Young apoE Research Articles

Differences in Grey Matter Concentrations and Functional Connectivity between Young Carriers and Non-Carriers of the APOE ε4 Genotype.

Background: The pathophysiology of Alzheimer's disease (AD) may begin developing years or even decades prior to the manifestation of its first symptoms. The APOE ε4 genotype is a prominent genetic risk for AD that has been found to be associated with brain changes across the lifespan since early adulthood. Thus, studying brain changes that may occur in young adults with an APOE ε4 status is highly relevant. Objective: Examine potential differences in grey matter (GM) and functional connectivity (FC) in brains of cognitively healthy young APOE ε4 carriers and non-carriers, denoted here as ε4(+) and ε4(-), respectively. Methods: Three Tesla magnetic resonance imaging (MRI) brain scans were acquired from cognitively healthy young participants aged approximately 20 years (n = 151). Voxel-based morphometry (VBM) analysis was employed to identify potential structural differences in GM between ε4(+) and ε4(-). In a subsequent seed-based connectivity (SBC) analysis, brain regions that structurally differed in the VBM analysis were considered as seeds and correlated with all the remaining voxels across the brains to then measure the differences in FC between groups. Results: The VBM analysis suggested that ε4(+) (n = 28) had greater GM densities relative to ε4(-) (n = 123) in the left hippocampus and the left posterior insula (puncorr < 0.001). However, the effect did not survive the correction for multiple comparisons, suggesting minimal structural differences in this age range. In contrast, the SBC analysis indicated that ε4(+) exhibited significantly decreased FC between the left hippocampus and areas of the left middle temporal gyrus (n = 27) compared to ε4(-) (n = 102). These results remained significant after multiple comparisons (pFDR < 0.05). Lastly, no statistically significant differences in FC between groups were observed for the left insular seed (pFDR > 0.05). Discussion: These results suggest early structural and functional brain changes associated with the APOE ε4 genotype on young adults. Yet, they must be cautiously interpreted and contrasted with both older adults with genetic risk for AD and patients diagnosed with AD.

Brain reserve in midlife is associated with executive function changes across 12 years

We examined how brain reserve in midlife, measured by brain-predicted age difference scores (Brain-PADs), predicted executive function concurrently and longitudinally into early old age, and whether these associations were moderated by young adult cognitive reserve or APOE genotype. 508 men in the Vietnam Era Twin Study of Aging (VETSA) completed neuroimaging assessments at mean age 56 and six executive function tasks at mean ages 56, 62, and 68 years. Results indicated that greater brain reserve at age 56 was associated with better concurrent executive function (r=.10, p=.040) and less decline in executive function over 12 years (r=.34, p=.001). These associations were not moderated by cognitive reserve or APOE genotype. Twin analysis suggested associations with executive function slopes were driven by genetic influences. Our findings suggest that greater brain reserve allowed for better cognitive maintenance from middle- to old age, driven by a genetic association. The results are consistent with differential preservation of executive function based on brain reserve that is independent of young adult cognitive reserve or APOE genotype.

Effects of Empagliflozin on Vascular and Skeletal Mineralization in Hyperlipidemic Mice

Cardiovascular disease and osteoporosis, major causes of morbidity and mortality, are associated with hyperlipidemia. Recent studies show that empagliflozin (EMPA), an inhibitor of sodium-glucose cotransporter-2 (SGLT2), improves cardiovascular health. In preclinical animal studies, EMPA mitigates vascular calcification in the males but its effects in the females are not known. Thus, we used female mice to test the effects of EMPA on calcification in the artery wall, cardiac function, and skeletal bone. By serial in vivo microCT imaging, we followed the progression of aortic calcification and bone mineral density in young and older female Apoe−/− mice fed a high-fat diet with or without EMPA. The two different age groups were used to compare early vs. advanced stages of aortic calcification. Results show that EMPA treatment increased urine glucose levels. Aortic calcium content increased in both the controls and the EMPA-treated mice, and EMPA did not affect progression of aortic calcium content in both young and older mice. However, 3-D segmentation analysis of aortic calcium deposits on microCT images revealed that EMPA-treated mice had significantly less surface area and volume of calcified deposits as well as fewer numbers of deposits than the control mice. To test for direct effects on vascular cell calcification, we treated murine aortic smooth muscle cells with EMPA, and results showed a slight inhibition of alkaline phosphatase activity and inflammatory matrix calcification. As for skeletal bone, EMPA-treated mice had significantly lower BMD than the controls in both the lumbar vertebrae and femoral bones in both young and older mice. The findings suggest that, in hyperlipidemic female mice, unlike males, SGLT2 inhibition with empagliflozin does not mitigate progression of aortic calcification and may even lower skeletal bone density.

