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Abu-Nejem R, Hannon TS. Insulin Dynamics and Pathophysiology in Youth-Onset Type 2 Diabetes. J Clin Endocrinol Metab 2024; 109:2411-2421. [PMID: 38963882 DOI: 10.1210/clinem/dgae463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2024] [Revised: 06/28/2024] [Accepted: 07/03/2024] [Indexed: 07/06/2024]
Abstract
Youth-onset type 2 diabetes (T2D) is increasing around the globe. The mounting disease burden of youth-onset T2D portends substantial consequences for the health outcomes of young people and for health care systems. The pathophysiology of this condition is characterized by insulin resistance and initial insulin hypersecretion ± an inherent insulin secretory defect, with progressive loss of stimulated insulin secretion leading to pancreatic β-cell failure. Research studies focusing on youth-onset T2D have illuminated key differences for youth- vs adult-onset T2D, with youth having more profound insulin resistance and quicker progression to loss of sufficient insulin secretion to maintain euglycemia. There is a need for therapies that are targeted to improve both insulin resistance and, importantly, maintain sufficient insulin secretory function over the lifespan in youth-onset T2D.
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Affiliation(s)
- Rozan Abu-Nejem
- Department of Pediatrics, Divisions of Pediatric Endocrinology and Diabetology and Pediatric Health Services Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Tamara S Hannon
- Department of Pediatrics, Divisions of Pediatric Endocrinology and Diabetology and Pediatric Health Services Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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2
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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.
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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
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3
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Petry SF, Römer A, Rawat D, Brunner L, Lerch N, Zhou M, Grewal R, Sharifpanah F, Sauer H, Eckert GP, Linn T. Loss and Recovery of Glutaredoxin 5 Is Inducible by Diet in a Murine Model of Diabesity and Mediated by Free Fatty Acids In Vitro. Antioxidants (Basel) 2022; 11:antiox11040788. [PMID: 35453472 PMCID: PMC9025089 DOI: 10.3390/antiox11040788] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 03/24/2022] [Accepted: 04/14/2022] [Indexed: 02/05/2023] Open
Abstract
Free fatty acids (FFA), hyperglycemia, and inflammatory cytokines are major mediators of β-cell toxicity in type 2 diabetes mellitus, impairing mitochondrial metabolism. Glutaredoxin 5 (Glrx5) is a mitochondrial protein involved in the assembly of iron–sulfur clusters required for complexes of the respiratory chain. We have provided evidence that islet cells are deprived of Glrx5, correlating with impaired insulin secretion during diabetes in genetically obese mice. In this study, we induced diabesity in C57BL/6J mice in vivo by feeding the mice a high-fat diet (HFD) and modelled the diabetic metabolism in MIN6 cells through exposure to FFA, glucose, or inflammatory cytokines in vitro. qRT-PCR, ELISA, immunohisto-/cytochemistry, bioluminescence, and respirometry were employed to study Glrx5, insulin secretion, and mitochondrial biomarkers. The HFD induced a depletion of islet Glrx5 concomitant with an obese phenotype, elevated FFA in serum and reactive oxygen species in islets, and impaired glucose tolerance. Exposure of MIN6 cells to FFA led to a loss of Glrx5 in vitro. The FFA-induced depletion of Glrx5 coincided with significantly altered mitochondrial biomarkers. In summary, we provide evidence that Glrx5 is regulated by FFA in type 2 diabetes mellitus and is linked to mitochondrial dysfunction and blunted insulin secretion.
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Affiliation(s)
- Sebastian Friedrich Petry
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
- Correspondence: ; Tel.: +49-641-985-57010
| | - Axel Römer
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
| | - Divya Rawat
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
| | - Lara Brunner
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
| | - Nina Lerch
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
| | - Mengmeng Zhou
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
| | - Rekha Grewal
- Laboratory for Nutrition in Prevention & Therapy, Department of Nutritional Sciences, Justus Liebig University, 35392 Giessen, Germany; (R.G.); (G.P.E.)
| | - Fatemeh Sharifpanah
- Faculty of Medicine, Philipps University, 35037 Marburg, Germany;
- Cyntegrity Germany GmbH, 60438 Frankfurt, Germany
| | - Heinrich Sauer
- Department of Physiology, Faculty of Medicine, Justus Liebig University, 35392 Giessen, Germany;
| | - Gunter Peter Eckert
- Laboratory for Nutrition in Prevention & Therapy, Department of Nutritional Sciences, Justus Liebig University, 35392 Giessen, Germany; (R.G.); (G.P.E.)
| | - Thomas Linn
- Clinical Research Unit, Medical Clinic and Polyclinic III, Center of Internal Medicine, Justus Liebig University, 35392 Giessen, Germany; (A.R.); (D.R.); (L.B.); (N.L.); (M.Z.); (T.L.)
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Diabetes and Familial Hypercholesterolemia: Interplay between Lipid and Glucose Metabolism. Nutrients 2022; 14:nu14071503. [PMID: 35406116 PMCID: PMC9002616 DOI: 10.3390/nu14071503] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/29/2022] [Accepted: 03/30/2022] [Indexed: 02/04/2023] Open
Abstract
Familial hypercholesterolemia (FH) is a genetic disease characterized by high low-density lipoprotein (LDL) cholesterol (LDL-c) concentrations that increase cardiovascular risk and cause premature death. The most frequent cause of the disease is a mutation in the LDL receptor (LDLR) gene. Diabetes is also associated with an increased risk of cardiovascular disease and mortality. People with FH seem to be protected from developing diabetes, whereas cholesterol-lowering treatments such as statins are associated with an increased risk of the disease. One of the hypotheses to explain this is based on the toxicity of LDL particles on insulin-secreting pancreatic β-cells, and their uptake by the latter, mediated by the LDLR. A healthy lifestyle and a relatively low body mass index in people with FH have also been proposed as explanations. Its association with superimposed diabetes modifies the phenotype of FH, both regarding the lipid profile and cardiovascular risk. However, findings regarding the association and interplay between these two diseases are conflicting. The present review summarizes the existing evidence and discusses knowledge gaps on the matter.
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Vilas-Boas EA, Almeida DC, Roma LP, Ortis F, Carpinelli AR. Lipotoxicity and β-Cell Failure in Type 2 Diabetes: Oxidative Stress Linked to NADPH Oxidase and ER Stress. Cells 2021; 10:cells10123328. [PMID: 34943836 PMCID: PMC8699655 DOI: 10.3390/cells10123328] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 12/17/2022] Open
Abstract
A high caloric intake, rich in saturated fats, greatly contributes to the development of obesity, which is the leading risk factor for type 2 diabetes (T2D). A persistent caloric surplus increases plasma levels of fatty acids (FAs), especially saturated ones, which were shown to negatively impact pancreatic β-cell function and survival in a process called lipotoxicity. Lipotoxicity in β-cells activates different stress pathways, culminating in β-cells dysfunction and death. Among all stresses, endoplasmic reticulum (ER) stress and oxidative stress have been shown to be strongly correlated. One main source of oxidative stress in pancreatic β-cells appears to be the reactive oxygen species producer NADPH oxidase (NOX) enzyme, which has a role in the glucose-stimulated insulin secretion and in the β-cell demise during both T1 and T2D. In this review, we focus on the acute and chronic effects of FAs and the lipotoxicity-induced β-cell failure during T2D development, with special emphasis on the oxidative stress induced by NOX, the ER stress, and the crosstalk between NOX and ER stress.
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Affiliation(s)
- Eloisa Aparecida Vilas-Boas
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo 05508-000, Brazil
- Department of Biochemistry, Institute of Chemistry, University of São Paulo (USP), São Paulo 05508-900, Brazil
- Correspondence: (E.A.V.-B.); (A.R.C.); Tel.: +55-(11)-3091-7246 (A.R.C.)
| | - Davidson Correa Almeida
- Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo 05508-000, Brazil; (D.C.A.); (F.O.)
| | - Leticia Prates Roma
- Center for Human and Molecular Biology (ZHMB), Department of Biophysics, Saarland University, 66424 Homburg, Germany;
| | - Fernanda Ortis
- Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo 05508-000, Brazil; (D.C.A.); (F.O.)
| | - Angelo Rafael Carpinelli
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo 05508-000, Brazil
- Correspondence: (E.A.V.-B.); (A.R.C.); Tel.: +55-(11)-3091-7246 (A.R.C.)
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Zhang M, Yang C, Zhu M, Qian L, Luo Y, Cheng H, Geng R, Xu X, Qian C, Liu Y. Saturated fatty acids entrap PDX1 in stress granules and impede islet beta cell function. Diabetologia 2021; 64:1144-1157. [PMID: 33569632 DOI: 10.1007/s00125-021-05389-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/16/2020] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Failure of pancreatic and duodenal homeobox factor 1 (PDX1) to localise in the nucleus of islet beta cells under high-fat diet (HFD) conditions may be an early functional defect that contributes to beta cell failure in type 2 diabetes; however, the mechanism of PDX1 intracellular mislocalisation is unclear. Stress granules (SGs) are membrane-less cytoplasmic structures formed under stress that impair nucleocytoplasmic transport by sequestering nucleocytoplasmic transport factors and components of the nuclear pore complex. In this study, we investigated the stimulators that trigger SG formation in islet beta cells and the effects of SGs on PDX1 localisation and beta cell function. METHODS The effect of palmitic acid (PA) on nucleocytoplasmic transport was investigated by using two reporters, S-tdTomato and S-GFP. SG assembly in rat insulinoma cell line INS1 cells, human islets under PA stress, and the pancreas of diet-induced obese mice was analysed using immunofluorescence and immunoblotting. SG protein components were identified through mass spectrometry. SG formation was blocked by specific inhibitors or genetic deletion of essential SG proteins, and then PDX1 localisation and beta cell function were investigated in vitro and in vivo. RESULTS We showed that saturated fatty acids (SFAs) are endogenous stressors that disrupted nucleocytoplasmic transport and stimulated SG formation in pancreatic beta cells. Using mass spectrometry approaches, we revealed that several nucleocytoplasmic transport factors and PDX1 were localised to SGs after SFA treatment, which inhibited glucose-induced insulin secretion. Furthermore, we found that SFAs induced SG formation in a phosphoinositide 3-kinase (PI3K)/eukaryotic translation initiation factor 2α (EIF2α) dependent manner. Disruption of SG assembly by PI3K/EIF2α inhibitors or genetic deletion of T cell restricted intracellular antigen 1 (TIA1) in pancreatic beta cells effectively suppressed PA-induced PDX1 mislocalisation and ameliorated HFD-mediated beta cell dysfunction. CONCLUSIONS/INTERPRETATION Our findings suggest a link between SG formation and beta cell dysfunction in the presence of SFAs. Preventing SG formation may be a potential therapeutic strategy for treating obesity and type 2 diabetes.
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Affiliation(s)
- Mu Zhang
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Chunjie Yang
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Meng Zhu
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Li Qian
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Yan Luo
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Huimin Cheng
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Rong Geng
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China
| | - Xiaojun Xu
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China.
| | - Cheng Qian
- Department of Nephrology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China.
| | - Yu Liu
- Department of Endocrinology, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China.
