Skip to main content
NCBI home page
PLOS One logoLink to PLOS One
. 2023 Jan 17;18(1):e0280378. doi: 10.1371/journal.pone.0280378

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

Dunlu Yuan 1, Jiaqing Li 1, Min Guo 2, Qing Yang 1, Jingjing Huang 3, Jingwen Nie 1, Ruomei Li 2, Qing Li 1,*
Editor: Gulali Aktas4
PMCID: PMC9844913  PMID: 36649363

Abstract

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.

Introduction

Chronic kidney disease (CKD) is a global health problem that affects more than 13% of the general population worldwide [1]. It is characterized by a possible progressive decline in kidney function leading to renal failure, which can eventually progress to end-stage renal disease (ESRD) or uremia. Moreover, recent studies have found that the incidence of sensorineural deafness in patients with chronic renal failure ranges from 40% to 90%, and the degree of deafness is positively correlated with the degree of renal failure [2, 3]. Hearing loss is the fifth leading cause of disability in the world [4]. It is one of the risk factors for cognitive decline that is independently associated with dementia [5, 6]. Hearing impairment in chronic renal failure leads to increased disability, further loss of quality of life, and increased disease burden in patients with renal failure [7].

Fibroblast growth factor-23 (FGF23), discovered by Yamashita et al. in 2000, is a regulatory factor produced and secreted by osteoblasts and osteofibroblasts, which has an important role in the regulation of serum phosphorus, parathyroid hormone (PTH) and 1,25-(OH)2-Vit-D3 [8]. Previous studies have found that CKD patients have elevated FGF23, and this increase appears to precede the increase in other serum parameters, including creatinine, urea nitrogen, and PTH [9]. Thus, elevated FGF23 is considered a sensitive biomarker for renal and extrarenal adverse effects in patients with CKD [10]. Furthermore, abnormally high expression of FGF23 in patients with chronic renal failure accelerates a series of extrarenal damages such as organismal calciphylaxis, atherosclerosis, secondary bone disease, and cognitive impairment of the nervous system [11–13].

D-serine is a non-essential amino acid involved in various physiological activities and pathological processes, including excitatory neurotransmission. Endogenous D-serine acts as a neurotransmitter released by neurons and plays an important regulatory role in neurodevelopment, neurotoxicity, learning, and memory [14]. Studies have also shown that chronic renal failure leads to abnormal amino acid metabolism and elevated levels of D-serine in the peripheral blood of patients with chronic renal failure, which is associated with disease progression [15].

In this study, we investigated the correlation between FGF23/D-serine and hearing impairment in MHD patients with ESRD, which is expected to provide a theoretical basis for the treatment of hearing impairment induced by chronic renal failure and a potential target for drug therapy.

Material and methods

Research subjects

The ethical review of the First Affiliated Hospital of Kunming Medical University approved the study, and consent was recorded via a paper form. Participants were presented with some information about this study followed by a consent statement: “I have read this Informed Consent. I have clearly understood the relevant content, and voluntarily cooperate to complete the questionnaire, physical examination and sampling work.” All enrolled participants signed the informed consent form.

Patients who underwent hearing tests by pure tone audiometry (PTA) during maintenance hemodialysis at the First Affiliated Hospital of Kunming Medical University from May to July 2022 were enrolled in this study. First, 30 MHD patients with ESRD complicated by hearing impairment were selected, and then 30 MHD patients with normal hearing and 30 healthy controls were matched 1:1 by age for the case-control study (Fig 1).

Fig 1. Study flow chart.

Fig 1

Open in a new tab

Inclusion and exclusion criteria for ESRD patients

Inclusion criteria were: age ≥ 18 years; glomerular filtration rate (GFR) < 15 mL/min-1.73 m2; receiving regular hemodialysis for more than 3 months, four hours per session, 3 times/week; conscious; willing to participate in the study.

Exclusion criteria were: age < 18 years; in the induction phase of hemodialysis; history of long-term noise exposure or ototoxic drug use; history of acute otitis media; family history of deafness; history of recent surgery; malignancy; unwillingness to cooperate with the study; history of severe mental illness.

Inclusion and exclusion criteria for the control group

Inclusion criteria were: age ≥ 18 years; no previous history of renal disease; normal audiometry; conscious and normal communication; willingness to participate in the study.

Exclusion criteria were: age < 18 years; previous history of renal disease; history of chronic noise exposure or ototoxic drug use; history of acute otitis media; family history of deafness; unwillingness to cooperate.

Hearing impairment definition

A Conera pure tone audiometer (MADSEN Co., Ltd., Copenhagen, Denmark) was used to measure at frequencies of 250, 500, 1000, 2000, 4000, and 8000, respectively, and monaural pure tone audiometry (PTA) of ≧ 25 dB at any one frequency was considered as hearing impairment [16].

Data collection

Questionnaire survey

A self-designed questionnaire form was used, which included questions regarding age, gender, marital status, education, history of previous diseases, history of ear disease, history of kidney disease, complications of kidney disease, etc. The respondents’ height, weight, and BMI were also analyzed. We had access to information that could identify individual participants during or after data collection.

Hearing tests

Binaural PTA was performed using a pure tone audiometer (MADSEN Co., Ltd., Copenhagen, Denmark) at frequencies of 250, 500, 1000, 2000, 4000, and 8000 in a dedicated audiometric room to obtain PTA values for each frequency.

Laboratory data

Laboratory data included blood creatinine, blood urea nitrogen (BUN), albumin (ALB), uric acid (UA), blood calcium, blood phosphorus, blood potassium, PTH, Hemoglobin (Hb), and red blood cell count (RBC).

Measurement of peripheral blood FGF23 and D-serine levels

All subjects fasted for at least 8 h. Then, 5 ml of venous blood was collected before 8:30 am. To avoid the influence of hemodialysis on laboratory data in MHD patients, blood was not collected during and 1 day after hemodialysis. Sampling for laboratory examination was carried out one-time.

