Sumire Sasaki, Yuji Shiozaki, Ai Hanazaki, Megumi Koike, Kazuya Tanifuji, Minori Uga, Kota Kawahara, Ichiro Kaneko, Yasuharu Kawamoto, Pattama Wiriyasermkul, Tomoka Hasegawa, Norio Amizuka, Ken-ichi Miyamoto, Shushi Nagamori, Yoshikatsu Kanai and Hiroko Segawa : Tmem174, a regulator of phosphate transporter prevents hyperphosphatemia., Scientific Reports, Vol.12, No.1, 2022.
(Summary)
Renal type II sodium-dependent inorganic phosphate (Pi) transporters NaPi2a and NaPi2c cooperate with other organs to strictly regulate the plasma Pi concentration. A high Pi load induces expression and secretion of the phosphaturic hormones parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) that enhance urinary Pi excretion and prevent the onset of hyperphosphatemia. How FGF23 secretion from bone is increased by a high Pi load and the setpoint of the plasma Pi concentration, however, are unclear. Here, we investigated the role of Transmembrane protein 174 (Tmem174) and observed evidence for gene co-expression networks in NaPi2a and NaPi2c function. Tmem174 is localized in the renal proximal tubules and interacts with NaPi2a, but not NaPi2c. In Tmem174-knockout (KO) mice, the serum FGF23 concentration was markedly increased but increased Pi excretion and hypophosphatemia were not observed. In addition, Tmem174-KO mice exhibit reduced NaPi2a responsiveness to FGF23 and PTH administration. Furthermore, a dietary Pi load causes marked hyperphosphatemia and abnormal NaPi2a regulation in Tmem174-KO mice. Thus, Tmem174 is thought to be associated with FGF23 induction in bones and the regulation of NaPi2a to prevent an increase in the plasma Pi concentration due to a high Pi load and kidney injury.
Sumire Sasaki, Megumi Koike, Kazuya Tanifuji, Minori Uga, Kota Kawahara, Aoi Komiya, Mizuki Miura, Yamato Harada, Yuki Hamaguchi, Shohei Sasaki, Yuji Shiozaki, Ichiro Kaneko, Ken-ichi Miyamoto and Hiroko Segawa : Dietary polyphosphate has a greater effect on renal damage and FGF23 secretion than dietary monophosphate, The Journal of Medical Investigation : JMI, Vol.69, No.3, 173-179, 2022.
(Summary)
Phosphate (Pi)-containing food additives are used in several forms. Polyphosphate (PPi) salt has more harmful effects than monophosphate (MPi) salt on bone physiology and renal function. This study aimed to analyze the levels of parathyroid hormone PTH and fibroblast growth factor 23 (FGF23) and the expression of renal / intestinal Pi transport-related molecules in mice fed with an MPi or PPi diet. There were no significant differences in plasma Pi concentration and fecal Pi excretion levels between mice fed with the high-MPi and PPi diet. However, more severe tubular dilatation, interstitial fibrosis, and calcification were observed in the kidneys of mice fed with the high PPi diet versus the MPi diet. Furthermore, there was a significant increase in serum FGF23 levels and a decrease in renal phosphate transporter protein expression in mice fed with the PPi diet versus the MPi diet. Furthermore, the high MPi diet was associated with significantly suppressed expression and activity of intestinal alkaline phosphatase protein. In summary, PPi has a more severe effect on renal damage than MPi, as well as induces more FGF23 secretion. Excess FGF23 may be more involved in inflammation, fibrosis, and calcification in the kidney. J. Med. Invest. 69 : 173-179, August, 2022.
Jennifer Price Hackney, J Bentley Hanish, E Carl Wagner, Ichiro Kaneko, W Peter Jurutka and A Pamela Marshall : Dataset on the response of Hut78 cells to novel rexinoids., Data in Brief, Vol.20, 1797-1803, 2018.
MS Sabir, MR Haussler, S Mallick, Ichiro Kaneko, DA Lucas, CA Haussler, GK Whitfield and PW Jurutka : Optimal vitamin D spurs serotonin: 1,25-dihydroxyvitamin D represses serotonin reuptake transport (SERT) and degradation (MAO-A) gene expression in cultured rat serotonergic neuronal cell lines., Genes & Nutrition, 13-19, 2018.
(Summary)
Diminished brain levels of two neurohormones, 5-hydroxytryptamine (5-HT; serotonin) and 1,25-dihydroxyvitamin D (1,25D; active vitamin D metabolite), are proposed to play a role in the atypical social behaviors associated with psychological conditions including autism spectrum disorders and depression. We reported previously that 1,25D induces expression of tryptophan hydroxylase-2 (TPH2), the initial and rate-limiting enzyme in the biosynthetic pathway to 5-HT, in cultured rat serotonergic neuronal cells. However, other enzymes and transporters in the pathway of tryptophan metabolism had yet to be examined with respect to the actions of vitamin D. Herein, we probed the response of neuronal cells to 1,25D by quantifying mRNA expression of serotonin synthesis isozymes, TPH1 and TPH2, as well as expression of the serotonin reuptake transporter (SERT), and the enzyme responsible for serotonin catabolism, monoamine oxidase-A (MAO-A). We also assessed the direct production of serotonin in cell culture in response to 1,25D. Employing quantitative real-time PCR, we demonstrate that mRNAs are 28- to 33-fold induced by 10 nM 1,25D treatment of cultured rat serotonergic neuronal cells (RN46A-B14), and the enhancement of mRNA by 1,25D is dependent on the degree of neuron-like character of the cells. In contrast, examination of , the gene product of which is a target for the SSRI-class of antidepressants, and , which encodes the predominant catabolic enzyme in the serotonin pathway, reveals that their mRNAs are 51-59% repressed by 10 nM 1,25D treatment of RN46A-B14 cells. Finally, serotonin concentrations are significantly enhanced (2.9-fold) by 10 nM 1,25D in this system. These results are consistent with the concept that vitamin D maintains extracellular fluid serotonin concentrations in the brain, thereby offering an explanation for how vitamin D could influence the trajectory and development of neuropsychiatric disorders. Given the profile of gene regulation in cultured RN46A-B14 serotonergic neurons, we conclude that 1,25D acts not only to induce serotonin synthesis, but also functions at an indirect, molecular-genomic stage to mimic SSRIs and MAO inhibitors, likely elevating serotonin in the CNS. These data suggest that optimal vitamin D status may contribute to improving behavioral pathophysiologies resulting from dysregulation of serotonergic neurotransmission.
Ichiro Kaneko, Hiroko Segawa, Ikuta Kayo, Hanazaki Ai, Fujii Toru, Sawako Tatsumi, Kido Shinsuke, Hasegawa Tomoka, Amizuka Norio, Saito Hitoshi and Ken-ichi Miyamoto : Eldecalcitol Causes FGF23 Resistance for Pi Reabsorption and Improves Rachitic Bone Phenotypes in the Male Hyp Mouse., Endocrinology, Vol.159, No.7, 2741-2758, 2018.
(Summary)
X-linked hypophosphatemia (XLH), the most common form of inheritable rickets, is caused by inactivation of phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and leads to fibroblast growth factor (FGF) 23-dependent renal inorganic phosphate (Pi) wasting. In the present study, we investigated whether maintaining Pi homeostasis with a potent vitamin D3 analog, eldecalcitol [1α,25-dihydroxy-2β-(3-hydroxypropyloxy) vitamin D3; ED71], could improve hypophosphatemic rickets in a murine model of XLH, the Hyp mouse. Vehicle, ED71, or 1,25-dihydroxyvitamin D was subcutaneously injected five times weekly in wild-type (WT) and Hyp mice for 4 weeks, from 4 to 8 weeks of age. Injection of ED71 into WT mice suppressed the synthesis of renal 1,25-dihydroxyvitamin D and promoted phosphaturic activity. In contrast, administration of ED71 to Hyp mice completely restored renal Pi transport and NaPi-2a protein levels, although the plasma-intact FGF23 levels were further increased. In addition, ED71 markedly increased the levels of the scaffold proteins, renal sodium-hydrogen exchanger regulatory factor 1, and ezrin in the Hyp mouse kidney. Treatment with ED71 increased the body weight and improved hypophosphatemia, the bone volume/total volume, bone mineral content, and growth plate structure in Hyp mice. Thus, ED71 causes FGF23 resistance for phosphate reabsorption and improves rachitic bone phenotypes in Hyp mice. In conclusion, ED71 has opposite effects on phosphate homeostasis in WT and Hyp mice. Analysis of Hyp mice treated with ED71 could result in an additional model for elucidating PHEX abnormalities.
BJ Hanish, JF Price Hackney, Ichiro Kaneko, N Ma, A der Vaart van, CE Wagner, PW Jurutka and PA Marshall : A novel gene expression analytics-based approach to structure aided design of rexinoids for development as next-generation cancer therapeutics., Steroids, Vol.135, 36-49, 2018.
(Summary)
Rexinoids are powerful ligands that bind to retinoid-X-receptors (RXRs) and show great promise as therapeutics for a wide range of diseases, including cancer. However, only one rexinoid, bexarotene (Targretin TM) has been successfully transitioned from the bench to the clinic and used to treat cutaneous T-cell lymphoma (CTCL). Our goal is to develop novel potent rexinoids with a less untoward side effect profile than bexarotene. To this end, we have synthesized a wide array of rexinoids with EC values and biological activity similar to bexarotene. In order to determine their suitability for additional downstream analysis, and to identify potential candidate analogs for clinical translation, we treated human CTCL cells in culture and employed microarray technology to assess gene expression profiles. We analyzed twelve rexinoids and found they could be stratified into three distinct categories based on their gene expression: similar to bexarotene, moderately different from bexarotene, and substantially different from bexarotene. Surprisingly, small changes in the structure of the bexarotene parent compound led to marked differences in gene expression profiles. Furthermore, specific analogs diverged markedly from our hypothesis in expression of genes expected to be important for therapeutic promise. However, promoter analysis of genes whose expression was analyzed indicates general regulatory trends along structural frameworks. Our results suggest that certain structural motifs, particularly the basic frameworks found in analog 4 and analog 9, represent important starting points to exploit in generating additional rexinoids for future study and therapeutic applications.
