Association Between Fluctuations in Blood Lipid Levels Over Time With Incident Alzheimer Disease and Alzheimer Disease-Related Dementias

Longitudinal associations between lipid panel and cognitive decline modified by APOE 4 carrier status in biracial community-dwelling older adults: Findings from the Chicago health and aging project

BACKGROUND

There have been contradictory findings on the associations between lipids and cognitive decline (CD), which may be attributed to the heterogeneity in the APOE4 carrier status, given APOE's lipid transportation roles. However, extant studies rarely examined the modifying effects of APOE4 carrier status on the associations between lipids and CD.

METHODS

We analyzed the Chicago Health and Aging Project, a 20-year cohort study comprising older adults with lipid panel assayed, i.e., total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL), and longitudinal cognitive tests. We ran adjusted linear mixed-effects models, regressing cognitive test composite on each of the four lipids independently, first with the total sample and subsequently using interaction and stratified subgroup analyses, examining the modifying effects of APOE4 carrier status on the associations.

RESULTS

3,496 biracial community-dwelling older adults were recruited from the South side of Chicago (58% African American & 64% women; mean follow-up = 4.6 years). In the total sample, there was a borderline association between TG and CD, estimate (SD, p-value) = 0.0001 (0.0000,0.0565). No associations were detected with other lipids. In the interaction and subgroup analyses, only in ε4 carriers that higher TC levels were significantly associated with accelerated CD, -0.020 (0.009,0.035), whereas higher TG levels were significantly associated with decelerated CD, 0.001 (0.001,0.045). No modifying effects of ε4 carrier status were detected with other lipids.

DISCUSSION

Specific lipids, i.e., TC and TG, were associated with CD only in the ε4 carriers, highlighting the potential importance of measuring APOE4 status to better inform risk prediction and treatment.

Association of Year-to-Year Lipid Variability With Risk of Cognitive Decline and Dementia in Community-Dwelling Older Adults

BACKGROUND AND OBJECTIVES

Lipid metabolism in older adults is affected by various factors including biological aging, functional decline, reduced physiologic reserve, and nutrient intake. The dysregulation of lipid metabolism could adversely affect brain health. This study investigated the association between year-to-year intraindividual lipid variability and subsequent risk of cognitive decline and dementia in community-dwelling older adults.

METHODS

ASPirin in Reducing Events in the Elderly (ASPREE) was a randomized trial of aspirin, involving 19,114 participants aged 65 years and older from Australia and the United States who were free of dementia and major cognitive impairment. ASPREE-eXTension is the post-trial observational follow-up of participants, currently to a maximum of 11 years. This post hoc analysis included participants who had lipid levels measured at baseline and in years 1, 2, and 3. Year-to-year variability in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and triglycerides over the first 3 years was quantified using variability independent of the mean. Individuals who initiated or discontinued lipid-lowering therapy during this period were excluded. Multivariable Cox proportional hazards regression was used to analyze associations with incident dementia, adjudicated by expert panels, and cognitive impairment with no dementia (CIND) confirmed by a battery of cognitive tests, occurring after year 3. A linear mixed model was used for assessing the association with changes in 4 cognitive function domains, including global, memory, processing speed, verbal fluency, and a composite score from baseline to the end of follow-up.

RESULTS

The analysis included 9,846 individuals (median [interquartile range] age: 73.9 [71.7-77.3] years, 54.9% female). 509 incident dementia and 1,760 CIND events were recorded over a median follow-up of 5.8 and 5.4 years after variability assessment. The hazard ratios (95% CI) comparing the highest and lowest quartiles of TC and LDL-c variability were 1.60 (1.23-2.08) and 1.48 (1.15-1.91) for dementia and 1.23 (1.08-1.41) and 1.27 (1.11-1.46) for CIND. Higher TC and LDL-c variability was also associated with a faster decline in global cognition, episodic memory, psychomotor speed, and the composite score (all p < 0.001). No strong evidence was found for an association of HDL-c and triglyceride variability with dementia and cognitive change.

DISCUSSION

Tracking variability of TC and LDL-c may serve as a novel biomarker of incident dementia and cognitive decline in older adults.

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 Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (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, 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 (PRSs) 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 total cholesterol [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 PRSs, providing important real-world perspectives on how longitudinal levels and variation of blood-lipid concentrations contribute to risk of cognitive decline.

