Elevated Serum Fibroblast Growth Factor Research Articles

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.

Estimated Proximal Tubule Fluid Phosphate Concentration and Renal Tubular Damage Biomarkers in Early Stages of Chronic Kidney Disease

IntroductionAn increase in proximal tubule fluid phosphate concentration is caused by increased serum fibroblast growth factor 23 (FGF23) levels, which resulted in renal tubular damage in a mouse model of chronic kidney disease (CKD). However, few human studies have supported this concept. This study aimed to explore the association among estimated proximal tubule fluid phosphate concentration (ePTFp), serum FGF23 levels, and renal tubular damage biomarkers in middle-aged and older populations with mild decline in renal function. MethodsThis cross-sectional study included 218 participants aged ≥45 with CKD stages G2–G4. Anthropometric measurements, blood tests, spot urine biomarkers, renal ultrasonography, cardiovascular assessment, smoking status, and medication usage were obtained in the morning in fasted states. The ePTFp was calculated using serum creatinine, urine phosphate, and creatinine concentrations. Urinary β2-microglobulin and liver-type fatty acid-binding protein (L-FABP) levels were evaluated to assess renal tubular damage.Results: ePTFp, serum FGF23, urinary β2-microglobulin, and urinary L-FABP levels increased with CKD stage progression (stages G2, G3, and G4). However, serum and urine phosphate concentrations were comparable across the CKD stages. Univariate analysis revealed a stronger correlation of ePTFp with serum FGF23, urinary β2-microglobulin, and urinary L-FABP levels than with the corresponding serum and urine phosphate concentrations. Multivariate analyses demonstrated that increased ePTFp was independently associated with elevated serum FGF23 and urinary β2-microglobulin levels, even after adjusting for potential covariates, including the estimated glomerular filtration rate and urinary albumin-to-creatinine ratio. ConclusionsOur results are consistent with the concept in mouse model and suggest that increased ePTFp are associated with increased serum FGF23 levels and renal tubular damage during the early stages of CKD.

Relationships of serum FGF23 and α-klotho with atherosclerosis in patients with type 2 diabetes mellitus

BackgroundCompelling evidence suggests that calcium/phosphorus homeostasis-related parameters may be linked to diabetes mellitus and cardiovascular events. However, few studies have investigated the association of fibroblast growth factor 23 (FGF23), α-klotho and FGF23/α-klotho ratio with atherosclerosis in patients with type 2 diabetes mellitus (T2DM).ObjectiveThis study was designed to evaluate whether FGF23, α-klotho and FGF23/α-klotho ratio are associated with T2DM and further to explore the relationships between these three factors and atherosclerosis in Chinese patients with T2DM.MethodsSerum FGF23 and α-klotho levels were measured via an enzyme-linked immunosorbent assay (ELISA) kit, and the carotid intima-media thickness (CIMT) was assessed via high-resolution color Doppler ultrasonography. The associations of serum FGF23, α-klotho and FGF23/α-klotho ratio with atherosclerosis in T2DM patients were evaluated using multivariable logistic regression models.ResultsThis cross-sectional study involved 403 subjects (207 with T2DM and 196 without T2DM), 41.7% of the patients had atherosclerosis, and 67.2% of the carotid intima were thickened to a thickness greater than 0.9 mm. Compared with those in the lowest tertile, higher tertiles of FGF23 levels and FGF23/α-klotho ratio were positively associated with T2DM after adjusting for covariates, and serum α-klotho concentration was inversely correlated with T2DM (all P values < 0.01). Moreover, elevated serum FGF23 levels and FGF23/α-klotho ratio were positively associated with CIMT and carotid atherosclerosis in T2DM patients (all P values < 0.01). Further spline analysis similarly revealed linear dose‒response relationship (all P values < 0.01). And there was still significant differences in CIMT and carotid atherosclerosis between the highest group of α-klotho and the reference group in T2DM patients (P values = 0.05).ConclusionsT2DM was positively linearly related to serum FGF23 concentration and FGF23/α-klotho ratio, and negatively correlated with serum α-klotho concentration. Furthermore, both FGF23 and FGF23/α-klotho ratio were positively correlated with CIMT and atherosclerosis in T2DM patients, while α-klotho was inversely correlated with both CIMT and atherosclerosis, although the associations were not completely significant. Prospective exploration and potential mechanisms underlying these associations remain to be further elucidated.

