Longitudinal Metabolic Impacts of Perinatal Exposure to Phthalates and Phthalate Mixtures in Mice

Abstract

Developmental exposures to phthalates are suspected to contribute to risk of metabolic syndrome. However, findings from human studies are inconsistent, and long-term metabolic impacts of early-life phthalate and phthalate mixture exposures are not fully understood. Furthermore, most animal studies investigating metabolic impacts of developmental phthalate exposures have focused on diethylhexyl phthalate (DEHP), whereas newer phthalates, such as diisononyl phthalate (DINP), are understudied. We used a longitudinal mouse model to evaluate long-term metabolic impacts of perinatal exposures to three individual phthalates, DEHP, DINP, and dibutyl phthalate (DBP), as well as two mixtures (DEHP+DINP and DEHP+DINP+DBP). Phthalates were administered to pregnant and lactating females through phytoestrogen-free chow at the following exposure levels: 25 mg of DEHP/kg of chow, 25 mg of DBP/kg of chow, and 75 mg of DINP/kg of chow. One male and female per litter (n = 9 to 13 per sex per group) were weaned onto control chow and followed until 10 months of age. They underwent metabolic phenotyping at 2 and 8 months, and adipokines were measured in plasma collected at 10 months. Longitudinally, females perinatally exposed to DEHP only had increased body fat percentage and decreased lean mass percentage, whereas females perinatally exposed to DINP only had impaired glucose tolerance. Perinatal phthalate exposures also modified the relationship between body fat percentage and plasma adipokine levels at 10 months in females. Phthalate-exposed males did not exhibit statistically significant differences in the measured longitudinal metabolic outcomes. Surprisingly, perinatal phthalate mixture exposures were statistically significantly associated with few metabolic effects and were not associated with larger effects than single exposures, revealing complexities in metabolic effects of developmental phthalate mixture exposures.

Short- and long-term effects of perinatal phthalate exposures on metabolic pathways in the mouse liver

“…Furthermore, alterations in hepatic acetyl-CoA and acylcarnitines were age-specific. This was consistent with our previous phenotyping studies that indicated females perinatally exposed to DEHP+DINP had increased body weight and relative liver weight at PND21, but did not exhibit these same phenotypes longitudinally ( 31 , 34 ). Additional work is needed to fully understand these complex mixture effects.…”

“…Females perinatally exposed to DINP exhibited the most prominent differential gene expression in the liver, and gene set enrichment analysis revealed different metabolic pathways impacted by developmental phthalate exposures in females and males. Furthermore, our previous studies indicated that females were more susceptible to long-term metabolic effects, including glucose intolerance and body fat accumulation, than males following perinatal phthalate exposures ( 34 ). In contrast, a previously published study examining liver reprogramming following developmental DEHP exposures found sex-specific reprogramming in males but not females; however, this study examined glycogen storage/depletion as the main outcome of interest, utilized higher doses of DEHP, analyzed younger mice, and only evaluated hepatic expression of one gene ( 74 ).…”

“…The overall experimental design is laid out in Fig. 1 and is described in detail in previous studies ( 31 , 34 ). Animals were obtained from a colony of viable yellow agouti ( A vy ) mice, maintained for over 220 generations with sibling mating and forced heterozygosity for the A vy allele through the male line ( 35 ).…”

“…We previously found that perinatal exposure to DEHP alone, DINP alone, and a combination of DEHP+DINP resulted in increased relative liver weights in weanling female mice at postnatal day 21 (PND21) ( 31 ), which may be indicative of PPARα activation ( 32 , 33 ). Longitudinally, female mice perinatally exposed to DEHP-only had increased body fat percentage and those perinatally exposed to DINP-only had impaired glucose tolerance ( 34 ). Building upon these findings, we hypothesized that early life exposures to phthalates resulted in long-lasting impacts on PPAR target gene expression in the liver by decreasing promoter region DNA methylation to influence metabolism across the life course.…”

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

“…In this study, we did not observe significant changes in relative heart weights with DEHP exposure, and we did not determine the effects of DEHP exposure on cardiac function. However, we have previously demonstrated that DEHP exposure in this model results in increased body fat and decreased lean mass in adult females, 64 suggesting that this chemical has long-term, sex-specific effects on metabolic health. Moreover, adverse effects of perinatal environmental exposures may not manifest until subsequent challenges later in life, such as hormonal stimulation, poor diet, or additional environmental exposures.…”