Cocoa Flavanols and Brain Perfusion

Nutrition, adult hippocampal neurogenesis and mental health

INTRODUCTION

Over the last 8 years, emerging studies bridging the gap between nutrition and mental health have resolutely established that learning and memory abilities as well as mood can be influenced by diet. However, the mechanisms by which diet modulates mental health are still not well understood. Sources of data In this article, a review of the literature was conducted using PubMed to identify studies that provide functional implications of adult hippocampal neurogenesis (AHN) and its modulation by diet.

AREAS OF AGREEMENT

One of the brain structures associated with learning and memory as well as mood is the hippocampus. Importantly, the hippocampus is one of the two structures in the adult brain where the formation of newborn neurons, or neurogenesis, persists.

AREAS OF CONTROVERSY

The exact roles of these newborn neurons in learning, memory formation and mood regulation remain elusive.

GROWING POINTS

Nevertheless, there has been accumulating evidence linking cognition and mood to neurogenesis occurring in the adult hippocampus. Therefore, modulation of AHN by diet emerges as a possible mechanism by which nutrition impacts on mental health.

AREAS TIMELY FOR DEVELOPING RESEARCH

This area of investigation is new and needs attention because a better understanding of the neurological mechanisms by which nutrition affect mental health may lead to novel dietary approaches for disease prevention, healthier ageing and discovery of new therapeutic targets for mental illnesses.

An alternative paradigm for the role of antimalarial plants in Africa

Most investigations into the antimalarial activity of African plants are centered on finding an indigenous equivalent to artemisinin, the compound from which current frontline antimalarial drugs are synthesized. As a consequence, the standard practice in ethnopharmacological research is to use in vitro assays to identify compounds that inhibit parasites at nanomolar concentrations. This approach fails to take into consideration the high probability of acquisition of resistance to parasiticidal compounds since parasite populations are placed under direct selection for genetic that confers a survival advantage. Bearing in mind Africa's long exposure to malaria and extensive ethnobotanical experimentation with both therapies and diet, it is more likely that compounds not readily overcome by Plasmodium parasites would have been retained in the pharmacopeia and cuisine. Such compounds are characterized by acting primarily on the host rather than directly targeting the parasite and thus cannot be adequately explored in vitro. If Africa's long history with malaria has in fact produced effective plant therapies, their scientific elucidation will require a major emphasis on in vivo investigation.

Flavonoids as modulators of memory and learning: molecular interactions resulting in behavioural effects

There is considerable interest in the potential of a group of dietary-derived phytochemicals known as flavonoids in modulating neuronal function and thereby influencing memory, learning and cognitive function. The present review begins by detailing the molecular events that underlie the acquisition and consolidation of new memories in the brain in order to provide a critical background to understanding the impact of flavonoid-rich diets or pure flavonoids on memory. Data suggests that despite limited brain bioavailability, dietary supplementation with flavonoid-rich foods, such as blueberry, green tea and Ginkgo biloba lead to significant reversals of age-related deficits on spatial memory and learning. Furthermore, animal and cellular studies suggest that the mechanisms underpinning their ability to induce improvements in memory are linked to the potential of absorbed flavonoids and their metabolites to interact with and modulate critical signalling pathways, transcription factors and gene and/or protein expression which control memory and learning processes in the hippocampus; the brain structure where spatial learning occurs. Overall, current evidence suggests that human translation of these animal investigations are warranted, as are further studies, to better understand the precise cause-and-effect relationship between flavonoid intake and cognitive outputs.

Flavonoids, cognition, and dementia: actions, mechanisms, and potential therapeutic utility for Alzheimer disease

There is increasing evidence that the consumption of flavonoid-rich foods can beneficially influence normal cognitive function. In addition, a growing number of flavonoids have been shown to inhibit the development of Alzheimer disease (AD)-like pathology and to reverse deficits in cognition in rodent models, suggestive of potential therapeutic utility in dementia. The actions of flavonoid-rich foods (e.g., green tea, blueberry, and cocoa) seem to be mediated by the direct interactions of absorbed flavonoids and their metabolites with a number of cellular and molecular targets. For example, their specific interactions within the ERK and PI3-kinase/Akt signaling pathways, at the level of receptors or kinases, have been shown to increase the expression of neuroprotective and neuromodulatory proteins and increase the number of, and strength of, connections between neurons. Concurrently, their effects on the vascular system may also lead to enhancements in cognitive performance through increased brain blood flow and an ability to initiate neurogenesis in the hippocampus. Additional mechanisms have been suggested for the ability of flavonoids to delay the initiation of and/or slow the progression of AD-like pathology and related neurodegenerative disorders, including a potential to inhibit neuronal apoptosis triggered by neurotoxic species (e.g., oxidative stress and neuroinflammation) or disrupt amyloid β aggregation and effects on amyloid precursor protein processing through the inhibition of β-secretase (BACE-1) and/or activation of α-secretase (ADAM10). Together, these processes act to maintain the number and quality of synaptic connections in key brain regions and thus flavonoids have the potential to prevent the progression of neurodegenerative pathologies and to promote cognitive performance.