Atsumi Miyagawa, Sawako Tatsumi, Wako Takahama, Osamu Fujii, Kenta Nagamoto, Emi Kinoshita, Kengo Nomura, Kayo Ikuta, Toru Fujii, Ai Hanazaki, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : The sodium phosphate cotransporter family and nicotinamide phosphoribosyltransferase contribute to the daily oscillation of plasma inorganic phosphate concentration., Kidney International, Vol.93, No.5, 1073-1085, 2018.
(Summary)
mice, NAD levels were significantly reduced in the liver, kidney, and intestine, and the daily oscillation (active and rest phases) of the plasma phosphate concentration was attenuated. Thus, the Nampt/NAD
CM Dussik, M Hockley, A Grozić, Ichiro Kaneko, L Zhang, MS Sabir, J Park, J Wang, CA Nickerson, SH Yale, CJ Rall, AE Foxx-Orenstein, CM Borror, TR Sandrin and PW Jurutka : Gene Expression Profiling and Assessment of Vitamin D and Serotonin Pathway Variations in Patients With Irritable Bowel Syndrome., Journal of Neurogastroenterology and Motility, Vol.24, No.1, 96-106, 2018.
Osamu Fujii, Sawako Tatsumi, Mao Ogata, Tomohiro Arakaki, Haruna Sakaguchi, Kengo Nomura, Atsumi Miyagawa, Kayo Ikuta, Ai Hanazaki, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : Effect of Osteocyte-Ablation on Inorganic Phosphate Metabolism: Analysis of Bone-Kidney-Gut Axis., Frontiers in Endocrinology, Vol.8, 2017.
(Summary)
In response to kidney damage, osteocytes increase the production of several hormones critically involved in mineral metabolism. Recent studies suggest that osteocyte function is altered very early in the course of chronic kidney disease. In the present study, to clarify the role of osteocytes and the canalicular network in mineral homeostasis, we performed four experiments. In Experiment 1, we investigated renal and intestinal Pi handling in osteocyte-less (OCL) model mice [transgenic mice with the dentin matrix protein-1 promoter-driven diphtheria toxin (DT)-receptor that were injected with DT]. In Experiment 2, we administered granulocyte colony-stimulating factor to mice to disrupt the osteocyte canalicular network. In Experiment 3, we investigated the role of osteocytes in dietary Pi signaling. In Experiment 4, we analyzed gene expression level fluctuations in the intestine and liver by comparing mice fed a high Pi diet and OCL mice. Together, the findings of these experiments indicate that osteocyte ablation caused rapid renal Pi excretion (
These findings indicate that abnormal Pi metabolism may also be involved in tight junction molecules such as Cldns that are affected by Npt2b deficiency.
Sawako Tatsumi, A Miyagawa, Ichiro Kaneko, Y Shiozaki, Hiroko Segawa and Ken-ichi Miyamoto : Regulation of renal phosphate handling: inter-organ communication in health and disease., Journal of Bone and Mineral Metabolism, Vol.34, No.1, 1-10, 2016.
(Summary)
In this review, we focus on the interconnection of inorganic phosphate (Pi) homeostasis in the network of the bone-kidney, parathyroid-kidney, intestine-kidney, and liver-kidney axes. Such a network of organ communication is important for body Pi homeostasis. Normalization of serum Pi levels is a clinical target in patients with chronic kidney disease (CKD). Particularly, disorders of the fibroblast growth factor 23/klotho system are observed in early CKD. Identification of phosphaturic factors from the intestine and liver may enhance our understanding of body Pi homeostasis and Pi metabolism disturbances in CKD patients.
Ichiro Kaneko, K Rimpi Saini, P Kristin Griffin, Kerr Graham Whitfield, R Mark Haussler and W Peter Jurutka : FGF23 gene regulation by 1,25-dihydroxyvitamin D: opposing effects in adipocytes and osteocytes., The Journal of Endocrinology, 2015.
(Summary)
In a closed endocrine loop, 1,25-dihydroxyvitamin D3 (1,25D) induces the expression of fibroblast growth factor-23 (FGF23) in bone, with the phosphaturic peptide in turn acting at kidney to feedback repress CYP27B1 and induce CYP24A1 to limit the levels of 1,25D. In 3T3-L1 differentiated adipocytes, 1,25D represses FGF23 and leptin expression, while not affecting leptin receptor transcription, but inducing C/EBP. Conversely, in UMR-106 osteoblast-like cells, FGF23 mRNA concentrations are upregulated by 1,25D, an effect that is blunted by lysophosphatidic acid, a cell-surface acting ligand. Progressive truncation of the mouse FGF23 proximal promoter linked in luciferase reporter constructs reveals a 1,25D-responsive region between -400 and -200 bp. A 0.6 kb fragment of the mouse FGF23 promoter, linked in a reporter construct, responds to 1,25D with a 4-fold enhancement of transcription in transfected K562 cells. Mutation of either an ETS1 site at -346 bp, or an adjacent candidate VDR/Nurr1-element, in the 0.6 kb reporter construct reduces the transcriptional activity elicited by 1,25D to a level that is not significantly different from a minimal promoter. This composite ETS1-VDR/Nurr1 cis-element may function as a switch between induction (osteocytes) and repression (adipocytes) of FGF23, depending on the cellular setting of transcription factors. Moreover, experiments demonstrate that a 1kb mouse FGF23 promoter-reporter construct, transfected into MC3T3 osteoblast-like cells, responds to high calcium challenge with a statistically significant 1.7-2.0-fold enhancement of transcription. Thus, the FGF23 proximal promoter harbors cis-elements that drive responsiveness to 1,25D and calcium, agents that induce FGF23 to curtail the pathologic consequences of their excess.
Ichiro Kaneko, S Marya Sabir, M Christopher Dussik, Kerr G Whitfield, Amitis Karrys, Jui-Cheng Hsieh, R Mark Haussler, B Mark Meyer, Wesley J Pike and W Peter Jurutka : 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D., The FASEB journal, Vol.29, No.9, 4023-4035, 2015.
(Summary)
To investigate vitamin D-related control of brain-expressed genes, candidate vitamin D responsive elements (VDREs) at -7/-10 kb in human tryptophan hydroxylase (TPH)2 were probed. Both VDREs bound the vitamin D receptor (VDR)-retinoid X receptor (RXR) complex and drove reporter gene transcription in response to 1,25-dihydroxyvitamin D3 (1,25D). Brain TPH2 mRNA, encoding the rate-limiting enzyme in serotonin synthesis, was induced 2.2-fold by 10 nM 1,25D in human U87 glioblastoma cells and 47.8-fold in rat serotonergic RN46A-B14 cells. 1,25D regulation of leptin (Lep), encoding a serotoninlike satiety factor, was also examined. In mouse adipocytes, 1,25D repressed leptin mRNA levels by at least 84%, whereas 1,25D induced leptin mRNA 15.1-fold in human glioblastoma cells. Chromatin immunoprecipitation sequencing analysis of the mouse Lep gene in response to 1,25D revealed a cluster of regulatory sites (cis-regulatory module; CRM) at -28 kb that 1,25D-dependently docked VDR, RXR, C/EBP, and RUNX2. This CRM harbored 3 VDREs and single C/EBP and RUNX2 sites. Therefore, the expression of human TPH2 and mouse Lep are governed by 1,25D, potentially via respective VDREs located at -7/-10 kb and -28 kb. These results imply that vitamin D affects brain serotonin concentrations, which may be relevant to psychiatric disorders, such as autism, and may control leptin levels and affect eating behavior.-Kaneko, I., Sabir, M. S., Dussik, C. M., Whitfield, G. K., Karrys, A., Hseih, J.-C., Haussler, M. R., Meyer, M. B., Pike, J. W., Jurutka, P. W. 1,25-dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D.
Yuji Shiozaki, Hiroko Segawa, Saori Ohnishi, Akiko Ohi, Mikiko Ito, Ichiro Kaneko, Shinsuke Kido, Sawako Tatsumi and Ken-ichi Miyamoto : Relationship between sodium-dependent phosphate transporter (NaPi-IIc) function and cellular vacuole formation in opossum kidney cells., The Journal of Medical Investigation : JMI, Vol.62, No.3-4, 209-218, 2015.
(Summary)
NaPi-IIc/SLC34A3 is a sodium-dependent inorganic phosphate (Pi) transporter in the renal proximal tubules and its mutations cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH). In the present study, we created a specific antibody for opossum SLC34A3, NaPi-IIc (oNaPi-IIc), and analyzed its localization and regulation in opossum kidney cells (a tissue culture model of proximal tubular cells). Immunoreactive oNaPi-IIc protein levels increased during the proliferative phase and decreased during differentiation. Moreover, stimulating cell growth upregulated oNaPi-IIc protein levels, whereas suppressing cell proliferation downregulated oNaPi-IIc protein levels. Immunocytochemistry revealed that endogenous and exogenous oNaPi-IIc proteins localized at the protrusion of the plasma membrane, which is a phosphatidylinositol 4,5-bisphosphate (PIP2) rich-membrane, and at the intracellular vacuolar membrane. Exogenous NaPi-IIc also induced cellular vacuoles and localized in the plasma membrane. The ability to form vacuoles is specific to electroneutral NaPi-IIc, and not electrogenic NaPi-IIa or NaPi-IIb. In addition, mutations of NaPi-IIc (S138F and R468W) in HHRH did not cause cellular PIP2-rich vacuoles. In conclusion, our data anticipate that NaPi-IIc may regulate PIP2 production at the plasma membrane and cellular vesicle formation.
A Pamela Marshall, W Peter Jurutka, E Carl Wagner, Arjan der Vaart van, Ichiro Kaneko, I Pedro Chavez, Ning Ma, S Jaskaran Bhogal, Pritika Shahani, C Johnathon Swierski and Mairi MacNeill : Analysis of differential secondary effects of novel rexinoids: select rexinoid X receptor ligands demonstrate differentiated side effect profiles., Pharmacology Research & Perspectives, Vol.3, No.2, 2015.
