Chapters authored
Normal Aging and Dementia
Normal aging begins after 60 years of age. According to Harman, the accumulation of free radicals, which results from weakening of repair and protective mechanisms, takes place in the aging brain. It is believed that especially in the population of the most elderly there is increased incidence of both dementia and depression. The causes of these central nervous system disorders in the aging human body are changes at the molecular level, such as changes in the biochemical parameters, the accumulation of mutations in nuclear and mitochondrial DNA, and epigenetic changes. Biomarkers associated with aging of the brain include accumulated deposits of β-amyloid (Aβ), disturbed cholesterol homeostasis, altered neuroimaging parameters, and impaired glucose metabolism. Genetic factors are also responsible for normal aging, for example, SIRT1, AKT1, and CDKN1A, and among them the longevity genes, such as FOXO3A and CETP. Dementia as well as cognitive decline may be modified by poly-T variants of TOMM40 and APOE alleles via influencing the level of apolipoprotein E (apoE) in the brain and in the plasma as well as by its ability of Aβ clearance.
Part of the book: Update on Dementia
Aging and Neurological Diseases
Current knowledge indicates that the aging process starts with subclinical changes at the molecular level. These include the accumulation of mutations, telomere attrition, and epigenetic alterations leading to genomic instability. Such defects multiply exponentially over time, resembling a “snowball effect,” and eventually leading to morphological and functional deterioration of the brain, including progressive neuronal loss, reduced levels of neurotransmitters, excessive inflammation, and disrupted integrity of vessels, followed by infarction and microbleeds. Additionally, the decreasing efficiency of DNA repair mechanisms increases the susceptibility to reactive oxygen species and spontaneous mutagenesis, resulting in age-related neoplasia. Moreover, the malnutrition and malabsorption seen commonly in the elderly may cause deficiency of vitamin B12 and folic acid, both necessary for homocysteine metabolism, and lead to vascular damage. Altogether, these lead to brain damage in old age and greatly increase the risk of developing diseases of the central nervous system, such as stroke, epilepsy, Parkinson’s disease, Alzheimer’s disease, and other dementias.
Part of the book: Senescence