the influence of gut microbiota on the speciation & toxicity of mercury during pregnancy:...
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The Influence of Gut Microbiota on the Speciation & Toxicity of Mercury During Pregnancy:
Results from a Feasibility Pilot
Sarah E. Rothenberg1 and Sharon Keiser2
1USC Department of Environmental Health Sciences, 2Greenville Health System,
Department of Obstetrics and Gynecology
March 21, 2014
The human gut is populated by up to 100 trillion (1014) microbes, with a vast majority in the distal gut
Gut ecology differ between life-stages, including early/late pregnancy
References: Biagi et al., 2010; Koenig et al., 2011; Koren et al., 2012
Inorganic Hg is less toxic than methylmercury (MeHg).
MeHg is a neurotoxin, that crosses the placental barrier.
Hg methylation and MeHg demethylation are microbially-mediated processes, and are both important in the gut.
References: Clarkson & Magos, 2006; Parks et al., 2013; Rowland, 1995
For mercury (Hg), speciation determines toxicity
Hypothesis: Shifts in gut microbiota during pregnancy will influence prenatal MeHg exposure.
Approach: In fall 2013, in collaboration with Greenville Health System (OB/GYN), complete a feasibility pilot including measurement of MeHg in maternal hair and stool samples, and cord blood samples.
• Pregnant women (36-39 wk gestation) were recruited
• Approx. 40 women were interviewed, 19 provided informed consent
• 17 mothers provided both hair and stool samples
• Cord blood was collected at parturition (n=7)
FEASIBILITY PILOT
Average Hair Total Mercury (THg): 0.057 g/g
Average Hair THg levels were >20 times lower than US reference dose (1.2 g/g)
Hair THg (g/g)
Fre
qu
ency
Average Hair Total Mercury (THg): 0.057 g/g
Average Hair THg levels were >20 times lower than US reference dose (1.2 g/g)
Fre
qu
ency EPA reference
dose: 1.2 g/g
Hair THg (g/g)
However, in the absence of dietary MeHg exposure, stool MeHg content was measurable
Stool MeHg (pg/g)
Fre
qu
ency
Percent MeHg (of THg): <1-5.8%
Log
10 S
tool
MeH
g (p
g/g)
Log10 Stool THg (ng/g)
Stool MeHg content was positively correlated with stool THg content (non-significant)
r-squared=0.06p=0.33
Log
10 S
tool
MeH
g (p
g/g)
Trimester 1 BMI (kg/m2)
Stool MeHg content was inversely correlated with trimester 1 Body Mass Index (BMI) (non-significant)
r-squared=0.09p=0.25
Log
10 S
tool
MeH
g (p
g/g)
Log10 Cord Blood MeHg (g/L)
Stool MeHg content was positively correlated with cord blood MeHg (non-significant)
r-squared=0.33p=0.18
Future work (among a larger cohort):
•Verify whether MeHg production in the gut results in higher prenatal MeHg exposure
•Address whether shifts in gut microbiota between 1rst and 3rd trimesters are associated with changes in net MeHg production
•Determine the dietary sources of inorganic Hg that promote Hg methylation in the gut.
ACKNOWLEDGEMENTS
Greenville Health System OB/GYN Research StaffUSC Department of Environmental Health Sciences
Students/postdocs: Chuan Hong for help with hair THg and MeHg analysesSi Chen for help with stool MeHg analyses