Effects of stress on functional connectivity during problem solving.

AIM: Our purpose was to examine how stress affects functional connectivity (FC) in language processing regions of the brain during a verbal problem solving task associated with creativity. We additionally explored how gender and the presence of the stress-susceptible short allele of the serotonin transporter gene polymorphism influenced this effect. METHODS: Forty-five healthy participants (Mean age: 19.6 â€‹± â€‹1.6 years; 28 females) were recruited to be a part of this study and genotyped to determine the presence or absence of at least one copy of the short (S) allele of the serotonin transporter gene, which is associated with greater susceptibility to stress. The participants underwent functional magnetic resonance imaging in two separate sessions (stress and no stress control). One session utilized a modified version of the Montreal Imaging Stress Test (MIST) to induce stress while the other session consisted of a no stress control task. The MIST and control tasks were interleaved with task blocks during which the participants performed the compound remote associates task, a convergent task that engages divergent thinking, which is a critical component of creativity. We examined the relationship between stress effects on performance and effects on connectivity of language processing regions activated during this task. RESULTS: There was no main effect of stress on functional connectivity for individual ROI pairs. However, in the examination of whether stress effects on performance related to effects on connectivity, changes in middle temporal gyrus connectivity with stress correlated positively with changes in solution latency for individuals with the S allele, but anti-correlated for those with only the L allele. A trend towards a gene â€‹× â€‹stress interaction on solution latency was also observed. DISCUSSION: Results from the study suggest that genetic susceptibility to stress, such as the presence of the S allele, affects neural correlates of performance on tasks related to verbal problem solving, as indicated by connectivity of the middle temporal gyrus. Future work will need to determine whether connectivity of the middle temporal gyrus serves as a marker for the effect of stress susceptibility on cognition, extending into stress susceptible patient populations.

Sex-specific effects of docosahexaenoic acid (DHA) on the microbiome and behavior of socially-isolated mice.

Dietary supplementation with the long-chain omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) has been shown to have a beneficial effect on reducing the symptoms associated with several neuropsychiatric conditions including anxiety and depression. However, the mechanisms underlying this effect remain largely unknown. Increasing evidence suggests that the vast repertoire of commensal bacteria within the gut plays a critical role in regulating various biological processes in the brain and may contribute to neuropsychiatric disease risk. The present study determined the contribution of DHA on anxiety and depressive-like behaviors through modulation of the gut microbiota in a paradigm of social isolation. Adult male and female mice were subjected to social isolation for 28days and then placed either on a control diet or a diet supplemented with 0.1% or 1.0% DHA. Fecal pellets were collected both 24h and 7days following the introduction of the new diets. Behavioral testing revealed that male mice fed a DHA diet, regardless of dose, exhibited reduced anxiety and depressive-like behaviors compared to control fed mice while no differences were observed in female mice. As the microbiota-brain-axis has been recently implicated in behavior, composition of microbial communities were analyzed to examine if these sex-specific effects of DHA may be associated with changes in the gut microbiota (GM). Clear sex differences were observed with males and females showing distinct microbial compositions prior to DHA supplementation. The introduction of DHA into the diet also induced sex-specific interactions on the GM with the fatty acid producing a significant effect on the microbial profiles in males but not in females. Interestingly, levels of Allobaculum and Ruminococcus were found to significantly correlate with the behavioral changes observed in the male mice. Predictive metagenome analysis using PICRUSt was performed on the fecal samples collected from males and identified enrichment in functional KEGG pathway terms relevant to processes such as the biosynthesis of unsaturated fatty acids and antioxidant metabolism. These results indicate that DHA alters commensal community composition and produces beneficial effects on anxiety and depressive-like behaviors in a sex-specific manner. The present study provides insight into the mechanistic role that gut microbes may play in the regulation of anxiety and depressive-like behaviors and how dietary intervention can modulate these effects.

Transcriptional Gene Silencing of the Autism-Associated Long Noncoding RNA MSNP1AS in Human Neural Progenitor Cells.