Cocoa and chocolate in human health and disease

Cocoa contains more phenolic antioxidants than most foods. Flavonoids, including catechin, epicatechin, and procyanidins predominate in antioxidant activity. The tricyclic structure of the flavonoids determines antioxidant effects that scavenge reactive oxygen species, chelate Fe2+ and Cu+, inhibit enzymes, and upregulate antioxidant defenses. The epicatechin content of cocoa is primarily responsible for its favorable impact on vascular endothelium via its effect on both acute and chronic upregulation of nitric oxide production. Other cardiovascular effects are mediated through anti-inflammatory effects of cocoa polyphenols, and modulated through the activity of NF-κB. Antioxidant effects of cocoa may directly influence insulin resistance and, in turn, reduce risk for diabetes. Further, cocoa consumption may stimulate changes in redox-sensitive signaling pathways involved in gene expression and the immune response. Cocoa can protect nerves from injury and inflammation, protect the skin from oxidative damage from UV radiation in topical preparations, and have beneficial effects on satiety, cognitive function, and mood. As cocoa is predominantly consumed as energy-dense chocolate, potential detrimental effects of overconsumption exist, including increased risk of weight gain. Overall, research to date suggests that the benefits of moderate cocoa or dark chocolate consumption likely outweigh the risks.

The neuroprotective potential of flavonoids: a multiplicity of effects

Flavonoids exert a multiplicity of neuroprotective actions within the brain, including a potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning and cognitive function. These effects appear to be underpinned by two common processes. Firstly, they interact with critical protein and lipid kinase signalling cascades in the brain leading to an inhibition of apoptosis triggered by neurotoxic species and to a promotion of neuronal survival and synaptic plasticity. Secondly, they induce beneficial effects on the vascular system leading to changes in cerebrovascular blood flow capable of causing angiogenesis, neurogenesis and changes in neuronal morphology. Through these mechanisms, the consumption of flavonoid-rich foods throughout life holds the potential to limit neurodegeneration and to prevent or reverse age-dependent loses in cognitive performance. The intense interest in the development of drugs capable of enhancing brain function means that flavonoids may represent important precursor molecules in the quest to develop of a new generation of brain enhancing drugs.

Flavonoid intake in relation to cognitive function in later life in the Lothian Birth Cohort 1936

Previous studies have suggested a link between flavonoid intake and better cognitive function in later life but have not been able to control for possible confounding by prior intelligence quotient (IQ). The aim of the present study was to address this issue in a cross-sectional survey of 1091 men and women born in 1936, in whom IQ was measured at age 11 years. At the age of 70 years, participants carried out various neuropsychological tests and completed a FFQ. Associations between test scores and nutrient intake were assessed by linear regression with adjustment for potentially confounding variables. Total fruit, citrus fruits, apple and tea intakes were initially found to be associated with better scores in a variety of cognitive tests, but the associations were no longer statistically significant after adjusting for confounding factors, including childhood IQ. Flavanone intake was initially found to be associated with better scores in verbal fluency (P = 0·003, with standardised regression coefficient 0·10), but, again, the association was no longer statistically significant after adjusting for confounding factors. These findings do not support a role for flavonoids in the prevention of cognitive decline in later life. Studies of diet and cognitive function should include measurement of potential confounding variables, including prior IQ wherever possible.

