Dietary saturated fatty acids and brain function

Postmortem Fatty Acid Abnormalities in the Cerebellum of Patients with Essential Tremor

Fatty acids play many critical roles in brain function but have not been investigated in essential tremor (ET), a frequent movement disorder suspected to involve cerebellar dysfunction. Here, we report a postmortem comparative analysis of fatty acid profiles by gas chromatography in the cerebellar cortex from ET patients (n = 15), Parkinson's disease (PD) patients (n = 15) and Controls (n = 17). Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI)/ phosphatidylserine (PS) were separated by thin-layer chromatography and analyzed separately. First, the total amounts of fatty acids retrieved from the cerebellar cortex were lower in ET patients compared with PD patients, including monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). The diagnosis of ET was associated with lower cerebellar levels of saturated fatty acids (SFA) and PUFA (DHA and ARA) in the PE fraction specifically, but with a higher relative content of dihomo-γ-linolenic acid (DGLA; 20:3 ω-6) in the PC fraction. In contrast, a diagnosis of PD was associated with higher absolute concentrations of SFA, MUFA and ω-6 PUFA in the PI + PS fractions. However, relative PI + PS contents of ω-6 PUFA were lower in both PD and ET patients. Finally, linear regression analyses showed that the ω-3:ω-6 PUFA ratio was positively associated with age of death, but inversely associated with insoluble α-synuclein. Although it remains unclear how these FA changes in the cerebellum are implicated in ET or PD pathophysiology, they may be related to an ongoing neurodegenerative process or to dietary intake differences. The present findings provide a window of opportunity for lipid-based therapeutic nutritional intervention.

Dietary Fatty Acid Composition Impacts the Fatty Acid Profiles of Different Regions of the Bovine Brain

Fatty acid composition across functional brain regions was determined in bovine brains collected from cattle that were provided supplements of calcium salts containing either palm or fish oil. The Angus cattle were divided into two groups, with one group offered the supplement of calcium salts of palm oil and the other offered the calcium salts of fish oil (n = 5 females and n = 5 males/supplement) for 220 days. These supplements to the basal forage diet were provided ad libitum as a suspension in dried molasses. The fish oil exclusively provided eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3). The functional regions were dissected from the entire brains following commercial harvest. While the cattle provided diets supplemented with the calcium salts of palm oil had increased (p < 0.01) liver concentrations of C18:1 n-9, C18:2 n-6, and arachidonic acid, the fish-oil-supplemented cattle had greater (p < 0.01) concentrations of liver EPA, DHA, and C18:3 n-3. In the brain, DHA was the most abundant polyunsaturated fatty acid. In the amygdala, pons, frontal lobe, internal capsule, and sensory cortex, DHA concentrations were greater (p < 0.05) in the brains of the cattle fed fish oil. Differences among the supplements were small, indicating that brain DHA content is resistant to dietary change. Arachidonic acid and C22:4 n-6 concentrations were greater across the regions for the palm-oil-supplemented cattle. EPA and C22:5 n-3 concentrations were low, but they were greater across the regions for the cattle fed fish oil. The effects of sex were inconsistent. The fatty acid profiles of the brain regions differed by diet, but they were similar to the contents reported for other species.

Fat-1 expression enhance hippocampal memory in scopolamine-induced amnesia

Omega-3 polyunsaturated fatty acids (PUFA) are critical for optimal brain health and are involved in psychiatric and neurological ailments. Here, we report the effects of higher endogenous omega-3 PUFA on memory impairment in the hippocampus by studying mice with transgenic expression of the fat-1 gene that converts omega-6 to omega-3 PUFA. We performed Y-maze and passive avoidance tests to evaluate the memory function of fat-1 mice treated with scopolamine. Fat-1 mice showed induced alternation in the Y-maze test and increased latency in the passive avoidance test. The effects of scopolamine on hippocampal neurogenesis were confirmed by increases in the number of Ki-67- and DCX-positive cells in the fat-1 mice. Western blotting revealed increased brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element-binding protein levels, and lower scopolamine-induced apoptosis based on the cleaved-caspase 3 protein level in fat-1 mice. These findings suggest that higher endogenous omega-3 PUFA prevented granular cell loss, increased BDNF signaling, and decreased apoptosis signaling in scopolamine-treated fat-1 mice. These processes may underlie granular cell survival and suggest potential therapeutic targets for memory impairment.

