Wannes D'Hertog

Publications (15) View all

• Article: The role of the saturated non-esterified fatty acid palmitate in beta cell dysfunction.

  Michael Maris, Sofie Robert, Etienne Waelkens, Rita Derua, Miriam Hernangomez, Wannes D'Hertog, Miriam Cnop, Chantal Mathieu, Lutgart Overbergh
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  ABSTRACT: Sustained elevated levels of saturated free fatty acids, such as palmitate, contribute to beta cell dysfunction, a phenomenon aggravated by high glucose levels. The aim of this study was to investigate the mechanisms of palmitate-induced beta cell dysfunction and death, combined or not with high glucose. Protein profiling of INS-1E cells, exposed to 0.5 mmol/l palmitate and combined or not with 25 mmol/l glucose, for 24 h was done by 2D-DIGE, both on full cell lysate and on an enriched endoplasmic reticulum (ER) fraction. 83 differentially expressed proteins (P < 0.05) were identified by MALDI-TOF/TOF mass spectrometry and proteomic results were confirmed by functional assays. 2D-DIGE analysis of whole cell lysates and ER enriched samples revealed a high number of proteins compared to previous reports. Palmitate induced beta cell dysfunction and death via ER stress, hampered insulin maturation, generation of harmful metabolites during triglycerides synthesis and altered intracellular trafficking. In combination with high glucose, palmitate induced increased shunting of excess glucose, increased mitochondrial reactive oxygen species production and an elevation in many transcription-related proteins. This study contributes to a better understanding and revealed novel mechanisms of palmitate-induced beta cell dysfunction and death and may provide new targets for drug discovery.
  Journal of Proteome Research 11/2012; · 5.11 Impact Factor
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  Article: Oleate-induced beta cell dysfunction and apoptosis: a proteomic approach to glucolipotoxicity by an unsaturated fatty acid.

  Michael Maris, Etienne Waelkens, Miriam Cnop, Wannes D'Hertog, Daniel A Cunha, Hannelie Korf, Tatsuro Koike, Lut Overbergh, Chantal Mathieu
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  ABSTRACT: High levels of fatty acids contribute to loss of functional beta cell mass in type 2 diabetes, in particular in combination with high glucose levels. The aim of this study was to elucidate the role of the unsaturated free fatty acid oleate in glucolipotoxicity and to unravel the molecular pathways involved. INS-1E cells were exposed to 0.5 mM oleate, combined or not with 25 mM glucose, for 24 h. Protein profiling of INS-1E cells was done by 2D-DIGE, covering pH ranges 4-7 and 6-9 (n = 4). Identification of differentially expressed proteins (P < 0.05) was based on MALDI-TOF analysis using Peptide Mass Fingerprint (PMF) and fragmentation (MS/MS) of the most intense peaks of PMF and proteomic results were confirmed by functional assays. Oleate impaired glucose-stimulated insulin secretion and decreased insulin content. 2D-DIGE analysis revealed 53 and 54 differentially expressed proteins for oleate and the combination of oleate and high glucose, respectively. Exposure to oleate down-regulated chaperones, hampered insulin processing and ubiquitin-related proteasomal degradation, and induced perturbations in vesicle transport and budding. In combination with high glucose, shunting of excess amounts of glucose toward reactive oxygen species production worsened beta cell death. The present findings provide new insights in oleate-induced beta cell dysfunction and identify target proteins for preservation of functional beta cell mass in type 2 diabetes.
  Journal of Proteome Research 06/2011; 10(8):3372-85. · 5.11 Impact Factor
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  Article: An integrated proteomics and genomics analysis to unravel a heterogeneous platelet secretion defect.

  Michela Di Michele, Chantal Thys, Etienne Waelkens, Lut Overbergh, Wannes D'Hertog, Chantal Mathieu, Rita De Vos, Kathelijne Peerlinck, Chris Van Geet, Kathleen Freson
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  ABSTRACT: Eight patients with clinical bleeding problems have evidence for platelet storage pool disease as they present with impaired platelet aggregation and secretion with low concentrations of ADP and collagen and an absence of second phase aggregation with epinephrine. Electron microscopy analysis further showed a reduced but not absent amount of platelet dense granules, and CD63 staining was decreased compared to healthy controls. The presence of alpha granules and CD62P expression after platelet activation was normal. This work aimed at identifying differentially expressed proteins in the platelet releasate and its remaining pellet after activation with A23187 and TRAP in patients and controls using DIGE-based proteomic technology. We identified 44 differentially expressed proteins in patients and the altered expression for some of them was confirmed by immunoblot analysis. Most of these proteins belong to the class of cytoskeleton-related proteins. In addition, 29 cytoskeleton-related genes showed an altered expression in platelet mRNA from patients using a real-time PCR array. In conclusion, our study shows that the dense granule secretion defect in patients with platelet storage pool disease is highly heterogeneous with evidence of an underlying cytoskeleton defect.
  Journal of proteomics 03/2011; 74(6):902-13. · 5.07 Impact Factor
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  Article: Two-dimensional gel proteome reference map of INS-1E cells.

  Wannes D'Hertog, Michael Maris, Lieven Thorrez, Etienne Waelkens, Lut Overbergh, Chantal Mathieu
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  ABSTRACT: The insulin-producing INS-1E rat cell line is widely used as a model for studying β-cells. It is a well-characterized cell line, mainly used in diabetes research. We established a 2-DE reference map for INS-1E cells. Using MALDI-TOF/TOF-MS/MS, we identified 546 spots. These included various proteins with an important role in β-cell physiology and with known roles as crucial proteins for diabetes development. We believe that the availability of this reference map will enhance our knowledge of β-cell physiology.
  Proteomics 02/2011; 11(7):1365-9. · 4.43 Impact Factor
• Article: High glucose induces dysfunction in insulin secretory cells by different pathways: a proteomic approach.

  Michael Maris, Gabriela B Ferreira, Wannes D'Hertog, Miriam Cnop, Etienne Waelkens, Lut Overbergh, Chantal Mathieu
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  ABSTRACT: Chronic hyperglycemia is a hallmark of type 2 diabetes and can contribute to progressive beta cell dysfunction and death. The aim of the present study was to identify pathways mediating high glucose-induced beta cell demise by a proteomic approach. INS-1E cells were exposed to 25 mM glucose for a sustained period of 24 h. Protein profiling of INS-1E cells was done by two-dimensional difference gel electrophoresis, covering the pH ranges 4-7 and 6-9 (n = 4). Differentially expressed proteins (P < 0.05) were identified by MALDI-TOF/TOF and proteomic results were confirmed by functional assays. High glucose levels impaired glucose-stimulated insulin secretion and decreased insulin content. 2D-DIGE analysis revealed 100 differentially expressed proteins that were involved in different pathways. Chaperone proteins were down-regulated, protein biosynthesis and ubiquitin-related proteasomal degradation were attenuated and perturbations in intracellular trafficking and vesicle transport and secretion could be observed. Moreover, several pathways were confirmed by functional assays and a direct role for eEF2 in insulin biosynthesis was demonstrated. The present findings provide new insights in glucotoxicity and identify key target proteins for the prevention and treatment of beta cell dysfunction in type 2 diabetes.
  Journal of Proteome Research 10/2010; 9(12):6274-87. · 5.11 Impact Factor