Early gut microbiome development may impact brain and behavioral development. Using a nonhuman primate model (Macaca mulatta), we investigated the association between social environments and the gut microbiome on infant neurodevelopment and cognitive function. Infant rhesus monkeys (n = 33) were either mother-peer-reared (MPR) or nursery-reared (NR). Neurodevelopmental outcomes, namely emotional responsivity, visual orientation, and motor maturity, were assessed with the Primate Neonatal Neurobehavioral Assessment (PNNA) at 14–30 days. Cognitive development was assessed through tasks evaluating infant reward association, cognitive flexibility, and impulsivity at 6–8 months. The fecal microbiome was quantified from rectal swabs via 16S rRNA sequencing. Factor analysis was used to identify “co-abundance factors” describing patterns of microbial composition. We used multiple linear regressions with AIC Model Selection and differential abundance analysis (MaAsLin2) to evaluate relationships between co-abundance factors, microbiome diversity, and neuro-/cognitive development outcomes. At 30 days of age, a gut microbiome co-abundance factor, or pattern, with high Prevotella and Lactobacillus (β = −0.88, p = 0.04, AIC Weight = 68%) and gut microbiome alpha diversity as measured by Shannon diversity (β = −1.33, p = 0.02, AIC Weight = 80%) were both negatively associated with infant emotional responsivity. At 30 days of age, being NR was also associated with lower emotional responsivity (Factor 1 model: β = −3.13, p < 0.01; Shannon diversity model: β = −3.77, p < 0.01). The infant gut microbiome, along with early-rearing environments, may shape domains of neuro-/cognitive development related to temperament.

Preterm birth exposes the neonate to hypoxic-ischaemic and excitotoxic insults that impair neurodevelopment and are magnified by the premature loss of placentally supplied, inhibitory neurosteroids. The cerebellum is a neuronally dense brain region, which undergoes critical periods of development during late gestation, when preterm births frequently occur. We propose that neurosteroid replacement therapy using tiagabine and zuranolone will protect the cerebellum against preterm-associated insults. Guinea pig dams received c-section surgery preterm (gestational age (GA) 64) or at term (GA70) with preterm pups administered tiagabine (2.5 mg/kg/day), zuranolone (1 mg/kg/day) or vehicle (15% β-cyclodextrin) until term equivalent age (GA70). Behavioural testing was performed at corrected postnatal day 8 (PND8) and PND41 with tissue collection occurring at PND42. Neurodevelopmental markers (MBP, OLIG2 and NeuN) were assessed within the cerebellum by immunohistochemistry, whilst GABAergic and glutamatergic pathway expression was quantified using high throughput RT-PCR. Zuranolone and, to a lesser extent, tiagabine were able to protect against hyperactive behaviour at PND8 in males, whilst in females, a less marked hyperactive phenotype was present with neither treatment impacting behaviour further. Both treatments improved MBP staining, whilst tiagabine was found to restore oligodendrocyte maturation in females only. GABAergic and glutamatergic pathway expression was found to be restored by both treatments in females. Overall, this study demonstrates the neuroprotective attributes of neurosteroid replacement therapy using tiagabine and zuranolone, thereby demonstrating their potential to mitigate long-term neurodevelopmental impairments. Furthermore, the sexually dimorphic effects observed suggest future investigations may show increased benefit by using sex-specific treatment regimes.

The nutritional environment during fetal and early postnatal life has a long-term impact on growth, development, and metabolic health of the offspring, a process termed “nutritional programming.” Rodent models studying programming effects of nutritional interventions use either purified or grain-based rodent diets as background diets. However, the impact of these diets on phenotypic outcomes in these models has not been comprehensively investigated. We used a previously validated (C57BL/6J) mouse model to investigate the effects of infant milk formula (IMF) interventions on nutritional programming. Specifically, we investigated the effects of maternal diet type (i.e., grain-based vs purified) during early lactation and prior to the intervention on offspring growth, metabolic phenotype, and gut microbiota profile. Maternal exposure to purified diet led to an increased post-weaning growth velocity in the offspring and reduced adult diet-induced obesity. Further, maternal exposure to purified diet reduced the offspring gut microbiota diversity and modified its composition post-weaning. These data not only reinforce the notion that maternal nutrition significantly influences the programming of offspring vulnerability to an obesogenic diet in adulthood but emphasizes the importance of careful selection of standard background diet type when designing any preclinical study with (early life) nutritional interventions.