(Summary)
In order to determine the feasibility of utilizing novel rexinoids for chemotherapeutics and as potential treatments for neurological conditions, we undertook an assessment of the side effect profile of select rexinoid X receptor (RXR) analogs that we reported previously. We assessed pharmacokinetic profiles, lipid and thyroid-stimulating hormone (TSH) levels in rats, and cell culture activity of rexinoids in sterol regulatory element-binding protein (SREBP) induction and thyroid hormone inhibition assays. We also performed RNA sequencing of the brain tissues of rats that had been dosed with the compounds. We show here for the first time that potent rexinoid activity can be uncoupled from drastic lipid changes and thyroid axis variations, and we propose that rexinoids can be developed with improved side effect profiles than the parent compound, bexarotene (1).
Kengo Nomura, Sawako Tatsumi, Atsumi Miyagawa, Yuji Shiozaki, Shohei Sasaki, Ichiro Kaneko, Mikiko Ito, Shinsuke Kido, Hiroko Segawa, Mitsue Sano, Tsutomu Fukuwatari, Katsumi Shibata and Ken-ichi Miyamoto : Hepatectomy-related hypophosphatemia: a novel phosphaturic factor in the liver-kidney axis., Journal of the American Society of Nephrology, Vol.25, No.4, 761-772, 2014.
(Summary)
Marked hypophosphatemia is common after major hepatic resection, but the pathophysiologic mechanism remains unknown. We used a partial hepatectomy (PH) rat model to investigate the molecular basis of hypophosphatemia. PH rats exhibited hypophosphatemia and hyperphosphaturia. In renal and intestinal brush-border membrane vesicles isolated from PH rats, Na(+)-dependent phosphate (Pi) uptake decreased by 50%-60%. PH rats also exhibited significantly decreased levels of renal and intestinal Na(+)-dependent Pi transporter proteins (NaPi-IIa [NaPi-4], NaPi-IIb, and NaPi-IIc). Parathyroid hormone was elevated at 6 hours after PH. Hyperphosphaturia persisted, however, even after thyroparathyroidectomy in PH rats. Moreover, DNA microarray data revealed elevated levels of nicotinamide phosphoribosyltransferase (Nampt) mRNA in the kidney after PH, and Nampt protein levels and total NAD concentration increased significantly in the proximal tubules. PH rats also exhibited markedly increased levels of the Nampt substrate, urinary nicotinamide (NAM), and NAM catabolites. In vitro analyses using opossum kidney cells revealed that NAM alone did not affect endogenous NaPi-4 levels. However, in cells overexpressing Nampt, the addition of NAM led to a marked decrease in cell surface expression of NaPi-4 that was blocked by treatment with FK866, a specific Nampt inhibitor. Furthermore, FK866-treated mice showed elevated renal Pi reabsorption and hypophosphaturia. These findings indicate that hepatectomy-induced hypophosphatemia is due to abnormal NAM metabolism, including Nampt activation in renal proximal tubular cells.
Itai-itai disease is thought to be the result of chronic cadmium (Cd) intoxication. Renal proximal tubules are a major target of Cd toxicity. The whole mechanism of the adverse effects of Cd remains unresolved, especially how renal damage is related to the development of bone lesions. Fibroblast growth factor 23 (FGF23) is a bone-derived phosphaturic factor that regulates vitamin D and inorganic phosphate metabolism in the kidney. To clarify the role of FGF23 on Cd toxicity, we investigated the mechanisms of Cd-induced FGF23 production in the bone. Cd injection into mice significantly increased plasma FGF23 concentrations, but did not change FGF23 mRNA expression in bone. GalNAc-T3 is involved in secreting intact FGF23. To determine potential roles of GalNAc-T3 in Cd-induced FGF23 production, we examined the effect of Cd on GalNAc-T3 mRNA expression in vivo and in vitro. GalNAc-T3 gene expression was significantly increased in the bones of Cd-injected mice. Cd also enhanced the expression of GalNAc-T3 in cultured osteosarcoma UMR106 cells and primary osteocytes. Cd activated aryl hydrocarbon receptors (AhR) and AhR were required for GalNAc-T3 gene expression induced by Cd. In addition, Cd-dependent FGF23 production was completely inhibited by an AhR antagonist. AhR siRNA markedly suppressed the stimulation of transcriptional activity by Cd. Furthermore, Cd induced AhR activation via phosphorylation of Ser-68 by p38 kinase in the nuclear export signal of AhR. Thus, Cd stimulated GalNAc-T3 gene transcription via enhanced AhR binding to the GalNAc-T3 promoter. These findings suggest that the Cd-induced increase in GalNAc-T3 suppresses proteolytic processing of FGF23 and increases serum FGF23 concentrations.
Otoki Nakahashi, Hironori Yamamoto, Sarasa Tanaka, Mina Kozai, Yuichiro Takei, Masashi Masuda, Ichiro Kaneko, Yutaka Taketani, Masayuki Iwano, Ken-ichi Miyamoto and Eiji Takeda : Short-term dietary phosphate restriction up-regulates ileal fibroblast growth factor 15 gene expression in mice., Journal of Clinical Biochemistry and Nutrition, Vol.54, No.2, 102-108, 2014.
(Summary)
Members of the fibroblast growth factor (FGF) 19 subfamily, including FGF23, FGF15/19, and FGF21, have a role as endocrine factors which influence the metabolism of inorganic phosphate (Pi) and vitamin D, bile acid, and energy. It has been reported that dietary Pi regulates circulating FGF23. In this study, the short-term effects of dietary Pi restriction on the expression of FGF19 subfamily members in mice were analyzed. An initial analysis confirmed plasma FGF23 levels positively correlated with the amount of dietary Pi. On the other hand, ileal Fgf15 gene expression, but not hepatic Fgf21 gene expression, was up-regulated by dietary Pi restriction. In addition, we observed the increase of plasma 1,25-dihydroxyvitamin D [1,25(OH)2D] levels by dietary Pi restriction, and the up-regulation of ileal Fgf15 mRNA expression by 1,25(OH)2D3 and vitamin D receptor (VDR). Importantly, dietary Pi restriction-induced Fgf15 gene expression was prevented in VDR-knockout mice. Furthermore, diurnal variations of plasma triglyceride concentrations and hepatic mRNA expression of the bile acid synthesis enzyme Cyp7a1 as one of Fgf15 negative target genes was influenced by dietary Pi restriction. These results suggest that dietary Pi restriction up-regulates ileal Fgf15 gene expression through 1,25(OH)2D3 and VDR, and may affect hepatic bile acid homeostasis.
Jui-Cheng Hsieh, C Rudolf Estess, Ichiro Kaneko, Kerr G Whitfield, W Peter Jurutka and R Mark Haussler : Vitamin D receptor-mediated control of Soggy, Wise, and Hairless gene expression in keratinocytes., The Journal of Endocrinology, Vol.220, No.2, 165-178, 2014.
(Summary)
The vitamin D receptor (VDR), but not its hormonal ligand, 1,25-dihydroxyvitamin D3 (1,25D), is required for the progression of the mammalian hair cycle. We studied three genes relevant to hair cycle signaling, DKKL1 (Soggy), SOSTDC1 (Wise), and HR (Hairless), to determine whether their expression is regulated by VDR and/or its 1,25D ligand. DKKL1 mRNA was repressed 49-72% by 1,25D in primary human and CCD-1106 KERTr keratinocytes; a functional vitamin D responsive element (VDRE) was identified at -9590 bp in murine Soggy. Similarly, SOSTDC1 mRNA was repressed 41-59% by 1,25D in KERTr and primary human keratinocytes; a functional VDRE was located at -6215 bp in human Wise. In contrast, HR mRNA was upregulated 1.56- to 2.77-fold by 1,25D in primary human and KERTr keratinocytes; a VDRE (TGGTGAgtgAGGACA) consisting of an imperfect direct repeat separated by three nucleotides (DR3) was identified at -7269 bp in the human Hairless gene that mediated dramatic induction, even in the absence of 1,25D ligand. In parallel, a DR4 thyroid hormone responsive element, TGGTGAggccAGGACA, was identified at +1304 bp in the human HR gene that conferred tri-iodothyronine (T3)-independent transcriptional activation. Because the thyroid hormone receptor controls HR expression in the CNS, whereas VDR functions in concert with the HR corepressor specifically in skin, a model is proposed wherein unliganded VDR upregulates the expression of HR, the gene product of which acts as a downstream comodulator to feedback-repress DKKL1 and SOSTDC1, resulting in integration of bone morphogenic protein and Wnt signaling to drive the mammalian hair cycle and/or influencing epidermal function.
W Peter Jurutka, Ichiro Kaneko, Joanna Yang, S Jaskaran Bhogal, C Johnathon Swierski, R Christa Tabacaru, A Luis Montano, C Chanh Huynh, A Rabia Jama, D Ryan Mahelona, T Joseph Sarnowski, M Lisa Marcus, Alexis Quezada, Brittney Lemming, A Maria Tedesco, J Audra Fischer, A Said Mohamed, W Joseph Ziller, Ning Ma, M Geoffrey Gray, Arjan der Vaart van, A Pamela Marshall and E Carl Wagner : Modeling, synthesis, and biological evaluation of potential retinoid X receptor (RXR) selective agonists: novel analogues of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (bexarotene) and (E)-3-(3-(1,2,3,4-tetrahydro-1,1,4,4,6-pentamethylnaphthalen-7-yl)-4-hydroxyphenyl)acrylic acid (CD3254)., Journal of Medicinal Chemistry, Vol.56, No.21, 8432-8454, 2013.
