1
|
Srivastava R, Horwitz M, Hershko-Moshe A, Bronstein S, Ben-Dov IZ, Melloul D. Posttranscriptional regulation of the prostaglandin E receptor spliced-isoform EP3-γ and its implication in pancreatic β-cell failure. FASEB J 2023; 37:e22958. [PMID: 37171267 DOI: 10.1096/fj.202201984r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 04/09/2023] [Accepted: 04/25/2023] [Indexed: 05/13/2023]
Abstract
In Type 2 diabetes (T2D), elevated lipid levels have been suggested to contribute to insulin resistance and β-cell dysfunction. We previously reported that the expression of the PGE2 receptor EP3 is elevated in islets of T2D individuals and is preferentially stimulated by palmitate, leading to β-cell failure. The mouse EP3 receptor generates three isoforms by alternative splicing which differ in their C-terminal domain and are referred to as mEP3α, mEP3β, and mEP3γ. We bring evidence that the expression of the mEP3γ isoform is elevated in islets of diabetic db/db mice and is selectively upregulated by palmitate. Specific knockdown of the mEP3γ isoform restores the expression of β-cell-specific genes and rescues MIN6 cells from palmitate-induced dysfunction and apoptosis. This study indicates that palmitate stimulates the expression of the mEP3γ by a posttranscriptional mechanism, compared to the other spliced isoforms, and that the de novo synthesized ceramide plays an important role in FFA-induced mEP3γ expression in β-cells. Moreover, induced levels of mEP3γ mRNA by palmitate or ceramide depend on p38 MAPK activation. Our findings suggest that mEP3γ gene expression is regulated at the posttranscriptional level and defines the EP3 signaling axis as an important pathway mediating β-cell-impaired function and demise.
Collapse
Affiliation(s)
- Rohit Srivastava
- Department of Endocrinology, Hadassah University Hospital, Jerusalem, Israel
| | - Margalit Horwitz
- Department of Endocrinology, Hadassah University Hospital, Jerusalem, Israel
| | - Anat Hershko-Moshe
- Department of Internal Medicine, Hadassah University Hospital, Jerusalem, Israel
| | - Shirly Bronstein
- Department of Endocrinology, Hadassah University Hospital, Jerusalem, Israel
| | - Iddo Z Ben-Dov
- Laboratory of Medical Transcriptomics, Nephrology Services, Hadassah University Hospital, Jerusalem, Israel
| | - Danielle Melloul
- Department of Endocrinology, Hadassah University Hospital, Jerusalem, Israel
| |
Collapse
|
2
|
Šrámek J, Němcová-Fürstová V, Kovář J. Molecular Mechanisms of Apoptosis Induction and Its Regulation by Fatty Acids in Pancreatic β-Cells. Int J Mol Sci 2021; 22:4285. [PMID: 33924206 PMCID: PMC8074590 DOI: 10.3390/ijms22084285] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/09/2021] [Accepted: 04/16/2021] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cell failure and death contribute significantly to the pathogenesis of type 2 diabetes. One of the main factors responsible for β-cell dysfunction and subsequent cell death is chronic exposure to increased concentrations of FAs (fatty acids). The effect of FAs seems to depend particularly on the degree of their saturation. Saturated FAs induce apoptosis in pancreatic β-cells, whereas unsaturated FAs are well tolerated and are even capable of inhibiting the pro-apoptotic effect of saturated FAs. Molecular mechanisms of apoptosis induction by saturated FAs in β-cells are not completely elucidated. Saturated FAs induce ER stress, which in turn leads to activation of all ER stress pathways. When ER stress is severe or prolonged, apoptosis is induced. The main mediator seems to be the CHOP transcription factor. Via regulation of expression/activity of pro- and anti-apoptotic Bcl-2 family members, and potentially also through the increase in ROS production, CHOP switches on the mitochondrial pathway of apoptosis induction. ER stress signalling also possibly leads to autophagy signalling, which may activate caspase-8. Saturated FAs activate or inhibit various signalling pathways, i.e., p38 MAPK signalling, ERK signalling, ceramide signalling, Akt signalling and PKCδ signalling. This may lead to the activation of the mitochondrial pathway of apoptosis, as well. Particularly, the inhibition of the pro-survival Akt signalling seems to play an important role. This inhibition may be mediated by multiple pathways (e.g., ER stress signalling, PKCδ and ceramide) and could also consequence in autophagy signalling. Experimental evidence indicates the involvement of certain miRNAs in mechanisms of FA-induced β-cell apoptosis, as well. In the rather rare situations when unsaturated FAs are also shown to be pro-apoptotic, the mechanisms mediating this effect in β-cells seem to be the same as for saturated FAs. To conclude, FA-induced apoptosis rather appears to be preceded by complex cross talks of multiple signalling pathways. Some of these pathways may be regulated by decreased membrane fluidity due to saturated FA incorporation. Few data are available concerning molecular mechanisms mediating the protective effect of unsaturated FAs on the effect of saturated FAs. It seems that the main possible mechanism represents a rather inhibitory intervention into saturated FA-induced pro-apoptotic signalling than activation of some pro-survival signalling pathway(s) or metabolic interference in β-cells. This inhibitory intervention may be due to an increase of membrane fluidity.
