scholarly journals Protein Kinase Cζ Is Required for Oleic Acid-Induced Secretion of Glucagon-Like Peptide-1 by Intestinal Endocrine L Cells

Endocrinology ◽  
2007 ◽  
Vol 148 (3) ◽  
pp. 1089-1098 ◽  
Author(s):  
Roman Iakoubov ◽  
Angelo Izzo ◽  
Andrea Yeung ◽  
Catharine I. Whiteside ◽  
Patricia L. Brubaker
Keyword(s):  
Oleic Acid ◽  
Protein Kinase ◽  
Monounsaturated Fatty Acids ◽  
L Cells ◽  
L Cell ◽  
Rna Transfection ◽  
Pkc Isoforms ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Long Chain

Long-chain, monounsaturated fatty acids (FAs) stimulate secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1) from the intestinal L cell. Because the atypical protein kinase C (PKC), PKCζ, is involved in FA signaling in many cells, the role of PKCζ in FA-induced GLP-1 secretion was investigated, using the murine GLUTag L cell line and primary rat intestinal L cells. GLUTag cells expressed mRNA for several PKC isoforms, including PKCζ, and PKCζ protein was localized throughout the cytoplasm in GLUTag and primary L cells as well as normal mouse and rat L cells. Treatment with oleic acid (150–1000 μm) for 2 h increased GLP-1 secretion (P < 0.001), and this was abrogated by the PKCζ inhibitor ZI (P < 0.05) and PKCζ small interfering RNA transfection (P < 0.05) but not inhibition of classical/novel PKC isoforms. Although most PKCζ was localized in the particulate compartment of GLUTag cells, oleate treatment did not alter PKCζ levels or activity in this cell fraction. GLUTag cells expressed mRNA for the Gq-coupled FA receptor GPR120; however, oleic acid did not induce any changes in Akt, MAPK, or calcium, and pretreatment with LY294002 and PD98059 to inhibit phosphatidylinositol 3-kinase and MAPK, respectively, did not prevent the effects of oleic acid. Finally, GLUTag cells also released GLP-1 in response to arachidonic acid (P < 0.001) but were not affected by other long-chain FAs. These findings demonstrate that PKCζ is required for oleic acid-induced GLP-1 secretion. This enzyme may therefore serve as a therapeutic target to enhance GLP-1 release in type 2 diabetes.

scholarly journals Novel Biological Action of the Dipeptidylpeptidase-IV Inhibitor, Sitagliptin, as a Glucagon-Like Peptide-1 Secretagogue

Endocrinology ◽  
2012 ◽  
Vol 153 (2) ◽  
pp. 564-573 ◽  
Author(s):  
Ganesh V. Sangle ◽  
Lina M. Lauffer ◽  
Anthony Grieco ◽  
Shivangi Trivedi ◽  
Roman Iakoubov ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Fold Increase ◽  
Dipeptidylpeptidase Iv ◽  
L Cells ◽  
L Cell ◽  
Dpp Iv ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted into the circulation by the intestinal L cell. The dipeptidylpeptidase-IV (DPP-IV) inhibitor, sitagliptin, prevents GLP-1 degradation and is used in the clinic to treat patients with type 2 diabetes mellitus, leading to improved glycated hemoglobin levels. When the effect of sitagliptin on GLP-1 levels was examined in neonatal streptozotocin rats, a model of type 2 diabetes mellitus, a 4.9 ± 0.9-fold increase in basal and 3.6 ± 0.4-fold increase in oral glucose-stimulated plasma levels of active GLP-1 was observed (P < 0.001), in association with a 1.5 ± 0.1-fold increase in the total number of intestinal L cells (P < 0.01). The direct effects of sitagliptin on GLP-1 secretion and L cell signaling were therefore examined in murine GLUTag (mGLUTag) and human hNCI-H716 intestinal L cells in vitro. Sitagliptin (0.1–2 μm) increased total GLP-1 secretion by mGLUTag and hNCI-H716 cells (P < 0.01–0.001). However, MK0626 (1–50 μm), a structurally unrelated inhibitor of DPP-IV, did not affect GLP-1 secretion in either model. Treatment of mGLUTag cells with the GLP-1 receptor agonist, exendin-4, did not modulate GLP-1 release, indicating the absence of feedback effects of GLP-1 on the L cell. Sitagliptin increased cAMP levels (P < 0.01) and ERK1/2 phosphorylation (P < 0.05) in both mGLUTag and hNCI-H716 cells but did not alter either intracellular calcium or phospho-Akt levels. Pretreatment of mGLUTag cells with protein kinase A (H89 and protein kinase inhibitor) or MAPK kinase-ERK1/2 (PD98059 and U0126) inhibitors prevented sitagliptin-induced GLP-1 secretion (P < 0.05–0.01). These studies demonstrate, for the first time, that sitagliptin exerts direct, DPP-IV-independent effects on intestinal L cells, activating cAMP and ERK1/2 signaling and stimulating total GLP-1 secretion.

