Racemization of the substrate and product by serine palmitoyltransferase from Sphingobacterium multivorum yields two enantiomers of the product from d-serine.

Serine palmitoyltransferase (SPT) catalyzes the pyridoxal-5'-phosphate (PLP)-dependent decarboxylative condensation of l-serine and palmitoyl-CoA to form 3-ketodihydrosphingosine (KDS). Although SPT was shown to synthesize corresponding products from amino acids other than l-serine, it is still arguable whether SPT catalyzes the reaction with d-serine, which is a question of biological importance. Using high substrate and enzyme concentrations, KDS was detected after the incubation of SPT from Sphingobacterium multivorum with d-serine and palmitoyl-CoA. Furthermore, the KDS comprised equal amounts of 2S and 2R isomers. 1H-NMR study showed a slow hydrogen-deuterium exchange at Cα of serine mediated by SPT. We further confirmed that SPT catalyzed the racemization of serine. The rate of the KDS formation from d-serine was comparable to those for the α-hydrogen exchange and the racemization reaction. The structure of the d-serine-soaked crystal (1.65 Å resolution) showed a distinct electron density of the PLP-l-serine aldimine, interpreted as the racemized product trapped in the active site. The structure of the α-methyl-d-serine-soaked crystal (1.70 Å resolution) showed the PLP-α-methyl-d-serine aldimine, mimicking the d-serine-SPT complex prior to racemization. Based on these enzymological and structural analyses, the synthesis of KDS from d-serine was explained as the result of the slow racemization to l-serine, followed by the reaction with palmitoyl-CoA, and SPT would not catalyze the direct condensation between d-serine and palmitoyl-CoA. It was also shown that the S. multivorum SPT catalyzed the racemization of the product KDS, which would explain the presence of (2R)-KDS in the reaction products.

Enhancing effect of the coexisting alpha-tocopherol on quercetin absorption and metabolism.

The aim of this study is to investigate the modulating effect of coexisting food components on the absorption and metabolism of quercetin and blood plasma antioxidant potentials. The combination of quercetin with α-tocopherol (αT), cellulose, or a commercially available vegetable beverage containing αT and dietary fiber was orally administered to mice. Compared to the single administration of quercetin aglycone, the coadministration of αT with quercetin significantly increased the plasma quercetin concentration at 0.5 h, whereas the combination of quercetin and cellulose decreased it. Interestingly, the administration of quercetin mixed with the vegetable beverage showed no significant change in the quercetin concentration in the mice plasma. The treatment of the cells with the blood plasma after the coadministration of αT with quercetin significantly upregulated the gene expression of the antioxidant enzyme (heme oxygenase-1), whereas the quercetin and cellulose combination did not. In the plasma of the quercetin-administered mice, eight types of quercetin metabolites were detected, and their quantities were affected by the combination with αT. The potentials of the heme oxygenase-1 gene expression by these metabolites were very limited, although several metabolites showed radical scavenging activities comparable to aglycone in the in vitro assays. These results suggested that the combination of αT potentiates the quercetin absorption and metabolism and thus the plasma antioxidant potentials, at least in part, by the quantitative changes in the quercetin metabolites.

The binding selectivity of quercetin and its structure-related polyphenols to human serum albumin using a fluorescent dye cocktail for multiplex drug-site mapping.

Human serum albumin (HSA) is a serum protein that carries flavonoids in blood circulation. In this report, the binding selectivity and strength of interactions to HSA-binding sites (sites I or II) by flavonoids were evaluated using competition experiments and the specific fluorescent dyes, dansylamide and BD140. Most tested flavonoids bound site I preferentially, with the binding strength dependent on the mother structure in the order flavonol > flavone > flavanone > flavan 3-ols. Glycosylation or glucuronidation reduced the binding of quercetin to site I of HSA, whereas sulfation increased binding. Quercetin 7-sulfate showed the strongest binding and molecular docking simulations supported this observation. Prenylation at any position or glucuronidation and sulfation at the C-4' or C-7 position of quercetin facilitated stronger binding to site II. The binding affinity of flavonoids toward site I correlated with the partition coefficient value (logP), whereas no corresponding correlation was observed for site II.

