Recent advances in protein tyrosine phosphatase 1B inhibitors

Therapeutic Potential of Hispidin-Fungal and Plant Polyketide

There is a large number of bioactive polyketides well-known for their anticancer, antibiotic, cholesterol-lowering, and other therapeutic functions, and hispidin is among them. It is a highly abundant secondary plant and fungal metabolite, which is investigated in research devoted to cancer, metabolic syndrome, cardiovascular, neurodegenerative, and viral diseases. This review summarizes over 20 years of hispidin studies of its antioxidant, anti-inflammatory, anti-apoptotic, antiviral, and anti-cancer cell activity.

Diterpenes from seeds of Phalaris canariensis and their PTP1B inhibitory activity and hypoglycemic effects in streptozotocin-induced diabetic mice

This present study was to evaluate the protein tyrosine phosphatase 1B (PTP1B) inhibitory activity of nine diterpenes isolated from seeds of Phalaris canariensis, as well as their effect on streptozotocin-nicotinamide-induced type 2 diabetic mice. Their structures were established by spectroscopic analyses. Diterpenes, 1, 4, and 2 exhibited the strongest inhibitory activity on PTP1B with IC₅₀ values of 6.9, 7.3, and 6.5 µM, respectively, The administration of 1-9 showed significant effect on hyperglycemia, among them 1, 4, and 2 reduced fasting glucose levels (55.65%, 54.27%, and 51.22%, respectively). Results revealed that diterpenes performed potential antidiabetic activity via inhibition of PTP1B.[Formula: see text].

Insight into the PTP1B Inhibitory Activity of Arylbenzofurans: An In Vitro and In Silico Study

Protein tyrosine phosphatase 1B (PTP1B) plays a specific role as a negative regulator of insulin signaling pathways and is a validated therapeutic target for Type 2 diabetes. Previously, arylbenzofurans were reported to have inhibitory activity against PTP1B. However, detailed investigation regarding their structure activity relationship (SAR) has not been elucidated. The main aim of this work was to investigate the PTP1B inhibitory activity of 2-arylbenzofuran analogs (sanggenofuran A (SA), mulberrofuran D2 (MD2), mulberrofuran D (MD), morusalfuran B (MB), mulberrofuran H (MH)) isolated from the root bark of Morus alba. All compounds demonstrated potent inhibitory activity with IC₅₀ values ranging from 3.11 to 53.47 µM. Among the tested compounds, MD2 showed the strongest activity (IC₅₀, 3.11 µM), followed by MD and MB, while SA and MH demonstrated the lowest activity. Lineweaver-Burk and Dixon plots were used for the determination of inhibition type whereas ligand and receptor interactions were investigated in modeled complexes via molecular docking. Our study clearly supports 2-arylbenzofuran analogs as a promising class of PTP1B inhibitors and illustrates the key positions responsible for the inhibitory activity, their correlation, the effect of prenyl/geranyl groups, and the influence of resorcinol scaffold, which can be further explored in-depth to develop therapeutic agents against T2DM.

Phyto- and Bio-Chemical evaluation of Diospyros kaki L. cultivated in Egypt and its biological activities

Diospyros kaki L. or Costata cultivar is the main persimmon variety progressively consumed in the Egyptian market and exportation. The objective of this study was to investigate the bioprotective effects of the alcoholic extract of fruits as well as leaves of D. kaki using in-vivo rat models. Petroleum ether extracts of fruits and leaves were analytically characterized for saponifiable and unsaponifiable compounds by GC/MS. Main flavonoids were chromatographically isolated from 80% aqueous methanol extract of leaves. Chemical evaluation for fruits and leaves namely, content of moisture, ash, proteins, fatty acids, amino acids, fat and water soluble vitamins, minerals, carotenoids was carried out. Total antioxidant activity was determined by radical scavenging effects using DPPH assay. The effect on biochemical parameters and its biological activity were also performed. Results revealed the identification of the major compounds of saponifiable and unsaponifiable matters of fruits and leaves. Scopoletin, as well as, kaempferol, luteolin, rutin and apigenin 7-O-glucoside were isolated and identified. It showed that this plant can provide a good nutritional value and it is safe regarding the kidney and liver functions, good source that help in enhancing the antioxidant defense against free radicals. No abnormal effects were found in lipids profile on experimental animals and there were good results in the ratio of HDL and LDL cholesterol. Also, this plant can help in optimizing blood sugar, enhancing the level of blood haemoglobin. It is concluded that D. kaki displays a good source of nutrients and bioactive compounds that may contribute to its therapeutic benefits against the risk of disease complications.

