CYP2E1 impairs GLUT4 gene expression and function: NRF2 as a possible mediator.

Area of Science:

• Biochemistry
• Molecular Biology
• Metabolic Diseases

Background:

• Impaired glucose transporter 4 (GLUT4) function and expression are hallmarks of insulin resistance in diabetes and obesity.
• Cytochrome P450 isoform 2E1 (CYP2E1) is known to induce oxidative stress and impair insulin action.

Purpose of the Study:

• To investigate the molecular mechanisms by which CYP2E1 affects GLUT4 gene expression and function in adipose and muscle cells.
• To elucidate the role of CYP2E1 in insulin resistance at the cellular level.

Main Methods:

• Overexpression and silencing of CYP2E1 in L6 muscle cells and primary rat adipose cells.
• Assays for insulin-stimulated glucose uptake, 2-deoxyglucose uptake, and GLUT4 translocation.
• Analysis of GLUT4 gene expression at promoter and mRNA levels.
• Chromatin immunoprecipitation (ChIP) assays and promoter analysis.
• Investigation of the role of transcription factor NF-E2-related factor 2 (NRF2).

Main Results:

• CYP2E1 overexpression inhibited insulin-stimulated GLUT4 translocation and glucose uptake in L6 cells, an effect partially blocked by vitamin E.
• CYP2E1 suppressed GLUT4 gene expression in L6 and adipose cells, while CYP2E1 silencing increased it.
• CYP2E1-induced suppression of GLUT4 was mediated by NRF2, involving direct NRF2 binding to the GLUT4 promoter.
• Antioxidants and a CYP2E1 inhibitor blocked CYP2E1's suppressive effect on GLUT4 expression.

Conclusions:

• CYP2E1 negatively regulates GLUT4 gene expression and function in insulin-sensitive cells through an NRF2-dependent mechanism.
• CYP2E1 and NRF2 act as key negative regulators of GLUT4 in cellular models of insulin resistance.
• These findings provide insights into the molecular pathways linking CYP2E1 to impaired glucose metabolism.