The proatherosclerotic function of BCAT1 in atherosclerosis development of aged-apolipoprotein E-deficient mice

Atherosclerosis (AS) is an inflammatory vascular disease. Branched-chain amino acid transaminase 1 (BCAT1) has been implicated in inflammatory diseases, while its role in AS is unclear yet. In ApoE−/− mice with a high fat diet (HDF), BCAT1 was highly up-regulated and more pronounced in aged than in young ApoE−/− mice, which was abundantly expressed in macrophages located in AS lesions. The function of BCAT1 in AS was explored using lentivirus-mediated BCAT1 overexpression. ApoE−/− mice fed a HFD with BCAT1 overexpression exhibited the worsening lipid deposition and pathological injury of aortic tissues, accompanied by aggravated hyperlipidemia as proved by increased serum triglyceride, total cholesterol, and low-density lipoprotein-cholesterol levels. Immunohistochemical staining of vascular cell adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1), and CD68 in the aortic root plaque suggested that BCAT1 overexpression could induce monocyte-endothelial cell adhesion and macrophages infiltration, thereby contributing inflammatory response by promoting TNF-α, IL-6, and IL-1β expression. Further, in vivo experiments, lipid accumulation, and inflammatory response induced by oxidized-LDL in RAW267.4 cells were also intensified or alleviated by BCAT1 overexpression or knockdown. Finally, BCAT1 overexpression aggravated AS development. These adverse effects of BCAT1 on hyperlipidemia, lipid accumulation, foaming cell formation, and inflammation suggested that the modulation of BCAT1 might be a potential approach to prevent AS disease.

Astrocyte calcium dysfunction causes early network hyperactivity in Alzheimer's disease.

SummaryDysfunctions of network activity and functional connectivity (FC) represent early events in Alzheimer’s disease (AD), but the underlying mechanisms remain unclear. Astrocytes regulate local neuronal activity in the healthy brain, but their involvement in early network hyperactivity in AD is unknown. We show increased FC in the human cingulate cortex several years before amyloid deposition. We find the same early cingulate FC disruption and neuronal hyperactivity in AppNL-F mice. Crucially, these network disruptions are accompanied by decreased astrocyte calcium signaling. Recovery of astrocytic calcium activity normalizes neuronal hyperactivity and FC, as well as seizure susceptibility and day/night behavioral disruptions. In conclusion, we show that astrocytes mediate initial features of AD and drive clinically relevant phenotypes.

Varying Dietary Component Ratios and Lingonberry Supplementation May Affect the Hippocampal Structure of ApoE-/- Mice.

ObjectiveThis study aimed to investigate and compare the morphological and biochemical characteristics of the hippocampus and the spatial memory of young adult ApoE–/– mice on a standard chow diet, a low-fat diet (LFD), a high-fat diet (HFD), and an HFD supplemented with lingonberries.MethodsEight-week-old ApoE–/– males were divided into five groups fed standard chow (Control), an LFD (LF), an HFD (HF), and an HFD supplemented with whole lingonberries (HF+WhLB) or the insoluble fraction of lingonberries (HF+InsLB) for 8 weeks. The hippocampal cellular structure was evaluated using light microscopy and immunohistochemistry; biochemical analysis and T-maze test were also performed. Structural synaptic plasticity was assessed using electron microscopy.ResultsApoE–/– mice fed an LFD expressed a reduction in the number of intact CA1 pyramidal neurons compared with HF+InsLB animals and the 1.6–3.8-fold higher density of hyperchromic (damaged) hippocampal neurons relative to other groups. The LF group had also morphological and biochemical indications of astrogliosis. Meanwhile, both LFD- and HFD-fed mice demonstrated moderate microglial activation and a decline in synaptic density. The consumption of lingonberry supplements significantly reduced the microglia cell area, elevated the total number of synapses and multiple synapses, and increased postsynaptic density length in the hippocampus of ApoE–/– mice, as compared to an LFD and an HFD without lingonberries.ConclusionOur results suggest that, in contrast to the inclusion of fats in a diet, increased starch amount (an LFD) and reduction of dietary fiber (an LFD/HFD) might be unfavorable for the hippocampal structure of young adult (16-week-old) male ApoE–/– mice. Lingonberries and their insoluble fraction seem to provide a neuroprotective effect on altered synaptic plasticity in ApoE–/– animals. Observed morphological changes in the hippocampus did not result in notable spatial memory decline.

