APOE Genotype Research Articles

Genetic assessment of apolipoprotein E polymorphism and PRNP genotypes in rapidly progressive dementias in Pakistan

ABSTRACT Rapidly progressive dementias (RPDs) are a type of fatal dementias that cause rapid progression of neuronal dysfunction. This study aimed to assess the prevalence of APOE genotypes (ε2, ε3, ε4) and PRNP mutations (E200K, M129V) in the general population of Pakistan because of their association with RPDs, including Rapidly Progressive Alzheimer’s Disease (rpAD) and Creutzfeldt-Jakob Disease (CJD). Blood samples (n = 100) were collected from healthy Pakistani population and the stated mutations were assessed using polymerase chain reaction. In the analysis of the APOE genotype, ε3/ε3 genotype was the most common (95%), followed by ε3/ε4 (5%) and ε2 allele was completely absent. A low frequency of ε4 allele and the absence of a protective ε2 allele is associated with an increased risk of rpAD. In the case of PRNP mutations, the most common genotype was M129-Ε200 (71%) and V129-Ε200 (29%). E200K mutation was completely absent from the given population. It is noteworthy that the MM homozygous genotype was present in 71 samples, VV genotype was present in 29. Homozygosity on codon 129, as observed in most of our samples, has been associated with more efficient production of PrPSc and disease pathology. This study provides preliminary data indicating that rpAD and CJD pose a significant threat to the Pakistani population.

Associations of posttraumatic stress disorder symptoms with amyloid burden in cognitively normal older adults

BackgroundPosttraumatic stress disorder (PTSD) is associated with the development of dementia. However, the link between PTSD and preclinical Alzheimer’s disease pathology (amyloid β [Aβ]) remains controversial. Moreover, the correlation between the severity of PTSD with Aβ levels remains unknown.MethodsThis cross-sectional study sought to investigate the associations of PTSD symptoms with global and regional brain Aβ burden. To this end, data were obtained from participants in the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s Disease (A4) Study. In addition, we explored the association between the severity of PTSD symptoms and Aβ levels.ResultsA total of 4,228 participants aged 65 to 85 years were included in the final analysis. The results showed that PTSD symptoms were significantly associated with higher global Aβ levels (1.15 ± 0.20 vs. 1.09 ± 0.19; β = 0.056; p < 0.001), after adjusting for covariates. The association between PTSD symptoms and Aβ levels was not affected by sex, age, ApoE genotype, or psychiatric diseases. Similarly, PTSD symptoms were significantly associated with Aβ levels in all subregions, including the anterior cingulate, posterior cingulate, parietal cortex, precuneus, temporal cortex, and frontal cortex. In addition, the group with severe PTSD symptoms (1.22 ± 0.24) exhibited higher global Aβ levels than the groups with moderate (1.14 ± 0.19) or mild (1.12 ± 0.20) symptoms or the control (1.08 ± 0.18), with p < 0.001.ConclusionThe findings imply a close relationship between PTSD and brain Aβ levels, irrespective of sex, age, ApoE genotype, or psychiatric diseases. More well-designed studies are needed to further explore the relationship and mechanism underlying the association between PTSD and Aβ burden.

Connectivity, Pathology, and ApoE4 Interactions Predict Longitudinal Tau Spatial Progression and Memory.

Tau pathology spread into neocortex indicates a transition from healthy aging to Alzheimer's disease (AD). Connectivity between tau epicenters and later accumulating regions of cortex has been proposed as a mechanism of tau spread, but how this relationship changes with greater AD pathology burden or genotype is not understood. We investigated tau accumulation in two key regions, precuneus and inferior temporal cortex, using resting state functional connectivity (rsFC) and longitudinal PET imaging from a multicohort sample of cognitively unimpaired older adults. We examined how baseline tau PET, Aβ PET, and ApoE4 genotype status interact with rsFC between hippocampus and these downstream regions to predict rate of tau accumulation in neocortex. We found that the 3-way interaction between connectivity, baseline tau, and baseline Aβ or ApoE4 status was associated with neocortical tau accumulation in precuneus and inferior temporal cortex. In addition, baseline tau, Aβ, and ApoE4 status also moderated the association between connectivity and rate of memory decline. Together, these results suggest that the extent and distribution of future tau accumulation may be predicted by the interaction of baseline connectivity, AD pathology, and genetic risk.

