Fibroblast Growth Factor 23 Expression Research Articles

Excess fibroblast growth factor 23 in alcoholic osteomalacia is derived from the bone.

Excess fibroblast growth factor 23 (FGF23), a mature osteocyte-derived phosphaturic hormone, causes chronic hypophosphatemic osteomalacia in adults. This rare condition was recently reported in 2 alcoholic patients, with marked improvement upon cessation of alcohol consumption, suggesting a link between alcohol and FGF23-related hypophosphatemia within the highly limited cases. This study aimed to investigate whether the source of excess FGF23 in alcohol-induced FGF23-related hypophosphatemic osteomalacia is the bone or the other organs. To achieve this goal, an immunohistochemical approach for the bone obtained from a patient was employed. Initial attempts at quantifying FGF23 in the bone using conventional immunohistochemistry (IHC) faced issues in quantifiability and sensitivity for low FGF23 expression levels. Therefore, next-generation IHC with phosphor-integrated dots (PIDs) was applied, which enabled the quantification of FGF23 expression in the bone across a broad range. Preliminary analyses using IHC with PIDs on normal bone samples (n = 12) provided a reference level (154.5 PID particles per cell). IHC with PIDs quantified suppressed physiological FGF23 expression in the bone samples from 3 patients with tumor-induced osteomalacia, where FGF23 is oversecreted from a tumor (13.6 PID particles per cell). Subsequently, bone samples obtained from a 70-yr-old male with alcohol-induced FGF23-related hypophosphatemic osteomalacia were analyzed, showing a higher number of PID particles per cell (199.4 PID particles per cell) than the reference level. This study suggests that orthotopic, bone-derived FGF23 is implicated in alcohol-induced FGF23-related hypophosphatemic osteomalacia. Furthermore, the study also demonstrated that highly sensitive IHC with PIDs could aid in the differential diagnosis of FGF23-related hypophosphatemia of unknown origin. Specifically, a bone sample with a low number of PID particles per cell indicates an excess ectopic secretion of FGF23; a bone sample with a normal to high number of PID particles per cell indicates an excess orthotopic secretion of FGF23.

Risk factors for radial artery calcification in patients with and without uremia

BackgroundCalcification of the radial artery is one of the main causes of anastomotic stenosis in autogenous arteriovenous fistulas in uremic patients. However, the pathogenesis of calcification is still unknown. This study attempted to screen and validate the risk factors for vascular calcification in patients with uremia.MethodsSerum of blood were collected and tissue samples from radial artery were obtained from 60 uremia patients with or without hemodialysis. General biochemical indicators and calcification-related molecules were collected and detected via ELISA or correlation analysis. In addition, pathological changes and calcification-related molecules in the radial artery were evaluated by HE or immunohistochemical staining.ResultsThere were differences in total calcium, calcium-phosphorus products, allograft inflammatory factor 1 (AIF-1), intact parathyroid hormone (iPTH), vitamin D (VD), fibroblast growth factor 23 (FGF23) and soluble klotho (sKlotho) in the blood of uremic patients with or without hemodialysis. Furthermore, these factors are related to calcification of the radial artery. The expression of AIF-1, PTHR1, VDR, FGF23 and sKlotho was also increased in the calcified radial artery.ConclusionsThe levels of AIF-1, PTH, VDR, FGF23 and sKlotho in serum were associated with calcification of the radial artery in patients with uremia. Furthermore, calcification of the radial artery was further aggravated by abnormalities in calcium and phosphorus in maintenance hemodialysis patients.

Expression profile of FGF23, alpha klotho, microRNA-126, and wnt signaling pathway gene polymorphism in patients with acute or chronic kidney diseases: relation to dialysis requirements