Collapse
Affiliation(s)
- Jan Šrámek
- Department of Biochemistry, Cell and Molecular Biology & Center for Research of Diabetes, Metabolism and Nutrition, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Prague, Czech Republic;
| | - Vlasta Němcová-Fürstová
- Department of Biochemistry, Cell and Molecular Biology & Center for Research of Diabetes, Metabolism and Nutrition, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Prague, Czech Republic;
| | | |
Collapse
|
3
|
Benito-Vicente A, Jebari-Benslaiman S, Galicia-Garcia U, Larrea-Sebal A, Uribe KB, Martin C. Molecular mechanisms of lipotoxicity-induced pancreatic β-cell dysfunction. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 359:357-402. [PMID: 33832653 DOI: 10.1016/bs.ircmb.2021.02.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type 2 diabetes (T2D), a heterogeneous disorder derived from metabolic dysfunctions, leads to a glucose overflow in the circulation due to both defective insulin secretion and peripheral insulin resistance. One of the critical risk factor for T2D is obesity, which represents a global epidemic that has nearly tripled since 1975. Obesity is characterized by chronically elevated free fatty acid (FFA) levels, which cause deleterious effects on glucose homeostasis referred to as lipotoxicity. Here, we review the physiological FFA roles onto glucose-stimulated insulin secretion (GSIS) and the pathological ones affecting many steps of the mechanisms and modulation of GSIS. We also describe in vitro and in vivo experimental evidences addressing lipotoxicity in β-cells and the role of saturation and chain length of FFA on the potency of GSIS stimulation. The molecular mechanisms underpinning lipotoxic-β-cell dysfunction are also reviewed. Among them, endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, inflammation, impaired autophagy and β-cell dedifferentiation. Finally therapeutic strategies for the β-cells dysfunctions such as the use of metformin, glucagon-like peptide 1, thiazolidinediones, anti-inflammatory drugs, chemical chaperones and weight are discussed.
Collapse
Affiliation(s)
- Asier Benito-Vicente
- Department of Molecular Biophysics, Biofisika Institute (University of Basque Country and Consejo Superior de Investigaciones Científicas (UPV/EHU, CSIC)), Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Shifa Jebari-Benslaiman
- Department of Molecular Biophysics, Biofisika Institute (University of Basque Country and Consejo Superior de Investigaciones Científicas (UPV/EHU, CSIC)), Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Unai Galicia-Garcia
- Department of Molecular Biophysics, Biofisika Institute (University of Basque Country and Consejo Superior de Investigaciones Científicas (UPV/EHU, CSIC)), Leioa, Spain; Department of Molecular Biophysics, Fundación Biofísica Bizkaia, Leioa, Spain
| | - Asier Larrea-Sebal
- Department of Molecular Biophysics, Biofisika Institute (University of Basque Country and Consejo Superior de Investigaciones Científicas (UPV/EHU, CSIC)), Leioa, Spain; Department of Molecular Biophysics, Fundación Biofísica Bizkaia, Leioa, Spain
| | - Kepa B Uribe
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Donostia San Sebastián, Spain
| | - Cesar Martin
- Department of Molecular Biophysics, Biofisika Institute (University of Basque Country and Consejo Superior de Investigaciones Científicas (UPV/EHU, CSIC)), Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Leioa, Spain.
| |
Collapse
|
4
|
Tran A, Loganathan N, McIlwraith EK, Belsham DD. Palmitate and Nitric Oxide Regulate the Expression of Spexin and Galanin Receptors 2 and 3 in Hypothalamic Neurons. Neuroscience 2020; 447:41-52. [DOI: 10.1016/j.neuroscience.2019.10.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/14/2019] [Accepted: 10/16/2019] [Indexed: 12/13/2022]
|
5
|
Loss of Caveolin-1 Is Associated with a Decrease in Beta Cell Death in Mice on a High Fat Diet. Int J Mol Sci 2020; 21:ijms21155225. [PMID: 32718046 PMCID: PMC7432291 DOI: 10.3390/ijms21155225] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 07/12/2020] [Accepted: 07/14/2020] [Indexed: 12/18/2022] Open
Abstract
Elevated free fatty acids (FFAs) impair beta cell function and reduce beta cell mass as a consequence of the lipotoxicity that occurs in type 2 diabetes (T2D). We previously reported that the membrane protein caveolin-1 (CAV1) sensitizes to palmitate-induced apoptosis in the beta pancreatic cell line MIN6. Thus, our hypothesis was that CAV1 knock-out (CAV1 KO) mice subjected to a high fat diet (HFD) should suffer less damage to beta cells than wild type (WT) mice. Here, we evaluated the in vivo response of beta cells in the pancreatic islets of 8-week-old C57Bl/6J CAV1 KO mice subjected to a control diet (CD, 14% kcal fat) or a HFD (60% kcal fat) for 12 weeks. We observed that CAV1 KO mice were resistant to weight gain when on HFD, although they had high serum cholesterol and FFA levels, impaired glucose tolerance and were insulin resistant. Some of these alterations were also observed in mice on CD. Interestingly, KO mice fed with HFD showed an adaptive response of the pancreatic beta cells and exhibited a significant decrease in beta cell apoptosis in their islets compared to WT mice. These in vivo results suggest that although the CAV1 KO mice are metabolically unhealthy, they adapt better to a HFD than WT mice. To shed light on the possible signaling pathway(s) involved, MIN6 murine beta cells expressing (MIN6 CAV) or not expressing (MIN6 Mock) CAV1 were incubated with the saturated fatty acid palmitate in the presence of mitogen-activated protein kinase inhibitors. Western blot analysis revealed that CAV1 enhanced palmitate-induced JNK, p38 and ERK phosphorylation in MIN6 CAV1 cells. Moreover, all the MAPK inhibitors partially restored MIN6 viability, but the effect was most notable with the ERK inhibitor. In conclusion, our results suggest that CAV1 KO mice adapted better to a HFD despite their altered metabolic state and that this may at least in part be due to reduced beta cell damage. Moreover, they indicate that the ability of CAV1 to increase sensitivity to FFAs may be mediated by MAPK and particularly ERK activation.
