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.

Public Health Relevance

Pancreatic ?-cell function inexorably declines during the course of type 2 diabetes mellitus. This deterioration is due, at least in part, to the metabolic perturbations associated with diabetes, chiefly chronic hyperglycemia and dyslipidemia, which themselves have detrimental effects on ?-cell function. By discovering the molecular mechanisms by which chronic excess of nutrients impair insulin production from the ?-cell we hope to identify potential therapeutic targets to curtail the degradation of glucose homeostasis in type 2 diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
4R01DK058096-11
Application #
8456890
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Appel, Michael C
Project Start
2000-07-01
Project End
2016-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
11
Fiscal Year
2013
Total Cost
$205,176
Indirect Cost
$15,198
Name
University of Montreal Hospital
Department
Type
DUNS #
208831198
City
Montreal
State
PQ
Country
Canada
Zip Code
H2W1T-8
Alquier, Thierry; Poitout, Vincent (2018) Considerations and guidelines for mouse metabolic phenotyping in diabetes research. Diabetologia 61:526-538
Moullé, Valentine S; Vivot, Kevin; Tremblay, Caroline et al. (2017) Glucose and fatty acids synergistically and reversibly promote beta cell proliferation in rats. Diabetologia 60:879-888
Moullé, Valentine S; Ghislain, Julien; Poitout, Vincent (2017) Nutrient regulation of pancreatic ?-cell proliferation. Biochimie 143:10-17
Ghislain, Julien; Fontés, Ghislaine; Tremblay, Caroline et al. (2016) Dual-Reporter ?-Cell-Specific Male Transgenic Rats for the Analysis of ?-Cell Functional Mass and Enrichment by Flow Cytometry. Endocrinology 157:1299-306
Koppe, Laetitia; Nyam, Elsa; Vivot, Kevin et al. (2016) Urea impairs ? cell glycolysis and insulin secretion in chronic kidney disease. J Clin Invest 126:3598-612
Mosser, Rockann E; Maulis, Matthew F; Moullé, Valentine S et al. (2015) High-fat diet-induced ?-cell proliferation occurs prior to insulin resistance in C57Bl/6J male mice. Am J Physiol Endocrinol Metab 308:E573-82
Oropeza, Daniel; Jouvet, Nathalie; Budry, Lionel et al. (2015) Phenotypic Characterization of MIP-CreERT1Lphi Mice With Transgene-Driven Islet Expression of Human Growth Hormone. Diabetes 64:3798-807
Oropeza, Daniel; Jouvet, Nathalie; Bouyakdan, Khalil et al. (2015) PGC-1 coactivators in ?-cells regulate lipid metabolism and are essential for insulin secretion coupled to fatty acids. Mol Metab 4:811-22
Fontés, Ghislaine; Ghislain, Julien; Benterki, Isma et al. (2015) The ?F508 Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator Is Associated With Progressive Insulin Resistance and Decreased Functional ?-Cell Mass in Mice. Diabetes 64:4112-22
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

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