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Murea M, Sirich TL. The Hemodialysis Prescription: Past, Present, and Future. Kidney360 2023; 4:990-993. [PMID: 37257086 PMCID: PMC10371267 DOI: 10.34067/kid.0000000000000164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 05/04/2023] [Indexed: 06/02/2023]
Affiliation(s)
- Mariana Murea
- Section on Nephrology, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Tammy L. Sirich
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
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2
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Meyer TW, Lee S, Whitmer LC, Blanco IJ, Suba JK, Sirich TL. Increasing the Clearance of Protein-Bound Solutes by Recirculating Dialysate through Activated Carbon. Kidney360 2023; 4:e744-e750. [PMID: 37211642 PMCID: PMC10371360 DOI: 10.34067/kid.0000000000000155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 04/05/2023] [Indexed: 05/23/2023]
Abstract
Key Points Conventional hemodialysis provides limited clearance of uremic solutes that bind to plasma proteins. No studies have yet tested whether increasing the clearance of bound solutes provides clinical benefit. Practical means to increase the dialytic clearance of bound solutes are required to perform such studies. Background Conventional hemodialysis provides limited clearance of uremic solutes that bind to plasma proteins. However, no studies have tested whether increasing the clearance of bound solutes provides clinical benefit. Practical means to increase the dialytic clearance of bound solutes are required to perform such studies. Methods Artificial plasma was dialyzed using two dialysis systems in series. In the first recirculating system, a fixed small volume of dialysate flowed rapidly through an activated carbon block before passing through two large dialyzers. In a second conventional system, a lower flow of fresh dialysate was passed through a single dialyzer. Chemical measurements tested the ability of the recirculating system to increase the clearance of selected solutes. Mathematical modeling predicted the dependence of solute clearances on the extent to which solutes were taken up by the carbon block and were bound to plasma proteins. Results By itself, the conventional system provided clearances of the tightly bound solutes p-cresol sulfate and indoxyl sulfate of only 18±10 and 19±11 ml/min, respectively (mean±SD). Because these solutes were effectively adsorbed by the carbon block, the recirculating system by itself provided p-cresol sulfate and indoxyl sulfate clearances of 45±11 and 53±16 ml/min. It further raised their clearances to 54±12 and 61±17 ml/min when operating in series with the conventional system (P < 0.002 versus conventional clearance both solutes). Modeling predicted that the recirculating system would increase the clearances of bound solute even if their uptake by the carbon block was incomplete. Conclusions When added to a conventional dialysis system, a recirculating system using a carbon block sorbent, a single pump, and standard dialyzers can greatly increase the clearance of protein-bound uremic solutes.
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Affiliation(s)
- Timothy W. Meyer
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Seolhyun Lee
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Luke C. Whitmer
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Ignacio J. Blanco
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Josef K. Suba
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Tammy L. Sirich
- The Department of Medicine, Stanford University, Palo Alto, California
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
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Sirich TL, Hostetter TH, Flythe JE. Effect of Furosemide on Proximal Tubular Secretion of Organic Solutes in Patients Receiving Hemodialysis. Clin J Am Soc Nephrol 2022; 17:1800-1801. [PMID: 36195434 PMCID: PMC9718024 DOI: 10.2215/cjn.08310722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Tammy L. Sirich
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
- Department of Medicine, Stanford University, Palo Alto, California
| | - Thomas H. Hostetter
- University of North Carolina Kidney Center, Division of Nephrology and Hypertension, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Jennifer E. Flythe
- University of North Carolina Kidney Center, Division of Nephrology and Hypertension, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina
- Cecil G. Sheps Center for Health Services Research, University of North Carolina, Chapel Hill, North Carolina
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Lee S, Sirich TL, Blanco IJ, Plummer NS, Meyer TW. Removal of Uremic Solutes from Dialysate by Activated Carbon. Clin J Am Soc Nephrol 2022; 17:1168-1175. [PMID: 35835518 PMCID: PMC9435996 DOI: 10.2215/cjn.01610222] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/30/2022] [Indexed: 01/05/2023]
Abstract
BACKGROUND AND OBJECTIVES Adsorption of uremic solutes to activated carbon provides a potential means to limit dialysate volumes required for new dialysis systems. The ability of activated carbon to take up uremic solutes has, however, not been adequately assessed. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Graded volumes of waste dialysate collected from clinical hemodialysis treatments were passed through activated carbon blocks. Metabolomic analysis assessed the adsorption by activated carbon of a wide range of uremic solutes. Additional experiments tested the ability of the activated carbon to increase the clearance of selected solutes at low dialysate flow rates. RESULTS Activated carbon initially adsorbed the majority, but not all, of 264 uremic solutes examined. Solute adsorption fell, however, as increasing volumes of dialysate were processed. Moreover, activated carbon added some uremic solutes to the dialysate, including methylguanidine. Activated carbon was particularly effective in adsorbing uremic solutes that bind to plasma proteins. In vitro dialysis experiments showed that introduction of activated carbon into the dialysate stream increased the clearance of the protein-bound solutes indoxyl sulfate and p-cresol sulfate by 77%±12% (mean±SD) and 73%±12%, respectively, at a dialysate flow rate of 200 ml/min, but had a much lesser effect on the clearance of the unbound solute phenylacetylglutamine. CONCLUSIONS Activated carbon adsorbs many but not all uremic solutes. Introduction of activated carbon into the dialysate stream increased the clearance of those solutes that it does adsorb.
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Affiliation(s)
- Seolhyun Lee
- The Department of Medicine, Stanford University, Palo Alto, California .,The Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Tammy L. Sirich
- The Department of Medicine, Stanford University, Palo Alto, California,The Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Ignacio J. Blanco
- The Department of Medicine, Stanford University, Palo Alto, California
| | - Natalie S. Plummer
- The Department of Medicine, Stanford University, Palo Alto, California,The Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Timothy W. Meyer
- The Department of Medicine, Stanford University, Palo Alto, California,The Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
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Abstract
The adequacy of hemodialysis is now assessed by measuring the removal of the single-solute urea. The urea clearance provided by contemporary dialysis is a large fraction of the blood flow through the dialyzer and therefore cannot be increased much further. Other solutes however likely contribute more than urea to the residual uremic illness suffered by hemodialysis patients. We here review methods which could be employed to increase the clearance of nonurea solutes. We will separately consider the clearances of free low-molecular-mass solutes, free larger solutes, and protein-bound solutes. New clinical studies will be required to test the extent to which increasing the clearance on nonurea solutes with these various characteristics can improve patients' health.
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Affiliation(s)
- Seolhyun Lee
- The Department of Medicine, Stanford University, Palo Alto, California, USA
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California, USA
| | - Tammy L. Sirich
- The Department of Medicine, Stanford University, Palo Alto, California, USA
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California, USA
| | - Timothy W. Meyer
- The Department of Medicine, Stanford University, Palo Alto, California, USA
- The Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California, USA
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Mair RD, Lee S, Plummer NS, Sirich TL, Meyer TW. Impaired Tubular Secretion of Organic Solutes in Advanced Chronic Kidney Disease. J Am Soc Nephrol 2021; 32:2877-2884. [PMID: 34408065 PMCID: PMC8806100 DOI: 10.1681/asn.2021030336] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/29/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The clearance of solutes removed by tubular secretion may be altered out of proportion to the GFR in CKD. Recent studies have described considerable variability in the secretory clearance of waste solutes relative to the GFR in patients with CKD. METHODS To test the hypothesis that secretory clearance relative to GFR is reduced in patients approaching dialysis, we used metabolomic analysis to identify solutes in simultaneous urine and plasma samples from 16 patients with CKD and an eGFR of 7±2 ml/min per 1.73 m2 and 16 control participants. Fractional clearances were calculated as the ratios of urine to plasma levels of each solute relative to those of creatinine and urea in patients with CKD and to those of creatinine in controls. RESULTS Metabolomic analysis identified 39 secreted solutes with fractional clearance >3.0 in control participants. Fractional clearance values in patients with CKD were reduced on average to 65%±27% of those in controls. These values were significantly lower for 18 of 39 individual solutes and significantly higher for only one. Assays of the secreted anions phenylacetyl glutamine, p-cresol sulfate, indoxyl sulfate, and hippurate confirmed variable impairment of secretory clearances in advanced CKD. Fractional clearances were markedly reduced for phenylacetylglutamine (4.2±0.6 for controls versus 2.3±0.6 for patients with CKD; P<0.001), p-cresol sulfate (8.6±2.6 for controls versus 4.1±1.5 for patients with CKD; P<0.001), and indoxyl sulfate (23.0±7.3 versus 7.5±2.8; P<0.001) but not for hippurate (10.2±3.8 versus 8.4±2.6; P=0.13). CONCLUSIONS Secretory clearances for many solutes are reduced more than the GFR in advanced CKD. Impaired secretion of these solutes might contribute to uremic symptoms as patients approach dialysis.
