Piroli, M. V. | bioRxiv Science

bioRxiv2026

Pregnancy Impacts Maternal Sleep: Focus on Kynurenine Pathway Activation in Female Rats

Study Objectives: Poor maternal sleep is associated with adverse health outcomes for women and their offspring, and perturbations to tryptophan metabolism through the kynurenine pathway (KP) may contribute. Kynurenic acid (KYNA), a neuroactive KP metabolite and endogenous modulator of glutamatergic and cholinergic neurotransmission, is of particular interest because elevated KYNA has been linked to altered sleep-wake behavior and neurodevelopmental outcomes. Because sleep patterns and KP metabolism change during pregnancy, we tested whether pregnancy modifies the effects of kynurenine supplementation on sleep-wake architecture. Methods: To model enhanced KP metabolism, we used the embryonic kynurenine (EKyn) model, in which the maternal diet is supplemented with kynurenine, the initial KP metabolite, during the last week of gestation. Using a within-subject design, we evaluated sleep-wake parameters in pregnant and non-pregnant female rats and assessed KYNA in brain and saliva. Results: Pregnancy increased dark phase NREM and REM sleep in control-fed (ECon) dams, a pattern largely maintained in EKyn dams. However, near parturition, EKyn dams exhibited reduced light phase REM sleep that was not observed in controls. In non-pregnant females, kynurenine supplementation produced a stronger phenotype, consistently reducing light phase REM sleep across treatment days. During pregnancy, kynurenine-associated sleep effects were detectable only when compared to within-subject non-pregnant baseline. Salivary KYNA distinguished kynurenine-fed females from matched controls and correlated with brain KYNA levels. Conclusion: These findings show that pregnancy reshapes sleep-wake architecture and attenuates, but does not eliminate, kynurenine-associated REM sleep disruption, implicating KP metabolism and potentially elevated brain KYNA in maternal sleep regulation.

neuroscience↗

bioRxiv2024

Parental kynurenine 3-monooxygenase genotype in mice directs sex-specific behavioral outcomes in offspring

