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 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.

Let-7e-5p Regulates GLP-1 Content and Basal Release From Enteroendocrine L Cells From DIO Male Mice

Endocrinology ◽  
2019 ◽  
Vol 161 (2) ◽  
Author(s):  
Sandra Handgraaf ◽  
Rodolphe Dusaulcy ◽  
Florian Visentin ◽  
Jacques Philippe ◽  
Yvan Gosmain
Keyword(s):  
Compensatory Mechanism ◽  
L Cells ◽  
Low Fat Diet ◽  
Obesity And Diabetes ◽  
Basal Release ◽  
Glucagon Like Peptide 1 ◽  
Cell Transcriptome ◽  
Microarray Analyses

Abstract Characterization of enteroendocrine L cells in diabetes is critical for better understanding of the role of glucagon-like peptide-1 (GLP-1) in physiology and diabetes. We studied L-cell transcriptome changes including microRNA (miRNA) dysregulation in obesity and diabetes. We evaluated the regulation of miRNAs through microarray analyses on sorted enteroendocrine L cells from control and obese glucose-intolerant (I-HFD) and hyperglycemic (H-HFD) mice after 16 weeks of respectively low-fat diet (LFD) or high-fat diet (HFD) feeding. The identified altered miRNAs were studied in vitro using the mouse GLUTag cell line to investigate their regulation and potential biological functions. We identified that let-7e-5p, miR-126a-3p, and miR-125a-5p were differentially regulated in L cells of obese HFD mice compared with control LFD mice. While downregulation of let-7e-5p expression was observed in both I-HFD and H-HFD mice, levels of miR-126a-3p increased and of miR-125a-5p decreased significantly only in I-HFD mice compared with controls. Using miRNA inhibitors and mimics we observed that modulation of let-7e-5p expression affected specifically GLP-1 cellular content and basal release, whereas Gcg gene expression and acute GLP-1 secretion and cell proliferation were not affected. In addition, palmitate treatment resulted in a decrease of let-7e-5p expression along with an increase in GLP-1 content and release, suggesting that palmitate acts on GLP-1 through let-7e-5p. By contrast, modulation of miR-125a-5p and miR-126a-3p in the same conditions did not affect content or secretion of GLP-1. We conclude that decrease of let-7e-5p expression in response to palmitate may constitute a compensatory mechanism contributing to maintaining constant glycemia in obese mice.

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 &lt; 0.001), and this was abrogated by the PKCζ inhibitor ZI (P &lt; 0.05) and PKCζ small interfering RNA transfection (P &lt; 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 &lt; 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.

Role of vesicle-associated membrane protein 2 in exocytosis of glucagon-like peptide-1 from the murine intestinal L cell

Diabetologia ◽  
2013 ◽  
Vol 57 (4) ◽  
pp. 809-818 ◽  
Author(s):  
Samantha K. Li ◽  
Dan Zhu ◽  
Herbert Y. Gaisano ◽  
Patricia L. Brubaker
Keyword(s):  
Membrane Protein ◽  
L Cell ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

scholarly journals Insulin Regulates Glucagon-Like Peptide-1 Secretion from the Enteroendocrine L Cell

Endocrinology ◽  
2009 ◽  
Vol 150 (2) ◽  
pp. 580-591 ◽  
Author(s):  
Gareth E. Lim ◽  
Guan J. Huang ◽  
Nina Flora ◽  
Derek LeRoith ◽  
Christopher J. Rhodes ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Oral Glucose ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Resistant ◽  
L Cell ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Phosphatidylinositol 3

