High glucose decreases endothelial cell proliferation via the extracellular signal regulated kinase/p15INK4b pathway

Anti-Inflammatory Effects of Quercetin on High-Glucose and Pro-Inflammatory Cytokine Challenged Vascular Endothelial Cell Metabolism

SCOPE

Pro-inflammatory stimuli such as hyperglycemia and cytokines have been shown to negatively affect endothelial cell functions. The aim of this study is to assess the potential of quercetin and its human metabolites to overcome the deleterious effects of hyperglycemic or inflammatory conditions on the vascular endothelium by modulating endothelial cell metabolism.

METHODS AND RESULTS

A metabolomics approach enabled identification and quantification of 27 human umbilical vein endothelial cell (HUVEC) metabolites. Treatment of HUVECs with high-glucose concentrations causes significant increases in lactate and glutamate concentrations. Quercetin inhibits glucose-induced increases in lactate and adenosine 5'-triphosphate (ATP) and also increased inosine concentrations. Tumor necrosis factor α-treatment (TNFα) of HUVECs causes increases in asparagine and decreases in aspartate concentrations. Co-treatment with quercetin reduces pyruvate concentrations compared to TNFα-only treated controls. Subsequently, it was shown that quercetin and its HUVEC phase-2 conjugates inhibit adenosine deaminase, xanthine oxidase and 5'nucleotidase (CD73) but not ectonucleoside triphosphate diphosphohydrolase-1 (CD39) or purine nucleoside phosphorylase activities.

CONCLUSION

Quercetin was shown to alter the balance of HUVEC metabolites towards a less inflamed phenotype, both alone and in the presence of pro-inflammatory stimuli. These changes are consistent with the inhibition of particular enzymes involved in purine metabolism by quercetin and its HUVEC metabolites.

Vaccarin Regulates Diabetic Chronic Wound Healing through FOXP2/AGGF1 Pathways

Background: Diabetes mellitus is a growing global health issue nearly across the world. Diabetic patients who are prone to develop diabetes-related complications often exhibit progressive neuropathy (painless and sensory loss). It is usual for small wounds to progress to ulceration, which especially worsens with peripheral arterial disease and in the presence of anaerobic bacteria, culminating into gangrene. In our study, vaccarin (VAC), the main active monomer extracted from Chinese herb vaccariae semen, is proven to have a role in promoting diabetic chronic wound healing through a cytoprotective role under high glucose conditions. Materials and methods: We constructed a pressure ulcer on both VAC-treated and control mice based on a type 1 diabetes (T1DM) model. The wound healing index was evaluated by an experimental wound assessment tool (EWAT). We also determined the effect of VAC on the proliferation and cell migration of human microvascular endothelial cells (HMEC-1) by a cell counting kit (CCK-8), a scratch and transwell assay. Results: The results demonstrated that VAC could promote the proliferation and migration of high glucose-stimulated HMEC-1 cells, which depend on the activation of FOXP2/AGGF1. Activation of the angiogenic factor with G patch and FHA domains 1 (AGGF1) caused enhanced phosphorylation of serine/threonine kinase (Akt) and extracellular regulated protein kinases (Erk1/2). By silencing the expression of forkhead box p2 (FOXP2) protein by siRNA, both mRNA and protein expression of AGGF1 were downregulated, leading to a decreased proliferation and migration of HMEC-1 cells. In addition, a diabetic chronic wound model in vivo unveiled that VAC had a positive effect on chronic wound healing, which involved the activation of the above-mentioned pathways. Conclusions: In summary, our study found that VAC promoted chronic wound healing in T1DM mice by activating the FOXP2/AGGF1 pathway, indicating that VAC may be a promising candidate for the treatment of the chronic wounds of diabetic patients.

The pleiotropic molecule NGF regulates the in vitro properties of fibroblasts, keratinocytes, and endothelial cells: implications for wound healing

Nerve growth factor (NGF) is recognized as a pleiotropic molecule, exerting a variety of biological effects on different cell types and pathophysiological conditions, and its role in tissue wound healing has been recently highlighted. However, the preferential cellular target of NGF is still elusive in the complex cellular and molecular cross talk that accompanies wound healing. Thus, to explore possible NGF cellular targets in skin wound healing, we investigated the in vitro NGF responsiveness of keratinocytes (cell line HEKa), fibroblasts (cell line BJ), and endothelial cells (cell line HUVEC), also in the presence of adverse microenvironmental conditions, e.g., hyperglycemia. The main results are summarized as follows: 1) NGF stimulates keratinocyte proliferation and HUVEC proliferation and angiogenesis in a dose-dependent manner although it has no effect on fibroblast proliferation; 2) NGF stimulates keratinocyte but not fibroblast migration in the wound healing assay; and 3) NGF completely reverts the proliferation impairment of keratinocytes and the angiogenesis impairment of HUVECs induced by high d-glucose concentration in the culture medium. These results contribute to better understanding possible targets for the therapeutic use of NGF in skin repair.

