Nutrition and neurodegeneration: epidemiological evidence and challenges for future research

Magnesium oxide use and reduced risk of dementia: a retrospective, nationwide cohort study in Taiwan

OBJECTIVE

Dietary magnesium may be associated with a lower risk of dementia; however, the impact of magnesium oxide (MgO), a common laxative, on dementia has yet to be elucidated. This study aimed to investigate the association between the usage of MgO and the risk of developing dementia.

METHODS

We used a dataset from the National Health Research Institute Database (NHRID) of Taiwan containing one million randomly sampled subjects to identify patients aged ≥50 years with no history of MgO usage. A total of 1547 patients who had used MgO were enrolled, along with 4641 controls who had not used the MgO propensity score matched by age, gender and comorbidity, at a ratio of 1:3. After adjusting for confounding risk factors, a Cox proportional hazards model was used to compare the risk of developing dementia during a 10 year follow-up period.

RESULTS

Of the enrolled patients, 44 (2.84%) developed dementia, when compared to 199 (4.28%) in the control group. The Cox proportional hazards regression analysis revealed that the patients who had used MgO were less likely to develop dementia with a crude hazard ratio of 0.617 (95% CI, 0.445-0.856, p = .004). After adjusting for age, gender, comorbidity, geographical area and urbanization level of residence, and monthly income, the adjusted hazard ratio was 0.517 (95% CI, 0.412-0.793, p = .001).

CONCLUSIONS

The patients who used MgO had a decreased risk of developing dementia. Further studies on the effects of MgO in reducing the risk of dementia are therefore warranted.

Vitamins Associated with Brain Aging, Mild Cognitive Impairment, and Alzheimer Disease: Biomarkers, Epidemiological and Experimental Evidence, Plausible Mechanisms, and Knowledge Gaps

The key to preventing brain aging, mild cognitive impairment (MCI), and Alzheimer disease (AD) via vitamin intake is first to understand molecular mechanisms, then to deduce relevant biomarkers, and subsequently to test the level of evidence for the impact of vitamins in the relevant pathways and their modulation of dementia risk. This narrative review infers information on mechanisms from gene and metabolic defects associated with MCI and AD, and assesses the role of vitamins using recent results from animal and human studies. Current evidence suggests that all known vitamins and some "quasi-vitamins" are involved as cofactors or influence ≥1 of the 6 key sets of pathways or pathologies associated with MCI or AD, relating to 1) 1-carbon metabolism, 2) DNA damage and repair, 3) mitochondrial function and glucose metabolism, 4) lipid and phospholipid metabolism and myelination, 5) neurotransmitter synthesis and synaptogenesis, and 6) amyloidosis and Tau protein phosphorylation. The contemporary level of evidence for each of the vitamins varies considerably, but it is notable that B vitamins are involved as cofactors in all of the core pathways or pathologies and, together with vitamins C and E, are consistently associated with a protective role against dementia. Outcomes from recent studies indicate that the efficacy and safety of supplementation with vitamins to prevent MCI and the early stages of AD will most likely depend on 1) which pathways are defective, 2) which vitamins are deficient and could correct the relevant metabolic defects, and 3) the modulating impact of nutrient-nutrient and nutrient-genotype interaction. More focus on a precision nutrition approach is required to realize the full potential of vitamin therapy in preventing dementia and to avoid causing harm.

Prevention of recognition memory loss and moderation of mitochondrial dynamic tendency toward fusion by flavone derivatives in Aβ-injected rats: a comparison between two flavonoids with different polarity

Growing evidence sheds light on the use of flavonoids as the promising alternatives for the treatment of chronic conditions, including cancer and neurodegenerative disorders. Accordingly, in the present study, we aimed at evaluating the effects of oral intake of two structurally different flavonoids 5-hydroxy-6,7,4'-trimethoxyflavone (flavone 1) and 5,7,4'-trihydroxyflavone (flavone 2) on recognition memory, hippocampal protein level of immediate early gene cFos and mitochondrial dynamic markers in Amyloid β (Aβ)-injected rats. Recognition aspect of memory and level of proteins were measured using novel object recognition test and Western blot, respectively. Our data indicated that even though flavone 1 was more effective than flavone 2 to prevent memory impairment, feeding with both flavones alleviated memory in Aβ-injected rats. Furthermore, in flavones-administered rats, mitochondrial dynamic balancing returned to the control level by the decline in Dynamin-related protein-1 protein level, a known marker for mitochondrial fission, and elevation in protein level of mitochondrial fusion factors Mitofusins 1 and 2. In parallel with behavior results, flavone 1 was more effectual on mitochondrial dynamic moderating. The more neuroprotective effects of flavone 1 could be attributed to its methylated structure leading to crossing of the blood-brain barrier with ease and metabolic stability and bioactivity.

Anti-inflammatory effects of flavonoids in neurodegenerative disorders

Neuroinflammation is one of the main mechanisms involved in the progression of several neurodegenerative diseases, such as Parkinson, Alzheimer, multiple sclerosis, amyotrophic lateral sclerosis and others. The activation of microglia is the main feature of neuroinflammation, promoting the release of pro-inflammatory cytokines and resulting in the progressive neuronal cell death. Natural compounds, such as flavonoids, possess neuroprotective potential probably related to their ability to modulate the inflammatory responses involved in neurodegenerative diseases. In fact, pure flavonoids (e.g., quercetin, genistein, hesperetin, epigallocatechin-3-gallate) or enriched-extracts, can reduce the expression of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β and COX-2), down-regulate inflammatory markers and prevent neural damage. This anti-inflammatory activity is primarily related to the regulation of microglial cells, mediated by their effects on MAPKs and NF-κB signalling pathways, as demonstrated by in vivo and in vitro data. The present work reviews the role of inflammation in neurodegenerative diseases, highlighting the potential therapeutic effects of flavonoids as a promising approach to develop innovative neuroprotective strategy.

Mushroom Consumption and Incident Dementia in Elderly Japanese: The Ohsaki Cohort 2006 Study

BACKGROUND

Both in vivo and in vitro studies have indicated that edible mushrooms may have preventive effects against cognitive impairment. However, few cohort studies have yet examined the relationship between mushroom consumption and incident dementia.

