Overexpression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in mouse liver lowers blood glucose by suppressing hepatic glucose production
Chaodong Wu, … , Christopher B. Newgard, Alex J. Lange
Chaodong Wu, … , Christopher B. Newgard, Alex J. Lange
Published January 1, 2001
Citation Information: J Clin Invest. 2001;107(1):91-98. https://doi.org/10.1172/JCI11103.
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Article

Overexpression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in mouse liver lowers blood glucose by suppressing hepatic glucose production

Abstract

Hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase is an important regulatory enzyme of glucose metabolism. By controlling the level of fructose-2,6-bisphosphate, an allosteric activator of the glycolytic enzyme 6-phosphofructo-1-kinase and an inhibitor of the gluconeogenic enzyme fructose-1,6-bisphosphatase, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase regulates hepatic glucose output. We studied the effects of adenovirus-mediated overexpression of this enzyme on hepatic glucose metabolism in normal or diabetic mice. These animals were treated with virus encoding either wild-type or bisphosphatase activity–deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Seven days after virus injection, hepatic fructose-2,6-bisphosphate levels increased significantly in both normal and diabetic mice, with larger increases observed in animals with overexpression of the mutant enzyme. Blood glucose levels in normal mice overexpressing either enzyme were lowered, accompanied by increased plasma lactate, triglycerides, and FFAs. Blood glucose levels were markedly reduced in diabetic mice overexpressing the wild-type enzyme, and still more so in mice overexpressing the mutant form of the enzyme. The lower blood glucose levels in diabetic mice were accompanied by partially normalized plasma triglycerides and FFAs, increased plasma lactate, and increased liver glycogen levels, relative to diabetic mice treated with a control adenovirus. Our findings underscore the critical role played by hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in control of fuel homeostasis and suggest that this enzyme may be considered as a therapeutic target in diabetes.

Authors

Chaodong Wu, David A. Okar, Christopher B. Newgard, Alex J. Lange

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Northern and Western blot analyses of 6PF-2K/F-2,6-P2ase overexpression....
Northern and Western blot analyses of 6PF-2K/F-2,6-P2ase overexpression. (a) Northern blot analysis of 6PF-2K/F-2,6-P2ase mRNA. Total RNA was extracted from fresh liver of all mice on day 7 after adenovirus infusion. For both protocols, only three animals of each group were chosen, without bias, and used for Northern blot analyses. A total of 30 μg RNA was loaded in each lane for electrophoresis. In protocol 1, samples were from normal mice treated with adenovirus (two representative animals of Ad-gal group, lanes 1 and 2; three animals of Ad-Bif-WT group, lanes 3–5; and three animals of Ad-Bif-DM group, lanes 6–8). In protocol 2, samples were from saline control mice and STZ-induced diabetic mice treated with adenovirus (two representative animals of each group are shown in blots). Saline control group, lanes 1 and 2; STZ-Ad-gal group, lanes 3 and 4; STZ-Ad-Bif-WT group, lanes 5 and 6; and STZ-Ad-Bif-DM group, lanes 7 and 8). (b) Western blot analysis of 6PF-2K/F-2,6-P2ase protein. Extracted protein was prepared from fresh liver tissue of mice sacrificed on day 7 after adenovirus infusion. For both protocols, only three animals of each group were chosen, without bias, and used for Western blot analyses. Concentration of extracted protein was measured by the BCA method. Equal amounts of extracted protein (100 μg) were used for electrophoresis. In protocol 1, samples were from the Ad-gal group (lanes 1–3), Ad-Bif-WT group (lanes 4–6), and Ad-Bif-DM group (lanes 7–9). In protocol 2, samples were from the saline control group (lanes 1–3), STZ-Ad-gal group (lanes 4–6), STZ-Ad-Bif-WT group (lanes 7–9), and STZ-Ad-Bif-DM group (lanes 10–12).