Hypericin Alleviates Chronic Kidney Disease-induced Left Ventricular Hypertrophy by Regulation of FGF23-FGFR4 Signaling Pathway.

Chronic kidney disease (CKD) is a significant global health threat that imposes a substantial burden on both individuals and societies. CKD frequently correlates with cardiovascular events, particularly left ventricular hypertrophy (LVH), which contributes to the high mortality rate associated with CKD. Fibroblast growth factor 23 (FGF23), a hormone primarily involved in regulating calcium and phosphorus metabolism, has been identified as a major risk factor for LVH in CKD patients. Elevated serum FGF23 levels are known to induce LVH and myocardial fibrosis by activating the fibroblast growth factor receptor 4 (FGFR4) signal pathway. Therefore, targeting FGFR4 and its downstream signaling pathways holds potential as a treatment strategy for cardiac dysfunction in CKD. In our current study, we have discovered that Hypericin, a key component derived from Hypericum perforatum , has the ability to alleviate CKD-related LVH by targeting the FGFR4/phospholipase C gamma 1 (PLCγ1) signaling pathway. Through in vitro experiments using rat cardiac myocyte H9c2 cells, we observed that Hypericin effectively inhibits FGF23-induced hypertrophy and fibrosis by suppressing the FGFR4/PLCγ1/calcineurin/nuclear factor of activated T-cell (NFAT3) signaling pathway. In addition, our in vivo studies using mice on a high-phosphate diet and rat models of 5/6 nephrectomy demonstrated that Hypericin has therapeutic effects against CKD-induced LVH by modulating the FGFR4/PLCγ1/calcineurin/NFAT3 signaling pathway. In conclusion, our research highlights the potential of Hypericin as a candidate for the treatment of CKD-induced cardiomyopathy. By suppressing the FGFR4/PLCγ1 signaling pathway, Hypericin shows promise in attenuating LVH and myocardial fibrosis associated with CKD.

Relationship of Fibroblast Growth Factor 23 Serum Levels with Disease Characteristics in Systemic Lupus Erythematosus Patients.

Fibroblast growth factor 23 (FGF23), a hormone secreted by osteocytes and osteoblasts, is a major regulator of vitamin D and phosphate homeostasis. FGF23 has been associated with the disturbance of mineral homeostasis, and with kidney and cardiovascular diseases. Systemic lupus erythematosus (SLE) is an autoimmune disorder that can affect virtually any organ. In the present work, we set out to analyze the relationship of FGF23 with the expression of SLE, including patterns of activity, damage, and severity. A total of 284 well-characterized patients with SLE were recruited. Activity (SLEDAI), severity (Katz), and damage index (SLICC-DI) scores were determined. The serum levels of FGF23 were also assessed. Multivariable linear regression analysis was performed to study the relationship between disease characteristics and FGF23. FGF23 and 25(OH) vitamin D were negatively correlated. Furthermore, prednisone use was associated with higher circulating FGF23 after an adjustment for confounding factors. SLICC-DI was related to higher serum levels of FGF23 after a multivariable analysis. However, when the SLICC-DI index items and domains were analyzed separately, apart from proteinuria ≥3.5 gm/24 h, only the musculoskeletal domain, encompassing arthritis and osteoporosis, was significantly associated with higher serum levels of FGF23. In conclusion, an association is observed between elevated serum FGF23 levels and disease damage, particularly related to musculoskeletal complications and proteinuria, in patients with SLE.

Pemafibrate prevents choroidal neovascularization in a mouse model of neovascular age-related macular degeneration.

Pathological choroidal neovascularization (CNV) is one of the major causes of visual impairment in neovascular age-related macular degeneration (AMD). CNV has been suppressed by using anti-vascular endothelial growth factor (VEGF) antibodies. However, some clinical cases have demonstrated the failure of anti-VEGF therapies. Furthermore, anti-VEGF agents might induce the development of ocular atrophy. Recently, peroxisome proliferator-activated receptor alpha (PPARα) activation using pemafibrate treatment was suggested as one of the promising therapeutic targets in the prevention of ocular ischemia. However, the preventive role of pemafibrate remains unclear in CNV. We aimed to examine the preventive role of pemafibrate on laser-induced pathological CNV. Adult male C57BL/6 mice were orally supplied pemafibrate (0.5 mg/kg) for four days, followed by laser irradiation. Then, pemafibrate was consecutively given to mice with the same condition. CNV was visualized with isolectin-IB4. The eye (retina and/or retinal pigment epithelium [RPE]-choroid), liver, and serum were used for biomolecular analyses. We found that pemafibrate administration suppressed CNV volumes. Pemafibrate administration activated PPARα downstream genes in the liver and eye (especially, RPE-choroid). Furthermore, pemafibrate administration elevated serum fibroblast growth factor 21 levels and reduced serum levels of triglycerides. Our data suggest a promising pemafibrate therapy for suppressing CNV in AMD.

