Clinical Research

Intracellular Phosphate and ATP Depletion Measured by Magnetic Resonance Spectroscopy in Patients Receiving Maintenance Hemodialysis

Guillaume Chazot, Sandrine Lemoine, Gabriel Kocevar, Emilie Kalbacher, Dominique Sappey-Marinier, Olivier Rouvière and Laurent Juillard
JASN January 2021, 32 (1) 229-237; DOI: https://doi.org/10.1681/ASN.2020050716

Significance Statement

The origin of most of the phosphate removed during hemodialysis has been uncertain. In this pilot study, the authors used phosphorus (31P) magnetic resonance spectroscopy to quantify intracellular inorganic phosphate (Pi), phosphocreatine, and ATP kinetics in 11 patients with ESKD during a 4-hour hemodialysis treatment. They found a decreased concentration of both intracellular Pi and ATP, confirming that Pi is, at least partially, released by the intracellular compartment. This finding raises the possibility that excessive dialytic removal of phosphate might adversely affect the intracellular availability of high-energy phosphates and ultimately, cellular metabolism.

Abstract

Background The precise origin of phosphate that is removed during hemodialysis remains unclear; only a minority comes from the extracellular space. One possibility is that the remaining phosphate originates from the intracellular compartment, but there have been no available data from direct assessment of intracellular phosphate in patients undergoing hemodialysis.

Methods We used phosphorus magnetic resonance spectroscopy to quantify intracellular inorganic phosphate (Pi), phosphocreatine (PCr), and βATP. In our pilot, single-center, prospective study, 11 patients with ESKD underwent phosphorus (31P) magnetic resonance spectroscopy examination during a 4-hour hemodialysis treatment. Spectra were acquired every 152 seconds during the hemodialysis session. The primary outcome was a change in the PCr-Pi ratio during the session.

Results During the first hour of hemodialysis, mean phosphatemia decreased significantly (−41%; P<0.001); thereafter, it decreased more slowly until the end of the session. We found a significant increase in the PCr-Pi ratio (+23%; P=0.001) during dialysis, indicating a reduction in intracellular Pi concentration. The PCr-βATP ratio increased significantly (+31%; P=0.001) over a similar time period, indicating a reduction in βATP. The change of the PCr-βATP ratio was significantly correlated to the change of depurated Pi.

Conclusions Phosphorus magnetic resonance spectroscopy examination of patients with ESKD during hemodialysis treatment confirmed that depurated Pi originates from the intracellular compartment. This finding raises the possibility that excessive dialytic depuration of phosphate might adversely affect the intracellular availability of high-energy phosphates and ultimately, cellular metabolism. Further studies are needed to investigate the relationship between objective and subjective effects of hemodialysis and decreases of intracellular Pi and βATP content.

Clinical Trial registry name and registration number Intracellular Phosphate Concentration Evolution During Hemodialysis by MR Spectroscopy (CIPHEMO), NCT03119818

Hyperphosphatemia has been associated with increased cardiovascular mortality in ESKD.1⇓–3 In order to reduce hyperphosphatemia, international recommendations suggest dietary restriction of phosphate intake, use of oral phosphate binders, and increased dialytic phosphate (inorganic phosphate [Pi]) removal.4 However, current understanding of Pi removal is imperfect. Pi kinetics do not display the same bicompartmental kinetic behavior as urea. Around 700 mg to 1 g of Pi can be removed during a hemodialysis (HD) session. Study of available circulating Pi compared with the total mass transfer (700–1000 mg) during HD strongly suggests that serum phosphate cannot be the sole source. The plateau phase of serum Pi concentration, observed 1 hour after the start of HD, suggests a replenishment from one or more additional compartments. Everything we currently know about such additional compartments is derived from mathematical modeling on the basis of patient’s serum Pi changes during the HD.5⇓⇓–8 All of these mathematical models make the same central assumption, namely that removed Pi originated exclusively from the intracellular compartment. There have been no available data concerning direct assessment of intracellular Pi in patients on HD. This remains an important question as consequences of intracellular Pi depletion on patients could be deleterious. Pi is indeed crucial for cell metabolism, especially because Pi allows ATP synthesis9 and reduction of intracellular Pi (as high-energy phosphate compounds) might lead to respiratory failure, depressed myocardial performance, and skeletal muscular weakness.10 Challenged cellular metabolism could be involved in a range of commonly observed objective and subjective consequences of HD.