The connection between chronic kidney disease (CKD) and acute kidney injury (AKI) is becoming more widely acknowledged, as the two conditions probably exacerbate one other. The purpose of the present study was to evaluate the circulating levels of fibroblast growth factor 23 (FGF23), αKlotho, and mircoRNA-126 (miR-126) and to explore the possible genetic role of single nucleotide polymorphisms (SNPs) in the klotho G-395A (rs1207568), C1818T (rs564481), and wnt signaling pathway AXIN-1 C > T (rs9921222) in AKI and CKD patients and their relation to progression of kidney disease and dialysis necessity. In this case–control study, there were 50 AKI patients, 100 CKD patients, and 50 healthy controls. ELISA assay kits were utilized to measure the plasma concentrations of FGF23 and α klotho, while reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was used to measure the expression levels of miR-126. Using conventional PCR methods, rs1207568, rs564481 and rs9921222 SNPs were genetically analyzed. Patients with AKI and CKD had significantly higher median FGF23 levels than controls (P < 0.05), with the AKI group showing much higher levels than the CKD patients (P < 0.05). Patients with AKI and CKD had significantly lower median αKlotho levels than controls (P < 0.001). When CKD patients were compared to controls and AKI patients, the expression levels of miR-126 were significantly greater, while significantly lower in AKI patients compared to controls, (P < 0.05). AKI and CKD patients had a significantly greater frequency of GG genotype of rs1207568 than the control group (< 0.001, and = 0.021 respectively). However, for klotho rs564481, all participants had CT genotype. In the CKD group compared to controls, rs9921222 SNP revealed a considerably greater frequency of mutant heterozygous CT genotype with a significantly lower wild CC genotype, P = < 0.001. Area under the curve (AUC) value of 0.638 for miR-126 expression levels indicate modest efficacy in identifying dialysis necessity among AKI patients. While miR-126 and plasma FGF23 expression levels among CKD patients demonstrated high efficacy, with AUC values of 0.924 and 0.845, respectively. αKlotho's AUC of 0.786 indicated a moderate level of discriminatory ability. AKI and CKD may be associated with disrupted expression levels of FGF23, αKlotho, and miR-126, which may serve as possible biomarkers for CKD patients requiring dialysis. An increased risk of developing CKD was shown to be associated with the GG genotype of the Klotho rs1207568 SNP and the CT genotype of the wnt signaling pathway rs9921222 SNP.

Klotho Is Cardioprotective in the mdx Mouse Model of Duchenne Muscular Dystrophy.

Klotho Is Cardioprotective in the mdx Mouse Model of Duchenne Muscular Dystrophy.

The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23

Fibroblast growth factor 23 (FGF23) plays an important role in phosphate homeostasis, and increased FGF23 levels result in hypophosphatemia; however, the molecular mechanism underlying increased FGF23 expression has not been fully elucidated. In this study, we found that mice lacking the bobby sox homolog (Bbx−/−) presented increased FGF23 expression and low phosphate levels in the serum and skeletal abnormalities such as a low bone mineral density (BMD) and bone volume (BV), as well as short and weak bones associated with low bone formation. Osteocyte-specific deletion of Bbx using Dmp-1-Cre resulted in similar skeletal abnormalities, elevated serum FGF23 levels, and reduced serum phosphate levels. In Bbx−/− mice, the expression of sodium phosphate cotransporter 2a (Npt2a) and Npt2c in the kidney and Npt2b in the small intestine, which are negatively regulated by FGF23, was downregulated, leading to phosphate excretion/wasting and malabsorption. An in vitro Fgf23 promoter analysis revealed that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-induced transactivation of the Fgf23 promoter was significantly inhibited by BBX overexpression, whereas it was increased following Bbx knockdown. Interestingly, 1,25(OH)2D3 induced an interaction of the 1,25(OH)2D3 receptor (VDR) with BBX and downregulated BBX protein levels. Cycloheximide (CHX) only partially downregulated BBX protein levels, indicating that 1,25(OH)2D3 regulates BBX protein stability. Furthermore, the ubiquitination of BBX followed by proteasomal degradation was required for the increase in Fgf23 expression induced by 1,25(OH)2D3. Collectively, our data demonstrate that BBX negatively regulates Fgf23 expression, and consequently, the ubiquitin-dependent proteasomal degradation of BBX is required for FGF23 expression, thereby regulating phosphate homeostasis and bone development in mice.

Causal association of serum calcium, phosphate, vitamin D, parathyroid hormone, and FGF23 with the risk of aortic stenosis

Abstract Aim Disorders of mineral metabolism, including elevated levels of serum calcium, phosphate, 25-hydroxyvitamin D (25OH-VitD), parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23), have been reported in patients with calcific aortic valve stenosis (CAVS). However, evidence of the causal role of mineral metabolism in CAVS is still lacking. We aimed to investigate the causality between mineral metabolism and CAVS. Methods A systematic pipeline combining Mendelian randomization (MR), Steiger directionality test, colocalization analysis, protein-protein network, and enrichment analysis was applied to investigate the causal effect. Genome-wide association study (GWAS) and protein quantitative trait loci data for mineral metabolism markers were extracted from large-scale meta-analyses. Summary statistics for CAVS were obtained from two independent GWAS datasets as discovery and replication cohorts (n=374,277 and 653,867). Results In MR analysis, genetic mimicry of serum FGF23 elevation was associated with increased CAVS risk [ORdiscovery=3.081 (1.649-5.760), Pdiscovery=4.21×10-4; ORreplication=2.280 (1.461-3.558), Preplication=2.82×10-4] without evidence of reverse causation (Psteiger=7.21×10-98). Strong colocalisation association with CAVS was observed for FGF23 expression in the blood (PP.H4 = 0.96). Additionally, we identified some protein-protein interactions between FGF23 and known CAVS causative genes. Serum calcium, phosphate, 25OH-VitD, and PTH failed to show causal effects on CAVS at Bonferroni-corrected significance (all P&amp;gt;0.05/5=0.01). Conclusions Elevated serum FGF23 level is a causal risk factor for CAVS, and its mechanism of action in CAVS development may be independent of its function in regulating mineral metabolism. Hence, FGF23 may serve as a circulating marker and a promising preventive target for CAVS, warranting further investigation.

