Association of Alzheimer disease pathology with abnormal lipid metabolism: the Hisayama Study

Amyloid-β and Phosphorylated Tau are the Key Biomarkers and Predictors of Alzheimer's Disease

Alzheimer's disease (AD) is a age-related neurodegenerative disease and is a major public health concern both in Texas, US and Worldwide. This neurodegenerative disease is mainly characterized by amyloid-beta (Aβ) and phosphorylated Tau (p-Tau) accumulation in the brains of patients with AD and increasing evidence suggests that these are key biomarkers in AD. Both Aβ and p-tau can be detected through various imaging techniques (such as positron emission tomography, PET) and cerebrospinal fluid (CSF) analysis. The presence of these biomarkers in individuals, who are asymptomatic or have mild cognitive impairment can indicate an increased risk of developing AD in the future. Furthermore, the combination of Aβ and p-tau biomarkers is often used for more accurate diagnosis and prediction of AD progression. Along with AD being a neurodegenerative disease, it is associated with other chronic conditions such as cardiovascular disease, obesity, depression, and diabetes because studies have shown that these comorbid conditions make people more vulnerable to AD. In the first part of this review, we discuss that biofluid-based biomarkers such as Aβ, p-Tau in cerebrospinal fluid (CSF) and Aβ & p-Tau in plasma could be used as an alternative sensitive technique to diagnose AD. In the second part, we discuss the underlying molecular mechanisms of chronic conditions linked with AD and how they affect the patients in clinical care.

Alteration of Metabolic Profiles during the Progression of Alzheimer's Disease

(1) Background: Alzheimer's disease (AD) is a progressive neurodegenerative disorder that threatens the population health of older adults. However, the mechanisms of the altered metabolism involved in AD pathology are poorly understood. The aim of the study was to identify the potential biomarkers of AD and discover the metabolomic changes produced during the progression of the disease. (2) Methods: Gas chromatography-mass spectrometry (GC-MS) was used to measure the concentrations of the serum metabolites in a cohort of subjects with AD (n = 88) and a cognitively normal control (CN) group (n = 85). The patients were classified as very mild (n = 25), mild (n = 27), moderate (n = 25), and severe (n = 11). The serum metabolic profiles were analyzed using multivariate and univariate approaches. Least absolute shrinkage and selection operator (LASSO) logistic regression was applied to identify the potential biomarkers of AD. Biofunctional enrichment analysis was performed using the Kyoto Encyclopedia of Genes and Genomes. (3) Results: Our results revealed considerable separation between the AD and CN groups. Six metabolites were identified as potential biomarkers of AD (AUC > 0.85), and the diagnostic model of three metabolites could predict the risk of AD with high accuracy (AUC = 0.984). The metabolic enrichment analysis revealed that carbohydrate metabolism deficiency and the disturbance of amino acid, fatty acid, and lipid metabolism were involved in AD progression. Especially, the pathway analysis highlighted that l-glutamate participated in four crucial nervous system pathways (including the GABAergic synapse, the glutamatergic synapse, retrograde endocannabinoid signaling, and the synaptic vesicle cycle). (4) Conclusions: Carbohydrate metabolism deficiency and amino acid dysregulation, fatty acid, and lipid metabolism disorders were pivotal events in AD progression. Our study may provide novel insights into the role of metabolic disorders in AD pathogenesis and identify new markers for AD diagnosis.

A systematic review of natural products for skin applications: Targeting inflammation, wound healing, and photo-aging

BACKGROUND

Every day the skin is constantly exposed to several harmful factors that induce oxidative stress. When the cells are incapable to maintain the balance between antioxidant defenses and reactive oxygen species, the skin no longer can keep its integrity and homeostasis. Chronic inflammation, premature skin aging, tissue damage, and immunosuppression are possible consequences induced by sustained exposure to environmental and endogenous reactive oxygen species. Skin immune and non-immune cells together with the microbiome are essential to efficiently trigger skin immune responses to stress. For this reason, an ever-increasing demand for novel molecules capable of modulating immune functions in the skin has risen the level of their development, particularly in the field of natural product-derived molecules.

PURPOSE

In this review, we explore different classes of molecules that showed evidence in modulate skin immune responses, as well as their target receptors and signaling pathways. Moreover, we describe the role of polyphenols, polysaccharides, fatty acids, peptides, and probiotics as possible treatments for skin conditions, including wound healing, infection, inflammation, allergies, and premature skin aging.

METHODS

Literature was searched, analyzed, and collected using databases, including PubMed, Science Direct, and Google Scholar. The search terms used included "Skin", "wound healing", "natural products", "skin microbiome", "immunomodulation", "anti-inflammatory", "antioxidant", "infection", "UV radiation", "polyphenols", "polysaccharides", "fatty acids", "plant oils", "peptides", "antimicrobial peptides", "probiotics", "atopic dermatitis", "psoriasis", "auto-immunity", "dry skin", "aging", etc., and several combinations of these keywords.

RESULTS

Natural products offer different solutions as possible treatments for several skin conditions. Significant antioxidant and anti-inflammatory activities were reported, followed by the ability to modulate immune functions in the skin. Several membrane-bound immune receptors in the skin recognize diverse types of natural-derived molecules, promoting different immune responses that can improve skin conditions.

CONCLUSION

Despite the increasing progress in drug discovery, several limiting factors need future clarification. Understanding the safety, biological activities, and precise mechanisms of action is a priority as well as the characterization of the active compounds responsible for that. This review provides directions for future studies in the development of new molecules with important pharmaceutical and cosmeceutical value.

Metabolic Overlap between Alzheimer's Disease and Metabolic Syndrome Identifies the PVRL2 Gene as a New Modulator of Diabetic Dyslipidemia

BACKGROUND

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) share metabolic alterations such as abnormal insulin and lipid metabolism and have some common genetic factors such as APOE genotype. Taking this into account, we hypothesized that we could identify common genetic factors involved in the development of diabetes and cardiovascular diseases.

METHODOLOGY

We first genotyped 48 single nucleotide polymorphisms (SNPs) previously associated with AD in a cohort composed of 330 patients with cognitive impairment (CI) to assess their association with plasma lipids. Second, we conducted pleiotropy-informed conjunctional false discovery rate (FDR) analysis designed to identify shared variants between AD and plasma lipid levels. Finally, we used the SNPs to be found associated with lipid parameters and AD to search for associations with lipoprotein parameters in 281 patients with cardiometabolic risk.

RESULTS

Five SNPs were significantly associated with lower levels of cholesterol transported in remnant lipoprotein particles (RLPc) in subjects with CI; among these SNPs was the rs73572039 variant in PVRL2. Stratified QQ-plots were conducted on GWAS designed for AD and triglycerides (TG). The cross-trait analysis resulted in a total of 22 independent genomic loci associated with both AD and TG levels with a conjFDR < 0.05. Among these loci, two pleiotropic variants were located in PVRL2 (rs12978931 and rs11667640). The three SNPs in PVRL2 were significantly associated with RLPc, TG, and number of circulating VLDL and HDL particles in subjects with cardiometabolic risk.

CONCLUSIONS

We have identified three variants in PVRL2 that predispose individuals to AD that also influence the lipid profile that confers cardiovascular risk in T2DM subjects. PVRL2 is a potential new modulating factor of atherogenic dyslipidemia.

