Background: Chronic alcohol consumption is known to induce cytochrome P450 2E1 (CYP2E1) leading to lipid peroxidation, mitochondrial dysfunction and hepatotoxicity. We showed that replacement of dietary long-chain triglycerides (LCT) by medium-chain triglycerides (MCT) could be protective. We now wondered whether the induction of mitochondrial CYP2E1 plays a role and whether liver injury could be avoided through mitochondrial intervention.
Methods: Rats were fed 4 different isocaloric liquid diets. The control group received our standard dextrin-maltose diet with intake limited to the average consumption of the 3 alcohol groups fed ad libitum the alcohol containing Lieber-DeCarli liquid diet. The fat was either 32% of calories as LCT (alcohol), or 16% as LCT + 16% as MCT (alcohol-MCT 16%), or 32% as MCT only (alcohol-MCT 32%).
Results: After 21 days, compared to the controls, the alcohol and both alcohol-MCT groups had a significant increase in mitochondrial CYP2E1 (p < 0.05 for both). As shown before, the same was found for the microsomal CYP2E1. When MCT replaced all the fat, like in the alcohol-MCT 32% group, CYP2E1 was significantly reduced by 40% in mitochondria (p < 0.05) and 30% in microsomes (p < 0.01). In mitochondria, 4-hydroxynonenal (4-HNE), a parameter of oxidative stress, paralleled CYP2E1. Compared to controls, alcohol and alcohol-MCT 16% significantly raised mitochondrial 4-HNE (p < 0.001), whereas the alcohol-MCT 32% diet brought it down to control levels (p < 0.001). Mitochondrial reduced glutathione (GSH) was also significantly lowered by alcohol consumption (p < 0.05), and it increased to almost normal levels with alcohol-MCT 32% (p = 0.006). These changes in the mitochondria reflected the reduction observed in total liver in which alcohol-MCT 32% decreased the alcohol-induced steatosis with a diminution of triglycerides (p < 0.001) and of the pro-inflammatory cytokine tumor necrosis factor-α (p < 0.001).
Conclusion: Mitochondria participate in the induction of CYP2E1 by alcohol and contribute to lipid peroxidation and GSH depletion. Thus, lipid composition of the diet is an important determinant for the beneficial effect of MCT, with a diet containing a mixture of LCT/MCT being ineffective.