Are we close to a practical test for Alzheimer’s?
It’s no news that Alzheimer’s disease is a serious problem. 1 in 9 people over the age of 65 suffer from Alzheimer’s, and 1 in 3 seniors of age 85 and older have the disease. In addition to wide-spread, the condition is debilitating, time-consuming, and expensive for both patients and care-givers. This makes Alzheimer’s research more urgent than ever.
Currently, Alzheimer’s disease is diagnosed by brain imaging, neurological exams, and mental status tests. This means that many patients are developing Alzheimer’s disease for years before they have symptoms that lead to a diagnosis.
Recent studies have focused on identifying biomarkers for Alzheimer’s disease. Biomarkers are substances that can be measured and indicate the presence of a disease or pathological process. For example, many diabetic patients monitor the level of glycated hemoglobin (HbA1c) in their blood to determine whether their blood sugar levels are increasing or decreasing over extended periods of time. Biomarkers are used for diagnosing everything from autoimmune diseases to cancer. Several biomarkers for Alzheimer’s have been proposed, some from blood and some from cerebrospinal fluid (CSF).
A group of Japanese scientists have recently discovered another biomarker for Alzheimer’s disease: a group of seven microRNAs found in the blood. MicroRNAs (miRNA) are small, non-coding pieces of RNA that can pair with messenger RNA (mRNA) to prevent their message from being translated into protein. MiRNA thus serves to silence or down-regulate gene expression. It’s estimated that approximately 60% of all genes are regulated by miRNA.
There are several advantages to this newest Alzheimer’s biomarker. First, it’s present in the blood, which is important for several reasons. Drawing blood is simple, inexpensive, and relatively painless. It is a much more attractive option than having a lumbar puncture done to collect CSF, which is expensive and painful. The ease of testing may lead more patients to be regularly screened and hopefully diagnosed earlier, which can greatly impact disease progression.
Secondly, the biomarker is miRNA instead of proteins. While protein expression can be increased or decreased for many reasons, miRNA indicates gene activity. This enables scientists to identify and study pathways which may be responsible for underlying pathology. A better understanding of disease mechanisms can lead to new therapeutic targets and drug development. There is currently no therapy to treat Alzheimer’s disease, this discovery offers new hope.
Photo: Flickr, Rosie O’ Beirne
Kumar P, Dezso Z, MacKenzie C, Oestreicher J, Agoulnik S, et al. (2013). Circulating miRNA Biomarkers for Alzheimer’s Disease PLoS ONE DOI: 10.1371/journal.pone.0069807
Blennow K, Zetterberg H. (2009). Cerebrospinal fluid biomarkers for Alzheimer’s disease. J Alzheimers Dis. DOI: 10.1602/neurorx.1.2.213
Podlesniy P, Figueiro-Silva J, Llado A, Antonell A, Sanchez-Valle R, Alcolea D, Lleo A, Molinuevo JL, Serra N, & Trullas R (2013). Low cerebrospinal fluid concentration of mitochondrial DNA in preclinical Alzheimer disease. Annals of neurology PMID: 23794434
Doecke JD, Laws SM, Faux NG, Wilson W, Burnham SC, Lam CP, Mondal A, Bedo J, Bush AI, Brown B, De Ruyck K, Ellis KA, Fowler C, Gupta VB, Head R, Macaulay SL, Pertile K, Rowe CC, Rembach A, Rodrigues M, Rumble R, Szoeke C, Taddei K, Taddei T, Trounson B, A (2012). Blood-based protein biomarkers for diagnosis of Alzheimer disease. Arch Neurol. DOI: 10.1001/archneurol.2012.1282
alzheimer’s, alzheimer, disease, dementia, blood, fluid, test, diagnose, detect, biomarker, csf, drug, therapy