Oleic acid synthesized in the periventricular zone promotes axonogenesis in the striatum during brain development

Integrating Nutrient Biomarkers, Cognitive Function, and Structural MRI Data to Build Multivariate Phenotypes of Healthy Aging

BACKGROUND

Research in the emerging field of Nutritional Cognitive Neuroscience demonstrates that many aspects of nutrition - from entire diets to specific nutrients - affect cognitive performance and brain health.

OBJECTIVE

While prior research has primarily examined the bivariate relationship between nutrition and cognition, or nutrition and brain health, the present study sought to investigate the joint relationship between these essential and interactive elements of human health.

METHODS

We applied a state-of-the-art data fusion method, Coupled Matrix Tensor Factorization, to characterize the joint association between measures of nutrition (52 nutrient biomarkers), cognition (Wechsler Abbreviated Test of Intelligence and Wechsler Memory Scale), and brain health (high-resolution Magnetic Resonance Imaging measures of structural brain volume) within a cross-sectional sample of 111 healthy older adults that had an average age of 69.1 years, were 62% female and had an average Body Mass Index of 26.0.

RESULTS

Data fusion uncovered 3 latent factors that capture the joint association between specific nutrient profiles, cognitive measures, and cortical volumes, demonstrating the respects in which these health domains are coupled. Hierarchical cluster analysis further revealed systematic differences between the observed latent factors, providing evidence for multivariate phenotypes that represent high versus low levels of performance across multiple health domains. The primary features that distinguish between each phenotype were: (i) nutrient biomarkers for monounsaturated and polyunsaturated fatty acids; (ii) cognitive measures of immediate, auditory, and delayed memory; and (iii) brain volumes within frontal, temporal, and parietal cortex.

CONCLUSIONS

By incorporating innovations in nutritional epidemiology (nutrient biomarker analysis), cognitive neuroscience (high-resolution structural brain imaging), and statistics (data fusion), the present study provides an interdisciplinary synthesis of methods that elucidate how nutrition, cognition, and brain health are integrated through lifestyle choices that affect healthy aging.

Fatty Acids: A Safe Tool for Improving Neurodevelopmental Alterations in Down Syndrome?

The triplication of chromosome 21 causes Down syndrome (DS), a genetic disorder that is characterized by intellectual disability (ID). The causes of ID start in utero, leading to impairments in neurogenesis, and continue into infancy, leading to impairments in dendritogenesis, spinogenesis, and connectivity. These defects are associated with alterations in mitochondrial and metabolic functions and precocious aging, leading to the early development of Alzheimer’s disease. Intense efforts are currently underway, taking advantage of DS mouse models to discover pharmacotherapies for the neurodevelopmental and cognitive deficits of DS. Many treatments that proved effective in mouse models may raise safety concerns over human use, especially at early life stages. Accumulating evidence shows that fatty acids, which are nutrients present in normal diets, exert numerous positive effects on the brain. Here, we review (i) the knowledge obtained from animal models regarding the effects of fatty acids on the brain, by focusing on alterations that are particularly prominent in DS, and (ii) the progress recently made in a DS mouse model, suggesting that fatty acids may indeed represent a useful treatment for DS. This scenario should prompt the scientific community to further explore the potential benefit of fatty acids for people with DS.

Metabolomic Differential Compounds Reflecting the Clinical Efficacy of Polyethylene Glycol Recombinant Human Growth Hormone in the Treatment of Childhood Growth Hormone Deficiency

Understanding metabolite profiles may aid in providing a reference for individualized treatment using PEG-rhGH. Therefore, this study aimed to evaluate the clinical efficacy of PEG-rhGH in treating GHD patients by using a metabolomic approach. Fifty-seven pediatric participants treated with PEG-rhGH were enrolled (28 GHD patients with high clinical efficacy and 29 GHD patients with lower clinical efficacy). Serum samples from all patients were first collected at baseline for biochemical detection; then metabolite levels were measured using gas chromatography time-of-flight mass spectrometry. The candidates included heptadecanoic acid, stearic acid, 2-hydroxybutyric acid, myristic acid, palmitoleic acid, D-galactose, dodecanoic acid, and oleic acid. The related metabolic pathways involved fatty acid metabolism and energy metabolism. This study suggested that growth gains of PEG-rhGH treatment might be differentiated by altered serum levels of fatty acid. Collectively, the metabolomic study provides unique insights into the use of PEG-rhGH as a therapeutic strategy for individualized treatment.

