Analysis of tissue-specific and PPARalpha-dependent induction of FABP gene expression in the mouse liver by an in vivo DNA electroporation method

Dynamic expression of L-FABP and PPAR-α mRNAs in nonalcoholic fatty liver disease in rats

AIM: To establish a rat model of nonalcoholic fatty liver disease (NAFLD) to detect the changes in the expression of liver fatty acid-binding protein (L-FABP) and peroxisome proliferator-activated receptor-α (PPAR-α) mRNAs in NAFLD and to explore the mechanism underlying the pathogenesis of the disease.

METHODS: Eighty-four male Wistar rats were randomly and equally divided into two groups: control group (fed a normal diet for 18 weeks) and model group (fed a high-fat diet for 12 wk and a normal diet for another 6 wk). Each group was further divided into 7 subgroups for testing at weeks 0, 2, 4, 8, 12, 16 and 18. Rats in the two groups were sacrificed at each time point. Blood samples were taken to measure serum ALT, TG, CHOL, HDL-C and LDL-C. Liver samples were taken for HE staining and for detection of the expression of L-FABP and PPAR-α mRNAs by real-time fluorescence quantitative RT-PCR.

RESULTS: The expression of L-FABP and PPAR-α mRNAs in control rats showed no obvious changes. No steatosis was observed at week 2 in rats fed a high-fat diet. The expression of L-FABP mRNA increased obviously in rats fed a high-fat diet at week 4 (0.59 ± 0.06 vs 0.52 ± 0.03, P < 0.05), reaching the peak at weeks 8 and 12 (0.91 ± 0.07 and 0.92 ± 0.08 vs 0.52 ± 0.03, respectively; both P < 0.01). At week 18, the expression level of L-FABP mRNA declined significantly (0.59 ± 0.04 vs 0.92 ± 0.08, P < 0.01) but was still higher than that in the control group (P < 0.05). The expression of PPAR-α mRNA decreased obviously in rats fed a high-fat diet at week 4 (1.05 ± 0.09 vs 1.13 ± 0.07, P < 0.05), reaching the lowest level at weeks 8 and 12 (0.89 ± 0.04 and 0.85 ± 0.07 vs 1.13 ± 0.07, respectively; both P < 0.01). At week 18, the expression level of PPAR-α mRNA was elevated obviously (1.04 ± 0.07 vs 0.85 ± 0.07, P < 0.01) but was still lower than that in the control group. Steatosis become worst at week 12 but was improved greatly at week 18.

CONCLUSION: In the progression of rat NAFLD, PPAR-α mRNA expression decreases and L-FABP mRNA expression increases as steatosis becomes worse. Steatosis can be improved through diet.