Hypoxia Activates FGF-23-ERK/MAPK Signaling Pathway in Ischemia-Reperfusion-Induced Acute Kidney Injury

Introduction: Both hypoxia and fibroblast growth factor-23 (FGF-23) are key factors in ischemia-reperfusion (I/R)-induced acute kidney injury (AKI). This study aimed to explore the relationship between hypoxia and FGF-23 in AKI. Methods: An I/R-AKI animal model was established using male BALB/c mice. HK-2 cells, a part of the human proximal tubular epithelial cell line, were subjected to hypoxia/reoxygenation (H/R). qPCR was used to measure FGF-23 and HIF1α, and ELISA was used to measure inflammatory and oxidative stress cytokines. Western blotting was used to measure the phosphorylation of extracellular signal-regulated kinase (ERK) level. Results: In I/R mice, the levels of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), malondialdehyde (MDA), and the phosphorylation of ERK (p-ERK) were increased, whereas the levels of interleukin-10 (IL-10), superoxide dismutase (SOD), glutathione peroxidase (GPx), and klotho were decreased, compared to the sham-operated mice. Silencing the FGF-23 expression in I/R mice normalized the levels of IL-6, IL-10, TNF-α, MDA, SOD, GPx, and p-ERK. In HK-2 cells, hypoxia-reperfusion (H/R) elevated the levels of IL-6, TNF-α, MDA, and p-ERK, but reduced IL-10, SOD, GPx, and klotho levels. Hypoxia induced apoptosis in HK-2 cells, but silencing of FGF-23 expression blocked the effects of hypoxia on cell apoptosis, pro-inflammatory factor levels, oxidative stress response, and p-ERK levels. Conclusion: FGF-23 is a key molecule in AKI, and hypoxia plays a crucial role in AKI by inducing cell apoptosis; however, its role is regulated by FGF-23. FGF-23 affects oxidative stress and the inflammatory response of kidney tissues by activating the ERK/mitogen-activated protein kinase (MAPK) signaling pathway.

Evaluation of alpha Klotho and fibroblast growth factor-23 levels in Iraqi patients with Graves’ disease

Background &amp; Objective: Graves’ disease (GD) is an autoimmune condition that targets the thyroid gland, resulting in excessive stimulation and synthesis of thyroid hormones. Excessive synthesis of these hormones can lead to symptoms such as loss of body weight, accelerated heart rate, irritability, reduced tolerance to heat, and excessive perspiration. Alpha-Klotho (KL), a protein crucial for physiological processes, is also involved in GD. The defective immunological condition of GD patients may increase Klotho expression, and the enhanced expression of fibroblast growth factor-23 (FGF23) in GD may be linked to the disease pathophysiology. We investigated serum levels of KL and FGF23 in Iraqi patients with Graves’ disease, analyzing correlations with clinical status and evaluating their potential as biomarkers for disease activity. Methodology: We conducted this cross-sectional study at The National Diabetes Center, Mustansiriyah University, between December 2022 and April 2023. The study involved 103 patients diagnosed with GD, and 103 patients, aged 21-70 y, as a control group. Patients with multinodular goiter, single thyroid nodules, thyroiditis, pregnant women, and those on medications or oral contraceptives, were excluded. Result: clinical significance of FGF23 and Klotho (KL) levels in patients with Graves’ disease (GD) compared to a control group. Results indicate that the median of KL levels are significantly higher in GD patients (KL = 6.31) compared to the control group (KL = 2.40), with a highly significant difference (P &lt; 0.001). In contrast, differences in median of FGF23 levels between GD patients (149) and controls (86.05) were not statistically significant (P = 0.07). Furthermore, KL levels were significantly higher in hyperthyroid patients compared to other thyroid statuses (P = 0.023), while FGF23 levels did not significantly differ across thyroid statuses (P = 0.255). Additionally, the study found a strong correlation between TRAb levels and both KL (r = 0.291, P &lt; 0.001) and FGF23 (r = 0.211, P = 0.003), and between KL and FGF23 directly (r = 0.412, P &lt; 0.001). These findings suggest that while KL may be a significant biomarker in GD, FGF23 relevance appears limited in this context. Conclusion: In Graves’ Disease patients have significantly higher levels of KL and FGF23 compared to controls, suggesting a distinct pathophysiological role for these biomarkers in mineral homeostasis and thyroid hormone regulation. Abbreviations: AITD - Autoimmune thyroid diseases; KL - Alpha-Klotho; FGF23 - fibroblast growth factor-23; GD - Graves’ disease; HT - Hashimoto's thyroiditis; IGF-1R - Insulin-like Growth Factor-1 Receptor; Keywords: Autoimmune Thyroid Disorders, Hyperthyroidism, Graves’ disease, Alpha-Klotho Citation: Rashid MF, Alammar HAJ, Rahmah AM. Evaluation of alpha Klotho and fibroblast growth factor-23 levels in Iraqi patients with Graves’ disease. Anaesth. pain intensive care 2024;28(5):836−841. DOI: 10.35975/apic.v28i5.2567 Received: June 16, 2024; Reviewed: July 07, 2024; Accepted: July 18, 2024

