Effect of haptoglobin on the metabolism of vitamin C.
Haptoglobin is a hemoglobin-binding antioxidant showing a genetic polymorphism with three types: Hp 1-1, Hp 2-1, and Hp 2-2. The Hp 2-2 type has been associated with an increased risk of atherosclerosis. We investigated vitamin C metabolism in vivo and in vitro according to haptoglobin type in a study group of 135 healthy volunteers. Serum vitamin C concentrations were associated with haptoglobin type, showing lowest values in serum from Hp 2-2 subjects (P < 0.01). Renal threshold for L-ascorbic acid was within the normal range and metabolization to oxalate was not different among haptoglobin-type groups. Serum concentrations of other endogenous antioxidants (uric acid, bilirubin, albumin, ceruloplasmin, and total antioxidative status) were not different among haptoglobin-type groups. In vitro experiments showed a lower stability of L-ascorbic acid in blood from subjects with the Hp 2-2 type (P < 0.01). L-Ascorbic acid depletion in vitro was inversely related to haptoglobin concentration (r = -0.738). The results of this study indicate a higher rate of L-ascorbic acid oxidation in Hp 2-2 carriers because they have less protection against hemoglobin-iron driven peroxidation.
Langlois
M R
MR
Central Laboratory, University Hospital Gent, Belgium.
Delanghe
J R
JR
De Buyzere
M L
ML
Bernard
D R
DR
Ouyang
J
J
D000328:Adult; D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D006242:Haptoglobins / Q000235:genetics / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010070:Oxalates / Q000652:urine
D000975:Antioxidants; D006242:Haptoglobins; D006454:Hemoglobins; D010070:Oxalates; D002097:C-Reactive Protein; D001205:Ascorbic Acid