Xi-Qiong Han

Nε-carboxymethyl-lysine promotes calcium deposition in VSMCs via intracellular oxidative stress-induced PDK4 activation and alters glucose metabolism

Diabetes and vascular calcification are intrinsically linked. We previously reported that advanced glycation end products (AGEs) accelerate calcium deposition in vascular smooth muscle cells (VSMCs) via excessive oxidative stress. However, the underlying mechanism remains poorly understood. Pyruvate dehydrogenase kinase 4 (PDK4) is an important mitochondrial matrix enzyme in cellular energy metabolism. Since hyperactivation of PDK4 has been reported in calcified vessels and in patients with diabetes mellitus, inhibition of PDK4 expression may be a strategy for the prevention of diabetic vascular calcification. In this study, we used a rat VSMC model to investigate the role of PDK4 in diabetic vascular calcification and further explore the underlying mechanisms. We observed that Nε-carboxymethyl-lysine (CML), which is a major immunogen of AGEs, accelerated calcium deposition in VSMCs through PDK4 activation. An elevated level of reactive oxygen species (ROS) acted as a signal transduction intermediate to increase PDK4 expression. Either inhibition of PDK4 expression or RAGE (receptor for AGEs) blockade attenuated CML-induced VSMC calcification, as shown by decreased alkaline phosphatase (ALP) activity and runt-related transcription factor 2 (RUNX2) expression. Glucose consumption and lactate production were increased during CML-induced VSMC calcification. Importantly, CML accelerates glycolysis in VSMCs via a PDK4-dependent pathway. In conclusion, this study demonstrates a novel mechanism by which CML promotes VSMC calcification via PDK4 activation and alters glucose metabolism in VSMCs.

Advanced glycation end products accelerate calcification in VSMCs through HIF-1α/PDK4 activation and suppress glucose metabolism

Arterial media calcification is associated with diabetes mellitus. Previous studies have shown that advanced glycation end products (AGEs) are responsible for vascular smooth muscle cell (VSMC) calcification, but the underlying mechanisms remain unclear. Hypoxia-inducible factor-1α (HIF-1α), one of the major factors during hypoxia, and pyruvate dehydrogenase kinase 4 (PDK4), an important mitochondrial matrix enzyme in cellular metabolism shift, have been reported in VSMC calcification. The potential link among HIF-1α, PDK4, and AGEs-induced vascular calcification was investigated in this study. We observed that AGEs elevated HIF-1α and PDK4 expression levels in a dose-dependent manner and that maximal stimulation was attained at 24 h. Two important HIF-1α-regulated genes, vascular endothelial growth factor A (VEGFA) and glucose transporter 1 (GLUT-1), were significantly increased after AGEs exposure. Stabilization or nuclear translocation of HIF-1α increased PDK4 expression. PDK4 inhibition attenuated AGEs-induced VSMC calcification, which was evaluated by measuring the calcium content, alkaline phosphatase (ALP) activity and runt-related transcription factor 2 (RUNX2) expression levels and by Alizarin red S staining. In addition, the glucose consumption, lactate production, key enzymes of glucose metabolism and oxygen consumption rate (OCR) were decreased during AGEs-induced VSMC calcification. In conclusion, this study suggests that AGEs accelerate vascular calcification partly through the HIF-1α/PDK4 pathway and suppress glucose metabolism.

Restoring mitochondrial biogenesis with metformin attenuates β-GP-induced phenotypic transformation of VSMCs into an osteogenic phenotype via inhibition of PDK4/oxidative stress-mediated apoptosis

Mitochondrial abnormalities have long been observed in the development of vascular calcification. Metformin, a member of the biguanide class of antidiabetic drugs, has recently received attention owing to new findings regarding its protective role in cardiovascular disease. Since the precise control of mitochondrial quantity and quality is critical for the survival and function of vascular smooth muscle cells (VSMCs), maintaining mitochondrial homeostasis may be a potential protective factor for VSMCs against osteoblast-like phenotypic transition. However, limited studies have been reported in this area. Here, we investigated the role of metformin in the phenotypic transformation of VSMCs, as well as its intracellular signal transduction pathways. We demonstrated that supplementation with metformin restored the β-glycerophosphate (β-GP)-mediated impairment of mitochondrial biogenesis in VSMCs, as evidenced by an increased mitochondrial DNA copy number, a restored mitochondrial membrane potential (MMP), and upregulated mitochondrial biogenesis-related gene expression, whereas the AMP-activated protein kinase (AMPK) inhibitor compound C suppressed these effects. We also observed that overexpression of pyruvate dehydrogenase kinase 4 (PDK4), an important mitochondrial matrix enzyme in cellular energy metabolism, exacerbated β-GP-induced oxidative stress and subsequent apoptosis in VSMCs but that these effects were suppressed by dichloroacetate, a widely reported PDK4 inhibitor. More importantly, enhanced mitochondrial biogenesis attenuated the β-GP-induced phenotypic transformation of VSMCs into an osteogenic phenotype through inhibition of the PDK4/oxidative stress-mediated apoptosis pathway, whereas disruption of mitochondrial biogenesis by zidovudine aggravated β-GP-induced apoptosis in VSMCs. In addition, inhibition of autophagy by small interfering RNA targeting Atg5 reduced mitochondrial biogenesis in VSMCs. In summary, we uncovered a novel mechanism by which metformin attenuates the phenotypic transformation of VSMCs into an osteogenic phenotype via inhibition of the PDK4/oxidative stress-mediated apoptosis pathway, and mitochondrial homeostasis is involved in this process.

