Dataset Information

Pancreas-Specific Sirt1-Deficiency in Mice Compromises Beta-Cell Function without Development of Hyperglycemia.

ABSTRACT:

Aims/hypothesis

Sirtuin 1 (Sirt1) has been reported to be a critical positive regulator of glucose-stimulated insulin secretion in pancreatic beta-cells. The effects on islet cells and blood glucose levels when Sirt1 is deleted specifically in the pancreas are still unclear.

Methods

This study examined islet glucose responsiveness, blood glucose levels, pancreatic islet histology and gene expression in Pdx1Cre; Sirt1ex4F/F mice that have loss of function and loss of expression of Sirt1 specifically in the pancreas.

Results

We found that in the Pdx1Cre; Sirt1ex4F/F mice, the relative insulin positive area and the islet size distribution were unchanged. However, beta-cells were functionally impaired, presenting with lower glucose-stimulated insulin secretion. This defect was not due to a reduced expression of insulin but was associated with a decreased expression of the glucose transporter Slc2a2/Glut2 and of the Glucagon like peptide-1 receptor (Glp1r) as well as a marked down regulation of endoplasmic reticulum (ER) chaperones that participate in the Unfolded Protein Response (UPR) pathway. Counter intuitively, the Sirt1-deficient mice did not develop hyperglycemia. Pancreatic polypeptide (PP) cells were the only other islet cells affected, with reduced numbers in the Sirt1-deficient pancreas.

Conclusions/interpretation

This study provides new mechanistic insights showing that beta-cell function in Sirt1-deficient pancreas is affected due to altered glucose sensing and deregulation of the UPR pathway. Interestingly, we uncovered a context in which impaired beta-cell function is not accompanied by increased glycemia. This points to a unique compensatory mechanism. Given the reduction in PP, investigation of its role in the control of blood glucose is warranted.

SUBMITTER: Pinho AV

PROVIDER: S-EPMC4457418 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Publications

Pancreas-Specific Sirt1-Deficiency in Mice Compromises Beta-Cell Function without Development of Hyperglycemia.

Pinho Andreia V AV Bensellam Mohammed M Wauters Elke E Rees Maxine M Giry-Laterriere Marc M Mawson Amanda A Ly Le Quan le Q Biankin Andrew V AV Wu Jianmin J Laybutt D Ross DR Rooman Ilse I

PloS one 20150605 6

<h4>Aims/hypothesis</h4>Sirtuin 1 (Sirt1) has been reported to be a critical positive regulator of glucose-stimulated insulin secretion in pancreatic beta-cells. The effects on islet cells and blood glucose levels when Sirt1 is deleted specifically in the pancreas are still unclear.<h4>Methods</h4>This study examined islet glucose responsiveness, blood glucose levels, pancreatic islet histology and gene expression in Pdx1Cre; Sirt1ex4F/F mice that have loss of function and loss of expression of ...[more]

PMID: 26046931

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Project description:In mammals, Sirt1, a member of the sirtuin family of proteins, functions as a nicotinamide adenine dinucleotide-dependent protein deactylase, and has important physiological roles, including the regulation of glucose metabolism, cell survival, and mitochondrial respiration. The initial investigations of Sirt1 deficient mice have revealed a phenotype that includes a reduced lifespan, small size, and an increased frequency of abnormal sperm. We have now performed a detailed analysis of the molecular and functional effects of Sirt1 deficiency in the germ line of Sirt1 knock-out (-/-) mice. We find that Sirt1 deficiency markedly attenuates spermatogenesis, but not oogenesis. Numbers of mature sperm and spermatogenic precursors, as early as d15.5 of development, are significantly reduced ( approximately 2-10-fold less; P</=0.004) in numbers in Sirt1-/- mice, whereas Sirt1 deficiency did not effect the efficiency oocyte production following superovulation of female mice. Furthermore, the proportion of mature sperm with elevated DNA damage ( approximately 7.5% of total epididymal sperm; P = 0.02) was significantly increased in adult Sirt1-/- males. Analysis of global gene expression by microarray analysis in Sirt1 deficient testis revealed dysregulated expression of 85 genes, which were enriched (P<0.05) for genes involved in spermatogenesis and protein sumoylation. To assess the function of Sirt1 deficient germ cells, we compared the efficiency of generating embryos and viable offspring in in vitro fertilization (IVF) experiments using gametes from Sirt1-/- and sibling Sirt1+/- mice. While viable animals were derived in both Sirt1-/- X wild type and Sirt1-/- X Sirt1-/- crosses, the efficiency of producing both 2-cell zygotes and viable offspring was diminished when IVF was performed with Sirt1-/- sperm and/or oocytes. Together, these data support an important role for Sirt1 in spermatogenesis, including spermatogenic stem cells, as well as germ cell function.

Dataset Information

Pancreas-Specific Sirt1-Deficiency in Mice Compromises Beta-Cell Function without Development of Hyperglycemia.

Aims/hypothesis

Methods

Results

Conclusions/interpretation

Publications

Pancreas-Specific Sirt1-Deficiency in Mice Compromises Beta-Cell Function without Development of Hyperglycemia.

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