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Affiliation(s)
- Robert D. Mair
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Seolhyun Lee
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Natalie S. Plummer
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Tammy L. Sirich
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Timothy W. Meyer
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
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Ganesan LL, O’Brien FJ, Sirich TL, Plummer NS, Sheth R, Fajardo C, Brakeman P, Sutherland SM, Meyer TW. Association of Plasma Uremic Solute Levels with Residual Kidney Function in Children on Peritoneal Dialysis. Clin J Am Soc Nephrol 2021; 16:1531-1538. [PMID: 34233922 PMCID: PMC8499013 DOI: 10.2215/cjn.01430121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 07/01/2021] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND OBJECTIVES Residual native kidney function confers health benefits in patients on dialysis. It can facilitate control of extracellular volume and inorganic ion concentrations. Residual kidney function can also limit the accumulation of uremic solutes. This study assessed whether lower plasma concentrations of uremic solutes were associated with residual kidney function in pediatric patients on peritoneal dialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Samples were analyzed from 29 pediatric patients on peritoneal dialysis, including 13 without residual kidney function and ten with residual kidney function. Metabolomic analysis by untargeted mass spectrometry compared plasma solute levels in patients with and without residual kidney function. Dialytic and residual clearances of selected solutes were also measured by assays using chemical standards. RESULTS Metabolomic analysis showed that plasma levels of 256 uremic solutes in patients with residual kidney function averaged 64% (interquartile range, 51%-81%) of the values in patients without residual kidney function who had similar total Kt/Vurea. The plasma levels were significantly lower for 59 of the 256 solutes in the patients with residual kidney function and significantly higher for none. Assays using chemical standards showed that residual kidney function provides a higher portion of the total clearance for nonurea solutes than it does for urea. CONCLUSIONS Concentrations of many uremic solutes are lower in patients on peritoneal dialysis with residual kidney function than in those without residual kidney function receiving similar treatment as assessed by Kt/Vurea.
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Affiliation(s)
- Lakshmi L. Ganesan
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, California,Department of Pediatrics, Stanford University School of Medicine, Palo Alto, California
| | - Frank J. O’Brien
- Department of Medicine, Washington University, St. Louis, Missouri
| | - Tammy L. Sirich
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California,Department of Medicine, Stanford University, Palo Alto, California
| | - Natalie S. Plummer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California,Department of Medicine, Stanford University, Palo Alto, California
| | - Rita Sheth
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, California
| | - Cecile Fajardo
- Department of Pediatrics, Children's Hospital Los Angeles, Los Angeles, California,Department of Pediatrics, University of Southern California, Los Angeles, California
| | - Paul Brakeman
- Department of Pediatrics, University of California, San Francisco, California
| | - Scott M. Sutherland
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, California
| | - Timothy W. Meyer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California,Department of Medicine, Stanford University, Palo Alto, California
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Meyer TW, Blanco IJ, Grimm JC, Leypoldt JK, Sirich TL. Barriers to Reducing Hemodialysis Time and Frequency in Patients with Residual Kidney Function. J Am Soc Nephrol 2021; 32:2112-2116. [PMID: 34465606 PMCID: PMC8729852 DOI: 10.1681/asn.2021030361] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Timothy W. Meyer
- Department of Medicine, Stanford University, Stanford, California,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - Ignacio J. Blanco
- Department of Medicine, Stanford University, Stanford, California,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - John C. Grimm
- Department of Medicine, Stanford University, Stanford, California,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - John K. Leypoldt
- Nalecz Institute of Biocybernetics and Biomedical Engineering PAS, Warsaw, Poland
| | - Tammy L. Sirich
- Department of Medicine, Stanford University, Stanford, California,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
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Abstract
The adequacy of hemodialysis is now assessed by measuring the removal of a single solute, urea. The urea clearance provided by current dialysis methods is a large fraction of the blood flow through the dialyzer, and, therefore, cannot be increased much further. However, other solutes, which are less effectively cleared than urea, may contribute more to the residual uremic illness suffered by patients on hemodialysis. Here, we review a variety of methods that could be used to increase the clearance of such nonurea solutes. New clinical studies will be required to test the extent to which increasing solute clearances improves patients' health.
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Affiliation(s)
- Seolhyun Lee
- Department of Medicine, Stanford University, Palo Alto, California,Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Tammy L. Sirich
- Department of Medicine, Stanford University, Palo Alto, California,Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
| | - Timothy W. Meyer
- Department of Medicine, Stanford University, Palo Alto, California,Department of Medicine, Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
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10
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Toth-Manikowski SM, Sirich TL, Meyer TW, Hostetter TH, Hwang S, Plummer NS, Hai X, Coresh J, Powe NR, Shafi T. Contribution of 'clinically negligible' residual kidney function to clearance of uremic solutes. Nephrol Dial Transplant 2020; 35:846-853. [PMID: 30879076 DOI: 10.1093/ndt/gfz042] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 02/03/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Residual kidney function (RKF) is thought to exert beneficial effects through clearance of uremic toxins. However, the level of native kidney function where clearance becomes negligible is not known. METHODS We aimed to assess whether levels of nonurea solutes differed among patients with 'clinically negligible' RKF compared with those with no RKF. The hemodialysis study excluded patients with urinary urea clearance >1.5 mL/min, below which RKF was considered to be 'clinically negligible'. We measured eight nonurea solutes from 1280 patients participating in this study and calculated the relative difference in solute levels among patients with and without RKF based on measured urinary urea clearance. RESULTS The mean age of the participants was 57 years and 57% were female. At baseline, 34% of the included participants had clinically negligible RKF (mean 0.7 ± 0.4 mL/min) and 66% had no RKF. Seven of the eight nonurea solute levels measured were significantly lower in patients with RKF than in those without RKF, ranging from -24% [95% confidence interval (CI) -31 to -16] for hippurate, -7% (-14 to -1) for trimethylamine-N-oxide and -4% (-6 to -1) for asymmetric dimethylarginine. The effect of RKF on plasma levels was comparable or more pronounced than that achieved with a 31% higher dialysis dose (spKt/Vurea 1.7 versus 1.3). Preserved RKF at 1-year follow-up was associated with a lower risk of cardiac death and first cardiovascular event. CONCLUSIONS Even at very low levels, RKF is not 'negligible', as it continues to provide nonurea solute clearance. Management of patients with RKF should consider these differences.
