Wannan Li

Magnolia officinalis Extract Contains Potent Inhibitors against PTP1B and Attenuates Hyperglycemia in db/db Mice

Protein tyrosine phosphatase 1B (PTP1B) is an established therapeutic target for type 2 diabetes mellitus (T2DM) and obesity. The aim of this study was to investigate the inhibitory activity of Magnolia officinalis extract (ME) on PTP1B and its anti-T2DM effects. Inhibition assays and inhibition kinetics of ME were performed in vitro. 3T3-L1 adipocytes and C2C12 myotubes were stimulated with ME to explore its bioavailability in cell level. The in vivo studies were performed on db/db mice to probe its anti-T2DM effects. In the present study, ME inhibited PTP1B in a reversible competitive manner and displayed good selectivity against PTPs in vitro. Furthermore, ME enhanced tyrosine phosphorylation levels of cellular proteins, especially the insulin-induced tyrosine phosphorylations of insulin receptor β-subunit (IRβ) and ERK1/2 in a dose-dependent manner in stimulated 3T3-L1 adipocytes and C2C12 myotubes. Meanwhile, ME enhanced insulin-stimulated GLUT4 translocation. More importantly, there was a significant decrease in fasting plasma glucose level of db/db diabetic mice treated orally with 0.5 g/kg ME for 4 weeks. These findings indicated that improvement of insulin sensitivity and hypoglycemic effects of ME may be attributed to the inhibition of PTP1B. Thereby, we pioneered the inhibitory potential of ME targeted on PTP1B as anti-T2DM drug discovery.

Hypoglycemic effect and mechanism of honokiol on type 2 diabetic mice.

Background Honokiol is one of the main bioactive constituents of the traditional Chinese herbal drug Magnolia bark (Cortex Magnoliae officinalis, Hou Po). The aim of this study was to probe its anti-type 2 diabetes mellitus effects and the underlying mechanism. Methods Type 2 diabetic mouse model was established by intraperitoneally injecting with streptozotocin. Fasting blood glucose, body weight, and lipid profile were measured. The subcutaneous adipose tissue, skeletal muscle, and liver were isolated as well as homogenized. The phospho-insulin receptor β-subunit (IRβ), IRβ, phospho-AKT, AKT, phospho-ERK1/2, ERK1/2, phosphotyrosine, and actin were examined by Western blot assay. Cell viability or cytotoxicity was analyzed by using MTT method. The inhibitory potencies of honokiol on the protein tyrosine phosphatase 1B (PTP1B) activity were performed in reaction buffer. Molecular docking and dynamic simulation were also analyzed. Results In in vivo studies, oral treatment with 200 mg/kg honokiol for 8 weeks significantly decreases the fasting blood glucose in type 2 diabetes mellitus mice. The phosphorylations of the IRβ and the downstream insulin signaling factors including AKT and ERK1/2 significantly increase in adipose, skeletal muscle, and liver tissue of the honokiol-treated mice. Moreover, honokiol enhanced the insulin-stimulated phosphorylations of IRβ, AKT, and ERK1/2 in a dose-dependent manner in C2C12 myotube cells. Meanwhile, honokiol enhanced insulin-stimulated GLUT4 translocation. Importantly, honokiol exhibited reversible competitive inhibitory activity against PTP1B with good selectivity in vitro and in vivo. Furthermore, using molecular docking and dynamic simulation approaches, we determined the potential binding mode of honokiol to PTP1B at an atomic level. Conclusion These findings indicated the hypoglycemic effects of honokiol and its mechanism that honokiol improved the insulin sensitivity by targeting PTP1B. Therefore, our study may highlight honokiol as a promising insulin sensitizer for the therapy of type 2 diabetes.

Expression, purification, and characterization of human osteoclastic protein-tyrosine phosphatase catalytic domain in Escherichia coli.

Osteoclastic protein tyrosine phosphatase (PTP-oc) is a structurally unique transmembrane protein tyrosine phosphatase (PTP) that contains only a relatively small intracellular PTP catalytic domain, does not have an extracellular domain, and lacks a signal peptide proximal to the NH2 terminus. The present study reports the expression, purification, and characterization of the intracellular catalytic domain of PTP-oc (ΔPTP-oc). ΔPTP-oc was expressed in Escherichia coli cells as a fusion with a six-histidine tag and was purified via nickel affinity chromatography. When with para-nitrophenylphosphate (p-NPP) as a substrate, ΔPTP-oc exhibited classical Michaelis-Menten kinetics. Its responses to temperature and ionic strength were similar to those of other PTPs. The optimal pH value of ΔPTP-oc is approximately 7.0, unlike other PTPs, whose optimal pH values are approximately 5.0.

