Search

Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that plays a major role in the regulation of phosphate and vitamin D metabolism. FGF23 primarily acts on the kidneys to induce urinary phosphate excretion by downregulating the sodium-dependent phosphate cotransporters Napi2a and Napi2c and suppress 1,25-dihydroxyvitamin D [1,25(OH)2D] synthesis by altering the vitamin D-metabolizing enzymes CYP27b1 and CYP24a1 [1–3]. These functions of FGF23 are mediated by binding to FGF receptor 1 (FGFR1) and the transmembrane protein Klotho, which forms a specific receptor complex for FGF23 [4,5]. Importantly, recent observational studies have shown strong associations between elevated FGF23 and greater risk of cardiovascular events, particularly congestive heart failure, in patients with chronic kidney disease [6–8], hemodialysis patients [9,10], and individuals with apparently normal kidney function [11–15]. Furthermore, elevated FGF23 has been linked to volume overload, a common manifestation of heart failure [16–18]. As a potential mechanism of these observations, FGF23 is reported to induce cardiac hypertrophy via Klotho-independent signaling through the FGFR4 [19,20]. In addition, FGF23 increases renal sodium reabsorption by upregulating the Na+:Cl− cotransporter in the distal tubules via a Klotho-dependent pathway, leading to volume expansion, hypertension, and cardiac hypertrophy [21]. Interestingly, recent studies demonstrated an opposite directional relationship—injured cardiomyocyte could produce substantial amounts of FGF23 after myocardial infarction [22] or during cardiac hypertrophy [23]. However, it remains to be determined whether acute volume expansion, which induces hemodynamic congestion and cardiac overload, stimulates FGF23 production by cardiomyocytes. Here, we report our investigations into the impact of volume expansion by acute saline injection on cardiac and skeletal expressions of FGF23 as well as circulating FGF23 levels in rats.

Epilepsy is associated with increased morbidity and mortality together and places a large financial burden on individuals and society. To evaluate the anticonvulsant action of protodioscin (PDSN) in experiments with animals with pilocarpine-induced convulsions. We assessed the activity of PDSN in pilocarpine induced seizures in combination with different agents which are acting via diverse receptors, such as atropine, memantine, nimodipine, diazepam, and flumazenil, to determine the exact receptors responsible for the action of PDSN. Furthermore, the level of antioxidant markers was investigated in the cerebellum and cerebral cortex in mice to define the antioxidant action of PDSN. The effects of PDSN on proapoptotic markers (i.e., Bcl-2, Bax, and caspase-3) was investigated via western blot analysis. PDSN significantly enhanced latency to the first convulsion and survival compared to the group treated with pilocarpine alone. Moreover, PDSN improved animal survival, and subjects experiencing no convulsions. Striatal glutamate and aspartate levels were not modified, and gamma amino butyric acid (GABA) levels increased, as a result of treatment with PDSN. The results suggest that the anticonvulsive action of PDSN is dependent on inhibitory amino acids. PDSN treatment also significantly decreased nitrite levels in the blood and brain cortex compared to the normal control. In the western blot analysis, PDSN exerted its neuroprotective effect via the upregulation of Bcl-2 and downregulation of Bax and caspase-3. The results of this study suggest that PDSN exerts neuroprotective effects via multiple mechanisms.

Fibroblast growth factor 23 (FGF23) is produced by bone cells and regulates renal phosphate and vitamin D metabolism, as well as causing left ventricular hypertrophy. FGF23 deficiency results in rapid aging, whereas high plasma FGF23 levels are found in several disorders, including kidney or cardiovascular diseases. Regulators of FGF23 production include parathyroid hormone (PTH), calcitriol, dietary phosphate, and inflammation. We report that insulin and insulin-like growth factor 1 (IGF1) are negative regulators of FGF23 production. In UMR106 osteoblast-like cells, insulin and IGF1 down-regulated FGF23 production by inhibiting the transcription factor forkhead box protein O1 (FOXO1) through phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB)/Akt signaling. Insulin deficiency caused a surge in the serum FGF23 concentration in mice, which was reversed by administration of insulin. In women, a highly significant negative correlation between FGF23 plasma concentration and increase in plasma insulin level following an oral glucose load was found. Our results provide strong evidence that insulin/IGF1-dependent PI3K/PKB/Akt/FOXO1 signaling is a powerful suppressor of FGF23 production in vitro as well as in mice and in humans.