Factors that positively or negatively mediate the effects of age on working memory across the adult life span

Working memory abilities significantly decrease with advancing age; hence, the search for factors that may increase or mitigate this decline is critical. Several factors have been identified that influence working memory; however, their effects have been mainly assessed separately and rarely together with other factors in the same sample. We examined 120 variables to search for factors that jointly act as mediators of working memory decay across the adult life span. A sample of 1652 healthy adults was assessed in spatial and verbal working memory domains. Structural equation modeling analyses were conducted to search for potential mediators that intervened between age and working memory. Only 14 and 10 variables reliably mediated spatial and verbal working memory, respectively. Factors from several domains remained in the models, such as individual characteristics, physiological traits, consumption habits, and regular activities. These factors are sufficiently powerful to influence working memory decline when they jointly interact, as in everyday living.

Fatty Acids, Antioxidants and Physical Activity in Brain Aging

Polyunsaturated fatty acids and antioxidants are important mediators in the central nervous system. Lipid derivatives may control the production of proinflammatory agents and regulate NF-κB activity, microglial activation, and fatty acid oxidation; on the other hand, antioxidants, such as glutathione and ascorbate, have been shown to signal through transmitter receptors and protect against acute and chronic oxidative stress, modulating the activity of different signaling pathways. Several authors have investigated the role of these nutrients in the brains of the young and the aged in degenerative diseases such as Alzheimer’s and Parkinson’s, and during brain aging due to adiposity- and physical inactivity-mediated metabolic disturbances, chronic inflammation, and oxidative stress. Through a literature review, we aimed to highlight recent data on the role of adiposity, fatty acids, antioxidants, and physical inactivity in the pathophysiology of the brain and in the molecular mechanisms of senescence. Data indicate the complexity and necessity of endogenous/dietary antioxidants for the maintenance of redox status and the control of neuroglial signaling under stress. Recent studies also indicate that omega-3 and -6 fatty acids act in a competitive manner to generate mediators for energy metabolism, influencing feeding behavior, neural plasticity, and memory during aging. Finding pharmacological or dietary resources that mitigate or prevent neurodegenerative affections continues to be a great challenge and requires additional effort from researchers, clinicians, and nutritionists in the field.

Polyunsaturated fatty acids and endocannabinoids in health and disease

Polyunsaturated fatty acids (PUFAs) are lipid derivatives of omega-3 (docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA) or of omega-6 (arachidonic acid, ARA) synthesized from membrane phospholipids and used as a precursor for endocannabinoids (ECs). They mediate significant effects in the fine-tune adjustment of body homeostasis. Phyto- and synthetic cannabinoids also rule the daily life of billions worldwide, as they are involved in obesity, depression and drug addiction. Consequently, there is growing interest to reveal novel active compounds in this field. Cloning of cannabinoid receptors in the 90s and the identification of the endogenous mediators arachidonylethanolamide (anandamide, AEA) and 2-arachidonyglycerol (2-AG), led to the characterization of the endocannabinoid system (ECS), together with their metabolizing enzymes and membrane transporters. Today, the ECS is known to be involved in diverse functions such as appetite control, food intake, energy balance, neuroprotection, neurodegenerative diseases, stroke, mood disorders, emesis, modulation of pain, inflammatory responses, as well as in cancer therapy. Western diet as well as restriction of micronutrients and fatty acids, such as DHA, could be related to altered production of pro-inflammatory mediators (e.g. eicosanoids) and ECs, contributing to the progression of cardiovascular diseases, diabetes, obesity, depression or impairing conditions, such as Alzheimer' s disease. Here we review how diets based in PUFAs might be linked to ECS and to the maintenance of central and peripheral metabolism, brain plasticity, memory and learning, blood flow, and genesis of neural cells.

Cross-sectional associations of cortical β-amyloid with erythrocyte membrane long-chain polyunsaturated fatty acids in older adults with subjective memory complaints