Characterization of Rickets Type II Model Rats to Reveal Functions of Vitamin D and Vitamin D Receptor.

Vitamin D has been known to exert a wide range of physiological effects, including calcemic, osteogenic, anticancer, and immune responses. We previously generated genetically modified (GM) rats and performed a comparative analysis of their physiological properties to elucidate the roles of vitamin D and vitamin D receptor (VDR). In this study, our primary goal was to investigate the manifestations of type II rickets in rats with the VDR(H301Q) mutation, analogous to the human VDR(H305Q). Additionally, we created a double-mutant rat with the VDR(R270L/H301Q) mutation, resulting in almost no affinity for 1,25-dihydroxy-vitamin D3 (1,25D3) or 25-hydroxy-vitamin D3 (25D3). Notably, the plasma calcium concentration in Vdr(R270L/H301Q) rats was significantly lower than in wild-type (WT) rats. Meanwhile, Vdr(H301Q) rats had calcium concentrations falling between those of Vdr(R270L/H301Q) and WT rats. GM rats exhibited markedly elevated plasma parathyroid hormone and 1,25D3 levels compared to those of WT rats. An analysis of bone mineral density in the cortical bone of the femur in both GM rats revealed significantly lower values than in WT rats. Conversely, the bone mineral density in the trabecular bone was notably higher, indicating abnormal bone formation. This abnormal bone formation was more pronounced in Vdr(R270L/H301Q) rats than in Vdr(H301Q) rats, highlighting the critical role of the VDR-dependent function of 1,25D3 in bone formation. In contrast, neither Vdr(H301Q) nor Vdr(R270L/H301Q) rats exhibited symptoms of alopecia or cyst formation in the skin, which were observed in the Vdr-KO rats. These findings strongly suggest that unliganded VDR is crucial for maintaining the hair cycle and normal skin. Our GM rats hold significant promise for comprehensive analyses of vitamin D and VDR functions in future research.

Gene therapy for alopecia in type II rickets model rats using vitamin D receptor-expressing adenovirus vector.

Type II rickets is a hereditary disease caused by a mutation in the vitamin D receptor (VDR) gene. The main symptoms of this disease are bone dysplasia and alopecia. Bone dysplasia can be ameliorated by high calcium intake; however, there is no suitable treatment for alopecia. In this study, we verified whether gene therapy using an adenoviral vector (AdV) had a therapeutic effect on alopecia in Vdr-KO rats. The VDR-expressing AdV was injected into six 7-week-old female Vdr-KO rats (VDR-AdV rats). On the other hand, control-AdV was injected into 7-week-old female rats (control-AdV rats); non-infected Vdr-KO rats (control rats) were also examined. The hair on the backs of the rats was shaved with hair clippers, and VDR-AdV or control-AdV was intradermally injected. Part of the back skin was collected from each rat after AdV administration. Hair follicles were observed using hematoxylin and eosin staining, and VDR expression was examined using immunostaining and western blotting. VDR-AdV rats showed significant VDR expression in the skin, enhanced hair growth, and low cyst formation, whereas control-AdV and non-infected rats did not show any of these effects. The effect of VDR-AdV lasted for nearly 60 days. These results indicate that gene therapy using VDR-AdV may be useful to treat alopecia associated with type II rickets, if multiple injections are possible after a sufficient period of time.

Effect of Oral Administration of Polyethylene Glycol 400 on Gut Microbiota Composition and Diet-Induced Obesity in Mice.