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Binayi F, Zardooz H, Ghasemi R, Hedayati M, Askari S, Pouriran R, Sahraei M. The chemical chaperon 4-phenyl butyric acid restored high-fat diet- induced hippocampal insulin content and insulin receptor level reduction along with spatial learning and memory deficits in male rats. Physiol Behav 2021; 231:113312. [PMID: 33412188 DOI: 10.1016/j.physbeh.2021.113312] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 01/01/2021] [Accepted: 01/02/2021] [Indexed: 12/18/2022]
Abstract
This study assessed the effect of a chronic high-fat diet (HFD) on plasma and hippocampal insulin and corticosterone levels, the hippocampus insulin receptor amount, and spatial learning and memory with or without receiving 4-phenyl butyric acid (4-PBA) in male rats. Rats were divided into high-fat and normal diet groups, then each group was subdivided into dimethyl sulfoxide (DMSO) and 4-PBA groups. After weaning, the rats were fed with HFD for 20 weeks. Then, 4-PBA or DMSO were injected for 3 days. Subsequently, oral glucose tolerance test was done. On the following day, spatial memory tests were performed. Then the hippocampus Bip, Chop, insulin, corticosterone, and insulin receptor levels were determined. HFD increased plasma glucose, leptin and corticosterone concentrations, hippocampus Bip, Chop and corticosterone levels, food intake, abdominal fat weight and body weight along with impaired glucose tolerance. It decreased plasma insulin, and insulin content, and its receptor amount in hippocampus. HFD lengthened escape latency and shortened the duration spent in target zone. 4-PBA administration improved the HFD- induced adverse changes. Chronic HFD possibly through the induction of endoplasmic reticulum (ER) stress and subsequent changes in the levels of hippocampal corticosterone, insulin and insulin receptor along with possible leptin resistance caused spatial learning and memory deficits.
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Affiliation(s)
- Fateme Binayi
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Homeira Zardooz
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Rasoul Ghasemi
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mehdi Hedayati
- Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sahar Askari
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ramin Pouriran
- School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Sahraei
- School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Das D, Das A, Sahu M, Mishra SS, Khan S, Bejugam PR, Rout PK, Das A, Bano S, Mishra GP, Raghav SK, Dixit A, Panda AC. Identification and Characterization of Circular Intronic RNAs Derived from Insulin Gene. Int J Mol Sci 2020; 21:ijms21124302. [PMID: 32560282 PMCID: PMC7352490 DOI: 10.3390/ijms21124302] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 06/02/2020] [Accepted: 06/09/2020] [Indexed: 01/09/2023] Open
Abstract
Circular RNAs (circRNAs) are a large family of noncoding RNAs that have emerged as novel regulators of gene expression. However, little is known about the function of circRNAs in pancreatic β-cells. Here, transcriptomic analysis of mice pancreatic islet RNA-sequencing data identified 77 differentially expressed circRNAs between mice fed with a normal diet and a high-fat diet. Surprisingly, multiple circRNAs were derived from the intron 2 of the preproinsulin 2 (Ins2) gene and are termed as circular intronic (ci)-Ins2. The expression of ci-Ins2 transcripts in mouse pancreatic islets, and βTC6 cells were confirmed by reverse transcription PCR, DNA sequencing, and RNase R treatment experiments. The level of ci-Ins2 was altered in βTC6 cells upon exposure to elevated levels of palmitate and glucose. Computational analysis predicted the interaction of several RNA-binding proteins with ci-Ins2 and their flanking region, suggesting their role in the ci-Ins2 function or biogenesis. Additionally, bioinformatics analysis predicted the association of several microRNAs with ci-Ins2. Gene ontology and pathway analysis of genes targeted by miRNAs associated with ci-Ins2 suggested the regulation of several key biological processes. Together, our findings indicate that differential expression of circRNAs, especially ci-Ins2 transcripts, may regulate β-cell function and may play a critical role in the development of diabetes.
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Affiliation(s)
- Debojyoti Das
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
- School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024, India
| | - Aniruddha Das
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
- School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024, India
| | - Mousumi Sahu
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Smruti Sambhav Mishra
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Shaheerah Khan
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Pruthvi R. Bejugam
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Pranita K. Rout
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Arundhati Das
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
- School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024, India
| | - Shehnaz Bano
- National Center for Cell Sciences (NCCS), Pune, Maharashtra 411007, India;
| | - Gyan Prakash Mishra
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Sunil K. Raghav
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Anshuman Dixit
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
| | - Amaresh C. Panda
- Institute of Life Sciences (ILS), Nalco Square, Bhubaneswar, Odisha 751023, India; (D.D.); (A.D.); (M.S.); (S.S.M.); (S.K.); (P.R.B.); (P.K.R.); (A.D.); (G.P.M.); (S.K.R.); (A.D.)
- Correspondence: ; Tel.: +91-674-230-43-14
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9
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VEGF-B ablation in pancreatic β-cells upregulates insulin expression without affecting glucose homeostasis or islet lipid uptake. Sci Rep 2020; 10:923. [PMID: 31969592 PMCID: PMC6976647 DOI: 10.1038/s41598-020-57599-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 12/18/2019] [Indexed: 02/07/2023] Open
Abstract
Type 2 diabetes mellitus (T2DM) affects millions of people and is linked with obesity and lipid accumulation in peripheral tissues. Increased lipid handling and lipotoxicity in insulin producing β-cells may contribute to β-cell dysfunction in T2DM. The vascular endothelial growth factor (VEGF)-B regulates uptake and transcytosis of long-chain fatty acids over the endothelium to tissues such as heart and skeletal muscle. Systemic inhibition of VEGF-B signaling prevents tissue lipid accumulation, improves insulin sensitivity and glucose tolerance, as well as reduces pancreatic islet triglyceride content, under T2DM conditions. To date, the role of local VEGF-B signaling in pancreatic islet physiology and in the regulation of fatty acid trans-endothelial transport in pancreatic islet is unknown. To address these questions, we have generated a mouse strain where VEGF-B is selectively depleted in β-cells, and assessed glucose homeostasis, β-cell function and islet lipid content under both normal and high-fat diet feeding conditions. We found that Vegfb was ubiquitously expressed throughout the pancreas, and that β-cell Vegfb deletion resulted in increased insulin gene expression. However, glucose homeostasis and islet lipid uptake remained unaffected by β-cell VEGF-B deficiency.
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10
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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: 219] [Impact Index Per Article: 43.8] [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.
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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.
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Marafie SK, Al-Shawaf EM, Abubaker J, Arefanian H. Palmitic acid-induced lipotoxicity promotes a novel interplay between Akt-mTOR, IRS-1, and FFAR1 signaling in pancreatic β-cells. Biol Res 2019; 52:44. [PMID: 31426858 PMCID: PMC6699284 DOI: 10.1186/s40659-019-0253-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 08/12/2019] [Indexed: 01/05/2023] Open
Abstract
Background Free fatty acid receptor 1 (FFAR1) is G-protein coupled receptor predominantly expressed in pancreatic β-cells that is activated by a variety of free fatty acids (FFAs). Once activated, it promotes glucose-stimulated insulin secretion (GSIS). However, increased levels of FFAs lead to lipotoxicity, inducing loss of β-cell function. FFAR1 plays a key role in the development of type 2 diabetes (T2D), and previous studies have indicated the importance of developing anti-diabetic therapies against FFAR1, although its role in the regulation of β-cell function remains unclear. The present study investigated the role of FFAR1 under lipotoxic conditions using palmitic acid (PA). The rat insulinoma 1 clone 832/13 (INS-1 832/13) cell line was used as a model as it physiologically resembles native pancreatic β-cells. Key players of the insulin signaling pathway, such as mTOR, Akt, IRS-1, and the insulin receptor (INSR1β), were selected as candidates to be analyzed under lipotoxic conditions. Results We revealed that PA-induced lipotoxicity affected GSIS in INS-1 cells and negatively modulated the activity of both IRS-1 and Akt. Reduced phosphorylation of both IRS-1 S636/639 and Akt S473 was observed, in addition to decreased expression of both INSR1β and FFAR1. Moreover, transient knockdown of FFAR1 led to a reduction in IRS-1 mRNA expression and an increase in INSR1β mRNA. Finally, PA affected localization of FFAR1 from the cytoplasm to the perinucleus. Conclusions In conclusion, our study suggests a novel regulatory involvement of FFAR1 in crosstalk with mTOR–Akt and IRS-1 signaling in β-cells under lipotoxic conditions.
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Affiliation(s)
- Sulaiman K Marafie
- Biochemistry & Molecular Biology Department, Dasman Diabetes Institute, P. O. Box 1180, 15462, Dasman, Kuwait.
| | - Eman M Al-Shawaf
- Biochemistry & Molecular Biology Department, Dasman Diabetes Institute, P. O. Box 1180, 15462, Dasman, Kuwait
| | - Jehad Abubaker
- Biochemistry & Molecular Biology Department, Dasman Diabetes Institute, P. O. Box 1180, 15462, Dasman, Kuwait
| | - Hossein Arefanian
- Microbiology & Immunology Department, Dasman Diabetes Institute, P. O. Box 1180, 15462, Dasman, Kuwait.
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Li Z, Zhou M, Cai Z, Liu H, Zhong W, Hao Q, Cheng D, Hu X, Hou J, Xu P, Xue Y, Zhou Y, Xu T. RNA-binding protein DDX1 is responsible for fatty acid-mediated repression of insulin translation. Nucleic Acids Res 2019; 46:12052-12066. [PMID: 30295850 PMCID: PMC6294501 DOI: 10.1093/nar/gky867] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 09/14/2018] [Indexed: 01/13/2023] Open
Abstract
The molecular mechanism in pancreatic β cells underlying hyperlipidemia and insulin insufficiency remains unclear. Here, we find that the fatty acid-induced decrease in insulin levels occurs due to a decrease in insulin translation. Since regulation at the translational level is generally mediated through RNA-binding proteins, using RNA antisense purification coupled with mass spectrometry, we identify a novel insulin mRNA-binding protein, namely, DDX1, that is sensitive to palmitate treatment. Notably, the knockdown or overexpression of DDX1 affects insulin translation, and the knockdown of DDX1 eliminates the palmitate-induced repression of insulin translation. Molecular mechanism studies show that palmitate treatment causes DDX1 phosphorylation at S295 and dissociates DDX1 from insulin mRNA, thereby leading to the suppression of insulin translation. In addition, DDX1 may interact with the translation initiation factors eIF3A and eIF4B to regulate translation. In high-fat diet mice, the inhibition of insulin translation happens at an early prediabetic stage before the elevation of glucose levels. We speculate that the DDX1-mediated repression of insulin translation worsens the situation of insulin resistance and contributes to the elevation of blood glucose levels in obese animals.
