Recent Advances in Protein Tyrosine Phosphatase 1B Targeted Drug Discovery for Type II Diabetes and Obesity

Curcumin inhibits proliferation of hepatocellular carcinoma cells by blocking PTPN1 and PTPN11 expression

The antitumor mechanism of curcumin is unclear, especially in hepatocellular carcinoma (HCC) cells. To clarify the mechanism of action of curcumin in the effective treatment of HCC, the targets of curcumin were screened and validated. Candidate genes of curcumin for HCC were screened using the traditional Chinese medicine systems pharmacology (TCMSP) database and validated using The Cancer Genome Atlas (TCGA) database. The correlation of mRNA expression levels between key candidate genes was identified in the TCGA liver hepatocellular carcinoma (LIHC) dataset. The effects on prognosis were analyzed to identify the target gene of curcumin, which inhibits HCC cell proliferation. Based on the subcutaneous xenograft model of human HCC in nude mice, the expression levels of target proteins were observed using immunohistochemistry. The analysis results of the present study identified the target genes of curcumin, which were obtained by screening the TCSMP database. The protein tyrosine phosphatase non-receptor type 1 (PTPN1) was obtained from TCGA database analysis of the targeted genes. The expression levels of PTPN1 and its homologous sequence genes in TCGA LIHC project was analyzed to identify the potential target gene of curcumin, for use in HCC treatment. Next, xenograft experiments were performed to investigate the therapeutic effects of curcumin in an animal model. Curcumin was demonstrated to inhibit the growth of HCC xenograft tumors in mice. Immunohistochemistry results demonstrated that the protein expression levels of PTPN1 and PTPN11 in the curcumin group were significantly lower compared with those in the control group. In conclusion, these results demonstrated that curcumin inhibits the proliferation of HCC cells by inhibiting the expression of PTPN1 and PTPN11.

Phytochemical and biological studies on rare and endangered plants endemic to China. Part XXV. Structurally diverse triterpenoids and diterpenoids from two endangered Pinaceae plants endemic to the Chinese Qinling Mountains and their bioactivities

A joint phytochemical investigation on the MeOH extracts of the twigs and needles of two endangered Pinaceae plants endemic to the Chinese Qinling Mountains, Picea neoveitchii (an evergreen spruce) and Larix potaninii var. chinensis (a deciduous larch), led to the isolation and characterization of 34 and 24 structurally diverse terpenoids, respectively. Among them, seven are previously undescribed, including a picane-type [i.e., 14(13 → 12)abeo-12αH-serratane] (neoveitchin A) and a serratane-type (neoveitchin B) triterpenoids, and an abietane-type (neoveitchin C) as well as four labdane-type (potalarxins A-D) diterpenoids. Their structures and absolute configurations were established by extensive spectroscopic methods and/or X-ray diffraction analyses. All isolates were evaluated for their inhibitory activities against the human protein tyrosine phosphatase 1B (PTP1B). Serrat-14-en-3α,21β-diol, betulinic acid, 3β-hydroxy-11-ursen-13(28)-olide, ursolic acid, and oleanolic acid were found to have considerable inhibitory effects against PTP1B, with IC₅₀ values ranging from 1.1 to 18.1 μM. The interactions of the bioactive triterpenoids with PTP1B were thereafter performed by employing molecular docking studies. In addition, 7-oxo-dehydroabietic acid (an abietane-type diterpenoid) and mangiferonic acid (a cycloartane-type triterpenoid) inhibited acetyl-coenzyme A carboxylase 1 (ACC1), with IC₅₀ values of 3.4 and 6.6 μM, respectively.

In vivo antihyperglycaemic and antihyperlipidemic activities and chemical constituents of Solanum anomalum

Solanum anomalum is a plant used ethnomedically for the treatment of diabetes. The study was aimed to validate ethnomedical claims in rat model and identify the likely antidiabetic compounds. Leaf extract (70-210 mg/kg/day) and fractions (140 mg/kg/day) of S. anomalum were evaluated in hyperglycaemic rats induced using alloxan for effects on blood glucose, lipids and pancreas histology. Phytochemical characterisation of isolated compounds and their identification were performed using mass spectrometry and NMR spectroscopy. Bioinformatics tool was used to predict the possible protein targets of the identified bioactive compounds. The leaf extract/fractions on administration to diabetic rats caused significant lowering of fasting blood glucose of the diabetic rats during single dose study and on repeated administration of the extract. The hydroethanolic leaf extracts also enhanced glucose utilization capacity of the diabetic rats and caused significant lowering of glycosylated hemoglobin levels and elevation of insulin levels in the serum. Furthermore, triglycerides, LDL-cholesterol, and VLDL-cholesterol levels were lowered significantly, while HDL-cholesterol levels were also elevated in the treated diabetic rats. There was absence or few pathological signs in the treated hyperglycaemic rat pancreas compared to that present in the pancreas of control group. Diosgenin, 25(R)-diosgenin-3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside, uracil, thymine, 1-octacosanol, and octacosane were isolated and identified. Protein phosphatases along with secreted proteins are predicted to be the major targets of diosgenin and the diosgenin glycoside. These results suggest that the leaf extract/fractions of S. anomalum possess antidiabetic and antihyperlipidemic properties, offer protection to the pancreas and stimulate insulin secretion, which can be attributable to the activities of its phytochemical constituents.