Lipid Trajectories Improve Risk Models for Alzheimer’s Disease and Mild Cognitive Impairment

In this retrospective, case-control study, we tested the hypothesis that blood-lipid concentrations during the decade prior to cognitive symptom onset can inform risk prediction for Alzheimer's disease (AD) and stable mild cognitive impairment (MCI). Clinically well-characterized cases were diagnosed using DSM-IV criteria; MCI cases had been stable for ≥5 years; and controls were propensity matched to cases at symptom onset (MCI: 116 cases, 435 controls; AD: 215 cases, 483 controls). Participants were grouped based on (i) longitudinal trajectories and (ii) quintile of variability independent of the mean (VIM) for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, non-HDL-C, and ln(triglycerides). Risk models evaluated the contributions of lipid trajectory and VIM groups relative to APOE genotype or polygenic risk scores (PRS) for AD and lipid levels and major lipoprotein confounders: age, lipid-lowering medications, comorbidities, and other longitudinal correlates of blood-lipid concentrations. In models with AD-PRS, higher MCI-risk was associated with the two lower HDL-C trajectories [odds ratios: 3.8(1.3−11.3; P=0.014), 3.2(1.1−9.3; P=0.038), relative to the high trajectory], and the lowest VIM quintile of non-HDL-C [odds ratio: 2.2 (1.3−3.8:P=0.004), relative to quintiles 2−5]. Higher AD-risk was associated with the two lower HDL-C trajectories [odds ratios: 2.8(1.5−5.1; P=0.001), 3.7 (2.0−7.0; P<0.001)], and the lowest VIM quintile of TC [odds ratio: 2.5(1.5−4.0: P<0.001)]. Inclusion of lipid-trajectory and VIM groups improved risk-model predictive performance independent of APOE and AD or lipid-level PRS. These results provide important real-world perspectives on how longitudinal levels and variation of blood-lipid concentrations contribute to risk of cognitive decline.

APOE4 and Chronic Health Risk Factors are Associated with Sex-Specific Preclinical Alzheimer's Disease Neuroimaging Biomarkers.

Two thirds of Alzheimer's disease (AD) patients are female. Genetic and chronic health risk factors for AD affect females more negatively compared to males. This exploratory multimodal neuroimaging study aimed to examine sex differences in cognitively unimpaired older adults on: (1) amyloid-β via 18F-AV-45 Florbetapir PET imaging, (2) neurodegeneration via T1 weighted MRI volumetrics, (3) cerebral blood flow via ASL-MRI. We identified AD risk factors including genetic (APOE genotype status) and health markers (fasting glucose, mean arterial pressure, waist-to-hip ratio, and android and gynoid body fat) associated with neuroimaging outcomes for which we observed sex differences. Participants were sedentary, amyloid-β positive older adults (N = 112, ages 65-87 years) without evidence of cognitive impairment (CDR = 0). Multivariate analysis of covariance models adjusted for intracranial volume, age, and years of education demonstrated lower volume (F (7, 102) = 2.67, p = 0.014) and higher blood flow F (6, 102) = 4.25, p =<0.001) among females compared to males in regions of interest connected to AD pathology and the estrogen receptor network. We did not observe sex differences in amyloid-β levels. Higher than optimal waist to hip ratio was most strongly associated with lower volume, while higher android fat percentage and APOE ε4 carrier status were most strongly associated with higher blood flow among female participants. Findings suggest genetic and chronic health risk factors are associated with sex-specific AD neuroimaging biomarkers. Underlying sex-specific biological pathways may explain these findings. Our results highlight the importance of considering sex differences in neuroimaging studies and when developing effective interventions for AD prevention and risk reduction.

Factors associated with unfavorable outcomes in older patients with traumatic brain injury: analysis from the "All of Us" research program.

Traumatic brain injury (TBI) afflicts approximately 70 million people worldwide annually, with patients aged 65 years and older accounting for an increasing proportion of TBI patients. Older patients also experience increased morbidity and mortality post-TBI compared to their younger counterparts. Nevertheless, clinical trials often exclude older TBI patients, and age-specific TBI treatment is lacking. We hypothesized that the APOE genotype and age-associated comorbidities, such as heart disease, are associated with unfavorable outcomes following TBI in older patients. We utilized a dataset from the "All of Us research" (AoU) to study this vulnerable population post-TBI. Launched by the National Institutes of Health (NIH), AoU is a nationwide prospective cohort study aiming to enroll 1 million or more individuals by emphasizing traditionally underrepresented populations in the United States. We defined patients diagnosed with post-concussion syndromes (PCS) as those with unfavorable TBI outcomes, and we also assessed the associations between PCS observed in older patients and different comorbidities variables/APOE genotypes via multiple logistic regression models. Consequently, APOE ε4 allele was strongly associated with PCS in patients aged 65 and older. Our findings provide direct evidence for developing better predictive tools and potentially improving the clinical guidance and management of older adults with TBI.