Lipid droplet availability affects neural stem/progenitor cell metabolism and proliferation

Neural stem/progenitor cells (NSPCs) generate new neurons throughout adulthood. However, the underlying regulatory processes are still not fully understood. Lipid metabolism plays an important role in regulating NSPC activity: build-up of lipids is crucial for NSPC proliferation, whereas break-down of lipids has been shown to regulate NSPC quiescence. Despite their central role for cellular lipid metabolism, the role of lipid droplets (LDs), the lipid storing organelles, in NSPCs remains underexplored. Here we show that LDs are highly abundant in adult mouse NSPCs, and that LD accumulation is significantly altered upon fate changes such as quiescence and differentiation. NSPC proliferation is influenced by the number of LDs, inhibition of LD build-up, breakdown or usage, and the asymmetric inheritance of LDs during mitosis. Furthermore, high LD-containing NSPCs have increased metabolic activity and capacity, but do not suffer from increased oxidative damage. Together, these data indicate an instructive role for LDs in driving NSPC behaviour.

The Majority of Brain Palmitic Acid is Maintained by Lipogenesis from Dietary Sugars and is Augmented in Mice fed Low Palmitic Acid Levels from Birth

Previously, results from studies investigating if brain palmitic acid (16:0; PAM) was maintained by either dietary uptake or lipogenesis de novo (DNL) varied. Here, we utilize naturally occurring carbon isotope ratios (¹³ C/¹² C; δ¹³ C) to uncover the origin of brain PAM. Additionally, we explored brain and liver fatty acid concentration, total brain metabolomic profile, and behaviour. BALB/c dams were equilibrated onto either a low PAM diet (LP; <2%) or high PAM diet (HP; >95%) prior to producing one generation of offspring. Offspring stayed on the respective diet of the dam until 15-weeks of age, at which time the Open Field test was conducted in the offspring, prior to euthanasia and tissue lipid extraction. Although liver PAM was lower in offspring fed the LP diet, as well as female offspring, brain PAM was not affected by diet or sex. Across offspring of either sex on both diets, brain ¹³ C-PAM revealed compared to dietary uptake, DNL from dietary sugars contributed 68.8%-79.5% and 46.6%-58.0% to the total brain PAM pool by both peripheral and local brain DNL, and local brain DNL alone, respectively. DNL was augmented in offspring fed the LP diet, and the ability to upregulate DNL in the liver or the brain depended on sex. Anxiety-like behaviours were decreased in offspring fed the LP diet and were correlated with markers of LP diet consumption including increased liver ¹³ C-PAM, warranting further investigation. Altogether, our results indicate that DNL from dietary sugars is a compensatory mechanism to maintain brain PAM in response to a LP diet.

Connexin43 peptide, TAT-Cx43266-283, selectively targets glioma cells, impairs malignant growth, and enhances survival in mouse models in vivo

Background

Malignant gliomas are the most frequent primary brain tumors and remain among the most incurable cancers. Although the role of the gap junction protein, connexin43 (Cx43), has been deeply investigated in malignant gliomas, no compounds have been reported with the ability to recapitulate the tumor suppressor properties of this protein in in vivo glioma models.

Methods

TAT-Cx43_266–283 a cell-penetrating peptide which mimics the effect of Cx43 on c-Src inhibition, was studied in orthotopic immunocompetent and immunosuppressed models of glioma. The effects of this peptide in brain cells were also analyzed.

Results

While glioma stem cell malignant features were strongly affected by TAT-Cx43_266–283, these properties were not significantly modified in neurons and astrocytes. Intraperitoneally administered TAT-Cx43_266–283 decreased the invasion of intracranial tumors generated by GL261 mouse glioma cells in immunocompetent mice. When human glioma stem cells were intracranially injected with TAT-Cx43_266–283 into immunodeficient mice, there was reduced expression of the stemness markers nestin and Sox2 in human glioma cells at 7 days post-implantation. Consistent with the role of Sox2 as a transcription factor required for tumorigenicity, TAT-Cx43_266–283 reduced the number and stemness of human glioma cells at 30 days post-implantation. Furthermore, TAT-Cx43_266–283 enhanced the survival of immunocompetent mice bearing gliomas derived from murine glioma stem cells.

Conclusion

TAT-Cx43_266–283 reduces the growth, invasion, and progression of malignant gliomas and enhances the survival of glioma-bearing mice without exerting toxicity in endogenous brain cells, which suggests that this peptide could be considered as a new clinical therapy for high-grade gliomas.

Elucidating the Neuroprotective Role of Formulated Camel α-Lactalbumin-Oleic Acid Complex by Curating the SIRT1 Pathway in Parkinson's Disease Model

Parkinson's Disease (PD) is characterized by increased oxidative stress and decreased level of dopamine. At present, the therapeutic interventions of PD are associated with undesirable adverse effects. To overcome these side effects, a new candidate bioinspired molecule is needed for the management of PD. Camel α-lactalbumin (α-LA) is the most abundant protein in camel's milk and has a potential to act as a nutraceutical supplement for neurological functions. Oleic acid, a monounsaturated fatty acid, has been widely associated with a reduced risk of PD. The present study aimed to formulate the camel α-LA and oleic acid (CLOA) complex under specific conditions and to evaluate its efficacy as a neuroprotective in rotenone induced PC12 cell model of PD. Our results demonstrated that removal of Ca++ ions from camel α-LA by EDTA enhances its binding efficiency with oleic acid, and the complex was characterized by UV-CD, ANS fluorescence spectroscopy, and NMR spectroscopy. Moreover, CLOA complex treatment reduced the oxidative stress and increased the cell viability by enhancing the level of dopamine and the expression of SIRT1, FOXO3a, HIF-1α, and HSF-1. We also validated the neuroprotective role of the complex by incubating the cells with CLOA complex prior to rotenone treatment. We inferred from the outcome of the results that the individual entity, i.e., α-LA or OA, is not as effective as the complex. Taken together, our study indicates that CLOA complex might be a potential candidate for the development of future therapeutic drugs for PD.