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.

The development of protein tyrosine phosphatase1B inhibitors defined by binding sites in crystalline complexes

Protein tyrosine phosphatase1B (PTP1B), a significant negative regulator in insulin and leptin signaling pathways, has emerged as a promising drug target for Type II diabetes mellitus and obesity. Numerous potent PTP1B inhibitors have been discovered within both academia and pharmaceutical industry. However, nearly all medicinal chemistry efforts have been severely hindered because a vast majority of them demonstrate poor membrane permeability and low-selectivity, especially over T-cell protein tyrosine phosphatase (TCPTP). To search the rules about the selectivity over TCPTP and membrane permeability of PTP1B inhibitors, based on the PTP1B/inhibitor crystal complexes, the development PTP1B inhibitors defined as AB, AC, ABC and ADC types have been concluded in the review.

Novel glitazones as PPARγ agonists: molecular design, synthesis, glucose uptake activity and 3D QSAR studies

BACKGROUND

An alarming requirement for finding newer antidiabetic glitazones as agonists to PPARγ are on its utmost need from past few years as the side effects associated with the available drug therapy is dreadful. In this context, herein, we have made an attempt to develop some novel glitazones as PPARγ agonists, by rational and computer aided drug design approach by implementing the principles of bioisosterism. The designed glitazones are scored for similarity with the developed 3D pharmacophore model and subjected for docking studies against PPARγ proteins. Synthesized by adopting appropriate synthetic methodology and evaluated for in vitro cytotoxicity and glucose uptake assay. Illustrations about the molecular design of glitazones, synthesis, analysis, glucose uptake activity and SAR via 3D QSAR studies are reported.

RESULTS

The computationally designed and synthesized ligands such as 2-(4-((substituted phenylimino)methyl)phenoxy)acetic acid derivatives were analysed by IR, ¹H-NMR, ¹³C-NMR and MS-spectral techniques. The synthesized compounds were evaluated for their in vitro cytotoxicity and glucose uptake assay on 3T3-L1 and L6 cells. Further the activity data was used to develop 3D QSAR model to establish structure activity relationships for glucose uptake activity via CoMSIA studies.

CONCLUSION

The results of pharmacophore, molecular docking study and in vitro evaluation of synthesized compounds were found to be in good correlation. Specifically, CPD03, 07, 08, 18, 19, 21 and 24 are the candidate glitazones exhibited significant glucose uptake activity. 3D-QSAR model revealed the scope for possible further modifications as part of optimisation to find potent anti-diabetic agents.

Function-Oriented Synthesis of Marine Phidianidine Derivatives as Potential PTP1B Inhibitors with Specific Selectivity

Phidianidines A and B are two novel marine indole alkaloids bearing an uncommon 1,2,4-oxadiazole ring and exhibiting various biological activities. Our previous research showed that the synthesized phidianidine analogs had the potential to inhibit the activity of protein tyrosine phosphatase 1B (PTP1B), a validated target for Type II diabetes, which indicates that these analogs are worth further structural modification. Therefore, in this paper, a series of phidianidine derivatives were designed and rapidly synthesized with a function-oriented synthesis (FOS) strategy. Their inhibitory effects on PTP1B and T-cell protein tyrosine phosphatase (TCPTP) were evaluated, and several compounds displayed significant inhibitory potency and specific selectivity over PTP1B. The structure–activity relationship (SAR) and molecular docking analyses are also described.

