Effect Of PPAR-α Aonist Fenofibrate On Hepatocyte Apoptosis In Rats With Nonalcoholic Fatty Liver Disease

Objective: To investigate the relationship between PPAR-α agonist fenofibrate andhepatocyte apoptosis.Methods: In this study，the rats with nonalcoholic fatty liver disease which wereinduced by high fat diet.66male Sprague-Dawley(SD) rats were randomly dividedinto three groups after fed with normal diet for7days. Control group(C,n=18) werefed with normal diet. Model group(M,n=24) were fed with high fat diet. Fenofibrategroup(F,n=24) were fed with high fat diet. In fenofibrate group with fenofibrate（10mg/kg/d,rat body weight, its concentration is2mg/ml cosolvent, one time everyday） intervention and the control group and model group with the same cosolventby intraperitoneal injection. After4、6、8weeks,6control group rats、8model grouprats and8fenofibrate group rats were sacrificed respectively. Livers were quicklyremoved. The level of steatosis and inflammaion avtivity in liver tissue were assessedby hematoxylin-eosin(HE) staining. The changes of hepatocyte aoptosis index weremeasured with Terminal deoxynucleotidyl Transferase-mediated dUTP nick endlabeling(TUNEL) staining. Immuno-histochemistry(IHC) staining was used to detectthe protein expression of bcl-2, bax and caspase-3in liver tissue.The PPAR-α receptorand apoptotic genes including bcl-2,bax and caspase-3mRNA levels were measuredby Reverse transcription polymerase chain reaction(RT-PCR) technology.Results: At the end of the fourth week, compared with the control group, the modelgroup showed mild steatosis mostly vesicles steatosis and ballooning degeneration inthe liver tissue. Inflammation activity score were significantly increased (1.62±0.92vs0.00±0.00, P <0.01); hepatocyte apoptosis index increased in the liver tissue（58.86±13.59vs39.55±3.99,P＜0.05); the expression of PPAR-α and Bcl-2mRNAwere significantly decreased (0.366±0.068vs0.570±0.061and0.234±0.099vs0.437±0.053, P <0.01); the expression of Bax和Caspase-3mRNA were significantly increased (0.368±0.064vs0.230±0.052and0.363±0.058vs0.218±0.031; P <0.01); the protein expression of Bcl-2were significantly decreased(0.0098±0.0002vs0.0155±0.0004, P <0.01); the protein expression of Bax andCaspase-3were significantly increased (0.1311±0.0050vs0.0947±0.0139and0.1297±0.0065vs0.0794±0.0038; P <0.01).Compared with the model group, thehepatocyte apoptosis index of the fenofibrate group were decreased (43.92±3.50vs58.86±13.59, P <0.05); the expression of PPAR-α and Bcl-2mRNA were increased（0.510±0.109vs0.366±0.068and0.425±0.042vs0.234±0.099，P＜0.01); theexpression of Bax和Caspase-3mRNA were significantly decreased (0.249±0.034vs0.368±0.064and0.226±0.055vs0.363±0.058, P <0.01); the protein expression ofBcl-2were significantly increased (0.0148±0.0004vs0.0098±0.0002, P <0.01); theprotein expression of Bax and Caspase-3were significantly decreased (0.0966±0.0069vs0.1311±0.0050and0.0911±0.0136vs0.1297±0.0065; P <0.01).At the end of the sixth week, compared with the control group, the modelgroup showed mild to severe steatosis ranging from the size of lipid droplets in thecytoplasm vacuoles appear pressed against the side of the nucleus, the nucleusunevenly distributed. Inflammation activity score were significantly increased (3.62±1.31vs0.00±0.00, P <0.01); hepatocyte apoptosis index increased in the liver tissue(74.07±3.88vs51.27±11.38, P <0.01); the expression of PPAR-α and Bcl-2mRNAWere significantly decreased (0.256±0.078vs0.497±0.098and0.249±0.036vs0.452±0.065, P <0.01); the expression of Bax和Caspase-3mRNA were significantlyincreased (0.449±0.097vs0.245±0.054and0.446±0.043vs0.245±0.054, P<0.01). The inflammation activity score of the fenofibrate group were significantlyincreased (3.12±2.90vs0.00±0.00, P <0.01); the protein expression of Bcl-2weresignificantly decreased (0.0084±0.0011vs0.0176±0.0005, P <0.01);the proteinexpression of Bax and Caspase-3were significantly increased(0.2331±0.0230vs0.0974±0.0056and0.1680±0.0081vs0.0915±0.0063; P <0.01). Compared withthe model group, the hepatocyte apoptosis index of the fenofibrate group weresignificantly decreased (51.38±10.54vs74.07±3.88, P <0.01); the expression ofPPAR-α and Bcl-2mRNA were significantly increased (0.426±0.052vs0.256± 0.078and0.376±0.078vs0.249±0.036, P <0.01); the expression of Bax和Caspase-3mRNA were significantly decreased (0.290±0.083vs0.449±0.097and0.291±0.077vs0.446±0.043, P <0.01); the protein expression of Bcl-2weresignificantly increased(0.0162±0.0010vs0.0084±0.0011, P <0.01); the proteinexpression of Bax and Caspase-3were significantly decreased (0.1081±0.0106vs0.2331±0.0230and0.1037±0.0272vs0.1680±0.0081; P <0.01).At the end of the eighth week, compared with the control group, the hepatic cellof the model group showed extensive swelling and ballooning degeneration. The livertissue appeared moderate and severe steatosis and showed bullous and mixed steatosis.Inflammation activity score were significantly increased (5.12±1.64vs0.00±0.00, P<0.01); hepatocyte apoptosis index were significantly increased (85.10±3.54vs53.31±4.45, P <0.01); the expression of PPAR-α and Bcl-2mRNA Weresignificantly decreased (0.201±0.035vs0.537±0.06and0.209±0.080vs0.490±0.084, P <0.01);the expression of Bax和Caspase-3mRNA were significantlyincreased (0.486±0.061vs0.260±0.039and0.521±0.080vs0.297±0.053, P<0.01). The inflammation activity score of the fenofibrate group were significantlyincreased (3.25±1.70vs0.00±0.00, P <0.01); hepatocyte apoptosis index increase(62.14±8.77vs53.31±4.45, P <0.05); the expression of PPAR-α mRNA weresignificantly decreased (0.381±0.097vs0.537±0.065, P <0.01); the expression ofBcl-2mRNA were significantly decreased (0.359±0.078vs0.490±0.084, P <0.01);the expression of Bax和Caspase-3mRNA were significantly increased (0.354±0.051vs0.260±0.039and0.395±0.086vs0.297±0.053,P <0.01); the proteinexpression of Bcl-2were significantly decreased (0.0053±0.0002vs0.0198±0.0012, P <0.01);the protein expression of Bax and Caspase-3were significantlyincreased(0.2817±0.0180vs0.1106±0.0114and0.2288±0.0355vs0.1564±0.0027; P <0.01).Compared with the model group, the inflammation activity score ofthe fenofibrate group were decreased (3.25±1.70vs5.12±1.64, P <0.05); thehepatocyte apoptosis index of the fenofibrate group were significantly decreased(62.14±8.77vs85.10±3.54, P <0.01); the expression of PPAR-α and Bcl-2mRNAwere significantly increased (0.381±0.097vs0.201±0.035and0.359±0.078vs 0.209±0.080, P <0.01); the expression of Bax和Caspase-3mRNA were significantlydecreased (0.354±0.051vs0.486±0.061and0.395±0.086vs0.521±0.080, P<0.01); the protein expression of Bcl-2were significantly increased(0.0173±0.0020vs0.0053±0.0002, P <0.01); the protein expression of Bax and Caspase-3weresignificantly decreased (0.1147±0.0114vs0.2817±0.0180and0.1465±0.0070vs0.2288±0.0355; P <0.01).Conclusion:(1) The NAFLD model of SD rats can be successfully replicated by highfat diet.(2) PPAR-α agonist fenofibrate can improve the steatosis andinflammation of the liver tissue and inhibit the hepatocyte apoptosisin every stage of NAFLD model.(3) PPAR-α may play an anti-apoptotic effcet by activating PeroxisomeProliferator-Activated Receptor-α (PPAR-α).