(Summary)
Three unreported analogues of 4-[1-(3,5,5,8,8-pentamethyl-5-6-7-8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (1), otherwise known as bexarotene, as well as four novel analogues of (E)-3-(3-(1,2,3,4-tetrahydro-1,1,4,4,6-pentamethylnaphthalen-7-yl)-4-hydroxyphenyl)acrylic acid (CD3254), are described and evaluated for their retinoid X receptor (RXR) selective agonism. Compound 1 has FDA approval as a treatment for cutaneous T-cell lymphoma (CTCL), although treatment with 1 can elicit side-effects by disrupting other RXR-heterodimer receptor pathways. Of the seven modeled novel compounds, all analogues stimulate RXR-regulated transcription in mammalian 2 hybrid and RXRE-mediated assays, possess comparable or elevated biological activity based on EC50 profiles, and retain similar or improved apoptotic activity in CTCL assays compared to 1. All novel compounds demonstrate selectivity for RXR and minimal crossover onto the retinoic acid receptor (RAR) compared to all-trans-retinoic acid, with select analogues also reducing inhibition of other RXR-dependent pathways (e.g., VDR-RXR). Our results demonstrate that further improvements in biological potency and selectivity of bexarotene can be achieved through rational drug design.
K Rimpi Saini, Ichiro Kaneko, W Peter Jurutka, Ryan Forster, Antony Hsieh, Jui-Cheng Hsieh, R Mark Haussler and Kerr G Whitfield : 1,25-dihydroxyvitamin D(3) regulation of fibroblast growth factor-23 expression in bone cells: evidence for primary and secondary mechanisms modulated by leptin and interleukin-6., Calcified Tissue International, Vol.92, No.4, 339-353, 2012.
(Summary)
Fibroblast growth factor-23 (FGF23) is a circulating hormone that acts to correct hyperphosphatemic states by inhibiting renal phosphate reabsorption and to prevent hypervitaminosis D by feedback repressing 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) biosynthesis. FGF23 gene expression in the osteoblast/osteocyte is induced by the nuclear vitamin D receptor (VDR) bound to 1,25(OH)2D3, but cycloheximide sensitivity of this induction suggests that it may occur largely via secondary mechanisms requiring cooperating transcription factors. We therefore sought to identify 1,25(OH)2D3-regulated transcription factors that might impact FGF23 expression. Although neither leptin nor interleukin-6 (IL-6) alone affects FGF23 expression, leptin treatment was found to potentiate 1,25(OH)2D3 upregulation of FGF23 in UMR-106 cells, whereas IL-6 treatment blunted this upregulation. Genomic analyses revealed conserved binding sites for STATs (signal transduction mediators of leptin and IL-6 action) along with transcription factor ETS1 in human and other mammalian FGF23 genes. Further, STAT3, STAT1, ETS1, and VDR mRNAs were induced in a dose-dependent manner by 1,25(OH)2D3 in UMR-106 cells. Bioinformatic analysis identified nine potential VDREs in a genomic interval containing human FGF23. Six of the putative VDREs were capable of mediating direct transcriptional activation of a heterologous reporter gene when bound by a 1,25(OH)2D3-liganded VDR complex. A model is proposed wherein 1,25(OH)2D3 upregulates FGF23 production directly via multiple VDREs and indirectly via induction of STAT3, ETS1, and VDR transcription factors that are then activated via cell surface and intracellular signaling to cooperate in the induction of FGF23 through DNA looping and generation of euchromatin architecture.
(Keyword)
Animals / Bone Neoplasms / Bone and Bones / COS Cells / Calcitriol / Cell Line / Cell Line, Tumor / Cercopithecus aethiops / Fibroblast Growth Factors / Gene Expression Regulation / HEK293 Cells / Humans / Interleukin-6 / Leptin / Models, Animal / Osteosarcoma / Rats / Receptors, Calcitriol / STAT Transcription Factors / Signal Transduction
K Julie Furmick, Ichiro Kaneko, N Angela Walsh, Joanna Yang, S Jaskaran Bhogal, M Geoffrey Gray, C Juan Baso, O Drew Browder, S Jessica L Prentice, A Luis Montano, C Chanh Huynh, M Lisa Marcus, G Dorian Tsosie, S Jungeun Kwon, Alexis Quezada, M Nicole Reyes, Brittney Lemming, Puneet Saini, Arjan der Vaart van, L Thomas Groy, A Pamela Marshall, W Peter Jurutka and E Carl Wagner : Modeling, synthesis and biological evaluation of potential retinoid X receptor-selective agonists: novel halogenated analogues of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (bexarotene)., ChemMedChem, Vol.7, No.9, 1551-1566, 2012.
(Summary)
The synthesis of halogenated analogues of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (1), known commonly as bexarotene, and their evaluation for retinoid X receptor (RXR)-specific agonist performance is described. Compound 1 is FDA approved to treat cutaneous T-cell lymphoma (CTCL); however, bexarotene treatment can induce hypothyroidism and elevated triglyceride levels, presumably by disrupting RXR heterodimer pathways for other nuclear receptors. The novel halogenated analogues in this study were modeled and assessed for their ability to bind to RXR and stimulate RXR homodimerization in an RXRE-mediated transcriptional assay as well as an RXR mammalian-2-hybrid assay. In an array of eight novel compounds, four analogues were discovered to promote RXR-mediated transcription with EC(50) values similar to that of 1 and are selective RXR agonists. Our approach also uncovered a periodic trend of increased binding and homodimerization of RXR when substituting a halogen atom for a proton ortho to the carboxylic acid on 1.
A Pamela Marshall, Zachary Hernandez, Ichiro Kaneko, Tim Widener, Christa Tabacaru, Izayadeth Aguayo and W Peter Jurutka : Discovery of novel vitamin D receptor interacting proteins that modulate 1,25-dihydroxyvitamin D3 signaling., The Journal of Steroid Biochemistry and Molecular Biology, Vol.132, No.1-2, 147-159, 2012.
(Summary)
The nuclear vitamin D receptor (VDR) modulates gene transcription in 1,25-dihydroxyvitamin D(3) (1,25D) target tissues such as kidney, intestine, and bone. VDR is also expressed in heart, and 1,25D deficiency may play a role in the acceleration of cardiovascular disease. Employing a yeast two-hybrid system and a human heart library, using both a 1,25D-independent and 1,25D-dependent screen, we discovered six candidate VDR interacting proteins (VIPs). These novel VIPs include CXXC5, FASTK, NR4A1, TPM2, MYL3 and XIRP1. Mammalian two-hybrid assays as well as GST pull-downs were used to confirm VIP-VDR interaction, and the combination of these two assays reveals that CXXC5, XIRP1, FASTK and NR4A1 interactions with VDR may be modulated by 1,25D. The functional effects of these VIPs on 1,25D-mediated gene expression were explored in transcriptional assays employing three separate and distinct 1,25D-responsive element (VDRE)-driven luciferase reporter genes in transfected Caco-2 and HEK-293 cells, and in a C2C12 myoblast line. FASTK and TPM2 activated expression in all cell line and promoter contexts, while CXXC5 and XIRP1 exhibited differing effects depending on the cell line and promoter employed, suggesting promoter and cell-specific effects of these unique VIPs on VDR signaling. Further evaluation of the interaction between CXXC5 and VDR revealed that CXXC5 acts in a dose-dependent manner to stimulate VDR-mediated transcription on select VDREs. Identification of novel heart VIPs and their influence on VDR activity may increase our understanding of how vitamin D impacts cardiac physiology and may facilitate development of VDR/VIP drug analogs to combat heart disease.
(Keyword)
Animals / Caco-2 Cells / Carrier Proteins / Cell Line / DNA-Binding Proteins / HCT116 Cells / HEK293 Cells / Humans / Mice / Myocardium / Nuclear Proteins / Nuclear Receptor Subfamily 4, Group A, Member 1 / Protein-Serine-Threonine Kinases / Receptors, Calcitriol / Tropomyosin / Two-Hybrid System Techniques / Vitamin D
Shoji Kuwahara, Fumito Aranami, Hiroko Segawa, Akemi Onitsuka, Naoko Honda, Rieko Tominaga, Etsuyo Hanabusa, Ichiro Kaneko, Setsuko Yamanaka, Shohei Sasaki, Akiko Ohi, Kengo Nomura, Sawako Tatsumi, Shinsuke Kido, Mikiko Ito and Ken-ichi Miyamoto : Identification and functional analysis of a splice variant of mouse sodium-dependent phosphate transporter Npt2c., The Journal of Medical Investigation : JMI, Vol.59, No.1-2, 116-126, 2012.
(Summary)
Mutations in the SLC34A3 gene, a sodium-dependent inorganic phosphate (Pi) cotransporter, also referred to as NaPi IIc, causes hereditary hypophosphatemic rickets with hypercalciuria (HHRH), an autosomal recessive disorder. In human and rodent, NaPi IIc is mainly localized in the apical membrane of renal proximal tubular cells. In this study, we identified mouse NaPi IIc variant (Npt2c-v1) that lacks the part of the exon 3 sequence that includes the assumed translation initiation site of Npt2c. Microinjection of mouse Npt2c-v1 cRNA into Xenopus oocytes demonstrated that Npt2c-v1 showed sodium-dependent Pi cotransport activity. The characterization of pH dependency showed activation at extracellular alkaline-pH. Furthermore, Npt2c-v1 mediated Pi transport activity was significantly higher at any pH value than those of Npt2c. In an in vitro study, the localization of the Npt2c-v1 protein was detected in the apical membrane in opossum kidney cells. The expression of Npt2c-v1 mRNA was detected in the heart, spleen, testis, uterus, placenta, femur, cerebellum, hippocampus, diencephalon and brain stem of mouse. Using mouse bone primary cultured cells, we showed the expression of Npt2c-v1 mRNA. In addition, the Npt2c protein was detected in the spermatozoa head. Thus, Npt2c-v1 was expressed in extra-renal tissues such as epididymal spermatozoa and may function as a sodium-dependent phosphate transporter.
(Keyword)
Alternative Splicing / Animals / COS Cells / Cercopithecus aethiops / Female / Kidney / Male / Mice / Mice, Inbred C57BL / Opossums / Osteoblasts / Osteocytes / Primary Cell Culture / Sodium-Phosphate Cotransporter Proteins, Type IIc
E Ryan Forster, W Peter Jurutka, Jui-Cheng Hsieh, A Carol Haussler, L Christine Lowmiller, Ichiro Kaneko, R Mark Haussler and G Whitfield Kerr : Vitamin D receptor controls expression of the anti-aging klotho gene in mouse and human renal cells., Biochemical and Biophysical Research Communications, Vol.414, No.3, 557-562, 2011.