Acute Treatment With Herbal Extracts Provides Neuroprotective Benefits in In Vitro and In Vivo Stroke Models, Characterized by Reduced Ischemic Cell Death and Maintenance of Motor and Neurological Functions

The present study explored the prophylactic and restorative benefits of cacao and red sage using both in vitro and in vivo models of stroke. For the in vitro study, we initially exposed primary rat cells to the established oxygen-glucose deprivation (OGD) stroke model followed by reperfusion under normoxic conditions, then added different cacao and sage concentrations to the cell culture media. Trypan blue cell viability results revealed specific cacao and sage dosages exerted significant therapeutic effects against OGD-induced cell death compared to cultured cells treated with extract vehicle. We next embarked on testing the therapeutic effects of cacao and sage in an in vivo model of stroke when extract treatment commenced either prior to or after transient middle cerebral artery occlusion (MCAo). Significant reduction in ischemic cell death within the peri-infarct area coupled with better performance in routine motor and neurological tasks were demonstrated by stroke animals that received cacao or sage extracts prior to MCAo compared to those that received the extracts or vehicle after MCAo. In summary, the present results demonstrate that neuroprotective effects were afforded by plant extract treatment, and that the in vitro stroke paradigm approximates in vivo efficacy when considering prophylactic treatment for stroke.

Urban air pollution targets the dorsal vagal complex and dark chocolate offers neuroprotection

Mexico City (MC) residents exposed to fine particulate matter and endotoxin exhibit inflammation of the olfactory bulb, substantia nigra, and vagus nerve. The goal of this study was to model these endpoints in mice and examine the neuroprotective effects of chocolate. Mice exposed to MC air received no treatment or oral dark chocolate and were compared to clean-air mice either untreated or treated intraperitoneally with endotoxin. Cyclooxygenase-2 (COX-2), interleukin 1 beta (IL-1β), and CD14 messenger RNA (mRNA) were quantified after 4, 8, and 16 months of exposure in target brain regions. After 16 months of exposure, the dorsal vagal complex (DVC) exhibited significant inflammation in endotoxin-treated and MC mice (COX-2 and IL-1β P<.001). Mexico City mice had olfactory bulb upregulation of CD14 (P=.002) and significant DVC imbalance in genes for antioxidant defenses, apoptosis, and neurodegeneration. These findings demonstrate sustained DVC inflammation in mice exposed to MC air, which is mitigated by chocolate administration.

Beyond antioxidants: the cellular and molecular interactions of flavonoids and how these underpin their actions on the brain

The consumption of flavonoid-rich foods and beverages has been suggested to limit the neurodegeneration associated with a variety of neurological disorders and to prevent or reverse normal or abnormal deteriorations in cognitive performance. Flavonoids mediate these effects via a number of routes, including a potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation and a potential to promote memory, learning and cognitive function. Originally, it was thought that such actions were mediated by the antioxidant capacity of flavonoids. However, their limited absorption and their low bioavailability in the brain suggest that this explanation is unlikely. Instead, this multiplicity of effects appears to be underpinned by three separate processes: first, through their interactions with important neuronal and glial signalling cascades in the brain, most notably the phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase pathways that regulate pro-survival transcription factors and gene expression; second, through an ability to improve peripheral and cerebral blood flow and to trigger angiogenesis and neurogenesis in the hippocampus; third, by their capacity to directly react with and scavenge neurotoxic species and pro-inflammatory agents produced in the brain as a result of both normal and abnormal brain ageing. The present review explores the potential inhibitory or stimulatory actions of flavonoids within these three systems and describes how such interactions are likely to underlie neurological effects.

Protective effect of quercetin against intracerebral streptozotocin induced reduction in cerebral blood flow and impairment of memory in mice

The aim of the present study is to investigate the effect of quercetin, a naturally occurring flavonoid, on cerebral blood flow (CBF), brain energy metabolism, memory impairment, oxidative stress and cholinergic dysfunction in brain following intracerebral (i.c.) streptozotocin (STZ) administration in mice. STZ (0.5mg/kg, i.c.) was administered twice at an interval of 48h. We found a significant reduction in CBF as measured by Laser Doppler Flowmetry (LDF). The brain energy metabolism was also altered as evidenced by significant reduction in brain ATP content. Daily treatment with quercetin (2.5, 5 and 10mg/kg, p.o.) starting from the first dose of STZ showed a dose-dependent restoration of CBF and ATP content. Further, quercetin prevented STZ induced memory impairment as assessed by Morris water maze and passive avoidance tests. Biochemical analysis revealed that STZ significantly increased malondialdehyde (MDA), nitrite and depleted glutathione (GSH) levels in the mice brain. Quercetin decreased oxidative and nitrosative stress as evidenced by a significant decrease in MDA, nitrite and increase in GSH levels. Quercetin also attenuated elevated acetylcholinesterase activity in the STZ-treated mice. Neither STZ (i.c.) nor quercetin showed any change in locomotor activity and blood glucose level. The present study demonstrates the beneficial effects of quercetin in improving CBF along with preventing memory impairment, oxidative stress, altered brain energy metabolism and cholinergic dysfunction caused by STZ in mice. Therefore, consumption of dietary stuff rich in quercetin should be encouraged to ward off dementia associated with vascular and neurodegenerative disorders.