7582 Genetic Profiling of Phosphaturic Mesenchymal Tumors Unravels Osterix's Significance in Tumor-Induced Osteomalacia

Abstract Disclosure: Y. Imanishi: None. Y. Nagata: None. M. Ohara: None. T. Maeda-Tateishi: None. T. Shoji: None. M. Emoto: None. Background &amp; Purpose: Tumor-induced osteomalacia (TIO) is a rare condition caused by tumors releasing too much fibroblast growth factor 23 (FGF23). These tumors, specifically called phosphaturic mesenchymal tumors, mixed connective tissue variant (PMTMCT), lead to osteomalacia due to low serum phosphate levels. However, a detailed study regarding the genetic makeup of these tumors and their similarity to bone cells (osteoblasts/osteocytes) has been lacking. Methods: Nineteen PMTMCTs were analyzed and compared their gene expressions to 6 non-TIO tumors. Our focus was on genes usually found in bone cells. Additionally, we examined the relationship between FGF23 and these genes in PMTMCTs. One gene, Osterix, showing significant correlation was further studied using UMR106 osteoblast cells. Results: Fourteen genes related to bone cells expressed significantly higher in PMTMCTs compared to non-TIO tumors. Immunoblotting and Immunohistochemical examinations confirmed the presence of FGF23, Runx2, and Osterix in PMTMCTs. Particularly, Osterix showed the strongest link with FGF23 in PMTMCTs. Immunohistochemical tests revealed similar patterns of distribution for Osterix and FGF23, even co-localizing in some instances. However, the distribution of another gene, DMP1, differed from that of FGF23. In UMR106 cells, silencing Osterix expression led to decreased FGF23 expression, irrespective of DMP1 levels. Conclusions: PMTMCTs exhibit higher levels of genes associated with bone cell functions compared to other tumors. These tumors likely originated from mesenchymal stem cells and transformed into bone cells. Furthermore, Osterix might play a crucial role in the excessive release of FGF23 in PMTMCTs. Presentation: 6/1/2024

Genetic association of serum calcium, phosphate, vitamin D, parathyroid hormone, and FGF23 with the risk of aortic stenosis

Disorders of mineral metabolism, including elevated levels of serum calcium, phosphate, 25-hydroxyvitamin D (25OH-VitD), parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23), have been reported in patients with calcific aortic valve stenosis (CAVS). However, evidence of the causal role of mineral metabolism in CAVS is still lacking. In this study, we employed a systematic pipeline combining Mendelian randomization (MR), Steiger directionality test, colocalization analysis, protein-protein network, and enrichment analysis to investigate the causal effect of mineral metabolism on CAVS. Genome-wide association study (GWAS) and protein quantitative trait loci data for mineral metabolism markers were extracted from large-scale meta-analyses. Summary statistics for CAVS were obtained from two independent GWAS datasets as discovery and replication cohorts (n = 374,277 and 653,867). In MR analysis, genetic mimicry of serum FGF23 elevation was associated with increased CAVS risk [ORdiscovery = 3.081 (1.649–5.760), Pdiscovery = 4.21 × 10−4; ORreplication = 2.280 (1.461 – 3.558), Preplication = 2.82 × 10−4] without evidence of reverse causation (Psteiger= 7.21 × 10−98). Strong colocalisation association with CAVS was observed for FGF23 expression in the blood (PP.H4 = 0.96). Additionally, we identified some protein-protein interactions between FGF23 and known CAVS-associated genes. Serum calcium, phosphate, 25OH-VitD, and PTH failed to show causal effects on CAVS at Bonferroni-corrected significance (all P > 0.05/5 = 0.01). In conclusion, elevated serum FGF23 level may act as a causal risk factor for CAVS, and its mechanism of action in CAVS development may be independent of its function in regulating mineral metabolism. Hence, FGF23 may serve as a circulating marker and a promising preventive target for CAVS, warranting further investigation.