Influence of genetic and cardiometabolic risk factors in Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder. Cardiometabolic and genetic risk factors play an important role in the trajectory of AD. Cardiometabolic risk factors including diabetes, mid-life obesity, mid-life hypertension and elevated cholesterol have been linked with cognitive decline in AD subjects. These potential risk factors associated with cerebral metabolic changes which fuel AD pathogenesis have been suggested to be the reason for the disappointing clinical trial results. In appreciation of the risks involved, using search engines such as PubMed, Scopus, MEDLINE and Google Scholar, a relevant literature search on cardiometabolic and genetic risk factors in AD was conducted. We discuss the role of genetic as well as established cardiovascular risk factors in the neuropathology of AD. Moreover, we show new evidence of genetic interaction between several genes potentially involved in different pathways related to both neurodegenerative process and cardiovascular damage.

Functional and Phenotypic Diversity of Microglia: Implication for Microglia-Based Therapies for Alzheimer’s Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease and is closely associated with the accumulation of β-amyloid (Aβ) and neurofibrillary tangles (NFTs). Apart from Aβ and NFT pathologies, AD patients also exhibit a widespread microglial activation in various brain regions with elevated production of pro-inflammatory cytokines, a phenomenon known as neuroinflammation. In healthy central nervous system, microglia adopt ramified, “surveying” phenotype with compact cell bodies and elongated processes. In AD, the presence of pathogenic proteins such as extracellular Aβ plaques and hyperphosphorylated tau, induce the transformation of ramified microglia into amoeboid microglia. Ameboid microglia are highly phagocytic immune cells and actively secrete a cascade of pro-inflammatory cytokines and chemokines. However, the phagocytic ability of microglia gradually declines with age, and thus the clearance of pathogenic proteins becomes highly ineffective, leading to the accumulation of Aβ plaques and hyperphosphorylated tau in the aging brain. The accumulation of pathogenic proteins further augments the neuroinflammatory responses and sustains the activation of microglia. The excessive production of pro-inflammatory cytokines induces a massive loss of functional synapses and neurons, further worsening the disease condition of AD. More recently, the identification of a subset of microglia by transcriptomic studies, namely disease-associated microglia (DAM), the progressive transition from homeostatic microglia to DAM is TREM2-dependent and the homeostatic microglia gradually acquire the state of DAM during the disease progression of AD. Recent in-depth transcriptomic analysis identifies ApoE and Trem2 from microglia as the major risk factors for AD pathogenesis. In this review, we summarize current understandings of the functional roles of age-dependent microglial activation and neuroinflammation in the pathogenesis of AD. To this end, the exponential growth in transcriptomic data provides a solid foundation for in silico drug screening and gains further insight into the development of microglia-based therapeutic interventions for AD.

Sex-specific lipid dysregulation in the Abca7 knockout mouse brain

Alzheimer’s disease is a devastating neurodegenerative disease that affects more women than men. The pathomechanism underlying the sex disparity, especially in the brain, is unclear. ABCA7 is one of the strongest susceptibility genes for Alzheimer’s disease. It mediates the transport of lipids across membranes and is associated with pathways related to amyloid-β neuropathology. However, the role of ABCA7 in the regulation of brain lipids is largely unknown. Sex-specific differences in the pathological link between brain lipid dysregulation and amyloid-β are also unknown. Here, we undertook quantitative discovery lipidomics of male and female Abca7 knockout (n = 52) and wild type (n = 35) mouse brain using sophisticated liquid chromatography/mass spectrometry. We identified 61 lipid subclasses in the mouse brain and found sex-specific differences in lipids that were altered with Abca7 deletion. The altered lipids belong to cellular pathways that control cell signalling, sterol metabolism, mitochondrial function and neuroprotection. We also investigated the relationship between lipids and amyloid-β levels in the Abca7 knockout mice and found elevated free cholesterol only in female mice that was significantly correlated with amyloid-β42 levels. In male Abca7 knockout mice, the neuroprotective ganglioside GD1a levels were elevated and inversely correlated with amyloid-β42 levels. Collectively, these results demonstrate that Abca7 deletion leads to sex-specific lipid dysregulation in the brain, providing insight into the underlying sex disparity in the aetiology of Alzheimer’s disease.

Therapeutic effects of crude extracts of Bacopa floribunda on beta-amyloid 1-42-induced Alzheimer’s disease via suppression of dyslipidemia, systemic inflammation and oxidative stress in male Wistar Rats

Aims

Bacopa floribunda (BF), an African traditional plant and its species have been widely used as brain tonic for memory enhancement. It has also been reported to help relieve anxiety and some psychological disorders. This study aimed to investigate the mechanisms of action of BF on Amyloid beta (Aβ) 1–42 peptides induced cognitive deficit in male Wistar rats.

Main methods

A total of 48 healthy male wistar rats were used for this study. Some groups were pre-treated with 200 mg/kg of BF extracts before a single bilateral injection of Aβ 1–42 while some were post-treated with BF for 21 days after Aβ1-42 exposure. Cognitive performance was evaluated using Y-Maze and Novel Object recognition tests. After treatments, hippocampal homogenates were assayed for the levels of Acetylcholinesterase, Na–K/ATPase activities, glutamate and Aβ1-42 concentrations among others.

Key findings

It was observed that Aβ1-42 caused cognitive impairment and BF extracts especially the ethanol extract was able to significantly (p < 0.05) reverse almost all the perturbations including lipid imbalance caused by Aβ1-42 assault mainly at the post-treatment level.

Significance

Administration of ethanol and aqueous extracts of BF mitigated the hazardous effect of Aβ1-42 observed in the blood plasma and hippocampal homogenates. In this context, we conclude that BF is an efficient cognitive enhancer that can help alleviate some symptoms associated with Alzheimer’s disease.

Mechanistic Link between Vitamin B12 and Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of dementia in the elderly population, affecting over 55 million people worldwide. Histopathological hallmarks of this multifactorial disease are an increased plaque burden and tangles in the brains of affected individuals. Several lines of evidence indicate that B12 hypovitaminosis is linked to AD. In this review, the biochemical pathways involved in AD that are affected by vitamin B12, focusing on APP processing, Aβ fibrillization, Aβ-induced oxidative damage as well as tau hyperphosphorylation and tau aggregation, are summarized. Besides the mechanistic link, an overview of clinical studies utilizing vitamin B supplementation are given, and a potential link between diseases and medication resulting in a reduced vitamin B12 level and AD are discussed. Besides the disease-mediated B12 hypovitaminosis, the reduction in vitamin B12 levels caused by an increasing change in dietary preferences has been gaining in relevance. In particular, vegetarian and vegan diets are associated with vitamin B12 deficiency, and therefore might have potential implications for AD. In conclusion, our review emphasizes the important role of vitamin B12 in AD, which is particularly important, as even in industrialized countries a large proportion of the population might not be sufficiently supplied with vitamin B12.

Abnormal amyloid beta metabolism in systemic abnormalities and Alzheimer's pathology: Insights and therapeutic approaches from periphery

Alzheimer's disease (AD) is an age-associated, multifactorial neurodegenerative disorder that is incurable. Despite recent success in treatments that partially improve symptomatic relief, they have failed in most clinical trials. Re-holding AD for accurate diagnosis and treatment is widely known as a challenging task. Lack of knowledge of basic molecular pathogenesis might be a possible reason for ineffective AD treatment. Historically, a majority of therapy-based studies have investigated the role of amyloid-β (Aβ peptide) in the central nervous system (CNS), whereas less is known about Aβ peptide in the periphery in AD. In this review, we provide a comprehensive summary of the current understanding of Aβ peptide metabolism (anabolism and catabolism) in the brain and periphery. We show that the abnormal metabolism of Aβ peptide is significantly linked with central-brain and peripheral abnormalities; the interaction between peripheral Aβ peptide metabolism and peripheral abnormalities affects central-brain Aβ peptide metabolism, suggesting the existence of significant communication between these two pathways of Aβ peptide metabolism. This close interaction between the central brain and periphery in abnormal Aβ peptide metabolism plays a key role in the development and progression of AD. In conclusion, we need to obtain a full understanding of the dynamic roles of Aβ peptide at the molecular level in both the brain and periphery in relation to the pathology of AD. This will not only provide new information regarding the complex disease pathology, but also offer potential new clues to improve therapeutic strategies and diagnostic biomarkers for the successful treatment of AD.