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Affiliation(s)
| | - Tammy L Sirich
- Department of Medicine, Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Timothy W Meyer
- Department of Medicine, Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Thomas H Hostetter
- Department of Medicine, Palo Alto Veterans Affairs Health Care System, Stanford University, Palo Alto, CA, USA
| | - Seungyoung Hwang
- Department of Medicine, Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Natalie S Plummer
- Department of Medicine, Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Xin Hai
- Department of Medicine, Palo Alto Veterans Affairs Health Care System, Stanford University, Palo Alto, CA, USA
| | - Josef Coresh
- Department of Medicine, Case Western Reserve University, Cleveland, OH, USA.,Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, MD, USA
| | - Neil R Powe
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Tariq Shafi
- Department of Medicine, Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA.,Department of Medicine, Case Western Reserve University, Cleveland, OH, USA.,Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, MD, USA.,Department of Medicine, Priscilla Chan and Mark Zuckerberg San Francisco General Hospital, University of California, San Francisco, San Francisco, CA, USA
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O’Brien FJ, Mair RD, Plummer NS, Meyer TW, Sutherland SM, Sirich TL. Impaired Tubular Secretion of Organic Solutes in Acute Kidney Injury. Kidney360 2020; 1:724-730. [PMID: 35252876 PMCID: PMC8815732 DOI: 10.34067/kid.0001632020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 06/24/2020] [Indexed: 06/14/2023]
Abstract
BACKGROUND Impairment of kidney function is routinely assessed by measuring the accumulation of creatinine, an organic solute cleared largely by glomerular filtration. We tested whether the clearance of solutes that undergo tubular secretion is reduced in proportion to the clearance of creatinine in humans with AKI. METHODS Four endogenously produced organic solutes (phenylacetylglutamine [PAG], hippurate [HIPP], indoxyl sulfate [IS], and p-cresol sulfate [PCS]) were measured in spot urine and plasma samples from ten patients with AKI and 17 controls. Fractional clearance relative to creatinine was calculated to assess tubular secretion. Fractional clearance values were calculated in terms of the free, unbound levels of HIPP, IS, and PCS that bind to plasma proteins. RESULTS Fractional clearance values for PAG, HIPP, IS, and PCS were >1.0 in patients with AKI as well as controls, indicating that these solutes were still secreted by the tubules of the injured kidneys. Fractional clearance values were, however, significantly lower in patients with AKI than controls, indicating that kidney injury reduced tubular secretion more than glomerular filtration (AKI versus control: PAG, 2.1±0.7 versus 4.6±1.4, P<0.001; HIPP, 10±5 versus 15±7, P=0.02; IS, 10±6 versus 28±7, P<0.001; PCS, 3.3±1.8 versus 10±3, P<0.001). Free plasma levels rose out of proportion to total plasma levels for each of the bound solutes in AKI, so that calculating their fractional clearance in terms of their total plasma levels failed to reveal their impaired secretion. CONCLUSIONS Tubular secretion of organic solutes can be reduced out of proportion to glomerular filtration in AKI. Impaired secretion of protein-bound solutes may be more reliably detected when clearances are expressed in terms of their free, unbound levels in the plasma.
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Affiliation(s)
- Frank J. O’Brien
- Department of Medicine, Washington University, St. Louis, Missouri
| | - Robert D. Mair
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California
| | - Natalie S. Plummer
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California
| | - Timothy W. Meyer
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California
| | - Scott M. Sutherland
- Department of Pediatrics, Lucile Packard Children’s Hospital, Stanford University, Palo Alto, California
| | - Tammy L. Sirich
- Department of Medicine, Stanford University, Palo Alto, California
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California
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12
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O'Brien FJ, Sirich TL, Taussig A, Fung E, Ganesan LL, Plummer NS, Brakeman P, Sutherland SM, Meyer TW. Plasma pseudouridine levels reflect body size in children on hemodialysis. Pediatr Nephrol 2020; 35:305-312. [PMID: 31728748 DOI: 10.1007/s00467-019-04369-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 08/16/2019] [Accepted: 09/13/2019] [Indexed: 11/30/2022]
Abstract
BACKGROUND Dialysis in children as well as adults is prescribed to achieve a target spKt/Vurea, where Vurea is the volume of distribution of urea. Waste solute production may however be more closely correlated with body surface area (BSA) than Vurea which rises in proportion with body weight. Plasma levels of waste solutes may thus be higher in smaller patients when targeting spKt/Vurea since they have higher BSA relative to body weight. This study measured levels of pseudouridine (PU), a novel marker solute whose production is closely proportional to BSA, to test whether prescription of dialysis to a target spKt/Vurea results in higher plasma levels of PU in smaller children. METHODS PU and urea nitrogen (ureaN) were measured in plasma and dialysate at the midweek hemodialysis session in 20 pediatric patients, with BSA ranging from 0.65-1.87m2. Mathematical modeling was employed to estimate solute production rates and average plasma solute levels. RESULTS The dialytic clearance (Kd) of PU was proportional to that of ureaN (average KdPU/KdUreaN 0.69 ± 0.13, r2 0.84, p < 0.001). Production of PU rose in proportion with BSA (r2 0.57, p < 0.001). The pretreatment plasma level of PU was significantly higher in smaller children (r2 0.20, p = 0.051) while the pretreatment level of ureaN did not vary with size. CONCLUSIONS Prescribing dialysis based on urea kinetics may leave uremic solutes at higher levels in small children. Measurement of a solute produced proportional to BSA may provide a better index of dialysis adequacy than measurement of urea.
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Affiliation(s)
- Frank J O'Brien
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Tammy L Sirich
- Departments of Medicine, VA Palo Alto HCS and Stanford University, 3801 Miranda Ave, Palo Alto, CA, 94304, USA
| | - Abigail Taussig
- Departments of Medicine, VA Palo Alto HCS and Stanford University, 3801 Miranda Ave, Palo Alto, CA, 94304, USA
| | - Enrica Fung
- Loma Linda University School of Medicine and VA Loma Linda HCS, Loma Linda, CA, USA
| | | | - Natalie S Plummer
- Departments of Medicine, VA Palo Alto HCS and Stanford University, 3801 Miranda Ave, Palo Alto, CA, 94304, USA
| | - Paul Brakeman
- Department of Pediatrics, University of California, San Francisco, CA, USA
| | | | - Timothy W Meyer
- Departments of Medicine, VA Palo Alto HCS and Stanford University, 3801 Miranda Ave, Palo Alto, CA, 94304, USA.
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13
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Mair RD, Nguyen H, Huang TT, Plummer NS, Sirich TL, Meyer TW. Accumulation of uremic solutes in the cerebrospinal fluid in experimental acute renal failure. Am J Physiol Renal Physiol 2019; 317:F296-F302. [PMID: 31141401 PMCID: PMC6732458 DOI: 10.1152/ajprenal.00100.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 05/02/2019] [Accepted: 05/20/2019] [Indexed: 01/30/2023] Open
Abstract
The accumulation of uremic solutes in kidney failure may impair mental function. The present study profiled the accumulation of uremic solutes in the cerebrospinal fluid (CSF) in acute renal failure. CSF and plasma ultrafiltrate were obtained from rats at 48 h after sham operation (control; n = 10) or bilateral nephrectomy (n = 10) and analyzed using an established metabolomic platform. Two hundred forty-eight solutes were identified as uremic based on their accumulation in the plasma ultrafiltrate of nephrectomized compared with control rats. CSF levels of 124 of these solutes were sufficient to allow calculation of CSF-to-plasma ultrafiltrate concentration ratios. Levels of many of the uremic solutes were normally lower in the CSF than in the plasma ultrafiltrate, indicating exclusion of these solutes from the brain. CSF levels of the great majority of the uremic solutes increased in renal failure. The increase in the CSF was, however, relatively less than in the plasma ultrafiltrate for most solutes. In particular, for the 31 uremic solutes with CSF-to-plasma ultrafiltrate ratios of <0.25 in control rats, the average CSF-to-plasma ultrafiltrate ratio decreased from 0.13 ± 0.07 in control rats to 0.09 ± 0.06 in nephrectomized rats, revealing sustained ability to exclude these solutes from the brain. In summary, levels of many uremic solutes are normally kept lower in the CSF than in the plasma ultrafiltrate by the action of the blood-brain and blood-CSF barriers. These barriers remain functional but cannot prevent accumulation of uremic solutes in the CSF when the kidneys fail.
