| 1. |
- Bacos, Karl, et al.
(författare)
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Blood-based biomarkers of age-associated epigenetic changes in human islets associate with insulin secretion and diabetes
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Aging associates with impaired pancreatic islet function and increased type 2 diabetes (T2D) risk. Here we examine whether age-related epigenetic changes affect human islet function and if blood-based epigenetic biomarkers reflect these changes and associate with future T2D. We analyse DNA methylation genome-wide in islets from 87 non-diabetic donors, aged 26-74 years. Aging associates with increased DNA methylation of 241 sites. These sites cover loci previously associated with T2D, for example, KLF14. Blood-based epigenetic biomarkers reflect age-related methylation changes in 83 genes identified in human islets (for example, KLF14, FHL2, ZNF518B and FAM123C) and some associate with insulin secretion and T2D. DNA methylation correlates with islet expression of multiple genes, including FHL2, ZNF518B, GNPNAT1 and HLTF. Silencing these genes in β-cells alter insulin secretion. Together, we demonstrate that blood-based epigenetic biomarkers reflect age-related DNA methylation changes in human islets, and associate with insulin secretion in vivo and T2D.
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| 2. |
- Bacos, Karl, et al.
(författare)
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Type 2 diabetes candidate genes, including PAX5, cause impaired insulin secretion in human pancreatic islets
- 2023
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Ingår i: The Journal of clinical investigation. - 0021-9738 .- 1558-8238. ; 133:4
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Tidskriftsartikel (refereegranskat)abstract
- Type 2 diabetes (T2D) is caused by insufficient insulin secretion from pancreatic β-cells. To identify candidates contributing to T2D pathophysiology, we studied human pancreatic islets from ~300 individuals. We found 395 differentially expressed genes (DEGs) in islets from individuals with T2D, including, to our knowledge, novel (OPRD1, PAX5, TET1) and previously identified (CHL1, GLRA1, IAPP) candidates. A third of the identified islet expression changes may predispose to diabetes, as they associated with HbA1c in individuals not previously diagnosed with T2D. Most DEGs were expressed in human β-cells based on single-cell RNA-sequencing data. Additionally, DEGs displayed alterations in open chromatin and associated with T2D-SNPs. Mouse knock-out strains demonstrated that T2D-associated candidates regulate glucose homeostasis and body composition in vivo. Functional validation showed that mimicking T2D-associated changes for OPRD1, PAX5, and SLC2A2 impaired insulin secretion. Impairments in Pax5-overexpressing β-cells were due to severe mitochondrial dysfunction. Finally, we discovered PAX5 as a potential transcriptional regulator of many T2D-associated DEGs in human islets. Overall, we identified molecular alterations in human pancreatic islets contributing to β-cell dysfunction in T2D pathophysiology.
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| 3. |
- Daneshpajooh, Mahboubeh, et al.
(författare)
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HDAC7 is overexpressed in human diabetic islets and impairs insulin secretion in rat islets and clonal beta cells
- 2017
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 60:1, s. 116-125
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis: Pancreatic beta cell dysfunction is a prerequisite for the development of type 2 diabetes. Histone deacetylases (HDACs) may affect pancreatic endocrine function and glucose homeostasis through alterations in gene regulation. Our aim was to investigate the role of HDAC7 in human and rat pancreatic islets and clonal INS-1 beta cells (INS-1 832/13). Methods: To explore the role of HDAC7 in pancreatic islets and clonal beta cells, we used RNA sequencing, mitochondrial functional analyses, microarray techniques, and HDAC inhibitors MC1568 and trichostatin A. Results: Using RNA sequencing, we found increased HDAC7 expression in human pancreatic islets from type 2 diabetic compared with non-diabetic donors. HDAC7 expression correlated negatively with insulin secretion in human islets. To mimic the situation in type 2 diabetic islets, we overexpressed Hdac7 in rat islets and clonal beta cells. In both, Hdac7 overexpression resulted in impaired glucose-stimulated insulin secretion. Furthermore, it reduced insulin content, mitochondrial respiration and cellular ATP levels in clonal beta cells. Overexpression of Hdac7 also led to changes in the genome-wide gene expression pattern, including increased expression of Tcf7l2 and decreased expression of gene sets regulating DNA replication and repair as well as nucleotide metabolism. In accordance, Hdac7 overexpression reduced the number of beta cells owing to enhanced apoptosis. Finally, we found that inhibiting HDAC7 activity with pharmacological inhibitors or small interfering RNA-mediated knockdown restored glucose-stimulated insulin secretion in beta cells that were overexpressing Hdac7. Conclusions/interpretation: Taken together, these results indicate that increased HDAC7 levels caused beta cell dysfunction and may thereby contribute to defects seen in type 2 diabetic islets. Our study supports HDAC7 inhibitors as a therapeutic option for the treatment of type 2 diabetes.
