(3-substituted benzyl)thiazolidine-2,4-diones as structurally new antihyperglycemic agents

Peroxisome Proliferator-Activated Receptors as Superior Targets for Treating Diabetic Disease, Design Strategies - Review Article

Thiazolidinedione (TZD), a class of drugs that are mainly used to control type 2 diabetes mellitus (T2DM), acts fundamentally as a ligand of peroxisome proliferator-activated receptors (PPARs). Besides activating pathways responsible for glycemic control by enhancing insulin sensitivity and lipid homeostasis, activating PPARs leads to exciting other pathways related to bone formation, inflammation, and cell proliferation. Unfortunately, this diverse effect of activating several pathways may show in some studies adverse health outcomes as osteological, hepatic, cardiovascular, and carcinogenic effects. Thus, a silver demand is present to find and develop new active and potent antiglycemic drugs for treating T2DM. To achieve this goal, the structure of TZD for research is considered a leading structure domain. This review will guide future research in the design of novel TZD derivatives by highlighting the general modifications conducted on the structure component of TZD scaffold affecting their potency, binding efficacy, and selectivity for the control of T2DM.

Structural Biology-Based Exploration of Subtype-Selective Agonists for Peroxisome Proliferator-Activated Receptors

Progress in understanding peroxisome proliferator-activated receptor (PPAR) subtypes as nuclear receptors that have pleiotropic effects on biological responses has enabled the exploration of new subtype-selective PPAR ligands. Such ligands are useful chemical biology/pharmacological tools to investigate the functions of PPARs and are also candidate drugs for the treatment of PPAR-mediated diseases, such as metabolic syndrome, inflammation and cancer. This review summarizes our medicinal chemistry research of more than 20 years on the design, synthesis, and pharmacological evaluation of subtype-selective PPAR agonists, which has been based on two working hypotheses, the ligand superfamily concept and the helix 12 (H12) holding induction concept. X-ray crystallographic analyses of our agonists complexed with each PPAR subtype validate our working hypotheses.

Rosiglitazone promotes glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway

The study aimed to explore the effects of rosiglitazone on glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway. The experiment was divided into five groups: normal starch group (32%, LC), high starch group (53%, HC), high starch +rosiglitazone group 1 (10 mg/kg, R1), high starch + rosiglitazone group 2 (20 mg/kg, R2), and high starch + rosiglitazone group 3 (30 mg/kg, R3). The results showed that a high starch diet supplemented with 10-20 mg/kg rosiglitazone had a better specific growth rate and protein efficiency that was beneficial for the growth of the tilapia. Rosiglitazone had no significant effect on the contents of crude lipid, crude protein, crude ash, and moisture of the whole fish body (p > 0.05). The contents of triglycerides and total cholesterol in the R1, R2, and R3 groups were lower than those in the HC group. The levels of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in R1 and R2 groups were significantly lower than those in the HC groups (p < 0.05). However, the GOT and GPT levels in the R3 groups were significantly higher than those in the R1 and R2 groups (p < 0.05). With an increase in the rosiglitazone concentration, the contents of serum glucose, insulin, and hepatic glycogen in the R1, R2, and R3 groups decreased gradually. Meanwhile, the muscle glycogen content in the R1, R2, and R3 groups increased gradually. The mRNA expression of the IRS-1, PI3K, GLUT-4, and Akt proteins in the R1, R2, and R3 groups was significantly higher than that in the HC group (p < 0.05). Compared with the HC group, the expression of the GSK-3 mRNA in the R1, R2, and R3 groups was significantly reduced (p < 0.05). The protein expression of p-Akt in the R1 and R2 groups was higher than that in the HC group (p > 0.05). The protein expression of p-GSK-3β in the R1 and R2 groups was significantly higher than that in the HC group (p < 0.05). In conclusion, a high starch diet supplemented with rosiglitazone can improve growth, enhance the serum biochemical indices, and increase the muscle glycogen content in the GIFT tilapia. It benefits in upregulating the IRS-1, PI3K, and GLUT-4 mRNA levels in the skeletal muscle and promotes glucose uptake. Meanwhile, the phosphorylation of Akt and GSK-3β increased significantly and resulted in the inactivation of GSK-3β and alleviation of insulin resistance.

