knocking down liver ccaat/enhancer-binding protein alpha by adenovirus-transduced silent interfering ribonucleic acid improves hepatic gluconeogenesis and lipid homeostasis in db/db mice.
CCAAT/enhancer-binding protein-alpha (C/EBPalpha) is a member of the basic leucine zipper transcription factor family and regulates expression of several enzymes in the liver that control glucose and lipid metabolism. Using adenovirus-transduced silent interfering (si)RNA against C/EBPalpha, endogenous liver C/EBPalpha protein was knocked down by 70-80% in 8-wk-old wild-type (WT) and db/db mice. In WT mice, fasting blood glucose concentrations were reduced approximately 24% without changes in plasma free fatty acid and triglycerides, when compared with LacZ adenovirus-treated control mice. Ad-C/EBPalpha siRNA treatment nearly normalized fasting glucose and significantly reduced plasma insulin and free fatty acid content, even though there was no elevation of C/EBPalpha protein in the livers of db/db mice. In parallel with the changes in glucose levels, hepatic glucose production was significantly reduced in C/EBPalpha siRNA-treated WT and db/db mice. mRNA levels of phyosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and liver glycogen synthase were decreased in the C/EBPalpha siRNA-treated WT and db/db mice. Interestingly, the magnitude of reduction in these enzymes was more profound in db/db mice. C/EBPalpha siRNA also decreased mRNA levels of proliferator activator protein-gamma coactivator-1alpha in both the WT and db/db mice but reduced cAMP response element-binding protein only in WT and did not alter hepatic nuclear factor-4alpha and CBP/p300 expression. Expression of genes involved in lipogenesis, such as fatty acid synthase, acetyl-CoA carboxylase, and sterol regulatory element-binding protein-1c was robustly suppressed in the C/EBPalpha siRNA-treated db/db mice. Taken together, these results indicate that C/EBPalpha plays an important role in maintaining glucose and lipid homeostasis in the liver.
Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, Kentucky 40536-0200, USA.
Liping
L
Qiao
Paul S
PS
MacLean
Hanning
H
You
Jerome
J
Schaack
Jianhua
J
Shao
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000037:antagonists & inhibitors* / Q000235:genetics; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics; D003920:Diabetes Mellitus / Q000378:metabolism*; D005943:Gluconeogenesis; D005947:Glucose / Q000378:metabolism; D005952:Glucose-6-Phosphatase / Q000235:genetics; D006706:Homeostasis; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism*; D000071518:Liver X Receptors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D057093:Orphan Nuclear Receptors; D047493:PPAR alpha / Q000235:genetics; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D022763:CCAAT-Enhancer-Binding Protein-alpha; D022782:CCAAT-Enhancer-Binding Protein-beta; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D047493:PPAR alpha; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D005952:Glucose-6-Phosphatase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D005947:Glucose