To address this question of the decreased Pi origin, we previously set up an experimental study in a swine model of HD.11 We measured intracellular Pi and βATP during the HD session using phosphorus magnetic resonance spectroscopy (31P-MRS) 2 days after binephrectomy. 31P-MRS recorded real-time changes in the relative concentrations of metabolites that are involved in high-energy phosphate metabolism, including ATP, phosphocreatine (PCr), and Pi, as well as changes in muscle intracellular pH. Intracellular Pi and βATP could be assessed noninvasively, continuously, and repeatably by 31P-MRS.12 We reported a surprising increase in intracellular Pi content and a decrease of βATP during an HD session. These unexpected findings, relating to Pi concentration, were contrary to current mathematic models on the basis of data from established patients on HD. Hence, we postulated that the observed changes might be the result of studying an AKI model that could be subjected to severe acidosis, a situation not fully comparable with maintenance HD. We hypothesized that intracellular Pi dynamics should be different (with an appreciable amount of depurated Pi originating from within the cell) in patients on maintenance HD. We, therefore, applied similar magnetic resonance (MR)–based methods developed in the initial preclinical study to directly investigate the effect of conventional 4-hour HD session on intracellular Pi and βATP.

Methods

Study Design

The study was a pilot, single-center (Edouard Herriot Hospital, Lyon, France), prospective trial. It was approved by an ethics committee (2017-A00020–53; CPP Ouest 6, Brest, France) and by the French National Medicine Agency in April 2017. Written informed consent was obtained for all participants (ClinicalTrials.gov: NCT03119818).

Inclusion criteria were patients with ESKD of 18–80 years of age on maintenance HD >6 months with predialysis serum Pi between 1.5 and 3 mmol/L (4.6–9.3 mg/dl). Major exclusion criteria were protein-energy wasting, obesity, severe secondary hyperparathyroidism (parathyroid hormone ≥1000 pg/ml), significant anemia (hemoglobin ≤100 g/L), temporary vascular access, and contraindication to magnetic resonance imaging (MRI).

Outcomes

The primary outcome was the change of the PCr-Pi ratio over the period of a single HD treatment session. Principal secondary outcome was the change of the PCr-βATP ratio over the same period.

Sample Size Considerations

Justification of the clinical significance margin was challenging for this pilot study. However, a change in intracellular Pi (measured by MR spectroscopy) of around 20% has been reported to be associated with respiratory failure.13 Using data derived from a previous preclinical study,11 we were able to derive the sample size needed to detect a similar magnitude of change. Assuming a reduction of the PCr-Pi ratio of 15% during the HD session, 12 patients would be required to deliver 90% power to this change at a 5% significance level.

HD Protocol

All patients underwent 31P-MRS during a standard 4-hour HD session. HD sessions were performed using a 5008 dialysis monitor (Fresenius, Bad Homburg, Germany) and a TS-2.1SL dialyzer (Toray Medical Co., Ltd, Tokyo, Japan). Dialysate composition was Na+=138 mmol/L, Cl−=107 mmol/L, K+=2 mmol/L, Ca2+=1.5 mmol/L, HCO3−=35 mmol/L, Mg2+=0.50 mmol/L, and acetate =3 mmol/L. The blood flow pump was set at 300 ml/min, and dialysate flow rate was set at 500 ml/min. Ultrafiltration was individually determined by interdialytic weight gain. Hemodynamic tolerance was assessed by the change in BP and heart rate. Because of the magnetic environment of MRI, the dialysis monitor was placed outside of the MRI examination room (4.2 m from the patient). The dialysis lines passed through a radiofrequency wave guide and had to be longer than usual in order to connect patients positioned on the bed of the MRI system. This setup increased the extracorporeal circuit by approximately 150 ml (18 ml/m of extended lines). Dialysate temperature was set to 37°C to prevent hypothermia given the low ambient temperature in the scanning room and extended extracorporeal circuit.

Plasma and Effluent Measurements

Sodium, potassium, chlorine, bicarbonate, protein, urea, creatinine, calcium, and Pi blood concentrations were measured before each dialysis session, as was blood gas for pH measurement. During the HD session, measurements were performed every 15 minutes for a period of 60 minutes and then every 60 minutes until the session was concluded. Parathyroid hormone (PTH) and 25-OH vitamin D were measured before and at the end of the session. During the session, effluent was harvested. Effluent phosphate concentrations were measured every 40 minutes, and effluent volumes were noted to measure phosphate mass transfer.

Intracellular Pi and βATP Measurements

31P-MRS was performed using a 3-Tesla MRI system (GE Healthcare, Boston, MA). The subjects were studied in the supine position, with the calf muscle of the right leg lying over a 20-cm-diameter surface coil. A sliding bed was used to move the patient’s leg in the center of the magnet. The surface coil was set to the phosphorus resonance frequency and positioned under the calf muscle to acquire the signal from a volume of interest of 4×4 cm, as previously described.11 Phosphorus MR spectra (repetition time =2.6 seconds; echo time ≤1 ms) were acquired at baseline (before the beginning of the HD session) with patients at rest and every 152 seconds during dialysis. A typical baseline spectrum is represented in Figure 1. Spectra were processed and analyzed using jMRUI software (v. 5.2, http://www.jmrui.eu). The content of phosphorus metabolites was estimated by measuring the peaks area of the spectra, and particularly, the resonance peaks of Pi, PCr, and βATP were analyzed. The use of βATP peak was preferred to α- and γATP peaks because they are known to be contaminated by NADP and ADP signals, respectively. In contrast, the βATP peak contains only ATP signal, allowing an accurate estimation of intracellular ATP concentration.

