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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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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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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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6
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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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7
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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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8
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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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9
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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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10
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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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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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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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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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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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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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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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Patel KP, Luo FJG, Plummer NS, Hostetter TH, Meyer TW. The production of p-cresol sulfate and indoxyl sulfate in vegetarians versus omnivores. Clin J Am Soc Nephrol 2012; 7:982-8. [PMID: 22490877 DOI: 10.2215/cjn.12491211] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES The uremic solutes p-cresol sulfate (PCS) and indoxyl sulfate (IS) are generated by colon bacteria acting on food components that escape absorption in the small bowel. The production of these potentially toxic compounds may thus be influenced by diet. This study examined whether production of PCS and IS is different in vegetarians and omnivores. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS The production of PCS and IS was assessed by measuring their urinary excretion rates in participants with normal kidney function. Studies were carried out in 15 vegetarians and 11 individuals consuming an unrestricted diet. Participants recorded food intake over 4 days and collected urine over the final 2 days of each of two study periods, which were 1 month apart. RESULTS Average PCS excretion was 62% lower (95% confidence interval [95% CI], 15-83) and average IS excretion was 58% lower (95% CI, 39-71) in vegetarians than in participants consuming an unrestricted diet. Food records revealed that lower excretion of PCS and IS in vegetarians was associated with a 69% higher (95% CI, 20-139) fiber intake and a 25% lower (95% CI, 3-42) protein intake. PCS and IS excretion rates varied widely among individual participants and were not closely correlated with each other but tended to remain stable in individual participants over 1 month. CONCLUSIONS PCS and IS production rates are markedly lower in vegetarians than in individuals consuming an unrestricted diet.
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Affiliation(s)
- Kajal P Patel
- Department of Medicine, Palo Alto VA Health Care System, Stanford University, Palo Alto, California, USA
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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
Microbes in the colon produce compounds, normally excreted by the kidneys, which are potential uremic toxins. Although p-cresol sulfate and indoxyl sulfate are well studied examples, few other compounds are known. Here, we compared plasma from hemodialysis patients with and without colons to identify and further characterize colon-derived uremic solutes. HPLC confirmed the colonic origin of p-cresol sulfate and indoxyl sulfate, but levels of hippurate, methylamine, and dimethylamine were not significantly lower in patients without colons. High-resolution mass spectrometry detected more than 1000 features in predialysis plasma samples. Hierarchical clustering based on these features clearly separated dialysis patients with and without colons. Compared with patients with colons, we identified more than 30 individual features in patients without colons that were either absent or present in lower concentration. Almost all of these features were more prominent in plasma from dialysis patients than normal subjects, suggesting that they represented uremic solutes. We used a panel of indole and phenyl standards to identify five colon-derived uremic solutes: α-phenylacetyl-l-glutamine, 5-hydroxyindole, indoxyl glucuronide, p-cresol sulfate, and indoxyl sulfate. However, compounds with accurate mass values matching most of the colon-derived solutes could not be found in standard metabolomic databases. These results suggest that colonic microbes may produce an important portion of uremic solutes, most of which remain unidentified.
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Affiliation(s)
- Pavel A Aronov
- Vincent Coates Foundation Mass Spectrometry Laboratory, Stanford University, Stanford, California, USA
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Marquez IO, Tambra S, Luo FY, Li Y, Plummer NS, Hostetter TH, Meyer TW. Contribution of residual function to removal of protein-bound solutes in hemodialysis. Clin J Am Soc Nephrol 2010; 6:290-6. [PMID: 21030575 DOI: 10.2215/cjn.06100710] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES This study evaluated the contribution of residual function to the removal of solutes for which protein binding limits clearance by hemdialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Solute concentrations were measured in 25 hemodialysis patients with residual urea clearances ranging from 0.1 to 6.2 ml/min per 1.73 m2. Mathematical modeling assessed the effect of residual function on time-averaged solute concentrations. RESULTS Dialytic clearances of the protein-bound solutes p-cresol sulfate, indoxyl sulfate, and hippurate were reduced in proportion to the avidity of binding and averaged 8±2, 10±3, and 44±13% of the dialytic urea clearance. For each bound solute, the residual clearance was larger in relation to the residual urea clearance. Residual kidney function therefore removed a larger portion of each of the bound solutes than of urea. Increasing residual function was associated with lower plasma levels of p-cresol sulfate and hippurate but not indoxyl sulfate. Wide variation in solute generation tended to obscure the dependence of plasma solute levels on residual function. Mathematical modeling that corrected for this variation indicated that increasing residual function will reduce the plasma level of each of the bound solutes more than the plasma level of urea. CONCLUSIONS In comparison to urea, solutes than bind to plasma proteins can be more effectively cleared by residual function than by hemodialysis. Levels of such solutes will be lower in patients with residual function than in patients without residual function even if the dialysis dose is reduced based on measurement of residual urea clearance in accord with current guidelines.
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Affiliation(s)
- Ilian O Marquez
- Department of Medicine, VA Palo Alto HCS and Stanford University, 3801 Miranda Avenue, Palo Alto, CA 94303, USA
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Luo FJG, Patel KP, Marquez IO, Plummer NS, Hostetter TH, Meyer TW. Effect of Increasing Dialyzer Mass Transfer Area Coefficient and Dialysate Flow on Clearance of Protein-Bound Solutes: A Pilot Crossover Trial. Am J Kidney Dis 2009; 53:1042-9. [DOI: 10.1053/j.ajkd.2009.01.265] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Accepted: 01/14/2009] [Indexed: 11/11/2022]
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Plummer NS. Book Review: The Genus Aspergillus. Proc R Soc Med 1966. [DOI: 10.1177/003591576605900846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Plummer NS. Hypoparathyroidism. Proc R Soc Med 1938; 31:1052-1053. [PMID: 19991580 PMCID: PMC2077000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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25
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Wigley JE, Plummer NS. Purpura associated with Bronchiectasis. Proc R Soc Med 1936; 30:23. [PMID: 19990908 PMCID: PMC2075745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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