Identification of the atherosclerosis phenotype in vivo by vascular duplex ultrasonography in ApoE-deficient dogs

Background and aimsThis study evaluated the atherosclerosis phenotype by vascular duplex ultrasonography (VDU) in ApoE-deficient dogs. MethodsA total of 108 beagle dogs were examined by VDU, which included 32 wild-type, 68 heterozygous (ApoE-/+) mutant and 8 homozygous (ApoE−/−) mutant dogs. According to age, wild-type and ApoE-/+ dogs were divided into two subgroups: young (6–15 months) and adult dogs (18–29 months). All homozygous dogs were young dogs. Dogs were feed with normal diet. The plasma lipid levels were tested. The diameter of the common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA), abdominal aorta and common iliac artery (CIA) and the intima-media thickness (IMT) of the CCA and abdominal aorta were measured by VDU. The artery sections of ApoE−/− and control dogs were analyzed by histological analysis. ResultsThe plasma triglycerides (2.5–3 fold), total cholesterol (4–5 fold) and LDL levels (35–40 fold) of ApoE−/− dogs were higher than those of the wild-type and ApoE-/+ dogs. Compared with the wild-type and young ApoE-/+ dogs, the IMT of CCA and aorta in ApoE−/− dogs were increased (p<0.05). The occurrence of atherosclerosis in ApoE−/− dogs was higher than that in ApoE-/+ dogs (50% vs. 10.3%, p=0.013) and the occurrence time was earlier. Histology confirmed that the aorta, carotid arteries and CIA had atherosclerotic lesions in ApoE−/− dogs. ConclusionsThe ApoE-deficient dogs were a reliable animal model of atherosclerosis. VDU is an optimal in vivo noninvasive method for evaluating atherosclerosis phenotypes in large animal models.

The influence of genetic predisposition for Alzheimer's disease on default mode network co‐activation in young adults: A Human Connectome Project replication study

AbstractBackgroundA landmark study by Filippini et al., where authors reported an increased default mode network (DMN) co‐activation during rest in young APOE ε4‐carriers, failed to replicate [1,2]. The rise of genome‐wide association studies (GWAS) in Alzheimer’s disease (AD) has shown there is a significant polygenic contribution of common genetic variants to AD, in addition to the larger effects of APOE variants. Therefore, in our replication study, we used polygenic risk scores (PRS) to better understand how polygenic variation may influence brain structure and function.MethodWe included participants with inferred European ancestry from the HCP S1200 dataset. We followed the methods of [1] for the resting‐state fMRI analysis. For structural MRI analysis, we assessed gray matter volume with FreeSurfer instead of gray matter density using voxel‐based morphometry. PRS allows data‐driven investigation of the aggregated effects of many common risk variants as determined in a large European GWAS [3]. We used the threshold determined as optimal for predicting AD status using PRS in Jansen et al., (P&lt;1.69x10‐5). Permutation Analysis of Linear Models (PALM) was used to test the association between PRS and both DMN co‐activation and gray matter volume. PALM controls for biases induced by the family structure of the HCP sample. Results were family‐wise error rate corrected at p &lt; 0.05.ResultThere was no significant association between DMN co‐activation and PRS (N=454). For the morphometric analyses (N=625), no association between gray matter volume and PRS was found. For both analyses, including covariates (different combinations of age, sex, education level, head motion) did not alter the results.ConclusionWe did not find evidence that genetic predisposition for AD, indicated by PRS, impacts DMN co‐activation in young adults. However, we may not be able to find any measurable effect decades before a clinical expression of AD. Repeating the analysis in an older cohort will inform us whether the influence of genetic predisposition for AD changes with age. 1) Filippini et al., PNAS, 2009. 2) Mentink et al., Default mode network co‐activation in young APOE ε4‐carriers: a Human Connectome Project replication study. AAIC 2020. 3) Jansen et al., Nature Genetics, 2019