Figure 1.
Figure 1.

31P-MRS MR spectrum acquisition from calf's muscle. (A) Axial T1-weighted MRI of the calf muscle showing the localization of the 31P-MRS acquisition from the volume of interest (red box) and (B) the acquired MR spectrum showing the different phosphorus containing compounds (Pi; PCr; and α-, β-, and γATP resonance peaks).

As the signal-noise ratio of the spectrum is dependent on technical parameters (such as surface coil tuning and sensitivity, magnetic field homogeneity, and radio-frequency power), we used a relative quantification method on the basis of metabolite ratios to follow the evolution of metabolite contents during time and between individuals.14 Metabolite ratios are thus proportional to the content variations of each compound, and the effect of technical variations is cancelled out. As PCr concentration is known to be stable in muscle at rest and in physiologic conditions, its content can be considered as an internal reference. Thus, we choose to use PCr-Pi and PCr-βATP ratios to describe the evolution of intracellular Pi and ATP concentrations during HD, consistently with our previous publication on this topic.11 As a result, a decrease of PCr-Pi meant an increase of Pi and vice versa.

Reported intracellular concentrations of Pi and ATP are considered to reflect only the intracellular cytosolic part of these two metabolites because metabolites signal coming from circulating red blood cells is cancelled out of the acquisition volume of interest.

The intracellular pH (pHi) was calculated using the Henderson–Hasselbach formula: pH=6.75+log(δ−3.27)/(5.69−δ), δ being the difference (in parts per million) between the chemical shifts of Pi and PCr peaks.15 During the HD sessions, acquisitions were stopped hourly for 5 minutes to allow BP and heart rate measurements.

Calcium Balance Measurement

Calcium balance was calculated using the formula (Cae−Cab)(Ve−UF)+(Cae×UF), where Cae is the calcium in the effluent, Cab is the calcium in the dialysis solution, Ve is the volume of effluent, and UF is the ultrafiltration.

Statistical Analyses

Statistical analyses was performed using GraphPad Prism version 8.0.0 for Mac OS X (GraphPad Software, San Diego, CA) and R (R for Windows, version 3.4.4 [R-Cran project, http://cran.r-project.org/]). Continuous variables were presented as mean ± SD. Categorical variables were expressed as percentages. Metabolic ratios of PCr-Pi and PCr-βATP were averaged by 20-minute intervals for better readability. Comparisons of continuous variables between the beginning Time 0 (T0 minutes) and the end of dialysis (T240 minutes) were assessed with a nonparametric paired test (Wilcoxon test). Correlations were assessed by calculating Spearman correlation coefficient.

A linear mixed effects regression model was applied separately to each metabolic ratio (PCr-Pi and PCr-βATP) to quantify the rate of concentration change during the dialysis. A deviance analysis was applied to this model to test the significance of the fixed effects (type 2 Wald F tests with Kenward–Roger estimation for the degrees of freedom). This analysis was conducted using the “lme4” and “lmertest” packages in R software. P values of 0.05 were considered statistically significant.

Results

Characteristics of Patients and HD Parameters

Characteristics of the 11 patients are described in Table 1. The mean (± SD) age was 54.5 (±16.0) years, 91% of participants were men, and mean (± SD) dry weight was 70.8 (±10.8) kg. The mean (± SD) dialysis vintage was equal to 3.4 (±2.1) years, the mean (± SD) ultrafiltration volume was 1.8±0.7 L, and the mean (± SD) Kt/V was 1.31 (±0.2) (Table 1). As shown in Figure 2, the mean (± SD) systolic BP at T0 minutes (139±14 mm Hg) was not significantly different from that at T240 minutes (130±13 mm Hg, P=0.28).

View this table:
Table 1.

Patient characteristics at screening visit

Figure 2.
Figure 2.

No hemodynamic instability occurred during HD session. Systolic and diastolic BPs (millimeters of mercury) measured every hour until T240 minutes.

Before dialysis (T0 minutes), the mean (± SD) calcium level was 2.20 (±0.16) mmol/L, and the mean (± SD) phosphate level was 1.65 (±0.34) mmol/L (Table 2). Urea concentration decreased significantly (P<0.001) by 75% between T0 minutes (19.9±7.8 mmol/L) and T240 minutes (4.9±1.9 mmol/L), as reported in Figure 3.

View this table:
Table 2.

Blood measurements before and after dialysis

Figure 3.
Figure 3.

Decrease of urea during HD session. Urea (millimoles per liter) measured every 15 minutes the first hour and then every hour until T240 minutes.

