Browsing by Subject "Hyperphosphatemia"

Now showing 1 - 8 of 8
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    A case of calciphylaxis in a patient with hypoparathyroidism and normal renal function
    (American Association of Clinical Endocrinologists, 2014-06-01) Erdel, Blake L.; Juneja, Rattan; Evans-Molina, Carmella; Department of Medicine, IU School of Medicine
    OBJECTIVE: To present the case of a patient with a history of thyroid cancer, postsurgical hypoparathyroidism, chronic calcitriol use, and normal renal function who presented with painful skin lesions secondary to calciphylaxis. METHODS: We describe the history, biochemistry, histopathology, evaluation, and management of this patient. RESULTS: A 47-year-old female with hypoparathyroidism, chronically treated with calcitriol and calcium, presented with exquisitely painful skin ulcerations. Four months prior to the onset of symptoms, she had initiated warfarin therapy for atrial fibrillation. Review of laboratory data from the past year revealed elevated calcium and phosphorus levels. A diagnosis of calciphylaxis was made based upon pathologic evaluation of a skin biopsy. Management included titration of calcitriol and calcium to maintain serum calcium and phosphate levels in the low-normal range. Sodium thiosulfate was administered at a dose of 25 mg intravenously 3 times a week with some resolution in the patient's pain. Unfortunately, the patient battled recurrent bacteremia and sepsis, presumably related to her calciphylaxis wounds, and ultimately succumbed to complications from sepsis. CONCLUSION: Although calciphylaxis is typically associated with renal insufficiency and secondary hyperparathyroidism, we highlight the case of a patient with normal renal function and hypoparathyroidism. Patients treated with chronic calcitriol should have serum calcium and phosphorus monitored closely and may benefit from non-calcium-based phosphate binders if hyperphosphatemia becomes unavoidable. This is especially important in the presence of other risk factors for calciphylaxis, including warfarin use.
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    The Case | Ectopic calcifications in a child
    (Nature Publishing Group, 2015-05) Keskar, Vaibhav S.; Imel, Erik A.; Kulkarni, Manjunath; Mane, Swati; Jamale, Tukaram E.; Econs, Michael J.; Hase, Niwrutti K.; Department of Medicine, IU School of Medicine
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    Chronic Hyperphosphatemia and Vascular Calcification Are Reduced by Stable Delivery of Soluble Klotho
    (American Society of Nephrology, 2017-04) Hum, Julia M.; O’Bryan, Linda M.; Tatiparthi, Arun K.; Cass, Taryn A.; Clinkenbeard, Erica L.; Cramer, Martin S.; Bhaskaran, Manoj; Johnson, Robert L.; Wilson, Jonathan M.; Smith, Rosamund C.; White, Kenneth E.; Medical and Molecular Genetics, School of Medicine
    αKlotho (αKL) regulates mineral metabolism, and diseases associated with αKL deficiency are characterized by hyperphosphatemia and vascular calcification (VC). αKL is expressed as a membrane-bound protein (mKL) and recognized as the coreceptor for fibroblast growth factor-23 (FGF23) and a circulating soluble form (cKL) created by endoproteolytic cleavage of mKL. The functions of cKL with regard to phosphate metabolism are unclear. We tested the ability of cKL to regulate pathways and phenotypes associated with hyperphosphatemia in a mouse model of CKD-mineral bone disorder and αKL-null mice. Stable delivery of adeno-associated virus (AAV) expressing cKL to diabetic endothelial nitric oxide synthase-deficient mice or αKL-null mice reduced serum phosphate levels. Acute injection of recombinant cKL downregulated the renal sodium-phosphate cotransporter Npt2a in αKL-null mice supporting direct actions of cKL in the absence of mKL. αKL-null mice with sustained AAV-cKL expression had a 74%-78% reduction in aorta mineral content and a 72%-77% reduction in mineral volume compared with control-treated counterparts (P<0.01). Treatment of UMR-106 osteoblastic cells with cKL + FGF23 increased the phosphorylation of extracellular signal-regulated kinase 1/2 and induced Fgf23 expression. CRISPR/Cas9-mediated deletion of fibroblast growth factor receptor 1 (FGFR1) or pretreatment with inhibitors of mitogen-activated kinase kinase 1 or FGFR ablated these responses. In summary, sustained cKL treatment reduced hyperphosphatemia in a mouse model of CKD-mineral bone disorder, and it reduced hyperphosphatemia and prevented VC in mice without endogenous αKL. Furthermore, cKL stimulated Fgf23 in an FGFR1-dependent manner in bone cells. Collectively, these findings indicate that cKL has mKL-independent activity and suggest the potential for enhancing cKL activity in diseases of hyperphosphatemia with associated VC.
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    Heritable and acquired disorders of phosphate metabolism: Etiologies involving FGF23 and current therapeutics
    (Elsevier, 2017-09) Clickenbeard, Erica L.; White, Kenneth E.; Medical and Molecular Genetics, School of Medicine
    Phosphate is critical for many cellular processes and structural functions, including as a key molecule for nucleic acid synthesis and energy metabolism, as well as hydroxyapatite formation in bone. Therefore it is critical to maintain tight regulation of systemic phosphate levels. Based upon its broad biological importance, disruption of normal phosphate homeostasis has detrimental effects on skeletal integrity and overall health. Investigating heritable diseases of altered phosphate metabolism has led to key discoveries underlying the regulation and systemic actions of the phosphaturic hormone Fibroblast growth factor-23 (FGF23). Both molecular and clinical studies have revealed novel targets for the development and optimization of therapies for disorders of phosphate handling. This review will focus upon the bridge between genetic discoveries involving disorders of altered FGF23 bioactivity, as well as describe how these findings have translated into pharmacologic application.
