New azolidinediones as inhibitors of protein tyrosine phosphatase 1B with antihyperglycemic properties

Discovery and structure–activity relationships of novel sulfonamides as potent PTP1B inhibitors

A series of novel sulfonamides containing a single difluoromethylene-phosphonate group were discovered to be potent inhibitors of protein tyrosine phosphatase 1B. Structure-activity relationships around the scaffold were investigated, leading to the identification of compounds with IC50 or Ki values in the low nanomolar range. These sulfonamide-based inhibitors exhibit 100 and 30 times higher inhibitory activity than the corresponding tertiary amines and carboxamides, respectively.

Development and application of rodent models for type 2 diabetes

The increasing worldwide incidence of diabetes in adults constitutes a global public health burden. It is predicted that by 2025, India, China and the United States will have the largest number of people with diabetes. According to the 2003 estimates of the International Diabetes Federation, the diabetes mellitus prevalence in the USA is 8.0% and approximately 90-95% of diabetic Americans have type 2 diabetes - about 16 million people. Type 2 diabetes is a complex, heterogeneous, polygenic disease characterized mainly by insulin resistance and pancreatic beta-cell dysfunction. Appropriate experimental models are essential tools for understanding the molecular basis, pathogenesis of the vascular and neural lesions, actions of therapeutic agents and genetic or environmental influences that increase the risks of type 2 diabetes. Among the animal models available, those developed in rodents have been studied most thoroughly for reasons such as short generation time, inherited hyperglycaemia and/or obesity in certain strains and economic considerations. In this article, we review the current status of most commonly used rodent diabetic models developed spontaneously, through means of genetic engineering or artificial manipulation. In addition to these models, the Psammomys obesus, rhesus monkeys and many other species are studied intensively and reviewed by Shafrir, Bailey and Flatt and Hansen.

Formylchromone derivatives as irreversible and selective inhibitors of human protein tyrosine phosphatase 1B. Kinetic and modeling studies

A series of formylchromone derivatives were synthesized as PTP1B inhibitors and some of them were potent against PTP1B with IC50 values as low as 1.0 microM. They exhibited remarkable selectivity for PTP1B over other human PTPases. Kinetic studies revealed that formylchromone derivatives are irreversible and active site-directed inhibitors. Molecular modeling study identified the orientation of the inhibitor bound at the active site of PTP1B.

Structure-based prediction of free energy changes of binding of PTP1B inhibitors

The goals were (1) to understand the driving forces in the binding of small molecule inhibitors to the active site of PTP1B and (2) to develop a molecular mechanics-based empirical free energy function for compound potency prediction. A set of compounds with known activities was docked onto the active site. The related energy components and molecular surface areas were calculated. The bridging water molecules were identified and their contributions were considered. Linear relationships were explored between the above terms and the binding free energies of compounds derived based on experimental inhibition constants. We found that minimally three terms are required to give rise to a good correlation (0.86) with predictive power in five-group cross-validation test (q2 = 0.70). The dominant terms are the electrostatic energy and non-electrostatic energy stemming from the intra- and intermolecular interactions of solutes and from those of bridging water molecules in complexes.

Design and synthesis of oxadiazolidinediones as inhibitors of plasminogen activator inhibitor-1

A novel series of PAI-1 inhibitors containing an oxadiazolidinedione moiety were identified by high through-put screening. Optimization of substituents by parallel synthesis and the iterative design toward understanding structure-activity relationship to improve potency are described.

Formylchromone derivatives as a novel class of protein tyrosine phosphatase 1B inhibitors

Formylchromone inhibits a human protein tyrosine phosphatase PTP1B with a IC(50) value of 73 microM. The chemical reactivity of formylchromone was adjusted by substitution at various positions of the formylchromone skeleton. In an initial assessment of the structure-activity relationship, the most potent inhibitor showed an IC(50) of 4.3 microM against PTP1B and strong or medium selectivity against other human PTPases, LAR and TC-PTP. This compound, however, was not selective against microbial PTPases, YPTP1 and YOP. The potency and selectivity of the formylchromone derivatives expecting further improvements provides a novel pharmacophore for the design of drugs for the treatment of type 2 diabetes and obesity.

