Discovery of Guanfacine as a Novel TAAR1 Agonist: A Combination Strategy through Molecular Modeling Studies and Biological Assays.

Trace amine-associated receptor 1 (TAAR1) is an attractive target for the design of innovative drugs to be applied in diverse pharmacological settings. Due to a non-negligible structural similarity with endogenous ligands, most of the agonists developed so far resulted in being affected by a low selectivity for TAAR1 with respect to other monoaminergic G protein-coupled receptors, like the adrenoreceptors. This study utilized comparative molecular docking studies and quantitative-structure activity relationship (QSAR) analyses to unveil key structural differences between TAAR1 and alpha2-adrenoreceptor (α2-ADR), with the aim to design novel TAAR1 agonists characterized by a higher selectivity profile and reduced off-target effects. While the presence of hydrophobic motives is encouraged towards both the two receptors, the introduction of polar/positively charged groups and the ligand conformation deeply affect the TAAR1 or α2-ADR putative selectivity. These computational methods allowed the identification of the α2A-ADR agonist guanfacine as an attractive TAAR1-targeting lead compound, demonstrating nanomolar activity in vitro. In vivo exploration of the efficacy of guanfacine showed that it is able to decrease the locomotor activity of dopamine transporter knockout (DAT-KO) rats. Therefore, guanfacine can be considered as an interesting template molecule worthy of structural optimization. The dual activity of guanfacine on both α2-ADR and TAAR1 signaling and the related crosstalk between the two pathways will deserve more in-depth investigation.

Discovery of Trace Amine Associated Receptor 1 (TAAR1) Agonist 2-(5-(4'-Chloro-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazol-3-yl)ethan-1-amine (LK00764) for the Treatment of Psychotic Disorders.

A focused in-house library of about 1000 compounds comprising various heterocyclic motifs in combination with structural fragments similar to ß-phenethylamine (PEA) or tyramine was screened for the agonistic activity towards trace amine-associated receptor 1 (TAAR1). The screening yielded two closely related hits displaying EC50 values in the upper submicromolar range. Extensive analog synthesis and testing for TAAR1 agonism in a BRET-based cellular assay identified compound 62 (LK00764) with EC50 = 4.0 nM. The compound demonstrated notable efficacy in such schizophrenia-related in vivo tests as MK-801-induced hyperactivity and spontaneous activity in rats, locomotor hyperactivity of dopamine transporter knockout (DAT-KO) rats, and stress-induced hyperthermia (i.p. administration). Further preclinical studies are necessary to evaluate efficacy, safety and tolerability of this potent TAAR1 agonist for the potential development of this compound as a new pharmacotherapy option for schizophrenia and other psychiatric disorders.

Association of tribbles homologue 1 gene expression in human umbilical vein endothelial cells with duration of intrauterine exposure to hyperglycaemia.

Maternal gestational diabetes mellitus (GDM) is considered to be an important factor that epigenetically predisposes offspring to metabolic and cardiovascular diseases. However, the mechanisms of how intrauterine hyperglycaemia affects offspring have not been thoroughly studied. The mammalian tribbles homologue 1 (TRIB1) gene is associated with plasma lipid concentrations and coronary artery disease (CAD). Our aim was to study the effect of GDM and its treatment terms on the level of TRIB1 gene expression in human umbilical vein endothelial cells (HUVECs) of newborns from women with and without GDM. The study included 50 women with GDM and 25 women without GDM (control group). Women with GDM were divided into three groups according to their gestational age when the treatment of GDM started: 24-28 weeks (GDM1, N = 16), 29-32 weeks (GDM2, N = 25) and >34 weeks (GDM3, N = 9). The levels of TRIB1 gene expression in GDM3, GDM2, GDM1 and control groups were 2.8 ± 1.1, 4.2 ± 2.4, 6.0 ± 3.4 and 8.1 ± 6.1, respectively (p = 0.001). After comparison in pairs the difference was significant for the following pairs: GDM2-control (p = 0.004), GDM3-control (p = 0.002), GDM1-GDM3 (p = 0.012). Notably, if treatment had been started before the 28th week of gestation, the difference in TRIB1 gene expression in HUVECs was not significant (p = 0.320 for comparison between GDM1 and control groups). Our findings support the hypothesis that TRIB1 gene expression in HUVECs depends on the duration of intrauterine exposure to hyperglycaemia.

