Glucotoxicity induces glucose-6-phosphatase catalytic unit expression by acting on the interaction of HIF-1α with CREB-binding protein.
The activation of glucose-6-phosphatase (G6Pase), a key enzyme of endogenous glucose production, is correlated with type 2 diabetes. Type 2 diabetes is characterized by sustained hyperglycemia leading to glucotoxicity. We investigated whether glucotoxicity mechanisms control the expression of the G6Pase catalytic unit (G6pc). We deciphered the transcriptional regulatory mechanisms of the G6pc promoter by glucotoxicity in a hepatoma cell line then in primary hepatocytes and in the liver of diabetic mice. High glucose exposure induced the production of reactive oxygen species (ROS) and, in parallel, induced G6pc promoter activity. In hepatocytes, glucose induced G6pc gene expression and glucose release. The decrease of ROS concentrations by antioxidants eliminated all the glucose-inductive effects. The induction of G6pc promoter activity by glucose was eliminated in the presence of small interfering RNA, targeting either the hypoxia-inducible factor (HIF)-1α or the CREB-binding protein (CBP). Glucose increased the interaction of HIF-1α with CBP and the recruitment of HIF-1 on the G6pc promoter. The same mechanism might occur in hyperglycemic mice. We deciphered a new regulatory mechanism induced by glucotoxicity. This mechanism leading to the induction of HIF-1 transcriptional activity may contribute to the increase of hepatic glucose production during type 2 diabetes.
Institut National de la Santé et de la Recherche Médicale, U855, Lyon, France. amandine.gautier-stein@univ-lyon1.fr
Amandine
A
Gautier-Stein
Maud
M
Soty
Julien
J
Chilloux
Carine
C
Zitoun
Fabienne
F
Rajas
Gilles
G
Mithieux
D000818:Animals; D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D005947:Glucose / Q000633:toxicity*; D005952:Glucose-6-Phosphatase / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism
C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017382:Reactive Oxygen Species; D050882:CREB-Binding Protein; D005952:Glucose-6-Phosphatase; D005947:Glucose