Agrimonia pilosa: A Phytochemical and Pharmacological Review

Agrimonia pilosa Ledeb., which belongs to Agrimonia and Rosaceae, is used in traditional Chinese medicine. It exhibits excellent medicinal properties and has been used to treat various diseases, such as tumors, trichomoniasis, vaginitis, diarrhea, and dysentery. Phytochemical studies have revealed that Agrimonia has over 100 secondary metabolites that can be categorized into six classes, i.e., flavonoids, isocoumarins, triterpenes, phloroglucinol derivatives, tannins, and organic acids. This review summarizes recently published literature on the chemical structures of 90 bioactive compounds that have been identified in A. pilosa and examines their pharmacological properties, including their antitumor, anti-inflammatory, antioxidant, antibacterial, and antidiabetic properties, as well as the potential development of parasitic resistance to these chemicals. This review highlights existing knowledge gap and serves as a basis for developing novel preparations of A. pilosa with medicinal value.

circMAP3K4 regulates insulin resistance in trophoblast cells during gestational diabetes mellitus by modulating the miR-6795-5p/PTPN1 axis

Background

Insulin resistance (IR) during gestational diabetes mellitus (GDM) has been linked to dysregulated insulin-PI3K/Akt pathway. A defective insulin-PI3K/Akt pathway and dysregulated circular RNA (circRNA) levels have been observed in the placentas of patients with GDM; however, the mechanisms underlying this association remain unclear.

Methods

circRNAs potentially associated with GDM were selected through bioinformatics analysis and initially identified by quantitative real-time PCR (qPCR) in 9 GDM patients and 9 healthy controls, of which circMAP3K4 was further validated in additional 84 samples by qPCR. circMAP3K4 identity and localization were verified. Pearson correlation analysis was applied to evaluate the correlation between circMAP3K4 expression in the placental tissues of GDM patients and IR-related indicators. An IR model of trophoblasts was constructed using glucosamine. Interactions between miR-6795-5p and circMAP3K4 or PTPN1 were confirmed using a dual-luciferase reporter assay. The circMAP3K4/miR-6795-5p/PTPN1 axis and key markers in the insulin-PI3K/Akt pathway in placentas and trophoblasts were evaluated through qRT-PCR, immunofluorescence, and western blotting. The role of circMAP3K4 in glucose metabolism and cell growth in trophoblasts was determined using the glucose uptake and CCK8 assay, respectively.

Results

circMAP3K4 was highly expressed in the placentas of patients with GDM and the IR trophoblast model; this was associated with a dysregulated insulin-PI3K/Akt pathway. circMAP3K4 in the placentas of GDM patients was positively correlated with weight gain during pregnancy and time-glucose area under the curve of OGTT. circMAP3K4 and PTPN1 could both bind to miR-6795-5p. miR-6795-5p and PTPN1 were downregulated and upregulated, respectively, in the placentas of GDM patients and the IR trophoblast model. circMAP3K4 silencing or miR-6795-5p overexpression partially reversed the decrease in glucose uptake, inhibition in cell growth, and downregulated IRS1 and Akt phosphorylation in IR-trophoblasts; this restoration was reversed upon co-transfection with an miR-6795-5p inhibitor or PTPN1.

Conclusion

circMAP3K4 could suppress the insulin-PI3K/Akt signaling pathway via miR-6795-5p/PTPN1 axis, probably contributing to GDM-related IR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03386-8.

Synthesis, structure and in vitro biological properties of a new copper(II) complex with 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid

The new copper(II) complex dichloridobis(4-{[3-(pyridin-2-yl-κN)-1H-pyrazol-1-yl-κN²]methyl}benzoic acid)copper(II) methanol sesquisolvate hemihydrate, [CuCl₂L₂]·1.5CH₃OH·0.5H₂O, (1), has been synthesized from CuCl₂·2H₂O and the ligand 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid (L, C₁₅H₁₁N₃O₂). The complex was characterized by elemental analysis, Fourier transform IR spectroscopy, electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Two chloride ligands and two bidentate L ligands coordinate the Cu^II centre in 1 in a Jahn-Teller-distorted octahedral geometry of rather unusual configuration: a chloride substituent and a pyrazole N atom of an N,N'-chelating ligand occupy the more distant axial positions. Classical O-H...O hydrogen bonds and O-H...Cl interactions link neighbouring complex molecules and cocrystallized methanol molecules into chains that propagate parallel to the b direction. The title compound shows intriguing bioactivity: the effects of 1 on the enzymatic activity of protein tyrosine phosphatase 1B (PTP1B) and on the viability of human breast cancer cells of cell line MCF7 were evaluated. Complex 1, with an IC₅₀ value of 0.51 µM, can efficiently inhibit PTP1B activity. An enzyme kinetic assay suggests that 1 inhibits PTP1B in a noncompetitive manner. A fluorescence titration assay indicates that 1 has a strong affinity for PTP1B, with a binding constant of 4.39 × 10⁶ M^-1. Complex 1 may also effectively decrease the viability of MCF7 cells in an extent comparable to that of cisplatin (IC₅₀ = 6.3 µM). The new copper complex therefore represents a promising PTP1B inhibitor and an efficient antiproliferation reagent against MCF7 cells.

