Propionate is a dominant inducer of bovine cytosolic phosphoenolpyruvate carboxykinase (PCK1) expression (818.11)

Expression of PCK1 is a critical control point for gluconeogenesis. Our objective was to determine the effects of propionate, insulin, and 8 Br‐cAMP (cAMP) on the bovine PCK1 promoter. Five promoter segments from ‐1238 to +221 relative to transcription initiation and nested 5’ truncation deletions at ‐815, ‐409, ‐281 and ‐85 to +221 were ligated to pGL3 Luciferase Reporter Vector and transfected into H4IIE cells. Following 5 h transfection, cells were exposed to treatments consisting of 2.5 mM propionate in combinations with insulin and cAMP for 23 h. Propionate induced ( P <0.001) expression of all PCK1 promoter constructs (up to 8‐fold) over the control, and the induction was further enhanced for the promoter ‐1238 to +221 construct. In the presence of 0.1 mM cAMP, activity of the ‐1238 to +221 PCK1 promoter was linearly induced ( P <0.0001) with increasing propionate (0.25, 0.5, 1.0, 2.5 mM propionate induced PCK1 by 1.4, 1.8, 2.6, 6.2‐fold over 0 mM, respectively). With 1.0 mM cAMP, propionate (1.0 vs. 2.5 mM) did not increase PCK1 activity. Induction of the ‐409 to +221 PCK1 promoter construct with 0.1 mM cAMP, was repressed by 10 nM insulin but 2.5 mM propionate prevented this response ( P <0.0001). The data demonstrate an inductive effect of propionate that is dominant to the repressive effects of insulin on the bovine PCK1 promoter. Grant Funding Source : Supported by USDA‐CSREES NRI Grant no. 2006‐35206‐16646