Low plasma N-3 fatty acids and dementia in older persons: the InCHIANTI study

The shift in the fatty acid composition of the circulating lipidome in Alzheimer's disease

INTRODUCTION

Fatty acids (FAs) are the building blocks of complex lipids and signaling compounds; the role of the lipidome fatty acid profile (LFA) in AD progression remains unclear.

METHODS

The LFA of plasma and cerebrospinal fluid (CSF) samples from 289 participants (103 AD patients, 92 MCI patients, and 94 controls) was determined by GC-FID. The MCI subjects were followed up for 58 ± 12.5 months.

RESULTS

In controls, CSF has a more neuroprotective LFA than plasma. In CSF, a higher content of docosahexaenoic acid was associated with a reduced risk of MCI-to-AD progression. In plasma, higher oleic acid content was associated with lower risk of AD, MCI, and MCI-to-AD progression, whereas higher levels of vaccenic acid and docosahexaenoic acid were associated with greater risk of AD and MCI, and higher rate of MCI-to-AD progression, respectively.

DISCUSSION

The circulating LFA is involved in the pathogenesis and progression of AD.

HIGHLIGHTS

The lipidome fatty acid profile in CSF and plasma was markedly different. Higher levels of vaccenic acid and lower levels of oleic acid in plasma were associated with greater risk of Alzheimer's disease. In plasma, higher levels of oleic acid were associated with a reduced risk of MCI-to-AD progression. Higher levels of docosahexaenoic acid in CSF were associated with a lower risk of MCI-to-AD progression. Higher levels of docosahexaenoic acid in plasma were associated with a greater rate of MCI-to-AD progression.

Red Blood Cell Fatty Acid Profiles Are Significantly Altered in South Australian Mild Cognitive Impairment and Alzheimer's Disease Cases Compared to Matched Controls

Nutritional imbalances have been associated with a higher risk for cognitive impairment. This study determined the red blood cell (RBC) fatty acid profile of newly diagnosed mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients compared to age and gender-matched controls. There was a significant increase in palmitic acid (p < 0.00001) for both MCI and AD groups. Saturated fatty acids were significantly elevated in the MCI group, including stearic acid (p = 0.0001), arachidic acid (p = 0.003), behenic acid (p = 0.0002), tricosanoic acid (p = 0.007) and lignoceric acid (p = 0.001). n-6 polyunsaturated fatty acids (PUFAs) were significantly reduced in MCI, including linoleic acid (p = 0.001), γ-linolenic acid (p = 0.03), eicosatrienoic acid (p = 0.009) and arachidonic acid (p < 0.00004). The n-3 PUFAs, α-linolenic acid and docosahexaenoic acid, were both significantly reduced in MCI and AD (p = 0.0005 and p = 0.00003). A positive correlation was evident between the Mini-Mental State Examination score and nervonic acid in MCI (r = 0.54, p = 0.01) and a negative correlation with γ-linolenic acid in AD (r = -0.43, p = 0.05). Differences in fatty acid profiles may prove useful as potential biomarkers reflecting increased risk for dementia.

APOE alleles modulate associations of plasma metabolites with variants from multiple genes on chromosome 19q13.3

The APOE ε2, ε3, and ε4 alleles differentially impact various complex diseases and traits. We examined whether these alleles modulated associations of 94 single-nucleotide polymorphisms (SNPs) harbored by 26 genes in 19q13.3 region with 217 plasma metabolites using Framingham Heart Study data. The analyses were performed in the E2 (ε2ε2 or ε2ε3 genotype), E3 (ε3ε3 genotype), and E4 (ε3ε4 or ε4ε4 genotype) groups separately. We identified 31, 17, and 22 polymorphism-metabolite associations in the E2, E3, and E4 groups, respectively, at a false discovery rate P FDR < 0.05. These entailed 51 and 19 associations with 20 lipid and 12 polar analytes. Contrasting the effect sizes between the analyzed groups showed 20 associations with group-specific effects at Bonferroni-adjusted P < 7.14E-04. Three associations with glutamic acid or dimethylglycine had significantly larger effects in the E2 than E3 group and 12 associations with triacylglycerol 56:5, lysophosphatidylethanolamines 16:0, 18:0, 20:4, or phosphatidylcholine 38:6 had significantly larger effects in the E2 than E4 group. Two associations with isocitrate or propionate and three associations with phosphatidylcholines 32:0, 32:1, or 34:0 had significantly larger effects in the E4 than E3 group. Nine of 70 SNP-metabolite associations identified in either E2, E3, or E4 groups attained P FDR < 0.05 in the pooled sample of these groups. However, none of them were among the 20 group-specific associations. Consistent with the evolutionary history of the APOE alleles, plasma metabolites showed higher APOE-cluster-related variations in the E4 than E2 and E3 groups. Pathway enrichment mainly highlighted lipids and amino acids metabolism and citrate cycle, which can be differentially impacted by the APOE alleles. These novel findings expand insights into the genetic heterogeneity of plasma metabolites and highlight the importance of the APOE-allele-stratified genetic analyses of the APOE-related diseases and traits.

Eicosanoid lipidome activation in post-mortem brain tissues of individuals with APOE4 and Alzheimer's dementia

BACKGROUND

Chronic neuroinflammation is one of the hallmarks of late-onset Alzheimer's disease (AD) dementia pathogenesis. Carrying the apolipoprotein ε4 (APOE4) allele has been associated with an accentuated response to brain inflammation and increases the risk of AD dementia progression. Among inflammation signaling pathways, aberrant eicosanoid activation plays a prominent role in neurodegeneration.

METHODS

Using brains from the Religious Order Study (ROS), this study compared measures of brain eicosanoid lipidome in older persons with AD dementia to age-matched controls with no cognitive impairment (NCI), stratified by APOE genotype.

RESULTS

Lipidomic analysis of the dorsolateral prefrontal cortex demonstrated lower levels of omega-3 fatty acids eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and DHA-derived neuroprotectin D1 (NPD-1) in persons with AD dementia, all of which associated with lower measures of cognitive function. A significant interaction was observed between carrying the APOE4 allele and higher levels of both pro-inflammatory lipids and pro-resolving eicosanoid lipids on measures of cognitive performance and on neuritic plaque burden. Furthermore, analysis of lipid metabolism pathways implicated activation of calcium-dependent phospholipase A2 (cPLA2), 5-lipoxygenase (5-LOX), and soluble epoxide hydrolase (sEH) enzymes.

CONCLUSION

These findings implicate activation of the eicosanoid lipidome in the chronic unresolved state of inflammation in AD dementia, which is increased in carriers of the APOE4 allele, and identify potential therapeutic targets for resolving this chronic inflammatory state.

Nutritional quality of calorie restricted diets in the CALERIE™ 1 trial

OBJECTIVES

The aim was to determine the nutritional adequacy of calorie restricted (CR) diets during CR interventions up to 12 months.

METHODS

The Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE™) phase 1 trial consisted of 3 single-site studies to test the feasibility and effectiveness of CR in adults without obesity. After baseline assessments, participants who were randomized to a CR intervention received education and training from registered dietitians on how to follow a healthful CR diet. Food diaries were completed at baseline and during the CR interventions (~6, 9, and 12 months) when participants were self-selecting CR diets. Diaries were analyzed for energy, macronutrients, fiber, 11 vitamins, and 9 minerals. Nutritional adequacy was defined by sex- and age-specific Estimated Average Requirement (EAR) or Adequate Intake (AI) criteria for each nutrient. Diet quality was evaluated using the PANDiet diet quality index.

RESULTS

Eighty-eight CR participants (67% women, age 40 ± 9 y, BMI 27.7 ± 1.5 kg/m²) were included in the analysis. Dietary intake of fiber and most vitamins and minerals increased during CR. More than 90% of participants achieved 100% of EAR or AI during CR for 2 of 4 macronutrients (carbohydrate and protein), 6 of 11 vitamins (A, B1, B2, B3, B6, B12), and 6 of 9 minerals assessed (copper, iron, phosphorus, selenium, sodium, zinc). Nutrients for which <90% of participants achieved adequacy included fiber, omega-3 fatty acids, vitamins B5, B9, C, E, and K, and the minerals calcium, magnesium, and potassium. The PANDiet diet quality index improved from 72.9 ± 6.0% at baseline to 75.7 ± 5.2% during CR (p < 0.0001).

