Insulin receptor binding motif tagged with IgG4 Fc (Yiminsu) works as an insulin sensitizer to activate Akt signaling in hepatocytes.

Insulin resistance is a key feature of obesity and type 2 diabetes mellitus (T2DM). Interaction of insulin with the insulin receptor (IR) leads to both its auto-phosphorylation and phosphorylation of tyrosine residues on the IR substrate (IRS) proteins, initiating the activation of intracellular signaling cascades. The metabolic effects of IRS are known to be mediated through pathways involving phosphatidyl-inositol 3-kinase (PI-3K), which result in the activation of Akt signaling. The C-terminal region of the IR ectodomain is required to facilitate the conformational changes that are required for high-affinity binding to insulin. Furthermore, the CH2 and CH3 domains in the Fc fragments of immunoglobulins are responsible for their binding to the Fc receptor, which triggers transcytosis. In this study, we created a fusion peptide of the C-terminal end of the human IR ectodomain with the IgG4 Fc fragment, including an intervening polyG fragment to ensure enough space for insulin binding. We named this new peptide "Yiminsu", meaning an insulin sensitizer. The results of our analyses show that Yiminsu significantly facilitates insulin signaling via the activation of Akt in hepatocytes in a dose- and time-dependent manner. Further studies are required to determine whether Yiminsu can act as an insulin sensitizer.

The economic burden of fracture patients with osteoporosis in western China.

UNLABELLED: To study the cost of osteoporotic fracture in China, we performed a prospective study and compared the costs of the disease in referral patients with fractures in three of the most common sites. Our results indicated that the economic burden of osteoporotic fracture to both Chinese patients and the nation is heavy. INTRODUCTION: This paper aims to study the cost of osteoporotic fracture in China and thus to provide essential information about the burden of this disease to individuals and society. METHODS: This prospective observational data collection study assessed the cost related to hip, vertebral, and wrist fracture 1 year after the fracture based on a patient sample consisting of 938 men and women. Information was collected using patient records, registry sources, and patient interviews. Both direct medical, direct non-medical, and indirect non-medical costs were considered. RESULTS: The annual total costs were highest in hip fracture patients (renminbi, RMB 27,283 or USD 4,330, with confidence interval (RMB 25715, 28851)), followed by patients with vertebral fracture (RMB 21,474 or USD 3,409, with confidence interval (RMB 20082, 22866)) and wrist fracture (RMB 8,828 or USD 1,401, with confidence interval (RMB 7829, 9827)). The direct medical care costs averaged approximately RMB 17,007 per year per patient, of which inpatient costs, drugs, and investigations accounted for the majority of the costs. Nonmedical direct costs were much less compared to direct healthcare costs and averaged approximately RMB 1,846. CONCLUSION: These results indicate that the economic burden of osteoporotic fracture to both Chinese patients and China was heavy, and the proportion of the costs in China demonstrated many similar features and some significant differences compared to other countries.

Screening of genes related with intervertebral disc disease by dynamic differential interaction network analysis.

AIM: Gene expression profiles for intervertebral disc (IVD) cells treated with different osmolarities were compared to identify key genes associated with intervertebral disc diseases. MATERIALS AND METHODS: Microarray data was downloaded from Gene Expression Omnibus (GEO) database and pre-processed using package of R. Gene co-expression was determined with Pearson correlation coefficient. Interaction networks were established with the protein-protein interaction (PPI) information obtained from Human Protein Reference Database (HPRD database) for the two conditions: isosmoticity and hyperosmosis, and then a comparative analysis was done to identify disease-related genes. The functional annotation was performed for these genes using network ontology analysis (NOA), which also confirmed the effectiveness of this method. RESULTS: A total of 45 feature genes were obtained through comparing 7 samples treated under isosmotic conditions and 9 high osmotic conditions. Biological processes and molecular functions were then revealed by NOA. CONCLUSIONS: A range of disease-related genes were obtained, which might serve as the potential biomarkers or drug targets. More works are needed to further elucidate their roles in the development of intervertebral disc diseases like intervertebral disc herniation.