Lipids, lipoproteins, and apolipoproteins: Associations with cognition and dementia

Due to increasing lifespan and aging populations globally there has been a steep rise in late-life dementia, which is now the second most common cause of death in high-income countries. In general, dementia can be divided into two major groups: Alzheimer's disease (AD) and vascular-related dementia (VD). AD is pathologically characterised by senile plaques containing amyloid-β and neurofibrillary tangles composed of hyperphosphorylated tau, whereas VD is dominated by vascular pathology such as cerebral small vessel disease, major strokes, and white matter lesions. Recently, the importance of vascular components in AD is increasingly recognized and it is estimated that up to 45 % of all dementia cases can be prevented by preventing or treating midlife cardiovascular risk factors such as physical inactivity, diabetes, and hypertension. Even though the brain contains approximately 25 % of the total body cholesterol pool, and several genetic variants related to the lipid metabolism have been identified in genome-wide associations studies of AD, the role of lipids, lipoproteins, and apolipoproteins in dementia risk is less well-known. In this review, we go through the current literature on lipids, lipoproteins, and apolipoproteins and risk of dementia. We conclude that the evidence is primarily insufficient or conflicting, possibly due to nonoptimal study designs. The future calls for large, prospective studies of midlife measurements of lipids, lipoproteins, and apolipoproteins and one-sample, individual level data Mendelian randomization studies to overcome survival bias. However, the current literature suggests that it is safe to say that what is good for the heart is good for the brain.

Cognitive function in dyslipidemia patients: exploring the impact of statins

Background

Evidence regarding the relationship between the use of statins and cognitive outcomes presents varying findings. This study aims to analyze the relationship between sustained statin use and cognitive performance in dyslipidemia patients.

Methods

This study presents findings from the Beijing Ageing Brain Rejuvenation Initiative (BABRI) study, in which a cohort of community-dwelling dyslipidemia patients (Entire sample, N = 1,062, aged 50-86) was recruited. Participants were divided into two groups based on their sustained use statins (Statins group, N = 677) or not use any lipid-lowering agents (Untreated group, N = 385). Furthermore, the entire sample was stratified by age into the middle-aged sample (N = 451) and the older people sample (N = 611), following a similar categorization based on statin application. ANCOVA was used to evaluate the relationship between sustained statin use and cognitive function.

Results

Overall, in the total sample, the statins group demonstrated better cognition in overall cognition, memory, visuospatial ability, attention, executive function, and language domains compared to the untreated group. Moreover, the statins group only showed better performance in attention among the middle-aged sample. In the older people sample, statins group exhibited superior cognitive performance across various cognitive domains compared to untreated group.

Conclusion

Among dyslipidemia patients in Beijing community, sustained statin users exhibited superior cognitive function across all domains compared to untreated individuals, with particularly noticeable improvements among those aged 65 and above. These findings underscore the protective effect of statins on cognitive function in dyslipidemia patients, highlighting significant benefits for the older people population.

Identifying the earliest-occurring clinically targetable precursors of late-onset Alzheimer's disease

Most cases of Alzheimer's disease (AD) are late-onset dementias (LOAD). However, research on AD is predominantly of early-onset disease (EOAD). The determinants of EOAD, gene variants of APP and presenilin proteins, are not the basic precursors of LOAD. Rather, multiple other genes and associated cellular processes underlie risk for LOAD. These determinants could be modified in individuals at risk for LOAD well before signs and symptoms appear. Studying brain cells produced from patient-derived induced-pluripotent-stem-cells (iPSC), in culture, will be instrumental in developing such interventions. This paper summarises evidence accrued from iPSC culture models identifying the earliest occurring clinically targetable determinants of LOAD. Results obtained and replicated, thus far, suggest that abnormalities of bioenergetics, lipid metabolism, digestive organelle function and inflammatory activity are primary processes underlying LOAD. The application of cell culture platforms will become increasingly important in research and also on LOAD detection, assessment, and treatment in the years ahead.

Temporal Characterization of the Amyloidogenic APPswe/PS1dE9;hAPOE4 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aβ) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aβ immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aβ deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aβ, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy.

New approach for early and specific Alzheimer disease diagnosis from different plasma biomarkers

BACKGROUND

Alzheimer Disease (AD) is a complex pathology, in which several biochemical pathways could be involved. Therefore, the development of clinical studies combining different nature biomarkers in an AD diagnosis approach is required. Specifically, the present study evaluated blood biomarkers from different molecular pathways (epigenomics, lipid metabolism, lipid peroxidation), to obtain an early and specific AD diagnosis approach.

METHODS

The participants were classified into early AD (n = 53), and non-AD (healthy controls, other dementias) (n = 83). Blood samples were collected and biochemical determinations (microRNAs, lipids, lipid peroxidation compounds) were carried out by quantitative PCR and liquid chromatography coupled to mass spectrometry, respectively. Then, a logistic regression model with a Bayesian variable selection procedure was developed.

RESULTS

The Bayesian variable selection procedure for microRNAs did not show any relevant variable. Therefore, microRNA biomarkers were excluded. So, the developed model considered only lipids and lipid peroxidation compounds. The corresponding selected variables were age, 18:0 LPC, PGE2, isoprostanes and, isofurans. The validated model (by leave-one-out cross-validation) provided satisfactory diagnosis indexes (AUC 0.83, Sensitivity 87 %, Specificity 79 %).

CONCLUSION

The developed model included biomarkers from different pathways (lipid metabolism, oxidative stress), achieving a promising approach to early, specific and, minimally invasive AD diagnosis. Nevertheless, further work to validate clinically these preliminary results with an external cohort is required. Also, the integration of different compounds coming from several biochemical pathways could constitute a relevant research field for the development of AD therapeutic targets.