Therapeutics for type-2 diabetes mellitus: a glance at the recent inclusions and novel agents under development for use in clinical practice

Diabetes mellitus (DM) is a chronic, progressive, and multifaceted illness resulting in significant physical and psychological detriment to patients. As of 2019, 463 million people are estimated to be living with DM worldwide, out of which 90% have type-2 diabetes mellitus (T2DM). Over the years, significant progress has been made in identifying the risk factors for developing T2DM, understanding its pathophysiology and uncovering various metabolic pathways implicated in the disease process. This has culminated in the implementation of robust prevention programmes and the development of effective pharmacological agents, which have had a favourable impact on the management of T2DM in recent times. Despite these advances, the incidence and prevalence of T2DM continue to rise. Continuing research in improving efficacy, potency, delivery and reducing the adverse effect profile of currently available formulations is required to keep pace with this growing health challenge. Moreover, new metabolic pathways need to be targeted to produce novel pharmacotherapy to restore glucose homeostasis and address metabolic sequelae in patients with T2DM. We searched PubMed, MEDLINE, and Google Scholar databases for recently included agents and novel medication under development for treatment of T2DM. We discuss the pathophysiology of T2DM and review how the emerging anti-diabetic agents target the metabolic pathways involved. We also look at some of the limiting factors to developing new medication and the introduction of unique methods, including facilitating drug delivery to bypass some of these obstacles. However, despite the advances in the therapeutic options for the treatment of T2DM in recent years, the industry still lacks a curative agent.

Khayalactone- and phragmalin-type limonoids with PTP1B inhibitory activity from Trichilia sinensis Bentv

An investigation on the extract from the plant Trichilia sinensis Bentv. led to the isolation of 13 new limonoids (1-13), in which two were of khayalactone skeleton and 11 were phragmalin-type limonoids, and eight known phragmalin-type limonoids (14-21). Their structures were elucidated by using spectroscopic techniques and HRESIMS experiment. Compounds 6 and 17 displayed potent protein tyrosine phosphatase 1B inhibitory activity with IC₅₀ values of 1.2 ± 0.1 and 8.1 ± 0.5 μM, respectively.

TRIM18-Regulated STAT3 Signaling Pathway via PTP1B Promotes Renal Epithelial-Mesenchymal Transition, Inflammation, and Fibrosis in Diabetic Kidney Disease

Diabetic kidney disease (DKD) has become a key cause of end-stage renal disease worldwide. Inflammation and fibrosis have been shown to play important roles in the pathogenesis of DKD. MID1, also known as TRIM18, is an E3 ubiquitin ligase of the tripartite motif (TRIM) subfamily of RING-containing proteins and increased in renal tubule in patients with DKD. However, the function and molecular mechanism of TRIM18 in DKD remain unexplored. Herein we report that TRIM18 expression levels were increased in patients with DKD. An animal study confirms that TRIM18 is involved in kidney injury and fibrosis in diabetic mice. TRIM18 knockdown inhibits high glucose (HG)-induced epithelial–mesenchymal transition (EMT), inflammation, and fibrosis of HK-2 cells. This is accompanied by decreased levels of tumor necrosis factor alpha, interleukin-6, hydroxyproline (Hyp), connective tissue growth factor, and α-smooth muscle actin. Additionally, TRIM18 knockdown inhibits HG-induced increase in the phosphorylated-/total signal transducer and activator of transcription (STAT3). Treatment with niclosamide (STAT3 inhibitor) or protein tyrosine phosphatase-1B (PTP1B) overexpression blocked the TRIM18 induced EMT, inflammation and fibrosis. Co-immunoprecipitation and Western blot assays showed that TRIM18 promoted the ubiquitination of PTP1B. These findings highlight the importance of the TRIM18/PTP1B/STAT3 signaling pathway in DKD and can help in the development of new therapeutics for DKD treatment.

Bioactive monoterpene phenol dimers from the fruits of Psoralea corylifolia L

Nine undescribed monoterpene phenol dimers, bisbakuchiols D-L (1-9), were isolated from the fruits of Psoralea corylifolia L. Their structures were elucidated based on extensive spectral analysis. The absolute configurations of 1-9 were specified by experimental and quantum chemical calculations of ECD spectra, and that of 1 was further established by X-ray diffraction analysis using Cu Kα radiation. Bisbakuchiols (1-4) were composed of two bakuchiols, one of which was cyclized via a C-7'/ C-12' single bond to form a six-member ring, and connect to each other by C-4-O-C-13' bonds. Bisbakuchiols (7-9) had a pyran ring by linkage of C-8-O-C-12. In the enzyme assay, compounds 5 and 9 exhibited significant PTP1B inhibitory activities with IC₅₀ values of 0.69 and 0.73 μM, and compounds 1 and 3 showed moderate PTP1B inhibitory activities. Furthermore, a molecular docking simulation of PTP1B and active compounds 5 and 9 showed that these active compounds possess low binding affinities ranging from -6.9 to -7.1 kcal/mol.

