The concentration of free holo-retinol binding protein is higher in vitamin A-sufficient than in deficient Nepalese women in late pregnancy.
Free holo-retinol binding protein (RBP) [i.e., unbound to transthyretin (TTR)] plays a role in transporting vitamin A across the placenta during pregnancy. In a cross-sectional study of clinically healthy urban women, we assessed the association among clinical and biochemical factors on estimated concentrations of free holo-RBP during the last trimester of pregnancy. Serum samples obtained from a subsample of women (n = 259), who had participated in the Night Vision Threshold Test study in Nepal, were analyzed for determinations of retinol by HPLC, and RBP, TTR, and alpha-1 acid glycoprotein by radial immunodiffusion. Free holo-RBP concentrations were calculated using dissociation constants for free holo- and apo-RBP. Among these women, 30% were vitamin A deficient based on either the RBP:TTR index < or = 0.36 or serum retinol < 1.05 micromol/L. Using stepwise regression analyses, the RBP:TTR index explained 75% of the variance in free holo-RBP concentrations, whereas retinol explained only 14%. Women were classified as vitamin A sufficient (n = 185) or deficient (n = 74) using the RBP:TTR index and were stratified into 3 gestational groups (I: 24-28 wk, II: 29-33 wk, III: >33 wk). Concentrations of free holo-RBP were higher in vitamin A-sufficient women than in vitamin A-deficient women (mean +/- SEM, 48.1 +/- 1.2 vs. 27.6 +/- 0.8 nmol/L; P < 0.001), and in a 3 x 2 factorial analysis, the interaction between gestational group and vitamin A status was significant. These results demonstrate that the RBP:TTR index is a useful proxy for free holo-RBP concentration and that vitamin A status affects its distribution.
Sankaranarayanan
Sandhya
S
The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, USA.
Suárez
Monica
M
Taren
Douglas
D
Genaro-Wolf
Denise
D
Duncan
Burris
B
Shrestha
Kamal
K
Shrestha
Narayani
N
Rosales
Francisco J
FJ
D000328:Adult; D001798:Blood Proteins / Q000378:metabolism; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D009390:Nepal; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood*; D011263:Pregnancy Trimester, Third; D012044:Regression Analysis; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000097:blood*
D001798:Blood Proteins; D012177:Retinol-Binding Proteins