High-Throughput Preosteoblastic Spheroids Elevate Fibroblast Growth Factor 23 via Parathyroid Hormone Signaling Pathway.

Fibroblast growth factor 23 (FGF23) plays a crucial role in managing renal phosphate and the synthesis of 1,25(OH)2-vitamin D3, which is essential for bone homeostasis. Developing robust in vitro systems to study FGF23-regulating mechanisms is crucial for advancing our knowledge and identifying potential therapeutic targets. The traditional in vitro 2D culture system results in relatively low expression of FGF23, complicating further exploration of its regulatory mechanisms and potential therapeutic targets. Herein, we reported a high-throughput approach to generate preosteoblastic cell spheroids with enhanced FGF23 production. For this purpose, murine preosteoblast cell line (MC3T3-E1) was cultured in our previously reported nonadherent microwells (200 µm in diameter, 148 µm in depth, and 100 µm space in between) and self-assembled into spheroids with a diameter of 92.3 ± 15.0 µm after 24 h. Compared with monolayer culture, the MC3T3-E1 spheroids showed a significant upregulation of FGF23 in both gene and protein levels after 24 h of serum-free induction. RNA sequencing and western blotting analysis further suggested that the enhanced FGF23 production in MC3T3-E1 spheroids was attributed to the activation of the parathyroid hormone (PTH)/PTH1R signaling pathway. Impressively, inhibition of PTH signaling through small molecular inhibitors or short hairpin RNA targeting PTH1R effectively reduced FGF23 production. In summary, the current study revealed the efficacy of the high-throughput formation of preosteoblast cell spheroid in stimulating FGF23 expression for mechanistic studies. Importantly, our findings highlight the potential of the current 3D spheroid system for target identification and drug discovery.

#977 Etelcalcetide improve left ventricular hypertrophy by suppressing the renin-angiotensin-aldosterone system and cardiac fibroblast growth factor 23

Abstract Background and Aims Calcimimetics are allosteric activators of the calcium-sensing receptor (CaSR) and are employed as therapeutic agents for managing secondary hyperparathyroidism in chronic kidney disease (CKD) patients undergoing dialysis. Although they have shown potential in reducing cardiovascular diseases and suppressing left ventricular hypertrophy (LVH), the mechanisms underlying these effects are not fully elucidated. In this study, we focused on exploring the mechanisms behind the suppression of LVH by calcimimetics using CKD, LVH, and CKD+LVH model rats. Specifically, we investigated the impact on CKD-mineral bone disorder (CKD-MBD) parameters, the renin-angiotensin-aldosterone system (RAAS), and calcineurin/nuclear factor of activated T cells (CaN/NFAT) pathway. Method In this study, we used etelcalcetide (ET) as a calcimimetic agent. At 8 weeks of age, LVH was induced in rats through transverse aortic coarctation, and CKD was induced by 5/6 nephrectomy at 9 and 10 weeks of age. The rats were divided into the four main groups: the sham group, the CKD group, the LVH group, and the CKD+LVH group. Each of the latter three groups were further subdivided into a vehicle-treated group and an ET-treated group for a duration of eight weeks. At 19 weeks of age, echocardiography was conducted on all rats prior to sacrifice. Subsequently, the rats were sacrificed, and blood and urine analyses, mRNA expression analysis, and renal histological analysis were performed. We evaluated LVH, CKD-MBD, RAAS, and CaN/NFAT pathways across these seven groups. Results In both the CKD and CKD+LVH groups, serum levels of parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) were significantly elevated, and these elevations were mitigated by ET. However, in the LVH group, serum PTH and FGF23 levels were not elevated, and ET did not induce any changes. No significant alterations in serum levels of phosphorus, calcium, 25(OH)vitamin, and 1,25(OH)2vitaminD levels due to ET were observed in any of the groups. Interestingly, ET suppressed the increase in myocardial weight/body weight ratios and the area of cardiomyocytes not only in the CKD and CKD+LVH group but also in the LVH group, despite no changes in serum PTH and FGF23 levels. Regarding the RAAS, ET attenuated the increase in serum aldosterone levels, expressions of cardiac angiotensin-converting enzyme (ACE), cardiac angiotensinogen, and cardiac angiotensin II in the LVH group and the CKD+LVH group. The expression of cardiac FGF23, which increased in the LVH group and the CKD+LVH group, was decreased by ET. Moreover, there was a significant correlation between cardiac RAAS parameters and cardiac FGF23 expressions. No alteration was observed in the CaN/NFAT pathway in response to ET. Conclusion Our findings indicated that ET effectively suppressed LVH in the CKD group and the CKD+LVH group, and it was also effective in the LVH group, independent of changes in serum CKD-MBD parameters. This suggests that ET may exert its LVH-suppressing effects through the RAAS pathway and cardiac FGF23.