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    Novel functions of circulating Klotho
    (Elsevier, 2017-07) Hum, Julia M.; O’Bryan, Linda; Smith, Rosamund C.; White, Kenneth E.; Medical and Molecular Genetics, School of Medicine
    A significant portion of the key biological functions of αKlotho (αKL) and its cognate ligand Fibroblast growth factor-23 (FGF23) have been revealed through the study of rare diseases of mineral metabolism. These findings have far reaching implications for common disorders such as chronic kidney disease-mineral bone disorder (CKD-MBD). αKL’s predominant effect on mineral homeostasis is through its actions in the kidney as a co-receptor for FGF23, however emerging data has shed light on its capacity to act as a circulating factor through the cleavage of the transmembrane form of αKL (‘mKL’) to produce ‘cleaved KL’ or ‘cKL’. This review summarizes new findings from studies using extended delivery of cKL to mouse models with phenotypes reflecting those arising in CKD-MBD.
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    Phosphate Binders and Non-Phosphate Effects in the Gastrointestinal Tract
    (Elsevier, 2020-01) Biruete, Annabel; Hill Gallant, Kathleen M.; Lindemann, Stephen R.; Wiese, Gretchen; Chen, Neal; Moe, Sharon; Medicine, School of Medicine
    Phosphate binders are commonly prescribed in patients with end-stage kidney disease to prevent and treat hyperphosphatemia. These binders are usually associated with gastrointestinal distress, may bind molecules other than phosphate, and may alter the gut microbiota, altogether having systemic effects unrelated to phosphate control. Sevelamer is the most studied of the available binders for nonphosphate-related effects including binding to bile acids, endotoxins, gut microbiota-derived metabolites, and advanced glycation end products. Other binders (calcium- and noncalcium-based binders) may bind vitamins, such as vitamin K and folic acid. Moreover, the relatively new iron-based phosphate binders may alter the gut microbiota, as some of the iron or organic ligands may be used by the gastrointestinal bacteria. The objective of this narrative review is to provide the current evidence for the nonphosphate effects of phosphate binders on gastrointestinal function, nutrient and molecule binding, and the gut microbiome.
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    Severe vascular calcification and tumoral calcinosis in a family with hyperphosphatemia: a fibroblast growth factor 23 mutation identified by exome sequencing
    (Oxford University Press, 2014-12) Shah, Anuja; Miller, Clinton J.; Nast, Cynthia C.; Adams, Mark D.; Truitt, Barbara; Tayek, John A.; Tong, Lili; Mehtani, Parag; Monteon, Francisco; Sedor, John R.; Clinkenbeard, Erica L.; White, Kenneth; Mehrotra, Rajnish; LaPage, Janine; Dickson, Patricia; Adler, Sharon G.; Iyengar, Sudha K.; Department of Medical & Molecular Genetics, IU School of Medicine
    BACKGROUND: Tumoral calcinosis is an autosomal recessive disorder characterized by ectopic calcification and hyperphosphatemia. METHODS: We describe a family with tumoral calcinosis requiring amputations. The predominant metabolic anomaly identified in three affected family members was hyperphosphatemia. Biochemical and phenotypic analysis of 13 kindred members, together with exome analysis of 6 members, was performed. RESULTS: We identified a novel Q67K mutation in fibroblast growth factor 23 (FGF23), segregating with a null (deletion) allele on the other FGF23 homologue in three affected members. Affected siblings had high circulating plasma C-terminal FGF23 levels, but undetectable intact FGF23 or N-terminal FGF23, leading to loss of FGF23 function. CONCLUSIONS: This suggests that in human, as in experimental models, severe prolonged hyperphosphatemia may be sufficient to produce bone differentiation proteins in vascular cells, and vascular calcification severe enough to require amputation. Genetic modifiers may contribute to the phenotypic variation within and between families.
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    Systemic Control of Bone Homeostasis by FGF23 Signaling
    (Springer, 2016-03-01) Clinkenbeard, Erica L.; White, Kenneth E.; Department of Medical & Molecular Genetics, IU School of Medicine
    The regulation of phosphate metabolism as an influence on bone homeostasis is profound. Recent advances in understanding the systemic control of Fibroblast growth factor-23 (FGF23) has uncovered novel effectors of endocrine feedback loops for calcium, phosphate, and vitamin D balance that interact with 'traditional' feedback loops for mineral metabolism. Not only are these findings re-shaping research studying phosphate handling and skeletal interactions, they have provided new therapeutic interventions. Emerging data support that the control of FGF23 production in bone and its circulating concentrations is a multi-layered process, with some influences affecting FGF23 transcription and some post-translational modification of the secreted, bioactive protein. Additionally, the actions of FGF23 on its target tissues via its co-receptor αKlotho, are subject to regulatory events just coming to light. The recent findings of systemic influences on circulating FGF23 and the downstream manifestations on bone homeostasis will be reviewed herein.