Perinatal exposures to phthalates and phthalate mixtures result in sex-specific effects on body weight, organ weights and intracisternal A-particle (IAP) DNA methylation in weanling mice

Abstract

Developmental exposure to phthalates has been implicated as a risk for obesity; however, epidemiological studies have yielded conflicting results and mechanisms are poorly understood. An additional layer of complexity in epidemiological studies is that humans are exposed to mixtures of many different phthalates. Here, we utilize an established mouse model of perinatal exposure to investigate the effects of three phthalates, diethylhexyl phthalate (DEHP), diisononyl phthalate (DINP) and dibutyl phthalate (DBP), on body weight and organ weights in weanling mice. In addition to individual phthalate exposures, we employed two mixture exposures: DEHP+DINP and DEHP+DINP+DBP. Phthalates were administered through phytoestrogen-free chow at the following exposure levels: 25 mg DEHP/kg chow, 25 mg DBP/kg chow and 75 mg DINP/kg chow. The viable yellow agouti (A vy ) mouse strain, along with measurement of tail DNA methylation, was used as a biosensor to examine effects of phthalates and phthalate mixtures on the DNA methylome. We found that female and male mice perinatally exposed to DINP alone had increased body weights at postnatal day 21 (PND21), and that exposure to mixtures did not exaggerate these effects. Females exposed to DINP and DEHP+DINP had increased relative liver weights at PND21, and females exposed to a mixture of DEHP+DINP+DBP had increased relative gonadal fat weight. Phthalate-exposed A vy /a offspring exhibited altered coat color distributions and altered DNA methylation at intracisternal A-particles (IAPs), repetitive elements in the mouse genome. These findings provide evidence that developmental exposures to phthalates influence body weight and organ weight changes in early life, and are associated with altered DNA methylation at IAPs.

Sex-Specific Programming of Cardiac DNA Methylation by Developmental Phthalate Exposure

“… 38 , 39 The 5 mg/kg-day dose used in this study falls within or below the range of no-observed-adverse-effect level (NOAELs) for oral DEHP exposure established by US and European agencies 4 , 40 and is estimated to result in an amniotic fluid concentration within the ranges observed in human amniotic fluid. 6 …”

“…38,39 The 5 mg/kg-day dose used in this study falls within or below the range of noobserved-adverse-effect level (NOAELs) for oral DEHP exposure established by US and European agencies 4,40 and is estimated to result in an amniotic fluid concentration within the ranges observed in human amniotic fluid. 6 After weaning at postnatal day 21, pups were weighed, and all animals received DEHP-free 7% corn oil control chow for the remainder of the study (Figure 1). Approximately 1 to 2 male and 1 to 2 female offspring per litter were followed until 5 months of age (n = 6 control animals per sex, n = 7 DEHP males, n = 5 DEHP females).…”

“… 19 , 20 Importantly, the majority of studies investigating the effects of gestational phthalate exposures on cardiovascular outcomes have focused only on males. 11 , 12 , 21 Although work from our lab and others demonstrate sexually dimorphic effects of endocrine-disrupting chemicals, including phthalates, in humans and animal models, 6 , 22 - 24 little is known about the sex-specific effects of gestational exposure to phthalates on the heart.…”

“… 3 , 5 In rodent models, phthalate exposure during gestation or the early postnatal period is associated with metabolic diseases and reproductive abnormalities. 6 - 9 Recent animal studies have also linked gestational phthalate exposures to altered heart development and function. 10 - 12 Likewise, human studies demonstrate an association between both pediatric and adult phthalate exposure and adverse cardiovascular outcomes.…”

Role of Obesogens in the Pathogenesis of Obesity

“…Another group of obesogens are phthalates, which are diesters of phthalic acid used to impart flexibility to plastic products and as carriers for fragrances in cosmetics. They can easily leach from these products and can be found in indoor air and house dust [21].…”