The long noncoding RNA MSNP1AS (moesin pseudogene 1, antisense) is a functional element that was previously associated with autism spectrum disorder (ASD) with genome-wide significance. Expression of MSNP1AS was increased 12-fold in the cerebral cortex of individuals with ASD and 22-fold in individuals with a genome-wide significantly associated ASD genetic marker on chromosome 5p14.1. Overexpression of MSNP1AS in human neuronal cells caused decreased expression of moesin protein, which is involved in neuronal process stability. In this study, we hypothesize that MSNP1AS knockdown impacts global transcriptome levels. We transfected the human neural progenitor cell line SK- N-SH with constructs that caused a 50% suppression of MSNP1AS expression. After 24 h, cells were harvested for total RNA isolation. Strand-specific RNA sequencing analysis indicated altered expression of 1,352 genes, including altered expression of 318 genes following correction for multiple comparisons. Expression of the OAS2 gene was increased >150-fold, a result that was validated by quantitative PCR. Gene ontology analysis of the 318 genes with altered expression following correction for multiple comparisons indicated that upregulated genes were significantly enriched for genes involved in immune response, and downregulated genes were significantly enriched for genes involved in chromatin remodeling. These data indicate multiple transcriptional and translational functions of MSNP1AS that impact ASD-relevant biological processes. Chromatin remodeling and immune response are biological processes implicated by genes with rare mutations associated with ASD. Our data suggest that the functional elements implicated by association of common genetic variants impact the same biological processes, suggesting a possible shared common molecular pathway of ASD.

Dissociable effects of dorsal and ventral hippocampal DHA content on spatial learning and anxiety-like behavior.

Chronic deficiency of dietary docosahexaenoic acid (DHA) during critical developmental windows results in severe deficits in spatial learning, anxiety and hippocampal neuroplasticity that parallel a variety of neuropsychiatric disorders. However, little is known regarding the influence of long-term, multigenerational exposure to dietary DHA enrichment on these same traits. To characterize the potential benefits of multigenerational DHA enrichment, mice were fed a purified 10:1 omega-6/omega-3 diet supplemented with either 0.1% preformed DHA/kg feed weight or 1.0% preformed DHA/kg feed weight through three generations. General locomotor activity, spatial learning, and anxiety-like behavior were assessed in adult male offspring of the third generation. Following behavioral assessments, ventral and dorsal hippocampus was collected for DHA and arachidonic acid (AA) analysis. Animals consuming the 0.1% and 1.0% DHA diet did not differ from control animals for locomotor activity or on performance during acquisition learning, but made fewer errors and showed more stable across-day performance during reversal learning on the spatial task and showed less anxiety-like behavior. Consumption of the DHA-enriched diets increased DHA content in the ventral and dorsal hippocampus in a region-specific manner. DHA content in the dorsal hippocampus predicted performance on the reversal training task. DHA content in the ventral hippocampus was correlated with anxiety-like behavior, but AA content in the dorsal hippocampus was a stronger predictor of this behavior. These results suggest that long-term, multigenerational DHA administration improves performance on some aspects of complex spatial learning, decreases anxiety-like behavior, and that modulation of DHA content in sub-regions of the hippocampus predicts which behaviors are likely to be affected.

The Relationship between Maternal Antibodies to Fetal Brain and Prenatal Stress Exposure in Autism Spectrum Disorder.

Environmental and genetic factors contribute to the etiology of autism spectrum disorder (ASD), but their interaction is less well understood. Mothers that are genetically more stress-susceptible have been found to be at increased risk of having a child with ASD after exposure to stress during pregnancy. Additionally, the presence of maternal antibodies for the fetal brain is associated with a diagnosis of ASD in children. However, the relationship between prenatal stress exposure and maternal antibodies in the mothers of children diagnosed with ASD has not yet been addressed. This exploratory study examined the association of maternal antibody response with prenatal stress and a diagnosis of ASD in children. Blood samples from 53 mothers with at least one child diagnosed with ASD were examined by ELISA. Maternal antibody presence, perceived stress levels during pregnancy (high or low), and maternal 5-HTTLPR polymorphisms were examined for their interrelationship in ASD. While high incidences of prenatal stress and maternal antibodies were found in the sample, they were not associated with each other (p = 0.709, Cramér's V = 0.051). Furthermore, the results revealed no significant association between maternal antibody presence and the interaction between 5-HTTLPR genotype and stress (p = 0.729, Cramér's V = 0.157). Prenatal stress was not found to be associated with the presence of maternal antibodies in the context of ASD, at least in this initial exploratory sample. Despite the known relationship between stress and changes in immune function, these results suggest that prenatal stress and immune dysregulation are independently associated with a diagnosis of ASD in this study population, rather than acting through a convergent mechanism. However, this would need to be confirmed in a larger sample.

Potential Neuroprotective Effects of Dietary Omega-3 Fatty Acids on Stress in Alzheimer's Disease.

