Regulation of PTP-1 and insulin receptor kinase by fractions from cinnamon: implications for cinnamon regulation of insulin signalling.
Bioactive compound(s) extracted from cinnamon potentiate insulin activity, as measured by glucose oxidation in the rat epididymal fat cell assay. Wortmannin, a potent PI 3'-kinase inhibitor, decreases the biological response to insulin and bioactive compound(s) from cinnamon similarly, indicating that cinnamon is affecting an element(s) upstream of PI 3'-kinase. Enzyme studies done in vitro show that the bioactive compound(s) can stimulate autophosphorylation of a truncated form of the insulin receptor and can inhibit PTP-1, a rat homolog of a tyrosine phosphatase (PTP-1B) that inactivates the insulin receptor. No inhibition was found with alkaline phosphate or calcineurin suggesting that the active material is not a general phosphatase inhibitor. It is suggested, then, that a cinnamon compound(s), like insulin, affects protein phosphorylation-dephosphorylation reactions in the intact adipocyte. Bioactive cinnamon compounds may find further use in studies of insulin resistance in adult-onset diabetes.
Imparl-Radosevich
J
J
Department of Biochemistry and Biophysics, Iowa State University, Ames, Iowa, USA.
Deas
S
S
Polansky
M M
MM
Baedke
D A
DA
Ingebritsen
T S
TS
Anderson
R A
RA
Graves
D J
DJ
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002935:Cinnamomum zeylanicum / Q000032:analysis*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007328:Insulin / Q000502:physiology*; D010744:Phosphoric Monoester Hydrolases / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D007328:Insulin; D010936:Plant Extracts; D011972:Receptor, Insulin; D010744:Phosphoric Monoester Hydrolases; D017027:Protein Tyrosine Phosphatases; D000077191:Wortmannin