Activation of Insulin Signaling by Botanical Products

Type 2 diabetes (T2D) is a worldwide health problem, ranked as one of the leading causes for severe morbidity and premature mortality in modern society. Management of blood glucose is of major importance in order to limit the severe outcomes of the disease. However, despite the impressive success in the development of new antidiabetic drugs, almost no progress has been achieved with regard to the development of novel insulin-sensitizing agents. As insulin resistance is the most eminent factor in the patho-etiology of T2D, it is not surprising that an alarming number of patients still fail to meet glycemic goals. Owing to its wealth of chemical structures, the plant kingdom is considered as an inventory of compounds exerting various bioactivities, which might be used as a basis for the development of novel medications for various pathologies. Antidiabetic activity is found in over 400 plant species, and is attributable to varying mechanisms of action. Nevertheless, relatively limited evidence exists regarding phytochemicals directly activating insulin signaling, which is the focus of this review. Here, we will list plants and phytochemicals that have been found to improve insulin sensitivity by activation of the insulin signaling cascade, and will describe the active constituents and their mechanism of action.

Virtual Screening Based Discovery of PTP1B Inhibitors and Their Biological Evaluations

Background :

The discovery of novel antidiabetics for the treatment of type 2 diabetes mellitus (T2DM) is an important task nowadays because the current treatment approaches have certain limitations. The reported studies showed that the protein tyrosine phosphatase 1B (PTP1B) is a valuable target, can be used to develop significant antidiabetic molecules.

Objective:

In the present investigation, computational methods and biological evaluation studies have been applied to develop novel PTP1B inhibitors with good enzyme binding affinity and activity.

Methods:

Virtual screening (docking) analysis of SPECS database compounds on PTP1B enzyme was performed using Schrodinger software. In vitro and in vivo biological evaluations had been conducted with the identified hits.

Results:

The results revealed that the molecules identified through these studies have shown significant interactions with the active site residues of the PTP1B enzyme. The compounds S1 and S2 provided significant binding interactions with the residues (Arg221 and Gln262) and have shown considerable in vitro PTP1B inhibitory activity and in vivo antidiabetic activity. The compounds S1 and S2 possessed 35.44±0.12% and 33.68±0.08% inhibitory activities, respectively.

Conclusion:

These identified hits will be used as a template for design and development of novel PTP1B inhibitors with a compatible pharmacokinetic profile.

Tubeimoside I Inhibits Cell Proliferation and Induces a Partly Disrupted and Cytoprotective Autophagy Through Rapidly Hyperactivation of MEK1/2-ERK1/2 Cascade via Promoting PTP1B in Melanoma

Tubeimoside I (TBMS1), also referred to as tubeimoside A, is a natural compound extracted from the plant Tu Bei Mu (Bolbostemma paniculatum), which is a traditional Chinese herb used to treat multiple diseases for more than 1,000 years. Studies in recent years reported its anti-tumor activity in several cancers. However, whether it is effective in melanoma remains unknown. In the current study, we discovered that TBMS1 treatment inhibited melanoma cell proliferation in vitro and tumorigenecity in vivo. Besides, we also observed that TBMS1 treatment induced a partly disrupted autophagy, which still remained a protective role, disruption of which by chloroquine (CQ) or 3-methyladenine (3-MA) enhanced TBMS1-induced cell proliferation inhibition. CQ combined with TBMS1 even induced cellular apoptosis. BRAF(V600E) mutation and its continuously activated downstream MEK1/2-ERK1/2 cascade are found in 50% of melanomas and are important for malanomagenesis. However, hyperactivating MEK1/2-ERK1/2 cascade can also inhibit tumor growth. Intriguingly, we observed that TBMS1 rapidly hyperactivated MEK1/2-ERK1/2, inhibition of which by its inhibitor SL-327 rescued the anti-cancerous effects of TBMS1. Besides, the targets of TBMS1 were predicted by the ZINC Database based on its structure. It is revealed that protein-tyrosine phosphatase 1B (PTP1B) might be one of the targets of TBMS1. Inhibition of PTP1B by its selective inhibitor TCS401 or shRNA rescued the anti-cancerous effects of TBMS1 in melanoma cells. These results indicated that TBMS1 might activate PTP1B, which further hyperactivates MEK1/2-ERK1/2 cascade, thereby inhibiting cell proliferation in melanoma. Our results provided the potentiality of TBMS1 as a drug candidate for melanoma therapy and confirmed that rapidly hyperactivating an oncogenic signaling pathway may also be a promising strategy for cancer treatment.

