Insulin stimulates the generation of two putative insulin mediators, inositol-glycan and diacylglycerol in BC3H-1 myocytes.
Recent evidence suggests that insulin induces hydrolysis of phosphatidylinositol-glycan (PI-G) and releases inositol-glycan (IG) and diacylglycerol (DAG). These two mediators are speculated to mediate different insulin actions. In this study, we examined metabolic labeling of PI-G in BC3H-1 myocytes with known precursors of PI-G. PI-G was metabolically labeled with [3H]myo-inositol, [3H]glucosamine, [3H]galactose, [3H]glycerol, and [3H]myristic acid. The treatment of 3H-labeled PI-G with phosphatidylinositol-specific phospholipase C liberated [3H]myo-inositol, [3H]glucosamine, or [3H]galactosamine-labeled IgGs, and [3H]glycerol or [3H]myristic acid-labeled DAG. In BC3H-1 myocytes, insulin induced phosphodiesteratic hydrolysis of PI-G and stimulated generation of IGs and DAG. Released IGs were labeled with [3H]myo-inositol, [3H]glucosamine, and [3H]galactose. Released DAG was labeled with [3H] glycerol and [3H]myristic acid. The IG had a dose-dependent insulin-like activity on glucose oxidation and lipogenesis without affecting glucose transport in rat adipocytes. Insulin increased 3H radioactivities of IG and insulin-mimicking activities of IG. These results provided further evidence that hydrolysis of PI-G and generation of IGs and DAG might be early steps in some insulin actions.
Suzuki
S
S
Third Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Sugawara
K
K
Satoh
Y
Y
Toyota
T
T
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D004075:Diglycerides / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D017261:Glycosylphosphatidylinositols; D007294:Inositol / Q000031:analogs & derivatives* / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007700:Kinetics; D008055:Lipids / Q000096:biosynthesis; D051379:Mice; D009000:Monocytes / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D010084:Oxidation-Reduction; D010716:Phosphatidylinositols / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004075:Diglycerides; D017261:Glycosylphosphatidylinositols; D007328:Insulin; D008055:Lipids; D010716:Phosphatidylinositols; D011134:Polysaccharides; C068698:inositol-glycan; D007294:Inositol; D005947:Glucose