Insulin stimulates the biosynthesis of chiro-inositol-containing phospholipids in a rat fibroblast line expressing the human insulin receptor.
HIRc-B cells (rat fibroblasts expressing the human insulin receptor) were incubated with myo-[3H]inositol for 48 hr, and the biosynthesis of chiro-[3H]inositol was investigated in the absence and presence of insulin following a time course up to 60 min. After phase separation, treatment with insulin for 15 min caused a 2.2-fold increase in the specific radioactivity of chiro-[3H]inositol-containing phospholipids in contrast to a 1.2-fold increase in the specific radioactivity of myo-[3H]inositol-containing phospholipids. No insulin-mediated change in the specific radioactivity was observed in the inositol phosphates or free inositols. Further detailed analysis of individual [3H]inositol-containing phospholipids demonstrated marked increases in specific activity of the chiro-[3H]inositol phospholipids after 15 min of incubation with insulin: phosphatidylinositol 4-phosphate and 4,5-bisphosphate, 4.2-fold; lysophosphatidylinositol, 1.5-fold; phosphatidylinositol, 3.2-fold. In contrast, myo-[3H]inositol-containing phospholipids demonstrated relatively small increases (1.1- to 1.4-fold) after 5 min of incubation with insulin. These findings indicate that insulin stimulates de novo synthesis of chiro-inositol-containing phospholipids at the inositol phospholipid level.
Pak
Y
Y
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville 22908.
Paule
C R
CR
Bao
Y D
YD
Huang
L C
LC
Larner
J
J
D000818:Animals; D002460:Cell Line; D002855:Chromatography, Thin Layer; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism*; D007295:Inositol Phosphates / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D010716:Phosphatidylinositols / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection; D014316:Tritium
D007295:Inositol Phosphates; D007328:Insulin; D010716:Phosphatidylinositols; D011994:Recombinant Proteins; D014316:Tritium; D007294:Inositol; D011972:Receptor, Insulin