Pimarane Diterpenoids from the Seeds of Caesalpinia minax as PTP1B Inhibitors and Insulin Sensitizers

Protein-tyrosine phosphatase 1B (PTP1B) has been considered as a promising target for treating insulin resistance. In searching for naturally occurring PTB1B antagonists, two new pimarane diterpenoids, named 2α-hydroxy-7-oxo-pimara-8(9),15-diene (1) and 19-hydroxy-2α-acetoxy-7-oxo-pimara-8(9),15-diene (2), were isolated from the seeds of Caesalpinia minax. Their structures were determined by extensive analysis of NMR and HR-ESIMS data, and their absolute configurations were determined by electronic circular dichroism (ECD) spectra. Compound 1 was disclosed as a competitive inhibitor of PTP1B with an IC50 (the half-maximal inhibitory concentration) value of 19.44 ± 2.39 µM and a Ki (inhibition constant) value of 13.69 ± 2.72 μM. Moreover, compound 1 dose-dependently promoted insulin-stimulated glucose uptake in C2C12 myotubes through activating insulin signaling pathway. Compound 1 might be further developed as an insulin sensitizer.

Novel oligomeric neolignans with PTP1B inhibitory activity from the bark of Magnolia officinalis var. biloba

The barks of Magnolia officinalis var. biloba, Magnoliae cortex, have been used as traditional Chinese medicines for several centuries. In this study, phytochemical investigation of M. officinalis var. biloba bark extract afforded five pairs of novel enantiomeric oligomeric neolignans, (±)-mooligomers A-E (1-5). (±)-1 and (±)-2 were two diastereomeric pairs of enantiomers with six C6-C3 subunits, and (±)-4 was a pair of previously unreported tetrameric neolignans bearing eight C6-C3 subunits. (±)-5 is the first example of a naturally occurring trilignan featuring an eight-membered ring with a magnolol moiety. The absolute configurations of (±)-1-(±)-5 were elucidated on the basis of HRESIMS, 1D and 2D NMR spectroscopy and electronic circular dichroism (ECD) calculations. Among the compounds tested for their PTP1B inhibitory activities, (±)-2, (±)-4 and (±)-5 displayed significant PTP1B inhibitory activities with IC₅₀ values of 0.14-2.10 μM. Furthermore, a Molecular docking simulation of PTP1B and active compounds [(±)-2, (±)-4 and (±)-5] exhibited that these active compounds possess low binding affinities ranging from - 5.9 to - 7.7 kcal/mol.

Screening of Indonesian Edible Plants for Bioactive Constituents and a New Protein Tyrosine Phosphatase 1B Inhibitory Acylbenzene Derivative from Leaves of Indonesian Syzygium polyanthum

Bioassay screening using Indonesian plants, such as traditional foods (vegetables, spices, and tea) and folk medicinal herbs, identified eight protein tyrosine phosphatase (PTP) 1B inhibitory and two antibacterial plants. The leaves of Syzygium polyanthum (Wight) Walp. were examined in more detail to define PTP1B inhibitory components, resulting in the isolation of a new active acylbenzene (1) along with four related congeners of 1 (2-5) and four oleanane triterpenes (6-9). The structure of 1 was elucidated as 12-oxo-12-(2,3,5-trihydroxy-4-methylphenyl)dodecanoic acid based on its spectroscopic data. The acylbenzenes 1 and 3-5 inhibited PTP1B activity with IC₅₀ values ranging between 9.5 and 14 µM, whereas the triterpenes 7-9 also suppressed this activity with IC₅₀ values of 3.3-5.7 µM.

Hepatic protein-tyrosine phosphatase 1B disruption and pharmacological inhibition attenuate ethanol-induced oxidative stress and ameliorate alcoholic liver disease in mice

Alcoholic liver disease (ALD) is a major health problem and a significant cause of liver-related death. Currently, the mainstay for ALD therapy is alcohol abstinence highlighting the need to develop pharmacotherapeutic approaches. Protein-tyrosine phosphatase 1B (PTP1B) is an established regulator of hepatic functions, but its role in ALD is mostly unexplored. In this study, we used mice with liver-specific PTP1B disruption as well as pharmacological inhibition to investigate the in vivo function of this phosphatase in ALD. We report upregulation of hepatic PTP1B in the chronic plus binge mouse model and, importantly, in liver biopsies of alcoholic hepatitis patients. Also, mice with hepatic PTP1B disruption attenuated ethanol-induced injury, inflammation, and steatosis compared with ethanol-fed control animals. Moreover, PTP1B deficiency was associated with decreased ethanol-induced oxidative stress in vivo and ex vivo. Further, pharmacological modulation of oxidative balance in hepatocytes identified diminished oxidative stress as a contributor to the salutary effects of PTP1B deficiency. Notably, PTP1B pharmacological inhibition elicited beneficial effects and mitigated hepatic injury, inflammation, and steatosis caused by ethanol feeding. In summary, these findings causally link hepatic PTP1B and ALD and define a potential therapeutic target for the management of this disease.

