Maternal L. Reuteri Rescues Offspring ASD-Like Behavior and Altered Thyroid Hormone Target Transcripts in Oxytocin Neurons in an Environmental Mouse Model of Autism

Polybrominated diphenyl ethers (PBDEs) are thyroid-disrupting chemicals with adverse neurodevelopmental effects in children. Our group has previously shown that PBDEs produce autism (ASD)-like traits, in combination with reduced hypothalamic oxytocin (OXT) expression, in developmentally exposed female mice offspring. Limosilactobacillus reuteri (LR) is a beneficial probiotic that can increase OXT and thyroid hormones (THs) in ASD mouse models. Therefore, we hypothesized that LR would ameliorate PBDE-induced deficits in social behavior, central OXT and TH status. C57BL/6N dams (n=8/group) were dosed with a commercial mixture of PBDE congeners, DE-71, at 0.1 mg/kg/d (DE-71), or corn oil vehicle control (VEH/CON) during preconception, gestation and lactation. Dams were supplemented with L. reuteri (LR) (ATCC-PTA-6475) probiotic at 107-108 CFU/mL (gift of Biogaia, Sweden). Cohort 1 pups (C1) received LR via dam until weaning (PND 21). Cohort 2 pups (C2) continued to receive gavage of LR daily from post-weaning through 6 mo of age. Fecal microbiome analysis confirmed colonization of LR in dams after 25 doses and their offspring at postnatal day 22 and 40. Beta diversity PCoA using unweighted Unifrac revealed effects of LR on disrupted microbial communities in DE-71 in 6-month-old female (p<.05-.01) and male offspring (apparent) (C2). LR treatment normalized DE-71-induced deficient social novelty preference (30 min retention) in adult male (p<.01, n=6-10/group) and females (p<.05, n=6-10/group) and deficient long-term social recognition memory (24 h retention) in adult C2 females (p<.001, n=6-10/group). On an emotional recognition task DE-71-exposed C2 male and female offspring were unable to distinguish the emotional state of stressed stimulus mice; LR supplementation provided normalization (p<.01 and p<.05, respectively). On a marble burying test DE-71 exposed offspring showed abnormally elevated scores compared to VEH/CON, an effect normalized by LR treatment only in C1 females (p<.05, n=6-12/group). LR treatment ameliorated DE-71-induced deficits compared to VEH/CON on an olfactory habituation test, i.e., reduced dishabituation from social odor 1 to 2 in C1 males and females (p<.0001, n=6-12/group). To test the hypothesis that DE-71 dysregulates brain TH markers on OXT neurons in the paraventricular hypothalamic nucleus (PVH), which regulates forebrain social recognition circuits, RNAscope combined with IHC was performed. C2 DE-71 females but not males showed upregulated TH transporter monocarboxylate transporter 8 (Mct8) and downregulated iodothyronine deiodinase 3 (Dio3) on OXT-positive neurons vs VEH/CON. Dio3 expression was normalized in DE-71+LR vs DE-71 (p<.05, n=3-5/group), suggesting that LR modulation can offset DE-71’s disruption of TH action in the female central OXTergic circuits. These results point to altered regulation of OXT signaling by brain TH in PBDE-induced ASD behavior. They also indicate that maternal probiotic treatment with LR provides normalization of ASD-relevant behavior and neuromolecular correlates in a sex-dependent manner. Danone NA. Gut Microbiome, Yogurt and Probiotics and UC President's Pre-Professoriate Fellowship to E.V.K., and an NIH/NIGMS R35GM124724 to A.H. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.