The Journey of Thiazolidinediones as Modulators of PPARs for the Management of Diabetes: A Current Perspective

Peroxisome Proliferator-Activated Receptors (PPARs) also known as glitazone receptors are a family of receptors that regulate the expression of genes and have an essential role in carbohydrate, lipid and protein metabolism apart from other functions. PPARs come in 3 sub-types: PPAR-α, PPAR-β/δ and PPAR-γ - with PPAR-γ having 2 isoforms - γ1 and γ2. Upon activation, the PPARs regulate the transcription of various genes involved in lipid and glucose metabolism, adipocyte differentiation, increasing insulin sensitivity, prevention of oxidative stress and to a certain extent, modulation of immune responses via macrophages that have been implicated in the pathogenesis of insulin resistance. Hence, PPARs are an attractive molecular target for designing new anti-diabetic drugs. This has led to a boost in the research efforts directed towards designing of PPAR ligands - particularly ones that can selectively and specifically activate one or more of the PPAR subtypes. Though, PPAR- γ full agonists such as Thiazolidinediones (TZDs) are well established agents for dyslipidemia and type 2 diabetes mellitus (T2D), the side effect profile associated with TZDs has potentiated an imminent need to come up with newer agents that act through this pathway. Several newer derivatives having TZD scaffold have been designed using structure based drug designing technique and computational tools and tested for their PPAR binding affinity and efficacy in combating T2D and some have shown promising activities. This review would focus on the role of PPARs in the management of T2D; recently reported TZD derivatives which acted as agonists of PPAR- γ and its subtypes and are potentially useful in the new drug discovery for the disease.

Discovery of a Novel Selective Dual Peroxisome Proliferator-Activated Receptor α/δ Agonist for the Treatment of Primary Biliary Cirrhosis

A novel peroxisome proliferator-activated receptor (PPAR) α/δ dual agonist 5c was developed with an EC₅₀ of 8 nM for PPARα, 5 nM for PPARδ, and >300-fold selectivity against PPARγ (EC₅₀ = 2939 nM), respectively. Further ADME and pharmacokinetic studies indicated 5c possessed distinguished in vitro and in vivo profiles. The excellent in vivo efficacy of compound 5c was demonstrated by the rat primary biliary cirrhosis (PBC) model.

2,4-Thiazolidinediones as PTP 1B Inhibitors: A Mini Review (2012-2018)

2,4-thiazolidinedione (TZD) scaffold is a synthetic versatile scaffold explored by medicinal chemists for the discovery of novel molecules for the target-specific approach to treat or manage number of deadly ailments. PTP 1B is the negative regulator of insulin signaling cascade, and its diminished activity results in abolishment of insulin resistance associated with T2DM. The present review focused on the seven years journey (2012-2018) of TZDs as PTP 1B inhibitors with the insight into the amendments in the structural framework of TZD scaffold in order to optimize/design potential PTP 1B inhibitors. We have investigated the synthesized molecules based on TZD scaffold with potential activity profile against PTP 1B. Based on the SAR studies, the combined essential pharmacophoric features of selective and potent TZDs have been mapped and presented herewith for further design and synthesis of novel inhibitors of PTP 1B. Compound 46 bearing TZD scaffold with N-methyl benzoic acid and 5-(3-methoxy-4-phenethoxy) benzylidene exhibited the most potent activity (IC50 1.1 µM). Imidazolidine-2,4-dione, isosteric analogue of TZD, substituted with 1-(2,4-dichlorobenzyl)-5-(3-(2,4- dichlorobenzyloxy)benzylidene) (Compound 15) also endowed with very good PTP inhibitory activity profile (IC50 0.57 µM). It is noteworthy that Z-configuration is essential in structural framework around the double bond of arylidene for the designing of bi-dentate ligands with optimum activity.

