| 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. |
- Dayeh, Tasnim, et al.
(författare)
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DNA methylation of loci within ABCG1 and PHOSPHO1 in blood DNA is associated with future type 2 diabetes risk
- 2016
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2294 .- 1559-2308. ; 11:7, s. 482-488
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Tidskriftsartikel (refereegranskat)abstract
- Identification of subjects with a high risk of developing type 2 diabetes (T2D) is fundamental for prevention of the disease. Consequently, it is essential to search for new biomarkers that can improve the prediction of T2D. The aim of this study was to examine whether 5 DNA methylation loci in blood DNA (ABCG1, PHOSPHO1, SOCS3, SREBF1, and TXNIP), recently reported to be associated with T2D, might predict future T2D in subjects from the Botnia prospective study. We also tested if these CpG sites exhibit altered DNA methylation in human pancreatic islets, liver, adipose tissue, and skeletal muscle from diabetic vs. non-diabetic subjects. DNA methylation at the ABCG1 locus cg06500161 in blood DNA was associated with an increased risk for future T2D (OR = 1.09, 95% CI = 1.02–1.16, P-value = 0.007, Q-value = 0.018), while DNA methylation at the PHOSPHO1 locus cg02650017 in blood DNA was associated with a decreased risk for future T2D (OR = 0.85, 95% CI = 0.75–0.95, P-value = 0.006, Q-value = 0.018) after adjustment for age, gender, fasting glucose, and family relation. Furthermore, the level of DNA methylation at the ABCG1 locus cg06500161 in blood DNA correlated positively with BMI, HbA1c, fasting insulin, and triglyceride levels, and was increased in adipose tissue and blood from the diabetic twin among monozygotic twin pairs discordant for T2D. DNA methylation at the PHOSPHO1 locus cg02650017 in blood correlated positively with HDL levels, and was decreased in skeletal muscle from diabetic vs. non-diabetic monozygotic twins. DNA methylation of cg18181703 (SOCS3), cg11024682 (SREBF1), and cg19693031 (TXNIP) was not associated with future T2D risk in subjects from the Botnia prospective study.
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| 3. |
- Dayeh, Tasnim, et al.
(författare)
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Identification of CpG-SNPs associated with type 2 diabetes and differential DNA methylation in human pancreatic islets.
- 2013
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 56:5, s. 1036-1046
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: To date, the molecular function of most of the reported type 2 diabetes-associated loci remains unknown. The introduction or removal of cytosine-phosphate-guanine (CpG) dinucleotides, which are possible sites of DNA methylation, has been suggested as a potential mechanism through which single-nucleotide polymorphisms (SNPs) can affect gene function via epigenetics. The aim of this study was to examine if any of 40 SNPs previously associated with type 2 diabetes introduce or remove a CpG site and if these CpG-SNPs are associated with differential DNA methylation in pancreatic islets of 84 human donors. METHODS: DNA methylation was analysed using pyrosequencing. RESULTS: We found that 19 of 40 (48%) type 2 diabetes-associated SNPs introduce or remove a CpG site. Successful DNA methylation data were generated for 16 of these 19 CpG-SNP loci, representing the candidate genes TCF7L2, KCNQ1, PPARG, HHEX, CDKN2A, SLC30A8, DUSP9, CDKAL1, ADCY5, SRR, WFS1, IRS1, DUSP8, HMGA2, TSPAN8 and CHCHD9. All analysed CpG-SNPs were associated with differential DNA methylation of the CpG-SNP site in human islets. Moreover, six CpG-SNPs, representing TCF7L2, KCNQ1, CDKN2A, ADCY5, WFS1 and HMGA2, were also associated with DNA methylation of surrounding CpG sites. Some of the type 2 diabetes CpG-SNP sites that exhibit differential DNA methylation were further associated with gene expression, alternative splicing events determined by splice index, and hormone secretion in the human islets. The 19 type 2 diabetes-associated CpG-SNPs are in strong linkage disequilibrium (r (2) > 0.8) with a total of 295 SNPs, including 91 CpG-SNPs. CONCLUSIONS/INTERPRETATION: Our results suggest that the introduction or removal of a CpG site may be a molecular mechanism through which some of the type 2 diabetes SNPs affect gene function via differential DNA methylation and consequently contributes to the phenotype of the disease.
