Clinical significance of fibroblast growth factor-23 and soluble alpha klotho in different stages of chronic kidney disease

Correlation between soluble klotho and chronic kidney disease-mineral and bone disorder in chronic kidney disease: a meta-analysis

We conducted a systematic search across medical databases, including PubMed, Web of Science, EMBASE, and Cochrane Library, up to March 2023. A total of 1944 subjects or individuals from 17 studies were included in our final analysis. The correlation coefficient (r) between sKlotho and calcium was [0.14, (0.02, 0.26)], and a moderate heterogeneity was observed (I2 = 66%, P < 0.05). The correlation coefficient (r) between Klotho and serum phosphate was [- 0.21, (- 0.37, - 0.04)], with apparent heterogeneity (I2 = 84%, P < 0.05). The correlation coefficient (r) between sKlotho and parathyroid hormone and vascular calcification was [- 0.23,(- 0.29, - 0.17); - 0.15, (- 0.23, - 0.08)], with no significant heterogeneity among the studies. (I2 = 40%, P < 0.05; I2 = 30%, P < 0.05). A significant correlation exists between low sKlotho levels and an increased risk of CKD-MBD in patients with CKD. According to the findings, sKlotho may play a role in alleviating CKD-MBD by lowering phosphorus and parathyroid hormone levels, regulating calcium levels, and suppressing vascular calcification. As analysis showed that sKlotho has an important impact on the pathogenesis and progression of CKD-MBD in CKD patients. Nonetheless, further comprehensive and high-quality studies are needed to validate our conclusions.

Relationship between Serum Indoxyl Sulfate and Klotho Protein and Vascular Calcification in Patients with Chronic Kidney Disease Stages 3-5

Objective

This study aims to explore the relationships between serum indoxyl sulfate (IS) and Klotho protein levels with vascular calcification in patients with chronic kidney disease (CKD) stages 3-5.

Methods

From December 2021 to January 2023, a total of 108 CKD patients in stages 3-5 were enrolled in this cross-sectional investigation. Demographic information and routine clinical biochemistry test results were gathered. Serum levels of IS and Klotho were quantified through enzyme-linked immunosorbent assays. Furthermore, multislice spiral computed tomography was employed to evaluate vascular calcification. The association between serum IS or Klotho levels and abdominal aorta calcification was assessed using univariate analysis and logistic regression analyses.

Results

With the progression of CKD stages, serum creatinine, phosphorus, intact parathyroid hormone (iPTH), serum IS, and abdominal aortic calcification exhibited incremental trends, while serum calcium and Klotho protein levels showed a diminishing trend, with statistically significant differences (P < 0.05). Significant differences were observed in age, blood phosphorus, calcium, total parathyroid hormone, serum IS, and Klotho protein levels between patients with and without aortic calcification (P < 0.05). Logistic regression analysis demonstrated that advanced age, high IS level, and low Klotho protein level were independent risk factors for abdominal aortic calcification in CKD patients (P < 0.05).

Conclusion

This study indicates elevated serum IS levels and decreased Klotho protein levels in CKD patients. High IS level and low Klotho level were independent risk factors for abdominal aortic calcification.

Changes of FGF23 and hearing in chronic renal failure and their correlation analysis

BACKGROUND

To explore the association between fibroblast growth factor 23 (FGF23) and hearing in chronic renal failure (CRF).

METHODS

Pure tone audiometry was used to detect the hearing of patients with CRF; the level of serum FGF23, creatinine, blood urea nitrogen (BUN), parathyroid hormone (PTH), and mean binaural hearing threshold were compared to the control group (people without kidney disease). The rat model of renal failure was established by 5/6 nephrectomy, and the auditory brainstem response (ABR) of rats after modeling was detected by the Tucker Davis Technologies (TDT) system; the expression level of FGF23 in the peripheral blood, renal and cochlear tissue was also detected.

RESULTS

The incidence of hearing loss (HL) and serum FGF23 were higher in CRF patients than the control group; the sFGF23 was positively correlated with the mean binaural hearing threshold. Animal studies showed that the ABR threshold, creatinine, FGF23, BUN, and PTH increased after modeling; although, an increase in FGF23 was observed earlier than other indicators. The HL of rats with renal failure was significantly correlated with BUN, phosphate, PTH, sFGF23, kFGF23/β-actin, eFGF23/β-actin, weight, and modeling cycle.

CONCLUSIONS

Both CRF patients and rat models showed high-frequency HL. FGF23 was highly expressed in the serum of HL renal failure patients and rats, as well as in the renal tissue and cochlea of renal failure rats. Therefore, FGF23 may be involved in the occurrence and development of HL caused by CRF.