Prenatal Administration of Oleic Acid or Linolenic Acid Reduces Neuromorphological and Cognitive Alterations in Ts65dn Down Syndrome Mice

BACKGROUND

The cognitive impairments that characterize Down syndrome (DS) have been attributed to brain hypocellularity due to neurogenesis impairment during fetal stages. Thus, enhancing prenatal neurogenesis in DS could prevent or reduce some of the neuromorphological and cognitive defects found in postnatal stages.

OBJECTIVES

As fatty acids play a fundamental role in morphogenesis and brain development during fetal stages, in this study, we aimed to enhance neurogenesis and the cognitive abilities of the Ts65Dn (TS) mouse model of DS by administering oleic or linolenic acid.

METHODS

In total, 85 pregnant TS females were subcutaneously treated from Embryonic Day (ED) 10 until Postnatal Day (PD) 2 with oleic acid (400 mg/kg), linolenic acid (500 mg/kg), or vehicle. All analyses were performed on their TS and Control (CO) male and female progeny. At PD2, we evaluated the short-term effects of the treatments on neurogenesis, cellularity, and brain weight, in 40 TS and CO pups. A total of 69 TS and CO mice were used to test the long-term effects of the prenatal treatments on cognition from PD30 to PD45, and on neurogenesis, cellularity, and synaptic markers, at PD45. Data were compared by ANOVAs.

RESULTS

Prenatal administration of oleic or linolenic acid increased the brain weight (+36.7% and +45%, P < 0.01), the density of BrdU (bromodeoxyuridine)- (+80% and +115%; P < 0.01), and DAPI (4',6-diamidino-2-phenylindole)-positive cells (+64% and +22%, P < 0.05) of PD2 TS mice with respect to the vehicle-treated TS mice. Between PD30 and PD45, TS mice prenatally treated with oleic or linolenic acid showed better cognitive abilities (+28% and +25%, P < 0.01) and a higher density of the postsynaptic marker PSD95 (postsynaptic density protein 95) (+65% and +44%, P < 0.05) than the vehicle-treated TS animals.

CONCLUSION

The beneficial cognitive and neuromorphological effects induced by oleic or linolenic acid in TS mice suggest that they could be promising pharmacotherapies for DS-associated cognitive deficits.

Afternoon distraction: a high-saturated-fat meal and endotoxemia impact postmeal attention in a randomized crossover trial

BACKGROUND

Saturated-fat intake and endotoxemia can impair cognition. However, their acute impact on cognitive performance is unknown.

OBJECTIVE

This study assessed the impact of 2 high-fat meals and endotoxemia on attention.

METHODS

In this double-blind, randomized crossover trial, 51 women (n = 32 breast cancer survivors, n = 19 noncancer controls; mean ± SD age: 53 ± 8 y) completed the Continuous Performance Test (CPT) and had their blood drawn to assess endotoxemia markers LPS binding protein (LBP), soluble CD14 (sCD14), and the LBP to sCD14 ratio 1 h prior to eating either a high-saturated-fat meal or a high-oleic-sunflower-oil meal. Women again completed the CPT 5 h postmeal. At 1 to 4 wk later, women completed the same protocol but consumed the other meal.

RESULTS

In adjusted models, women had more difficulty distinguishing target stimuli from distractors after consuming the high-saturated-fat meal than they did after the oleic-sunflower-oil meal (B = 4.44, SE = 1.88, P = 0.02). Women with higher baseline LBP had less consistent response times (B = 0.002, SE = 0.0008, P = 0.04). Those with higher LBP and LBP:sCD14 were less able to sustain their attention throughout the entire CPT, as reflected by their progressively slower (B = 0.002, SE = 0.0006, P = 0.003; and B = 2.43, SE = 0.090, P = 0.008, respectively) and more erratic (B = 0.003, SE = 0.0008, P < 0.0001; and B = 3.29, SE = 1.17, P = 0.006, respectively) response times. Additionally, women with higher baseline LBP or sCD14 were less able to maintain or increase response speeds at higher interstimulus intervals (B = 0.002, SE = 0.0006, P = 0.02; and B = 0.006, SE = 0.003, P = 0.03, respectively), indicating greater difficulty adapting to changing task demands. Significant meal type by LBP and LBP:sCD14 interactions emerged (P < 0.05), such that high LBP and LBP:sCD14 erased between-meal cognitive differences, uniformly impairing performance.

