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Prolonged oxidative stress impairs insulin-induced GLUT4 translocation in 3T3-L1 adipocytes
A Rudich1, A Tirosh, R Potashnik
1Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Abstract:
Prolonged exposure of 3T3-L1 adipocytes to micromolar concentrations of H2O2 results in an impaired response to the acute metabolic effects of insulin. In this study, we further characterized the mechanisms by which oxidative stress impairs insulin stimulation of glucose transport activity. Although insulin induced a 2.5-fold increase in plasma membrane GLUT4 content and a 50% reduction in its abundance in the low-density microsomal (LDM) fraction in control cells, oxidation completely prevented these responses. The net effect of insulin on 2-deoxyglucose uptake activity was reduced in oxidized cells and could be attributed to GLUT1 translocation. Insulin stimulation of insulin receptor substrate (IRS) 1 tyrosine phosphorylation and the association of IRS-1 with phosphatidylinositol (PI) 3-kinase were not impaired by oxidative stress. However, a 1.9-fold increase in the LDM content of the p85 subunit of PI 3-kinase after insulin stimulation was observed in control, but not in oxidized, cells. Moreover, although insulin induced an increase in IRS-1-associated PI 3-kinase activity in the LDM in control cells, this effect was prevented by oxidation. These findings suggest that prolonged low-grade oxidative stress impairs insulin-stimulated GLUT4 translocation, potentially by interfering with compartment-specific activation of PI 3-kinase.
Insights
Oxidative stress from hydrogen peroxide (H2O2) impairs insulin
Area of Science:
- Cell biology
- Metabolic research
- Oxidative stress studies
Background:
- Insulin regulates glucose uptake in adipocytes via GLUT4 translocation.
- Oxidative stress is implicated in metabolic dysfunction.
- 3T3-L1 adipocytes are a model system for studying insulin signaling.
Purpose of the Study:
- To investigate the mechanisms by which oxidative stress impairs insulin-stimulated glucose transport.
- To determine the effects of oxidative stress on GLUT4 and GLUT1 translocation.
- To examine the impact of oxidative stress on insulin receptor substrate (IRS) signaling and phosphatidylinositol 3-kinase (PI 3-kinase) activation.
Main Methods:
- 3T3-L1 adipocytes were exposed to hydrogen peroxide (H2O2) to induce oxidative stress.
- Insulin stimulation and its effects on glucose uptake were measured.
- Cellular fractions (plasma membrane, low-density microsomes) were analyzed for protein content (GLUT4, GLUT1, PI 3-kinase p85 subunit).
- Insulin receptor substrate 1 (IRS-1) tyrosine phosphorylation and PI 3-kinase activity were assessed.
Main Results:
- Oxidative stress prevented insulin-induced GLUT4 translocation to the plasma membrane.
- Insulin's effect on glucose uptake was reduced in oxidized cells, with GLUT1 translocation playing a role.
- While IRS-1 phosphorylation and association with PI 3-kinase were unaffected, compartment-specific PI 3-kinase activation in low-density microsomes was impaired by oxidative stress.
- Oxidative stress blocked the insulin-stimulated increase in PI 3-kinase p85 subunit content in low-density microsomes.
Conclusions:
- Prolonged oxidative stress interferes with insulin-stimulated GLUT4 translocation in 3T3-L1 adipocytes.
- The impairment may stem from disrupted compartment-specific activation of PI 3-kinase.
- These findings highlight a potential mechanism linking oxidative stress to insulin resistance.