CONCLUSION

Long-term, calorie-restricted diets were nutritionally equal or superior to baseline ad libitum diets among adults without obesity. Our results support modest calorie restriction as a safe strategy to promote healthy aging without compromising nutritional adequacy or diet quality.

Dietary intake of trace elements from commercially important fish and shellfish of Thoothukudi along the southeast coast of India and implications for human health risk assessment

The concentrations of eight trace elements (chromium, cobalt, copper, zinc, arsenic, cadmium, mercury and lead) in14 commercially important fish and shellfish collected from Thoothukudi along the southeast coast of India was investigated using inductively coupled plasma mass spectrometry in order to assess the health risks associated with their consumption. The concentration of trace elements ranged from 0.001 to 39.5 μg/g. The estimated weekly intake of cadmium in seven fish and shellfish (0.0081-0.0996 mg/kg body weight) were above the provisional tolerable weekly intake set by the Joint FAO/WHO Expert Committee on Food Additives. The risk assessment analysis indicated that there was non- carcinogenic risk upon lifetime consumption of rock crab, C. natator (TTHQ >1) and carcinogenic risks upon lifetime consumption of S. jello, P. semisulcatus, P. sanguinolentus C. natator, Uroteuthis duvaceli, Sepia pharaonis and Cistopus indicus due to cadmium exposure indicating a potential health risk to the exposed consumers.

Adherence to the Mediterranean diet assessed by a novel dietary biomarker score and mortality in older adults: the InCHIANTI cohort study

BACKGROUND

Dietary biomarkers may complement dietary intake assessment made by dietary questionnaires. We developed an a-posteriori dietary biomarkers score based on Mediterranean diet food groups and evaluated its association with mortality.

METHODS

642 participants (56% female), aged ≥65 years, with complete data on dietary biomarkers were followed during 20 years in the InCHIANTI cohort study (Tuscany, Italy). The main outcomes were all-cause, cardiovascular, and cancer mortality. Dietary biomarkers were selected from literature and from correlation analyses with dietary intakes of Mediterranean diet food groups in the study. The baseline levels of the following dietary biomarkers were chosen: urinary total polyphenols and resveratrol metabolites, and plasma carotenoids, selenium, vitamin B12, linolenic, eicosapentaenoic and docosahexaenoic acids, and the mono-unsaturated/saturated fatty acid ratio. Associations of the Mediterranean diet score using dietary biomarkers and a validated food frequency questionnaire (FFQ) (as tertiles) with mortality were assessed through Cox regression.

RESULTS

During the 20-year follow-up [median (Q1-Q3), 14 (8-18) years], and 435 deaths occurred (139 from cardiovascular diseases and 89 from cancer-related causes). In the fully adjusted models, the dietary biomarker-Mediterranean diet score was inversely associated with all-cause (HR_T3vs.T1 0.72; 95%CI 0.56-0.91) and cardiovascular (HR_T3vs.T1 0.60; 95%CI 0.38-0.93), but not with cancer mortality. Associations between the FFQ-Mediterranean diet score and mortality were not statistically significant.

CONCLUSIONS

A greater adherence at baseline to a Mediterranean diet assessed by a dietary biomarker score was associated with a lower risk of mortality in older adults during a 20-year follow-up. The measurement of dietary biomarkers may contribute to guide individualized dietary counseling to older people.

TRIAL REGISTRATION

NCT01331512.

Associations between dietary fatty acid patterns and cognitive function in the Hispanic Community Health Study/Study of Latinos

Our objective was to quantify the cross-sectional associations between dietary fatty acid (DFA) patterns and cognitive function among Hispanic/Latino adults. This study included data from 8,942 participants of the Hispanic Community Health Study/Study of Latinos, a population-based cohort study (weighted age 56.2 y and proportion female 55.2%). The NCI (National Cancer Institute) method was used to estimate dietary intake from two 24-hr recalls. We derived DFA patterns using principal components analysis with 26 fatty acid and total plant and animal monounsaturated fatty acid (MUFA) input variables. Global cognitive function was calculated as the average z-score of 4 neurocognitive tests. Survey linear regression models included multiple potential confounders such as age, sex, education, depressive symptoms, physical activity, energy intake, and cardiovascular disease. DFA patterns were characterized by consumption of long-chain saturated fatty acids (SFA), animal-based MUFA, and trans fatty acids (Factor 1); short to medium-chain SFA (Factor 2); very-long-chain omega-3 polyunsaturated fatty acids (PUFA) (Factor 3); very-long-chain SFA and plant-based MUFA and PUFA (Factor 4). Factor 2 was associated with greater scores for global cognitive function (β=0.037 ± 0.012) and the Digit Symbol Substitution (DSS) (β=0.56±0.17), Brief Spanish English Verbal Learning-Sum (B-SEVLT) (β=0.23 ± 0.11), and B-SEVLT-Recall (β=0.11 ± 0.05) tests (P<0.05 for all). Factors 1 (β=0.04 ± 0.01) and 4 (β=0.70 ± 0.18) were associated with the DSS test (P<0.05 for all). Consumption of short to medium-chain SFA may be associated with higher cognitive function among U.S.-residing Hispanic/Latino adults. Prospective studies are necessary to confirm these findings.

The role of docosahexaenoic acid (DHA) in the prevention of cognitive impairment in the elderly

Aging is an inevitable and progressive biological process that leads to irreversible physiological and functional changes, also in the nervous system. Cognitive decline occurring with age can significantly affect the quality of life of older people. Docosahexaenoic acid (DHA) is necessary for the proper functioning of the nervous system; it can affect its action directly through its impact on neurogenesis and neuroplasticity, but also indirectly by affecting the functioning of the cardiovascular system or anti-inflammatory effect. Literature analysis shows that good nutritional status of n-3 fatty acids, determined on the basis of their level in blood plasma or erythrocytes, is associated with a lower risk of cognitive decline in selected cognitive domains, as well as a lower risk of dementia or Alzheimer’s disease, although studies are also available where the above relationship has not been confirmed. Apart from this, studies on DHA and EPA diet intake, as well as in the form of dietary supplements, show their beneficial effects in the context of cognitive functioning and the risk of dementia. Also, the results of intervention studies, although not explicit, suggest that high doses of DHA and EPA in the form of dietary supplements may slow down the process of deteriorating the cognitive functioning of the elderly within selected domains. Based on the review of the literature, it can be concluded that DHA and EPA play an essential role in the prevention of cognitive impairment.

Genetic variants in FADS1 and ELOVL2 increase level of arachidonic acid and the risk of Alzheimer's disease in the Tunisian population

Polyunsaturated fatty acids (PUFAs) are closely related to various physiological conditions. In several age-related diseases including Alzheimer's disease (AD) altered PUFAs metabolism has been reported. However, the mechanism behind PUFAs impairment and AD developpement remains unclear. In humans, PUFAs biosynthesis requires delta-5 desaturase (D5D), delta-6 desaturase (D6D) and elongase 2 activities; which are encoded by fatty acid desaturase 1 (FADS1), fatty acid desaturase 2 (FADS2), and elongation of very-long-chain fatty acids-like 2 (ELOVL2) genes, respectively. In the present work, we aim to assess whether genetic variants in FADS1, FADS2 and ELOVL2 genes influence plasma and erythrocyte PUFA composition and AD risk. A case-control study was carried out in 113 AD patients and 161 healthy controls.Rs174556, rs174617, and rs3756963 of FADS1, FADS2, and ELOVL2 genes, respectively were genotyped using PCR-RFLP. PUFA levels were quantified using Gas Chromatography. Genotype distributions of rs174556 (FADS1) and rs3756963 (ELOVL2) were different between case and control groups. The genotype TT of rs174556 and rs3756963 single nucleotide polymorphism (SNP) increases significantly the risk of AD in our population. PUFA analysis showed higher plasma and erythrocyte arachidonic acid (AA) level in patients with AD, whereas only plasma docosahexaenoic acid (DHA) was significantly decreased in AD patients. The indexes AA/Dihomo-gamma-linolenic acid (DGLA) and C24:4n-6/Adrenic acid (AdA) were both higher in the AD group. Interestingly, patients with TT genotype of rs174556 presented higher AA level and AA/DGLA index in both plasma and erythrocyte. In addition, higher AA and AA/DGLA index were observed in erythrocyte of TT genotype ofrs3756963 carrier's patients. Along with, positive correlation between AA/DGLA index, age or Gamma-linolenic acid (GLA)/ Linoleic acid (LA) index was seen in erythrocyte and /or plasma of AD patients. After adjustment for confounding factors, the genotype TT of rs174556, erythrocyte AA and AA/DGLA index were found to be predictive risk factors for AD while plasma DHA was found associated with lower AD risk. Both rs174556 and rs3756963 influence AD risk in the Tunisian population and they are likely associated with high AA level. The combination of the two variants increases further the susceptibility to AD. We suggest that FADS1 and ELOVL2 variants could likely regulate the efficiency of AA biosynthesis which could be at the origin of inflammatory derivate.