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| 4. |
- Dekker Nitert, Marloes, et al.
(författare)
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Impact of an Exercise Intervention on DNA Methylation in Skeletal Muscle From First-Degree Relatives of Patients With Type 2 Diabetes.
- 2012
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797.
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Tidskriftsartikel (refereegranskat)abstract
- To identify epigenetic patterns, which may predispose to type 2 diabetes (T2D) due to a family history (FH) of the disease, we analyzed DNA methylation genome-wide in skeletal muscle from individuals with (FH(+)) or without (FH(-)) an FH of T2D. We found differential DNA methylation of genes in biological pathways including mitogen-activated protein kinase (MAPK), insulin, and calcium signaling (P ≤ 0.007) and of individual genes with known function in muscle, including MAPK1, MYO18B, HOXC6, and the AMP-activated protein kinase subunit PRKAB1 in skeletal muscle of FH(+) compared with FH(-) men. We further validated our findings from FH(+) men in monozygotic twin pairs discordant for T2D, and 40% of 65 analyzed genes exhibited differential DNA methylation in muscle of both FH(+) men and diabetic twins. We further examined if a 6-month exercise intervention modifies the genome-wide DNA methylation pattern in skeletal muscle of the FH(+) and FH(-) individuals. DNA methylation of genes in retinol metabolism and calcium signaling pathways (P < 3 × 10(-6)) and with known functions in muscle and T2D including MEF2A, RUNX1, NDUFC2, and THADA decreased after exercise. Methylation of these human promoter regions suppressed reporter gene expression in vitro. In addition, both expression and methylation of several genes, i.e., ADIPOR1, BDKRB2, and TRIB1, changed after exercise. These findings provide new insights into how genetic background and environment can alter the human epigenome.
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| 5. |
- Ekman, Carl, et al.
(författare)
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Less pronounced response to exercise in healthy relatives to type 2 diabetic subjects compared with controls
- 2015
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 119:9, s. 953-960
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Tidskriftsartikel (refereegranskat)abstract
- Healthy first-degree relatives with heredity of type 2 diabetes (FH+) are known to have metabolic inflexibility compared with subjects without heredity for diabetes (FH-). In this study, we aimed to test the hypothesis that FH+ individuals have an impaired response to exercise compared with FH-. Sixteen FH+ and 19 FH- insulin-sensitive men similar in age, peak oxygen consumption ((V) over dot(O2 peak)), and body mass index completed an exercise intervention with heart rate monitored during exercise for 7 mo. Before and after the exercise intervention, the participants underwent a physical examination and tests for glucose tolerance and exercise capacity, and muscle biopsies were taken for expression analysis. The participants attended, on average, 39 training sessions during the intervention and spent 18.8 MJ on exercise. (V) over dot(O2 peak)/kg increased by 14%, and the participants lost 1.2 kg of weight and 3 cm waist circumference. Given that the FH- group expended 61% more energy during the intervention, we used regression analysis to analyze the response in the FH+ and FH- groups separately. Exercise volume had a significant effect on (V) over dot(O2 peak), weight, and waist circumference in the FH- group, but not in the FH+ group. After exercise, expression of genes involved in metabolism, oxidative phosphorylation, and cellular respiration increased more in the FH- compared with the FH+ group. This suggests that healthy, insulin-sensitive FH+ and FH- participants with similar age, (V) over dot(O2 peak), and body mass index may respond differently to an exercise intervention. The FH+ background might limit muscle adaptation to exercise, which may contribute to the increased susceptibility to type 2 diabetes in FH+ individuals.
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| 6. |
- Ling, Charlotte, et al.
(författare)
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Genetic and epigenetic factors are associated with expression of respiratory chain component NDUFB6 in human skeletal muscle.