Polyethylene glycol (PEG) is a commonly used dispersant for oral administration of hydrophobic agents. PEG is partly absorbed in the small intestine, and the unabsorbed fraction reaches the large intestine; thus, oral administration of PEG may impact the gut microbial community. However, to the best of our knowledge, no study evaluated the effects of PEG on gut commensal bacteria. Herein, we aimed to determine whether oral administration of PEG modifies the gut microbiota. Administration of PEG400 and PEG4000 altered gut microbial diversity in a concentration-dependent manner. Taxonomic analysis revealed that Akkermansia muciniphila and particularly Parabacteroides goldsteinii were overrepresented in mice administered with 40% PEG. PEG400 administration ameliorated the high-fat diet (HFD)-induced obesity and adipose tissue inflammation. Fecal microbiome transplantation from PEG400-administered donors counteracted the HFD-induced body and epididymal adipose tissue weight gain, indicating that PEG400-associated bacteria are responsible for the anti-obesity effect. Conversely, carboxymethyl cellulose, also used as a dispersant, did not affect the abundance of these two bacterial species or HFD-induced obesity. In conclusion, we demonstrated that oral administration of a high concentration of PEG400 (40%) alters the gut microbiota composition and ameliorates HFD-induced obesity.

Analysis of vitamin D metabolites in biological samples using a nanoluc-based vitamin D receptor ligand sensing system: NLucVDR.

Many assays are currently being developed to measure the levels of vitamin D metabolites in various samples (such as blood, urine, and saliva). This study focused on the measurement of vitamin D metabolites in serum and urine using the NLucVDR assay system, which consists of a split-type nanoluciferase and ligand-binding domain (LBD) of the human vitamin D receptor. Blood and urine samples were collected from 23 participants to validate the NLucVDR assay. The 25(OH)D3 levels in the serum and urine determined by the NLucVDR assay showed good correlations with those determined by standard analytical methods (ECLIA for serum and LC-MS/MS for urine), with correlation coefficients of 0.923 and 0.844 for serum and urine samples, respectively. In the case of serum samples, 25(OH)D3 levels determined by the NLucVDR assay were in good agreement with those determined by ECLIA. Therefore, the NLucVDR assay is a useful tool for measuring serum 25(OH)D3 levels. The contribution of each vitamin D metabolite to the luminescence intensity obtained during the NLucVDR assay depends on its concentration and affinity for NLucVDR. Thus, the contribution of 25(OH)D3 in serum appears to be much higher than that of the other metabolites. In contrast, the 25(OH)D3 levels in the urine determined by the NLucVDR assay were more than 20-fold higher than those determined by a standard analytical method (LC-MS/MS), suggesting that some vitamin D metabolite(s) in the urine remarkably increased the luminescence intensity of the NLucVDR assay. Notably, the 25(OH)D3 concentration in the urine determined by the NLucVDR assay and the serum 25(OH)D3 concentration determined by standard analytical methods showed a significant positive correlation (r = 0.568). These results suggest that the analysis of a small amount of urine using the NLucVDR assay may be useful for predicting the serum 25(OH)D3 levels.

Covalent adduction of serotonin-derived quinones to the SARS-CoV-2 main protease expressed in a cultured cell.

The SARS-CoV-2 main protease is an essential molecule for viral replication and is often targeted by medications to treat the infection. In this study, we investigated the possible inhibitory action of endogenous quinones on the enzyme. Recombinant SARS-CoV-2 main protease was exposed to tryptamine-4,5-dione (TD) or quinone from 5-hydroxyindoleacetic acid (Q5HIAA). As a result, the protease activity was considerably decreased in a dose-dependent manner. The IC50 values of the quinones toward the enzyme were approximately 0.28 µM (TD) and 0.49 µM (Q5HIAA). Blot analyses using specific antibodies to quinone-modified proteins revealed that quinones were adducted to the enzyme at concentrations as low as 0.12 µM. Intact mass analyses showed that one or two quinone molecules were covalently adducted onto the main protease. Chymotrypsin-digested main protease analyses revealed that the quinones bind to thiol residues at the enzyme's active site. When TD or Q5HIAA were exposed to cultured cells expressing the viral enzyme, quinone-modified enzyme was identified in the cell lysate, suggesting that even extracellularly generated quinones could react with the viral enzyme expressed in an infected cell. Thus, these endogenous quinones could act as inhibitors of the viral enzyme.

Effect of Wheat-Derived Arabinoxylan on the Gut Microbiota Composition and Colonic Regulatory T Cells.