The novel estrogen receptor beta agonist EGX358 and APOE genotype influence memory, vasomotor, and anxiety outcomes in an Alzheimer's mouse model.

Alzheimer's disease (AD) prevalence and severity are associated with increased age, female sex, and apolipoprotein E4 (APOE4) genotype. Although estrogen therapy (ET) effectively reduces symptoms of menopause including hot flashes and anxiety, and can reduce dementia risk, it is associated with increased risks of breast and uterine cancer due to estrogen receptor alpha (ERα)-mediated increases in cancer cell proliferation. Because ERβ activation reduces this cell proliferation, selective targeting of ERβ may provide a safer method of improving memory and reducing hot flashes in menopausal women, including those with AD. APOE genotype influences the response to ET, although it is unknown whether effects of ERβ activation vary by genotype. Here, we tested the ability of long-term oral treatment with a novel highly selective ERβ agonist, EGX358, to enhance object recognition and spatial recognition memory, reduce drug-induced hot flashes, and influence anxiety-like behaviors in female mice expressing 5 familial AD mutations (5xFAD-Tg) and human APOE3 (E3FAD) or APOE3 and APOE4 (E3/4FAD). Mice were ovariectomized at 5 months of age and were then treated orally with vehicle (DMSO) or EGX358 (10 mg/kg/day) via hydrogel for 8 weeks. Spatial and object recognition memory were tested in object placement (OP) and object recognition (OR) tasks, respectively, and anxiety-like behaviors were tested in the open field (OF) and elevated plus maze (EPM). Hot flash-like symptoms (change in tail skin temperature) were measured following injection of the neurokinin receptor agonist senktide (0.5 mg/kg). EGX358 enhanced object recognition memory in E3FAD and E3/4FAD mice but did not affect spatial recognition memory. EGX358 also reduced senktide-induced tail temperature elevations in E3FAD, but not E3/4FAD, females. EGX358 did not influence anxiety-like behaviors or body weight. These data indicate that highly selective ERβ agonism can facilitate object recognition memory in both APOE3 homozygotes and APOE3/4 heterozygotes, but only reduce the magnitude of a drug-induced hot flash in APOE3 homozygotes, suggesting that APOE4 genotype may blunt the beneficial effects of ET on hot flashes. Collectively, these data suggest a potentially beneficial effect of selective ERβ agonism for memory and hot flashes in females with AD-like pathology, but that APOE genotype plays an important role in responsiveness.

Functional near-infrared spectroscopy and vagus somatosensory evoked potentials add to the power of established parameters such as poor cognitive performance, dsyosmia and APOe genotype to predict cognitive decline over 8 years in the elderly.

Alzheimer's dementia is the main cause of cognitive impairment in people over the age of 65, with Alzheimer's disease starting presumably 10-15 years before the onset of clinical symptoms. It is therefore important to recognize dementia at an early stage and identify possible predictors. The existing methods, like different parameters of ß-Amyloid and Tau quantification in cerebrospinal fluid (CSF) or the living brain by measure of PET, are invasive and expensive. Therefore, the present study investigates the predictive value of a battery of clinical, neuropsychological, and blood parameters as well as two neurophysiological methods (functional near-infrared spectroscopy [fNIRS] and vagus somatosensory evoked potentials [VSEP]) which are easy to perform, less invasive and cost-efficient, for developing cognitive impairments in the elderly.In this longitudinal, prospective study, we enrolled 604 healthy participants between 70 and 77 years of age. The participants were invited back after a mean time interval of 3 years and 11 months, and after 7 years and 8 months, and their cognitive impairments were determined.Here we show that the development of cognitive impairments after approximately 8 years can be predicted not only by previously known risk factors such as ApoE4 risk alleles, dysosmia, or poor cognitive performance at baseline but that latency prolongation in the VSEP and altered functional activation patterns measured by NIRS at baseline also provide additional predictive value.We therefore suggest that both neurophysiological parameters, VSEP and NIRS, should be included in future studies, investigating the prediction of dementia. Dementia ClinicalTrials.gov Identifier: NCT02224326.