Multiflorumisides HK, stilbene glucosides isolated from Polygonum multiflorum and their in vitro PTP1B inhibitory activities

A phytochemical study on a 70% EtOH extract of dried roots of Polygonum multiflorum resulted in the isolation of four undescribed stilbene glucosides, namely multiflorumisides HK (1-4). The structures of the natural products were elucidated by 1D and 2D nuclear magnetic resonance (NMR) as well as mass spectroscopy analyses. Among them, multiflorumiside J (3) and multiflorumiside K (4) belong to rare tetramer stilbene glucosides. Moreover, the in vitro inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) were evaluated and the putative biosynthetic pathway was proposed. Notably, compounds 1-4 showed the inhibitory activity against PTP1B with the IC₅₀ values of 1.2, 1.7, 1.5 and 4.6 μm, respectively. Based on the obtained results, stilbene glucosides could be the potential PTP1B inhibitors of P. multiflorum.

Turn and Face the Strange: A New View on Phosphatases

Phosphorylation as a post-translational modification is critical for cellular homeostasis. Kinases and phosphatases regulate phosphorylation levels by adding or removing, respectively, a phosphate group from proteins or other biomolecules. Imbalances in phosphorylation levels are involved in a multitude of diseases. Phosphatases are often thought of as the black sheep, the strangers, of phosphorylation-mediated signal transduction, particularly when it comes to drug discovery and development. This is due to past difficulties to study them and unsuccessful attempts to target them; however, phosphatases have regained strong attention and are actively pursued now in clinical trials. By giving examples for current hot topics in phosphatase biology and for new approaches to target them, it is illustrated here how and why phosphatases made their comeback, and what is envisioned to come in the future.

Identification of natural products as selective PTP1B inhibitors via virtual screening

Protein tyrosine phosphatase 1B (PTP1B) is emerging as a promising yet challenging target for drug discovery. To identify natural products as new prototypes for PTP1B inhibitors, we employed a hierarchical protocol combining ligand-based and structure-based approaches for virtual screening against natural product libraries. Twenty-six compounds were prioritized for enzymatic evaluation against PTP1B, and ten of them were recognized as potent PTP1B inhibitors with IC₅₀ values at the micromolar level. Notably, nine compounds demonstrated evident selectivity to PTP1B over four other PTPs, including the most homologous T-cell protein tyrosine phosphatase (TCPTP). The results implicated that the structural uniqueness of the natural products might be a potential solution to the selectivity issue associated with the target PTP1B.

Advances in the Treatment of Explicit Water Molecules in Docking and Binding Free Energy Calculations

Background:

The inclusion of direct effects mediated by water during the ligandreceptor recognition is a hot-topic of modern computational chemistry applied to drug discovery and development. Docking or virtual screening with explicit hydration is still debatable, despite the successful cases that have been presented in the last years. Indeed, how to select the water molecules that will be included in the docking process or how the included waters should be treated remain open questions.

Objective:

In this review, we will discuss some of the most recent methods that can be used in computational drug discovery and drug development when the effect of a single water, or of a small network of interacting waters, needs to be explicitly considered.

Results:

Here, we analyse the software to aid the selection, or to predict the position, of water molecules that are going to be explicitly considered in later docking studies. We also present software and protocols able to efficiently treat flexible water molecules during docking, including examples of applications. Finally, we discuss methods based on molecular dynamics simulations that can be used to integrate docking studies or to reliably and efficiently compute binding energies of ligands in presence of interfacial or bridging water molecules.

Conclusions:

Software applications aiding the design of new drugs that exploit water molecules, either as displaceable residues or as bridges to the receptor, are constantly being developed. Although further validation is needed, workflows that explicitly consider water will probably become a standard for computational drug discovery soon.

Discovery of highly functionalized 5,6-seco-grayanane diterpenoids as potent competitive PTP1B inhibitors

Three competitive PTP1B inhibitory diterpenoids with a 5,6-seco-grayanane carbon skeleton (1–3) were isolated and identified fromRhododendron molle. A more potent competitive PTP1B inhibitor (9) was designed and prepared based on a docking study.

Protein Tyrosine Phosphatase 1B Inhibitory Iridoids from Psydrax subcordata

Phytochemical investigation of the leaves and bark of Psydrax subcordata has led to the isolation of six new iridoids, subcordatanols I-V (1-4 and 6) and 1-O-methylcrescentin I (5), along with two known analogues (7 and 8). Among them, subcordatanol I (1) is the first example of a 3,8-monoepoxy-iridoid featuring a caged 2-oxa-bicyclo[3.2.1]octane core. The absolute stereochemistry at C-4 of 3, 4, and 6 was established through their acid-catalyzed reaction products subcordatalactones A (3a), B (4a), and C (6a), respectively. Subcordatanols I (1) and II (2), as well as subcordatalactones A (3a) and B (4a), displayed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B). Enzyme kinetic studies indicated that 3a and 4a are competitive inhibitors. A molecular docking study is also reported.