Omega-3 (n-3) and 6 (n-6) polyunsaturated fatty acids (PUFAs) have been associated with reduced cognitive decline in observational studies. Hence, we examined the cross-sectional associations between cortical β-amyloid (Aβ) and erythrocyte membrane PUFAs in 61 non-demented elderly individuals reporting subjective memory complaints from the Multidomain Alzheimer Preventive Trial placebo arm. Cortical-to-cerebellar standard uptake value ratios were obtained using [¹⁸ F] florbetapir positron emission tomography. Fatty acids were measured in erythrocyte membranes by gas chromatography. Associations were explored using adjusted multiple linear regression models and were considered significant at p ≤ 0.005 after correction for multiple testing (10 comparisons). We found no significant associations between cortical Aβ and erythrocyte membrane PUFAs. The associations closest to significance after adjustment were those between Aβ and erythrocyte membrane arachidonic acid (without apolipoprotein E status adjustment: B-coefficient, 0.03; CI, 0.01, 0.05; p = 0.02. Including Apolipoprotein E adjustment: B-coefficient, 0.03; CI, 0.00, 0.06; p = 0.04) and Aβ and erythrocyte membrane linoleic acid (without apolipoprotein E status adjustment: B-coefficient, -0.02; CI, -0.04, 0.00; p = 0.02. Including Apolipoprotein E adjustment: B-coefficient, -0.02; CI, -0.04, 0.00; p = 0.09). Furthermore, the association between Aβ and erythrocyte membrane arachidonic acid seemed to be specific to Apolipoprotein E ε4 non-carriers (B-coefficient 0.03, CI: 0.00, 0.06, p = 0.03, n = 36). In contrast, no association was found between Aβ and erythrocyte membrane linoleic acid in Apolipoprotein E ε4 stratified analysis. Investigating the relationships between Aβ and PUFAs longitudinally would provide further evidence as to whether fatty acids, particularly arachidonic acid and linoleic acid, might modulate cognition through Aβ-dependent mechanisms.

Cerebral Ketone Body Oxidation Is Facilitated by a High Fat Diet Enriched with Advanced Glycation End Products in Normal and Diabetic Rats

Diabetes mellitus (DM) causes important modifications in the availability and use of different energy substrates in various organs and tissues. Similarly, dietary manipulations such as high fat diets also affect systemic energy metabolism. However, how the brain adapts to these situations remains unclear. To investigate these issues, control and alloxan-induced type I diabetic rats were fed either a standard or a high fat diet enriched with advanced glycation end products (AGEs) (HAGE diet). The HAGE diet increased their levels of blood ketone bodies, and this effect was exacerbated by DM induction. To determine the effects of diet and/or DM induction on key cerebral bioenergetic parameters, both ketone bodies (β-hydroxybutyric acid) and lactate oxidation were measured. In parallel, the expression of Monocarboxylate Transporter 1 (MCT1) and 2 (MCT2) isoforms in hippocampal and cortical slices from rats submitted to these diets was assessed. Ketone body oxidation increased while lactate oxidation decreased in hippocampal and cortical slices in both control and diabetic rats fed a HAGE diet. In parallel, the expression of both MCT1 and MCT2 increased only in the cerebral cortex in diabetic rats fed a HAGE diet. These results suggest a shift in the preferential cerebral energy substrate utilization in favor of ketone bodies in animals fed a HAGE diet, an effect that, in DM animals, is accompanied by the enhanced expression of the related transporters.

Sex-specific effects of dietary fatty acids on saliva cortisol and social behavior in guinea pigs under different social environmental conditions

BACKGROUND

Unbalanced dietary intakes of saturated (SFAs) and polyunsaturated (PUFAs) fatty acids can profoundly influence the hypothalamic-pituitary-adrenal (HPA)-axis and glucocorticoid secretions in relation to behavioral performances. The beneficial effects of higher dietary PUFA intakes and PUFA:SFA ratios may also affect social interactions and social-living per se, where adequate physiological and behavioral responses are essential to cope with unstable social environmental conditions.

METHODS

Effects of diets high in PUFAs or SFAs and a control diet were investigated in male and female guinea pigs after 60 days of supplementation. Plasma fatty acid patterns served as an indicator of the general fatty acid status. HPA-axis activities, determined by measuring saliva cortisol concentrations, social behaviors, and hierarchy ranks were analyzed during group housing of established single-sexed groups and during challenging social confrontations with unfamiliar individuals of the other groups.

RESULTS

The plasma PUFA:SFA ratio was highest in PUFA supplemented animals, with female levels significantly exceeding males, and lowest in SFA animals. SFA males and females showed increased saliva cortisol levels and decreased aggressiveness during group housing, while sociopositive behaviors were lowest in PUFA males. Males generally showed higher cortisol increases in response to the challenging social confrontations with unfamiliar individuals than females. While increasing cortisol concentrations were detected in control and PUFA animals, no such effect was found in SFA animals. During social confrontations, PUFA males showed higher levels of agonistic and sociopositive behaviors and also gained higher dominance ranks among males, which was not detected for females.

