Bisphenol A exposure during pregnancy disrupts glucose homeostasis in mothers and adult male offspring

Abstract

Background: Bisphenol A (BPA) is a widespread endocrine-disrupting chemical used as the base compound in the manufacture of polycarbonate plastics. In humans, epidemiological evidence has associated BPA exposure in adults with higher risk of type 2 diabetes and heart disease.

Objective: We examined the action of environmentally relevant doses of BPA on glucose metabolism in mice during pregnancy and the impact of BPA exposure on these females later in life. We also investigated the consequences of in utero exposure to BPA on metabolic parameters and pancreatic function in offspring.

Methods: Pregnant mice were treated with either vehicle or BPA (10 or 100 microg/kg/day) during days 9-16 of gestation. Glucose metabolism experiments were performed on pregnant mice and their offspring.

Results: BPA exposure aggravated the insulin resistance produced during pregnancy and was associated with decreased glucose tolerance and increased plasma insulin, triglyceride, and leptin concentrations relative to controls. Insulin-stimulated Akt phosphorylation was reduced in skeletal muscle and liver of BPA-treated pregnant mice relative to controls. BPA exposure during gestation had long-term consequences for mothers: 4 months post-partum, treated females weighed more than untreated females and had higher plasma insulin, leptin, triglyceride, and glycerol levels and greater insulin resistance. At 6 months of age, male offspring exposed in utero had reduced glucose tolerance, increased insulin resistance, and altered blood parameters compared with offspring of untreated mothers. The islets of Langerhans from male offspring presented altered Ca2+ signaling and insulin secretion. BrdU (bromodeoxyuridine) incorporation into insulin-producing cells was reduced in the male progeny, yet beta-cell mass was unchanged.

Conclusions: Our findings suggest that BPA may contribute to metabolic disorders relevant to glucose homeostasis and that BPA may be a risk factor for diabetes.

Figure 1

BPA exposure during pregnancy on blood glucose homeostasis in F₀ mice. (A) IPGTT performed in F0-C (n = 11), F0-BPA10 (n = 8), and F0-BPA100 (n = 8); the inset shows mean total AUC in response to glucose load. (B) IPITT in F0-C (n = 12), F0-BPA10 (n = 9), and F0-BPA100 (n = 7) mice. (C and D) Western blots (top) and analysis (bottom) of insulin-stimulated Akt phosphorylation (Thr³⁰⁸; pAkt) in liver (C) and in gastrocnemius muscle (D); tissue for these experiments was collected 15 min after intraperitoneal injection of insulin (0.6 U/kg) or saline in F0-C (n = 4) and F0-BPA10 (n = 6) mice. Values for analysis are in arbitrary units (AU). Data are expressed as mean ± SE. *p < 0.05.

Figure 2

Analysis of glucose and insulin sensitivity in F0-C, F0-BPA10, and F0-BPA100 female mice (F0) 4 months after delivery. (A) Mean body weight. (B) IPITT. (C) IPGTT in the same mothers as in B; the inset represents the AUC. Data are expressed as mean ± SE (n = 6/group). *p < 0.05 for F0-BPA100 mice compared with F0-C.

Figure 3

Body weight of F1-C, F1-BPA10, and F1-BPA100 mice. Mean body weight (A) and percentage of control weight (B) from birth to weaning for males and females combined. (C, D) Mean body weight from weaning to adulthood (22 through 180 days of age) for males (C) and females (D). n = 25–60 animals/group; some SEs are not visible because of their low values. *p < 0.05 for F1-BPA10 compared with F1-C. ^#p < 0.05 for F1-BPA100 compared with F1-C.

Figure 4

Blood glucose homeostasis in F1-C, F1-BPA10, and F1-BPA100 mice at 6 months of age shown by (A) IPITT and (B) IPGTT performed in the same group of animals. The inset in B represents the mean total glucose AUC. Data are expressed as mean ± SE (n = 8). *p < 0.05 for F1-BPA10 and F1-BPA100 mice compared with F1-C. ^##p = 0.05.

Figure 5

Pancreatic islet function in male F1-C, F1-BPA10, and F1-BPA100 mice. In vivo plasma insulin levels 15 min after a glucose load (2 g/kg; A) and ex vivo glucose-induced insulin secretion from isolated islets (3, 7, and 16 mM glucose; B); n = 8–10 animals/group. (C) [Ca²⁺]_i response of a representative islet of Langerhans in the presence of 3, 7 and 16 mM glucose applied for 10, 10, and 15 min, respectively (n = 10/group). (D) AUC for traces in C. (E) Measurement of β-cell area (area occupied by insulin-positive cells expressed as a percentage of the total area). (F) Quantification of BrdU incorporation in insulin-positive cells. Data are expressed as mean ± SE. *p < 0.05 compared with F1-C. **p < 0.005.