Chronic administration of UMP ameliorates the impairment of hippocampal-dependent memory in impoverished rats

5'-CMP and 5'-UMP alleviate dexamethasone-induced muscular atrophy in C2C12 myotubes

Atrogin-1 and muscle RING finger 1 (MuRF1) are ubiquitin ligases specifically expressed during skeletal muscle atrophy and mediate muscle protein degradation. In contrast, PGC-1α (peroxisome proliferator-activated receptor γ coactivator 1α), which is a master regulator of mitochondrial biosynthesis, protects skeletal muscle from atrophy. Pyrimidine nucleoside 5'-monophosphates, such as cytidine 5'-monophosphate (5'-CMP) and uridine 5'-monophosphate (5'-UMP), induce PGC-1α expression and promote myotube formation in mouse C2C12 cells. In this study, we determined the effect of 5'-CMP and 5'-UMP on muscular atrophy in C2C12 myotube cells. 5'-UMP decreased Atrogin-1 and MuRF1 mRNA levels that were upregulated by dexamethasone treatment. 5'-CMP and 5'-UMP ameliorated dexamethasone-mediated atrophy in C2C12 myotubes. Furthermore, the combination of 5'-CMP and 5'-UMP further alleviated dexamethasone-mediated atrophy. In addition, cytidine and uridine, the precursors of 5'-CMP and 5'-UMP, markedly ameliorated dexamethasone-mediated atrophy. Considering nucleotide metabolism and absorption, the active metabolites underlying the observed effects of 5'-CMP and 5'-UMP appear to be cytidine and uridine. Our results indicate that 5'-CMP alleviates muscle atrophy by activating PGC-1α and differentiation, and 5'-UMP alleviates muscle atrophy by suppressing the activation of the myolytic system, whereas the combined use of both enhances the muscle atrophy inhibitory effect. 5'-CMP and 5'-UMP may be an effective and safe treatment for muscular atrophy.

5′-CMP and 5′-UMP promote myogenic differentiation and mitochondrial biogenesis by activating myogenin and PGC-1α in a mouse myoblast C2C12 cell line

Ribonucleotides are basic monomeric building blocks for RNA considered as conditionally essential nutrients. They are normally produced in sufficient quantity, but can become insufficient upon stressful challenges. The administration of pyrimidine nucleotides, such as cytidine-5′-monophosphate (5′-CMP) and uridine-5′-monophosphate (5′-UMP), enables rats to endure prolonged exercise. However, the underlying mechanisms have remained elusive. To investigate these mechanisms, we studied the effect of 5′-CMP and 5′-UMP on muscular differentiation and mitochondrial biogenesis in myoblast C2C12 cells. 5′-CMP and 5′-UMP were found to increase the mRNA levels of myogenin, which is a myogenic regulatory protein expressed during the final differentiation step and fusion of myoblasts into myotubes. 5′-CMP and 5′-UMP also promoted myoblast differentiation into myotube cells. 5′-CMP and 5′-UMP further increased the mRNA levels of PGC-1α which regulates mitochondrial biogenesis and skeletal muscle fiber type. In addition, 5′-CMP and 5′-UMP increased mitochondrial DNA copy number and enhanced mRNA levels of slow-muscle myosin heavy chains. Moreover, cytidine and uridine, nucleosides corresponding to 5′-CMP and 5′-UMP, markedly promoted myotube formation in C2C12 cells. Considering the metabolism and absorption of nucleotides, the active bodies underlying the effects observed with 5′-CMP and 5′-UMP could be cytidine and uridine. In conclusion, our results indicate that 5′-CMP and 5′-UMP can promote myogenic differentiation and mitochondrial biogenesis, as well as increase slow-twitch fiber via the activation of myogenin and PGC-1α. In addition, 5′-CMP and 5′-UMP may be considered as safe and effective agents to enhance muscle growth and improve the endurance in skeletal muscles.

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5′-CMP and 5′-UMP enhanced myogenin expression and myotube formation in C2C12 cells.

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5′-CMP and 5′-UMP enhanced the expression of PGC-1α and slow-muscle myosin heavy chains in C2C12 cells.

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5′-CMP and 5′-UMP promoted mitochondrial biogenesis in C2C12 cells.

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Corresponding nucleosides promoted myotube formation in C2C12 cells.

