the expression level of mitochondrial DNA and the mRNA expression levels of PPAR-a and CPT-I and the gross activity of fatty acid oxidation. It suggested that these genes regulate related functional of mitochondria were changed, then lead to the formation of fatty liver.3. The expression level of mitochondrial DNA had a negative correlation with hepatic TG, the fatty acid oxidation and liver mass.