Design and synthesis of novel 1,2-dithiolan-4-yl benzoate derivatives as PTP1B inhibitors

A series of novel 1,2-dithiolan-4-yl benzoate compounds were synthesized and evaluated for in vitro PTP1B inhibitory activity. Some derivatives exhibited improved PTP1B inhibitory activity and selectivity compared to hit 6a, a compound from in-house library screening inspired by marine cyclic disulfide. The preliminary SAR analysis with assistance of molecular modeling approach revealed 6j (IC50=0.59μM) as the most potent PTP1B inhibitor among all derivatives.

Canthinone alkaloids are novel protein tyrosine phosphatase 1B inhibitors

Considerable attention has been paid to protein tyrosine phosphatase 1B (PTP1B) inhibitors as a potential therapy for diabetes. Screening of a natural compound library resulted in six canthinone alkaloids, namely, picrasidine L (1), 3,4-dimethyl-canthin-5,6-dione (2), 4-ethyl-3-methyl-canthin-5,6-dione (3), eurycomine E (4), 5-methoxy-canthin-6-one (5), and 5-acethoxy-canthin-6-one (6), as novel PTP1B inhibitors. Among these, 1 is the competitive PTP1B inhibitor with the best inhibitory selectivity between PTP1B and other PTPs and was shown to promote activity in the insulin signaling pathway in cell-based assays. Molecular docking simulations and structure-activity relationship analysis of 1 will add to its potential as a lead compound in future anti-insulin-resistant drug developments.

Natural products possessing protein tyrosine phosphatase 1B (PTP1B) inhibitory activity found in the last decades

This article provides an overview of approximately 300 secondary metabolites with inhibitory activity against protein tyrosine phosphatase 1B (PTP1B), which were isolated from various natural sources or derived from synthetic process in the last decades. The structure-activity relationship and the selectivity of some compounds against other protein phosphatases were also discussed. Potential pharmaceutical applications of several PTP1B inhibitors were presented.

Bromophenols as inhibitors of protein tyrosine phosphatase 1B with antidiabetic properties

A series of bromophenol derivatives were synthesized and evaluated as protein tyrosine phosphatase 1B (PTP1B) inhibitors in vitro and in vivo based on bromophenol 4e (IC(50)=2.42 μmol/L), which was isolated from red algae Rhodomela confervoides. The results showed that all of the synthesized compounds displayed weak to good PTP1B inhibition at tested concentration. Among them, highly brominated compound 4g exhibited promising inhibitory activity against PTP1B with IC(50) 0.68 μmol/L, which was approximately fourfold more potent than lead compound 4e. Further, compound 4g demonstrated high selectivity against other PTPs (TCPTP, LAR, SHP-1 and SHP-2). More importantly, in vivo antidiabetic activities investigations of compound 4g also demonstrated inspiring results.

Vomifoliol 9-O-α-arabinofuranosyl (1→6)-β-D-glucopyranoside from the leaves of Diospyros Kaki stimulates the glucose uptake in HepG2 and 3T3-L1 cells

A novel α-glucosidase inhibitor, vomifoliol 9-O-α-arabinofuranosyl (1→6)-β-D-glucopyranoside, was isolated for the first time from leaves of Diospyros Kaki and its bioactivity analyzed. This inhibitor exhibited strong anti-α-glucosidase activity with an IC50 value of 170.62nM and stimulated a dose-dependent increase in the uptake of a fluorescent d-glucose analog, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose (2-NBDG), in HepG2 cells at a rate higher than that of insulin controls. It was also found to be associated with adipocyte differentiation and moderate increases in 2-NBDG uptake by 3T3-L1 cells. These findings suggest that vomifoliol 9-O-α-arabinofuranosyl (1→6)-β-D-glucopyranoside could augment peripheral glucose as an insulin-sensitizing agent against Type 2 diabetes mellitus.