The health benefits of wheat-derived arabinoxylan, a commonly consumed dietary fiber, have been studied for decades. However, its effect on the gut microenvironment and inflammatory bowel disease remains unclear. The objective of this study was to understand the effect of wheat-derived arabinoxylan on gut microbiota, colonic regulatory T cells (Tregs), and experimental colitis. In this study, healthy and chronic colitis model mice were fed chow containing cellulose or wheat-derived arabinoxylan for 2-6 weeks and subjected to subsequent analysis. A 16S-based metagenomic analysis of the fecal DNA revealed that Lachnospiraceae, comprising butyrate-producing and Treg-inducing bacteria, were overrepresented in arabinoxylan-fed mice. In line with the changes in the gut microbiota, both the fecal butyrate concentration and the colonic Treg population were elevated in the arabinoxylan-fed mice. In a T cell transfer model of chronic colitis, wheat-derived arabinoxylan ameliorated body weight loss and colonic tissue inflammation, which may, in part, be mediated by Treg induction. Moreover, wheat-derived arabinoxylan suppressed TNFα production from type 1 helper T cells in this colitis model. In conclusion, wheat-derived arabinoxylans, by altering the gut microenvironment, may be a promising prebiotic for the prevention of colitis.

Augmentation of Pectoral Fin Teratogenicity by Thalidomide in Human Cytochrome P450 3A-Expressing Zebrafish.

The pharmacological and toxicological effects of active metabolites of enzymes including cytochrome P450 (CYP) are important. While it has been believed for a long time that thalidomide causes characteristic limb malformation only in rabbits and primates including humans, the involvement of their CYP3A subtypes (CYP3As) has been suggested. Recently, however, it was reported that zebrafish were sensitive to thalidomide, showing defects of pectoral fins, homologous organs of forelimbs in mammals, as well as other deformities. In this study, we prepared human CYP3A7 (hCYP3A7)-expressing zebrafish (F0) using a transposon system. Thalidomide caused pectoral fin defects and other malformations including pericardial edema in hCYP3A7-expressing embryos/larvae but not in wild-type and hCYP1A1-expressing embryos/larvae. Thalidomide also reduced the expression of fibroblast growth factor 8 in pectoral fin buds in only hCYP3A7-expressing embryos/larvae. The results suggest the involvement of human-type CYP3A in thalidomide teratogenicity.

Transgenic Zebrafish Expressing Rat Cytochrome P450 2E1 (CYP2E1): Augmentation of Acetaminophen-Induced Toxicity in the Liver and Retina.

Metabolic activation is the primary cause of chemical toxicity including hepatotoxicity. Cytochrome P450 2E (CYP2E) is involved in this process for many hepatotoxicants, including acetaminophen (APAP), one of the most common analgesics and antipyretics. Although the zebrafish is now used as a model for toxicology and toxicity tests, the CYP2E homologue in zebrafish has not been identified yet. In this study, we prepared transgenic zebrafish embryos/larvae expressing rat CYP2E1 and enhanced green fluorescent protein (EGFP) using a ß-actin promoter. Rat CYP2E1 activity was confirmed by the fluorescence of 7-hydroxycoumarin (7-HC), a metabolite of 7-methoxycoumarin that was specific for CYP2 in transgenic larvae with EGFP fluorescence (EGFP [+]) but not in transgenic larvae without EGFP fluorescence (EGFP [-]). APAP (2.5 mM) caused reduction in the size of the retina in EGFP [+] larvae but not in EGFP [-] larvae, while APAP similarly reduced pigmentation in both larvae. APAP at even 1 mM reduced the liver size in EGFP [+] larvae but not in EGFP [-] larvae. APAP-induced reduction of liver size was inhibited by N-acetylcysteine. These results suggest that rat CYP2E1 is involved in some APAP-induced toxicological endpoints in the retina and liver but not in melanogenesis of the developing zebrafish.

Effect of soluble oat fiber on intestinal microenvironment and TNBS-induced colitis.