- 2007
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Ingår i: The Journal of clinical investigation. - 0021-9738. ; 117:11, s. 3427-35
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Tidskriftsartikel (refereegranskat)abstract
- Insulin resistance and type 2 diabetes are associated with decreased expression of genes that regulate oxidative phosphorylation in skeletal muscle. To determine whether this defect might be inherited or acquired, we investigated the association of genetic, epigenetic, and nongenetic factors with expression of NDUFB6, a component of the respiratory chain that is decreased in muscle from diabetic patients. Expression of NDUFB6 was influenced by age, with lower gene expression in muscle of elderly subjects. Heritability of NDUFB6 expression in muscle was estimated to be approximately 60% in twins. A polymorphism in the NDUFB6 promoter region that creates a possible DNA methylation site (rs629566, A/G) was associated with a decline in muscle NDUFB6 expression with age. Although young subjects with the rs629566 G/G genotype exhibited higher muscle NDUFB6 expression, this genotype was associated with reduced expression in elderly subjects. This was subsequently explained by the finding of increased DNA methylation in the promoter of elderly, but not young, subjects carrying the rs629566 G/G genotype. Furthermore, the degree of DNA methylation correlated negatively with muscle NDUFB6 expression, which in turn was associated with insulin sensitivity. Our results demonstrate that genetic, epigenetic, and nongenetic factors associate with NDUFB6 expression in human muscle and suggest that genetic and epigenetic factors may interact to increase age-dependent susceptibility to insulin resistance.
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| 7. |
- Ling, Charlotte, et al.
(författare)
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Impact of the peroxisome proliferator activated receptor-gamma coactivator-1 beta (PGC-1 beta) Ala203Pro polymorphism on in vivo metabolism, PGC-1 beta expression and fibre type composition in human skeletal muscle
- 2007
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 50:8, s. 1615-1620
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis Peroxisome proliferator activated receptor-gamma coactivator-lp (PGC-1 beta, also known as PPARGCIB) expression is reduced in skeletal muscle from patients with type 2 diabetes mellitus and in elderly subjects. Ala203Pro, a common variant in the PGC-1 beta gene is associated with obesity. The aim of this study was to investigate whether the PGC-1 beta Ala203Pro polymorphism influences the age-related decline in skeletal muscle PGC-1 beta expression, in vivo metabolism and markers for muscle fibre type composition. Materials and methods The PGC-1 beta Ala203Pro polymerphism was genotyped in 110 young (age 28.0 +/- 1.9 years) and 86 elderly (age 62.4 +/- 2.0 years) twins and related to muscle PGC-1 beta expression, in vivo metabolism and markers for fibre type composition. Results Insulin-stimulated non-oxidative glucose metabolism (NOGM; p=0.025) and glycolytic flux rate (GF; p=0.026) were reduced in young Ala/Ala carriers compared with carriers of a 203Pro allele. In addition, a regression analysis, correcting for covariates, showed that the PGC-1 beta 203Pro allele was positively related to insulin-stimulated NOGM and GF in the young twins. While muscle expression of PGC-1 beta was reduced in elderly compared with young carriers of the Ala/Ala genotype (p <= 0.001), there was no significant age-related decline in PGC-1 beta expression in carriers of the 203Pro allele (p >= 0.4). However, a regression analysis, correcting for covariates, showed that only age was significantly related to muscle PGC-1 beta expression. Finally, PGC-1 beta expression correlated positively with markers for oxidative fibres in human muscle. Conclusions/interpretation This study suggests that young carriers of a PGC-1 beta 203Pro allele have enhanced insulin-stimulated glucose metabolism and may be protected against an age-related decline in PGC-1 beta expression in muscle.
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| 8. |
- Ling, Charlotte, et al.
(författare)
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Multiple environmental and genetic factors influence skeletal muscle PGC-1alpha and PGC-1beta gene expression in twins.