Rational Design and Structure Validation of a Novel Peptide Inhibitor of the Adenomatous-Polyposis-Coli (APC)-Rho-Guanine-Nucleotide-Exchange-Factor-4 (Asef) Interaction

In colorectal cancer, adenomatous polyposis coli (APC) interacts with Rho guanine-nucleotide-exchange factor 4 (Asef), thereby stimulating aberrant colorectal-cancer-cell migration. Consequently, the APC-Asef interaction represents a promising therapeutic target for mitigating colorectal-cancer migration. In this study, we adopted the rational-design strategy involving the introduction of intramolecular hydrogen bonds and optimization of the lipophilic substituents to improve the binding affinities of peptides, leading to the discovery of MAI-400, the best inhibitor of the APC-Asef interaction known to date ( K_d = 0.012 μM, IC₅₀ = 0.25 μM). Comprehensive evaluation of MAI-400 by biochemical and biophysical assays revealed the formation and effect of an intramolecular hydrogen bond. A cell-based assay showed MAI-400 efficiently blocking the APC-Asef interaction in a dose-dependent manner. Therefore, our study provides a best-in-class inhibitor, MAI-400, based on the rational drug design and structural validation, that can effectively inhibit the APC-Asef interaction.

The Opportunities and Challenges of Peroxisome Proliferator-Activated Receptors Ligands in Clinical Drug Discovery and Development

Peroxisome proliferator-activated receptors (PPARs) are a well-known pharmacological target for the treatment of multiple diseases, including diabetes mellitus, dyslipidemia, cardiovascular diseases and even primary biliary cholangitis, gout, cancer, Alzheimer's disease and ulcerative colitis. The three PPAR isoforms (α, β/δ and γ) have emerged as integrators of glucose and lipid metabolic signaling networks. Typically, PPARα is activated by fibrates, which are commonly used therapeutic agents in the treatment of dyslipidemia. The pharmacological activators of PPARγ include thiazolidinediones (TZDs), which are insulin sensitizers used in the treatment of type 2 diabetes mellitus (T2DM), despite some drawbacks. In this review, we summarize 84 types of PPAR synthetic ligands introduced to date for the treatment of metabolic and other diseases and provide a comprehensive analysis of the current applications and problems of these ligands in clinical drug discovery and development.

Targeting Peroxisome Proliferator-Activated Receptors Using Thiazolidinediones: Strategy for Design of Novel Antidiabetic Drugs

Thiazolidinediones are a class of well-established antidiabetic drugs, also named as glitazones. Thiazolidinedione structure has been an important structural domain of research, involving design and development of new drugs for the treatment of type 2 diabetes. Extensive research on the mechanism of action and the structural requirements has revealed that the intended antidiabetic activity in type 2 diabetes is due to their agonistic effect on peroxisome proliferator-activated receptor (PPAR) belonging to the nuclear receptor super family. Glitazones have specific affinity to PPARγ, one of the subtypes of PPARs. Certain compounds under development have dual PPARα/γ agonistic activity which might be beneficial in obesity and diabetic cardiomyopathy. Interesting array of hybrid compounds of thiazolidinedione PPARγ agonists exhibited therapeutic potential beyond antidiabetic activity. Pharmacology and chemistry of thiazolidinediones as PPARγ agonists and the potential of newer analogues as dual agonists of PPARs and other emerging targets for the therapy of type 2 diabetes are presented. This review highlights the possible modifications of the structural components in the general frame work of thiazolidinediones with respect to their binding efficacy, potency, and selectivity which would guide the future research in design of novel thiazolidinedione derivatives for the management of type 2 diabetes.

Thiazolidinediones and PPAR orchestra as antidiabetic agents: From past to present

Thiazolidinediones a class of drug, that provided a major breakthrough in the management of type 2 diabetes since 1990. Following the discovery of PPARs, TZDs were the first class to be reported as PPARγ modulators. This review is an attempt to summarize the chemical modifications around TZDs in past two decades to obtain a potent antidiabetic molecule. TZDs literature were initially dominated by their hypoglycemic & hypolipidemic activities, later PPARγ activity was also been incorporated. Moreover, in some cases, both benzyl and benzylidene derivatives were reported in the same manuscript for the sake of comparison. We thought of presenting the review on the basis of the variation in the linker region. Optimal linker at the time of discovery of the Ciglitazone was oxymethyl and it went on to evolve as oxyethyl (Pioglitazone) and oxyethylamino (Rosiglitazone). Few attempts were made to restrict the flexibility of the linker by introducing the cyclic structures and were summarized immediately after the respective linker class.