scholarly journals Essential Role for Protein Kinase Cζ in Oleic Acid-Induced Glucagon-Like Peptide-1 Secretion in Vivo in the Rat

Endocrinology ◽  
2011 ◽  
Vol 152 (4) ◽  
pp. 1244-1252 ◽  
Author(s):  
Roman Iakoubov ◽  
Ausma Ahmed ◽  
Lina M. Lauffer ◽  
Richard P. Bazinet ◽  
Patricia L. Brubaker
Keyword(s):  
Oleic Acid ◽  
Protein Kinase ◽  
Fatty Acid Transport ◽  
Physiological Relevance ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Fatty Acid Transport Proteins ◽  
Interfering Rna

Abstract Luminal monounsaturated long-chain fatty acids [e.g. oleic acid (OA)] increase secretion of the incretin, glucagon-like peptide-1 (GLP-1) from the ileocolonic L cell. However, it is not known whether OA ingestion causes a sufficient increase in distal luminal concentrations to directly enhance GLP-1 secretion. Furthermore, we have demonstrated that protein kinase Cζ (PKCζ) is required for OA-induced GLP-1 secretion in vitro; however, the physiological relevance of this finding remains unknown. Therefore, we have determined luminal OA concentrations in OA-fed rats and examined the effects of direct OA stimulation on GLP-1 secretion using a novel model of intestinal-specific PKCζ knockdown. Murine GLUTag L cells express numerous fatty acid transport proteins and take up OA in a saturable manner. Oral administration of OA increased the ileal chyme content of OA by 140-fold over 60–120 min (P < 0.05–0.01), peaking at 105 ± 50 μmol/g. To evaluate the direct effects of OA on GLP-1 secretion, 125 mm OA was rectally infused into the colon and terminal ileum of rats. Plasma bioactive GLP-1 increased from 20 ± 6 to 102 ± 21 pg/ml at 60 min (P < 0.01). However, pretreatment with ileocolonic adenoviral PKCζ small interfering RNA resulted in a 68 ± 8% reduction in the GLP-1 response to rectal OA (P < 0.001). The results of these studies indicate that OA levels in the rat terminal gut after oral ingestion are sufficient to induce GLP-1 secretion and that PKCζ is necessary for the effects of OA on GLP-1 secretion in vivo. PKCζ may therefore serve as a novel therapeutic target to enhance GLP-1 levels in patients with type 2 diabetes.

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

2012 ◽  
Vol 303 (7) ◽  
pp. E899-E907 ◽  
Author(s):  
M. A. Poreba ◽  
C. X. Dong ◽  
S. K. Li ◽  
A. Stahl ◽  
J. H. Miner ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Fatty Acid ◽  
Cell Model ◽  
Fatty Acid Transport ◽  
Acid Transport ◽  
L Cell ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

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, [3H]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 3H[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 [3H]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.

scholarly journals High-Fat Diet and Palmitate Alter the Rhythmic Secretion of Glucagon-Like Peptide-1 by the Rodent L-cell

Endocrinology ◽  
2015 ◽  
Vol 157 (2) ◽  
pp. 586-599 ◽  
Author(s):  
Manuel Gil-Lozano ◽  
W. Kelly Wu ◽  
Alexandre Martchenko ◽  
Patricia L. Brubaker
Keyword(s):  
Molecular Clock ◽  
Rhythmic Activity ◽  
Induced Responses ◽  
High Fat ◽  
L Cells ◽  
L Cell ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
The Impact ◽  
High Sucrose

Abstract Secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1), by the intestinal L-cell is rhythmically regulated by an independent molecular clock. However, the impact of factors known to affect the activity of similar cell-autonomous clocks, such as circulating glucocorticoids and high-fat feeding, on GLP-1 secretory patterns remains to be elucidated. Herein the role of the endogenous corticosterone rhythm on the pattern of GLP-1 and insulin nutrient-induced responses was examined in corticosterone pellet-implanted rats. Moreover, the impact of nutrient excess on the time-dependent secretion of both hormones was assessed in rats fed a high-fat, high-sucrose diet. Finally, the effects of the saturated fatty acid, palmitate, on the L-cell molecular clock and GLP-1 secretion were investigated in vitro using murine GLUTag L-cells. Diurnal variations in GLP-1 and insulin nutrient-induced responses were maintained in animals lacking an endogenous corticosterone rhythm, suggesting that glucocorticoids are not the predominant entrainment factor for L-cell rhythmic activity. In addition to hyperglycemia, hyperinsulinemia, insulin resistance, and disorganization of feeding behavior, high-fat high-sucrose-fed rats showed a total abrogation of the diurnal variation in GLP-1 and insulin nutrient-induced responses, with comparable levels of both hormones at the normal peak (5:00 pm) and trough (5:00 am) of their daily pattern. Finally, palmitate incubation induced profound derangements in the rhythmic expression of circadian oscillators in GLUTag L-cells and severely impaired the secretory activity of these cells. Collectively our findings demonstrate that obesogenic diets disrupt the rhythmic activity of the L-cell, partially through a direct effect of specific nutritional components.