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Affiliation(s)
- Zonghong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China.,Jilin Province Key Laboratory on Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, China
| | - Maoge Zhou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhaokui Cai
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Hongyang Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Wen Zhong
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiang Hao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Dongwan Cheng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Xihao Hu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Junjie Hou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
| | - Pingyong Xu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yuanchao Xue
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yifa Zhou
- Jilin Province Key Laboratory on Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, China
| | - Tao Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China
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Gerst F, Wagner R, Oquendo MB, Siegel-Axel D, Fritsche A, Heni M, Staiger H, Häring HU, Ullrich S. What role do fat cells play in pancreatic tissue? Mol Metab 2019; 25:1-10. [PMID: 31113756 PMCID: PMC6600604 DOI: 10.1016/j.molmet.2019.05.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/10/2019] [Accepted: 05/01/2019] [Indexed: 02/07/2023] Open
Abstract
Background It is now generally accepted that obesity is a major risk factor for type 2 diabetes mellitus (T2DM). Hepatic steatosis in particular, as well as visceral and ectopic fat accumulation within tissues, is associated with the development of the disease. We recently presented the first study on isolated human pancreatic adipocytes and their interaction with islets [Gerst, F., Wagner, R., Kaiser, G., Panse, M., Heni, M., Machann, J., et al., 2017. Metabolic crosstalk between fatty pancreas and fatty liver: effects on local inflammation and insulin secretion. Diabetologia 60(11):2240–2251.]. The results indicate that the function of adipocytes depends on the overall metabolic status in humans which, in turn, differentially affects islet hormone release. Scope of Review This review summarizes former and recent studies on factors derived from adipocytes and their effects on insulin-secreting β-cells, with particular emphasis on the human pancreas. The adipocyte secretome is discussed with a special focus on its influence on insulin secretion, β-cell survival and apoptotic β-cell death. Major Conclusions Human pancreatic adipocytes store lipids and release adipokines, metabolites, and pro-inflammatory molecules in response to the overall metabolic, humoral, and neuronal status. The differentially regulated adipocyte secretome impacts on endocrine function, i.e., insulin secretion, β-cell survival and death which interferes with glycemic control. This review attempts to explain why the extent of pancreatic steatosis is associated with reduced insulin secretion in some studies but not in others.
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Affiliation(s)
- Felicia Gerst
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany
| | - Robert Wagner
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Morgana Barroso Oquendo
- German Center for Diabetes Research (DZD), Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Dorothea Siegel-Axel
- German Center for Diabetes Research (DZD), Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Andreas Fritsche
- German Center for Diabetes Research (DZD), Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Martin Heni
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Harald Staiger
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany; Institute of Pharmaceutical Sciences, Department of Pharmacy and Biochemistry, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Hans-Ulrich Häring
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany; Department of Internal Medicine IV, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
| | - Susanne Ullrich
- German Center for Diabetes Research (DZD), Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard Karls University of Tübingen, Tübingen, Germany.
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Kutoh E, Wada A, Hayashi J. REGULATION OF FREE FATTY ACID BY SITAGLIPTIN MONOTHERAPY IN DRUG-NAÏVE SUBJECTS WITH TYPE 2 DIABETES. Endocr Pract 2018; 24:1063-1072. [PMID: 30289315 DOI: 10.4158/ep-2018-0287] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE The aim of this study was to investigate the effects of sitagliptin on the regulation of free fatty acid (FFA) and other metabolic parameters in drug-naïve subjects with type 2 diabetes mellitus (T2DM). METHODS This was a prospective, nonrandomized, observational study. Drug-naïve subjects with T2DM received 25 to 50 mg/day sitagliptin monotherapy (n = 64). At 3 months, FFA and other metabolic parameters were compared with those at baseline. FFA was measured by colorimetry with enzymatic reactions. As a comparator, 12.5 to 25 mg/day alogliptin monotherapy was given to drug-naïve subjects with T2DM (n = 55). RESULTS Significant reductions in FFA (-13.2%, P<0.01) levels were observed with sitagliptin but not alogliptin. Both drugs showed similar glycemic efficacies. Significant correlations were observed between the changes (Δ) of FFA and Δglycated hemoglobin A1c (HbA1c), Dtotal cholesterol (TC), Δnon-high-density lipoprotein cholesterol (HDL-C), or Δlow-density lipoprotein cholesterol (LDL-C), and significant negative correlations were seen between ΔFFA and Δhomeostasis model assessment-B (HOMA-B), ΔC-peptide immunoreactivity (CPR)-index or Δbody mass index (BMI) in the sitagliptin group. The subjects in the sitagliptin group were further divided into 2 subgroups (n = 32 each) according to the changes of FFA (group B [above the median] ΔFFA = 23.1 %, P<.0005; group A [below the median] ΔFFA = -37.3 %, P<.00001). At baseline, FFA levels were significantly higher in group A versus group B ( P<.001). Higher degrees of reductions of FBG (-14.6% vs. -9.3%, P<0.05) or HbA1c (-20.6% vs. -16.9%, P<.05), and increases of HOMA-B (52.7% vs. 38.3%, P<.03) or CPR-index (37.5% vs. 18.8%, P<.02) were observed in group A versus group B. Significant reductions of TC (-5.8%, P<.002), non-HDL-C (-7.8%, P<.001) or LDL-C (-6.3%, P<.02), and significant increases of C-peptide (11.3%, P<.05) were seen only in group A. CONCLUSION Sitagliptin could downregulate high FFA levels. Subjects with reductions of FFA levels had better glycemic efficacies and higher degrees of enhancement of beta-cell function than others. Reductions of atherogenic cholesterols were seen in these populations. ABBREVIATIONS CPR = C-peptide immunoreactivity; DPP-4 = dipeptidyl peptidase 4; FBG = fasting blood glucose; FFA = free fatty acid; HbA1c = glycated hemoglobin A1c; HDL-C = high-density lipoprotein cholesterol; HOMA-R = homeostasis model assessment-R; HOMA-B = homeostasis model assessment-B; non-HDL-C = non-HDL-cholesterol; LDL-C = low-density lipoprotein cholesterol; TC = total cholesterol; T2DM = type 2 diabetes; TG = triglyceride; UA = uric acid.
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Feng XT, Duan HM, Li SL. Protective role of Pollen Typhae total flavone against the palmitic acid-induced impairment of glucose-stimulated insulin secretion involving GPR40 signaling in INS-1 cells. Int J Mol Med 2017; 40:922-930. [DOI: 10.3892/ijmm.2017.3070] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 07/05/2017] [Indexed: 11/05/2022] Open
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Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate. Int J Mol Sci 2017; 18:ijms18061188. [PMID: 28574454 PMCID: PMC5486011 DOI: 10.3390/ijms18061188] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 05/23/2017] [Accepted: 05/26/2017] [Indexed: 02/07/2023] Open
Abstract
Consistent evidence from both experimental and human studies indicates that Type 2 diabetes mellitus (T2DM) is a complex disease resulting from the interaction of genetic, epigenetic, environmental, and lifestyle factors. Nutrients and dietary patterns are important environmental factors to consider in the prevention, development and treatment of this disease. Nutritional genomics focuses on the interaction between bioactive food components and the genome and includes studies of nutrigenetics, nutrigenomics and epigenetic modifications caused by nutrients. There is evidence supporting the existence of nutrient-gene and T2DM interactions coming from animal studies and family-based intervention studies. Moreover, many case-control, cohort, cross-sectional cohort studies and clinical trials have identified relationships between individual genetic load, diet and T2DM. Some of these studies were on a large scale. In addition, studies with animal models and human observational studies, in different countries over periods of time, support a causative relationship between adverse nutritional conditions during in utero development, persistent epigenetic changes and T2DM. This review provides comprehensive information on the current state of nutrient-gene interactions and their role in T2DM pathogenesis, the relationship between individual genetic load and diet, and the importance of epigenetic factors in influencing gene expression and defining the individual risk of T2DM.
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Tzeng CY, Lee YC, Chung JJ, Tsai JC, Chen YI, Hsu TH, Lin JG, Lee KR, Chang SL. 15 hz Electroacupuncture at St36 Improves Insulin Sensitivity and Reduces Free Fatty Acid Levels in Rats with Chronic Dexamethasone-Induced Insulin Resistance. Acupunct Med 2016; 34:296-301. [DOI: 10.1136/acupmed-2015-010956] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2016] [Indexed: 02/01/2023]
Abstract
Objective To evaluate the effect of electroacupuncture (EA) in a rat model of chronic steroid-induced insulin resistance (SIIR). Methods An SIIR rat model was created using daily intraperitoneal injections of clinically relevant doses of dexamethasone (1 mg/kg) for 5 days to induce chronic insulin resistance. Thirty-six SIIR rats were randomly divided into the SIIR+EA group (n=18), which received 15 Hz EA at ST36 for 60 min, and the SIIR group (n=18), which remained untreated. Plasma glucose and free fatty acid (FFA) levels were measured in serial blood samples taken without further manipulation (n=6 per group) and during insulin challenge test (ICT, n=6 per group) and intravenous glucose tolerance test (ivGTT, n=6 per group). Insulin receptor substrate (IRS)-1 and glucose transporter (GLUT)-4 were measured using Western blotting and expressed relative to β-actin. Results Following EA, area-under-the-curve (AUC) for glucose was reduced (7340±291 vs 10 705±1474 mg/dL/min, p=0.049) and FFA levels significantly lower at 30/60 min in the SIIR+EA versus SIIR groups. Similar effects on glucose AUC were seen during the ICT (5568±275 vs 7136±594 mg/dL/min, p<0.05) and igVTT (11 498±1398 vs 16 652±1217 mg/dL/min, p<0.01). FFA levels were lower at 30 and/or 60 min in SIIR+EA versus SIIR groups (p<0.01). Relative expression of IRS-1 and GLUT4 were significantly increased by EA (p<0.01). Conclusions EA decreased the FFA level and increased insulin sensitivity in SIIR rats. Further clinical studies are needed to determine whether EA is an effective alternative treatment for the reduction of insulin resistance in patients requiring chronic use of dexamethasone.
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Affiliation(s)
- Chung-Yuh Tzeng
- Department of Orthopedics, Taichung Veterans General Hospital, Taichung City, Taiwan
- Institute of Molecular Medicine, College of Life Science, National Tsing Hua University, Hsinchu City, Taiwan
- Department of Nursing, Hung-Kuang University, Taichung city, Taiwan
| | - Yu-Chen Lee
- Department of Acupuncture, China Medical University Hospital, Taichung City, Taiwan
| | - Jui-Jung Chung
- Department of Pharmacy, Cheng-Ching Hospital, Taichung City, Taiwan
| | - Jen-Chieh Tsai
- Department of Medicinal Botanicals and Health Applications, Da-Yeh University, Changhua County, Taiwan
| | - Ying-I Chen
- Department of Medicinal Botanicals and Health Applications, Da-Yeh University, Changhua County, Taiwan
| | - Tai-Hao Hsu
- Department of BioIndustry Technology, Da-Yeh University, Changhua County, Taiwan
| | - Jaung-Geng Lin
- School of Chinese Medicine, China Medical University, Taichung City, Taiwan
| | - Kuan-Rong Lee
- Institute of Molecular Medicine, College of Life Science, National Tsing Hua University, Hsinchu City, Taiwan
| | - Shih-Liang Chang
- Department of Medicinal Botanicals and Health Applications, Da-Yeh University, Changhua County, Taiwan
- School of Chinese Medicine, China Medical University, Taichung City, Taiwan
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Durning SP, Flanagan-Steet H, Prasad N, Wells L. O-Linked β-N-acetylglucosamine (O-GlcNAc) Acts as a Glucose Sensor to Epigenetically Regulate the Insulin Gene in Pancreatic Beta Cells. J Biol Chem 2015; 291:2107-18. [PMID: 26598517 DOI: 10.1074/jbc.m115.693580] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Indexed: 11/06/2022] Open
Abstract
The post-translational protein modification O-linked β-N-acetylglucosamine (O-GlcNAc) is a proposed nutrient sensor that has been shown to regulate multiple biological pathways. This dynamic and inducible enzymatic modification to intracellular proteins utilizes the end product of the nutrient sensing hexosamine biosynthetic pathway, UDP-GlcNAc, as its substrate donor. Type II diabetic patients have elevated O-GlcNAc-modified proteins within pancreatic beta cells due to chronic hyperglycemia-induced glucose overload, but a molecular role for O-GlcNAc within beta cells remains unclear. Using directed pharmacological approaches in the mouse insulinoma-6 (Min6) cell line, we demonstrate that elevating nuclear O-GlcNAc increases intracellular insulin levels and preserves glucose-stimulated insulin secretion during chronic hyperglycemia. The molecular mechanism for these observed changes appears to be, at least in part, due to elevated O-GlcNAc-dependent increases in Ins1 and Ins2 mRNA levels via elevations in histone H3 transcriptional activation marks. Furthermore, RNA deep sequencing reveals that this mechanism of altered gene transcription is restricted and that the majority of genes regulated by elevated O-GlcNAc levels are similarly regulated by a shift from euglycemic to hyperglycemic conditions. These findings implicate the O-GlcNAc modification as a potential mechanism for hyperglycemic-regulated gene expression in the beta cell.