BACKGROUND: A large number of individual potentially modifiable factors are associated with risk for Alzheimer's disease (AD). However, less is known about the interactions between the individual factors. METHODS: In order to begin to examine the relationship between a pair of factors, we performed a pilot study, surveying patients with AD and controls for stress exposure and dietary omega-3 fatty acid intake to explore their relationship for risk of AD. RESULTS: For individuals with the greatest stress exposure, omega-3 fatty acid intake was significantly greater in healthy controls than in AD patients. There was no difference among those with low stress exposure. CONCLUSIONS: These initial results begin to suggest that omega-3 fatty acids may mitigate AD risk in the setting of greater stress exposure. This will need to be examined with larger populations and other pairs of risk factors to better understand these important relationships. Examining how individual risk factors interact will ultimately be important for learning how to optimally decrease the risk of AD.

Maternal DHA supplementation influences sex-specific disruption of placental gene expression following early prenatal stress.

Early life adversity is widely recognized as a key risk factor for early developmental perturbations and contributes to the presentation of neuropsychiatric disorders in adulthood. Neurodevelopmental disorders exhibit a strong sex bias in susceptibility, presentation, onset, and severity, although the underlying mechanisms conferring vulnerability are not well understood. Environmental perturbations during pregnancy, such as malnutrition or stress, have been associated with sex-specific reprogramming that contribute to increased disease risk in adulthood, whereby stress and nutritional insufficiency may be additive and further exacerbate poor offspring outcomes. To determine whether maternal supplementation of docosahexanoic acid (DHA) exerts an effect on offspring outcome following exposure to early prenatal stress (EPS), dams were fed a purified 10:1 omega-6/omega-3 diet supplemented with either 1.0% preformed DHA/kg feed weight (DHA-enriched) or no additional DHA (denoted as the control diet, CTL). Dams were administered chronic variable stress during the first week of pregnancy (embryonic day, E0.5-7.5), and developmental milestones were assessed at E 12.5. Exposure to early prenatal stress (EPS) decreased placenta and embryo weight in males, but not females, exposed to the CTL diet. DHA enrichment reversed the sex-specific decrease in placenta and embryo weight following EPS. Early prenatal exposure upregulated expression of genes associated with oxygen and nutrient transport, including hypoxia inducible factor 3α (HIF3α), peroxisome proliferator-activated receptor alpha (PPARα), and insulin-like growth binding factor 1 (IGFBP1), in the placenta of CTL diet males exposed to EPS. DHA enrichment in EPS-exposed animals abrogated the male-specific upregulation of PPARα, HIF3α, and IGFBP1. Taken together, these studies suggest that maternal dietary DHA enrichment may buffer against maternal stress programming of sex-specific outcomes during early development.

Effects of stress on functional connectivity during verbal processing.

Effects of stress on functional connectivity (FC) in specific language processing regions of the brain during verbal fluency tasks were explored. Roles of gender and serotonin transporter gene polymorphisms (5-HTTLPR), associated with stress susceptibility, were also examined to understand their effect. Forty-five healthy volunteers (Mean age: 19.6 ± 1.6 years; 28 females) participated. Functional magnetic resonance imaging was carried out while participants performed letter and category fluency tasks. These tasks were interposed with the Montreal Imaging Stress Test to induce stress or a no-stress control task. Buccal swabs collected were used to genotype for the presence of polymorphisms on the SLC6A4 gene known to contribute to atypical stress responses. Significant variations in strength of FC were noted between several ROIs, including left inferior frontal gyrus and left middle temporal gyrus. Overall, males showed regional increases in FC strength over long and short distances during task under stress. Additionally, variability in effects of stress on task performance was associated with effects of stress on FC. Results suggest that long distance FC may be strengthened to compensate for additional cognitive load of the stressor but that specific short distance functional connections may be strengthened in a gender specific manner. Additionally, FC may serve as a marker for effects of stress on performance. This is the first study exploring stress effects on language tasks with imaging markers. Future studies will need to explore stress susceptible populations and establish the role of FC as a marker, with implications for targeted therapeutic interventions.

Maternal serotonin transporter genotype affects risk for ASD with exposure to prenatal stress.