OBJECTIVE

We examined the relationship between mushroom consumption and incident dementia in a population of elderly Japanese subjects.

DESIGN

Prospective cohort study.

SETTING

Ohsaki Cohort 2006 Study.

PARTICIPANTS

13,230 individuals aged ≥65 years living in Ohsaki City, northeastern Japan.

MEASUREMENTS

Daily mushroom consumption, other lifestyle factors, and dementia incidence.

RESULTS

The 5.7 years incidence of dementia was 8.7%. In comparison with participants who consumed mushrooms <1 time/wk, the multi-adjusted HRs (95% CI) for incident dementia among those did so 1-2 times/week and ≥3 times/week were 0.95 (0.81, 1.10) and 0.81 (0.69, 0.95), respectively (P-trend <.01). The inverse association persisted after excluding participants whose dementia event occurred in the first 2 years of follow-up and whose baseline cognitive function was lower. The inverse association did not differ statistically in terms of vegetable consumption (P-interaction = .10).

CONCLUSIONS

This cohort study suggests that frequent mushroom consumption is significantly associated with a lower risk of incident dementia, even after adjustment for possible confounding factors.

Nutrition and AGE-ing: Focusing on Alzheimer's Disease

Recently, the role of food and nutrition in preventing or delaying chronic disability in the elderly population has received great attention. Thanks to their ability to influence biochemical and biological processes, bioactive nutrients are considered modifiable factors capable of preserving a healthy brain status. A diet rich in vitamins and polyphenols and poor in saturated fatty acids has been recommended. In the prospective of a healthy diet, cooking methods should be also considered. In fact, cooking procedures can modify the original dietary content, contributing not only to the loss of healthy nutrients, but also to the formation of toxins, including advanced glycation end products (AGEs). These harmful compounds are adsorbed at intestinal levels and can contribute to the ageing process. The accumulation of AGEs in ageing (“AGE-ing”) is further involved in the exacerbation of neurodegenerative and many other chronic diseases. In this review, we discuss food's dual role as both source of bioactive nutrients and reservoir for potential toxic compounds—paying particular attention to the importance of proper nutrition in preventing/delaying Alzheimer's disease. In addition, we focus on the importance of a good education in processing food in order to benefit from the nutritional properties of an optimal diet.

The influence of vitamins E and C and exercise on brain aging

Age-related declines in motor and cognitive function have been associated with increases in oxidative stress. Accordingly, interventions capable of reducing the oxidative burden would be capable of preventing or reducing functional declines occurring during aging. Popular interventions such as antioxidant intake and moderate exercise are often recommended to attain healthy aging and have the capacity to alter redox burden. This review is intended to summarize the outcomes of antioxidant supplementation (more specifically of vitamins C and E) and exercise training on motor and cognitive declines during aging, and on measures of oxidative stress. Additionally, we will address whether co-implementation of these two types of interventions can potentially further their individual benefits. Together, these studies highlight the importance of using translationally-relevant parameters for interventions and to study their combined outcomes on healthy brain aging.

Omega-3 Fatty Acid Status Enhances the Prevention of Cognitive Decline by B Vitamins in Mild Cognitive Impairment

A randomized trial (VITACOG) in people with mild cognitive impairment (MCI) found that B vitamin treatment to lower homocysteine slowed the rate of cognitive and clinical decline. We have used data from this trial to see whether baseline omega-3 fatty acid status interacts with the effects of B vitamin treatment. 266 participants with MCI aged ≥70 years were randomized to B vitamins (folic acid, vitamins B6 and B12) or placebo for 2 years. Baseline cognitive test performance, clinical dementia rating (CDR) scale, and plasma concentrations of total homocysteine, total docosahexaenoic and eicosapentaenoic acids (omega-3 fatty acids) were measured. Final scores for verbal delayed recall, global cognition, and CDR sum-of-boxes were better in the B vitamin-treated group according to increasing baseline concentrations of omega-3 fatty acids, whereas scores in the placebo group were similar across these concentrations. Among those with good omega-3 status, 33% of those on B vitamin treatment had global CDR scores >0 compared with 59% among those on placebo. For all three outcome measures, higher concentrations of docosahexaenoic acid alone significantly enhanced the cognitive effects of B vitamins, while eicosapentaenoic acid appeared less effective. When omega-3 fatty acid concentrations are low, B vitamin treatment has no effect on cognitive decline in MCI, but when omega-3 levels are in the upper normal range, B vitamins interact to slow cognitive decline. A clinical trial of B vitamins combined with omega-3 fatty acids is needed to see whether it is possible to slow the conversion from MCI to AD.

Putative Role of Red Wine Polyphenols against Brain Pathology in Alzheimer's and Parkinson's Disease

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common age-related neurodegenerative disorders and hence pose remarkable socio-economical burdens to both families and state. Although AD and PD have different clinical and neuropathological features, they share common molecular mechanisms that appear to be triggered by multi-factorial events, such as protein aggregation, mitochondrial dysfunction, oxidative stress (OS), and neuroinflammation, ultimately leading to neuronal cell death. Currently, there are no established and validated disease-modifying strategies for either AD or PD. Among the various lifestyle factors that may prevent or slow age-related neurodegenerative diseases, epidemiological studies on moderate consumption of red wine, especially as part of a holistic Mediterranean diet, have attracted increasing interest. Red wine is particularly rich in specific polyphenolic compounds that appear to affect the biological processes of AD and PD, such as quercetin, myricetin, catechins, tannins, anthocyanidins, resveratrol, and ferulic acid. Indeed, there is now a consistent body of in vitro and in vivo data on the neuroprotective effects of red wine polyphenols (RWP) showing that they do not merely possess antioxidant properties, but may additionally act upon, in a multi-target manner, the underlying key mechanisms featuring in both AD and PD. Furthermore, it is important that bioavailability issues are addressed in order for neuroprotection to be relevant in a clinical study scenario. This review summarizes the current knowledge about the major classes of RWP and places into perspective their potential to be considered as nutraceuticals to target neuropathology in AD and PD.