Abstract 4136289: Aortic Valve Calcium as a Predictor of Chronic Kidney Disease in a Multi-Ethnic Cohort: The MESA Study

Background: Aortic valve calcium (AVC) is associated with an increased risk of cardiovascular disease, non-cardiovascular disease such as dementia, and all-cause mortality. Traditional atherosclerotic cardiovascular disease risk factors are associated with both AVC and chronic kidney disease (CKD), but whether there is an association between AVC and CKD is unknown. Objectives: To ascertain whether AVC quantified by cardiac CT scanning is independently associated with the long-term risk of incident CKD among individuals without a previous history of cardiovascular disease. Methods: We examined 6,346 Multi-Ethnic Study of Atherosclerosis (MESA) participants who underwent cardiac CT scanning at Visit 1 (2000-02) and had an eGFR of ≥ 60 mL/min/1.73 m 2 . AVC was quantified using the Agatston method and categorized as 0, 1-99, and ≥100. Incident CKD was defined as an eGFR &lt; 60 mL/min/1.73 m 2 accompanied with an at least 40% decline in eGFR from baseline, and/or a diagnosis of CKD and indicators of end stage renal disease extracted from hospital records using the International Classification of Disease (ICD) codes. We performed Kaplan-Meier survival curve analyses along with multivariable Cox proportional hazard regression models, adjusted for age, gender, race/ethnicity, highest level of education and traditional cardiovascular risk factors along with coronary artery calcium (CAC), lipoprotein (a) (Lp[a]), and the APOE-ε4 genotype to examine the association between AVC (categorical and log-transformed) and incident CKD. Results: Participants had a mean age 62.2±10.1 years, 53% were women, and AVC &gt;0 was present in 795 (12%) participants. During a median follow-up time of 16.9 years, 982 (15%) participants developed incident CKD. AVC examined as a continuous variable was associated with a significantly increased risk of developing CKD (per log-unit [AVC+1] HR 1.06 [95% CI: 1.02-1.10]; p = 0.005). There was a stepwise increased risk for CKD with higher AVC levels ( Figure ). Similarly, in the multivariable adjusted Cox models, participants with AVC ≥100 had a higher risk of incident CKD, compared with the AVC=0 group (HR 1.48 [95% CI: 1.15-1.89]; p = 0.002). The observed associations remained after further adjusting for CAC score ( p = 0.024), Lp (a) ( p = 0.004), and the APOE-ε4 genotype ( p = 0.004). Conclusions: In a multi-ethnic cohort of participants free of CKD at baseline, AVC was independently associated with a higher risk of incident CKD.

NCMP-06. GENOTYPE AND SEX IMPACT MEMORY FUNCTION AFTER BRAIN IRRADIATION

Abstract PURPOSE/OBJECTIVE Cognitive changes are a serious complication that can occur after brain radiotherapy. There is a need to better understand which individuals are more susceptible to develop strategies to preserve their function. The apolipoprotein E type 4 allele (APOEe4) APOE4 is the most prevalent genetic risk factor for Alzheimer Disease. We hypothesized that APOE genotype influences memory function after a subtherapeutic dose of whole brain irradiation in male and female mice. MATERIALS/METHODS Age-matched adult female and male mice engineered with either human APOE3 or APOE4 gene knocked-in were randomized to no treatment or whole brain irradiation (0 Gy or 5 Gy x 2), then evaluated with longitudinal neurobehavioral tests of learning, memory, pain threshold and anxiety. We performed immunohistochemical analyses of mouse brain sections at 1 month and at 4 months post-radiation to quantify extracellular amyloid beta plaques and other neuropathologic hallmarks associated with neurodegeneration. RESULTS Neurobehavioral testing identified significant sex and genotype-dependent changes in memory and anxiety measures developing longitudinally after brain irradiation. At baseline (unirradiated), APOE4 mice (male and female) performed worse on multiple memory measures. However after irradiation, sex and genotype each independently impacted multiple neurobehavioral function tests and also interacted with each other to significantly influence the timing and magnitude of changes in memory function. ApoE4 significantly impacted the toxicity of radiation in a sex-dependent manner. Neuropathologic analyses including amyloid beta plaque deposition and ApoE levels are ongoing. CONCLUSIONS After brain irradiation of relatively moderate dose, neurobehavioral performance including memory are impacted in a genotype and sex-dependent manner and dynamically over time. In addition to suggesting important sex-dependent differences in memory vulnerability, these data point to new opportunities for personalizing care for patients receiving brain irradiation.

