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Vogt J, Wolf L, Hoelzle LE, Feger M, Föller M. AMP-dependent kinase stimulates the expression of αKlotho. FEBS Open Bio 2024. [PMID: 39090792 DOI: 10.1002/2211-5463.13872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 06/14/2024] [Accepted: 07/17/2024] [Indexed: 08/04/2024] Open
Abstract
Renal αKlotho along with fibroblast growth factor 23 regulates phosphate and vitamin D metabolism. Its cleavage yields soluble Klotho controlling intracellular processes. αKlotho has anti-inflammatory and antioxidant effects and is nephro- and cardioprotective. AMP-dependent kinase (AMPK) is a nephro- and cardioprotective energy sensor. Given that both αKlotho and AMPK have beneficial effects in similar organs, we studied whether AMPK regulates αKlotho gene expression in Madin-Darby canine kidney, normal rat kidney 52E, and human kidney 2 cells. Using quantitative real-time PCR and western blotting, we measured αKlotho expression upon pharmacological manipulation or siRNA-mediated knockdown of AMPKα. AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) enhanced αKlotho expression, an effect reduced in the presence of AMPK inhibitor compound C or siRNA targeting AMPK catalytic α-subunits (α1 and α2). Similarly, AMPK activators metformin and phenformin upregulated αKlotho transcripts. Taken together, our results suggest that AMPK is a powerful inducer of αKlotho and could thereby contribute to the development of future therapeutic interventions.
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Affiliation(s)
- Julia Vogt
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Lisa Wolf
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Ludwig E Hoelzle
- Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Martina Feger
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Michael Föller
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
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Courbon G, David V. Fibroblast growth factor 23 is pumping iron: C-terminal-fibroblast growth factor 23 cleaved peptide and its function in iron metabolism. Curr Opin Nephrol Hypertens 2024; 33:368-374. [PMID: 38661434 DOI: 10.1097/mnh.0000000000000995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
PURPOSE OF REVIEW Iron deficiency regulates the production of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) but also its cleavage, to generate both intact (iFGF23) and C-terminal (Cter)-FGF23 peptides. Novel studies demonstrate that independently of the phosphaturic effects of iFGF23, Cter-FGF23 peptides play an important role in the regulation of systemic iron homeostasis. This review describes the complex interplay between iron metabolism and FGF23 biology. RECENT FINDINGS C-terminal (Cter) FGF23 peptides antagonize inflammation-induced hypoferremia to maintain a pool of bioavailable iron in the circulation. A key mechanism proposed is the down-regulation of the iron-regulating hormone hepcidin by Cter-FGF23. SUMMARY In this manuscript, we discuss how FGF23 is produced and cleaved in response to iron deficiency, and the principal functions of cleaved C-terminal FGF23 peptides. We also review possible implications anemia of chronic kidney disease (CKD).
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Affiliation(s)
- Guillaume Courbon
- INSERM U1059 SAINBIOSE, University of St Etienne, Mines St Etienne, St Etienne, France
| | - Valentin David
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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Edmonston D, Fuchs MAA, Burke EJ, Isakova T, Wolf M. Klotho and Clinical Outcomes in CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study. Am J Kidney Dis 2024:S0272-6386(24)00690-5. [PMID: 38583756 DOI: 10.1053/j.ajkd.2024.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 02/08/2024] [Accepted: 02/09/2024] [Indexed: 04/09/2024]
Abstract
RATIONALE & OBJECTIVE Klotho deficiency may affect clinical outcomes in chronic kidney disease (CKD) through fibroblast growth factor-23 (FGF23)-dependent and -independent pathways. However, the association between circulating Klotho and clinical outcomes in CKD remains unresolved and was the focus of this study. STUDY DESIGN Prospective observational study. SETTING & PARTICIPANTS 1,088 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study with an estimated glomerular filtration rate (eGFR) of 20-70mL/min/1.73m2. EXPOSURE Plasma Klotho level at the year-1 study visit. OUTCOMES 5-year risks of all-cause mortality, heart failure hospitalization, atherosclerotic cardiovascular events, and a composite kidney end point that comprised a sustained 50% decrease in eGFR, dialysis, kidney transplant, or eGFR<15mL/min/1.73m2. ANALYTICAL APPROACH We divided Klotho into 6 groups to account for its nonnormal distribution. We used Cox proportional hazards regression and subdistribution hazards models to compare survival and clinical outcomes, respectively, between Klotho groups. We sequentially adjusted for demographic characteristics, kidney function, cardiovascular risk factors, sample age, and FGF23. RESULTS Mean eGFR was 42mL/min/1.73m2, and median Klotho concentration was 0.31ng/mL (IQR, 0.10-3.27ng/mL). When compared with the lowest Klotho group, survival (HR, 0.77; 95% CI, 0.32-1.89), heart failure hospitalization (HR, 1.10; 95% CI, 0.38-3.17), atherosclerotic cardiovascular events (HR, 1.19; 95% CI, 0.57-2.52), and CKD progression (HR, 1.05; 95% CI, 0.58-1.91) did not differ in the high Klotho group. In contrast, FGF23 was significantly associated with mortality and heart failure hospitalization independent of Klotho levels. LIMITATIONS Despite adjustments, we cannot exclude the potential influence of residual confounding or sample storage on the results. A single measurement of plasma Klotho concentration may not capture Klotho patterns over time. CONCLUSIONS In a large, diverse, well-characterized CKD cohort, Klotho was not associated with clinical outcomes, and Klotho deficiency did not confound the association of FGF23 with mortality or heart failure hospitalization. PLAIN-LANGUAGE SUMMARY Klotho is a protein that is vital to mineral metabolism and aging and may protect against cardiovascular disease. Klotho levels decrease in chronic kidney disease (CKD), but the association between Klotho and clinical outcomes in CKD remains uncertain. In a prospective cohort study of more than 1,000 people with CKD, circulating Klotho levels were not associated with kidney disease progression, cardiovascular outcomes, or mortality. These results suggest that the decrease in circulating Klotho levels in CKD does not play a prominent role in the development of poor clinical outcomes.