Subacute sarin exposure disrupted the homeostasis of purine and pyrimidine metabolism in guinea pig striatum studied by integrated metabolomic, lipidomic and proteomic analysis

Sarin was used as a chemical weapon due to its high neurotoxicity and mortality. Subacute sarin induced cognitive and behavioral disorder. However, the underlying mechanism is still unclear. Here we offered a multi-omic approach for the analysis of altered metabolites, lipids, and proteins to explore the neurotoxicity of subacute sarin. Guinea pigs were administered between the shoulder blades 16.8 μg/kg of sarin in a volume of 1.0 ml/kg body weight by subcutaneous injection once daily for 14 days. At the end of the final injection, guinea pigs were sacrificed, and striatum were dissected for analysis. A total of 138 different metabolites were identified in the metabolome analysis. Lipids and lipid-like molecules is the largest group (38.41%). For lipidomic analysis, a total of 216 lipids were identified. In proteomic study, over 4300 proteins were identified and quantified. By integrating these enriched components, we demonstrated that the joint pathways disturbed by subacute sarin mainly involving lipid, purine and pyrimidine metabolism in guinea pig striatum. Overall, this study highlights the powerfulness of omics platforms to deepen the understanding of nerve agents caused neurotoxicity.

Development and evaluation of a simultaneous strategy for pyrimidine metabolome quantification in multiple biological samples

Pyrimidines are critical nutrients and key biomolecules in nucleic acid biosynthesis and carbohydrate and lipid metabolism. Here, we proposed the concept of the pyrimidine metabolome, which covers 14 analytes in pyrimidine de novo and salvage synthetic pathways, and established a novel analytical strategy with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to efficiently illustrate pyrimidine transient distribution and dynamic balance. The lower limits of quantification (LLOQs) of all analytes were less than 10 ng/mL. Acceptable inter- and intra-day relative deviation (<15%) was detected, and good stability was obtained under different storage conditions. Metabolomics analysis revealed pyrimidine metabolic diversity in the plasma and brain among species, and a visualization strategy exhibited that pyrimidine biosynthetic metabolism is quite active in brain. Distinct metabolic features were also observed in cells with pyrimidine metabolomic disorders during proliferation and apoptosis. Absolute concentrations of pyrimidine metabolites in different bio-samples offered reference data for future pyrimidine studies.

Brain pyrimidine nucleotide synthesis and Alzheimer disease

Many patients suffering late-onset Alzheimer disease show a deficit in respiratory complex IV activity. The de novo pyrimidine biosynthesis pathway connects with the mitochondrial respiratory chain upstream from respiratory complex IV. We hypothesized that these patients would have decreased pyrimidine nucleotide levels. Then, different cell processes for which these compounds are essential, such as neuronal membrane generation and maintenance and synapses production, would be compromised. Using a cell model, we show that inhibiting oxidative phosphorylation function reduces neuronal differentiation. Linking these processes to pyrimidine nucleotides, uridine treatment recovers neuronal differentiation. To unmask the importance of these pathways in Alzheimer disease, we firstly confirm the existence of the de novo pyrimidine biosynthesis pathway in adult human brain. Then, we report altered mRNA levels for genes from both de novo pyrimidine biosynthesis and pyrimidine salvage pathways in brain from patients with Alzheimer disease. Thus, uridine supplementation might be used as a therapy for those Alzheimer disease patients with low respiratory complex IV activity.

Uridine treatment prevents REM sleep deprivation-induced learning and memory impairment

Previous studies have shown that sleep plays an important role in cognitive functions and sleep deprivation impairs learning and memory. Uridine is the main pyrimidine nucleoside found in human blood circulation and has beneficial effects on cognitive functions. The aim of the present study was to investigate the effects of uridine administration on learning and memory impairment in sleep-deprived rats. Flower pot method was used to induce REM sleep deprivation. Uridine-treated groups received 1 mmol/kg uridine and control groups received 1 ml/kg saline (0.9% NaCl) twice a day for four days and once a day on the 5th day intraperitoneally. Learning and memory performances were measured using Morris water maze (MWM) test. We also measured the ratios of total calcium-calmodulin dependent kinase II (tCaMKII)/β-tubulin and phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (pCREB)/β-tubulin, long-term potentiation (LTP) related molecules, using western blot analysis on the hippocampus. The results showed that REM sleep deprivation impaired learning and memory and also decreased the ratios of tCaMKII and pCREB. Uridine treatment enhanced learning and memory parameters in REM sleep-deprived rats. Additionally, decreases in tCaMKII and pCREB were prevented by uridine treatment. These data suggest that administration of uridine for five consecutive days prevents REM sleep deprivation-induced deficits in learning and memory associated with enhanced tCaMKII and pCREB ratios in the hippocampus.