Down-regulation of Suv39h1 attenuates neointima formation after carotid artery injury in diabetic rats

Patients with diabetes have an increased risk of vascular complications. Suv39h1, a histone methyltransferase, plays a protective role against myocardial injury in diabetes. Herein, we intend to explore whether Suv39h1 could affect neointimal formation after vascular injury in diabetic rats and reveal the underlying mechanism. In this study, we generated adenovirus expressing Suv39h1 as well as lentivirus expressing Suv39h1‐targeting shRNA and evaluated the significance of Suv39h1 in vascular smooth muscle cells (VSMCs) under diabetic conditions. In vitro, we examined proliferative and migratory behaviours as well as the underlying signalling mechanisms in VSMCs in response to high glucose treatment. In vivo, we induced diabetes in SD rats with streptozocin and established the common carotid artery balloon injury model. Suv39h1 was found to be both necessary and sufficient to promote VSMC proliferation and migration under high glucose conditions. We observed corresponding changes in intracellular signalling molecules including complement C3 and phosphor‐ERK1/2. However, either up‐regulating or down‐regulating Suv39h1, phosphor‐p38 level was not significantly affected. Consistently, Suv39h1 overexpression led to accelerated neointima formation, while knocking down Suv39h1 reduced it following carotid artery injury in diabetic rats. Using microarray analyses, we showed that altering the Suv39h1 level in vivo dramatically altered the expression of myriad genes mediating different biological processes and molecular function. This study reveals the novel role of Suv39h1 in VSMCs of diabetes and suggests its potential role as a therapeutic target in diabetic vascular injury.

High glucose and low specific cell growth but not mild hypothermia improve specific r-protein productivity in chemostat culture of CHO cells

In the biopharmaceutical sector, Chinese hamster ovary (CHO) cells have become the host of choice to produce recombinant proteins (r-proteins) due to their capacity for correct protein folding, assembly, and posttranslational modification. However, the production of therapeutic r-proteins in CHO cells is expensive and presents insufficient production yields for certain proteins. Effective culture strategies to increase productivity (q_p) include a high glucose concentration in the medium and mild hypothermia (28–34 °C), but these changes lead to a reduced specific growth rate. To study the individual and combined impacts of glucose concentration, specific growth rate and mild hypothermia on culture performance and cell metabolism, we analyzed chemostat cultures of recombinant human tissue plasminogen activator (rh-tPA)-producing CHO cell lines fed with three glucose concentrations in feeding media (20, 30 and 40 mM), at two dilution rates (0.01 and 0.018 1/h) and two temperatures (33 and 37 °C). The results indicated significant changes in cell growth, cell cycle distribution, metabolism, and rh-tPA productivity in response to the varying environmental culture conditions. High glucose feed led to constrained cell growth, increased specific rh-tPA productivity and a higher number of cells in the G2/M phase. Low specific growth rate and temperature (33 °C) reduced glucose consumption and lactate production rates. Our findings indicated that a reduced specific growth rate coupled with high feed glucose significantly improves r-protein productivity in CHO cells. We also observed that low temperature significantly reduced q_p, but not cell growth when dilution rate was manipulated, regardless of the glucose concentration or dilution rate. In contrast, we determined that feed glucose concentration and consumption rate were the dominant aspects of the growth and productivity in CHO cells by using multivariate analysis.

The role of miR-328 in high glucose-induced endothelial-to-mesenchymal transition in human umbilical vein endothelial cells

AIMS

Endothelial-to-mesenchymal transition (EndMT) contribute to diabetic cardiac fibrosis, the underlying mechanisms are poorly understood. In the study, we aimed to investigate the role of miR-328 in EndMT mediated by high glucose (HG) and the signaling pathways implicated in human umbilical vein endothelial cells (HUVECs).

