End-stage renal disease increases plasma transcobalamin and neutralizes influence of TCN 776C>G polymorphism.

2092 Letters to the Editor

at any current frequency [4]. Linearity supports validity of monitoring with only pre- and postdialysis measure- ments.

A NTONIO P ICCOLI and M ARTA C ODOGNOTTO

Padova, Italy Correspondence to Prof. Antonio Piccoli, Dept. Scienze Mediche e Chirurgiche, Policlinico IV piano, Via Giustiniani, 2, I-35128 Padova, Italy.

E-mail: apiccoli@unipd.it

REFERENCES

1. D

I

I

ORIO

BR, S

CALFI

L, T

ERRACCIANO

V, B

ELLIZZI

V: A systematic evaluation of bioelectrical impedance measurement after hemodial- ysis session. Kidney Int 65:2435–2440, 2004

2. P

ICCOLI

A, N

IGRELLI

S, C

ABERLOTTO

A, et al: Bivariate normal values of the bioelectrical impedance vector in adult and elderly popula- tions. Am J Clin Nutr 61:269–270, 1995

3. P

ICCOLI

A,

FOR THE

I

TALIAN

HD-BIA S

TUDY

G

ROUP

: Identification of operational clues to dry weight prescription in hemodialysis using bioimpedance vector analysis. Kidney Int 53:1036–1043, 1998 4. P

ICCOLI

A, P

ASTORI

G, G

UIZZO

M, et al: Equivalence of information

from single versus multiple frequency bioimpedance vector analysis in hemodialysis. Kidney Int, in press

Reply from the Authors

We appreciate Piccoli’s interest in our article [1], and thank him for further analysis of the data we presented.

We fully agree that a cyclical variation in BIA variables was apparent in hemodialysis patients during both dialy- sis and interdialysis periods according to the concept that dialysis causes a reduction of total body water, and es- pecially (or only) of extracellular body water, and that total body water progressively increases between dialysis sessions due to water retention.

Indeed, change in resistance, reactance, and phase an- gle during a hemodialysis session can be affected by other factors, such as an increase in hematocrit, variations in electrolytes concentration, a rapid shift from intracellu- lar to extracellular water, and others [2]. As a matter of fact, acute changes in body water induced by dialysis are not predicted well by data derived from BIA [3], and when BIA was applied to estimate the fluid loss during hemodialysis, overestimation usually occurred. As a con- sequence, changes in BIA variables during either dialysis or interdialysis periods are expected to reflect variation in total body water and its extracellular/intracellular dis- tribution, but also to be affected by other factors. Further studies seem necessary to us to understand to which ex- tent these data can be compared with those obtained in a healthy population or in predialysis patients. In addition, our results indicate that the measurement timing with re- spect to dialysis session is a crucial aspect in assessing BIA in such patients. Furthermore, since phase angle is considered an independent marker of survival [ 4–6], the

point of time for performing the analysis may influence the prognostic significance of such a parameter.

V INCENZO B ELLIZZI , L UCA S CALFI , and B IAGIO R. D I I ORIO

Avellino, Italy Correspondence to Dr. Vincenzo Bellizzi, Unit`a Operativa Complessa di Nefrologia e Dialisi, Ospedale “A. Landolfi,” Via Melito, 83029 Solofra (AV), Italy.

E-mail: vincenzo.bellizzi@tin.it

REFERENCES

1. D

I

I

ORIO

BR, S

CAL

fi L, T

ERRACCIANO

V, B

ELLIZZI

V: A systematic evaluation of bioelectrical impedance measurement after hemodial- ysis session. Kidney Int 65:2435–2440, 2004

2. K

USHNER

RF,

DE

V

RIES

PM, G

UDIVAKA

R: Use of bioelectrical impedance analysis measurements in the clinical management of pa- tients undergoing dialysis. Am J Clin Nutr 64(Suppl 3):503S–509S, 1996

3. K

URTIN

PS, S

HAPIRO

AC, T

OMITA

H, R

AIZMAN

D: Volume status and body composition of chronic dialysis patients: Utility of bioelectric impedance plethysmography. Am J Nephrol 10:363–367, 1990 4. M

AGGIORE

Q, N

IGRELLI

S, C

ICCARELLI

C, et al: Nutritional and prog-

nostic correlates of bioimpedance indexes in hemodialysis patients.

Kidney Int 50:2103–2108, 1996

5. C

HERTOW

GM, J

ACOBS

DO, L

AZARUS

JM, et al: Phase angle predicts survival in hemodialysis patients. J Renal Nutr 7:204–207, 1997 6. D

I

I

ORIO

B, T

ERRACCIANO

V, Q

UERQUES

M, et al: Bioimpedance in-

dexes predict survival in hemodialysis patients. J Renal Nutr 7:216–

217, 1997

End-stage renal disease increases plasma

transcobalamin and neutralizes influence of TCN 776C > G

polymorphism

To the Editor: A lack of influence of TCN 776C>G

has been recently reported on transcobalamin and ho-

mocysteine plasma levels in two series of patients with

kidney transplant and end-stage renal disease (ESRD),

contrary to what was previously observed in a healthy

population [1–3]. In the ESRD series, which included

66 hemodialysis patients, influences of MTHFR 677TT

(P = 0.024) and TCN 776CC (P = 0.036) on homocysteine

disappeared in a multivariate model that included a com-

bination of 677TTx776CC genotypes, a confounder of

each polymorphism [2]. The lack of influence of MTHFR

agreed with some of the previous data [4]. We performed

a similar study in 55 nonsupplemented hemodialysis pa-

tients. We confirmed the lack of influence of either TCN

Letters to the Editor 2093

Table 1. Independent determinants of homocysteine and transcobalamin in 55 hemodialysis patients