Recommendations for Development of New Standardized Forms of Cocoa Breeds and Cocoa Extract Processing for the Prevention of Alzheimer's Disease: Role of Cocoa in Promotion of Cognitive Resilience and Healthy Brain Aging

It is currently thought that the lackluster performance of translational paradigms in the prevention of age-related cognitive deteriorative disorders, such as Alzheimer's disease (AD), may be due to the inadequacy of the prevailing approach of targeting only a single mechanism. Age-related cognitive deterioration and certain neurodegenerative disorders, including AD, are characterized by complex relationships between interrelated biological phenotypes. Thus, alternative strategies that simultaneously target multiple underlying mechanisms may represent a more effective approach to prevention, which is a strategic priority of the National Alzheimer's Project Act and the National Institute on Aging. In this review article, we discuss recent strategies designed to clarify the mechanisms by which certain brain-bioavailable, bioactive polyphenols, in particular, flavan-3-ols also known as flavanols, which are highly represented in cocoa extracts, may beneficially influence cognitive deterioration, such as in AD, while promoting healthy brain aging. However, we note that key issues to improve consistency and reproducibility in the development of cocoa extracts as a potential future therapeutic agent requires a better understanding of the cocoa extract sources, their processing, and more standardized testing including brain bioavailability of bioactive metabolites and brain target engagement studies. The ultimate goal of this review is to provide recommendations for future developments of cocoa extracts as a therapeutic agent in AD.

Prevention of Age-Related Cognitive Decline: Which Strategies, When, and for Whom?

Brain aging is characterized by the progressive and gradual accumulation of detrimental changes in structure and function, which increase risk of age-related cognitive decline and dementia. This devastating chronic condition generates a huge social and economic burden and accounts for 11.2% of years of disability. The increase in lifespan has contributed to the increase in dementia prevalence; however, there is currently no curative treatment for most causes of dementias. This paper reviews evidence-based strategies to build, enhance, and preserve cognition over the lifespan by examining approaches that work best, proposing when in the life course they should be implemented, and in which population group(s). Recent work shows a tendency to decreased age-specific prevalence and incidence of cognitive problems and dementia among people born later in the first half of the 20th century, citing higher educational levels, improvements in lifestyle, and better handling of vascular risk factors. This implies that we can target modifiable environmental, lifestyle, and health risk factors to modify the trajectory of cognitive decline before the onset of irreversible dementia. Because building cognitive reserve and prevention of cognitive decline are of critical importance, interventions are needed at every stage of the life course to foster cognitive stimulation, and enable healthy eating habits and physical activity throughout the lifespan. Preventive interventions to decrease and delay cognitive decline and its consequences in old age will also require collaboration and action on the part of policy-makers at the political and social level.

Possible Predictors of Involuntary Weight Loss in Patients with Alzheimer's Disease

Loss in body mass (∆BM) is a common feature in patients with Alzheimer’s disease (AD). However, the etiology of this phenomenon is unclear. The aim of this cohort study was to observe possible ∆BM in AD patients following a standard institutionalized diet. Secondary objective was to identify possible predictors of ∆BM. To this end, 85 AD patients (age: 76±4 yrs; stature: 165±3 cm; BM: 61.6±7.4 kg; mean±standard deviation) and 86 controls (CTRL; age: 78±5 yrs; stature: 166±4 cm; BM: 61.7±6.4 kg) were followed during one year of standard institutionalized diet (~1800 kcal/24h). BM, daily energy expenditure, albuminemia, number of medications taken, and cortisolism, were recorded PRE and POST the observation period. Potential predictors of ∆BM in women (W) and men (M) with AD were calculated with a forward stepwise regression model. After one year of standard institutionalized diet, BM decreased significantly in AD (-2.5 kg; p < 0.01), while in CTRL remained unchanged (-0.4 kg; p = 0.8). AD patients and CTRL exhibited similar levels of daily energy expenditure (~1625 kcal/24h). The combination of three factors, number of medications taken, albuminemia, and cortisolism, predicted ∆BM in W with AD. At contrary, the best predictor of ∆BM in M with AD was the cortisolism. Despite a controlled energy intake and similar energy expenditure, both W and M with AD suffered of ∆BM. Therefore, controlled diet did not prevent this phenomenon. The assessments of these variables may predict W and M with AD at risk of weight loss.

Long-term association between the dietary inflammatory index and cognitive functioning: findings from the SU.VI.MAX study

PURPOSE

Inflammation is a ubiquitous underlying mechanism of the links between diet and cognitive functioning. No study has yet evaluated the overall inflammatory potential of the diet, using the dietary inflammatory index (DII), in relation to cognitive functioning. In a French cohort of middle-aged adults, we evaluated the association between the DII, assessed in midlife, and cognitive performance evaluated 13 years later.

METHODS

The DII is a literature-derived dietary index developed to determine the inflammatory potential of diet. The DII was estimated at baseline (1994-1996) among 3080 subjects of the SU.VI.MAX (supplementation with antioxidant vitamins and minerals) cohort. Cognitive performance was assessed in 2007-2009 via a battery of standardized neuropsychological tests. Principal component analysis was performed to extract a summary score of cognitive performance. Multivariable-adjusted linear regression analyses were performed to provide regression coefficients and 95 % confidence intervals (95 % CI).

RESULTS

In a multivariate model, a strong inverse association was observed between a higher DII (reflecting a more inflammatory diet) and overall cognitive functioning (mean difference Q4 vs. Q1 = -1.76; 95 % CI = -2.81, -0.72, P for trend =0.002). With regard to specific cognitive domains, similar associations were observed with scores reflecting verbal memory, but not executive functioning.

CONCLUSION

This study suggests that a pro-inflammatory diet at midlife might be associated with subsequent lower cognitive functioning. A diet exhibiting anti-inflammatory properties may help to maintain cognitive health during aging.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov (number NCT00272428).

