Mechanistic insights into glucose induced vascular epigenetic reprogramming in type 2 diabetes.

Endothelial cells lining the vessel wall regulate thrombosis, inflammation, angiogenesis and balance between vasoconstriction and vasodilatory functions. Subjects with Type 2 diabetes (T2D) accrue a multitude of vasculopathies causing high morbidity and mortality across the globe. High glucose and its modified products such as advanced glycation end products lead to a bidirectional activation of inflammatory and epigenetic machinery in endothelial cells resulting in a state of chronic inflammatory milieu and eventually into vascular complications. Clinical and experimental studies have shown that despite the therapeutic normalization of glucose levels, subjects with T2D overt to vascular complications through a process of metabolic memory which is associated with significant epigenetic reprogramming in endothelial cells. In normal physiological conditions, vascular endothelial cells display a quiescent state and only in response to either physiological or pathological response, endothelial cells undergo proliferation. During the pathogenesis of T2D, DNA methylation, histone marks and non-coding RNAs forming the epigenetic landscape are dysregulated and activate quiescent endothelial cells to switch on a diverse set of molecular activities and lead to endothelial dysfunction. In the present review, we provide a comprehensive overview of how hyperglycemia in T2D reprograms endothelial epigenome and lead to functional consequences in the pathogenesis of vascular complications. Further, we catalogue and discuss epi-drugs that may ameliorate endothelial functions during T2D.

Evidence for perturbed metabolic patterns in bipolar disorder subjects associated with lithium responsiveness.

Bipolar disorder (BD) is multifactorial mood disorder characterized by alternating episodes of hyperactive mania and severe depression. Lithium is one of the most preferred drug used as mood stabilizer in treating BD. In this study, we examined the changes in plasma metabolome in BD subjects in the context of lithium responsiveness. Plasma samples from clinically defined, age and gender matched unrelated healthy controls and BD subjects (lithium responders and non-responders) were obtained and processed in positive and negative mode using untargeted liquid chromatography/mass spectrometry analysis. We identified significant alterations in plasma levels of dopamine along with its precursors (tyrosine and phenylalanine), branched chain amino acid such as valine and excitatory neurotransmitter glutamate between healthy control and BD subjects. Lipid molecules such as, eicosenoic acid and retinyl ester also showed distinguished patterns between control and BD individuals. Lithium responsiveness was markedly associated with significant differences in proline, L-gamma-glutamyl-isoleucine, dopamine, palmitic acid methyl ester, cholesterol sulfate, androsterone sulfate and 9S,12S,13S-triHOME levels. Altered metabolites enriched with key biochemical pathways associated with neuropsychiatry disorders. We hypothesize that BD pathogenesis and lithium responsiveness is associated with impaired homeostasis of amino acid and lipid metabolism.

Interleukin-6 determines protein stabilization of DNA methyltransferases and alters DNA promoter methylation of genes associated with insulin signaling and angiogenesis.

Individuals with type 2 diabetes (T2D) display vascular insulin resistance and decreased nitric oxide production leading to vasoconstriction and atherosclerosis. Soluble factors such as pro-inflammatory molecules, and various genetic and epigenetic mechanisms have been implicated to induce insulin resistance in vascular endothelial cells. Epigenetic mechanisms such as altered promoter DNA methylation have been demonstrated in development and progression of metabolic disorders and atherosclerosis. However, underlying precise epigenetic mechanisms regulating cross talk between insulin signaling genes and inflammation in vascular cells remains to be fully understood. Human endothelial cells when (a) treated with interleukin-6 (IL-6) and insulin together, (b) pretreated with IL-6, and (c) under hyperinsulinemic conditions led to a state of vascular insulin resistance resulting in decreased Akt/eNOS activation and subsequent stabilization of STAT3 phosphorylation. IL-6 abrogated insulin effects on angiogenesis in 3D spheroid and matrigel assays. IL-6-induced insulin resistance was associated with decreased activity of DNA methyltransferase isoforms and global DNA hypomethylation, which inversely correlated with S-phase of cell cycle. CpG microarray analysis in IL-6 treated endothelial cells revealed promoters associated hypo- and hypermethylation of 199 and 98 genes respectively. Promoter DNA methylation status of genes associated with insulin signaling and angiogenesis such as RPS6KA2, PIK3R2, FOXD3, EXOC7, MAP3K8, ITPKB, EPHA6, IGF1R, and FOXC2 were validated by bisulfite DNA sequencing. Concentration and time-dependent analysis revealed that IL-6 reduced DNMT1 and DNMT3B but not DNMT3A protein levels. Our data indicate a causal link between IL-6-induced changes in global and promoter-specific DNA methylation, due to reduced DNMT1 and DNMT3B protein levels leading to altered expression of critical genes involved in insulin signaling and angiogenesis.