Elevated Serum Fibroblast Growth Factor 23 (FGF-23) Perseveres into a Convalescence Period After Elective Cardiac Surgery, with Receptor Activator of Nuclear Factor κB Ligand (RANKL) and Cartilage Oligomeric Matrix Protein (COMP) Being Part of the Peri-Surgical -Pro-Arteriosclerotic Inflammatory Response.

BACKGROUND Receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), cartilage oligomeric matrix protein (COMP), bone morphogenetic protein (BMP-2), and fibroblast growth factor 23 (FGF-23) are involved in inflammation, calcium deposition, and fibrosis of blood vessels. Acute changes in these factors may contribute to the progression of arteriosclerosis, especially if their elevated serum levels persist postoperatively. MATERIAL AND METHODS A total of 90 patients (79 White, 4 African American, and 7 Other) undergoing elective heart surgery were enrolled in the study. Blood was collected before surgery and after surgery at 24 hours, 7 days, and 3 months to allow for longitudinal comparisons. After the plasma isolation, several biomarkers levels were studied using an enzymatic-linked assay. Demographic and clinical information were obtained from electronic health records. RESULTS At 24 hours after surgery, RANKL (RANKLbaseline=248.7±215.7 vs RANKLt24h=376.4±329.7; P=0.035), and BMP-2 (BMP-2baseline=283.7±255.4 vs BMP-2t24h=482.4; P=0.015) were significantly elevated compared to baseline, with levels returning to baseline at 7 days. FGF-23 increased significantly from baseline (FGF-23baseline=1020±1210) to 7 days (FGF-237d=2191±5188; P=0.029) and remained significantly higher than baseline at 3 months (FGF-233m=2041±3521; P=0.044). White blood cells (WBC) remained elevated at discharge (WBCbaseline=6.8±2.1 vs WBC24h=15.0±5.3 vs WBCdischarge=8.8±3.4). IL-8 and C-reactive protein normalized at 3 months. Estimated blood loss was significantly correlated with RANKL at 24 hours (r²=0.33; P=0.035). Serum creatinine levels after surgery at 24 hours (r²=0.41; p=0.008) and 7 days (r²=0.59; P=0.000) was strongly correlated with COMP. CONCLUSIONS Persistent elevation of serum FGF-23 indicates a potential for accelerated arteriosclerosis after cardiac surgery.

Inappropriate secretion of fibroblast growth factor 23 despite hypophosphataemia with changes in bone turnover markers in a girl with systemic lupus erythematosus: Case report and review of the literature.

We report an 11-year-old girl with systemic lupus erythematosus (SLE) who showed hypophosphataemia (1.7 mg/dl, normal range: 3.9-5.8 mg/dl), a decrease in the tubular maximum reabsorption of phosphate/glomerular filtration rate (TmP/GFR) (0.77 mg/dl, normal range: 3.4-5.6 mg/dl), and an elevated serum fibroblast growth factor 23 (FGF23) (circulating phosphate-regulatory hormone) concentration (FGF23: 282 pg/ml, normal range: <52 pg/ml) at the onset. The patient was treated with intravenous pulse methylprednisolone, oral prednisolone, mycophenolate mofetil, hydroxychloroquine, and phosphorus supplement. Serum FGF23 concentrations decreased to near the reference value at 5 months after the onset of SLE, and the TmP/GFR (4.61 mg/dl) simultaneously improved. The urinary deoxypyridinoline (bone resorption marker) concentration on admission (18.9 nmol/mmol creatinine, normal range: 75.4 ± 6.8 nmol/mmol creatinine) was greatly reduced, and the bone-type alkaline phosphatase (bone formation marker) concentration (30.6 µg/l, normal range: 58.6 ± 15.3 µg/l) was also reduced during the increase in FGF23 concentrations before steroid therapy was initiated. The reason for the inappropriate secretion of FGF23, despite hypophosphataemia, remains unknown. The findings in our case suggest that changes in bone turnover markers can occur in patients with SLE and excess inappropriate secretion of FGF23, despite severe and persistent hypophosphataemia.