Soluble oat fibers, including ß-glucan, have been shown to alter the gut microbiome composition and ameliorate DSS-induced colitis; however, the beneficial effect of soluble oat fiber on colonic inflammation is not yet fully understood. In this study, we demonstrated that soluble oat fibers ameliorate T cell-dependent colitis through the induction of peripherally induced regulatory T cells (pTregs). Soluble oat fibers elevated colonic butyrate production dose-dependently, which coincided with the overrepresentation of Faecalibaculum rodentium (an analog of butyrate-producing Holdemanella biformis) in the gut microbiome. Soluble oat fibers promoted the growth of F. rodentium and H. biformis even in vitro, and increased the concentration of butyrate in the culture supernatant. These results indicate that soluble oat fibers are an energy source for butyrate-producing bacteria and are a fermentation substrate. Soluble oat fibers increased the percentage of colonic pTregs and ameliorated the weight loss and inflammation in acute 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis; this may in part be mediated by the increase in IL-10-producing T cells. In conclusion, our results suggest that the administration of soluble oat fibers is a promising prebiotic treatment for the prevention of colitis mediated via altered gut microbiota composition and elevated butyrate production.

Functional analysis of vitamin D receptor (VDR) using adenovirus vector.

Recently, we generated type II rickets model rats, including Vdr(R270L), Vdr(H301Q), Vdr(R270L/H301Q), and Vdr-knockout (KO), by genome editing. All generated animals showed symptoms of rickets, including growth retardation and abnormal bone formation. Among these, only Vdr-KO rats exhibited abnormal skin formation and alopecia. To elucidate the relationship between VDR function and rickets symptoms, each VDR was expressed in human HaCaT-VDR-KO cells using an adenovirus vector. We also constructed an adenovirus vector expressing VDR(V342M) corresponding to human VDR(V346M) which causes alopecia. We compared the nuclear translocation of VDRs after adding 1α,25-dihydroxyvitamin D3 (1,25D3) or 25-hydroxyvitamin D3 (25D3) at final concentrations of 10 and 100 nM, respectively. Both 25D3 and 1,25D3 induced the nuclear translocation of wild type VDR and VDR(V342M). Conversely, VDR(R270L) translocation was observed in the presence of 100 nM 25D3, with almost no translocation following treatment with 10 nM 1,25D3. VDR(R270L/H301Q) failed to undergo nuclear translocation. These results were consistent with their affinity for each ligand. Notably, VDR(R270L/H301Q) may exist in an unliganded form under physiological conditions, and factors interacting with VDR(R270L/H301Q) may be involved in the hair growth cycle. Thus, this novel system using an adenovirus vector could be valuable in elucidating vitamin D receptor functions.

Transfer of quercetin ingested by maternal mice to neonatal mice via breast milk.

This is the first study that quantified quercetin (QUE) and its 16 metabolites in the breast milk of QUE-fed maternal mice, the plasma and urine of that, and neonatal mice. Interestingly, the QUE aglycone concentration in the milk was much higher than in the plasma of maternal mice, suggesting that QUE may exert biological activity in neonates.

Effects of common genetic variants of human uridine diphosphate glucuronosyltransferase subfamilies on irinotecan glucuronidation.

The adverse effects (diarrhea and neutropenia) of irinotecan (7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin) are associated with genetic variants of uridine diphosphate glucuronosyltransferase 1A subfamilies (UGT1As). UGT1As are enzymes that metabolize the active form of irinotecan, 7-ethyl-10 hydroxycamptothecin (SN-38), by glucuronidation in the liver. They are widely known as predictive factors of severe adverse effects, such as neutropenia and diarrhea. Some studies have suggested that variants of UGT1As affect SN-38 glucuronidation activities, thus exerting severe adverse effects. We aimed to identify UGT1A isoforms that show SN-38 glucuronidation activity and determine the relationship between UGT1A variants and SN-38 glucuronidation in vitro. We found that UGT1A1 and UGT1A6-UGT1A10 displayed SN-38 glucuronidation activity. Among these, UGT1A1 was the most active. Furthermore, the variants of these isoforms showed decreased SN-38 glucuronidation activity. In our study, we compared the different variants of UGT1As, such as UGT1A1.6, UGT1A1.7, UGT1A1.27, UGT1A1.35, UGT1A7.3, UGT1A8.4, UGT1A10M59I, and UGT1A10T202I, to determine the differences in the reduction of glucuronidation. Our study elucidates the relationship between UGT1A variants and the level of glucuronidation associated with each variant. Therefore, testing can be done before the initiation of irinotecan treatment to predict potential toxicities and adverse effects.