Comparative lipid profiling of murine and human atherosclerotic plaques using high-resolution MALDI MSI

The distribution of atherosclerotic lesions in the aorta and its branches of ApoE knockout (ApoE−/−) mice is like that of patients with atherosclerosis. By using high-resolution MALDI mass spectrometry imaging (MSI), we aimed at characterizing universally applicable physiological biomarkers by comparing the murine lipid marker profile with that of human atherosclerotic arteries. Therefore, the aorta or carotid artery of male ApoE−/− mice at different ages, human arteries with documented atherosclerotic changes originated from amputated limbs, and corresponding controls were analysed. Obtained data were subjected to multivariate statistical analysis to identify potential biomarkers. Thirty-one m/z values corresponding to individual lipid species of cholesterol esters, lysophosphatidylcholines, lysophosphatidylethanolamines, and cholesterol derivatives were found to be specific in aortic atherosclerotic plaques of old ApoE−/− mice. The lipid composition at related vessel positions of young ApoE−/− mice was more comparable with wild-type mice. Twenty-six m/z values of the murine lipid markers were found in human atherosclerotic peripheral arteries but also control vessels and showed a more patient-dependent diverse distribution. Extensive data analysis without marker preselection based on mouse data revealed lysophosphatidylcholine and glucosylated cholesterol species, the latter not being detected in the murine atherosclerotic tissue, as specific potential novel human atherosclerotic vessel markers. Despite the heterogeneous lipid profile of atherosclerotic peripheral arteries derived from human patients, we identified lipids specifically colocalized to atherosclerotic human tissue and plaques in ApoE−/− mice. These data highlight species-dependent differences in lipid profiles between peripheral artery disease and aortic atherosclerosis.

A brain proteomic signature of incipient Alzheimer's disease in young APOE ε4 carriers identifies novel drug targets.

Aptamer-based proteomics revealed differentially abundant proteins in Alzheimer’s disease (AD) brains in the Baltimore Longitudinal Study of Aging and Religious Orders Study (mean age, 89 ± 9 years). A subset of these proteins was also differentially abundant in the brains of young APOE ε4 carriers relative to noncarriers (mean age, 39 ± 6 years). Several of these proteins represent targets of approved and experimental drugs for other indications and were validated using orthogonal methods in independent human brain tissue samples as well as in transgenic AD models. Using cell culture–based phenotypic assays, we showed that drugs targeting the cytokine transducer STAT3 and the Src family tyrosine kinases, YES1 and FYN, rescued molecular phenotypes relevant to AD pathogenesis. Our findings may accelerate the development of effective interventions targeting the earliest molecular triggers of AD.

Methylmercury chronic exposure affects the expression of DNA single-strand break repair genes, induces oxidative stress, and chromosomal abnormalities in young dyslipidemic APOE knockout mice