CONCLUSIONS

These results suggest that higher LBP, sCD14, and LBP:sCD14 and saturated-fat intake individually and jointly influence attention. Endotoxemia may override the relative cognitive benefit of healthier oil choices.This trial is registered at clinicaltrials.gov as NCT04247763.

Whole exome sequencing identifies SCD5 as a novel causative gene for autosomal dominant nonsyndromic deafness

We report a genetic assessment of autosomal dominant, nonsyndromic, progressive sensorineural hearing loss in a Chinese family, combining whole-exome sequencing and genome-wide linkage analysis. A novel missense mutation, c.626G > C, in the SCD5 gene was identified in this family. The heterozygous missense mutation could segregate hearing loss cases among family members, and was predicted to be deleterious by Polyphen-2, LRT and Mutation Taster. SCD5 is an endoplasmic reticulum enzyme, catalyzing the formation of monounsaturated fatty acids (MUFAs) from saturated fatty acids (SFAs). It plays a crucial role in regulating lipid metabolism. The SCD5 protein is expressed in inner and outer hair cells of the organ of Corti, the stria vascularis, cells of the lateral cochlear wall behind the spiral prominence, and more strongly in spiral ganglion cells of guinea pig and human fetal cochleas. SCD5 protein was also expressed in the brain, consistent with the hearing loss feature: the patients had a poor speech discrimination score at young age and mild hearing loss as evaluated by pure tone audiometry. In summary, we identified SCD5 as a novel gene responsible for autosomal dominant nonsyndromic deafness.

Fatty acid metabolism in the progression and resolution of CNS disorders

Recent advances in lipidomics and metabolomics have unveiled the complexity of fatty acid metabolism and the fatty acid lipidome in health and disease. A growing body of evidence indicates that imbalances in the metabolism and level of fatty acids drive the initiation and progression of central nervous system (CNS) disorders such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. Here, we provide an in-depth overview on the impact of the β-oxidation, synthesis, desaturation, elongation, and peroxidation of fatty acids on the pathophysiology of these and other neurological disorders. Furthermore, we discuss the impact of individual fatty acids species, acquired through the diet or endogenously synthesized in mammals, on neuroinflammation, neurodegeneration, and CNS repair. The findings discussed in this review highlight the therapeutic potential of modulators of fatty acid metabolism and the fatty acid lipidome in CNS disorders, and underscore the diagnostic value of lipidome signatures in these diseases.

Neuroprotective effects of oleic acid in rodent models of cerebral ischaemia

Oleic acid (OA) is released from brain phospholipids after cerebral ischaemia; however, its role in ischaemic injury remains unknown. We hypothesised that OA has neuroprotective effects after cerebral ischaemia, which may be exerted through peroxisome proliferator-activated receptor gamma (PPAR-γ) activation, since OA is an endogenous ligand of PPAR-γ. The effects of OA administration were evaluated in rodent models of middle cerebral artery occlusion (MCAO), photothrombosis, and four-vessel occlusion (4-VO). We determined the time window of therapeutic opportunity and examined the ability of the PPAR-γ antagonist GW9662 to reverse OA’s protective effects after MCAO. We found that OA administration decreased the MCAO-induced infarct volume and functional deficits, photothrombosis-induced infarct volume, and 4-VO-induced hippocampal neuronal death. Additionally, OA was highly efficacious when administered up to 3 h after MCAO. Pre-treatment with GW9662 abolished the inhibitory effects of OA on the infarct volume and immunoreactivity of key inflammatory mediators in the ischaemic cortex. Our results indicate that OA has neuroprotective effects against transient and permanent focal cerebral ischaemia, as well as global cerebral ischaemia. It may have therapeutic value for the ischaemic stroke treatment with a clinically feasible therapeutic window. The OA-mediated neuroprotection might be attributable to its anti-inflammatory actions through PPAR-γ activation.

Metabonomics reveals peripheral and central short-chain fatty acid and amino acid dysfunction in a naturally occurring depressive model of macaques

PURPOSE

Depression is a complex psychiatric disorder. Various depressive rodent models are usually constructed based on different pathogenesis hypotheses.

MATERIALS AND METHODS

Herein, using our previously established naturally occurring depressive (NOD) model in a non-human primate (cynomolgus monkey, Macaca fascularis), we performed metabolomics analysis of cerebrospinal fluid (CSF) from NOD female macaques (N=10) and age-and gender-matched healthy controls (HCs) (N=12). Multivariate statistical analysis was used to identify the differentially expressed metabolites between the two groups. Ingenuity Pathways Analysis and MetaboAnalyst were applied for predicted pathways and biological functions analysis.