CONCLUSIONS

While SFAs seemingly impaired cortisol responses and social behaviors, PUFAs enabled adequate behavioral responses in male individuals under stressful new social environmental conditions. This sex-specific effect was possibly related to a general sex difference in the n-3 PUFA bioavailability and cortisol responses, which may indicate that males are more susceptible to changing environmental conditions, and shows how dietary fatty acids can shape social systems.

Neurochemical and behavioural impact of C18 fatty acids in male mice postweaning

Dietary components, particularly essential fatty acids, affect the expression and maintenance of normal physiological phenotypes. However, the influence of C18 fatty acids that are abundantly present in the normal diet is unclear. We focused on the behavioural and neurochemical effects of C18 fatty acids during postweaning development in male mice. An AIN-93G diet supplemented with 8% stearic acid (C18:0), 3% oleic acid (C18:1), 3% linoleic acid (C18:2) or 3% α-linolenic acid (C18:3) was provided from four weeks of age for eight weeks. At 12 weeks of age, novel exploratory behaviour and social interaction tests were carried out. One week after the last behavioural test, the brain of each mouse was removed. The frequency of social interactive behaviour was decreased by approximately 70% in the C18:0 group compared to the basal diet group, but there was no difference in cumulative time. The frequency of social interaction showed a positive correlation to cumulative time in mice fed with the experimental diets except for C18:0. Dietary C18 fatty acids following weaning had no impact on brain fatty acid composition except for the C18:3 diet. Furthermore, the neurochemical properties to be especially noted were that choline acetyltransferase activity was absolutely higher in C18:0 diet-fed mice than in the other groups, especially in the frontal cortex where it was 1.7-fold higher than in the basal diet-fed group. The present results reveal a significant possibility of neurochemical and behavioural effects of dietary fatty acids, and saturated fatty acids are of special importance during the postweaning period.

Effect of diet oils on lipid levels of the brain of rats

The effects of sunflower oil, olive oil, margarine, soybean oil and butter on cholesterol and triglyceride levels were investigated in the brain of rats. Rats were fed with a diet containing 15% of the oils for a period of 8 weeks. The rats were then decapitated, brain samples were removed, homogenized and cholesterol and TG levels were measured. Brain cholesterol and Triglycerides levels of all animals receiving different oils were significantly higher according to the contol except TG level of animals receiving margarine. Brain cholesterol levels of the vegetable oils were statistically higher than those receiving saturated oil. Thus, cholesterol level of the rats fed with olive oil group was significantly higher than that of the other groups but those receiving sunflower oil group and Triglycerides level of the animals receiving olive oil was significantly higher than that of the other groups except animal supplemented with soybean oil. Thus, it is concluded that brain lipid levels of rats are differently effected by various oils and mechanism of which needs to be investigated.

Impairment of fear-conditioning responses and changes of brain neurotrophic factors in diet-induced obese mice

Recent epidemiological studies demonstrate that obesity is related to a high incidence of cognitive impairment. In the present study, cognitive behaviours in diet-induced obese (DIO) mice fed 60% high-fat diet for 16 weeks were compared with those in mice fed a control diet (CD) in fear-conditioning tests including both contextual and cued elements that preferentially depend on the hippocampus and amygdala, respectively. Furthermore, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) content in the brain areas was examined in both CD and DIO mice. In fear-conditioning tests, the freezing percentages of both contextual fear and cued fear responses in DIO mice were significantly lower than in CD mice. BDNF content in the cerebral cortex and hippocampus of DIO mice was significantly lower than that in CD mice. Its receptor, full-length TrkB, in the amygdala of DIO mice was significantly decreased compared to that in CD mice, although not in the cerebral cortex, hippocampus and hypothalamus. By contrast, NT-3 content in the hippocampus, amygdala and hypothalamus of DIO mice was significantly higher than that in CD mice. Its receptor, full-length TrkC, was not significantly different between CD and DIO mice. The present study demonstrates that DIO mice show impairment of both hippocampus-dependent contextual and amygdala-dependent cued responses in the fear-conditioning tests, as well as an imbalance in the interaction between the BDNF and NT-3 systems in the cerebral cortex, hippocampus and amygdala related to cognition and fear.

Functional relationships between serum total cholesterol levels, executive control, and sustained attention

This study investigated the potential relationship between serum total cholesterol (TC) and two specific aspects of cognition (executive control and sustained attention) in a non-elderly sample, after controlling for life stress and several sociodemographic and health variables. For each participant (n = 46), measurements of TC, physical health, and life stress were obtained, and executive control and sustained attention were assessed using the Tower of London and the Digit Vigilance Test. The outcomes of these cognitive assessments were correlated with TC, and a covariate-adjusted analysis was performed. After controlling for several co-variates, TC was found to be significantly negatively associated with components of executive control and sustained attention. Because these cognitive functions are crucial in the moment-to-moment regulation of behavior, elevated TC may have negative behavioral consequences in everyday life situations.

