Progress and challenges of selective Farnesoid X Receptor modulation.

Bile acids are amphipathic molecules that were previously known to serve as fat solubilizers in the intestine in postprandial conditions. In the last two decades, bile acids have been recognized as signaling molecules regulating energy metabolism pathways via, amongst others, the farnesoid X receptor (FXR). Upon bile acid activation, FXR controls expression of genes involved in bile acid, lipid, glucose and amino acid metabolism. In addition, FXR activation has been shown to limit the inflammatory response. The central role of FXR in various aspects of metabolism and inflammation makes FXR an attractive drug target for several diseases, such as obesity, metabolic syndrome, non-alcoholic steatohepatitis, cholestasis and chronic inflammatory diseases of the liver and intestine. However, most of the currently available compounds impact on all discovered FXR-mediated functions and may have, on top of beneficial effects, undesired biological actions depending on the disease. Therefore, research efforts are increasingly focused on the development of selective FXR modulators, i.e. selective bile acid receptor modulators (SBARMs), aimed at limiting the potential side-effects of conventional full FXR agonists upon chronic treatment. Here, we review the rationale for the design of SBARMs comprising dissociation between metabolic and inflammatory signaling, gene-selective and tissue-specific targeting. We discuss the potential structural mechanisms underlying the binding properties of dissociating ligands of FXR in light of ongoing efforts on the generation of dissociated ligands for otxher nuclear receptors, as well as their pharmacological and therapeutic potential

Bile Acid Recognition by NAPE-PLD

The membrane-associated enzyme NAPE-PLD (N-acyl phosphatidylethanolamine specific-phospholipase D) generates the endogenous cannabinoid arachidonylethanolamide and other lipid signaling amides, including oleoylethanolamide and palmitoylethanolamide. These bioactive molecules play important roles in several physiological pathways including stress and pain response, appetite and lifespan. Recently, we reported the crystal structure of human NAPE-PLD and discovered specific binding sites for the bile acid deoxycholic acid. In this study we demonstrate that in the presence of this secondary bile acid, the stiffness of the protein measured by elastic neutron scattering increases, and NAPE-PLD results ~7 times faster to catalyze the hydrolysis of the more unsaturated substrate N-arachidonyl-phosphatidylethanolamine, compared with N-palmitoyl-phosphatidylethanolamine. Chenodeoxycholic acid and glyco- or tauro-dihydroxy conjugates can also bind to NAPE-PLD and drive its activation. The only natural monohydroxy bile acid, lithocholic acid, shows an affinity of ~20 μM and acts instead as a reversible inhibitor (IC(50) ≈ 68 μM). Overall, these findings provide important insights into the allosteric regulation of the enzyme mediated by bile acid cofactors, and reveal that NAPE-PLD responds primarily to the number and position of their hydroxyl groups

Garcinoic acid prevents β-amyloid (Aβ) deposition in the mouse brain

Garcinoic acid (GA or δ-T3-13'COOH), is a natural vitamin E metabolite that has preliminarily been identified as a modulator of nuclear receptors involved in β-amyloid (Aβ) metabolism and progression of Alzheimer's disease (AD). In this study, we investigated GA's effects on Aβ oligomer formation and deposition. Specifically, we compared them with those of other vitamin E analogs and the soy isoflavone genistein, a natural agonist of peroxisome proliferator-activated receptor γ (PPARγ) that has therapeutic potential for managing AD. GA significantly reduced Aβ aggregation and accumulation in mouse cortical astrocytes. Similarly to genistein, GA up-regulated PPARγ expression and apolipoprotein E (ApoE) efflux in these cells with an efficacy that was comparable with that of its metabolic precursor δ-tocotrienol and higher than those of α-tocopherol metabolites. Unlike for genistein and the other vitamin E compounds, the GA-induced restoration of ApoE efflux was not affected by pharmacological inhibition of PPARγ activity, and specific activation of pregnane X receptor (PXR) was observed together with ApoE and multidrug resistance protein 1 (MDR1) membrane transporter up-regulation in both the mouse astrocytes and brain tissue. These effects of GA were associated with reduced Aβ deposition in the brain of TgCRND8 mice, a transgenic AD model. In conclusion, GA holds potential for preventing Aβ oligomerization and deposition in the brain. The mechanistic aspects of GA's properties appear to be distinct from those of other vitamin E metabolites and of genistein

Nat Metab.

