Linoleic acid activates GPR40/FFA1 and phospholipase C to increase [Ca2+]i release and insulin secretion in islet beta-cells.
OBJECTIVE
To elucidate GPR40/FFA1 and its downstream signaling pathways in regulating insulin secretion.


METHODS
GPR40/FFA1 expression was detected by immunofluorescence imaging. We employed linoleic acid (LA), a free fatty acid that has a high affinity to the rat GPR40, and examined its effect on cytosolic free calcium concentration ([Ca2+]i) in primary rat beta-cells by Fluo-3 intensity under confocal microscopy recording. Downregulation of GPR40/FFA1 expression by antisense oligonucleotides was performed in pancreatic beta-cells, and insulin secretion was assessed by enzyme-linked immunosorbent assay.


RESULTS
LA acutely stimulated insulin secretion from primary cultured rat pancreatic islets. LA induced significant increase of [Ca2+]i in the presence of 5.6 mmol/L and 11.1 mmol/L glucose, which was reflected by increased Fluo-3 intensity under confocal microscopy recording. LA-stimulated increase in [Ca2+]i and insulin secretion were blocked by inhibition of GPR40/FFA1 expression in beta-cells after GPR40/FFA1-specific antisense treatment. In addition, the inhibition of phospholipase C (PLC) activity by U73122, PLC inhibitor, also markedly inhibited the LA-induced [Ca2+]i increase.


CONCLUSIONS
LA activates GPR40/FFA1 and PLC to stimulate Ca2+ release, resulting in an increase in [Ca2+]i and insulin secretion in rat islet beta-cells.
Department of Endocrinology and Metabolism, Fourth Affiliated Hospital, China Medical University, Shenyang 110034, China. zhoudoctor@163.com
Yi-Jun
YJ
Zhou
Yu-Ling
YL
Song
Hui
H
Zhou
Yan
Y
Li
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D019787:Linoleic Acid / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology*
C473035:G-protein-coupled receptor 40, rat; D007328:Insulin; D043562:Receptors, G-Protein-Coupled; D019787:Linoleic Acid; D010738:Type C Phospholipases; D002118:Calcium