Blood fatty acids in Alzheimer's disease and mild cognitive impairment: A meta-analysis and systematic review

Plasma fatty acids have been reported to be dysregulated in mild cognitive impairment (MCI) and Alzheimer's disease (AD), though outcomes are not always consistent, and subject numbers often small. Our aim was to use a meta-analysis and systematic review approach to identify if plasma fatty acid dysregulation would be observed in case control studies of AD and MCI. Six databases were searched for studies reporting quantified levels of fatty acids in MCI and/or AD individuals, relative to cognitively normal controls. Docosahexaenoic (DHA) and vaccenic acids were significantly lower and higher respectively in MCI relative to controls. Total fatty acids were 27.2% lower in AD relative to controls, and this was reflected almost uniformly in all specific fatty acids in AD. Changes to plasma/serum fatty acids were identified in both MCI and AD relative to age and gender matched controls. Differences were greatest in AD, in both total number of fatty acids significantly altered, and the degree of change. Docosahexaenoic acid was lower in both MCI and AD, suggesting that it may be a driver of pathology.

Involvement of Lipids in Alzheimer's Disease Pathology and Potential Therapies

Lipids constitute the bulk of the dry mass of the brain and have been associated with healthy function as well as the most common pathological conditions of the brain. Demographic factors, genetics, and lifestyles are the major factors that influence lipid metabolism and are also the key components of lipid disruption in Alzheimer's disease (AD). Additionally, the most common genetic risk factor of AD, APOE ϵ4 genotype, is involved in lipid transport and metabolism. We propose that lipids are at the center of Alzheimer's disease pathology based on their involvement in the blood-brain barrier function, amyloid precursor protein (APP) processing, myelination, membrane remodeling, receptor signaling, inflammation, oxidation, and energy balance. Under healthy conditions, lipid homeostasis bestows a balanced cellular environment that enables the proper functioning of brain cells. However, under pathological conditions, dyshomeostasis of brain lipid composition can result in disturbed BBB, abnormal processing of APP, dysfunction in endocytosis/exocytosis/autophagocytosis, altered myelination, disturbed signaling, unbalanced energy metabolism, and enhanced inflammation. These lipid disturbances may contribute to abnormalities in brain function that are the hallmark of AD. The wide variance of lipid disturbances associated with brain function suggest that AD pathology may present as a complex interaction between several metabolic pathways that are augmented by risk factors such as age, genetics, and lifestyles. Herewith, we examine factors that influence brain lipid composition, review the association of lipids with all known facets of AD pathology, and offer pointers for potential therapies that target lipid pathways.

Habitual Nut Exposure, Assessed by Dietary and Multiple Urinary Metabolomic Markers, and Cognitive Decline in Older Adults: The InCHIANTI Study

SCOPE

The association between self-reported dietary intake and urinary metabolomic markers of habitual nut exposure with cognitive decline over a 3-year follow-up in an older Italian population is prospectively evaluated.

METHODS AND RESULTS

A total of 119 older participants are selected, based on self-referred nut intake: the non-nut consumer (n = 72) and the regular consumer (≥2.9 g d^-1 , n = 47). Nut exposure is measured at baseline either with the use of a validated food frequency questionnaire or with an HPLC-Q-ToF-MS metabolomic approach. Three years after, 28 from the nonconsumers and 10 from the consumers experienced cognitive decline. Dietary nut exposure is characterized by urinary metabolites of polyphenols and fatty acids pathways. Nut consumption estimated either by the dietary marker or by the urinary marker model is in both cases associated with less cognitive decline (OR: 0.78, 95% CI: 0.61,0.99; p = 0.043 and OR: 0.995, 95% CI: 0.991,0.999; p = 0.016, respectively) with AUCs 73.2 (95% CI: 62.9, 83.6) and 73.1 (62.5, 83.7), respectively.

CONCLUSIONS

A high intake of nuts may protect older adults from cognitive decline. Metabolomics provides accurate and complementary information of the nut exposure and reinforces the results obtained using dietary information.

Decreased Blood Level of MFSD2a as a Potential Biomarker of Alzheimer's Disease

The protein Major Facilitator Superfamily Domain containing 2A (MFSD2a) was recently described as the primary carrier for docosahexaenoic acid (DHA) into the brain. Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by lower DHA levels in blood lipids. The aim of this study was to investigate the expression of MFSD2a in the whole blood and brain as a potential biomarker of AD. Three groups were established: 38 healthy controls, 48 subjects with moderate AD (GDS4), and 47 with severe AD (GDS6). We analyzed postmortem brain samples from the hippocampus of 11 healthy controls and 11 severe AD patients. Fatty acid (FA) was determined in serum and brain by gas chromatography. Blood and brain MFSD2a protein expression was analyzed by Western blotting. We found a significant and progressive decline of MFSD2a levels in blood of AD patients (Control 0.83 ± 0.13, GDS4 0.72 ± 0.09, GDS6 0.48 ± 0.05*, p ˂ 0.01). We also corroborated a significant reduction of DHA and other n-3 long-chain polyunsaturated FA in serum of AD. No differences were found in MFSD2a expression or FA levels in brain of controls and AD subjects. MFSD2A carrier was analyzed in AD patients for the first time and the level of MFSD2a in the whole blood could be a potential biomarker of this disease.

Converging and Differential Brain Phospholipid Dysregulation in the Pathogenesis of Repetitive Mild Traumatic Brain Injury and Alzheimer's Disease

Repetitive mild traumatic brain injury (rmTBI) is a major epigenetic risk factor for Alzheimer’s disease (AD). The precise nature of how rmTBI leads to or precipitates AD pathology is currently unknown. Numerous neurological conditions have shown an important role for dysfunctional phospholipid metabolism as a driving factor for the pathogenesis of neurodegenerative diseases. However, the precise role in rmTBI and AD remains elusive. We hypothesized that a detailed phospholipid characterization would reveal profiles of response to injury in TBI that overlap with age-dependent changes in AD and thus provide insights into the TBI-AD relationship. We employed a lipidomic approach examining brain phospholipid profiles from mouse models of rmTBI and AD. Cortex and hippocampal tissue were collected at 24 h, 3, 6, 9, and 12 months post-rmTBI, and at ages representing ‘pre’, ‘peri’ and ‘post’ onset of amyloid pathology (i.e., 3, 9, 15 months-old). Total levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), LysoPE, and phosphatidylinositol (PI), including their monounsaturated, polyunsaturated and saturated fatty acid (FA) containing species were significantly increased at acute and/or chronic time points post-injury in both brain regions. However, levels of most phospholipid species in PS1/APP mice were nominal in the hippocampus, while in the cortex, levels were significantly decreased at ages post-onset of amyloid pathology. Sphingomyelin and LysoPC levels showed coincidental trends in our rmTBI and AD models within the hippocampus, an increase at acute and/or chronic time points examined. The ratio of arachidonic acid (omega-6 FA) to docosahexaenoic acid (omega-3 FA)-containing PE species was increased at early time points in the hippocampus of injured versus sham mice, and in PS1/APP mice there was a coincidental increase compared to wild type littermates at all time points. This study demonstrates some overlapping and diverse phospholipid profiles in rmTBI and AD models. Future studies are required to corroborate our findings in human post-mortem tissue. Investigation of secondary mechanisms triggered by aberrant downstream alterations in bioactive metabolites of these phospholipids, and their modulation at the appropriate time-windows of opportunity could help facilitate development of novel therapeutic strategies to ameliorate the neurodegenerative consequences of rmTBI or the potential triggering of AD pathogenesis by rmTBI.