The supernatant was extracted by centrifugation at 3000 rpm/min for 10 min. The levels of FGF23 in serum were measured using a commercially available ELISA assay kit (Elabscience Co., Wuhan, China) according to the manufacturer’s instructions. In addition, serum D-serine levels were measured at 535/587 nm endpoint mode using a micro 2D-HPLC platform in combination with a multi-well fluorescence enzyme marker according to the D-serine assay reagent instructions.

Statistical analysis

EpiData 3.1 software was used to establish the database, and SPSS 22.0 (IBM, Armonk, NY, USA) was used for statistical analysis. The categorical variables were compared as ratios or rates using the chi-square test; continuous variables were described using "Mean±SD," and differences between groups were analyzed using the F-test; dichotomous logistic regression was used to analyze the factors influencing hearing impairment in ESRD patients. The Person correlation coefficient was used to describe the correlation between continuous variables. The test level of bilateral α was 0.05, and P<0.05 was considered statistically significant.

Results

A total of 90 subjects were selected for this study, including 30 MHD patients complicated by hearing impairment, 30 MHD patients with normal hearing, and 30 controls. As seen in Table 1, the two MHD groups had a higher prevalence of hypertension, blood creatinine, BUN, PTH, blood phosphorus, FGF23, and D-serine than the control group, but also lower Hb, RBC, and ALB (all P < 0.01). Furthermore, among the three study groups, the highest levels of FGF23 and D-serine were found in the MHD group with hearing impairment, followed by the group with normal hearing in MHD (all P < 0.01) (Figs 2 and 3).

Table 1. Basic information.

Characteristic Control group (n = 30) MHD+NH group (n = 30) MHD+HI group (n = 30) P
Age(y) mean(SD) 43.17±8.95 43.43±8.79 43.90±10.38 0.954
Male no. (%) 16(53.3) 15(50.0) 22(73.3) 0.139
BMI (Kg/m2) mean(SD) 23.96±3.19 22.30±3.90 22.53±3.61 0.156
History of hypertension no. (%)** 12(40.0) 30(100.0) 30(100.0) <0.001
History of diabetes mellitus no. (%) 3 (10.0) 3(10.0) 6(20.0) 0.421
CKD etiology no. (%)** <0.001
    Chronic glomerulonephritis 0(0.0) 18(60.0) 14(46.7)
    Diabetic nephropathy 0(0.0) 3(10.0) 6(20.0)
    Hypertensive nephropathy 0(0.0) 7(23.3) 9(30.0)
    Other 0(0.0) 2(6.7) 1(3.3)
Creatinine (umol/L) mean(SD)** 71.4±11.66 1179±289.28 1104.41±290.44 <0.001
BUN (mmol/L) mean(SD)** 5.44±1.32 28.83±6.58 28.38±7.65 <0.001
e-GFR (mL/min-1.73 m2)** 104.42±15.48 3.82±0.97 4.27±1.33 <0.001
Duration of dialysis(Month) 0.00±0.00 43.57±25.58 46.83±45.32 0.732
Hb (g/L) mean(SD)** 154.37±15.41 104.8±18.03 108.17±18.48 <0.001
RBC (1012/L) mean(SD) ** 5.05±0.54 3.61±0.68 3.64±0.60 <0.001
ALB (g/L) mean(SD) ** 45.67±2.80 41.66±3.58 42.06±5.49 <0.001
PTH (pg/mL) mean(SD) ** 38.52±16.03 609.71±468.27 634.57±657.44 <0.001
Phosphorus (mmol/L) mean(SD)** 1.22±0.16 2.53±0.62 2.4±0.71 <0.001
Calcium (mmol/L) mean(SD) 2.34±0.09 2.31±0.18 2.28±0.20 0.317
FGF23 (pg/ml) mean(SD)** 26.62±23.40 96.52±65.07 167.26±81.93 <0.001
D-serine(μM) mean(SD)** 1.97±0.66 9.09±2.71 12.27±2.18 <0.001
Open in a new tab

Notes. NH, Normal hearing; HI, Hearing impairment

** P < 0.01

Fig 2. Comparing the FGF23 levels among 3 groups.

Fig 2

Open in a new tab

Fig 3. Comparing the D-serine levels among 3 groups.

Fig 3

Open in a new tab

Analysis of factors influencing hearing impairment in patients with ESRD

The presence of hearing impairment in MHD patients was a dependent variable (0 = none, 1 = yes), while gender (0 = male, 1 = female), diabetes mellitus (0 = none, 1 = yes), hyperuricemia (0 = none, 1 = yes), anemia (0 = none, 1 = yes), hypoalbuminemia (0 = none, 1 = yes), blood potassium (0<5.3mmo/l, 1≧5.3mmo/l), blood calcium (0<2.52mmol/l, 1≧2.52mmol/l), blood phosphorus (0<1.51mmol/l, 1≧1.51mmol/l), PTH (0<300pg/ml, 1≧300pg/ml), FGF23 (0<132pg/ml, 1≧132pg/ml), and D-serine (0<10μM, 1≧10μM) as independent variables. In addition, dichotomous logistic regression analysis was performed on the factors influencing the combined hearing impairment in patients with renal failure, and the results showed that rising FGF23 and D-serine were risk factors for hearing impairment in MHD patients (P < 0.01), as detailed in Table 2.

Table 2. Factors influencing hearing impairment in MHD patients.

Variables B SE Wald P Exp(B) 95%CI
Gender 0.043 0.796 0.003 0.957 1.044 (0.219–4.967)
Diabetes mellitus -0.019 1.2 0 0.988 0.981 (0.093–10.313)
Hyperuricemia 1.047 1.003 1.091 0.296 2.85 (0.399–20.341)
Anemia -0.908 0.87 1.089 0.297 0.403 (0.073–2.22)
Hypoalbuminemia 3.297 1.868 3.114 0.078 27.018 (0.694–1051.512)
Potassium 0.265 0.933 0.081 0.777 1.303 (0.209–8.12)
Calcium 0.121 1.128 0.012 0.914 1.129 (0.124–10.301)
Phosphorus -1.753 1.374 1.627 0.202 0.173 (0.012–2.561)
PTH -0.784 0.883 0.789 0.374 0.457 (0.081–2.576)
FGF23 2.806 0.916 9.389 0.002 16.541 (2.749–99.549)
D-serine 2.723 0.904 9.075 0.003 15.223 (2.589–89.511)
Constant -8.357 4.948 2.853 0.091
Open in a new tab

Analysis of factors associated with FGF23

Person correlation analysis of FGF23 with other test parameters was performed on 90 study participants, FGF23 was moderately positively correlated with BUN, blood creatinine, blood potassium, blood phosphorus, PTH, and D-serine, a low positive correlation with UA and a low negative correlation with Hb and RBC (Table 3).