MATERIALS AND METHODS

EndMT of HUVECs was determined by immunofluorescent staining and western blot of the markers CD31 and α-SMA. Real-time polymerase chain reaction was used to detect mRNA expression of miR-328 and transforming growth factor β₁ (TGF-β₁). SB431542 was used to study the relation of miR-328 and TGF-β₁ during EndMT induced by HG. Over-expression and inhibition of miR-328 were achieved by transduction of miR-328 and antagomiR-328. The effects of miR-328 on expression of type I and III collagen, p-MEK1/2, p-ERK1/2 were examined by Western blot.

KEY FINDINGS

The level of miR-328 was significantly up-regulated in HG-induced EndMT. MiR-328 showed the independent capability of inducing EndMT, which was not related to TGF-β₁, and this effect was abrogated by antagomiR-328. MiR-328 affected type I collagen in a time- and dose-dependent manner and enhanced protein expression of type I and III collagens. Further investigation displayed that a significantly higher expression of p-MEK1/2 and p-ERK1/2 in HUVECs transduced with miR-328, and a lower expression of p-MEK1/2 and p-ERK1/2 in cells transduced with antagomiR-328.

SIGNIFICANCE

These results suggest a novel role for miR-328 in HG-induced EndMT, MEK1/2-ERK1/2 pathway is likely to be involved in the associated effects. Our findings may suggest antagomiR-328 as an alternative agent in prevention of HG-induced EndMT.

FOXF1 transcription factor promotes lung regeneration after partial pneumonectomy

FOXF1, a member of the forkhead box family of transcription factors, has been previously shown to be critical for lung development, homeostasis, and injury responses. However, the role of FOXF1 in lung regeneration is unknown. Herein, we performed partial pneumonectomy, a model of lung regeneration, in mice lacking one Foxf1 allele in endothelial cells (PDGFb-iCre/Foxf1 ^fl/+ mice). Endothelial cell proliferation was significantly reduced in regenerating lungs from mice deficient for endothelial Foxf1. Decreased endothelial proliferation was associated with delayed lung regeneration as shown by reduced respiratory volume in Foxf1-deficient lungs. FACS-sorted endothelial cells isolated from regenerating PDGFb-iCre/Foxf1 ^fl/+ and control lungs were used for RNAseq analysis to identify FOXF1 target genes. Foxf1 deficiency altered expression of numerous genes including those regulating extracellular matrix remodeling (Timp3, Adamts9) and cell cycle progression (Cdkn1a, Cdkn2b, Cenpj, Tubb4a), which are critical for lung regeneration. Deletion of Foxf1 increased Timp3 mRNA and protein, decreasing MMP14 activity in regenerating lungs. ChIPseq analysis for FOXF1 and histone methylation marks identified DNA regulatory regions within the Cd44, Cdkn1a, and Cdkn2b genes, indicating they are direct FOXF1 targets. Thus FOXF1 stimulates lung regeneration following partial pneumonectomy via direct transcriptional regulation of genes critical for extracellular matrix remodeling and cell cycle progression.

Activation of Nrf2-mediated anti-oxidant genes by antrodin C prevents hyperglycemia-induced senescence and apoptosis in human endothelial cells

In the present study, we investigated the effects of antrodin C (ADC), a maleimide derivative isolated from mycelia of Antrodia cinnamomea, on high glucose (HG, 30 mM)-accelerated endothelial dysfunction in vitro. HG-induced cytotoxicity in human umbilical vein endothelial cells (HUVECs) was significantly ameliorated by ADC. In addition, treatment with ADC significantly prevented HG-induced senescence, growth arrest at the G₁-S transition phase and apoptosis in HUVECs. Moreover, the increased level of intracellular reactive oxygen species (ROS) under HG condition was significantly ameliorated by ADC. Further analysis revealed that ADC-mediated anti-oxidant effects were due to up-regulation of cellular anti-oxidant genes, such as HO-1 and NQO-1 via promotion of the transcriptional activity of Nrf2, which was further confirmed by the failure of ADC to protect HUVECs from HG-induced dysfunction under HO-1 inhibition or Nrf2 silencing. Furthermore, hyperosmotic glucose (HOG, 60 mM)-induced uncontrolled production of ROS, rapid apoptotic cell death and HUVEC injury were significantly prevented by ADC, whereas these preventive effects were barely observed in HO-1 inhibited or Nrf2 silenced cells. Taken together, these results suggest that ADC may represent a promising intervention in diabetic-associated cardiovascular diseases by activating the Nrf2-dependent cellular anti-oxidant defense system.