Age, environment, object recognition and morphological diversity of GFAP-immunolabeled astrocytes

Background

Few studies have explored the glial response to a standard environment and how the response may be associated with age-related cognitive decline in learning and memory. Here we investigated aging and environmental influences on hippocampal-dependent tasks and on the morphology of an unbiased selected population of astrocytes from the molecular layer of dentate gyrus, which is the main target of perforant pathway.

Results

Six and twenty-month-old female, albino Swiss mice were housed, from weaning, in a standard or enriched environment, including running wheels for exercise and tested for object recognition and contextual memories. Young adult and aged subjects, independent of environment, were able to distinguish familiar from novel objects. All experimental groups, except aged mice from standard environment, distinguish stationary from displaced objects. Young adult but not aged mice, independent of environment, were able to distinguish older from recent objects. Only young mice from an enriched environment were able to distinguish novel from familiar contexts. Unbiased selected astrocytes from the molecular layer of the dentate gyrus were reconstructed in three-dimensions and classified using hierarchical cluster analysis of bimodal or multimodal morphological features. We found two morphological phenotypes of astrocytes and we designated type I the astrocytes that exhibited significantly higher values of morphological complexity as compared with type II. Complexity = [Sum of the terminal orders + Number of terminals] × [Total branch length/Number of primary branches]. On average, type I morphological complexity seems to be much more sensitive to age and environmental influences than that of type II. Indeed, aging and environmental impoverishment interact and reduce the morphological complexity of type I astrocytes at a point that they could not be distinguished anymore from type II.

Conclusions

We suggest these two types of astrocytes may have different physiological roles and that the detrimental effects of aging on memory in mice from a standard environment may be associated with a reduction of astrocytes morphological diversity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0111-2) contains supplementary material, which is available to authorized users.

Souvenaid®: a new approach to management of early Alzheimer's disease

Synaptic loss correlates closely with cognitive deficits in Alzheimer's disease and represents a new target for intervention. Souvenaid® is the first medical nutrition product to be designed to support synapse formation and function in early Alzheimer's disease, and has undergone an extensive, 12-year development programme. The relatively large amount of clinical data available for Souvenaid® is unusual for a medical nutrition product. Souvenaid® contains omega-3 polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid), uridine (as uridine monophosphate) and choline which are nutritional precursors required for synaptic membrane phospholipid synthesis, together with phospholipids and other cofactors. Souvenaid® has demonstrated cognitive benefits in patients with mild Alzheimer's disease but not in patients with mild-to-moderate Alzheimer's disease. Two randomised, double-blind, controlled trials (duration 12 and 24 weeks) in patients with mild Alzheimer's disease untreated with acetylcholinesterase inhibitors and/or memantine have demonstrated that Souvenaid® is well tolerated and improves episodic memory performance. The daily intake of Souvenaid® has not been associated with any harmful effects or interactions with medications and none are anticipated. The ongoing, 24-month, European Union-funded LipiDiDiet trial in subjects with prodromal Alzheimer's disease is evaluating the potential benefits of Souvenaid® on memory and in slowing progression to Alzheimer's dementia. If Souvenaid® induces synaptogenesis and improved synaptic function, it may provide benefits in other clinical conditions characterised by neurodegeneration. A number of trials are ongoing and planned to evaluate the potential wider benefits of Souvenaid®.

Translational research in nicotine dependence

Nicotine addiction accounts for 4.9 million deaths each year. Furthermore, although smoking represents a significant health burden in the United States, at present there are only three FDA-approved pharmacotherapies currently on the market: (1) nicotine replacement therapy, (2) bupropion, and (3) varenicline. Despite this obvious gap in the market, the complexity of nicotine addiction in addition to the increasing cost of drug development makes targeted drug development prohibitive. Furthermore, using combinations of mouse and human studies, additional treatments could be developed from off-the-shelf, currently approved medication lists. This article reviews translational studies targeting manipulations of the cholinergic system as a viable therapeutic target for nicotine addiction.

