The overall objective of this proposal is to elucidate the molecular mechanisms by which elevated levels of glucose and fatty acids adversely affect the pancreatic ?-cell, a phenomenon referred to as glucolipodysfunction. The underlying hypothesis, based on our previous findings and preliminary data, proposes that early stages of glucolipodysfunction involve two complementary mechanisms: 1- Inhibition of expression of the enzyme Per Arnt Sim kinase (PASK) which results in diminished expression and activity of the transcription factors pancreatic-duodenal homeobox-1 (Pdx-1) and mammalian homologue of avian MafA/l-Maf (MafA), leading to decreased insulin expression via alterations of the histone code and a closed chromatin conformation;and 2- Nutrient-induced ?-cell proliferation driven by elevated circulating levels of fibroblast growth factor 21 (FGF21) activating FoxM1 signaling and leading to a dysfunctional ?-cell mass.
In specific Aim 1 we will determine how inhibition of PASK expression impairs insulin gene expression in glucolipodysfunction. Our working hypothesis is that PASK phosphorylates, and thereby inactivates, glycogen synthase kinase (GSK) 3? which alleviates proteasomal degradation of Pdx-1 and MafA. Using rodent genetic models we propose to further delineate the functional relationship between PASK and GSK3 ? and its consequences on Pdx-1 and MafA expression and function under conditions of glucolipodysfunction.
In specific Aim 2 we will characterize the modifications of the histone code and DNA methylation profile at the Pdx-1, MafA, and insulin promoters associated with glucolipodysfunction. Our working hypothesis is that Pdx-1 deficiency in glucolipodysfunction results in defective recruitment of the histone methyltransferase Set7/9 and alterations of the histone methylation profile at the insulin, Pdx-1, and MafA promoters. Using ex vivo and in vivo models we propose to identify the epigenetic modifications responsible for the initiation of glucolipodysfunction.
In specific Aim 3 we will ascertain how insulin resistance induces ? -cell proliferation in glucolipodysfunction. Our working hypothesis is that insulin resistance in response to nutrient excess in 6-mo-old rats is associated with a rise in circulating factors, FGF21 being a likely candidate, which stimulate FoxM1- mediated ?-cell proliferation. Using in vivo models we propose to identify the mechanisms whereby insulin resistance promotes ?-cell growth under conditions of nutrient excess. We expect that the studies described in this application will reveal the molecular signature of glucolipodysfunction in the pancreatic ?-cell. We anticipate that these findings will serve as a basis to design novel therapeutic approaches to prevent the deterioration of ?-cell function in T2D.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
Project #
Application #
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Sato, Sheryl M
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Montreal Hospital
Zip Code
Ghislain, Julien; Fontés, Ghislaine; Tremblay, Caroline et al. (2016) Dual-Reporter β-Cell-Specific Male Transgenic Rats for the Analysis of β-Cell Functional Mass and Enrichment by Flow Cytometry. Endocrinology 157:1299-306
Koppe, Laetitia; Nyam, Elsa; Vivot, Kevin et al. (2016) Urea impairs β cell glycolysis and insulin secretion in chronic kidney disease. J Clin Invest 126:3598-612
Fontés, Ghislaine; Ghislain, Julien; Benterki, Isma et al. (2015) The ΔF508 Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator Is Associated With Progressive Insulin Resistance and Decreased Functional β-Cell Mass in Mice. Diabetes 64:4112-22
Mosser, Rockann E; Maulis, Matthew F; Moullé, Valentine S et al. (2015) High-fat diet-induced β-cell proliferation occurs prior to insulin resistance in C57Bl/6J male mice. Am J Physiol Endocrinol Metab 308:E573-82
Semache, Meriem; Ghislain, Julien; Zarrouki, Bader et al. (2014) Pancreatic and duodenal homeobox-1 nuclear localization is regulated by glucose in dispersed rat islets but not in insulin-secreting cell lines. Islets 6:e982376
Zarrouki, Bader; Benterki, Isma; Fontes, Ghislaine et al. (2014) Epidermal growth factor receptor signaling promotes pancreatic *-cell proliferation in response to nutrient excess in rats through mTOR and FOXM1. Diabetes 63:982-93
Kilic, Gamze; Alvarez-Mercado, Ana I; Zarrouki, Bader et al. (2014) The islet estrogen receptor-α is induced by hyperglycemia and protects against oxidative stress-induced insulin-deficient diabetes. PLoS One 9:e87941
Fergusson, Grace; Ethier, Mélanie; Guévremont, Mélanie et al. (2014) Defective insulin secretory response to intravenous glucose in C57Bl/6J compared to C57Bl/6N mice. Mol Metab 3:848-54
d'Assignies, Gaspard; Fontés, Ghislaine; Kauffmann, Claude et al. (2013) Early detection of liver steatosis by magnetic resonance imaging in rats infused with glucose and intralipid solutions and correlation to insulin levels. Metabolism 62:1850-7
Fergusson, Grace; Ethier, Mélanie; Zarrouki, Bader et al. (2013) A model of chronic nutrient infusion in the rat. J Vis Exp :

Showing the most recent 10 out of 34 publications