Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR.
Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR. DNA methylation was analyzed in DNA extracted from SAT (subcutaneous adipose tissue) and VAT (visceral adipose tissue) pieces, as well as PBMCs (peripheral blood mononuclear cells), using the Infinium Human Methylation 450 BeadChip assay. This data is from PBMCs.
Project description:Insulin resistance arises when the nutrient storage pathways evolved to maximize efficient energy utilization are exposed to chronic energy surplus. Ectopic lipid accumulation in liver and skeletal muscle triggers pathways that impair insulin signaling, leading to reduced muscle glucose uptake and decreased hepatic glycogen synthesis. Muscle insulin resistance, due to ectopic lipid, precedes liver insulin resistance and diverts ingested glucose to the liver, resulting in increased hepatic de novo lipogenesis and hyperlipidemia. Subsequent macrophage infiltration into white adipose tissue (WAT) leads to increased lipolysis, which further increases hepatic triglyceride synthesis and hyperlipidemia due to increased fatty acid esterification. Macrophage-induced WAT lipolysis also stimulates hepatic gluconeogenesis, promoting fasting and postprandial hyperglycemia through increased fatty acid delivery to the liver, which results in increased hepatic acetyl-CoA content, a potent activator of pyruvate carboxylase, and increased glycerol conversion to glucose. These substrate-regulated processes are mostly independent of insulin signaling in the liver but are dependent on insulin signaling in WAT, which becomes defective with inflammation. Therapies that decrease ectopic lipid storage and diminish macrophage-induced WAT lipolysis will reverse the root causes of type 2 diabetes.
Project description:Autophagy, a well-observed intracellular lysosomal degradation process, is particularly important to the cell viability in diabetic cardiomyopathy (DCM). Peroxidasin (PXDN) is a heme-containing peroxidase that augments oxidative stress and plays an essential role in cardiovascular diseases, while whether PXDN contributes to the pathogenesis of DCM remains unknown. Here we reported the suppression of cell viability and autophagic flux, as shown by autophagosomes accumulation and increased expression level of LC3-II and p62 in cultured H9C2 and human AC16 cells that treated with 400 μM palmitate acid (PA) for 24 h. Simultaneously, PXDN protein level increased. Moreover, cell death, autophagosomes accumulation as well as increased p62 expression were suppressed by PXDN silence. In addition, knockdown of PXDN reversed PA-induced downregulated forkhead box-1 (FoxO1) and reduced FoxO1 phosphorylation, whereas did not affect AKT phosphorylation. Not consistent with the effects of si-PXDN, double-silence of PXDN and FoxO1 significantly increased cell death, suppressed autophagic flux and declined the level of FoxO1 and PXDN, while the expression of LC3-II was unchanged under PA stimulation. Furthermore, inhibition of FoxO1 in PA-untreated cells induced cell death, inhibited autophagic flux, and inhibited FoxO1 and PXDN expression. Thus, we come to conclusion that PXDN plays a key role in PA-induced cell death by impairing autophagic flux through inhibiting FoxO1, and FoxO1 may also affect the expression of PXDN. These findings may develop better understanding of potential mechanisms regarding autophagy in insulin-resistant cardiomyocytes.
Project description:Iron overload, a common clinical occurrence, is implicated in the metabolic syndrome although the contributing pathophysiological mechanisms are not fully defined. We show that prolonged iron overload results in an autophagy defect associated with accumulation of dysfunctional autolysosomes and loss of free lysosomes in skeletal muscle. These autophagy defects contribute to impaired insulin-stimulated glucose uptake and insulin signaling. Mechanistically, we show that iron overload leads to a decrease in Akt-mediated repression of tuberous sclerosis complex (TSC2) and Rheb-mediated mTORC1 activation on autolysosomes, thereby inhibiting autophagic-lysosome regeneration. Constitutive activation of mTORC1 or iron withdrawal replenishes lysosomal pools via increased mTORC1-UVRAG signaling, which restores insulin sensitivity. Induction of iron overload via intravenous iron-dextran delivery in mice also results in insulin resistance accompanied by abnormal autophagosome accumulation, lysosomal loss, and decreased mTORC1-UVRAG signaling in muscle. Collectively, our results show that chronic iron overload leads to a profound autophagy defect through mTORC1-UVRAG inhibition and provides new mechanistic insight into metabolic syndrome-associated insulin resistance.