A specific multi-nutrient formulation enhances M1 muscarinic acetylcholine receptor responses in vitro

Recent evidence indicates that supplementation with a specific combination of nutrients may affect cell membrane synthesis and composition. To investigate whether such nutrients may also modify the physical properties of membranes, and affect membrane-bound processes involved in signal transduction pathways, we studied the effects of nutrient supplementation on G protein-coupled receptor activation in vitro. In particular, we investigated muscarinic receptors, which are important for the progression of memory deterioration and pathology of Alzheimer's disease. Nerve growth factor differentiated pheochromocytoma cells that were supplemented with specific combinations of nutrients showed enhanced responses to muscarinic receptor agonists in a membrane potential assay. The largest effects were obtained with a combination of nutrients known as Fortasyn™ Connect, comprising docosahexaenoic acid, eicosapentaenoic acid, uridine monophosphate as a uridine source, choline, vitamin B6, vitamin B12, folic acid, phospholipids, vitamin C, vitamin E, and selenium. In subsequent experiments, it was shown that the effects of supplementation could not be attributed to single nutrients. In addition, it was shown that the agonist-induced response and the supplement-induced enhancement of the response were blocked with the muscarinic receptor antagonists atropine, telenzepine, and AF-DX 384. In order to determine whether the effects of Fortasyn™ Connect supplementation were receptor subtype specific, we investigated binding properties and activation of human muscarinic M1, M2 and M4 receptors in stably transfected Chinese hamster ovary cells after supplementation. Multi-nutrient supplementation did not change M1 receptor density in plasma membranes. However, M1 receptor-mediated G protein activation was significantly enhanced. In contrast, supplementation of M2- or M4-expressing cells did not affect receptor signaling. Taken together, these results indicate that a specific combination of nutrients acts synergistically in enhancing muscarinic M1 receptor responses, probably by facilitating receptor-mediated G protein activation.

Impoverished environment, cognition, aging and dementia

Animals living in an impoverished environment, i.e., without the possibility of physical and social activity, perform worse on cognitive tests compared to animals in an enriched environment. The same cognitive difference is also observed in humans. However, it is not clear whether this difference is caused by a decrease in cognition due to an impoverished environment or an increase due to an enriched environment. This review discusses the impact of an impoverished environment on cognition in animal experimental studies and human experimental studies with community-dwelling and institutionalized older people. Results show that the cognitive functioning of old rats is more affected by an impoverished environment than young rats. Similarly, sedentary and lonely people (impoverished environment) have worse cognitive functioning and show a faster cognitive decline than physically and socially active people. Institutionalization further aggravates cognitive decline, probably due to the impoverished environment of nursing homes. In institutions, residents spend an unnecessary and excessive amount of time in bed; out of bed they show mainly sedentary or completely passive behavior. In conclusion, older people, especially those that have been institutionalized, have poor levels of physical and social activity, which in turn has a negative impact on cognitive functioning.

Nutritional modifiers of aging brain function: use of uridine and other phosphatide precursors to increase formation of brain synapses

Brain phosphatide synthesis requires three circulating compounds: docosahexaenoic acid (DHA), uridine, and choline. Oral administration of these phosphatide precursors to experimental animals increases the levels of phosphatides and synaptic proteins in the brain and per brain cell as well as the numbers of dendritic spines on hippocampal neurons. Arachidonic acid fails to reproduce these effects of DHA. If similar increases occur in human brain, administration of these compounds to patients with diseases that cause loss of brain synapses, such as Alzheimer's disease, could be beneficial.

Environmental impoverishment and aging alter object recognition, spatial learning, and dentate gyrus astrocytes

Environmental and age-related effects on learning and memory were analysed and compared with changes observed in astrocyte laminar distribution in the dentate gyrus. Aged (20 months) and young (6 months) adult female albino Swiss mice were housed from weaning either in impoverished conditions or in enriched conditions, and tested for episodic-like and water maze spatial memories. After these behavioral tests, brain hippocampal sections were immunolabeled for glial fibrillary acid protein to identify astrocytes. The effects of environmental enrichment on episodic-like memory were not dependent on age, and may protect water maze spatial learning and memory from declines induced by aging or impoverished environment. In the dentate gyrus, the number of astrocytes increased with both aging and enriched environment in the molecular layer, increased only with aging in the polymorphic layer, and was unchanged in the granular layer. We suggest that long-term experience-induced glial plasticity by enriched environment may represent at least part of the circuitry groundwork for improvements in behavioral performance in the aged mice brain.

