Perinatal exposure to bisphenol-a and the development of metabolic syndrome in CD-1 mice

Abstract

Bisphenol-A (BPA) is an endocrine-disrupting chemical used in the production of plastic food and beverage containers, leading to ubiquitous low-dose human exposure. It has been suggested that exposure to even low doses of BPA during development may be associated with increased susceptibility to obesity and diabetes later in life. Despite growing public concern, the existing empirical data are equivocal, prompting The Endocrine Society, the National Institute of Environmental Health Sciences, and others to call for further research. In this study, we tested the hypothesis that perinatal exposure to an ecologically relevant dose of BPA (1 part per billion via the diet) results in increased susceptibility to high-fat diet-induced obesity and glucose intolerance in adult CD-1 mice. The data did not support this hypothesis. In agreement with previous reports, we find that weanling mice exposed to BPA during gestation and lactation are heavier compared with control mice. We also find that BPA mice are longer than controls at 4 wk of age, but these differences are no longer apparent when the mice reach adulthood, even when tested on a high-fat diet. We conclude that this larger size-for-age represents a faster rate of growth early in development rather than an obese, diabetic phenotype in adulthood.

Figure 1

Effects of perinatal exposure to BPA and DES on traits of dams and their litters. Length of gestation in days (e0–p0) (A), sex ratio (B), and litter size (C) of dams eating either control diet (n = 31) or diet containing 4-ppb BPA (n = 34) or 1-ppb DES (n = 32). There were no significant differences among the groups for these endpoints (ANOVA, P > 0.05). D, Average daily food intake of dams (and their pups) exposed to BPA is higher at wk 6 compared with mice eating the control or DES diets [repeated-measures (RM) ANCOVA followed by Tukey post hoc tests: P (litter size) <0.000001, P (time × maternal treatment) <0.000001; within wk 6, P (BPA vs. control) <0.001, P (BPA vs. DES) <0.001]. ***, P < 0.001.

Figure 2

Body size of weanlings. A, Male and female BPA pups were heavier at 3 wk of age compared with control and DES pups [ANCOVA followed by Tukey post hoc tests: for males, P (maternal treatment) <0.000001, P (BPA vs. control) <0.01, P (BPA vs. DES) <0.01, P (litter size) <0.000001; for females, P (maternal treatment) <0.000001, P (BPA vs. control) <0.01, P (BPA vs. DES) <0.001, P (litter size) <0.000001]. B, Body length was measured in a subset of animals (n = 10 sex/maternal treatment) at 4 wk of age. Among males, control mice were significantly shorter than both BPA and DES mice. Among females, the trend was similar, but the differences were not significant when litter size was included in the model [ANCOVA followed by Tukey post hoc tests: for males, P (maternal treatment) <0.01, P (control vs. BPA) <0.05, P (control vs. DES) <0.01, P (litter size) <0.059; for females, P (maternal treatment) <0.098, P (litter size) <0.05]. *, P < 0.05; **, P < 0.01; ***, P < 0.001.

Figure 3

Growth on LFD from 4–9 wk of age. Cumulative LFD intake by male (A) and female (B) mice did not differ according to maternal treatment [ANCOVA: P (maternal treatment) >0.05, P (litter size) >0.05]. C, Among males, body weight differences among the maternal treatment groups were lost after weaning [repeated-measures (RM) ANCOVA: P (maternal treatment) >0.05, P (litter size) <0.01, P (litter size × time) <0.01]. D, Among females, body weight differences among the maternal treatment groups were lost after weaning [RM ANCOVA: P (maternal treatment) >0.05, P (litter size) <0.01, P (litter size × time) <0.001, P (maternal treatment × time) <0.000001]. E, At 7 wk of age, BPA males had more body fat than DES males [ANCOVA followed by Tukey post hoc tests: P (maternal treatment) <0.05, P (BPA vs. DES) <0.05, P (litter size) >0.05]. At 7 wk of age, there were no body fat differences among the females [ANCOVA: P (maternal treatment) >0.05, P (litter size) >0.05]. F, There were no differences in lean mass among the groups for either sex [ANCOVA: P (maternal treatment) >0.05, P (litter size) >0.05]. *, P < 0.05.