RESULTS

Totally, 37 metabolites responsible for discriminating the two groups were identified. The NOD macaques were mainly characterized by perturbations of fatty acid biosynthesis, ABC transport system, and amino acid metabolism (eg, aspartate, glycine, serine, and threonine metabolism). Interestingly, we found that eight altered CSF metabolites belonging to short-chain fatty acids and amino acids were also observed in the serum of NOD macaques (N=13 per group).

CONCLUSION

Our findings suggest that peripheral and central short-chain fatty acids and amino acids are implicated in the onset of depression.

Brain Fatty Acid Composition and Inflammation in Mice Fed with High-Carbohydrate Diet or High-Fat Diet

Both high fat diet (HFD) and high carbohydrate diet (HCD) modulate brain fatty acids (FA) composition. Notwithstanding, there is a lack of information on time sequence of brain FA deposition either for HFD or HCD. The changes in brain FA composition in mice fed with HFD or HCD for 7, 14, 28, or 56 days were compared with results of 0 (before starting given the diets). mRNA expressions of allograft inflammatory factor 1 (Aif1), cyclooxygenase-2 (Cox 2), F4/80, inducible nitric oxide synthase (iNOS), integrin subunit alpha m (Itgam), interleukin IL-1β (IL-1β), IL-6, IL-10, and tumor necrosis factor alpha (TNF-α) were measured. The HFD group had higher speed of deposition of saturated FA (SFA), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA) at the beginning of the experimental period. However, on day 56, the total amount of SFA, MUFA, and PUFA were similar. mRNA expressions of F4/80 and Itgam, markers of microglia infiltration, were increased (p < 0.05) in the brain of the HCD group whereas inflammatory marker index (IMI) was higher (46%) in HFD group. In conclusion, the proportion of fat and carbohydrates in the diet modulates the speed deposition of FA and expression of inflammatory gene markers.

Treatment with corn oil improves neurogenesis and cognitive performance in the Ts65Dn mouse model of Down syndrome

Individuals with Down syndrome (DS), a genetic condition due to triplication of Chromosome 21, are characterized by intellectual disability that worsens with age. Since impairment of neurogenesis and dendritic maturation are very likely key determinants of intellectual disability in DS, interventions targeted to these defects may translate into a behavioral benefit. While most of the neurogenesis enhancers tested so far in DS mouse models may pose some caveats due to possible side effects, substances naturally present in the human diet may be regarded as therapeutic tools with a high translational impact. Linoleic acid and oleic acid are major constituents of corn oil that positively affect neurogenesis and neuron maturation. Based on these premises, the goal of the current study was to establish whether treatment with corn oil improves hippocampal neurogenesis and hippocampus-dependent memory in the Ts65Dn model of DS. Four-month-old Ts65Dn and euploid mice were treated with saline or corn oil for 30 days. Evaluation of behavior at the end of treatment showed that Ts65Dn mice treated with corn oil underwent a large improvement in hippocampus-dependent learning and memory. Evaluation of neurogenesis and dendritogenesis showed that in treated Ts65Dn mice the number of new granule cells of the hippocampal dentate gyrus and their dendritic pattern became similar to those of euploid mice. In addition, treated Ts65Dn mice underwent an increase in body and brain weight. This study shows for the first time that fatty acids have a positive impact on the brain of the Ts65Dn mouse model of DS. These results suggest that a diet that is rich in fatty acids may exert beneficial effects on cognitive performance in individuals with DS without causing adverse effects.

Restrained Phosphatidylcholine Synthesis in a Cellular Model of Down's Syndrome is Associated with the Overexpression of Dyrk1A

Aberrant formation of the cerebral cortex could be attributed to the lack of suitable substrates that direct the migration of neurons. Previous work carried out at our laboratory has shown that oleic acid is a neurotrophic factor. In order to characterize the effect of oleic acid in a cellular model of Down's syndrome (DS), here, we used immortalized cell lines derived from the cortex of trisomy Ts16 and euploid mice. We report that in the plasma membrane of euploid cells, an increase in phosphatidylcholine concentrations occurs in the presence of oleic acid. However, in trisomic cells, oleic acid failed to increase phosphatidylcholine incorporation into the plasma membrane. Gene expression analysis of trisomic cells revealed that the phosphatidylcholine biosynthetic pathway was deregulated. Taken together, these results suggest that the overdose of specific genes in trisomic lines delays differentiation in the presence of oleic acid. The dual-specificity tyrosine (Y) phosphorylation-regulated kinase 1A (DYRK1A) gene is located on human chromosome 21. DYRK1A contributes to intellectual disability and the early onset of Alzheimer's disease in DS patients. Here, we explored the potential role of Dyrk1A in the reduction of phosphatidylcholine concentrations in trisomic cells in the presence of oleic acid. The downregulation of Dyrk1A by small interfering RNA (siRNA) in trisomic cells returned phosphatidylcholine concentrations up to similar levels to those of euploid cells in the presence of oleic acid. Thus, our results highlight the role of Dyrk1A in brain development through the modulation of phosphatidylcholine location, levels and synthesis.