Retinal Vasculopathy in Alzheimer's Disease

The retina has been increasingly investigated as a site of Alzheimer’s disease (AD) manifestation for over a decade. Early reports documented degeneration of retinal ganglion cells and their axonal projections. Our group provided the first evidence of the key pathological hallmarks of AD, amyloid β-protein (Aβ) plaques including vascular Aβ deposits, in the retina of AD and mild cognitively impaired (MCI) patients. Subsequent studies validated these findings and further identified electroretinography and vision deficits, retinal (p)tau and inflammation, intracellular Aβ accumulation, and retinal ganglion cell-subtype degeneration surrounding Aβ plaques in these patients. Our data suggest that the brain and retina follow a similar trajectory during AD progression, probably due to their common embryonic origin and anatomical proximity. However, the retina is the only CNS organ feasible for direct, repeated, and non-invasive ophthalmic examination with ultra-high spatial resolution and sensitivity. Neurovascular unit integrity is key to maintaining normal CNS function and cerebral vascular abnormalities are increasingly recognized as early and pivotal factors driving cognitive impairment in AD. Likewise, retinal vascular abnormalities such as changes in vessel density and fractal dimensions, blood flow, foveal avascular zone, curvature tortuosity, and arteriole-to-venule ratio were described in AD patients including early-stage cases. A rapidly growing number of reports have suggested that cerebral and retinal vasculopathy are tightly associated with cognitive deficits in AD patients and animal models. Importantly, we recently identified early and progressive deficiency in retinal vascular platelet-derived growth factor receptor-β (PDGFRβ) expression and pericyte loss that were associated with retinal vascular amyloidosis and cerebral amyloid angiopathy in MCI and AD patients. Other studies utilizing optical coherence tomography (OCT), retinal amyloid-fluorescence imaging and retinal hyperspectral imaging have made significant progress in visualizing and quantifying AD pathology through the retina. With new advances in OCT angiography, OCT leakage, scanning laser microscopy, fluorescein angiography and adaptive optics imaging, future studies focusing on retinal vascular AD pathologies could transform non-invasive pre-clinical AD diagnosis and monitoring.

Impact of age, hypercholesterolemia, and the vitamin D receptor on brain endogenous β-amyloid peptide accumulation in mice

Age, hypercholesterolemia, and vitamin D deficiency are risk factors that increase the brain accumulation of pathogenic β-amyloid peptides (40 and 42), precursors leading to Alzheimer's disease (AD) in humans. The relative changes accompanying aging, high cholesterol, and/or treatment of calcitriol, active vitamin D receptor (VDR) ligand, under normal physiology are unknown. We examined these relative changes in C57BL/6 mice of ages 2, 4-8, and more than 10 months old, which were fed a normal or high fat / high cholesterol diet and treated with calcitriol, active ligand of the vitamin D receptor (0 or 2.5 μg/kg ×4, intraperitoneally, every other day to elicit cholesterol lowering in liver). Aβ₄₀ but not Aβ₄₂ accumulation in brain and lower P-glycoprotein (P-gp) and neprilysin protein expressions for Aβ efflux and degradation, respectively, were found to be associated with aging. But there was no trend for BACE1 (β-secretase 1, a cholesterol-sensitive enzyme) toward Aβ synthesis with age. In response to calcitriol treatment, P-gp was elevated, mitigating partially the age-related changes. Although age-dependent decreasing trends in mRNA expression levels existed for Cyp46a1, the brain cholesterol processing enzyme, whose inhibition increases BACE1 and ApoE to facilitate microglia Aβ degradation, mRNA changes for other cholesterol transporters: Acat1 and Abca1, and brain cholesterol levels remained unchanged. There was no observable change in the mRNA expression of amyloid precursor protein (APP) and the influx (RAGE) and efflux (LRP1) transporters with respect to age, diet, or calcitriol treatment. Overall, aging poses as a risk factor contributing to Aβ accumulation in brain, and VDR-mediated P-gp activation partially alleviates the outcome.

Concurrent cardiac transthyretin and brain β amyloid accumulation among the older adults: The Hisayama study

Previous studies have revealed risk for cognitive impairment in cardiovascular diseases. We investigated the relationship between degenerative changes of the brain and heart, with reference to Alzheimer's disease (AD) pathologies, cardiac transthyretin amyloid (ATTR) deposition, and cardiac fibrosis. A total of 240 consecutive autopsy cases of a Japanese population‐based study were examined. β amyloid (Aβ) of senile plaques, phosphorylated tau protein of neurofibrillary tangles, and ATTR in the hearts were immunohistochemically detected and graded according to the NIH‐AA guideline for AD pathology and as Tanskanen reported, respectively. Cerebral amyloid angiopathy (CAA) was graded according to the Vonsattel scale. Cardiac fibrosis was detected by picrosirius red staining, followed by image analysis. Cardiac ATTR deposition occurred after age 75 years and increased in an age‐dependent manner. ATTR deposition was more common, and of higher grades, in the dementia cases. We subdivided the cases into two age groups: ≤90 years old (n = 173) and >90 years old (n = 67), which was the mean and median age at death of the AD cases. When adjusted for age and sex, TTR deposition grades correlated with Aβ phase score (A2–3), the Consortium to Establish a Registry for AD score (sparse to frequent), and high Braak stage (V–VI) only in those aged ≤90 years at death. No significant correlation was observed between the cardiac ATTR deposition and CAA stages, or between cardiac fibrosis and AD pathologies. Collectively, AD brain pathology correlated with cardiac TTR deposition among the older adults ≤90 years.

Blood Pressure Level Is Associated With Changes in Plasma Aβ1 -40 and Aβ1-42 Levels: A Cross-sectional Study Conducted in the Suburbs of Xi'an, China

Objectives: Amyloid-β (Aβ) deposition in the brain is the hallmark of Alzheimer’s disease (AD) pathology. Hypertension is a risk factor for AD, but the effects of hypertension on Aβ deposition are not fully determined. Considering peripheral Aβ closely relates to Aβ deposition in the brain, we investigated the relationships between blood pressure (BP) level and plasma Aβ concentrations.

Methods: One-thousand and sixty-nine participants (age above 45) from a village in the suburbs of Xi’an, China were enrolled. Questionnaires and validated Chinese versions of the Mini-Mental State Examination (MMSE) were used to collect information about vascular risk factors and assess cognition function. The apolipoprotein E (ApoE) genotype was detected using PCR and sequencing. Plasma Aβ levels were measured using ELISA. The associations between BP and plasma Aβ levels were analyzed by using multivariate linear regression.