MiRNA-21 reverses high glucose and high insulin induced insulin resistance in 3T3-L1 adipocytes through targeting phosphatase and tensin homologue.

AIMS/HYPOTHESIS: Our previous study showed there was a change of microRNA (miRNA) expression profile, and miR-21 was significantly down regulated in insulin-resistant adipocytes (IR-adipocytes). Phosphatase and tensin homologs deleted on chromosome 10 (PTEN), a negative regulator of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, was identified to be a target gene of miR-21, which suggested miR-21 might be associated with insulin resistance (IR) or diabetes. However, it is not known whether miR-21 play any role in the development of IR in 3T3-L1 adipocytes. METHODS: Normal adipocytes and adipocytes transfected with pre-miR-21(pmiR-21) or negative control (pNeg) were treated with high glucose and high insulin for 24 h, insulin-stimulated glucose uptake was determined by 2-Deoxyglucose transport assay, miR-21 expression level was measured by using quantitative real-time RT-PCR (qRT-PCR). The protein expression levels of PTEN, Akt, phospho-Akt (Ser473), IRß, GSK3ß, phospho-GSK3ß (Ser9) and GLUT4 were detected by western blotting assay. RESULTS: We further confirmed that miR-21 was down regulated in IR-adipocytes by qRT-PCR. Over-expression of miR-21 significantly increased insulin-induced glucose uptake and decreased PTEN protein expression, while it had no significant effect on PTEN mRNA expression in IR-adipocytes. Moreover, over-expressing miR-21 significantly increased insulin-induced phosphorylation of AKT (Ser473), GSK3ß (Ser9) and the translocation of glucose transporter 4 (GLUT4) in IR-adipocytes. CONCLUSIONS: In this study, our data demonstrate that miR-21 reverses high glucose and high insulin induced IR in 3T3-L1 adipocytes, possibly through modulating the PTEN-AKT pathway, and miR-21 may be a new therapeutic target for metabolic diseases such as T2DM and obesity.

Cyclophilin A is a secreted growth factor induced by oxidative stress.

Reactive oxygen species have been implicated in the pathogenesis of atherosclerosis, hypertension, and restenosis, in part by promoting vascular smooth muscle cell (VSMC) growth. Many VSMC growth factors are secreted by VSMC and act in an autocrine manner. Here we demonstrate that cyclophilin A (CyPA), a member of the immunophilin family, is secreted by VSMCs in response to oxidative stress and mediates extracellular signal-regulated kinase (ERK1/2) activation and VSMC growth by reactive oxygen species. Human recombinant CyPA can mimic the effects of secreted CyPA to stimulate ERK1/2 and cell growth. The peptidyl-prolyl isomerase activity is required for ERK1/2 activation by CyPA. In vivo, CyPA expression and secretion are increased by oxidative stress and vascular injury. These findings are the first to identify CyPA as a secreted redox-sensitive mediator, establish CyPA as a VSMC growth factor, and suggest an important role for CyPA and enzymes with peptidyl-prolyl isomerase activity in the pathogenesis of vascular diseases.

Stimulation of 90- and 70-kDa ribosomal protein S6 kinases by arginine vasopressin and lysophosphatidic acid in rat cardiomyocytes.