Structure-based design and discovery of novel inhibitors of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs) are important in the regulation of signal transduction processes. Certain enzymes of this class are considered as potential therapeutic targets in the treatment of a variety of diseases such as diabetes, inflammation, and cancer. However, many PTP inhibitors identified to date are peptide-based and contain a highly charged phosphate-mimicking component. These compounds usually lack membrane permeability and this limits their utility in the inhibition of intracellular phosphatases. In the present study, we have used structure-based design and modeling techniques to explore catalytic-site directed, reversible inhibitors of PTPs. Employing a non-charged phosphate mimic and non-peptidyl structural components, we have successfully designed and synthesized a novel series of trifluoromethyl sulfonyl and trifluoromethyl sulfonamido compounds as PTP inhibitors. This is the first time that an uncharged phosphate mimic is reported in the literature for general, reversible, and substrate-competitive inhibition of PTPs. It is an important discovery because the finding may provide a paradigm for the development of phosphatase inhibitors that enter cells and modify signal transduction.

Treatment of non-insulin-dependent diabetes mellitus

Diabetes mellitus has been declared to be at an epidemic level by the World Health Organization. The syndrome is characterised as either Type I (insulin-dependent) or Type II (non-insulin-dependent) diabetes mellitus. Impaired glucose tolerance for extended periods of time results in serious complications such as kidney damage and impaired blood circulation and is the main cause for blindness and amputations in patients with diabetes. A combination of life-style change, dietary change and oral medications can treat Type II diabetes mellitus effectively and prevent long-term complications. Combination therapy appears to be the most effective approach in controlling blood glucose levels. This review updates the progress made in medicinal chemistry towards promising biological targets, with the development of a new generation of small molecules having improved efficacy and safety profiles.

Insulin sensitisation in the treatment of Type 2 diabetes

Type 2 diabetes is reaching epidemic proportions worldwide, fueled by the increasing prevalence of obesity as many populations adopt a western lifestyle. Secondary complications affecting both the microvascular and macrovascular systems are responsible for premature mortality in Type 2 diabetes, with two thirds or more dying of cardiovascular disease. Two interacting metabolic defects, insulin resistance and beta-cell dysfunction are present in Type 2 diabetes. It is now recognised that insulin resistance is central to a cluster of metabolic abnormalities--called the insulin resistance syndrome--that are responsible for the excess of cardiovascular disease. Older antidiabetic agents such as the sulfonylureas, metformin and insulin are more effective than lifestyle modification in reducing microvascular complications of Type 2 diabetes, but overall do not reduce cardiovascular risk. Metformin, although no more effective as a glucose-lowering agent than sulfonylureas or insulin, does significantly reduce cardiovascular disease, probably as a result of its weak insulin-sensitising action. The newly-marketed thiazolidinedione insulin-sensitising antidiabetic agents also improve multiple biomarkers of cardiovascular risk, suggesting that novel approaches to insulin sensitisation will not only provide effective long-term glycaemic control but improve cardiovascular outcomes in Type 2 diabetes. Multiple therapeutic targets within the insulin signalling cascade are being explored, together with follow-up compounds to the first generation thiazolidinediones. These initiatives, together with developments in beta(3)-adrenoceptor agonists, 11 beta-hydroxysteroid dehydrogenase Type 1 inhibitors and modulators of the glucagon-like peptide 1 axis, all of which also potentially enhance insulin sensitivity, are critically evaluated.

Palladium-catalyzed cleavage of O/N-propargyl protecting groups in aqueous media under a copper-free condition

[reaction: see text] A copper-free palladium-mediated cleavage of O/N-propargyl bonds in aqueous media has been investigated, affording a mild and convenient method for the deprotection of phenols and anilines. The methodology could be utilized for the selective removal of propargyl groups from aryl ethers and amines without affecting a variety of unprotected functional groups present in the substrates. The mechanism and scope of the reaction is discussed.

Insulin Resistant States and Insulin Signaling

The incidence of type 2 diabetes mellitus (T2D) and obesity is increasing rapidly worldwide, reaching epidemic proportions. Insulin resistance is a key feature in both conditions and plays an important pathophysiological role. Over the last two decades a central role in the origin of insulin resistance has emerged for defects in the intracellular insulin signaling cascade leading to glucose uptake. Herein, we will 1) review insulin signaling pathways leading to glucose uptake, 2) review mouse models of insulin resistance that demonstrate the pathophysiologic importance of specific defects of these pathways and 3) discuss the molecular basis for insulin resistance in some human disease states known to be associated with insulin resistance. Finally, we will briefly mention some novel treatment targets for T2D stemming from this knowledge.

Synthesis and PTP1B inhibition of 1,2-naphthoquinone derivatives as potent anti-diabetic agents

A new series of 1,2-naphthoquinone derivatives was synthesized by various synthetic methods and evaluated for their ability to inhibit protein tyrosine phosphatase 1B (PTP1B). 1,2-Naphthoquinone derivatives with substituent at R(4) position showed submicromolar inhibitory activity, and compound 24 demonstrated 10- to 60-fold selectivity against the tested phosphatases. Also, several 4-aryl-1,2-naphthoquinone derivatives with substituents at R(3), R(6), R(7), or/and R(8) showed submicromolar inhibitory activity and good plasma stability.