Results: Plasma Aβ_1–40 level was higher in high BP group than that in normal BP group (53.34 ± 8.50 pg/ml vs. 51.98 ± 8.96 pg/ml, P = 0.013), in high SBP group than that in normal SBP group (53.68 ± 8.69 pg/ml vs. 51.88 ± 8.80 pg/ml, P = 0.001) and in high MABP group than that in normal MABP group (54.05 ± 8.78 pg/ml vs. 52.04 ± 8.75 pg/ml, P = 0.001). After controlling for the confounding factors, SBP (b = 0.078, P < 0.001), DBP (b = 0.090, P = 0.008) and MABP (b = 0.104, P < 0.001) correlated with plasma Aβ_1–40 level positively in ApoE ε4 non-carriers, but not ApoE ε4 carriers.

Conclusions: Elevated BP levels were associated with increased plasma Aβ_1–40 levels in middle-aged and elderly ApoE ε4 non-carriers.

Inclusion of African American/Black adults in a pilot brain proteomics study of Alzheimer's disease

Alzheimer's disease (AD) disproportionately affects certain racial and ethnic subgroups, such as African American/Black and Hispanic adults. Genetic, comorbid, and socioeconomic risk factors contribute to this disparity; however, the molecular contributions have been largely unexplored. Herein, we conducted a pilot proteomics study of postmortem brains from African American/Black and non-Hispanic White adults neuropathologically diagnosed with AD compared to closely-matched cognitively normal individuals. Examination of hippocampus, inferior parietal lobule, and globus pallidus regions using quantitative proteomics resulted in 568 differentially-expressed proteins in AD. These proteins were consistent with the literature and included glial fibrillary acidic protein, peroxiredoxin-1, and annexin A5. In addition, 351 novel proteins in AD were identified, which could partially be due to cohort diversity. From linear regression analyses, we identified 185 proteins with significant race x diagnosis interactions across various brain regions. These differences generally were reflective of differential expression of proteins in AD that occurred in only a single racial/ethnic group. Overall, this pilot study suggests that disease understanding can be furthered by including diversity in racial/ethnic groups; however, this must be done on a larger scale.

Carotid artery wave intensity in mid- to late-life predicts cognitive decline: the Whitehall II study

AIMS

Excessive arterial pulsatility may contribute to cognitive decline and risk of dementia via damage to the fragile cerebral microcirculation. We hypothesized that the intensity of downstream-travelling pulsatile waves measured by wave intensity analysis in the common carotid artery during mid- to late-life would be associated with subsequent cognitive decline.

METHODS AND RESULTS

Duplex Doppler ultrasound was used to calculate peak forward-travelling compression wave intensity (FCWI) within the common carotid artery in 3191 individuals [mean ± standard deviation (SD), age = 61 ± 6 years; 75% male] assessed as part of the Whitehall II study in 2003-05. Serial measures of cognitive function were taken between 2002-04 and 2015-16. The relationship between FCWI and cognitive decline was adjusted for sociodemographic variables, genetic and health-related risk factors, and health behaviours. Mean (SD) 10-year change in standardized global cognitive score was -0.39 (0.18). Higher FCWI at baseline was associated with accelerated cognitive decline during follow-up [difference in 10-year change of global cognitive score per 1 SD higher FCWI = -0.02 (95% confidence interval -0.04 to -0.00); P = 0.03]. This association was largely driven by cognitive changes in individuals with the highest FCWI [Q4 vs. Q1-Q3 = -0.05 (-0.09 to -0.01), P = 0.01], equivalent to an age effect of 1.9 years. Compared to other participants, this group was ∼50% more likely to exhibit cognitive decline (defined as the top 15% most rapid reductions in cognitive function during follow-up) even after adjustments for multiple potential confounding factors [odds ratio 1.49 (1.17-1.88)].

CONCLUSION

Elevated carotid artery wave intensity in mid- to late-life predicts faster cognitive decline in long-term follow-up independent of other cardiovascular risk factors.

Association Between Migraine Headaches and Dementia in More than 7,400 Patients Followed in General Practices in the United Kingdom

BACKGROUND

Most previous studies focusing on the migraine headache-dementia relationship have failed to simultaneously adjust for several common comorbidities.

OBJECTIVE

The goal of this retrospective cohort study was to investigate the association between migraine headaches and dementia in general practices in the UK.

METHODS

The current study sample included patients who received a migraine diagnosis in one of 67 general practices in the UK between January 1997 and December 2016 (index date). Patients without migraine diagnoses were matched 1 : 1 to patients with migraine diagnoses based on propensity scores using a greedy algorithm and derived from the logistic regression using age, sex, index year, and co-diagnoses. The main outcome of the study was the association between migraine headaches and the incidence of dementia within 10 years of the index date.

RESULTS

This study included 7,454 individuals with or without migraine diagnoses. Mean age was 67.7 years (SD = 5.8 years), and 72.9% of patients were women. Within 10 years of the index date, 5.2% of participants with and 3.7% of those without migraine headaches were diagnosed with dementia (log-rank p < 0.001). The respective figures were 5.8% and 3.6% in women (log-rank p < 0.001) and 4.5% and 3.4% in men (log-rank p = 0.722). We observed a positive association between migraine diagnoses and all-cause dementia (hazard ratio [HR] = 1.43) as well as Alzheimer's disease (HR = 1.87). Sensitivity analyses further revealed that these associations were only significant in women (all-cause dementia: HR = 1.65; Alzheimer's disease: HR = 2.27).

CONCLUSION

Migraine diagnoses were positively associated with all-cause dementia and Alzheimer's disease in women.

Abnormal lipid metabolism induced apoptosis of spermatogenic cells by increasing testicular HSP60 protein expression

Long-term consumption of high-fat and high-calorie foods not only causes obesity, but also may cause a decline in sperm quality in men. Rats with abnormal lipid metabolism (high-fat rats) were established by high-fat diet for 24 weeks. HE staining was used to observe the morphological changes of testis in rats, TUNEL and flow cytometer was used to detect the cell apoptosis in rat testis and in vitro. Immunohistochemistry and Western blotting were used to detect the expression of protein. After 24 weeks of high-fat food feeding, the body weight, serum lipids and number of apoptotic spermatogenic cells in the high-fat group rat were significantly higher than those in the control group. In vivo, the expression of HSP60 protein in testis of high-fat rats was positive related to apoptosis of spermatogenic cells, cleaved caspase 3/caspase 3 protein expression and Bax/Bcl2 protein expression in testis of high-fat rats. Proportion of apoptotic spermatogenic cells was increased by up-regulation of HSP60 protein expression in vitro. Long-term consumption of high-fat diets can cause high expression of HSP60 and spermatogenic cells apoptosis in rats, while HSP60 over-expression promotes spermatogenic cell apoptosis and MAPK signal pathway in vitro.

Lipid lowering and Alzheimer disease risk: A mendelian randomization study

Objective

To examine whether genetic variation affecting the expression or function of lipid‐lowering drug targets is associated with Alzheimer disease (AD) risk, to evaluate the potential impact of long‐term exposure to corresponding therapeutics.

Methods

We conducted Mendelian randomization analyses using variants in genes that encode the protein targets of several approved lipid‐lowering drug classes: HMGCR (encoding the target for statins), PCSK9 (encoding the target for PCSK9 inhibitors, eg, evolocumab and alirocumab), NPC1L1 (encoding the target for ezetimibe), and APOB (encoding the target of mipomersen). Variants were weighted by associations with low‐density lipoprotein cholesterol (LDL‐C) using data from lipid genetics consortia (n up to 295,826). We meta‐analyzed Mendelian randomization estimates for regional variants weighted by LDL‐C on AD risk from 2 large samples (total n = 24,718 cases, 56,685 controls).