Identification of common differentially‑expressed miRNAs in ovarian cancer cells and their exosomes compared with normal ovarian surface epithelial cell cells

The aim of the present study was to identify common microRNAs (miRNAs) in ovarian cancer (OC) cells and their exosomes using microarray data (accession number GSE76449) available from the Gene Expression Omnibus database, including exosomal samples from 3 OC cell lines, 1 normal ovarian surface epithelial cell line and their original cell samples. Differentially-expressed miRNAs (DE-miRNAs) were identified using the Linear Models for Microarray data method, and mRNA targets of DE-miRNAs were predicted using the miRWalk2 database. The potential functions of the target genes of the DE-miRNAs were analyzed using the Database for Annotation, Visualization and Integrated Discovery tool. The association between crucial miRNAs and target genes, and their clinical associations, were validated using The Cancer Genome Atlas data. As a result, 12 upregulated and 12 downregulated DE-miRNAs were shared by the 3 OC cell lines compared with normal controls in the exosomal samples, while 5 upregulated and 65 downregulated DE-miRNAs were shared between the original cells. Among them, 9 downregulated DE-miRNAs were shared between exosomal and original cells. The target genes of 4 common DE-miRNAs between exosomal and original cells (miR-127-3p, miR-339-5p, miR-409-3p and miR-654-3p) were predicted. Functional enrichment analysis indicated that these target genes may be involved in the Wnt signaling pathway (miR-409-3p-CTBP1 and miR-339-5p-CHD8) and Proteoglycans in cancer (miR-127-3p-PPP1CA). The negative associations between these 3 miRNAs and target genes were confirmed by a Pearsons correlation analysis. miR-127 was negatively associated with tumor grade. In conclusion, our results describe a set of miRNAs involved in OC development, in exosomal and non-exosomal manners, by regulating their target genes. They may be potential targets for treatment of OC.

Association of ACP1 gene polymorphisms and coronary artery disease in northeast Chinese population

Coronary artery disease (CAD) is the major cause of death in most countries including China (He et al. 2005). A number of susceptible variants of candidate genes have been recognized as genetic risk factors that are associated with pathogenesis of coronary heart disease (Wu et al. 2001; Achour et al. 2011; Zhou et al. 2011). Recently, Banci et al. (2009) have reported acid phosphatase 1 (ACP1) gene *C allele as a risk factor for CAD in Caucasian (OR= 3.188). Here, we show that the genotype GA of rs79716074 (ACP1 gene, exon 6) is associated with decreased risk of CAD in northeast Chinese population especially in females. The ACP1 gene is the only member of class II cysteinebased protein tyrosine phophatase (PTP) family in human and encodes the low molecular weight PTP (LMW-PTP), a group of 18-kDa proteins widely expressed in many tissues. LMW-PTP is involved in the regulation of important physiological processes including stress resistance and synthesis of the polysaccharide capsule, etc. (Souza et al. 2009). There are three common codominant alleles of ACP1: ACP1*A, ACP1*B and ACP1*C. which contains single base substitutions located at specific sites. The ACP1*C allele differs from ACP1*A and ACP1*B alleles at rs11553742, while ACP1*A and ACP1*B alleles differ in an A–G transition at rs79716074. Previous studies reported that ACP1 gene polymorphisms may be important pathogenic factors of immune dysregulation such as rheumatoid arthritis, systemic lupus erythematosis process, endometriosis and allergy (Ammendola et al. 2008, Teruel et al. 2011, 2012).