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Affiliation(s)
- Sean P Durning
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
| | - Heather Flanagan-Steet
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
| | - Nripesh Prasad
- HudsonAlpha Institute of Biotechnology, Genomic Services Laboratory, Huntsville, Alabama 35806
| | - Lance Wells
- From the Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-1516 and
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Kanekura K, Ou J, Hara T, Zhu LJ, Urano F. Research resource: Monitoring endoplasmic reticulum membrane integrity in β-cells at the single-cell level. Mol Endocrinol 2015; 29:473-80. [PMID: 25584413 DOI: 10.1210/me.2014-1260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Endoplasmic reticulum (ER) membrane integrity is an emerging target for human chronic diseases associated with ER stress. Despite the underlying importance of compromised ER membrane integrity in disease states, the entire process leading to ER membrane permeabilization and cell death is still not clear due to technical limitations. Here we describe a novel method for monitoring ER membrane integrity at the single-cell level in real time. Using a β-cell line expressing ER-targeted redox sensitive green fluorescent protein, we could identify a β-cell population undergoing ER membrane permeabilization induced by palmitate and could monitor cell fate and ER stress of these cells at the single-cell level. Our method could be used to develop a novel therapeutic modality targeting the ER membrane for ER-associated disorders, including β-cell death in diabetes, neurodegeneration, and Wolfram syndrome.
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Affiliation(s)
- Kohsuke Kanekura
- Department of Medicine (K.K., T.H., F.U.), Division of Endocrinology, Metabolism, and Lipid Research, and Department of Pathology and Immunology (F.U.), Washington University School of Medicine, St Louis, Missouri 63110; and Programs in Gene Function and Expression, Molecular Medicine, and Bioinformatics and Integrative Biology (J.O., L.J.Z.), University of Massachusetts Medical School, Worcester, Massachusetts 01655
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Berná G, Oliveras-López MJ, Jurado-Ruíz E, Tejedo J, Bedoya F, Soria B, Martín F. Nutrigenetics and nutrigenomics insights into diabetes etiopathogenesis. Nutrients 2014; 6:5338-69. [PMID: 25421534 PMCID: PMC4245593 DOI: 10.3390/nu6115338] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 10/17/2014] [Accepted: 11/04/2014] [Indexed: 01/17/2023] Open
Abstract
Diabetes mellitus (DM) is considered a global pandemic, and the incidence of DM continues to grow worldwide. Nutrients and dietary patterns are central issues in the prevention, development and treatment of this disease. The pathogenesis of DM is not completely understood, but nutrient-gene interactions at different levels, genetic predisposition and dietary factors appear to be involved. Nutritional genomics studies generally focus on dietary patterns according to genetic variations, the role of gene-nutrient interactions, gene-diet-phenotype interactions and epigenetic modifications caused by nutrients; these studies will facilitate an understanding of the early molecular events that occur in DM and will contribute to the identification of better biomarkers and diagnostics tools. In particular, this approach will help to develop tailored diets that maximize the use of nutrients and other functional ingredients present in food, which will aid in the prevention and delay of DM and its complications. This review discusses the current state of nutrigenetics, nutrigenomics and epigenomics research on DM. Here, we provide an overview of the role of gene variants and nutrient interactions, the importance of nutrients and dietary patterns on gene expression, how epigenetic changes and micro RNAs (miRNAs) can alter cellular signaling in response to nutrients and the dietary interventions that may help to prevent the onset of DM.
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Affiliation(s)
- Genoveva Berná
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - María Jesús Oliveras-López
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Enrique Jurado-Ruíz
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Juan Tejedo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), CIBER of Diabetes and Associated Metabolic Diseases, Instituto de Salud Carlos III, Madrid 28029, Spain.
| | - Francisco Bedoya
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), CIBER of Diabetes and Associated Metabolic Diseases, Instituto de Salud Carlos III, Madrid 28029, Spain.
| | - Bernat Soria
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Franz Martín
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
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21
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Wang J, Xiao R. G protein-coupled receptors in energy homeostasis. SCIENCE CHINA-LIFE SCIENCES 2014; 57:672-80. [PMID: 24969703 DOI: 10.1007/s11427-014-4694-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 06/13/2014] [Indexed: 12/25/2022]
Abstract
G-protein coupled receptors (GPCRs) compromise the largest membrane protein superfamily which play vital roles in physiological and pathophysiological processes including energy homeostasis. Moreover, they also represent the up-to-date most successful drug target. The gut hormone GPCRs, such as glucagon receptor and GLP-1 receptor, have been intensively studied for their roles in metabolism and respective drugs have developed for the treatment of metabolic diseases such as type 2 diabetes (T2D). Along with the advances of biomedical research, more GPCRs have been found to play important roles in the regulation of energy homeostasis from nutrient sensing, appetite control to glucose and fatty acid metabolism with various mechanisms. The investigation of their biological functions will not only improve our understanding of how our body keeps the balance of energy intake and expenditure, but also highlight the possible drug targets for the treatment of metabolic diseases. The present review summarizes GPCRs involved in the energy control with special emphasis on their pathophysiological roles in metabolic diseases and hopefully triggers more intensive and systematic investigations in the field so that a comprehensive network control of energy homeostasis will be revealed, and better drugs will be developed in the foreseeable future.
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Affiliation(s)
- Jue Wang
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China,
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22
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Roles of Sphingolipid Metabolism in Pancreatic β Cell Dysfunction Induced by Lipotoxicity. J Clin Med 2014; 3:646-62. [PMID: 26237395 PMCID: PMC4449690 DOI: 10.3390/jcm3020646] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/10/2014] [Accepted: 04/11/2014] [Indexed: 12/31/2022] Open
Abstract
Pancreatic β cells secrete insulin in order to maintain glucose homeostasis. However, various environmental stresses such as obesity have been shown to induce loss of secretory responsiveness in pancreatic β cells and pancreatic β cell apoptosis which can favor the development of type 2 diabetes (T2D). Indeed, elevated levels of free fatty acids (FFAs) have been shown to induce β cell apoptosis. Importantly, the chronic adverse effects of FFAs on β cell function and viability are potentiated in the presence of hyperglycaemia, a phenomenon that has been termed gluco-lipotoxicity. The molecular mechanisms underlying the pathogenesis of gluco-lipotoxicity in pancreatic β cells are not completely understood. Recent studies have shown that sphingolipid metabolism plays a key role in gluco-lipotoxicity induced apoptosis and loss of function of pancreatic β cells. The present review focuses on how the two main sphingolipid mediators, ceramides and sphingoid base-1-phosphates, regulate the deleterious effects of gluco-lipotoxicity on pancreatic β cells. The review highlights the role of a sphingolipid biostat on the dysregulation of β cell fate and function induced by gluco-lipotoxicity, offering the possibility of new therapeutic targets to prevent the onset of T2D.
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23
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Nagao M, Asai A, Inaba W, Kawahara M, Shuto Y, Kobayashi S, Sanoyama D, Sugihara H, Yagihashi S, Oikawa S. Characterization of pancreatic islets in two selectively bred mouse lines with different susceptibilities to high-fat diet-induced glucose intolerance. PLoS One 2014; 9:e84725. [PMID: 24454742 PMCID: PMC3890274 DOI: 10.1371/journal.pone.0084725] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 11/18/2013] [Indexed: 12/26/2022] Open
Abstract
Hereditary predisposition to diet-induced type 2 diabetes has not yet been fully elucidated. We recently established 2 mouse lines with different susceptibilities (resistant and prone) to high-fat diet (HFD)-induced glucose intolerance by selective breeding (designated selectively bred diet-induced glucose intolerance-resistant [SDG-R] and -prone [SDG-P], respectively). To investigate the predisposition to HFD-induced glucose intolerance in pancreatic islets, we examined the islet morphological features and functions in these novel mouse lines. Male SDG-P and SDG-R mice were fed a HFD for 5 weeks. Before and after HFD feeding, glucose tolerance was evaluated by oral glucose tolerance test (OGTT). Morphometry and functional analyses of the pancreatic islets were also performed before and after the feeding period. Before HFD feeding, SDG-P mice showed modestly higher postchallenge blood glucose levels and lower insulin increments in OGTT than SDG-R mice. Although SDG-P mice showed greater β cell proliferation than SDG-R mice under HFD feeding, SDG-P mice developed overt glucose intolerance, whereas SDG-R mice maintained normal glucose tolerance. Regardless of whether it was before or after HFD feeding, the isolated islets from SDG-P mice showed impaired glucose- and KCl-stimulated insulin secretion relative to those from SDG-R mice; accordingly, the expression levels of the insulin secretion-related genes in SDG-P islets were significantly lower than those in SDG-R islets. These findings suggest that the innate predispositions in pancreatic islets may determine the susceptibility to diet-induced diabetes. SDG-R and SDG-P mice may therefore be useful polygenic animal models to study the gene–environment interactions in the development of type 2 diabetes.
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Affiliation(s)
- Mototsugu Nagao
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Akira Asai
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Wataru Inaba
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Momoyo Kawahara
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Yuki Shuto
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Shunsuke Kobayashi
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Daisuke Sanoyama
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Hitoshi Sugihara
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Soroku Yagihashi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Shinichi Oikawa
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
- * E-mail:
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Li X, Chen Y, Liu J, Yang G, Zhao J, Liao G, Shi M, Yuan Y, He S, Lu Y, Cheng J. Serum metabolic variables associated with impaired glucose tolerance induced by high-fat-high-cholesterol diet in Macaca mulatta. Exp Biol Med (Maywood) 2013; 237:1310-21. [PMID: 23239442 DOI: 10.1258/ebm.2012.012157] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Dyslipidemia caused by 'Western-diet pattern' is a strong risk factor for the onset of diabetes. This study aimed to disclose the relationship between the serum metabolite changes induced by habitual intake of high-fat and high-cholesterol (HFHC) diet and the development of impaired glucose tolerance (IGT) and insulin resistance through animal models of Macaca mulatta. Sixteen M. mulatta (six months old) were fed a control diet or a HFHC diet for 18 months. The diet effect on serum metabolic profiles was investigated by longitudinal research. Islet function was assessed by intravenous glucose tolerance and hyperinsulinemic-euglycemic clamp test. Metabonomics were determined by (1)H proton nuclear magnetic resonance spectroscopy. Prolonged diet-dependent hyperlipidemia facilitated visceral fat accumulation in liver and skeletal muscle and disorder of glucose homeostasis in juvenile monkeys. Glucose disappearance rate (K(Glu)) and insulin response to the glucose challenge effects in HFHC monkeys were significantly lower than in control monkeys. Otherwise, serum trimethylamine-N-oxide (TMAO), lactate and leucine/isoleucine were significantly higher in HFHC monkeys. Sphingomyelin and choline were the most positively correlated with K(Glu) (R(2) = 0.778), as well as negative correlation (R(2) = 0.64) with total cholesterol. The HFHC diet induced visceral fat, abnormal lipid metabolism and IGT prior to weight gain and body fat content increase in juvenile monkeys. We suggest that increased serum metabolites, such as TMAO, lactate, branched-chain amino acids and decreased sphingomyelin and choline, may serve as possible predictors for the evaluation of IGT and insulin resistance risks in the prediabetic state.