APOE from astrocytes restores Alzheimer’s Aβ-pathology and DAM-like responses in APOE deficient microglia

The major genetic risk factor for Alzheimer’s disease (AD), APOE4, accelerates beta-amyloid (Aβ) plaque formation, but whether this is caused by APOE expressed in microglia or astrocytes is debated. We express here the human APOE isoforms in astrocytes in an Apoe-deficient AD mouse model. This is not only sufficient to restore the amyloid plaque pathology but also induces the characteristic transcriptional pathological responses in Apoe-deficient microglia surrounding the plaques. We find that both APOE4 and the protective APOE2 from astrocytes increase fibrillar plaque deposition, but differentially affect soluble Aβ aggregates. Microglia and astrocytes show specific alterations in function of APOE genotype expressed in astrocytes. Our experiments indicate a central role of the astrocytes in APOE mediated amyloid plaque pathology and in the induction of associated microglia responses.

Influence of APOE4 genotype on PCSK9-lipids association in cerebrospinal fluid and serum of patients in the Alzheimer's disease continuum.

Alterations in factors involved in cholesterol homeostasis are critical in Alzheimer's disease (AD), but the stage of occurrence, their specific association, and a possible relationship with the APOE4 genotype are not clarified. We aimed to quantify and correlate specific lipid factors in patients with different degrees of cognitive decline, namely patients with AD and patients with mild cognitive impairment due to AD (MCI-AD), carriers or non-carriers of the APOE4 genotype. We evaluated Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9), cholesterol and the oxidative metabolites 24-, 25-, 27-hydroxycholesterol (HC) in the cerebrospinal fluid (CSF) and serum of AD (n = 28) and MCI-AD (n = 27) patients. CSF and serum PCSK9 and lipids were similar, except for higher serum PCSK9 and triglycerides in MCI-AD compared to AD. In CSF, AD APOE4 carriers showed higher PCSK9 and 24-HC (+61.3%, p = 0.027 and +32.7%, p = 0.037), compared to non-carriers. There was a negative association between CSF PCSK9 and 27-HC in AD (r = -0.444, p = 0.049) and, exclusively among AD APOE4 carriers, a negative association between CSF PCSK9 and 24-HC (r = -0.786, p = 0.028). A positive correlation was observed between CSF and serum PCSK9 in AD (r = 0.520, p = 0.004), driven by APOE4 carriers (r = 0.544, p = 0.038), suggesting PCSK9 exchange between brain and periphery. A positive correlation was detected between serum and CSF 27-HC (r = 0.465, p = 0.039) in AD. None of these results were found in MCI-AD patients. PCSK9 and 24-HC might be specific markers of ApoE4-associated lipid alterations in AD, possibly contributing to clinical progression in the AD continuum.

Clinical association of habitual breakfast skipping with cognitive decline and neurodegeneration among older adults

ObjectiveUnhealthy lifestyles have a considerable impact on the incidence of dementia. Skipping breakfast disturbs energy homeostasis and impairs brain function. In this study, we investigated the association between breakfast skipping and cognitive performance among community-dwelling adults. MethodsWe recruited 859 community-dwelling adults aged ≥60 years from January 1 to December 31, 2021. Participants’ sociodemographic information and breakfast skipping habits were self-reported. Participants were followed up for 36 months and cognitive function was assessed using the Mini-Mental State Examination (MMSE) with an interval of 18 months. Trajectories of cognitive change were compared between individuals with and without breakfast skipping. To reduce the risk of bias owing to unmatched sample sizes between the groups, we conducted 1:1 propensity score matching (PSM) based on age, sex, education level, and ApoE genotype. ResultsAt baseline and 18-month follow-up, no difference was found in MMSE scores between participants with and without breakfast skipping. However, those who habitually skipped breakfast had significantly lower MMSE scores than those who did not at 36-month follow-up. Individuals with habitual breakfast skipping had a steeper rate of cognitive decline than those without habitual breakfast skipping during follow-up. Breakfast skipping was a risk factor for longitudinal cognitive decline, defined as a decrease in MMSE scores of ≥3, adjusted for age, sex, education, body mass index, ApoE ε4 carrier status, hypertension, diabetes, and hyperlipidemia. At the last follow-up, participants who habitually skipped breakfast had significantly higher levels of ptau181 and NfL than those who did not. In the PSM cohort, similar findings were obtained regarding cognitive trajectories and plasma biomarkers. ConclusionBreakfast skipping was linked to an increased risk of long-term cognitive decline and neurodegeneration among older adults. The link between unhealthy dietary habits and cognitive decline may be attributed to a deficiency in neurorestoration resulting from inadequate energy consumption.