Results

Models for HMGCR, APOB, and NPC1L1 did not suggest that the use of related lipid‐lowering drug classes would affect AD risk. In contrast, genetically instrumented exposure to PCSK9 inhibitors was predicted to increase AD risk in both of the AD samples (combined odds ratio per standard deviation lower LDL‐C inducible by the drug target = 1.45, 95% confidence interval = 1.23–1.69). This risk increase was opposite to, although more modest than, the degree of protection from coronary artery disease predicted by these same methods for PCSK9 inhibition.

Interpretation

We did not identify genetic support for the repurposing of statins, ezetimibe, or mipomersen for AD prevention. Notwithstanding caveats to this genetic evidence, pharmacovigilance for AD risk among users of PCSK9 inhibitors may be warranted. ANN NEUROL 2020;87:30–39

Peripheral clearance of brain-derived Aβ in Alzheimer's disease: pathophysiology and therapeutic perspectives

Alzheimer’s disease (AD) is the most common type of dementia, and no disease-modifying treatments are available to halt or slow its progression. Amyloid-beta (Aβ) is suggested to play a pivotal role in the pathogenesis of AD, and clearance of Aβ from the brain becomes a main therapeutic strategy for AD. Recent studies found that Aβ clearance in the periphery contributes substantially to reducing Aβ accumulation in the brain. Therefore, understanding the mechanism of how Aβ is cleared in the periphery is important for the development of effective therapies for AD. In this review, we summarized recent findings on the mechanisms of Aβ efflux from the brain to the periphery and discuss where and how the brain-derived Aβ is cleared in the periphery. Based on these findings, we propose future strategies to enhance peripheral Aβ clearance for the prevention and treatment of AD. This review provides a novel perspective to understand the pathogenesis of AD and develop interventions for this disease from a systemic approach.

Acidifying Endolysosomes Prevented Low-Density Lipoprotein-Induced Amyloidogenesis

Cholesterol dyshomeostasis has been linked to the pathogenesis of sporadic Alzheimer's disease (AD). In furthering the understanding of mechanisms by which increased levels of circulating cholesterol augments the risk of developing sporadic AD, others and we have reported that low-density lipoprotein (LDL) enters brain parenchyma by disrupting the blood-brain barrier and that endolysosome de-acidification plays a role in LDL-induced amyloidogenesis in neurons. Here, we tested the hypothesis that endolysosome de-acidification was central to amyloid-β (Aβ) generation and that acidifying endolysosomes protects against LDL-induced increases in Aβ levels in neurons. We demonstrated that LDL, but not HDL, de-acidified endolysosomes and increased intraneuronal and secreted levels of Aβ. ML-SA1, an agonist of endolysosome-resident TRPML1 channels, acidified endolysosomes, and TRPML1 knockdown attenuated ML-SA1-induced endolysosome acidification. ML-SA1 blocked LDL-induced increases in intraneuronal and secreted levels of Aβ as well as Aβ accumulation in endolysosomes, prevented BACE1 accumulation in endolysosomes, and decreased BACE1 activity levels. LDL downregulated TRPML1 protein levels, and TRPML1 knockdown worsens LDL-induced increases in Aβ. Our findings suggest that endolysosome acidification by activating TRPML1 may represent a protective strategy against sporadic AD.

Association of Hypercholesterolemia with Alzheimer's Disease Pathology and Cerebral Amyloid Angiopathy

BACKGROUND

Animal studies have shown that diet-induced hypercholesterolemia (HC) increases amyloid-β (Aβ) accumulation and accelerates Alzheimer's disease (AD) pathology. However, the association of HC with AD in human studies has not been consistently established.

OBJECTIVE

We aimed to investigate the relationship between HC and risk of AD neuropathology in a large national sample with autopsies.

METHODS

This study used neuropathological and clinical data from 3,508 subjects from the National Alzheimer's Coordinating Center (NACC) who underwent autopsies from 2005 to 2017. Demographic and clinical characteristics, as well as neuropathological outcomes were compared between subjects with and without HC. Associations between HC and AD neuropathology were examined by multivariate ordinal logistic regressions adjusting for potential confounders.

RESULTS

HC was not associated with any AD neuropathology in a model only adjusting for demographic variables. However, HC was significantly associated with higher CERAD neuritic and diffuse plaque burden, higher Braak stage, and more severe cerebral amyloid angiopathy when analyzed in a multivariate model controlling for comorbidities. Additional adjusting for cerebrovascular conditions did not diminish these associations. The association between HC and increased risk of neuritic plaques weakened but remained significant even after controlling for ApoE genotype.

CONCLUSION

This study suggested that HC was associated with increased severity of AD pathology, which could only be partially accounted for by ApoE genotype. The associations were not mediated by cerebrovascular conditions.

Metabolomics study to identify plasma biomarkers in alzheimer disease: ApoE genotype effect

Alzheimer Disease (AD) is the main cause of dementia, and it has a great social and economic impact worldwide. It is a complex multifactorial disease, and we still do not know enough about its causes. For this reason, omics studies could be a useful tool for the search for new biomarkers and for enhancing the knowledge of different metabolic pathways that may be altered in the initial stages of the disease. Metabolomic analysis was carried out for plasma samples from early AD patients and healthy controls. Obtained data were normalized and analyzed by volcano plot and supervised orthogonal-least-squares-discriminant analysis. Fifteen variables were selected as the most important variables for the groups' discrimination, and the different levels of 6 identified metabolites could discriminate between patients with different ApoE4 genotypes (ε4-carriers and non ε4-carriers). In conclusion, ApoE4 genotype is associated with changes in lipid metabolomics profile in AD patients, and it could be relevant for the development of AD since early stages.

APOE Gene polymorphism among Jordanian Alzheimer`s patients with relation to lipid profile

Objectives:

To investigate the frequencies of the apolipoprotein E (APOE) alleles and genotypes and study their relationship with the lipid profile in Jordanian patients with late-onset Alzheimer’s disease (AD).

Methods:

This case-control study was carried out on 71 Jordanian individuals: 38 patients with late-onset AD (age ≥65 years) and 33 age-matched healthy controls. All participants were recruited from senior homes and Jordan University Hospital, Amman, Jordan between January 2010 and December 2013. Each sample was examined for APOE’s 3 major isoforms (e2, e3, e4) using the polymerase chain reaction technique (PCR) followed by the sequencing technique. In addition, samples were screened for lipid profiles (total cholesterol (TC), high-density lipoprotein (HDL), lower-density lipoprotein (LDL), and triglyceride (TG) levels.

Results:

The e3/e4 genotype and e4 allele prevalence were higher in AD patients compared to healthy controls (26.3% vs. 3.0%, p=0.03 and 15.8% vs. 4.5%, p=0.03; respectively). In the AD group, the e2 carriers showed the lowest levels of total and LDL cholesterol, and the e4 carriers showed the highest levels of total and LDL cholesterol, although the difference was not statistically significant (p>0.05).

Conclusion:

APOE-e4 frequency was almost 4 times higher in the AD group compared to the control group, and this difference was statistically significant. A trend that was observed in the AD group regarding the lipid profile and e2 and e4 carriers requires further investigation using a larger sample size.

Association of plasma endothelial lipase levels on cognitive impairment

BACKGROUND

Peripheral high-density lipoprotein cholesterol (HDL-C) has been known to influx into the brain and be inversely associated with the risk of Alzheimer's disease (AD). However, recent prospective studies of the association between HDL-C and AD have yielded inconsistent results. Here, we examined the association between the endothelial lipase (EL), which is known to be major determinant of HDL-C levels, and cognitive function.