Important Hydrogen Bond Networks in Indoleamine 2,3-Dioxygenase 1 (IDO1) Inhibitor Design Revealed by Crystal Structures of Imidazoleisoindole Derivatives with IDO1

Indoleamine 2,3-dioxygenase 1 (IDO1), promoting immune escape of tumors, is a therapeutic target for the cancer immunotherapy. A number of IDO1 inhibitors have been identified, but only limited structural biology studies of IDO1 inhibitors are available to provide insights on the binding mechanism of IDO1. In this study, we present the structure of IDO1 in complex with 24, a NLG919 analogue with potent activity. The complex structure revealed the imidazole nitrogen atom of 24 to coordinate with the heme iron, and the imidazoleisoindole core situated in pocket A with the 1-cyclohexylethanol moiety extended to pocket B to interact with the surrounding residues. Most interestingly, 24 formed an extensive hydrogen bond network with IDO1, which is a distinct feature of IDO1/24 complex structure and is not observed in the other IDO1 complex structures. Further structure-activity relationship, UV spectra, and structural biology studies of several analogues of 24 demonstrated that extensive hydrophobic interactions and the unique hydrogen bonding network contribute to the great potency of imidazoleisoindole derivatives. These results are expected to facilitate the structure-based drug design of new IDO inhibitors.

Synthesis of new thiazolylmethoxyphenyl pyrimidines and antihyperglycemic evaluation of the pyrimidines, analogues isoxazolines and pyrazolines

New thiazolylmethoxyphenyl pyrimidines (7a-g) have been conveniently synthesized with better yields by cyclocondensing 3-(4-((2-phenylthiazol-4-yl)methoxy)phenyl)-1-(4-substituted phenyl)prop-2-en-1-ones (4a-g) with thiourea in aqueous emulsion of tetradecyltrimethylammonium bromide (TTAB) at 80 °C. Antihyperglycemic activity of the new thiazolylmethoxyphenyl pyrimidines (7a-d), thiazolylmethoxyphenyl pyrazolines (5a-d) and thiazolylmethoxyphenyl isoxazolines (6a-d) has been evaluated in sucrose loaded rat model. Among these compounds; 5a, 5c, 6b, 7c and 7d have displayed noticeable antihyperglycemic activity. Pyrimidines and pyrazolines have displayed better antihyperglycemic activity than the analogues isoxazolines.

A green, multicomponent, regio- and stereo-selective 1,3-dipolar cycloaddition of azides and azomethine ylides generated in situ with bifunctional dipolarophiles using PEG-400

A series of novel dispiropyrrolidine-linked 1,2,3-triazole derivatives have been prepared by one-pot, four-component protocol that employed 5-arylidene-3-(prop-2-ynyl)thiazolidine-2,4-dione, isatin, sarcosine and substituted azides using Cu(I) generated in situ as catalyst in PEG-400 as a highly efficient and green media. This is the first report of a four-component reaction involving a classical Huisgen reaction, in which the two dipolar moieties (substituted azides and in situ generated azomethine ylides) react with acetylenic and olefinic dipolarophiles, respectively. The 1,3-dipolar cycloaddition proceeds in a highly regio- and stereo-selective manner. This methodology can be an ideal tool for the preparation of biologically important five-membered heterocyclic compounds in one pot.

Charge density distribution of 3-(1-aminoethylidene)-2-methoxy-2-oxo-2,3-dihydro-2λ(5)-benzo[e][1,2]oxaphosphinin-4-one

A combined experimental and theoretical study of one oxaphosphinane derivative was made on the basis of a topological analysis of its electron density distributions. The electron density was determined from a high-resolution X-ray diffraction data set measured with synchrotron radiation at 100 K, whereas theoretical calculations were performed using density functional theory (DFT) methods at the B3LYP\6-311++G(3df,3pd) level of approximation. The charge-density distribution and analysis of topological properties revealed that the P-O bond is of the transit closed-shell type. The crystal structure possesses one intra- and several intermolecular hydrogen bonds. They were characterized quantitatively by topological properties using Bader's Atoms in Molecules theory. All hydrogen bonds were classified as weak. Further analysis of the experimental electron density by the source function allowed the intramolecular hydrogen bond to be characterized as an isolated hydrogen bond, in contrast to the resonance-assisted hydrogen bond in related molecules, such as chromone derivatives.

