Degenerative neurological disease means a gradual structural and functional loss of neurons. Degenerative neurological diseases develop mainly due to infiltration into particular sites of the nervous system, and can be accompanied by symptoms such as dementia, extrapyramidal abnormality, cerebellar abnormality, sensory disturbance, and movement disorders. In several cases, degenerative neurological diseases may develop due to simultaneous infiltration into various sites of the nervous system, and thus accompanied by complex symptoms. The diagnosis is made according to the clinical manifestation of the patient. In this case, it is difficult to accurately diagnose disease because the symptoms are various and different diseases have common clinical symptoms (Soc. Sci. Med. Vol. 40. No. 6, pp. 847-858, 1995).
Dementia, one of the neurological disorders, is a disorder accompanied by general impairment of systemic functions such as memory impairment and loss of judgment. Although the symptoms are rarely seen before age 50, their development frequency gradually increases after age 60. As the elderly population increases due to the development of medical technology and quality of life, the population having dementia is a rapidly growing worldwide as well as in Korea. The number of dementia patients aged 65 years or older registered in 2008 is 421,000, accounting for 8.4% of the total population of the elderly, and by 2030, the number is expected to be 1,135,000, or 9.6% of the total elderly population. In 2008, the Ministry of Health and Welfare studied the prevalence of dementia and found that dementia has various onsets. About 70% of domestic dementias are of Alzheimer type, about 25% of them are of vascular type, and the remaining 5% or less are other alcoholic dementia and Parkinson's disease dementia.
Alzheimer's disease (AD), the most onset type of dementia, has two distinct lesions: formation of neurofibrillary tangles inside cells by hyperphosphorylation and coagulation of tau proteins in the neurons of the cerebral cortex and hippocampus of the brain; and formation of a plague outside cells by the coagulation of amyloid β-1/42.
The cause of Alzheimer's disease has not yet been clearly identified, but it is said that the tangle or the plague, which is the coagulated form of two proteins involved in coagulation, or precursors are deposited on neural cell sites responsible for brain memory and recognition, leading to dysfunction and death of neurons, thereby causing Alzheimer's disease. Tau proteins are charged in stabilizing with microtubules. However, due to the coagulation, tau proteins are decreased in number and fail to perform their normal functions, resulting in weaker binding force with microtubules and a long-term dysfunction. Therefore, individual neurons deteriorate in terms of function and further die.
On the other hand, osmotin derived from plants is involved in fatty acid oxidation regulation, glucose uptake, phosphorylation (AMP kinase) and signal transduction pathways. Osmotin (24 kDa) is a stable protein belonging to the PR-5 family, which is homologous to the sweet-testing protein thaumatin, and is known to induce intracellular signaling in yeast. Osmotin is resistant to heat, acid, and enzymes and can circulate through the body without digestion. These osmotins are known to be homologues of adiponectin present in animals. Adiponectin has been known to have anti-inflammatory, anti-diabetic and anti-atherosclerotic potentials. Osmotin is widely known for its effects on obesity and diabetes, and Korean Patent No. 1308232 discloses a composition for the prevention and treatment of neurological disease, the composition containing osmotin. However, there are no known compositions including osmotin peptide alone to prevent or ameliorate, or treat neurological diseases.