Mitochondrial Dysfunction in Alzheimer's Disease and the Rationale for Bioenergetics Based Therapies

Alzheimer’s disease (AD) is a debilitating neurodegenerative disorder characterized by the progressive loss of cholinergic neurons, leading to the onset of severe behavioral, motor and cognitive impairments. It is a pressing public health problem with no effective treatment. Existing therapies only provide symptomatic relief without being able to prevent, stop or reverse the pathologic process. While the molecular basis underlying this multifactorial neurodegenerative disorder remains a significant challenge, mitochondrial dysfunction appears to be a critical factor in the pathogenesis of this disease. It is therefore important to target mitochondrial dysfunction in the prodromal phase of AD to slow or prevent the neurodegenerative process and restore neuronal function. In this review, we discuss mechanisms of action and translational potential of current mitochondrial and bioenergetic therapeutics for AD including: mitochondrial enhancers to potentiate energy production; antioxidants to scavenge reactive oxygen species and reduce oxidative damage; glucose metabolism and substrate supply; and candidates that target apoptotic and mitophagy pathways to remove damaged mitochondria. While mitochondrial therapeutic strategies have shown promise at the preclinical stage, there has been little progress in clinical trials thus far.

Dietary Patterns High in Red Meat, Potato, Gravy, and Butter Are Associated with Poor Cognitive Functioning but Not with Rate of Cognitive Decline in Very Old Adults

BACKGROUND

Healthy dietary patterns (DPs) have been linked to better cognition and reduced risk of dementia in older adults, but their role in cognitive functioning and decline in the very old (aged ≥85 y) is unknown.

OBJECTIVE

We investigated the association between previously established DPs from the Newcastle 85+ Study and global and attention-specific cognition over 5 y.

METHODS

We followed up with 302 men and 489 women (1921 birth cohort from Northeast United Kingdom) for change in global cognition [measured by the Standardized Mini-Mental State Examination (SMMSE)] over 5 y and attention (assessed by the cognitive drug research attention battery) over 3 y. We used 2-step clustering to derive DPs and mixed models to determine the relation between DPs and cognition in the presence of the dementia susceptibility gene.

RESULTS

Previously, we characterized 3 DPs that differed in intake of red meat, potato, gravy, and butter and varied with key health measures. When compared with participants in DP1 (high red meat) and DP3 (high butter), participants in DP2 (low meat) had higher SMMSE scores at baseline (P < 0.001) and follow-ups, and better initial attention (P < 0.05). Membership in DP1 and DP3 was associated with overall worse SMMSE scores (β = 0.09, P = 0.01 and β = 0.08, P = 0.02, respectively) than membership in DP2 after adjustment for sociodemographic factors, lifestyle, multimorbidity, and body mass index (BMI). Additional adjustment for apolipoprotein (apoE) ε4 genotype attenuated the association to nonsignificant in women but not in men in DP1 (β = 0.13, P = 0.02). Participants in DP1 and DP3 also had overall worse concentration (β = 0.04, P = 0.002 and β = 0.028, P = 0.03, respectively) and focused attention (β = 0.02, P = 0.01 and β = 0.02, P = 0.03, respectively), irrespective of apoE ε4 genotype, but similar rate of decline in all cognitive measures over time.

CONCLUSION

DPs high in red meat, potato, gravy (DP1), or butter (DP3) were associated with poor cognition but not with the rate of cognitive decline in very old adults.

Effect of Nutrients, Dietary Supplements and Vitamins on Cognition: a Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background

Observational studies have suggested that various nutrients, dietary supplements, and vitamins may delay the onset of age-associated cognitive decline and dementia. We systematically reviewed recent randomized controlled trials investigating the effect of nutritional interventions on cognitive performance in older non-demented adults.

Methods

We searched MEDLINE, CINAHL, Embase, and the Cochrane Library for articles published between 2003 and 2013. We included randomized trials of ≥ 3 months’ duration that examined the cognitive effects of a nutritional intervention in non-demented adults > 40 years of age. Meta-analyses were done when sufficient trials were available.

Results

Twenty-four trials met inclusion criteria (six omega-3 fatty acids, seven B vitamins, three vitamin E, eight other interventions). In the meta-analyses, omega-3 fatty acids showed no significant effect on Mini-Mental State Examination (MMSE) scores (four trials, mean difference 0.06, 95% CI −0.08 – 0.19) or digit span forward (three trials, mean difference −0.02, 95% CI −0.30 – 0.25), while B vitamins showed no significant effect on MMSE scores (three trials, mean difference 0.02, 95% CI −0.22 – 0.25). None of the vitamin E studies reported significant effects on cognitive outcomes. Among the other nutritional interventions, statistically significant differences between the intervention and control groups on at least one cognitive domain were found in single studies of green tea extract, Concord grape juice, chromium picolinate, beta-carotene, two different combinations of multiple vitamins, and a dietary approach developed for the control of hypertension.

Conclusions

Omega-3 fatty acids, B vitamins, and vitamin E supplementation did not affect cognition in non-demented middle-aged and older adults. Other nutritional interventions require further evaluation before their use can be advocated for the prevention of age-associated cognitive decline and dementia.

Early Shifts of Brain Metabolism by Caloric Restriction Preserve White Matter Integrity and Long-Term Memory in Aging Mice

Preservation of brain integrity with age is highly associated with lifespan determination. Caloric restriction (CR) has been shown to increase longevity and healthspan in various species; however, its effects on preserving living brain functions in aging remain largely unexplored. In the study, we used multimodal, non-invasive neuroimaging (PET/MRI/MRS) to determine in vivo brain glucose metabolism, energy metabolites, and white matter structural integrity in young and old mice fed with either control or 40% CR diet. In addition, we determined the animals' memory and learning ability with behavioral assessments. Blood glucose, blood ketone bodies, and body weight were also measured. We found distinct patterns between normal aging and CR aging on brain functions - normal aging showed reductions in brain glucose metabolism, white matter integrity, and long-term memory, resembling human brain aging. CR aging, in contrast, displayed an early shift from glucose to ketone bodies metabolism, which was associated with preservations of brain energy production, white matter integrity, and long-term memory in aging mice. Among all the mice, we found a positive correlation between blood glucose level and body weight, but an inverse association between blood glucose level and lifespan. Our findings suggest that CR could slow down brain aging, in part due to the early shift of energy metabolism caused by lower caloric intake, and we were able to identify the age-dependent effects of CR non-invasively using neuroimaging. These results provide a rationale for CR-induced sustenance of brain health with extended longevity.