Sustained Release of IGF-1 by 3D Mesoporous Scaffolds Promoting Cardiac Stem Cell Migration and Proliferation

Background/Aims: C-kit-positive cardiac stem cells (CSCs) may have potential as a treatment for cardiovascular disease. However, the low survival rates of c-kit-positive CSCs present a major challenge during the transplantation process. Methods: The hierarchical structure of the 3D cell scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption-desorption isotherms. Analyses of the proliferation and migration performances of the IGF-1 scaffold on c-kit-positive CSCs were conducted by experiments including QuantiT PicoGreen dsDNA and transwell assays. Results: In this study, we synthesized for the first time a novel hierarchical macro-mesoporous silica material (denoted MS15-c) in a one-pot procedure for the release of insulin-like growth factor-1 (IGF-1) and a three-dimensional (3D) cell scaffold. Both macropores and mesopores were visible in MS15-c and enabled the sustained release of IGF-1, extending its half-life and enhancing CSC proliferation and migration. Proliferation and migration were detected by QuantiT PicoGreen dsDNA and transwell assays, respectively. Moreover, an in vivo experiment was conducted to detect heart function with the addition of MS15-c. The new strategy proposed in this paper may extend the bio-applications of 3D cell scaffolds, thus permitting the sustained release of growth factors and efficient promotion of cell proliferation. Conclusion: This work successfully demonstrated an effective strategy for the construction of MS15-c cell scaffolds with hierarchical macro-mesoporous structures. The macro-mesoporous structures gave cell scaffolds the ability to release a growth factor to facilitate cell growth, while the scaffold structure promoted cell proliferation.

Associations between LPL gene polymorphisms and coronary artery disease: evidence based on an updated and cumulative meta-analysis

Lipoprotein lipase (LPL) is widely linked to lipid and lipoprotein metabolism, but its effects on coronary artery disease (CAD) are not clearly elucidated. The aim of the present study was to clarify the association between LPL gene polymorphisms and CAD susceptibility. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated to estimate the strength of the relationship between LPL gene polymorphisms and CAD risk. Comprehensive electronic databases, including PubMed, EMBASE, Web of Science, and the Cochrane Library, were systematically searched. A total of 45 records containing 80 eligible studies were analyzed. The results indicated an increased risk between the LPL D9N polymorphism and susceptibility to CAD in the dominant genetic model (AA + GA vs. GG: OR = 1.46, 95% CI = 1.14–1.87), whereas the LPL HindIII polymorphism showed a protective effect against CAD under all tested models (GG + GT vs. TT: OR = 0.85, 95% CI = 0.75–0.97; GG vs. TT + TG: OR = 0.62, 95% CI = 0.47–0.83; G vs. T: OR = 0.81, 95% CI = 0.71–0.92). No significant association was identified for the LPL N291S and PvuII polymorphisms. Stratification analysis by ethnicity suggested a significant correlation between the LPL S447X polymorphism and CAD susceptibility in Caucasians under the dominant and allele genetic models. In summary, our meta-analysis indicated that the LPL D9N polymorphism was associated with an increased risk of CAD, whereas the S447X and HindIII polymorphisms showed protective effects. There was no association observed between the N291S and PvuII polymorphisms and CAD risk.