Fibroblast growth factor (FGF23) plasma levels are elevated in cardiac and renal failure and correlate with poor clinical prognosis of those disorders. Both disorders are associated with inflammation and activation of the inflammatory transcription factor NFκB. An excessive FGF23 level is further observed in Klotho-deficient mice. The present study explored a putative sensitivity of FGF23 expression to transcription factor NFκB, which is known to upregulate Orai1, the Ca(2+) channel accomplishing store-operated Ca(2+) entry (SOCE). In osteoblastic cells (UMR106) and immortalized primary periosteal (IPO) cells, protein abundance was determined by Western blotting, and in UMR106 cells, transcript levels were quantified by RT-PCR, cytosolic Ca(2+) activity utilizing Fura-2-fluorescence, and SOCE from Ca(2+) entry following store depletion by thapsigargin. As a result, UMR106 and IPO cells expressed Ca(2+) channel Orai1. SOCE was lowered by NFκB inhibitor wogonin as well as by Orai1 inhibitors 2-APB and YM58483. UMR106 cell Fgf23 transcripts were increased by stimulation of SOCE and Ca(2+) ionophore ionomycin and decreased by Orai inhibitors 2-APB, YM58483 and SKF96365, by Orai1 silencing, as well as by NFκB inhibitors wogonin, withaferin A, and CAS 545380-34-5. In conclusion, Fgf23 expression is upregulated by stimulation of NFκB-sensitive, store-operated Ca(2+) entry.Osteoblast UMR106 and IPO cells express Ca(2+) channel Orai1. Osteoblast store-operated Ca(2+) entry is accomplished by NFκB-sensitive Orai1. Osteoblast Fgf23 transcription is upregulated by increase in the cytosolic Ca(2+) activity. Fgf23 transcription is decreased by Orai inhibitors and Orai1 silencing. Fgf23 transcription is lowered by NFκB inhibitors.

Calcitriol, a powerful regulator of phosphate metabolism and immune response, is generated by 25-hydroxyvitamin D 1α-hydroxylase in the kidney and macrophages. Renal 1α-hydroxylase expression is suppressed by Klotho and FGF23, the expression of which is stimulated by calcitriol. Interferon γ (INFγ) regulates 1α-hydroxylase expression in macrophages through transcription factor interferon regulatory factor-1. INFγ-signaling includes Janus kinase 3 (JAK3) but a role of JAK3 in the regulation of 1α-hydroxylase expression and mineral metabolism has not been shown. Thus, the impact of JAK3 deficiency on calcitriol formation and phosphate metabolism was measured. Renal interferon regulatory factor-1 and 1α-hydroxylase transcript levels, serum calcitriol and FGF23 levels, intestinal phosphate absorption as well as absolute and fractional renal phosphate excretion were significantly higher in jak3 knockout than in wild-type mice. Coexpression of JAK3 increased the phosphate-induced current in renal sodium–phosphate cotransporter–expressing Xenopus oocytes. Thus, JAK3 is a powerful regulator of 1α-hydroxylase expression and phosphate transport. Its deficiency leads to marked derangement of phosphate metabolism.

// Shiwei Song 1 , Abul Fajol 2 , Xiankun Tu 1 , Baogang Ren 1 , Songsheng Shi 1 1 Department of Neurosurgery, Fujian Medical University Affiliated Union Hospital, Fujian Neurosurgical Institute, Fuzhou, 350001, China 2 Department of Clinical Sciences, CRC, Lund University, Malmo, 20502, Sweden Correspondence to: Shiwei Song, email: songshiweifmu@163.com Keywords: miR-204, GBM, suppressor Received: June 21, 2016 Accepted: August 16, 2016 Published: August 31, 2016 ABSTRACT In human cancers, miRNAs are important regulators of multiple cellular processes, and aberrant miRNA expression has been observed, and their alterations contribute to multiple cancer development and progression. Till now, little has been known about the role of miR-204 in human glioblastoma (GBM). In the present study, we used in-vitro assays to investigate the mechanisms of miR-204 in GBM cell lines and 60 cases of GBM tissues. Here, we found that miR-204 expression is downregulated in both GBM cell lines A172, U87 and U251 cells and GBM tissues as compared with NHA cells and normal tissues (all p

