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


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.
Li
J
J
Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China.
Liu
X
X
Ran
X
X
Chen
J
J
Li
X
X
Wu
W
W
Huang
H
H
Huang
H
H
Long
Y
Y
Liang
J
J
Cheng
J
J
Tian
H
H
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D002460:Cell Line; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology; D019301:Oleic Acid / Q000494:pharmacology; D010168:Palmitates / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000302:isolation & purification; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014280:Triglycerides / Q000302:isolation & purification; D015854:Up-Regulation
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D010168:Palmitates; D034741:RNA, Small Interfering; D051780:Sterol Regulatory Element Binding Protein 1; D014280:Triglycerides; D019301:Oleic Acid; D005947:Glucose