Recent pharmacological developments on rhodanines and 2,4-thiazolidinediones

Thiazolidines are five-member heterocyclic having sulfur, nitrogen, and oxygen atoms in their ring structure and exhibiting potent as well as wide range of pharmacological activities. In this minireview, recent updates on synthesis and pharmacological evaluations of molecules based on 2,4-thiazolidine and rhodanine are discussed.

Thiazolidin-4-one and thiazinan-4-one derivatives analogous to rosiglitazone as potential antihyperglycemic and antidyslipidemic agents

A number of thiazolidin-4-one and thiazinan-4-one derivatives were prepared by three component condensation in one pot reaction method. These compounds were evaluated for anti-hyperglycemic activity by in vitro and in vivo assay systems. The compounds with thiazolidin-4-one and thiazinan-4-one moieties exhibited significant anti-hyperglycemic activity. A few compounds (3a, 3b, 4a and 4b) have exhibited both anti-hyperglycemic and anti-dyslipidemic activities. Among them the thiazinan-4-one derivative 4a showed maximal (45%) improvement in oral glucose tolerance test in db/db mice at 30 mg/kg oral dose.

Structural Development Studies of Subtype-Selective Ligands for Peroxisome Proliferator-Activated Receptors (PPARs) Based on the 3,4-Disubstituted Phenylpropanoic Acid Scaffold as a Versatile Template

Improvements in our understanding of the functions of the nuclear receptor peroxisome proliferator-activated receptor (PPAR) subtypes as pleiotropic regulators of biological responses, including lipid, lipoprotein, glucose homeostasis, inflammation, differentiation and proliferation of various cancer cells, and memory, have provided an opportunity to develop novel PPAR ligands with characteristic subtype selectivity. Such ligands are not only chemical tools to investigate the functions of PPARs, but also candidates for the treatment of PPAR-mediated diseases, including metabolic syndrome, inflammation, dementia, and cancer. This minireview summarizes our work on the design, synthesis, and pharmacological evaluation of subtype-selective PPAR agonists based on the use of 3,4-disubstituted phenylpropanoic acid as a versatile template.

Novel bisaryl substituted thiazoles and oxazoles as highly potent and selective peroxisome proliferator-activated receptor delta agonists

The discovery, synthesis, and optimization of compound 1 from a high-throughput screening hit to highly potent and selective peroxisome proliferator-activated receptor delta (PPARdelta) agonists are reported. The synthesis and structure-activity relationship in this series are described in detail. On the basis of a general schematic PPAR pharmacophore model, scaffold 1 was divided into headgroup, linker, and tailgroup and successively optimized for PPAR activation using in vitro PPAR transactivation assays. A (2-methylphenoxy)acetic acid headgroup, a flexible linker, and a five-membered heteroaromatic center ring with two hydrophobic aryl substituents were required for efficient and selective PPARdelta activation. The fine-tuning of these aryl substituents led to an array of highly potent and selective compounds such as compound 38c, displaying an excellent pharmacokinetic profile in mouse. In an in vivo acute dosing model, selected members of this array were shown to induce the expression of pyruvate dehydrogenase kinase-4 (PDK4) and uncoupling protein-3 (UCP3), genes that are known to be involved in energy homeostasis and regulated by PPARdelta in skeletal muscle.

Pyranocoumarins: a new class of anti-hyperglycemic and anti-dyslipidemic agents

A series of pyranocoumarin derivatives were synthesized and evaluated in vivo for their anti-hyperglycemic as well as anti-dyslipidemic activities. Compounds 7a, 7c, 8a, 8b, 8c, 8e and 8f have shown promising anti-hyperglycemic activities in sucrose loaded model (SLM) as well as sucrose challenged streptozotocin induced diabetic rat model (STZ). Compounds 8a and 8b were showing 38.0% and 42.0% blood glucose lowering activity in db/db mice model. In vitro anti-hyperglycemic activity evaluation exhibited that compounds 8a (IC(50)=24.5 microM) and 8b (IC(50)=36.2 microM) are potential PTP-1B inhibitors thereby revealing their possible mechanism of anti-diabetic action. Compounds 7a, 7b, 8a, 8b, 8d, 8e and 8f have shown significant anti-dyslipidemic activity in triton induced dyslipidemia in rats.