Protein tyrosine phosphatase 1B inhibitory activity of 24-norursane triterpenes isolated from Weigela subsessilis

During the screening effort to discover new types of protein tyrosine phosphatase 1B (PTP1B) inhibitors, it was found that a MeOH extract of the leaves and stems of Weigela subsessilis (Caprifoliaceae) inhibited the enzyme activity. By means of an in vitro bioassay-guided fractionation on the MeOH extract, two 24-norursane triterpenes, ilekudinol A (1) and ilekudinol B (2), were isolated as active metabolites. Compounds 1 and 2 inhibited PTP1B with IC(50) values of 29.1 ± 2.8 and 5.3 ± 0.5 μM, respectively. Kinetic studies suggest that both 1 and 2 are non-competitive inhibitors of PTP1B. The findings indicate that the free carboxyl group at C-28 in this type of triterpenes plays a critical role in the inhibition of PTP1B.

Inhibition of Protein Tyrosine Phosphatase 1β by Hispidin Derivatives Isolated from the Fruiting Body of Phellinus linteus

Protein tyrosine phosphatase 1β (PTP1β) acts as a negative regulator of insulin signaling. Selective inhibition of PTP1β has served as a potential drug target for the treatment of type 2 diabetes mellitus. We evaluated the inhibitory effect of Phellinus linteus against PTP1β as part of our ongoing search for natural therapeutic and preventive agents for diabetes mellitus. Fractions of the P. linteus extract were found to exhibit significant inhibitory activities against PTP1β. In an attempt to identify bioactive components, we isolated, from the most active ethyl acetate fraction, five hispidin derivatives (phelligridimer A, davallialactone, hypholomine B, interfungins A, and inoscavin A) and four phenolic compounds (protocatechuic acid, protocatechualdehyde, caffeic acid, and ellagic acid). The chemical structures of these compounds were elucidated from spectroscopic evidence and by comparison with published data. All the compounds strongly inhibited PTP1β activity in an in vitro assay; their IC50 values ranged from 9.0 ± 0.01 to 58.2 ± 0.3 μM. Our results indicated that the hispidin skeleton may be an important moiety for inhibitory activity of the above compounds against PTP1β. Thus, hispidin derivatives could be a potent new class of natural PTP1β inhibitors.

Inhibition of protein tyrosine phosphatase 1B by lupeol and lupenone isolated from Sorbus commixta

Protein tyrosine phosphatase 1B (PTP1B) appears to be an attractive target for the development of new drugs for type 2 diabetes and obesity. In our preliminary test, a MeOH extract of the stem barks of Sorbus commixta Hedl. (Rosaceae) showed strong PTP1B inhibitory activity. Bioassay-guided fractionation of the MeOH extract resulted in the isolation of two lupane-type triterpenes, lupenone (1) and lupeol (2). Compounds 1 and 2 inhibited PTP1B with IC(50) values of 13.7 +/- 2.1 and 5.6 +/- 0.9 microM, respectively. Kinetic studies revealed that both the compounds 1 and 2 are non-competitive inhibitors of PTP1B that decrease V(max) values with no effect on K(m) values.

Synthesis and biological evaluation of heterocyclic ring-substituted maslinic acid derivatives as novel inhibitors of protein tyrosine phosphatase 1B

A series of maslinic acid derivatives have been synthesized by introducing various fused heterocyclic rings at C-2 and C-3 positions. Their inhibitory effects on PTP1B, TCPTP and related PTPs are evaluated. Most of the compounds exhibited a dramatic increase in inhibitory potency and selectivity, the two most potent PTP1B inhibitors 20 (IC(50)=0.61 microM) and 29 (IC(50)=0.64 microM) showed about 10-fold more potent than lead compound maslinic acid. More importantly, 29 possesses the best selectivity of 6.9-fold for PTP1B over TCPTP.

