Effect of vitamin B-6 deficiency on fasting plasma homocysteine concentrations.
The catabolism of homocysteine through cystathionine synthesis requires pyridoxal-5'-phosphate, thus the effect of vitamin B-6 deficiency on plasma homocysteine concentrations was evaluated. Total fasting plasma homocysteine concentrations were measured in 11 elderly subjects aged 64.4 +/- 1.7 y (mean +/- SE) who consumed a vitamin B-6-deficient diet for less than or equal to 20 d. Only 1 of the 11 subjects was found to have elevated homocysteine concentrations even though all subjects exhibited high urinary xanthurenic acid concentrations after a tryptophan load, a measure indicative of vitamin B-6 deficiency. In a supporting study, fasting plasma homocysteine concentrations were measured in 3- and 23-mo-old rats fed vitamin B-6-deficient diets and were compared with those of vitamin B-6-replete, pair-fed controls. There was no difference in homocysteine concentrations between deficient and pair-fed animals after 6 wk of the dietary regimen for either age group; after 9 wk a modest elevation was observed in the 3-mo-old deficient rats whereas no difference was observed for the 23-mo-old rats. It is concluded that fasting plasma homocysteine concentrations are not initially elevated in vitamin B-6 deficiency and therefore fasting plasma homocysteine concentrations are not a good indicator of vitamin B-6 status.
Miller
J W
JW
USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111.
Ribaya-Mercado
J D
JD
Russell
R M
RM
Shepard
D C
DC
Morrow
F D
FD
Cochary
E F
EF
Sadowski
J A
JA
Gershoff
S N
SN
Selhub
J
J
D000368:Aged; D000818:Animals; D001835:Body Weight; D004435:Eating; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D051381:Rats; D011916:Rats, Inbred F344; D014364:Tryptophan; D026681:Vitamin B 6 Deficiency / Q000097:blood*; D014977:Xanthurenates / Q000652:urine
D014977:Xanthurenates; D006710:Homocysteine; C028330:xanthurenic acid; D014364:Tryptophan