Competitive Binding Assay with an Umbelliferone-Based Fluorescent Rexinoid for Retinoid X Receptor Ligand Screening

Ligands for retinoid X receptors (RXRs), "rexinoids", are attracting interest as candidates for therapy of type 2 diabetes and Alzheimer's and Parkinson's diseases. However, current screening methods for rexinoids are slow and require special apparatus or facilities. Here, we created 7-hydroxy-2-oxo-6-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-2H-chromene-3-carboxylic acid (10, CU-6PMN) as a new fluorescent RXR agonist and developed a screening system of rexinoids using 10. Compound 10 was designed based on the fact that umbelliferone emits strong fluorescence in a hydrophilic environment, but the fluorescence intensity decreases in hydrophobic environments such as the interior of proteins. The developed assay using 10 enabled screening of rexinoids to be performed easily within a few hours by monitoring changes of fluorescence intensity with widely available fluorescence microplate readers, without the need for processes such as filtration

Spontaneous Polarization and Polarization-Induced Electron Sheet Charge of YbAlN on GaN: A First-Principles Study

The high spontaneous polarization in scandium-doped AlN (ScAlN) is being actively investigated for applications to various electronic devices. In this study, spontaneous polarization of ytterbium-doped AlN (YbxAl1–xN) was investigated by first-principles calculations. The magnitude of spontaneous polarization increases with increasing Yb concentration and reaches the maximum value of −0.3 C/m2 at x = 0.5, which is comparable with that of ScAlN. Moreover, the results revealed the correlation between the lattice-constant ratio (c/a) of the wurtzite structure and spontaneous polarization. The value of spontaneous polarization is affected by the length of the Yb–N bonds along the c-axis in the wurtzite structure. The shorter Yb–N bonds compared with Al–N bonds and higher Born effective charge of Yb compared with Al are considered to be the main factors for the high spontaneous polarization of YbAlN. The polarization-induced electron sheet charge in YbAlN/GaN heterostructures is estimated to be comparable with that in ScAlN/GaN. These results suggest that YbAlN is a promising barrier layer for GaN-based high-electron-mobility transistors. At low Yb concentration, the lattice mismatch between YbxAl1–xN and the GaN buffer layer is very small. The polarization-induced interface sheet charge is affected by the sum of the spontaneous and piezoelectric polarization. In the case of YbAlN/GaN, the piezoelectric polarization is suppressed to a low level, and the effect of spontaneous polarization increases and leads to higher polarization-induced interface sheet charge

Effectiveness of countermeasure for polypharmacy by multidisciplinary team review in patients with diabetes mellitus

ABSTRACT Aims/Introduction Polypharmacy in diabetes patients is related to worse clinical outcomes. The aim of this study was to evaluate the usefulness of our countermeasure for polypharmacy, which combines a pharmacist check followed by a multidisciplinary team review in diabetic patients with polypharmacy. Methods A single‐center, retrospective observational study was conducted at Gifu University Hospital. Study participants included diabetic patients taking six or more drugs on admission to the diabetes ward between July 2021 and June 2022. Drugs which were discontinued by the present countermeasure were examined, and the number of drugs being taken by each patient was compared between admission and discharge. Results 102 of 308 patients were taking six or more drugs on admission. The drugs being taken by these patients were evaluated by pharmacists using a checklist for polypharmacy. Eighty‐four drugs which were evaluated as inappropriate or potentially inappropriate medications by pharmacists were discontinued following the multidisciplinary team review. The median and mean number of drugs taken by the 102 patients significantly decreased from 9.0 (IQR: 8–12) and 9.26 ± 2.64 on admission to 9.0 (IQR: 6–10) and 8.42 ± 2.95 on discharge (P = 0.0002). We followed up with these patients after discontinuation of the drugs and confirmed that their clinical status had not deteriorated. Conclusion The present countermeasure for polypharmacy, which combines a pharmacist check based on a checklist for evaluating polypharmacy followed by a multidisciplinary team review, was useful for reducing the number of inappropriate or potentially inappropriate medications taken by diabetes patients with polypharmacy

Positron Emission Tomography to Elucidate Pharmacokinetic Differences of Regioisomeric Retinoid X Receptor Agonists

RXR partial agonist NEt-4IB (<b>2a</b>, 6-[ethyl-(4-isobutoxy-3-isopropylphenyl)­amino]­pyridine-3-carboxylic acid: EC₅₀ = 169 nM, <i>E</i>_max = 55%) showed a blood concentration higher than its <i>E</i>_max after single oral administration at 30 mg/kg to mice, and repeated oral administration at 10 mg/kg/day to KK-A^y mice afforded antitype 2 diabetes activity without the side effects caused by RXR full agonists. However, RXR full agonist NEt-3IB (<b>1a</b>), in which the isobutoxy and isopropyl groups of <b>2a</b> are interchanged, gave a much lower blood concentration than <b>2a</b>. Here we used positron emission tomography (PET) with tracers [¹¹C]<b>1a</b>, [¹¹C]<b>2a</b> and fluorinated derivatives [¹⁸F]<b>1b</b>, [¹⁸F]<b>2b</b>, which have longer half-lives, to examine the reason why <b>1a</b> and <b>2a</b> exhibited significantly different blood concentrations. As a result, the reason for the high blood concentration of <b>2a</b> after oral administration was found to be linked to higher intestinal absorbability together with lower biliary excretion, compared with <b>1a</b>

Synthesis of ¹¹C‑Labeled RXR Partial Agonist 1‑[(3,5,5,8,8-Pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)amino]benzotriazole-5-carboxylic Acid (CBt-PMN) by Direct [¹¹C]Carbon Dioxide Fixation via Organolithiation of Trialkyltin Precursor and PET Imaging Thereof