Actinomycetes for marine drug discovery isolated from mangrove soils and plants in China

The mangrove ecosystem is a largely unexplored source for actinomycetes with the potential to produce biologically active secondary metabolites. Consequently, we set out to isolate, characterize and screen actinomycetes from soil and plant material collected from eight mangrove sites in China. Over 2,000 actinomycetes were isolated and of these approximately 20%, 5%, and 10% inhibited the growth of Human Colon Tumor 116 cells, Candida albicans and Staphylococcus aureus, respectively, while 3% inhibited protein tyrosine phosphatase 1B (PTP1B), a protein related to diabetes. In addition, nine isolates inhibited aurora kinase A, an anti-cancer related protein, and three inhibited caspase 3, a protein related to neurodegenerative diseases. Representative bioactive isolates were characterized using genotypic and phenotypic procedures and classified to thirteen genera, notably to the genera Micromonospora and Streptomyces. Actinomycetes showing cytotoxic activity were assigned to seven genera whereas only Micromonospora and Streptomyces strains showed anti-PTP1B activity. We conclude that actinomycetes isolated from mangrove habitats are a potentially rich source for the discovery of anti-infection and anti-tumor compounds, and of agents for treating neurodegenerative diseases and diabetes.

Triterpenoids and a sterol from the stem-bark of Styrax japonica and their protein tyrosine phosphatase 1B inhibitory activities

Five pentacyclic triterpenoids (1-5) and a sterol (6) were isolated from the stem-bark of Styrax japonica. The six compounds, 1-6, were determined to be 3beta-acetoxy-28-hydroxyolean-12-ene (1), 3beta-acetoxyolean-12-en-28-acid (2), 3beta-acetoxyolean-12-en-28-aldehyde (3), 3beta-acetoxy-17beta-hydroxy-28-norolean-12-ene (4), taraxerol (5) and stigmasterol (6), respectively, by spectroscopic means, including the 2D-NMR technique. Compound 4 is a newly discovered natural compound. The protein tyrosine phosphatase 1B (PTP1B) inhibitory activities of the isolated compounds (1-6) were determined in vitro. Among the isolated compounds, 3beta-acetoxyolean-12-en-28-acid (2) and 3beta-acetoxyolean-12-en-28-aldehyde (3) had the most potent inhibitory PTP1B activity, with IC50 values of 7.8 and 9.3 microm, respectively.

Lipidyl pseudopteranes A-F: isolation, biomimetic synthesis, and PTP1B inhibitory activity of a new class of pseudopteranoids from the Gorgonian Pseudopterogorgia acerosa

Novel lipidyl pseudopteranoids, lipidyl pseudopteranes A-F (1-6), have been isolated from the soft coral Pseudopterogorgia acerosa collected from the Bahamas. Structure elucidation of the six new compounds was based on 1D and 2D NMR data and mass spectrometry, and a biomimetic synthesis of 1 from pseudopterolide (7) was used to help establish its absolute configuration. These structures represent the first report of a pseudopterane diterpene with a fatty acid moiety. Lipidyl pseudopteranes A and D exhibited modest yet selective inhibitory activity against protein tyrosine phosphatase 1B, a promising drug target.

Triterpenoids from the leaves of Diospyros kaki (persimmon) and their inhibitory effects on protein tyrosine phosphatase 1B

Phytochemical study on a methanol-soluble extract of the leaves of persimmon (Diospyros kaki) resulted in the isolation of two new ursane-type triterpenoids, 3alpha,19alpha-dihydroxyurs-12,20(30)-dien-24,28-dioic acid (1) and 3alpha,19alpha-dihydroxyurs-12-en-24,28-dioic acid (2), together with 12 known ursane- and oleanane-type triterpenoids (3-14). Triterpenoids with a 3beta-hydroxy group were found to inhibit protein tyrosine phosphatase 1B (PTP1B) activity, with IC50 values ranging from 3.1+/-0.2 to 18.8+/-1.3 microM, whereas those with a 3alpha-hydroxy moiety were not active.

