Overcoming diabetes-induced hyperglycemia through inhibition of hepatic phosphoenolpyruvate carboxykinase (GTP) with RNAi.
Phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) is the rate-controlling enzyme in gluconeogenesis. In diabetic individuals, altered rates of gluconeogenesis are responsible for increased hepatic glucose output and sustained hyperglycemia. Liver-specific inhibition of PEPCK has not been assessed to date as a treatment for diabetes. We have designed a therapeutic, vector-based RNAi approach to induce posttranscriptional gene silencing of hepatic PEPCK using nonviral gene delivery. A transient reduction of PEPCK enzymatic activity (7.6 +/- 0.6 vs 9.7 +/- 1.1 mU/mg, P < 0.05) that correlated with decreased protein content of up to 50% was achieved using this strategy in diabetic mice. PEPCK partial silencing was sufficient to demonstrate lowered blood glucose (218 +/- 26 vs 364 +/- 33 mg/dl, P < 0.001) and improved glucose tolerance together with decreased circulating FFA (0.89 +/- 0.10 vs 1.44 +/- 0.11 mEq/dl, P < 0.001) and TAG (65 +/- 11 vs 102 +/- 16 mg/dl, P < 0.01), in the absence of liver steatosis or lactic acidosis. SREBP1c was down-regulated in PEPCK-silenced animals, suggesting a role for this pathway in the alterations of lipid metabolism. These data reinforce the significance of PEPCK in sustaining diabetes-induced hyperglycemia and validate liver-specific intervention at the level of PEPCK for diabetes gene therapy.
Gómez-Valadés
Alicia G
AG
Biophysics Unit, Department of Physiological Sciences II, IDIBELL-University of Barcelona, L'Hospitalet del Llobregat, Spain.
Vidal-Alabró
Anna
A
Molas
Maria
M
Boada
Jordi
J
Bermúdez
Jordi
J
Bartrons
Ramon
R
Perales
José C
JC
D000818:Animals; D045744:Cell Line, Tumor; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000201:enzymology / Q000628:therapy*; D020868:Gene Silencing; D018390:Gene Targeting / Q000379:methods; D018014:Gene Transfer Techniques; D006801:Humans; D006943:Hyperglycemia / Q000201:enzymology / Q000209:etiology / Q000628:therapy*; D007372:Interferons / Q000502:physiology; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000235:genetics*; D034622:RNA Interference; D019892:eIF-2 Kinase / Q000502:physiology
D007372:Interferons; D019892:eIF-2 Kinase; D010729:Phosphoenolpyruvate Carboxykinase (GTP)