Practical prevention of cardiac remodeling and atrial fibrillation with full-spectrum antioxidant therapy and ancillary strategies

A wealth of research data points to increased oxidative stress as a key driver of the cardiac remodeling triggered by chronic pressure overload, loss of functional myocardial tissue, or atrial fibrillation. Oxidative stress is a mediator of the cardiomyocyte hypertrophy and apoptosis, the cardiac fibrosis, and the deficits in cardiac function which typify this syndrome, and may play a role in initiating and sustaining atrial fibrillation. Nox2- and Nox4-dependent NADPH oxidase activity appears to be a major source of this oxidative stress, and oxidants can induce conformational changes in xanthine dehydrogenase, nitric oxide synthase, and the mitochondrial respiratory chain which increase their capacity to generate superoxide as well. Consistent with these insights, various synthetic antioxidants have been shown to suppress cardiac remodeling in rodents subjected to myocardial infarction, aortic constriction, or rapid atrial pacing. It may prove feasible to achieve comparable benefits in humans through use of a "full-spectrum antioxidant therapy" (FSAT) that features a complementary array of natural antioxidants. Spirulina is a rich source of phycocyanobilin, a derivative and homolog of biliverdin that appears to mimic the potent inhibitory impact of biliverdin and free bilirubin on NADPH oxidase activity. Mega-doses of folate can markedly increase intracellular levels of tetrahydrofolates which have potent and versatile radical-scavenging activities - including efficient quenching of peroxynitrite-derived radicals Supplemental coenzyme Q10, already shown to improve heart function in clinical congestive failure, can provide important antioxidant protection to mitochondria. Phase 2 inducer nutraceuticals such as lipoic acid, administered in conjunction with N-acetylcysteine, have the potential to blunt the impact of oxidative stress by boosting myocardial levels of glutathione. While taurine can function as an antioxidant for myeloperoxidase-derived radicals, its positive inotropic effect on the failing heart seems more likely to reflect an effect on intracellular calcium dynamics. These measures could aid control of cardiac modeling less directly by lowering elevated blood pressure, or by aiding the perfusion of ischemic cardiac regions through an improvement in coronary endothelial function. Since nitric oxide functions physiologically to oppose cardiomyocyte hypertrophy and cardiac fibrosis, and is also a key regulator of blood pressure and endothelial function, cocoa flavanols - which provoke endothelial release of nitric oxide - might usefully complement the antioxidant measures recommended here.

Natural cocoa as diet-mediated antimalarial prophylaxis

BACKGROUND

The Maya of Central America are credited with the first consumption of cocoa and maintaining its ancient Olmec name kakawa translated in English as "God Food", in recognition of its multiple health benefits. The legend of cocoa is receiving renewed attention in recent years, on account of epidemiological and scientific studies that support its cardiovascular health benefits. Increasing numbers of scientific reports corroborating cocoa's antiquated reputation as health food persuaded this author to promote regular consumption of cocoa in Ghana since 2004. Cocoa is readily available in Ghana; the country is the second largest producer accounting for 14% of the world's output. Numerous anecdotal reports of reduced episodic malaria in people who daily drink natural unsweetened cocoa beverage prompted a search for scientific mechanisms that possibly account for cocoa's antimalarial effects. This paper presents the outcome as a hypothesis.

METHODS

Internet search for literature on effects of cocoa's ingredients on malaria parasites and illness using a variety of search tools.

RESULTS

Evidential literature suggests five mechanisms that possibly underpin cocoa's anecdotal antimalarial effects. (i) Increased availability of antioxidants in plasma, (ii) membrane effects in general and erythrocyte membrane in particular, (iii) increased plasma levels of nitric oxide, (iv) antimalarial activity of cocoa flavanoids and their derivatives, and (v) boosted immune system mediated by components of cocoa including cocoa butter, polyphenols, magnesium, and zinc.

CONCLUSION

A hypothesis is formulated that cocoa offers a diet-mediated antimalarial prophylaxis; and an additional novel tool in the fight against the legendary scourge.