Alteration of Bile Acids and Omega-6 PUFAs Are Correlated With the Progression and Prognosis of Drug-Induced Liver Injury.

Background & AimsDrug-induced liver injury (DILI) is one of the leading causes of liver failure with some of the patients progressed to chronic DILI. The mechanisms underlying the severity and chronicity of DILI are poorly elucidated and the biomarkers are limited. Metabolites and gut microbiota played a crucial role in the development of various liver diseases. Herein, a systematic analysis of serum metabolites and gut microbiota was performed in DILI patients, aiming to identify metabolites correlated with the progression and clinical prognosis of DILI.MethodsVarious serum metabolites were quantitated using a metabolite array technology in this prospective study. Gut microbiome compositions and the expression profiles of liver genes were determined in patients with DILI and healthy controls.ResultsMetabolomic analysis revealed that bile acids (BAs) and polyunsaturated fatty acids (PUFAs) were closely related to DILI severity and chronicity respectively. The ratios of serum primary/secondary BAs and omega-6/omega-3 PUFAs were elevated in DILI patients. A model established by adrenic acid (AdA) and aspartic acid (Asp) exerts good performance for predicting the chronicity of DLIL. Hepatic transcriptome revealed enhanced expression of PUFA peroxidation and supressed expression of BA synthesis related genes in DILI patients. In addition, Lactic acid bacteria and BA converting bacteria were increased in gut of DILI patients. Besides, elevated serum malondialdehyde (MDA) and fibroblast growth factor 19 (FGF19) was observed in DILI patients.ConclusionBAs and PUFAs could be potent markers for the severity and chronicity of DILI respectively. The panel of AdA and Asp could be ideal predictive model for the risk of chronicity at the acute stage of DILI. Gut microbiota might act as a negative feedback mechanism to maintain the homeostasis of BAs and PUFAs via FGF19 signalling and PUFA saturation, respectively. Our study revealed novel biomarkers for severe and chronic DILI and provided new therapeutic targets for DILI.

Elevated Serum Fibroblast Growth Factor 21 Is Relevant to Heart Failure Patients with Reduced Ejection Fraction.

Objective The aim of this study was to evaluate the roles of fibroblast growth factor 21 (FGF21) in heart failure patients with reduced ejection fraction and its association with Heart Failure with reduced Ejection Fraction (HFrEF). Methods The level of FGF21 was measured by enzyme-linked immunosorbent assay (ELISA) in 199 subjects enrolled in this study, including 128 subjects with HFrEF and 71 control subjects. The mean follow-up time was 13.36 months. The left ventricular end-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) percentage were evaluated by the 2D echocardiography. Serum brain natriuretic peptide (BNP) was measured in the routine clinical laboratory. Results The serum FGF21 level was evidently higher in patients with HFrEF than in the control group (228.72 ± 24.04 vs. 171.60 ± 12.98, p < 0.001). After 1 year of follow-up, 61 patients (47.66%) with heart failure were readmitted to the hospital, including 8 deaths (13.11%). The AUC of the receiver operating characteristic (ROC) curve for the predictive value of FGF21 for prognosis was 0.964. Kaplan-Meier analysis results showed that there were significant differences in the 1-year mortality and heart failure readmission events between the grouped subjects. A poor prognosis was correlated with the serum level of FGF21, BNP, LVEDD, and LVEF, which was confirmed by the univariate Cox analysis. Conclusion FGF21 was independently associated with an increased risk of mortality and readmission HFrEF patients. Therefore, FGF21 has the potential to be a biomarker for the progression of HFrEF in patients.