Identification of lipid-like salicylic acid-based derivatives as potent and membrane-permeable PTP1B inhibitors

Developing protein tyrosine phosphatase-1B (PTP1B) inhibitors is an important strategy to treat type 2 diabetes mellitus (T2DM). Most existing ionic PTP1B inhibitors aren't of clinical useful due to their low cell-permeability, however. Herein, we introduced a series of lipid-like acid-based (salicylic acid) modules to prepare PTP1B inhibitors, and demonstrated a marked improvement of cell-permeability while maintaining excellent PTP1B inhibitory activity (e.g. compound B12D, IC₅₀ = 0.37 μM against PTP1B and P_app = 1.5 × 10^-6 cm/s). We believe that this strategy can be widely utilized to modify potent lead compounds with low cell-permeability.

Identification and characterization of potent and selective inhibitors targeting protein tyrosine phosphatase 1B (PTP1B)

Protein tyrosine phosphatase 1B (PTP1B) plays an important role in the negative regulation of insulin and leptin signaling. The development of small molecular inhibitors targeting PTP1B has been validated as a potential therapeutic strategy for Type 2 diabetes (T2D). In this work, we have identified a series of compounds containing dihydropyridine thione and particular chiral structure as novel PTP1B inhibitors. Among those, compound 4b showed moderate activity with IC₅₀ value of 3.33 μM and meanwhile with good selectivity (>30-fold) against TCPTP. The further MOA study of PTP1B demonstrated that compounds 4b is a substrate-competitive inhibitor. The binding mode analysis suggested that compound 4b simultaneously occupies the active site and the second phosphotyrosine (pTyr) binding site of PTP1B. Furthermore, the cell viability assay of compound 4b showed tolerable cytotoxicity in L02 cells, thus 4b may be prospectively used to further in vivo study.

Experimental and Computational Study to Reveal the Potential of Non-Polar Constituents from Hizikia fusiformis as Dual Protein Tyrosine Phosphatase 1B and α-Glucosidase Inhibitors

Hizikia fusiformis (Harvey) Okamura is an edible marine alga that has been widely used in Korea, China, and Japan as a rich source of dietary fiber and essential minerals. In our previous study, we observed that the methanol extract of H. fusiformis and its non-polar fractions showed potent protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase inhibition. Therefore, the aim of the present study was to identify the active ingredient in the methanol extract of H. fusiformis. We isolated a new glycerol fatty acid (13) and 20 known compounds including 9 fatty acids (1-3, 7-12), mixture of 24R and 24S-saringosterol (4), fucosterol (5), mixture of 24R,28R and 24S,28R-epoxy-24-ethylcholesterol (6), cedrusin (14), 1-(4-hydroxy-3-methoxyphenyl)-2-[2-hydroxy -4-(3-hydroxypropyl)phenoxy]-1,3-propanediol (15), benzyl alcohol alloside (16), madhusic acid A (17), glycyrrhizin (18), glycyrrhizin-6'-methyl ester (19), apo-9'-fucoxanthinone (20) and tyramine (21) from the non-polar fraction of H. fusiformis. New glycerol fatty acid 13 was identified as 2-(7'- (2″-hydroxy-3″-((5Z,8Z,11Z)-icosatrienoyloxy)propoxy)-7'-oxoheptanoyl)oxymethylpropenoic acid by spectroscopic analysis using NMR, IR, and HR-ESI-MS. We investigated the effect of the 21 isolated compounds and metabolites (22 and 23) of 18 against the inhibition of PTP1B and α-glucosidase enzymes. All fatty acids showed potent PTP1B inhibition at low concentrations. In particular, new compound 13 and fucosterol epoxide (6) showed noncompetitive inhibitory activity against PTP1B. Metabolites of glycyrrhizin, 22 and 23, exhibited competitive inhibition against PTP1B. These findings suggest that H. fusiformis, a widely consumed seafood, may be effective as a dietary supplement for the management of diabetes through the inhibition of PTP1B.

Novel benzamido derivatives as PTP1B inhibitors with anti-hyperglycemic and lipid-lowering efficacy

Based on a non-competitive and selective PTP1B inhibitor reported by us previously, thirty-nine benzamido derivatives were designed and synthesized as novel PTP1B inhibitors. Among them, twelve compounds exhibited IC₅₀ values at micromolar level against human recombinant PTP1B, and most of them exhibited significant selectivity to PTP1B over TC-PTP and CD45. Further evaluation of the most potent compound 27 on high-fat diet (HFD)-induced insulin-resistant (IR) obese mice indicated that 27 could modulate glucose metabolism and ameliorate dyslipidemia simultaneously.