High glucose enhances cAMP level and extracellular signal-regulated kinase phosphorylation in Chinese hamster ovary cell: Usage of Br-cAMP in foreign protein β-galactosidase expression

Glucose is a carbon source for Chinese hamster ovary (CHO) cell growth, while low growth rate is considered to enhance the production of recombinant proteins. The present study reveals that glucose concentrations higher than 1 g/L reduce the growth rate and substantially increase in cAMP (∼300%) at a high glucose concentration (10 g/L). High glucose also enhances the phosphorylation of extracellular signal-regulated kinase (ERK) and p27^kip by Western blot analysis. To determine whether the phosphorylation of ERK is involved in the mechanism, a cyclic-AMP dependent protein kinase A (PKA) inhibitor (H-8) or MEK (MAPKK) inhibitor (PD98059) was added to block ERK phosphorylation. We show that both the high glucose-induced ERK phosphorylation and growth rate return to baseline levels. These results suggest that the cAMP/PKA and MAP signaling pathways are involved in the abovementioned mechanism. Interestingly, the direct addition of 8-bromo-cAMP (Br-cAMP), a membrane-permeable cAMP analog, can mimic the similar effects produced by high glucose. Subsequently Br-cAMP could induce β-galactosidase (β-Gal) recombinant protein expression by 1.6-fold. Furthermore, Br-cAMP can additionally enhance the β-Gal production (from 2.8- to 4.5-fold) when CHO cells were stimulated with glycerol, thymidine, dimethyl sulfoxide, pentanoic acid, or sodium butyrate. Thus, Br-cAMP may be used as an alternative agent in promoting foreign protein expression for CHO cells.

Angelica sinensis polysaccharides inhibit endothelial progenitor cell senescence through the reduction of oxidative stress and activation of the Akt/hTERT pathway

CONTEXT

Angelica sinensis (Oliv.) Diels (Apiaceae) polysaccharides (ASP) may play a key role in anti-ischemic activity. However, the anti-atherosclerotic activity and mechanism are unknown.

OBJECTIVE

This study investigated the protective effects of ASP against ox-LDL-induced senescence of EPCs and explored its underlying molecular mechanisms.

MATERIALS AND METHODS

Mononuclear cells were isolated from bone marrow (BM) of SD rats and differentiated to EPCs. EPCs were exposed to oxidized low-density lipoprotein (ox-LDL, 10 µg/mL, 24 h) and incubated with or without high-dose (100 µg/mL, 48 h) or low-dose (20 µg/mL, 48 h) ASP. Another group of EPCs was pre-treated with Wortmannin (100 nM, 45 min), a PI3K/Akt inhibitor. EPC senescence, telomerase activity, and superoxide anion levels were assessed using SA-β-galactosidase staining, telomerase PCR-ELISA analysis, and DHE staining, respectively. The expression of related proteins, including Akt, p-Akt, hTERT, p-hTERT, and gp91phox, were detected using western blot.

RESULTS

EPCs (47.3%) were SA-β-gal positive after treatment by ox-LDL, additionally, ox-LDL significantly increased superoxide anion levels (375% versus 100%), and inhibited telomerase activity (42% versus 100%). However, the pro-senescent effect of ox-LDL was attenuated about three-fold (16.7%), superoxide anion levels were decreased more than two-fold (148%), and telomerase activity was recovered partly (88% versus 42%) in the EPCs when treated with ASP (100 µg/mL). The immunoblotting confirmed that ASP attenuated inhibition of phosphorylation of Akt and hTERT induced by ox-LDL and down-regulated increased the expression of gp91-phox. Moreover, some effects of ASP were partially abrogated in the presence of Wortmannin.

DISCUSSION

Ox-LDL induced senescence of EPCs via inhibition of telomerase activity, which was influenced by oxidative stress and the Akt/hTERT pathway. The inhibition of EPC senescence by ASP could be important for potential therapeutics.

CONCLUSION

Treatment of EPCs with ASP remarkably attenuates the harmful effects of ox-LDL via augmentation of Akt/hTERT phosphorylation and inhibition of oxidative stress.