Does Long-Term High Fat Diet Always Lead to Smaller Hippocampi Volumes, Metabolite Concentrations, and Worse Learning and Memory? A Magnetic Resonance and Behavioral Study in Wistar Rats

Background

Obesity is a worldwide epidemic with more than 600 million affected individuals. Human studies have demonstrated some alterations in brains of otherwise healthy obese individuals and elevated risk of neurodegenerative disease of old age; these studies have also pointed to slightly diminished memory and executive functions among healthy obese individuals. Similar findings were obtained in animal models of obesity induced by high fat diet. On the other hand, low carbohydrate high fat diets are currently promoted for losing weight (e.g., Atkin’s style diets). However, the long-term effects of such diets are not known. Additionally, high fat diets leading to (mild) ketonemia were shown to improve brain function in elderly humans and in some animal models.

Aim

To evaluate the hypothesis that long-term use of a high fat diet was associated with decreases in spatial memory, smaller hippocampi and hippocampi metabolite concentrations in Wistar rats.

Methods

Twenty five male Wistar rats were put on high fat diet (HFD; 60% calories from fat, 30% from carbohydrates) on their 55^th day of life, while 25 control male rats (CONs) remained on chow. Adequate levels of essential nutrients were provided. Both groups underwent memory tests in 8-arm radial maze at 3^rd, 6^th, 9^th, and 12^th month. ¹H magnetic resonance spectroscopy was employed to measure concentrations of tNAA (marker of neuronal integrity) at one month and one year, whereas MRI was used to evaluate hippocampal volumes.

Results

Obese rats (OBRs) consumed similar amount of calories as CONs, but less proteins. However, their protein intake was within recommended amounts. Throughout the experiment OBRs had statistically higher concentrations of blood ketone bodies than CONs, but still within normal values. At post-mortem assessment, OBRs had 38% larger fat deposits than CONs (p<0.05), as evaluated by volume of epididymis fat, an acknowledged marker of fat deposits in rats. Contrary to our expectations, OBRs had better scores of memory behavioral tasks than CONs throughout the experiment. At one year, their hippocampi were by 2.6% larger than in CONs (p = 0.05), whereas concentration of tNAA was 9.8% higher (p = 0.014).

Conclusion

Long-term HFD in our study resulted in better memory, larger hippocampal volumes, as well as higher hippocampal metabolite concentrations, possibly due to increased levels of blood ketone bodies. The results should be interpreted with caution, as results from animal models do not necessarily directly translate in human condition.

Altered one-carbon metabolism in posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with increased morbidity and mortality through somatic conditions, particularly cardiovascular disease. The one-carbon metabolism in connection with the hypothalamic-pituitary-adrenal (HPA)-axis may be an important mediator of this increased cardiovascular risk.

METHODS

In a mixed-gender sample of 49 PTSD patients and 45 healthy controls we therefore investigated: (1) alterations in the one-carbon metabolism as reflected in fasting plasma concentrations of homocysteine, folate, vitamins B6 and B12, and (2) associations of these one-carbon metabolites with the HPA-axis hormones cortisol, dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S).

RESULTS

After correction for confounders, PTSD patients had significantly elevated homocysteine (z = 2.963, p = .003) compared to controls, but normal levels of folate, vitamin B6 and B12. Comorbid depression did not explain the observed higher homocysteine levels. Patients showed increased risk for moderate hyperhomocysteinemia (OR = 7.0, χ(2) = 7.436, p = .006). Additionally, homocysteine was associated with PTSD severity (z = 2.281, p = .005). Moreover, all HPA-axis hormones were associated with folate in both patients and controls (all p's ≤ .011), while DHEA-S influenced folate in patients (z = 2.089, p = .037).

LIMITATIONS

Our clinical sample is relatively small and therefore small-sized effects may have remained undetected.

CONCLUSIONS

Our study indicates that: (1) the one-carbon metabolism is altered in PTSD patients, (2) earlier findings of higher homocysteine in male PTSD patients are generalized to female patients, (3) homocysteine is negatively associated with PTSD severity, and (4) HPA-axis alterations are associated with the one-carbon metabolism. Longitudinal studies are needed to determine whether elevated homocysteine levels reflect preexisting risk factors and/or consequences of psychological trauma.

The effects of a protein enriched diet with lean red meat combined with a multi-modal exercise program on muscle and cognitive health and function in older adults: study protocol for a randomised controlled trial

Background

Age-related muscle wasting has been strongly implicated with falls and fractures in the elderly, but it has also been associated with cognitive decline and dementia. Progressive resistance training (PRT) and adequate dietary protein are recognised as important contributors to the maintenance of muscle health and function in older adults. However, both factors also have the potential to improve brain function and prevent cognitive decline via several pathways, including the regulation of various growth and neurotrophic factors [insulin-like growth factor-1 (IGF-1)]; brain-derived growth factor (BDNF)] and/or the modulation of systemic inflammation. The primary aim of this study is to investigate whether a modest increase in dietary protein achieved through the consumption of lean red meat three days per week, when combined with PRT, can enhance muscle mass, size and strength and cognitive function in community-dwelling older people.

Methods/Design

The study design is a 48-week randomised controlled trial consisting of a 24-week intervention with a 24-week follow-up. Men and women (n=152) aged 65 years and over residing in the community will be randomly allocated to: 1) PRT and provided with 220 g (raw weight) of lean red meat to be cooked and divided into two 80 g servings on each of the three days that they complete their exercise session, or 2) control PRT in which participants will be provided with and advised to consume ≥1 serving (~1/2 cup) of rice and/or pasta or 1 medium potato on each of the three training days. The primary outcome measures will be muscle mass, size and strength and cognitive function. Secondary outcomes will include changes in: muscle function, neural health (corticospinal excitability and inhibition and voluntary activation), serum IGF-1 and BDNF, adipokines and inflammatory markers, fat mass and inter-/intra-muscular fat, blood pressure, lipids and health-related quality of life. All outcome measures will be assessed at baseline and 24 weeks, with the exception of cognitive function and the various neurobiological and inflammatory markers which will also be assessed at week 12.