Flavonoids and cognition: the molecular mechanisms underlying their behavioural effects

Evidence suggests that a group of phytochemicals known as flavonoids are highly effective in reversing age-related declines in neuro-cognitive performance through their ability to interact with the cellular and molecular architecture of the brain responsible for memory and by reducing neuronal loss due to neurodegenerative processes. In particular, they may increase the number of, and strength of, connections between neurons, via their specific interactions with the ERK and Akt signalling pathways, leading to an increase in neurotrophins such as BDNF. Concurrently, their effects on the peripheral and cerebral vascular system may also lead to enhancements in cognitive performance through increased brain blood flow and an ability to initiate neurogenesis in the hippocampus. Finally, they have also been shown to reduce neuronal damage and losses induced by various neurotoxic species and neuroinflammation. Together, these processes act to maintain the number and quality of synaptic connections in the brain, a factor known to be essential for efficient LTP, synaptic plasticity and ultimately the efficient working of memory.

Flavonoids and brain health: multiple effects underpinned by common mechanisms

The neuroprotective actions of dietary flavonoids involve a number of effects within the brain, including a potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning and cognitive function. This multiplicity of effects appears to be underpinned by two processes. Firstly, they interact with important neuronal signalling cascades leading to an inhibition of apoptosis triggered by neurotoxic species and to a promotion of neuronal survival and differentiation. These interactions include selective actions on a number of protein kinase and lipid kinase signalling cascades, most notably the PI3K/Akt and MAP kinase pathways which regulate pro-survival transcription factors and gene expression. Secondly, they induce peripheral and cerebral vascular blood flow in a manner which may lead to the induction of angiogenesis, and new nerve cell growth in the hippocampus. Therefore, the consumption of flavonoid-rich foods, such as berries and cocoa, throughout life holds a potential to limit the neurodegeneration associated with a variety of neurological disorders and to prevent or reverse normal or abnormal deteriorations in cognitive performance.

Impact of diet on adult hippocampal neurogenesis

Research over the last 5 years has firmly established that learning and memory abilities, as well as mood, can be influenced by diet, although the mechanisms by which diet modulates mental health are not well understood. One of the brain structures associated with learning and memory, as well as mood, is the hippocampus. Interestingly, the hippocampus is one of the two structures in the adult brain where the formation of newborn neurons, or neurogenesis, persists. The level of neurogenesis in the adult hippocampus has been linked directly to cognition and mood. Therefore, modulation of adult hippocampal neurogenesis (AHN) by diet emerges as a possible mechanism by which nutrition impacts on mental health. In this study, we give an overview of the mechanisms and functional implications of AHN and summarize recent findings regarding the modulation of AHN by diet.

Potential complementarity of high-flavanol cocoa powder and spirulina for health protection

Recent studies show that ingestion of flavanol-rich cocoa powder provokes increased endothelial production of nitric oxide - an effect likely mediated by epicatchin - and thus may have considerable potential for promoting vascular health. The Kuna Indians of Panama, who regularly consume large amounts of flavanol-rich cocoa, are virtually free of hypertension and stroke, even though they salt their food. Of potentially complementary merit is the cyanobacterium spirulina, which has been used as a food in certain cultures. Spirulina is exceptionally rich in phycocyanobilin (PCB), which recently has been shown to act as a potent inhibitor of NADPH oxidase; this effect likely rationalizes the broad range of anti-inflammatory, cytoprotective, and anti-atherosclerotic effects which orally administered spirulina has achieved in rodent studies. In light of the central pathogenic role which NADPH oxidase-derived oxidant stress plays in a vast range of disorders, spirulina or PCB-enriched spirulina extracts may have remarkable potential for preserving and restoring health. Joint administration of flavanol-rich cocoa powder and spirulina may have particular merit, inasmuch as cocoa can mask the somewhat disagreeable flavor and odor of spirulina, whereas the antioxidant impact of spirulina could be expected to amplify the bioactivity of the nitric oxide evoked by cocoa flavanols in inflamed endothelium. Moreover, there is reason to suspect that, by optimizing cerebrovascular perfusion while quelling cerebral oxidant stress, cocoa powder and spirulina could collaborate in prevention of senile dementia. Thus, food products featuring ample amounts of both high-flavanol cocoa powder and spirulina may have considerable potential for health promotion, and merit evaluation in rodent studies and clinical trials.