Elevated homocysteine levels in type 2 diabetes induce constitutive neutrophil extracellular traps.

Constitutively active neutrophil extracellular traps (NETs) and elevated plasma homocysteine are independent risk factors for Type 2 Diabetes (T2D) associated vascular diseases. Here, we show robust NETosis due to elevated plasma homocysteine levels in T2D subjects and increased components of NETs such as neutrophil elastase and cell free DNA. Cooperative NETs formation was observed in neutrophils exposed to homocysteine, IL-6 and high glucose suggesting acute temporal changes tightly regulate constitutive NETosis. Homocysteine induced NETs by NADPH oxidase dependent and independent mechanisms. Constitutively higher levels of calcium and mitochondrial superoxides under hyperglycemic conditions were further elevated in response to homocysteine leading to accelerated NETosis. Homocysteine showed robust interaction between neutrophils and platelets by inducing platelet aggregation and NETosis in an interdependent manner. Our data demonstrates that homocysteine can alter innate immune function by promoting NETs formation and disturbs homeostasis between platelets and neutrophils which may lead to T2D associated vascular diseases.

Copy number variations are progressively associated with the pathogenesis of colorectal cancer in ulcerative colitis.

AIM: To evaluate the association of known copy number variations (CNVs) in ulcerative colitis (UC) progressing to colorectal cancer. METHODS: Microsatellite instability analysis using the National Cancer Institute's panel of markers, and CNV association studies using Agilent 2 × 105 k arrays were done in tissue samples from four patient groups with UC: those at low risk (LR) or high risk of developing colorectal cancer, those with premalignant dysplastic lesions, and those with colitis-associated colorectal cancer (CAC). DNA from tissue samples of these groups were independently hybridized on arrays and analyzed. The data obtained were further subjected to downstream bioinformatics enrichment analysis to examine the correlation with CAC progression. RESULTS: Microarray analysis highlighted a progressive increase in the total number of CNVs [LR (n = 178) vs CAC (n = 958), 5.3-fold], gains and losses [LR (n = 37 and 141) vs CAC (n = 495 and 463), 13.4- and 3.3-fold, respectively], size [LR (964.2 kb) vs CAC (10540 kb), 10.9-fold] and the number of genes in such regions [LR (n = 119) vs CAC (n = 455), 3.8-fold]. Chromosome-wise analysis of CNVs also showed an increase in the number of CNVs across each chromosome. There were 38 genes common to all four groups in the study; 13 of these were common to cancer genes from the Genetic Disease Association dataset. The gene set enrichment analysis and ontology analysis highlighted many cancer-associated genes. All the samples in the different groups were microsatellite stable. CONCLUSION: Increasing numbers of CNVs are associated with the progression of UC to CAC, and warrant further detailed exploration.

High glucose modulates IL-6 mediated immune homeostasis through impeding neutrophil extracellular trap formation.

Neutrophils serve as an active constituent of innate immunity and are endowed with distinct ability for producing neutrophil extracellular traps (NETs) to eliminate pathogens. Earlier studies have demonstrated a dysfunction of the innate immune system in diabetic subjects leading to increased susceptibility to infections; however, the influence of hyperglycemic conditions on NETs is unknown. In the present study we demonstrate that (a) NETs are influenced by glucose homeostasis, (b) IL-6 is a potent inducer of energy dependent NET formation and (c) hyperglycemia mimics a state of constitutively active pro-inflammatory condition in neutrophils leading to reduced response to external stimuli making diabetic subjects susceptible to infections.