Nutrition and Alzheimer's disease: pre-clinical concepts

Alzheimer's disease (AD) is a progressive condition characterized by neurodegeneration and the dense deposition of proteins in the brain. There is no cure for AD and current treatments usually only provide a temporary reduction of symptoms. There is thus a strong unmet need for effective preventative and therapeutic strategies and the potential role for nutrition in such strategies is rapidly gaining interest. An Alzheimer's brain contains fewer synapses and reduced levels of synaptic proteins and membrane phosphatides. Brain membrane phosphatide synthesis requires at least three dietary precursors: polyunsaturated fatty acids, uridine monophosphate (UMP) and choline. Animal studies have shown that administration of these nutrients increases the level of phosphatides, specific pre- or post-synaptic proteins and the number of dendritic spines - a requirement for new synapse formation. These effects are markedly enhanced when animals receive all three compounds together. This multi-nutrient approach in animals has also been shown to decrease amyloid beta protein (Abeta) plaque burden, improve learning and memory through increased cholinergic neurotransmission and have a neuroprotective effect in several mouse models of AD. Whether these potential therapeutic effects of a multi-nutrient approach observed in animal models can also be replicated in a clinical setting warrants further investigation.

Use of phosphatide precursors to promote synaptogenesis

New brain synapses form when a postsynaptic structure, the dendritic spine, interacts with a presynaptic terminal. Brain synapses and dendritic spines, membrane-rich structures, are depleted in Alzheimer's disease, as are some circulating compounds needed for synthesizing phosphatides, the major constituents of synaptic membranes. Animals given three of these compounds, all nutrients-uridine, the omega-3 polyunsaturated fatty acid docosahexaenoic acid, and choline-develop increased levels of brain phosphatides and of proteins that are concentrated within synaptic membranes (e.g., PSD-95, synapsin-1), improved cognition, and enhanced neurotransmitter release. The nutrients work by increasing the substrate-saturation of low-affinity enzymes that synthesize the phosphatides. Moreover, uridine and its nucleotide metabolites activate brain P2Y receptors, which control neuronal differentiation and synaptic protein synthesis. A preparation containing these compounds is being tested for treating Alzheimer's disease.

Synapse formation is enhanced by oral administration of uridine and DHA, the circulating precursors of brain phosphatides

OBJECTIVE

The loss of cortical and hippocampal synapses is a universal hallmark of Alzheimer's disease, and probably underlies its effects on cognition. Synapses are formed from the interaction of neurites projecting from "presynaptic" neurons with dendritic spines projecting from "postsynaptic" neurons. Both of these structures are vulnerable to the toxic effects of nearby amyloid plaques, and their loss contributes to the decreased number of synapses that characterize the disease. A treatment that increased the formation of neurites and dendritic spines might reverse this loss, thereby increasing the number of synapses and slowing the decline in cognition.

DESIGN SETTING, PARTICIPANTS, INTERVENTION, MEASUREMENTS AND RESULTS

We observe that giving normal rodents uridine and the omega-3 fatty acid docosahexaenoic acid (DHA) orally can enhance dendritic spine levels (3), and cognitive functions (32). Moreover this treatment also increases levels of biochemical markers for neurites (i.e., neurofilament-M and neurofilament-70) (2) in vivo, and uridine alone increases both these markers and the outgrowth of visible neurites by cultured PC-12 cells (9). A phase 2 clinical trial, performed in Europe, is described briefly.

DISCUSSION AND CONCLUSION

Uridine and DHA are circulating precursors for the phosphatides in synaptic membranes, and act in part by increasing the substrate-saturation of enzymes that synthesize phosphatidylcholine from CTP (formed from the uridine, via UTP) and from diacylglycerol species that contain DHA: the enzymes have poor affinities for these substrates, and thus are unsaturated with them, and only partially active, under basal conditions. The enhancement by uridine of neurite outgrowth is also mediated in part by UTP serving as a ligand for neuronal P2Y receptors. Moreover administration of uridine with DHA activates many brain genes, among them the gene for the m-1 metabotropic glutamate receptor [Cansev, et al, submitted]. This activation, in turn, increases brain levels of that gene's protein product and of such other synaptic proteins as PSD-95, synapsin-1, syntaxin-3 and F-actin, but not levels of non-synaptic brain proteins like beta-tubulin. Hence it is possible that giving uridine plus DHA triggers a neuronal program that, by accelerating phosphatide and synaptic protein synthesis, controls synaptogenesis. If administering this mix of phosphatide precursors also increases synaptic elements in brains of patients with Alzheimer 's disease, as it does in normal rodents, then this treatment may ameliorate some of the manifestations of the disease.