Discussion

The findings from this study will provide important new information on whether a modest increase in dietary protein achieved through the ingestion of lean red meat can enhance the effects of PRT on muscle mass, size and strength as well as cognitive function in community-dwelling older adults. If successful, the findings will form the basis for more precise exercise and nutrition guidelines for the management and prevention of age-related changes in muscle and neural health and cognitive function in the elderly.

Trial registration

Australian New Zealand Clinical Trials Registry: ACTRN12613001153707. Date registered 16^th October, 2013.

The Ambiguous Relationship of Oxidative Stress, Tau Hyperphosphorylation, and Autophagy Dysfunction in Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia. The pathological hallmarks of AD are amyloid plaques [aggregates of amyloid-beta (Aβ)] and neurofibrillary tangles (aggregates of tau). Growing evidence suggests that tau accumulation is pathologically more relevant to the development of neurodegeneration and cognitive decline in AD patients than Aβ plaques. Oxidative stress is a prominent early event in the pathogenesis of AD and is therefore believed to contribute to tau hyperphosphorylation. Several studies have shown that the autophagic pathway in neurons is important under physiological and pathological conditions. Therefore, this pathway plays a crucial role for the degradation of endogenous soluble tau. However, the relationship between oxidative stress, tau protein hyperphosphorylation, autophagy dysregulation, and neuronal cell death in AD remains unclear. Here, we review the latest progress in AD, with a special emphasis on oxidative stress, tau hyperphosphorylation, and autophagy. We also discuss the relationship of these three factors in AD.

Improved blood biomarkers but no cognitive effects from 16 weeks of multivitamin supplementation in healthy older adults

Supplementation with vitamins, minerals and phytonutrients may be beneficial for cognition, especially in older adults. The aim of this study was to assess the effects of multivitamin supplementation in older adults on cognitive function and associated blood biomarkers. In a randomised, double blind, placebo-controlled trial, healthy women (n = 68) and men (n = 48) aged 55–65 years were supplemented daily for 16 weeks with women’s and men’s formula multivitamin supplements. Assessments at baseline and post-supplementation included computerised cognitive tasks and blood biomarkers relevant to cognitive aging. No cognitive improvements were observed after supplementation with either formula; however, several significant improvements were observed in blood biomarkers including increased levels of vitamins B₆ and B₁₂ in women and men; reduced C-reactive protein in women; reduced homocysteine and marginally reduced oxidative stress in men; as well as improvements to the lipid profile in men. In healthy older people, multivitamin supplementation improved a number of blood biomarkers that are relevant to cognition, but these biomarker changes were not accompanied by improved cognitive function.

Healthy eating and reduced risk of cognitive decline: A cohort from 40 countries

OBJECTIVE

We sought to determine the association of dietary factors and risk of cognitive decline in a population at high risk of cardiovascular disease.

METHODS

Baseline dietary intake and measures of the Mini-Mental State Examination were recorded in 27,860 men and women who were enrolled in 2 international parallel trials of the ONTARGET (Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial) and TRANSCEND (Telmisartan Randomised Assessment Study in ACE Intolerant Subjects with Cardiovascular Disease) studies. We measured diet quality using the modified Alternative Healthy Eating Index. Cox proportional hazards regression was used to determine the association between diet quality and risk of ≥3-point decline in Mini-Mental State Examination score, and reported as hazard ratio with 95% confidence intervals with adjustment for covariates.

RESULTS

During 56 months of follow-up, 4,699 cases of cognitive decline occurred. We observed lower risk of cognitive decline among those in the healthiest dietary quintile of modified Alternative Healthy Eating Index compared with lowest quintile (hazard ratio 0.76, 95% confidence interval 0.66-0.86, Q5 vs Q1). Lower risk of cognitive decline was consistent regardless of baseline cognitive level.

CONCLUSION

We found that higher diet quality was associated with a reduced risk of cognitive decline. Improved diet quality represents an important potential target for reducing the global burden of cognitive decline.

Cognitive aspects of frailty: mechanisms behind the link between frailty and cognitive impairment

Whereas physical impairment is the main hallmark of frailty, evidence suggests that other dimensions, such as psychological, cognitive and social factors also contribute to this multidimensional condition. Cognition is now considered a relevant domain of frailty. Cognitive and physical frailty interact: cognitive problems and dementia are more prevalent in physically frail individuals, and those with cognitive impairment are more prone to become frail. Disentangling the relationship between cognition and frailty may lead to new intervention strategies for the prevention and treatment of both conditions. Both frailty and cognitive decline share common potential mechanisms. This review examines the relationship between frailty and cognitive decline and explores the role of vascular changes, hormones, vitamin D, inflammation, insulin resistance, and nutrition in the development of physical frailty and cognitive problems, as potential underlying mechanisms behind this link. Dual tasking studies may be a useful way to explore and understand the relation between cognitive and physical frailty. Further studies are needed to elucidate this complex relation to improve the outcomes of frailty.

