title: Role of fatty acid transport protein 4 in oleic acid-induced glucagon-like peptide-1 secretion from murine intestinal L cells.
abstract: The antidiabetic intestinal L cell hormone glucagon-like peptide-1 (GLP-1) enhances glucose-dependent insulin secretion and inhibits gastric emptying. GLP-1 secretion is stimulated by luminal oleic acid (OA), which crosses the cell membrane by an unknown mechanism. We hypothesized that L cell fatty acid transport proteins (FATPs) are essential for OA-induced GLP-1 release. Therefore, the murine GLUTag L cell model was used for immunoblotting, [(3)H]OA uptake assay, and GLP-1 secretion assay as determined by radioimmunoassay following treatment with OA ± phloretin, sulfo-N-succinimidyl oleate, or siRNA against FATP4. FATP4(-/-) and cluster-of-differentiation 36 (CD36)(-/-) mice received intraileal OA, and plasma GLP-1 was measured by sandwich immunoassay. GLUTag cells were found to express CD36, FATP1, FATP3, and FATP4. The cells demonstrated specific (3)H[OA] uptake that was dose-dependently inhibited by 500 and 1,000 μM unlabeled OA (P < 0.001). Cell viability was not altered by treatment with OA. Phloretin and sulfo-N-succinimidyl oleate, inhibitors of protein-mediated transport and CD36, respectively, also decreased [(3)H]OA uptake, as did knockdown of FATP4 by siRNA transfection (P < 0.05-0.001). OA dose-dependently increased GLP-1 secretion at 500 and 1,000 μM (P < 0.001), whereas phloretin, sulfo-N-succinimidyl oleate, and FATP4 knockdown decreased this response (P < 0.05-0.01). FATP4(-/-) mice displayed lower plasma GLP-1 at 60 min in response to intraileal OA (P < 0.05), whereas, unexpectedly, CD36(-/-) mice displayed higher basal GLP-1 levels (P < 0.01) but a normal response to intraileal OA. Together, these findings demonstrate a key role for FATP4 in OA-induced GLP-1 secretion from the murine L cell in vitro and in vivo, whereas the precise role of CD36 remains unclear.
authors.affiliation: Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Poreba
authors.forename: C X
authors.initials: CX
authors.lastname: Dong
authors.forename: S K
authors.initials: SK
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Stahl
authors.forename: J H
authors.initials: JH
authors.lastname: Miner
authors.forename: P L
authors.initials: PL
authors.lastname: Brubaker
mesh_terms: D000818:Animals; D018955:CD36 Antigens / Q000032:analysis / Q000235:genetics; D002478:Cells, Cultured; D019858:Enteroendocrine Cells / Q000187:drug effects / Q000378:metabolism*; D050612:Fatty Acid Transport Proteins / Q000032:analysis / Q000097:blood* / Q000235:genetics; D005260:Female; D020868:Gene Silencing; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019301:Oleic Acid / Q000494:pharmacology*; D009829:Oleic Acids / Q000494:pharmacology; D010693:Phloretin / Q000494:pharmacology; D013388:Succinimides / Q000494:pharmacology
chemical_list: D018955:CD36 Antigens; D050612:Fatty Acid Transport Proteins; D009829:Oleic Acids; C493569:Slc27a1 protein, mouse; C493572:Slc27a4 protein, mouse; D013388:Succinimides; C120556:sulfo-N-succinimidyl oleate; D019301:Oleic Acid; D052216:Glucagon-Like Peptide 1; D010693:Phloretin