Peroxisomal dysfunction in neurodegenerative diseases

Peroxisomes and their (patho-)physiological importance in heath and disease have attracted increasing interest during last few decades. Together with mitochondria, peroxisomes comprise key metabolic platforms for oxidation of various fatty acids and redox regulation. In addition, peroxisomes contribute to bile acid, cholesterol, and plasmalogen biosynthesis. The importance of functional peroxisomes for cellular metabolism is demonstrated by the marked brain and systemic organ abnormalities occuring in peroxisome biogenesis disorders and peroxisomal enzyme deficiencies. Current evidences indicate that peroxisomal function is declined with aging, with peroxisomal dysfunction being linked to early onset of multiple age-related diseases including neurodegenerative diseases. Herein, we review recent progress toward understanding the physiological roles and pathological implications of peroxisomal dysfunctions, focusing on neurodegenerative disease.

Omega-6:3 Ratio More Than Absolute Lipid Level in Diet Affects Associative Learning in Honey Bees

Floral pollen is a major source of honey bee nutrition that provides them with micro- and macro-nutrients, including proteins, fatty acids, vitamins, and minerals. Different pollens vary in composition, including in the essential fatty acids, alpha-linolenic acid (omega-3) and linoleic acid (omega-6). Monocultures, prevalent in modern agriculture, may expose honey bee colonies to unbalanced omega-6:3 diets. The importance of omega-3 in the diet for adequate learning and cognitive function, with a focus on suitable omega-6:3 ratio, is well documented in mammals. We have recently shown, for the first time in invertebrates, the importance of omega-3 in diets for associative learning ability in honey bees. In the current work, we examine the effect of the absolute amount of omega-3 in diet compared to the omega-6:3 ratio on honey bee associative learning. We fed newly emerged bees for 1 week on different artificial diets, which had lipid concentration of 1, 2, 4, or 8%, with omega-6:3 ratios of 0.3, 1, or 5, respectively. We then tested the bees in a proboscis-extension response olfactory conditioning assay. We found that both omega-6:3 ratio and total lipid concentration affected learning. The most detrimental diet for learning was that with a high omega-6:3 ratio of 5, regardless of the absolute amount of omega-3 in the diet. Bees fed an omega-6:3 ratio of 1, with 4% total lipid concentration achieved the best performance. Our results with honey bees are consistent with those found in mammals. Best cognitive performance is achieved by a diet that is sufficiently rich in essential fatty acids, but as long as the omega-6:3 ratio is not high.

A brief history of meat in the human diet and current health implications

Anthropological investigations have confirmed many times over, through multiple fields of research the critical role of consumption of animal source foods (ASF) including meat in the evolution of our species. As early as four million years ago, our early bipedal hominin ancestors were scavenging ASFs as evidenced by cut marks on animal bone remains, stable isotope composition of these hominin remains and numerous other lines of evidence from physiological and paleo-anthropological domains. This ASF intake marked a transition from a largely forest dwelling frugivorous lifestyle to a more open rangeland existence and resulted in numerous adaptations, including a rapidly increasing brain size and altered gut structure. Details of the various fields of anthropological evidence are discussed, followed by a summary of the health implications of meat consumption in the modern world, including issues around saturated fat and omega-3 fatty acid intake and discussion of the critical nutrients ASFs supply, with particular emphasis on brain function.

Of Meat and Men: Sex Differences in Implicit and Explicit Attitudes Toward Meat

Modern attitudes to meat in both men and women reflect a strong meat-masculinity association. Sex differences in the relationship between meat and masculinity have not been previously explored. In the current study we used two IATs (implicit association tasks), a visual search task, and a questionnaire to measure implicit and explicit attitudes toward meat in men and women. Men exhibited stronger implicit associations between meat and healthiness than did women, but both sexes associated meat more strongly with 'healthy' than 'unhealthy' concepts. As 'healthy' was operationalized in the current study using terms such as "virile" and "powerful," this suggests that a meat-strength/power association may mediate the meat-masculinity link readily observed across western cultures. The sex difference was not related to explicit attitudes to meat, nor was it attributable to a variety of other factors, such as a generally more positive disposition toward meat in men than women. Men also exhibited an attention bias toward meats, compared to non-meat foods, while females exhibited more caution when searching for non-meat foods, compared to meat. These biases were not related to implicit attitudes, but did tend to increase with increasing hunger levels. Potential ultimate explanations for these differences, including sex differences in bio-physiological needs and receptivity to social signals are discussed.

Association between Red Blood Cells Omega-3 Polyunsaturated Fatty Acids and White Matter Hyperintensities: The MAPT Study

OBJECTIVES

The association between circulating biomarkers of red blood cells (RBC) omega-3 polyunsaturated fatty acids (PUFAs) and cerebral white matter hyperintensities (WMH) on the brain MRI remains yet unclear. We investigated the cross-sectional and prospective associations of RBC omega-3 PUFAs with WMH in dementia-free older adults with subjective memory complaints.

DESIGN

Participants were 234 older adults with assessments for both PUFA and MRI near to baseline; among them, 79 also had an MRI assessment at 3-year follow-up. The measurement of WMH volume was obtained by an automated segmentation algorithm. We related individual or combinational baseline RBC omega-3 PUFAs levels with baseline WMH volumes and WMH evolution over 3 years. We carried out multiple (cross-sectional) and mixed-effect (prospective analysis, with random effects at participant's level) linear regressions with adjustment for age, sex, time interval between date of blood draw for measurement of fatty acids and date of brain MRI, the status of APOE e4 carrier, body mass index, and vascular risk factors. Associations were considered significant at p ≤ 0.006 to take into account multiplicity (8 comparisons).

RESULTS

None of the eight RBC omega-3 PUFAs tested was significantly associated with WMH at both cross-sectional and prospective analyses.

CONCLUSIONS

We did not find any association between omega-3 PUFAs and WMH in non-demented older adults with memory complaints. A longer longitudinal study with data on omega-3 PUFAs and WMH would contribute important information to this field.

Lower brain and blood nutrient status in Alzheimer's disease: Results from meta-analyses

INTRODUCTION

Alzheimer's disease (AD) patients are at risk of nutritional insufficiencies because of physiological and psychological factors. Recently, we showed the results of the meta-analyses indicating lower plasma levels of vitamins A, B12, C, E, and folate in AD patients compared with cognitively intact elderly controls (controls). Now, additional and more extensive literature searches were performed selecting studies which compare blood and brain/cerebrospinal fluid (CSF) levels of vitamins, minerals, trace elements, micronutrients, and fatty acids in AD patients versus controls.

METHODS

The literature published after 1980 in Cochrane Central Register of Controlled Trials, Medline, and Embase electronic databases was systematically analyzed using Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines to detect studies meeting the selection criteria. Search terms used are as follows: AD patients, Controls, vitamins, minerals, trace elements, micronutrients, and fatty acids. Random-effects meta-analyses using a linear mixed model with correction for age differences between AD patients and controls were performed when four or more publications were retrieved for a specific nutrient.

RESULTS

Random-effects meta-analyses of 116 selected publications showed significant lower CSF/brain levels of docosahexaenoic acid (DHA), choline-containing lipids, folate, vitamin B12, vitamin C, and vitamin E. In addition, AD patients showed lower circulatory levels of DHA, eicosapentaenoic acid, choline as phosphatidylcholine, and selenium.

CONCLUSION

The current data show that patients with AD have lower CSF/brain availability of DHA, choline, vitamin B12, folate, vitamin C, and vitamin E. Directionally, brain nutrient status appears to parallel the lower circulatory nutrient status; however, more studies are required measuring simultaneously circulatory and central nutrient status to obtain better insight in this observation. The brain is dependent on nutrient supply from the circulation, which in combination with nutrient involvement in AD-pathophysiological mechanisms suggests that patients with AD may have specific nutritional requirements. This hypothesis could be tested using a multicomponent nutritional intervention.