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Affiliation(s)
- Xinli Li
- Key Laboratory of Transplant Engineering and Immunology, Ministry of Health, Regenerative Medicine Research Center, Sichuan, PR China
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25
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Kwon MJ, Chung HS, Yoon CS, Lee EJ, Kim TK, Lee SH, Ko KS, Rhee BD, Kim MK, Park JH. Low glibenclamide concentrations affect endoplasmic reticulum stress in INS-1 cells under glucotoxic or glucolipotoxic conditions. Korean J Intern Med 2013; 28:339-46. [PMID: 23682228 PMCID: PMC3654132 DOI: 10.3904/kjim.2013.28.3.339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 04/05/2012] [Accepted: 04/17/2012] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND/AIMS β-Cell apoptosis caused by increased endoplasmic reticulum (ER) stress is an important pathogenic component of type 2 diabetes mellitus. In theory, sulfonylureas, used for the treatment of diabetes, can contribute to ER stress. We assessed changes in ER stress in pancreatic β-cells under glucotoxic or glucolipotoxic conditions using low concentrations of the sulfonylurea, glibenclamide (GB). METHODS Low concentrations of GB (10 or 100 nM) were added to INS-1 cells cultured under glucotoxic or glucolipotoxic conditions. The degree of viability, level of apoptosis and levels of markers associated with ER stress were measured. RESULTS Apoptosis decreased in response to low concentrations of GB under glucolipotoxic but not glucotoxic conditions. Most ER stress markers decreased upon the addition of GB. Under glucotoxic conditions, changes in the levels of ER stress markers were not consistent. However, all decreased significantly under glucolipotoxic conditions. CONCLUSIONS Low concentrations of GB exerted antiapoptotic effects through the attenuation of ER stress under glucolipotoxic conditions.
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Affiliation(s)
- Min Jeong Kwon
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Hye Suk Chung
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Chang Shin Yoon
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Eun Ju Lee
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Tae Kyun Kim
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Soon Hee Lee
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Kyung Soo Ko
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Byoung Doo Rhee
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Mi Kyung Kim
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
| | - Jeong Hyun Park
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University College of Medicine, Busan, Korea
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26
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Cui W, Ma J, Wang X, Yang W, Zhang J, Ji Q. Free fatty acid induces endoplasmic reticulum stress and apoptosis of β-cells by Ca2+/calpain-2 pathways. PLoS One 2013; 8:e59921. [PMID: 23527285 PMCID: PMC3604010 DOI: 10.1371/journal.pone.0059921] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Accepted: 02/19/2013] [Indexed: 12/28/2022] Open
Abstract
Dysfunction of β-cells is a major characteristic in the pathogenesis of type 2 diabetes mellitus (T2DM). The combination of obesity and T2DM is associated with elevated plasma free fatty acids (FFAs). However, molecular mechanisms linking FFAs to β-cell dysfunction remain poorly understood. In the present study, we identified that the major endoplasmic reticulum stress (ERS) marker, Grp78 and ERS-induced apoptotic factor, CHOP, were time-dependently increased by exposure of β-TC3 cells to FFA. The expression of ATF6 and the phosphorylation levels of PERK and IRE1, which trigger ERS signaling, markedly increased after FFA treatments. FFA treatments increased cell apoptosis by inducing ERS in β-TC3 cells. We also found that FFA-induced ERS was mediated by the store-operated Ca2+ entry through promoting the association of STIM1 and Orai1. Moreover, calpain-2 was required for FFA-induced expression of CHOP and activation of caspase-12 and caspase-3, thus promoting cell apoptosis in β-TC3 cells. Together, these results reveal pivotal roles for Ca2+/calpain-2 pathways in modulating FFA-induced β-TC3 cell ERS and apoptosis.
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Affiliation(s)
- Wei Cui
- Department of Endocrinology and Metabolism, Xijing Hospital, Fourth Military Medical University, Xi’an, China
| | - Jie Ma
- Department of Neurosurgery, Tangdu Hospital, Forth Military Medical University, Xi’an, China
| | - Xingqin Wang
- Department of Neurosurgery, Tangdu Hospital, Forth Military Medical University, Xi’an, China
| | - Wenjuan Yang
- Department of Endocrinology and Metabolism, Xijing Hospital, Fourth Military Medical University, Xi’an, China
| | - Jing Zhang
- No. 371 Central Hospital of People’s Liberation Army, Xinxiang, China
| | - Qiuhe Ji
- Department of Endocrinology and Metabolism, Xijing Hospital, Fourth Military Medical University, Xi’an, China
- * E-mail:
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Feng XT, Leng J, Xie Z, Li SL, Zhao W, Tang QL. GPR40: a therapeutic target for mediating insulin secretion (review). Int J Mol Med 2012; 30:1261-6. [PMID: 23023155 DOI: 10.3892/ijmm.2012.1142] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 08/26/2012] [Indexed: 11/05/2022] Open
Abstract
G-protein-coupled receptor 40 (GPR40), known as free fatty acid receptor 1, is mainly expressed in pancreatic β-cells and activated by medium- and long-chain fatty acids. Increasing evidence indicates that the activation of GPR40 in cells causes insulin secretion, and GPR40 has become an attractive therapeutic target for type 2 diabetes. Recently, certain novel GPR40 agonists have been identified that regulate glucose-stimulated insulin secretion, leading to the development of new drugs for the treatment of type 2 diabetes. In this review, we focus on progress in the physiological role of GPR40 and potential drugs targeting GPR40 over the past decade.
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Affiliation(s)
- Xiao-Tao Feng
- Guangxi Scientific Experimental Center of Traditional Chinese Medicine, Guangxi University of Chinese Medicine, Nanning, P.R. China
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Inhibition of fatty acid translocase cluster determinant 36 (CD36), stimulated by hyperglycemia, prevents glucotoxicity in INS-1 cells. Biochem Biophys Res Commun 2012; 420:462-6. [PMID: 22430143 DOI: 10.1016/j.bbrc.2012.03.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 03/05/2012] [Indexed: 11/24/2022]
Abstract
The purpose of the present study was to determine whether exposure of pancreatic islets to glucotoxic conditions changes fatty acid translocase cluster determinant 36 (CD36) and examine the role of CD36 on the induction of glucotoxicity. We measured the changes of CD36 and insulin secretion in high glucose (30 mM) exposed INS-1 cells and CD36 suppressed INS-1 cells by transfection of CD36 siRNA. The intracellular peroxide level of INS-1 cells increased in the high glucose media compared to normal glucose (5.6mM) media. The mRNA levels of insulin and PDX-1, as well as glucose stimulated insulin secretion (GSIS) were decreased in INS-1 cells exposed to high glucose media compared to normal glucose media, while CD36 and palmitate uptake were significantly elevated with exposure to high glucose media for 12h. The inhibition of CD36 reversed the decreased GSIS and intracellular peroxide level in INS-1 cells. These results suggest that high glucose may exacerbate glucotoxicity via increasing fatty acid influx by elevation of CD36 expression, and that CD36 may be a possible target molecule for preventing glucotoxicity in pancreatic beta-cells.
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Mediation of glucolipotoxicity in INS-1 rat insulinoma cells by small heterodimer partner interacting leucine zipper protein (SMILE). Biochem Biophys Res Commun 2012; 419:768-73. [PMID: 22387546 DOI: 10.1016/j.bbrc.2012.02.098] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 02/16/2012] [Indexed: 12/25/2022]
Abstract
Sustained elevations of glucose and free fatty acid concentration have deleterious effects on pancreatic beta cell function. One of the hallmarks of such glucolipotoxicity is a reduction in insulin gene expression, resulting from decreased insulin promoter activity. Sterol regulatory element binding protein-1c (SREBP-1c), a lipogenic transcription factor, is related to the development of beta cell dysfunction caused by elevated concentrations of glucose and free fatty acid. Small heterodimer partner (SHP) interacting leucine zipper protein (SMILE), also known as Zhangfei, is a novel protein which interacts with SHP that mediates glucotoxicity in INS-1 rat insulinoma cells. Treatment of INS-1 cells with high concentrations of glucose and palmitate increased SREBP-1c and SMILE expression, and decreased insulin gene expression. Adenovirus-mediated overexpression of SREBP-1c in INS-1 cells induced SMILE expression. Moreover, adenovirus-mediated overexpression of SMILE (Ad-SMILE) in INS-1 cells impaired glucose-stimulated insulin secretion as well as insulin gene expression. Ad-SMILE overexpression also inhibited the expression of beta-cell enriched transcription factors including pancreatic duodenal homeobox factor-1, beta cell E box transactivator 2 and RIPE3b1/MafA, in INS-1 cells. Finally, in COS-1 cells, expression of SMILE inhibited the insulin promoter activity induced by these same beta-cell enriched transcription factors. These results collectively suggest that SMILE plays an important role in the development of beta cell dysfunction induced by glucolipotoxicity.
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Weickert MO. Nutritional modulation of insulin resistance. SCIENTIFICA 2012; 2012:424780. [PMID: 24278690 PMCID: PMC3820526 DOI: 10.6064/2012/424780] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 09/02/2012] [Indexed: 05/15/2023]
Abstract
Insulin resistance has been proposed as the strongest single predictor for the development of Type 2 Diabetes (T2DM). Chronic oversupply of energy from food, together with inadequate physical activity, have been recognized as the most relevant factors leading to overweight, abdominal adiposity, insulin resistance, and finally T2DM. Conversely, energy reduced diets almost invariably to facilitate weight loss and reduce abdominal fat mass and insulin resistance. However, sustained weight loss is generally difficult to achieve, and distinct metabolic characteristics in patients with T2DM further compromise success. Therefore, investigating the effects of modulating the macronutrient composition of isoenergetic diets is an interesting concept that may lead to additional important insights. Metabolic effects of various different dietary concepts and strategies have been claimed, but results from randomized controlled studies and particularly from longer-term-controlled interventions in humans are often lacking. However, some of these concepts are supported by recent research, at least in animal models and short-term studies in humans. This paper provides an update of the current literature regarding the role of nutrition in the modulation of insulin resistance, which includes the discussion of weight-loss-independent metabolic effects of commonly used dietary concepts.