The "Hit and Run" Hypothesis for Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is a devastating neurodegenerative disorder affecting millions worldwide. Emerging research has challenged the conventional notion of a direct correlation between amyloid deposition and neurodegeneration in AD. Recent studies have suggested that amyloid and Tau deposition act as a central nervous system (CNS) innate immune driver event, inducing chronic microglial activation that increases the susceptibility of the AD brain to the neurotoxicity of infectious insults. Although modifiable risk factors account for up to 50% of AD risk, the mechanisms by which they interact with the core process of misfolded protein deposition and neuroinflammation in AD are unclear and require further investigation. This update introduces a novel perspective, suggesting that modifiable risk factors act as external insults that, akin to infectious agents, cause neurodegeneration by inducing recurrent acute neurotoxic microglial activation. This pathological damage occurs in AD pathology-primed regions, creating a "hit and run" mechanism that leaves no discernible pathological trace of the external insult. This model, highlighting microglia as a pivotal player in risk factor-mediated neurodegeneration, offers a new point of view on the complex associations of modifiable risk factors and proteinopathy in AD pathogenesis, which may act in parallel to the thoroughly studied amyloid-driven Tau pathology, and strengthens the therapeutic rationale of combining immune modulation with tight control of risk factor-driven insults.

Gut microbiota in combination with blood metabolites reveals characteristics of the disease cluster of coronary artery disease and cognitive impairment: a Mendelian randomization study

Background

The coexistence of coronary artery disease (CAD) and cognitive impairment has become a common clinical phenomenon. However, there is currently limited research on the etiology of this disease cluster, discovery of biomarkers, and identification of precise intervention targets.

Methods

We explored the causal connections between gut microbiota, blood metabolites, and the disease cluster of CAD combined with cognitive impairment through two-sample Mendelian randomization (TSMR). Additionally, we determine the gut microbiota and blood metabolites with the strongest causal associations using Bayesian model averaging multivariate Mendelian randomization (MR-BMA) analysis. Furthermore, we will investigate the mediating role of blood metabolites through a two-step Mendelian randomization design.

Results

We identified gut microbiota that had significant causal associations with cognitive impairment. Additionally, we also discovered blood metabolites that exhibited significant causal associations with both CAD and cognitive impairment. According to the MR-BMA results, the free cholesterol to total lipids ratio in large very low density lipoprotein (VLDL) was identified as the key blood metabolite significantly associated with CAD. Similarly, the cholesteryl esters to total lipids ratio in small VLDL emerged as the primary blood metabolite with a significant causal association with dementia with lewy bodies (DLB). For the two-step Mendelian randomization analysis, we identified blood metabolites that could potentially mediate the association between genus Butyricicoccus and CAD in the potential causal links.

Conclusion

Our study utilized Mendelian randomization (MR) to identify the gut microbiota features and blood metabolites characteristics associated with the disease cluster of CAD combined with cognitive impairment. These findings will provide a meaningful reference for the identification of biomarkers for the disease cluster of CAD combined with cognitive impairment as well as the discovery of targets for intervention to address the problems in the clinic.

Melanin: a unifying theory of disease as exemplified by Parkinson's, Alzheimer's, and Lewy body dementia

Melanin, a ubiquitous dark pigment, plays important roles in the immune system, including scavenging reactive oxygen species formed in response to ultraviolet radiation absorption, absorbing metals, thermal regulation, drug uptake, innate immune system functions, redox, and energy transduction. Many tissue types, including brain, heart, arteries, ovaries, and others, contain melanin. Almost all cells contain precursors to melanin. A growing number of diseases in which there is a loss of melanin and/or neuromelanin are increasingly thought to have infectious etiologies, for example, Alzheimer's disease (AD), Parkinson's disease (PD), Lewy Body Dementia (LBD), and vitiligo. AD, PD, LBD, and vitiligo have been linked with herpesvirus, which enters melanosomes and causes apoptosis, and with gut dysbiosis and inflammation. Herpesvirus is also linked with gut dysbiosis and inflammation. We theorize that under normal healthy states, melanin retains some of the energy it absorbs from electromagnetic radiation, which is then used to fuel cells, and energy from ATP is used to compliment that energy supply. We further theorize that loss of melanin reduces the energy supply of cells, which in the case of AD, PD, and LBD results in an inability to sustain immune system defenses and remove the plaques associated with the disease, which appear to be part of the immune system's attempt to eradicate the pathogens seen in these neurodegenerative diseases. In addition, in an attempt to explain why removing these plaques does not result in improvements in cognition and mood and why cognitions and moods in these individuals have ebbs and flows, we postulate that it is not the plaques that cause the cognitive symptoms but, rather, inflammation in the brain resulting from the immune system's response to pathogens. Our theory that energy retained in melanin fuels cells in an inverse relationship with ATP is supported by studies showing alterations in ATP production in relationship to melanin levels in melanomas, vitiligo, and healthy cells. Therefore, alteration of melanin levels may be at the core of many diseases. We propose regulating melanin levels may offer new avenues for treatment development.