Collapse
|
6
|
Role of c-Jun N-terminal Kinase (JNK) in Obesity and Type 2 Diabetes. Cells 2020; 9:cells9030706. [PMID: 32183037 PMCID: PMC7140703 DOI: 10.3390/cells9030706] [Citation(s) in RCA: 89] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/16/2020] [Accepted: 03/11/2020] [Indexed: 12/13/2022] Open
Abstract
Obesity has been described as a global epidemic and is a low-grade chronic inflammatory disease that arises as a consequence of energy imbalance. Obesity increases the risk of type 2 diabetes (T2D), by mechanisms that are not entirely clarified. Elevated circulating pro-inflammatory cytokines and free fatty acids (FFA) during obesity cause insulin resistance and ß-cell dysfunction, the two main features of T2D, which are both aggravated with the progressive development of hyperglycemia. The inflammatory kinase c-jun N-terminal kinase (JNK) responds to various cellular stress signals activated by cytokines, free fatty acids and hyperglycemia, and is a key mediator in the transition between obesity and T2D. Specifically, JNK mediates both insulin resistance and ß-cell dysfunction, and is therefore a potential target for T2D therapy.
Collapse
|
7
|
Lytrivi M, Castell AL, Poitout V, Cnop M. Recent Insights Into Mechanisms of β-Cell Lipo- and Glucolipotoxicity in Type 2 Diabetes. J Mol Biol 2019; 432:1514-1534. [PMID: 31628942 DOI: 10.1016/j.jmb.2019.09.016] [Citation(s) in RCA: 192] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 09/15/2019] [Accepted: 09/16/2019] [Indexed: 12/24/2022]
Abstract
The deleterious effects of chronically elevated free fatty acid (FFA) levels on glucose homeostasis are referred to as lipotoxicity, and the concurrent exposure to high glucose may cause synergistic glucolipotoxicity. Lipo- and glucolipotoxicity have been studied for over 25 years. Here, we review the current evidence supporting the role of pancreatic β-cell lipo- and glucolipotoxicity in type 2 diabetes (T2D), including lipid-based interventions in humans, prospective epidemiological studies, and human genetic findings. In addition to total FFA quantity, the quality of FFAs (saturation and chain length) is a key determinant of lipotoxicity. We discuss in vitro and in vivo experimental models to investigate lipo- and glucolipotoxicity in β-cells and describe experimental pitfalls. Lipo- and glucolipotoxicity adversely affect many steps of the insulin production and secretion process. The molecular mechanisms underpinning lipo- and glucolipotoxic β-cell dysfunction and death comprise endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, impaired autophagy, and inflammation. Crosstalk between these stress pathways exists at multiple levels and may aggravate β-cell lipo- and glucolipotoxicity. Lipo- and glucolipotoxicity are therapeutic targets as several drugs impact the underlying stress responses in β-cells, potentially contributing to their glucose-lowering effects in T2D.
Collapse
Affiliation(s)
- Maria Lytrivi
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium; Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Anne-Laure Castell
- CRCHUM, Montréal, QC, Canada; Department of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Vincent Poitout
- CRCHUM, Montréal, QC, Canada; Department of Medicine, Université de Montréal, Montréal, QC, Canada.
| | - Miriam Cnop
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium; Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium.
| |
Collapse
|
8
|
Li J, Xu S, Liu Y, Yan Z, Zhang F, Lv Q, Tong N. Activated PPARβ/δ Protects Pancreatic β Cells in Type 2 Diabetic Goto-Kakizaki Rats from Lipoapoptosis via GPR40. Lipids 2019; 54:603-616. [PMID: 31364177 DOI: 10.1002/lipd.12182] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 06/17/2019] [Accepted: 07/08/2019] [Indexed: 02/05/2023]
Abstract
GW501516-activated peroxisome proliferator-activated receptor (PPAR) β/δ and G-protein-coupled receptor (GPR) 40 were shown to protect pancreatic β cells against lipoapoptosis. Therefore, this study aimed to investigate whether activated PPARβ/δ could protect type 2 diabetic rats from lipoapoptosis through regulation of GPR40 and to compare the protective effects of activated PPARβ/δ and PPARγ. We made an animal model of type 2 diabetic lipoapoptosis by feeding spontaneously type 2 diabetic Goto-Kakizaki (GK) rats with a high-fat diet (HFD) to evaluate the effects of PPARβ/δ on islet β cell apoptosis. And, treated INS-1 cells with 0.5 mM palmitate (PAM) in the absence/presence of GW501516 (a specific agonist of PPAR β/δ) and with/without transfection of GPR40 siRNA to explore the underlying molecular mechanism. HFD aggravated GK rats' poorer INSR30, lower mass, greater apoptosis of β cells, lower mass, and lower expression of GPR40, which were similarly improved by GW501516 at 3 or 6 mg/kg day and pioglitazone. Compared with pioglitazone, GW501516 caused more weight loss and had no effect on insulin resistance. GW501516 protected INS-1 cells from PAM-induced apoptosis by upregulating GPR40 and activating Akt/Bcl-2/caspase-3. Activated extracellular regulated protein kinases (ERK) was relevant to the lipoapoptosis in INS-1 cells, but was not involved in the antilipoapoptotic effect of GW501516. These results showed that the PPARβ/δ agonist GW501516 protected β cells from lipoapoptosis and improved β cell mass by upregulating GPR40 and activating the Akt/Bcl-2/caspase-3 pathway, but not the ERK-signaling pathway.