Arginine vasopressin (AVP) and lysophosphatidic acid (LPA) have been shown to stimulate protein kinase C (PKC) and mitogen-activated protein (MAP) kinases and the proliferation of vascular smooth muscle cells. However, the actions of these two agents in cardiomyocytes are less well understood. To investigate the signal transduction pathways of AVP and LPA, freshly isolated adult rat cardiomyocytes were examined. Both AVP and LPA induced concentration- and time-dependent stimulation of the phosphotransferase activities of p90 ribosomal S6 kinases (RSK) and their upstream activators, extracellularly regulated kinases (ERK) 1 and 2. The activation of ERK1 and ERK2 by LPA was PKC- and phosphatidylinositol 3-kinase (PI 3-kinase)-dependent. However, AVP-induced activation of RSK2, a downstream substrate of ERK1 and ERK2, was PKC-dependent and PI 3-kinase-independent. AVP and LPA were also observed to increase the phosphotransferase activity of p70 ribosomal protein S6 kinase (p70 S6K) in a time- and concentration-dependent manner. The activation of p70 S6K by LPA and AVP was PI 3-kinase-dependent. PKC was necessary in AVP- but not in LPA-induced activation of p70 S6K. Since RSK and p70 S6K have been implicated in the regulation of translational control of protein synthesis, we concluded that AVP and LPA may stimulate the growth of cardiomyocytes through these two protein kinase cascades.

Purification and identification of secreted oxidative stress-induced factors from vascular smooth muscle cells.

Reactive oxygen species have been implicated in the pathogenesis of atherosclerosis and hypertension, in part by promoting vascular smooth muscle cell (VSMC) growth. We have previously shown that LY83583, a generator of O-(2), activated extracellular signal-regulated kinases (ERK1/2) with early (10 min) and late (2 h) peaks and stimulated VSMC growth. To investigate whether secreted oxidative stress-induced factors (termed SOXF) from VSMC were responsible for late ERK1/2 activation in response to LY83583, we purified putative SOXF proteins from conditioned medium (2 h of LY83583 exposure) by sequential chromatography based on activation of ERK1/2. Proteins identified by capillary chromatography, electrospray ionization tandem mass spectrometry, and data base searching included heat shock protein 90-alpha (HSP90-alpha) and cyclophilin B. Western blot analysis of conditioned medium showed specific secretion of HSP90-alpha but not HSP90-beta. Immunodepletion of HSP90-alpha from conditioned medium significantly inhibited conditioned medium-induced ERK1/2 activation. Human recombinant HSP90-alpha reproduced the effect of conditioned medium on ERK1/2 activation. These results show that brief oxidative stress causes sustained release of protein factors from VSMC that can stimulate ERK1/2. These factors may be important mediators for the effects of reactive oxygen species on vascular function.

Probucol inhibits lipid peroxidation of macrophage and affects its secretory properties.

AIM: To investigate the mechanisms of anti-atherogenic actions of probucol. METHODS: Human peripheral blood monocytes were cultured, and treated by copper ion (10 mumol/L) and/or probucol (PBC). Lipid peroxidation was measured by assaying malondialdehyde (MDA). The cytokine interleukin-1 beta (IL-1 beta) and apolipoprotein E (apo E) secreted by monocyte were assayed by enzyme linked immunoassay (ELISA). RESULTS: PBC 10-80 mumol/L inhibited copper ion-induced cellular lipid peroxidation from 15.30 to 7.74 mumol MDA/g cell protein. PBC 40 mumol/L inhibited oxidized macrophage-mediated oxidation of LDL from 5.18 to 1.65 mumol MDA/g cell protein, and attenuated secretory properties of monocytes induced by copper ion. The release of apo E, which is involved in reverse cholesterol transport, increased by 65%. And the release of IL-1 beta, which was shown to enhance vascular smooth muscle cell proliferation, decreased by 45%. CONCLUSION: Probucol inhibits lipid peroxidation of macrophages and affects their secretory properties.

Probucol inhibits oxidized-low density lipoprotein-induced adhesion of monocytes to endothelial cells by reducing P-selectin synthesis in vitro.