Synapse formation and cognitive brain development: effect of docosahexaenoic acid and other dietary constituents

The brain is unusual among organs in that the rates of many of its characteristic enzymatic reactions are controlled by the local concentrations of their substrates, which also happen to be nutrients that cross the blood-brain barrier. Thus, for example, brain levels of tryptophan, tyrosine, or choline can control the rates at which neurons synthesize serotonin, dopamine, or acetylcholine, respectively. The rates at which brain cells produce membrane phospholipids such as phosphatidylcholine (PC) are also under such control, both in adult animals and, especially, during early development. If pregnant rats are fed the 3 dietary constituents needed for PC synthesis- docosahexaenoic acid, uridine, and choline-starting 10 days before parturition and continuing for 20 days during nursing, brain levels of PC, and of the other membrane phosphatides (per cell or per mg protein), are increased by 50% or more. In adult animals, this treatment is also known to increase synaptic proteins (eg, synapsin-l, syntaxin-3, GluR-l, PSD-95) but not ubiquitous proteins like beta-tubulin and to increase (by 30% or more) the number of dendritic spines on hippocampal neurons. Docosahexaenoic acid currently is widely used, in human infants, to diminish the negative effects of prematurity on cognitive development. Moreover, docosahexaenoic acid, uridine (as uridine monophosphate), and choline are all found in mother's milk, and included in most infant formulas. It is proposed that these substances are part of a regulatory mechanism through which plasma composition influences brain development.

Dietary uridine enhances the improvement in learning and memory produced by administering DHA to gerbils

This study examined the effects on cognitive behaviors of giving normal adult gerbils three compounds, normally in the circulation, which interact to increase brain phosphatides, synaptic proteins, dendritic spines, and neurotransmitter release. Animals received supplemental uridine (as its monophosphate, UMP; 0.5%) and choline (0.1%) via the diet, and docosahexaenoic acid (DHA; 300 mg/kg/day) by gavage, for 4 wk, and then throughout the subsequent period of behavioral training and testing. As shown previously, giving all three compounds caused highly significant (P<0.001) increases in total brain phospholipids and in each major phosphatide; giving DHA or UMP (plus choline) produced smaller increases in some of the phosphatides. DHA plus choline improved performance on the four-arm radial maze, T-maze, and Y-maze tests; coadministering UMP further enhanced these increases. (Uridine probably acts by generating both CTP, which can be limiting in phosphatide synthesis, and UTP, which activates P2Y receptors coupled to neurite outgrowth and protein synthesis. All three compounds also act by enhancing the substrate-saturation of phosphatide-synthesizing enzymes.) These findings demonstrate that a treatment that increases synaptic membrane content can enhance cognitive functions in normal animals.

Chronic administration of DHA and UMP improves the impaired memory of environmentally impoverished rats

Living in an enriched environment (EC) during development enhances memory function in adulthood; living in an impoverished environment (IC) impairs memory function. Compounds previously demonstrated to improve memory among IC rats include CDP-choline and uridine monophosphate (UMP). Brain phosphatidylcholine (PC) synthesis utilizes both the uridine formed from the metabolism of exogenous CDP-choline and UMP, and the choline formed from that of CDP-choline. It also uses the polyunsaturated fatty acid (PUFA) DHA, a precursor for the diacylglycerol incorporated into PC. DHA administration also improves cognition in young and aged rodents and humans; its effects on cognitively impaired IC rats have not been characterized. We have thus examined the consequences of administering DHA (300 mg/kg) by gavage, UMP (0.5% in the diet), or both compounds on hippocampal- and striatal-dependent forms of memory among rats exposed to EC or IC conditions for 1 month starting at weaning, and consuming a choline-containing diet. We observe that giving IC rats either dietary UMP or gavaged DHA improves performance on the hidden version of the Morris water maze (all P<0.05), a hippocampal-dependent task; co-administration of both phosphatide precursors further enhances the IC rats' performance on this task (P<0.001). Neither UMP nor DHA, nor giving both compounds, affects the performance of EC rats on the hidden version of the Morris water maze (P>0.05), nor the performance by IC or EC rats on the visible version of the Morris water maze (all P>0.05), a striatal-dependent task. We confirm that co-administration of UMP and DHA to rats increases brain levels of the phosphatides PC, PE, SM, PS, PI, and total brain phospholipid levels (all P<0.05), and show that rearing animals in an enriched environment also elevates brain PC, PS, and PI levels (all P<0.01) and total brain phospholipids (P<0.01) compared with their levels in animals reared in an IC environment. These findings suggest that giving DHA plus UMP can ameliorate memory deficits associated with rearing under impoverished conditions, and that this effect may be mediated in part through enhanced synthesis of brain membrane phosphatides.