Table 3. Analysis of factors associated with FGF23.

FGF23 r P
BUN 0.566 <0.001
Creatinine 0.577 <0.001
UA 0.333 0.001
Hb -0.391 <0.001
RBC -0.392 <0.001
ALB -0.119 0.262
Potassium 0.405 <0.001
Calcium -0.002 0.983
Phosphorus 0.485 <0.001
PTH 0.497 <0.001
D-serine 0.683 <0.001
Open in a new tab

Discussion

Chronic kidney failure and hearing impairment have been treated and studied as separate diseases without much attention to the association between the two diseases. However, the ear and the kidney begin to develop during the same gestation period (5–8 weeks of gestation) in the embryonic stage. Also, the kidney and the cochlea share similarities in anatomy, physiological characteristics, antigenic properties, and even genome [17]. They are also organs with abundant blood supply, high metabolism, and high oxygen consumption, very sensitive to ischemia and hypoxia. Furthermore, there is a correlation between the kidney and the cochlea in terms of enzyme content and distribution, water and electrolyte balance, and pharmacological response to certain drugs (most nephrotoxic drugs are also ototoxic). In addition, the structure of the tubular epithelial cells of the renal tubules is very similar to that of the cells of the vascular rim of the inner ear, and there are similarities between the mechanisms of the inner ear and kidney damage [18]; thus, it is speculated that there is a possibility of "ear-kidney homologation".

In our previous study, we found that the rate of hearing impairment in ESRD patients was significantly higher than in the general population, and the incidence of non-genetic hearing impairment in maintenance hemodialysis patients was as high as 80.5%. Men had significantly higher hearing impairment than women, and a higher proportion of impairment in both ears than in one ear [2]; yet, the exact mechanism of action remained unclear. Furthermore, another study indicated that hearing impairment significantly improved in patients with renal failure after successful renal transplantation when the renal failure was eliminated [19]. Therefore, this study further examined a correlation between ESRD patients and hearing impairment.

The risk of hearing impairment in MHD patients with abnormally high expression of FGF23 and D-serine was 16.54 and 15.22 times higher than in MHD patients with lower FGF23 and D-serine levels, respectively. Yet, due to the limitations associated with the small sample size, future trials with expanded sample size are needed to further validate the associated risks. In the early stage of renal insufficiency, the body compensates by increasing FGF23 to inhibit the synthesis of 1,25(OH)2VitD3 and promote urinary phosphorus excretion in order to maintain normal blood phosphorus levels. Thus, it is believed that the elevated FGF23 level in the body is a response to the reduced renal phosphorus excretion; yet, when renal function continues to decline and the ability to excrete phosphorus is further reduced, a loss of compensation will occur, i.e., hyper-FGF23 blood and hyperphosphatemia co-exist. Also, high FGF23 levels can cause a variety of mineral and bone metabolism imbalance diseases in the body, such as atherosclerosis, secondary bone disease, calciphylaxis, and cognitive impairment. Previous studies found that FGF23 regulates the immune response and host defense against bacterial infections. Inflammatory cytokines, such as C-reactive protein and IL-6, increase with FGF23 elevation [20]. Inflammatory conditions may also contribute to elevated FGF23 levels in circulation [21]. In addition, diabetes mellitus is associated with inflammation and may lead to diabetic nephropathy. Preclinical studies found that insulin deficiency increases serum FGF23 concentration in mice, a process that can be reversed by administering insulin [22]. Moreover, the elevation of FGF23 can result in inflammation in diabetic nephropathy. Therefore, FGF23 may be an inflammatory marker in diabetic nephropathy, which triggers a series of pathological changes in renal tissue [23].

FGF23 neutralization effectively improves bone quality and osseointegration in CKD mice, suggesting FGF23 as a key factor in CKD-related bone diseases [24]. In addition, the risk of hearing impairment is significantly higher in ESRD patients with higher FGF23 levels than in those with lower FGF23 levels [2], which is consistent with the results of this study. So, FGF23 not only has an important biomarker in the development of CKD but also has a direct pathological effect on its complications.

FGF23 acts through FGFR and α-Klotho. A combination of Klotho/FGFR/FGF23 regulates FGF signal transduction [25]. However, whether a series of pathological changes of FGF23 is essential for Klotho-mediated actions is still under debate [26]. Research shows that Klotho and FGF23 are independently associated with concentric hypertrophy in CKD patients [27]. Our previous study demonstrated that high levels of FGF23 are associated with hearing impairment in ESRD patients, independently of Klotho [2]. So, the Klotho’s serum level wasn’t evaluated in this study.

D-serine is a physiological co-agonist of the N-methyl-D-aspartate receptor (NMDAR) involved in synaptic plasticity, neurodevelopment, neurodegeneration, and various physiological and pathological activity processes, including excitatory neurotransmission. The conversion of L-serine to D -serine in neurons is facilitated by the action of serine racemase, a pathway called serine shuttle [28]. Overexpression of D-serine mediates the overactivation of NMDAR, causing excitatory neurotoxicity, which leads to neurodevelopmental defects and neurodegeneration. D-serine participates in neurodegeneration and schizophrenia [29, 30]. When D-serine is injected into mice, D-serine rapidly accumulates in the kidney, induces tubular cytotoxicity and contributes to a fibrous phenotype, and accelerates renal remodeling, suggesting that the kidney is an important target organ for D-serine [31] and that D-serine, in addition to being a biomarker, accelerates CKD progression and renal aging, and is a uremic toxin [32]. In addition to being expressed in the central nervous system, D-serine is also expressed in the heart and kidneys and is not only nephrotoxic but also neurotoxic [33].