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Affiliation(s)
- Martin O. Weickert
- Warwickshire Institute for the Study of Diabetes, Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry CV2 2DX, UK
- Division of Metabolic and Vascular Health, Warwick Medical School, The University of Warwick, Coventry CV4 7AL, UK
- *Martin O. Weickert:
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Ceramide synthase 4 and de novo production of ceramides with specific N-acyl chain lengths are involved in glucolipotoxicity-induced apoptosis of INS-1 β-cells. Biochem J 2011; 438:177-89. [PMID: 21592087 DOI: 10.1042/bj20101386] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Pancreatic β-cell apoptosis induced by palmitate requires high glucose concentrations. Ceramides have been suggested to be important mediators of glucolipotoxicity-induced β-cell apoptosis. In INS-1 β-cells, 0.4 mM palmitate with 5 mM glucose increased the levels of dihydrosphingosine and dihydroceramides, two lipid intermediates in the de novo biosynthesis of ceramides, without inducing apoptosis. Increasing glucose concentrations to 30 mM amplified palmitate-induced accumulation of dihydrosphingosine and the formation of (dihydro)ceramides. Of note, glucolipotoxicity specifically induced the formation of C(18:0), C(22:0) and C(24:1) (dihydro)ceramide molecular species, which was associated with the up-regulation of CerS4 (ceramide synthase 4) levels. Fumonisin-B1, a ceramide synthase inhibitor, partially blocked apoptosis induced by glucolipotoxicity. In contrast, apoptosis was potentiated in the presence of D,L-threo-1-phenyl-2-palmitoylamino-3-morpholinopropan-1-ol, an inhibitor of glucosylceramide synthase. Moreover, overexpression of CerS4 amplified ceramide production and apoptosis induced by palmitate with 30 mM glucose, whereas down-regulation of CerS4 by siRNA (short interfering RNA) reduced apoptosis. CerS4 also potentiates ceramide accumulation and apoptosis induced by another saturated fatty acid: stearate. Collectively, our results suggest that glucolipotoxicity induces β-cell apoptosis through a dual mechanism involving de novo ceramide biosynthesis and the formation of ceramides with specific N-acyl chain lengths rather than an overall increase in ceramide content.
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Kwon MJ, Chung HS, Yoon CS, Ko JH, Jun HJ, Kim TK, Lee SH, Ko KS, Rhee BD, Kim MK, Park JH. The Effects of Glyburide on Apoptosis and Endoplasmic Reticulum Stress in INS-1 Cells in a Glucolipotoxic Condition. Diabetes Metab J 2011; 35:480-8. [PMID: 22111039 PMCID: PMC3221023 DOI: 10.4093/dmj.2011.35.5.480] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/29/2010] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND β-cell death due to endoplasmic reticulum (ER) stress has been regarded as an important pathogenic component of type 2 diabetes. The possibility has been suggested that sulfonylurea, currently being used as one of the main oral hypoglycemic agents of type 2 diabetes, increases ER stress, which could lead to sulfonylurea failure. The authors of the present study examined ER stress of β-cells in a glucolipotoxic condition using glyburide (GB) in an environment mimicking type 2 diabetes. METHODS Apoptosis was induced by adding various concentrations of GB (0.001 to 200 µM) to a glucolipotoxic condition using 33 mM glucose, and the effects of varied concentrations of palmitate were evaluated via annexin V staining. The markers of ER stress and pro-apoptotic markers were assessed by Western blotting and semi-quantitative reverse transcription-polymerase chain reaction. Additionally, the anti-apoptotic markers were evaluated. RESULTS Addition of any concentration of GB in 150 µM palmitate and 33 mM glucose did not increase apoptosis. The expression of phosphorylated eukaryotic initiation factor (eIF-2α) was increased and cleaved caspase 3 was decreased by adding GB to a glucolipotoxic condition. However, other ER stress-associated markers such as Bip-1, X-box binding protein-1, ATF-4 and C/EBP-homologous protein transcription factor and anti-apoptotic markers phosphor-p85 phosphatidylinositol 3-kinase and phosphorylation of Akt did not change significantly. CONCLUSION GB did not show further deleterious effects on the degree of apoptosis or ER stress of INS-1 cells in a glucolipotoxic condition. Increased phosphorylation of eIF-2α may attenuate ER stress for adaptation to increased ER protein load.
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Affiliation(s)
- Min Jeong Kwon
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Hye Suk Chung
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Chang Shin Yoon
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Jung Hae Ko
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Hae Jung Jun
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Tae Kyun Kim
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Soon Hee Lee
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Kyung Soo Ko
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Byoung Doo Rhee
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
| | - Mi Kyung Kim
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
- Department of Internal Medicine, Maryknoll Medical Center, Busan, Korea
| | - Jeong Hyun Park
- Paik Diabetes Center, Department of Internal Medicine, Inje University College of Medicine, Busan, Korea
- Molecular Therapy Lab, Paik Memorial Institute for Clinical Research, Inje University, Busan, Korea
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Yuan H, Zhang X, Huang X, Lu Y, Tang W, Man Y, Wang S, Xi J, Li J. NADPH oxidase 2-derived reactive oxygen species mediate FFAs-induced dysfunction and apoptosis of β-cells via JNK, p38 MAPK and p53 pathways. PLoS One 2010; 5:e15726. [PMID: 21209957 PMCID: PMC3012098 DOI: 10.1371/journal.pone.0015726] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 11/20/2010] [Indexed: 01/08/2023] Open
Abstract
Dysfunction of β-cell is one of major characteristics in the pathogenesis of type 2 diabetes. The combination of obesity and type 2 diabetes, characterized as ‘diabesity’, is associated with elevated plasma free fatty acids (FFAs). Oxidative stress has been implicated in the pathogenesis of FFA-induced β-cell dysfunction. However, molecular mechanisms linking between reactive oxygen species (ROS) and FFA-induced β-cell dysfunction and apoptosis are less clear. In the present study, we test the hypothesis that NOX2-derived ROS may play a critical role in dysfunction and apoptosis of β-cells induced by FFA. Our results show that palmitate and oleate (0.5 mmol/L, 48 h) induced JNK activation and AKT inhibition which resulted in decreased phosphorylation of FOXO1 following nuclear localization and the nucleocytoplasmic translocation of PDX-1, leading to the reducing of insulin and ultimately dysfunction of pancreatic NIT-1 cells. We also found that palmitate and oleate stimulated apoptosis of NIT-1 cells through p38MAPK, p53 and NF-κB pathway. More interestingly, our data suggest that suppression of NOX2 may restore FFA-induced dysfunction and apoptosis of NIT-1 cells. Our findings provide a new insight of the NOX2 as a potential new therapeutic target for preservation of β-cell mass and function.
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Affiliation(s)
- Huiping Yuan
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
| | - Xiaoyong Zhang
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Xiuqing Huang
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
| | - Yonggang Lu
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Weiqing Tang
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
| | - Yong Man
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
| | - Shu Wang
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
| | - Jianzhong Xi
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
- * E-mail: (JL); (JX)
| | - Jian Li
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, Beijing, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
- * E-mail: (JL); (JX)
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Feng X, Wang W, Liu J, Liu Y. β-Arrestins: multifunctional signaling adaptors in type 2 diabetes. Mol Biol Rep 2010; 38:2517-28. [PMID: 21086182 DOI: 10.1007/s11033-010-0389-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 11/08/2010] [Indexed: 02/06/2023]
Abstract
β-arrestins are not only well-known negative regulators of G protein-coupled receptor (GPCR) signaling, but also important adaptors in modulating the strength and duration of cellular signaling by scaffolding and interacting with a lot of cytoplasmic proteins. While β-arrestins are rather well described signal-mediated molecules, they are not generally associated with insulin signaling. But recent work has confirmed the difference from original thought. The current review aims to explore the emerging roles for β-arrestins in regulating insulin action, inflammatory signal pathway and other cellular signaling which are associated with type 2 diabetes.
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Affiliation(s)
- Xiaotao Feng
- Institute of Chinese Integrative Medicine, Huashan Hospital, Fudan University, No.12 Wulumuqi Zhong Road, Shanghai, 200040, China
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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: 269] [Impact Index Per Article: 17.9] [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.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Department of Medicine, University of Montreal, Montreal, QC, Canada.
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Fowler MA, Champagne CD, Houser DS, Crocker DE. Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris). ACTA ACUST UNITED AC 2008; 211:2943-9. [PMID: 18775931 DOI: 10.1242/jeb.018176] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Northern elephant seals exhibit the rare strategy of fasting and lactating concomitantly. We investigated hormonal regulation of glucose clearance in northern elephant seals using glucose tolerance tests (GTT) performed early in lactation and again just prior to weaning. For comparison, identical measurements were made on separate females late in the molt fast. Serial blood samples were used to assess glucose clearance and hormone responses for 3 h post glucose injection. Plasma glucose remained elevated at the end of the sampling period in all groups. Glucose clearance rates were not significantly different among test groups. A significant insulin response was observed in early lactation, no significant response was observed late in lactation and an intermediate response was observed late in the molt fast. The insulin response to a glucose load decreased with adipose tissue proportions. Plasma glucagon decreased significantly following GTT in early and late lactation, although the magnitude of the depression was small in comparison to other species. Hypoinsulemia may be critical to facilitate net lipolysis late in lactation. Consistently low glucose clearance among test groups suggests insulin insensitivity within peripheral tissues. Glucagon suppression independent of insulin release suggests modification of the typical insulin-glucagon counter-regulation. These findings suggest that metabolic features of diabetic-like conditions may be adaptive in the context of long-term fasting.
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Affiliation(s)
- Melinda A Fowler
- Sonoma State University, Biology Department, 1801 E. Cotati Ave, Rohnert Park, CA 94928, USA.
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Abstract
Type 2 diabetes mellitus is a complex disease characterized by beta-cell failure in the setting of insulin resistance. In early stages of the disease, pancreatic beta-cells adapt to insulin resistance by increasing mass and function. As nutrient excess persists, hyperglycemia and elevated free fatty acids negatively impact beta-cell function. This happens by numerous mechanisms, including the generation of reactive oxygen species, alterations in metabolic pathways, increases in intracellular calcium and the activation of endoplasmic reticulum stress. These processes adversely affect beta-cells by impairing insulin secretion, decreasing insulin gene expression and ultimately causing apoptosis. In this review, we will first discuss the regulation of beta-cell mass during normal conditions. Then, we will discuss the mechanisms of beta-cell failure, including glucotoxicity, lipotoxicity and endoplasmic reticulum stress. Further research into mechanisms will reveal the key modulators of beta-cell failure and thus identify possible novel therapeutic targets. Type 2 diabetes mellitus is a multifactorial disease that has greatly risen in prevalence in part due to the obesity and inactivity that characterize the modern Western lifestyle. Pancreatic beta-cells possess the potential to greatly expand their function and mass in both physiologic and pathologic states of nutrient excess and increased insulin demand. beta-cell response to nutrient excess occurs by several mechanisms, including hypertrophy and proliferation of existing beta-cells, increased insulin production and secretion, and formation of new beta-cells from progenitor cells [1, 2]. Failure of pancreatic beta-cells to adequately expand in settings of increased insulin demand results in hyperglycemia and diabetes. In this review, we will first discuss the factors involved in beta-cell growth and then discuss the mechanisms by which beta-cell expansion fails and leads to beta-cell failure and diabetes (Fig. 1).