Role of dietary pattern analysis in determining cognitive status in elderly Australian adults

Principal Component Analysis (PCA) was used to determine the association between dietary patterns and cognitive function and to examine how classification systems based on food groups and food items affect levels of association between diet and cognitive function. The present study focuses on the older segment of the Australian Diabetes, Obesity and Lifestyle Study (AusDiab) sample (age 60+) that completed the food frequency questionnaire at Wave 1 (1999/2000) and the mini-mental state examination and tests of memory, verbal ability and processing speed at Wave 3 (2012). Three methods were used in order to classify these foods before applying PCA. In the first instance, the 101 individual food items asked about in the questionnaire were used (no categorisation). In the second and third instances, foods were combined and reduced to 32 and 20 food groups, respectively, based on nutrient content and culinary usage—a method employed in several other published studies for PCA. Logistic regression analysis and generalized linear modelling was used to analyse the relationship between PCA-derived dietary patterns and cognitive outcome. Broader food group classifications resulted in a greater proportion of food use variance in the sample being explained (use of 101 individual foods explained 23.22% of total food use, while use of 32 and 20 food groups explained 29.74% and 30.74% of total variance in food use in the sample, respectively). Three dietary patterns were found to be associated with decreased odds of cognitive impairment (CI). Dietary patterns derived from 101 individual food items showed that for every one unit increase in ((Fruit and Vegetable Pattern: p = 0.030, OR 1.061, confidence interval: 1.006–1.118); (Fish, Legumes and Vegetable Pattern: p = 0.040, OR 1.032, confidence interval: 1.001–1.064); (Dairy, Cereal and Eggs Pattern: p = 0.003, OR 1.020, confidence interval: 1.007–1.033)), the odds of cognitive impairment decreased. Different results were observed when the effect of dietary patterns on memory, processing speed and vocabulary were examined. Complex patterns of associations between dietary factors and cognition were evident, with the most consistent finding being the protective effects of high vegetable and plant-based food item consumption and negative effects of ‘Western’ patterns on cognition. Further long-term studies and investigation of the best methods for dietary measurement are needed to better understand diet-disease relationships in this age group.

Mediterranean diet and cognitive health: an update of available knowledge

PURPOSE OF REVIEW

Nutrition constitutes an interesting approach for the prevention of age-related brain disorders. The objective of this review was to examine the most recent evidence on the association between adherence to a Mediterranean diet (MeDi) and cognitive health among elderly individuals.

RECENT FINDINGS

Based on available epidemiological studies, two meta-analyses published in 2013 have underlined a protective effect of a greater MeDi adherence on cognitive health, including a reduced risk of Alzheimer's disease and cognitive impairment. Since then, six additional studies, from longitudinal cohorts or post-hoc analyses of randomized controlled trials conducted in the USA and Europe, have been published and provided mixed results. Potential reasons for such discrepancies include methodological limitations inherent to observational studies, and interactions between diet, environmental factors, such as those enhancing cognitive reserve, chronic diseases, and genetic factors.

SUMMARY

Overall, available evidence suggests that the MeDi might exert a long-term beneficial effect on brain functioning. However, more high-powered observational studies with long-term follow-up for cognition and randomized controlled trials assessing the impact of shifting to a MeDi on cognitive functions are still needed in various populations.

Effects of vitamin E on cognitive performance during ageing and in Alzheimer's disease

Vitamin E is an important antioxidant that primarily protects cells from damage associated with oxidative stress caused by free radicals. The brain is highly susceptible to oxidative stress, which increases during ageing and is considered a major contributor to neurodegeneration. High plasma vitamin E levels were repeatedly associated with better cognitive performance. Due to its antioxidant properties, the ability of vitamin E to prevent or delay cognitive decline has been tested in clinical trials in both ageing population and Alzheimer’s disease (AD) patients. The difficulty in performing precise and uniform human studies is mostly responsible for the inconsistent outcomes reported in the literature. Therefore, the benefit of vitamin E as a treatment for neurodegenerative disorders is still under debate. In this review, we focus on those studies that mostly have contributed to clarifying the exclusive function of vitamin E in relation to brain ageing and AD.

Brain insulin resistance in Alzheimer's disease and its potential treatment with GLP-1 analogs

The prevalence of Alzheimer's disease is increasing rapidly in the absence of truly effective therapies. A promising strategy for developing such therapies is the treatment of brain insulin resistance, a common and early feature of Alzheimer's disease, closely tied to cognitive decline and capable of promoting many biological abnormalities in the disorder. The proximal cause of brain insulin resistance appears to be neuronal elevation in the serine phosphorylation of IRS-1, most likely due to amyloid-β-triggered microglial release of proinflammatory cytokines. Preclinically, the first line of defense is behavior-lowering peripheral insulin resistance (e.g., physical exercise and a Mediterranean diet supplemented with foods rich in flavonoids, curcumin and ω-3 fatty acids). More potent remediation is required, however, at clinical stages. Fortunately, the US FDA-approved antidiabetics exenatide (Byetta; Amylin Pharmaceuticals, Inc., CA, USA) and liraglutide (Victoza; Novo Nordisk A/S, Bagsvaerd, Denmark) are showing much promise in reducing Alzheimer's disease pathology and in restoring normal brain insulin responsiveness and cognitive function.

Long-term omega-3 supplementation modulates behavior, hippocampal fatty acid concentration, neuronal progenitor proliferation and central TNF-α expression in 7 month old unchallenged mice

Dietary polyunsaturated fatty acid (PUFA) manipulation is being investigated as a potential therapeutic supplement to reduce the risk of developing age-related cognitive decline (ARCD). Animal studies suggest that high omega (Ω)-3 and low Ω-6 dietary content reduces cognitive decline by decreasing central nervous system (CNS) inflammation and modifying neuroimmune activity. However, no previous studies have investigated the long term effects of Ω-3 and Ω-6 dietary levels in healthy aging mice leaving the important question about the preventive effects of Ω-3 and Ω-6 on behavior and underlying molecular pathways unaddressed. We aimed to investigate the efficacy of long-term Ω-3 and Ω-6 PUFA dietary supplementation in mature adult C57BL/6 mice. We measured the effect of low, medium, and high Ω-3:Ω-6 dietary ratio, given from the age of 3–7 months, on anxiety and cognition-like behavior, hippocampal tissue expression of TNF-α, markers of neuronal progenitor proliferation and gliogenesis and serum cytokine concentration. Our results show that a higher Ω-3:Ω-6 PUFA diet ratio increased hippocampal PUFA, increased anxiety, improved hippocampal dependent spatial memory and reduced hippocampal TNF-α levels compared to a low Ω-3:Ω-6 diet. Furthermore, serum TNF-α concentration was reduced in the higher Ω-3:Ω-6 PUFA ratio supplementation group while expression of the neuronal progenitor proliferation markers KI67 and doublecortin (DCX) was increased in the dentate gyrus as opposed to the low Ω-3:Ω-6 group. Conversely, Ω-3:Ω-6 dietary PUFA ratio had no significant effect on astrocyte or microglia number or cell death in the dentate gyrus. These results suggest that supplementation of PUFAs may delay aging effects on cognitive function in unchallenged mature adult C57BL/6 mice. This effect is possibly induced by increasing neuronal progenitor proliferation and reducing TNF-α.