METHOD

We compared plasma from 20 patients with Alzheimer's disease (AD), 38 persons with mild cognitive impairment, and 51 cognitively normal controls. Plasma EL levels were measured using the enzyme-linked immunosorbent assay.

RESULTS

EL levels were inversely correlated with HDL-C, as previously reported; however, there were no mean differences in plasma EL between the diagnostic groups. An analysis by classification of dementia severity according to clinical dementia rating (CDR) showed that the EL levels were significantly higher in the CDR1 group (mild dementia), as compared to CDR0 (no dementia), CDR0.5 (very mild), and CDR2 (moderate) groups. Prior to moderate dementia stage, trends analysis showed that EL levels tended to increase with increasing severity (p for trend = 0.013). Consistently, elevated EL levels were significantly correlated with the mini-mental state examination (MMSE) score (r = - 0.29, p = 0.003). Logistic regression for association between plasma EL and cognitive impairment (MMSE score ≤ 25) showed that participants with EL levels in the upper range (> 31.6 ng/ml) have a higher adjusted odds ratio of cognitive impairment than those within the lower EL range.

CONCLUSION

Findings from the present study reflect the association of EL and cognition, suggesting that the individuals with elevated plasma EL concentration are at an increased risk of cognitive impairment.

Vascular Dysfunction in Alzheimer's Disease: A Prelude to the Pathological Process or a Consequence of It?

Alzheimer's disease (AD) is the most prevalent form of dementia. Despite decades of research following several theoretical and clinical lines, all existing treatments for the disorder are purely symptomatic. AD research has traditionally been focused on neuronal and glial dysfunction. Although there is a wealth of evidence pointing to a significant vascular component in the disease, this angle has been relatively poorly explored. In this review, we consider the various aspects of vascular dysfunction in AD, which has a significant impact on brain metabolism and homeostasis and the clearance of β-amyloid and other toxic metabolites. This may potentially precede the onset of the hallmark pathophysiological and cognitive symptoms of the disease. Pathological changes in vessel haemodynamics, angiogenesis, vascular cell function, vascular coverage, blood-brain barrier permeability and immune cell migration may be related to amyloid toxicity, oxidative stress and apolipoprotein E (APOE) genotype. These vascular deficits may in turn contribute to parenchymal amyloid deposition, neurotoxicity, glial activation and metabolic dysfunction in multiple cell types. A vicious feedback cycle ensues, with progressively worsening neuronal and vascular pathology through the course of the disease. Thus, a better appreciation for the importance of vascular dysfunction in AD may open new avenues for research and therapy.

Development of AD-Like Pathology in Skeletal Muscle

Effective therapeutic strategy against Alzheimer's disease (AD) requires early detection of AD; however, clinical diagnosis of Alzheimer's disease (AD) is not precise and a definitive diagnosis of AD is only possible via postmortem examination for AD pathological hallmarks including senile plaques composed of Aβ and neuro fibrillary tangles composed of phosphorylated tau. Although a variety of biomarker has been developed and used in clinical setting, none of them robustly predicts subsequent clinical course of AD. Thus, it is essential to identify new biomarkers that may facilitate the diagnosis of early stages of AD, prediction of subsequent clinical course, and development of new therapeutic strategies. Given that pathological hallmarks of AD including Aβaccumulation and the presence of phosphorylated tau are also detected in peripheral tissues, AD is considered a systemic disease. Without the protection of blood-brain barrier, systemic factors can affect peripheral tissues much earlier than neurons in brain. Here, we will discuss the development of AD-like pathology in skeletal muscle and the potential use of skeletal muscle biopsy (examination for Aβaccumulation and phosphorylated tau) as a biomarker for AD.

Prediction of Alzheimer's disease with serum lipid levels in Asian individuals: a meta-analysis

Background: The serum lipid profile has become a routine clinical test and used as an important predictor for Alzheimer's disease (AD), although its predictive value remains undetermined. Objective: To evaluate the role of serum lipid levels in predicting the risk of AD. Methods: Meta-analyses were conducted using Comprehensive Meta-analyses (CMA) software to investigate the association between four conventional serum lipid profile parameters and the risk of AD, focused on samples from Asian. Results: In total, 3423 AD patients and 6127 healthy participants were involved. The results demonstrated that AD patients showed higher LDL-C and TC levels (SMD = 0.27, 95% CI: 0.04-0.51, p = 0.02 for LDL-C; SMD = 0.25, 95% CI: 0.05-0.46, p = 0.02 for TC) compared with those of healthy controls. People with higher LDL-C and/or TC levels had an increased risk of AD (OR = 1.64, 95% CI: 1.07-2.51 for LDL-C and OR = 1.58, 95% CI: 1.10-2.92 for TC). Conclusions: This study provided evidence that serum LDL-C and TC levels were associated with the risk of AD in Asian individuals. The routine lipid profile may be useful for AD diagnosis, monitoring and treatment.

CAIDE Dementia Risk Score, Alzheimer and cerebrovascular pathology: a population-based autopsy study

BACKGROUND

CAIDE Dementia Risk Score is a tool for estimating dementia risk in the general population. Its longitudinal associations with Alzheimer or vascular neuropathology in the oldest old are not known.

AIM

To explore the relationship between CAIDE Dementia Risk Score at baseline and neuritic plaques, neurofibrillary tangles, cerebral infarcts and cerebral amyloid angiopathy (CAA) after up to 10-year follow-up in the Vantaa 85 +  population.

METHODS

Study population included 149 participants aged ≥85 years, without dementia at baseline, and with available clinical and autopsy data. Methenamine silver staining was used for β-amyloid and modified Bielschowsky method for neurofibrillary tangles and neuritic plaques. Macroscopic infarcts were identified from cerebral hemispheres, brainstem and cerebellum slices. Standardized methods were used to determine microscopic infarcts, CAA and α-synuclein pathologies. The CAIDE Dementia Risk Score was calculated based on scores for age, sex, BMI, total cholesterol, systolic blood pressure, physical activity and APOEε4 carrier status (range 0-18 points).

RESULTS

A CAIDE Dementia Risk Score above 11 points was associated with more cerebral infarctions up to 10 years later: OR (95% CI) was 2.10 (1.06-4.16). No associations were found with other neuropathologies.

CONCLUSION

In a population of elderly aged ≥85 years, higher CAIDE Dementia Risk Score was associated with increased risk of cerebral infarcts.

The assessment of serum lipid profiles of children with attention deficit hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders in children and the pathophysiology remains obscure. Some studies show that lipid imbalances are associated with ADHD etiology. We studied the association of serum total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglyceride (TG) levels in ADHD. We examined 88 children aged 8-12 years who were diagnosed with ADHD and 88 healthy children. The exclusion criteria were as follows: obesity, any psychotropic use in the last 3 months, presence of a chronic disease and/or malignancy, history of medically treated lipid metabolism disease in family members, intelligence quotient (IQ) < 70, and comorbidities, with the exception of oppositional defiant disorder. The sample was evaluated using a semi-structured clinical assessment interview and Conners' rating scales. Despite controlling for age, sex, and body mass index (BMI) variables, the total cholesterol and LDL levels were significantly higher in the ADHD group than the levels of healthy controls, whereas the TG and HDL cholesterol levels were similar among groups. Conners' rating scales, reflecting symptom severity, and total cholesterol, TG, HDL, and LDL levels of the ADHD group were not correlated. The study results support the difference in serum lipid and lipoprotein profiles of children with ADHD compared with healthy controls. This difference is thought to be related with changes in oxidant/antioxidant balance states in ADHD.