Cocoa procyanidins attenuate 4-hydroxynonenal-induced apoptosis of PC12 cells by directly inhibiting mitogen-activated protein kinase kinase 4 activity

Neurodegenerative disorders such as Alzheimer's disease (AD) are associated with oxidative stress, and it has been suggested that apoptosis is a crucial pathway in neuronal cell death in AD patients. 4-Hydroxynonenal (HNE), one of the aldehydic products of membrane lipid peroxidation, is reported to be elevated in the brains of AD patients and mediates the induction of neuronal apoptosis in the presence of oxidative stress. In this study, we investigated the HNE-induced apoptosis mechanism and the protective effects of the cocoa procyanidin fraction (CPF) and its major antioxidant procyanidin B2 against the apoptosis induced by HNE in rat pheochromocytoma (PC12) cells. HNE-induced nuclear condensation and increased sub-G1 fraction, both of which are markers of apoptotic cell death, were inhibited by CPF and procyanidin B2. Intracellular reactive oxygen species (ROS) accumulation was attenuated by pretreatment with CPF and procyanidin B2. CPF and procyanidin B2 also prevented HNE-induced poly(ADP-ribose) polymerase cleavage, antiapoptotic protein (Bcl-2 and Bcl-X(L)) down-regulation, and caspase-3 activation. Activation of c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase kinase 4 (MKK4) was attenuated by CPF and procyanidin B2. Moreover, CPF and procyanidin B2 bound directly to MKK4 and inhibited its activity. Data obtained with SP600125, a selective inhibitor of JNK, revealed that JNK is involved in HNE-induced apoptosis through the inhibition of PARP cleavage and caspase-3 activation in PC12 cells. Collectively, these results indicate that CPF and procyanidin B2 protect PC12 cells against HNE-induced apoptosis by blocking MKK4 activity as well as ROS accumulation.

The prevention of dementia

OBJECTIVE

Dementia is prevalent in older adults and the population is ageing. Many factors have been associated with dementia and anything that may aid the prevention of dementia is of importance.

METHOD

The literature in this area was evaluated and information relating to the various factors that may impact upon the prevention of dementia is presented below.

RESULTS

Factors that have been associated with a possible increased risk of developing dementia include high blood pressure, (at least in midlife), high body mass index, smoking and possibly diabetes although the evidence is mixed. There is currently no clear evidence with regard to cholesterol and metabolic syndrome although both may be implicated. Having education and maintaining a Mediterranean diet, including vegetable, fruit and fish intake, have been linked to a lower incidence of dementia as has low to moderate alcohol intake. Although care must be taken with the latter given the different characteristics of the studies reporting on alcohol and dementia.

CONCLUSION

It may be that risk and protective factors vary with age, however, in the absence of prophylactic treatment it seems likely that the maintenance of a healthy lifestyle may represent the best option with regard to the prevention of dementia.

Cerebral blood flow regulation by nitric oxide: recent advances

Nitric oxide (NO) is undoubtedly quite an important intercellular messenger in cerebral and peripheral hemodynamics. This molecule, formed by constitutive isomers of NO synthase, endothelial nitric-oxide synthase, and neuronal nitric-oxide synthase, plays pivotal roles in the regulation of cerebral blood flow and cell viability and in the protection of nerve cells or fibers against pathogenic factors associated with cerebral ischemia, trauma, and hemorrhage. Cerebral blood flow is increased and cerebral vascular resistance is decreased by NO derived from endothelial cells, autonomic nitrergic nerves, or brain neurons under resting and stimulated conditions. Somatosensory stimulation also evokes cerebral vasodilatation mediated by neurogenic NO. Oxygen and carbon dioxide alter cerebral blood flow and vascular tone mainly via constitutively formed NO. Endothelial dysfunction impairs cerebral hemodynamics by reducing the bioavailability of NO and increasing the production of reactive oxygen species (ROS). The NO-ROS interaction is an important issue in discussing blood flow and cell viability in the brain. Recent studies on brain circulation provide quite useful information concerning the physiological roles of NO produced by constitutive isoforms of nitric-oxide synthase and how NO may promote cerebral pathogenesis under certain conditions, including cerebral ischemia/stroke, cerebral vasospasm after subarachnoid hemorrhage, and brain injury. This information would contribute to better understanding of cerebral hemodynamic regulation and its dysfunction and to development of novel therapeutic measures to treat diseases of the central nervous system.