Effects of N-3 Polyunsaturated Fatty Acids on Dementia

N-3 polyunsaturated fatty acids (PUFAs) including α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have anti-inflammatory effects and neuronal protective functions and may benefit prevention of dementia; however, the epidemiological evidence is very limited. Therefore, the literature about the association between n-3 PUFA and dementia was searched, by using Pubmed. In the analyses of observational studies, n-3 PUFA has been reported to be beneficially associated with dementia in 17 studies; however, the beneficial association between n-3 PUFA and dementia was denied by three studies. In the analyses of intervention studies, n-3 PUFA supplementation was beneficially associated with dementia in eight studies; however, five studies reported the negligible effect of n-3 PUFA for dementia. N-3 PUFA may improve Alzheimer’s disease by increasing clearance of amyloid-β peptide, neurotrophic and neuroprotective factors, and by anti-inflammatory effects. In conclusion, patients with mild memory and/or cognitive impairment can be treated by a long-term and higher intake of n-3 PUFA.

Serum α-linolenic and other ω-3 fatty acids, and risk of disabling dementia: Community-based nested case-control study

BACKGROUND & AIMS

It has been hypothesized that ω-3 polyunsaturated fatty acids have anti-atherosclerotic and neuronal protective functions and may benefit prevention of dementia, but the epidemiological evidence, especially for α-linolenic acid, is quite limited. The aim of this study was to examine whether serum ω-3 polyunsaturated fatty acids are associated with risk of dementia.

METHODS

We performed an intracohort case-control study nested in a community-based cohort, the Circulatory Risk in Communities Study, involving 7586 Japanese individuals aged 40-74 years at the baseline period of 1984-1994. Omega-3 polyunsaturated fatty acid constituents (α-linolenic, eicosapentaenoic, and docosahexaenoic acids) in serum total lipid were measured in 315 cases of incident disabling dementia in the above-mentioned cohort between 1999 and 2004, and in 630 controls whose age, sex, area, and baseline year were matched with the cases.

RESULTS

As we had postulated, serum α-linolenic acid was inversely associated with risk of disabling dementia: the multivariate odds ratios (95% confidence intervals) were 0.57 (0.39-0.85), 0.51 (0.34-0.76), and 0.61 (0.41-0.90) for persons with the second, third, and highest quartiles of serum α-linolenic acid, respectively, as compared with the lowest quartile (P for trend = 0.01). Associations of other ω-3 fatty acids with disabling dementia were not statistically significant.

CONCLUSIONS

Serum α-linolenic acid was inversely associated with risk of disabling dementia. Although the causality needs to be confirmed by randomized control trials, we identified serum α-linolenic acid as a biomarker that predicts future dementia.

Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults

Studies reporting blood levels of the omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were systematically identified in order to create a global map identifying countries and regions with different blood levels. Included studies were those of healthy adults, published in 1980 or later. A total of 298 studies met all inclusion criteria. Studies reported fatty acids in various blood fractions including plasma total lipids (33%), plasma phospholipid (32%), erythrocytes (32%) and whole blood (3.0%). Fatty acid data from each blood fraction were converted to relative weight percentages (wt.%) and then assigned to one of four discrete ranges (high, moderate, low, very low) corresponding to wt.% EPA+DHA in erythrocyte equivalents. Regions with high EPA+DHA blood levels (>8%) included the Sea of Japan, Scandinavia, and areas with indigenous populations or populations not fully adapted to Westernized food habits. Very low blood levels (≤4%) were observed in North America, Central and South America, Europe, the Middle East, Southeast Asia, and Africa. The present review reveals considerable variability in blood levels of EPA+DHA and the very low to low range of blood EPA+DHA for most of the world may increase global risk for chronic disease.

Nutrition and Inflammation in Older Individuals: Focus on Vitamin D, n-3 Polyunsaturated Fatty Acids and Whey Proteins

Chronic activation of the inflammatory response, defined as inflammaging, is the key physio-pathological substrate for anabolic resistance, sarcopenia and frailty in older individuals. Nutrients can theoretically modulate this phenomenon. The underlying molecular mechanisms reducing the synthesis of pro-inflammatory mediators have been elucidated, particularly for vitamin D, n-3 polyunsaturated fatty acids (PUFA) and whey proteins. In this paper, we review the current evidence emerging from observational and intervention studies, performed in older individuals, either community-dwelling or hospitalized with acute disease, and evaluating the effects of intake of vitamin D, n-3 PUFA and whey proteins on inflammatory markers, such as C-Reactive Protein (CRP), interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α). After the analysis, we conclude that there is sufficient evidence for an anti-inflammatory effect in aging only for n-3 PUFA intake, while the few existing intervention studies do not support a similar activity for vitamin D and whey supplements. There is need in the future of large, high-quality studies testing the effects of combined dietary interventions including the above mentioned nutrients on inflammation and health-related outcomes.

Docosahexaenoic Acid and Cognition throughout the Lifespan

Docosahexaenoic acid (DHA) is the predominant omega-3 (n-3) polyunsaturated fatty acid (PUFA) found in the brain and can affect neurological function by modulating signal transduction pathways, neurotransmission, neurogenesis, myelination, membrane receptor function, synaptic plasticity, neuroinflammation, membrane integrity and membrane organization. DHA is rapidly accumulated in the brain during gestation and early infancy, and the availability of DHA via transfer from maternal stores impacts the degree of DHA incorporation into neural tissues. The consumption of DHA leads to many positive physiological and behavioral effects, including those on cognition. Advanced cognitive function is uniquely human, and the optimal development and aging of cognitive abilities has profound impacts on quality of life, productivity, and advancement of society in general. However, the modern diet typically lacks appreciable amounts of DHA. Therefore, in modern populations, maintaining optimal levels of DHA in the brain throughout the lifespan likely requires obtaining preformed DHA via dietary or supplemental sources. In this review, we examine the role of DHA in optimal cognition during development, adulthood, and aging with a focus on human evidence and putative mechanisms of action.

Docosahexaenoic Acid and Cognition throughout the Lifespan

Docosahexaenoic acid (DHA) is the predominant omega-3 (n-3) polyunsaturated fatty acid (PUFA) found in the brain and can affect neurological function by modulating signal transduction pathways, neurotransmission, neurogenesis, myelination, membrane receptor function, synaptic plasticity, neuroinflammation, membrane integrity and membrane organization. DHA is rapidly accumulated in the brain during gestation and early infancy, and the availability of DHA via transfer from maternal stores impacts the degree of DHA incorporation into neural tissues. The consumption of DHA leads to many positive physiological and behavioral effects, including those on cognition. Advanced cognitive function is uniquely human, and the optimal development and aging of cognitive abilities has profound impacts on quality of life, productivity, and advancement of society in general. However, the modern diet typically lacks appreciable amounts of DHA. Therefore, in modern populations, maintaining optimal levels of DHA in the brain throughout the lifespan likely requires obtaining preformed DHA via dietary or supplemental sources. In this review, we examine the role of DHA in optimal cognition during development, adulthood, and aging with a focus on human evidence and putative mechanisms of action.

Intakes of fish and polyunsaturated fatty acids and mild-to-severe cognitive impairment risks: a dose-response meta-analysis of 21 cohort studies

BACKGROUND

The intake of fish and polyunsaturated fatty acids (PUFAs) may benefit cognitive function. However, optimal intake recommendations for protection are unknown.

OBJECTIVE

We systematically investigated associations between fish and PUFA intake and mild-to-severe cognitive impairment risk.

DESIGN

Studies that reported risk estimates for mild cognitive impairment (MCI), cognitive decline, dementia, Alzheimer disease (AD), or Parkinson disease (PD) from fish, total PUFAs, total n-3 (ω-3) PUFAs, or at least one n-3 PUFA were included. Study characteristics and outcomes were extracted. The pooled RR was estimated with the use of a random-effects model meta-analysis. A dose-response analysis was conducted with the use of the 2-stage generalized least-squares trend program.