Our data suggested that abnormally high expression of FGF23 and D-serine increases the risk of developing hearing damage in chronic renal failure. Studies have shown that FGF23 regulates multiple signaling pathways in the body, affecting mineral metabolism, insulin resistance, energy balance, and premature aging [34, 35]. In the renal failure setting, high levels of FGF23 regulate downstream signaling pathways, affecting enzyme activity and ion exchange in the inner ear, damaging cochlear capillaries, leading to cochlear sclerosis, and ultimately affecting normal cochlear function [36]. Meanwhile, the large accumulation of D-serine in chronic renal failure may further lead to hyperfunction of the auditory nerve NMDAR in the brain, exacerbating oxidative stress and excitatory neurotoxicity [37], thus promoting auditory damage.

The present study also found a positive correlation between FGF23 and D-serine in ESRD patients, i.e., as FGF23 increases, D-serine increases accordingly. It is hypothesized that during chronic renal failure, the abnormally high expression of FGF23 activates the downstream signaling pathway and increases the conversion of D-serine through the serine shuttle, which overactivates the NMDAR of the auditory nerve and increases excitatory neurotoxicity, leading to auditory damage. It has also been demonstrated that D-amino acid oxidase (an antagonist of D-serine) reduces endogenous D-serine levels, thereby decreasing NMDAR-mediated neurotoxicity in the hippocampus. Moreover, it was demonstrated that D-serine synergizes with NMDAR to produce neurotoxicity in the brain [38]. Therefore, it is assumed that the FGF23/D-serine axis has a regulatory role in hearing impairment in chronic renal failure and that lowering FGF23 levels may mediate a decrease in D-serine production, ultimately attenuating the effects of excitatory neurotoxicity in the central nervous system on the cochlea and preventing hearing impairment. It provides a potential target for preventing and treating hearing damage in chronic renal failure. In our next study, we plan to use a rat model of hearing impairment in kidney failure to test this hypothesis by targeting the expression of FGF23/D-serine in kidney tissue and cochlea, downstream signaling pathways, and its regulation of NMDAR.

For regular monitoring of hearing status, FGF23 and D-serine levels are needed to assess the risk of hearing impairment in patients with chronic renal failure in order to prevent and detect hearing impairment in a timely manner and to reduce the increased disability, decreased quality of life, and increased disease burden in patients with chronic renal failure due to hearing loss.

Conclusions

In the present study, we found that FGF23/D-serine levels were significantly higher in MHD patients with hearing impairment than in those with normal hearing and healthy subjects. Also, FGF23 was positively correlated with D-serine; it is hypothesized that in the chronic renal failure setting, abnormally high expression of FGF23 promotes increased production of D-serine (i.e., the presence of an FGF23/D-serine axis), which overactivates the auditory nerve NMDAR and causes excitatory neurotoxicity, thereby promoting auditory damage. This study provides insights into amino acid imbalance in chronic renal failure and potential biomarkers for early detection of hearing impairment complicated by renal failure. Lowering FGF23/D-serine may provide a new strategy for the pharmacological treatment of hearing impairment complicated by renal failure.

Study limitations

There are some limitations in the present study. First, it is a single-center study with a small sample size. Therefore, we plan to expand the sample size and perform a multicenter study to reduce the selection bias. Secondly, the pathophysiological regulatory mechanism of FGF23/D-serine in the cochlea and kidney was not fully clarified. In our next study, we plan to conduct animal studies to verify the above hypothesis. Finally, the effect of hemodialysis on hearing in ESRD patients was not included in this study, and the correlation study of this factor of hemodialysis should be addressed by future studies.

Supporting information

S1 Data

(XLSX)

Click here for additional data file. (23.6KB, xlsx)

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

This study was supported by grants from the Major Teaching Educational Reform Project of Kunming Medical University (2022-JY-Z-12), the Project of College Education Cooperation Project of Yunnan Province (SYSX202034), the Subproject of Fund of CKD Clinical Research Center in Yunnan Province (202102AA100060), the Project of Yunnan health training project of high level talents (H-2018052), and Hundred of young and middle-aged academic and technical talent in Kunming Medical University (60118260103). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