Perceptions of key informant neurologists before implementing anti-amyloid drugs in the Spanish departments of neurology.

A deep knowledge of the healthcare system and the organization of neurology departments is important for planning and optimizing changes to facilitate the successful implementation of anti-amyloid antibodies treatments. We aimed to assess the necessary changes prior to introducing these therapies in our setting. We conducted a key informant survey among heads of departments of neurology from 16 hospitals in Spain. The questionnaire comprised questions about changes in the organization and functioning of the departments of neurology with the introduction of anti-amyloid drugs, changes in diagnosis and patient care, use of diagnostic techniques, patients, families and public information, resources allocation, and research. Sixteen key informants completed the survey. They strongly agreed that the introduction of anti-amyloid drugs will impact the functioning of neurology services, especially in hospitals with dementia units. Consensus was reached regarding referring all Alzheimer's disease patients eligible for therapy to dementia units. There was also agreement on the need to expand the neurology services, day hospital units, extend visit durations, and hire more professionals, especially neurologists, neuropsychologists, and nuclear medicine physicians. Furthermore, consensus was achieved on increasing the use of MRI, amyloid PET, cerebrospinal fluid biomarkers, APOE genotyping, and the necessity of advancing blood biomarkers and tau tracers. Our study highlights the need for extensive changes within Spanish neurological departments to effectively integrate anti-amyloid antibodies. Implementing these changes is essential for the timely and equitable adoption of novel therapies.

Exploring mitochondrial blood-based and genetic markers in older adults with mild cognitive impairment and remitted major depressive disorder

Mild cognitive impairment (MCI) is a prodromal stage in aging to possible progression to Alzheimer’s disease and related dementia (ADRD), where co-occurrence of major depressive disorder (MDD) accelerates the progression. Metabolic and mitochondrial abnormalities in ADRD and other neurodegenerative disorders have been widely suggested, while possible mitochondrial dysfunction has been associated with etiopathology of both MCI and MDD. Hence, investigation of mitochondrial markers in MCI, MDD, and presence of both conditions is warranted. In total, 332 older adult participants were included: 168 with MCI, 108 with MCI plus remitted MDD (rMDD), and 56 with rMDD but without MCI. We measured plasma circulating mitochondrial DNA (ccf-mtDNA), lactate, and extracted nuclear mitochondrial encoded (NMt) single-nucleotide variants (SNVs) (n = 312). Non-parametric statistical tests on ccf-mtDNA and lactate levels were performed on the diagnosis, clinical and cardiometabolic variables. Binary sequence kernel association test (SKAT-O) and burden test were performed on NMt-SNV, adjusted for age, race, gender, type II diabetes, and APOE genotype. Lower level of lactate was observed in MCI (KW χ2 = 14.8, P = 0.0024), more specifically, significant differences of lower plasma lactate between MCI only and rMDD, but not between MCI+rMDD and MCI were found, suggesting potential roles in MCI driving lactate lower levels. While higher levels of ccf-mtDNA were observed in APOE-ε4 carrier (χ2 = 5.04, P = 0.05). This relationship was present only in MCI (P = 0.043) and MCI+rMDD groups (P = 0.023). No significant nuclear-encoded mitochondrial gene associations were observed with MCI or MDD. The results suggest decreased level of plasma lactate in individuals with MCI and MCI+rMDD, with inverse correlation with ccf-mtDNA, in addition to effect of APOE-ε4 in further increasing ccf-mtDNA specifically in participants with cognitive impairment. These findings contribute to a deeper understanding of the mitochondrial markers in MCI and MDD, warranting further research to explore the precise roles of mitochondrial abnormalities in the development and progression of MCI.

The Association Between Constipation and Positron Emission Tomography and Blood-Based Biomarkers in Older Cognitively Unimpaired Adults with Higher Amyloid-β Burden.