Mercury (Hg) is one of the most toxic environmental pollutants, especially when methylated, forming methylmercury (MeHg). MeHg affects DNA repair, increases oxidative stress, and predisposes to cancer. MeHg neurotoxicity is well-known, but recently MeHg-associated cardiovascular effects were recognized. This study evaluated circulating lipids, oxidative stress, and genotoxicity after MeHg-chronic exposure (20 mg/L in drinking water) in C57BL/6J wild-type and APOE knockout (ko) mice, the latter, being spontaneously dyslipidemic. Experimental mice were assigned to four groups: non-intoxicated and MeHg-intoxicated wild-type mice and non-intoxicated and MeHg-intoxicated APOE ko mice. Plasma levels of triglycerides, total cholesterol (TC), HDL, and LDL were analyzed. Liver lipid peroxidation and splenic gene expression of xeroderma pigmentosum complementation groups A, C, D, and G (XPA, XPC, XPD, and XPG), X-ray repair cross-complementing protein 1 (XRCC1), and telomerase reverse transcriptase (TERT) were measured. Fur Hg levels confirmed chronic MeHg intoxication. MeHg exposure raises TC levels both in wild-type and APOE ko mice. HDL and LDL-cholesterol levels were increased only in the MeHg-challenged APOE ko mice. MeHg increased liver lipid peroxidation, regardless of the genetic background. Unintoxicated APOE ko mice showed higher expression of TERT than all other groups. APOE deficiency increases XPA expression, regardless of MeHg intoxication. Furthermore, MeHg-intoxicated mice had more cytogenetic abnormalities, effect which was independent of APOE deficiency. More studies are needed to dissect the interactions between circulating lipids, MeHg intoxication, and DNA-repair pathways even at young age, interactions that likely play critical roles in cell senescence and the risk for chronic disorders later in life.

NEIL3-deficiency increases gut permeability and contributes to a pro-atherogenic metabolic phenotype

Atherosclerosis and its consequences cause considerable morbidity and mortality world-wide. We have previously shown that expression of the DNA glycosylase NEIL3 is regulated in human atherosclerotic plaques, and that NEIL3-deficiency enhances atherogenesis in Apoe−/− mice. Herein, we identified a time point prior to quantifiable differences in atherosclerosis between Apoe−/−Neil3−/− mice and Apoe−/− mice. Mice at this age were selected to explore the metabolic and pathophysiological processes preceding extensive atherogenesis in NEIL3-deficient mice. Untargeted metabolomic analysis of young Apoe−/−Neil3−/− mice revealed significant metabolic disturbances as compared to mice expressing NEIL3, particularly in metabolites dependent on the gut microbiota. 16S rRNA gene sequencing of fecal bacterial DNA indeed confirmed that the NEIL3-deficient mice had altered gut microbiota, as well as increased circulating levels of the bacterially derived molecule LPS. The mice were challenged with a FITC-conjugated dextran to explore gut permeability, which was significantly increased in the NEIL3-deficient mice. Further, immunohistochemistry showed increased levels of the proliferation marker Ki67 in the colonic epithelium of NEIL3-deficient mice, suggesting increased proliferation of intestinal cells and gut leakage. We suggest that these metabolic alterations serve as drivers of atherosclerosis in NEIL3-deficient mice.

Functional co-activation of the default mode network in APOE ε4-carriers: A replication study

Structural and functional alterations of the brain in persons genetically at-risk for Alzheimer's disease (AD) are crucial in unravelling AD development. Filippini et al. found that the default mode network (DMN) is already affected in young APOE ε4-carriers, with increased co-activation of the DMN during rest and increased hippocampal task activation. We aimed to replicate the early findings of Filippini et al, using the APOE gene, still the principal AD risk gene, and extended this with a polygenic risk score (PRS) analysis for AD, using the Human Connectome Project dataset (HCP). We included participants from the HCP S1200 dataset (age range: 22-36 years). We studied morphometric features, functional DMN co-activation and functional task activation of recollection performance. Permutation Analysis of Linear Models (PALM) was used to test for group differences between APOE ε4-carriers and non-carriers, and to test the association with PRS. PALM controls for biases induced by the family structure of the HCP sample. Results were family-wise error rate corrected at p < 0.05. Our primary analysis did not replicate the early findings of Filippini et al. (2009). However, compared with non-carriers, APOE ε4-carriers showed increased functional activation during the encoding of subsequently recollected items in areas related to facial recognition (p<0.05, t>756.11). This increased functional activation was also positively associated with PRS (APOE variants included) (p<0.05, t>647.55). Our results are supportive for none to limited genetic effects on brain structure and function in young adults. Taking the methodological considerations of replication studies into account, the true effect of APOE ε4-carriership is likely smaller than indicated in the Filippini paper. However, it still holds that we may not yet be able to detect already present measurable effects decades before a clinical expression of AD. Since the mechanistic pathway of AD is likely to encompass many different factors, further research should be focused on the interactions of genetic risk, biomarkers, aging and lifestyle factors over the life course. Sensitive functional neuroimaging as used here may help disentangling these complex interactions.