Sternal Phosphaturic Mesenchymal Tumor-Induced Osteomalacia, Diagnosis and Management: A Case Report

Background: Tumor induced osteomalacia (TIO) is a rare paraneoplastic disorder in which overproduction of fibroblast growth factor-23 (FGF-23) by mesenchymal tumor results in decreased renal phosphorus reabsorption and low to inappropriately normal 1,25-dihydroxyvitamin D, leading to hypophosphatemia and osteomalacia. Patients often present with bone pain, fractures, muscle weakness, and progressive decline in mobility. Due to the nonspecific nature of presenting symptoms of TIO diagnosis is often delayed. Clinical Case: A 55-year-old male presented with complaints of chest pain, shortness of breath, and generalized weakness following a ground level fall. Patient also reported a 10-year history of osteoarthritis with chronic back pain and 1-year history of generalized weakness, resulting in significant decline in functional status. On work-up, the initial CT scan of chest revealed multiple fractures including ribs, manubrium, scapula, and pubic rami. Subsequent biochemical evaluation was remarkable for hypophosphatemia to low of 1.3 mg/dL (2.4 - 5.0 mg/dL), low of 1,25-dihydroxyvitamin D of 13.1 pg/ml (19.9 - 79.3 pg/mL), reduced tubular phosphate reabsorption rate of 28% (normal > 80%) ratifying for renal phosphate wasting, normal iPTH level, and elevated serum FGF-23 level of 460 (normal < 180). Then, localization imaging for TIO was performed. After PET/CT scan showing increased uptake at the sternal area suggestive of lytic metastasis, subsequent CT angiogram of the chest identified mottled, irregular, mildly expansile appearance of the sternal manubrium. Sternal biopsy revealed phosphaturic mesenchymal tumor with positive FGF 23 mRNA expression. Surgical resection was delayed due to poor functional status and concurrent discovery of an EBV-positive nasopharyngeal carcinoma. Prior to surgery patient was treated with phosphorus and calcitriol supplements. Post-operatively serum phosphorus and FGF-23 levels were normalized. Patient also improved clinically. Patients treatment course was complicated by secondary hyperparathyroidism; however, this improved following surgery. Conclusion: Diagnosis of TIO can be delayed due to its nonspecific symptoms. Thus, in patients with chronic bone pain, muscle weakness, and atraumatic fractures, TIO should be kept on the differential and these patients should undergo thorough biochemical and imaging evaluation. Tumor localization could be challenging. Patients should be managed with supplements of active vitamin D and phosphorus with goal to normalize phosphorus level to prevent further bone demineralization prior to surgery. However, surgical intervention remains the mainstay of management as this is curative of TIO.

Diagnostic value of fibroblast growth factor 23 for abdominal aortic calcification in Indonesian hemodialysis patients.

Objective:Homeostasis of serum phosphorus and calcitriol level is regulated mainly by fibroblast growth factor 23 (FGF23). Studies show that elevated serum FGF23 level was significantly associated with aortic calcification severity, peripheral blood vessels, and a higher score of coronary artery calcification in patients undergoing hemodialysis. We did this cross-sectional study to determine the FGF23 diagnostic value for abdominal aortic calcification in Indonesian hemodialysis patients.Materials and Methods:This study included seventy-five, chronic hemodialysis patients. An enzyme-linked immunosorbent assay method was used to measure serum intact FGF23 level, and abdominal aortic calcification was detected by lateral lumbar X-ray. The diagnostic value of FGF23 was analyzed using receiver operating characteristic (ROC) curves.Results:fifty-one (68.0%) patients had abdominal aortic calcification (AAC). Serum intact FGF23 level ranged from 217 to 950 pg/mL with a median level of 328 pg/mL. The FGF23 levels in the serum of patients with AAC were significantly higher than those without AAC (P < 0.001). The best cutoff point was 277 pg/mL. The calculated area under the ROC curves was 0.959 (95% confidence interval, 0.912–1.00); sensitivity was 94.0% and specificity was 84.0% (P < 0.001).Conclusion:serum intact FGF23 level may be proposed as a proper tool for abdominal aortic calcification in Indonesian hemodialysis patients.

Molecular Diagnoses of X-Linked and Other Genetic Hypophosphatemias: Results From a Sponsored Genetic Testing Program.