BackgroundDisruptions in brain development can impact behavioral traits and increase the risk of neurodevelopmental conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder, often in sex-specific ways. Dysregulation of the kynurenine pathway (KP) of tryptophan metabolism has been implicated in cognitive and neurodevelopmental disorders. Increased brain kynurenic acid (KYNA), a neuroactive metabolite implicated in cognition and sleep homeostasis, and variations in the Kmo gene, which encodes kynurenine 3-monooxygenase (KMO), have been identified in these patients. We hypothesize that parental Kmo genetics influence KP biochemistry, sleep behavior and brain energy demands, contributing to impairments in cognition and sleep in offspring through the influence of parental genotype and genetic nurture mechanisms. MethodsA mouse model of partial Kmo deficiency, Kmo heterozygous (HET-Kmo+/-), was used to examine brain KMO activity, KYNA levels, and sleep behavior in HET-Kmo+/- compared to wild-type control (WT-Control) mice. Brain mitochondrial respiration was assessed, and KP metabolites and corticosterone levels were measured in breast milk. Behavioral assessments were conducted on wild-type offspring from two parental groups: i) WT-Control from WT-Control parents, ii) wild-type Kmo (WT-Kmo+/+) from Kmo heterozygous parents (HET-Kmo+/-). All mice were C57Bl/6J background strain. Adult female and male offspring underwent behavioral testing for learning, memory, anxiety-like behavior and sleep-wake patterns. ResultsHET-Kmo+/- mice exhibited reduced brain KMO activity, increased KYNA levels, and disrupted sleep architecture and electroencephalogram (EEG) power spectra. Mitochondrial respiration (Complex I and complex II activity) and electron transport chain protein levels were impaired in the hippocampus of HET-Kmo+/- females. Breast milk from HET-Kmo+/- mothers increased kynurenine exposure during lactation but corticosterone levels were unchanged. Compared to WT-Control offspring, WT-Kmo+/+ females showed impaired spatial learning, heightened anxiety, reduced sleep and abnormal EEG spectral power. WT-Kmo+/+ males had deficits in reversal learning but no sleep disturbances or anxiety-like behaviors. ConclusionsThese findings suggest that Kmo deficiency impacts KP biochemistry, sleep behavior, and brain mitochondrial function. Even though WT-Kmo+/+ inherit identical genetic material as WT-Control, their development might be shaped by the parents physiology, behavior, or metabolic state influenced by their Kmo genotype, leading to phenotypic sex-specific differences in offspring. Plain English summaryInteractions between genetic and environmental factors are carefully regulated during the intricate process of brain development. While genetic information is directly inherited from parents, emerging evidence suggests that parental genetic factors can also shape the environment influencing childrens development in a sex-specific ways. Disruptions in brain development can impact cognitive and behavioral traits and increase the risk of neurodevelopmental conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder, schizophrenia, and bipolar disorder. This study explored how kynurenine 3-monooxygenase (Kmo) genotype affects female and male mice, focusing on potential sex-specific behavioral changes in offspring born to parents with a genetic disruption in Kmo. We found that female and male mice with partial Kmo deficiency experienced reduced sleep and increased sleep pressure. In female mice, Kmo deficiency impaired mitochondrial energy production in the brain. We also observed alterations in tryptophan metabolism and nutrient composition in the breast milk of Kmo-deficient females. In adult offspring born to Kmo-deficient parents, females exhibited learning difficulties, heightened anxiety-like behaviors, and sleep disturbances. In contrast, male offspring showed mild cognitive impairments but no major sleep issues. These findings highlight that parental Kmo genotype can influence sex differences in cognitive and sleep-related behaviors in offspring. This underscores the importance of considering parental genetic factors when studying neurodevelopmental disorders and associated behavioral outcomes. HighlightsO_LIMice with a partial Kmo deficiency, Kmo heterozygous (HET-Kmo+/-), were used to evaluate the impact of parental Kmo genetics on kynurenine pathway biochemistry, brain mitochondrial function, sleep patterns, and cognitive performance. C_LIO_LIFemale and male HET-Kmo+/- mice exhibited elevated brain KYNA levels and had reduced sleep, prolonged wakefulness, and altered spectra power during sleep. In HET-Kmo+/- females, hippocampal mitochondrial respiration and electron transport chain protein levels were significantly altered. Breast milk from HET-Kmo+/- females increased kynurenine exposure during lactation to offspring, including their wild-type (WT-Kmo+/+) offspring. C_LIO_LISex differences were observed in learning and memory, anxiety-like behavior, and sleep-wake patterns between WT-Control, from wild-type parents, and WT-Kmo+/+ offspring from HET-Kmo+/- parents. Female WT-Kmo+/+ offspring had impaired spatial learning, increased anxiety-like behavior, reduced sleep, but elevated delta power during sleep. Male WT-Kmo+/+ offspring exhibited deficits in reversal learning only and not sleep impairments. C_LI

neuroscience↗

bioRxiv2022

Reducing brain kynurenic acid synthesis precludes kynurenine-induced sleep disturbances

Patients with neurocognitive disorders often battle sleep disturbances. Kynurenic acid (KYNA) is a tryptophan metabolite of the kynurenine pathway implicated in the pathology of these illnesses. Modest increases in KYNA, an antagonist at glutamatergic and cholinergic receptors, result in cognitive impairments and sleep dysfunction. We explored the hypothesis that inhibition of the KYNA synthesizing enzyme, kynurenine aminotransferase II (KAT II), may alleviate sleep disturbances. At the start of the light phase, adult male and female Wistar rats received systemic injections of either i) vehicle, ii) kynurenine (100mg/kg; i.p.), iii) the KAT II inhibitor, PF-04859989 (30 mg/kg; s.c.), or iv) PF-04859989 and kynurenine in combination. Kynurenine and KYNA levels were evaluated in the plasma and brain. Separate animals were implanted with electroencephalogram (EEG) and electromyogram (EMG) telemetry devices to record polysomnography and evaluate vigilance states wake, rapid eye movement sleep (REMS) and non-REM sleep (NREMS) following each treatment. Kynurenine challenge increased brain KYNA and resulted in reduced REMS duration, NREMS delta power and sleep spindles. PF-04859989 reduced brain KYNA formation when given prior to kynurenine, prevented disturbances in REM sleep and sleep spindles, and enhanced NREM sleep. Our findings suggest that reducing KYNA in conditions where the kynurenine pathway is activated may serve as a potential strategy for improving sleep dynamics.

neuroscience↗