Copper deficiency induces hepatic fatty acid synthase gene transcription in rats by increasing the nuclear content of mature sterol regulatory element binding protein 1.
Dietary copper (Cu) deficiency results in an accelerated rate of hepatic fatty acid synthase gene transcription and an enhanced rate of hepatic lipid synthesis. Because the nuclear transcription factor sterol regulatory element binding protein-1 (SREBP-1) is a strong enhancer of fatty acid synthase promoter activity, it was hypothesized that Cu deficiency induces fatty acid synthase gene transcription by increasing the nuclear localization of mature SREBP-1. Male weanling rats were pair-fed a Cu-adequate (6.0 mg/kg) or Cu-deficient (0.6 mg/kg) diet (AIN-93) for 28 d. DNase I hypersensitivity site mapping of the hepatic fatty acid synthase gene revealed the presence of four major hypersensitivity sites located at -8700 to -8600, -7300 to -6900, -600 to -400 and -100 to +50. Although Cu deficiency did not change the hypersensitivity site pattern or intensity, in vitro footprinting of the region between -100 and +50 indicated that Cu deficiency enhanced DNA protein interactions within this region. The sequence between -68 and -58 contains the DNA recognition sequence for SREBP-1 and upstream stimulatory element-1 (USF-1). Western blot analysis revealed that the dietary Cu deficiency increased the hepatic nuclear content of mature SREBP-1 by 150% (P: < 0.05), and it concomitantly decreased the membrane content of precursor SREBP-1 by 45% (P: < 0.05). Changes in the hepatic distribution of SREBP-1 associated with Cu deficiency were not accompanied by changes in SREBP-1 mRNA. The nuclear content of USF-1 was unaffected by dietary Cu status. The hepatic increase in mature SREBP-1 of Cu-deficient rats was accompanied by a 400% increase and an 80% decrease in the abundance of fatty acid synthase and cholesterol 7-alpha hydroxylase mRNA, respectively. hepatic These data indicate that a Cu deficiency stimulates hepatic lipogenic gene expression by increasing the hepatic translocation of mature SREBP-1.
Tang
Z
Z
Graduate Program of Nutritional Sciences and the Institute of Cellular and Molecular Biology, The University of Texas, Austin, TX, 78712, USA.
Gasperkova
D
D
Xu
J
J
Baillie
R
R
Lee
J H
JH
Clarke
S D
SD
D000818:Animals; D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics*; D003300:Copper / Q000172:deficiency* / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics*; D015253:Deoxyribonucleases, Type I Site-Specific; D064429:Fatty Acid Synthases / Q000235:genetics*; D050356:Lipid Metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D014158:Transcription, Genetic
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D003300:Copper; D064429:Fatty Acid Synthases; D015253:Deoxyribonucleases, Type I Site-Specific