ABSTRACTX‐linked hypophosphatemia (XLH), a dominant disorder caused by pathogenic variants in the PHEX gene, affects both sexes of all ages and results in elevated serum fibroblast growth factor 23 (FGF23) and below‐normal serum phosphate. In XLH, rickets, osteomalacia, short stature, and lower limb deformity may be present with muscle pain and/or weakness/fatigue, bone pain, joint pain/stiffness, hearing difficulty, enthesopathy, osteoarthritis, and dental abscesses. Invitae and Ultragenyx collaborated to provide a no‐charge sponsored testing program using a 13‐gene next‐generation sequencing panel to confirm clinical XLH or aid diagnosis of suspected XLH/other genetic hypophosphatemia. Individuals aged ≥6 months with clinical XLH or suspected genetic hypophosphatemia were eligible. Of 831 unrelated individuals tested between February 2019 and June 2020 in this cross‐sectional study, 519 (62.5%) individuals had a pathogenic or likely pathogenic variant in PHEX (PHEX‐positive). Among the 312 PHEX‐negative individuals, 38 received molecular diagnoses in other genes, including ALPL, CYP27B1, ENPP1, and FGF23; the remaining 274 did not have a molecular diagnosis. Among 319 patients with a provider‐reported clinical diagnosis of XLH, 88.7% (n = 283) had a reportable PHEX variant; 81.5% (n = 260) were PHEX‐positive. The most common variant among PHEX‐positive individuals was an allele with both the gain of exons 13–15 and c.*231A>G (3′UTR variant) (n = 66/519). Importantly, over 80% of copy number variants would have been missed by traditional microarray analysis. A positive molecular diagnosis in 41 probands (4.9%; 29 PHEX positive, 12 non‐PHEX positive) resulted in at least one family member receiving family testing. Additional clinical or family member information resulted in variant(s) of uncertain significance (VUS) reclassification to pathogenic/likely pathogenic (P/LP) in 48 individuals, highlighting the importance of segregation and clinical data. In one of the largest XLH genetic studies to date, 65 novel PHEX variants were identified and a high XLH diagnostic yield demonstrated broad insight into the genetic basis of XLH. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Phosphaturic Mesenchymal Tumor; A Diagnostically Elusive Cause Of Oncogenic Osteomalacia; Case Study

Abstract Casestudy: Phosphaturic mesenchymal tumor (PMT) is a rare, benign neoplasm. It is associated with oncogenic osteomalacia, a paraneoplastic condition caused by secretion of a peptide hormone-like substance, fibroblast growth factor 23, which increases renal clearance of phosphate and increased mobilization of calcium and phosphate from bone. PMT is difficult to diagnose as a primary etiology because patients usually experience non- specific symptoms associated with hypophosphatemia like bone pain, muscular weakness, and pathologic fractures. Because PMT is a benign neoplasm, surgical excision is curative and rapid resolution of symptoms typically ensues. Discussed here is a case of PMT arising in the soft tissue of the medial thigh of a 65 year old man with a five year history of osteomalacia with pathologic fractures and complicated healing. Lab studies revealed hypophosphatemia, hyperphosphaturia, hypercalcemia, and elevated serum fibroblast growth factor 23 during workup for fracture. A small superficial soft tissue mass was discovered in the proximal thigh via octreotide scan which was subsequently excised. On histologic examination it was composed of an encapsulated proliferation of spindle cells in a chondromyxoid background with distinctive areas of flocculent calcification and osteoclast-like giant cells. A diagnosis of PMT was rendered. The patient’s symptoms resolved rapidly after surgery. Despite the benign characteristics and behavior of this rare neoplasm; delayed or mis-diagnosis can have severe implications for patient’s health. Interdisciplinary communication, shrewd clinical index of suspicion, and awareness of the causes of, and the tests available to diagnose oncogenic osteomalacia can speed accurate diagnosis leading to better outcomes for patients.

The Role of Fibroblast Growth Factor 23 in Inflammation and Anemia.

In patients with chronic kidney disease (CKD), adverse outcomes such as systemic inflammation and anemia are contributing pathologies which increase the risks for cardiovascular mortality. Amongst these complications, abnormalities in mineral metabolism and the metabolic milieu are associated with chronic inflammation and iron dysregulation, and fibroblast growth factor 23 (FGF23) is a risk factor in this context. FGF23 is a bone-derived hormone that is essential for regulating vitamin D and phosphate homeostasis. In the early stages of CKD, serum FGF23 levels rise 1000-fold above normal values in an attempt to maintain normal phosphate levels. Despite this compensatory action, clinical CKD studies have demonstrated powerful and dose-dependent associations between FGF23 levels and higher risks for mortality. A prospective pathomechanism coupling elevated serum FGF23 levels with CKD-associated anemia and cardiovascular injury is its strong association with chronic inflammation. In this review, we will examine the current experimental and clinical evidence regarding the role of FGF23 in renal physiology as well as in the pathophysiology of CKD with an emphasis on chronic inflammation and anemia.