PPARβ activation restores the high glucose-induced impairment of insulin signalling in endothelial cells

BACKGROUND AND PURPOSE

PPARβ enhances insulin sensitivity in adipocytes and skeletal muscle cells, but its effects on insulin signalling in endothelial cells are not known. We analysed the effects of the PPARβ/δ (PPARβ) agonists, GW0742 and L165041, on impaired insulin signalling induced by high glucose in HUVECs and aortic and mesenteric arteries from diabetic rats.

EXPERIMENTAL APPROACH

Insulin-stimulated NO production, Akt-Ser(473) and eNOS-Ser(1177) phosphorylation, and reactive oxygen species (ROS) production were studied in HUVECs incubated in low- or high-glucose medium. Insulin-stimulated relaxations and protein phosphorylation in vessels from streptozotocin (STZ)-induced diabetic rats were also analysed.

KEY RESULTS

HUVECs incubated in high-glucose medium showed a significant reduction in insulin-stimulated production of NO. High glucose also reduced insulin-induced Akt-Ser(473) and eNOS-Ser(1177) phosphorylation, increased IRS-1-Ser(636) and ERK1/2-Thr(183) -Tyr(185) phosphorylation and increased ROS production. The co-incubation with the PPARβ agonists GW0742 or L165041 prevented all these effects induced by high glucose. In turn, the effects induced by the agonists were suppressed when HUVEC were also incubated with the PPARβ antagonist GSK0660, the pyruvate dehydrogenase kinase (PDK)4 inhibitor dichloroacetate or after knockdown of both PPARβ and PDK4 with siRNA. The ERK1/2 inhibitor PD98059, ROS scavenger catalase, inhibitor of complex II thenoyltrifluoroacetone or uncoupler of oxidative phosphorylation, carbonyl cyanide m-chlorophenylhydrazone, also prevented glucose-induced insulin resistance. In STZ diabetic rats, oral GW0742 also improved insulin signalling and the impaired NO-mediated vascular relaxation.

CONCLUSION AND IMPLICATIONS

PPARβ activation in vitro and in vivo restores the endothelial function, preserving the insulin-Akt-eNOS pathway impaired by high glucose, at least in part, through PDK4 activation.

Transcriptome analysis of human primary endothelial cells (HUVEC) from umbilical cords of gestational diabetic mothers reveals candidate sites for an epigenetic modulation of specific gene expression

Within the complex pathological picture associated to diabetes, high glucose (HG) has "per se" effects on cells and tissues that involve epigenetic reprogramming of gene expression. In fetal tissues, epigenetic changes occur genome-wide and are believed to induce specific long term effects. Human umbilical vein endothelial cells (HUVEC) obtained at delivery from gestational diabetic women were used to study the transcriptomic effects of chronic hyperglycemia in fetal vascular cells using Affymetrix microarrays. In spite of the small number of samples analyzed (n=6), genes related to insulin sensing and extracellular matrix reorganization were found significantly affected by HG. Quantitative PCR analysis of gene promoters identified a significant differential DNA methylation in TGFB2. Use of Ea.hy926 endothelial cells confirms data on HUVEC. Our study corroborates recent evidences suggesting that epigenetic reprogramming of gene expression occurs with persistent HG and provides a background for future investigations addressing genomic consequences of chronic HG.

High glucose facilitates cell cycle arrest of rat bone marrow multipotent adult progenitor cells through transforming growth factor-β1 and extracellular signal-regulated kinase 1/2 signalling without changing Oct4 expression

1. The transcription factor Oct4 is critical to the pluripotency, self-renewal and differentiation of stem cells. The aim of the present study was to investigate the effects of high glucose (HG) on the cell cycle progression of bone marrow multipotent adult progenitor cells (MAPC) and Oct4 expression, as well as the underlying mechanisms. 2. Rat MAPC were cultured in normal (5.5 mmol/L D-glucose) and HG (25.5 mmol/L D-glucose) media for up to 14 days. L-Glucose served as a high osmolarity control. Culture in HG media substantially increased the number of cells in the G(0)/G(1) phase and decreased the number in the S phase without changing the cell population in the G(2) phase. Expression of the cell cycle regulatory protein p21CIP/WAF-1 (p21), but not that of p27KIP-1 (p27), was significantly upregulated in cells cultured in HG media. Significant increases were seen in transforming growth factor (TGF)-β1 levels in cells and MAPC-conditioned medium in the presence of HG, and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was enhanced in cells cultured in the presence of HG medium without any changes in Akt phosphorylation. 3. Neutralizing TGF-β1 antibody effectively prevented HG-induced increases in ERK1/2 phosphorylation, p21 expression and suppression of cell cycle progression of MAPC. Inhibiting ERK1/2 phosphorylation with PD98059 completely blocked HG-induced p21 expression and markedly reversed HG-induced inhibition of cell cycle progression in MAPC. The HG-induced suppression of cell cycle progression was not accompanied by inhibition of cell proliferation or Oct4 expression in these cells. 4. The data indicate that HG facilitates cell cycle arrest of rat MAPC through TGF-β1-induced activation of ERK1/2 signalling and p21 expression, and that Oct4 expression in MAPC is independent of the cell cycle and/or TGF-β1 or ERK1/2 signalling in HG medium.