Constipation may be linked to cognitive decline and a higher risk of Alzheimer's disease (AD). We aimed to investigate the association between constipation and positron emission tomography (PET) and blood-based AD biomarkers in older cognitively unimpaired (CU) adults with higher Aβ burden. Constipation was diagnosed according to Rome IV criteria and the severity of constipation was evaluated by using a validated self-reported questionnaire. The participants underwent the examination of plasma AD biomarkers and 18F-florbetapir PET and 18F-MK6240 PET scans; the latter was only performed in the validation cohort. Correlation and multiple linear regression analyses were used to investigate the association between constipation and AD biomarkers. Two cohorts were included in our study. A total of 404 older participants with 126 of whom Aβ-PET positive were enrolled in the development cohort. Multiple linear regression analysis showed constipation was associated with plasma t-Tau, p-Tau-181, and neurofilament light chain (NfL) in participants with Aβ-PET (+). Meanwhile, no/mild constipation was associated with lower Aβ-PET standard uptake value ratio. The association between constipation and plasma biomarkers was different in the subgroups stratified by age, sex and APOE ε4 genotype. The above associations were further validated in the validation cohort containing 36 Aβ-PET (+) participants. Importantly, no/mild constipation was associated with lessTau burden evaluated by 18F-MK6240 PET Braak stages. Our data indicate that no/mild constipation may be associated with lower plasma t-Tau, p-Tau-181, and NfL as well as less Aβ and Tau burden in older CU adults with Aβ deposition. Improving constipation and being away from defecation disorders may help reduce the risk of AD development.

Development and assessment of algorithms for predicting brain amyloid positivity in a population without dementia

BackgroundThe accumulation of amyloid-β (Aβ) peptide in the brain is a hallmark of Alzheimer’s disease (AD), occurring years before symptom onset. Current methods for quantifying in vivo amyloid load involve invasive or costly procedures, limiting accessibility. Early detection of amyloid positivity in non-demented individuals is crucial for aiding early AD diagnosis and for initiating anti-amyloid immunotherapies at early stages. This study aimed to develop and validate predictive models to identify brain amyloid positivity in non-demented patients, using routinely collected clinical data.MethodsPredictive models for amyloid positivity were developed using data from 853 non-demented participants in the MEMENTO cohort. Amyloid levels were measured potentially repeatedly during study course through Positron Emision Tomography or CerebroSpinal Fluid analysis.The probability of amyloid positivity was modelled using mixed-effects logistic regression. Predictors included demographic information, cognitive assessments, visual brain MRI evaluations of hippocampal atrophy and lobar microbleeds, AD-related blood biomarkers (Aβ42/40 and P-tau181), and ApoE4 status. Models were subjected to internal cross-validation and external validation using data from the Amsterdam Dementia Cohort. Performance also was evaluated in a subsample that met the main criteria of the Appropriate Use Recommendations (AUR) for lecanemab.ResultsThe most effective model incorporated demographic data, cognitive assessments, ApoE status, and AD-related blood biomarkers, achieving AUCs of 0.82 [95%CI 0.81-0.82] in MEMENTO sample and 0.90 [95%CI 0.86-0.94] in the external validation sample. This model significantly outperformed a reference model based solely on demographic and cognitive data, with an AUC difference in MEMENTO of 0.10 [95%CI 0.10-0.11]. A similar model without ApoE genotype achieved comparable discriminatory performance. MRI markers did not improve model performance. Performances in AUR of lecanemab subsample were comparable.ConclusionA predictive model integrating demographic, cognitive, and blood biomarker data offers a promising method to help identify amyloid status in non-demented patients. ApoE genotype and brain MRI data were not necessary for strong discriminatory ability, suggesting that ApoE genotyping may be deferred when assessing the risk-benefit ratio of immunotherapies in amyloid-positive patients who desire treatment. The integration of this model into clinical practice could reduce the need for lumbar puncture or PET examinations to confirm amyloid status.

TOMM40-APOE chimera linking Alzheimer's highest risk genes: a new pathway for mitochondria regulation and APOE4 pathogenesis.