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Affiliation(s)
- Daniel Edmonston
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, NC; Duke Clinical Research Institute, Duke University School of Medicine, Durham, NC.
| | - Michaela A A Fuchs
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, NC
| | - Emily J Burke
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, NC
| | - Tamara Isakova
- Division of Nephrology and Hypertension, Department of Medicine and Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Myles Wolf
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, NC; Duke Clinical Research Institute, Duke University School of Medicine, Durham, NC
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Yang Z, Zarbl H, Guo GL. Circadian Regulation of Endocrine Fibroblast Growth Factors on Systemic Energy Metabolism. Mol Pharmacol 2024; 105:179-193. [PMID: 38238100 PMCID: PMC10877735 DOI: 10.1124/molpharm.123.000831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Accepted: 01/05/2024] [Indexed: 02/17/2024] Open
Abstract
The circadian clock is an endogenous biochemical timing system that coordinates the physiology and behavior of organisms to earth's ∼24-hour circadian day/night cycle. The central circadian clock synchronized by environmental cues hierarchically entrains peripheral clocks throughout the body. The circadian system modulates a wide variety of metabolic signaling pathways to maintain whole-body metabolic homeostasis in mammals under changing environmental conditions. Endocrine fibroblast growth factors (FGFs), namely FGF15/19, FGF21, and FGF23, play an important role in regulating systemic metabolism of bile acids, lipids, glucose, proteins, and minerals. Recent evidence indicates that endocrine FGFs function as nutrient sensors that mediate multifactorial interactions between peripheral clocks and energy homeostasis by regulating the expression of metabolic enzymes and hormones. Circadian disruption induced by environmental stressors or genetic ablation is associated with metabolic dysfunction and diurnal disturbances in FGF signaling pathways that contribute to the pathogenesis of metabolic diseases. Time-restricted feeding strengthens the circadian pattern of metabolic signals to improve metabolic health and prevent against metabolic diseases. Chronotherapy, the strategic timing of medication administration to maximize beneficial effects and minimize toxic effects, can provide novel insights into linking biologic rhythms to drug metabolism and toxicity within the therapeutical regimens of diseases. Here we review the circadian regulation of endocrine FGF signaling in whole-body metabolism and the potential effect of circadian dysfunction on the pathogenesis and development of metabolic diseases. We also discuss the potential of chrononutrition and chronotherapy for informing the development of timing interventions with endocrine FGFs to optimize whole-body metabolism in humans. SIGNIFICANCE STATEMENT: The circadian timing system governs physiological, metabolic, and behavioral functions in living organisms. The endocrine fibroblast growth factor (FGF) family (FGF15/19, FGF21, and FGF23) plays an important role in regulating energy and mineral metabolism. Endocrine FGFs function as nutrient sensors that mediate multifactorial interactions between circadian clocks and metabolic homeostasis. Chronic disruption of circadian rhythms increases the risk of metabolic diseases. Chronological interventions such as chrononutrition and chronotherapy provide insights into linking biological rhythms to disease prevention and treatment.
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Affiliation(s)
- Zhenning Yang
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy (Z.Y., G.L.G.), Environmental and Occupational Health Sciences Institute (Z.Y., H.Z., G.L.G.), Department of Environmental and Occupational Health Justice, School of Public Health (H.Z.), Rutgers Center for Lipid Research (G.L.G.), Rutgers, The State University of New Jersey, New Brunswick, New Jersey; and VA New Jersey Health Care System, Veterans Administration Medical Center, East Orange, New Jersey (G.L.G.)
| | - Helmut Zarbl
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy (Z.Y., G.L.G.), Environmental and Occupational Health Sciences Institute (Z.Y., H.Z., G.L.G.), Department of Environmental and Occupational Health Justice, School of Public Health (H.Z.), Rutgers Center for Lipid Research (G.L.G.), Rutgers, The State University of New Jersey, New Brunswick, New Jersey; and VA New Jersey Health Care System, Veterans Administration Medical Center, East Orange, New Jersey (G.L.G.)
| | - Grace L Guo
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy (Z.Y., G.L.G.), Environmental and Occupational Health Sciences Institute (Z.Y., H.Z., G.L.G.), Department of Environmental and Occupational Health Justice, School of Public Health (H.Z.), Rutgers Center for Lipid Research (G.L.G.), Rutgers, The State University of New Jersey, New Brunswick, New Jersey; and VA New Jersey Health Care System, Veterans Administration Medical Center, East Orange, New Jersey (G.L.G.)