Meta-Analysis of the Association between Fibroblast Growth Factor 23 and Mortality and Cardiovascular Events in Hemodialysis Patients

Introduction: This study was conducted to ensure the correlation between fibroblast growth factor 23 (FGF23) and death and cardiovascular events in hemodialysis patients. Methods: We conducted a literature search of PubMed database to April 2018 for relevant articles that reported the association between FGF23 and risk of all-cause mortality and cardiovascular disease (CVD) events. The meta-analysis was performed using the Revman 5.3 software. Results: A total of 7 articles were included, and all reported mortality in hemodialysis patients, and 3 reported cardiovascular events in hemodialysis patients. Since the current reagent can detect C-terminal FGF23 (cFGF23) and intact-FGF23 (iFGF23), we discuss the association between cFGF23 and iFGF23 and death and cardiovascular events in hemodialysis patients. The correlation between serum iFGF23 levels and death in hemodialysis patients: high levels of iFGF23 vs. low levels of iFGF23: RR 1.14, 95% CI (1.01–1.30), p = 0.04 (I² = 0%, p = 0.38). The correlation between serum C-terminal levels and death in hemodialysis patients: high levels of cFGF23 versus low levels of cFGF23: RR 1.39, 95% CI (1.21–1.59), p < 0.001 (I² = 2%, p = 0.38). The correlation of serum iFGF23 levels with cardiovascular events: high levels of iFGF23 versus low levels of iFGF23: RR 1.21, 95% CI (1.13–1.30), p < 0.001 (I² = 0%, p = 0.49). A paper has reported the association between cFGF23 and CVD events, so we did not conduct meta-analysis. Conclusions: Elevated serum FGF23 levels are positively associated with all-cause mortality and cardiovascular events in hemodialysis patients, with a 14 or 39% increase in all-cause mortality and a 21% increased risk of cardiovascular events.

Perilipin-2 deletion promotes carbohydrate-mediated browning of white adipose tissue at ambient temperature

Mice lacking perilipin-2 (Plin2-null) are resistant to obesity, insulin resistance, and fatty liver induced by Western or high-fat diets. In the current study, we found that, compared with WT mice on Western diet, Plin2-null adipose tissue was more insulin sensitive and inguinal subcutaneous white adipose tissue (iWAT) exhibited profound browning and robust induction of thermogenic and carbohydrate-responsive genetic programs at room temperature. Surprisingly, these Plin2-null responses correlated with the content of simple carbohydrates, rather than fat, in the diet, and were independent of adipose Plin2 expression. To define Plin2 and sugar effects on adipose browning, WT and Plin2-null mice were placed on chow diets containing 20% sucrose in their drinking water for 6 weeks. Compared with WT mice, iWAT of Plin2-null mice exhibited pronounced browning and striking increases in the expression of thermogenic and insulin-responsive genes on this diet. Significantly, Plin2-null iWAT browning was associated with reduced sucrose intake and elevated serum fibroblast growth factor (FGF)21 levels, which correlated with greatly enhanced hepatic FGF21 production. These data identify Plin2 actions as novel mediators of sugar-induced adipose browning through indirect effects of hepatic FGF21 expression, and suggest that adipose browning mechanisms may contribute to Plin2-null resistance to obesity.

Developments in rare bone diseases and mineral disorders.

In the last decade, there have been a number of significant advances made in the field of rare bone diseases. In this review, we discuss the expansion of the classification system for osteogenesis imperfecta (OI) and the resultant increase in therapeutic options available for management of OI. Bisphosphonates remain the most widely used intervention for OI, although the effect on fracture rate reduction is equivocal. We review the other therapies showing promising results, including denosumab, teriparatide, sclerostin, transforming growth factor β inhibition and gene targeted approaches. X-linked hypophosphataemia (XLH) is the most common heritable form of osteomalacia and rickets caused by a mutation in the phosphate regulating endopeptidase gene resulting in elevated serum fibroblast growth factor 23 (FGF23) and decreased renal phosphate reabsorption. The traditional treatment is phosphate replacement. We discuss the development of a human anti-FGF23 antibody (KRN23) as a promising development in the treatment of XLH. The current management of primary hypoparathyroidism is replacement with calcium and active vitamin D. This can be associated with under or over replacement and its inherent complications. We review the use of recombinant parathyroid hormone (1-84), which can significantly reduce the requirements for calcium and vitamin D resulting in greater safety and quality of life for individuals with hypoparathyroidism. The use of receptor activator of nuclear factor κB ligand infusions in the treatment of a particular form of osteopetrosis and enzyme replacement therapy for hypophosphatasia are also discussed.

