Stimulation of hepatocyte glucose metabolism by novel small molecule glucokinase activators.
Glucokinase (GK) has a major role in the control of blood glucose homeostasis and is a strong potential target for the pharmacological treatment of type 2 diabetes. We report here the mechanism of action of two novel and potent direct activators of GK: 6-[(3-isobutoxy-5-isopropoxybenzoyl)amino]nicotinic acid(GKA1) and 5-([3-isopropoxy-5-[2-(3-thienyl)ethoxy]benzoyl]amino)-1,3,4-thiadiazole-2-carboxylic acid(GKA2), which increase the affinity of GK for glucose by 4- and 11-fold, respectively. GKA1 increased the affinity of GK for the competitive inhibitor mannoheptulose but did not affect the affinity for the inhibitors palmitoyl-CoA and the endogenous 68-kDa regulator (GK regulatory protein [GKRP]), which bind to allosteric sites or to N-acetylglucosamine, which binds to the catalytic site. In hepatocytes, GKA1 and GKA2 stimulated glucose phosphorylation, glycolysis, and glycogen synthesis to a similar extent as sorbitol, a precursor of fructose 1-phosphate, which indirectly activates GK through promoting its dissociation from GKRP. Consistent with their effects on isolated GK, these compounds also increased the affinity of hepatocyte metabolism for glucose. GKA1 and GKA2 caused translocation of GK from the nucleus to the cytoplasm. This effect was additive with the effect of sorbitol and is best explained by a "glucose-like" effect of the GK activators in translocating GK to the cytoplasm. In conclusion, GK activators are potential antihyperglycemic agents for the treatment of type 2 diabetes through the stimulation of hepatic glucose metabolism by a mechanism independent of GKRP.
Brocklehurst
Katy J
KJ
Cardiovascular and Gastrointestinal Department, AstraZeneca, Macclesfield, Cheshire, U.K.
Payne
Victoria A
VA
Davies
Rick A
RA
Carroll
Debra
D
Vertigan
Helen L
HL
Wightman
Heather J
HJ
Aiston
Susan
S
Waddell
Ian D
ID
Leighton
Brendan
B
Coghlan
Matthew P
MP
Agius
Loranne
L
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism; D005941:Glucokinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D022781:Hepatocytes / Q000201:enzymology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D016133:Polymerase Chain Reaction; D051381:Rats; D017208:Rats, Wistar; D013012:Sorbitol / Q000494:pharmacology
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; C485100:GCKR protein, human; C499484:Gckr protein, rat; D047908:Intracellular Signaling Peptides and Proteins; C080906:glucokinase regulatory protein; D013012:Sorbitol; D005941:Glucokinase; D005947:Glucose