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Affiliation(s)
- KJ Chang-Chen
- Washington University School of Medicine, Division of Endocrinology, Metabolism & Lipid Research, St. Louis, Missouri, USA
| | - R Mullur
- Division of Medical Education, Department of Internal Medicine, Washington University School of Medicine
| | - E Bernal-Mizrachi
- To whom correspondence should be addressed: Ernesto Bernal-Mizrachi, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8127, St. Louis, MO 63110, USA. Phone: (314) 362-7693 Fax: (314) 747-2692
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Nino-Fong R, Collins T, Chan C. Nutrigenomics, beta-cell function and type 2 diabetes. Curr Genomics 2008; 8:1-29. [PMID: 18645625 PMCID: PMC2474685 DOI: 10.2174/138920207780076947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 08/12/2006] [Accepted: 10/13/2006] [Indexed: 01/15/2023] Open
Abstract
INTRODUCTION The present investigation was designed to investigate the accuracy and precision of lactate measurement obtained with contemporary biosensors (Chiron Diagnostics, Nova Biomedical) and standard enzymatic photometric procedures (Sigma Diagnostics, Abbott Laboratories, Analyticon). MATERIALS AND METHODS Measurements were performed in vitro before and after the stepwise addition of 1 molar sodium lactate solution to samples of fresh frozen plasma to systematically achieve lactate concentrations of up to 20 mmol/l. RESULTS Precision of the methods investigated varied between 1% and 7%, accuracy ranged between 2% and -33% with the variability being lowest in the Sigma photometric procedure (6%) and more than 13% in both biosensor methods. CONCLUSION Biosensors for lactate measurement provide adequate accuracy in mean with the limitation of highly variable results. A true lactate value of 6 mmol/l was found to be presented between 4.4 and 7.6 mmol/l or even with higher difference. Biosensors and standard enzymatic photometric procedures are only limited comparable because the differences between paired determinations presented to be several mmol. The advantage of biosensors is the complete lack of preanalytical sample preparation which appeared to be the major limitation of standard photometry methods.
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Affiliation(s)
- R Nino-Fong
- Department of Biomedical Sciences, University of Prince Edward Island, Charlottetown, PE C1A 4P3 Canada
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Abstract
Glucotoxicity, lipotoxicity, and glucolipotoxicity are secondary phenomena that are proposed to play a role in all forms of type 2 diabetes. The underlying concept is that once the primary pathogenesis of diabetes is established, probably involving both genetic and environmental forces, hyperglycemia and very commonly hyperlipidemia ensue and thereafter exert additional damaging or toxic effects on the beta-cell. In addition to their contribution to the deterioration of beta-cell function after the onset of the disease, elevations of plasma fatty acid levels that often accompany insulin resistance may, as glucose levels begin to rise outside of the normal range, also play a pathogenic role in the early stages of the disease. Because hyperglycemia is a prerequisite for lipotoxicity to occur, the term glucolipotoxicity, rather than lipotoxicity, is more appropriate to describe deleterious effects of lipids on beta-cell function. In vitro and in vivo evidence supporting the concept of glucotoxicity is presented first, as well as a description of the underlying mechanisms with an emphasis on the role of oxidative stress. Second, we discuss the functional manifestations of glucolipotoxicity on insulin secretion, insulin gene expression, and beta-cell death, and the role of glucose in the mechanisms of glucolipotoxicity. Finally, we attempt to define the role of these phenomena in the natural history of beta-cell compensation, decompensation, and failure during the course of type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Montreal Diabetes Research Center, CR-CHUM, Technopole Angus, 2901 Rachel Est, Montreal, Quebec, Canada H1W 4A4.
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40
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Effects of ethanol on pancreatic beta-cell death: interaction with glucose and fatty acids. Cell Biol Toxicol 2008; 25:141-52. [PMID: 18330713 DOI: 10.1007/s10565-008-9067-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 02/14/2008] [Indexed: 01/01/2023]
Abstract
Western lifestyle plays an important role in the prevalence of type 2 diabetes by causing insulin resistance and pancreatic beta-cell dysfunction, a prerequisite for the development of diabetes. High fat diet and alcohol are major components of the western diet. The aim of the present study was to investigate the effects of ethanol and fatty acids on beta-cell survival and metabolism. We treated the rat beta-cell line RINm5F with ethanol, a mixture of palmitic and oleic acids, or both. Reactive oxygen species (ROS) were determined by (5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate) (CM-H2DCFDA) fluorescence assay, and mitochondrial activity was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) reduction assay and by determining ATP production. Cell viability was assessed with a cell counter and trypan blue exclusion, and the mode of cell death by Hoechst33342 and propidium iodide staining. With both ethanol and fatty acid treatments, MTT reduction and ATP production decreased, whereas ROS production increased. Ethanol treatment had no effect on cell number, whereas fatty acid treatment reduced the cell number. Cell incubation with ethanol, fatty acids, or both increased the number of Hoechst 33342-positive nuclei. However, the majority of nuclei from fatty acid-treated cells were stained with propidium iodide, indicating a loss of plasma membrane integrity. We conclude that both ethanol and fatty acids generate cellular oxidative stress, and affect mitochondrial function in RINm5F beta-cells. However, ethanol causes beta-cell death by apoptosis, whereas fatty acids cause cell death predominantly by necrosis. It is not known whether these results are applicable to human beta-cells.
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41
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Hagman DK, Latour MG, Chakrabarti SK, Fontes G, Amyot J, Tremblay C, Semache M, Lausier JA, Roskens V, Mirmira RG, Jetton TL, Poitout V. Cyclical and alternating infusions of glucose and intralipid in rats inhibit insulin gene expression and Pdx-1 binding in islets. Diabetes 2008; 57:424-31. [PMID: 17991758 PMCID: PMC2979006 DOI: 10.2337/db07-1285] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Prolonged exposure of isolated islets of Langerhans to elevated levels of fatty acids, in the presence of high glucose, impairs insulin gene expression via a transcriptional mechanism involving nuclear exclusion of pancreas-duodenum homeobox-1 (Pdx-1) and loss of MafA expression. Whether such a phenomenon also occurs in vivo is unknown. Our objective was therefore to ascertain whether chronic nutrient oversupply inhibits insulin gene expression in vivo. RESEARCH DESIGN AND METHODS Wistar rats received alternating 4-h infusions of glucose and Intralipid for a total of 72 h. Control groups received alternating infusions of glucose and saline, saline and Intralipid, or saline only. Insulin and C-peptide secretion were measured under hyperglycemic clamps. Insulin secretion and gene expression were assessed in isolated islets, and beta-cell mass was quantified by morphometric analysis. RESULTS Neither C-peptide secretion nor insulin sensitivity was different among infusion regimens. Insulin content and insulin mRNA levels were lower in islets isolated from rats infused with glucose plus Intralipid. This was associated with reduced Pdx-1 binding to the endogenous insulin promoter, and an increased proportion of Pdx-1 localized in the cytoplasm versus the nucleus. In contrast, MafA mRNA and protein levels and beta-cell mass and proliferation were unchanged. CONCLUSIONS Cyclical and alternating infusions of glucose and Intralipid in normal rats inhibit insulin gene expression without affecting insulin secretion or beta-cell mass. We conclude that fatty acid inhibition of insulin gene expression, in the presence of high glucose, is an early functional defect that may contribute to beta-cell failure in type 2 diabetes.
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Affiliation(s)
- Derek K. Hagman
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - Martin G. Latour
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - Swarup K. Chakrabarti
- Department of Medicine and the Diabetes Center, University of Virginia, Charlottesville, Virginia
| | - Ghislaine Fontes
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - Julie Amyot
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - Caroline Tremblay
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - Meriem Semache
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
| | - James A. Lausier
- Division of Endocrinology, Diabetes and Metabolism, University of Vermont College of Medicine, Burlington, Vermont
| | - Violet Roskens
- Division of Endocrinology, Diabetes and Metabolism, University of Vermont College of Medicine, Burlington, Vermont
| | - Raghavendra G. Mirmira
- Department of Medicine and the Diabetes Center, University of Virginia, Charlottesville, Virginia
| | - Thomas L. Jetton
- Division of Endocrinology, Diabetes and Metabolism, University of Vermont College of Medicine, Burlington, Vermont
| | - Vincent Poitout
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada
- Departments of Medicine, Nutrition, and Biochemistry, Université de Montréal, Montréal, Quebec, Canada
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Vandewalle B, Moerman E, Lefebvre B, Defrance F, Gmyr V, Lukowiak B, Kerr Conte J, Pattou F. PPARγ-dependent and -independent effects of Rosiglitazone on lipotoxic human pancreatic islets. Biochem Biophys Res Commun 2008; 366:1096-101. [DOI: 10.1016/j.bbrc.2007.12.088] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 12/14/2007] [Indexed: 10/22/2022]
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Evans-Molina C, Garmey JC, Ketchum R, Brayman KL, Deng S, Mirmira RG. Glucose regulation of insulin gene transcription and pre-mRNA processing in human islets. Diabetes 2007; 56:827-35. [PMID: 17327454 PMCID: PMC3705758 DOI: 10.2337/db06-1440] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Glucose is the primary regulator of insulin granule release from pancreatic islets. In rodent islets, the role of glucose in the acute regulation of insulin gene transcription has remained unclear, primarily because the abundance and long half-life of insulin mRNA confounds analysis of transcription by traditional methods that measure steady-state mRNA levels. To investigate the nature of glucose-regulated insulin gene transcription in human islets, we first quantitated the abundance and half-lives of insulin mRNA and pre-mRNAs after addition of actinomycin D (to stop transcription). Our results indicated that intron 1-and intron 2-containing pre-mRNAs were approximately 150- and 2,000-fold less abundant, respectively, than mature mRNA. 5' intron 2-containing pre-mRNAs displayed half-lives of only approximately 60 min, whereas all other transcripts displayed more extended lifetimes. In response to elevated glucose, pre-mRNA species increased within 60 min, whereas increases in mature mRNA did not occur until 48 h, suggesting that measurement of mature mRNA species does not accurately reflect the acute transcriptional response of the insulin gene to glucose. The acute increase in pre-mRNA species was preceded by a sixfold increase in histone H4 acetylation and a twofold increase in RNA polymerase II recruitment at the insulin promoter. Taken together, our data suggest that pre-mRNA species may be a more reliable reflection of acute changes to human insulin gene transcriptional rates and that glucose acutely enhances insulin transcription by a mechanism that enhances chromatin accessibility and leads to recruitment of basal transcriptional machinery.