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Affiliation(s)
- Robert DeWolfe Mair
- Division of Nephrology, Stanford University , Stanford, California
- Department of Medicine, Veterans Affair Palo Alto Health Care System, Palo Alto, California
| | - Huy Nguyen
- Department of Neurology and Neurological Sciences, Stanford University , Stanford, California
| | - Ting-Ting Huang
- Department of Neurology and Neurological Sciences, Stanford University , Stanford, California
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California
| | - Natalie S Plummer
- Department of Medicine, Veterans Affair Palo Alto Health Care System, Palo Alto, California
| | - Tammy L Sirich
- Division of Nephrology, Stanford University , Stanford, California
- Department of Medicine, Veterans Affair Palo Alto Health Care System, Palo Alto, California
| | - Timothy W Meyer
- Division of Nephrology, Stanford University , Stanford, California
- Department of Medicine, Veterans Affair Palo Alto Health Care System, Palo Alto, California
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14
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Sirich TL, Chertow GM. Asymmetric dimethylarginine, erythropoietin resistance, and anemia in CKD. Ann Transl Med 2019; 7:S86. [PMID: 31576295 PMCID: PMC6685898 DOI: 10.21037/atm.2019.04.22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 04/04/2019] [Indexed: 11/06/2022]
Affiliation(s)
- Tammy L. Sirich
- Nephrology Section, VA Palo Alto Health Care System, Palo Alto, CA, USA
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Glenn M. Chertow
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
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15
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Affiliation(s)
- Robert D Mair
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and.,Department of Medicine, Stanford University, Palo Alto, California
| | - Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and .,Department of Medicine, Stanford University, Palo Alto, California
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16
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Abstract
Intradialytic hypotension (IDH) is a prevalent yet serious complication of hemodialysis, associated with decreased quality of life, inadequate dialysis, vascular access thrombosis, global hypoperfusion, and increased cardiovascular and all-cause mortality. Current guidelines recommend antihypertensive medications be given at night and held the morning of dialysis for affected patients. Despite little evidence to support this recommendation, more than half of patients on dialysis may employ some form of this method. In this article, we will review the available evidence and clinical considerations regarding timing of blood pressure medications and occurrence of IDH, and conclude that witholding BP medications before hemodialysis should not be a routine practice.
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Affiliation(s)
- Katherine M Wang
- Department of Medicine, Stanford Division of Nephrology, Palo Alto, California
| | - Tammy L Sirich
- Department of Medicine, Stanford Division of Nephrology, Palo Alto, California.,Department of Medicine, VA Palo Alto Healthcare System, Palo Alto, California
| | - Tara I Chang
- Department of Medicine, Stanford Division of Nephrology, Palo Alto, California
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17
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Abstract
BACKGROUND AND OBJECTIVES Colon microbial metabolism produces solutes that are normally excreted in the urine and accumulate in the plasma when the kidneys fail. This study sought to further identify and characterize human colon-derived uremic solutes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Colon-derived solutes normally excreted in the urine were identified by comparing urine from controls (n=17) and patients with total colectomies (n=12), using an established metabolomic platform. Colon-derived solutes that accumulate in kidney failure were then identified by comparing the plasma of the control patients with that of patients on dialysis (n=14). RESULTS Ninety-one urinary solutes were classified as colon-derived on the basis of the finding of a urine excretion rate at least four-fold higher in control patients than in patients with total colectomies. Forty-six were solutes with known chemical structure, 35 of which had not previously been identified as colon-derived. Sixty of the colon-derived solutes accumulated in the plasma of patients with ESKD to a degree greater than urea and were therefore classified as uremic. The estimated urinary clearance for 27 out of the 32 colon-derived solutes for which clearance could be calculated exceeded that of creatinine, consistent with tubular secretion. Sulfatase treatment revealed that 42 out of the 91 colon-derived solutes detected were likely conjugates. CONCLUSIONS Metabolomic analysis identified numerous colon-derived solutes that are normally excreted in human urine. Clearance by tubular secretion limits plasma levels of many colon-derived solutes.
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Affiliation(s)
- Robert D Mair
- Department of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California
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18
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Abstract
Uremic solutes contribute to cardiovascular disease in renal insufficiency. In this review we describe the clearance of selected uremic solutes, which have been associated with cardiovascular disease. These solutes-indoxyl sulfate (IS), p-cresol sulfate (PCS), phenylacetylglutamine (PAG), trimethylamine-n-oxide (TMAO), and kynurenine-exemplify different mechanisms of clearance. IS and PCS are protein-bound solutes efficiently cleared by the native kidney through tubular secretion. PAG and TMAO are not protein-bound but are also cleared by the native kidney through tubular secretion, while kynurenine is not normally cleared by the kidney. Increases in the plasma levels of the normally secreted solutes IS, PCS, TMAO, and PAG in chronic kidney disease (CKD) are attributable to a reduction in their renal clearances. Levels of each of these potential toxins are even higher in patients on dialysis than in those with advanced chronic kidney disease, which can be accounted for in part by a low ratio of dialytic to native kidney clearance. The rise in plasma kynurenine in CKD and dialysis patients, by contrast, remains to be explained. Our ability to detect lower levels of the potential uremic cardiovascular toxins with renal replacement therapy may be limited by the intermittency of treatment, by increases in solute production, and by the presence of non-renal clearance. Reduction in the levels of uremic cardiovascular toxins may in the future be achieved more effectively by inhibiting their production.
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Affiliation(s)
- Robert D Mair
- The Departments of Medicine, VA Palo Alto Healthcare System, 111R, 3801 Miranda Ave., Palo Alto, CA 94304, USA.
- Division of Nephrology, Stanford University, 777 Welch Road, Suite DE, Palo Alto, CA 94304, USA.
| | - Tammy L Sirich
- The Departments of Medicine, VA Palo Alto Healthcare System, 111R, 3801 Miranda Ave., Palo Alto, CA 94304, USA.
- Division of Nephrology, Stanford University, 777 Welch Road, Suite DE, Palo Alto, CA 94304, USA.
| | - Timothy W Meyer
- The Departments of Medicine, VA Palo Alto Healthcare System, 111R, 3801 Miranda Ave., Palo Alto, CA 94304, USA.
- Division of Nephrology, Stanford University, 777 Welch Road, Suite DE, Palo Alto, CA 94304, USA.
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19
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Leong SC, Sao JN, Taussig A, Plummer NS, Meyer TW, Sirich TL. Residual Function Effectively Controls Plasma Concentrations of Secreted Solutes in Patients on Twice Weekly Hemodialysis. J Am Soc Nephrol 2018; 29:1992-1999. [PMID: 29728422 DOI: 10.1681/asn.2018010081] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 04/08/2018] [Indexed: 11/03/2022] Open
Abstract
Background Most patients on hemodialysis are treated thrice weekly even if they have residual kidney function, in part because uncertainty remains as to how residual function should be valued and incorporated into the dialysis prescription. Recent guidelines, however, have increased the weight assigned to residual function and thus reduced the treatment time required when it is present. Increasing the weight assigned to residual function may be justified by knowledge that the native kidney performs functions not replicated by dialysis, including solute removal by secretion. This study tested whether plasma concentrations of secreted solutes are as well controlled in patients with residual function on twice weekly hemodialysis as in anuric patients on thrice weekly hemodialysis.Methods We measured the plasma concentration and residual clearance, dialytic clearance, and removal rates for urea and the secreted solutes hippurate, phenylacetylglutamine, indoxyl sulfate, and p-cresol sulfate in nine patients on twice weekly hemodialysis and nine patients on thrice weekly hemodialysis.Results Compared with anuric patients on thrice weekly dialysis with the same standard Kt/Vurea, patients on twice weekly hemodialysis had lower hippurate and phenylacetylglutamine concentrations and similar indoxyl sulfate and p-cresol sulfate concentrations. Mathematical modeling revealed that residual secretory function accounted for the observed pattern of solute concentrations.Conclusions Plasma concentrations of secreted solutes can be well controlled by twice weekly hemodialysis in patients with residual kidney function. This result supports further study of residual kidney function value and the inclusion of this function in dialysis adequacy measures.
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Affiliation(s)
- Sheldon C Leong
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and.,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
| | - Justin N Sao
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
| | - Abigail Taussig
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
| | - Natalie S Plummer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and.,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
| | - Timothy W Meyer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and.,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
| | - Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and .,Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California; and
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20
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Abstract
The application of molecular methods has provided a new picture of the colon microbial flora, or microbiome. The microbiome has been found to be a complex ecosystem with multiple influences on its human host. In renal medicine, interest has focused on the microbiome as a source of toxic waste chemicals and a stimulant to unwanted systemic inflammation. Early attempts to manipulate the microbiome have yielded limited benefit, but further research is strongly motivated.
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California, USA; Department of Medicine, Stanford University, Palo Alto, California, USA
| | - Timothy W Meyer
- Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California, USA; Department of Medicine, Stanford University, Palo Alto, California, USA.