Development of nanoluciferase-based sensing system that can specifically detect 1α,25-dihydroxyvitamin D in living cells.

Previously, we reported a FLucN-LXXLL+LBD-FLucC system that detects VDR ligands using split firefly luciferase techniques, ligand binding domain (LBD) of VDR, and LXXLL sequences that interact with LBD after VDR ligand binding. In vivo, 25-hydroxyvitamin D3 (25(OH)D3) and 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) act as VDR ligands that bind to VDR, and regulate bone-related gene expression. Therefore, the amount of 25(OH)D3 and 1α,25(OH)2D3 are indicators of bone-related diseases such as rickets and osteoporosis. In this study, we have developed a novel LgBiT-LXXLL+LBD-SmBiT system using NanoLuc Binary Technology (NanoBiT), which has an emission intensity several times higher than that of the split-type firefly luciferase. Furthermore, by using genetic engineering techniques, we attempted to construct a novel system that can specifically detect 1α,25(OH)2D3. Because histidine residues at positions 305 and 397 play important roles in forming a hydrogen bond with a hydroxyl group at position C25 of 25(OH)D3 and 1α,25(OH)2D3, His305 and His397 were each substituted by other amino acids. Consequently, the three mutant VDRs, H305D, H397N, and H397E were equally useful to detect 1α,25(OH)2D3 specifically. In addition, among the 58 variants of the LXXLL sequences, LPYEGSLLLKLLRAPVEE showed the greatest increase in luminescence upon the addition of 25(OH)D3 or 1α,25(OH)2D3. Thus, our novel system using NanoBiT appear to be useful for detecting native vitamin D or its derivatives.

The Impact of Low-Viscosity Soluble Dietary Fibers on Intestinal Microenvironment and Experimental Colitis: A Possible Preventive Application of Alpha-Cyclodextrin in Intestinal Inflammation.

SCOPE: The purpose of this study is to compare the impact of four low-viscosity soluble dietary fibers (DFs) on the intestinal microenvironment, in terms of microbiota composition, short-chain fatty acid (SCFA) production, proportion of colonic peripherally induced regulatory T cells (pTregs), and experimental colitis in mice. METHODS AND RESULTS: Mice are administered 5% w/v low-viscosity soluble DFs in drinking water for 2 weeks. The gut microbiota composition is determined using 16S rRNA sequencing. Luminal SCFAs are quantified by gas chromatography, and colonic pTregs are analyzed using flow cytometry. All low-viscosity soluble DFs promote the growth of beneficial bacteria such as Akkermansia muciniphila and Bacteroides acidifaciens, while eliminating pathogenic bacteria such as Clostridium perfringens. Moreover, two low-viscosity soluble DFs significantly increase the abundance of commensal bacteria and promote the accumulation of propionate and butyrate, leading to marked induction of colonic pTregs. Consistently, these two fibers, in particular α-cyclodextrin, show remarkable anti-inflammatory properties in a colitis mouse model. CONCLUSION: Mice administered any low-viscosity soluble DF show comparable gut microbiota compositions, but differ in terms of bacterial abundance, SCFA concentration, pTreg population, and colitis development. This exploratory study suggests that administration of α-cyclodextrin may be a possible strategy for the prevention of colitis.

Comparison of metabolism and biological properties among positional isomers of quercetin glucuronide in LPS- and RANKL-challenged RAW264.7 cells.