Insulin resistance and type 2 diabetes mellitus are associated with impaired postprandial secretion of glucagon-like peptide-1 (GLP-1), a potent insulinotropic hormone. The direct effects of insulin and insulin resistance on the L cell are unknown. We therefore hypothesized that the L cell is responsive to insulin and that insulin resistance impairs GLP-1 secretion. The effects of insulin and insulin resistance were examined in well-characterized L cell models: murine GLUTag, human NCI-H716, and fetal rat intestinal cells. MKR mice, a model of chronic hyperinsulinemia, were used to assess the function of the L cell in vivo. In all cells, insulin activated the phosphatidylinositol 3 kinase-Akt and MAPK kinase (MEK)-ERK1/2 pathways and stimulated GLP-1 secretion by up to 275 ± 58%. Insulin resistance was induced by 24 h pretreatment with 10−7m insulin, causing a marked reduction in activation of Akt and ERK1/2. Furthermore, both insulin-induced GLP-1 release and secretion in response to glucose-dependent insulinotropic peptide and phorbol-12-myristate-13-acetate were significantly attenuated. Whereas inhibition of phosphatidylinositol 3 kinase with LY294002 potentiated insulin-induced GLP-1 release, secretion was abrogated by inhibiting the MEK-ERK1/2 pathway with PD98059 or by overexpression of a kinase-dead MEK1-ERK2 fusion protein. Compared with controls, MKR mice were insulin resistant and displayed significantly higher fasting plasma insulin levels. Furthermore, they had significantly higher basal GLP-1 levels but displayed impaired GLP-1 secretion after an oral glucose challenge. These findings indicate that the intestinal L cell is responsive to insulin and that insulin resistance in vitro and in vivo is associated with impaired GLP-1 secretion. Insulin is a novel secretagogue of the incretin hormone, glucagon-like peptide-1 (GLP-1), and L cell insulin resistance impairs heterologous secretagogue-induced GLP-1 secretion in vitro and in vivo.

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 &lt; 0.001), in association with a 1.5 ± 0.1-fold increase in the total number of intestinal L cells (P &lt; 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 &lt; 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 &lt; 0.01) and ERK1/2 phosphorylation (P &lt; 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 &lt; 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.

Anti-inflammatory role of DPP-4 inhibitors in a nondiabetic model of glomerular injury

2015 ◽  
Vol 308 (8) ◽  
pp. F878-F887 ◽  
Author(s):  
Yoshiki Higashijima ◽  
Tetsuhiro Tanaka ◽  
Junna Yamaguchi ◽  
Shinji Tanaka ◽  
Masaomi Nangaku
Keyword(s):  
Kidney Disease ◽  
Ex Vivo ◽  
Experimental Studies ◽  
Peritoneal Macrophages ◽  
Macrophage Infiltration ◽  
Glomerular Injury ◽  
Glucose Levels ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Dipeptidyl peptidase (DPP)-4 is an enzyme that cleaves and inactivates incretin hormones capable of stimulating insulin secretion from pancreatic β-cells. DPP-4 inhibitors are now widely used for the treatment of type 2 diabetes. Experimental studies have suggested a renoprotective role of DPP-4 inhibitors in various models of diabetic kidney disease, which may be independent of lowering blood glucose levels. In the present study, we examined the effect of DPP-4 inhibitors in the rat Thy-1 glomerulonephritis model, a nondiabetic glomerular injury model. Rats were injected with OX-7 (1.2 mg/kg iv) and treated with the DPP-4 inhibitor alogliptin (20 mg·kg−1·day−1) or vehicle for 7 days orally by gavage. Alogliptin significantly reduced the number of CD68-positive inflammatory macrophages in the kidney, which was associated with a nonsignificant tendency to ameliorate glomerular injury and reduce proteinuria. Another DPP-4 inhibitor, anagliptin (300 mg·kg−1·day−1 mixed with food) and a glucagon-like peptide-1 receptor agonist, exendin-4 (10 mg/kg sc), similarly reduced CD68-positive macrophage infiltration to the kidney. Furthermore, ex vivo transmigration assays using peritoneal macrophages revealed that exendin-4, but not alogliptin, dose dependently reduced monocyte chemotactic protein-1-stimulated macrophage infiltration. These data suggest that DPP-4 inhibitors reduced macrophage infiltration directly via glucagon-like peptide-1-dependent signaling in the rat Thy-1 nephritis model and indicate that the control of inflammation by DPP-4 inhibitors is useful for the treatment of nondiabetic kidney disease models.

scholarly journals The Role of the Bacterial Muramyl Dipeptide in the Regulation of GLP-1 and Glycemia