Association of genetic polymorphisms in vascular endothelial growth factor with susceptibility to coronary artery disease: a meta–analysis

BackgroundSingle nucleotide polymorphisms (SNPs) located in the vascular endothelial growth factor (VEGF) gene may be correlated with the susceptibility to coronary artery disease (CAD) – although results have been controversial. The aim of this meta–analysis is to clarify the effects of VEGF –2578A/C (rs699947), −1154G/A (rs1570360), +405C/G (rs2010963), and + 936C/T (rs3025039) polymorphisms on CAD risk.MethodsPooled odds ratio (OR) and corresponding 95% confidence intervals (CIs) were calculated to estimate the strength of the association between VEGF gene polymorphisms and CAD risk. Fixed- or random-effects model was used depending on the heterogeneity between studies.ResultsIn total, 13 eligible articles containing 29 studies were analysed. The pooled analysis indicated that the VEGF gene polymorphisms of rs699947, rs2010963, and rs3025039 were associated with an increased risk of CAD, whereas no significant associations were observed with the rs1570360 polymorphism. A subgroup analysis stratified by ethnicity revealed that the rs699947 and rs3025039 polymorphisms were associated with CAD risk in Asian populations. In addition, stratification by control source indicated an increased risk of CAD susceptibility with the rs699947 polymorphism for population–based studies of reduced heterogeneity.ConclusionsIn summary, we concluded that the VEGF gene polymorphisms rs699947, rs2010963, and rs3025039 are correlated with an elevated CAD risk.

Association between brain-derived neurotrophic factor and von Willebrand factor levels in patients with stable coronary artery disease

BackgroundBrain-derived neurotrophic factor (BDNF) is a neurotrophin involved in angiogenesis and maintenance of endothelial integrity. Whether circulating BDNF levels are associated with von Willebrand factor (vWF) levels, which are indicators of endothelial dysfunction is not known. This study investigated the association between plasma BNDF and vWF levels and whether these biomarkers could predict cardiovascular events at a 12-month follow-up in patients with stable coronary artery disease (CAD).MethodsWe recruited 234 patients with suspected angina pectoris. Subjects were divided into CAD (n = 143) and control (n = 91) groups based on coronary angiography. Plasma BDNF and vWF levels were measured using ELISA. Patients were followed-up for one year, and information on adverse cardiac events was collected.ResultsCAD patients exhibited significantly lower plasma BDNF and higher vWF levels than those of control patients. High vWF levels were associated with low BDNF levels even after adjustment for age, gender, low-density lipoprotein (LDL) levels, and the presence of diabetes mellitus. A receiver operating characteristic curve was used to determine whether low BDNF and high vWF levels could predict adverse cardiovascular events. The area under the curve for vWF and the inverse of BDNF were 0.774 and 0.804, respectively.ConclusionsThese findings suggest that endothelial dysfunction is an important determinant of the impaired circulating BDNF levels, and they further reflected cardiovascular prognosis in stable CAD patients.

Associations between XRCC1 Gene Polymorphisms and Coronary Artery Disease: A Meta-Analysis

Genetic variations that influence DNA repair efficiency may contribute to coronary artery disease (CAD) susceptibility. Previous studies have investigated whether there was evidence of an association between polymorphisms at the X-ray repair cross complementing 1 (XRCC1) gene and susceptibility to CAD, but findings have been inconclusive. We identified eligible studies through a comprehensive literature search to determine whether an association exists between XRCC1 gene polymorphisms and CAD susceptibility. Findings were assessed using the odds ratio (OR) and corresponding 95% confidence interval (CI), which were calculated using a fixed- or random-effects model, based on the heterogeneity of the studies. Ten eligible studies were finally included in this meta-analysis. Our pooled analysis found that XRCC1 polymorphisms were significantly associated with CAD susceptibility under recessive (Arg194Trp: OR = 1.47, 95% CI = 1.13–1.93; Arg399Gln: OR = 1.45, 95% CI = 1.12–1.89), homozygous (Arg194Trp: OR = 1.37, 95% CI = 1.03–1.81; Arg399Gln: OR = 1.56, 95% CI = 1.19–2.05), and allele (Arg399Gln: OR = 1.18, 95% CI = 1.06–1.32) genetic models. Following subgroup analysis by ethnicity, in Asian populations, we found evidence of associations between the XRCC1 Arg194Trp polymorphism and CAD under recessive and homozygous genetic models, and between the XRCC1 Arg399Gln polymorphism and CAD under recessive, homozygous, and allele genetic models. Subgroup analysis stratified by control source revealed associations between the Arg194Trp and Arg399Gln polymorphisms and susceptibility to CAD under recessive and homozygous modes of inheritance, respectively. In addition, subgroup analysis stratified by sample size found that findings of the Arg194Trp polymorphism in large sample sizes were comparable to those found using pooled eligible studies. Based on our meta-analysis, we concluded that the XRCC1 gene polymorphisms, Arg194Trp and Arg399Gln, are associated with CAD susceptibility, specifically in Asian populations. However, additional, comprehensive and well-designed studies are warranted to confirm these findings.