Commentary on “Perspective on a pathogenesis and treatment of Alzheimer's disease.” Apolipoprotein E and the mitochondrial metabolic hypothesis

The Early Events That Initiate β-Amyloid Aggregation in Alzheimer's Disease

Alzheimer’s disease (AD) is characterized by the development of amyloid plaques and neurofibrillary tangles (NFTs) consisting of aggregated β-amyloid (Aβ) and tau, respectively. The amyloid hypothesis has been the predominant framework for research in AD for over two decades. According to this hypothesis, the accumulation of Aβ in the brain is the primary factor initiating the pathogenesis of AD. However, it remains elusive what factors initiate Aβ aggregation. Studies demonstrate that AD has multiple causes, including genetic and environmental factors. Furthermore, genetic factors, many age-related events and pathological conditions such as diabetes, traumatic brain injury (TBI) and aberrant microbiota also affect the aggregation of Aβ. Here we provide an overview of the age-related early events and other pathological processes that precede Aβ aggregation.

Novel natural structure corrector of ApoE4 for checking Alzheimer's disease: benefits from high throughput screening and molecular dynamics simulations

A major genetic suspect for Alzheimer's disease is the pathological conformation assumed by apolipoprotein E4 (ApoE4) through intramolecular interaction. In the present study, a large library of natural compounds was screened against ApoE4 to identify novel therapeutic molecules that can prevent ApoE4 from being converted to its pathological conformation. We report two such natural compounds PHC and IAH that bound to the active site of ApoE4 during the docking process. The binding analysis suggested that they have a strong mechanistic ability to correct the pathological structural orientation of ApoE4 by preventing repulsion between Arg 61 and Arg 112, thus inhibiting the formation of a salt bridge between Arg 61 and Glu 255. However, when the molecular dynamics simulations were carried out, structural changes in the PHC-bound complex forced PHC to move out of the cavity thus destabilizing the complex. However, IAH was structurally stable inside the binding pocket throughout the simulations trajectory. Our simulations results indicate that the initial receptor-ligand interaction observed after docking could be limited due to the receptor rigid docking algorithm and that the conformations and interactions observed after simulation runs are more energetically favored and should be better representations of derivative poses in the receptor.

Complex disease-associated pharmacogenetics: drug efficacy, drug safety, and confirmation of a pathogenetic hypothesis (Alzheimer's disease)

Safety and efficacy pharmacogenetics can be applied successfully to the drug discovery and development pipeline at multiple phases. We review drug-target screening using high throughput SNP associations with complex diseases testing more than 1,800 candidate targets with approximately 7,000 SNPs. Alzheimer's disease data are provided as an example. The supplementation of target-selected screening with genome-wide SNP association, to also define susceptibility genes and relevant disease pathways for human diseases, is discussed. Applications for determining predictive genetic or genomic profiles, or derived biomarkers, for drug efficacy and safety during clinical development are exemplified by several successful experiments at different phases of development. A Phase I-IIA study of side effects using an oral drug for the treatment of breast cancer is used as an example of early pipeline pharmacogenetics to predict side effects and allow optimization of dosing. References are provided for several other recently published genetic association studies of adverse events during drug development. We illustrate the early identification of gene variant candidates related to efficacy in a Phase IIA obesity drug trial to generate hypotheses for testing in subsequent development. How these genetic data generated in Phase IIA are subsequently incorporated as hypotheses into later Phase clinical protocols is discussed. A Phase IIB clinical trial for Alzheimer's disease is described that exemplifies the major pipeline decision between program attrition and further clinical development. In this case, there was no significant improvement in 511 intention-to-treat patients but, applying a confirmed prognostic biomarker (APOE4) to segment the clinical trial population, all three doses of rosiglitazone demonstrated improvement in patients who did not carry the APOE4 allele. The data for the APOE4 carriers demonstrated no significant improvement but suggested that there may be a need for higher doses. Thus, a development program that would have been terminated progressed to Phase III registration trials based on the results of prospective efficacy pharmacogenetic analyses. The implications of using APOE genotype as a biomarker to predict efficacy and possibly dose, as well as supporting the basic neurobiology and pharmacology that provided the original target validation, is discussed. Citations are provided that support a slow neurotoxic effect over many years of a specific fragment of apoE protein (over-produced by apoE4 substrate compared to apoE3) on mitochondria and the use of rosiglitazone to increase mitochondrial biogenesis and improve glucose utilization. Pharmacogenetics is currently being used across the pipeline to prevent attrition and to create safer and more effective medicines.