(Summary)
Isoforms of the mammalian klotho protein serve as membrane co-receptors that regulate renal phosphate and calcium reabsorption. Phosphaturic effects of klotho are mediated in cooperation with fibroblast growth factor receptor-1 and its FGF23 ligand. The vitamin D receptor and its 1,25-dihydroxyvitamin D(3) ligand are also crucial for calcium and phosphate regulation at the kidney and participate in a feedback loop with FGF23 signaling. Herein we characterize vitamin D receptor-mediated regulation of klotho mRNA expression, including the identification of vitamin D responsive elements (VDREs) in the vicinity of both the mouse and human klotho genes. In keeping with other recent studies of vitamin D-regulated genes, multiple VDREs control klotho expression, with the most active elements located at some distance (-31 to -46 kb) from the klotho transcriptional start site. We therefore postulate that the mammalian klotho gene is up-regulated by liganded VDR via multiple remote VDREs. The phosphatemic actions of 1,25-dihydroxyvitamin D(3) are thus opposed via the combined phosphaturic effects of FGF23 and klotho, both of which are upregulated by the liganded vitamin D receptor.
(Keyword)
Aging / Animals / Cell Line / Gene Expression Regulation / Glucuronidase / Humans / Kidney / Ligands / Mice / RNA, Messenger / Receptors, Calcitriol / Vitamin D / Vitamin D Response Element
An inorganic phosphate (P(i))-restricted diet is important for patients with chronic kidney disease and patients on hemodialysis. Phosphate binders are essential for preventing hyperphosphatemia and ectopic calcification. The sodium-dependent P(i) (Na/P(i)) transport system is involved in intestinal P(i) absorption and is regulated by several factors. The type II sodium-dependent P(i) transporter Npt2b is expressed in the brush-border membrane in intestinal epithelial cells and transports P(i). In the present study, we analyzed the phenotype of Npt2b(-/-) and hetero(+/-) mice. Npt2b(-/-) mice died in utero soon after implantation, indicating that Npt2b is essential for early embryonic development. At 4 wk of age, Npt2b(+/-) mice showed hypophosphatemia and low urinary P(i) excretion. Plasma fibroblast growth factor 23 levels were significantly decreased and 1,25(OH)(2)D(3) levels were significantly increased in Npt2b(+/-) mice compared with Npt2b(+/+) mice. Npt2b mRNA levels were reduced to 50% that in Npt2b(+/+) mice. In contrast, renal Npt2a and Npt2c transporter protein levels were significantly increased in Npt2b(+/-) mice. At 20 wk of age, Npt2b(+/-) mice showed hypophosphaturia and reduced Na/P(i) cotransport activity in the distal intestine. Npt2b(+/+) mice with adenine-induced renal failure had hyperphosphatemia and high plasma creatinine levels. Npt2b(+/-) mice treated with adenine had significantly reduced plasma P(i) levels compared with Npt2b(+/+) mice. Intestinal Npt2b protein and Na(+)/P(i) transport activity levels were significantly lower in Npt2b(+/-) mice than in the Npt2b(+/+) mice. The findings of the present studies suggest that Npt2b is an important target for the prevention of hyperphosphatemia.
Ichiro Kaneko, Hiroko Segawa, Junya Furutani, Shoji Kuwahara, Fumito Aranami, Etsuyo Hanabusa, Rieko Tominaga, Hector Giral, Yupanqui Caldas, Moshe Levi, Shigeaki Kato and Ken-ichi Miyamoto : Hypophosphatemia in vitamin D receptor null mice: effect of rescue diet on the developmental changes in renal Na+ -dependent phosphate cotransporters., Pflügers Archiv : European Journal of Physiology, Vol.461, No.1, 77-90, 2010.
(Summary)
We analyzed vitamin D receptor (VDR) (-/-) mice fed either a normal diet or a rescue diet. Weanling VDR (-/-) mice had hypophosphatemia and hyperphosphaturia. Renal Na(+)-dependent inorganic phosphate (Pi) cotransport activity was significantly decreased in weanling VDR (-/-) mice. In VDR (+/+) mice, renal Npt2a/Npt2c/PiT-2 protein levels were significantly increased at 21 and 28 days of age compared with that at 1 day of age. Npt2c and PiT-2 protein levels were maximally expressed at 28 days of age. Npt2a protein levels were significantly decreased in mice at 28 days of age compared with 21 and 60 days of age. In VDR (-/-) mice, Npt2a/Npt2c/PiT-2 protein levels were considerably lower than those in age-matched VDR (+/+) mice at 21 and 28 days of age. The reduced Npt2a/Npt2c/PiT-2 protein recovered completely in VDR-null mice fed the rescue diet. Although Pi transport activity and Npt2b were reduced in the proximal intestine in VDR (-/-) mice, Npt2b protein levels were not reduced in the distal intestine in VDR (-/-) mice. The rescue diet did not affect intestinal Npt2b protein levels in VDR (-/-) mice. Thus, reduced intestinal Pi absorption in VDR (-/-) mice does not seem to be the only factor that causes hypophosphatemia; reduced Npt2a, Npt2c, or PiT-2 protein levels during development might also cause hypophosphatemia and rickets in VDR (-/-) mice. Furthermore, dietary intervention completely normalized the expression of the renal phosphate transporters (Npt2a/Npt2c/PiT-2) in VDR (-/-) mice, suggesting that the lack of VDR activity is not the cause of impaired renal phosphate reabsorption.
Yuka Tomoe, Hiroko Segawa, Kazuyo Shiozawa, Ichiro Kaneko, Rieko Tominaga, Etsuyo Hanabusa, Fumito Aranami, Junya Furutani, Shoji Kuwahara, Sawako Tatsumi, Mitsuru Matsumoto, Mikiko Ito and Ken-ichi Miyamoto : Phosphaturic action of fibroblast growth factor 23 in Npt2 null mice, American Journal of Physiology, Renal Physiology, Vol.298, No.6, F1341-F1350, 2010.
(Summary)
In the present study, we evaluated the roles of type II and type III sodium-dependent P(i) cotransporters in fibroblast growth factor 23 (FGF23) activity by administering a vector encoding FGF23 with the R179Q mutation (FGF23M) to wild-type (WT) mice, Npt2a knockout (KO) mice, Npt2c KO mice, and Npt2a(-/-)Npt2c(-/-) mice (DKO mice). In Npt2a KO mice, FGF23M induced severe hypophosphatemia and markedly decreased the levels of Npt2c, type III Na-dependent P(i) transporter (PiT2) protein, and renal Na/P(i) transport activity. In contrast, in Npt2c KO mice, FGF23M decreased plasma phosphate levels comparable to those in FGF23M-injected WT mice. In DKO mice with severe hypophosphatemia, FGF23M administration did not induce an additional increase in urinary phosphate excretion. FGF23 administration significantly decreased intestinal Npt2b protein levels in WT mice but had no effect in Npt2a, Npt2c, and DKO mice, despite marked suppression of plasma 1,25(OH)(2)D(3) levels in all the mutant mice. The main findings were as follow: 1) FGF23-dependent phosphaturic activity in Npt2a KO mice is dependent on renal Npt2c and PiT-2 protein; 2) in DKO mice, renal P(i) reabsorption is not further decreased by FGF23M, but renal vitamin D synthesis is suppressed; and 3) downregulation of intestinal Npt2b may be mediated by a factor(s) other than 1,25(OH)(2)D(3). These findings suggest that Npt2a, Npt2c, and PiT-2 are necessary for the phosphaturic activity of FGF23. Thus complementary regulation of Npt2 family proteins may be involved in systemic P(i) homeostasis.
(Keyword)
Animals / Calcitriol / calcium / Fibroblast Growth Factors / Gene Transfer Techniques / Humans / hypophosphatemia / Hypophosphatemia, Familial / Injections, Intravenous / Mice / Mice, Inbred C57BL / Mice, Knockout / Mutation / Phosphates / Sodium-Phosphate Cotransporter Proteins, Type III / Sodium-Phosphate Cotransporter Proteins, Type IIa / Sodium-Phosphate Cotransporter Proteins, Type IIb / Sodium-Phosphate Cotransporter Proteins, Type IIc
Hiroko Segawa, Akemi Onitsuka, Junya Furutani, Ichiro Kaneko, Fumito Aranami, Natsuki Matsumoto, Yuka Tomoe, Masashi Kuwahata, Mikiko Ito, Mitsuru Matsumoto, Minqi Li, Norio Amizuka and Ken-ichi Miyamoto : Npt2a and Npt2c in mice play distinct and synergistic roles in inorganic phosphate metabolism and skeletal development, American Journal of Physiology, Renal Physiology, Vol.297, No.3, F671-678, 2009.
(Summary)
Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare autosomal recessively inherited disorder, characterized by hypophosphatemia, short stature, rickets and/or osteomalacia, and secondary absorptive hypercalciuria. HHRH is caused by a defect in the sodium-dependent phosphate transporter (NaPi-IIc/Npt2c/NPT2c), which was thought to have only a minor role in renal phosphate (P(i)) reabsorption in adult mice. In fact, mice that are null for Npt2c (Npt2c(-/-)) show no evidence for renal phosphate wasting when maintained on a diet with a normal phosphate content. To obtain insights and the relative importance of Npt2a and Npt2c, we now studied Npt2a(-/-)Npt2c(+/+), Npt2a(+/-)Npt2c(-/-), and Npt2a(-/-)Npt2c(-/-) double-knockout (DKO). DKO mice exhibited severe hypophosphatemia, hypercalciuria, and rickets. These findings are different from those in Npt2a KO mice that show only a mild phosphate and bone phenotype that improve over time and from the findings in Npt2c KO mice that show no apparent abnormality in the regulation of phosphate homeostasis. Because of the nonredundant roles of Npt2a and Npt2c, DKO animals showed a more pronounced reduction in P(i) transport activity in the brush-border membrane of renal tubular cells than that in the mice with the single-gene ablations. A high-P(i) diet after weaning rescued plasma phosphate levels and the bone phenotype in DKO mice. Our findings thus showed in mice that Npt2a and Npt2c have independent roles in the regulation of plasma P(i) and bone mineralization.