Effect of thyme oil and thymol dietary supplementation on the antioxidant status and fatty acid composition of the ageing rat brain

The present study measured changes in antioxidant enzyme activity in, and the phospholipid fatty acid composition of the ageing rat brain and tested whether dietary supplementation with thyme oil or thymol could provide beneficial effects. There were significant declines in superoxide dismutase (EC 1.15.1.1) and glutathione peroxidase (EC 1.11.1.9) activities and the total antioxidant status in the untreated rats with age, while thyme-oil- and thymol-fed rats maintained significantly higher antioxidant enzyme activities and total antioxidant status. The proportions of 18: 2n−6, 20: 1n−9, 22: 4n−6 and 22: 5n−3 in the brain phospholipids resulting from all three dietary treatments were significantly higher in 28-month-old rats than in 7-month-old rats. Only 20: 1n−9 levels in 28-month-old thyme-oil- and thymol-treated rats were significantly higher than in the age-matched control. The proportion of 22: 6n−3 in brain phospholipids, which declined with age in control rats, was also significantly higher in rats given either supplement. This latter finding is particularly important as optimum levels of 22: 6n−3 are required for normal brain function. These results highlight the potential benefit of thyme oil as a dietary antioxidant.

High-fat diets, insulin resistance and declining cognitive function

Results from our work in rats and others findings from human epidemiologic studies demonstrate deficits in cognitive performance following chronic ingestion of high fat, high saturated fat, diets. Yet, the precise physiologic mechanism underlying these deficits is not well understood. We report that older adults with insulin resistance show remarkably similar deficits in cognitive function and respond to glucose ingestion in a comparable manner to rodents fed a high-fat diet, suggesting that insulin resistance is a probable mediator of these diet-induced deficits. As insulin resistance worsens to overt type 2 diabetes, profound deficits in cognitive functions, especially those dependent on the medial temporal lobes, are apparent in both obese Zucker rats and humans with type 2 diabetes. Unlike the older adult with insulin resistance, glucose ingestion further impairs medial temporal lobe function in adults with type 2 diabetes. Collectively, the human and rodent data point to a role of diet-induced endocrine abnormalities, including the development of insulin resistance, as mediating the cognitive deficits associated with high fat consumption.

Nociception and locomotor activity are increased in ketogenic diet fed rats

Ketogenic diets have been used to treat epilepsy in children for almost 80 years. However, there are only few studies concerning behavioral effects of these diets, besides their efficacy in treating seizure disorders induced by kainic acid or pentylenetetrazol in rats. Here, rats were fed with a ketogenic diet and locomotion, anxiety and nociception were investigated after 10 weeks. Male Wistar rats were weight matched and divided into two groups: control rats, that received regular laboratory ration, and KD rats, that received ketogenic diet (70% fat, 24% protein and no carbohydrate). Behavioral tests were applied after 10-12 weeks of treatment, and included tests to evaluate exploration (habituation to the open field), anxiety (plus-maze), and nociception (tail-flick measurement). Performance of the animals in the open field revealed a significant difference in the number of crossings, suggesting a higher locomotor activity in animals fed with a ketogenic diet. No differences in anxiety were observed, as evaluated by the plus-maze test. Nociception was measured by the latency in the tail-flick test, and ketogenic rats presented a hypernociceptive response. Yet, these animals responded to a stressor with the classic analgesia, similarly to the controls. The response of ketogenic diet fed rats to the stressor, however, was more prolonged. Exposure to a ketogenic diet may induce higher locomotor activity, together with a hypernociceptive state in the animals, possibly as a result of some alteration in the neural systems involved in the modulation of these behaviors.