Hypoglycemic effect and mechanism of isoquercitrin as an inhibitor of dipeptidyl peptidase-4 in type 2 diabetic mice

Glucagon-like peptide (GLP)-1 is a potent glucose-dependent insulinotropic gut hormone released from intestinal L cells. The aim of this study was to investigate isoquercitrin as an inhibitor of dipeptidyl peptidase IV (DPP-IV) and determine whether it affects GLP-1 release in normal mice and NCI-H716 cells. In vitro, we used chromogenic substrate method detection methods to measure DPP-IV. We found that isoquercitrin was a competitive inhibitor, with IC50 and Ki values of 96.8 and 236 μM, respectively. Isoquercitrin and sitagliptin also stimulated GLP-1 release in NCI-H716 cells. In vivo, a type 2 diabetic mouse model was established, and oral treatment with different concentration of isoquercitrin and sitagliptin for 8 weeks significantly decreased the fasting blood glucose level. The weight and the levels of serum GLP-1 and insulin of the mice in the isoquercitrin group were higher than those in the model group (P < 0.001). An oral glucose tolerance test showed that the isoquercitrin significantly inhibited postprandial blood glucose changes in a dose-dependent manner. These findings demonstrated the hypoglycemic effects of isoquercitrin and indicated that isoquercitrin improved insulin sensitivity by targeting DPP-IV.

2-SeCD treatment extends lifespan, improves healthspan and enhances resistance to stress in Caenorhabditis elegans

Aging is primarily caused by reactive oxygen species (ROS). 2-Selenium-bridged β-cyclodextrin (2-SeCD) is an enzyme with glutathione peroxidase (GPX)-like activity, which indicates that it might be an important ROS scavenger in vivo. However, its effects on aging are unknown. In this study, we studied the dose-dependent effects of 2-SeCD on the lifespan, healthspan and resistance to stress of Caenorhabditis elegans. The mean lifespan of nematodes treated with 0.05, 0.5, and 5 mM 2-SeCD increased significantly in a dose-dependent manner. Healthspan also improved, as revealed by increased motility and GPX activity and decreased lipid peroxidation and ROS level, indicating that DNA damage was curbed. In addition, nematodes treated with 2-SeCD were more resistant to heat stress, UV irradiation and H2O2-induced oxidative stress. Our findings indicate that 2-SeCD extends the lifespan of C. elegans, improves the healthspan and enhances the resistance to stress.

Arbutin increases Caenorhabditis elegans longevity and stress resistance

Arbutin (p-hydroxyphenyl-β-D-glucopyranoside), a well-known tyrosinase inhibitor, has been widely used as a cosmetic whitening agent. Although its natural role is to scavenge free radicals within cells, it has also exhibited useful activities for the treatment of diuresis, bacterial infections and cancer, as well as anti-inflammatory and anti-tussive activities. Because function of free radical scavenging is also related to antioxidant and the effects of arbutin on longevity and stress resistance in animals have not yet been confirmed, here the effects of arbutin on Caenorhabditis elegans were investigated. The results demonstrated that optimal concentrations of arbutin could extend lifespan and enhance resistance to oxidative stress. The underlying molecular mechanism for these effects involves decreased levels of reactive oxygen species (ROS), improvement of daf-16 nuclear localization, and up-regulated expression of daf-16 and its downstream targets, including sod-3 and hsp16.2. In this work the roles of arbutin in lifespan and health are studied and the results support that arbutin is an antioxidant for maintaining overall health.

Effect of Candesartan Cilexetil as a Sensitive and Effective Inhibitor of SHP-1 on Insulin Signaling Pathway

The protein tyrosine phosphatases(PTPs) comprise a family of enzymes that specifically dephosphorylate tyrosyl residues. Among them, SHP-1 has been regarded as one of the best validated intracellular tyrosine phosphatases. Downregulation of SHP-1 has shown remarkable efficacy in improving insulin sensitivity in vivo in insulin signaling pathway. In this study, we found the role of Candesartan cilexetil targeting at SHP-1. The results indicate that Candesartan cilexetil was a competitive inhibitor to SHP-1(IC50=85.6 μmol/L and Ki=24 μmol/L). We also found that Candesartan cilexetil was more sensitive towards SHP-1 compared with other PTPs. Through the consequence of Western blotting, it showed that Candesartan cilexetil can strengthen the level of tyrosine phosphorylation of several key cellular proteins[such as insulin receptor(IR), insulin receptor substrate(IRS) and ERK]_in insulin signaling pathway in HepG2 cells and improve the insulin sensitivity through inhibiting the protein phosphorylation of SHP-1. These findings showed that Candesartan cilexetil might be an important inhibitor of SHP-1 and had a great application potential in the treatment of diabetes through inhibiting the level of SHP-1 in insulin signaling pathway.