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21
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System and Stanford University, Palo Alto, California
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22
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Sirich TL, Aronov PA, Fullman J, Nguyen K, Plummer NS, Meyer TW. Untargeted mass spectrometry discloses plasma solute levels poorly controlled by hemodialysis. PLoS One 2017; 12:e0188315. [PMID: 29145509 PMCID: PMC5690664 DOI: 10.1371/journal.pone.0188315] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 11/03/2017] [Indexed: 11/18/2022] Open
Abstract
Many solutes have been reported to remain at higher plasma levels relative to normal than the standard index solute urea in hemodialysis patients. Untargeted mass spectrometry was employed to compare solute levels in plasma and plasma ultrafiltrate of hemodialysis patients and normal subjects. Quantitative assays were employed to check the accuracy of untargeted results for selected solutes and additional measurements were made in dialysate and urine to estimate solute clearances and production. Comparison of peak areas indicated that many solutes accumulated to high levels in hemodialysis patients, with average peak areas in plasma ultrafiltrate of dialysis patients being more than 100 times greater than those in normals for 123 features. Most of these mass spectrometric features were identified only by their mass values. Untargeted analysis correctly ranked the accumulation of 5 solutes which were quantitatively assayed but tended to overestimate its extent. Mathematical modeling showed that the elevation of plasma levels for these solutes could be accounted for by a low dialytic to native kidney clearance ratio and a high dialytic clearance relative to the volume of the accessible compartment. Numerous solutes accumulate to high levels in hemodialysis patients because dialysis does not replicate the clearance provided by the native kidney. Many of these solutes remain to be chemically identified and their pathogenic potential elucidated.
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Affiliation(s)
- Tammy L. Sirich
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
- * E-mail:
| | - Pavel A. Aronov
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Jonathan Fullman
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Khanh Nguyen
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Natalie S. Plummer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Timothy W. Meyer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
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23
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Shafi T, Sirich TL, Meyer TW, Hostetter TH, Plummer NS, Hwang S, Melamed ML, Banerjee T, Coresh J, Powe NR. Results of the HEMO Study suggest that p-cresol sulfate and indoxyl sulfate are not associated with cardiovascular outcomes. Kidney Int 2017; 92:1484-1492. [PMID: 28739139 DOI: 10.1016/j.kint.2017.05.012] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 04/09/2017] [Accepted: 05/04/2017] [Indexed: 01/22/2023]
Abstract
Cardiovascular disease, the leading cause of mortality in hemodialysis patients, is not fully explained by traditional risk factors. To help define non-traditional risk factors, we determined the association of predialysis total p-cresol sulfate, indoxyl sulfate, phenylacetylglutamine, and hippurate with cardiac death, sudden cardiac death, and first cardiovascular event in the 1,273 participants of the HEMO Study. The results were adjusted for potential demographic, clinical, and laboratory confounders. The mean age of the patients was 58 years, 63% were Black and 42% were male. Overall, there was no association between the solutes and outcomes. However, in sub-group analyses, among patients with lower serum albumin (under 3.6 g/dl), a twofold higher p-cresol sulfate was significantly associated with a 12% higher risk of cardiac death (hazard ratio 1.12; 95% confidence interval, 0.98-1.27) and 22% higher risk of sudden cardiac death (1.22, 1.06-1.41). Similar trends were also noted with indoxyl sulfate. Trial interventions did not modify the association between these solutes and outcomes. Routine clinical and lab data explained less than 22% of the variability in solute levels. Thus, in prevalent hemodialysis patients participating in a large U.S. hemodialysis trial, uremic solutes p-cresol sulfate, indoxyl sulfate, hippurate, and phenylacetylglutamine were not associated with cardiovascular outcomes. However, there were trends of toxicity among patients with lower serum albumin.
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Affiliation(s)
- Tariq Shafi
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, Maryland, USA; Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA.
| | - Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA
| | - Timothy W Meyer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA
| | - Thomas H Hostetter
- Department of Medicine, Case Western University School of Medicine, Cleveland, Ohio, USA
| | - Natalie S Plummer
- Department of Medicine, Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA
| | - Seungyoung Hwang
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
| | - Michal L Melamed
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Tanushree Banerjee
- Department of Medicine, University of California, San Francisco, California, USA
| | - Josef Coresh
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, Maryland, USA; Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Neil R Powe
- Department of Medicine, University of California, San Francisco, California, USA
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24
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Affiliation(s)
- Tammy L. Sirich
- The Department of Medicine; VA Palo Alto Health Care System and Stanford University; Palo Alto CA USA
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25
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Abstract
Indoxyl sulfate is an extensively studied uremic solute. It is a small molecule that is more than 90% bound to plasma proteins. Indoxyl sulfate is derived from the breakdown of tryptophan by colon microbes. The kidneys achieve high clearances of indoxyl sulfate by tubular secretion, a function not replicated by hemodialysis. Clearance by hemodialysis is limited by protein binding since only the free, unbound solute can diffuse across the membrane. Since the dialytic clearance is much lower than the kidney clearance, indoxyl sulfate accumulates to relatively high plasma levels in hemodialysis patients. Indoxyl sulfate has been most frequently implicated as a contributor to renal disease progression and vascular disease. Studies have suggested that indoxyl sulfate also has adverse effects on bones and the central nervous system. The majority of studies have assessed toxicity in cultured cells and animal models. The toxicity in humans has not yet been proven, as most data have been from association studies. Such toxicity data, albeit inconclusive, have prompted efforts to lower the plasma levels of indoxyl sulfate through dialytic and non-dialytic means. The largest randomized trial showed no benefit in renal disease progression with AST-120. No trials have yet tested cardiovascular or mortality benefit. Without such trials, the toxicity of indoxyl sulfate cannot be firmly established.
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Affiliation(s)
- Sheldon C Leong
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Nephrology 111R, Palo Alto VAHCS, 3801 Miranda Ave., Palo Alto, CA 94304, USA.
| | - Tammy L Sirich
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Nephrology 111R, Palo Alto VAHCS, 3801 Miranda Ave., Palo Alto, CA 94304, USA.
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26
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Abstract
Patients maintained on standard three times weekly hemodialysis have a high mortality rate and a limited quality of life. Some of this illness is due to systemic diseases that have caused kidney failure, and thus may be irreversible. But we presume that imperfect replacement of normal kidney function by dialysis contributes importantly. Patients on hemodialysis are subject to fluctuations in extracellular fluid volume and inorganic ion concentrations and their plasma levels of many organic waste solutes remain very high. It is thus natural to suppose that their health could be improved by increasing the intensity of dialysis treatment. But despite a great deal of work over the past 20 years, evidence that such improvement can be obtained is generally lacking. Specific benefits can indeed be achieved. Patients who cannot control their intradialytic weight gains or plasma phosphate levels with standard therapy can benefit from extending treatment time. But we cannot promise the average patient that longer or more frequent treatment will reduce mortality or improve the quality of life.
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Affiliation(s)
- Frank J O'Brien
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California.
| | - Kara D Fong
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
| | - Tammy L Sirich
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
| | - Timothy W Meyer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
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27
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Kurella Tamura M, Chertow GM, Depner TA, Nissenson AR, Schiller B, Mehta RL, Liu S, Sirich TL. Metabolic Profiling of Impaired Cognitive Function in Patients Receiving Dialysis. J Am Soc Nephrol 2016; 27:3780-3787. [PMID: 27444566 DOI: 10.1681/asn.2016010039] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 03/29/2016] [Indexed: 11/03/2022] Open
Abstract
Retention of uremic metabolites is a proposed cause of cognitive impairment in patients with ESRD. We used metabolic profiling to identify and validate uremic metabolites associated with impairment in executive function in two cohorts of patients receiving maintenance dialysis. We performed metabolic profiling using liquid chromatography/mass spectrometry applied to predialysis plasma samples from a discovery cohort of 141 patients and an independent replication cohort of 180 patients participating in a trial of frequent hemodialysis. We assessed executive function with the Trail Making Test Part B and the Digit Symbol Substitution test. Impaired executive function was defined as a score ≥2 SDs below normative values. Four metabolites-4-hydroxyphenylacetate, phenylacetylglutamine, hippurate, and prolyl-hydroxyproline-were associated with impaired executive function at the false-detection rate significance threshold. After adjustment for demographic and clinical characteristics, the associations remained statistically significant: relative risk 1.16 (95% confidence interval [95% CI], 1.03 to 1.32), 1.39 (95% CI, 1.13 to 1.71), 1.24 (95% CI, 1.03 to 1.50), and 1.20 (95% CI, 1.05 to 1.38) for each SD increase in 4-hydroxyphenylacetate, phenylacetylglutamine, hippurate, and prolyl-hydroxyproline, respectively. The association between 4-hydroxyphenylacetate and impaired executive function was replicated in the second cohort (relative risk 1.12; 95% CI, 1.02 to 1.23), whereas the associations for phenylacetylglutamine, hippurate, and prolyl-hydroxyproline did not reach statistical significance in this cohort. In summary, four metabolites related to phenylalanine, benzoate, and glutamate metabolism may be markers of cognitive impairment in patients receiving maintenance dialysis.