Rational design, chemical synthesis and biological evaluation of novel biguanides exploring species-specificity responsiveness of TAAR1 agonists.

The design of novel chemical classes acting towards several G-protein-coupled receptors (GPCRs) represents a leading strategy in drug discovery, aimed at deriving effective and safe candidates for further assessment. During the last years, TAAR1 arose as a promising druggable target in medicinal chemistry, being of interest in the treatment of several pathologies, such as neuropsychiatric disorders, type 2 diabetes and obesity. Nevertheless, the limited number of known potent and selective ligands and the species-specificity responsiveness exhibited by those derivatives nowadays available make the discovery of novel compounds a challenging task. Herein, we discuss the development of two quantitative-structure activity relationship (QSAR) models around the agonism ability experienced by different chemo-types toward murine and human TAAR1 (m/hTAAR1) with the aim at deciphering some clues involved in their species-specificity responsiveness. Qualitatively, these information were evaluated guiding for the synthesis of novel ligands, which proved to feature selective agonism ability with respect to the mTAAR1 and hTAAR1 orthologues.

TAAR5 receptor agonist affects sensory gating in rats.

Trace amines are structurally close to classical monoamines and dysregulation in trace amines and/or their receptors might contribute to pathology of mental disorders. The study was aimed to investigate the effect of recently identified Trace Amine-Associated Receptor 5 (TAAR5) agonist 2-(alpha-naphthoyl)ethyltrimethylammonium iodide (alpha-NETA) on sensory gating (SG) in awake freely moving rats. SG was studied in paired-click paradigm and SG index was calculated as difference in event related potentials component N40 amplitudes to the first and second stimulus in the pair. The 1 mg/kg dose of alpha-NETA as well as the control injection of saline had no significant effects on the SG index. However, higher doses of alpha-NETA (3 and 5 mg/kg) significantly decreased the SG index. The change in the SG index was mainly due to a decrease in the N40 amplitude, and the 5 mg/kg dose caused the N40 decrease both in response to the first and second stimulus in the pair. Thus, TAAR5 activation can influence SG, indicating the potential role of trace amines and TAAR5 in sensory information dosing.

Effect of gene-lifestyle interaction on gestational diabetes risk.

We hypothesized that the association of certain lifestyle parameters with gestational diabetes mellitus (GDM) risk would depend on susceptibility loci. In total, 278 Russian women with GDM and 179 controls completed questionnaires about lifestyle habits (food consumption, physical activity and smoking). GDM was diagnosed according to the criteria of the International Association of Diabetes and Pregnancy Study Groups. Maternal blood was sampled for genotyping single-nucleotide polymorphisms (SNPs) in MTNR1B (rs10830963 and rs1387153), GCK (rs1799884), KCNJ11 (rs5219), IGF2BP2 (rs4402960), TCF7L2 (rs7903146 and rs12255372), CDKAL1 (rs7754840), IRS1 (rs1801278) and FTO (rs9939609). Binary logistic regression revealed an interaction effect of sausage intake and the number of risk alleles of two SNPs (rs10830963 in MTNR1B and rs1799884 in GCK) on GDM risk (P < 0.001). Among women without risk alleles of these two SNPs, sausage consumption was positively associated with GDM risk (P trend = 0.045). This difference was not revealed in women carrying 1 or more risk alleles. The risk of GDM increased as the number of risk alles increased in participants with low and moderate sausage consumption (P trend <0.001 and 0.006, respectively), while the risk of GDM in women with high sausage consumption remained relatively high, independent of the number of risk alleles. These findings indicate that the association of sausage consumption with GDM risk can be determined based on the number of risk alleles of rs10830963 in MTNR1B and rs1799884 in GCK.

In-vivo pharmacology of Trace-Amine Associated Receptor 1.

Trace-amines (TAs) are endogenous amines that are implicated in several physiological processes including modulation of aminergic neurotransmission. These compounds exert their effect by activating a class of G protein-coupled receptors termed Trace-Amine Associated Receptors (TAARs), where TAAR1 is the only human receptor that has been shown to bind endogenous TAs. Most of the studies have focused on studying the role of TAAR1 on modulation of the dopamine transmission. These studies indicate that TAAR1 is a negative regulator of dopamine transmission making TAAR1 a novel target for neuropsychiatric disorders that arises from dopamine dysfunction such as schizophrenia. This review discusses the unique pharmacology of TAAR1 with the major focus on the physiological role of TAAR1 and its modulation of dopamine transmission.