Discovery of [(3-bromo-7-cyano-2-naphthyl)(difluoro)methyl]phosphonic acid, a potent and orally active small molecule PTP1B inhibitor

A series of quinoline/naphthalene-difluoromethylphosphonates were prepared and were found to be potent PTP1B inhibitors. Most of these compounds bearing polar functionalities or large lipophilic residues did not show appreciable oral bioavailability in rodents while small and less polar analogs displayed moderate to good oral bioavailability. The title compound was found to have the best overall potency and pharmacokinetic profile and was found to be efficacious in animal models of diabetes and cancer.

Structural genomics of protein phosphatases

The New York SGX Research Center for Structural Genomics (NYSGXRC) of the NIGMS Protein Structure Initiative (PSI) has applied its high-throughput X-ray crystallographic structure determination platform to systematic studies of all human protein phosphatases and protein phosphatases from biomedically-relevant pathogens. To date, the NYSGXRC has determined structures of 21 distinct protein phosphatases: 14 from human, 2 from mouse, 2 from the pathogen Toxoplasma gondii, 1 from Trypanosoma brucei, the parasite responsible for African sleeping sickness, and 2 from the principal mosquito vector of malaria in Africa, Anopheles gambiae. These structures provide insights into both normal and pathophysiologic processes, including transcriptional regulation, regulation of major signaling pathways, neural development, and type 1 diabetes. In conjunction with the contributions of other international structural genomics consortia, these efforts promise to provide an unprecedented database and materials repository for structure-guided experimental and computational discovery of inhibitors for all classes of protein phosphatases.

Inhibition of the protein tyrosine phosphatase PTP1B: potential therapy for obesity, insulin resistance and type-2 diabetes mellitus

The global epidemic of obesity and type-2 diabetes mellitus (T2DM) has highlighted the need for new therapeutic approaches. The association of insulin resistance with these disorders and the knowledge that insulin receptor signaling is mediated by tyrosine (Tyr) phosphorylation have generated great interest in the regulation of the balance between Tyr phosphorylation and dephosphorylation. Several protein Tyr phosphatases (PTPs) have been implicated in the regulation of insulin action, with the most convincing data for PTP1B. Murine models targeting PTP1B, PTP1B(-/-)mice, demonstrate enhanced insulin sensitivity without the weight gain seen with other insulin sensitizers such as peroxisome proliferator-activated receptor gamma (PPARgamma) agonists, probably due to a second action of PTP1B as a negative regulator of leptin signaling. Despite intensive efforts and recent progress, a safe, selective and efficacious PTP1B inhibitor has yet to be identified.

Generation of inhibitor-sensitive protein tyrosine phosphatases via active-site mutations

Protein tyrosine phosphatases (PTPs) catalyze the dephosphorylation of phosphotyrosine, a central control element in mammalian signal transduction. Small-molecule inhibitors that are specific for each cellular PTP would be valuable tools in dissecting phosphorylation networks and for validating PTPs as therapeutic targets. However, the common architecture of PTP active sites impedes the discovery of selective PTP inhibitors. Our laboratory has recently used enzyme/inhibitor-interface engineering to generate selective PTP inhibitors. The crux of the strategy resides in the design of "inhibitor-sensitized" PTPs through protein engineering of a novel binding pocket in the target PTP. "Allele-specific" inhibitors that selectively target the sensitized PTP can be synthesized by modifying broad-specificity inhibitors with bulky chemical groups that are incompatible with wild-type PTP active sites; alternatively, specific inhibitors that serendipitously recognize the sensitized PTP's non-natural pocket may be discovered from panels of "non-rationally" designed compounds. In this review, we describe the current state of the PTP-sensitization strategy, with emphases on the methodology of identifying PTP-sensitizing mutations and synthesizing the compounds that have been found to target PTPs in an allele-specific manner. Moreover, we discuss the scope of PTP sensitization in regard to the potential application of the approach across the family of classical PTPs.

