Protein Tyrosine Phosphatase (PTP) 1B Inhibition Improves Endoplasmic Reticulum Stress-Induced Apoptosis and Impaired Angiogenic Response in Endothelial Cells

Insulin is not only important for glucose homeostasis, but also plays a critical role in the activation of endothelial nitric oxide synthase (eNOS) to synthesize nitric oxide (NO) and keeping the endothelium functional. Conditions which result in insulin resistance, such as diabetes and obesity, cause impairment of endothelial function, a condition known as endothelial dysfunction that features a reduced release of NO. Protein tyrosine phosphatase (PTP) 1B, is a known negative regulator of insulin receptor, that has been implicated in the pathogenesis of insulin resistance and endothelial dysfunction. Owing to its critical location at the surface of the endoplasmic reticulum (ER), PTP1B has been found to play an important role in ER stress response. However, the role of ER stress in PTP1B-mediated endothelial dysfunction is not fully elucidated. Toa address this, ER stress was induced pharmacologically in endothelial cells using thapsigargin, in the presence or absence of either a small molecule inhibitor of PTP1B or silencing siRNA duplexes, followed by the assessment of the expression of key ER stress markers, angiogenic capacity and apoptotic signals. We report here, that PTP1B inhibition protected cells against ER stress and ER stress-induced impairment in eNOS activation and angiogenic capacity. PTP1B inhibition or silencing also protected against ER stress-induced endothelial cell apoptosis. Moreover, PTP1B blockade also suppressed ER stress-activated autophagy. Our data emphasize on the critical role of PTP1B in ER stress-mediated endothelial cell dysfunction and highlights the therapeutic potential of PTP1B inhibition against ER stress-mediated cell death and impairment of endothelial function to prevent cardiovascular disease in pathologies charactereized by the activation of ER stress such as diabetes.

Characteristics of Food Protein-Derived Antidiabetic Bioactive Peptides: A Literature Update

Diabetes, a glucose metabolic disorder, is considered one of the biggest challenges associated with a complex complication of health crises in the modern lifestyle. Inhibition or reduction of the dipeptidyl peptidase IV (DPP-IV), alpha-glucosidase, and protein-tyrosine phosphatase 1B (PTP-1B) enzyme activities or expressions are notably considered as the promising therapeutic strategies for the management of type 2 diabetes (T2D). Various food protein-derived antidiabetic bioactive peptides have been isolated and verified. This review provides an overview of the DPP-IV, PTP-1B, and α-glucosidase inhibitors, and updates on the methods for the discovery of DPP-IV inhibitory peptides released from food-protein hydrolysate. The finding of novel bioactive peptides involves studies about the strategy of separation fractionation, the identification of peptide sequences, and the evaluation of peptide characteristics in vitro, in silico, in situ, and in vivo. The potential of bioactive peptides suggests useful applications in the prevention and management of diabetes. Furthermore, evidence of clinical studies is necessary for the validation of these peptides’ efficiencies before commercial applications.

ANTIOXIDANT, PTP 1B INHIBITION AND Α-AMYLASE INHIBITION PROPERTY AND GC-MS ANALYSIS OF METHANOLIC LEAVES EXTRACT OF ACHYRANTHES ASPERA AND CATHARANTHUS ROSEUS OF NEPAL

Objective: The present study was designed to study phytochemicals and biological activities of the methanolic extracts of two traditional medicine plants Achyranthes aspera and Catharanthus roseus of Nepalese origin. Methods: Plant extracts were prepared by cold percolation method. Antioxidant activity, brine shrimp lethality assay, and analysis of phytochemical constituents were carried out using standard methods. The dinitro salicylic acid (DNS) method was used to study the inhibition effect of extracts on α-amylase enzyme. Furthermore, PTP 1B inhibitory activity was evaluated using p-nitrophenyl phosphate (p-NPP) as substrate. Results: Phytochemical analysis showed the presence of phytochemicals like alkaloids, flavonoids, glycosides, reducing sugars, etc. in both plants. Brine shrimp lethality assay suggested the presence of pharmacologically active compounds. Total phenolic content and total flavonoid content of C. roseus were found to be higher with 73.21 mg GAE/g and 33.15 mg Q/g respectively than that of A. aspera, which was found to be 57.09 mg GAE/g and 28.96 mg Q/g respectively. Similarly, the α-amylase inhibition of A. aspera and C. roseus was found to be 97.60±1.11 µg/ml and 94.05±1.18 µg/ml comparative with IC50 68.13±0.46 µg/ml of standard acarbose. Protein tyrosine phosphatase 1B (PTP1B) inhibition showed IC50 for A. aspera and C. roseus to be 48.72±0.46 and 50.21±1.03 µg/ml, respectively. Qualitative GC-MS analysis of both plant hexane fractions showed acid and ester type of phytoconstituents. Conclusion: These results suggested that both plants i. e A. aspera and C. roseus, Nepal origin showed biological activity by targeting multiple drug targets which justifies their traditional uses.