The Role of Intestinal Dysbacteriosis Induced Arachidonic Acid Metabolism Disorder in Inflammaging in Atherosclerosis.

BackgroundAging induced chronic systemic inflammatory response is an important risk factor for atherosclerosis (AS) development; however, the detailed mechanism is yet to be elucidated.ObjectiveTo explore the underlying mechanism of how aging aggravates AS advancement.MethodsA young (five-week-old, YM) and aged group (32-week-old, OM) male apoE-/- mice with a high fat diet were used as models, and age-matched male wild-type C57BL/6J (WT) mice were used as controls. AS lesion size, serum lipid profile, cytokines, and gut microbiota-derived LPS were analyzed after 32 weeks of diet intervention. A correlation analysis between the 16S rRNA sequencing of the feces and serum metabolomics profiles was applied to examine the effect of their interactions on AS.ResultsApoE-/- mice developed severe atherosclerosis and inflammation in the aorta compared to the WT groups, and aged apoE-/- mice suffered from a more severe AS lesion than their younger counterparts and had low-grade systemic inflammation. Furthermore, increased levels of serum LPS, decreased levels of SCFAs production, as well as dysfunction of the ileal mucosal barrier were detected in aged mice compared with their younger counterparts. There were significant differences in the intestinal flora composition among the four groups, and harmful bacteria such as Lachnospiraceae_FCS020, Ruminococcaceae_UCG-009, Acetatifactor, Lachnoclostridium and Lactobacillus_gasseri were significantly increased in the aged apoE-/- mice compared with the other groups. Concurrently, metabolomics profiling revealed that components involved in the arachidonic acid (AA) metabolic pathway such as 20-HETE, PGF2α, arachidonic acid, and LTB4 were significantly higher in the aged AS group than in the other groups. This suggested that metabolic abnormalities and disorders of intestinal flora occurred in AS mice.ConclusionsAging not only altered the gut microbiome community but also substantially disturbed metabolic conditions. Our results confirm that AA metabolism is associated with the imbalance of the intestinal flora in the AS lesions of aged mice. These findings may offer new insights regarding the role of gut flora disorders and its consequent metabolite changed in inflammaging during AS development.

APOE genotype influences P3b amplitude and response to smoking abstinence in young adults.

There is strong evidence that nicotine can enhance cognitive functions and growing evidence that this effect may be larger in young healthy APOE ε4 carriers. However, the moderating effects of the APOE ε4 allele on cognitive impairments caused by nicotine deprivation in chronic smokers have not yet been studied with brain indices. We sought to determine whether young female carriers of the APOE ε4 allele, relative to noncarriers, would exhibit larger abstinence-induced decreases in P3b amplitude during a two-stimulus auditory oddball task. We compared parietal P3bs in female chronic smokers with either APOE ε3/ε3 (n = 54) or ε3/ε4 (n = 20) genotype under nicotine-sated conditions and after 12-17-h nicotine deprivation. Nicotine deprivation significantly reduced P3b amplitudes in APOE ε4 carriers, but not in APOE-ε3/ε3 individuals, such that the difference seen prior to nicotine deprivation was eliminated. The results suggest that subjects with the APOE ε4 allele are more sensitive to nicotine, which could influence smoking patterns, the risk for nicotine dependence, and the cognitive effects of nicotine use in these individuals.