Probucol (PBC) is an unique antiatherogenic drug producing its effect by antioxidant action rather than hypolipidaemic effect. However, the exact mechanism of its antiatherogenic effect is unclear. Therefore we investigated the PBC effects on the adhesion of monocytes to endothelial cells, an early event in atherogenesis. Monocyte adhesion to cultured pig aortic endothelial cells (EC) was induced by oxidized low density lipoprotein (Ox-LDL). To elucidate the mechanisms of the inhibition on adhesion, PBC effects on the Ox-LDL-induced expression of P-selectin, on the synthesis of von Willebrand factor (vWF) and prostacyclin (PGI2) were examined. The results showed that Ox-LDL enhanced the adhesion of monocytes to EC in a concentration-dependent and time-related manner. PBC 25, 50 and 75 micromol/L inhibited the Ox-LDL-induced adhesion index from 37.3% to 19.7, 16.6 and 14.6% respectively (p all < 0.05), and inhibited the Ox-LDL-induced expression of P-selectin from 293.0 ng/ml to 180.0, 132.9 and 132.6 ng/ml respectively. Furthermore, PBC significantly attenuated the Ox-LDL-impaired synthesis of PGI2 and vWF. These results indicate that PBC may provide a new approach in the prevention of atherosclerosis (AS) by intervention of monocyte adhesion to EC. In conclusion, PBC inhibits the Ox-LDL-induced adhesion of monocytes to EC. This effect is associated with the inhibition of the Ox-LDL-induced expression of P-selectin and the protection on the synthesis of PGI2.

Protein kinase C-zeta mediates angiotensin II activation of ERK1/2 in vascular smooth muscle cells.

Activation of 44 and 42 kDa extracellular signal-regulated kinases (ERK)1/2 by angiotensin II (angII) plays an important role in vascular smooth muscle cell (VSMC) function. The dual specificity mitogen-actived protein (MAP) kinase/ERK kinase (MEK) activates ERK1/2 in response to angII, but the MEK activating kinases remain undefined. Raf is a candidate MEK kinase. However, a kinase other than Raf appears responsible for angII-mediated signal transduction because we showed previously that treatment with 1 microM phorbol 12, 13-dibutyrate (PDBU) for 24 h completely blocked Raf-Ras association in VSMC but did not inhibit activation of MEK and ERK1/2 by angII. We hypothesized that an atypical protein kinase C (PKC) isoform, which lacks a phorbol ester binding domain, mediated ERK1/2 activation by angII. Western blot analysis of rat aortic VSMC with PKC isoform-specific antibodies showed PKC-alpha, -beta1, -delta, -epsilon, and -zeta in relative abundance. All isoforms except PKC-zeta were down-regulated by 1 microM PDBU for 24 h suggesting that PKC-zeta was responsible for angII-mediated ERK1/2 activation. In response to angII, PKC-zeta associated with Ras as shown by co-precipitation of PKC-zeta with anti-H-Ras antibody. To characterize further the role of PKC-zeta, PKC-zeta protein was depleted specifically by transfection with antisense PKC-zeta oligonucleotides. Antisense PKC-zeta oligonucleotide treatment significantly decreased PKC-zeta protein expression (without effect on other PKC isoforms) and angII-mediated ERK1/2 activation in a concentration-dependent manner. In contrast, ERK1/2 activation by platelet-derived growth factor and phorbol ester was not significantly inhibited. These results demonstrate an important difference in signal transduction by angII compared with PDGF and phorbol ester in VSMC, and suggest a critical role for PKC-zeta and Ras in angII stimulation of ERK1/2.

Angiotensin II stimulates MAP kinase kinase kinase activity in vascular smooth muscle cells, Role of Raf.

