Soumya P. Sahoo

NOVEL PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR) GAMMA AND PPARDELTA LIGANDS PRODUCE DISTINCT BIOLOGICAL EFFECTS

The peroxisome proliferator-activated receptors (PPARs) include three receptor subtypes encoded by separate genes: PPARα, PPARδ, and PPARγ. PPARγ has been implicated as a mediator of adipocyte differentiation and the mechanism by which thiazolidinedione drugs exert in vivo insulin sensitization. Here we characterized novel, non-thiazolidinedione agonists for PPARγ and PPARδ that were identified by radioligand binding assays. In transient transactivation assays these ligands were agonists of the receptors to which they bind. Protease protection studies showed that ligand binding produced specific alterations in receptor conformation. Both PPARγ and PPARδ directly interacted with a nuclear receptor co-activator (CREB-binding protein) in an agonist-dependent manner. Only the PPARγ agonists were able to promote differentiation of 3T3-L1 preadipocytes. In diabeticdb/db mice all PPARγ agonists were orally active insulin-sensitizing agents producing reductions of elevated plasma glucose and triglyceride concentrations. In contrast, selectivein vivo activation of PPARδ did not significantly affect these parameters. In vivo PPARα activation with WY-14653 resulted in reductions in elevated triglyceride levels with minimal effect on hyperglycemia. We conclude that: 1) synthetic non-thiazolidinediones can serve as ligands of PPARγ and PPARδ; 2) ligand-dependent activation of PPARδ involves an apparent conformational change and association of the receptor ligand binding domain with CREB-binding protein; 3) PPARγ activation (but not PPARδ or PPARα activation) is sufficient to potentiate preadipocyte differentiation; 4) non-thiazolidinedione PPARγ agonists improve hyperglycemia and hypertriglyceridemia in vivo; 5) although PPARα activation is sufficient to affect triglyceride metabolism, PPARδ activation does not appear to modulate glucose or triglyceride levels.

A Novel Liver X Receptor Agonist Establishes Species Differences in the Regulation of Cholesterol 7α-Hydroxylase (CYP7a)

The liver X receptors, LXRα and LXRβ, are members of the nuclear receptor superfamily. Originally identified as orphans, both receptor subtypes have since been shown to be activated by naturally occurring oxysterols. LXRα knockout mice fail to regulate cyp7a mRNA levels upon cholesterol feeding, implicating the role of this receptor in cholesterol homeostasis. LXR activation also induces the expression of the lipid pump involved in cholesterol efflux, the gene encoding ATP binding cassette protein A1 (ABCA1). Therefore, LXR is believed to be a sensor of cholesterol levels and a potential therapeutic target for atherosclerosis. Here we describe a synthetic molecule named F3MethylAA [3-chloro-4-(3-(7-propyl-3-trifluoromethyl-6-(4,5)-isoxazolyl)propylthio)-phenyl acetic acid] that is more potent than 22(R)-hydroxycholesterol in LXR in vitro assays. F3MethylAA is capable not only of inducing ABCA1 mRNA levels, but also increasing cholesterol efflux from THP-1 macrophages. In rat hepatocytes, F3MethylAA induce...

Identification of a potent synthetic FXR agonist with an unexpected mode of binding and activation.

The farnesoid X receptor (FXR), a member of the nuclear hormone receptor family, plays important roles in the regulation of bile acid and cholesterol homeostasis, glucose metabolism, and insulin sensitivity. There is intense interest in understanding the mechanisms of FXR regulation and in developing pharmaceutically suitable synthetic FXR ligands that might be used to treat metabolic syndrome. We report here the identification of a potent FXR agonist (MFA-1) and the elucidation of the structure of this ligand in ternary complex with the human receptor and a coactivator peptide fragment using x-ray crystallography at 1.9-Å resolution. The steroid ring system of MFA-1 binds with its D ring-facing helix 12 (AF-2) in a manner reminiscent of hormone binding to classical steroid hormone receptors and the reverse of the pose adopted by naturally occurring bile acids when bound to FXR. This binding mode appears to be driven by the presence of a carboxylate on MFA-1 that is situated to make a salt-bridge interaction with an arginine residue in the FXR-binding pocket that is normally used to neutralize bound bile acids. Receptor activation by MFA-1 differs from that by bile acids in that it relies on direct interactions between the ligand and residues in helices 11 and 12 and only indirectly involves a protonated histidine that is part of the activation trigger. The structure of the FXR:MFA-1 complex differs significantly from that of the complex with a structurally distinct agonist, fexaramine, highlighting the inherent plasticity of the receptor.