Vascular action of polyphenols

Dietary patterns are widely recognised as contributors to cardiovascular and cerebrovascular disease. Endothelial function, the elastic properties of large arteries and the magnitude and timing of wave reflections are important determinants of cardiovascular performance. Several epidemiological studies suggest that the regular consumption of foods and beverages rich in flavonoids is associated with a reduction in the risk of several pathological conditions ranging from hypertension to coronary heart disease, stroke and dementia. The impairment of endothelial function is directly related to ageing and an association between decreased cerebral perfusion and dementia has been shown to exist. Cerebral blood flow (CBF) must be maintained to ensure a constant delivery of oxygen and glucose as well as the removal of waste products. Increasing blood flow is one potential way for improving brain function and the prospect for increasing CBF with dietary polyphenols is extremely promising. The major polyphenols shown to have some of these effects in humans are primarily from cocoa, wine, grape seed, berries, tea, tomatoes (polyphenolics and nonpolyphenolics), soy and pomegranate. There has been a significant paradigm shift in polyphenol research during the last decade. This review summarises our current knowledge in this area and points the way for the development of new types of functional foods targeted to brain health through improving vascular health.

Intake of flavonoid-rich wine, tea, and chocolate by elderly men and women is associated with better cognitive test performance

In a cross-sectional study, we examined the relation between intake of 3 common foodstuffs that contain flavonoids (chocolate, wine, and tea) and cognitive performance. 2031 participants (70-74 y, 55% women) recruited from the population-based Hordaland Health Study in Norway underwent cognitive testing. A cognitive test battery included the Kendrick Object Learning Test, Trail Making Test, part A (TMT-A), modified versions of the Digit Symbol Test, Block Design, Mini-Mental State Examination, and Controlled Oral Word Association Test. Poor cognitive performance was defined as a score in the highest decile for the TMT-A and in the lowest decile for all other tests. A self-reported FFQ was used to assess habitual food intake. Participants who consumed chocolate, wine, or tea had significantly better mean test scores and lower prevalence of poor cognitive performance than those who did not. Participants who consumed all 3 studied items had the best test scores and the lowest risks for poor test performance. The associations between intake of these foodstuffs and cognition were dose dependent, with maximum effect at intakes of approximately 10 g/d for chocolate and approximately 75-100 mL/d for wine, but approximately linear for tea. Most cognitive functions tested were influenced by intake of these 3 foodstuffs. The effect was most pronounced for wine and modestly weaker for chocolate intake. Thus, in the elderly, a diet high in some flavonoid-rich foods is associated with better performance in several cognitive abilities in a dose-dependent manner.

Food for thought: the role of dietary flavonoids in enhancing human memory, learning and neuro-cognitive performance

Emerging evidence suggests that dietary-derived flavonoids have the potential to improve human memory and neuro-cognitive performance via their ability to protect vulnerable neurons, enhance existing neuronal function and stimulate neuronal regeneration. Long-term potentiation (LTP) is widely considered to be one of the major mechanisms underlying memory acquisition, consolidation and storage in the brain and is known to be controlled at the molecular level by the activation of a number of neuronal signalling pathways. These pathways include the phosphatidylinositol-3 kinase/protein kinase B/Akt (Akt), protein kinase C, protein kinase A, Ca-calmodulin kinase and mitogen-activated protein kinase pathways. Growing evidence suggests that flavonoids exert effects on LTP, and consequently memory and cognitive performance, through their interactions with these signalling pathways. Of particular interest is the ability of flavonoids to activate the extracellular signal-regulated kinase and the Akt signalling pathways leading to the activation of the cAMP-response element-binding protein, a transcription factor responsible for increasing the expression of a number of neurotrophins important in LTP and long-term memory. One such neurotrophin is brain-derived neurotrophic factor, which is known to be crucial in controlling synapse growth, in promoting an increase in dendritic spine density and in enhancing synaptic receptor density. The present review explores the potential of flavonoids and their metabolite forms to promote memory and learning through their interactions with neuronal signalling pathways pivotal in controlling LTP and memory in human subjects.

Flavonoids: modulators of brain function?

Emerging evidence suggests that dietary phytochemicals, in particular flavonoids, may exert beneficial effects on the central nervous system by protecting neurons against stress-induced injury, by suppressing neuroinflammation and by improving cognitive function. It is likely that flavonoids exert such effects, through selective actions on different components of a number of protein kinase and lipid kinase signalling cascades, such as the phosphatidylinositol-3 kinase (PI3K)/Akt, protein kinase C and mitogen-activated protein kinase (MAPK) pathways. This review explores the potential inhibitory or stimulatory actions of flavonoids within these pathways, and describes how such interactions are likely to underlie neurological effects through their ability to affect the activation state of target molecules and/or by modulating gene expression. Future research directions are outlined in relation to the precise site(s) of action of flavonoids within signalling pathways and the sequence of events that allow them to regulate neuronal function.

