Glucocorticoids reduce Slc2a2 (GLUT2) gene expression through HNF1 in pancreatic β-cells

Area of Science:

• * Molecular Endocrinology
• * Diabetes Pathophysiology
• * Gene Regulation

Background:

• * Glucose transporter type 2 (GLUT2) is crucial for insulin secretion in pancreatic beta cells and its low expression is linked to type 2 diabetes.
• * Glucocorticoids, via the glucocorticoid receptor (GR), can induce beta-cell dysfunction and diabetes, but the underlying mechanisms affecting Slc2a2 gene expression are unclear.

Purpose of the Study:

• * To investigate the effects of glucocorticoids on Slc2a2 gene expression in pancreatic beta cells.
• * To identify regulatory elements and transcription factors involved in glucocorticoid-mediated repression of Slc2a2.
• * To elucidate the mechanism linking glucocorticoid exposure to beta-cell dysfunction.

Main Methods:

• * Quantitative analysis of GSIS-related gene expression in MIN6 beta-cell line.
• * Bioinformatics analysis and reporter assays to identify Slc2a2 gene enhancers.
• * Dexamethasone (DEX) and GR manipulation to assess effects on gene expression and transcription factor activity.

Main Results:

• * Dexamethasone (DEX) selectively reduced Slc2a2 mRNA expression in MIN6 beta cells.
• * An enhancer element (E3c), located 40 kb downstream of Slc2a2, mediated DEX-induced repression.
• * DEX and GR repressed the transcriptional activity of HNF1α and HNF1β, key activators of the E3c enhancer.

Conclusions:

• * Glucocorticoid-induced repression of Slc2a2 occurs via the E3c enhancer and involves decreased HNF1α/HNF1β activity.
• * This study reveals a novel mechanism for glucocorticoid-induced beta-cell dysfunction and diabetes.
• * Findings provide a functional link between HNF1α/HNF1β, GR, and beta-cell function in diabetes pathogenesis.