Open Journal of Endocrine and Metabolic Diseases, 2013, 3, 14-19 http://dx.doi.org/10.4236/ojemd.2013.32A003 Published Online May 2013 (http://www.scirp.org/journal/ojemd) Mitochondrial Dysfunction and Alzheimer’s Disease Fatimah M. Albrekkan, Marie Kelly-Worden Ball State University, Muncie, USA Email: mlkellyworde@bsu.edu Received February 28, 2013; revised March 26, 2013; accepted April 26, 2013 Copyright © 2013 Fatimah M. Albrekkan, Marie Kelly-Worden. This is an open access article distributed under the Creative Com- mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Alzheimer’s disease (AD) is a neurodegenerative disorder that is characterized by progressive loss of basal forebrain cholinergic neurons, leading to reduction in transmission through cholinergic fibers involved in processes of attention, learning, and memory. Mitochondria provide and regulate cellular energy and are crucial for proper neuronal activity and survival. Mitochondrial dysfunction is evident in early stages of AD and is involved in AD pathogenesis. This re- view focuses on the evidence supporting a clear association between amyloid-β toxicity, mitochondrial dysfunction, oxidative stress and neuronal damage/death in Alzheimer’s disease. To date, the beta amyloid (Aβ) cascade hypothesis still remains the main pathogenetic model of Alzheimer’s disease (AD), but its role in the majority of sporadic AD cases is uncertain. Furthermore, the “mitochondrial cascade hypothesis” could explain many of the biochemical, genetic, and pathological features of sporadic AD. This hypothesis promotes mutations in mitochondrial DNA (mtDNA) as the basis for Alzheimer’s disease. The mutations could lead to energy failure, increased oxidative stress, and accumulation of Aβ, which in a vicious cycle reinforces the mtDNA damage and oxidative stress. Keywords: Alzheimer’s; Mitochondria; Cybrid; Oxidative Stress 1. Introduction Alzheimer’s disease (AD) is the most common cause of dementia in the elderly. It is an epidemic disease with approximately 27 million people affected worldwide and because it is incurable, this number is only expected to rise (quadrupling by 2050). Alzheimer’s disease (AD) is a progressive and irreversible neurodegenerative disorder that is characterized by the appearance of amyloid fibrils and plaques. These plaques are formed by the polymeri- zation of the β-amyloid (Aβ) proteins that are derived from the β-amyloid precursor protein (APP). APP is hy- drolyzed by β-secretase and by the γ-secretase complex. The amyloid cascade hypothesis suggests that AD arises when the amount of amyloid or nature of amyloid is al- tered disrupting normal function. This leads to memory loss and neuronal cell death [1]. This is supported in the- ory by the main pathological feature of AD which is ex- tensive neurodegeneration of the brain in the regions of the median temporal lobe (the hippocampus in particular), parietal lobe, select regions of the frontal cortex and the cingulate gyrus [2]. The hippocampus is the region of the brain involved in the conversion of short term memory into long term memory; a process known as consolida- tion. There are two main forms of Alzheimer’s disease (AD). The first type, sporadic AD or SAD, is the most common form of AD and is characterized by a severe progressive decline in cognition and increased neuronal cell death. The second form, familial AD or FAD, progresses much faster and is initiated by mutations in components of the amyloid pathway such as APP, apolipoprotein E4 (Ap- oE4), presenilin-1 and presenilin-2 (PS1 and PS2) and sortilin-related receptor 1 (SORL1) [1]. The pathogenesis of Alzheimer’s disease is very co- mplex, and involves many molecular, cellular and phy- siological pathologies. Researchers have implicated solu- ble Aβ oligomers (also referred to as ADDLs) as the toxic component responsible for the development of AD- associated pathology including tau hyperphosphorylation, spine loss and abnormal spine morphology, formation of reactive oxygen species, prolonged long-term depression and inhibition of long-term potentiation as well as cell death [3]. Although the amyloid-β cascade hypothesis remains the main pathogenetic model of AD, this cascade is pos- sibly viable only for familial AD cases with mutations in AβPP and PS genes and its role in SAD is still uncertain. As a result, research has been directed to the role of mi- tochondria and oxidative phosphorylation defects in AD Copyright © 2013 SciRes. OJEMD