Dual Effects of Maternal Diet and Perinatal Organophosphate Flame Retardant Treatment on Offspring Development, Behavior and Metabolism

Abstract

The maternal-fetal environment is influenced by multiple factors, including nutrition and environmental contaminants, which can impact long-term development. Perinatal exposure to organophosphate flame retardants (OPFRs) disrupts energy homeostasis and causes maladaptive behaviors in mice. Maternal obesity affects development by impairing blood-brain barrier (BBB) formation, influencing brain regions involved in energy regulation and behavior. This study examined the combined effects of maternal obesity and perinatal OPFR treatment on offspring development. Female mice were fed either a low-fat (LFD) or a high-fat diet (HFD) for 8 weeks, mated, and treated with either sesame oil or an OPFR mixture (tris(1,3-dichloro-2-propyl)phosphate, tricresyl phosphate, and triphenyl phosphate, 1 mg/kg each) from gestational day 7 to postnatal day 14. Results showed that both maternal diet and OPFR treatment disrupted blood-brain barrier integrity, energy balance, and reproductive gene expression in the hypothalamus of neonates. The expression of hepatic genes related to lipid and xenobiotic metabolism was also altered. In adulthood, LFD OPFR-treated female offspring exhibited increased avoidance behavior, while HFD OPFR-treated females demonstrated memory impairments. Metabolic assessments revealed decreased energy expenditure and nighttime activity in LFD OPFR-treated females. These findings suggest that maternal diet and OPFR treatment alter hypothalamic and liver gene expression in neonates, potentially leading to long-term metabolic and behavioral changes.

Keywords: anxiety; endocrine disruption; memory; neurodevelopment; organophosphate flame retardants.

Figure 1

(A) Schematic of experimental design. GD, gestational day; PND, postnatal day. Dams were fed diets from 6 weeks of age until sacrifice. Metabolic phenotyping was completed after 8 weeks of diet, including (B) body weight (a = p < 0.05, b = p < 0.01, d = p < 0.0001), (C) fat mass, and (D) lean mass normalized to body mass. (E) Five-hour fasting glucose levels were measured after 8 weeks of diet intervention using a standard glucometer (** = p < 0.01, *** = p < 0.001).

Figure 2

PND 7 anogenital distance (AGD) measurements in male and female pups that were perinatally treated with oil or OPFR and maternally treated with low-fat/high-fat diet (LFD/HFD). Data are represented as mean ± SEM, and dots represent the sample size (number of litters) per treatment per sex (** = p < 0.01, **** = p < 0.0001).

Figure 3

Avoidant-related behavior tests. Open field test (OFT)—(A) distance traveled (m), (B) latency to 1st entry into the 20 cm center and (C) percent time spent in the 10 cm center zone. Elevated plus maze (EPM)—(D) distance traveled (m), (E) distance traveled (m) in the closed arms, and (F) number of closed-arm entries. Light/dark box emergence test (LDB)—(G) distance traveled (m), (H) number of light zone entries, and (I) light zone exits. Data are represented as mean ± SEM and dots represent the sample size (number of litters) per treatment per sex (* = p < 0.05, ** = p < 0.01, **** = p < 0.0001).

Figure 4

Y-maze Test. (A) Distance traveled. (B) Mean speed. (C) Percent time spent in unknown arm. Data are represented as mean ± SEM and dots represent the sample size (number of litters) per treatment per sex (* = p < 0.05).

Figure 5

(A) Body weights and body composition of maternally treated adult offspring. Lean mass (B) and fat mass (C) normalized to body weight for adult offspring. Lowercase ‘a’ denotes significance (p < 0.05) between sex across treatment groups. Data are represented as mean ± SEM and dots represent the sample size (number of litters) per treatment per sex (* = p < 0.05).

Figure 6

Metabolic phenotyping. Nighttime (A) V.O₂, (B) V.CO₂, (C) respiratory exchange ratio, (D) Heat, and (E) wheel running. Data are presented as mean +/− SEM and analyzed by litter (n = 8–12/group) and by two-way ANOVA with Tukey’s multiple comparisons test (* = p < 0.05, ** = p < 0.01, *** = p < 0.001, **** = p < 0.0001). (F) Female hourly wheel count across 24 h. Dark line below X-axis represents dark hours. Letters denote a significance between maternal diet and treatment at each hour (a = p < 0.05 for LFD oil and LFD OPFR; b = p < 0.05 for HFD oil and HFD OPFR; c = p < 0.05 for LFD oil and HFD oil; d = p < 0.05 for LFD OPFR and HFD OPFR).

Figure 7

Tolerance tests. Glucose tolerance test (GTT) for (A) male and (B) female adult offspring. (C) Area under the curve (AUC) analysis for adult offspring. Insulin tolerance test (ITT) for (D) male and (E) female adult offspring. (F) AUC analysis for adult offspring. Lowercase letters denote significance between perinatal treatment within maternal diet at the time point, and uppercase letters denote significance between maternal diet within perinatal treatment. Data are represented as mean ± SEM and dots represent the sample size (number of litters) per treatment per sex (A/a = p < 0.05, * = p < 0.05, *** = p < 0.001).