definition and new insights in uremic toxins r vanholder, university hospital, gent, belgium
TRANSCRIPT
DEFINITION AND NEW INSIGHTS IN UREMIC
TOXINS
R Vanholder, University Hospital, Gent, Belgium
UREMIC TOXICITY: DEFINITIONS
• The uremic syndrome is a clinical condition, developing during the progression of renal failure, characterized by the loss of numerous biochemical and physiologic functions, and attributed to the retention of various solutes.
• Uremic toxins are uremic retention solutes which affect specific physiologic and biochemical functions. All these disturbed functions together are responsible for the uremic syndrome.
DEFINITION TOXIN (1)
• Compound should be chemically identified and accurate quantitative analysis in biological fluids should be possible
• The plasma level should be higher in uremic than in non-uremic subjects
• High concentrations should be related to specific uremic symptoms that decrease or disappear when concentration is reduced
• Concentrations in in vivo or in vitro studies should conform to those found in body fluids or tissue of uremic patients
Vanholder et al, IJAO, 24, 695-725, 2001
DEFINITION TOXIN (2)
• Only a few solutes conform more or less with this strict defintion:– H2O?
– Phosphate?– Potassium?
– ß2-microglobulin?
– ……?
UREMIC RETENTION SOLUTES
1) adrenomedullin; 2) advanced glycation end products (AGE); 3) advanced oxidation protein products (AOPP); 4) angiogenin; 5) atrial natriuretic peptide; 6) ß2-microglobulin; 7) 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF); 8) chloramines; 9) Clara cell protein (CC16); 10) complement factor D; 11) cystatine C; 12) creatinine; 13) dimethylarginine (ADMA); 14) ß-endorphin; 15) glomerulopressin; 16) granulocyte inhibiting protein I (GIP I); 17) granulocyte inhibiting protein II; 18) guanidines; 19) hippuric acid; 20) homocysteine; 21) hyaluronic acid; 22) hypoxanthine; 23) indoles; 24) indoxyl sulfate; 25) leptin; 26) ß-lipotropin; 27) melatonin; 28) methionine-enkephalin; 29) methylamines; 30) myoinositol; 31) neuropeptide Y; 32) nitric oxide; 33) o-hydroxyhippuric acid; 34) oxalate; 35) parathyroid hormone; 36) p-cresol; 37) p-hydroxyhippuric acid; 38) peptides; 39) phenols; 40) phenylacetylglutamine; 41) phosphorus; 42) polyamines; 43) pseudouridine; 44) retinol binding protein; 45) trace elements; 46) trihalomethanes; 47) tryptophan; 48) urea; 49) uric acid; 50) xanthine; 51) xanthopterin
REVIEW ON UREMIC TOXINS: CLASSIFICATION, CONCENTRATION AND INTERINDIVIDUAL
VARIABILITY
EUToX: European Uremic Toxin Work Groupwithin the context of ESAO
Aim: to discuss and analyse matters related to theidentification, characterization, analytical determination and evaluation of biological activityof uremic retention solutes
Website: http://www.uremic-toxins.org
EUROPEAN UREMIC TOXIN WORK GROUP (EUToX)
• A Argiles
• P Brunet
• G Cohen
• PP De Deyn
• B Descamps-Latscha
• T Henle
• A Jörres
• ZA Massy
• M Rodriguez
• B Stegmayr
• P Stenvinkel
• R Vanholder
• C Wanner
• W Zidek
• U Baurmeister
• W Clark
• R Deppisch
• H Lemke
• J Passlick-Deetjen
• C Tetta
RESULTS MAPPING ANALYSIS• Literature search of 857 publications• 141 dealth with concentration (1968-2002)• Data retained from 55 publications• 90 solutes• 68 with MW < 500 D, 22 middle molecules• 12 > 12,000 D• 25 solutes protein bound (mostly small compounds
but also leptin and retinol binding protein)
• Concentrations range from ng/L (methionine-
enkephalin) up to g/L (urea)
Vanholder et al
CONCLUSIONS
• Concentrations of retention solutes in uremia vary over a broad range, from ng/L to g/L
• Low concntrations rae found especially for the MM
• A substantial number of molecules are protein bound and/or MM and hence difficult to remove
• Uremic retention is a complex problem which concerns much more solutes than the current markers urea and creatinine
SMALL WATER SOLUBLE COMPOUNDS
0
100
200
300
400
500
UREA AND CELLULAR K-
INFLUX.