Phosphate Kinetics and Intracellular PCr-Pi Ratio

We were able to measure phosphate in the effluent in only five patients. The mean (± SD) cumulative amount of Pi removed at the end of dialysis was 38.5 (±4.7) mmol (Figure 4A). The plasmatic Pi concentration (1.65±0.35 mmol/L at T0 minutes) decreased significantly compared with its concentration at T60 minutes (0.97±0.38 mmol/L; −41%, P<0.001), which continues to decrease slowly to reach a plateau at T240 minutes (0.71±0.16 mmol/L). Between T0 and T240 minutes, we observed a significant (P=0.002) decrease of Pi content (−57%), as shown in Figure 4B. The PCr-Pi ratio increased significantly (+23%, P=0.001) from T0 to T240 minutes, meaning that intracellular Pi decreased during the HD session (Figure 4C).

Figure 4.
Figure 4.

Decrease of intracellular Pi regarding decrease of extracellular Pi during a HD session. (A) Cumulative concentration of mean phosphate removal (in millimoles) during the HD session. (B) Phosphatemia level changes over the time. (C) PCr-Pi ratio changes over HD session. Dashed lines note the first hours of treatment when Pi starts to decrease.

Kinetics of PCr-βATP

The PCr-βATP ratio increased significantly (+31%, P=0.001) from T0 to T240 minutes, meaning that βATP decreased during the HD session (Figure 5A). The change in PCr-βATP ratio is significantly correlated to the amount of depurated Pi (P=0.002) (Figure 5B) and negatively to serum phosphate content (P=0.01) (Figure 5C).

Figure 5.
Figure 5.

Decrease of ATP during a HD session. (A) PCr-βATP over the time. The rate of PCR-Pi changes during the HD session increased significantly using a mixed effects regression model (+31%, P=0.001). (B) Correlation between changes of the PCr-βATP ratios and the depurated phosphate content using the Spearman test (P=0.002). (C) Correlation between the PCr-βATP ratios and the phosphatemia-depurated Pi using the Spearman test (P=0.01).

Calcium Balance and Factors Important in Bone and Mineral Metabolism

The mean (± SD) calcium concentration increased significantly from 2.2 (±0.2) at T0 minutes to 2.4 (±0.2) mmol/L at T240 minutes (+9%, P=0.01). The mean (± SD) PTH concentration significantly decreased from 164 (±161) at T0 minutes to 94 (±98) ng/L at T240 minutes (P=0.002). There was no significant difference in 25-OH vitamin D concentration between T0 minutes (80±49 nmol/L) and T240 minutes (77±46 nmol/L, P=0.15) (Table 2). Mass balance of calcium was calculated at +17.1 mmol.

Bicarbonate Concentrations, Blood pH, and pHi Kinetics during HD

The mean (± SD) bicarbonate concentration increased significantly from 21 (±3) at T0 minutes to 26 (±2) mmol/L at T240 minutes (+24%, P<0.001) (Figure 6A, Table 2). Blood pH increased significantly from 7.37 (±0.02) at T0 minutes to 7.48 (±0.03) at T240 minutes (P<0.001) (Figure 6B), and there was no significant difference in pHi between T0 minutes (6.90±0.05) and T240 minutes (6.94±0.02, P=0.80) (Figure 6C).

Figure 6.
Figure 6.

Normalization of the acid base status during HD session. Measurements (mean ± SD) during the HD session of (A) bicarbonates concentration, (B) blood pH, and (C) intracellular pH.

Discussion

We have conducted the first clinical study to report a significant reduction of intracellular Pi during HD, with an associated reduction in intracellular high-energy phosphates. Furthermore, we have demonstrated that MR spectroscopy is feasible to use as a metabolic probe in humans during HD itself and is worth further consideration as a research tool.

Our results confirmed previous mathematical assumptions supposing that Pi content belongs to the intracellular compartment for the most part. We report a biphasic kinetic of intracellular Pi concentration, whereby after a threshold (calculated herein to be 0.97 mmol/L), intracellular Pi content started to decrease. Interestingly, Daugirdas8 described the same phosphate threshold in a previous modified two-pool phosphate kinetic model, showing that intercompartmental phosphate clearance significantly increased after serum Pi concentration fell below 0.97 mmol/L. Previous modeling also hypothesized that Pi could be provided by the bone compartment.5,16 To assess this question, we calculated the calcium balance that remained positive during the HD session as previously reported.17,18 This positive calcium balance and concomitant decrease in PTH might not be in favor of massive phosphate release by the bone compartment, as these two factors are known to limit bone remodeling.

Results of this study differ from those obtained from our previous swine study showing an increase in intracellular Pi content during HD. First, this discrepancy could be explained by the experimental model used. Our swine model was an AKI model with acute ionic perturbation without the adaptive/maladaptive changes that accompany CKD. Pi pathophysiology in AKI has different pathophysiology and probably does not reflect existing mathematical models on the basis of data from patients on maintenance HD. Second, pigs had relative hypophosphatemia compared with their baseline serum phosphate, suggesting that animals had an acute negative phosphate balance. Hence, it could be hypothesized that this increase of intracellular Pi could result from an intracellular compensation mechanism. Lastly, the animals, when subjected to this very severe model of AKI (bilateral nephrectomy), exhibited particularly severe metabolic acidosis, leading to a low intracellular pH. The increase of Pi might be due to this acidosis, suggesting that free Pi was mobilized from polyphosphate or another Pi bond to proteins to buffer intracellular compartment.

