7. Maternal blood metal levels and fetal markers of metabolic function (lay summary)

Ashley-Martin J, Dodds L, Arbuckle TE, Ettinger AS, Shapiro GD, Fisher M, Taback S, Bouchard MF, Monnier P, Dallaire R, Fraser WD. Environmental Research. 2015;136:27-34. doi: 10.1016/j.envres.2014.10.024

In this study, researchers investigated the possible harmful effects of prenatal exposure to metals on fetal markers of metabolic function and fetal growth using data from the MIREC Study. The fetal period is a time of greater susceptibility to the potential harmful effects of environmental contaminants, and previous research has suggested that maternal exposure to metals commonly found in the environment may have harmful effects on fetal growth. Examining indicators, or biomarkers, of metabolic function in the fetus allows us to assess the susceptibility of fetal development to environmental contaminants. (A biomarker is any measurable substance in an organism that can be used as an indicator of a particular disease, environmental exposure, or some other biological state).

People may be exposed to metals through contaminated food or water, industrial emissions, or cigarette smoking. In this study, researchers looked at the relationship between prenatal exposure to four metals – lead, mercury, arsenic, and cadmium – and fetal metabolic function using biomarkers in the umbilical cord blood of newborn infants. In addition, average levels of these metals in maternal blood samples taken in the 1st and 3rd trimester were used to gauge prenatal exposure to the four metals.

Certain hormones are involved in metabolic function, and two in particular – leptin and adiponectin (known as adipokines) – may help to predict childhood growth patterns. Low levels of adiponectin and high levels of leptin may be associated with adverse metabolic function. The levels of these hormones were measured in 1,363 umbilical cord blood samples and served as biomarkers of fetal metabolic function in this study.

It was found that the levels of leptin in the cord blood of newborn infants were higher among females than males, while the levels of adiponectin were about the same among males and females. The study also found that, compared to women with low levels of exposure, women with higher blood levels of cadmium were more likely to have infants with high levels of leptin in their cord blood. But this association, or link, was seen only among male infants. No meaningful relationships were found between the other metals and these biomarkers of metabolic function. However, when birth weight was considered, lead was linked to increased odds of high leptin levels.

The results of this research suggest that prenatal exposure to some metals may affect the metabolic development of the fetus, and that the influence of maternal levels of cadmium on the levels of the hormones leptin and adiponectin in the umbilical cord blood of newborn infants is sex-dependent. However, further research is needed to corroborate these findings and to better understand how prenatal exposures to contaminants, such as cadmium, may potentially affect growth patterns in childhood.