Lim et al, JCI, 96, 2126-2132, 1995.Control Urea 45mM
Bu
met
an
ide
sen
sit
ive
K in
flu
x µ
mo
l/(lo
c.h
)
EFFECT OF INCREASING
PLASMA UREA.
Johnson et al, Mayo Clin. Proc., 47, 21-29, 1972.
600
500
400
300
20015010050B
loo
d u
rea
(mg
/100
mL
)
350
340
330
320
310
280
Ser
um
(m
Osm
/Kg
)
400200
0
Dia
lys
ate
ure
a(m
g/1
00
ml)
5 10 15 20 30 40 50 60 70 80 90 100 110
Days
2520151050
Plasm
a crea
tinin
e (mg
/100mL
)
286
596
Lethargy + + 0 0 0 0 0 0 + + + 0 0 0 + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Headache 3+ 3+ 0 0 0 1+ 1+ 2+0 1+ 0 2+ 0 0 2+ 1+ 1+ 2+ 1+ 1+ 1+ 1+ 1+1+ 0 3+ 1+ 1+ 0 0 Emesis 0 0 0 0 1+ 0 2+ 1+1+1+ 0 2+ 0 0 2+1+ 2+ 2+ 2+ 2+ 2+ 0 0 0 0 2+ 2+ 1+ 0 0Bleeding 0 2+ 2+ 2+ 0 1+ 1+ 1+1+1+ 2+ 2+ 1+ 0 0 1+ 1+ 1+ 1+ 0 0 0 0 0 0 0 1+ 0 0 0 0 Cramps 0 0 0 0 0 0 0 0 0 1+ 0 0 0 0 0 0 0 1+ 1+ 1+ 01+ 0 0 0 0 0 0 0 0 0 Tremor 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2+ 0 0 0
UREA: CORRELATION OF PERCENTAGE REMOVAL
• Significant correlation– pseudouridine: 0.62– uric acid: 0.73– peak 4: 0.54– peak 5: 0.46– creatinine: 0.66– pOHhippurate: 0.47– hippuric acid: 0.46– potassium: 0.26
• No correlation– hypoxanthine: NS– xanthine: NS– indoxyl sulfate: NS– phosphate: NS
Vanholder et al, Clin Chem, 1992.
SMALL WATER SOLUBLE COMPOUNDS
Guanidines Neurotoxicity Inhibition NO-synthesis (?)
Oxalate Tissue deposition
Phosphate Vascular damage Hyperparathyroidism
Purines Resistance to vitamin D
Urea Isolated biochemical functions
PHOSPHATE AND MORTALITY RISK.
Block et al, AJKD, 31, 607-617, 1998.
2.0
1.5
1.0
0.5
RR
1.1-4.5 4.4-5.5 5.6-6.5 6.6-7.8 7.9-16.9
reference
* p=0.03** p<0.0001
1.0 1.01.02
1.18*1.39**
Serum phosphorus Quintile (mg/dL)
PROTEIN BOUND COMPOUNDS
****
P-CRESOL : PHAGOCYTE FUNCTION.
TIME (min)
0 10 20 30 40 50 60
0
20
40
60
80
1000 µg cresol/ml
10 µg cresol/ml
30 µg cresol/ml
50 µg cresol/ml
(CPM)Counts (x103 )
Vanholder et al, KI, 47, 510-517, 1995.
CHEMILUMINESCENCEFACSCAN :
PHAGOTEST/BURSTTEST
Cel
l nu
mb
er
101
102103
1040 µg/mL PC
30µg/mL PC
0 µg/mL PC
30µg/mL PC
Burst
Phago
Log fluorescence units
0
20
40
60
80
100
C pCS pC pCS+pC
CO
2 p
rod
uct
ion
(D
PM
x10³
)
P-CRESOL vs. P-CRESYLSULPHATE
PCS : p-cresylsulphatepC : p-cresol
P-CRESOL
• decrease oxygen uptake rat cerebral cortex slices (Lascelles 1968)
• increase free warfarin and diazepam (MacNamara 1981)• change cell membrane permeability (Keweloh 1991)• growth retardation in the weanling pig (Yokoyama 1992)• LDH-leakage from liver cell slices (Thompson 1994)• susceptibility to epilepsy (Yehuda 1994)• inhibition phagocytic destruction of invading germs (Vanholder
1995)• blockage cell K+ channels (Elliott 1997)• increase cellular toxicity aluminum (Abreo 1997)
• inhibition PAF-synthesis (Wratten 1999)
HOSPITALIZATION RATEIn vivo longitudinal study (n=44)
< 1 week > 1 week< 1 month
> 1 month
mg/
dL *
*: p<0.05 vs hospitalization < 1 week
0.00
0.05
0.10
0.15
0.20
0.25 free p-cresol
MIDDLE MOLECULES
2-M AMYLOID DEPOSITION.
van Ypersele, KI, 39, 1012-1019, 1991.