Protein tyrosine phosphatase 1B: a new target for the treatment of obesity and associated co-morbidities

Impaired insulin action is important in the pathophysiology of multiple metabolic abnormalities such as obesity and type 2 diabetes. Protein tyrosine phosphatase 1B (PTP1B) is considered a negative regulator of insulin signalling. This is best evidenced by studies on knockout mice showing that lack of PTP1B is associated with increased insulin sensitivity as well as resistance to obesity and in vitro studies whilst studies in animals and humans have given contradictory results. However, several studies support the notion that insulin signalling can be enhanced by the inhibition of PTP1B providing an attractive target for therapy against type 2 diabetes and obesity. In addition, recent genetic studies support the association between PTP1B with insulin resistance. The development of PTP1B inhibitors has already begun although it has become clear that is not easy to find both a selective, safe and effective PTP1B inhibitor. The objective of this paper is to review the current evidence of PTP1B in the pathophysiology of obesity, type 2 diabetes and cancer as well as in the treatment of these disorders.

Orally active insulin mimics: where do we stand now?

The war against diabetes through the development of new drugs is an ongoing continuous process to counter the alarming global increase in the prevalence of diabetes and its complications, particularly in developing countries like India. Unfortunately, the speed with which our knowledge of diabetes and its effects is expanding is not matched by the availability of new drugs. Following the identification of the insulin receptor (IR), its intrinsic kinase activity and molecular cloning, many studies have looked at IR as an ideal drug target. This review summarizes in brief the latest advancements in this field with particular reference to the current situation in respect of the development of orally active insulin mimetics in the treatment of type 2 diabetes.

alpha-Ketocarboxylic acid-based inhibitors of protein tyrosine phosphatases

A series of aryl alpha-ketocarboxylic acids was synthesized and investigated as inhibitors for the protein tyrosine phosphatase from Yersinia enterocolitica. IC(50) values for these compounds range from 79 to 2700 microM. Larger aromatic groups, and aromatic groups with high electron density, lead to more potent inhibitors. In general, the related aryl alpha-hydroxycarboxylic acids show lower activity.

Insulin-stimulated hydrogen peroxide reversibly inhibits protein-tyrosine phosphatase 1b in vivo and enhances the early insulin action cascade

The insulin signaling pathway is activated by tyrosine phosphorylation of the insulin receptor and key post-receptor substrate proteins and balanced by the action of specific protein-tyrosine phosphatases (PTPases). PTPase activity, in turn, is highly regulated in vivo by oxidation/reduction reactions involving the cysteine thiol moiety required for catalysis. Here we show that insulin stimulation generates a burst of intracellular H(2)O(2) in insulin-sensitive hepatoma and adipose cells that is associated with reversible oxidative inhibition of up to 62% of overall cellular PTPase activity, as measured by a novel method using strictly anaerobic conditions. The specific activity of immunoprecipitated PTP1B, a PTPase homolog implicated in the regulation of insulin signaling, was also strongly inhibited by up to 88% following insulin stimulation. Catalase pretreatment abolished the insulin-stimulated production of H(2)O(2) as well as the inhibition of cellular PTPases, including PTP1B, and was associated with reduced insulin-stimulated tyrosine phosphorylation of its receptor and high M(r) insulin receptor substrate (IRS) proteins. These data provide compelling new evidence for a redox signal that enhances the early insulin-stimulated cascade of tyrosine phosphorylation by oxidative inactivation of PTP1B and possibly other tyrosine phosphatases.

New oxadiazolidinedione derivatives as potent and selective human beta3 agonists

As part of our investigation into the development of potent and selective human beta3 agonists, a series of thiazolidinedione analogues was prepared and evaluated for their biological activity on the human beta3-adrenergic receptor. The oxadiazolidinedione derivative 17 was found to be the most potent and selective compound in this study, with an EC50 value of 0.02 microM at the beta3 receptor, 259-fold selectivity over the beta1 receptor, and 745-fold selectivity over the beta2 receptor.

Sulfonylated aminothiazoles as new small molecule inhibitors of protein phosphatases

Based on a previously identified lead structure, SC-alphaalphadelta9, we have developed a versatile new chemical scaffold that can be readily modified to generate libraries of both Tyr and dual specificity phosphatase inhibitors with reduced molecular weight and lipophilicity. The most potent analogue identified to date, aminothiazole 8z, inhibits the dual specificity phosphatase Cdc25B with a Ki of 4.6+/-0.4 microM and a Hill coefficient of 2.