5-Aryl thiazolidine-2,4-diones: discovery of PPAR dual α/γ agonists as antidiabetic agents

A novel series of 5-aryl thiazolidine-2,4-diones based dual PPARα/γ agonists was identified. A number of highly potent and orally bioavailable analogues were synthesized. Efficacy study results of some of these analogues in the db/db mice model of type 2 diabetes showed them superior to rosiglitazone in correcting hyperglycemia and hypertriglyceridemia.

Identification of Anabolic Selective Androgen Receptor Modulators with Reduced Activities in Reproductive Tissues and Sebaceous Glands

Androgen replacement therapy is a promising strategy for the treatment of frailty; however, androgens pose risks for unwanted effects including virilization and hypertrophy of reproductive organs. Selective Androgen Receptor Modulators (SARMs) retain the anabolic properties of androgens in bone and muscle while having reduced effects in other tissues. We describe two structurally similar 4-aza-steroidal androgen receptor (AR) ligands, Cl-4AS-1, a full agonist, and TFM-4AS-1, which is a SARM. TFM-4AS-1 is a potent AR ligand (IC50, 38 nm) that partially activates an AR-dependent MMTV promoter (55% of maximal response) while antagonizing the N-terminal/C-terminal interaction within AR that is required for full receptor activation. Microarray analyses of MDA-MB-453 cells show that whereas Cl-4AS-1 behaves like 5α-dihydrotestosterone (DHT), TFM-4AS-1 acts as a gene-selective agonist, inducing some genes as effectively as DHT and others to a lesser extent or not at all. This gene-selective agonism manifests as tissue-selectivity: in ovariectomized rats, Cl-4AS-1 mimics DHT while TFM-4AS-1 promotes the accrual of bone and muscle mass while having reduced effects on reproductive organs and sebaceous glands. Moreover, TFM-4AS-1 does not promote prostate growth and antagonizes DHT in seminal vesicles. To confirm that the biochemical properties of TFM-4AS-1 confer tissue selectivity, we identified a structurally unrelated compound, FTBU-1, with partial agonist activity coupled with antagonism of the N-terminal/C-terminal interaction and found that it also behaves as a SARM. TFM-4AS-1 and FTBU-1 represent two new classes of SARMs and will allow for comparative studies aimed at understanding the biophysical and physiological basis of tissue-selective effects of nuclear receptor ligands.

Aryloxazolidinediones: identification of potent orally active PPAR dual α/γ agonists

Abstract A series of novel aryloxazolidine-2,4-diones was synthesized. A structure–activity relationship study of these compounds led to the identification of potent, orally active PPAR dual α/γ agonists. Based on the results of efficacy studies in the db/db mice model of type 2 diabetes and the desired pharmacokinetic parameters, compound 12 was selected for further profiling.

5-Aryl thiazolidine-2,4-diones as selective PPARγ agonists

A series of 5-aryl thiazolidine-2,4-diones containing 4-phenoxyphenyl side chains was designed, synthesized, and evaluated for PPAR agonist activities. One such compound 28 exhibited comparable levels of glucose correction to rosiglitazone in the db/db mouse type 2 diabetes animal model.

Phenylacetic acid derivatives as hPPAR agonists.

Beginning with the weakly active lead structure 1, a new series of hPPAR agonists was developed. In vivo glucose and triglyceride lowering activity was obtained by homologation and oxamination to 3, then conversion to substituted benzisoxazoles 4 and 5. Further manipulation afforded benzofurans 6 and 7. Compound 7 was of comparable potency as a glucose and triglyceride lowering agent in insulin resistant rodents to BRL 49653.

Phosphinic acid inhibitors of matrix metalloproteinases

Abstract The matrix metalloproteinase stromelysin-1 (MMP-3) is inhibited more strongly by peptidyl phosphinic acid 7 than by its corresponding phosphonamidate and phosphonate analogs. Extending a benzyl group at P′ 1 to a phenylethyl group in 8 further increases the potency (K i = 1.4 nM). Enhanced potency with an extended substituent into the P 3 region was observed.

Synthesis and biological activity of MK 287 (L-680,573): a potent, specific and orally active paf receptor antagonist

Abstract An enantioselective synthesis of MK 287 (L-680,573), a member of a family of trans-,5-diaryltetrahydrofurans, and its biological activity are described.