Isolation, structure, synthesis, and bioactivity of a novel putative insulin mediator. A galactosamine chiro-inositol pseudo-disaccharide Mn2+ chelate with insulin-like activity.
We isolated from beef liver a putative insulin mediator termed INS-2, 1. Its structure was determined to be a novel inositol glycan pseudo-disaccharide Mn(2+) chelate containing D-chiro-inositol 2a (as pinitol) and galactosamine. Purification methods were scaled up from those previously reported to isolate an inositol glycan with similar composition from rat liver.(1) Structure of the beef liver glycan was determined by degradative chemistry and 2D NMR spectroscopy and confirmed by chemical synthesis. Its structure is 4-O-(2-amino-2-deoxy-beta-D-galactopyranosyl)-3-O-methyl-D-chiro-inositol 1 (INS-2, Figure 1). Its role as an insulin mimetic was demonstrated by its action in vivo to decrease elevated blood glucose injected to low-dose streptozotocin diabetic rats in a stereospecific and dose-dependent manner. The pseudo-disaccharide also stimulated [(14)C]glucose incorporation into [(14)C]glycogen in a dose-dependent manner in H4IIE hepatoma cells in the presence of insulin, thus enhancing insulin action. Only when chelated to Mn(2+) did it activate pyruvate dehydrogenase phosphatase in vitro in a dose-dependent manner. To our knowledge, this is the first example of a beta-1,4-linked inositol glycan consisting of D-chiro-inositol and galactosamine isolated from animal tissues with insulin mimetic actions.
Larner
Joseph
J
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908-0735, USA. jl6d@virginia.edu
Price
John D
JD
Heimark
Douglas
D
Smith
Leigh
L
Rule
Gordon
G
Piccariello
Thomas
T
Fonteles
Manasses C
MC
Pontes
Carla
C
Vale
Daniele
D
Huang
Laura
L
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle; D002614:Chelating Agents / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000097:blood; D004187:Disaccharides / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis; D007004:Hypoglycemic Agents / Q000138:chemical synthesis / Q000302:isolation & purification / Q000494:pharmacology; D007294:Inositol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D007328:Insulin / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D000078790:Insulin Secretion; D008099:Liver / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008345:Manganese / Q000737:chemistry; D018716:Molecular Mimicry; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013237:Stereoisomerism; D014407:Tumor Cells, Cultured
C476439:4-(2-amino-2-deoxygalactopyranosyl)-3-O-methylinositol; D001786:Blood Glucose; D002614:Chelating Agents; D004187:Disaccharides; D007004:Hypoglycemic Agents; D007328:Insulin; D008345:Manganese; D007294:Inositol; D006003:Glycogen; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase; D005947:Glucose