Metabolic syndrome is characterized by insulin resistance, obesity, and dyslipidemia. It is the consequence of an imbalance between caloric intake and energy consumption. Adiponectin protects against metabolic syndrome. Insulin-induced signaling includes activation of PI3 kinase and protein kinase B (PKB)/Akt. PKB/Akt in turn inactivates glycogen synthase kinase (GSK) 3, a major regulator of metabolism. Here, we studied the significance of PI3K-dependent GSK3 inactivation for adiponectin formation in diet-induced metabolic syndrome. Mice expressing PI3K-insensitive GSK3 (gsk3(KI)) and wild-type mice (gsk3(WT)) were fed a high-fat diet. Compared with gsk3(WT) mice, gsk3(KI) mice were protected against the development of metabolic syndrome as evident from a markedly lower weight gain, lower total body and liver fat accumulation, better glucose tolerance, stronger hepatic insulin-dependent PKB/Akt phosphorylation, lower serum insulin, cholesterol, and triglyceride levels, as well as higher energy expenditure. Serum adiponectin concentration and the activity of transcription factor C/EBPα controlling the expression of adiponectin in adipose tissue was significantly higher in gsk3(KI) mice than in gsk3(WT) mice. Treatment with GSK3 inhibitor lithium significantly decreased the serum adiponectin concentration of gsk3(KI) mice and abrogated the difference in C/EBPα activity between the genotypes. Taken together, our data demonstrate that the expression of PI3K-insensitive GSK3 stimulates the production of adiponectin and protects from diet-induced metabolic syndrome.

To the Editor Depression is a multifaceted disorder with diverse causes and has been associated with the risk to develop severe medical disorders.1 Indeed, depression increases the risk of cardiovascular disease by 1.5-fold to 2-fold, of stroke by 1.8-fold, of Alzheimer disease by 2.1-fold, of diabetes by 60%, and of cancer by 1.3-fold to 1.8-fold.1 Fibroblast growth factors (FGFs) are best known for their regulatory roles in cell growth, differentiation, and morphogenesis in early stages of neural development and have been discussed as switch genes, biomarkers, and treatment targets for affective disorders recently.2,3 However, at least FGF-23 has also been proposed as a cardiovascular risk marker,4 a central player of disordered mineral metabolism,5 and acts to decrease phosphate, 1,25-dihydroxyvitamin D, and parathyroid hormone levels.5 A close, bidirectional relationship exists between depression and cardiovascular disease.1 Indeed, major depression is associated with an increased risk of coronary artery disease, myocardial infarction, congestive heart failure, and isolated systolic hypertension leading to increased mortality and morbidity in patients.1 Moreover, a strong relationship has been described between severe coronary and aortic calcifications, intima thickness, osteoporosis, and depressive disorders.1 Fibroblast growth factor 23 lowers serum levels of 1,25(OH)2D3, which in turn up-regulates renal and intestinal phosphate and calcium transport.6–9 In mice, it was shown recently that lithium treatment up-regulates FGF-23 formation, an effect paralleled by substantial decrease of serum 1,25(OH)2D3 and phosphate concentrations.10 The present study explores the effect of lithium treatment on serum FGF-23, 1,25(OH)2D3, calcium, and phosphate concentrations in depressed patients. A total of 95 acute depressive patients (age 48 ± 14 years) were recruited for this study. Inclusion criteria consist of unipolar depression, age older than 18 years, indication for antidepressant pharmacotherapy, insufficient response to an adequate antidepressant pretreatment and clinical indication for lithium augmentation, hamilton depression rating score greater than 12, and written informed consent. Diagnosis was confirmed on the basis of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders. Fibroblast growth factor 23 serum concentrations were measured first in medicated patients before lithium augmentation and then after 4 weeks of medication with lithium. Detailed clinical data of the patients have already been published.11 All patients reached a lithium serum level of more than 0.4 mmol/L. Serum FGF-23 concentrations were measured by enzyme-linked immunosorbent assay (Immutopics International, California; AVP EIA kit, Phoenix Europe, Karlsruhe, Germany). enzyme-linked immunosorbent assay kits were employed to determine serum concentrations of 1,25(OH)2D3 (IDS, Boldon, United Kingdom). Data are provided as mean ± SEM; n represents the number of independent experiments. All data were tested for significance using unpaired Student t test. Only results with P < 0.05 were considered statistically significant. As illustrated in Figure ​Figure1,1, lithium treatment was followed by a marked increase of serum FGF-23 concentration. As shown in Figure ​Figure1,1, lithium treatment significantly decreased serum 1,25(OH)2D3 concentration. Lithium treatment significantly decreased serum phosphate concentrations (data not shown). FIGURE 1 Serum FGF-23 and 1,25(OH)2D3 levels/concentrations before and after lithium treatment. Arithmetic means ± SEM (n = 95) of serum FGF-23 (A) and 1,25(OH)2D3 levels (B) before (white bars) and after (black bars) lithium treatment. **P < 0.01 ...