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| 4. |
- Daneshpajooh, Mahboubeh, et al.
(författare)
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MC1568 improves insulin secretion in islets from type 2 diabetes patients and rescues β-cell dysfunction caused by Hdac7 upregulation
- 2018
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Ingår i: Acta Diabetologica. - : Springer Science and Business Media LLC. - 0940-5429 .- 1432-5233. ; 55:12, s. 1231-1235
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Tidskriftsartikel (refereegranskat)abstract
- Aims: It has in recent years been established that epigenetic changes contribute to β-cell dysfunction and type 2 diabetes (T2D). For example, we have showed that the expression of histone deacetylase 7 (HDAC7) is increased in pancreatic islets of individuals with T2D and that increased levels of Hdac7 in β-cells impairs insulin secretion. The HDAC inhibitor MC1568 rescued this secretory impairment, suggesting that inhibitors specific for HDAC7 may be useful clinically in the treatment of T2D. The aim of the current study was to further explore HDAC7 as a novel therapeutic target in T2D. Methods: Hdac7 was overexpressed in clonal β-cells followed by the analysis of insulin secretion, mitochondrial function, as well as cell number and apoptosis in the presence or absence of MC1568. Furthermore, the effect of MC1568 on insulin secretion in human pancreatic islets from non-diabetic donors and donors with T2D was also studied. Results: Overexpression of Hdac7 in clonal β-cells significantly reduced insulin secretion, mitochondrial respiration, and ATP content, while it increased apoptosis. These impairments were all rescued by treatment with MC1568. The inhibitor also increased glucose-stimulated insulin secretion in islets from donors with T2D, while having no effect on islets from non-diabetic donors. Conclusions: HDAC7 inhibition protects β-cells from mitochondrial dysfunction and apoptosis, and increases glucose-stimulated insulin secretion in islets from human T2D donors. Our study supports specific HDAC7 inhibitors as novel options in the treatment of T2D.
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| 5. |
- Dayeh, Tasnim, et al.
(författare)
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Genome-wide DNA methylation analysis of human pancreatic islets from type 2 diabetic and non-diabetic donors identifies candidate genes that influence insulin secretion.
- 2014
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Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Impaired insulin secretion is a hallmark of type 2 diabetes (T2D). Epigenetics may affect disease susceptibility. To describe the human methylome in pancreatic islets and determine the epigenetic basis of T2D, we analyzed DNA methylation of 479,927 CpG sites and the transcriptome in pancreatic islets from T2D and non-diabetic donors. We provide a detailed map of the global DNA methylation pattern in human islets, β- and α-cells. Genomic regions close to the transcription start site showed low degrees of methylation and regions further away from the transcription start site such as the gene body, 3'UTR and intergenic regions showed a higher degree of methylation. While CpG islands were hypomethylated, the surrounding 2 kb shores showed an intermediate degree of methylation, whereas regions further away (shelves and open sea) were hypermethylated in human islets, β- and α-cells. We identified 1,649 CpG sites and 853 genes, including TCF7L2, FTO and KCNQ1, with differential DNA methylation in T2D islets after correction for multiple testing. The majority of the differentially methylated CpG sites had an intermediate degree of methylation and were underrepresented in CpG islands (∼7%) and overrepresented in the open sea (∼60%). 102 of the differentially methylated genes, including CDKN1A, PDE7B, SEPT9 and EXOC3L2, were differentially expressed in T2D islets. Methylation of CDKN1A and PDE7B promoters in vitro suppressed their transcriptional activity. Functional analyses demonstrated that identified candidate genes affect pancreatic β- and α-cells as Exoc3l silencing reduced exocytosis and overexpression of Cdkn1a, Pde7b and Sept9 perturbed insulin and glucagon secretion in clonal β- and α-cells, respectively. Together, our data can serve as a reference methylome in human islets. We provide new target genes with altered DNA methylation and expression in human T2D islets that contribute to perturbed insulin and glucagon secretion. These results highlight the importance of epigenetics in the pathogenesis of T2D.