95% P value P value

Dependent Independent Correlation confidence univariate multiple

determinant determinant coefficient interval regression regression

^a

Homocysteine

Creatinine 0.448 0.249, 0.685 0.0002 <0.0001

Folate − 0.462 − 0.652, − 0.216 0.0005 0.0005

Cholesterol 0.314 0.018, 0.559 0.0377 0.1268

Triglycerides 0.279 − 0.019, 0.532 0.0664 0.1417

Albumin 0.213 − 0.076, 0.469 0.1471 0.9518

Vitamin B

₁₂

− 0.167 − 0.418, 0.234 0.2342

C-reactive prot − 0.142 − 0.415, 0.155 0.3496

Transcobalamin 0.103 − 0.184, 0.373 0.4841

ALAT 0.132 − 0.416, 0.175 0.5562

Transcobalamin

ALAT 0.636 0.417, 0.784 < 0.0001 < 0.0001

Creatinine 0.190 − 0.099, 0.450 0.1179 0.0609

Cholesterol − 0.225 − 0.486, 0.073 0.1380 0.0655

Albumin − 0.123 − 0.391, 0.164 0.4013

Folate − 0.117 − 0.383, 0.167 0.4197

Homocysteine 0.103 − 0.184, 0.373 0.4841

C-reactive prot − 0.083 − 0.367, 0.216 0.5920

Vitamin B

₁₂

− 0.076 − 0.344, 0.204 0.5978

Triglycerides − 0.032 − 0.322, 0.264 0.8375

a

The multiple regression analysis included only the parameters that presented a P value lower than 0.2 in univariate analysis.

or MTHFR polymorphisms, and found a weak effect of TCN 776G × MTHFR 677T allele combination on ho- mocysteine (carriers vs. noncarriers 40.5 ± 11.3 vs. 30.9 ± 10.7 lmol/L, P = 0.0158). The single determi- nant of plasma apo-transcobalamin was alanine- aminotransferase, while creatinine was under the limit of significance (Table 1). The level was higher in ESRD, compared to 109 matched controls (719 ± 354 vs. 464 ± 160 pmol/L, P < 0.0001). ESRD increased plasma transcobalamin by an unknown mechanism, possibly re- lated to glomerular filtration and tubular uptake. Un- der these conditions, the influence of TCN 776C>G on plasma transcobalamin may be limited, despite its effect on TCN transcription and transcobalamin intracellular concentration [3]. Therefore, in our opinion, the data of the authors are less conflicting than suggested because the weak influence of TCN 776C>G was initially reported in a healthy population without low serum B 12 [1], drug use [1], and renal dysfunction [2].

W AFAA A NWAR , P HILIPPE G ´ ERARD , A BDERAHIM M OUTABARREK , F AR ES ` N AMOUR , and J EAN -L OUIS G U EANT ´ Vandoeuvre-Nancy, France, and Casablanca, Morocco Correspondence to Professor Jean-Louis Gu´eant, Laboratoire de Pathologie Cellulaire et Mol´eculaire en Nutrition, Equipe INSERM 00- 14, Facult´e de M´edecine, B.P. 184, 54505 Vandoeuvre-l`es-Nancy Cedex, France.

E-mail: Jean-Louis.Gueant@facmed.u-nancy.fr

REFERENCES

1. W

INKELMAYER

WG, S

KOUPY

S, E

BERLE

C, et al: Effects of TCN2 776C>G on vitamin B

12

, folate, and total homocysteine levels in kidney transplant patients. Kidney Int 65:1877–1881, 2004

2. F ¨

ODINGER

M, V

EITL

M, S

KOUPY

S, et al: Effect of TCN2 776C>G on vitamin cellular availability in end-stage disease patients. Kidney Int 64:1095–1100, 2003

3. N

AMOUR

F, O

LIVIER

JL, A

BDELMOUTTALEB

I, et al: Transcobalamin codon 259 polymorphism in HT-29 and Caco-2 cells and in Cau- casians: Relation to transcobalamin and homocysteine concentration in blood. Blood 97:1092–1098, 2001

4. A

NWAR

W, G

UEANT

JL, A

BDELMOUTTALEB

I, et al: Hyperhomocys- teinemia is related to residual glomerular filtration and folates but not to methylenetetrahydrofolate-reductase and methionine syn- thase polymorphisms, in supplemented end-stage renal disease pa- tients undergoing hemodialysis. Clin Chem Lab Med 39:747–752, 2001

Microinflammation versus inflammation in chronic renal failure patients

To the Editor: In their study, Pupim et al [1] show that

patients with end-stage renal failure (ESRF) in the high-

est quartile of C-reactive protein (CRP) and interleukin-6

(IL-6) before hemodialysis (HD) initiation have a signif-

icant decrease in the serum level of both markers after

12 months of HD treatment. The baseline levels for IL-6

and CRP in these subgroups were about 58 pg/mL and

62 mg/L, respectively. As the authors note, no exclusion

criteria were used for enrollment in the study. These CRP

and IL-6 serum levels are probably indicative of an infec-

tion or other cause of “real inflammation” (trauma, ma-

lignancy, etc.). In the referred study microinflammation

investigation is warranted. It is low-grade inflammation