Collapse
Affiliation(s)
- Juan Li
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Shishi Xu
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Yuqi Liu
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Zhe Yan
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Fang Zhang
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Qingguo Lv
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| | - Nanwei Tong
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, 37 Guoxuexiang, Chengdu, 610041, China
| |
Collapse
|
9
|
Effect of Saturated Stearic Acid on MAP Kinase and ER Stress Signaling Pathways during Apoptosis Induction in Human Pancreatic β-Cells Is Inhibited by Unsaturated Oleic Acid. Int J Mol Sci 2017; 18:ijms18112313. [PMID: 29099080 PMCID: PMC5713282 DOI: 10.3390/ijms18112313] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 12/13/2022] Open
Abstract
It has been shown that saturated fatty acids (FAs) have a detrimental effect on pancreatic β-cells function and survival, leading to apoptosis, whereas unsaturated FAs are well tolerated and are even capable of inhibiting the pro-apoptotic effect of saturated FAs. Molecular mechanisms of apoptosis induction and regulation by FAs in β-cells remain unclear; however, mitogen-activated protein (MAP) kinase and endoplasmic reticulum (ER) stress signaling pathways may be involved. In this study, we tested how unsaturated oleic acid (OA) affects the effect of saturated stearic acid (SA) on the p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) pathways as well as the ER stress signaling pathways during apoptosis induction in the human pancreatic β-cells NES2Y. We demonstrated that OA is able to inhibit all effects of SA. OA alone has only minimal or no effects on tested signaling in NES2Y cells. The point of OA inhibitory intervention in SA-induced apoptotic signaling thus seems to be located upstream of the discussed signaling pathways.
Collapse
|
10
|
Kinase Signaling in Apoptosis Induced by Saturated Fatty Acids in Pancreatic β-Cells. Int J Mol Sci 2016; 17:ijms17091400. [PMID: 27626409 PMCID: PMC5037680 DOI: 10.3390/ijms17091400] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic exposure to increased concentrations of fatty acids, mainly saturated fatty acids. Molecular mechanisms of apoptosis induction by saturated fatty acids in β-cells are not completely clear. It has been proposed that kinase signaling could be involved, particularly, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt kinases and their pathways. In this review, we discuss these kinases and their signaling pathways with respect to their possible role in apoptosis induction by saturated fatty acids in pancreatic β-cells.
Collapse
|
11
|
p38 MAPK Is Activated but Does Not Play a Key Role during Apoptosis Induction by Saturated Fatty Acid in Human Pancreatic β-Cells. Int J Mol Sci 2016; 17:159. [PMID: 26861294 PMCID: PMC4783893 DOI: 10.3390/ijms17020159] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 12/29/2015] [Accepted: 01/22/2016] [Indexed: 12/25/2022] Open
Abstract
Saturated stearic acid (SA) induces apoptosis in the human pancreatic β-cells NES2Y. However, the molecular mechanisms involved are unclear. We showed that apoptosis-inducing concentrations of SA activate the p38 MAPK signaling pathway in these cells. Therefore, we tested the role of p38 MAPK signaling pathway activation in apoptosis induction by SA in NES2Y cells. Crosstalk between p38 MAPK pathway activation and accompanying ERK pathway inhibition after SA application was also tested. The inhibition of p38 MAPK expression by siRNA silencing resulted in a decrease in MAPKAPK-2 activation after SA application, but it had no significant effect on cell viability or the level of phosphorylated ERK pathway members. The inhibition of p38 MAPK activity by the specific inhibitor SB202190 resulted in inhibition of MAPKAPK-2 activation and noticeable activation of ERK pathway members after SA treatment but in no significant effect on cell viability. p38 MAPK overexpression by plasmid transfection produced an increase in MAPKAPK-2 activation after SA exposure but no significant influence on cell viability or ERK pathway activation. The activation of p38 MAPK by the specific activator anisomycin resulted in significant activation of MAPKAPK-2. Concerning the effect on cell viability, application of the activator led to apoptosis induction similar to application of SA (PARP cleavage and caspase-7, -8, and -9 activation) and in inhibition of ERK pathway members. We demonstrated that apoptosis-inducing concentrations of SA activate the p38 MAPK signaling pathway and that this activation could be involved in apoptosis induction by SA in the human pancreatic β-cells NES2Y. However, this involvement does not seem to play a key role. Crosstalk between p38 MAPK pathway activation and ERK pathway inhibition in NES2Y cells seems likely. Thus, the ERK pathway inhibition by p38 MAPK activation does not also seem to be essential for SA-induced apoptosis.