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| 6. |
- Dos Santos, Cristiane, et al.
(författare)
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Glucocorticoids and glucolipotoxicity alter the DNA methylome and function of human EndoC-βH1 cells
- 2022
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Ingår i: Life Sciences. - : Elsevier BV. - 1879-0631 .- 0024-3205. ; 307
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: Synthetic glucocorticoids, including dexamethasone (DEX), are clinically prescribed due to their immunoregulatory properties. In excess they can perturb glucose homeostasis, with individuals predisposed to glucose intolerance more sensitive to these negative effects. While DEX is known to negatively impact β-cell function, it is unclear how. Hence, our aim was to investigate the effect of DEX on β-cell function, both alone and in combination with a diabetogenic milieu in the form of elevated glucose and palmitate.MAIN METHODS: Human pancreatic EndoC-βH1 cells were cultured in the presence of high glucose and palmitate (glucolipotoxicity) and/or a pharmacological concentration of DEX, before functional and molecular analyses.KEY FINDINGS: Either treatment alone resulted in reduced insulin content and secretion, while the combination of DEX and glucolipotoxicity promoted a strong synergistic effect. These effects were associated with reduced insulin biosynthesis, likely due to downregulation of PDX1, MAFA, and the proinsulin converting enzymes, as well as reduced ATP response upon glucose stimulation. Genome-wide DNA methylation analysis found changes on PDE4D, MBNL1 and TMEM178B, all implicated in β-cell function, after all three treatments. DEX alone caused very strong demethylation of the glucocorticoid-regulated gene ZBTB16, also known to influence the β-cell, while the combined treatment caused altered methylation of many known β-cell regulators and diabetes candidate genes.SIGNIFICANCE: DEX treatment and glucolipotoxic conditions separately alter the β-cell epigenome and function. The combination of both treatments exacerbates these changes, showing that caution is needed when prescribing potent glucocorticoids in patients with dysregulated metabolism.
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| 7. |
- Hall, Elin, et al.
(författare)
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Glucolipotoxicity alters insulin secretion via epigenetic changes in human islets
- 2019
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 68:10, s. 1965-1974
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Tidskriftsartikel (refereegranskat)abstract
- Type 2 diabetes (T2D) is characterized by insufficient insulin secretion and elevated glucose levels, often in combination with high levels of circulating fatty acids. Long-term exposure to high levels of glucose or fatty acids impair insulin secretion in pancreatic islets, which could partly be due to epigenetic alterations. We studied the effects of high concentrations of glucose and palmitate combined for 48 h (glucolipotoxicity) on the transcriptome, the epigenome, and cell function in human islets. Glucolipotoxicity impaired insulin secretion, increased apoptosis, and significantly (false discovery rate <5%) altered the expression of 1,855 genes, including 35 genes previously implicated in T2D by genomewide association studies (e.g., TCF7L2 and CDKN2B). Additionally, metabolic pathways were enriched for downregulated genes. Of the differentially expressed genes, 1,469 also exhibited altered DNA methylation (e.g., CDK1, FICD, TPX2, and TYMS). A luciferase assay showed that increased methylation of CDK1 directly reduces its transcription in pancreatic β-cells, supporting the idea that DNA methylation underlies altered expression after glucolipotoxicity. Follow-up experiments in clonal β-cells showed that knockdown of FICD and TPX2 alters insulin secretion. Together, our novel data demonstrate that glucolipotoxicity changes the epigenome in human islets, thereby altering gene expression and possibly exacerbating the secretory defect in T2D.
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| 8. |
- Hall, Elin, et al.