Brain APOE expression quantitative trait loci-based association study identified one susceptibility locus for Alzheimer's disease by interacting with APOE ε4

Some studies have demonstrated interactions of AD-risk single nucleotide polymorphisms (SNPs) in non-APOE regions with APOE genotype. Nevertheless, no study reported interactions of expression quantitative trait locus (eQTL) for APOE with APOE genotype. In present study, we included 9286 unrelated AD patients and 8479 normal controls from 12 cohorts of NIA Genetics of Alzheimer’s Disease Data Storage Site (NIAGADS) and Alzheimer’s Disease Neuroimaging Initiative (ADNI). 34 unrelated brain eQTLs for APOE were compiled from BRAINEAC and GTEx. We used multi-covariate logistic regression analysis to identify eQTLs interacted with APOE ε4. Adjusted for age and gender, substantia nigra eQTL rs438811 for APOE showed significantly strong interaction with APOE ε4 status (OR, 1.448; CI, 1.124–1.430; P-value = 7.94 × 10⁻⁶). APOE ε4-based sub-group analyses revealed that carrying one minor allele T of rs438811 can increase the opportunity of developing to AD by 26.75% in APOE ε4 carriers but not in non-carriers. We revealed substantia nigra eQTL rs438811 for APOE can interact with APOE ε4 and confers risk in APOE ε4 carriers only.

Association between Cholesterol Exposure and Neuropathological Findings: The ACT Study

We characterized the relationship between late life cholesterol exposure and neuropathological outcomes in a community-based, older adult cohort. Adult Changes in Thought (ACT) is a cohort study that enrolls consenting, randomly selected, non-demented people aged ≥65 from a healthcare delivery system. We used late life HDL and total cholesterol lab values from Group Health computerized records, and calculated HDL and non-HDL levels. We evaluated neuropathological outcomes of Alzheimer's disease, cerebral amyloid angiopathy, vascular brain injury, and Lewy body disease. Using linear mixed models with age and antilipemic medication as predictors, we obtained predicted cholesterol values at age 70 and 10 years prior to death for individuals with available cholesterol data in 10-year exposure windows. We used logistic regression to determine whether predicted late life cholesterol levels were associated with neuropathological outcomes controlling for age at death, APOE genotype, sex, and their interactions with cholesterol levels. 525 decedents came to autopsy by 08/2014. Of these, plasma cholesterol concentration was available for 318 (age 70, model 1) and 396 (10 years prior to death, model 2) participants. We did not find associations between late life cholesterol and Alzheimer's disease neuropathological changes, and there were no associations between cholesterol levels and amyloid angiopathy or vascular brain injury. We observed an association between predicted non-HDL cholesterol at age 70 and Lewy body disease. Our study suggests an association between late life non-HDL cholesterol exposure and Lewy body disease. We did not observe associations between late life cholesterol levels and Braak stage or CERAD score.

Dysregulated bile acid synthesis and dysbiosis are implicated in Western diet-induced systemic inflammation, microglial activation, and reduced neuroplasticity

The goal of this study was to identify the intrinsic links that explain the effect of a Western diet (WD) on cognitive dysfunction. Specific pathogen-free, wild-type mice were fed either a control diet (CD) or a high-fat, high-sucrose WD after weaning and were euthanized at 10 mo of age to study the pathways that affect cognitive health. The results showed that long-term WD intake reduced hippocampal synaptic plasticity and the level of brain-derived neurotrophic factor mRNA in the brain and isolated microglia. A WD also activated ERK1/2 and reduced postsynaptic density-95 in the brain, suggesting postsynaptic damage. Moreover, WD-fed mice had increased inflammatory signaling in the brain, ileum, liver, adipose tissue, and spleen, which was accompanied by microglia activation. In the brain, as well as in the digestive tract, a WD reduced signaling regulated by retinoic acid and bile acids (BAs), whose receptors form heterodimers to control metabolism and inflammation. Furthermore, a WD intake caused dysbiosis and dysregulated BA synthesis with reduced endogenous ligands for BA receptors, i.e., farnesoid X receptor and G-protein-coupled bile acid receptor in the liver and brain. Together, dysregulated BA synthesis and dysbiosis were accompanied by systemic inflammation, microglial activation, and reduced neuroplasticity induced by WD.-Jena, P. K., Sheng, L., Di Lucente, J., Jin, L.-W., Maezawa, I., Wan, Y.-J. Y. Dysregulated bile acid synthesis and dysbiosis are implicated in Western diet-induced systemic inflammation, microglial activation, and reduced neuroplasticity.

Increased midlife triglycerides predict brain β-amyloid and tau pathology 20 years later

OBJECTIVE

To evaluate the effect of midlife lipid levels on Alzheimer brain pathology 20 years later in cognitively normal elderly individuals.

METHODS

This is a longitudinal cohort study of 318 cognitively normal individuals with data on fasting lipid levels at midlife (mean age 54 years). Presence of β-amyloid (Aβ) and tau pathologies 20 years later (mean age 73 years) were detected by quantifying Alzheimer disease (AD) biomarkers in CSF. In a subset (n = 134), Aβ (¹⁸F-flutemetamol) PET was also performed.

RESULTS

CSF Aβ₄₂ and Aβ PET revealed Aβ pathology in approximately 20% of the cognitively healthy population and CSF Aβ₄₂/phosphorylated tau (p-tau) ratio indicated both Aβ and tau pathology in 16%. Higher levels of triglycerides in midlife were independently associated with abnormal CSF Aβ₄₂ (odds ratio [OR] 1.34, 95% confidence interval [CI] 1.03-1.75, p = 0.029) and abnormal Aβ₄₂/p-tau ratio (OR 1.46, 95% CI 1.10-1.93; p = 0.009) adjusting for age, sex, APOE ε4, education, and multiple vascular risk factors. Triglycerides were also associated with abnormal Aβ PET in multivariable regression models, but the association was attenuated in the fully adjusted model. Increased levels of medium and large low-density lipoprotein subfractions were significantly associated with abnormal Aβ PET and large high-density lipoprotein particles were associated with decreased risk of abnormal Aβ PET.

CONCLUSIONS

Increased levels of triglycerides at midlife predict brain Aβ and tau pathology 20 years later in cognitively healthy individuals. Certain lipoprotein subfractions may also be risk factors for Aβ pathology. These findings further support an involvement of lipids in the very early stages of AD development.

APP Function and Lipids: A Bidirectional Link

Extracellular neuritic plaques, composed of aggregated amyloid-β (Aβ) peptides, are one of the major histopathological hallmarks of Alzheimer's disease (AD), a progressive, irreversible neurodegenerative disorder and the most common cause of dementia in the elderly. One of the most prominent risk factor for sporadic AD, carrying one or two aberrant copies of the apolipoprotein E (ApoE) ε4 alleles, closely links AD to lipids. Further, several lipid classes and fatty acids have been reported to be changed in the brain of AD-affected individuals. Interestingly, the observed lipid changes in the brain seem not only to be a consequence of the disease but also modulate Aβ generation. In line with these observations, protective lipids being able to decrease Aβ generation and also potential negative lipids in respect to AD were identified. Mechanistically, Aβ peptides are generated by sequential proteolytic processing of the amyloid precursor protein (APP) by β- and γ-secretase. The α-secretase appears to compete with β-secretase for the initial cleavage of APP, preventing Aβ production. All APP-cleaving secretases as well as APP are transmembrane proteins, further illustrating the impact of lipids on Aβ generation. Beside the pathological impact of Aβ, accumulating evidence suggests that Aβ and the APP intracellular domain (AICD) play an important role in regulating lipid homeostasis, either by direct effects or by affecting gene expression or protein stability of enzymes involved in the de novo synthesis of different lipid classes. This review summarizes the current literature addressing the complex bidirectional link between lipids and AD and APP processing including lipid alterations found in AD post mortem brains, lipids that alter APP processing and the physiological functions of Aβ and AICD in the regulation of several lipid metabolism pathways.