FGF23 regulates renal phosphate and vitamin D metabolism. Loss of FGF23 results in massive calcification and rapid aging. FGF23 production is stimulated by 1,25(OH)2D3 and NFκB signaling. Here, we report that treatment of UMR106 osteoblast-like cells with 1,25(OH)2D3, inducing Fgf23 transcription, resulted in actin polymerization which was blocked by NFκB inhibitor wogonin. Interestingly, 1,25(OH)2D3-induced Fgf23 gene transcription was abolished by the actin microfilament-disrupting agent cytochalasin B, as well as by the inhibition of actin-regulating Rac1/PAK1 signaling. Our results provide strong evidence that actin redistribution regulated by the Rac1/PAK1 pathway participates in 1,25(OH)2D3-induced Fgf23 gene transcription.

Glycogen synthase kinase (GSK)-3 is a ubiquitously expressed kinase inhibited by insulin-dependent Akt/PKB/SGK. Mice expressing Akt/PKB/SGK-resistant GSK3α/GSK3β (gsk3(KI)) exhibit enhanced sympathetic nervous activity and phosphaturia with decreased bone density. Hormones participating in phosphate homeostasis include fibroblast growth factor (FGF)-23, a bone-derived hormone that inhibits 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3); calcitriol) formation and phosphate reabsorption in the kidney and counteracts vascular calcification and aging. FGF23 secretion is stimulated by the sympathetic nervous system. We studied the role of GSK3-controlled sympathetic activity in FGF23 production and phosphate metabolism. Serum FGF23, 1,25(OH)(2)D(3), and urinary vanillylmandelic acid (VMA) were measured by ELISA, and serum and urinary phosphate and calcium were measured by photometry in gsk3(KI) and gsk3(WT) mice, before and after 1 wk of oral treatment with the β-blocker propranolol. Urinary VMA excretion, serum FGF23, and renal phosphate and calcium excretion were significantly higher, and serum 1,25(OH)(2)D(3) and phosphate concentrations were lower in gsk3(KI) mice than in gsk3(WT) mice. Propranolol treatment decreased serum FGF23 and loss of renal calcium and phosphate and increased serum phosphate concentration in gsk3(KI) mice. We conclude that Akt/PKB/SGK-sensitive GSK3 inhibition participates in the regulation of FGF23 release, 1,25(OH)(2)D(3) formation, and thus mineral metabolism, by controlling the activity of the sympathetic nervous system.—Fajol, A., Chen, H., Umbach, A. T., Quarles, L. D., Lang, F., Föller, M. Enhanced FGF23 production in mice expressing PI3K-insensitive GSK3 is normalized by β-blocker treatment.

The mitogen- and stress-activated kinase MSK1/2 plays a decisive role in apoptosis. In analogy to apoptosis of nucleated cells, suicidal erythrocyte death called eryptosis is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine (PS) externalization. Here, we explored whether MSK1/2 participates in the regulation of eryptosis. To this end, erythrocytes were isolated from mice lacking functional MSK1/2 (msk−/−) and corresponding wild-type mice (msk+/+). Blood count, hematocrit, hemoglobin concentration and mean erythrocyte volume were similar in both msk−/− and msk+/+ mice, but reticulocyte count was significantly increased in msk−/− mice. Cell membrane PS exposure was similar in untreated msk−/− and msk+/+ erythrocytes, but was enhanced by pathophysiological cell stressors ex vivo such as hyperosmotic shock or energy depletion to significantly higher levels in msk−/− erythrocytes than in msk+/+ erythrocytes. Cell shrinkage following hyperosmotic shock and energy depletion, as well as hemolysis following decrease of extracellular osmolarity was more pronounced in msk−/− erythrocytes. The in vivo clearance of autologously-infused CFSE-labeled erythrocytes from circulating blood was faster in msk−/− mice. The spleens from msk−/− mice contained a significantly greater number of PS-exposing erythrocytes than spleens from msk+/+ mice. The present observations point to accelerated eryptosis and subsequent clearance of erythrocytes leading to enhanced erythrocyte turnover in MSK1/2-deficient mice.