Protection against gamma-radiation injury by protein tyrosine phosphatase 1B

Protein tyrosine phosphatase 1B (PTP1B) is widely expressed in mammalian tissues, in particular in immune cells, and plays a pleiotropic role in dephosphorylating many substrates. Moreover, PTP1B expression is enhanced in response to pro-inflammatory stimuli and to different cell stressors. Taking advantage of the use of mice deficient in PTP1B we have investigated the effect of γ-radiation in these animals and found enhanced lethality and decreased respiratory exchange ratio vs. the corresponding wild type animals. Using bone-marrow derived macrophages and mouse embryonic fibroblasts (MEFs) from wild-type and PTP1B-deficient mice, we observed a differential response to various cell stressors. PTP1B-deficient macrophages exhibited an enhanced response to γ-radiation, UV-light, LPS and S-nitroso-glutathione. Macrophages exposed to γ-radiation show DNA damage and fragmentation, increased ROS production, a lack in GSH elevation and enhanced acidic β-galactosidase activity. Interestingly, these differences were not observed in MEFs. Differential gene expression analysis of WT and KO macrophages revealed that the main pathways affected after irradiation were an up-regulation of protein secretion, TGF-β signaling and angiogenesis among other, and downregulation of Myc targets and Hedgehog signaling. These results demonstrate a key role for PTP1B in the protection against the cytotoxicity of irradiation in intact animal and in macrophages, which might be therapeutically relevant.

Current anti-diabetic agents and their molecular targets: A review

Diabetes mellitus is a medical condition characterized by the body's loss of control over blood sugar. The frequency of diagnosed cases and consequential increases in medical costs makes it a rapidly growing chronic disease that threatens human health worldwide. In addition, its unnerving statistical projections are perilous to both the economy of the nation and man's life expectancy. Type-I and type-II diabetes are the two clinical forms of diabetes mellitus. Type-II diabetes mellitus (T2DM) is illustrated by the abnormality of glucose homeostasis in the body, resulting in hyperglycemia. Although significant research attention has been devoted to the development of diabetes regimens, which demonstrates success in lowering blood glucose levels, their efficacies are unsustainable due to undesirable side effects such as weight gain and hypoglycemia. Over the years, heterocyclic scaffolds have been the basis of anti-diabetic chemotherapies; hence, in this review we consolidate the use of bioactive scaffolds, which have been evaluated for their biological response as inhibitors against their respective anti-diabetic molecular targets over the past five years (2012-2017). Our investigation reveals a diverse target set which includes; protein tyrosine phosphatase 1 B (PTP1B), dipeptidly peptidase-4 (DPP-4), free fatty acid receptors 1 (FFAR1), G protein-coupled receptors (GPCR), peroxisome proliferator activated receptor-γ (PPARγ), sodium glucose co-transporter-2 (SGLT2), α-glucosidase, aldose reductase, glycogen phosphorylase (GP), fructose-1,6-bisphosphatase (FBPase), glucagon receptor (GCGr) and phosphoenolpyruvate carboxykinase (PEPCK). This review offers a medium on which future drug design and development toward diabetes management may be modelled (i.e. optimization via structural derivatization), as many of the drug candidates highlighted show promise as an effective anti-diabetic chemotherapy.

Harnessing insulin- and leptin-induced oxidation of PTP1B for therapeutic development

The protein tyrosine phosphatase PTP1B is a major regulator of glucose homeostasis and energy metabolism, and a validated target for therapeutic intervention in diabetes and obesity. Nevertheless, it is a challenging target for inhibitor development. Previously, we generated a recombinant antibody (scFv45) that recognizes selectively the oxidized, inactive conformation of PTP1B. Here, we provide a molecular basis for its interaction with reversibly oxidized PTP1B. Furthermore, we have identified a small molecule inhibitor that mimics the effects of scFv45. Our data provide proof-of-concept that stabilization of PTP1B in an inactive, oxidized conformation by small molecules can promote insulin and leptin signaling. This work illustrates a novel paradigm for inhibiting the signaling function of PTP1B that may be exploited for therapeutic intervention in diabetes and obesity.

The activity of protein tyrosine phosphatase PTP1B, a major metabolic regulator, depends on its oxidation state. Here the authors identify and characterize a small molecule that targets the oxidized, inactive form of PTP1B, suggesting a new therapeutic approach to diabetes and obesity.

A potent, selective, and orally bioavailable inhibitor of the protein-tyrosine phosphatase PTP1B improves insulin and leptin signaling in animal models

The protein-tyrosine phosphatase PTP1B is a negative regulator of insulin and leptin signaling and a highly validated therapeutic target for diabetes and obesity. Conventional approaches to drug development have produced potent and specific PTP1B inhibitors, but these inhibitors lack oral bioavailability, which limits their potential for drug development. Here, we report that DPM-1001, an analog of the specific PTP1B inhibitor trodusquemine (MSI-1436), is a potent, specific, and orally bioavailable inhibitor of PTP1B. DPM-1001 also chelates copper, which enhanced its potency as a PTP1B inhibitor. DPM-1001 displayed anti-diabetic properties that were associated with enhanced signaling through insulin and leptin receptors in animal models of diet-induced obesity. Therefore, DPM-1001 represents a proof of concept for a new approach to therapeutic intervention in diabetes and obesity. Although the PTPs have been considered undruggable, the findings of this study suggest that allosteric PTP inhibitors may help reinvigorate drug development efforts that focus on this important family of signal-transducing enzymes.