Association of vascular endothelial growth factor (VEGF) protein levels and gene polymorphism with the risk of chronic kidney disease

Vascular endothelial growth factor (VEGF) is a heparin-specific growth factor specific for vascular endothelial cells and induces angiogenesis via binding to vascular endothelial growth factor receptor (VEGFR). Chronic kidney disease (CKD), accompanied by microvascular disease, is recognized as an irreversible reduction of renal function. The effects of VEGF on CKD risk were evaluated in this study. 121 CKD patients and 50 healthy volunteers were evaluated in the current study. Data mining using the China Biological Medicine (CBM) and NCBI/PubMed databases, was performed and applicable investigations were pursued. Pooled mean differences (MD) and pooled odds ratios (OR), with corresponding confidence intervals (CIs), were calculated by meta-analysis. The levels of Scr, BUN and VEGF in the CKD group were significantly higher, when compared with the control group (P < 0.01). For the meta-analysis, thirteen articles and our current study were evaluated. VEGF levels was found to be associated with CKD risk (P < 0.00001). In the sub-group meta-analysis, we found that the pooled MD of VEGF levels was related to the early CKD group, although the difference was not notable. However, the meta-analysis itself indicated that the pooled MD of VEGF levels were in accordance with severe CKD group (P < 0.00001). Furthermore, VEGF +936C/T T allele was not associated with CKD risk (P = 0.69). VEGF levels are apparently associated with CKD risk, especially in more severe CKD. Gene polymorphism analysis indicates that the VEGF +936C/T T allele is not associated with CKD risk.

Pathophysiological Implications and Therapeutic Approach of Klotho in Chronic Kidney Disease. A Systematic Review

The Klotho protein, known as an anti-aging protein, is expressed mainly in the kidney, and kidney disorders may contribute to disrupted expression of renal Klotho. The purpose of this systematic review was to determine if there are biological and nutraceutical therapies that increase the expression of Klotho and can help prevent complications associated with CKD. A systematic literature review was carried out through the consultation of PubMed, Scopus, and Web of Science. Records between the years 2012 and 2022 in Spanish and English were selected. Cross-sectional or prevalence and analytical studies were included that evaluated the effects of Klotho therapy. A total of 22 studies were identified after the critical reading of these selected studies. Three investigated the association between Klotho and growth factors; two evaluated the relationship between the concentration of Klotho and the type of fibrosis; three focused on the relationship between vascular calcifications and vitamin D; two assessed the relationship between Klotho and bicarbonate; two investigated the relationship between proteinuria and Klotho; one demonstrated the applicability of synthetic antibodies as a support for Klotho deficiency; one investigated Klotho hypermethylation as a renal biomarker; two investigated the relationship between proteinuria and Klotho; four linked Klotho as an early marker of CKD; one investigated Klotho levels in patients with autosomal dominant polycystic kidney disease. In conclusion, no study has addressed the comparison of these therapies in the context of their use with nutraceutical agents that raise the expression of Klotho.

Correlation study of FGF23/D-serine in maintenance hemodialysis patients with combined hearing impairment

BACKGROUND

Recent studies have reported an association between chronic renal failure and hearing impairment. Yet, the exact mechanism of action is still not fully understood. In this study, we investigated the expression of fibroblast growth factor 23 (FGF23) and D-serine in maintenance hemodialysis (MHD) patients with end-stage renal disease (ESRD) complicated with hearing impairment and further investigated the correlation between FGF23/D-serine and hearing impairment.

METHODS

A total of 90 subjects, including 30 MHD patients complicated with hearing impairment, 30 MHD patients with normal hearing, and 30 controls, were included in this case-control study. Relevant data were obtained by questionnaire survey, audiometric test, enzyme-linked immunosorbent assay (ELISA) to determine FGF23 level, and high-performance liquid chromatography to determine D-serine level.

RESULTS

MHD patients showed abnormally high expression of FGF23 and D-serine, where FGF23 and D-serine levels were significantly higher in the group with hearing impairment than in the group with normal hearing and normal controls (all P<0.01). Also, elevated FGF23 and D-serine were identified as risk factors for hearing impairment in ESRD, with ORs of 16.54 (95%CI, 2.75-99.55) and 15.22 (95%CI, 2.59-89.51), respectively. Further Person correlation analysis showed a moderate positive correlation between FGF23 and D-serine (r = 0.683, P<0.001).

CONCLUSION

This study provides potential biomarkers for the early detection of hearing impairment complicated by chronic renal failure, and the reduction of FGF23/D-serine may provide a potential target for the treatment of hearing impairment complicated by chronic renal failure.

The controversy of klotho as a potential biomarker in chronic kidney disease

Klotho is an identified longevity gene with beneficial pleiotropic effects on the kidney. Evidence shows that a decline in serum Klotho level occurs in early chronic kidney disease (CKD) and continues as CKD progresses. Klotho deficiency is associated with poor clinical outcomes and CKD mineral bone disorders (CKD-MBD). Klotho has been postulated as a candidate biomarker in the evaluation of CKD. However, the evidence for the clinical significance of the relationship between Klotho and kidney function, CKD stage, adverse kidney and/or non-kidney outcomes, and CKD-MBD remains inconsistent and in some areas, contradictory. Therefore, there is uncertainty as to whether Klotho is a potential biomarker in CKD; a general consensus regarding the clinical significance of Klotho in CKD has not been reached, and there is limited evidence synthesis in this area. To address this, we have systematically assessed the areas of controversy, focusing on the inconsistencies in the evidence base. We used a PICOM strategy to search for relevant studies and the Newcastle–Ottawa Scale scoring to evaluate included publications. We reviewed the inconsistent clinical findings based on the relationship of Klotho with CKD stage, kidney and/or non-kidney adverse outcomes, and CKD-MBD in human studies. Subsequently, we assessed the underlying sources of the controversies and highlighted future directions to resolve these inconsistencies and clarify whether Klotho has a role as a biomarker in clinical practice in CKD.