Pi depletion can result in multiple organ system dysfunction, such as respiratory19 or cardiac20 failure. Muscle fatigue has been shown to be related to the decrease in pHi and to Pi depletion.21 We did not report change in pHi suggesting that intracellular Pi depletion could lead to muscle weakness. The 23% decrease of Pi in our study corresponds to what has been described in patients with acute respiratory failure in chronic obstuctive pulmonary disease, emphasizing the potential harmful effect of intracellular Pi drop resulting from precipitous Pi depletion.13 Compared with a severe model of hypophosphatemia, patients with X-linked hypophosphatemia exhibit a 55% intracellular Pi decrease compared with controls at baseline, and these patients also experienced muscle weakness and fatigue.22

These results questioned, therefore, the benefit of increasing phosphate removal during HD (at least within standard relatively short time delivery of 4 hours) as it seems such practices could alter cell metabolism. It is known that daily HD sessions23 or longer nocturnal session lengths improve phosphate control. It is possible that daily short HD treatment would be more favorable for cell metabolism because the Pi depletion would be lower. Equilibrium between pools has been demonstrated to be very fast during exercise and probably exhibits the same kinetics in patients on HD. In a nocturnal long HD session, reduction in serum Pi is so marked that it is often necessary to introduce phosphorus into the dialysate to compensate and prevent clinically significant hypophosphatemia.24 Further studies are needed to directly investigate the difference in Pi and ATP depletion between daily, classic, and long HD sessions.

Because intracellular Pi is an essential substrate for the formation of high-energy phosphate compounds and modulation of several key enzymes,25 we hypothesized that the immediate implication of intracellular Pi drop would be reduced ATP synthesis. Pesta and coworkers26 confirmed that muscle Pi depletion correlated with decreased ATP synthetic flux and thus, could lead to organ injury/dysfunction. The 15% reduction of ATP measured in our study is comparable with the ATP reduction reported after intense exercise reaching muscle exhaustion in patients on HD.27 This decrease is also equivalent to those described in hypertrophy cardiomyopathy28 and in dilated cardiomyopathy,29 where PCr-ATP has been shown to be correlated with severity of heart failure. The magnitude of ATP reduction observed herein may, therefore, be implicated in both objective hemodynamic and subjective symptomatic intolerance of HD, commonly encountered in clinical practice.

Change in PCr-βATP ratio seemed to begin early, during the initial hour of dialysis, when serum P was >1.0 mmol/L. Even though the change in ATP correlated with phosphorus removal, we could also speculate that decrease of ATP could be explained by other mechanisms. Indeed, although patients with X-linked hypophosphatemia exhibit a decreased Pi-PCr ratio compared with the control group, Clarke and coworkers30 did not report any difference in PCr-ATP compared with controls, suggesting that Pi depletion is not always associated with ATP depletion at rest. It is also likely that decrease of ATP could be the consequence of several mechanisms including: 1) dialysis induced circulatory stress inducing muscle vascular beds damage31 or 2) collapse of muscle mitochondrial membrane potential, as previously described in lymphocytes of patients on HD, although this observation remains contentious.32

However, muscle is supposed to tolerate a reduction in resting cell Pi concentration of around 30%–40% without exhibiting bioenergetics. Mean intracellular Pi decrease was 22% in our study, suggesting that the depletion of ATP is not only a simple consequence of reduced intracellular Pi. Moreover, patients with X-linked hypophosphatemia exhibiting a decreased Pi-PCr ratio compared with the control group did not show any difference in PCr-ATP compared with controls. However, because previous report showed that HD leads to the collapse of mitochondrial membrane potential of lymphocytes, we could hypothesize that decrease of ATP concentration could be a consequences of this collapse of mitochondrial potential membrane. Finally, it is also well described that HD stress leads to ischemic episodes induced by dialysis itself. Although data are currently lacking, it is clearly possible that other vascular beds might also be damaged during conventional HD. Possible candidates include muscle with recurrent ischemic injury (including, perhaps, wasting as a cumulative effect) as well as the kidney itself.