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Affiliation(s)
- Manjula Kurella Tamura
- Geriatric Research and Education Clinical Center, Palo Alto Veterans Administration Health Care System, Palo Alto, California; .,Division of Nephrology, Stanford University School of Medicine, Palo Alto, California
| | - Glenn M Chertow
- Division of Nephrology, Stanford University School of Medicine, Palo Alto, California
| | - Thomas A Depner
- Division of Nephrology, University of California Davis School of Medicine, Davis, California
| | - Allen R Nissenson
- David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and
| | - Brigitte Schiller
- Division of Nephrology, Stanford University School of Medicine, Palo Alto, California
| | - Ravindra L Mehta
- Division of Nephrology, University of California San Diego, San Diego, California
| | - Sai Liu
- Division of Nephrology, Stanford University School of Medicine, Palo Alto, California
| | - Tammy L Sirich
- Geriatric Research and Education Clinical Center, Palo Alto Veterans Administration Health Care System, Palo Alto, California.,Division of Nephrology, Stanford University School of Medicine, Palo Alto, California
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28
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Camacho O, Rosales MC, Shafi T, Fullman J, Plummer NS, Meyer TW, Sirich TL. Effect of a sustained difference in hemodialytic clearance on the plasma levels of p-cresol sulfate and indoxyl sulfate. Nephrol Dial Transplant 2016; 31:1335-41. [PMID: 27190347 DOI: 10.1093/ndt/gfw100] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 04/06/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The protein-bound solutes p-cresol sulfate (PCS) and indoxyl sulfate (IS) accumulate to high plasma levels in renal failure and have been associated with adverse events. The clearance of these bound solutes can be altered independently of the urea clearance by changing the dialysate flow and dialyzer size. This study tested whether a sustained difference in clearance would change the plasma levels of PCS and IS. METHODS Fourteen patients on thrice-weekly nocturnal hemodialysis completed a crossover study of two periods designed to achieve widely different bound solute clearances. We compared the changes in pre-dialysis plasma PCS and IS levels from baseline over the course of the two periods. RESULTS The high-clearance period provided much higher PCS and IS clearances than the low-clearance period (PCS: 23 ± 4 mL/min versus 12 ± 3 mL/min, P < 0.001; IS: 30 ± 5 mL/min versus 17 ± 4 mL/min, P < 0.001). Despite the large difference in clearance, the high-clearance period did not have a different effect on PCS levels than the low-clearance period [from baseline, high: +11% (-5, +37) versus low: -8% (-18, +32), (median, 25th, 75th percentile), P = 0.50]. In contrast, the high-clearance period significantly lowered IS levels compared with the low-clearance period [from baseline, high: -4% (-17, +1) versus low: +22% (+14, +31), P < 0.001). The amount of PCS removed in the dialysate was significantly greater at the end of the high-clearance period [269 (206, 312) versus 199 (111, 232) mg per treatment, P < 0.001], while the amount of IS removed was not different [140 (87, 196) versus 116 (89, 170) mg per treatment, P = 0.15]. CONCLUSIONS These findings suggest that an increase in PCS generation prevents plasma levels from falling when the dialytic clearance is increased. Suppression of solute generation may be required to reduce plasma PCS levels in dialysis patients.
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Affiliation(s)
- Orlando Camacho
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
| | - Maria Carmela Rosales
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
| | - Tariq Shafi
- Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Jonathan Fullman
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
| | - Natalie S Plummer
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
| | - Timothy W Meyer
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
| | - Tammy L Sirich
- The Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA
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29
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Meyer TW, Sirich TL, Fong KD, Plummer NS, Shafi T, Hwang S, Banerjee T, Zhu Y, Powe NR, Hai X, Hostetter TH. Kt/Vurea and Nonurea Small Solute Levels in the Hemodialysis Study. J Am Soc Nephrol 2016; 27:3469-3478. [PMID: 27026365 DOI: 10.1681/asn.2015091035] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 02/17/2016] [Indexed: 01/18/2023] Open
Abstract
The Hemodialysis (HEMO) Study showed that high-dose hemodialysis providing a single-pool Kt/Vurea of 1.71 provided no benefit over a standard treatment providing a single-pool Kt/Vurea of 1.32. Here, we assessed whether the high-dose treatment used lowered plasma levels of small uremic solutes other than urea. Measurements made ≥3 months after randomization in 1281 patients in the HEMO Study showed a range in the effect of high-dose treatment compared with that of standard treatment: from no reduction in the level of p-cresol sulfate or asymmetric dimethylarginine to significant reductions in the levels of trimethylamine oxide (-9%; 95% confidence interval [95% CI], -2% to -15%), indoxyl sulfate (-11%; 95% CI, -6% to -15%), and methylguanidine (-22%; 95% CI, -18% to -27%). Levels of three other small solutes also decreased slightly; the level of urea decreased 9%. All-cause mortality did not significantly relate to the level of any of the solutes measured. Modeling indicated that the intermittency of treatment along with the presence of nondialytic clearance and/or increased solute production accounted for the limited reduction in solute levels with the higher Kt/Vurea In conclusion, failure to achieve greater reductions in solute levels may explain the failure of high Kt/Vurea treatment to improve outcomes in the HEMO Study. Furthermore, levels of the nonurea solutes varied widely among patients in the HEMO Study, and achieved Kt/Vurea accounted for very little of this variation. These results further suggest that an index only on the basis of urea does not provide a sufficient measure of dialysis adequacy.
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Affiliation(s)
- Timothy W Meyer
- Department of Medicine, Palo Alto Veterans Affairs Health Care System and Stanford University, Palo Alto, California;
| | - Tammy L Sirich
- Department of Medicine, Palo Alto Veterans Affairs Health Care System and Stanford University, Palo Alto, California
| | - Kara D Fong
- Department of Medicine, Palo Alto Veterans Affairs Health Care System and Stanford University, Palo Alto, California
| | - Natalie S Plummer
- Department of Medicine, Palo Alto Veterans Affairs Health Care System and Stanford University, Palo Alto, California
| | - Tariq Shafi
- Department of Medicine and Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, Maryland
| | - Seungyoung Hwang
- Department of Medicine and Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, Maryland
| | - Tanushree Banerjee
- Department of Medicine, University of California, San Francisco, California; and
| | - Yunnuo Zhu
- Department of Medicine, University of California, San Francisco, California; and
| | - Neil R Powe
- Department of Medicine, University of California, San Francisco, California; and
| | - Xin Hai
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Thomas H Hostetter
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
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Suchy-Dicey AM, Laha T, Hoofnagle A, Newitt R, Sirich TL, Meyer TW, Thummel KE, Yanez ND, Himmelfarb J, Weiss NS, Kestenbaum BR. Tubular Secretion in CKD. J Am Soc Nephrol 2015; 27:2148-55. [PMID: 26614381 DOI: 10.1681/asn.2014121193] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 10/15/2015] [Indexed: 11/03/2022] Open
Abstract
Renal function generally is assessed by measurement of GFR and urinary albumin excretion. Other intrinsic kidney functions, such as proximal tubular secretion, typically are not quantified. Tubular secretion of solutes is more efficient than glomerular filtration and a major mechanism for renal drug elimination, suggesting important clinical consequences of secretion dysfunction. Measuring tubular secretion as an independent marker of kidney function may provide insight into kidney disease etiology and improve prediction of adverse outcomes. We estimated secretion function by measuring secreted solute (hippurate, cinnamoylglycine, p-cresol sulfate, and indoxyl sulfate) clearance using liquid chromatography-tandem mass spectrometric assays of serum and timed urine samples in a prospective cohort study of 298 patients with kidney disease. We estimated GFR by mean clearance of creatinine and urea from the same samples and evaluated associations of renal secretion with participant characteristics, mortality, and CKD progression to dialysis. Tubular secretion rate modestly correlated with eGFR and associated with some participant characteristics, notably fractional excretion of electrolytes. Low clearance of hippurate or p-cresol sulfate associated with greater risk of death independent of eGFR (hazard ratio, 2.3; 95% confidence interval, 1.1 to 4.7; hazard ratio, 2.5; 95% confidence interval, 1.0 to 6.1, respectively). Hazards models also suggested an association between low cinnamoylglycine clearance and risk of dialysis, but statistical analyses did not exclude the null hypothesis. Therefore, estimates of proximal tubular secretion function correlate with glomerular filtration, but substantial variability in net secretion remains. The observed associations of net secretion with mortality and progression of CKD require confirmation.