Collapse
|
12
|
Brajkovic S, Ferdaoussi M, Pawlowski V, Ezanno H, Plaisance V, Zmuda E, Hai T, Annicotte JS, Waeber G, Abderrahmani A. Islet Brain 1 Protects Insulin Producing Cells against Lipotoxicity. J Diabetes Res 2016; 2016:9158562. [PMID: 26665154 PMCID: PMC4655268 DOI: 10.1155/2016/9158562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 03/06/2015] [Indexed: 01/09/2023] Open
Abstract
Chronic intake of saturated free fatty acids is associated with diabetes and may contribute to the impairment of functional beta cell mass. Mitogen activated protein kinase 8 interacting protein 1 also called islet brain 1 (IB1) is a candidate gene for diabetes that is required for beta cell survival and glucose-induced insulin secretion (GSIS). In this study we investigated whether IB1 expression is required for preserving beta cell survival and function in response to palmitate. Chronic exposure of MIN6 and isolated rat islets cells to palmitate led to reduction of the IB1 mRNA and protein content. Diminution of IB1 mRNA and protein level relied on the inducible cAMP early repressor activity and proteasome-mediated degradation, respectively. Suppression of IB1 level mimicked the harmful effects of palmitate on the beta cell survival and GSIS. Conversely, ectopic expression of IB1 counteracted the deleterious effects of palmitate on the beta cell survival and insulin secretion. These findings highlight the importance in preserving the IB1 content for protecting beta cell against lipotoxicity in diabetes.
Collapse
Affiliation(s)
- Saška Brajkovic
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Mourad Ferdaoussi
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Valérie Pawlowski
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- University of Lille, EGID FR 3508, Department of Endocrine Surgery, Lille University Hospital, UMR INSERM 1190, Lille, France
| | - Hélène Ezanno
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Valérie Plaisance
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Erik Zmuda
- Department of Molecular and Cellular Biochemistry, Ohio State University, 1060 Carmack Road, Columbus, OH, USA
| | - Tsonwin Hai
- Department of Molecular and Cellular Biochemistry, Ohio State University, 1060 Carmack Road, Columbus, OH, USA
| | - Jean-Sébastien Annicotte
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Gérard Waeber
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
| | - Amar Abderrahmani
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- *Amar Abderrahmani:
| |
Collapse
|
13
|
Marković J, Uskoković A, Grdović N, Dinić S, Mihailović M, Jovanović JA, Poznanović G, Vidaković M. Identification of transcription factors involved in the transcriptional regulation of the CXCL12 gene in rat pancreatic insulinoma Rin-5F cell line. Biochem Cell Biol 2014; 93:54-62. [PMID: 25453873 DOI: 10.1139/bcb-2014-0104] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Diabetes is characterized by a deficit in the number of functional pancreatic β-cells. Understanding the mechanisms that stimulate neogenesis of β-cells should contribute to improved maintenance of β-cell mass. Chemokine CXCL12 has recently become established as a novel β-cell growth factor, however the mechanisms controlling its expression require clarification. We investigated the proteins involved in the transcriptional regulation of the rat β-cell CXCL12 gene (Cxcl12). Using the electrophoretic mobility shift assay and chromatin immunoprecipitation, we established the in vitro and in vivo binding of C/EBPβ, C/EBPα, STAT3, p53, FOXO3a, and HMG I/Y to the Cxcl12 promoter. Co-immunoprecipitation experiments revealed protein-protein interactions between YY1 and PARP-1, FOXO3a and PARP-1, Sp1 and PARP-1, p53 and PARP-1, C/EBPβ and PARP-1, YY1 and p53, YY1 and FOXO3a, p53 and FOXO3a, Sp1 and FOXO3a, C/EBPβ and FOXO3a, C/EBPα and FOXO3a, Sp1 and STAT3. Our data lay the foundation for research into the interplay of signaling pathways that determine the β-cell Cxcl12 expression profile.
Collapse
Affiliation(s)
- Jelena Marković
- a Department of Molecular Biology, Institute for Biological Research, University of Belgrade, Bulevar despota Stefana 142, 10060 Belgrade, Serbia
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Plaisance V, Rolland L, Gmyr V, Annicotte JS, Kerr-Conte J, Pattou F, Abderrahmani A. The class I histone deacetylase inhibitor MS-275 prevents pancreatic beta cell death induced by palmitate. J Diabetes Res 2014; 2014:195739. [PMID: 25610877 PMCID: PMC4294305 DOI: 10.1155/2014/195739] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 11/26/2014] [Accepted: 12/07/2014] [Indexed: 01/04/2023] Open
Abstract
Elevation of the dietary saturated fatty acid palmitate contributes to the reduction of functional beta cell mass in the pathogenesis of type 2 diabetes. The diabetogenic effect of palmitate is achieved by increasing beta cell death through induction of the endoplasmic reticulum (ER) stress markers including activating transcription factor 3 (Atf3) and CAAT/enhancer-binding protein homologous protein-10 (Chop). In this study, we investigated whether treatment of beta cells with the MS-275, a HDAC1 and HDAC3 activity inhibitor which prevents beta cell death elicited by cytokines, is beneficial for combating beta cell dysfunction caused by palmitate. We show that culture of isolated human islets and MIN6 cells with MS-275 reduced apoptosis evoked by palmitate. The protective effect of MS-275 was associated with the attenuation of the expression of Atf3 and Chop. Silencing of HDAC3, but not of HDAC1, mimicked the effects of MS-275 on the expression of the two ER stress markers and apoptosis. These data point to HDAC3 as a potential drug target for preserving beta cells against lipotoxicity in diabetes.