This study has several limitations. First of all, we hypothesized that Pi and/or βATP depletions could be associated with fatigue and muscle weakness but did not include direct assessment of objective weakness or associated patient symptomatology. This study was constructed to explore kinetics of Pi and βATP and was not constructed to study consequences of these changes. It would certainly have been of interest to have included assessments, such as grip strength and sit-to-stand testing, as objective markers or time to recovery as a subjective marker. However, the experimental design and associated recruitment issues were already challenging, and this militated against increasing protocol complexity/burden further. We were not able to correlate βATP decrease and hemodynamic stress, but we can also suppose that patients with intradialytic hypotension could have a greater βATP decrease, and these patients were systematically excluded on the basis of patient safety in the setting of remote dialysis and limited monitoring possible within the MR scanner. These tests could be of interest to further explore in dedicated studies. We used as an inclusion criterion a serum Pi concentration between 1.5 and 3.0 mmol/L. This criterion was chosen to increase total quantity of depurated phosphate, aiming to increase phosphate transfers between compartments during HD sessions and our ability to measure them. However, it would also be interesting to test patients with lower or higher range of Pi to increase the generalizability of our findings. We did not quite attain the number of subjects defined a priori by power calculation, but a significant difference was found for the primary outcome. However, we have probably chosen a high threshold regarding the clinically significant margin by using observed Pi depletion in acute respiratory failure (a severe condition). Finally, providing that 31P-MRS measures intracellular Pi, we were not able to differentiate the Pi coming from the mitochondria, whereas it would be interesting to know as suggested previously by Spalding et al.5

Nevertheless, this study has strengths. We were able to safely measure intracellular βATP and Pi concentrations during HD for this technically challenging study in order to provide a better understanding of phosphate transfers between compartments during HD. Furthermore, no hemodynamic instability occurred, even after the lengthening of extracorporeal circuit lines (increasing extracorporeal blood volume to around 150 ml).

In conclusion, we confirmed by a direct in vivo measurement that depurated Pi comes from the intracellular compartment. These results question the benefit of increasing phosphate removal during HD as it could alter cell metabolism. Further studies are needed to investigate the relationship between HD symptoms and decreases of intracellular Pi and βATP contents. 31P-MRS may be an effective tool to monitor phosphate removal but also, to monitor energy consumption in patients on HD to optimize dialysis prescription.

Disclosures

L. Juillard reports consultancy agreements with Amgen, Hemotech, Baxter, Vifor, Otsuka, Astellas, Fresenius, Novartis, Leo, and Sanofi; research funding from Amgen, Baxter, and Sanofi; honoraria from Amgen, Hemotech, Baxter, Vifor, Otsuka, Astellas, Fresenius, Novartis, Leo, and Sanofi; scientific advisor to or membership with Amgen, Hemotech, Baxter, Vifor, Astellas, Fresenius, Novartis, and Leo. S. Lemoine reports honoraria from Chiesei and Anylam. All remaining authors have nothing to disclose.

Funding

This work was supported by Hospices Civils de Lyon.

Acknowledgments

The authors thank Emmanuelle Nunes, RN, Sébastien Abadie, RN, and Lilian Gonthier, RNfor their help as dialysis nurses; Hélène Hamelin, Maryline Vivian, and Christophe Peyroche for their contributions as MRI technologists; Dr. Annie Varennes, Dr. Marie Christine Carlier, and Dr. Laurence Chardon for their contributions in the realization of biologic assays; Vincent Guers and Thierry Imbert for technical help; the Hemodia Company for specifically having designed longer dialysis lines used in this study out of charge; and Philip Robinson for help in manuscript preparation.

Footnotes

  • G.C. and S.L. are co-first authors.

  • Published online ahead of print. Publication date available at www.jasn.org.

