L-Serine Influences Epigenetic Modifications to Improve Cognition and Behaviors in Growth Hormone-Releasing Hormone Knockout Mice

Serine metabolism in aging and age-related diseases

Non-essential amino acids are often overlooked in biomedical research; however, they are crucial components of organismal metabolism. One such metabolite that is integral to physiological function is serine. Serine acts as a pivotal link connecting glycolysis with one-carbon and lipid metabolism, as well as with pyruvate and glutathione syntheses. Interestingly, increasing evidence suggests that serine metabolism may impact the aging process, and supplementation with serine may confer benefits in safeguarding against aging and age-related disorders. This review synthesizes recent insights into the regulation of serine metabolism during aging and its potential to promote healthy lifespan and mitigate a spectrum of age-related diseases.

Epigenetic underpinnings of the autistic mind: Histone modifications and prefrontal excitation/inhibition imbalance

Autism spectrum disorder (ASD) is complex neurobehavioral condition influenced by several cellular and molecular mechanisms that are often concerned with synaptogenesis and synaptic activity. Based on the excitation/inhibition (E/I) imbalance theory, ASD could be the result of disruption in excitatory and inhibitory synaptic transmission across the brain. The prefrontal cortex (PFC) is the chief regulator of executive function and can be affected by altered neuronal excitation and inhibition in the course of ASD. The molecular mechanisms involved in E/I imbalance are subject to epigenetic regulation. In ASD, altered enrichment and spreading of histone H3 and H4 modifications such as the activation-linked H3K4me2/3, H3K9ac, and H3K27ac, and repression-linked H3K9me2, H3K27me3, and H4K20me2 in the PFC result in dysregulation of molecules mediating synaptic excitation (ARC, EGR1, mGluR2, mGluR3, GluN2A, and GluN2B) and synaptic inhibition (BSN, EphA7, SLC6A1). Histone modifications are a dynamic component of the epigenetic regulatory elements with a pronounced effect on patterns of gene expression with regards to any biological process. The excitation/inhibition imbalance associated with ASD is based on the excitatory and inhibitory synaptic activity in different regions of the brain, including the PFC, the ultimate outcome of which is highly influenced by transcriptional activity of relevant genes.

Alterations in microbiota-metabolism-circRNA crosstalk in autism spectrum disorder-like behaviours caused by maternal exposure to glyphosate-based herbicides in mice

Epidemiological evidence indicates exposure to glyphosate-based herbicides (GBHs) increases the risk for autism spectrum disorder (ASD). The gut microbiota has been found to influence ASD behaviours through the microbiota-gut-brain axis. However, the underlying links between early life GBH exposure and ASD-like phenotypes through the microbiota-gut-brain axis remain unclear. Therefore, we exposed mice to low-dose GBH (0.10, 0.25, 0.50, and 1.00 %) and determined the effects on ASD-like behaviours. Furthermore, three kinds of omics (gut microbiomics, metabolomics, and transcriptomics) were conducted to investigate the effects of GBH exposure on gut microbiota, gut metabolites, and circular RNAs (circRNAs) in the prefrontal cortex (PFC) using a cross-generational mouse model. Behavioural analyses suggested social impairment and repetitive/stereotypic behaviours in the GBH-exposed offspring. Furthermore, maternal exposure to glyphosate significantly altered the ASD-associated gut microbiota of offspring, and ASD-associated gut metabolites were identified. Specifically, we found that alterations in the gut microenvironment may contribute to changes in gut permeability and the blood-brain barrier, which are related to changes in the levels of circRNAs in the PFC. Our results suggest a potential effect of circRNAs through the disruption of the gut-brain interaction, which is an important factor in the pathogenesis of ASD in offspring induced by maternal exposure to GBH.

Effects of photon irradiation in the presence and absence of hindlimb unloading on the behavioral performance and metabolic pathways in the plasma of Fischer rats

Introduction: The space environment astronauts experience during space missions consists of multiple environmental challenges, including microgravity. In this study, we assessed the behavioral and cognitive performances of male Fisher rats 2 months after sham irradiation or total body irradiation with photons in the absence or presence of simulated microgravity. We analyzed the plasma collected 9 months after sham irradiation or total body irradiation for distinct alterations in metabolic pathways and to determine whether changes to metabolic measures were associated with specific behavioral and cognitive measures. Methods: A total of 344 male Fischer rats were irradiated with photons (6 MeV; 3, 8, or 10 Gy) in the absence or presence of simulated weightlessness achieved using hindlimb unloading (HU). To identify potential plasma biomarkers of photon radiation exposure or the HU condition for behavioral or cognitive performance, we performed regression analyses. Results: The behavioral effects of HU on activity levels in an open field, measures of anxiety in an elevated plus maze, and anhedonia in the M&M consumption test were more pronounced than those of photon irradiation. Phenylalanine, tyrosine, and tryptophan metabolism, and phenylalanine metabolism and biosynthesis showed very strong pathway changes, following photon irradiation and HU in animals irradiated with 3 Gy. Here, 29 out of 101 plasma metabolites were associated with 1 out of 13 behavioral measures. In the absence of HU, 22 metabolites were related to behavioral and cognitive measures. In HU animals that were sham-irradiated or irradiated with 8 Gy, one metabolite was related to behavioral and cognitive measures. In HU animals irradiated with 3 Gy, six metabolites were related to behavioral and cognitive measures. Discussion: These data suggest that it will be possible to develop stable plasma biomarkers of behavioral and cognitive performance, following environmental challenges like HU and radiation exposure.