Figure 4

Blood glucose in 8-wk-old male and female mice after an ip glucose load. A and C, Among males, there were no differences in glucose tolerance [repeated-measures (RM) ANCOVA, ANCOVA]. B, DES females exhibited impaired glucose tolerance compared with control and BPA mice [RM ANCOVA followed by Tukey post hoc tests: P (maternal treatment) <0.01, P (litter size) >0.05, P (DES vs. control) <0.01, P (DES vs. BPA) <0.0.05]. Symbols indicate significant Tukey post hoc comparisons (*, P < 0.05; **, P < 0.01; ***, P < 0.001) vs. control. D, DES females exhibited impaired glucose tolerance as compared by area under the curve (AUC) [ANCOVA followed by Tukey post hoc tests: P (maternal treatment) <0.05, P (litter size) >0.05, P (DES vs. control <0.05)].

Figure 5

Growth on HFD vs. LFD from 9–14 wk of age. Cumulative caloric intake was increased in male and female mice eating a HFD vs. LFD. A, Among males, there was no effect of maternal treatment on caloric intake [ANCOVA: P (diet) <0.001, P (maternal treatment) >0.05, P (litter size) >0.05]. B, Among females, control mice ate fewer calories compared with either BPA or DES mice [ANCOVA followed by Tukey post hoc tests: P (diet) <0.0001, P (maternal treatment) <0.01, P (control vs. BPA) <0.05, P (control vs. DES) <0.05, P (litter size) <0.05]. Male mice gained more weight while eating a HFD (C) vs. LFD (E). DES males tended to be lighter than either control or BPA males, although this difference did not reach statistical significance [repeated-measures (RM) ANCOVA followed by Tukey post hoc tests: P (maternal treatment) <0.05, P (diet × time) <0.000001, P (maternal treatment × time) <0.0001, P (DES vs. control) <0.058, P (DES vs. BPA) <0.058, P (litter size) >0.05]. Female mice gained more weight while eating a HFD (D) vs. LFD (F). There were no differences in body weight among the groups [RM ANCOVA: P (maternal treatment) >0.05, P (diet × time) <0.001, P (litter size) <0.05, P (litter size × time) <0.05]. *, P < 0.05.

Figure 6

Body composition after 5 wk of HFD vs. LFD feeding. A, Among 14-wk-old males, HFD-fed mice had more body fat than LFD-fed mice. Control males also had more body fat than DES males [ANCOVA followed by Tukey post hoc tests: P (diet) <0.001, P (maternal treatment) <0.05, P (control vs. DES) <0.05, P (litter size) >0.05]. B, Control females had more body fat than either BPA or DES females [ANCOVA followed by Tukey post hoc tests: P (maternal treatment) <0.01, P (control vs. BPA) <0.01, P (control vs. DES) <0.05, P (litter size) >0.05]. There were no differences in lean mass among the groups in either males (C) or females (D) (ANCOVA). However, litter size did significantly predict lean body mass in 14-wk-old females (P < 0.05). *, P < 0.05; **, P < 0.01.

Figure 7

Blood glucose in 15-wk-old male and female mice after an ip glucose load. Among males, there were no differences in glucose tolerance regardless of whether the mice ate a HFD (A) or LFD (C) [repeated-measures (RM) ANCOVA]. B, Among females eating HFD, DES females exhibited impaired glucose tolerance [RM ANCOVA: P (maternal treatment) <0.05, P (time × maternal treatment) <0.01; symbols indicate significant Tukey post hoc comparisons (*, P < 0.05; **, P < 0.01) vs. the control females]. D, Among females eating LFD, there were no differences in glucose tolerance (RM ANCOVA).

Figure 8

Area under the curve (AUC) for 15-wk-old male and female mice after an ip glucose load. Among males, there were no differences in AUC regardless of whether the mice ate a HFD (A) or LFD (C) (ANCOVA). B, Among females eating a HFD, DES females had significantly higher AUC compared with BPA females [ANCOVA followed by Tukey post hoc comparisons: P (maternal treatment) <0.05, P (DES vs. BPA) <0.01]. D, Among females eating a LFD, there were no significant differences in AUC (ANCOVA). **, P < 0.01.