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Wolf L, Vogt J, Alber J, Franjic D, Feger M, Föller M. PKC regulates αKlotho gene expression in MDCK and NRK-52E cells. Pflugers Arch 2024; 476:75-86. [PMID: 37773536 PMCID: PMC10758369 DOI: 10.1007/s00424-023-02863-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 09/20/2023] [Accepted: 09/20/2023] [Indexed: 10/01/2023]
Abstract
Particularly expressed in the kidney, αKlotho is a transmembrane protein that acts together with bone hormone fibroblast growth factor 23 (FGF23) to regulate renal phosphate and vitamin D homeostasis. Soluble Klotho (sKL) is released from the transmembrane form and controls various cellular functions as a paracrine and endocrine factor. αKlotho deficiency accelerates aging, whereas its overexpression favors longevity. Higher αKlotho abundance confers a better prognosis in cardiovascular and renal disease owing to anti-inflammatory, antifibrotic, or antioxidant effects and tumor suppression. Serine/threonine protein kinase C (PKC) is ubiquitously expressed, affects several cellular responses, and is also implicated in heart or kidney disease as well as cancer. We explored whether PKC is a regulator of αKlotho. Experiments were performed in renal MDCK or NRK-52E cells and PKC isoform and αKlotho expression determined by qRT-PCR and Western Blotting. In both cell lines, PKC activation with phorbol ester phorbol-12-myristate-13-acetate (PMA) downregulated, while PKC inhibitor staurosporine enhanced αKlotho mRNA abundance. Further experiments with PKC inhibitor Gö6976 and RNA interference suggested that PKCγ is the major isoform for the regulation of αKlotho gene expression in the two cell lines. In conclusion, PKC is a negative regulator of αKlotho gene expression, an effect which may be relevant for the unfavorable effect of PKC on heart or kidney disease and tumorigenesis.
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Affiliation(s)
- Lisa Wolf
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany
| | - Julia Vogt
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany
| | - Jana Alber
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany
| | - Domenic Franjic
- Core Facility Hohenheim, Data and Statistical Consulting, University of Hohenheim, 70599, Stuttgart, Germany
| | - Martina Feger
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany
| | - Michael Föller
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
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Feger M, Alber J, Strotmann J, Grund A, Leifheit-Nestler M, Haffner D, Föller M. Short-term fasting of mice elevates circulating fibroblast growth factor 23 (FGF23). Acta Physiol (Oxf) 2023; 239:e14049. [PMID: 37746883 DOI: 10.1111/apha.14049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 08/24/2023] [Accepted: 09/04/2023] [Indexed: 09/26/2023]
Abstract
AIMS Phosphate and vitamin D homeostasis are controlled by fibroblast growth factor 23 (FGF23) from bone suppressing renal phosphate transport and enhancing 24-hydroxylase (Cyp24a1), thereby inactivating 1,25(OH)2 D3 . Serum FGF23 is correlated with outcomes in several diseases. Fasting stimulates the production of ketone bodies. We hypothesized that fasting can induce FGF23 synthesis through the production of ketone bodies. METHODS UMR106 cells and isolated neonatal rat ventricular myocytes (NRVM) were treated with ketone body β-hydroxybutyrate. Mice were fasted overnight, fed ad libitum, or treated with β-hydroxybutyrate. Proteins and further blood parameters were determined by enzyme-linked immunoassay (ELISA), western blotting, immunohistochemistry, fluorometric or colorimetric methods, and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS β-Hydroxybutyrate stimulated FGF23 production in UMR106 cells in a nuclear factor kappa-light-chain enhancer of activated B-cells (NFκB)-dependent manner, and in NRVMs. Compared to fed animals, fasted mice exhibited higher β-hydroxybutyrate and FGF23 serum levels (based on assays either detecting C-terminal or intact, biologically active FGF23 only), cardiac, pancreatic, and thymic Fgf23 and renal Cyp24a1 expression, and lower 1,25(OH)2 D3 serum concentration as well as renal Slc34a1 and αKlotho (Kl) expression. In contrast, Fgf23 expression in bone and serum phosphate, calcium, plasma parathyroid hormone (PTH) concentration, and renal Cyp27b1 expression were not significantly affected by fasting. CONCLUSION Short-term fasting increased FGF23 production, as did administration of β-hydroxybutyrate, effects possibly of clinical relevance in view of the increasing use of FGF23 as a surrogate parameter in clinical monitoring of diseases. The fasting state of patients might therefore affect FGF23 tests.
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Affiliation(s)
- Martina Feger
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Jana Alber
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Jörg Strotmann
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Andrea Grund
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Pediatric Research Center, Hannover Medical School, Hannover, Germany
| | - Maren Leifheit-Nestler
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Pediatric Research Center, Hannover Medical School, Hannover, Germany
| | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Pediatric Research Center, Hannover Medical School, Hannover, Germany
| | - Michael Föller
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
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Hammer N, Legouis D, Pasch A, Huber A, Al-Qusairi L, Martin PY, de Seigneux S, Berchtold L. Calcification Propensity (T50) Predicts a Rapid Decline of Renal Function in Kidney Transplant Recipients. J Clin Med 2023; 12:3965. [PMID: 37373661 DOI: 10.3390/jcm12123965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 06/04/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND Serum creatinine level, proteinuria, and interstitial fibrosis are predictive of renal prognosis. Fractional excretion of phosphate (FEP)/FGF23 ratio, tubular reabsorption of phosphate (TRP), serum calcification propensity (T50), and Klotho's serum level are emerging as determinants of poor kidney outcomes in CKD patients. We aimed at analysing the use of FGF23, FEP/FGF23, TRP, T50, and Klotho in predicting the rapid decline of renal function in kidney allograft recipients. METHODS We included 103 kidney allograft recipients in a retrospective study with a prospective follow-up of 4 years. We analysed the predictive values of FGF23, FEP/FGF23, TRP, T50, and Klotho for a rapid decline of renal function defined as a drop of eGFR > 30%. RESULTS During a follow-up of 4 years, 23 patients displayed a rapid decline of renal function. Tertile of FGF23 (p value = 0.17), FEP/FGF23 (p value = 0.78), TRP (p value = 0.62) and Klotho (p value = 0.31) were not associated with an increased risk of rapid decline of renal function in kidney transplant recipients. The lower tertile of T50 was significantly associated with eGFR decline >30% with a hazard ratio of 3.86 (p = 0.048) and remained significant in multivariable analysis. CONCLUSION T50 showed a strong association with a rapid decline of renal function in kidney allograft patients. This study underlines its role as an independent biomarker of loss of kidney function. We found no association between other phosphocalcic markers, such as FGF23, FEP/FGF23, TRP and Klotho, with a rapid decline of renal function in kidney allograft recipients.
