FGF23

A Case of X-Linked Hypophosphatemia: Exploring the Burden in a Single Family and the Significance of a Multidisciplinary Approach

Published on: 24th September, 2023

A 46-year-old lady was diagnosed clinically with X-linked hypophosphatemia (XLH) with a rare pathogenic variant detected using exome sequencing. Phosphate-regulating endopeptidase homologous X linked (PHEX) is normally expressed in osteoblasts and osteocytes, and senses phosphate regulation. More than 1000 PHEX variants have been detected to date, which are caused by missense, nonsense, and frameshift mutations in addition to splice variants and copy number changes. The aberration in the PHEX gene leads to the upregulation of fibroblastic growth factor 23 (FGF23), which leads to defects in phosphate metabolism. This results in impaired bone growth and mineralization, short and disproportionate stature, leg bowing, musculoskeletal pain, spontaneous dental abscesses, rickets, and osteomalacia in XLH patients. The spectrum of manifestations differs between pediatric and adult patients. In our case study, two of the patient’s children started showing symptoms at a younger age, unlike their mother. Timely diagnosis and the start of treatment would help in their better management and improved quality of life.
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Circulating Levels of Fibroblast Growth Factor 23 Selective for C-Terminal (FGF23-CT) in Hemodialysis Patients

Published on: 13th October, 2023

Background: In hemodialysis patients, fibroblast growth factor 23 (FGF23) has reportedly been associated with the development of cardiovascular complications and a high risk of mortality. Our objective here was to study the cleavage characteristics of FGF23 in hemodialysis patients. Methods: This study design is a cross-sectional observational investigation of three facilities without intervention. To assess FGF23 concentrations, we obtained plasma samples from 97 hemodialysis patients before the hemodialysis session and from 16 healthy volunteers. We measured the FGF23 C-terminal fragment and intact FGF23 concentrations by using a commercial enzyme-linked immunosorbent assay. Results: Serum levels of the FGF23 C-terminal fragment were 189 ± 121 ng/mL in healthy volunteers and 306 ± 206 ng/mL in hemodialysis patients. The ratios of intact FGF23 to total FGF23 were 0.03 ± 0.03 in healthy volunteers and 0.44 ± 0.28 in hemodialysis patients. The ratios were positively correlated with levels of inorganic phosphate in hemodialysis patients (p < 0.001, r = 0.52). Conclusion: We measured actual levels of the serum FGF23 C-terminal fragment in hemodialysis patients by using a new commercial kit for the first time. The ratio of intact FGF23 to total FGF23 was lower in healthy controls than the ratio in hemodialysis patients. The cleavage percentage of FGF23 was considerably higher in both groups of subjects than previously thought. We suggest that hyperphosphatemia in hemodialysis patients was associated with impaired cleavage of FGF23.
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Is there a Place for Klotho in Alzheimer’s disease?

Published on: 29th February, 2024

Alzheimer’s disease, a major healthcare concern, lacks an effective pharmacological therapy to change its irreversible progression. In this work, we present Klotho, a protein associated with aging that is involved in the regulation of numerous physiological processes and is a serious candidate to be a pharmacological target to act on. Klotho’s mRNA has been found in neurons of a variety of brain regions (cortex, hippocampus). The best studied and prominent function of Klotho is as the co-receptor of fibroblast growth factor 23 (FGF23), through which Klotho controls renal phosphate excretion and vitamin D metabolism. Reduced serum levels of Klotho in mice have been associated with a shorter life expectancy and with numerous pathological conditions such as renal disease, vascular calcification, neurodegeneration, and others. Moreover, overexpression of Klotho leads to opposite effects resulting in increased survival rates. In this review we address different signaling pathways in which Klotho is involved in one way or another, focusing on those pathways that could serve as pharmacological targets to modify the evolution of Alzheimer’s disease. We describe how Klotho inhibits signaling cascades involved in cellular senescence, fibrosis, inflammation, and apoptosis all of which are mediated by tumor growth factor β (TGF- β), nuclear factor kappa K (NF- κ B), insulin-like growth factor 1 (IGF-1) or Wnt. We also highlight how Klotho is able to activate anti-inflammatory and antioxidant signaling pathways.  Although there are no drugs that act specifically on Klotho, compounds currently on the market such as hormone-based drugs, pravastatin, losartan, fosinopril, and rapamycin have been shown to increase the expression of this protein and are also discussed.
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