Hormonal Regulation of Osteocyte Perilacunar and Canalicular Remodeling in the Hyp Mouse Model of X-Linked Hypophosphatemia.

Osteocytes remodel their surrounding perilacunar matrix and canalicular network to maintain skeletal homeostasis. Perilacunar/canalicular remodeling is also thought to play a role in determining bone quality. X-linked hypophosphatemia (XLH) is characterized by elevated serum fibroblast growth factor 23 (FGF23) levels, resulting in hypophosphatemia and decreased production of 1,25 dihydroxyvitamin D (1,25D). In addition to rickets and osteomalacia, long bones from mice with XLH (Hyp) have impaired whole-bone biomechanical integrity accompanied by increased osteocyte apoptosis. To address whether perilacunar/canalicular remodeling is altered in Hyp mice, histomorphometric analyses of tibia and 3D intravital microscopic analyses of calvaria were performed. These studies demonstrate that Hyp mice have larger osteocyte lacunae in both the tibia and calvaria, accompanied by enhanced osteocyte mRNA and protein expression of matrix metalloproteinase 13 (MMP13) and genes classically used by osteoclasts to resorb bone, such as cathepsin K (CTSK). Hyp mice also exhibit impaired canalicular organization, with a decrease in number and branching of canaliculi extending from tibial and calvarial lacunae. To determine whether improving mineral ion and hormone homeostasis attenuates the lacunocanalicular phenotype, Hyp mice were treated with 1,25D or FGF23 blocking antibody (FGF23Ab). Both therapies were shown to decrease osteocyte lacunar size and to improve canalicular organization in tibia and calvaria. 1,25D treatment of Hyp mice normalizes osteocyte expression of MMP13 and classic osteoclast markers, while FGF23Ab decreases expression of MMP13 and selected osteoclast markers. Taken together, these studies point to regulation of perilacunar/canalicular remodeling by physiologic stimuli including hypophosphatemia and 1,25D. © 2017 American Society for Bone and Mineral Research.

Elevated serum fibroblast growth factor 23 levels as an indicator of lower extremity atherosclerotic disease in Chinese patients with type 2 diabetes mellitus

BackgroundRecently, basic and clinical studies have provided evidence supporting the relationship between circulating levels of fibroblast growth factor (FGF) 23 and the development of atherosclerosis. Given that diabetes is an established risk factor for lower extremity atherosclerotic disease (LEAD), the goal of the present study was to explore the relationship between serum FGF23 levels and LEAD, as well as the related factors, in Chinese patients with type 2 diabetes mellitus (T2DM).MethodsA total of 401 hospitalized T2DM patients (201 subjects with LEAD and 200 subjects without LEAD) were enrolled in this study. Serum FGF23 levels were determined by a sandwich enzyme-linked immunosorbent assay. Femoral intima-media thickness (F-IMT) and lower limb atherosclerotic plaque were assessed through color Doppler ultrasound.ResultsThe median (interquartile range) serum FGF23 levels in the entire study population was 42.08 (35.59–49.17) pg/mL. Subjects with LEAD had significantly higher serum FGF23 levels compared with those without LEAD (44.00 [37.54–51.30] pg/mL versus 40.42 [32.61–48.23] pg/mL, P < 0.001). Logistic regression showed that serum FGF23 levels were independently and positively correlated with the presence of LEAD (odds ratio 1.039, 95% confidence interval 1.012–1.067, P = 0.004). In addition, multiple liner regression analysis revealed that serum FGF23 levels were positively associated with F-IMT (standardized β = 0.175, P < 0.001). Furthermore, this relationship remained significant after additional adjustment for gender and factors potentially affecting serum FGF23 levels (serum calcium, serum phosphorus, and glomerular filtration rate), respectively (both P < 0.01).ConclusionsIn Chinese patients with T2DM, serum FGF23 levels were independently and positively correlated with the presence of LEAD.