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Affiliation(s)
| | - David Legouis
- Division of Intensive Care, University Hospital of Geneva, 1205 Geneva, Switzerland
| | - Andreas Pasch
- Calciscon AG, 2503 Biel, Switzerland
- Department of Physiology and Pathophysiology, Johannes Kepler University, 4040 Linz, Austria
| | - Aurélie Huber
- Service of Internal Medicine, Hospital La Chaux-de-Fonds, 2000 Neuchatel, Switzerland
| | - Lama Al-Qusairi
- Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
| | - Pierre-Yves Martin
- Service of Nephrology, Department of Internal Medicine Specialties, University Hospital of Geneva, 1205 Geneva, Switzerland
| | - Sophie de Seigneux
- Service of Nephrology, Department of Internal Medicine Specialties, University Hospital of Geneva, 1205 Geneva, Switzerland
| | - Lena Berchtold
- Service of Nephrology, Department of Internal Medicine Specialties, University Hospital of Geneva, 1205 Geneva, Switzerland
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Zuo J, Hasan AA, Hocher CF, Kalk P, Kleuser B, Krämer BK, Hocher B. Inverse correlation of intact PTH, oxidized PTH as well as non-oxidized PTH with 25-hydroxyvitamin D3 in kidney transplant recipients. Front Endocrinol (Lausanne) 2023; 14:1178166. [PMID: 37324252 PMCID: PMC10264784 DOI: 10.3389/fendo.2023.1178166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 05/17/2023] [Indexed: 06/17/2023] Open
Abstract
Background 25-hydroxyvitamin D (25(OH)D) and potentially also 1,25-dihydroxyvitamin D (1,25(OH)2D) inhibits the synthesis of parathyroid hormone (PTH) in the chief cells of the parathyroid gland. Clinical studies showing a negative correlation between (25(OH)D and PTH are in good agreement with these findings in basic science studies. However, PTH was measured in these studies with the currently clinically used 2nd or 3rd generation intact PTH (iPTH) assay systems. iPTH assays cannot distinguish between oxidized forms of PTH and non-oxidized PTH. Oxidized forms of PTH are the by far most abundant form of PTH in the circulation of patients with impaired kidney function. Oxidation of PTH causes a loss of function of PTH. Given that the clinical studies done so far were performed with an PTH assay systems that mainly detect oxidized forms of PTH, the real relationship between bioactive non-oxidized PTH and 25(OH)D as well as 1,25(OH)2D is still unknown. Methods To address this topic, we compared for the first time the relationship between 25(OH)D as well as 1,25(OH)2D and iPTH, oxPTH as well as fully bioactive n-oxPTH in 531 stable kidney transplant recipients in the central clinical laboratories of the Charité. Samples were assessed either directly (iPTH) or after oxPTH (n-oxPTH) was removed using a column that used anti-human oxPTH monoclonal antibodies, a monoclonal rat/mouse parathyroid hormone antibody (MAB) was immobilized onto a column with 500 liters of plasma samples. Spearman correlation analysis and Multivariate linear regression were used to evaluate the correlations between the variables. Results There was an inverse correlation between 25(OH)D and all forms of PTH, including oxPTH (iPTH: r=-0.197, p<0.0001; oxPTH: r=-0.203, p<0.0001; n-oxPTH: r=-0.146, p=0.001). No significant correlation was observed between 1,25(OH)2D and all forms of PTH. Multiple linear regression analysis considering age, PTH (iPTH, oxPTH and n-oxPTH), serum calcium, serum phosphor, serum creatinine, fibroblast growth factor 23 (FGF23), osteoprotegerin (OPG), albumin, and sclerostin as confounding factors confirmed these findings. Subgroup analysis showed that our results are not affected by sex and age. Conclusion In our study, all forms of PTH are inversely correlated with 25-hydroxyvitamin D (25(OH)D). This finding would be in line with an inhibition of the synthesis of all forms of PTH (bioactive n-oxPTH and oxidized forms of PTH with minor or no bioactivity) in the chief cells of the parathyroid glad.