The potential role of nutritional components in the management of Alzheimer's Disease

Epidemiological evidence linking nutrition to the incidence and risk of Alzheimer Disease is rapidly increasing. The specific nutritional deficiencies in Alzheimer patients may suggest a relative shortage of specific macro- and micronutrients. These include omega-3 fatty acids, several B-vitamins and antioxidants such as vitamins E and C. Recent mechanistic studies in cell systems and animal models also support the idea that nutritional components are able to counteract specific aspects of the neurodegenerative and pathological processes in the brain. In addition, it has been shown that several nutritional components can also effectively stimulate membrane formation and synapse formation as well as improve behavior and cerebrovascular health. The suggested synergy between nutritional components to improve neuronal plasticity and function is supported by epidemiological studies as well as experimental studies in animal models. The ability of nutritional compositions to stimulate synapse formation and effectively reduce Alzheimer Disease neuropathology in these preclinical models provides a solid basis to predict potential to modify the disease process, especially during the early phases of Alzheimer Disease.

Uracil nucleotides: from metabolic intermediates to neuroprotection and neuroinflammation

Uracil nucleotides (i.e., UTP and UDP) have been known for years as fundamental intermediates in the de novo synthesis of the other pyrimidine nucleotides, which altogether represent key building blocks for nucleic acid synthesis. In addition, their sugar conjugates (i.e., UDP-glucose and UDP-galactose) enter in several biochemical routes, for example leading to glycogen biosynthesis, and protein and lipid glycosylation, which in turn contribute to the synthesis of essential components of the cellular plasma membrane. More recently, the existence of a "pyrimidinergic transmission" has arisen from the discovery that several purinergic G protein-coupled P2Y receptors can be activated also or exclusively by uracil nucleotides and sugar conjugates. The number of these receptors is continuously growing over years with the discovery that previously "orphan" G protein-coupled receptors are actually responding to this class of molecules. Therefore, new unforeseen effects mediated by uracil derivatives have emerged, in particular in the nervous system, and previously unexplored avenues for the pharmacological manipulation of this system are currently under investigation. In this commentary we shall try to put together our current knowledge on the biochemical and receptor-mediated effects of uracil nucleotide derivatives with a specific focus on the nervous system in order to depict a clearer view of the importance of the pyrimidinergic system in both physiological and pathological conditions.

Oral administration of circulating precursors for membrane phosphatides can promote the synthesis of new brain synapses

Although cognitive performance in humans and experimental animals can be improved by administering omega-3 fatty acid docosahexaenoic acid (DHA), the neurochemical mechanisms underlying this effect remain uncertain. In general, nutrients or drugs that modify brain function or behavior do so by affecting synaptic transmission, usually by changing the quantities of particular neurotransmitters present within synaptic clefts or by acting directly on neurotransmitter receptors or signal-transduction molecules. We find that DHA also affects synaptic transmission in mammalian brain. Brain cells of gerbils or rats receiving this fatty acid manifest increased levels of phosphatides and of specific presynaptic or postsynaptic proteins. They also exhibit increased numbers of dendritic spines on postsynaptic neurons. These actions are markedly enhanced in animals that have also received the other two circulating precursors for phosphatidylcholine, uridine (which gives rise to brain uridine diphosphate and cytidine triphosphate) and choline (which gives rise to phosphocholine). The actions of DHA aere reproduced by eicosapentaenoic acid, another omega-3 compound, but not by omega-6 fatty acid arachidonic acid. Administration of circulating phosphatide precursors can also increase neurotransmitter release (acetylcholine, dopamine) and affect animal behavior. Conceivably, this treatment might have use in patients with the synaptic loss that characterizes Alzheimer's disease or other neurodegenerative diseases or occurs after stroke or brain injury.