# The Role of Beetroot Ingredients in the Prevention of Alzheimer's Disease
## 2 General Characteristics of Alzheimer's Disease  
AD is among the most common conditions classified as neurodegenerative. It is an insidious disease developing over the course of many years without acute symptoms. When the early symptoms are observed, they are often ignored and attributed to age or stress [1; 8]. Based on the bulk of current medical knowledge on this topic, AD is classified as a progressive and incurable disease. It is manifested by dementia, and as such is a condition that significantly hinders the patients' ability to function normally by affecting their capacity for rational thought and remembering. It also negatively affects communicative abilities and food ingestion (swallowing reflex) [9]. A number of hypotheses as to the causes of the disease are currently explored, in particular: the cholinergic hypothesis, amyloid hypothesis, and tau hypothesis. However, there are also others that link the development of the disease to biochemical disorders related to neurotransmitters, infectious stimuli, genetic factors associated with gene defects, or increased levels of oxidative stress [10; 11]. One posited explanation regarding the etiology of the disease is the cholinergic hypothesis that pertains to the transmission of neural impulses within the cholinergic system. The system is involved in the regulation of higher cortical functions, specifically the ability to concentrate and focus one's attention on particular tasks, as well as the capacity to learn and remember [12]. It is hypothesized that AD may be caused by the insufficient concentration of the neurotransmitter acetylcholine in the central nervous system. To improve the efficiency of neurotransmission, therapeutics stimulating adequate (nicotinic and muscarinic) receptors are used alongside blockers of acetylcholinesterase, the enzyme responsible for acetylcholine hydrolysis [13]. The amyloid hypothesis posits that AD is in fact amyloidosis and explains that the direct cause of the disease is excessive, pathological accumulation of amyloid proteins. The cause of the disease is related to the gene encoding proteins present in the cytoplasmic membrane of neurons. The gene is located on chromosome 21 and encodes a peptide composed of approx. 700 amino acids, the so-called \(\beta\)-amyloid precursor protein [11; 14; 15]. Under physiological conditions, non-amyloidogenic cleavage of beta-amyloid precursor protein occurs with the participation of \(\alpha\)-secretase. As a result, a soluble form of the protein is formed. In amyloidogenic conditions, the beta-amyloid precursor protein is cleaved by \(\beta\)-secretase and \(\gamma\)-secretase. The final products of these transformations are insoluble, toxic \(\beta\)-amyloid polypeptides containing 40 or 42 amino acids. They are characterized by a higher predisposition for the formation of larger amyloid structures. Due to the extracellular emergence and accumulation of \(\beta\)-amyloid protein, so-called amyloid plaques (senile plaques) are formed. Amyloid plaques bind with neuronal receptors and modify the structure of intraneuronal connections, disrupting the transfer of neural impulses [16]. Yet another hypothesis aiming to explain the onset of AD connects it to excessive phosphorylation of the tau protein. Tau proteins are related to the microtubules responsible for the correct neuronal cytoskeleton. Tau proteins contribute to stabilizing the structures responsible for the formation of the cytoskeleton. They maintain the correct distance between microtubules. Physiologically, tau proteins are present in six distinct forms. All those forms are encoded by the same gene (MAPT), located on chromosome 17. The differences between the respective forms of tau proteins result from varying combinations of encoding sequences (exons). MAPT mutation leads to the formation of tau proteins with excessive phosphorylation. The structure of proteins produced due to the transcription of the faulty gene differs from that of the physiological protein.