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Affiliation(s)
| | | | | | - Rick Newitt
- Kidney Research Institute, School of Medicine
| | - Tammy L Sirich
- School of Medicine, Stanford University, Stanford, California
| | - Timothy W Meyer
- School of Medicine, Stanford University, Stanford, California
| | - Ken E Thummel
- Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, Washington; and
| | | | | | | | - Bryan R Kestenbaum
- Departments of Epidemiology and Kidney Research Institute, School of Medicine
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Abstract
BACKGROUND Colon microbes produce a large number of organic compounds that are foreign to mammalian cell metabolism. SUMMARY Some of the compounds made by microbes are absorbed in the colon and then normally excreted by the kidneys. Accumulation of these compounds in the plasma as uremic solutes may contribute to illness in patients whose kidneys have failed. Mass spectrometry is expanding our knowledge of the chemical identity of the colon-derived uremic solutes, and DNA sequencing technologies are providing new knowledge of the microbes and metabolic pathways by which they are made. Because they are made in an isolated compartment by microbes, their production may prove simpler to suppress than the production of other uremic solutes. KEY MESSAGES To the extent that they are toxic, suppressing their production could improve the health of renal failure patients without the need for more intensive or prolonged dialysis.
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Affiliation(s)
- Hisae Tanaka
- Health Evaluation and Promotion Center, Tokai University Hospital, Isehara, Kanagawa, Japan
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Abstract
Better knowledge of the uremic solutes that accumulate when the kidneys fail could lead to improved renal replacement therapy. This study employed the largest widely available metabolomic platform to identify such solutes. Plasma and plasma ultrafiltrate from 6 maintenance hemodialysis (HD) patients and 6 normal controls were first compared using a platform combining gas and liquid chromatography with mass spectrometry. Further studies compared plasma from 6 HD patients who had undergone total colectomy and 9 with intact colons. We identified 120 solutes as uremic including 48 that had not been previously reported to accumulate in renal failure. Combination of the 48 newly identified solutes with those identified in previous reports yielded an extended list of more than 270 uremic solutes. Among the solutes identified as uremic in the current study, 9 were shown to be colon-derived, including 6 not previously identified as such. Literature search revealed that many uremic phenyl and indole solutes, including most of those shown to be colon-derived, come from plant foods. Some of these compounds can be absorbed directly from plant foods and others are produced by colon microbial metabolism of plant polyphenols that escape digestion in the small intestine. A limitation of the metabolomic method was that it underestimated the elevation in concentration of uremic solutes which were measured using more quantitative assays.
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Affiliation(s)
- Hisae Tanaka
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Tammy L. Sirich
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Natalie S. Plummer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
| | - Daniel S. Weaver
- Bioinformatics Research Group, SRI International, Menlo Park, CA, United States of America
| | - Timothy W. Meyer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, United States of America
- * E-mail:
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Abstract
Prior to the availability of hemodialysis, dietary protein restriction played a large part in the treatment of uremia. This therapy was based on observations that uremic symptoms increased with high protein intake. Early investigators thus presumed that "uremic toxins" were derived from the breakdown of dietary protein; its restriction improved uremic symptoms but caused malnutrition. After the availability of hemodialysis, protein restriction was no longer recommended. Studies in healthy subjects have shown that an intake of 0.6-0.8 g/kg/day is adequate to prevent protein malnutrition. Guidelines for hemodialysis patients, however, currently recommend higher protein intakes of 1.2 g/kg/day. A downside to higher intake may be increased production of protein-derived uremic solutes that caused the symptoms observed by early investigators. Some of these solutes are produced by colon microbes acting on protein which escapes digestion in the small intestine. Increasing dietary fiber may reduce the production of colon-derived solutes in hemodialysis patients without adverse effects of protein restriction. Fiber comprises carbohydrates and related substances that are resistant to digestion in the small intestine. Upon delivery to the colon, fiber is broken down to short chain fatty acids, providing energy to both the microbes and the host. With an increased energy supply, the microbes can incorporate dietary protein for growth rather than breaking them down to uremic solutes. Increasing fiber intake in hemodialysis patients has been shown to reduce the plasma levels of selected colon-derived solutes. Further studies are needed to test whether this provides clinical benefit.
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Affiliation(s)
- Tammy L Sirich
- Departments of Medicine, VA Palo Alto Health Care System and Stanford University, Palo Alto, California
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Sirich TL, Plummer NS, Gardner CD, Hostetter TH, Meyer TW. Effect of increasing dietary fiber on plasma levels of colon-derived solutes in hemodialysis patients. Clin J Am Soc Nephrol 2014; 9:1603-10. [PMID: 25147155 DOI: 10.2215/cjn.00490114] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND AND OBJECTIVES Numerous uremic solutes are derived from the action of colon microbes. Two such solutes, indoxyl sulfate and p-cresol sulfate, have been associated with adverse outcomes in renal failure. This study tested whether increasing dietary fiber in the form of resistant starch would lower the plasma levels of these solutes in patients on hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Fifty-six patients on maintenance hemodialysis were randomly assigned to receive supplements containing resistant starch (n=28) or control starch (n=28) daily for 6 weeks in a study conducted between October 2010 and May 2013. Of these, 40 patients (20 in each group) completed the study and were included in the final analysis. Plasma indoxyl sulfate and p-cresol sulfate levels were measured at baseline and week 6. RESULTS Increasing dietary fiber for 6 weeks significantly reduced the unbound, free plasma level of indoxyl sulfate (median -29% [25th percentile, 75th percentile, -56, -12] for fiber versus -0.4% [-20, 34] for control, P=0.02). The reduction in free plasma levels of indoxyl sulfate was accompanied by a reduction in free plasma levels of p-cresol sulfate (r=0.81, P<0.001). However, the reduction of p-cresol sulfate levels was of lesser magnitude and did not achieve significance (median -28% [-46, 5] for fiber versus 4% [-28, 36] for control, P=0.05). CONCLUSIONS Increasing dietary fiber in hemodialysis patients may reduce the plasma levels of the colon-derived solutes indoxyl sulfate and possibly p-cresol sulfate without the need to intensify dialysis treatments. Further studies are required to determine whether such reduction provides clinical benefits.
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Affiliation(s)
- Tammy L Sirich
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Natalie S Plummer
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Christopher D Gardner
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Thomas H Hostetter
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Timothy W Meyer
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
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Abstract
Many small solutes excreted by the kidney are bound to plasma proteins, chiefly albumin, in the circulation. The combination of protein binding and tubular secretion allows the kidney to reduce the free, unbound concentrations of such solutes to lower levels than could be obtained by tubular secretion alone. Protein-bound solutes accumulate in the plasma when the kidneys fail, and the free, unbound levels of these solutes increase more than their total plasma levels owing to competition for binding sites on plasma proteins. Given the efficiency by which the kidney can clear protein-bound solutes, it is tempting to speculate that some compounds in this class are important uremic toxins. Studies to date have focused largely on two specific protein-bound solutes: indoxyl sulfate and p-cresyl sulfate. The largest body of evidence suggests that both of these compounds contribute to cardiovascular disease, and that indoxyl sulfate contributes to the progression of chronic kidney disease. Other protein-bound solutes have been investigated to a much lesser extent, and could in the future prove to be even more important uremic toxins.
