Sterol regulatory element-binding protein-1c knockdown protected INS-1E cells from lipotoxicity.

Abstract

OBJECTIVE:

The reduction in insulin secretory capacity and beta-cell mass has been attributed, at least partially, to lipotoxicity, which may contribute to the development of type 2 diabetes. Chronic free fatty acids (FFA) exposure impairs pancreatic beta-cell function and induces beta-cell apoptosis. This study is to elucidate the underlying molecular mechanisms.

RESEARCH DESIGN AND METHODS:

We exposed INS-1E pancreatic beta-cell line to palmitate or oleate, and measured the glucose stimulated insulin secretion (GSIS). The effect of FFA on sterol regulatory element-binding protein (SREBP)-1c lipogenic pathway, and expression of genes involved in beta-cell functions, including AMPK (AMP-activated protein kinase), UCP-2 (uncoupling protein-2), IRS-2 (insulin receptor substrate-2), PDX-1 (pancreatic duodenal homeobox-1), GLUT-2 (glucose transporter-2) and B cell lymphoma/leukaemia-2 (Bcl-2) were investigated. Apoptosis of these exposed cells was determined by MitoCapture, Annexin V-Cy3 or terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Cell lipid accumulation was measured by oil red O staining or TG extraction. Also SREBP-1c expression knockdown were used.

RESULTS:

FFA treatment resulted in SREBP-1c overexpression, impaired GSIS, lipid accumulation, apoptosis of INS-1E cells. In addition, the expression of lipogenic genes and UCP-2 were upregulated, but AMPK, IRS-2, PDX-1, GLUT-2 and Bcl-2 were downregulated in the exposed cells. However, these lipotoxic effects of FFA were largely prevented by induction of a SREBP-1c small interfering RNA.

CONCLUSIONS:

These data suggest a strong correlation between FFA treatment and SREBP-1c activation in INS-1E cells. SREBP-1c might be a major factor responsible for beta-cell lipotoxicity, and SREBP-1c knockdown could protect INS-1E cells from lipotoxicity, which is implicating a therapeutic potential for treating diabetes related to lipotoxicity.

• Authors: J Li, X Liu, X Ran, J Chen, X Li, W Wu, H Huang, H Huang, Y Long, J Liang, J Cheng, H Tian
• Journal: Diabetes, obesity & metabolism (Diabetes Obes Metab) Vol. 12 Issue 1 Pg. 35-46 (Jan 2010) ISSN: 1463-1326 [Electronic] England
• PMID: 19758361 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Fatty Acids, Nonesterified
• Insulin
• Palmitates
• RNA, Small Interfering
• Sterol Regulatory Element Binding Protein 1
• Triglycerides
• Oleic Acid
• Glucose

Topics

• Animals
• Apoptosis (physiology)
• Blotting, Western
• Cell Line
• Diabetes Mellitus, Type 2 (metabolism)
• Fatty Acids, Nonesterified (pharmacology)
• Gene Expression
• Gene Knockdown Techniques
• Glucose (pharmacology)
• Humans
• Insulin (metabolism)
• Insulin Secretion
• Insulin-Secreting Cells (cytology, drug effects, metabolism)
• Lipid Metabolism (physiology)
• Oleic Acid (pharmacology)
• Palmitates (pharmacology)
• RNA, Small Interfering (isolation & purification)
• Sterol Regulatory Element Binding Protein 1 (genetics, metabolism)
• Transcription, Genetic (drug effects)
• Triglycerides (isolation & purification)
• Up-Regulation