Patterns of default mode network co‐activation in young APOE ε4‐carriers: An HCP replication study

AbstractBackgroundFilippini et al. reported an increased default mode network (DMN) co‐activation during rest in young APOE ε4‐carriers [1]. This work has been of substantial importance, often used to illustrate the trajectory of DMN alterations in APOE ε4‐carriers from young adults and normal aging to mild cognitive impairment and AD. However, this study only assessed a small sample. Here, we aimed to replicate their finding in a substantially larger sample from the Human Connectome Project (HCP).MethodWe included participants from the HCP S1200 dataset. We followed the methods of [1] for structural MRI and resting‐state fMRI data, with the following deviations: instead of using voxel‐based morphometry to assess gray matter density, we assessed gray matter volume with FreeSurfer. To test for differences in DMN co‐activation and gray matter volume between APOE ε4‐carriers and non‐carriers, we used Permutation Analysis of Linear Models (PALM). PALM controls for biases induced by the family structure of the HCP sample. Results were family‐wise error rate corrected at p &lt; 0.05.ResultWe included 167 APOE ε4‐carriers and 419 non‐carriers for the DMN analysis. In contrast to [1], we did not find significant differences in DMN co‐activation between carriers and non‐carriers. For the morphometric analyses, 243 carriers and 544 non‐carriers were included. No differences in brain volume were found between carriers and non‐carriers. For both analyses, including covariates (different combinations of age, sex, education level, head motion) did not alter the results.ConclusionWe could not replicate the early findings of [1] in a large sample. Our results suggest that solely APOE ε4‐carriership does not influence brain function at a young age. Future work will focus on the use of polygenic risk scores to study whether any genetic predisposition for AD influences brain function in young adults. Still, genetic predisposition for AD might not have any measurable effect decades before clinical expression of AD. Therefore, repeating the analysis in a healthy, middle‐aged cohort could inform us whether the influence of genetic predisposition for AD increases over time. Altogether, our replication study is an important step forward in unravelling AD development. Resource: (1) Filippini et al., PNAS, 2009.

Insulin BBB pharmacokinetics in young apoE male and female transgenic mice.

In addition to age, apolipoprotein E4 (E4), female sex, or a combination of both synergistically increase the risk for the development of Alzheimer’s disease (AD). Why these risk factors predispose an individual to developing AD later in life is the target of the current investigation. Central nervous system (CNS) insulin resistance is associated with cognitive impairment and AD. CNS insulin is acquired primarily from the circulation and therefore must negotiate the blood-brain barrier (BBB). Thus, changes in BBB transport of insulin could lead to alterations in CNS insulin signaling and resistance, which would then lead to changes in cognition. There has been recent evidence suggesting the relationship between CNS insulin; E4, a risk factor to develop AD as compared to E3; and the female sex in aged individuals and in pre-clinical models. However, this relationship has been largely unexplored at a younger age, in which some of these risk factors could predispose an individual to dysregulation of CNS insulin later in life. Here, we present the first findings of BBB insulin pharmacokinetics in young E3 and E4 male and female targeted replacement (TR) mice. We found that levels of insulin binding the vasculature at the BBB are different due to genotype and sex which could impact the function of the brain endothelial cell. These early alterations could contribute to or fully explain the age-related cognitive changes observed due to CNS insulin signaling in E4 and/or female individuals.

Female mice with apolipoprotein E4 domain interaction demonstrated impairments in spatial learning and memory performance and disruption of hippocampal cyto-architecture.

We have previously reported cognitive impairments in both young and old mice, particularly in female mice expressing mouse Arg-61 apoE, with a point mutation to mimic the domain interaction feature of human apoE4, as compared to the wildtype mouse (C57BL/6J) apoE. In this study, we further evaluated water maze performance in the female Arg-61 mice at an additional time point and then investigated related hippocampal cyto-architecture in these young female Arg-61 apoE mice vs. the wildtype mice. The results of behavioral performance consistently support our previous report that the young female Arg-61 apoE showed cognitive impairment versus C57BL/6J at the same age. The cyto-architectural results showed that volume of the granular cell layer (GCL) was significantly larger in both 5- and 10-month old Arg-61 apoE mice versus C57BL/6J mice. While the number of newborn calretinin-positive neurons was greater in the sub-granular zone (SGZ) in 5-month old Arg-61 mice, this number dropped significantly in 10-month old Arg-61 mice to a lower level than in age-matched C57BL/6J mice. In addition, the amyloid β species was significantly higher in 5-month old Arg-61 mice versus age-matched C57BL/6J mice. In conclusion, impaired cognitive functions in female Arg-61 apoE mice appear correlated with larger GCL volume and higher calretinin-positive cell number and suggest a compensatory cellular response that may be related to amyloid beta perturbations early in life. Therefore this study suggests a novel cyto-architectural mechanism of apoE4-dependent pathologies and increased susceptibility of APOEε4 subjects to Alzheimer's disease.