Collapse
Affiliation(s)
- Valérie Plaisance
- European Genomic Institute for Diabetes (EGID) FR 3508, University of Lille, CNRS UMR 8199, and Faculty of Medicine West, 1 Place de Verdun, 59045 Lille, France
| | - Laure Rolland
- European Genomic Institute for Diabetes (EGID) FR 3508, University of Lille, CNRS UMR 8199, and Faculty of Medicine West, 1 Place de Verdun, 59045 Lille, France
| | - Valéry Gmyr
- Department of Endocrine Surgery, Lille University Hospital, INSERM UMR 859, University of Lille, EGID FR 3508, Biotherapies for Diabetes, Lille, France
| | - Jean-Sébastien Annicotte
- European Genomic Institute for Diabetes (EGID) FR 3508, University of Lille, CNRS UMR 8199, and Faculty of Medicine West, 1 Place de Verdun, 59045 Lille, France
| | - Julie Kerr-Conte
- Department of Endocrine Surgery, Lille University Hospital, INSERM UMR 859, University of Lille, EGID FR 3508, Biotherapies for Diabetes, Lille, France
| | - François Pattou
- Department of Endocrine Surgery, Lille University Hospital, INSERM UMR 859, University of Lille, EGID FR 3508, Biotherapies for Diabetes, Lille, France
| | - Amar Abderrahmani
- European Genomic Institute for Diabetes (EGID) FR 3508, University of Lille, CNRS UMR 8199, and Faculty of Medicine West, 1 Place de Verdun, 59045 Lille, France
- *Amar Abderrahmani:
| |
Collapse
|
15
|
Natalicchio A, Labarbuta R, Tortosa F, Biondi G, Marrano N, Peschechera A, Carchia E, Orlando MR, Leonardini A, Cignarelli A, Marchetti P, Perrini S, Laviola L, Giorgino F. Exendin-4 protects pancreatic beta cells from palmitate-induced apoptosis by interfering with GPR40 and the MKK4/7 stress kinase signalling pathway. Diabetologia 2013; 56:2456-66. [PMID: 23995397 DOI: 10.1007/s00125-013-3028-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 07/29/2013] [Indexed: 12/24/2022]
Abstract
AIMS/HYPOTHESIS The mechanisms of the protective effects of exendin-4 on NEFA-induced beta cell apoptosis were investigated. METHODS The effects of exendin-4 and palmitate were evaluated in human and murine islets, rat insulin-secreting INS-1E cells and murine glucagon-secreting alpha-TC1-6 cells. mRNA and protein expression/phosphorylation were measured by real-time RT-PCR and immunoblotting or immunofluorescence, respectively. Small interfering (si)RNAs for Ib1 and Gpr40 were used. Cell apoptosis was quantified by two independent assays. Insulin release was assessed with an insulin ELISA. RESULTS Exposure of human and murine primary islets and INS-1E cells, but not alpha-TC1-6 cells, to exendin-4 inhibited phosphorylation of the stress kinases, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), and prevented apoptosis in response to palmitate. Exendin-4 increased the protein content of islet-brain 1 (IB1), an endogenous JNK blocker; however, siRNA-mediated reduction of IB1 did not impair the ability of exendin-4 to inhibit JNK and prevent apoptosis. Exendin-4 reduced G-protein-coupled receptor 40 (GPR40) expression and inhibited palmitate-induced phosphorylation of mitogen-activated kinase kinase (MKK)4 and MKK7. The effects of exendin-4 were abrogated in the presence of the protein kinase A (PKA) inhibitors, H89 and KT5720. Knockdown of GPR40, as well as use of a specific GPR40 antagonist, resulted in diminished palmitate-induced JNK and p38 MAPK phosphorylation and apoptosis. Furthermore, inhibition of JNK and p38 MAPK activity prevented palmitate-induced apoptosis. CONCLUSIONS/INTERPRETATION Exendin-4 counteracts the proapoptotic effects of palmitate in beta cells by reducing GPR40 expression and inhibiting MKK7- and MKK4-dependent phosphorylation of the stress kinases, JNK and p38 MAPK, in a PKA-dependent manner.
Collapse
Affiliation(s)
- Annalisa Natalicchio
- Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology, Andrology and Metabolic Diseases, University of Bari Aldo Moro, Piazza Giulio Cesare, 11, 70124, Bari, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Oh YS, Lee YJ, Kang Y, Han J, Lim OK, Jun HS. Exendin-4 inhibits glucolipotoxic ER stress in pancreatic β cells via regulation of SREBP1c and C/EBPβ transcription factors. J Endocrinol 2013; 216:343-52. [PMID: 23257266 DOI: 10.1530/joe-12-0311] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Prolonged exposure to high glucose (HG) and palmitate (PA) results in increased ER stress and subsequently induces β-cell apoptosis. Exendin-4, a glucagon-like peptide-1 agonist, is known to protect β cells from toxicity induced by cytokines, HG, or fatty acids by reducing ER stress. However, the detailed molecular mechanisms for this protective effect are still not known. In this study, we investigated the role of exendin-4 in the inhibition of glucolipotoxicity-induced ER stress and β-cell apoptosis. Exendin-4 treatment protected INS-1 β cells from apoptosis in response to HG/PA (25 mM glucose+400 μM PA). HG/PA treatment increased cleaved caspase-3 and induced ER stress maker proteins such as PERK (EIF2AK3), ATF6, and phosphorylated forms of PERK, eIF2α, IRE1α (ERN1), and JNK (MAPK8), and these increases were significantly inhibited by exendin-4 treatment. HG/PA treatment of INS-1 cells increased SREBP1 (SREBF1) protein and induced its nuclear translocation and subsequently increased C/EBPβ (CEBPB) protein and its nuclear translocation. Exendin-4 treatment attenuated this increase. Knockdown of SREBP1c reduced the activation of C/EBPβ and also blocked the expression of ER stress markers induced by HG/PA treatment. Our results indicate that exendin-4 inhibits the activation of SREBP1c and C/EBPβ, which, in turn, may reduce glucolipotoxicity-induced ER stress and β-cell apoptosis.
