[Expression of uncoupling protein 2 and its relationship to the content of adenosine triphosphate in the nonalcoholic fatty livers of rats fed a high-fat diet].
OBJECTIVE
To investigate the expression of uncoupling protein 2 (UCP2) and its relationship to the content of adenosine triphosphate (ATP) in livers of nonalcoholic fatty liver disease (NAFLD) rats fed a fat-rich diet.


METHODS
To produce a NAFLD model, a fat-rich diet, consisting of 10% lard oil + 2% cholesterol, was given to Sprague-Dawley rats for a period of 8, 12, 16 and 24 weeks. The normal control rats were fed normal diets. The expressions of UCP2 in the liver were detected by immunohistochemistry and semi-quantitative RT-PCR. The content of ATP of liver was measured by fluorometry.


RESULTS
Simple fatty livers were observed in the model group after 8 weeks. From 12 week to 24 week, the livers of the model group rats gradually progressed from simple steatohepatitis to steatohepatitis with pericellular fibrosis. Both immunohistochemistry and semi-quantitive RT-PCR suggested the up-regulated expression of UCP2 in these NAFLD rat livers. The hepatic expression of UCP2 mRNA in the model group was increased with time, and peaked in 24 week by 4.2 times compared to the control group ( t = 16.474, P < 0.01). The ATP content of livers was significantly reduced in the model group compared with the control group at 16 weeks [(2.97+/-0.48) x 10(-8) micromol/g vs. (2.25+/-0.55) x 10(-8) micromol/g, t = 2.419, P < 0.05] and 24 weeks [(2.97+/-0.48) x 10(-8) micromol/g vs. (1.99+/-0.66) x 10(-8) micromol/g, t = 3.248, P < 0.01]. Furthermore, there was a negative correlation between the UCP2 mRNA expression and the content of ATP in the livers of the NAFLD group (r = -0.93, P < 0.01).


CONCLUSIONS
The rat model of NAFLD could be replicated sucessfully by feeding a fat-rich diet for 24 weeks, and the mRNA and its protein of UCP2 were expressed un-regulated in livers of NAFLD. The increasing UCP2 might play a role in the reduction of ATP content in livers of the NAFLD rats.
Fan
Jian-gao
JG
Department of Gastroenterology, Shanghai First People's Hospital, Jiaotong University, Shanghai 200080, China. fanjg@citiz.net
Ding
Xiao-dong
XD
Wang
Guo-liang
GL
Xu
Zheng-jie
ZJ
Tian
Li-yan
LY
Zheng
Xiao-ying
XY
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D004041:Dietary Fats; D005234:Fatty Liver / Q000209:etiology / Q000378:metabolism*; D007473:Ion Channels / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D024101:Mitochondrial Proteins / Q000096:biosynthesis* / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071246:Uncoupling Protein 2
D004041:Dietary Fats; D007473:Ion Channels; D024101:Mitochondrial Proteins; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D000255:Adenosine Triphosphate