Project description:Rationale: Sirtuins are NAD+-dependent protein deacylases known to have protective effects against age-related diseases such as diabetes, cancer, and neurodegenerative disease. SIRT2 is the only primarily cytoplasmic isoform and its overall role in glucose homeostasis remains uncertain. Methods: SIRT2-knockout (KO) rats were constructed to evaluate the role of SIRT2 in glucose homeostasis. The effect of SIRT2 on β-cell function was detected by investigating the morphology, insulin secretion, and metabolomic state of islets. The deacetylation and stabilization of GKRP in β-cells by SIRT2 were determined by western blot, adenoviral infection, and immunoprecipitation. Results: SIRT2-KO rats exhibited impaired glucose tolerance and glucose-stimulated insulin secretion (GSIS), without change in insulin sensitivity. SIRT2 deficiency or inhibition by AGK2 decreased GSIS in isolated rat islets, with lowered oxygen consumption rate. Adenovirus-mediated overexpression of SIRT2 enhanced insulin secretion from rat islets. Metabolomics analysis revealed a decrease in metabolites of glycolysis and tricarboxylic acid cycle in SIRT2-KO islets compared with control islets. Our study further demonstrated that glucokinase regulatory protein (GKRP), an endogenous inhibitor of glucokinase (GCK), was expressed in rat islets. SIRT2 overexpression deacetylated GKRP in INS-1 β-cells. SIRT2 knockout or inhibition elevated GKRP protein stability in islet β-cells, leading to an increase in the interaction of GKRP and GCK. On the contrary, SIRT2 inhibition promoted the protein degradation of ALDOA, a glycolytic enzyme. Conclusions: SIRT2 ablation inhibits GSIS through blocking GKRP protein degradation and promoting ALDOA protein degradation, resulting in a decrease in glycolytic flux.
Project description:Acupuncture (Acup) and moxibustion (Moxi) are commonly used interventions in clinical practice. However, the difference between Acup and moxibustion mechanisms is unclear. In current study, blood perfusion responses resulted from Acup or Moxi at Weishu acupoint (BL21) and control points were explored, respectively. The time series of blood flux signals at BL21 and control points were transformed with Morlet wavelet, and the differences in each frequency interval were observed. The results suggested that acupoint response to different stimulation is a comprehensive process which related to all components of blood perfusion signals. Whereas the different response at control points was not observed, there has been significant difference coherence value between Acup and Moxi stimulation. The results suggested the influence of Acup and Moxi not only on the level of blood perfusion at local area; the intrinsic relevance after stimulation which can be evaluated by coherence analysis is also an appropriate index to distinguish different stimulations.
Project description:Following a multivariant analysis we demonstrated that children and adolescents with Burkitt lymphoma (BL) and a 13q14.3 deletion have a significant decrease in event free survival (EFS) despite identical short intensive multi-agent chemotherapy. However, how this deletion in the 13q14.3 region is associated with a significant decrease in EFS in children and adolescents with BL is largely unknown. The gene Deleted in Lymphocytic Leukemia 1 (DLEU1) is located in the region of 13q14.3. Here, we report that DLEU1 expression is implicated in the regulation of BL programmed cell death, cell proliferation, and expression of apoptotic genes in transcription activator-like effector nuclease (TALEN)s-induced DLEU1 knockdown and DLEU1 overexpressing BL cell lines. Furthermore, NSG mice xenografted with DLEU1 knockdown BL cells had significantly shortened survival (p < 0.05 and p < 0.005), whereas those xenografted with DLEU1 overexpressing BL cells had significantly improved survival (p < 0.05 and p < 0.0001), following treatment with rituximab and/or cyclophosphamide. These data suggest that DLEU1 may in part function as a tumor suppressor gene and confer chemoimmunotherapy resistance in children and adolescents with BL.