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Affiliation(s)
- Jiao Zuo
- Department of Nephrology, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology, Pneumonology), University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany
| | - Ahmed A. Hasan
- Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology, Pneumonology), University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany
- Institute of Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Carl-Friedrich Hocher
- Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology, Pneumonology), University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany
- Institute of Pharmacy, Freie Universität Berlin, Berlin, Germany
- Klinik für Innere Medizin, Bundeswehrkrankenhaus Berlin, Berlin, Germany
| | - Philipp Kalk
- Department of Nephrology, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Diaverum Renal Care Center, Diaverum MVZ Am Neuen Garten Standort Ludwigsfelde, Potsdam, Germany
| | - Burkhard Kleuser
- Institute of Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Bernhard K. Krämer
- Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology, Pneumonology), University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany
- European Center for Angioscience ECAS, Medical Faculty Mannheim of the University of Heidelberg, Mannheim, Germany
| | - Berthold Hocher
- Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology, Pneumonology), University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany
- Reproductive, Genetic Hospital of CITIC-Xiangya, Changsha, China
- Institute of Medical Diagnostics, IMD, Berlin, Germany
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Ramos P, Larson B, Ashrafzadeh-Kian S, Ito N, Kato H, Bornhorst JA, Algeciras-Schimnich A. Intact Fibroblast Growth Factor 23 Concentrations in Hypophosphatemic Disorders. Endocr Pract 2023; 29:193-198. [PMID: 36627024 DOI: 10.1016/j.eprac.2023.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/23/2022] [Accepted: 01/03/2023] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Evaluation of circulating fibroblast growth factor 23 (FGF23) concentrations plays a key role in the differential diagnosis of patients presenting with hypophosphatemia. FGF23 concentrations obtained by different immunoassays are not comparable and subsequently, differences in the clinical performance of the assays might arise. In this study, we evaluated the clinical performance of the Medfrontier FGF23 Intact immunoassay (MedFrontier, Minaris Medical Co, Ltd, Tokyo, Japan) in clinically relevant hypophosphatemic conditions. METHODS Intact FGF23 (iFGF23) was measured in serum samples from 61 patients with FGF23-dependent hypophosphatemia (42-tumor induced osteomalacia [TIO] and 19-X-linked hypophosphatemia [XLH]); 8 patients with FGF23-independent hypophosphatemia (6-Fanconi Syndrome and 2-Vitamin D dependent rickets); 10 normophosphatemic patients; 15 chronic kidney disease (CKD) stage-2/3 and 20 CKD stage-4/5 patients; and a healthy control population. Disease-specific differences in measured iFGF23 concentrations and FGF23 concentration association with phosphate concentrations were reported. RESULTS iFGF23 concentrations were significantly elevated in 90% and 84% of TIO and XLH hypophosphatemia patients as compared to healthy controls (both TIO and XLH, P = .0001). There was no significant correlation between iFGF23 and phosphate concentrations (P = .74 and P = .86) for TIO and XLH, respectively. Patients with CKD showed a significant increase in serum iFGF23 as the estimated glomerular filtration rate decreased (ρ = -0.79, P ≤ 0.0001). CONCLUSIONS This study evaluated the clinical performance of the MedFrontier iFGF23 assay in a large cohort of XLH and TIO Caucasian and Asian patients. The clinical sensitivity of this iFGF23 assay is appropriate for clinical use.
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Affiliation(s)
- Paola Ramos
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Bethany Larson
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | | | - Nobuaki Ito
- Division of Nephrology and Endocrinology, The University of Tokyo Hospital, Tokyo, Japan; Osteoporosis Center, The University of Tokyo Hospital, Tokyo, Japan
| | - Hajime Kato
- Division of Nephrology and Endocrinology, The University of Tokyo Hospital, Tokyo, Japan; Osteoporosis Center, The University of Tokyo Hospital, Tokyo, Japan
| | - Joshua A Bornhorst
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
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Wolf L, Föller M, Feger M. The impact of SGLT2 inhibitors on αKlotho in renal MDCK and HK-2 cells. Front Endocrinol (Lausanne) 2023; 14:1069715. [PMID: 36967770 PMCID: PMC10032406 DOI: 10.3389/fendo.2023.1069715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 02/16/2023] [Indexed: 03/11/2023] Open
Abstract
αKlotho is a transmembrane protein predominantly expressed in the kidney serving as a co-receptor for phosphate homeostasis-regulating hormone FGF23 and has an extracellular domain that can be cleaved off and is a hormone. αKlotho deficiency results in accelerated aging and early onset of aging-associated diseases while its overexpression strongly expands the lifespan of mice. Moreover, αKlotho exerts health-beneficial anti-inflammatory, anti-neoplastic, anti-fibrotic, and anti-oxidant effects. Higher αKlotho levels are associated with better outcomes in renal and cardiovascular diseases. SGLT2 inhibitors are novel drugs in the treatment of diabetes by inhibiting renal glucose transport and have additional nephro- and cardioprotective effects. We explored whether SGLT2 inhibitors affect αKlotho gene expression and protein secretion. Experiments were performed in renal MDCK and HK-2 cells, and αKlotho transcripts were determined by qRT-PCR and Klotho protein by ELISA. SGLT2 inhibitors canagliflozin, sotagliflozin, and dapagliflozin enhanced whereas empagliflozin reduced αKlotho gene expression in MDCK cells. By the same token, canagliflozin, sotagliflozin, dapagliflozin, but not empagliflozin down-regulated p65 subunit of pro-inflammatory NFκB. In HK-2 cells, all SGLT2 inhibitors reduced αKlotho transcripts. Canagliflozin and sotagliflozin, however, increased Klotho protein concentration in the cell culture supernatant, an effect paralleled by up-regulation of ADAM17. Taken together, our investigations demonstrate complex effects of different SGLT2 inhibitors on αKlotho gene expression and protein secretion in renal MDCK and HK-2 cells.