Bile acids (BAs) are signalling molecules that mediate various cellular responses in both physiological and pathological processes. Several studies report that BAs can be detected in the brain1, yet their physiological role in the central nervous system is still largely unknown. Here we show that postprandial BAs can reach the brain and activate a negative-feedback loop controlling satiety in response to physiological feeding via TGR5, a G-protein-coupled receptor activated by multiple conjugated and unconjugated BAs2 and an established regulator of peripheral metabolism3,4,5,6,7,8. Notably, peripheral or central administration of a BA mix or a TGR5-specific BA mimetic (INT-777) exerted an anorexigenic effect in wild-type mice, while whole-body, neuron-specific or agouti-related peptide neuronal TGR5 deletion caused a significant increase in food intake. Accordingly, orexigenic peptide expression and secretion were reduced after short-term TGR5 activation. In vitro studies demonstrated that activation of the Rho–ROCK–actin-remodelling pathway decreases orexigenic agouti-related peptide/neuropeptide Y (AgRP/NPY) release in a TGR5-dependent manner. Taken together, these data identify a signalling cascade by which BAs exert acute effects at the transition between fasting and feeding and prime the switch towards satiety, unveiling a previously unrecognized role of physiological feedback mediated by BAs in the central nervous system.Développment d'une infrastructure française distribuée coordonnéeLa signalisation des acides biliaires dans le cerveau et son rôle dans le contrôle métaboliqueInnovations instrumentales et procédurales en psychopathologie expérimentale chez le rongeu

Controlled Flow Precipitation as a Valuable Tool for Synthesis

In most standard flow process, the formation of solids represents a major problem often leading to obstruction of the flow device and reactor shutdown. However, many reactions produce solid products, and therefore finding ways to process these materials is an important area of research. In this article we demonstrate how a dynamically agitated flow reactor can be a powerful tool to facilitate workup and processing of biphasic solid–liquid flow streams at scale

Continuous Flow Synthesis of Thieno[2,3-c]isoquinolin-5(4H)-one Scaffold: A Valuable Source of PARP-1 Inhibitors

An efficient multistep method for the continuous flow synthesis of thieno[2,3- c]isoquinolin-5(4H)-one-A (TIQ-A), an important pharmacological tool and building block for PARP-1 inhibitors, has been developed. The synthesis involves a Suzuki coupling reaction to generate 3-phenylthiophene-2-carboxylic acid which is transformed into the corresponding acyl azide and readily cyclized by thermal Curtius rearrangement. Statistical Design of Experiments (DoE) was employed as a valuable support for decision-making of further experiments enabling the development of a robust and reliable protocol for large scale preparation. As a result, the reactions are facile, safe, and easy to scale-up. The large scale applicability of this improved flow method was tested by conducting the reactions on multigram scale to produce the desired product in high yield and quality for bio-pharmacological appraisals

In-Flow Flash Nanoprecipitation of Size-Controlled D-Leucine Nanoparticles for Spray-Drying Formulations

In this work we report the development of a cheap and scalable flow-based flash nanoprecipitation approach to prepare D-leucine nanoparticles particularly useful as glidants in dry powder for inhalation. Starting from preliminary batch screens, the process was successfully optimized and scaled-up under mesofluidic conditions. The nebulization with both mini and nano spray-dryer, the SEM analysis of nanoparticles and the aerodynamic evaluation of a formulation obtained by physical mixing of atomized D-leucine powders with budenoside showed an excellent decrease in particle size without altering the morphology, and a marked improvement in the aerodynamic properties of the drug. This simple and economic method by physical mixing of leucine with micronized active pharmaceutical ingredients can represent a valid alternative to co-spray-drying.</p

BF₃·Et₂O-Promoted Decomposition of Cyclic α-Diazo-β-Hydroxy Ketones: Novel Insights into Mechanistic Aspects

We report novel insights into the cascade rearrangement of destabilized vinyl cations deriving from the BF3&#183;Et2O-induced decomposition of cyclic &#945;-diazo-&#946;-hydroxy ketones in turn prepared by aldol-type condensation of cycloalkanones with diazoacetone. Complexation of the hydroxy group of the &#945;-diazo-&#946;-hydroxy compound with the Lewis acid is the first event, followed by the generation of the cycloalkanylidenediazonium salt that, after nitrogen loss, produces the highly reactive vinyl cation. The subsequent ring expansion results in the formation of a cycloalkenyl vinyl cation that affords the allylic cation by 1,2-methylene shift and ring contraction. The cation can then trap the solvent, the fluoride or the hydroxide released from the [BF3OH]&#8722; to afford different reaction products. The effect of both solvent and substrate ring size on products types and ratios were analyzed and discussed from a mechanistic point of view

Steroids interfere with human carbonic anhydrase activity by using alternative binding mechanisms

Bile acids have been shown to inhibit human (h) carbonic anhydrases (CA, EC 4.2.1.1) along the gastrointestinal tract, including hCA II. The elucidation of the hormonal inhibition mechanism of the bile acid cholate to hCA II was provided in 2014 by X-ray crystallography. Herein, we extend the inhibition study to a wealth of steroids against four relevant hCA isoforms. Steroids displaying pendants and functional groups of the carboxylate, phenolic or sulfonate types appended at the tetracyclic ring were shown to inhibit the cytosolic CA II and the tumor-associated, transmembrane CA IX in a medium micromolar range (38.9–89.9 µM). Docking studies displayed the different chemotypes CA inhibition mechanisms. Molecular dynamics (MD) gave insights on the stability over time of hyocholic acid binding to CA II