Fibroblast growth factor receptor as a potential candidate for phosphate sensing

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Plasma Calcium and Phosphorus Levels and Cardiovascular Disease Risks in Egyptian Type 2 Diabetic Patients

Background: Cardiovascular complication of diabetes is considered an important issue that needs deep investigations. The levels of plasma calcium (Ca) and phosphorus (P) have been implicated as having an association to cardiovascular diseases. AIM: The objective of the present research was to study the plasma levels of both Ca and P and their association to the atherogenic ratio; total cholesterol: high density lipoprotein-cholesterol and the plasma albumin in male and female patients with type 2-diabetes. The interrelation between anthropometric parameters represented by body mass index (BMI), waist circumference and waist/hip ratio with Ca and P were studied. Also, the association between plasma Ca and P with their dietary intake were investigated. Subjects and METODS: Thirty-one type 2-diabetic male and female patients participated in the study, in addition of ten healthy subjects. Biochemical parameters, anthropometric measurements and nutrients′ intake were assessed. Biochemical parameters include plasma Ca, P, lipid profile, albumin, liver function tests and creatinine. RESULTS: Plasma Ca levels of female patients of BMI> 30 kg/m2 demonstrated significant increase compared to the control group.  All male and female patients showed significant increase in plasma P compared to the control group. Glycosylated hemoglobin of male and females showed significant high values compared to the control group except for diabetic male of BMI>30 kg/m2 that showed insignificant increase. No significant changes in plasma TG and LDL-C levels were noticed compared to the control.  Plasma TC of patients showed significant high levels compared to the control group. The levels of HDL-C of patients were significantly lower than that of the control. The ratios of TC/HDL-C diabetic patients either male or female and whatever their BMI were significantly higher than that of the control. No significant changes in plasma activities of ALT and AST and bilirubin levels were observed among the different groups including the control.  Plasma albumin levels demonstrated significant reduction compared to the control group whatever their sexes or BMI. Plasma creatinine levels of the different diabetic groups showed insignificant change from the control group except for the male group of BMI<30 kg/m2 that showed significant elevation. In male, plasma Ca showed significant negative correlation with albumin and positive correlation with creatinine and dietary vitamin D. In female, a significant positive correlation was noticed between plasma and dietary P while a negative correlation was observed between plasma Ca and dietary iron. CONCLUSION: Elevated of plasma P together with reduced plasma albumin and elevated TC/HDL-C may reflect an association of plasma P to CVD in male and female diabetic subjects while high plasma Ca might predict CVD in only female diabetic patients of BMI > 30 kg/m2.

Understanding the Stony Bridge between Osteoporosis and Vascular Calcification: Impact of the FGF23/Klotho axis

A relationship between osteoporosis (OP) and vascular calcification (VC) is now proposed. There are common mechanisms underlying the regulation of them. Fibroblast growth factor- (FGF-) 23 and Klotho are hormones associated with the metabolic axis of osteovascular metabolism. Most recently, it was suggested that the FGF23-klotho axis is associated with increasing incidence of fractures and is potentially involved in the progression of the aortic-brachial stiffness ratio. Herein, we discussed the potential role of the FGF23/Klotho axis in the pathophysiology of OP and VC. We want to provide an update review in order to allow a better understanding of the potential role of the FGF23/Klotho axis in comorbidity of OP and VC. We believe that a better understanding of the relationship between both entities can help in proposing new therapeutic targets for reducing the increasing prevalence of OP and VC in the aging population.

A Comprehensive Analysis of Metabolomics and Transcriptomics Reveals Novel Biomarkers and Mechanistic Insights on Lorlatinib Crosses the Blood-Brain Barrier

Of late, lorlatinib has played an increasingly pivotal role in the treatment of brain metastasis from non-small cell lung cancer. However, its pharmacokinetics in the brain and the mechanism of entry are still controversial. The purpose of this study was to explore the mechanisms of brain penetration by lorlatinib and identify potential biomarkers for the prediction of lorlatinib concentration in the brain. Detection of lorlatinib in lorlatinib-administered mice and control mice was performed using liquid chromatography and mass spectrometry. Metabolomics and transcriptomics were combined to investigate the pathway and relationships between metabolites and genes. Multilayer perceptron was applied to construct an artificial neural network model for prediction of the distribution of lorlatinib in the brain. Nine biomarkers related to lorlatinib concentration in the brain were identified. A metabolite-reaction-enzyme-gene interaction network was built to reveal the mechanism of lorlatinib. A multilayer perceptron model based on the identified biomarkers provides a prediction accuracy rate of greater than 85%. The identified biomarkers and the neural network constructed with these metabolites will be valuable for predicting the concentration of drugs in the brain. The model provides a lorlatinib to treat tumor brain metastases in the clinic.

Glycerol-3-phosphate and fibroblast growth factor 23 regulation

PURPOSE OF REVIEW

Both classical and nonclassical factors regulate fibroblast growth factor 23 (FGF23), with impacts on gene expression and proteolytic cleavage. Here, we review recent publications that extend current knowledge on these factors.

RECENT FINDINGS

Emerging nonclassical FGF23 regulators such as erythropoietin cause a balanced increase in FGF23 expression and cleavage, with minimal or no increase in biologically active intact FGF23 (iFGF23) in blood. However, circulating FGF23 profiles may not reflect the bone marrow microenvironment. For example, granulocyte colony-stimulating factor increases local marrow iFGF23 levels without impacting circulating iFGF23 levels. The view that phosphate does not increase bone FGF23 production also warrants reconsideration, as phosphate can reduce iFGF23 cleavage and phosphate-containing calciprotein particles increase FGF23 expression. Finally, a screen of renal venous plasma identifies glycerol-3-phosphate as a kidney-derived molecule that circulates to bone and bone marrow, where it is converted to lysophosphatidic acid and signals through a G-protein coupled receptor to increase FGF23 synthesis.

SUMMARY

FGF23 regulation is complex, requiring consideration of known and emerging stimuli, expression and cleavage, and circulating and local levels. Recent work identifies glycerol-3-phosphate as an FGF23 regulator derived from the injured kidney; whether it participates in FGF23 production downstream of classical or nonclassical factors requires further study.

Hyperphosphatemia and Cardiovascular Disease

Hyperphosphatemia or even serum phosphate levels within the “normal laboratory range” are highly associated with increased cardiovascular disease risk and mortality in the general population and patients suffering from chronic kidney disease (CKD). As the kidney function declines, serum phosphate levels rise and subsequently induce the development of hypertension, vascular calcification, cardiac valvular calcification, atherosclerosis, left ventricular hypertrophy and myocardial fibrosis by distinct mechanisms. Therefore, phosphate is considered as a promising therapeutic target to improve the cardiovascular outcome in CKD patients. The current therapeutic strategies are based on dietary and pharmacological reduction of serum phosphate levels to prevent hyperphosphatemia in CKD patients. Large randomized clinical trials with hard endpoints are urgently needed to establish a causal relationship between phosphate excess and cardiovascular disease (CVD) and to determine if lowering serum phosphate constitutes an effective intervention for the prevention and treatment of CVD.