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Li L, Gan H. Intact Fibroblast Growth Factor 23 Regulates Chronic Kidney Disease–Induced Myocardial Fibrosis by Activating the Sonic Hedgehog Signaling Pathway. J Am Heart Assoc 2022; 11:e026365. [DOI: 10.1161/jaha.122.026365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background
Clinically, myocardial fibrosis is one of the most common complications caused by chronic kidney disease (CKD). However, the potential mechanisms of CKD‐induced myocardial fibrosis have not been clarified.
Methods and Results
In our in vivo study, a rat model of CKD with 5/6 nephrectomy was established. The CKD model was treated with the glioma 1 (Gli‐1) inhibitor GANT‐61, and myocardial fibrosis and serum intact fibroblast growth factor 23 levels were assessed 16 weeks after nephrectomy. Finally, we found that Gli‐1 and Smoothened in the Sonic Hedgehog (Shh) signaling pathway were activated and that collagen‐1 and collagen‐3, which constitute the fibrotic index, were expressed in CKD myocardial tissue. After administering the Gli‐1 inhibitor GANT‐61, the degree of myocardial fibrosis was reduced, and Gli‐1 expression was also inhibited. We also measured blood pressure, cardiac biomarkers, and other indicators in rats and performed hematoxylin‐eosin staining of myocardial tissue. Furthermore, in vitro studies showed that intact fibroblast growth factor 23 promoted cardiac fibroblast proliferation and transdifferentiation into myofibroblasts by activating the Shh signaling pathway, thereby promoting cardiac fibrosis, as manifested by increased expression of the Shh, Patch 1, and Gli‐1 mRNAs and Shh, Smoothened, and Gli‐1 proteins in the Shh signaling pathway. The protein and mRNA levels of other fibrosis indicators, such as α‐smooth muscle actin, which are also markers of transdifferentiation, collagen‐1, and collagen‐3, were increased.
Conclusions
On the basis of these results, intact fibroblast growth factor 23 promotes CKD‐induced myocardial fibrosis by activating the Shh signaling pathway.
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Affiliation(s)
- Lanlan Li
- Department of Nephrology The First Affiliated Hospital of Chongqing Medical University Chongqing China
| | - Hua Gan
- Department of Nephrology The First Affiliated Hospital of Chongqing Medical University Chongqing China
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12
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Münz S, Wolf L, Hoelzle LE, Chernyakov D, Edemir B, Föller M. Impact of cytotoxic agents or apoptosis stimulants on αklotho in MDCK, NRK-52E and HK2 kidney cells. Aging (Albany NY) 2022; 14:7282-7299. [PMID: 35997650 PMCID: PMC9550246 DOI: 10.18632/aging.204238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 08/09/2022] [Indexed: 11/25/2022]
Abstract
αKlotho is a transmembrane protein acting as a co-receptor for FGF23, a bone hormone regulating renal phosphate and vitamin D metabolism. αKlotho expression is controlled by PPARγ. Soluble αklotho (sKL) regulates cellular signaling impacting stress resistance and death. αKlotho deficiency causes early onset of aging-associated diseases while its overexpression markedly increases lifespan. Cellular stress due to cytotoxic therapeutics or apoptosis induction through caspase activation or serum deficiency may result in cell death. Owing to αklotho's role in cellular stress and aging, this study explored the effect of cytotoxic agents or apoptosis stimulants on cellular αklotho expression. Experiments were performed in renal MDCK, NRK-52E and HK-2 cells. Gene expression was determined by qRT-PCR, sKL by ELISA, apoptosis and necrosis by annexin V binding and a fluorescent DNA dye, and cell viability by MTT assay. Cytostatic drugs cisplatin, paclitaxel, and doxorubicin as well as apoptosis induction with caspase 3 activator PAC-1 and serum deprivation induced αklotho and PPARG gene expression while decreasing viability and proliferation and inducing apoptosis of MDCK and NRK-52E cells to a variable extent. PPARγ antagonism attenuated up-regulation of αklotho in MDCK cells. In HK-2 cells, αklotho gene expression and sKL protein were down-regulated by chemotherapeutics. SKL serum levels in patients following chemotherapy were not significantly changed. In summary, potentially fatal stress results in up-regulation of αKlotho gene expression in MDCK and NRK-52E cells and down-regulation in HK-2 cells. These results indicate that different renal cell lines may exhibit completely different regulation of αklotho.