A novel miR-466l-3p/FGF23 axis promotes osteogenic differentiation of human bone marrow mesenchymal stem cells

A novel miR-466l-3p/FGF23 axis promotes osteogenic differentiation of human bone marrow mesenchymal stem cells

S100a8/9 (S100 Calcium Binding Protein a8/9) Promotes Cardiac Hypertrophy Via Upregulation of FGF23 (Fibroblast Growth Factor 23) in Mice.

S100a8/9 (S100 calcium binding protein a8/9) belongs to the S100 family and has gained a lot of interest as a critical regulator of inflammatory response. Our previous study found that S100a8/9 homolog promoted aortic valve sclerosis in mice with chronic kidney disease. However, the role of S100a8/9 in pressure overload-induced cardiac hypertrophy remains unclear. The present study was to explore the role of S100a8/9 in cardiac hypertrophy. Cardiomyocyte-specific S100a9 loss or gain of function was achieved using an adeno-associated virus system, and the model of cardiac hypertrophy was established by aortic banding-induced pressure overload. The results indicate that S100a8/9 expression was increased in response to pressure overload. S100a9 deficiency alleviated pressure overload-induced hypertrophic response, whereas S100a9 overexpression accelerated cardiac hypertrophy. S100a9-overexpressed mice showed increased FGF23 (fibroblast growth factor 23) expression in the hearts after exposure to pressure overload, which activated calcineurin/NFAT (nuclear factor of activated T cells) signaling in cardiac myocytes and thus promoted hypertrophic response. A specific antibody that blocks FGFR4 (FGFreceptor 4) largely abolished the prohypertrophic response of S100a9 in mice. In conclusion, S100a8/9 promoted the development of cardiac hypertrophy in mice. Targeting S100a8/9 may be a promising therapeutic approach to treat cardiac hypertrophy.

ERRγ-inducible FGF23 promotes alcoholic liver injury through enhancing CYP2E1 mediated hepatic oxidative stress

Fibroblast growth factor 23 (FGF23) is a member of endocrine FGF family, along with FGF15/19 and FGF21. Recent reports showed that under pathological conditions, liver produces FGF23, although the role of hepatic FGF23 remains nebulous. Here, we investigated the role of hepatic FGF23 in alcoholic liver disease (ALD) and delineated the underlying molecular mechanism. FGF23 expression was compared in livers from alcoholic hepatitis patients and healthy controls. The role of FGF23 was examined in hepatocyte-specific knock-out (LKO) mice of cannabinoid receptor type 1 (CB1R), estrogen related receptor γ (ERRγ), or FGF23. Animals were fed with an alcohol-containing liquid diet alone or in combination with ERRγ inverse agonist. FGF23 is mainly expressed in hepatocytes in the human liver, and it is upregulated in ALD patients. In mice, chronic alcohol feeding leads to liver damage and induced FGF23 in liver, but not in other organs. FGF23 is transcriptionally regulated by ERRγ in response to alcohol-mediated activation of the CB1R. Alcohol induced upregulation of hepatic FGF23 and plasma FGF23 levels is lost in ERRγ-LKO mice, and an inverse agonist mediated inhibition of ERRγ transactivation significantly improved alcoholic liver damage. Moreover, hepatic CYP2E1 induction in response to alcohol is FGF23 dependent. In line, FGF23-LKO mice display decreased hepatic CYP2E1 expression and improved ALD through reduced hepatocyte apoptosis and oxidative stress. We recognized CBIR-ERRγ-FGF23 axis in facilitating ALD pathology through hepatic CYP2E1 induction. Thus, we propose FGF23 as a potential therapeutic target to treat ALD.

Phosphate Restriction Prevents Metabolic Acidosis and Curbs Rise in FGF23 and Mortality in Murine Folic Acid-Induced AKI.