References

  1. ↵
    1. Block GA,
    2. Hulbert-Shearon TE,
    3. Levin NW,
    4. Port FK
    : Association of serum phosphorus and calcium x phosphate product with mortality risk in chronic hemodialysis patients: A national study. Am J Kidney Dis 31: 607–617, 1998 pmid:9531176
    OpenUrlCrossRefPubMed
  2. ↵
    1. Tentori F,
    2. Blayney MJ,
    3. Albert JM,
    4. Gillespie BW,
    5. Kerr PG,
    6. Bommer J, et al
    .: Mortality risk for dialysis patients with different levels of serum calcium, phosphorus, and PTH: The Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis 52: 519–530, 2008 pmid:18514987
    OpenUrlCrossRefPubMed
  3. ↵
    1. Young EW,
    2. Albert JM,
    3. Satayathum S,
    4. Goodkin DA,
    5. Pisoni RL,
    6. Akiba T, et al
    .: Predictors and consequences of altered mineral metabolism: The dialysis outcomes and practice patterns study. Kidney Int 67: 1179–1187, 2005 pmid:15698460
    OpenUrlCrossRefPubMed
  4. ↵
    1. Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD update work group
    : KDIGO 2017 clinical practice guideline update for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). Kidney Int Suppl 7: 1–59, 2017
    OpenUrl
  5. ↵
    1. Spalding EM,
    2. Chamney PW,
    3. Farrington K
    : Phosphate kinetics during hemodialysis: Evidence for biphasic regulation. Kidney Int 61: 655–667, 2002 pmid:11849409
    OpenUrlCrossRefPubMed
  6. ↵
    1. Leypoldt JK,
    2. Agar BU,
    3. Akonur A,
    4. Hutchcraft AM,
    5. Story KO,
    6. Culleton BF
    : Determinants of phosphorus mobilization during hemodialysis. Kidney Int 84: 841–848, 2013 pmid:23715125
    OpenUrlCrossRefPubMed
  7. ↵
    1. Daugirdas JT
    : Removal of phosphorus by hemodialysis. Semin Dial 28: 620–623, 2015 pmid:26358370
    OpenUrlPubMed
  8. ↵
    1. Daugirdas JT
    : A two-pool kinetic model predicts phosphate concentrations during and shortly following a conventional (three times weekly) hemodialysis session. Nephrol Dial Transplant 33: 76–84, 2018
    OpenUrl
  9. ↵
    1. Brautbar N,
    2. Carpenter C,
    3. Baczynski R,
    4. Kohan R,
    5. Massry SG
    : Impaired energy metabolism in skeletal muscle during phosphate depletion. Kidney Int 24: 53–57, 1983 pmid:6620852
    OpenUrlPubMed
  10. ↵
    1. Amanzadeh J,
    2. Reilly RF Jr.
    : Hypophosphatemia: An evidence-based approach to its clinical consequences and management. Nat Clin Pract Nephrol 2: 136–148, 2006 pmid:16932412
    OpenUrlPubMed
  11. ↵
    1. Lemoine S,
    2. Fournier T,
    3. Kocevar G,
    4. Belloi A,
    5. Normand G,
    6. Ibarrola D, et al
    .: Intracellular phosphate dynamics in muscle measured by magnetic resonance spectroscopy during hemodialysis. J Am Soc Nephrol 27: 2062–2068, 2016 pmid:26561642
    OpenUrlAbstract/FREE Full Text
  12. ↵
    1. Dawson MJ
    : Quantitative analysis of metabolite levels in normal human subjects by 31P topical magnetic resonance. Biosci Rep 2: 727–733, 1982 pmid:7139081
    OpenUrlAbstract/FREE Full Text
  13. ↵
    1. Fiaccadori E,
    2. Coffrini E,
    3. Fracchia C,
    4. Rampulla C,
    5. Montagna T,
    6. Borghetti A
    : Hypophosphatemia and phosphorus depletion in respiratory and peripheral muscles of patients with respiratory failure due to COPD. Chest 105: 1392–1398, 1994 pmid:8181325
    OpenUrlCrossRefPubMed
  14. ↵
    1. Meyerspeer M,
    2. Boesch C,
    3. Cameron D,
    4. Dezortová M,
    5. Forbes SC,
    6. Heerschap A, et al
    .; Experts’ Working Group on 31P MR Spectroscopy of Skeletal Muscle: 31 P magnetic resonance spectroscopy in skeletal muscle: Experts’ consensus recommendations [published online ahead of print February 10, 2020]. NMR Biomed 10.1002/nbm.4246pmid:32037688
    OpenUrlPubMed
  15. ↵
    1. Arnold DL,
    2. Matthews PM,
    3. Radda GK
    : Metabolic recovery after exercise and the assessment of mitochondrial function in vivo in human skeletal muscle by means of 31P NMR. Magn Reson Med 1: 307–315, 1984 pmid:6571561
    OpenUrlCrossRefPubMed
  16. ↵
    1. Carney SL,
    2. Gillies AH
    : Acute dialysis hypercalcemia and dialysis phosphate loss. Am J Kidney Dis 11: 377–382, 1988 pmid:3369442
    OpenUrlPubMed
  17. ↵
    1. Hou SH,
    2. Zhao J,
    3. Ellman CF,
    4. Hu J,
    5. Griffin Z,
    6. Spiegel DM, et al
    .: Calcium and phosphorus fluxes during hemodialysis with low calcium dialysate. Am J Kidney Dis 18: 217–224, 1991 pmid:1867178
    OpenUrlCrossRefPubMed
  18. ↵
    1. Goldenstein PT,
    2. Graciolli FG,