Association of adipocyte enhancer-binding protein 1 with Alzheimer's disease pathology in human hippocampi

Adipocyte enhancer binding protein 1 (AEBP1) activates inflammatory responses via the NF-κB pathway in macrophages and regulates adipogenesis in preadipocytes. Up-regulation of AEBP1 in the hippocampi of patients with Alzheimer's disease (AD) has been revealed by microarray analyses of autopsied brains from the Japanese general population (the Hisayama study). In this study, we compared the expression patterns of AEBP1 in normal and AD brains, including in the hippocampus, using immunohistochemistry. The subjects were 24 AD cases and 52 non-AD cases. Brain specimens were immunostained with antibodies against AEBP1, tau protein, amyloid β protein, NF-κB, GFAP and Iba-1. In normal brains, AEBP1 immunoreactivity mainly localized to the perikarya of hippocampal pyramidal neurons, and its expression was elevated in the pyramidal neurons and some astrocytes in AD hippocampi. Although AEBP1 immunoreactivity was almost absent in neurons containing neurofibrillary tangles, AEBP1 was highly expressed in neurons with pretangles and in the tau-immunopositive, dystrophic neurites of senile plaques. Nuclear localization of NF-κB was also observed in certain AEBP1-positive neurons in AD cases. Comparison of AD and non-AD cases suggested a positive correlation between the expression level of AEBP1 and the degree of amyloid β pathology. These findings imply that AEBP1 protein has a role in the progression of AD pathology.

Current Research Therapeutic Strategies for Alzheimer's Disease Treatment

Alzheimer's disease (AD) currently presents one of the biggest healthcare issues in the developed countries. There is no effective treatment capable of slowing down disease progression. In recent years the main focus of research on novel pharmacotherapies was based on the amyloidogenic hypothesis of AD, which posits that the beta amyloid (Aβ) peptide is chiefly responsible for cognitive impairment and neuronal death. The goal of such treatments is (a) to reduce Aβ production through the inhibition of β and γ secretase enzymes and (b) to promote dissolution of existing cerebral Aβ plaques. However, this approach has proven to be only modestly effective. Recent studies suggest an alternative strategy centred on the inhibition of the downstream Aβ signalling, particularly at the synapse. Aβ oligomers may cause aberrant N-methyl-D-aspartate receptor (NMDAR) activation postsynaptically by forming complexes with the cell-surface prion protein (PrPC). PrPC is enriched at the neuronal postsynaptic density, where it interacts with Fyn tyrosine kinase. Fyn activation occurs when Aβ is bound to PrPC-Fyn complex. Fyn causes tyrosine phosphorylation of the NR2B subunit of metabotropic glutamate receptor 5 (mGluR5). Fyn kinase blockers masitinib and saracatinib have proven to be efficacious in treating AD symptoms in experimental mouse models of the disease.

Polygenic Overlap Between C-Reactive Protein, Plasma Lipids, and Alzheimer Disease

BACKGROUND

Epidemiological findings suggest a relationship between Alzheimer disease (AD), inflammation, and dyslipidemia, although the nature of this relationship is not well understood. We investigated whether this phenotypic association arises from a shared genetic basis.

METHODS AND RESULTS

Using summary statistics (P values and odds ratios) from genome-wide association studies of >200 000 individuals, we investigated overlap in single-nucleotide polymorphisms associated with clinically diagnosed AD and C-reactive protein (CRP), triglycerides, and high- and low-density lipoprotein levels. We found up to 50-fold enrichment of AD single-nucleotide polymorphisms for different levels of association with C-reactive protein, low-density lipoprotein, high-density lipoprotein, and triglyceride single-nucleotide polymorphisms using a false discovery rate threshold <0.05. By conditioning on polymorphisms associated with the 4 phenotypes, we identified 55 loci associated with increased AD risk. We then conducted a meta-analysis of these 55 variants across 4 independent AD cohorts (total: n=29 054 AD cases and 114 824 healthy controls) and discovered 2 genome-wide significant variants on chromosome 4 (rs13113697; closest gene, HS3ST1; odds ratio=1.07; 95% confidence interval=1.05-1.11; P=2.86×10(-8)) and chromosome 10 (rs7920721; closest gene, ECHDC3; odds ratio=1.07; 95% confidence interval=1.04-1.11; P=3.38×10(-8)). We also found that gene expression of HS3ST1 and ECHDC3 was altered in AD brains compared with control brains.

CONCLUSIONS

We demonstrate genetic overlap between AD, C-reactive protein, and plasma lipids. By conditioning on the genetic association with the cardiovascular phenotypes, we identify novel AD susceptibility loci, including 2 genome-wide significant variants conferring increased risk for AD.

The role of dietary coconut for the prevention and treatment of Alzheimer's disease: potential mechanisms of action

Coconut, Cocos nucifera L., is a tree that is cultivated to provide a large number of products, although it is mainly grown for its nutritional and medicinal values. Coconut oil, derived from the coconut fruit, has been recognised historically as containing high levels of saturated fat; however, closer scrutiny suggests that coconut should be regarded more favourably. Unlike most other dietary fats that are high in long-chain fatty acids, coconut oil comprises medium-chain fatty acids (MCFA). MCFA are unique in that they are easily absorbed and metabolised by the liver, and can be converted to ketones. Ketone bodies are an important alternative energy source in the brain, and may be beneficial to people developing or already with memory impairment, as in Alzheimer's disease (AD). Coconut is classified as a highly nutritious 'functional food'. It is rich in dietary fibre, vitamins and minerals; however, notably, evidence is mounting to support the concept that coconut may be beneficial in the treatment of obesity, dyslipidaemia, elevated LDL, insulin resistance and hypertension - these are the risk factors for CVD and type 2 diabetes, and also for AD. In addition, phenolic compounds and hormones (cytokinins) found in coconut may assist in preventing the aggregation of amyloid-β peptide, potentially inhibiting a key step in the pathogenesis of AD. The purpose of the present review was to explore the literature related to coconut, outlining the known mechanistic physiology, and to discuss the potential role of coconut supplementation as a therapeutic option in the prevention and management of AD.

Cholesterol, statins, and dementia: what the cardiologist should know

Alzheimer dementia (AD) is an important clinical problem that appears to be closely tied to comorbid cardiovascular disease, making it a relevant topic for the clinical cardiologist. Determinants of cardiovascular health, especially midlife dyslipidemia, are associated with an increased risk of dementia based on molecular and epidemiologic data. Given the potential role of dyslipidemia in the development of dementia, statins have been investigated as potential therapeutic options to slow or prevent disease. This review discusses the role of dyslipidemia and other cardiovascular risk factors in the pathogenesis of AD, with a focus on the existing evidence for the use of statin medications in the treatment and prevention of AD from observational studies and randomized clinical trials. Clinical questions for the practicing cardiologist are addressed.