Inhibitory effect of 2-arylbenzofurans from Erythrina addisoniae on protein tyrosine phosphatase-1B

Bioassay-guided fractionation of an EtOAc-soluble extract of the stem bark of Erythrina addisoniae (Leguminosae), using an in vitro PTP1B inhibitory assay, resulted in the isolation of three new (1-3) and three known (4-6) 2-arylbenzofuran derivatives. The new compounds were identified as 2-[2',4'-dihydroxy-3'-(3-methylbut-2-enyl)phenyl]-6-hydroxybenzofuran (1), 2-[2'-methoxy-4'-hydroxy-5'-(3-methylbut-2-enyl)phenyl]-6-hydroxybenzofuran (2), and 2-(2'-methoxy-4'-hydroxyphenyl)-5-(3-methylbut-2-enyl)-6-hydroxybenzofuran (3). The new 2-arylbenzofurans 1-3 inhibited PTP1B activity with IC(50) values ranging from 13.6+/-1.1 to 17.5+/-1.2 microM in vitro assay. On the basis of the data obtained, 2-arylbenzofurans with prenyl group may be considered as a new class of PTP1B inhibitors.

Benzoquinones fromArdisia japonica with Inhibitory Activity towards Human Protein Tyrosine Phosphatase 1B (PTP1B)

From the whole plant of Ardisia japonica, four [1,4]benzoquinones were isolated by means of bioassay-directed fractionation of the EtOH extract. Apart from the two known compounds maesanin (1) and its congener 2, two new benzoquinones, i.e., 5-ethoxy-2-hydroxy-3-[(10Z)-pentadec-10-en-1-yl][1,4]benzoquinone (3) and 5-ethoxy-2-hydroxy-3-[(8Z)-tridec-8-en-1-yl][1,4]benzoquinone (4), were identified. All compounds showed significant in vitro bioactivities against the PTP1B enzyme, with IC50 values in the range of ca. 3-19 microM.

Probing acid replacements of thiophene PTP1B inhibitors

The following account describes our systematic effort to replace one of the carboxylate groups of our diacid thiophene PTP1B inhibitors. Active hits were validated using enzymatic assays before pursuing efforts to improve the potency. Only when the C2 carboxylic acid was replaced with another ionizable functional group was reversible and competitive inhibition retained. Use of a tetrazole ring or 1,2,5-thiadiazolidine-3-one-1,1-dioxide as a carboxylate mimetic led to the discovery of two unique starting series that showed improved permeability (PAMPA) and potency of the order of 300nM. The SAR from these efforts underscores some of the major challenges in developing small molecule inhibitors for PTP1B.

Thermogenic and metabolic antiobesity drugs: rationale and opportunities

Antiobesity drugs that target peripheral metabolism may avoid some of the problems that have been encountered with centrally acting anorectic drugs. Moreover, if they cause weight loss by increasing fat oxidation, they not only address a cause of obesity but also should promote loss of fat rather than lean tissue and improve insulin sensitivity. Weight loss may be slow but more sustained than with anorectic drugs, and thermogenesis may be insufficient to cause any discomfort. Some thermogenic approaches are the activation of adrenergic, thyroid hormone or growth hormone receptors and the inhibition of glucocorticoid receptors; the modulation of transcription factors [e.g. peroxisome proliferator-activated receptor delta (PPARdelta) activators] or enzymes [e.g. glutamine fructose-6-phosphate amidotransferase (GFAT) inhibitors] that promote mitochondrial biogenesis, and the modulation of transcription factors (PPAR alpha activators) or enzymes (AMP-activated protein kinase) that promote fatty acid oxidation. More surprisingly, studies on genetically modified animals and with enzyme inhibitors suggest that inhibitors of fatty acid synthesis [e.g. ATP citrate lyase, fatty acid synthase, acetyl-CoA carboxylase (ACC)], fatty acid interconversion [stearoyl-CoA desaturase (SCD)] and triglyceride synthesis (e.g. acyl-CoA : diacylglycerol acyltransferase) may all be thermogenic. Some targets have been validated only by deleting genes in the whole animal. In these cases, it is possible that deletion of the protein in the brain is responsible for the effect on adiposity, and therefore a centrally penetrant drug would be required. Moreover, whilst a genetically modified mouse may display resistance to obesity in response to a high fat diet, it requires a tool compound to demonstrate that a drug might actually cause weight loss. Even then, it is possible that differences between rodents and humans, such as the greater thermogenic capacity of rodents, may give a misleading impression of the potential of a drug.