Fibroblast Growth Factor-23-Klotho Axis in Cardiorenal Syndrome: Mediators and Potential Therapeutic Targets

Cardiorenal syndrome (CRS) is a complex disorder that refers to the category of acute or chronic kidney diseases that induce cardiovascular disease, and inversely, acute or chronic heart diseases that provoke kidney dysfunction. There is a close relationship between renal and cardiovascular disease, possibly due to the presence of common risk factors for both diseases. Thus, it is well known that renal diseases are associated with increased risk of developing cardiovascular disease, suffering cardiac events and even mortality, which is aggravated in those patients with end-stage renal disease or who are undergoing dialysis. Recent works have proposed mineral bone disorders (MBD) as the possible link between kidney dysfunction and the development of cardiovascular outcomes. Traditionally, increased serum phosphate levels have been proposed as one of the main factors responsible for cardiovascular damage in kidney patients. However, recent studies have focused on other MBD components such as the elevation of fibroblast growth factor (FGF)-23, a phosphaturic bone-derived hormone, and the decreased expression of the anti-aging factor Klotho in renal patients. It has been shown that increased FGF-23 levels induce cardiac hypertrophy and dysfunction and are associated with increased cardiovascular mortality in renal patients. Decreased Klotho expression occurs as renal function declines. Despite its expression being absent in myocardial tissue, several studies have demonstrated that this antiaging factor plays a cardioprotective role, especially under elevated FGF-23 levels. The present review aims to collect the recent knowledge about the FGF-23-Klotho axis in the connection between kidney and heart, focusing on their specific role as new therapeutic targets in CRS.

The correlation between fibroblast growth factor-23 and ESRD patients with hearing impairment

Background

End-stage renal disease (ESRD) patients often experience hearing impairment, resulting in a high rate of disability and a decline in their quality of life. Fibroblast growth factor-23 (FGF23) is a diagnostic biomarker for chronic kidney disease (CKD) and a pathogenic contributor to CKD progression. However, the correlation between FGF23 level and CKD patients with hearing impairment remains elusive. This study aimed to investigate the relationship between the FGF23 and ESRD accompanied with hearing impairment.

Methods

A total of 144 ESRD patients, who were admitted to the First Affiliated Hospital of Kunming Medical University from November to December 2020, were enrolled in this study. Firstly, 144 ESRD patients underwent pure-tone audiometry (PTA). Secondly, it was attempted to randomly select 20 ESRD patients with normal hearing, and 20 ESRD patients with hearing impairment (match ratio, 1:1). Age- and gender-matched healthy people (n = 20) were also recruited as controls group. The expression levels of FGF23 was detected by enzyme-linked immunosorbent assay (ELISA).

Results

The results of pure-tone audiometry showed that the prevalence of hearing impairment in ESRD patients was 80.5%. Male ESRD patients were more likely to develop hearing impairment compared to female patients. The incidence rate of hearing impairment at a high frequency was significantly higher than that at a low frequency (P < 0.01). The serum levels of FGF23, phosphorus, and parathyroid hormone (PTH) in ESRD patients with hearing impairment significantly increased compared with those with normal hearing and healthy controls.

Conclusion

ESRD patients had a higher risk of hearing loss, especially high-frequency hearing impairment. As FGF23 level increased, the risk of hearing loss was also elevated. The hearing impairment in ESRD patients was associated with the degree of kidney injury, and serum FGF23 level.

Serum and urinary soluble α-Klotho levels in patients with chronic kidney disease

Background: Chronic kidney disease is an epidemic global health problem that leads to death. To prevent any disease progression and treatment, the diagnosis must be made in the early stage by studying renal damage. Klotho is a protein found in many organs of the human body, but it is mainly abundant in the kidney. Objectives: This study is aimed to evaluate klotho’s clinical significance as an additional biomarker for diagnosing chronic kidney disease in its early stages. Methods: One hundred subjects were included in this study to measure their serum and urinary klotho. Forty patients with chronic kidney disease (pre-dialysis) and sixty normal subjects were enrolled in this study. Serum and urinary klotho were determined using the ELISA technique in addition to other renal function tests. Results: Serum and urinary alpha klotho were decreased in CKD patients when compared with control subjects. A positive correlation was found between serum creatinine and urinary alpha klotho in the patients’ group. Conclusion: Serum and urinary alpha klotho levels were decreased significantly in patients with chronic kidney disease compared with healthy controls.