Impact of Phthalate exposure in fathers on programming of offspring neurological phenotype
Chief Investigator: Professor Sarah Robertson
Funding Amount: $73,445
Recipient: University of Adelaide
Autism spectrum disorder (ASD) is a complex developmental disorder which effects 1:100 Australians. It is accepted that unknown environmental factors contribute to ASD risk, with studies linking changes in the gametes and conception environment to increased risk. There is speculation that endocrine disrupting compound (EDC) exposure contributes to ASD. Animal models indicate that maternal preconception EDC exposure alters offspring brain development, but few studies evaluate paternal EDC exposure, despite epidemiological data linking male pre-conception EDC exposure to poor childhood health.
Researchers: Professor Sarah Robertson, Dr John Schjenken, Emeritus Professor Emilie Rissman, Dr Jimmy Breen, Dr Lachlan Moldenhauer
Research Completed: 2020
Research Findings: Endocrine Disrupting chemicals (EDC) interfere with hormone biology and have consequences for reproduction. Here, we examined the consequences of male exposure to a common EDC present in many household products, di-2-ethylhexyl phthalate (DEHP). We demonstrated that while the chances of conceiving was not impacted after 10 week’s exposure to DEHP, offspring born from exposed males had reduced survival rates and altered growth after birth, as well as a higher chance of cardiovascular defects. These results help build the evidence base for avoiding phthalates prior to pregnancy in men as well as women, and highlight the need for further investigation of similar effects in humans, and to understand the mechanisms by which male EDC exposure alters fertility and child health.
Parental health prior to conception shapes fetal development, the health of the child after birth, and substantially impacts life-course trajectory. Both parents contribute, with recent studies highlighting a critical role of fathers as well as mothers. One important aspect that is only recently coming to light is the role of paternal exposures to environmental toxins, including endocrine-disrupting chemicals (EDCs). EDCs are present in a wide range of household objects including plastic food containers, cosmetics and body-care products, cleaning products, and furniture and computer equipment.
While the impacts of maternal EDC exposure to offspring health and behaviour are well established, there is almost no research to date on the contribution of paternal exposures. Epidemiological evidence has shown clear associations between EDC chemicals and negative effects on human reproduction, with male exposure impacting sperm quality. Despite this knowledge, there has been little research undertaken in Australia to investigate developmental impacts of paternal EDC exposure, despite emerging evidence of its importance to child health and links to various conditions. Also, there no information on the mechanisms by which low doses of EDCs can affect fertility – whether this is mediated at the level of sperm, or other components of seminal fluid that are important for conception and pregnancy health.
In this project, we investigated the impacts of paternal EDC exposure on reproductive parameters, pregnancy outcomes and offspring health. We used the model EDC, di-2-ethylhexyl phthalate (DEHP) to do this. Male C56Bl/6 mice (N = 5/group) were administered DEHP (0.4, 2, 10, 50 mg/kg/day) on cocoa-flavoured treats at doses which mimic average to high exposures in humans. As controls we used ethanol and untreated cocoa-flavoured treats. Male mice were treated with DEHP daily for 10 weeks prior to mating with females to assess pregnancy outcomes and offspring health and behaviour. Males were then necropsied to assess the impact of DEHP exposure on their reproductive tissues and overall health.
We initially assessed the detectable levels of DEHP in males at necropsy and showed a dose dependent increase in serum DEHP and its metabolites across treated groups that matched with the doses provided. However, despite this, males showed no impact of paternal DEHP exposure on body composition or sperm quality. Females mated with DEHP treated males showed no impacts on pregnancy outcomes when assessed towards the end of gestation (d17.5 post coitus). However, following birth, we observed a decrease in survival rates in offspring of males treated with DEHP. Further, in those offspring that survived, offspring sired by a DEHP-treated male had increased body weight and evidence of cardiac dysfunction. This was evident even at low doses of DEHP, consistent with other studies showing low dose effects. In summary, this study provides new evidence indicating that paternal DEHP exposure prior to conception impacts the health of offspring, with life-long consequences, even without overt impact on male fertility and capacity to conceive. The data raise questions that warrant further investigation. In particular, we wish to know more about which other aspects of offspring development are affected as well as growth and cardiovascular health. To further assess this we have performed behavioural analysis of offspring (analysis to be finalised) and collected components of the ejaculate (sperm and seminal vesicle fluid) for assessment of factors impacted by DEHP in the male ejaculate. This work helps to build the case for human studies, and will inform the design of studies aiming to investigate the effects of EDCs on sperm and seminal plasma constituents in men. Additionally, through defining the underlying mechanisms, new targets for therapeutic interventions and preventative strategies can be developed, in an effort to mitigate the risk to future generations exposed to EDCs in early life.
Publications in preparation:
- Schjenken JE, Green ES, Talarovicova A, Mah S, Overduin TS, Moldenhauer LM, Rissman EF, and Robertson SA. Inflammatory effects of endocrine disrupting chemicals and dysregulation of reproductive function.
A Review paper in preparation, anticipated submission date of May 2020
- The impact of paternal phthalate exposure on male reproductive function and offspring health
The results of the study require further analysis, but when this is completed the work will be submitted for publication to a high quality peer-reviewed journal, anticipated submission date of July 2020.