- 2004
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 114:10, s. 1518-1526
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Tidskriftsartikel (refereegranskat)abstract
- Genetic and environmental factors contribute to age-dependent susceptibility to type 2 diabetes. Recent studies have reported reduced expression of PPAR{gamma} coactivator 1{alpha} (PGC-1{alpha}) and PGC-1ß genes in skeletal muscle from type 2 diabetic patients, but it is not known whether this is an inherited or acquired defect. To address this question we studied expression of these genes in muscle biopsies obtained from young and elderly dizygotic and monozygotic twins without known diabetes before and after insulin stimulation and related the expression to a Gly482Ser variant in the PGC-1{alpha} gene. Insulin increased and aging reduced skeletal muscle PGC-1{alpha} and PGC-1ß mRNA levels. This age-dependent decrease in muscle gene expression was partially heritable and influenced by the PGC-1{alpha} Gly482Ser polymorphism. In addition, sex, birth weight, and aerobic capacity influenced expression of PGC-1{alpha} in a complex fashion. Whereas expression of PGC-1{alpha} in muscle was positively related to insulin-stimulated glucose uptake and oxidation, PGC-1ß expression was positively related to fat oxidation and nonoxidative glucose metabolism. We conclude that skeletal muscle PGC-1{alpha} and PGC-1ß expression are stimulated by insulin and reduced by aging. The data also suggest different regulatory functions for PGC-1{alpha} and PGC-1ß on glucose and fat oxidation in muscle cells. The finding that the age-dependent decrease in the expression of these key genes regulating oxidative phosphorylation is under genetic control could provide an explanation by which an environmental trigger (age) modifies genetic susceptibility to type 2 diabetes.
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| 9. |
- Lyssenko, Valeriya, et al.
(författare)
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Mechanisms by which common variants in the TCF7L2 gene increase risk of type 2 diabetes.
- 2007
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 117:8, s. 2155-2163
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Tidskriftsartikel (refereegranskat)abstract
- Genetic variants in the gene encoding for transcription factor-7-like 2 (TCF7L2) have been associated with type 2 diabetes (T2D) and impaired beta cell function, but the mechanisms have remained unknown. We therefore studied prospectively the ability of common variants in TCF7L2 to predict future T2D and explored the mechanisms by which they would do this. Scandinavian subjects followed for up to 22 years were genotyped for 3 SNPs (rs7903146, rs12255372, and rs10885406) in TCF7L2, and a subset of them underwent extensive metabolic studies. Expression of TCF7L2 was related to genotype and metabolic parameters in human islets. The CT/TT genotypes of SNP rs7903146 strongly predicted future T2D in 2 independent cohorts (Swedish and Finnish). The risk T allele was associated with impaired insulin secretion, incretin effects, and enhanced rate of hepatic glucose production. TCF7L2 expression in human islets was increased 5-fold in T2D, particularly in carriers of the TT genotype. Overexpression of TCF7L2 in human islets reduced glucose-stimulated insulin secretion. In conclusion, the increased risk of T2D conferred by variants in TCF7L2 involves the enteroinsular axis, enhanced expression of the gene in islets, and impaired insulin secretion.
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| 10. |
- Nilsson, Emma A, et al.
(författare)
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Altered DNA Methylation and Differential Expression of Genes Influencing Metabolism and Inflammation in Adipose Tissue From Subjects With Type 2 Diabetes
- 2014
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 63:9, s. 2962-2976
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Tidskriftsartikel (refereegranskat)abstract
- Genetics, epigenetics, and environment may together affect the susceptibility for type 2 diabetes (T2D). Our aim was to dissect molecular mechanisms underlying T2D using genome-wide expression and DNA methylation data in adipose tissue from monozygotic twin pairs discordant for T2D and independent case-control cohorts. In adipose tissue from diabetic twins, we found decreased expression of genes involved in oxidative phosphorylation; carbohydrate, amino acid, and lipid metabolism; and increased expression of genes involved in inflammation and glycan degradation. The most differentially expressed genes included ELOVL6, GYS2, FADS1, SPP1 (OPN), CCL18, and IL1RN. We replicated these results in adipose tissue from an independent case-control cohort. Several candidate genes for obesity and T2D (e.g., IRS1 and VEGFA) were differentially expressed in discordant twins. We found a heritable contribution to the genome-wide DNA methylation variability in twins. Differences in methylation between monozygotic twin pairs discordant for T2D were subsequently modest. However, 15,627 sites, representing 7,046 genes including PPARG, KCNQ1, TCF7L2, and IRS1, showed differential DNA methylation in adipose tissue from unrelated subjects with T2D compared with control subjects. A total of 1,410 of these sites also showed differential DNA methylation in the twins discordant for T2D. For the differentially methylated sites, the heritability estimate was 0.28. We also identified copy number variants (CNVs) in monozygotic twin pairs discordant for T2D. Taken together, subjects with T2D exhibit multiple transcriptional and epigenetic changes in adipose tissue relevant to the development of the disease.
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