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The impact of aging on beta-cell functionality and structural integrity under metabolic stress conditions in diabetes-prone and diabetes-resistant mice.

ABSTRACT: Overnutrition contributes to insulin resistance, obesity and metabolic stress, initiating a loss of functional beta-cells and diabetes development. Whether these damaging effects are amplified in advanced age is barely investigated. Therefore, New Zealand Obese (NZO) mice, a well-established model for the investigation of human obesity-associated type 2 diabetes, were fed a metabolically challenging diet with a high-fat, carbohydrate restricted period followed by a carbohydrate intervention in young as well as advanced age. Interestingly, while young NZO mice developed massive hyperglycemia in response to carbohydrate feeding, leading to beta-cell dysfunction and cell death, aged counterparts compensated the increased insulin demand by persistent beta-cell function and beta-cell mass expansion. Beta-cell loss in young NZO islets was linked to increased expression of thioredoxin-interacting protein (TXNIP), presumably initiating an apoptosis-signaling cascade via caspase-3 activation. In contrast, islets of aged NZOs exhibited a sustained redox balance without changes in TXNIP expression, associated with higher proliferative potential by cell cycle activation. These findings support the relevance of a maintained proliferative potential and redox homeostasis for preserving islet functionality under metabolic stress, with the peculiarity that this adaptive response emerged with advanced age in diabetes-prone NZO mice.

ORGANISM(S): Mus musculus

PROVIDER: GSE150281 | GEO | 2020/11/02

REPOSITORIES: GEO

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Project description:Purpose: The complete understanding of how genetic and epigenetic components control beta cell differentiation and function is key to the discovery of novel therapeutic approaches to prevent beta cell dysfunction and failure in the progression of type 2 diabetes. Our goal was to elucidate the role of histone deacetylase SIRT6 in beta-cell development and homeostasis. Methods: The Sirt6 endocrine progenitor cell conditional knockout (EKO) and beta-cell-specific knockout (BKO) mice were generated using the Cre-loxP system. Mice were assayed for islet morphology, glucose tolerance, glucose-stimulated insulin secretion, and susceptibility to streptozotocin. Transcriptional regulatory functions of SIRT6 in primary islets were evaluated by RNA-seq analysis. RT-qPCR and immunoblot were used to verify and investigate the gene expression changes. Chromatin occupancies of SIRT6, H3K9Ac, H3K56Ac, and active RNA Polymerase II were evaluated by chromatin immunoprecipitation. Results: Deletion of Sirt6 in pancreatic endocrine progenitor cells did not affect endocrine morphology, beta cell mass, or insulin production, but did result in glucose intolerance and defective glucose-stimulated insulin secretion in mice. Conditional deletion of Sirt6 in adult beta cells reproduced the insulin secretion defect. Loss of Sirt6 resulted in aberrant upregulation of TXNIP. SIRT6 deficiency led to increased accumulations of H3K9Ac, H3K56Ac, and active RNA polymerase II at the promoter region of Txnip. SIRT6-deficient beta cells exhibited a time-dependent increase of H3K9Ac, H3K56Ac, and TXNIP levels. Furthermore, beta-cell-specific SIRT6 deficient mice showed increased sensitivity to streptozotocin. Conclusions: Our results reveal that SIRT6 suppresses Txnip expression in beta-cells via deacetylation of histone H3 and plays a critical role in maintaining beta-cell function and viability. Agents that preserve SIRT6 activity may be beneficial for preventing the progression of type 2 diabetes.

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The impact of aging on beta-cell functionality and structural integrity under metabolic stress conditions in diabetes-prone and diabetes-resistant mice.

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