The occurrence of cerebrovascular atherosclerosis in Alzheimer's disease patients

Characterization of Blood Surrogate Immune-Methylation Biomarkers for Immune Cell Infiltration in Chronic Inflammaging Disorders

Alzheimer’s disease (AD) and atherosclerosis are both chronic age- and inflammation-dependent diseases. In addition, atherosclerosis is frequently observed in AD patients indicating common involvement of vascular components in both disease etiologies. Recently, epigenome-wide association studies have identified epigenetic alterations, and in particularly DNA methylation changes for both disorders. We hypothesized the existence of a common DNA methylation profile in atherosclerosis and AD which may be valuable as a blood-based DNA methylation inflammaging biomarker. Using publicly available 450k Illumina methylation datasets, we identified a co-methylation network associated with both atherosclerosis and AD in whole blood samples. This methylation profile appeared to indicate shifts in blood immune cell type distribution. Remarkably, similar methylation changes were also detected in disease tissues, including AD brain tissues, atherosclerotic plaques, and tumors and were found to correlate with immune cell infiltration. In addition, this immune-related methylation profile could also be detected in other inflammaging diseases, including Parkinson’s disease and obesity, but not in multiple sclerosis, schizophrenia, and osteoporosis. In conclusion, we identified a blood-based immune-related DNA methylation signature in multiple inflammaging diseases associated with changes in blood immune cell counts and predictive for immune cell infiltration in diseased tissues. In addition to epigenetic clock measurements, this immune-methylation signature may become a valuable blood-based biomarker to prevent chronic inflammatory disease development or monitor lifestyle intervention strategies which promote healthy aging.

Pharmacogenetics of Vascular Risk Factors in Alzheimer's Disease

Alzheimer’s disease (AD) is a polygenic/complex disorder in which genomic, epigenomic, cerebrovascular, metabolic, and environmental factors converge to define a progressive neurodegenerative phenotype. Pharmacogenetics is a major determinant of therapeutic outcome in AD. Different categories of genes are potentially involved in the pharmacogenetic network responsible for drug efficacy and safety, including pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes. However, most drugs exert pleiotropic effects that are promiscuously regulated for different gene products. Only 20% of the Caucasian population are extensive metabolizers for tetragenic haplotypes integrating CYP2D6-CYP2C19-CYP2C9-CYP3A4/5 variants. Patients harboring CYP-related poor (PM) and/or ultra-rapid (UM) geno-phenotypes display more irregular profiles in drug metabolism than extensive (EM) or intermediate (IM) metabolizers. Among 111 pentagenic (APOE-APOB-APOC3-CETP-LPL) haplotypes associated with lipid metabolism, carriers of the H26 haplotype (23-TT-CG-AG-CC) exhibit the lowest cholesterol levels, and patients with the H104 haplotype (44-CC-CC-AA-CC) are severely hypercholesterolemic. Furthermore, APOE, NOS3, ACE, AGT, and CYP variants influence the therapeutic response to hypotensive drugs in AD patients with hypertension. Consequently, the implementation of pharmacogenetic procedures may optimize therapeutics in AD patients under polypharmacy regimes for the treatment of concomitant vascular disorders.

Elevated levels of serum cholesterol are associated with better performance on tasks of episodic memory

We examined how serum cholesterol, an established risk factor for cerebrovascular disease (CVD), relates to cognitive function in healthy middle-older aged individuals with no neurologic or CVD history. A complete lipid panel was obtained from a cohort of one hundred twenty individuals, ages 43-85, who also underwent a comprehensive neuropsychological examination. In order to reduce the number of variables and empirically identify broad cognitive domains, scores from neuropsychological tests were submitted into a factor analysis. This analysis revealed three explainable factors: Memory, Executive Function and Memory/Language. Three separate hierarchical multiple regression analyses were conducted using individual cholesterol metrics (total cholesterol, low density lipoprotein; LDL, high density lipoprotein; HDL, and triglycerides), as well as age, education, medication status (lipid lowering agents), ApoE status, and additional risk factors for CVD to predict neuropsychological function. The Memory Factor was predicted by a combination of age, LDL, and triglyceride levels; both age and triglycerides were negatively associated with factor score, while LDL levels revealed a positive relationship. Both the Executive and Memory/Language factor were only explained by education, whereby more years were associated with better performance. These results provide evidence that individual cholesterol lipoproteins and triglycerides may differentially impact cognitive function, over and above other common CVD risk factors and ApoE status. Our findings demonstrate the importance of consideration of vascular risk factors, such as cholesterol, in studies of cognitive aging.

White matter hypoperfusion and damage in dementia: post-mortem assessment

Neuroimaging has revealed a range of white matter abnormalities that are common in dementia, some that predict cognitive decline. The abnormalities may result from structural diseases of the cerebral vasculature, such as arteriolosclerosis and amyloid angiopathy, but can also be caused by nonstructural vascular abnormalities (eg, of vascular contractility or permeability), neurovascular instability or extracranial cardiac or vascular disease. Conventional histopathological assessment of the white matter has tended to conflate morphological vascular abnormalities with changes that reflect altered interstitial fluid dynamics or white matter ischemic damage, even though the latter may be of extracranial or nonstructural etiology. However, histopathology is being supplemented by biochemical approaches, including the measurement of proteins involved in the molecular responses to brain ischemia, myelin proteins differentially susceptible to ischemic damage, vessel-associated proteins that allow rapid measurement of microvessel density, markers of blood-brain barrier dysfunction and axonal injury, and mediators of white matter damage. By combining neuroimaging with histopathology and biochemical analysis, we can provide reproducible, quantitative data on the severity of white matter damage, and information on its etiology and pathogenesis. Together these have the potential to inform and improve treatment, particularly in forms of dementia to which white matter hypoperfusion makes a significant contribution.