Increased IL-1beta in cortex of aged rats is accompanied by downregulation of ERK and PI-3 kinase

Ageing is accompanied by a myriad of changes, which lead to deficits in synaptic function and recent studies have identified an increase in concentration of the proinflammatory cytokine, interleukin-1beta (IL-1beta), as a factor which significantly contributes to deterioration of cell function. Here, we consider that increased IL-1beta concentration and upregulation of IL-1beta-induced cell signalling cascades may be accompanied by downregulation of survival signals, perhaps as a consequence of decreased neurotrophins-associated signalling. The data indicate that increased IL-1beta concentration was coupled with downregulation of ERK and phosphoinositide-3 kinase (PI-3 kinase) in cortical tissue prepared from aged rats. These changes could not be attributed to decreased concentration of NGF or BDNF but the evidence suggested that they may be a consequence of an age-related change in the anti-inflammatory cytokine, IL-4. Significantly, treatment of aged rats with eicosapentaenoic acid reversed the age-related increases in IL-1beta and IL-1beta-induced signalling and also the age-related changes in IL-4, ERK and PI-3 kinase.

Dietary fat type affects vitamins C and E and biomarkers of oxidative status in peripheral and brain tissues of golden Syrian hamsters

Oxidative stress is an important trigger in the complex chain of events leading to neurodegenerative diseases. On the other hand, dietary fatty acids play an essential role in brain function. The objectives of this study were to assess the effect of dietary fat type on vitamin C and vitamin E (alpha-and gamma-tocopherol) concentrations in peripheral and brain tissues and its effect on 8-epiPGF(2)alpha (F(2)-isoprostanes). Male Golden Syrian hamsters (n = 120, 8 wk old) were fed diets enriched in butter, hydrogenated fat (margarine), and canola and soybean oils. After 12 wk, hamsters were deprived of food, anesthetized with isoflurane, and killed via terminal exsanguination. Analyses of vitamins C, E, and 8-epiPGF(2)alpha were performed in peripheral tissues and brain. Hamsters consuming the margarine-enriched diet had lower (P < 0.05) vitamin C and alpha-tocopherol concentrations in liver, plasma, and brain, and higher (P < 0.02) plasma 8-epiPGF(2)alpha than groups fed the butter, and the canola and soybean oil diets. Liver and plasma gamma-tocopherol concentration was higher (P < 0.001) among the groups fed the soybean- and margarine-enriched diets compared with the other groups. alpha-Tocopherol was higher (P < 0.05) and 8-epiPGF(2)alpha lower (P < 0.01) among the groups fed the canola and soybean oil diets compared with the other groups. Across the groups, an inverse correlation between plasma levels of vitamin C and 8-epiPGF(2)alpha (r = -0.37, P = 0.03) and a positive correlation between plasma levels of vitamin C and alpha-tocopherol were observed (r = 0.341, P = 0.003). Hamsters fed the butter-enriched diet had a higher (P < 0.03) plasma uric acid concentration than the other groups. The results of this study provide new evidence concerning the effect of dietary fat on antioxidant status, which is important for the maintenance of good health.

Cognitive decline and fatty acid composition of erythrocyte membranes--The EVA Study

BACKGROUND

Dietary factors might modify cognitive decline that results from aging. Fatty acids, which are limiting factors in brain development, are prime candidates.

OBJECTIVE

We studied the relation between erythrocyte membrane fatty acid composition and cognitive decline in free-living volunteers.

DESIGN

In 1995, erythrocyte membrane fatty acid composition was measured in 246 men and women (aged 63-74 y) from the Etude du Vieillissement Artériel (EVA) cohort. During a 4-y follow-up, cognitive abilities were assessed longitudinally with the Mini-Mental State Examination. Moderate cognitive decline was defined as a > or = 2-point decrease over the 4 y. The predictive value of fatty acid proportions on cognitive decline was assessed with a multivariate logistic model that included age, sex, education level, and initial Mini-Mental State Examination score as covariates.

RESULTS

Higher proportions of both stearic acid (saturated, 18:0) and total n-6 polyunsaturated fatty acids were associated with greater risk of cognitive decline; the odds ratios were 1.91 (95% CI: 1.16, 3.15) and 1.59 (95% CI: 1.04, 2.44), respectively, for 1-SD differences in fatty acid proportions. Conversely, a higher proportion of total n-3 fatty acids was associated with a lower risk of cognitive decline; the odds ratio was 0.59 (95% CI: 0.38, 0.93).

CONCLUSIONS

The inverse association between cognitive decline and the ratio of n-3 to n-6 fatty acids in erythrocyte membranes agrees with results obtained in some studies that assessed fatty acid intake by using dietary questionnaires. These results require confirmation but provide new rationale for studying how these modifiable risk factors might be implicated in the cognitive aging process.