WESTERN BLOTTING EXPERIMENTS.
Niwa et al, KI, 50, 1303-1309, 1996Lanes 2 : 2M-dimer
SERUM ß2-MICROGLOBULIN AND TREATMENT MODALITY
25
30
35
40
45
50
0 6 12 18 24
Time (months)
2-m
icro
glo
bu
lin
(m
g/d
l)
Cu-HD
LfPS-HD
HfPS-HD
HfPS-HDF
Locatelli et al. Kidney Int 50: 1293-1302, 1996
RELATIVE RISK OF CARPAL TUNNEL SYNDROME
1,00
0,50
1,001,06
0,00
0,20
0,40
0,60
0,80
1,00
1,20
Rel
ativ
e R
isk
Conventional High Flux Age Age + 1 Membrane
Koda et al. Kidney Int 52: 1096-1101, 1997
SERUM LEPTIN vs. EVOLUTION LEAN BODY MASS.
Stenvinkel et al, JASN, 11, 1303-1309, 2000
60
50
40
30
20
10
0
Se
rum
lep
tin
(n
g/m
L)
Gained LBMLost LBM
Initial examination Follow-up
***
EFFECT OF AGE AND AOPP ON LEUKOCYTE RESPONSE
Witko-Sarsat J Immunol 161 : 2524, 1998
Stimulatory effect : increased oxidative stress
HBBS
Opsonized Zymosan
PMA
Control HSA
AGE-HSA
Control HSA
AOPP-HSA
Glycosylationproducts
Oxidationproducts
*
**
0 200 400
Lucigenin CL(counts/20min/monocyte)
GRANULOCYTE INHIBITORY PROTEINSISOLATED FROM HEMO- AND/OR
PERITONEAL DIALYSIS PATIENTS.
• Granulocyte inhibitory protein I:
• Immunoglobulin light chains :• Granulocyte inhibitory
protein II :• Degranulation
inhibiting protein I : • Degranulation
inhibiting protein II :• Chemotaxis inhibiting
protein:
• MW 28kDa, 80% homology to and 40% homology to light chains
• MW 25kDa for monomers, MW 50kDa for dimers
• MW 9.5kDa, homology for 2-microglobulin
• MW 14.4kDa, identical to angiotensin
• MW 24kDa, identical to complement factor D
• MW 8.5kDa, homology to ubiquitin
Cohen et al, KI, 52, S62, S79-S82, 1997.
MM WITH BIOLOGICAL POTENTIAL
• Adrenomedullin• AGE• Angiogenin• AOPP • Atrial natriuretic peptide• Cholecystokin• Clara cell protein• Complement factor D• Cystatin C• Cytokines• Delta sleep inducing
protein
• Endothelin -Endorphin• Glomerulopressin• GIP I• GIP II• Leptin -Lipotropin• Methionine-enkephalin
• ß2-Microglobulin
• Neuropeptide Y • Retinol binding protein
CONCLUSIONS (1)
• Small water soluble compounds do not exert much toxicity. The most toxic ones show a kinetic behavior that is different from that of urea.
• Several protein bound compounds exert toxic effects. Their removal pattern is different from that of urea. Adding flux has no effect on removal of most of these molecules. Alternative removal concepts will have to be developed.
CONCLUSIONS (2)
• Several middle molecules exert toxic effects, especially in the area of inflammation/atherogenesis. Increasing membrane pore size and flux has improved their removal, but concentrations remain far above normal. More removal will have to be persued by changing concepts, although multicompartmental behavior might limit adequacy of removal.
STRATEGIC MODIFICATIONS
• Extracorporeal adsorption
• Intestinal adsorption• Changes in dietary
habits• Prokinetics,
probiotics• Modification of
metabolism, drug therapy
• Neutralisation of biochemical impact (e.g. scavengers)
• Modification protein binding in the devices
• Regenerative medicine– Artificial liver– Artificial tubule