Nutrition and prevention of Alzheimer's dementia

A nutritional approach to prevent, slow, or halt the progression of disease is a promising strategy that has been widely investigated. Much epidemiologic data suggests that nutritional intake may influence the development and progression of Alzheimer’s dementia (AD). Modifiable, environmental causes of AD include potential metabolic derangements caused by dietary insufficiency and or excess that may be corrected by nutritional supplementation and or dietary modification. Many nutritional supplements contain a myriad of health promoting constituents (anti-oxidants, vitamins, trace minerals, flavonoids, lipids, …etc.) that may have novel mechanisms of action affecting cellular health and regeneration, the aging process itself, or may specifically disrupt pathogenic pathways in the development of AD. Nutritional modifications have the advantage of being cost effective, easy to implement, socially acceptable and generally safe and devoid of significant adverse events in most cases. Many nutritional interventions have been studied and continue to be evaluated in hopes of finding a successful agent, combination of agents, or dietary modifications that can be used for the prevention and or treatment of AD. The current review focuses on several key nutritional compounds and dietary modifications that have been studied in humans, and further discusses the rationale underlying their potential utility for the prevention and treatment of AD.

Clustering of midlife lifestyle behaviors and subsequent cognitive function: a longitudinal study

OBJECTIVES

We examined the association between individual and clustered lifestyle behaviors in middle age and later in cognitive functioning.

METHODS

Middle-aged participants (n = 2430) in the Supplémentation en Vitamines et Minéraux Antioxydant study self-reported their low physical activity, sedentary behavior, alcohol use, smoking, low fruit and vegetable consumption, and low fish consumption. We assessed cognition 13 years later via 6 neuropsychological tests. After standardization, we summed the scores for a composite cognitive measure. We estimated executive functioning and verbal memory scores using principal component analysis. We estimated the mean differences (95% confidence intervals [CIs]) in cognitive performance by the number of unhealthy behaviors using analysis of covariance. We identified latent unhealthy behavior factor via structural equation modeling.

RESULTS

Global cognitive function and verbal memory were linearly, negatively associated with the number of unhealthy behaviors: adjusted mean differences = -0.36 (95% CI = -0.69, -0.03) and -0.46 (95% CI = -0.80, -0.11), respectively, per unit increase in the number of unhealthy behaviors. The latent unhealthy behavior factor with low fruit and vegetable consumption and low physical activity as main contributors was associated with reduced verbal memory (RMSEA = 0.02; CFI = 0.96; P = .004). No association was found with executive functioning.

CONCLUSIONS

Comprehensive public health strategies promoting healthy lifestyles might help deter cognitive aging.

Nutrition, the brain and cognitive decline: insights from epigenetics

Nutrition affects the brain throughout life, with profound implications for cognitive decline and dementia. These effects are mediated by changes in expression of multiple genes, and responses to nutrition are in turn affected by individual genetic variability. An important layer of regulation is provided by the epigenome: nutrition is one of the many epigenetic regulators that modify gene expression without changes in DNA sequence. Epigenetic mechanisms are central to brain development, structure and function, and include DNA methylation, histone modifications and non-protein-coding RNAs. They enable cell-specific and age-related gene expression. Although epigenetic events can be highly stable, they can also be reversible, highlighting a critical role for nutrition in prevention and treatment of disease. Moreover, they suggest key mechanisms by which nutrition is involved in the pathogenesis of age-related cognitive decline: many nutrients, foods and diets have both immediate and long-term effects on the epigenome, including energy status, that is, energy intake, physical activity, energy metabolism and related changes in body composition, and micronutrients involved in DNA methylation, for example, folate, vitamins B6 and B12, choline, methionine. Optimal brain function results from highly complex interactions between numerous genetic and environmental factors, including food intake, physical activity, age and stress. Future studies linking nutrition with advances in neuroscience, genomics and epigenomics should provide novel approaches to the prevention of cognitive decline, and treatment of dementia and Alzheimer's disease.

Lipids in the nervous system: from biochemistry and molecular biology to patho-physiology

Lipids in the nervous system accomplish a great number of key functions, from synaptogenesis to impulse conduction, and more. Most of the lipids of the nervous system are localized in myelin sheaths. It has long been known that myelin structure and brain homeostasis rely on specific lipid-protein interactions and on specific cell-to-cell signaling. In more recent years, the growing advances in large-scale technologies and genetically modified animal models have provided valuable insights into the role of lipids in the nervous system. Key findings recently emerged in these areas are here summarized. In addition, we briefly discuss how this new knowledge can open novel approaches for the treatment of diseases associated with alteration of lipid metabolism/homeostasis in the nervous system. This article is part of a Special Issue entitled Linking transcription to physiology in lipidomics.

n-3 LCPUFA improves cognition: the young, the old and the sick

Due to the implication of docosahexaenoic acid (DHA) in neurogenesis, synaptogenesis, neurite outgrowth and to its high incorporation into the brain, this n-3 long chain polyunsaturated fatty acid (LCPUFA) is considered as crucial in the development and maintenance of the learning memory performance throughout life. In the present chapter we aimed at reviewing data investigating the relation between DHA and cognition during the perinatal period, young adult- and adulthood and neurodegenerative diseases such as Alzheimer disease (AD). In Humans, dietary DHA supplementation from the perinatal period to adulthood does not reveal a clear and consistent memory improvement whereas it is the case in animal studies. The positive effects observed in animal models may have been enhanced by using n-3 PUFA deficient animal models as controls. In animal models of AD, a general consensus on the beneficial effects of n-3 LCPUFA in attenuating cognitive impairment was established. These studies make DHA a potential suitable micronutrient for the maintenance of cognitive performance at all periods of life.