Differential gene expression in young and senescent endothelial cells under static and laminar shear stress conditions

Laminar shear stress (LSS) caused by blood flow is known to regulate endothelial function and to contribute to vascular health. By way of contrast, endothelial cell senescence seems to increase the incidence of vascular disorders. In an attempt to identify genes associated with vascular health/disease states, this study assessed the differential gene expression of young and senescent human umbilical vein endothelial cells (HUVECs) under static and LSS conditions. Replicative cell senescence was induced by continuous subculture in vitro, and LSS was provided using a cone-and-plate device. Young (p4) and senescent (p18) cells were subjected to LSS at 12 dyn.cm(-2) or maintained under static conditions for 24 h. Total mRNA was subjected to cDNA microarray analysis using the Affymetrix GeneChip. Welch t test at a significance level of p < 0.05 provided 961 "LSS-responsive" genes, whose expression was altered by LSS in both young and senescent cells, and 529 "senescence-responsive" genes differentially expressed in young vs senescent cells under both static and LSS conditions. The LSS-responsive and senescence-responsive gene groups included 74 genes held in common; these may prove useful for the study of cellular responses commonly affected by LSS and senescence. Among them, 20 genes whose expression was increased by LSS and simultaneously decreased by cellular senescence are suggested as potential vascular health markers in the sense that LSS is antiatherogenic, whereas senescence is proatherogenic. These genes included argininosuccinate synthetase 1, which was determined to be critical for both basal and LSS-induced NO production in young HUVECs. Furthermore, its diminished expression, and not that of nitric oxide synthase 3, was implicated in the insufficient NO production exhibited by senescent HUVECs under LSS conditions. The genes identified in this study are expected to facilitate improvements in our current level of understanding regarding endothelial physiology in association with age-associated vascular disease.

Common Genetic Variants on Chromosome 9p21 Confers Risk of Ischemic Stroke

Background— Epidemiological studies indicate a genetic contribution to ischemic stroke risk, but specific genetic variants remain unknown, with the exception of a few rare variants. Recent genome-wide association studies identified and replicated common genetic variants on chromosome 9p21 to confer risk of coronary heart disease. We examined whether these variants are associated with ischemic stroke.

Methods and Results— We genotyped 6 common genetic variants on chromosome 9p21, previously associated with coronary artery disease in genome-wide association studies, in 2 population-based studies in southern Sweden, the Lund Stroke Register (n=1837 cases, 947 controls) and the Malmö Diet and Cancer study (MDC; n=888 cases, 893 controls). We examined association in each study and in the pooled dataset. Adjustments were made for cardiovascular risk factors and further for previous myocardial infarction in MDC. We found a modest increase in ischemic stroke risk for 2 common (minor allele frequencies 0.46 to 0.49) variants, rs2383207 ( P =0.04 in Lund Stroke Register, P =0.01 in MDC) and rs10757274 ( P =0.03 in Lund Stroke Register, P =0.03 in MDC), in each sample independently. The strength of the association increased when samples were pooled with an odds ratio of 1.15 (95% CI, 1.05 to 1.25; P =0.002) for the strongest variant rs2383207. Results were similar after adjustment for clinical covariates. rs1333049 also showed significant association in MDC, which increased in the pooled sample ( P =0.004).

Conclusions— In this large sample (n=4565), we detected common genetic determinants for ischemic stroke on chromosome 9p21. Our findings indicate that ischemic stroke shares pathophysiological determinants with coronary heart disease and other arterial diseases and highlight the need for large sample sizes in stroke genetics.