The patho-mechanism of apolipoprotein variant, APOE4, the strongest genetic risk for late-onset Alzheimer's disease (AD) and longevity, remains unclear. APOE's neighboring gene, TOMM40 (mitochondria protein transport channel), is associated with brain trauma outcome and aging-related cognitive decline, however its role in AD APOE4-independently is controversial. We report that TOMM40 is prone to transcription readthrough into APOE that can generate spliced TOMM40-APOE mRNA chimera (termed T9A2) detected in human neurons and other cells and tissues. T9A2 translation tethers APOE (normal APOE3 or APOE4) to near-full-length TOM40 that is targeted to mitochondria. Importantly, T9A2-APOE3 boosts mitochondrial bioenergetic capacity and decreases oxidative stress significantly more than T9A2-APOE4 and APOE3, and lacking in APOE4. We describe detailed interactomes of these actors that may inform about the activities and roles in pathogenesis. T9A2 uncovers a new candidate pathway for mitochondria regulation and oxidative stress-protection that are impaired in APOE4 genotypes and could initiate neurodegeneration.

Early CA2 Tau Inclusions Do Not Distinguish an Age-Related Tauopathy from Early Alzheimer's Disease.

Neuropathologic studies of brains from autopsy series show tau inclusions (pretangles, neuropils threads, neurofibrillary tangles) are detectable more than a decade before amyloid-β (Aβ) deposition in Alzheimer's disease (AD) and develop in a characteristic manner that forms the basis for AD staging. An alternative position views pathological tau without Aβ deposition as a 'primary age-related tauopathy' (PART) rather than prodromal AD. Recently, an early focus of tau inclusions in the Ammon's horn second sector (CA2) with relative sparing of CA1 that occurs before tau inclusions develop in the entorhinal cortex (EC) was proposed as an additional feature of PART. To test the 'definite PART' hypothesis. We used AT8-immunohistochemistry in 100μm sections to examine the EC, transentorhinal cortex (TRE), and Ammon's horn in 325 brains with tau inclusions lacking Aβ deposits (average age at death 66.7 years for females, 66.4 years for males). 100% of cases displayed tau inclusions in the TRE. In 89% of cases, the CA1 tau rating was greater than or equal to that in CA2. In 25%, CA2 was devoid of tau inclusions. Only 4% displayed a higher tau score in CA2 than in the TRE, EC, and CA1. The perforant path also displayed early tau changes. APOE genotyping was available for 199/325 individuals. Of these, 44% had an ɛ4 allele that placed them at greater risk for developing later NFT stages and, therefore, clinical AD. Our new findings call into question the PART hypothesis and are consistent with the idea that our cases represent prodromal AD.

The Relationship Between Physical Activity and Non-Modifiable Risk Factors on Alzheimer's Disease and Brain Health Markers: A UK Biobank Study.

Modifiable (physical activity) and non-modifiable (sex and genotype) risk factors interact to affect Alzheimer's disease (AD) risk. Further investigation is necessary to understand if these factors influence brain volume and cognition. The study aimed to assess the effect of physical activity, APOE genotype, and sex on AD risk, brain volume, and cognition. UK Biobank data from 2006 to 2023 was accessed. Physical activity was measured by accelerometers, and International Physical Activity Questionnaire. Outcomes were AD incidence; brain volume (ventricular cerebrospinal fluid and total brain); and cognition (executive function, memory, visuospatial ability, processing speed, and reaction time). Logistic and linear regression models were conducted. 69,060 participants met inclusion criteria (mean age: 62.28 years, SD: 7.84; 54.64% female). Higher self-reported (OR = 0.63, 95% CI [0.40, 1.00], p = 0.047) and accelerometer-assessed (OR = 0.96 [0.93, 0.98], p = 0.002) physical activity was associated with lower disease incidence. Smaller ventricular cerebrospinal fluid volume (β= - 65.43 [- 109.68, - 17.40], p = 0.007), and larger total brain volume (β= 4398.46 [165.11, 8631.82], p < 0.001) was associated with increased accelerometer-assessed and self-reported physical activity respectively. Both brain volume analyses were moderated by sex. Increased accelerometer-assessed physical activity levels were associated with faster reaction time (β= - 0.43 [- 0.68, - 0.18], p = 0.001); though poorer visuospatial ability (β= - 0.06 [- 0.09, - 0.03], p < 0.001), and executive function (β= 0.49 [0.31, 0.66], p < 0.001; β= 0.27 [0.10, 0.45], p = 0.002) was related to self-reported physical activity levels. Higher levels of physical activity reduce AD risk independently of non-modifiable risk factors. Moderation of sex on brain volume highlighted the importance of incorporating non-modifiable risk factors in analysis.