Collapse
Affiliation(s)
- Yoon Sin Oh
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 7-45 Songdo-dong, Yeonsu-ku, Incheon, Korea
| | | | | | | | | | | |
Collapse
|
17
|
Abstract
Recent technical advances have re-invigorated the study of sphingolipid metabolism in general, and helped to highlight the varied and important roles that sphingolipids play in pancreatic β-cells. Sphingolipid metabolites such as ceramide, glycosphingolipids, sphingosine 1-phosphate and gangliosides modulate many β-cell signaling pathways and processes implicated in β-cell diabetic disease such as apoptosis, β-cell cytokine secretion, ER-to-golgi vesicular trafficking, islet autoimmunity and insulin gene expression. They are particularly relevant to lipotoxicity. Moreover, the de novo synthesis of sphingolipids occurs on many subcellular membranes, in parallel to secretory vesicle formation, traffic and granule maturation events. Indeed, the composition of the plasma membrane, determined by the activity of neutral sphingomyelinases, affects β-cell excitability and potentially insulin exocytosis while another glycosphingolipid, sulfatide, determines the stability of insulin crystals in granules. Most importantly, sphingolipid metabolism on internal membranes is also strongly implicated in regulating β-cell apoptosis.
Collapse
Affiliation(s)
- Ebru Boslem
- Diabetes and Obesity Program; Garvan Institute of Medical Research; Darlinghurst, NSW Australia
- St Vincent’s Clinical School; Faculty of Medicine; University of New South Wales; Sydney, NSW Australia
| | - Peter J. Meikle
- Baker IDI Heart and Diabetes Institute; Melbourne, VIC Australia
| | - Trevor J. Biden
- Diabetes and Obesity Program; Garvan Institute of Medical Research; Darlinghurst, NSW Australia
- St Vincent’s Clinical School; Faculty of Medicine; University of New South Wales; Sydney, NSW Australia
- Correspondence to: Trevor J. Biden,
| |
Collapse
|
18
|
The transcription factor C/EBP delta has anti-apoptotic and anti-inflammatory roles in pancreatic beta cells. PLoS One 2012; 7:e31062. [PMID: 22347430 PMCID: PMC3275575 DOI: 10.1371/journal.pone.0031062] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 01/01/2012] [Indexed: 12/31/2022] Open
Abstract
In the course of Type 1 diabetes pro-inflammatory cytokines (e.g., IL-1β, IFN-γ and TNF-α) produced by islet-infiltrating immune cells modify expression of key gene networks in β-cells, leading to local inflammation and β-cell apoptosis. Most known cytokine-induced transcription factors have pro-apoptotic effects, and little is known regarding “protective” transcription factors. To this end, we presently evaluated the role of the transcription factor CCAAT/enhancer binding protein delta (C/EBPδ) on β-cell apoptosis and production of inflammatory mediators in the rat insulinoma INS-1E cells, in purified primary rat β-cells and in human islets. C/EBPδ is expressed and up-regulated in response to the cytokines IL-1β and IFN-γ in rat β-cells and human islets. Small interfering RNA-mediated C/EBPδ silencing exacerbated IL-1β+IFN-γ-induced caspase 9 and 3 cleavage and apoptosis in these cells. C/EBPδ deficiency increased the up-regulation of the transcription factor CHOP in response to cytokines, enhancing expression of the pro-apoptotic Bcl-2 family member BIM. Interfering with C/EBPδ and CHOP or C/EBPδ and BIM in double knockdown approaches abrogated the exacerbating effects of C/EBPδ deficiency on cytokine-induced β-cell apoptosis, while C/EBPδ overexpression inhibited BIM expression and partially protected β-cells against IL-1β+IFN-γ-induced apoptosis. Furthermore, C/EBPδ silencing boosted cytokine-induced production of the chemokines CXCL1, 9, 10 and CCL20 in β-cells by hampering IRF-1 up-regulation and increasing STAT1 activation in response to cytokines. These observations identify a novel function of C/EBPδ as a modulatory transcription factor that inhibits the pro-apoptotic and pro-inflammatory gene networks activated by cytokines in pancreatic β-cells.
Collapse
|
19
|
Liu Z, Luo Y, Jeppesen PB, Gregersen S, Hermansen K. Amino acid-induced gene expression profiling in clonal β-cell line INS-1E cells. Diabetes Metab Res Rev 2011; 27:120-76. [PMID: 21294238 DOI: 10.1002/dmrr.1153] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND There is abundant evidence that glucotoxicity and lipotoxicity contribute to impaired β-cell function in type 2 diabetes. Interestingly, amino acid (AA) derangement is also a characteristic part of the diabetic state. The acute effects of AA on pancreatic β-cell function have been widely explored; however, to our knowledge, the chronic effects of AA, e.g. proline (Pro), homocysteine (Hcy), and leucine (Leu), on pancreatic β-cell function and integrity have not yet been studied. We aimed to investigate global alterations in β-cell gene expression after long-term exposure of clonal INS-1E cells to elevated level of specific AA in vitro. METHODS Global gene expression profiling was performed to characterize genes differently modified by Pro, Hcy, and Leu, respectively, in INS-1E cells. RESULTS Gene expression profiling revealed significant changes in INS-1E cell mRNAs involved in the control of several aspects of β-cell function, e.g. epigenetic regulation of gene expression, metabolism, innate and adaptive immune responses, cellular signalling, protein synthesis, apoptosis, and cellular stress response. After 72 h, INS-1E cells were differentially regulated (≥1.5- or ≤ -1.5-fold) by Pro (295 transcripts), Hcy (301 transcripts), and Leu (701 transcripts). It appears that Hcy effects changes opposite to those induced by Leu and/or Pro. CONCLUSIONS AA appears to participate in and to influence many physiological processes including those involved in cholesterol metabolism, immune responses, and oxidative phosphorylation. Whether such events promote the β-cell dysfunction and the β-cell failure in diabetes remains to be elucidated. Our data strongly indicate that AA elevation may take part in the progressive development of type 2 diabetes.