Hiroko Segawa, Akemi Onitsuka, Masashi Kuwahata, Etsuyo Hanabusa, Junya Furutani, Ichiro Kaneko, Yuka Tomoe, Fumito Aranami, Natsuki Matsumoto, Mikiko Ito, Mitsuru Matsumoto, Minqi Li, Norio Amizuka and Ken-ichi Miyamoto : Type IIc sodium dependent phosphate transporter regulates calcium metabolism, Journal of the American Society of Nephrology, Vol.20, No.1, 104-113, 2009.
(Summary)
Primary renal inorganic phosphate (Pi) wasting leads to hypophosphatemia, which is associated with skeletal mineralization defects. In humans, mutations in the gene encoding the type IIc sodium-dependent phosphate transporter lead to hereditary hypophophatemic rickets with hypercalciuria, but whether Pi wasting directly causes the bone disorder is unknown. Here, we generated Npt2c-null mice to define the contribution of Npt2c to Pi homeostasis and to bone abnormalities. Homozygous mutants (Npt2c(-/-)) exhibited hypercalcemia, hypercalciuria, and elevated plasma 1,25-dihydroxyvitamin D(3) levels, but they did not develop hypophosphatemia, hyperphosphaturia, renal calcification, rickets, or osteomalacia. The increased levels of 1,25-dihydroxyvitamin D(3) in Npt2c(-/-) mice compared with age-matched Npt2c(+/+) mice may be the result of reduced catabolism, because we observed significantly reduced expression of renal 25-hydroxyvitamin D-24-hydroxylase mRNA but no change in 1alpha-hydroxylase mRNA levels. Enhanced intestinal absorption of calcium (Ca) contributed to the hypercalcemia and increased urinary Ca excretion. Furthermore, plasma levels of the phosphaturic protein fibroblast growth factor 23 were significantly decreased in Npt2c(-/-) mice. Sodium-dependent Pi co-transport at the renal brush border membrane, however, was not different among Npt2c(+/+), Npt2c(+/-), and Npt2c(-/-) mice. In summary, these data suggest that Npt2c maintains normal Ca metabolism, in part by modulating the vitamin D/fibroblast growth factor 23 axis.
(Keyword)
Animals / Biological Transport / Bone and Bones / Calcium / Calcium Channels / Calcium-Binding Protein, Vitamin D-Dependent / Fasting / Female / Fibroblast Growth Factors / Male / Mice / Mice, Inbred C57BL / Phosphates / RNA, Messenger / Sodium-Phosphate Cotransporter Proteins, Type IIc / TRPV Cation Channels
Yoshio Inoue, Hiroko Segawa, Ichiro Kaneko, Setsuko Yamanaka, Kenichiro Kusano, Eri Kawakami, Junya Furutani, Mikiko Ito, Masashi Kuwahata, Hitoshi Saito, Naoshi Fukushima, Shigeaki Kato, Hiro-omi Kanayama and Ken-ichi Miyamoto : Role of the vitamin D receptor in FGF23 action on phosphate metabolism, The Biochemical Journal, Vol.390, No.1, 325-331, 2005.
(Summary)
FGF23 (fibroblast growth factor 23) is a novel phosphaturic factor that influences vitamin D metabolism and renal re-absorption of Pi. The goal of the present study was to characterize the role of the VDR (vitamin D receptor) in FGF23 action using VDR(-/-) (VDR null) mice. Injection of FGF23M (naked DNA encoding the R179Q mutant of human FGF23) into VDR(-/-) and wildtype VDR(+/+) mice resulted in an elevation in serum FGF23 levels, but had no effect on serum calcium or parathyroid hormone levels. In contrast, injection of FGF23M resulted in significant decreases in serum Pi levels, renal Na/Pi co-transport activity and type II transporter protein levels in both groups when compared with controls injected with mock vector or with FGFWT (naked DNA encoding wild-type human FGF23). Injection of FGF23M resulted in a decrease in 25-hydroxyvitamin D 1a-hydroxylase mRNA levels in VDR(-/-) and VDR(+/+) mice, while 25-hydroxyvitamin D 24-hydroxylase mRNA levels were significantly increased in FGF23M-treated animals compared with mock vector control- or FGF23WT-treated animals. The degree of 24-hydroxylase induction by FGF23M was dependent on the VDR, since FGF23M significantly reduced the levels of serum 1,25(OH)2D3 [1,25-hydroxyvitamin D3] in VDR(+/+) mice, but not in VDR(-/-) mice. We conclude that FGF23 reduces renal Pi transport and 25-hydroxyvitamin D 1a-hydroxylase levels by a mechanism that is independent of the VDR. In contrast, the induction of 25-hydroxyvitamin D 24-hydroxylase and the reduction of serum 1,25(OH)2D3 levels induced by FGF23 are dependent on the VDR.
(Keyword)
fibroblast growth factor 23 / kidney / phosphate transport / vitamin D receptor
Hiroko Segawa, Ichiro Kaneko, Setsuko Yamanaka, Mikiko Ito, Masashi Kuwahata, Yoshio Inoue, Shigeaki Kato and Ken-ichi Miyamoto : Intestinal Na-Pi cotransporter adaptation to dietary Pi content in vitamin D receptor null mice., American Journal of Physiology, Renal Physiology, Vol.287, No.1, F39-F47, 2004.
(Summary)
Recent studies suggest that vitamin D may play a role in intestinal Na(+)-dependent phosphate transport adaptation to variable levels of dietary P(i). Therefore, the goal of the current study was to assess Na(+)-dependent P(i) cotransport activity in transgenic mice to determine whether vitamin D is an essential mediator of this process. Intestinal brush-border membrane (BBM), Na(+)-dependent P(i) cotransport activity was significantly decreased in vitamin D receptor (VDR) null [VDR (-/-)] mice compared with wild-type (VDR+/+) mice. While intestinal Na-P(i) cotransporter (type IIb) mRNA levels were similar in VDR (-/-) and VDR (+/+) mice, type IIb Na-P(i) cotransporter protein expression was markedly suppressed in VDR (-/-) mice compared with VDR (+/+) mice. Furthermore, Na-P(i) cotransport activity in renal BBM was similar in VDR (-/-) and VDR (+/+) mice, but type IIa Na-P(i) cotransporter protein expression was decreased in VDR (-/-) mice. After administration of a low-P(i) diet, type IIb protein expression was significantly increased in VDR (+/+) and VDR (-/-) mice, and type IIb protein expression was present in the intestinal BBM of VDR (-/-) mice. These data demonstrate that intestinal Na-P(i) cotransport adaptation to a low-P(i) diet occurs independently of vitamin D.
Hiroko Segawa, Eri Kawakami, Ichiro Kaneko, Masashi Kuwahata, Mikiko Ito, Kenichiro Kusano, Hitoshi Saito, Naoshi Fukushima and Ken-ichi Miyamoto : Effect of hydrolysis-resistant FGF23-R179Q on dietary phosphate regulation of the renal type-II Na/Pi transporter., Pflügers Archiv : European Journal of Physiology, Vol.446, No.5, 585-592, 2003.
(Summary)
Fibroblast growth factor 23 (FGF23), a phosphaturic factor, is involved in the regulation of renal inorganic phosphate (Pi) reabsorption. Proteolysis-resistant FGF23 mutants expressed in rodents reduce Pi uptake in both intestine and kidney, independent of parathyroid hormone action. In the present study, we investigated whether FGF23 affects dietary regulation of Na(+)-dependent Pi (Na/Pi) cotransport in the rat kidney using wild-type FGF23 and an R179Q mutant, which disrupts a consensus proteolytic cleavage motif. Rats injected with naked human FGF23 DNA (wild-type or R179Q mutant) expressed the human FGF23 transcript in the liver. In those animals, plasma calcium and parathyroid hormone levels were not affected by FGF23 (either wild-type or R179Q mutant). FGF23-R179Q did, however, significantly decrease plasma Pi and renal Na/Pi cotransport activity and also the level of type-IIc Na/Pi cotransporter protein in brush-border membrane vesicles (BBMVs) from normal rat kidney. Western blot and immunohistochemical analyses in rats fed a low-Pi diet showed the levels of types-IIa and -IIc Na/Pi cotransporters to be markedly increased. After injection of FGF23-R179Q DNA into the rats fed a low-Pi diet, the levels of the types-IIa and -IIc transporter proteins were decreased. The FGF23 mutant thus blunts the signalling of Pi deprivation to the renal type-II Na/Pi cotransporter, suggesting that the FGF23 pathway could be involved in the signalling of dietary Pi.
Sawako Tatsumi, Kanako Katai, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : NAD metabolism and the SLC34 family: evidence for a liver-kidney axis regulating inorganic phosphate., Pflügers Archiv : European Journal of Physiology, Vol.471, No.1, 109-122, Sep. 2018.
Ichiro Kaneko, MS Sabir, CM Dussik, GK Whitfield, A Karrys, JC Hsieh, MR Haussler, MB Meyer, JW Pike and PW Jurutka : 活性型ビタミンDは，トリプトファン水酸化酵素およびレプチン遺伝子発現を制御する, Vitamins, Vol.91, No.2, 132-134, Feb. 2017.
4.
Ichiro Kaneko, Sawako Tatsumi, Hiroko Segawa and Ken-ichi Miyamoto : Control of phosphate balance by the kidney and intestine., Clinical and Experimental Nephrology, Vol.21, No.Suppl 1, 21-26, Nov. 2016.