Stress exposure during gestation is implicated in several neuropsychiatric conditions, including autism spectrum disorder (ASD). Previous research showed that prenatal stress increases risk for ASD with peak exposure during the end of the second and the beginning of the third trimester. However, exposures to prenatal stress do not always result in ASD, suggesting that other factors may interact with environmental stressors to increase ASD risk. The present study examined a maternal genetic variation in the promoter region of the serotonin transporter gene (5-HTTLPR) affecting stress tolerance and its interaction with the effect of environmental stressors on risk for ASD. Two independent cohorts of mothers of ASD children recruited by the University of Missouri and Queen's University were surveyed regarding the prenatal environment and genotyping on 5-HTTLPR was performed to explore this relationship. In both samples, mothers of children with ASD carrying the stress susceptible short allele variant of 5-HTTLPR experienced a greater number of stressors and greater stress severity when compared to mothers carrying the long allele variant. The temporal peak of stressors during gestation in these mothers was consistent with previous findings. Additionally, increased exposure to prenatal stress was not reported in the pregnancies of typically developing siblings from the same mothers, regardless of maternal genotype, suggesting against the possibility that the short allele might increase the recall of stress during pregnancy. The present study provides further evidence of a specific maternal polymorphism that may affect the risk for ASD with exposure to prenatal stress. Autism Res 2016, 9: 1151-1160. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Noncoding RNA in the transcriptional landscape of human neural progenitor cell differentiation.

Increasing evidence suggests that noncoding RNAs play key roles in cellular processes, particularly in the brain. The present study used RNA sequencing to identify the transcriptional landscape of two human neural progenitor cell lines, SK-N-SH and ReNcell CX, as they differentiate into human cortical projection neurons. Protein coding genes were found to account for 54.8 and 57.0% of expressed genes, respectively, and alignment of RNA sequencing reads revealed that only 25.5-28.1% mapped to exonic regions of the genome. Differential expression analysis in the two cell lines identified altered gene expression in both protein coding and noncoding RNAs as they undergo neural differentiation with 222 differentially expressed genes observed in SK-N-SH cells and 19 differentially expressed genes in ReNcell CX. Interestingly, genes showing differential expression in SK-N-SH cells are enriched in genes implicated in autism spectrum disorder, but not in gene sets related to cancer or Alzheimer's disease. Weighted gene co-expression network analysis (WGCNA) was used to detect modules of co-expressed protein coding and noncoding RNAs in SK-N-SH cells and found four modules to be associated with neural differentiation. These modules contain varying levels of noncoding RNAs ranging from 10.7 to 49.7% with gene ontology suggesting roles in numerous cellular processes important for differentiation. These results indicate that noncoding RNAs are highly expressed in human neural progenitor cells and likely hold key regulatory roles in gene networks underlying neural differentiation and neurodevelopmental disorders.

Beta-adrenergic antagonist effects on a novel cognitive flexibility task in rodents.

Previous work examining animal models of cognitive flexibility have focused on tasks where animals are required to shift between cues in order to reach a food reward from among a limited set of choices. Performance by nonhuman animals on these tasks, including reversal learning, intradimensional set-shifting, and extradimensional set-shifting, are affected by pharmacological action on serotonergic, dopaminergic, and alpha-adrenergic, but not beta-adrenergic receptors. However, beta-adrenergic antagonists, such as propranolol, are widely utilized for conditions such as test anxiety. Propranolol improves performance in humans during cognitive flexibility tasks where there is a broad set of potential solutions. The current investigation utilized a digging task where the rodent must develop a novel solution in order to obtain a reward. Similar to the effects observed in humans, propranolol improved performance on this task, while not affecting performance on set-shifting tasks, as with previous animal studies. This may allow future investigation of the neurobiological mechanism by which propranolol affects context-specific anxiety, and could provide insight into the neurobiology of creativity.

Maternal diet rich in omega-6 polyunsaturated fatty acids during gestation and lactation produces autistic-like sociability deficits in adult offspring.

Multiple studies have reported prenatal stress as a potential risk factor for the development of autism spectrum disorder (ASD). In rodents, a significant reduction in sociability is seen in prenatally stressed offspring of genetically stress-susceptible dams. Certain dietary factors that contribute to stress reactivity may, therefore, exacerbate prenatal stress-mediated behavioral changes in adult offspring. Adults with a diet rich in omega-6 polyunsaturated fatty acids (PUFAs) display increased stress reactivity. In the current study, the effects of prenatal diet and prenatal stress on social behavior in adult offspring mice were examined. Pregnant C57BL/6J dams received either chronic variable stress or no stress, and were also placed on a control diet or a diet rich in omega-6 PUFAs, in a 2×2 design. We subsequently tested the adult offspring for sociability, anxiety, and locomotor behaviors using a 3-chambered social approach task, an elevated-plus maze, an open field task and a rotarod task. Results indicated that a maternal diet rich in omega-6 PUFAs during gestation and lactation produce changes in sociability consistent with those observed in ASD. Additionally, offspring exposed to a diet rich in omega-6 PUFAs during gestation and lactation had increased levels of anxiety in the elevated-plus maze. Prenatal stress had no effect on offspring behavior. These findings provide evidence for a possible environmental risk factor that contributes to the production of autistic-like behavior in mice.