    3. Antunes GL,
    4. Dominguez WV,
    5. Dos Reis LM,
    6. Moe S, et al
    .: A prospective study of the influence of the skeleton on calcium mass transfer during hemodialysis. PLoS One 13: e0198946, 2018 pmid:30059531
    OpenUrlPubMed
  19. ↵
    1. Demirjian S,
    2. Teo BW,
    3. Guzman JA,
    4. Heyka RJ,
    5. Paganini EP,
    6. Fissell WH, et al
    .: Hypophosphatemia during continuous hemodialysis is associated with prolonged respiratory failure in patients with acute kidney injury. Nephrol Dial Transplant 26: 3508–3514, 2011
    OpenUrlCrossRefPubMed
  20. ↵
    1. Ariyoshi N,
    2. Nogi M,
    3. Ando A,
    4. Watanabe H,
    5. Umekawa S
    : Hypophosphatemia-induced Cardiomyopathy. Am J Med Sci 352: 317–323, 2016 pmid:27650239
    OpenUrlPubMed
  21. ↵
    1. Sapega AA,
    2. Sokolow DP,
    3. Graham TJ,
    4. Chance B
    : Phosphorus nuclear magnetic resonance: A non-invasive technique for the study of muscle bioenergetics during exercise. Med Sci Sports Exerc 19: 410–420, 1987 pmid:3309542
    OpenUrlPubMed
  22. ↵
    1. Smith R,
    2. Newman RJ,
    3. Radda GK,
    4. Stokes M,
    5. Young A
    : Hypophosphataemic osteomalacia and myopathy: Studies with nuclear magnetic resonance spectroscopy. Clin Sci (Lond) 67: 505–509, 1984
    OpenUrlAbstract/FREE Full Text
  23. ↵
    1. Daugirdas JT,
    2. Chertow GM,
    3. Larive B,
    4. Pierratos A,
    5. Greene T,
    6. Ayus JC, et al
    .; Frequent Hemodialysis Network (FHN) Trial Group: Effects of frequent hemodialysis on measures of CKD mineral and bone disorder. J Am Soc Nephrol 23: 727–738, 2012 pmid:22362907
    OpenUrlAbstract/FREE Full Text
  24. ↵
    1. Mahadevan K,
    2. Pellicano R,
    3. Reid A,
    4. Kerr P,
    5. Polkinghorne K,
    6. Agar J
    : Comparison of biochemical, haematological and volume parameters in two treatment schedules of nocturnal home haemodialysis. Nephrology (Carlton) 11: 413–418, 2006 pmid:17014555
    OpenUrlPubMed
  25. ↵
    1. Lemasters JJ,
    2. Sowers AE
    : Phosphate dependence and atractyloside inhibition of mitochondrial oxidative phosphorylation. The ADP-ATP carrier is rate-limiting. J Biol Chem 254: 1248–1251, 1979 pmid:762127
    OpenUrlFREE Full Text
  26. ↵
    1. Pesta DH,
    2. Tsirigotis DN,
    3. Befroy DE,
    4. Caballero D,
    5. Jurczak MJ,
    6. Rahimi Y, et al
    .: Hypophosphatemia promotes lower rates of muscle ATP synthesis. FASEB J 30: 3378–3387, 2016 pmid:27338702
    OpenUrlCrossRefPubMed
  27. ↵
    1. Durozard D,
    2. Pimmel P,
    3. Baretto S,
    4. Caillette A,
    5. Labeeuw M,
    6. Baverel G, et al
    .: 31P NMR spectroscopy investigation of muscle metabolism in hemodialysis patients. Kidney Int 43: 885–892, 1993 pmid:8479125
    OpenUrlCrossRefPubMed
  28. ↵
    1. Crilley JG,
    2. Boehm EA,
    3. Blair E,
    4. Rajagopalan B,
    5. Blamire AM,
    6. Styles P, et al
    .: Hypertrophic cardiomyopathy due to sarcomeric gene mutations is characterized by impaired energy metabolism irrespective of the degree of hypertrophy. J Am Coll Cardiol 41: 1776–1782, 2003 pmid:12767664
    OpenUrlFREE Full Text
  29. ↵
    1. Neubauer S,
    2. Horn M,
    3. Pabst T,
    4. Gödde M,
    5. Lübke D,
    6. Jilling B, et al
    .: Contributions of 31P-magnetic resonance spectroscopy to the understanding of dilated heart muscle disease. Eur Heart J 16[Suppl O]: 115–118, 1995 pmid:8682076
    OpenUrlCrossRefPubMed
  30. ↵
    1. Clarke GD,
    2. Kainer G,
    3. Conway WF,
    4. Chan JC
    : Intramyocellular phosphate metabolism in X-linked hypophosphatemic rickets. J Pediatr 116: 288–292, 1990 pmid:2299505
    OpenUrlCrossRefPubMed
  31. ↵
    1. McIntyre CW
    : Recurrent circulatory stress: The dark side of dialysis. Semin Dial 23: 449–451, 2010 pmid:21039872
    OpenUrlCrossRefPubMed
  32. ↵
    1. Raj DSC,
    2. Boivin MA,
    3. Dominic EA,
    4. Boyd A,
    5. Roy PK,
    6. Rihani T, et al
    .: Haemodialysis induces mitochondrial dysfunction and apoptosis. Eur J Clin Invest 37: 971–977, 2007 pmid:18036031
    OpenUrlCrossRefPubMed
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Intracellular Phosphate and ATP Depletion Measured by Magnetic Resonance Spectroscopy in Patients Receiving Maintenance Hemodialysis
Guillaume Chazot, Sandrine Lemoine, Gabriel Kocevar, Emilie Kalbacher, Dominique Sappey-Marinier, Olivier Rouvière, Laurent Juillard
JASN Jan 2021, 32 (1) 229-237; DOI: 10.1681/ASN.2020050716
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