(Summary)
The prevention and correction of hyperphosphatemia are major goals of the treatment of chronic kidney disease (CKD)-bone mineral disorders, and thus, Pi balance requires special attention. Pi balance is maintained by intestinal absorption, renal excretion, and bone accretion. The kidney is mainly responsible for the plasma Pi concentration. In CKD, reduced glomerular filtration rate leads to various Pi metabolism abnormalities, and Pi absorption in the small intestine also has an important role in Pi metabolism. Disturbances in Pi metabolism are mediated by a series of complex changes in regulatory hormones originating from the skeleton, intestine, parathyroid gland, and kidney. In this review, we describe the regulation of type II sodium-dependent Pi co-transporters by the kidney and intestine, including the regulation of Pi transport, circadian rhythm, and the vicious circle between salivary Pi secretion and intestinal Pi absorption in animals with and without CKD.
MR Haussler, RK Saini, MS Sabir, CM Dussik, Z Khan, GK Whitfield, KP Griffin, Ichiro Kaneko and PW Jurutka : Vitamin D Nutrient-Gene Interactions and Healthful Aging, Molecular Basis of Nutrition and Aging, 441-461, Apr. 2016.
Hiroko Segawa, Yuji Shiozaki, Ichiro Kaneko and Ken-ichi Miyamoto : The Role of Sodium-Dependent Phosphate Transporter in Phosphate Homeostasis., Journal of Nutritional Science and Vitaminology, Vol.61 Suppl, S119-121, 2015.
(Summary)
Inorganic phosphate (Pi) is an essential compound for several biologic functions. Pi levels outside the normal range, however, contribute to several pathological processes. Hypophosphatemia leads to bone abnormalities, such as rickets/osteomalacia. Hyperphosphatemia contributes to vascular calcification in patients with chronic kidney disease and hemodialysis patients and is independently associated with cardiac mortality.Pi homeostasis is regulated by the coordinated function of renal and intestinal sodium-dependent phosphate (NaPi) transporters with dietary Pi, parathyroid hormone, 1,25-dihydroxyvitamin D3, and fibroblast growth factor 23. The type II NaPi transporter/SLC34 family, with three members identified to date, is mainly responsible for Pi homeostasis in the body. SLC34A1 and SCL34A3 are predominantly expressed in the kidney, whereas SLC34A2 is expressed in the small intestine. The role of each SLC34 in the body was recently established by studies of gene-targeted mice. Mutation of SLC34A1 causes Fanconi syndrome and mutation of SLC34A3 causes autosomal recessive hereditary hypophosphatemic rickets with hypercalciuria. SLC34A2 is thought to be a major intestinal NaPi transporter and mutation of SLC34A2 causes pulmonary alveolar microlithiasis. A detailed understanding of Pi regulation in the body is important toward maintaining health.
Shinsuke Kido, Ichiro Kaneko, Sawako Tatsumi, Hiroko Segawa and Ken-ichi Miyamoto : Vitamin D and type II sodium-dependent phosphate cotransporters., Contributions to Nephrology, Vol.180, 86-97, May 2013.
(Summary)
The type II sodium-dependent Pi (NaPi) cotransporters (NaPi-IIa, NaPi-IIb and NaPi-IIc) contribute to renal and intestinal Pi absorption. 1,25-Dihydroxyvitamin D [1,25(OH)2D3] is an important factor for NaPi-II transporters in the small intestine and kidney. In a previous study, low levels of 1,25(OH)2D3 appeared to suppress the expression of renal NaPi cotransporters. We identified a functional vitamin D receptor-responsive element in the human NaPi-IIa and NaPi-IIc genes in renal epithelial cells. In an analysis of vitamin D receptor (VDR)-null mice, we observed early onset of hypophosphatemia. The cause of the hypophosphatemia in VDR-null mice before weaning appeared to be increased plasma parathyroid hormone (PTH) levels during the suckling periods. A rescue diet (high calcium diet) decreased plasma PTH levels in VDR-null mice. The reduced plasma PTH levels normalized the renal Npt2a and Npt2c protein levels in weanling animals. Thus, the dietary intervention completely normalized the expression of the renal Pi transporters (Npt2a/Npt2c) in VDR-null mice, suggesting that the lack of VDR activity was not the cause of the impaired renal Pi reabsorption. In suckling animals, 1,25(OH)2D3 may be essential for the prevention of the phosphaturic action of PTH. In adult animals, 1,25(OH)2D3 is thought to be an important factor for posttranscriptional regulation of the Npt2b gene in the small intestine. Fibroblast growth factor 23 (FGF23) is a novel phosphaturic factor that influences vitamin D metabolism and renal reabsorption of Pi. We characterized the role of the VDR in the action of FGF23 using VDR-null mice. FGF23 reduced renal Pi transport and 25-hydroxyvitamin D 1a-hydroxylase levels by a mechanism that was independent of the VDR. By contrast, the induction of 25-hydroxyvitamin D 24-hydroxylase and the reduction in serum 1,25(OH)2D3 levels induced by FGF23 were dependent on the VDR. Thus, the VDR is not essential for the phosphaturic action of FGF23, but is essential for control of the plasma 1,25(OH)2D3 level. Moreover, FGF23 reduces intestinal NaPi transport activity and Npt2b protein levels by a mechanism that is dependent on the VDR. Klotho functions as a co-receptor for FGF23 and is increased by 1,25(OH)2D3. Klotho induces phosphaturia by inhibiting the renal NaPi-IIa transporter. In this review, we discuss the roles of 1,25(OH)2D3/VDR in the regulation of renal type II NaPi cotransporters in the kidney and small intestine.
R Mark Haussler, Kerr G Whithfield, Ichiro Kaneko, A Carol Haussler, David Hsieh, Jui-Cheng Hsieh and W Peter Jurutka : Molecular mechanisms of vitamin D action., Calcified Tissue International, Vol.92, No.2, 77-98, Jul. 2012.
(Summary)
The hormonal metabolite of vitamin D, 1α,25-dihydroxyvitamin D(3) (1,25D), initiates biological responses via binding to the vitamin D receptor (VDR). When occupied by 1,25D, VDR interacts with the retinoid X receptor (RXR) to form a heterodimer that binds to vitamin D responsive elements in the region of genes directly controlled by 1,25D. By recruiting complexes of either coactivators or corepressors, ligand-activated VDR-RXR modulates the transcription of genes encoding proteins that promulgate the traditional functions of vitamin D, including signaling intestinal calcium and phosphate absorption to effect skeletal and calcium homeostasis. Thus, vitamin D action in a particular cell depends upon the metabolic production or delivery of sufficient concentrations of the 1,25D ligand, expression of adequate VDR and RXR coreceptor proteins, and cell-specific programming of transcriptional responses to regulate select genes that encode proteins that function in mediating the effects of vitamin D. For example, 1,25D induces RANKL, SPP1 (osteopontin), and BGP (osteocalcin) to govern bone mineral remodeling; TRPV6, CaBP(9k), and claudin 2 to promote intestinal calcium absorption; and TRPV5, klotho, and Npt2c to regulate renal calcium and phosphate reabsorption. VDR appears to function unliganded by 1,25D in keratinocytes to drive mammalian hair cycling via regulation of genes such as CASP14, S100A8, SOSTDC1, and others affecting Wnt signaling. Finally, alternative, low-affinity, non-vitamin D VDR ligands, e.g., lithocholic acid, docosahexaenoic acid, and curcumin, have been reported. Combined alternative VDR ligand(s) and 1,25D/VDR control of gene expression may delay chronic disorders of aging such as osteoporosis, type 2 diabetes, cardiovascular disease, and cancer.
(Keyword)
Animals / Gene Expression Regulation / Humans / Receptors, Calcitriol / Signal Transduction / Vitamin D
R Mark Haussler, Kerr G Whitfield, Ichiro Kaneko, Ryan Forster, Rimpi Saini, Jui-Cheng Hsieh, A Carol Haussler and W Peter Jurutka : The role of vitamin D in the FGF23, klotho, and phosphate bone-kidney endocrine axis., Reviews in Endocrine & Metabolic Disorders, Vol.13, No.1, 57-69, Mar. 2012.
(Summary)
1,25-dihydroxyvitamin D (1,25D), through association with the nuclear vitamin D receptor (VDR), exerts control over a novel endocrine axis consisting of the bone-derived hormone FGF23, and the kidney-expressed klotho, CYP27B1, and CYP24A1 genes, which together prevent hyperphosphatemia/ectopic calcification and govern the levels of 1,25D to maintain bone mineral integrity while promoting optimal function of other vital tissues. When occupied by 1,25D, VDR interacts with RXR to form a heterodimer that binds to VDREs in the region of genes directly controlled by 1,25D (e.g., FGF23, klotho, Npt2c, CYP27B1 and CYP24A1). By recruiting complexes of comodulators, activated VDR initiates a series of events that induces or represses the transcription of genes encoding proteins such as: the osteocyte-derived hormone, FGF23; the renal anti-senescence factor and protein co-receptor for FGF23, klotho; other mediators of phosphate transport including Npt2a/c; and vitamin D hormone metabolic enzymes, CYP27B1 and CYP24A1. The mechanism whereby osteocytes are triggered to release FGF23 is yet to be fully defined, but 1,25D, phosphate, and leptin appear to play major roles. The kidney responds to FGF23 to elicit CYP24A1-catalyzed detoxification of the 1,25D hormone while also repressing both Npt2a/c to mediate phosphate elimination and CYP27B1 to limit de novo 1,25D synthesis. Comprehension of these skeletal and renal actions of 1,25D should facilitate the development of novel mimetics to prevent ectopic calcification, chronic renal and vascular disease, and promote healthful aging.
(Keyword)
Animals / Bone and Bones / Fibroblast Growth Factors / Glucuronidase / Humans / Kidney / Models, Biological / Receptors, Calcitriol / Retinoid X Receptors / Vitamin D
Ken-ichi Miyamoto, Sakiko Haito-Sugino, Shoji Kuwahara, Akiko Ohi, Kengo Nomura, Mikiko Ito, Masashi Kuwahata, Shinsuke Kido, Sawako Tatsumi, Ichiro Kaneko and Hiroko Segawa : Sodium-dependent phosphate cotransporters: lessons from gene knockout and mutation studies., Journal of Pharmaceutical Sciences, Vol.100, No.9, 3719-3730, May 2011.