RESULTS

We included 21 studies (181,580 participants) with 4438 cases identified during follow-up periods (2.1-21 y). A 1-serving/wk increment of dietary fish was associated with lower risks of dementia (RR: 0.95; 95% CI: 0.90, 0.99; P = 0.042, I(2) = 63.4%) and AD (RR: 0.93; 95% CI: 0.90, 0.95; P = 0.003, I(2) = 74.8%). Pooled RRs of MCI and PD were 0.71 (95% CI: 0.59, 0.82; P = 0.733, I(2) = 0%) and 0.90 (95% CI: 0.80, 0.99; P = 0.221, I(2) = 33.7%), respectively, for an 8-g/d increment of PUFA intake. As an important source of marine n-3 PUFAs, a 0.1-g/d increment of dietary docosahexaenoic acid (DHA) intake was associated with lower risks of dementia (RR: 0.86; 95% CI: 0.76, 0.96; P < 0.001, I(2) = 92.7%) and AD (RR: 0.63; 95% CI: 0.51, 0.76; P < 0.001, I(2) = 94.5%). Significant curvilinear relations between fish consumption and risk of AD and between total PUFAs and risk of MCI (both P-nonlinearity < 0.001) were observed.

CONCLUSIONS

Fishery products are recommended as dietary sources and are associated with lower risk of cognitive impairment. Marine-derived DHA was associated with lower risk of dementia and AD but without a linear dose-response relation.

A genome-wide association study of n-3 and n-6 plasma fatty acids in a Singaporean Chinese population

Polyunsaturated fatty acids (PUFAs) have a major impact on human health. Recent genome-wide association studies (GWAS) have identified several genetic loci that are associated with plasma levels of n-3 and n-6 PUFAs in primarily subjects of European ancestry. However, the relevance of these findings has not been evaluated extensively in other ethnic groups. The primary aim of this study was to evaluate for genetic loci associated with n-3 and n-6 PUFAs and to validate the role of recently identified index loci using data from a Singaporean Chinese population. Using a GWAS approach, we evaluated associations with plasma concentrations of three n-3 PUFAs [alphalinolenic acid (ALA), eicosapentaenoic acid and docosahexaenoic acid], four n-6 PUFAs [linoleic acid (LA), gammalinolenic acid, dihomogammalinolenic acid (DGLA) and arachidonic acid], and estimates of delta-5 desaturase and delta-6 desaturase activities among the participants (N = 1361) of the Singaporean Chinese Health Study. Our results reveal robust genome-wide associations (p value <5 × 10(-8)) with ALA, all four n-6 PUFAs, and delta-6 desaturase activity at the FADS1/FADS2 locus. We further replicated the associations between common index variants at the NTAN1/PDXDC1 locus and n-6 PUFAs LA and DGLA, and between the JMJD1C locus and n-6 PUFA LA (p value between 0.0490 and 9.88 × 10(-4)). These associations were independent of dietary intake of PUFAs. In aggregate, we show that genetic loci that influence plasma concentrations of n-3 and n-6 PUFAs are shared across different ethnic groups.

Diet-Induced Cognitive Deficits: The Role of Fat and Sugar, Potential Mechanisms and Nutritional Interventions

It is of vital importance to understand how the foods which are making us fat also act to impair cognition. In this review, we compare the effects of acute and chronic exposure to high-energy diets on cognition and examine the relative contributions of fat (saturated and polyunsaturated) and sugar to these deficits. Hippocampal-dependent memory appears to be particularly vulnerable to the effects of high-energy diets and these deficits can occur rapidly and prior to weight gain. More chronic diet exposure seems necessary however to impair other sorts of memory. Many potential mechanisms have been proposed to underlie diet-induced cognitive decline and we will focus on inflammation and the neurotrophic factor, brain-derived neurotrophic factor (BDNF). Finally, given supplementation of diets with omega-3 and curcumin has been shown to have positive effects on cognitive function in healthy ageing humans and in disease states, we will discuss how these nutritional interventions may attenuate diet-induced cognitive decline. We hope this approach will provide important insights into the causes of diet-induced cognitive deficits, and inform the development of novel therapeutics to prevent or ameliorate such memory impairments.

Omega-3 Fatty Acids in Early Prevention of Inflammatory Neurodegenerative Disease: A Focus on Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia and the most common neurodegenerative disease in the elderly. Furthermore, AD has provided the most positive indication to support the fact that inflammation contributes to neurodegenerative disease. The exact etiology of AD is unknown, but environmental and genetic factors are thought to contribute, such as advancing age, family history, presence of chronic diseases such as cardiovascular disease (CVD) and diabetes, and poor diet and lifestyle. It is hypothesised that early prevention or management of inflammation could delay the onset or reduce the symptoms of AD. Normal physiological changes to the brain with ageing include depletion of long chain omega-3 fatty acids and brains of AD patients have lower docosahexaenoic acid (DHA) levels. DHA supplementation can reduce markers of inflammation. This review specifically focusses on the evidence in humans from epidemiological, dietary intervention, and supplementation studies, which supports the role of long chain omega-3 fatty acids in the prevention or delay of cognitive decline in AD in its early stages. Longer term trials with long chain omega-3 supplementation in early stage AD are warranted. We also highlight the importance of overall quality and composition of the diet to protect against AD and dementia.

Palmitic acid-induced neuron cell cycle G2/M arrest and endoplasmic reticular stress through protein palmitoylation in SH-SY5Y human neuroblastoma cells

Obesity-related neurodegenerative diseases are associated with elevated saturated fatty acids (SFAs) in the brain. An increase in SFAs, especially palmitic acid (PA), triggers neuron cell apoptosis, causing cognitive function to deteriorate. In the present study, we focused on the specific mechanism by which PA triggers SH-SY5Y neuron cell apoptosis. We found that PA induces significant neuron cell cycle arrest in the G₂/M phase in SH-SY5Y cells. Our data further showed that G₂/M arrest is involved in elevation of endoplasmic reticular (ER) stress according to an increase in p-eukaryotic translation inhibition factor 2α, an ER stress marker. Chronic exposure to PA also accelerates beta-amyloid accumulation, a pathological characteristic of Alzheimer’s disease. Interestingly, SFA-induced ER stress, G₂/M arrest and cell apoptosis were reversed by treatment with 2-bromopalmitate, a protein palmitoylation inhibitor. These findings suggest that protein palmitoylation plays a crucial role in SFA-induced neuron cell cycle G₂/M arrest, ER stress and apoptosis; this provides a novel strategy for preventing SFA-induced neuron cell dysfunction.

Mercury contamination in Khramulia (Capoeta capoeta) from the Cheshme Kile and Zarrin Gol Rivers in Iran and human health risk assessment

Total mercury concentrations were determined in muscle tissue of Khramulia (Capoeta capoeta) captured in the Cheshme Kile and Zarrin Gol Rivers, Iran. In Cheshme Kile River, 49 fish samples were collected. The mean total mercury concentration in the muscles of C. capoeta from this area was 249 ng g(-1) dw. In Zarrin Gol River, where 62 fish samples were collected, the total mercury in muscles averaged 164 ng g(-1) dw. A significant difference was found between means of mercury in the rivers (p < 0.001). All samples from the two rivers had mean mercury concentrations below the maximum allowable limits for mercury set by the Food and Agriculture Organization, World Health Organization, Standardization Administration of China and Environmental Protection Agency. The results of this study indicate that the values of hazard target quotient and estimated weekly intake are low and represent a negligible risk for human health.

Plasma phospholipid and dietary α-linolenic acid, mortality, CHD and stroke: the Cardiovascular Health Study

Previous studies have suggested that long-chain n-3 fatty acids derived from seafood are associated with a lower risk of mortality, CHD and stroke. Whether α-linolenic acid (ALA, 18 : 3n-3), a plant-derived long-chain essential n-3 fatty acid, is associated with a lower risk of these outcomes is unclear. The aim of the present study was to examine the associations of plasma phospholipid and dietary ALA with the risk of mortality, CHD and stroke among older adults who participated in the Cardiovascular Health Study, a cohort study of adults aged ≥ 65 years. A total of 2709 participants were included in the plasma phospholipid ALA analysis and 2583 participants were included in the dietary ALA analysis. Cox regression was used to assess the associations of plasma phospholipid and dietary ALA with the risk of mortality, incident CHD and stroke. In minimally and multivariable-adjusted models, plasma phospholipid ALA was found to be not associated with the risk of mortality, incident CHD or stroke. After adjustment for age, sex, race, enrolment site, education, smoking status, diabetes, BMI, alcohol consumption, treated hypertension and total energy intake, higher dietary ALA intake was found to be associated with a lower risk of total and non-cardiovascular mortality; on comparing the highest quintiles of dietary ALA with the lowest quintiles, the HR for total mortality and non-cardiovascular mortality were found to be 0·73 (95 % CI 0·61, 0·88) and 0·64 (95 % CI 0·52, 0·80), respectively. Dietary ALA was found to be not associated with the risk of cardiovascular mortality, incident CHD or stroke. In conclusion, the results of the present suggest study that dietary ALA, but not plasma phospholipid ALA, is associated with a lower risk of total and non-cardiovascular mortality in older adults.

Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis

Background

Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer’s disease (AD) is the most frequent cause of dementia, increasing in prevalence from <1% below the age of 60 years to >40% above 85 years of age.

Methods

We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias.

Results

In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ~38.9% for caffeine to ~89% for physical activity. Education also had a significantly higher propensity for “a positive finding” compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found.

Conclusions

Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

The omega-6/omega-3 ratio and dementia or cognitive decline: a systematic review on human studies and biological evidence

It has been suggested that the intake of certain fatty acids may influence the risk of dementia. However, current reviews have focused only on the therapeutic effects of omega-3 fatty acids, mostly as supplements. To date, the evidence for the relevance of the omega-6/omega-3 ratio has been neglected. Therefore, we searched the databases Alois, Medline, Biosis, Embase, Cochrane Central Register of Controlled Trials, and The Cochrane Database of Systematic Reviews for "essential fatty acids" and "dementia" and aimed to conduct a comprehensive review across study types. All studies that reported on the association between the n-6/n-3 ratio and dementia or cognitive decline were selected. In the 13 animal studies we examined, the dietary n-6/n-3 ratio was shown to affect brain composition, Alzheimer's disease pathology, and behavior. Our review of the 14 studies in humans that fulfilled the selection criteria (7 prospective studies, 3 cross-sectional studies, 1 controlled trial, 3 case-control studies) provided evidence, albeit limited, supporting an association between the n-6/n-3 ratio, cognitive decline, and incidence of dementia. This review supports growing evidence of a positive association between the dietary n-6/n-3 ratio and the risk of Alzheimer's disease.

Circulating omega-3 polyunsaturated fatty acids and subclinical brain abnormalities on MRI in older adults: the Cardiovascular Health Study

Background

Consumption of tuna or other broiled or baked fish, but not fried fish, is associated with fewer subclinical brain abnormalities on magnetic resonance imaging (MRI). We investigated the association between plasma phospholipid omega‐3 polyunsaturated fatty acids (PUFAs), objective biomarkers of exposure, and subclinical brain abnormalities on MRI.

Methods and Results

In the community‐based Cardiovascular Health Study, 3660 participants aged ≥65 underwent brain MRI in 1992–1994, and 2313 were rescanned 5 years later. MRIs were centrally read by neuroradiologists in a standardized, blinded manner. Participants with recognized transient ischemic attacks or stroke were excluded. Phospholipid PUFAs were measured in stored plasma collected in 1992–1993 and related to cross‐sectional and longitudinal MRI findings. After multivariable adjustment, the odds ratio for having a prevalent subclinical infarct was 0.60 (95% CI, 0.44 to 0.82; P for trend=0.001) in the highest versus lowest long‐chain omega‐3 PUFA quartile. Higher long‐chain omega‐3 PUFA content was also associated with better white matter grade, but not with sulcal or ventricular grades, markers of brain atrophy, or with incident subclinical infarcts. The phospholipid intermediate‐chain omega‐3 PUFA alpha‐linolenic acid was associated only with modestly better sulcal and ventricular grades. However, this finding was not supported in the analyses with alpha‐linolenic acid intake.

Conclusions

Among older adults, higher phospholipid long‐chain omega‐3 PUFA content was associated with lower prevalence of subclinical infarcts and better white matter grade on MRI. Our results support the beneficial effects of fish consumption, the major source of long‐chain omega‐3 PUFAs, on brain health in later life. The role of plant‐derived alpha‐linolenic acid in brain health requires further investigation.

Ageing and apoE change DHA homeostasis: relevance to age-related cognitive decline

Epidemiological studies fairly convincingly suggest that higher intakes of fatty fish and n-3 fatty acids are associated with reduced risk of Alzheimer's disease (AD). DHA in plasma is normally positively associated with DHA intake. However, despite being associated with lower fish and DHA intake, unexpectedly, plasma (or brain) DHA is frequently not lower in AD. This review will highlight some metabolic and physiological factors such as ageing and apoE polymorphism that influence DHA homeostasis. Compared with young adults, blood DHA is often slightly but significantly higher in older adults without any age-related cognitive decline. Higher plasma DHA in older adults could be a sign that their fish or DHA intake is higher. However, our supplementation and carbon-13 tracer studies also show that DHA metabolism, e.g. transit through the plasma, apparent retroconversion and β-oxidation, is altered in healthy older compared with healthy young adults. ApoE4 increases the risk of AD, possibly in part because it too changes DHA homeostasis. Therefore, independent of differences in fish intake, changing DHA homeostasis may tend to obscure the relationship between DHA intake and plasma DHA which, in turn, may contribute to making older adults more susceptible to cognitive decline despite older adults having similar or sometimes higher plasma DHA than in younger adults. In conclusion, recent development of new tools such as isotopically labelled DHA to study DHA metabolism in human subjects highlights some promising avenues to evaluate how and why DHA metabolism changes during ageing and AD.

Docosahexaenoic acid homeostasis, brain aging and Alzheimer's disease: Can we reconcile the evidence?

A crossroads has been reached on research into docosahexaenoic acid (DHA) and Alzheimer's disease (AD). On the one hand, several prospective observational studies now clearly indicate a protective effect of higher fish and DHA intake against risk of AD. On the other hand, once AD is clinically evident, supplementation trials demonstrate essentially no benefit of DHA in AD. Despite apparently low DHA intake in AD, brain DHA levels are frequently the same as in controls, suggesting that low DHA intake results in low plasma DHA but does not necessarily reduce brain DHA in humans. Animal models involving dietary omega-3 fatty acid deficiency to deplete brain DHA may therefore not be appropriate in AD research. Studies in the healthy elderly suggest that DHA homeostasis changes during aging. Tracer methodology now permits estimation of DHA half-life in the human brain and whole body. Apolipoprotein E alleles have an important impact not only on AD but also on DHA homeostasis in humans. We therefore encourage further development of innovative approaches to the study of DHA metabolism and its role in human brain function. A better understanding of DHA metabolism in humans will hopefully help explain how higher habitual DHA intake protects against the risk of deteriorating cognition during aging and may eventually give rise to a breakthrough in the treatment of AD.

High normal plasma triglycerides are associated with preserved cognitive function in Chinese oldest-old

OBJECTIVE

to explore the relationship between blood lipids/lipoproteins and cognitive function in the Chinese oldest-old.

DESIGN

multivariate statistical analysis using cross-sectional data.

SETTING

community-based setting in longevity areas in China.

SUBJECTS

eight hundred and thirty-six subjects aged 80 and older were included in the sample.

METHODS

plasma total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, blood pressure and fasting plasma glucose were measured and information about demographics and lifestyle was collected. Cognitive status was assessed using the Mini-Mental State Examination (MMSE).

RESULTS

cumulative logit model analysis showed that triglyceride was significantly negatively associated with cognitive impairment. By general linear modelling, there was a significant linear trend of MMSE scores with the level of triglyceride, but not with levels of cholesterol after adjustment. The odds ratio (OR) of cognitive impairment (MMSE score < 18) was significantly reduced for the highest quartile of plasma triglyceride concentration (OR: 0.52, 95% CI: 0.33-0.84), but not for the second or third quartile, compared with the lowest quartile (adjusted models). There were no significant associations between cognitive impairment and cholesterol.

CONCLUSION

we concluded that high normal plasma triglyceride was associated with preservation of cognitive function while lower concentrations were not in the Chinese oldest-old.

