Effects of Inflammation on Biomarkers of Vitamin A Status among a Cohort of Bolivian Infants

Abstract

Globally, vitamin A deficiency (VAD) affects nearly 200 million children with negative health consequences. VAD can be measured by a retinol-binding protein (RBP) and serum retinol concentrations. Their concentrations are not always present in a 1:1 molar ratio and are affected by inflammation. This study sought to quantify VAD and its impact on infant mortality and infectious morbidity during the first 18 months of life in a cohort of mother-infant dyads in El Alto, Bolivia, while accounting for the previously mentioned measurement issues. Healthy mother-infant dyads (n = 461) were enrolled from two hospitals and followed for 12 to 18 months. Three serum samples were collected (at one to two, six to eight, and 12 to 18 months of infant age) and analyzed for RBP, and a random 10% subsample was analyzed for retinol. Linear regression of RBP on retinol was used to generate RBP cut-offs equivalent to retinol <0.7 µmol/L. All measures of RBP and retinol were adjusted for inflammation, which was measured by a C-reactive protein and alpha (1)-acid glycoprotein serum concentrations using linear regression. Infant mortality and morbidity rates were calculated and compared by early VAD status at two months of age. Retinol and RBP were weakly affected by inflammation. This association varied with infant age. Estimated VAD (RBP < 0.7 µmol/L) decreased from 71.0% to 14.8% to 7.7% at two, six to eight, and 12 to 18 months of age. VAD was almost nonexistent in mothers. Early VAD was not significantly associated with infant mortality or morbidity rates. This study confirmed a relationship between inflammation and vitamin A biomarkers for some subsets of the population and suggested that the vitamin A status in early infancy improves with age and may not have significantly affected morbidity in this population of healthy infants.

Keywords: global micronutrient malnutrition; infant nutrition; micronutrient deficiencies; vitamin A deficiency.

Figure 1

Prevalence of infant vitamin A deficiency (VAD; RBP < 0.70 µmol/L) and mean RBP by quintiles of the C-reactive protein (CRP) and the alpha(1)-acid glycoprotein (AGP) and by blood draw. Panels (A–C) show VAD by CRP quintiles for blood drawn at ~2, 6–8, and 12–18 months, respectively. Panels (D–F) show VAD by AGP quintiles for the same time periods. The prevalence of VAD was not significantly different (Cochran Armitage trend test, p = 0.23) by CRP quintile for infants measured at the first blood draw (~2 months of age, panel (A)) even though VAD seemed to decrease slightly by the AGP quintile at the first blood draw (Cochran Armitage trend test, p = 0.0001, panel (D)). However, prevalence of VAD significantly increased by CRP and AGP quintile for infants at the second and third blood draws (6–8 and 12–18 months of age).

Figure 2

The mean maternal retinol binding protein (RBP) by quintiles of the alpha(1)-acid glycoprotein (AGP) and the C-reactive protein (CRP) by blood draw. Panel (A) shows results for the first blood draw (~1 month postpartum) and panel (B) shows results for the second blood draw (~6 months postpartum). The mean RBP was not significantly different (Wilcoxon signed rank test, p > 0.05) by CRP or AGP quintile for mothers at either blood draw.