Cellular Inhibition of Protein Tyrosine Phosphatase 1B by Uncharged Thioxothiazolidinone Derivatives

As important regulators of cellular signal transduction, members of the protein tyrosine phosphatase (PTP) family are considered to be promising drug targets. However, to date, the most effective in vitro PTP inhibitors have tended to be highly charged, thus limiting cellular permeability. Here, we have identified an uncharged thioxothiazolidinone derivative (compound 1), as a competitive inhibitor of a subset of PTPs. Compound 1 effectively inhibited protein tyrosine phosphatase 1B (PTP1B) in two cell-based systems: it sensitized wild-type, but not PTP1B-null fibroblasts to insulin stimulation and prevented PTP1B-dependent dephosphorylation of the FLT3-ITD receptor tyrosine kinase. We have also tested a series of derivatives in vitro against PTP1B and proposed a model of the PTP1B-inhibitor interaction. These compounds should be useful in the elucidation of cellular PTP function and could represent a starting point for development of therapeutic PTP inhibitors.

PTP1B inhibitory activity of kaurane diterpenes isolated from Siegesbeckia glabrescens

Protein tyrosine phosphatase 1B (PTP1B) is considered as a therapeutic target for the treatment of diabetes and obesity. In our preliminary screening study, a MeOH extract of the aerial part of Siegesbeckia glabrescens was found to inhibit PTP1B activity at 30 microg/mL. Bioassay-guided fractionation led to the isolation of two active diterpenes, ent-16betaH, 17-isobutyryloxy-kauran-19-oic acid (1) and ent-16betaH, 17-acetoxy-18-isobutyryloxy-kauran-19-oic acid (2), along with ent- 16betaH, 17-hydroxykauran-19-oic acid (3). Compounds 1 and 2 inhibited the PTP1B activity with IC50 values of 8.7 +/- 0.9 and 30.6 +/- 2.1 microM, respectively. Kinetic studies suggest that both 1 and 2 are non-competitive inhibitors of PTP1B. However, compound 3 substituted with a hydroxyl group at C-17 in kaurane-type showed no inhibitory effects towards PTP1B.

Protein Tyrosine Phosphatase 1B Inhibitory Activity of Amentoflavone and Its Cellular Effect on Tyrosine Phosphorylation of Insulin Receptors

Inhibition of protein tyrosine phosphatase 1B (PTP1B) has been proposed as a strategy for the treatment of type 2 diabetes and obesity. Bioassay-guided fractionation of MeOH extract of Selaginella tamariscina (Selaginellaceae) afforded a PTP1B inhibitory compound, amentoflavone. The compound inhibited PTP1B with an IC50 value of 7.3+/-0.5 microM. Kinetic study suggested that amentoflavone is a non-competitive inhibitor of PTP1B, with a Ki value of 5.2 microM. Treatment of 32D cells overexpressing the insulin receptor (IR) with amentoflavone resulted in a dose-dependent increase in tyrosine phosphorylation of IR. These results indicate that amentoflavone may enhance insulin-induced intracellular signaling possibly through inhibition of PTP1B activity.