References

  • 1.Kalantar-Zadeh K, Jafar TH, Nitsch D, Neuen BL, Perkovic V. Chronic et al. disease. Lancet (London, England). 2021;398(10302):786–802. [DOI] [PubMed] [Google Scholar]
  • 2.Nie J, Li Q, Guo M, Li J, Yang J, Chang Q, et al. The correlation between fibroblast growth factor-23 and ESRD patients with hearing impairment. PeerJ. 2021;9:e12295. doi: 10.7717/peerj.12295 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Wu KL, Shih CP, Chan JS, Chung CH, Lin HC, Tsao CH, et al. Investigation of the relationship between sensorineural hearing loss and associated comorbidities in patients with chronic kidney disease: A nationwide, population-based cohort study. PloS one. 2020;15(9):e0238913. doi: 10.1371/journal.pone.0238913 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Wilson BS, Tucci DL, O’Donoghue GM, Merson MH, Frankish H. A Lancet Commission to address the global burden of hearing loss. Lancet (London, England). 2019;393(10186):2106–8. doi: 10.1016/S0140-6736(19)30484-2 [DOI] [PubMed] [Google Scholar]
  • 5.Tai SY, Shen CT, Wang LF, Chien CY. Association of sudden sensorineural hearing loss with dementia: a nationwide cohort study. BMC neurology. 2021;21(1):88. doi: 10.1186/s12883-021-02106-x [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Di Stadio A, Ralli M, Roccamatisi D, Scarpa A, Della Volpe A, Cassandro C, et al. Hearing loss and dementia: radiologic and biomolecular basis of their shared characteristics. A systematic review. Neurological sciences: official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. 2021;42(2):579–88. doi: 10.1007/s10072-020-04948-8 [DOI] [PubMed] [Google Scholar]
  • 7.Wu H, Li Q, Cai Y, Zhang J, Cui W, Zhou Z. Economic burden and cost-utility analysis of three renal replacement therapies in ESRD patients from Yunnan Province, China. International urology and nephrology. 2020;52(3):573–9. [DOI] [PubMed] [Google Scholar]
  • 8.Ho BB, Bergwitz C. FGF23 signalling and physiology. Journal of molecular endocrinology. 2021;66(2):R23–r32. doi: 10.1530/JME-20-0178 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Zeng S, Querfeld U, Feger M, Haffner D, Hasan AA, Chu C, et al. Relationship between GFR, intact PTH, oxidized PTH, non-oxidized PTH as well as FGF23 in patients with CKD. FASEB journal: official publication of the Federation of American Societies for Experimental Biology. 2020;34(11):15269–81. doi: 10.1096/fj.202000596R [DOI] [PubMed] [Google Scholar]
  • 10.Rodríguez M. FGF23: Is It Another Biomarker for Phosphate-Calcium Metabolism? Advances in therapy. 2020;37(Suppl 2):73–9. doi: 10.1007/s12325-019-01181-4 [DOI] [PubMed] [Google Scholar]
  • 11.Campos I, Faul C. The bone at the intersection of kidney and heart disease. Trends in pharmacological sciences. 2022;43(2):84–6. doi: 10.1016/j.tips.2021.11.014 [DOI] [PubMed] [Google Scholar]
  • 12.Rausch S, Föller M. The regulation of FGF23 under physiological and pathophysiological conditions. Pflugers Archiv: European journal of physiology. 2022;474(3):281–92. doi: 10.1007/s00424-022-02668-w [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Haffner D, Leifheit-Nestler M. Extrarenal effects of FGF23. Pediatric nephrology (Berlin, Germany). 2017;32(5):753–65. doi: 10.1007/s00467-016-3505-3 [DOI] [PubMed] [Google Scholar]
  • 14.Beesley S, Sullenberger T, Ailani R, D’Orio C, Crockett MS, Kumar SS. d-Serine Intervention In The Medial Entorhinal Area Alters TLE-Related Pathology In CA1 Hippocampus Via The Temporoammonic Pathway. Neuroscience. 2021;453:168–86. doi: 10.1016/j.neuroscience.2020.10.025 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Kimura T, Hesaka A, Isaka Y. Utility of d-serine monitoring in kidney disease. Biochimica et biophysica acta Proteins and proteomics. 2020;1868(9):140449. doi: 10.1016/j.bbapap.2020.140449 [DOI] [PubMed] [Google Scholar]
  • 16.Kuro-o M, Matsumura Y, Aizawa H, Kawaguchi H, Suga T, Utsugi T, et al. Mutation of the mouse klotho gene leads to a syndrome resembling ageing. Nature. 1997;390(6655):45–51. doi: 10.1038/36285 [DOI] [PubMed] [Google Scholar]
  • 17.Antwi S. Hearing loss in patients with chronic kidney disease and psychological burden in their caregivers. Ghana medical journal. 2019;53(3):189. doi: 10.4314/gmj.v53i3.1 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Zeigelboim BS, Mangabeira-Albernaz PL, Fukuda Y. High frequency audiometry and chronic renal failure. Acta oto-laryngologica. 2001;121(2):245–8. doi: 10.1080/000164801300043686 [DOI] [PubMed] [Google Scholar]
  • 19.Bains KS, Chopra H, Sandhu JS, Aulakh BS. Cochlear function in chronic kidney disease and renal transplantation: a longitudinal study. Transplantation proceedings. 2007;39(5):1465–8. doi: 10.1016/j.transproceed.2007.02.085 [DOI] [PubMed] [Google Scholar]
  • 20.Zheng Z, Zheng F. Immune cells and inflammation in diabetic nephropathy. J Diabetes Res. 2016;2016:1841690. doi: 10.1155/2016/1841690 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Rossaint J, Unruh M, Zarbock A. Fibroblast growth factor 23 actions in inflammation: a key factor in CKD outcomes. Nephrol Dial Transplant.2017; 32(9):1448–53. doi: 10.1093/ndt/gfw331 [DOI] [PubMed] [Google Scholar]
  • 22.Bär L, Feger M, Fajol A.Insulin suppresses the production of fibroblast growth factor 23 (FGF23).Proceedings of the national academy of sciences of the United States of America.2018;115 (22): 5804–9. doi: 10.1073/pnas.1800160115 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.David V, Martin A, Isakova T, Spaulding C, Qi L, Ramirez V, et al. Inflammation and functional iron deficiency regulate fibroblast growth factor 23 production. Kidney Int. 2016;89(1):135–46. doi: 10.1038/ki.2015.290 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Sun N, Guo Y, Liu W, Densmore M, Shalhoub V, Erben RG, et al.FGF23 neutralization improves bone quality and osseointegration of titanium implants in chronic kidney disease mice. Scientific reports. 2015; 5:8304. doi: 10.1038/srep08304 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Muñoz-CJR, Rodelo HC, Pendon RMV, Martin MA, Santamaria R, Rodriguez M; Klotho/FGF23 and Wnt Signaling as Important Players in the Comorbidities Associated with Chronic Kidney Disease.Toxins(Basel), 2020; 12(3): 185. doi: 10.3390/toxins12030185 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Tanaka S, Fujita S, Kizawa S, Morita H, Ishizaka N. Association between FGF23, α-Klotho, and Cardiac Abnormalities among Patients with Various Chronic Kidney Disease Stages. PLoS ONE, 2016;11, e0156860. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Silva AP, Mendes F, Carias E, Gonçalves RB, Fragoso A, Dias C, et al.Plasmatic Klotho and FGF23 Levels as Biomarkers of CKD-Associated Cardiac Disease in Type 2 Diabetic Patients. International journal of molecular sciences,2019;20 (7): 1536. doi: 10.3390/ijms20071536 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.Wolosker H. The Neurobiology of d-Serine Signaling. Advances in pharmacology (San Diego, Calif). 2018;82:325–48. doi: 10.1016/bs.apha.2017.08.010 [DOI] [PubMed] [Google Scholar]
  • 29.Kolodney G, Dumin E, Safory H, Rosenberg D, Mori H, Radzishevsky I, et al. Nuclear Compartmentalization of Serine Racemase Regulates D-Serine Production: IMPLICATIONS FOR N-METHYL-D-ASPARTATE (NMDA) RECEPTOR ACTIVATION. The Journal of biological chemistry. 2015;290(52):31037–50. doi: 10.1074/jbc.M115.699496 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Kantrowitz JT, Malhotra AK, Cornblatt B, Silipo G, Balla A, Suckow RF, et al. High dose D-serine in the treatment of schizophrenia. Schizophrenia research. 2010;121(1–3):125–30. doi: 10.1016/j.schres.2010.05.012 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Hesaka A, Tsukamoto Y, Nada S, Kawamura M, Ichimaru N, Sakai S, et al. d-Serine Mediates Cellular Proliferation for Kidney Remodeling. Kidney360. 2021;2(10):1611–24. doi: 10.34067/KID.0000832021 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Okada A, Nangaku M, Jao TM, Maekawa H, Ishimono Y, Kawakami T, et al. D-serine, a novel uremic toxin, induces senescence in human renal tubular cells via GCN2 activation. Scientific reports. 2017;7(1):11168. doi: 10.1038/s41598-017-11049-8 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Balu DT, Presti KT, Huang CCY, Muszynski K, Radzishevsky I, Wolosker H, et al. Serine Racemase and D-serine in the Amygdala Are Dynamically Involved in Fear Learning. Biological psychiatry. 2018;83(3):273–83. doi: 10.1016/j.biopsych.2017.08.012 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Lacroix JS, Urena-Torres P. [Potential application of fibroblast growth factor 23-klotho axis in chronic kidney disease]. Nephrologie & therapeutique. 2020;16(2):83–92. [DOI] [PubMed] [Google Scholar]
  • 35.Milovanova LY, Dobrosmyslov IA, Milovanov YS, Taranova MV, Kozlov VV, Milovanova SY, et al. Fibroblast growth factor-23 (FGF-23) / soluble Klotho protein (sKlotho) / sclerostin glycoprotein ratio disturbance is a novel risk factor for cardiovascular complications in ESRD patients receiving treatment with regular hemodialysis or hemodiafiltration. Terapevticheskii arkhiv. 2018;90(6):48–54. doi: 10.26442/terarkh201890648-54 [DOI] [PubMed] [Google Scholar]
  • 36.Khodeir SA, Okda HI, Abdalal HM. Clinical significance of fibroblast growth factor-23 and soluble alpha klotho in different stages of chronic kidney disease. Saudi journal of kidney diseases and transplantation: an official publication of the Saudi Center for Organ Transplantation, Saudi Arabia. 2019;30(1):108–18. [PubMed] [Google Scholar]
  • 37.Tseng YS, Liao CH, Wu WB, Ma MC. N-methyl-d-aspartate receptor hyperfunction contributes to d-serine-mediated renal insufficiency. American journal of physiology Renal physiology. 2021;320(5):F799–f813. doi: 10.1152/ajprenal.00461.2020 [DOI] [PubMed] [Google Scholar]
  • 38.Shleper M, Kartvelishvily E, Wolosker H. D-serine is the dominant endogenous coagonist for NMDA receptor neurotoxicity in organotypic hippocampal slices. The Journal of neuroscience: the official journal of the Society for Neuroscience. 2005;25(41):9413–7. [DOI] [PMC free article] [PubMed] [Google Scholar]