2020 ◽  
Vol 21 (15) ◽  
pp. 5252
Author(s):  
Laura Williams ◽  
Amal Alshehri ◽  
Bianca Robichaud ◽  
Alison Cudmore ◽  
Jeffrey Gagnon
Keyword(s):  
Glucose Tolerance ◽  
Muramyl Dipeptide ◽  
Gut Hormones ◽  
Oral Glucose ◽  
L Cells ◽  
Nucleotide Oligomerization ◽  
Mouse Intestine ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

The host’s intestinal microbiota contributes to endocrine and metabolic responses, but a dysbiosis in this environment can lead to obesity and insulin resistance. Recent work has demonstrated a role for microbial metabolites in the regulation of gut hormones, including the metabolic hormone, glucagon-like peptide-1 (GLP-1). Muramyl dipeptide (MDP) is a bacterial cell wall component which has been shown to improve insulin sensitivity and glucose tolerance in diet-induced obese mice by acting through the nucleotide oligomerization domain 2 (NOD2) receptor. The purpose of this study was to understand the effects of MDP on GLP-1 secretion and glucose regulation. We hypothesized that MDP enhances glucose tolerance by inducing intestinal GLP-1 secretion through NOD2 activation. First, we observed a significant increase in GLP-1 secretion when murine and human L-cells were treated with a fatty acid MDP derivative (L18-MDP). Importantly, we demonstrated the expression of the NOD2 receptor in mouse intestine and in L-cells. In mice, two intraperitoneal injections of MDP (5 mg/kg body weight) caused a significant increase in fasting total GLP-1 in chow-fed mice, however this did not lead to an improvement in oral glucose tolerance. When mice were exposed to a high-fat diet, they eventually lost this MDP-induced GLP-1 release. Finally, we demonstrated in L-cells that hyperglycemic conditions reduce the mRNA expression of NOD2 and GLP-1. Together these findings suggest MDP may play a role in enhancing GLP-1 during normal glycemic conditions but loses its ability to do so in hyperglycemia.

scholarly journals MicroRNA-194: a novel regulator of glucagon-like peptide-1 synthesis in intestinal L cells

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jiao Wang ◽  
Di Zhao ◽  
Cheng-Zhi Ding ◽  
Feng Guo ◽  
Li-Na Wu ◽  
...  
Keyword(s):  
Mrna Level ◽  
Beta Catenin ◽  
Mrna Levels ◽  
Obese Mice ◽  
L Cells ◽  
The Status ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Induced Apoptosis

AbstractIn the status of obesity, the glucagon-like peptide-1 (GLP-1) level usually declines and results in metabolic syndrome. This study aimed to investigate the intracellular mechanism of GLP-1 synthesis in L cells from the perspective of microRNA (miRNA). In the present study, we found that GLP-1 level was down-regulated in the plasma and ileum tissues of obese mice, while the ileac miR-194 expression was up-regulated. In vitro experiments indicated that miR-194 overexpression down-regulated GLP-1 level, mRNA levels of proglucagon gene (gcg) and prohormone convertase 1/3 gene (pcsk1), and the nuclear protein level of beta-catenin (β-catenin). Further investigation confirmed that β-catenin could promote gcg transcription through binding to transcription factor 7-like 2 (TCF7L2). miR-194 suppressed gcg mRNA level via negatively regulating TCF7L2 expression. What’s more, forkhead box a1 (Foxa1) could bind to the promoter of pcsk1 and enhanced its transcription. miR-194 suppressed pcsk1 transcription through targeting Foxa1. Besides, the interference of miR-194 reduced palmitate (PA)-induced cell apoptosis and the anti-apoptosis effect of miR-194 inhibitor was abolished by TCF7L2 knockdown. Finally, in HFD-induced obese mice, the silence of miR-194 significantly elevated GLP-1 level and improved the metabolic symptoms caused by GLP-1 deficiency. To sum up, our study found that miR-194 suppressed GLP-1 synthesis in L cells via inhibiting TCF7L2-mediated gcg transcription and Foxa1-mediated pcsk1 transcription. Meanwhile, miR-194 took part in the PA-induced apoptosis of L cells.

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.

Sign in / Sign up

Export Citation Format

Share Document