The major quercetin metabolite, quercetin-3-glucuronide, exerts various biological activities, including anti-inflammatory effects. This study aimed to evaluate the metabolic profiles and biological properties of the positional isomers of quercetin monoglucuronides (Q3G, Q7G, Q3'G, and Q4'G) in activated macrophages. In addition to quercetin aglycone, Q7G was more cytotoxic than the other quercetin monoglucuronides (QGs), which corresponded to its lower stability under neutral pH conditions. Q3G was most effective in inhibiting both LPS-dependent induction of IL-6 and RANKL-dependent activation of tartrate-resistant acid phosphatase; however, Q3'G and Q4'G may also help exert biological activities without potential cytotoxicity. The deconjugation efficacy to generate quercetin aglycone differed among QGs, with the highest efficacy in Q3G. These results suggest that the chemical or biological properties and metabolic profiles may depend on the stability of QGs to generate quercetin aglycone using ß-glucuronidase.

Regioselective Glucuronidation of Flavones at C5, C7, and C4' Positions in Human Liver and Intestinal Microsomes: Comparison among Apigenin, Acacetin, and Genkwanin.

Flavones, which are distributed in a variety of plants and foods in nature, possess significant biological activities, including antitumor and anti-inflammatory effects, and are metabolized into glucuronides by uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT) enzymes in humans. In this study, apigenin, acacetin, and genkwanin, flavones having hydroxyl groups at C5, C7, and/or C4'positions were focused on, and the regioselective glucuronidation in human liver and intestinal microsomes was examined. Two glucuronides (namely, AP-7G and AP-4'G for apigenin, AC-5G and AC-7G for acacetin, and GE-5G and GE-4'G for genkwanin) were formed from each flavone by liver and intestinal microsomes, except for only GE-4'G formation from genkwanin by intestinal microsomes. The order of total glucuronidation activities was liver microsomes > intestinal microsomes for apigenin and acacetin, and liver microsomes < intestinal microsomes for genkwanin. The order of CLint values (x-intercept) based on v versus V/[S] plots for apigenin glucuronidation was AP-7G > AP-4'G in liver microsomes and AP-7G < AP-4'G in intestinal microsomes. The order of CLint values was AC-5G < AC-7G for acacetin and GE-5G < GE-4'G genkwanin glucuronidation in both liver and intestinal microsomes. This suggests that the abilities and roles of UGT enzymes in the glucuronidation of apigenin, acacetin, and genkwanin in humans differ depending on the chemical structure of flavones.

Robust osteogenic efficacy of 2α-heteroarylalkyl vitamin D analogue AH-1 in VDR (R270L) hereditary vitamin D-dependent rickets model rats.

Active vitamin D form 1α,25-dihydroxtvitamin D3 (1,25(OH)2D3) plays pivotal roles in calcium homeostasis and osteogenesis via its transcription regulation effect via binding to vitamin D receptor (VDR). Mutated VDR often causes hereditary vitamin D-dependent rickets (VDDR) type II, and patients with VDDR-II are hardly responsive to physiological doses of 1,25(OH)D3. Current therapeutic approaches, including high doses of oral calcium and supraphysiologic doses of 1,25(OH)2D3, have limited success and fail to improve the quality of life of affected patients. Thus, various vitamin D analogues have been developed as therapeutic options. In our previous study, we generated genetically modified rats with mutated Vdr(R270L), an ortholog of human VDR(R274L) isolated from the patients with VDDR-II. The significant reduced affinity toward 1,25(OH)2D3 of rat Vdr(R270L) enabled us to evaluate biological activities of exogenous VDR ligand without 1α-hydroxy group such as 25(OH)D3. In this study, 2α-[2-(tetrazol-2-yl)ethyl]-1α,25(OH)2D3 (AH-1) exerted much higher affinity for Vdr(R270L) in in vitro ligand binding assay than both 25(OH)D3 and 1,25(OH)2D3. A robust osteogenic activity of AH-1 was observed in Vdr(R270L) rats. Only a 40-fold lower dose of AH-1 than that of 25(OH)D3 was effective in ameliorating rickets symptoms in Vdr(R270L) rats. Therefore, AH-1 may be promising for the therapy of VDDR-II with VDR(R274L).