Role of fatty acid transport protein 4 in oleic acid-induced glucagon-like peptide-1 secretion from murine intestinal L cells

Abstract

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 Ϯ phloretin, sulfo-N-succinimidyl oleate, or siRNA against FATP4. FATP4Ϫ/Ϫ and cluster-of-differentiation 36 (CD36) Ϫ/Ϫ 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 M unlabeled OA (P Ͻ 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 Ͻ 0.05-0.001). OA dose-dependently increased GLP-1 secretion at 500 and 1,000 M (P Ͻ 0.001), whereas phloretin, sulfo-N-succinimidyl oleate, and FATP4 knockdown decreased this response (P Ͻ 0.05-0.01). FATP4 Ϫ/Ϫ mice displayed lower plasma GLP-1 at 60 min in response to intraileal OA (P Ͻ 0.05), whereas, unexpectedly, CD36 Ϫ/Ϫ mice displayed higher basal GLP-1 levels (P Ͻ 0.01) but a normal response to intraileal OA. Together, these findings demonstrate a key role for FATP4 in OAinduced GLP-1 secretion from the murine L cell in vitro and in vivo, whereas the precise role of CD36 remains unclear.

Long chain saturated and unsaturated fatty acids exert opposing effects on viability and function of GLP-1-producing cells: Mechanisms of lipotoxicity

“…In agreement with effects on insulin-producing β-cells, short-term exposure of GLP-1-producing cells to fatty acids has previously been shown to increase GLP-1 secretion without affecting cell viability [26, 31]. Further, lipids are well-recognized stimuli of GLP-1 secretion in humans[32, 33].…”

Targeting the gastrointestinal tract to treat type 2 diabetes

“…However, both oleoylethanolamide and 2-monoacylglycerols, which are derived from triglycerides, activate a GPR119-G s signalling cascade (Overton et al 2006, Hansen et al 2012b, leading to the hypothesis that triglyceride-induced gut peptide signalling is likely due to a combined effect of direct LCFA-FFAR1-G q signalling and activation of the G s signalling pathway in EECs (Hauge et al 2015). In addition to a direct action on FFARs, fatty acids are also taken up by the intestine, and mice lacking absorptive proteins such as CD36 or FAT4 results in impaired gut peptide release (Poreba et al 2012, Sundaresan et al 2013. This may be due to intracellular metabolism and activation of PKC-ζ or PKC-δ to induce GLP-1 or CCK release, respectively (Iakoubov et al 2007, Breen et al 2011, or via alteration of cellular respiration and stimulation of glycolysis (Clara et al 2016).…”

The modulatory role of high fat feeding on gastrointestinal signals in obesity

“…This effect is not a function of impaired lipid absorption as in-vitro release of peptides from intestinal segments of CD36 KO mice is also reduced, indicating that CD36 may act as a lipid sensor for enteroendocrine cells that promotes peptide release through generation of cAMP and subsequent protein kinase A activation [65]. Additionally, other fatty acid transporters are found on enteroendocrine cell lines [64], such as fatty acid transport protein 4 that has been shown to promote GLP-1 release through activation of PKC signaling pathway [66].…”