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Affiliation(s)
- Sina Münz
- Department of Physiology, University of Hohenheim, Stuttgart 70599, Germany
| | - Lisa Wolf
- Department of Physiology, University of Hohenheim, Stuttgart 70599, Germany
| | - Ludwig E Hoelzle
- Institute of Animal Science, University of Hohenheim, Stuttgart 70599, Germany
| | - Dmitry Chernyakov
- Department of Oncology, Martin-Luther-University Halle-Wittenberg, Halle (Saale) 06120, Germany
| | - Bayram Edemir
- Department of Oncology, Martin-Luther-University Halle-Wittenberg, Halle (Saale) 06120, Germany
| | - Michael Föller
- Department of Physiology, University of Hohenheim, Stuttgart 70599, Germany
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Silva AP, Viegas CSB, Guilherme P, Tavares N, Dias C, Rato F, Santos N, Faísca M, de Almeida E, Neves PL, Simes DC. Gla-Rich Protein, Magnesium and Phosphate Associate with Mitral and Aortic Valves Calcification in Diabetic Patients with Moderate CKD. Diagnostics (Basel) 2022; 12:diagnostics12020496. [PMID: 35204586 PMCID: PMC8870734 DOI: 10.3390/diagnostics12020496] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 02/07/2022] [Accepted: 02/10/2022] [Indexed: 02/04/2023] Open
Abstract
Accelerated and premature cardiovascular calcification is a hallmark of chronic kidney disease (CKD) patients. Valvular calcification (VC) is a critical indicator of cardiovascular disease and all-cause mortality in this population, lacking validated biomarkers for early diagnosis. Gla-rich protein (GRP) is a cardiovascular calcification inhibitor recently associated with vascular calcification, pulse pressure, mineral metabolism markers and kidney function. Here, we examined the association between GRP serum levels and mitral and aortic valves calcification in a cohort of 80 diabetic patients with CKD stages 2–4. Mitral and aortic valves calcification were detected in 36.2% and 34.4% of the patients and associated with lower GRP levels, even after adjustments for age and gender. In this pilot study, univariate, multivariate and Poisson regression analysis, show that low levels of GRP and magnesium (Mg), and high levels of phosphate (P) are associated with mitral and aortic valves calcification. Receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) values of GRP for mitral (0.762) and aortic (0.802) valves calcification were higher than those of Mg and P. These results suggest that low levels of GRP and Mg, and high levels of P, are independent and cumulative risk factors for VC in this population; the GRP diagnostic value might be potentially useful in cardiovascular risk assessment.
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Affiliation(s)
- Ana P. Silva
- Department of Nephrology, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (A.P.S.); (P.L.N.)
- Department of Biomedical Sciences and Medicine, Universidade do Algarve, 8005-139 Faro, Portugal;
| | - Carla S. B. Viegas
- Centre of Marine Sciences (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal;
- GenoGla Diagnostics, Centre of Marine Sciences (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal
| | - Patrícia Guilherme
- Department of Cardiology, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (P.G.); (N.T.)
| | - Nelson Tavares
- Department of Cardiology, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (P.G.); (N.T.)
| | - Carolina Dias
- Department of Biomedical Sciences and Medicine, Universidade do Algarve, 8005-139 Faro, Portugal;
- Centre of Marine Sciences (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal;
| | - Fátima Rato
- Pathology Clinic, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (F.R.); (N.S.); (M.F.)
| | - Nélio Santos
- Pathology Clinic, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (F.R.); (N.S.); (M.F.)
| | - Marília Faísca
- Pathology Clinic, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (F.R.); (N.S.); (M.F.)
| | - Edgar de Almeida
- Centro Cardiovascular da Universidade de Lisboa (CCUL), 1649-028 Lisboa, Portugal;
| | - Pedro L. Neves
- Department of Nephrology, Centro Hospitalar Universitário do Algarve, 8000-386 Faro, Portugal; (A.P.S.); (P.L.N.)
- Department of Biomedical Sciences and Medicine, Universidade do Algarve, 8005-139 Faro, Portugal;
| | - Dina C. Simes
- Centre of Marine Sciences (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal;
- GenoGla Diagnostics, Centre of Marine Sciences (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal
- Correspondence: ; Tel.: +351-289-800100
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Alber J, Föller M. Lactic acid induces fibroblast growth factor 23 (FGF23) production in UMR106 osteoblast-like cells. Mol Cell Biochem 2022; 477:363-370. [PMID: 34731356 PMCID: PMC8800909 DOI: 10.1007/s11010-021-04287-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 10/23/2021] [Indexed: 01/04/2023]
Abstract
Endocrine and paracrine fibroblast growth factor 23 (FGF23) is a protein predominantly produced by bone cells with strong impact on phosphate and vitamin D metabolism by targeting the kidney. Plasma FGF23 concentration early rises in kidney and cardiovascular diseases correlating with progression and outcome. Lactic acid is generated in anaerobic glycolysis. Lactic acidosis is the consequence of various physiological and pathological conditions and may be fatal. Since FGF23 production is stimulated by inflammation and lactic acid induces pro-inflammatory signaling, we investigated whether and how lactic acid influences FGF23. Experiments were performed in UMR106 osteoblast-like cells, Fgf23 mRNA levels estimated from quantitative real-time polymerase chain reaction, and FGF23 protein determined by enzyme-linked immunosorbent assay. Lactic acid dose-dependently induced Fgf23 gene expression and up-regulated FGF23 synthesis. Also, Na+-lactate as well as formic acid and acetic acid up-regulated Fgf23. The lactic acid effect was significantly attenuated by nuclear factor kappa-light-chain enhancer of activated B-cells (NFκB) inhibitors wogonin and withaferin A. Lactic acid induces FGF23 production, an effect at least in part mediated by NFκB. Lactic acidosis may, therefore, be paralleled by a surge in plasma FGF23.
