Pck1 gene silencing in the liver improves glycemia control, insulin sensitivity, and dyslipidemia in db/db mice.
OBJECTIVE
Cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C; encoded by Pck1) catalyzes the first committed step in gluconeogenesis. Extensive evidence demonstrates a direct correlation between PEPCK-C activity and glycemia control. Therefore, we aimed to evaluate the metabolic impact and their underlying mechanisms of knocking down hepatic PEPCK-C in a type 2 diabetic model.


METHODS
PEPCK-C gene targeting was achieved using adenovirus-transduced RNAi. The study assessed several clinical symptoms of diabetes and insulin signaling in peripheral tissues, in addition to changes in gene expression, protein, and metabolites in the liver. Liver bioenergetics was also evaluated.


RESULTS
Treatment resulted in reduced PEPCK-C mRNA and protein. After treatment, improved glycemia and insulinemia, lower triglyceride, and higher total and HDL cholesterol were measured. Unsterified fatty acid accumulation was observed in the liver, in the absence of de novo lipogenesis. Despite hepatic lipidosis, treatment resulted in improved insulin signaling in the liver, muscle, and adipose tissue. O(2) consumption measurements in isolated hepatocytes demonstrated unaltered mitochondrial function and a consequent increased cellular energy charge. Key regulatory factors (FOXO1, hepatocyte nuclear factor-4alpha, and peroxisome proliferator-activated receptor-gamma coactivator [PGC]-1alpha) and enzymes (G6Pase) implicated in gluconeogenesis were downregulated after treatment. Finally, the levels of Sirt1, a redox-state sensor that modulates gluconeogenesis through PGC-1alpha, were diminished.


CONCLUSIONS
Our observations indicate that silencing PEPCK-C has direct impact on glycemia control and energy metabolism and provides new insights into the potential significance of the enzyme as a therapeutic target for the treatment of diabetes.
Gómez-Valadés
Alicia G
AG
Biophysics Unit, Department de Ciències Fisiològuiques II, IDIBELL-University of Barcelona, Barcelona, Spain.
Méndez-Lucas
Andrés
A
Vidal-Alabró
Anna
A
Blasco
Francese X
FX
Chillon
Miguel
M
Bartrons
Ramon
R
Bermúdez
Jordi
J
Perales
José C
JC
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D003600:Cytosol / Q000201:enzymology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000235:genetics / Q000473:pathology*; D050171:Dyslipidemias / Q000097:blood / Q000235:genetics / Q000473:pathology*; D004734:Energy Metabolism / Q000235:genetics; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D005943:Gluconeogenesis / Q000235:genetics; D005951:Glucose Tolerance Test; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D001786:Blood Glucose; D010729:Phosphoenolpyruvate Carboxykinase (GTP)