Nutritional manipulation and psychiatric conditions: focus on mood and cognition

In this paper, several experimental models of human depression and cognitive dysfunction, which are designed specifically to mimic the proposed mechanisms of action of many nutritional supplements, are illustrated. These mechanisms of interest are antioxidant effects, glucose utilization, neuronal membrane function and neurotransmitter effects, with particular reference to nutrient-based amino acid manipulations of neurotransmission, such as tryptophan depletion. It is concluded that the application of experimental human models of altered mood and cognitive function may illuminate substantially the quest for nutritional enhancement of human mood and cognitive function.

Behavioral responses to ingestion of different sources of fat. Involvement of serotonin?

In previous experiments, we described a decrease in extracellular hypothalamic serotonin, 5-hydroxy-tryptamine (5-HT), in response to ingestion of a lard meal. This effect was related to the low satiating potency of lard as compared with other nutrients. Since the composition in fatty acids might be important for these effects, the purpose of this study was to analyze the neurochemical and behavioral responses to ingestion of different sources of fat. Unique meals of three margarines used in human feeding were compared with a meal of lard with regard to their effects on hypothalamic 5-HT, satiety, anxiety-like behavior and sucrose consumption. A vegetable margarine with a high content in saturated fatty acids also decreased hypothalamic 5-HT while ingestion of a sunflower oil and an olive oil enriched margarines, both high in polyunsaturated fatty acids, did not affect significantly 5-HT levels. However, these two last ones were not the most satiating. The olive oil margarine induced a tendency to an anxiety-like behavior while lard increased sucrose consumption. Thus, ingestion of fats may alter specifically behavioral responses. The involvement of 5-HT is likely in the case of lard ingestion but probably not for the other sources of fat.

Glucose treatment reduces memory deficits in young adult rats fed high-fat diets

Feeding rats high-fat diets for 3 months produces a widespread cognitive deficit that affects performance on a wide range of learning and memory tasks. The present study tested the hypothesis that this effect is related to a fat-induced impairment in glucose metabolism. Following 3 months of dietary intervention (20% by weight fat diets, composed primarily of either beef tallow or soybean oil versus standard laboratory chow), male Long-Evans rats were tested on a variable interval delayed alternation (VIDA) task that measures learning and memory functions that differentially involve specific brain regions. Relative to rats fed chow, rats consuming the high-fat diets were impaired on all aspects of VIDA performance. Following baseline testing, rats were maintained on their respective diets and the effect of glucose administration (100 mg/kg BW; i.p.) was examined. For the next 6 days, animals alternately received injections of saline or glucose 30 min prior to VIDA testing. Glucose treatment improved performance, with the effect being most pronounced at the longer intertrial intervals where task performance is sensitive to hippocampal impairment. Importantly, the beneficial effect of glucose were confined to those animals consuming the high-fat diets and were not observed in rats fed chow. These results demonstrate that glucose administration can overcome those deficits associated with hippocampal function in rats fed high-fat diets and are consistent with the hypothesis that high-fat diets, in part, mediate their effect through the development of insulin resistance and glucose intolerance.

Macronutrients and mental performance

There is currently intense interest in the effects of macronutrients on psychological states, mental performance, and well-being. A strong theoretical perspective has guided work on carbohydrates and their relation to brain serotoninergic function with concomitant effects on performance. The clearest and most reliable effects have been observed for the beneficial action of glucose on cognitive performance, supported by investigations of hypoglycemia, which is associated with general impairment of cognitive performance. The effects of complex carbohydrates are less distinct and change with time of day; e.g., carbohydrate at breakfast tends to improve morning performance. However, these studies are rarely decisive. Far fewer experiments have been performed on protein and fat, and it is difficult to draw any firm conclusions. Macronutrients are seldom given alone, proportions of protein and fat differ greatly between studies, and comparisons are frequently performed with no food at all. Food intake may mitigate the effects of low doses but not of high doses of alcohol on performance. Effects of macronutrients on cognitive performance may be dependent on their effects on glucose metabolism, metabolic activation, or serotonin. Other factors that modify effects include time of day, circadian rhythms, type of task, habitual diet, and vulnerability of the population.

Cognitive performance is associated with glucose regulation in healthy elderly persons and can be enhanced with glucose and dietary carbohydrates

BACKGROUND

A glucose drink has been shown to improve memory in persons with poor glucose regulation and poor cognition.

OBJECTIVE

The objective of this study was to determine 1) whether an association between cognition and glucose regulation is apparent in healthy seniors and 2) the effects of dietary carbohydrates on cognition.