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Affiliation(s)
- Jana Alber
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany
| | - Michael Föller
- Department of Physiology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
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15
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The regulation of FGF23 under physiological and pathophysiological conditions. Pflugers Arch 2022; 474:281-292. [PMID: 35084563 PMCID: PMC8837506 DOI: 10.1007/s00424-022-02668-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 12/18/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is an important bone hormone that regulates phosphate homeostasis in the kidney along with active vitamin D (1,25(OH)2D3) and parathyroid hormone (PTH). Endocrine effects of FGF23 depend, at least in part, on αKlotho functioning as a co-receptor whereas further paracrine effects in other tissues are αKlotho-independent. Regulation of FGF23 production is complex under both, physiological and pathophysiological conditions. Physiological regulators of FGF23 include, but are not limited to, 1,25(OH)2D3, PTH, dietary phosphorus intake, and further intracellular and extracellular factors, kinases, cytokines, and hormones. Moreover, several acute and chronic diseases including chronic kidney disease (CKD) or further cardiovascular disorders are characterized by early rises in the plasma FGF23 level pointing to further mechanisms effective in the regulation of FGF23 under pathophysiological conditions. Therefore, FGF23 also serves as a prognostic marker in several diseases. Our review aims to comprehensively summarize the regulation of FGF23 in health and disease.
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Münz S, Feger M, Edemir B, Föller M. Up-Regulation of Fibroblast Growth Factor 23 Gene Expression in UMR106 Osteoblast-like Cells with Reduced Viability. Cells 2021; 11:40. [PMID: 35011602 PMCID: PMC8750768 DOI: 10.3390/cells11010040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 02/07/2023] Open
Abstract
Fibroblast growth factor 23 (FGF23) controls vitamin D and phosphate homeostasis in the kidney and has additional paracrine effects elsewhere. As a biomarker, its plasma concentration is associated with progression of inflammatory, renal, and cardiovascular diseases. Major stimuli of FGF23 synthesis include active vitamin D and inflammation. Antineoplastic chemotherapy treats cancer by inducing cellular damage ultimately favoring cell death (apoptosis and necrosis) and causing inflammation. Our study explored whether chemotherapeutics and other apoptosis inducers impact on Fgf23 expression. Experiments were performed in osteoblast-like UMR106 cells, Fgf23 gene expression and protein synthesis were determined by qRT-PCR and ELISA, respectively. Viability was assessed by MTT assay and NFκB activity by Western Blotting. Antineoplastic drugs cisplatin and doxorubicin as well as apoptosis inducers procaspase-activating compound 1 (PAC-1), a caspase 3 activator, and serum depletion up-regulated Fgf23 transcripts while reducing cell proliferation and viability. The effect of cisplatin on Fgf23 transcription was paralleled by Il-6 up-regulation and NFκB activation and attenuated by Il-6 and NFκB signaling inhibitors. To conclude, cell viability-decreasing chemotherapeutics as well as apoptosis stimulants PAC-1 and serum depletion up-regulate Fgf23 gene expression. At least in part, Il-6 and NFκB may contribute to this effect.
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Affiliation(s)
- Sina Münz
- Department of Physiology, University of Hohenheim, 70599 Stuttgart, Germany; (S.M.); (M.F.)
| | - Martina Feger
- Department of Physiology, University of Hohenheim, 70599 Stuttgart, Germany; (S.M.); (M.F.)
| | - Bayram Edemir
- Department of Hematology and Oncology, Martin Luther University Halle-Wittenberg, 06120 Halle, Germany;
| | - Michael Föller
- Department of Physiology, University of Hohenheim, 70599 Stuttgart, Germany; (S.M.); (M.F.)
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Alber J, Freisinger P, Föller M. The synthesis of fibroblast growth factor 23 is upregulated by homocysteine in UMR106 osteoblast-like cells. Nutrition 2021; 96:111573. [PMID: 35091320 DOI: 10.1016/j.nut.2021.111573] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/06/2021] [Accepted: 12/13/2021] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Fibroblast growth factor 23 (FGF23) controls the production and degradation of biologically active vitamin D, 1,25(OH)2D3, and phosphate reabsorption in the kidney as a hormone synthesized by bone cells. Additional paracrine effects in other organs exist as well. As a biomarker, the FGF23 plasma concentration increases in renal and cardiovascular diseases, and is correlated with outcome. The regulation of FGF23 is incompletely understood and dependent on several factors, including oxidative stress. L-homocysteine is an amino acid produced in methionine metabolism, and can be converted into further metabolites depending on the availability of vitamin B. Hyperhomocysteinemia is a potential cardiovascular risk factor. Our study aimed to explore whether homocysteine impacts FGF23 synthesis. METHODS Experiments were performed in UMR106 osteoblast-like cells. Fgf23 gene expression and FGF23 protein concentration were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Oxidative stress was determined by 2',7'-dichlorofluorescein diacetate fluorescence. RESULTS Homocysteine dose-dependently upregulated Fgf23 gene expression and protein synthesis. Moreover, homocysteine imposed oxidative stress on UMR106 cells. The effect of homocysteine on Fgf23 was abrogated by antioxidant ascorbic acid. CONCLUSIONS Homocysteine is a potent stimulator of FGF23 production, an effect at least in part mediated by oxidative stress. The homocysteine-dependent upregulation of FGF23 presumably contributes to its role as a cardiovascular risk factor.
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Affiliation(s)
- Jana Alber
- University of Hohenheim, Department of Physiology, Stuttgart, Germany
| | - Peter Freisinger
- Kreiskliniken Reutlingen, Department of Pediatrics, Reutlingen, Germany
| | - Michael Föller
- University of Hohenheim, Department of Physiology, Stuttgart, Germany.
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