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Circulating unmethylated CHTOP and INS DNA fragments provide evidence of possible islet cell death in youth with obesity and diabetes.

ABSTRACT: BACKGROUND:Identification of islet ? cell death prior to the onset of type 1 diabetes (T1D) or type 2 diabetes (T2D) might allow for interventions to protect ? cells and reduce diabetes risk. Circulating unmethylated DNA fragments arising from the human INS gene have been proposed as biomarkers of ? cell death, but this gene alone may not be sufficiently specific to report ? cell death. RESULTS:To identify new candidate genes whose CpG sites may show greater specificity for ? cells, we performed unbiased DNA methylation analysis using the Infinium HumanMethylation 450 array on 64 human islet preparations and 27 non-islet human tissues. For verification of array results, bisulfite DNA sequencing of human ? cells and 11 non-? cell tissues was performed on 5 of the top 10 CpG sites that were found to be differentially methylated. We identified the CHTOP gene as a candidate whose CpGs show a greater frequency of unmethylation in human islets. A digital PCR strategy was used to determine the methylation pattern of CHTOP and INS CpG sites in primary human tissues. Although both INS and CHTOP contained unmethylated CpG sites in non-islet tissues, they occurred in a non-overlapping pattern. Based on Naïve Bayes classifier analysis, the two genes together report 100% specificity for islet damage. Digital PCR was then performed on cell-free DNA from serum from human subjects. Compared to healthy controls (N = 10), differentially methylated CHTOP and INS levels were higher in youth with new onset T1D (N = 43) and, unexpectedly, in healthy autoantibody-negative youth who have first-degree relatives with T1D (N = 23). When tested in lean (N = 32) and obese (N = 118) youth, increased levels of unmethylated INS and CHTOP were observed in obese individuals. CONCLUSION:Our data suggest that concurrent measurement of circulating unmethylated INS and CHTOP has the potential to detect islet death in youth at risk for both T1D and T2D. Our data also support the use of multiple parameters to increase the confidence of detecting islet damage in individuals at risk for developing diabetes.

SUBMITTER: Syed F

PROVIDER: S-EPMC7393900 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Circulating unmethylated CHTOP and INS DNA fragments provide evidence of possible islet cell death in youth with obesity and diabetes.

Syed Farooq F Tersey Sarah A SA Turatsinze Jean-Valery JV Felton Jamie L JL Kang Nicole Jiyun NJ Nelson Jennifer B JB Sims Emily K EK Defrance Mathieu M Bizet Martin M Fuks Francois F Cnop Miriam M Bugliani Marco M Marchetti Piero P Ziegler Anette-Gabriele AG Bonifacio Ezio E Webb-Robertson Bobbie-Jo BJ Balamurugan Appakalai N AN Evans-Molina Carmella C Eizirik Decio L DL Mather Kieren J KJ Arslanian Silva S Mirmira Raghavendra G RG

Clinical epigenetics 20200731 1

<h4>Background</h4>Identification of islet β cell death prior to the onset of type 1 diabetes (T1D) or type 2 diabetes (T2D) might allow for interventions to protect β cells and reduce diabetes risk. Circulating unmethylated DNA fragments arising from the human INS gene have been proposed as biomarkers of β cell death, but this gene alone may not be sufficiently specific to report β cell death.<h4>Results</h4>To identify new candidate genes whose CpG sites may show greater specificity for β cell ...[more]

PMID: 32736653

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Project description:Physiologically the liver is exposed to higher insulin concentrations than other organs. To evaluate functional consequences of insulin-deficient diabetes mellitus for the liver, we used a genetically engineered pig model of mutant INS gene induced diabetes of youth (MIDY). Liver samples of MIDY pigs and wild-type (WT) littermate controls were analyzed by RNA sequencing, label-free proteomics and targeted metabolomics/lipidomics to reveal pathways and key drivers significantly affected by chronic insulin deficiency and hyperglycemia. Gene set enrichment analysis of the ~500 transcripts that were differently abundant between MIDY and WT samples revealed pathways related to amino acid metabolism, beta-oxidation of fatty acids, gluconeogenesis and ketogenesis to be enriched in MIDY samples, whereas pathways related to extra cellular matrix and inflammation/pathogen defense response were enriched in the WT samples. Reduced insulin receptor activation and phosphorylation of protein kinase B (PKB, AKT) was associated with markedly increased levels of retinol dehydrogenase 16 (RDH16) and 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2), the apparent key drivers of stimulated gluconeogenesis and ketogenesis in MIDY pigs. Profiling of acylcarnitines provided evidence for increased activity of carnitine palmitoyltransferase 1 (CPT1) shuttling fatty acids into the mitochondrial matrix for beta-oxidation and for increased omega-oxidation. In addition, several enzymes involved in amino acid degradation and enzymes of the urea cycle were increased in abundance, consistent with an increased use of amino acids for gluconeogenesis. Transcripts and proteins related to extracellular matrix, such as collagens, and inflammatory/immune mechanisms, such as C-reactive protein, proteins involved in or regulated by Toll-like receptor signaling and components of major histocompatibility complexes, were less abundant in MIDY vs. WT liver samples. Our study provides the first multi-omics analysis of liver in a clinically relevant large animal model for insulin-deficient diabetes mellitus.