The retinoid X receptor (RXR) partial agonist 1-[(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)­amino]­benzotriazole-5-carboxylic acid (<b>1</b>; CBt-PMN, <i>E</i>_max = 75%, EC₅₀ = 143 nM) is a candidate for treatment of central nervous system (CNS) diseases such as Alzheimer’s and Parkinson’s diseases based on reports that RXR-full agonist 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)­ethynyl]­benzoic acid (bexarotene) shows therapeutic effects on these disease in rodent models. Here, we synthesized carbon-11-labeled ([¹¹C]<b>1</b>) as a tracer for positron emission tomography (PET) and used it in a PET imaging study to examine the brain uptake and biodistribution of <b>1</b>. We found that ¹¹CO₂ fixation after tin–lithium exchange at −20 °C afforded [¹¹C]<b>1</b>. This methodology may also be useful for synthesizing ¹¹CO₂H-PET tracer derivatives of other compounds bearing π-rich heterocyclic rings. A PET/CT imaging study of [¹¹C]<b>1</b> in mice indicated <b>1</b> is distributed to the brain and is thus a candidate for treatment of CNS diseases

RXR Partial Agonist Produced by Side Chain Repositioning of Alkoxy RXR Full Agonist Retains Antitype 2 Diabetes Activity without the Adverse Effects

We previously reported RXR partial agonist CBt-PMN (1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)-1<i>H</i>-benzotriazole-5-carboxylic acid: <b>5</b>, EC₅₀ = 143 nM, <i>E</i>_max = 75%), which showed a potent glucose-lowering effect without causing serious adverse effects. However, it remains important to elucidate the structural requirements for RXR efficacy and the glucose-lowering effect because RXR-permissive heterodimers such as PPAR/RXR or LXR/RXR are reported to be activated differently depending upon the chemical structure of RXR agonists. In this work, we show that an RXR partial agonist, NEt-4IB (6-[ethyl-(4-isobutoxy-3-isopropylphenyl)­amino]­pyridine-3-carboxylic acid: <b>8b</b>, EC₅₀ = 169 nM, <i>E</i>_max = 55%), can be obtained simply by repositioning the side chains (interchanging the isobutoxy and isopropoxy groups) at the hydrophobic moiety of the RXR full agonist NEt-3IB (6-[ethyl-(3-isobutoxy-4-isopropylphenyl)­amino]­pyridine-3-carboxylic acid: <b>7b</b>, EC₅₀ = 19 nM). NEt-4IB (<b>8b</b>) showed antitype 2 diabetes activity without the above side effects upon repeated oral administration to mice at 10 mg/kg/day, similarly to <b>5</b>

Mechanism of Retinoid X Receptor Partial Agonistic Action of 1‑(3,5,5,8,8-Pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)‑1<i>H</i>‑benzotriazole-5-carboxylic Acid and Structural Development To Increase Potency

We have reported that retinoid X receptor (RXR) partial agonist 1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)-1<i>H</i>-benzotriazole-5-carboxylic acid (CBt-PMN, <b>4a</b>) shows a significant antidiabetes effect in the KK-A^y type 2 diabetes model mice, with reduced side effects compared to RXR full agonists. To elucidate the mechanism of the RXR partial agonist activity of <b>4a</b>, we synthesized derivatives of <b>4a</b>, evaluated their RXR agonist activity, and performed structure–activity relationship analysis. Reporter gene assay revealed that though <b>6b</b>, which possesses an amino group at the 2-position of 5-carboxybenzimidazole, showed RXR full-agonist activity, compounds <b>6d</b> and <b>6e</b>, which possess an oxygen atom and a sulfur atom at the corresponding position, respectively, showed weak RXR agonist activity. On the other hand, <b>6c</b>, which has a trifluoromethyl group at the corresponding position, acts as an RXR partial agonist, having similar <i>E</i>_max (67 ± 2%) and lower EC₅₀ (15 ± 0 nM) compared to those of <b>4a</b> (<i>E</i>_max = 75 ± 4%, EC₅₀ = 143 ± 2 nM). A fluorescence polarization assay of cofactor recruitment confirmed that fluorescein-labeled D22 coactivator peptide was less efficiently recruited to RXR by <b>4a</b> and <b>6c</b> than by LGD1069 (<b>1</b>), a known RXR full agonist. Electrostatic potential field calculations and computational docking studies suggested that full agonists show an electrostatic attraction, which stabilizes the holo structure and favors coactivator recruitment, between the side chain at the benzimidazole 2-position and the α-carbonyl oxygen of asparagine-306 in helix 4 (H4) of the RXR receptor. However, RXR partial agonists <b>4a</b> and <b>6c</b> lack this interaction. Like <b>4a</b>, <b>6c</b> showed a significant antidiabetes effect in KK-A^y type 2 diabetes model mice with reduced levels of the side effects associated with RXR full agonists. These findings should aid the design of new RXR partial agonists as antitype 2 diabetes drug candidates

RXR Partial Agonist CBt-PMN Exerts Therapeutic Effects on Type 2 Diabetes without the Side Effects of RXR Full Agonists

Treating insulin resistance and type 2 diabetes in rodents, currently known retinoid X receptor (RXR) agonists induce significant adverse effects. Here we introduce a novel RXR partial agonist CBt-PMN (<b>11b</b>), which shows a potent glucose-lowering effect and improvements of insulin secretion and glucose tolerance without the serious adverse effects caused by RXR full agonists. We suggest that RXR partial agonists may be a new class of antitype 2 diabetes drug candidates