Decision Letter 0

Gulali Aktas

28 Nov 2022

PONE-D-22-30210Correlation study of FGF23/D-serine in end-stage renal disease patients with combined hearing impairmentPLOS ONE

Dear Dr. Li,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Jan 12 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Gulali Aktas

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at 

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and 

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match. 

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

3. Your ethics statement should only appear in the Methods section of your manuscript. If your ethics statement is written in any section besides the Methods, please move it to the Methods section and delete it from any other section. Please ensure that your ethics statement is included in your manuscript, as the ethics statement entered into the online submission form will not be published alongside your manuscript. 

4. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information. 

5. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Additional Editor Comments:

Authors studied association between FGF23/D-serine in end-stage renal disease patients with hearing loss in the manuscript titled "Correlation study of FGF23/D-serine in end-stage renal disease patients with combined hearing impairment". FGF23 is an inflammatory marker and on the other hand, chronic kidney disease, especially diabetic kidney injury is also characterized with change in serum levels of inflammatory cytokines. I recommend authors discussing this issue.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Dear Authors

Thank you very much for the opportunity of reviewing the manuscript entitled ‘Correlation study of FGF23/D-serine in end-stage renal disease patients with combined hearing impairment’ for your journal. The article is about clinically significant FGF23/D-serine on hearing impairment in patients with CRD. Indeed, the article is very interesting and of utmost importance to the field.

Title is appropriate for article, summary abstracted the manuscript adequately, the keyword is enough. The background and the rationale of the study sufficiently expressed in introduction. Study cohort, laboratory and statistical analyses are well issued in methodology. Results of the study are interesting and given in an easy to read way. Discussion is faultless and is the most perfect section of the manuscript. It does not require any more revisions. References are accurate. Figures are clear. Table is informative. As a result, the article should be accepted for publication in the journal.

Sincerely

Reviewer #2: There are a few comments or questions that need clarification from the authors:

1. Why is the title ... in ESRD patients, not CKD patients with routine HD (MHD)? Given that HD plays an important role in phosphate removal, and influences fluctuations in phosphate levels, PTH, and possibly serum FGF-23 levels.

2. OR must be accompanied by 95% CI, because it can describe the accuracy of the data.

3. It is known that FGF-23 plays an important role in the metabolism of vitamin D and phosphate by increasing phosphate excretion with the end result being inhibition of secondary hyperparathyroidism. In this regard, is the presence of FGF-23 serum not just a marker or does it have a direct pathological effect?

4. To be able to bind to its receptor, FGF-23 requires the presence of Klotho. Why wasn't Klotho's serum level evaluated?

5. This study was conducted on patients with GFR < 15 mL/min/1.73 m2. Are all ESRD patients on dialysis?

6. Regarding point 5, it is important to inform the average eGFR and duration of HD in the data on the characteristics of the research subjects.

7. Considering that the HD process can affect the results of laboratory examinations directly or indirectly, the timing of blood sampling is very important related to the HD therapy itself, so further explanation is needed.