Association between polymorphisms in SLC30A8, HHEX, CDKN2A/B, IGF2BP2, FTO, WFS1, CDKAL1, KCNQ1 and type 2 diabetes in the Korean population

According to recent genome-wide association studies, a number of single nucleotide polymorphisms (SNPs) are reported to be associated with type 2 diabetes mellitus (T2DM). The aim of the present study was to investigate the association among the polymorphisms of SLC30A8, HHEX, CDKN2A/B, IGF2BP2, FTO, WFS1, CDKAL1 and KCNQ1 and the risk of T2DM in the Korean population. This study was based on a multicenter case-control study, including 908 patients with T2DM and 502 non-diabetic controls. We genotyped rs13266634, rs1111875, rs10811661, rs4402960, rs8050136, rs734312, rs7754840 and rs2237892 and measured the body weight, body mass index and fasting plasma glucose in all patients and controls. The strongest association was found in a variant of CDKAL1 [rs7754840, odds ratio (OR) = 1.77, 95% CI = 1.50-2.10, p = 5.0 x 10(-11)]. The G allele of rs1111875 (OR = 1.43, 95% CI = 1.18-1.72, p = 1.8 x 10(-4)) in HHEX), the T allele of rs10811661 (OR = 1.47, 95% CI = 1.23-1.75, p = 2.1 x 10(-5)) in CDKN2A/B) and the C allele of rs2237892 (OR = 1.31, 95% CI = 1.10-1.56, p = 0.003) in KCNQ1 showed significant associations with T2DM. Rs13266634 (OR = 1.19, 95% CI = 1.00-1.42, p = 0.045) in SLC30A8 showed a nominal association with the risk of T2DM, whereas SNPs in IGF2BP2, FTO and WFS1 were not associated. In conclusion, we have shown that SNPs in HHEX, CDKN2A/B, CDKAL1, KCNQ1 and SLC30A8 confer a risk of T2DM in the Korean population.

Advanced glycation end-product-inhibited cell proliferation and protein expression of beta-catenin and cyclin D1 are dependent on glycogen synthase kinase 3beta in LLC-PK1 cells

Glycogen synthase kinase 3beta (GSK3beta) is increased by high glucose in mesangial cells. Thus, we studied the role of GSK3beta in advanced glycation end-product (AGE)-induced effects in the proximal tubule-like LLC-PK1 cells. We found that AGE (100 microg/ml) time-dependently (8-48 h) increased phospho-GSK3beta-Tyr216 (active GSK3beta) and time-dependently (4-24 h) decreased phospho-GSK3beta-Ser21/9 (inactive GSK3beta) protein expression. Meanwhile, AGE (100 microg/ml) activated GSK3beta kinase at 8-48 h. AGE (100 microg/ml) dose-dependently (75-100 microg/ml) decreased beta-catenin protein expression but AGE did not decrease beta-catenin protein expression until 48 h. SB216763 (a GSK3beta inhibitor) and GSK3beta shRNA attenuated AGE (100 microg/ml)-inhibited cell proliferation and protein expression of beta-catenin and cyclin D1 at 48 h. SB216763 also attenuated AGE-induced type IV collagen. We conclude that AGE activates GSK3beta in LLC-PK1 cells. AGE-inhibited beta-catenin and cyclin D1 protein expression are dependent on GSK3beta. Moreover, AGE-inhibited cell proliferation and AGE-induced type IV collagen protein expression are dependent on GSK3beta.

The roles of hyperglycaemia and oxidative stress in the rise and collapse of the natural protective mechanism against vascular endothelial cell dysfunction in diabetes

Vascular endothelial cell (VEC) dysfunction in diabetes has been associated with hyperglycaemia-induced intra- and extracellular glycation of proteins and to overproduction of glucose-derived free radicals. VEC protect their intracellular environment against an increased influx of glucose in face of hyperglycaemia by reducing the expression and plasma membrane abundance of their glucose transporter-1 (GLUT-1). We investigated the hypothesis that glucose-derived free radicals induce this down-regulatory mechanism in VEC, but proved the contrary. In fact, pro-oxidants significantly increased the expression and plasma membrane abundance of GLUT-1 and the rate of glucose transport in VEC while abolishing high-glucose-induced down-regulation of the hexose transport system. The resulting uncontrolled influx of glucose followed by overproduction of glucose-derived ROS further up-regulates the rate of glucose transport, and vice versa. This perpetuating glycoxidative stress finally leads to the collapse of the auto-regulatory protective mechanism and accelerates the development of dysfunctional endothelium in blood vessels.