A double-blind, placebo-controlled, randomized trial of the effects of dark chocolate and cocoa on variables associated with neuropsychological functioning and cardiovascular health: clinical findings from a sample of healthy, cognitively intact older adults

BACKGROUND

In recent years, there has been increased interest in the potential health-related benefits of antioxidant- and phytochemical-rich dark chocolate and cocoa.

OBJECTIVE

The objective of the study was to examine the short-term (6 wk) effects of dark chocolate and cocoa on variables associated with neuropsychological functioning and cardiovascular health in healthy older adults.

DESIGN

A double-blind, placebo-controlled, fixed-dose, parallel-group clinical trial was used. Participants (n = 101) were randomly assigned to receive a 37-g dark chocolate bar and 8 ounces (237 mL) of an artificially sweetened cocoa beverage or similar placebo products each day for 6 wk.

RESULTS

No significant group (dark chocolate and cocoa or placebo)-by-trial (baseline, midpoint, and end-of-treatment assessments) interactions were found for the neuropsychological, hematological, or blood pressure variables examined. In contrast, the midpoint and end-of-treatment mean pulse rate assessments in the dark chocolate and cocoa group were significantly higher than those at baseline and significantly higher than the midpoint and end-of-treatment rates in the control group. Results of a follow-up questionnaire item on the treatment products that participants believed they had consumed during the trial showed that more than half of the participants in both groups correctly identified the products that they had ingested during the experiment.

CONCLUSIONS

This investigation failed to support the predicted beneficial effects of short-term dark chocolate and cocoa consumption on any of the neuropsychological or cardiovascular health-related variables included in this research. Consumption of dark chocolate and cocoa was, however, associated with significantly higher pulse rates at 3- and 6-wk treatment assessments.

Cocoa procyanidins protect PC12 cells from hydrogen-peroxide-induced apoptosis by inhibiting activation of p38 MAPK and JNK

Oxidative stress induced by reactive oxygen species has been strongly associated with the pathogenesis of neurodegenerative disorders, including Alzheimer's disease. In this study, we investigated the possible protective effects of a cocoa procyanidin fraction (CPF) and procyanidin B2 (epicatechin-(4beta-8)-epicatechin) - a major polyphenol in cocoa - against apoptosis of PC12 rat pheochromocytoma (PC12) cells induced by hydrogen peroxide (H(2)O(2)). CPF (1 and 5 microg/ml) and procyanidin B2 (1 and 5 microM) reduced PC12 cell death caused by H(2)O(2), as determined by MTT and trypan blue exclusion assays. CPF and procyanidin B2 attenuated the H(2)O(2)-induced fragmentation of nucleus and DNA in PC12 cells. Western blot data demonstrated that H(2)O(2) induced cleavage of poly(ADP-ribose)polymerase (PARP), downregulated Bcl-X(L) and Bcl-2 in PC12 cells. Pretreatment with CPF or procyanidin B2 before H(2)O(2) treatment diminished PARP cleavage and increased Bcl-X(L) and Bcl-2 expression compared with those only treated with H(2)O(2). Activation of caspase-3 by H(2)O(2) was inhibited by pretreatment with CPF or procyanidin B2. Furthermore, H(2)O(2)-induced rapid and significant phosphorylation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), and both of these effects were attenuated by CPF or procyanidin B2 treatment. These results suggest that the protective effects of CPF and procyanidin B2 against H(2)O(2)-induced apoptosis involve inhibiting the downregulation of Bcl-X(L) and Bcl-2 expression through blocking the activation of JNK and p38 MAPK.

Plant-derived flavanol (-)epicatechin enhances angiogenesis and retention of spatial memory in mice

Diet and exercise have a profound impact on brain function. In particular, natural nutrients found in plants may influence neuronal survival and plasticity. Here, we tested whether consumption of a plant-derived flavanol, (-)epicatechin, enhances cognition in sedentary or wheel-running female C57BL/6 mice. Retention of spatial memory in the water maze was enhanced by ingestion of (-)epicatechin, especially in combination with exercise. Improved spatial memory was associated with increased angiogenesis and neuronal spine density, but not newborn cell survival, in the dentate gyrus of the hippocampus. Moreover, microarray analysis showed upregulation of genes associated with learning and downregulation of markers of neurodegeneration in the hippocampus. Together, our data show that ingestion of a single flavanol improves spatial memory retention in adult mammals.