8. Similarly, laboratory data is dynamic in nature, whereas hearing loss is a relatively more static condition. Is sampling for laboratory examination carried out once or several times?

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: mehmet zahid kocak

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2023 Jan 17;18(1):e0280378. doi: 10.1371/journal.pone.0280378.r002

Author response to Decision Letter 0

20 Dec 2022

Dear Editor,

Thank you for carefully reviewing our manuscript previously titled “Correlation study of FGF23/D-serine in maintenance hemodialysis patients with combined hearing impairment” for possible publication in the PLOS ONE. We are grateful to you and your reviewers for their constructive critique. We have revised the manuscript, highlighting our revisions in yellow and have attached point-by-point responses detailing how we have revised the manuscript in response to the reviewers' comments below.

Thank you for your consideration and further review of our manuscript. Please do not hesitate to contact us with any further questions or recommendations.

Yours Sincerely,

Qing Li

Department of Nephrology, the First Affiliated Hospital of Kunming Medical University, Kunming, 650032, Yunnan, China

Position: Associate chief physician

E-mail: liqing@kmmu.edu.cn；

Tel.: +86-0871-65324888

ORCID of the author: 0000-0001-5452-2734

Reviewer Comments:

Manuscript Number: PONE-D-22-30210

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

Additional Editor Comments

Authors studied association between FGF23/D-serine in end-stage renal disease patients with hearing loss in the manuscript titled "Correlation study of FGF23/D-serine in end-stage renal disease patients with combined hearing impairment". FGF23 is an inflammatory marker and on the other hand, chronic kidney disease, especially diabetic kidney injury is also characterized with change in serum levels of inflammatory cytokines. I recommend authors discussing this issue.

Response:

Done as what you suggested. We deeply appreciate your good suggestion. We have added discussion about this issue. Please see Discussion section: Page 15, Line 232-242, References section: Page23, Line 414-424.

Previous studies found that FGF23 regulates the immune response and host defense against bacterial infections. Inflammatory cytokines, such as C-reactive protein and IL-6, increase with FGF23 elevation(20). Inflammatory conditions may also contribute to elevated FGF23 levels in circulation(21). In addition, diabetes mellitus is associated with inflammation and may lead to diabetic nephropathy. Preclinical studies found that insulin deficiency increases serum FGF23 concentration in mice, a process that can be reversed by administering insulin(22). Moreover, the elevation of FGF23 can result in inflammation in diabetic nephropathy. Therefore, FGF23 may be an inflammatory marker in diabetic nephropathy, which triggers a series of pathological changes in renal tissue (23).

References

20. Zheng Z, Zheng F. Immune cells and inflammation in diabetic nephropathy. J Diabetes Res. 2016;2016:1841690.

21. Rossaint J, Unruh M, Zarbock A. Fibroblast growth factor 23 actions in inflammation: a key factor in CKD outcomes. Nephrol Dial Transplant.2017; 32(9):1448-53.

22. Bär L,Feger M,Fajol A.Insulin suppresses the production of fibroblast growth factor 23 (FGF23).Proceedings of the national academy of sciences of the United States of America.2018;115 (22):5804-9.

23. David V, Martin A, Isakova T, Spaulding C, Qi L, Ramirez V, et al. Inflammation and functional iron deficiency regulate fibroblast growth factor 23 production. Kidney Int. 2016;89(1):135-46.

Reviewer 2

1. Why is the title ... in ESRD patients, not CKD patients with routine HD (MHD)? Given that HD plays an important role in phosphate removal, and influences fluctuations in phosphate levels, PTH, and possibly serum FGF-23 levels.

Response:

Done as what you suggested. We deeply appreciate your good suggestion. We have corrected the title: Correlation study of FGF23/D-serine in maintenance hemodialysis patients with combined hearing impairment

Please see the title section: Page 1, Line 1-3.

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

2. OR must be accompanied by 95% CI, because it can describe the accuracy of the data.

Response:

We deeply appreciate your good suggestion. We have added 95%CI.

Please see Abstract section: Page 2, Line40-41.

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.

3. It is known that FGF-23 plays an important role in the metabolism of vitamin D and phosphate by increasing phosphate excretion with the end result being inhibition of secondary hyperparathyroidism. In this regard, is the presence of FGF-23 serum not just a marker or does it have a direct pathological effect?

Response:

We deeply appreciate your good suggestion. We have added the discussion.

Please see Introduction section: Page4-5, Line69-74；Discussion section: Page15, Line 243-249，References：Line 425-427.

.

Thus, elevated FGF23 is considered a sensitive biomarker for renal and extrarenal adverse effects in patients with CKD (10). Furthermore, abnormally high expression of FGF23 in patients with chronic renal failure accelerates a series of extrarenal damages such as organismal calciphylaxis, atherosclerosis, secondary bone disease, and cognitive impairment of the nervous system.

FGF23 neutralization effectively improves bone quality and osseointegration in CKD mice, suggesting FGF23 as a key factor in CKD-related bone diseases (24). In addition, the risk of hearing impairment is significantly higher in ESRD patients with higher FGF23 levels than in those with lower FGF23 levels (2), which is consistent with the results of this study. So, FGF23 not only has an important biomarker in the development of CKD but also has a direct pathological effect on its complications.

References

24.Sun N, Guo Y, Liu W, Densmore M, Shalhoub V, Erben RG , et al.FGF23 neutralization improves bone quality and osseointegration of titanium implants in chronic kidney disease mice. Scientific reports. 2015; 5:8304.

4. To be able to bind to its receptor, FGF-23 requires the presence of Klotho. Why wasn't Klotho's serum level evaluated?

Response:

We deeply appreciate your good suggestion. We have added the explanation.

Please see Discussion section: Page15, Line 250-257. References：Line 429-438.

FGF23 acts through FGFR and α-Klotho. A combination of Klotho/FGFR/FGF23 regulates FGF signal transduction (25). However, whether a series of pathological changes of FGF23 is essential for Klotho-mediated actions is still under debate (26). Research shows that Klotho and FGF23 are independently associated with concentric hypertrophy in CKD patients (27). Our previous study demonstrated that high levels of FGF23 are associated with hearing impairment in ESRD patients, independently of Klotho (2). So, the Klotho's serum level wasn’t evaluated in this study.