(Summary)
Inorganic phosphate (Pi) is an essential physiological compound, highlighted by the syndromes caused by hypo or hyperphosphatemic states. Hyperphosphatemia is associated with ectopic calcification, cardiovascular disease, and increased mortality in patients with chronic kidney disease (CKD). As phosphate control is not efficient with diet or dialysis, oral Pi binders are used in over 90% of patients with renal failure. However, achieving tight control of serum Pi is difficult, and lower levels of serum Pi (severe hypophosphatemia) do not lead to better outcomes. The inhibition of sodium-dependent Pi (NaPi) transporter would be a preferable method to control serum Pi levels in patients with CKD or patients undergoing dialysis. Three types of NaPi transporters (types I-III) have been identified: solute carrier series SLC17A1 (NPT1/NaPi-I/OATv1), SLC34 (NaPi-IIa, NaPi-IIb, NaPi-IIc), and SLC20 (PiT1, PiT2), respectively. Knockout mice have been created for types I-III NaPi transporters. In this review, we discuss the roles of the NaPi transporters in Pi homeostasis.
Hiroko Segawa, Fumito Aranami, Ichiro Kaneko, Yuka Tomoe and Ken-ichi Miyamoto : The roles of Na/Pi-II transporters in phosphate metabolism., Bone, Vol.45 Suppl 1, S2-7, Feb. 2009.
(Summary)
The renal type II Na/Pi cotransporters, Na/Pi-IIa and Na/Pi-IIc, are expressed in the brush border membrane (BBM) of the renal proximal tubule cells. Because it has long been thought that Na/Pi-IIa alone can regulate the reabsorption of phosphate in the proximal renal tubules, Na/Pi-IIc has not been paid much attention by the renal research community. Recent studies, however, have identified Na/Pi-IIc mutations as the defective cause of hereditary hypophosphatemic rickets with hypercalciuria (HHRH). This finding indicates that Na/Pi-IIc has a rather important role in renal Pi reabsorption and bone mineralization, and that it may be a key determinant of plasma Pi concentrations in humans. Studies of Na/Pi-IIc mice indicate that Na/Pi-IIc is necessary for normal calcium homeostasis, but its role in the regulation of Pi metabolism and bone physiology may be different from that in HHRH patients. Of note, Na/Pi-IIc KO mice display abnormal vitamin D regulation without hypophosphatemia or hyperphosphaturia. Thus, Na/Pi-IIc may be involved in regulating renal vitamin D synthesis in the proximal tubular cells. The identification of proteins that interact with Na/Pi-IIc is an important area of future research. The physiologic roles of Na/Pi-IIa and Na/Pi-IIc require future elucidation.
Uga Minori, Ichiro Kaneko, Sasaki Sumire, Koike Megumi, Tanifuji Kazuya, Yuji Shiozaki, Jurutka W. Peter and Hiroko Segawa : The role of intestinal Cytochrome P450 in vitamin D metabolism, 22nd International Congress of Nutrition in Tokyo, Dec. 2022.
2.
Sawako Tatsumi, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : Daily oscillation of the plasma inorganic phosphate concentration; Impact of Nampt deficient mice., ASN (American Society of Nephrology), Kidney Week 2018, Oct. 2018.
3.
T Fujii, Hiroko Segawa, A Hamazaki, K Ikuta, A Kushi, Ichiro Kaneko, Sawako Tatsumi and Ken-ichi Miyamoto : In Vivo Responses of Phosphorus-Based Food Additives with Different Forms, American Society of Nephrology Kidney week., Nov. 2017.
4.
Sawako Tatsumi, Miyagawa Atsumi, Fujii Osamu, Ogata Mao, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : Hepatectomy-Induced Hypophosphatemia: Mechanisms Underlying Downregulation of Phophate Transport in the Small Intestine., American Society of Nephrology. Kidney Week2016., Nov. 2016.
5.
Ikuta Kayo, Hiroko Segawa, Yuki Shihoko, Ichiro Kaneko, Hanazaki Ai, Fujii Toru, Kushi Aoi, Sawako Tatsumi and Ken-ichi Miyamoto : Salivary Pi Handling May Be under the Control of Gastrointestinal Pi Sensing., American Society of Nephrology.Kidney Week2016., Nov. 2016.
6.
Ichiro Kaneko, Saini K. Rimpi, Witfield Kerr G., Ito Mikiko, Hiroko Segawa, Sawako Tatsumi, Ken-ichi Miyamoto, Haussler R. Mark and Jurutka W. Peter : FGF23: A Nurr1-dependent Phosphaturic Hormone Gene That is Transcriptionally Regulated by 1,25-dihydroxyvitamin D, XVIII International Congress on Nutrition and Metabolism in Renal Disease 2016, Apr. 2016.
7.
Ichiro Kaneko, Saini K Rimpi, Whitfield G.Kerr, Mikiko Ito, Hiroko Segawa, Sawako Tatsumi, Ken-ichi Miyamoto, R.Haussler Mark and W.Jurutka Peter : A Nurr1-dependent phosphaturic hormonegene that is transcriptionally regulated by 1.25-dihydroxyvitamin D., XVIII International Congress on Nutrition and Metabolism in Renal Desease(ICRNM2016), Apr. 2016.
8.
Wagner E. Carl, Jurutka W. Peter, Marshall A. Pamela, Ichiro Kaneko, Shahani Pritika, Seto H. David, Varkey Julia, Hum L. Cindy, Sarnowski T. Joseph, Wentzel R. Michael and Chhun Christine : Synthesis and Biological Characterization of Novel CD3254 Analogs, American Chemical Society Annual Meeting, Mar. 2016.
9.
Hanazaki Ai, Hiroko Segawa, Ikuta Kayo, Fujii Toru, Ichiro Kaneko, Yuki Shihoko, Nishiguchi Shiori, Notsu Keijiro, Shiozaki Yuji, Sawako Tatsumi and Ken-ichi Miyamoto : Genetic Deletion of NaPi-2c Rescue Phenotype of klotho Knockout Mice wi thout Improving Severe Hyperphosphat emia., American Society of Nephrology Kidney week., Nov. 2015.
10.
Yuki Shihoko, Hiroko Segawa, Sasaki Shohei, Ikuta Kayo, Ichiro Kaneko, Fujii Toru, Hanazaki Ai, Nishiguchi Shiori, Keijiro Notsu, Aki Eriko, Shiozaki Yuji, Sawako Tatsumi and Ken-ichi Miyamoto : Disruption of intestinal alkaline phosphatase (Akp3) affects the phosphate homeostasis., ACN2015 Asian Congress of Nutrition., May 2015.
11.
Haruna Sakaguchi, Sawako Tatsumi, Ogata Mao, Osamu Fujii, Arakaki Tomohiro, Miyagawa Atsumi, Nagamoto Kenta, Takahama Wako, Hirobata Yukiko, Yasui Akihiro, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : Bone-kidney axis regulating phosphate homeostasis: Study of osteocyte-ablated mice., ACN2015 Asian Congress of Nutrition., May 2015.
12.
Ichiro Kaneko, Hsieh Jui-Cheng, Whitfield Kerr G., Hiroko Segawa, Ken-ichi Miyamoto, Haussler R. Mark and Jurutka W. Peter : 1,25-Dihydroxyvitamin D enhances human tryptophan hydroxylase gene expression through vitamin D responsive elements in human brain cells., 12th Asian Congress of Nutrition 2015, May 2015.
13.
Hiroko Segawa, Ichiro Kaneko, Yuji Shiozaki, Sawako Tatsumi and Ken-ichi Miyamoto : The role of Na+-dependent Phosphate transporters in the body., ACN2015 Asian Congress of Nutrition., May 2015.
14.
生田 かよ, Hiroko Segawa, 佐々木 祥平, Ichiro Kaneko, 塩崎 雄治, Sawako Tatsumi and Ken-ichi Miyamoto : Inorganic Phosphate Handling in Salivary Glands., American Society of Nephrology (米国腎臓学会), ペ ンシルバニアコンベ ンションセンター(フィラデルフィア), Nov. 2014.
Hiroko Segawa, 佐々木 祥平, 結城 志帆子, Ichiro Kaneko, Sawako Tatsumi and Ken-ichi Miyamoto : The role of intestinal alkaline phosphatase on phosphate homeostasis., 第71回日本栄養·食糧学会大会, May 2017.
29.
Sawako Tatsumi, 緒方 雅央, 新垣 友啓, 藤井 理, Ichiro Kaneko, Hiroko Segawa and Ken-ichi Miyamoto : 骨ー腎臓連関を介した食餌性リン感受機Sensing of dietary phosphate loading in the bone-kidney axis., 第71回日本栄養·食糧学会大会, May 2017.
30.
Hiroko Segawa, Ichiro Kaneko, Sawako Tatsumi and Ken-ichi Miyamoto : Nutrient transporter and Health/Disease [Intestinal Phosphate absorption and Chronic Kidney Disease], 第71回日本栄養·食糧学会大会, May 2017.
31.
Hiroko Segawa, 佐々木 祥平, 結城 志帆子, Ichiro Kaneko, Sawako Tatsumi and Ken-ichi Miyamoto : 生体内リン恒常性におけるIntestinal Alkaline Phosphatase(IAP)の役割, 第1回CKD‐MBD研究会学術集会・総会, Mar. 2017.
Hiroko Segawa, 佐々木 祥平, 結城 志帆子, Ichiro Kaneko, Sawako Tatsumi and Ken-ichi Miyamoto : 生体内リン恒常性におけるIntestinal Alkaline Phosphatase(IAP)の役割, 第1回CKD‐MBD研究会学術集会・総会, Mar. 2016.
36.
Ichiro Kaneko, Jui-Cheng Hsieh, G.Kerr Whitfield, Sawako Tatsumi, Hiroko Segawa, Ken-ichi Miyamoto, R Mark Haussler and W Peter Jurutka : 脳機能におけるビタミンDの役割について, 第19会日本病態栄養学会年次学術集会, Jan. 2016.