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Affiliation(s)
| | - James C. Garmey
- Department of Medicine, University of Virginia, Charlottesville, Virginia
| | - Robert Ketchum
- Department of Surgery, University of Virginia, Charlottesville, Virginia
| | - Kenneth L. Brayman
- Department of Surgery, University of Virginia, Charlottesville, Virginia
| | - Shaoping Deng
- Human Islet Laboratory, Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
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Arantes VC, Reis MAB, Latorraca MQ, Ferreira F, Stoppiglia LF, Carneiro EM, Boschero AC. Palmitic acid increase levels of pancreatic duodenal homeobox-1 and p38/stress-activated protein kinase in islets from rats maintained on a low protein diet. Br J Nutr 2007; 96:1006-12. [PMID: 17181874 DOI: 10.1017/bjn20061950] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A severe reduction in insulin release in response to glucose is consistently noticed in protein-deprived rats and is attributed partly to the chronic exposure to elevated levels of NEFA. Since the pancreatic and duodenal transcription factor homeobox 1 (PDX-1) is important for the maintenance of beta-cell physiology, and since PDX-1 expression is altered in the islets of rats fed a low protein (LP) diet and that rats show high NEFA levels, we assessed PDX-1 and insulin mRNA expression, as well as PDX-1 and p38/stress activated protein kinase 2 (SAPK2) protein expression, in islets from young rats fed low (6%) or normal (17%; control) protein diets and maintained for 48 h in culture medium containing 5.6 mmol/l glucose, with or without 0.6 mmol/l palmitic acid. We also measured glucose-induced insulin secretion and glucose metabolism. Insulin secretion by isolated islets in response to 16.7 mmol/l glucose was reduced in LP compared with control rats. In the presence of NEFA, there was an increase in insulin secretion in both groups. At 2.8 mmol/l glucose, the metabolism of this sugar was reduced in LP islets, regardless of the presence of this fatty acid. However, when challenged with 16.7 mmol/l glucose, LP and control islets showed a severe reduction in glucose oxidation in the presence of NEFA. The PDX-1 and insulin mRNA were significantly higher when NEFA was added to the culture medium in both groups of islets. The effect of palmitic acid on PDX-1 and p38/SAPK2 protein levels was similar in LP and control islets, but the increase was much more evident in LP islets. These results demonstrate the complex interrelationship between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis by affecting molecular mechanisms and stimulus/secretion coupling pathways.
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Affiliation(s)
- Vanessa C Arantes
- Departamento de Alimentos e Nutrição, Faculdade de Nutrição, Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil.
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Abstract
The secretagogue, the incretin-like, and the suppressive activities of long-chain fatty acids (LCFAs) in modulating insulin secretion in vivo and in cultured islets were simulated here by beta,beta'-tetramethyl-hexadecanedioic acid (M16) and alpha,alpha'-tetrachloro-tetradecanedioic acid (Cl-DICA). M16, but not Cl-DICA, serves as a substrate for ATP-dependent CoA thioesterification but is not further metabolized. M16, but not Cl-DICA, acted as a potent insulin secretagogue in islets cultured in basal but not high glucose. Short-term exposure to M16 or Cl-DICA resulted in activation of glucose- but not arginine-stimulated insulin secretion. Long-term exposure to M16, but not to Cl-DICA, resulted in suppression of glucose-, arginine-, and K(+)-stimulated insulin secretion; inhibition of glucose-induced proinsulin biosynthesis; and depletion of islets insulin. beta-Cell mass and islet ATP content remained unaffected. Hence, nonmetabolizable LCFA analogs may highlight discrete LCFA metabolites and pathways involved in modulating insulin secretion, which could be overlooked due to the rapid turnover of natural LCFA.
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Affiliation(s)
- Guy Las
- Department of Human Nutrition and Metabolism, Hebrew University Medical School, Jerusalem, P.O. box 12272, Israel 91120
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46
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Poitout V, Hagman D, Stein R, Artner I, Robertson RP, Harmon JS. Regulation of the insulin gene by glucose and fatty acids. J Nutr 2006; 136:873-6. [PMID: 16549443 PMCID: PMC1853259 DOI: 10.1093/jn/136.4.873] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The insulin gene is expressed almost exclusively in pancreatic beta-cells. Metabolic regulation of insulin gene expression enables the beta-cell to maintain adequate stores of intracellular insulin to sustain the secretory demand. Glucose is the major physiologic regulator of insulin gene expression; it coordinately controls the recruitment of transcription factors [e.g., pancreatic/duodenal homeobox-1 (PDX-1), mammalian homologue of avian MafA/L-Maf (MafA), Beta2/Neuro D (B2), the rate of transcription, and the stability of insulin mRNA. However, chronically elevated levels of glucose (glucotoxicity) and lipids (lipotoxicity) also contribute to the worsening of beta-cell function in type 2 diabetes, in part via inhibition of insulin gene expression. The mechanisms of glucotoxicity, which involve decreased binding activities of PDX-1 and MafA and increased activity of C/EBPbeta, are mediated by high-glucose-induced generation of oxidative stress. On the other hand, lipotoxicity is mediated by de novo ceramide synthesis and involves inhibition of PDX-1 nuclear translocation and MafA gene expression. Glucotoxicity and lipotoxicity have common targets, which makes their combination particularly harmful to insulin gene expression and beta-cell function in type 2 diabetes.
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Affiliation(s)
- Vincent Poitout
- Department of Medicine, University of Montréal, Montréal, QC, Canada.
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Hagman DK, Hays LB, Parazzoli SD, Poitout V. Palmitate inhibits insulin gene expression by altering PDX-1 nuclear localization and reducing MafA expression in isolated rat islets of Langerhans. J Biol Chem 2005; 280:32413-8. [PMID: 15944145 PMCID: PMC1361267 DOI: 10.1074/jbc.m506000200] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Abnormalities in lipid metabolism have been proposed as contributing factors to both defective insulin secretion from the pancreatic beta cell and peripheral insulin resistance in type 2 diabetes. Previously, we have shown that prolonged exposure of isolated rat islets of Langerhans to excessive fatty acid levels impairs insulin gene transcription. This study was designed to assess whether palmitate alters the expression and binding activity of the key regulatory factors pancreas-duodenum homeobox-1 (PDX-1), MafA, and Beta2, which respectively bind to the A3, C1, and E1 elements in the proximal region of the insulin promoter. Nuclear extracts of isolated rat islets cultured with 0.5 mm palmitate exhibited reduced binding activity to the A3 and C1 elements but not the E1 element. Palmitate did not affect the overall expression of PDX-1 but reduced its nuclear localization. In contrast, palmitate blocked the stimulation of MafA mRNA and protein expression by glucose. Combined adenovirus-mediated overexpression of PDX-1 and MafA in islets completely prevented the inhibition of insulin gene expression by palmitate. These results demonstrate that prolonged exposure of islets to palmitate inhibits insulin gene transcription by impairing nuclear localization of PDX-1 and cellular expression of MafA.
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Affiliation(s)
- Derek K. Hagman
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Lori B. Hays
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Susan D. Parazzoli
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
| | - Vincent Poitout
- From the Pacific Northwest Research Institute, Seattle, Washington 98122 and the
- Department of Medicine, University of Washington, Seattle, Washington 98195
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Assimacopoulos-Jeannet F. Fat storage in pancreas and in insulin-sensitive tissues in pathogenesis of type 2 diabetes. Int J Obes (Lond) 2005; 28 Suppl 4:S53-7. [PMID: 15592487 DOI: 10.1038/sj.ijo.0802857] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Obesity is associated with increased storage of lipids in nonadipose tissues like skeletal muscle, liver, and pancreatic beta cells. These lipids constitute a continuous source of long-chain fatty acyl CoA (LC-CoA) and derived metabolites like diacylglycerol and ceramide, acting as signalling molecules on protein kinases activities (in particular, the family of PKCs), ion channel, gene expression, and protein acylation. In skeletal muscle, the increase in LC-CoA and diacylglycerol translocates and activates specific protein kinase C (PKC) isoforms, which will phosphorylate IRS-1 on serine, preventing its phosphorylation on tyrosine and association with PI3 kinase. This interrupts the insulin signalling pathway leading to the stimulation of glucose transport. In pancreatic beta cells, short-term excess of fatty acids or LC-CoA activates PKC and also directly stimulates insulin exocytosis. Long-term exposure to free fatty acids (FFA) leads to an increased basal and blunted glucose-stimulated insulin secretion by affecting gene expression, increase in K(ATP) channel activity, and uncoupling of the mitochondria. In addition, the saturated FFA palmitate increases cell death by apoptosis via increase in ceramide synthesis.
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Affiliation(s)
- F Assimacopoulos-Jeannet
- Department of Cellular Physiology and Metabolism, Medical Faculty, University of Geneva, Switzerland.
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Iype T, Francis J, Garmey JC, Schisler JC, Nesher R, Weir GC, Becker TC, Newgard CB, Griffen SC, Mirmira RG. Mechanism of insulin Gene Regulation by the Pancreatic Transcription Factor Pdx-1. J Biol Chem 2005; 280:16798-807. [PMID: 15743769 DOI: 10.1074/jbc.m414381200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The homeodomain factor Pdx-1 regulates an array of genes in the developing and mature pancreas, but whether regulation of each specific gene occurs by a direct mechanism (binding to promoter elements and activating basal transcriptional machinery) or an indirect mechanism (via regulation of other genes) is unknown. To determine the mechanism underlying regulation of the insulin gene by Pdx-1, we performed a kinetic analysis of insulin transcription following adenovirus-mediated delivery of a small interfering RNA specific for pdx-1 into insulinoma cells and pancreatic islets to diminish endogenous Pdx-1 protein. insulin transcription was assessed by measuring both a long half-life insulin mRNA (mature mRNA) and a short half-life insulin pre-mRNA species by real-time reverse transcriptase-PCR. Following progressive knock-down of Pdx-1 levels, we observed coordinate decreases in pre-mRNA levels (to about 40% of normal levels at 72 h). In contrast, mature mRNA levels showed strikingly smaller and delayed declines, suggesting that the longer half-life of this species underestimates the contribution of Pdx-1 to insulin transcription. Chromatin immunoprecipitation assays revealed that the decrease in insulin transcription was associated with decreases in the occupancies of Pdx-1 and p300 at the proximal insulin promoter. Although there was no corresponding change in the recruitment of RNA polymerase II to the proximal promoter, its recruitment to the insulin coding region was significantly reduced. Our results suggest that Pdx-1 directly regulates insulin transcription through formation of a complex with transcriptional coactivators on the proximal insulin promoter. This complex leads to enhancement of elongation by the basal transcriptional machinery.
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Affiliation(s)
- Tessy Iype
- Department of Internal Medicine and the Diabetes Center, University of Virginia, Charlottesville, Virginia 22908, USA
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Moore PC, Ugas MA, Hagman DK, Parazzoli SD, Poitout V. Evidence against the involvement of oxidative stress in fatty acid inhibition of insulin secretion. Diabetes 2004; 53:2610-6. [PMID: 15448091 DOI: 10.2337/diabetes.53.10.2610] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Prolonged exposure to elevated levels of fatty acids adversely affects pancreatic beta-cell function. Here we investigated 1) whether ceramide synthesis, which we reported to mediate fatty acid inhibition of insulin gene expression, also inhibits insulin secretion and 2) whether fatty acid inhibition of insulin secretion involves the generation of reactive oxygen species (ROS), nitric oxide (NO), or prostaglandin E(2) (PGE(2)). A 72-h culture of islets in the presence of palmitate or oleate resulted in a marked decrease in glucose-induced insulin release assessed in 1-h static incubations. This effect was reproduced by exogenous diacylglycerol, but not by a cell-permeable analog of ceramide. Culture in the presence of fatty acids was not associated with an increase in intracellular peroxide or NO levels, neither was insulin secretion restored by antioxidants or an inhibitor of NO production. Exposure to fatty acids led to an increase in PGE(2) release, but an inhibitor of cyclooxygenase 2 was unable to prevent fatty acid inhibition of insulin secretion. These results indicate that fatty acid inhibition of insulin secretion 1) is not mediated by de novo ceramide synthesis, ROS, NO, or PGE(2), and 2) is likely to be caused by the generation of signals or metabolites downstream of diacylglycerol.
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Affiliation(s)
- Patrick C Moore
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA
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