References

25. Muñoz-CJR,Rodelo HC, Pendon RMV, Martin MA, Santamaria R, Rodriguez M; Klotho/FGF23 and Wnt Signaling as Important Players in the Comorbidities Associated with Chronic Kidney Disease .Toxins(Basel) , 2020; 12(3): 185.

26.Tanaka S, Fujita S, Kizawa S, Morita H, Ishizaka N. Association between FGF23, α-Klotho, and Cardiac Abnormalities among Patients with Various Chronic Kidney Disease Stages. PLoS ONE , 2016;11, e0156860.

27. Silva AP,Mendes F,Carias E, Gonçalves RB, Fragoso A, Dias C, et al.Plasmatic Klotho and FGF23 Levels as Biomarkers of CKD-Associated Cardiac Disease in Type 2 Diabetic Patients. International journal of molecular sciences,2019;20 (7) :1536.

5. This study was conducted on patients with GFR < 15 mL/min/1.73 m2. Are all ESRD patients on dialysis?

Response:

Yes，all ESRD patients on dialysis in the present study.

Please see Material and Methods section: Page 6, Line98-100.

Inclusion criteria were: age ≥ 18 years; glomerular filtration rate (GFR) < 15 mL/min-1.73m2; receiving regular hemodialysis for more than 3 months, four hours per session, 3 times/week

6. Regarding point 5, it is important to inform the average eGFR and duration of HD in the data on the characteristics of the research subjects.

Response:

Done as what you suggested. We deeply appreciate your good suggestion. We have added the average eGFR and duration of HD in the data on the characteristics of the research subjects.

Please see Material and Methods section: Page 6, Line98-100, Results section: Page 10-11, Table 1.

Inclusion criteria were: age ≥ 18 years; glomerular filtration rate (GFR) < 15 mL/min-1.73 m2; receiving regular hemodialysis for more than 3 months, four hours per session, 3 times/week; conscious; willing to participate in the study.

Characteristic Control group (n=30) MHD+NH

group

(n=30) MHD+HI

group

(n=30) P

Age(y) mean(SD) 43.17±8.95 43.43±8.79 43.90±10.38 0.954

Male no. (%) 16(53.3) 15(50.0) 22(73.3) 0.139

BMI (Kg/m2) mean(SD) 23.96±3.19 22.30±3.90 22.53±3.61 0.156

History of hypertension no. (%)** 12(40.0) 30(100.0) 30(100.0) ＜0.001

History of diabetes mellitus no. (%) 3 (10.0) 3(10.0) 6(20.0) 0.421

CKD etiology no. (%)** ＜0.001

Chronic glomerulonephritis 0(0.0) 18(60.0) 14(46.7)

Diabetic nephropathy 0(0.0) 3(10.0) 6(20.0)

Hypertensive nephropathy 0(0.0) 7(23.3) 9(30.0)

Other 0(0.0) 2(6.7) 1（3.3）

Creatinine (umol/L) mean(SD)** 71.4±11.66 1179±289.28 1104.41±290.44 ＜0.001

BUN (mmol/L) mean(SD)** 5.44±1.32 28.83±6.58 28.38±7.65 ＜0.001

e-GFR（mL/min-1.73 m2)** 104.42±15.48 3.82±0.97 4.27±1.33 ＜0.001

Duration of dialysis(Month) 0.00±0.00 43.57±25.58 46.83±45.32 0.732

Hb (g/L) mean(SD)** 154.37±15.41 104.8±18.03 108.17±18.48 ＜0.001

RBC (1012/L) mean(SD) ** 5.05±0.54 3.61±0.68 3.64±0.60 ＜0.001

ALB (g/L) mean(SD) ** 45.67±2.80 41.66±3.58 42.06±5.49 ＜0.001

PTH (pg/mL) mean(SD) ** 38.52±16.03 609.71±468.27 634.57±657.44 ＜0.001

Phosphorus (mmol/L) mean(SD)** 1.22±0.16 2.53±0.62 2.4±0.71 ＜0.001

Calcium (mmol/L) mean(SD) 2.34±0.09 2.31±0.18 2.28±0.20 0.317

FGF23 (pg/ml) mean(SD)** 26.62±23.40 96.52±65.07 167.26±81.93 ＜0.001

D-serine(μM）mean(SD)** 1.97±0.66 9.09±2.71 12.27±2.18 ＜0.001

Notes. NH, Normal hearing ; HI, Hearing impairment ; ** P < 0.01

7. Considering that the HD process can affect the results of laboratory examinations directly or indirectly, the timing of blood sampling is very important related to the HD therapy itself, so further explanation is needed.

Response:

Done as what you suggested. We deeply appreciate your good suggestion. We have added the explanation.

Please see Data Collection section: Page 7, Line134-137.

All subjects fasted for at least 8 h. Then, 5 ml of venous blood was collected before 8:30 am. To avoid the influence of hemodialysis on laboratory data in MHD patients, blood was not collected during and 1 day after hemodialysis. Sampling for laboratory examination was carried out one-time.

8. Similarly, laboratory data is dynamic in nature, whereas hearing loss is a relatively more static condition. Is sampling for laboratory examination carried out once or several times?

Response:

We deeply appreciate your good suggestion. We have added the explanation.

Please see Data Collection section: Page 7, Line135-137.

To avoid the influence of hemodialysis on laboratory data in MHD patients, blood was not collected during and 1 day after hemodialysis.Sampling for laboratory examination was carried out one time.

We deeply appreciate your constructive comments.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (45.4KB, docx)

Decision Letter 1

Gulali Aktas

28 Dec 2022

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

PONE-D-22-30210R1

Dear Dr. Li,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Gulali Aktas

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Authors successfully revised the paper in accordance with the reviewers' suggestions.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: (No Response)

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

Acceptance letter

Gulali Aktas

6 Jan 2023

PONE-D-22-30210R1

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

Dear Dr. Li:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Professor Gulali Aktas

Academic Editor

PLOS ONE

Articles from PLOS ONE are provided here courtesy of PLOS

RESOURCES