Patients with AKI suffer a staggering mortality rate of approximately 30%. Fibroblast growth factor 23 (FGF23) and phosphate (P i ) rise rapidly after the onset of AKI and have both been independently associated with ensuing morbidity and mortality. This study demonstrates that dietary P i restriction markedly diminished the early rise in plasma FGF23 and prevented the rise in plasma P i , parathyroid hormone, and calcitriol in mice with folic acid-induced AKI (FA-AKI). Furthermore, the study provides evidence for P i -sensitive osseous Fgf23 mRNA expression and reveals that P i restriction mitigated calciprotein particles (CPPs) formation, inflammation, acidosis, cardiac electrical disturbances, and mortality in mice with FA-AKI. These findings suggest that P i restriction may have a prophylactic potential in patients at risk for AKI. In AKI, plasma FGF23 and P i rise rapidly and are independently associated with disease severity and outcome. The effects of normal (NP) and low (LP) dietary P i were investigated in mice with FA-AKI after 3, 24, and 48 hours and 14 days. After 24 hours of AKI, the LP diet curbed the rise in plasma FGF23 and prevented that of parathyroid hormone and calcitriol as well as of osseous but not splenic or thymic Fgf23 mRNA expression. The absence of Pth prevented the rise in calcitriol and reduced the elevation of FGF23 in FA-AKI with the NP diet. Furthermore, the LP diet attenuated the rise in renal and plasma IL-6 and mitigated the decline in renal α -Klotho. After 48 hours, the LP diet further dampened renal IL-6 expression and resulted in lower urinary neutrophil gelatinase-associated lipocalin. In addition, the LP diet prevented the increased formation of CPPs. Fourteen days after AKI induction, the LP diet group maintained less elevated plasma FGF23 levels and had greater survival than the NP diet group. This was associated with prevention of metabolic acidosis, hypocalcemia, hyperkalemia, and cardiac electrical disturbances. This study reveals P i -sensitive FGF23 expression in the bone but not in the thymus or spleen in FA-AKI and demonstrates that P i restriction mitigates CPP formation, inflammation, acidosis, and mortality in this model. These results suggest that dietary P i restriction could have prophylactic potential in patients at risk for AKI.

Fibroblast Growth Factor 23 is a Potential Prognostic Biomarker in Uterine Sarcoma.

Uterine sarcoma (US) is a highly malignant cancer with poor prognosis and high mortality in women. In this study, we evaluated the expression of human fibroblast growth factor 23 (FGF23) in different US subtypes and the relationship between survival and clinicopathological characteristics. We conducted a comparative analysis of FGF23 gene expression in different pathological types of US. Utilizing a cohort from The Cancer Genome Atlas of 57 patients, a 50-patient microarray dataset (GSE119043) from the Gene Expression Omnibus and a Suining cohort of 44 patients, we analyzed gene expression profiles and corresponding clinicopathological information. Immunohistochemistry was used to examine the expression level of FGF23 in four US subtypes. Survival analysis was used to assess the relationship between FGF23 expression and prognosis in US patients. Compared with uterine normal smooth muscle and uterine leiomyoma, FGF23 expression was significantly upregulated in US and was differentially expressed in four US subtypes. Uterine carcinosarcoma exhibited the highest expression of FGF23 among the subtypes. Survival analysis revealed no correlation between FGF23 expression and either overall survival or progression-free survival in US (P > 0.05). Similar results were obtained from the validation cohorts. Univariate and multivariate analyses showed no significant correlation between FGF23 expression and the US prognosis. Tumor stage, CA125, and tumor recurrence were independent prognostic factors for survival of US patients. FGF23 was highly expressed in US and was promising as a novel potential biomarker for the diagnosis and prognosis of US.

Exploring the implications of blocking renin-angiotensin-aldosterone system and fibroblast growth factor 23 in early left ventricular hypertrophy without chronic kidney disease.

Whether fibroblast growth factor 23 (FGF23) directly induces left ventricular hypertrophy (LVH) remains controversial. Recent studies showed an association between FGF23 and the renin-angiotensin-aldosterone system (RAAS). The aim of this study was to investigate changes in FGF23 levels and RAAS parameters and their influences on LVH. In the first experiment, male C57BL/6J mice were divided into sham and transverse aortic constriction (TAC) groups. The TAC group underwent TAC at 8 weeks of age. At 1, 2, 3, and 4 weeks after TAC, the mice were sacrificed, and blood and urine samples were obtained. Cardiac expressions of FGF23 and RAAS-related factors were evaluated, and cardiac histological analyses were performed. In the second experiment, the sham and TAC groups were treated with vehicle, angiotensin-converting enzyme (ACE) inhibitor, or FGF receptor 4 (FGFR4) inhibitor and then evaluated in the same way as in the first experiment. In the early stage of LVH without chronic kidney disease, serum FGF23 levels did not change but cardiac FGF23 expression significantly increased along with LVH progression. Moreover, serum aldosterone and cardiac ACE levels were significantly elevated, and cardiac ACE2 levels were significantly decreased. ACE inhibitor did not change serum FGF23 levels but significantly decreased cardiac FGF23 levels with improvements in LVH and RAAS-related factors, while FGFR4 inhibitor did not change the values. Not serum FGF23 but cardiac FGF23 levels and RAAS parameters significantly changed in the early stage of LVH without chronic kidney disease. RAAS blockade might be more crucial than FGF23 blockade for preventing LVH progression in this condition.

