Predictors of selenium biomarker kinetics in 4-9-year-old Bangladeshi children
Helena Skröder1, Maria Kippler1, Jessica De Loma1
1Unit of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden.
Insights
Selenium biomarker concentrations vary due to malnutrition, genetics, and metal exposure. These factors may impact the assessment of selenium status, particularly when relying on plasma or serum levels.
Area of Science:
- Environmental Health
- Nutritional Science
- Biomarker Research
Background:
- Selenium biomarker concentrations exhibit significant inter-study variability.
- Discrepancies in erythrocyte, urine, and hair selenium levels, even with similar plasma concentrations, indicate unknown distribution factors.
Purpose of the Study:
- To identify predictors of varying selenium biomarker levels in children.
- To investigate the influence of environmental and genetic factors on selenium distribution across different body compartments.
Main Methods:
- Utilized a mother-child cohort from a supplementation trial in Bangladesh (MINIMat).
- Measured selenium, arsenic, and cadmium in plasma, erythrocytes, urine, and hair using inductively coupled plasma mass spectrometry.
- Genotyped for the INMT gene, involved in selenium metabolism.
Main Results:
- Plasma selenium levels varied by season and were inversely associated with plasma arsenic.
- Erythrocyte selenium correlated positively with erythrocyte arsenic and inversely with erythrocyte cadmium.
- Selenium in hair and urine were influenced by INMT polymorphisms, while malnutrition appeared to increase selenium retention.
Conclusions:
- Selenium biomarker levels are influenced by malnutrition, genetic factors (INMT), and exposure to metal pro-oxidants (arsenic, cadmium).
- These influencing factors may complicate the accurate assessment of selenium deficiency or sufficiency, typically evaluated using plasma/serum selenium concentrations.
Background:
Biomarker selenium concentrations vary greatly between studies. Concentrations in erythrocytes, urine, and hair vary even at similar plasma concentrations, suggesting that unknown factors influence the distribution of selenium between body compartments.
Objective:
To assess predictors of the different selenium biomarkers in children.
Design:
We used a mother-child cohort, nested in a population-based supplementation trial in rural Bangladesh (MINIMat), established for evaluation of arsenic toxicity. Selenium was measured in plasma (n = 223), erythrocytes, urine, and hair at 9 years (n = 395) and in erythrocytes and urine at 4.5 years (n = 259) using inductively coupled plasma mass spectrometry. We also measured concentrations of arsenic (all biospecimen) and cadmium (erythrocytes and urine). Genotyping for INMT, a methyltransferase involved in selenium metabolism, was performed using TaqMan probes.
Results:
At 9 years, the selenium concentrations ranged 51-139 μg/L in plasma, 128-281 μg/L in erythrocytes, 2.2-55 μg/L in urine, and 258-723 μg/kg in hair. Correlations (rS) between biomarkers ranged 0.12-0.37, and were strongest between blood compartments and between erythrocytes and hair (long-term markers). In multivariable-adjusted linear regression analyses, plasma selenium differed by sampling season (highest in food-secure pre-monsoon season) and was inversely associated with plasma arsenic (range < 0.0080-20 μg/L; B = -1.1, 95% CI: -1.8, -0.41). In contrast, erythrocyte selenium was positively associated with erythrocyte arsenic (range 0.95-50 μg/L; B = 0.58, 95% CI: 0.26, 0.91) and inversely associated with erythrocyte cadmium (range 0.27-3.1 μg/L; B = -12, 95% CI: -17, -6.9). These associations were similar at 4.5 years. Only selenium in hair and urine were influenced by INMT polymorphisms. Finally, chronic malnutrition seemed to increase selenium retention, measured as the ratio plasma/urinary selenium.
Conclusions:
Selenium biomarkers seem to be influenced by malnutrition, genetics, and exposure to metal pro-oxidants. This might affect the evaluation of deficiency/sufficiency, normally assessed by selenium in plasma/serum.
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