(författare)
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Sex differences in the genome-wide DNA methylation pattern and impact on gene expression, microRNA levels and insulin secretion in human pancreatic islets
- 2014
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Ingår i: GenomeBiology. - : Springer Science and Business Media LLC. - 1465-6906. ; 15:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Epigenetic factors regulate tissue-specific expression and X-chromosome inactivation. Previous studies have identified epigenetic differences between sexes in some human tissues. However, it is unclear whether epigenetic modifications contribute to sex-specific differences in insulin secretion and metabolism. Here, we investigate the impact of sex on the genome-wide DNA methylation pattern in human pancreatic islets from 53 males and 34 females, and relate the methylome to changes in expression and insulin secretion. Results: Glucose-stimulated insulin secretion is higher in female versus male islets. Genome-wide DNA methylation data in human islets clusters based on sex. While the chromosome-wide DNA methylation level on the X-chromosome is higher in female versus male islets, the autosomes do not display a global methylation difference between sexes. Methylation of 8,140 individual X-chromosome sites and 470 autosomal sites shows sex-specific differences in human islets. These include sites in/near AR, DUSP9, HNF4A, BCL11A and CDKN2B. 61 X-chromosome genes and 18 autosomal genes display sex-specific differences in both DNA methylation and expression. These include NKAP, SPESP1 and APLN, which exhibited lower expression in females. Functional analyses demonstrate that methylation of NKAP and SPESP1 promoters in vitro suppresses their transcriptional activity. Silencing of Nkap or Apln in clonal beta-cells results in increased insulin secretion. Differential methylation between sexes is associated with altered levels of microRNAs miR-660 and miR-532 and related target genes. Conclusions: Chromosome-wide and gene-specific sex differences in DNA methylation associate with altered expression and insulin secretion in human islets. Our data demonstrate that epigenetics contribute to sex-specific metabolic phenotypes.
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| 9. |
- Rönn, Tina, et al.
(författare)
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Genes with epigenetic alterations in human pancreatic islets impact mitochondrial function, insulin secretion, and type 2 diabetes
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Epigenetic dysregulation may influence disease progression. Here we explore whether epigenetic alterations in human pancreatic islets impact insulin secretion and type 2 diabetes (T2D). In islets, 5,584 DNA methylation sites exhibit alterations in T2D cases versus controls and are associated with HbA1c in individuals not diagnosed with T2D. T2D-associated methylation changes are found in enhancers and regions bound by β-cell-specific transcription factors and associated with reduced expression of e.g. CABLES1, FOXP1, GABRA2, GLR1A, RHOT1, and TBC1D4. We find RHOT1 (MIRO1) to be a key regulator of insulin secretion in human islets. Rhot1-deficiency in β-cells leads to reduced insulin secretion, ATP/ADP ratio, mitochondrial mass, Ca2+, and respiration. Regulators of mitochondrial dynamics and metabolites, including L-proline, glycine, GABA, and carnitines, are altered in Rhot1-deficient β-cells. Islets from diabetic GK rats present Rhot1-deficiency. Finally, RHOT1methylation in blood is associated with future T2D. Together, individuals with T2D exhibit epigenetic alterations linked to mitochondrial dysfunction in pancreatic islets.
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| 10. |
- Volkov, Petr, et al.
(författare)
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Whole-genome Bisulfite Sequencing of Human Pancreatic Islets Reveals Novel Differentially Methylated Regions in Type 2 Diabetes Pathogenesis
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 66:4, s. 1074-1085
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Tidskriftsartikel (refereegranskat)abstract
- Current knowledge about the role of epigenetics in type 2 diabetes (T2D) remains limited. Only a few studies have investigated DNA methylation of selected candidate genes or a very small fraction of genomic CpG sites in human pancreatic islets, the tissue of primary pathogenic importance for diabetes. Our aim was to characterize the whole-genome DNA methylation landscape in human pancreatic islets, to identify differentially methylated regions (DMRs) in diabetic islets, and to investigate the function of DMRs in islet biology.Here, we performed whole-genome bisulfite sequencing, which is a comprehensive and unbiased method to study DNA methylation throughout the genome on a single nucleotide resolution, in pancreatic islets from donors with T2D and non-diabetic controls. We identified 25,820 DMRs in islets from individuals with T2D. These DMRs cover loci with known islet function e.g. PDX1, TCF7L2 and ADCY5 Importantly, binding sites previously identified by ChIP-seq for islet-specific transcription factors, enhancer regions and different histone marks were enriched in the T2D associated DMRs. We also identified 457 genes, including NR4A3, PARK2, PID1, SLC2A2 and SOCS2 that had both DMRs and significant expression changes in T2D islets. To mimic the situation in T2D islets, candidate genes were overexpressed or silenced in cultured β-cells. This resulted in impaired insulin secretion, thereby connecting differential methylation to islet dysfunction. We further explored the islet methylome and found a strong link between methylation levels and histone marks. Additionally, DNA methylation in different genomic regions and of different transcript types (i.e. protein-coding, non-coding and pseudogenes) was associated with islet expression levels.Our study provides a comprehensive picture of the islet DNA methylome in both non-diabetic and diabetic individuals and highlights the importance of epigenetic dysregulation in pancreatic islets and T2D pathogenesis.
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