Low Density Lipoprotein Receptor Related Proteins as Regulators of Neural Stem and Progenitor Cell Function

The central nervous system (CNS) is a highly organised structure. Many signalling systems work in concert to ensure that neural stem cells are appropriately directed to generate progenitor cells, which in turn mature into functional cell types including projection neurons, interneurons, astrocytes, and oligodendrocytes. Herein we explore the role of the low density lipoprotein (LDL) receptor family, in particular family members LRP1 and LRP2, in regulating the behaviour of neural stem and progenitor cells during development and adulthood. The ability of LRP1 and LRP2 to bind a diverse and extensive range of ligands, regulate ligand endocytosis, recruit nonreceptor tyrosine kinases for direct signal transduction and signal in conjunction with other receptors, enables them to modulate many crucial neural cell functions.

Human pluripotent stem cell-derived neural constructs for predicting neural toxicity

Human pluripotent stem cell-based in vitro models that reflect human physiology have the potential to reduce the number of drug failures in clinical trials and offer a cost-effective approach for assessing chemical safety. Here, human embryonic stem (ES) cell-derived neural progenitor cells, endothelial cells, mesenchymal stem cells, and microglia/macrophage precursors were combined on chemically defined polyethylene glycol hydrogels and cultured in serum-free medium to model cellular interactions within the developing brain. The precursors self-assembled into 3D neural constructs with diverse neuronal and glial populations, interconnected vascular networks, and ramified microglia. Replicate constructs were reproducible by RNA sequencing (RNA-Seq) and expressed neurogenesis, vasculature development, and microglia genes. Linear support vector machines were used to construct a predictive model from RNA-Seq data for 240 neural constructs treated with 34 toxic and 26 nontoxic chemicals. The predictive model was evaluated using two standard hold-out testing methods: a nearly unbiased leave-one-out cross-validation for the 60 training compounds and an unbiased blinded trial using a single hold-out set of 10 additional chemicals. The linear support vector produced an estimate for future data of 0.91 in the cross-validation experiment and correctly classified 9 of 10 chemicals in the blinded trial.

Aberrant Lipid Metabolism in the Forebrain Niche Suppresses Adult Neural Stem Cell Proliferation in an Animal Model of Alzheimer's Disease

Lipid metabolism is fundamental for brain development and function, but its roles in normal and pathological neural stem cell (NSC) regulation remain largely unexplored. Here, we uncover a fatty acid-mediated mechanism suppressing endogenous NSC activity in Alzheimer's disease (AD). We found that postmortem AD brains and triple-transgenic Alzheimer's disease (3xTg-AD) mice accumulate neutral lipids within ependymal cells, the main support cell of the forebrain NSC niche. Mass spectrometry and microarray analyses identified these lipids as oleic acid-enriched triglycerides that originate from niche-derived rather than peripheral lipid metabolism defects. In wild-type mice, locally increasing oleic acid was sufficient to recapitulate the AD-associated ependymal triglyceride phenotype and inhibit NSC proliferation. Moreover, inhibiting the rate-limiting enzyme of oleic acid synthesis rescued proliferative defects in both adult neurogenic niches of 3xTg-AD mice. These studies support a pathogenic mechanism whereby AD-induced perturbation of niche fatty acid metabolism suppresses the homeostatic and regenerative functions of NSCs.

Oleic acid synthesized by stearoyl-CoA desaturase (SCD-1) in the lateral periventricular zone of the developing rat brain mediates neuronal growth, migration and the arrangement of prospective synapses

Our previous work has shown that oleic acid synthesized by astrocytes in response to serum albumin behaves as a neurotrophic factor in neurons, upregulating the expression of GAP-43 and MAP-2 proteins, which are respectively markers of axonal and dendrite growth. In addition, oleic acid promoted neuron migration and aggregation, resulting in clusters of neurons connected each other by the newly formed neurites. In this work we show that the presence of albumin or albumin plus oleic acid increases neuron migration in cultured explants of the lateral periventricular zone, resulting in an increase in the number of GAP-43-positive neurons leaving the explant. Upon silencing stearoyl-CoA desaturase-1 (SCD-1), a key enzyme in oleic acid synthesis by RNA of interference mostly prevented the effect of albumin but not that of albumin plus oleic acid, suggesting that the oleic acid synthesized due to the effect of albumin would be responsible for the increase in neuron migration. Oleic acid increased doublecortin (DCX) expression in cultured neurons, explants and organotypic slices, suggesting that DCX may mediate in the effect of oleic acid on neuron migration. The effect of oleic acid on neuron migration may be destined for the formation of synapses because the presence of oleic acid increased the expression of synaptotagmin and that of postsynaptic density protein (PDS-95), respectively markers of the pre- and postsynaptic compartments. In addition, confocal microscopy revealed the occurrence of points of colocalization between synaptotagmin and PDS-95, which is consistent with the idea that oleic acid promotes synapse arrangement.