Collapse
Affiliation(s)
- Zhenping Liu
- Department of Endocrinology and Metabolism MEA, Aarhus University Hospital, Aarhus Sygehus THG, Tage-Hansens Gade 2, Aarhus C, Denmark
| | | | | | | | | |
Collapse
|
20
|
Fontés G, Semache M, Hagman DK, Tremblay C, Shah R, Rhodes CJ, Rutter J, Poitout V. Involvement of Per-Arnt-Sim Kinase and extracellular-regulated kinases-1/2 in palmitate inhibition of insulin gene expression in pancreatic beta-cells. Diabetes 2009; 58:2048-58. [PMID: 19502418 PMCID: PMC2731539 DOI: 10.2337/db08-0579] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Prolonged exposure of pancreatic beta-cells to simultaneously elevated levels of fatty acids and glucose (glucolipotoxicity) impairs insulin gene transcription. However, the intracellular signaling pathways mediating these effects are mostly unknown. This study aimed to ascertain the role of extracellular-regulated kinases (ERKs)1/2, protein kinase B (PKB), and Per-Arnt-Sim kinase (PASK) in palmitate inhibition of insulin gene expression in pancreatic beta-cells. RESEARCH DESIGN AND METHODS MIN6 cells and isolated rat islets were cultured in the presence of elevated glucose, with or without palmitate or ceramide. ERK1/2 phosphorylation, PKB phosphorylation, and PASK expression were examined by immunoblotting and real-time PCR. The role of these kinases in insulin gene expression was assessed using pharmacological and molecular approaches. RESULTS Exposure of MIN6 cells and islets to elevated glucose induced ERK1/2 and PKB phosphorylation, which was further enhanced by palmitate. Inhibition of ERK1/2, but not of PKB, partially prevented the inhibition of insulin gene expression in the presence of palmitate or ceramide. Glucose-induced expression of PASK mRNA and protein levels was reduced in the presence of palmitate. Overexpression of wild-type PASK increased insulin and pancreatic duodenal homeobox-1 gene expression in MIN6 cells and rat islets incubated with glucose and palmitate, whereas overexpression of a kinase-dead PASK mutant in rat islets decreased expression of insulin and pancreatic duodenal homeobox-1 and increased C/EBPbeta expression. CONCLUSIONS Both the PASK and ERK1/2 signaling pathways mediate palmitate inhibition of insulin gene expression. These findings identify PASK as a novel mediator of glucolipotoxicity on the insulin gene in pancreatic beta-cells.
Collapse
Affiliation(s)
- Ghislaine Fontés
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
| | - Meriem Semache
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Derek K. Hagman
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
| | - Caroline Tremblay
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
| | - Ramila Shah
- Kovler Diabetes Center, University of Chicago, Chicago, Illinois
| | | | - Jared Rutter
- Division of Endocrinology, University of Utah School of Medicine, Salt Lake City, Utah
| | - Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, University of Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Québec, Canada
- Corresponding author: Vincent Poitout,
| |
Collapse
|
21
|
Poitout V, Amyot J, Semache M, Zarrouki B, Hagman D, Fontés G. Glucolipotoxicity of the pancreatic beta cell. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1801:289-98. [PMID: 19715772 DOI: 10.1016/j.bbalip.2009.08.006] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/13/2009] [Accepted: 08/13/2009] [Indexed: 02/07/2023]
Abstract
The concept of glucolipotoxicity refers to the combined, deleterious effects of elevated glucose and fatty acid levels on pancreatic beta-cell function and survival. Significant progress has been made in recent years towards a better understanding of the cellular and molecular basis of glucolipotoxicity in the beta cell. The permissive effect of elevated glucose on the detrimental actions of fatty acids stems from the influence of glucose on intracellular fatty acid metabolism, promoting the synthesis of cellular lipids. The combination of excessive levels of fatty acids and glucose therefore leads to decreased insulin secretion, impaired insulin gene expression, and beta-cell death by apoptosis, all of which probably have distinct underlying mechanisms. Recent studies from our laboratory have identified several pathways implicated in fatty acid inhibition of insulin gene expression, including the extracellular-regulated kinase (ERK1/2) pathway, the metabolic sensor Per-Arnt-Sim kinase (PASK), and the ATF6 branch of the unfolded protein response. We have also confirmed in vivo in rats that the decrease in insulin gene expression is an early defect which precedes any detectable abnormality in insulin secretion. While the role of glucolipotoxicity in humans is still debated, the inhibitory effects of chronically elevated fatty acid levels has been clearly demonstrated in several studies, at least in individuals genetically predisposed to developing type 2 diabetes. It is therefore likely that glucolipotoxicity contributes to beta-cell failure in type 2 diabetes as well as to the decline in beta-cell function observed after the onset of the disease.
Collapse
Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, Montreal, QC, Canada.
| | | | | | | | | | | |
Collapse
|