scholarly journals Essential Role of Syntaxin-Binding Protein-1 in the Regulation of Glucagon-Like Peptide-1 Secretion

Endocrinology ◽  
2020 ◽  
Vol 161 (5) ◽  
Author(s):  
Jhenielle R Campbell ◽  
Alexandre Martchenko ◽  
Maegan E Sweeney ◽  
Michael F Maalouf ◽  
Arianna Psichas ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Binding Protein ◽  
Peak Time ◽  
L Cells ◽  
L Cell ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Time Point

Abstract Circadian secretion of the incretin, glucagon-like peptide-1 (GLP-1), correlates with expression of the core clock gene, Bmal1, in the intestinal L-cell. Several SNARE proteins known to be circadian in pancreatic α- and β-cells are also necessary for GLP-1 secretion. However, the role of the accessory SNARE, Syntaxin binding protein-1 (Stxbp1; also known as Munc18-1) in the L-cell is unknown. The aim of this study was to determine whether Stxbp1 is under circadian regulation in the L-cell and its role in the control of GLP-1 secretion. Stxbp1 was highly-enriched in L-cells, and STXBP1 was expressed in a subpopulation of L-cells in mouse and human intestinal sections. Stxbp1 transcripts and protein displayed circadian patterns in mGLUTag L-cells line, while chromatin-immunoprecipitation revealed increased interaction between BMAL1 and Stxbp1 at the peak time-point of the circadian pattern. STXBP1 recruitment to the cytosol and plasma membrane within 30 minutes of L-cell stimulation was also observed at this time-point. Loss of Stxbp1 in vitro and in vivo led to reduced stimulated GLP-1 secretion at the peak time-point of circadian release, and impaired GLP-1 secretion ex vivo. In conclusion, Stxbp1 is a circadian regulated exocytotic protein in the intestinal L-cell that is an essential regulatory component of GLP-1 secretion.

scholarly journals Bile acids drive colonic secretion of glucagon-like-peptide 1 and peptide-YY in rodents

2019 ◽  
Vol 316 (5) ◽  
pp. G574-G584 ◽  
Author(s):  
Charlotte Bayer Christiansen ◽  
Samuel Addison Jack Trammell ◽  
Nicolai Jacob Wewer Albrechtsen ◽  
Kristina Schoonjans ◽  
Reidar Albrechtsen ◽  
...  
Keyword(s):  
Bile Acids ◽  
G Protein ◽  
Peptide Yy ◽  
Whole Body ◽  
Rat Colon ◽  
G Protein Coupled Receptor ◽  
L Cells ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
G Protein Coupled

A large number of glucagon-like-peptide-1 (GLP-1)- and peptide-YY (PYY)-producing L cells are located in the colon, but little is known about their contribution to whole body metabolism. Since bile acids (BAs) increase GLP-1 and PYY release, and since BAs spill over from the ileum to the colon, we decided to investigate the ability of BAs to stimulate colonic GLP-1 and PYY secretion. Using isolated perfused rat/mouse colon as well as stimulation of the rat colon in vivo, we demonstrate that BAs significantly enhance secretion of GLP-1 and PYY from the colon with average increases of 3.5- and 2.9-fold, respectively. Furthermore, we find that responses depend on BA absorption followed by basolateral activation of the BA-receptor Takeda-G protein-coupled-receptor 5. Surprisingly, the apical sodium-dependent BA transporter, which serves to absorb conjugated BAs, was not required for colonic conjugated BA absorption or conjugated BA-induced peptide secretion. In conclusion, we demonstrate that BAs represent a major physiological stimulus for colonic L-cell secretion.NEW & NOTEWORTHY By the use of isolated perfused rodent colon preparations we show that bile acids are potent and direct promoters of colonic glucagon-like-peptide 1 and peptide-YY secretion. The study provides convincing evidence that basolateral Takeda-G protein-coupled-receptor 5 activation is mediating the effects of bile acids in the colon and thus add to the existing literature described for L cells in the ileum.

scholarly journals Nateglinide Stimulates Glucagon-Like Peptide-1 Release by Human Intestinal L Cells via a KATP Channel-Independent Mechanism

2011 ◽  
Vol 34 (5) ◽  
pp. 671-676 ◽  
Author(s):  
Yoshiro Kitahara ◽  
Kyoko Miura ◽  
Reiko Yasuda ◽  
Haruka Kawanabe ◽  
Shimpei Ogawa ◽  
...  
Keyword(s):  
Katp Channel ◽  
L Cells ◽  
Independent Mechanism ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1
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