Cognitive enhancement by omega-3 fatty acids from child-hood to old age: findings from animal and clinical studies

Omega-(n)-3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are major components of neuronal membranes and have a wide range of functions, from modulating synaptic plasticity and neurochemistry, to neuroimmune-modulation and neuroprotection. Thus, it is not surprising that n-3 PUFA are widely acknowledged to have cognitive-enhancing effects. Although clinical evidence is somewhat conflicting, probably in large part due to methodological issues, animal studies have consistently demonstrated that n-3 PUFA are indispensable for proper brain development, may enhance cognitive function in healthy, adult individuals and attenuate cognitive impairment in aging and age-related disorders, such as dementia. This review discusses and integrates up to date evidence from clinical and animal studies investigating the cognitive-enhancing effects of n-3 PUFA during development, child- and adult-hood, as well as old-age with associated neurodegenerative diseases, such as Alzheimer's disease. Furthermore, we cover the major underlying biochemical and neurophysiological mechanisms by which n-3 PUFA mediate these effects on cognition. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Omega 3 fatty acids and cognitive health in older people

Oily fish and other sources of long-chain n-3 polyunsaturated fatty acids (n-3 LCPs) have been proposed as protective against dementia and age related cognitive impairment. The basic mechanisms underlying these proposed benefits have been postulated and experimental studies supporting the plausibility of the putative effects have been published. Observational epidemiological and case control studies also largely support a protective role of fish consumption on cognitive function with advancing age, albeit with important unexplained heterogeneity in findings. In this review we report the findings of the latest Cochrane review on the benefits of n-3 LCP supplementation on cognitive function among cognitively healthy older people and expand the review by including trials conducted with individuals with prevalent poor cognitive function or dementia. We identified seven relevant trials, four among cognitively healthy older people, and three among individuals with pre-existing cognitive decline or dementia, and overall conclude that there is no evidence to support the routine use of n-3 LCPs supplements for the prevention, or amelioration, of cognitive decline in later life. We identified several challenges in the design of intervention studies for the prevention of dementia and cognitive decline in older people that require careful consideration especially in recruitment and retention in long-term trials. Whether the lack of agreement in findings from mechanistic and observational data and from intervention studies reflects a real absence of benefit on cognitive function from n-3 LCP supplementation, or whether it reflects intrinsic limitations in the design of published studies remains open to question.

Associations between n-3 PUFA concentrations and cognitive function after recovery from late-life depression

BACKGROUND

Lower concentrations of n-3 PUFAs have been reported to be associated with cognitive impairment and dementia, but also with depression-itself a potential risk factor for cognitive decline.

OBJECTIVE

The aims of this study were to investigate associations between n-3 PUFA concentrations in erythrocyte membrane or plasma and cognitive function in an at-risk sample of older people with previous major depression and to explore specificity with respect to cognitive domains.

DESIGN

A cross-sectional sample of 132 eligible participants who had recovered from major depression (mean ± SD age: 67.8 ± 6.6 y) were enrolled from outpatient psychiatric services. A series of cognitive tests and a structured questionnaire were administered. Fasting blood samples were collected for n-3 PUFA measurements.

RESULTS

Higher EPA and total n-3 PUFA concentrations and a lower ratio of arachidonic acid to EPA in erythrocyte membranes were associated with a higher cognitive composite score: independent of age and sex, but no longer significant after adjustment for education. No associations were found with plasma concentrations of any fatty acid. Considering individual cognitive tests, the strongest and most consistent correlations were found between immediate recall and concentrations of total n-3 PUFAs and α-linolenic acid (ALA) in erythrocytes, which were observed only in participants with recurrent depression.

CONCLUSIONS

Total erythrocyte n-3 PUFA concentrations are positively associated with cognitive function, particularly immediate recall, in older people with previous depression. Lower concentrations of n-3 PUFAs or ALA in erythrocyte membranes may be good predictors for cognitive impairment in older people with previous recurrent depression.

Towards a whole-body systems [multi-organ] lipidomics in Alzheimer's disease

Preclinical and clinical evidence suggests that docosahexaenoic acid (DHA), an omega-3 fatty acid derived from diet or synthesized in the liver, decreases the risk of developing Alzheimer's disease (AD). DHA levels are reduced in the brain of subjects with AD, but it is still unclear whether human dementias are associated with dysregulations of DHA metabolism. A systems biological view of omega-3 fatty acid metabolism offered unexpected insights on the regulation of DHA homeostasis in AD [1]. Results of multi-organ lipidomic analyses were integrated with clinical and gene-expression data sets to develop testable hypotheses on the functional significance of lipid abnormalities observed and on their possible mechanistic bases. One surprising outcome of this integrative approach was the discovery that the liver of AD patients has a limited capacity to convert shorter chain omega-3 fatty acids into DHA due to a deficit in the peroxisomal d-bifunctional protein. This deficit may contribute to the decrease in brain DHA levels and contribute to cognitive impairment.

Cerebrospinal fluid fatty acids in glucocerebrosidase-associated Parkinson's disease

BACKGROUND

Heterozygous mutations in the glucocerebrosidase gene lead to an increased risk for and to more severe alpha-synuclein-associated pathology in Parkinson's disease. As both glucocerebrosidase and alpha-synuclein interact with fatty acids, we hypothesized that cerebrospinal fluid fatty acid levels are altered in these Parkinson's disease patients.

METHODS

Cerebrospinal fluid levels of 13 fatty acids in 8 Parkinson's disease patients with a heterozygous glucocerebrosidase mutation were compared with those of 41 idiopathic Parkinson's disease patients and 30 controls using gas chromatography.

RESULTS

Parkinson's disease patients with a heterozygous glucocerebrosidase mutation had lower levels of palmitoleic (P ≤ .007), oleic (P ≤ .016), linoleic (P ≤ .005), arachidonic (P ≤ .003), eicosapentaenoic (P ≤ .003) and decosahexaenoic (P ≤ .03) acids and lower levels of total fatty acids (P < .005) compared with both idiopathic Parkinson's disease patients and control subjects.

CONCLUSIONS

These results suggest that abnormalities of fatty acid metabolism are specifically involved in the pathogenesis of Parkinson's disease associated with a heterozygous glucocerebrosidase mutation.

Effects of n-3 fatty acids on cognitive decline: a randomized, double-blind, placebo-controlled trial in stable myocardial infarction patients

BACKGROUND

Epidemiological studies suggest a protective effect of n-3 fatty acids derived from fish (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) against cognitive decline. For α-linolenic acid (ALA) obtained from vegetable sources, the effect on cognitive decline is unknown. We examined the effect of n-3 fatty acid supplementation on cognitive decline in coronary heart disease patients.

METHODS

The analysis included 2911 coronary patients (78% men) aged 60 to 80 years who participated in a double-blind placebo-controlled trial of n-3 fatty acids and cardiovascular diseases (Alpha Omega Trial). By using a 2 × 2 factorial design, patients were randomly assigned to margarines that provided 400 mg/d of EPA-DHA, 2 g/d of ALA, both EPA-DHA and ALA, or placebo for 40 months. Cognitive function was assessed by the Mini-Mental State Examination (MMSE) at baseline and after 40 months. The effect of n-3 fatty acids on change in MMSE score was assessed using analysis of variance. Logistic regression analysis was used to examine the effects on risk of cognitive decline, defined as a decrease of 3 or more points in MMSE score or incidence of dementia.

RESULTS

Patients in the active treatment groups had an additional intake of 384 mg of EPA-DHA, 1.9 g of ALA, or both. The overall MMSE score in this cohort was 28.3 ± 1.6 points, which decreased by 0.67 ± 2.25 points during follow-up. Changes in MMSE score during intervention did not differ significantly between EPA-DHA and placebo (-0.65 vs -0.69 points, P = .44) or between ALA and placebo (-0.60 vs -0.74 points, P = .12). The risk of cognitive decline was 1.03 (95% confidence interval: 0.84-1.26, P = .80) for EPA-DHA (vs placebo) and 0.90 (0.74-1.10, P = .31) for ALA (vs placebo).

CONCLUSION

This large intervention study showed no effect of dietary doses of n-3 fatty acids on global cognitive decline in coronary heart disease patients.