In vitro regulation of fibroblast growth factor 23 by 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D synthesized by osteocyte-like MC3T3-E1 cells.

Fibroblast growth factor 23 (FGF23) is produced and secreted by osteocytes and is essential for maintaining phosphate homeostasis. One of the main regulators of FGF23, 1,25-dihydroxyvitamin D (1,25(OH)2D3), is primarily synthesized in the kidney from 25-hydroxyvitamin D (25(OH)D) by 1α-hydroxylase (encoded by CYP27B1). Hitherto, it is unclear whether osteocytes can convert 25(OH)D and thereby allow for 1,25(OH)2D3 to induce FGF23 production and secretion locally. Here, we differentiated MC3T3-E1 cells toward osteocyte-like cells expressing and secreting FGF23. Treatment with 10-6 M 25(OH)D resulted in conversion of 25(OH)D to 150 pmol/L 1,25(OH)2D3 and increased FGF23 expression and secretion, but the converted amount of 1,25(OH)2D3 was insufficient to trigger an FGF23 response, so the effect on FGF23 was most likely directly caused by 25(OH)D. Interestingly, combining phosphate with 25(OH)D resulted in a synergistic increase in FGF23 expression and secretion, likely due to activation of additional signaling pathways by phosphate. Blockage of the vitamin D receptor (VDR) only partially abolished the effects of 25(OH)D or 25(OH)D combined with phosphate on Fgf23, while completely inhibiting the upregulation of cytochrome P450 family 24 subfamily A member 1 (Cyp24a1), encoding for 24-hydroxylase. RNA sequencing and in silico analyses showed that this could potentially be mediated by the nuclear receptors Retinoic Acid Receptor β (RARB) and Estrogen Receptor 2 (ESR2). Taken together, we demonstrate that osteocytes are able to convert 25(OH)D to 1,25(OH)2D3, but this is insufficient for FGF23 activation, implicating a direct effect of 25(OH)D in the regulation of FGF23, which occurs at least partially independent from its cognate VDR. Moreover, phosphate and 25(OH)D synergistically increase expression and secretion of FGF23, which warrants investigating consequences in patients receiving a combination of vitamin D analogues and phosphate supplements. These observations help us to further understand the complex relations between phosphate, vitamin D, and FGF23.

Expression of FGF-23 and FGFR1 is increased in uremic rat skin.

Alterations in skin structure and function are very common in uremic patients, but still there is no unifying hypothesis for uremic skin disorders. Fibroblast growth factor-23 (FGF-23) deficiency has been linked to skin disorders in non-uremic animals. We aimed to study alterations in FGF-23 and fibroblast growth factor-23 receptor 1 (FGFR1) expression in uremic rat skins. Wistar albino rats were divided into two groups: sham group (SG, n=8) and uremic group (UG, n=8). Uremia was induced by reduction of the total kidney mass in the UG. Animals were sacrificed after 14 weeks of the follow-up. Serum creatinine and blood urea nitrogen levels in the UG increased significantly, compared to the SG, at the end of the experiment (0.69±0.08 vs. 0.3±0.04 Mann-Whitney U test (MWU), p=0,003 and 55.2±8.9 vs. 29.6±6.8 MWU, p=0.002, respectively). Serum FGF-23 level in the UG was increased non-significantly, compared to the SG (53.5±20.9 vs. 37.2±9.7 MWU, p=0.072), whereas serum 1,25(OH)2D3 level was significantly lower in the UG (149.4±33.5 vs. 213.8±43.8 MWU, p < 0.05). Expression of FGF-23 in UG skins, assessed by western blot, was significantly higher than that in the SG (186.3±16.8 vs. 148.9±25.9, MWU, p < 0.01). FGFR1 expression was increased in almost all parts of the uremic skin. Receptor expression was most dense at the epidermis and hair follicles. Normal skin appendages and cells either expressed no receptor, or expressed it very weakly. This study shows increased FGF-23 levels and FGFR1 expression in uremic rat skins. It deserves further study to fully place this finding in the pathophysiology and clinical picture of uremic skin diseases.