DESIGN

After an overnight fast, 10 men and 10 women (aged 60-82 y) consumed 50 g carbohydrate as glucose, potatoes, or barley or a placebo on 4 separate mornings. Cognitive tests were administered 15, 60, and 105 min after ingestion of the carbohydrate. Plasma glucose and serum insulin were measured.

RESULTS

In a multiple regression analysis, poor baseline (placebo) verbal declarative memory (immediate and 20-min delayed paragraph recall and word list recall) and visuomotor task performance were predicted by poor beta cell function, high incremental area under the glucose curve, low insulin resistance, and low body mass index. The difference in plasma glucose after food consumption [glucose > potatoes > barley > placebo (P: < 0.03)] did not predict performance. Although overall performance did not differ with consumption of the different test foods, baseline score and beta cell function correlated with improvements in immediate and delayed paragraph recall for all 3 carbohydrates (compared with placebo); the poorer the baseline memory or beta cell function, the greater the improvement (correlation between beta cell function and improvement in delayed paragraph recall: r > -0.50, P: < 0.03). Poor beta cell function correlated with improvement for all carbohydrates in visuomotor task performance but not on an attention task.

CONCLUSIONS

Glucose regulation was associated with cognitive performance in elderly subjects with normal glucose tolerance. Dietary carbohydrates (potatoes and barley) enhanced cognition in subjects with poor memories or beta cell function independently of plasma glucose.

Essential fatty acids and the brain: possible health implications

Linoleic and alpha-linolenic acid are essential for normal cellular function, and act as precursors for the synthesis of longer chained polyunsaturated fatty acids (PUFAs) such as arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), which have been shown to partake in numerous cellular functions affecting membrane fluidity, membrane enzyme activities and eicosanoid synthesis. The brain is particularly rich in PUFAs such as DHA, and changes in tissue membrane composition of these PUFAs reflect that of the dietary source. The decline in structural and functional integrity of this tissue appears to correlate with loss in membrane DHA concentrations. Arachidonic acid, also predominant in this tissue, is a major precursor for the synthesis of eicosanoids, that serve as intracellular or extracellular signals. With aging comes a likely increase in reactive oxygen species and hence a concomitant decline in membrane PUFA concentrations, and with it, cognitive impairment. Neurodegenerative disorders such as Parkinson's and Alzheimer's disease also appear to exhibit membrane loss of PUFAs. Thus it may be that an optimal diet with a balance of n-6 and n-3 fatty acids may help to delay their onset or reduce the insult to brain functions which these diseases elicit.

Nutritional Contributions to the CNS Pathophysiology of HIV-1 Infection and Implications for Treatment

Nutritional deficiencies are commonplace in patients with human immunodeficiency virus type 1 (HIV-1) infection, and recent research has indicated that nutritional factors may play an important role in the pathogenesis of HIV-1 disease. Although nutritional deficiencies are unlikely to be the primary causative factor in disease progression, they may contribute to cognitive dysfunction, neurologic abnormalities, mood disturbance, and immune dysregulation associated with HIV-1 infection. Furthermore, deficiencies of specific micronutrients have been associated with increased risk of HIV-1-associated mortality. This article will briefly summarize the role of macronutrient deficiency, the interactions of specific micronutrient deficiencies with neuropsychiatric functioning, and the role of these factors in HIV-1 disease progression. Since recent research has shown that normalization of many nutritional deficits and supplementation beyond normal levels are associated with improvements in neuropsychiatric functioning, potential treatment implications will also be discussed.

The effects of high fat diets and environmental influences on cognitive performance in rats

As part of a continuing investigation of the relationship between dietary factors and cognitive function, the present study examined the combined effects of environmental influences and high-fat diets on learning and memory. Following 3 months of dietary (20% by weight fat diets, composed primarily of either beef tallow or soybean oil versus standard laboratory chow) and environmental treatments (standard, enriched or impoverished), subjects were tested on a variable interval delayed alternation (VIDA) task which measures learning and memory functions that differentially involve specific brain regions. The results confirmed the negative effects of high fat diets, relative to chow, on all aspects of VIDA performance and showed that environmental enrichment overcame deficits associated with dietary fat. Housing rats fed high-fat diets in an impoverished environment did not further exacerbate cognitive deficits observed in such rats living under standard conditions. By comparison, chow-fed rats exhibited no benefit associated with the enriched environment on any aspect of task performance, and only a transitory learning impairment when housed in an impoverished environment. The results show that high fat diets and environmental conditions influence cognitive function and that these two factors interact with one another to produce different profiles of benefits and impairments.