Project description:Aim/hypothesisHuman enteroviral infections are suggested to be associated with type 1 diabetes. However, the mechanism by which enteroviruses can trigger disease remains unknown. The present study aims to investigate the impact of enterovirus on autophagy, a cellular process that regulates beta cell homeostasis, using the clonal beta cell line INS(832/13) and human islet cells as in vitro models.MethodsINS(832/13) cells and human islet cells were infected with a strain of echovirus 16 (E16), originally isolated from the stool of a child who developed type 1 diabetes-associated autoantibodies. Virus production and release was determined by 50% cell culture infectious dose (CCID50) assay and FACS analysis. The occurrence of autophagy, autophagosomes, lysosomes and autolysosomes was detected by western blot, baculoviral-mediated expression of microtubule-associated protein light chain 3 (LC3)II-GFP and LysoTracker Red, and quantified by Cellomics ArrayScan. Autophagy was also monitored with a Cyto-ID detection kit. Nutrient deprivation (low glucose [2.8 mmol/l]), amino acid starvation (Earle's Balanced Salt Solution [EBSS]) and autophagy-modifying agents (rapamycin and chloroquine) were used in control experiments. Insulin secretion and the expression of autophagy-related (Atg) genes and genes involved in autophagosome-lysosome fusion were determined.ResultsE16-infected INS(832/13) cells displayed an accumulation of autophagosomes, compared with non-treated (NT) cells (grown in complete RPMI1640 containing 11.1 mmol/l glucose) (32.1 ± 1.7 vs 21.0 ± 1.2 μm2/cell; p = 0.05). This was accompanied by increased LC3II ratio both in E16-infected cells grown in low glucose (LG) (2.8 mmol/l) (0.42 ± 0.03 vs 0.11 ± 0.04 (arbitrary units [a.u.]); p < 0.0001) and grown in media containing 11.1 mmol/l glucose (0.37 ± 0.016 vs 0.05 ± 0.02 (a.u.); p < 0.0001). Additionally, p62 accumulated in cells after E16 infection when grown in LG (1.23 ± 0.31 vs 0.36 ± 0.12 (a.u.); p = 0.012) and grown in media containing 11.1 mmol/l glucose (1.79 ± 0.39 vs 0.66 ± 0.15 (a.u.); p = 0.0078). mRNA levels of genes involved in autophagosome formation and autophagosome-lysosome fusion remained unchanged in E16-infected cells, except Atg7, which was significantly increased when autophagy was induced by E16 infection, in combination with LG (1.48 ± 0.08-fold; p = 0.02) and at 11.1 mmol/l glucose (1.26 ± 0.2-fold; p = 0.001), compared with NT controls. Moreover, autophagosomes accumulated in E16-infected cells to the same extent as when cells were treated with the lysosomal inhibitor, chloroquine, clearly indicating that autophagosome turnover was blocked. Upon infection, there was an increased viral titre in the cell culture supernatant and a marked reduction in glucose-stimulated insulin secretion (112.9 ± 24.4 vs 209.8 ± 24.4 ng [mg protein]-1 h-1; p = 0.006), compared with uninfected controls, but cellular viability remained unaffected. Importantly, and in agreement with the observations for INS(832/13) cells, E16 infection impaired autophagic flux in primary human islet cells (46.5 ± 1.6 vs 34.4 ± 2.1 μm2/cell; p = 0.01).Conclusions/interpretationEnteroviruses disrupt beta cell autophagy by impairing the later stages of the autophagic pathway, without influencing expression of key genes involved in core autophagy machinery. This results in increased viral replication, non-lytic viral spread and accumulation of autophagic structures, all of which may contribute to beta cell demise and type 1 diabetes. Graphical abstract.

Dataset Information

Circulating unmethylated CHTOP and INS DNA fragments provide evidence of possible islet cell death in youth with obesity and diabetes.

Publications

Circulating unmethylated CHTOP and INS DNA fragments provide evidence of possible islet cell death in youth with obesity and diabetes.

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