Both angiotensin II (Ang II) and platelet-derived growth factor (PDGF) rapidly increase intracellular Ca2+ and activate protein kinase C (PKC) and MAP kinase in vascular smooth muscle cells (VSMCs). However, Ang II causes cell hypertrophy, whereas PDGF causes hyperplasia. These findings indicate that VSMCs are a good model for studying the relationship between cell growth and the MAP kinase pathway. In this study, we investigated the role of Raf in activation of 42- and 44-kD MAP kinases. Western blot analysis showed that c-Raf-1 was the predominant Raf isozyme in cultured rat aortic VSMCs. In response to Ang II, there was translocation of Raf to the membrane, which occurred significantly earlier than MAP kinase activation, suggesting that Raf activation precedes MAP kinase activation. Translocation of Raf to the membrane resulted in association with H-Ras as shown by c-Raf-1 coprecipitation with anti-Ras anti-bodies. Western blot analysis of H-Ras immunoprecipitates revealed c-Raf-1, but c-mos, MEK (MAP kinase/extracellular signal-regulated kinase) kinase-1 (MEKK-1), and Raf-B were not present. MAP kinase kinase kinase (MAPKKK) activity was assayed in c-Raf-1 and H-Ras immunoprecipitates by MAP kinase kinase-dependent phosphorylation of catalytically inactive 42-kD MAP kinase. In Ras immunoprecipitates, MAPKKK activity was stimulated approximately threefold by both Ang II and PDGF, with a peak at 5 minutes. Downregulation of PKC by 24-hour exposure to phorbol ester significantly inhibited Ang II-stimulated and PDGF-stimulated MAPKKK activity (approximately 80% decrease) and Raf translocation (approximately 90% decrease), suggesting that a phorbol-responsive PKC is upstream from MAPKKK and Raf. In contrast, Ang II (but not PDGF) stimulation of MAP kinase was unaffected by PKC downregulation or pharmacological PKC inhibition. These findings demonstrate for the first time that Ang II stimulation of MAP kinase may occur via a pathway independent of c-Raf-1 and of the phorbol-responsive PKC isozymes. The differing effects of Ang II and PDGF on VSMC growth may be a consequence of specific signal transduction events, as demonstrated here for activation of MAP kinase.

Effects of gypenosides on mouse splenic lymphocyte transformation and DNA polymerase II activity in vitro.

AIM: To study the effects of gypenosides (Gyp) on lymphocyte transformation and DNA polymerase II activity. METHODS: Lymphocyte transformation response was induced by concanavalin A and lipopolysaccharides respectively. The activity of DNA polymerase II and DNA synthesis were assayed with TTP and [3H]TdR incorporation respectively in mixed lymphocyte culture test. RESULTS: Gyp 2.5-20 mg L-1 enhanced splenic T- and B- cell transformation, increased the DNA synthesis and potentiated the activity of DNA polymerase II. However, Gyp > 40 mg L-1 showed contrary effects. CONCLUSION: Gyp regulated lymphocyte transformation and DNA synthesis by regulating DNA polymerase II activity.

Prostacyclin-mediated protection by angiotensin-converting enzyme inhibitors against injury of aortic endothelium by free radicals.

We report here the protective effect of the angiotensin converting enzyme inhibitors captopril and ramiprilat against damage due to oxygen free radicals on aortic endothelium in a superfusion cascade system. Oxygen free radicals were generated by electrolysis of Krebs solution. Acetylcholine was infused through the donor aortic segment and relaxation of the detector aortic ring was used to indicate the release of endothelium-derived relaxing factor (EDRF). The percentage of relaxation before and after electrolysis was compared to calculate the relaxation index. Electrolyzed Krebs solution impaired the release of EDRF, as shown by a reduction in the relaxation index with a concomitant decrease in the tissue levels of superoxide dismutase and 6-keto PGF1 alpha and increase in malondialdehyde in the donor vessel. Captopril (100 microM), 15 microM ramiprilat and 30 nM iloprost had a protective effect as shown by a significantly smaller reduction in the relaxation index and the level of 6-keto PGF1 alpha and by an attenuation of the production of malondialdehyde. In addition, 1 microM indomethacin almost eliminated the protection by captopril. We conclude that both the SH-containing angiotensin-converting enzyme inhibitor captopril and the non-SH-containing ramiprilat, as well as iloprost, a stable analog of prostacyclin, can protect rabbit aortic endothelium against damage due to oxygen free radicals. The mechanism of such protection may be partly associated with the facilitation of the release of prostacyclin and consequent reduction in lipid peroxidation.