Development of new biomarker in alzheimer's disease: interleukin 18

Alzheimer?s disease (AD) is the most common form of dementia in elderly. It is characterized by progressive deterioration of cognitive functions. In clinical practice, current criteria for diagnosis of AD are still largely based on the exclusion of secondary causes and other dementive disorders. In addition to AD, cerebrovascular stroke (CvS) is also a common cause of dementia in elderly. Despite the heterogeneous nature of both AD and CvS, the inflammatory aspects of the pathogenesis of these diseases are prominent. Interleukin-18 (IL-18) is a proinflammatory cytokine that induces IFN stimulation in T and NK cells. It has been accepted as a biomarker in ischemic coronary disease. In this project, we aimed to search IL-18 as possible diagnostic biomarker to distinguish AD patients from control subjects and CvS patients. In this study 19 AD, 10 CvS patients and 15 control subjects were included. IL-18 seum levels determined by enzyme linked immunosorbent immunoassay (ELISA) and IL-18 gen expressions analyzed with real-time PCR absolute quantification from peripheral lymphocytes. The IL-18 gene expression is elevated in AD patients compared to CvS patients and control subjects (p=0,006).There were no significant differences in the serum levels of IL-18 neither between AD and CvS patients nor between control subject and patient groups. Despite this, there was a correlation between Mini Mental State Examination (MMSE) and serum levels of AD patients. Taken together, these results indicate that IL- 18 can be a candidate diagnostic biomarker for AD. Key words: Alzheimer?s disease, cerebrovascular disease, stroke, interleukin-18, biomarker