SIRT6-mediated transcriptional suppression of Txnip is critical for pancreatic beta cell function and survival in mice
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Better 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 sirtuin 6 (SIRT6) in beta cell development and homeostasis.
Sirt6 endocrine progenitor cell conditional knockout and beta cell-specific knockout 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. Reverse transcription-quantitative (RT-q)PCR 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.
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 thioredoxin-interacting protein (TXNIP) in beta cells. SIRT6 deficiency led to increased acetylation of histone H3 lysine residue at 9 (H3K9Ac), acetylation of histone H3 lysine residue at 56 (H3K56Ac) and active RNA polymerase II at the promoter region of Txnip. SIRT6-deficient beta cells exhibited a time-dependent increase in H3K9Ac, H3K56Ac and TXNIP levels. Finally, beta cell-specific SIRT6-deficient mice showed increased sensitivity to streptozotocin.
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.
Sequence data have been deposited in the National Institutes of Health (NIH) Gene Expression Omnibus (GEO) with the accession code GSE104161.
KeywordsBeta cell Diabetes H3K9Ac Insulin secretion SIRT6 TXNIP
Beta cell-specific knockout
Endocrine pancreas-specific knockout
Acetylation of histone H3 lysine residue at 9
Acetylation of histone H3 lysine residue at 18
Acetylation of histone H3 lysine residue at 56
Mouse insulin promoter 1-driven, inducible CreERT transgenic line
National Institutes of Health
Reactive oxygen species
Transcriptional start site
We thank Y. Liu (Department of Cell Systems & Anatomy, Greehey Children’s Cancer Research Institute, University of Texas Health Science Centre at San Antonio, USA) for assistance in analysing the RNA-Seq data and thank C. Cervantes (Department of Pharmacology, University of Texas Health Science Centre at San Antonio, USA) and C. Dong (Biochemistry Molecular Biology, Indiana University, USA) for critical reading of the manuscript.
KQ and PW were responsible for designing the experiments. KQ, NZ, ZZ, MN, ZXZ and JL were responsible for acquisition of data. KQ, NZ, KX, NM and PW analysed and interpreted data. KQ drafted the manuscript. All authors critically revised the manuscript and approved the final version. PW is the guarantor of this work.
PW and KX are CPRIT Scholars and are supported by the Cancer Prevention and Research Institute of Texas. This work was supported by grants from the NIH (R01-DK80157 and R01-DK089229) and the American Diabetes Association to NM. This research also was supported by the San Antonio Nathan Shock Centre of Excellence in Aging Biology (P30 AG013319) and San Antonio Claude D. Pepper Older Americans Independence Centre (P30 AG044271).
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
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