[3H]myoinositol incorporation into phospholipids in liver microsomes from humans with and without type II diabetes. The lack of synthesis of glycosylphosphatidylinositol, precursor of the insulin mediator inositol phosphate glycan.
A class of inositol phosphate-containing oligosaccharides (IPG) derived from a membrane glycan-phosphatidylinositol precursor (GPI) has been identified as a possible mediator of insulin action. Saltiel's laboratory has recently communicated an in vitro assay for the synthesis of GPI in rat liver microsomes. Herein we have established this method in rat and human liver microsomes, it being our end point to evaluate if the pool of GPI was normal in diabetes and if failure of insulin to generate IPG from GPI could be involved in the mechanism of insulin resistance in Type II diabetes. However, subsequent to the detailed study of [3H]myoinositol incorporation into phospholipids in liver microsomes from our study subjects, we demonstrated by gas chromatography/mass spectrometry analysis that the material reported to be GPI is a mixture of lysophospholipids that does not contain hexosamine, ethanolamine, or amino acids.
Thakkar
J K
JK
Department of Medicine, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
Raju
M S
MS
Kennington
A S
AS
Foil
B
B
Caro
J F
JF
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003567:Cytidine Diphosphate Diglycerides / Q000378:metabolism / Q000494:pharmacology; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006017:Glycolipids / Q000096:biosynthesis*; D017261:Glycosylphosphatidylinositols; D006801:Humans; D007294:Inositol / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000096:biosynthesis*; D010743:Phospholipids / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D011498:Protein Precursors; D051381:Rats
D003567:Cytidine Diphosphate Diglycerides; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D010743:Phospholipids; D011134:Polysaccharides; D011498:Protein Precursors; C028039:inositol phosphate glycan; D008345:Manganese; D007294:Inositol; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D008274:Magnesium; D002118:Calcium