Spinal cord injury induced changes of nuclear receptors PPARα and LXRβ and modulation with oleic acid/albumin treatment

In previous studies with animal models of spinal cord injury (SCI) pharmacological activation of peroxisome proliferator activated receptors (PPAR) and liver X receptors (LXR) were used to reduce tissue damage and promote behavioral recovery in animal models. We have studied the endogenous expression of the transcription factors PPARα and LXRβ in the chronic stage after SCI in rats. The immunohistochemical investigation revealed a long lasting increase in the level of PPARα in white matter in the vicinity of the lesion site. The source of this signal was identified in a subpopulation of astrocytes outside of the glial scar area. Intrathecal injections of oleic acid/albumin reduced the lesion-induced PPARα immunoreactivity. In addition, ependymal cells displayed a prominent PPARα signal in the non-injured spinal cord, and continued to express the receptor as they proliferated and migrated within the damaged tissue. The nuclear receptor LXRβ was detected at similar levels after SCI as in sham operated animals. We found high levels of immunoreactivity in the gray matter, while in the white matter it was present in subpopulations of astrocytes and oligodendrocytes. Macrophages that had accumulated within the center of the lesion contained LXRβ in their cell nuclei. Possible endogenous functions of PPARα and LXRβ after SCI are discussed, specifically the control of fatty acid and cholesterol metabolism and the regulation of inflammatory reactions.

Relationship between central and peripheral fatty acids in humans

Background

In recent years the physiological and pathological importance of fatty acids in both the periphery and central nervous system (CNS) has become increasingly apparent. However surprisingly limited research has been conducted comparing the fatty acid composition of central and peripheral lipid stores.

Methods

The present study compared the distribution of polyunsaturated (PUFA), as well as specific saturated (SFA) and monounsaturated (MUFA) fatty acids in the whole blood and cerebrospinal fluid (CSF) of humans. Gas chromatography with flame ionization detection was used to determine the fatty acid profiles of twenty-eight matched CSF and whole blood samples. Multiple linear regression modeling, controlling for age, was used to identify significant relationships.

Results

A significant positive relationship was seen between whole blood total omega-3 fatty acids and the CSF omega-3 subfractions, docosapentaenoic acid (DPA) (P = 0.019) and docosahexaenoic acid (DHA) (P = 0.015). A direct association was also observed between the whole blood and CSF omega-6 PUFA, arachidonic acid (AA) (P = 0.045). Interestingly an inverse association between central and peripheral oleic acid was also found (P = 0.045).

Conclusions

These findings indicate a relationship between central and peripheral fatty acids of varying degrees of unsaturation and chain length and support the view that some systemic fatty acids are likely to cross the human blood brain barrier (BBB) and thereby influence central fatty acid concentrations.

Overexpression of DYRK1A inhibits choline acetyltransferase induction by oleic acid in cellular models of Down syndrome

Histological brain studies of individuals with DS have revealed an aberrant formation of the cerebral cortex. Previous work from our laboratory has shown that oleic acid acts as a neurotrophic factor and induces neuronal differentiation. In order to characterize the effects of oleic acid in a cellular model of DS, immortalized cell lines derived from the cortex of trisomy Ts16 (CTb) and normal mice (CNh) were incubated in the absence or presence of oleic acid. Oleic acid increased choline acetyltransferase expression (ChAT), a marker of cholinergic differentiation in CNh cells. However, in trisomic cells (CTb line) oleic acid failed to increase ChAT expression. These results suggest that the overdose of specific genes in trisomic lines delays differentiation in the presence of oleic acid by inhibiting acetylcholine production mediated by ChAT. The dual-specificity tyrosine (Y) phosphorylation-regulated kinase 1A (DYRK1A) gene is located on human chromosome 21 and encodes a proline-directed protein kinase. It has been proposed that DYRK1A plays a prominent role in several biological functions, leading to mental retardation in DS patients. Here we explored the potential role of DYRK1A in the modulation of ChAT expression in trisomic cells and in the signaling pathways of oleic acid. Down-regulation of DYRK1A by siRNA in trisomic CTb cells rescued ChAT expression up to levels similar to those of normal cells in the presence of oleic acid. In agreement with these results, oleic acid was unable to increase ChAT expression in neuronal cultures of transgenic mice overexpressing DYRK1A. In summary, our results highlight the role played by DYRK1A in brain development through the control of ChAT expression. In addition, the overexpression of DYRK1A in DS models prevented the neurotrophic effect of oleic acid, a fact that may account for mental retardation in DS patients.