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, VA Palo Alto Healthcare System and Stanford University, Palo Alto, CA
| | - Timothy W Meyer
- Department of Medicine, VA Palo Alto Healthcare System and Stanford University, Palo Alto, CA.
| | - Bertrand Gondouin
- Aix-Marseille University, INSERM UMR_S 1076, Marseille, France; Centre de Nephrologie et Transplantation Renale, Assistance-Publique Hopitaux de Marseille, Marseille, France
| | - Philippe Brunet
- Aix-Marseille University, INSERM UMR_S 1076, Marseille, France; Centre de Nephrologie et Transplantation Renale, Assistance-Publique Hopitaux de Marseille, Marseille, France
| | - Toshimitsu Niwa
- Department of Advanced Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Sirich TL, Funk BA, Plummer NS, Hostetter TH, Meyer TW. Prominent accumulation in hemodialysis patients of solutes normally cleared by tubular secretion. J Am Soc Nephrol 2013; 25:615-22. [PMID: 24231664 DOI: 10.1681/asn.2013060597] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dialytic clearance of urea is efficient, but other small solutes normally secreted by the kidney may be cleared less efficiently. This study tested whether the high concentrations of these solutes in hemodialysis patients reflect a failure of passive diffusion methods to duplicate the efficacy of clearance by tubular secretion. We compared the plasma concentrations and clearance rates of four solutes normally cleared by tubular secretion with the plasma concentrations and clearance rates of urea and creatinine in patients receiving maintenance hemodialysis and normal subjects. The predialysis concentrations (relative to normal subjects) of unbound phenylacetylglutamine (122-fold), hippurate (108-fold), indoxyl sulfate (116-fold), and p-cresol sulfate (41-fold) were much greater than the concentrations of urea (5-fold) and creatinine (13-fold). The dialytic clearance rates (relative to normal subjects) of unbound phenylacetylglutamine (0.37-fold), hippurate (0.16-fold), indoxyl sulfate (0.21-fold), and p-cresol sulfate (0.39-fold) were much lower than the rates of urea (4.2-fold) and creatinine (1.3-fold). Mathematical modeling showed that prominent accumulation of the normally secreted solutes in hemodialysis patients could be accounted for by lower dialytic clearance relative to physiologic clearance combined with the intermittency of treatment. Whether or not more efficient removal of normally secreted solutes improves outcomes in dialysis patients remains to be tested.
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System and Stanford University, Palo Alto, California; and
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Sirich TL, Luo FJG, Plummer NS, Hostetter TH, Meyer TW. Selectively increasing the clearance of protein-bound uremic solutes. Nephrol Dial Transplant 2012; 27:1574-9. [PMID: 22231033 DOI: 10.1093/ndt/gfr691] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND The toxicity of bound solutes could be better evaluated if we could adjust the clearance of such solutes independent of unbound solutes. This study assessed whether bound solute clearances can be increased while maintaining urea clearance constant during the extended hours of nocturnal dialysis. METHODS Nine patients on thrice-weekly nocturnal dialysis underwent two experimental dialysis treatments 1 week apart. The experimental treatments were designed to provide the same urea clearance while providing widely different bound solute clearance. One treatment employed a large dialyzer and high dialyzate flow rate (Qd) of 800 mL/min while blood flow (Qb) was 270 mL/min. The other treatment employed a smaller dialyzer and Qd of 300 mL/min while Qb was 350 mL/min. RESULTS Treatment with the large dialyzer and higher Qd greatly increased the clearances of the bound solutes p-cresol sulfate (PCS: 27±9 versus 14±6 mL/min) and indoxyl sulfate (IS: 26±8 versus 14±5 mL/min) without altering the clearance of urea (204±20 versus 193±16 mL/min). Increasing PCS and IS clearances increased the removal of these solutes (PCS: 375±200 versus 207±86 mg/session; IS: 201±137 versus 153±74 mg/session), while urea removal was not different. CONCLUSIONS The removal of bound solutes can thus be increased by raising the dialyzate flow and dialyzer size above the low levels sufficient to achieve target Kt/V(urea) during extended treatment. Selectively increasing the clearance of bound solutes provides a potential means to test their toxicity.
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, CA, USA.
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Abstract
Adequate dialysis is difficult to define because we have not identified the toxic solutes that contribute most to uremic illness. Dialysis prescriptions therefore cannot be adjusted to control the levels of these solutes. The current solution to this problem is to define an adequate dose of dialysis on the basis of fraction of urea removed from the body. This has provided a practical guide to treatment as the dialysis population has grown over the past 25 years. Indeed, a lower limit to Kt/V(urea) (or the related urea reduction ratio) is now established as a quality indicator by the Centers for Medicare and Medicaid for chronic hemodialysis patients in the United States. For the present, this urea-based standard provides a useful tool to avoid grossly inadequate dialysis. Dialysis dosing, however, based on measurement of a single, relatively nontoxic solute can provide only a very limited guide toward improved treatment. Prescriptions which have similar effects on the index solute can have widely different effects on other solutes. The dose concept discourages attempts to increase the removal of such solutes independent of the index solute. The dose concept further assumes that important solutes are produced at a constant rate relative to body size, and discourages attempts to augment dialysis treatment by reducing solute production. Identification of toxic solutes would provide a more rational basis for the prescription of dialysis and ultimately for improved treatment of patients with renal failure.
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Affiliation(s)
- Timothy W. Meyer
- Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
| | - Tammy L. Sirich
- Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California
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Ge X, Sirich TL, Beyer MK, Desaire H, Leary JA. A strategy for the determination of enzyme kinetics using electrospray ionization with an ion trap mass spectrometer. Anal Chem 2001; 73:5078-82. [PMID: 11721902 DOI: 10.1021/ac0105890] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A simple and rapid means of enzyme kinetic analysis was achieved using electrospray ionization mass spectrometry and a one-point normalization factor. The model system used, glutathione S-transferase from porcine liver, is a two-substrate enzyme catalyzing the conjugation of glutathione with a variety of compounds containing an electrophilic center. An internal standard that is structurally similar to the product was added to the reaction quench solution, and a single-point normalization factor was used to determine the product concentration without the need of a calibration curve. Kinetic parameters, such as Km, Vmax and Ki (for thyroxine), obtained by electrospray mass spectrometry agreed with those obtained from traditional UV-vis spectroscopy, and competitive vs noncompetitive inhibition reactions could be delineated via mass spectrometry. These results suggest that our method can be applied to enzymatic processes in which spectrophotometric or spectrofluorometric assays are not feasible or when the relevant substrates do not incorporate chromophores or fluorophores. This new method is competitive with traditional UV assays in that it is facile and it involves very little analysis time.
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Affiliation(s)
- X Ge
- Department of Chemistry, University of California, Berkeley 94720, USA
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Desaire H, Sirich TL, Leary JA. Evidence of block and randomly sequenced chondroitin polysaccharides: sequential enzymatic digestion and quantification using ion trap tandem mass spectrometry. Anal Chem 2001; 73:3513-20. [PMID: 11510812 DOI: 10.1021/ac010385j] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A method for determining the sequence type of the disaccharide repeat region of cartilage samples is introduced. The samples are sequentially subjected to selective and nonselective enzymatic digestion, and the isomeric products from each step are quantified using tandem mass spectrometry. The two-step digestion/quantification protocol identifies whether the global makeup of the polymer is "alternating", "random", or "blocked" with respect to the two main components of the cartilage, 4- and 6-sulfated disaccharides. Using this procedure, the sequence type of two biologically isolated chondroitin polysaccharides was identified. The results for chondroitin sulfate A, isolated from bovine trachea, are consistent with the 4- and 6-sulfated disaccharides randomly distributed throughout the repeat region of the polysaccharide. For chondroitin sulfate C, shark cartilage, the 6-sulfated disaccharides are adjacent to each other to a larger extent than one would expect for a randomly distributed polymer, indicating that "blocks" of repeating disaccharides with the same sulfation site are present.
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Affiliation(s)
- H Desaire
- College of Chemistry, University of California Berkeley 94720, USA
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