Omega-(2-Naphthyloxy) amino alkanes as a novel class of anti-hyperglycemic and lipid lowering agents

omega-(2-Naphthyloxy) amino alkanes, obtained as major by-product during course of synthesis of carbamate esters from omega-(2-naphthyloxy) alkyl halides and amines, showed significant anti-hyperglycemic and lipid lowering activities in various test models as a novel class of compounds. Compounds were tested in rat GLM, SLM, STZ, and STZ-S models at 100mg/kg dose. Of these compound 13 was found to be the most active which caused lowering of sugar by 33.6%, 31.0%, 28.5%, and 73.8% in GLM, SLM, STZ, STZ-S, and db/db mice models, respectively. It also significantly effected lowering of LDL in rat model and also in Hamster model without reducing HDL. Most of the compounds showing anti-diabetic and lipid lowering activity have shown promising PPAR-alpha/gamma/delta-activity. Compounds 6, 13, and 19 have shown very good PPAR-alpha/gamma/delta activity.

Design, synthesis, and evaluation of potent, structurally novel peroxisome proliferator-activated receptor (PPAR) δ-selective agonists

A series of 3-(4-alkoxyphenyl)propanoic acid derivatives was prepared as candidate peroxisome proliferator-activated receptor (PPAR) delta-selective agonists, based on our previously discovered potent human PPARalpha/delta dual agonist TIPP-401 as a lead compound. Structure-activity relationship studies clearly indicated the importance of the chain length of the alkoxy group at the 4-position, and the n-butoxy compound exhibited the most potent PPARdelta transactivation activity and highest PPARdelta selectivity. The (S)-enantiomer of a representative compound exhibited extremely potent PPARdelta transactivation activity, comparable with or somewhat superior to that of the known PPARdelta-selective agonist, GW-501516. The representative compound regulated the expression of genes involved in lipid and glucose homeostasis, and should be useful not only as a chemical tool to study PPARdelta function, but also as a candidate drug for the treatment of metabolic syndrome.

Design, synthesis, and evaluation of a novel series of α-substituted phenylpropanoic acid derivatives as human peroxisome proliferator-activated receptor (PPAR) α/δ dual agonists for the treatment of metabolic syndrome

A series of alpha-alkyl-substituted phenylpropanoic acids was prepared as dual agonists of peroxisome proliferator-activated receptors alpha and delta (PPARalpha/delta). Structure-activity relationship studies indicated that the shape of the linking group and the shape of the substituent at the distal benzene ring play key roles in determining the potency and the selectivity of PPAR subtype transactivation. Structure-activity relationships among the amide series (10) and the reversed amide series (13) are similar, but not identical, especially in the case of the compounds bearing a bulky hydrophobic substituent at the distal benzene ring, indicating that the hydrophobic tail part of the molecules in these two series binds at somewhat different positions in the large binding pocket of PPAR. alpha-Alkyl-substituted phenylpropanoic acids of (S)-configuration were identified as potent human PPARalpha/delta dual agonists. Representative compounds exhibited marked nuclear receptor selectivity for PPARalpha and PPARdelta. Subtype-selective PPAR activation was also examined by analysis of the mRNA expression of PPAR-regulated genes.

4-Hydroxyisoleucine an unusual amino acid as antidyslipidemic and antihyperglycemic agent

Trigonella foenum-graecum, commonly known as fenugreek, is an annual herbaceous plant. From the seeds of T. foenum-graecum an unusual amino acid, 4-hydroxyisoleucine 5, has been isolated, which significantly decreased the plasma triglyceride levels by 33% (P<0.002), total cholesterol (TC) by 22% (P<0.02), and free fatty acids by 14%, accompanied by an increase in HDL-C/TC ratio by 39% in the dyslipidemic hamster model.