Anti-diabetic drug discovery using bioactive compounds: Molecular docking insights

Diabetes mellitus is a metabolic disorder that has become a global health problem. About 500 million people were estimated to be living with diabetes in 2018 with about 20 million in Africa and 2 million cases in Nigeria. Bioactive compounds offer an advanced starting point in the search for highly specific and potent modulator of bimolecular function as well as novel drugs, which can be studied with more precision by using computer aided drug design (CADD). Molecular docking employed for predicting the interactions between receptor and ligands is an integral aspect in drug discovery. The main objective is to attain ligand-receptor complex with optimized conformation and with the intention of possessing less binding free energy. Several studies have used this method to explore the potency of bioactive compounds to predict better alternatives in the search for an anti-diabetic drug with very effective therapeutic role and minimal side effects. This has been carried out by using several compounds such as Quercetin, against endogenous targets such as Glycogen phosphorylase, Peroxisome Proliferator-activated Receptor (PPAR)-y, Glucokinase, Protein Tyrosine Phosphatase 1-beta (PTP-1B), GLUT4, etc. In Silico tools such as Protein Database (PDB), GenBank and softwares such as Autodock and modeller are of major importance to these studies. The paper seeks to examine bioactive compounds basically quercetin that have been successfully identified through molecular docking and their molecular targets as well as recent advances in the use of molecular docking in the novel discovery and explanation of mechanisms of actions of some bioactive compounds in anti-diabetic drug discovery.

Water Extract of Mungbean (Vigna radiata L.) Inhibits Protein Tyrosine Phosphatase-1B in Insulin-Resistant HepG2 Cells

The present study aimed to investigate the effects of mungbean water extract (MWE) on insulin downstream signaling in insulin-resistant HepG2 cells. Whole seed mungbean was extracted using boiling water, mimicking a traditional cooking method. Vitexin and isovitexin were identified in MWE. The results showed that MWE inhibited protein tyrosine phosphatase (PTP)-1B (IC50 = 10 μg/mL), a negative regulator of insulin signaling. MWE enhanced cellular glucose uptake and altered expression of genes involved in glucose metabolism, including forkhead box O1 (FOXO1), phosphoenolpyruvate carboxykinase (PEPCK), and glycogen synthase kinase (GSK)-3β in the insulin-resistant HepG2 cells. In addition, MWE inhibited both α-amylase (IC50 = 36.65 mg/mL) and α-glucosidase (IC50 = 3.07 mg/mL). MWE also inhibited the formation of advanced glycation end products (AGEs) (IC50 = 2.28 mg/mL). This is the first study to show that mungbean water extract increased cellular glucose uptake and improved insulin sensitivity of insulin-resistant HepG2 cells through PTP-1B inhibition and modulating the expression of genes related to glucose metabolism. This suggests that mungbean water extract has the potential to be a functional ingredient for diabetes.

B-cell clonogenic activity of HIV-1 p17 variants is driven by PAR1-mediated EGF transactivation

Combined antiretroviral therapy (cART) for HIV-1 dramatically slows disease progression among HIV+ individuals. Currently, lymphoma represents the main cause of death among HIV-1-infected patients. Detection of p17 variants (vp17s) endowed with B-cell clonogenic activity in HIV-1-seropositive patients with lymphoma suggests their possible role in lymphomagenesis. Here, we demonstrate that the clonogenic activity of vp17s is mediated by their binding to PAR1 and to PAR1-mediated EGFR transactivation through Gq protein. The entire vp17s-triggered clonogenic process is MMPs dependent. Moreover, phosphoproteomic and bioinformatic analysis highlighted the crucial role of EGFR/PI3K/Akt pathway in modulating several molecules promoting cancer progression, including RAC1, ABL1, p53, CDK1, NPM, Rb, PTP-1B, and STAT1. Finally, we show that a peptide (F1) corresponding to the vp17s functional epitope is sufficient to trigger the PAR1/EGFR/PI3K/Akt pathway and bind PAR1. Our findings suggest novel potential therapeutic targets to counteract vp17-driven lymphomagenesis in HIV+ patients.