Free fatty acids increase cytosolic free calcium and stimulate insulin secretion from beta-cells through activation of GPR40.
Free fatty acids (FFA) cause a rise in cytosolic free Ca2+ ([Ca2+]i) and stimulate insulin release from pancreatic beta-cells. The G-protein coupled receptor GPR40 can be activated by medium- and long-chain FFA. We investigated a potential role for GPR40 in the generation of the FFA-induced Ca2+ signal and insulin secretion. [Ca2+]i was measured in primary mouse beta-cells and in INS-1 cells, and insulin secretion was assessed from INS-1 cells. GPR40 expression was determined by RT-PCR and downregulation of GPR40 expression by siRNA transfection was carried out in INS-1 cells. A number of saturated, mono- and polyunsaturated medium- and long-chain FFA caused a rise in [Ca2+]i both in primary mouse beta-cells and in INS-1 cells. By contrast, the short-chain saturated caproic acid was ineffective at concentrations up to 300 microM. In INS-1 cells, the FFA-induced Ca2+ signal required mobilization of internal Ca2+ and Ca2+ influx through voltage-sensitive Ca2+ channels. RT-PCR analysis revealed that GPR40 is expressed in INS-1 cells. Downregulation of GPR40 by specific siRNA treatment lead to a significant inhibition of the FFA-induced [Ca2+]i response and insulin secretion, indicating that the FFA-stimulated Ca2+ signal and insulin secretion involve activation of GPR40 in pancreatic beta-cells.
Schnell
Susanne
S
Abteilung Endokrinologie, Diabetes und Ernährungsmedizin, Charité Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany.
Schaefer
Michael
M
Schöfl
Christof
C
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002450:Cell Communication; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D005260:Female; D005947:Glucose / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D007340:Insulinoma / Q000378:metabolism / Q000473:pathology; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism; D051379:Mice; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D005230:Fatty Acids, Nonesterified; C473036:Ffar1 protein, mouse; C473035:G-protein-coupled receptor 40, rat; D007004:Hypoglycemic Agents; D007328:Insulin; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D005947:Glucose; D002118:Calcium