StearoylCoA desaturase-5: a novel regulator of neuronal cell proliferation and differentiation

Recent studies have demonstrated that human stearoylCoA desaturase-1 (SCD1), a Δ9-desaturase that converts saturated fatty acids (SFA) into monounsaturated fatty acids, controls the rate of lipogenesis, cell proliferation and tumorigenic capacity in cancer cells. However, the biological function of stearoylCoA desaturase-5 (SCD5), a second isoform of human SCD that is highly expressed in brain, as well as its potential role in human disease, remains unknown. In this study we report that the constitutive overexpression of human SCD5 in mouse Neuro2a cells, a widely used cell model of neuronal growth and differentiation, displayed a greater n-7 MUFA-to-SFA ratio in cell lipids compared to empty-vector transfected cells (controls). De novo synthesis of phosphatidylcholine and cholesterolesters was increased whereas phosphatidylethanolamine and triacylglycerol formation was reduced in SCD5-expressing cells with respect to their controls, suggesting a differential use of SCD5 products for lipogenic reactions. We also observed that SCD5 expression markedly accelerated the rate of cell proliferation and suppressed the induction of neurite outgrowth, a typical marker of neuronal differentiation, by retinoic acid indicating that the desaturase plays a key role in the mechanisms of cell division and differentiation. Critical signal transduction pathways that are known to modulate these processes, such epidermal growth factor receptor (EGFR)Akt/ERK and Wnt, were affected by SCD5 expression. Epidermal growth factor-induced phosphorylation of EGFR, Akt and ERK was markedly blunted in SCD5-expressing cells. Furthermore, the activity of canonical Wnt was reduced whereas the non-canonical Wnt was increased by the presence of SCD5 activity. Finally, SCD5 expression increased the secretion of recombinant Wnt5a, a non-canonical Wnt, whereas it reduced the cellular and secreted levels of canonical Wnt7b. Our data suggest that, by a coordinated modulation of key lipogenic pathways and transduction signaling cascades, SCD5 participates in the regulation of neuronal cell growth and differentiation.

Dietary intake of unsaturated fatty acids modulates physiological properties of entorhinal cortex neurons in mice

Dietary lipids modify brain fatty acid profile, but evidence of their direct effect on neuronal function is sparse. The enthorinal cortex (EC) neurons connecting to the hippocampus play a critical role in learning and memory. Here, we have exposed mice to diets based on canola:soybean oils (40 : 10, g/kg) or safflower : corn oils (25 : 25, g/kg) to investigate the relationship between the lipid profile of brain fatty acids and the intrinsic properties of EC neurons. Consumption of canola : soybean oil-enriched diet led to the increase of the monounsaturated fatty acid oleic acid and to a decrease of arachidonic acid in ethanolamine glycerophospholipids of the white matter. We also found an important rise in docosahexaenoic acid (DHA) within ethanolamine glycerophospholipids and phosphatidylserine of gray matter. The canola:soybean oil treatment led to a shorter duration of action potential (-21%), a reduction in the duration of postsynaptic response (-21%) and increased firing activity (+43%). Data from additional experiments with animals fed DHA alone or DHA with canola oil suggested that dietary monounsaturated fatty acid may have contributed to these effects on EC neuron physiology. Since neuronal function within the enthorhinal-hippocampal loop is critical to learning and memory processes, the present data may provide a functional basis for the beneficial cognitive effects of canola oil-based diets.

Glia determine the course of brain-derived neurotrophic factor-mediated dendritogenesis and provide a soluble inhibitory cue to dendritic growth in the brainstem

Cardiorespiratory control neurons in the brainstem nucleus tractus solitarius (NTS) undergo dramatic expansion of dendritic arbors during the early postnatal period, when functional remodeling takes place within the NTS circuitry. However, the underlying molecular mechanisms of morphological maturation of NTS neurons are largely unknown. Our previous studies point to the neurotrophin brain-derived neurotrophic factor (BDNF), which is abundantly expressed by NTS-projecting primary sensory neurons, as a candidate mediator of NTS dendritogenesis. In the current study, we used neonatal rat NTS neurons in vitro to examine the role of BDNF in the dendritic development of neurochemically identified subpopulations of NTS neurons. In the presence of abundant glia, BDNF promoted NTS dendritic outgrowth and complexity, with the magnitude of the BDNF effect dependent on neuronal phenotype. Surprisingly, BDNF switched from promoting to inhibiting NTS dendritogenesis upon glia depletion. Moreover, glia depletion alone led to a significant increase in NTS dendritic outgrowth. Consistent with this result, astrocyte-conditioned medium (ACM), which promoted hippocampal dendritogenesis, inhibited dendritic growth of NTS neurons. The latter effect was abolished by heat-inactivation of ACM, pointing to a diffusible astrocyte-derived negative regulator of NTS dendritic growth. Together, these data demonstrate a role for BDNF in the postnatal development of NTS neurons, and reveal novel effects of glia on this process. Moreover, previously documented dramatic increases in NTS glial proliferation in victims of sudden infant death syndrome (SIDS) underscore the importance of our findings and the need to better understand the role of glia and their interactions with BDNF during NTS circuit maturation. Furthermore, while it has previously been demonstrated that the specific effects of BDNF on dendritic growth are context-dependent, the role of glia in this process is unknown. Thus, our data carry important implications for mechanisms of dendritogenesis likely beyond the NTS.