The Effects of Endurance Exercise and Diet on Atherosclerosis in Young and Aged ApoE–/– and Wild-Type Mice

Background: Atherosclerosis is the leading cause of death worldwide. The disease development is by and large driven by old age and lifestyle factors, such as diet, physical activity, and smoking. In the present study, we have investigated the effect of exercise and diet on the development of atherosclerosis in young and aged mice. Objective: This study aimed at comparing multiple age-dependent factors that may influence atherosclerosis in a transgenic mouse model. Methods: Young (14 weeks) and aged (49–52 weeks) C57BL/6 wild-type (WT) and atherosclerosis-prone ApoE^–/– mice were subjected to physical endurance exercise on a treadmill, with or without a high-fat diet. Five weeks later, the frequencies of regulatory T cells (T_REGs) in lymph nodes were assessed by flow cytometry, plasmatic cytokines (interleukin [IL]-1β, IL-6, IL-10, IL-17, interferon-γ, tumor necrosis factor-α, and transforming growth factor [TGF]-β₁) levels were determined by Luminex assay. Lipids (cholesterol and triglycerides) and anti-heat shock protein 60 (HSP60) autoantibodies were measured by ELISA. Aortic lesion sizes were assessed by en face imaging. Microarray analysis and qPCR of skeletal muscle gene expression were also performed. Results: Exercise leads to a reduction of aortic lesions in young ApoE^–/– and aged WT mice independent of diet. In most groups, this reduction was followed by an increased proportion of T_REGs and TGF-β₁ levels. Moreover, gene expression analysis showed that exercise seems to affect the AMPK signaling pathway. In particular, PGC-1α₁ mRNA was induced in aged WT mice, whereas it was reduced in young ApoE^–/– mice. In addition, GSEA analysis showed a marked reduction in the insulin signaling pathway in aged ApoE^–/– mice. Conclusion: Practicing endurance exercise seems to be enough for reducing early aortic lesion formation, independent of diet. However, this was only true in mice with smaller aortic lesions, since mice with large, advanced, complicated atherosclerotic plaques did not show any reduction in lesion size with exercise training.

Apolipoprotein E favours the blunting by high-fat diet of prostacyclin receptor activation in the mouse aorta.

NO-mediated, endothelium-dependent relaxations of isolated arteries are blunted by ageing and high-fat diets, as well as by apolipoprotein E deletion. The present study was designed to test the hypothesis that apolipoprotein E deletion impairs endothelium-dependent responses to prostacyclin (IP) receptor activation. Five-week-old ApoE+/+ and ApoE-/- mice were fed normal chow or high-fat diet for 29weeks. The aortae were isolated for the measurements of isometric tension in Halpern-Mulvany myographs. Levels of proteins were assessed by Western blotting and immunofluorescence, and cyclic nucleotide levels by elisa. The IP receptor agonist, iloprost, induced endothelium-, NO-synthase- and IP-dependent relaxations in aortae of young ApoE+/+ mice. High-fat diet favoured activation of thromboxane receptors by iloprost, causing contraction. Apolipoprotein E was present in aortae of ApoE+/+ mice, especially in endothelium. Its presence was augmented by high-fat diet. Its deletion potentiated iloprost-induced relaxations in aortae of young mice and prevented the blunting of this response by high-fat diet. Levels of cAMP were higher, but those of cGMP were lower in the aorta of ApoE-/- than in ApoE+/+ mice of the same age. The levels of IP receptor protein were not different between ApoE+/+ and ApoE-/- mice. Iloprost induced an endothelium-dependent relaxation in the aorta of young healthy mice which involved both the cGMP and cAMP pathways. This response was blunted by prolonged exposure to a high-fat diet. Apolipoprotein E deletion potentiated relaxations to IP receptor activation, independently of age and diet.