Mitochondria in liver diseases

Mitochondria are not only the main energy source in the hepatocytes but also play a major role in the cell redox homeostasis and maintain normal liver function including signalling pathways and the metabolism of exogenous substances. These roles assign mitochondria a gateway function in protecting hepatocyte from injury since unbalanced mitochondrial function unequivocally affects cell survival by actively causing the onset and perpetuation of liver diseases. Abnormal mitochondrial function is reported to be involved in a variety of liver diseases including drug-induced liver injury, alcoholic liver disease, non-alcoholic fatty liver disease, viral hepatitis, primary and secondary cholestasis, hemochromatosis, and Wilson's disease. These changes lead to the impairment of the electron transport chain and/or oxidative phosphorylation, which induces a decrease in oxidative degradation of many exogenous and endogenous substrates and ATP synthesis, and in general, reduces hepatocyte tolerance towards potentially damaging insults. Structural changes accompany functional impairment of mitochondria, resulting in swelling and formation of aggregates and inclusions within the mitochondrial matrix. In chronic liver diseases, adequate mitochondrial function is maintained by mitochondrial proliferation and/or by an increased activity of critical enzymes. The assessment of mitochondrial functions in vivo is a useful tool in patients with liver diseases for diagnostic and prognostic purposes in patients with liver diseases and for the evaluation of therapeutic interventions.