Homocysteine in chronic kidney disease: Effect of low protein diet and repletion with B vitamins.
BACKGROUND
Data are limited on the determinants of homocysteine (tHcy) and its relationship with nutritional indices, and dietary protein intake, in the earlier stages of chronic kidney disease (CKD).


METHODS
Levels of tHcy were assayed at baseline (N= 804) and 1 year postrandomization (N= 678) in the Modification of Diet in Renal Disease (MDRD) Study [study A, glomerular filtration rate (GFR) 25 to 55 mL/min/1.73 m(2) and study B GFR 13 to 24 mL/min/1.73 m(2)]. Participants were randomly assigned to different blood pressure targets and protein diets and all subjects received a multivitamin supplement containing 1 mg of folic acid, 10 mg pyridoxal 5'-phosphate (PLP) and 6 mug of vitamin B(12). Multivariable analyses were used to evaluate determinants of tHcy at baseline and 1 year.


RESULTS
The prevalence of hyperhomocysteinemia (tHcy >15 mumol/L) at baseline was 56% in study A and 85% in study B. Baseline tHcy was negatively correlated with measures of body fat and dietary protein intake. Folate, vitamin B(12), and GFR were the major determinants of tHcy levels. Of the patients with hyperhomocysteinemia at baseline, 49% and 24% reduced their tHcy levels at 1 year to < or =15 micromol/L in study A and study B, respectively. There was no association between dietary protein intake and odds of developing hyperhomocysteinemia at 1 year in study A (P= 0.94) or study B (P= 0.10).


CONCLUSIONS
Hyperhomocysteinemia is partly amenable to correction by vitamin supplementation in CKD stages 3 and 4. There is insufficient evidence to suggest that low tHcy is associated with poor nutritional status in the MDRD Study cohort. B vitamins and GFR, but not dietary protein, are the major determinants of tHcy in this patient population.
Menon
Vandana
V
Department of Medicine, Division of Nephrology, Tufts-New England Medical Center, Boston, Massachusetts 02111, USA.
Wang
Xuelei
X
Greene
Tom
T
Beck
Gerald J
GJ
Kusek
John W
JW
Selhub
Jacob
J
Levey
Andrew S
AS
Sarnak
Mark J
MJ
D000704:Analysis of Variance; D018753:Diet, Protein-Restricted; D019587:Dietary Supplements; D005260:Female; D005919:Glomerular Filtration Rate; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000453:epidemiology; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000178:diet therapy*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D014803:Vitamin B Complex / Q000008:administration & dosage / Q000627:therapeutic use*
D006710:Homocysteine; D014803:Vitamin B Complex