Friday, 16 March 2012

New Research for Alzheimer’s Disease, A Debilitating Disorder

Initially identified as ‘presenile dementia’ by Aloysius Alzheimer in 1907, Alzheimer’s disease (AD) is a cumulative neurodegenerative disease. It causes a gradual deterioration of mental health, worsening from memory loss to dementia, escalating to even death in an average of approximately eight years. It is rife in old age with the risk escalating close to fifty percent in the proximity of age eighty-five years. An estimated 160,000 Australians are affected by dementia with Alzheimer’s disease constituting 50-75 percent of these cases. 26.6 million people worldwide were affected by AD in 2006 and it is gauged that 1 in 85 people around the globe will be influenced by Alzheimer’s disease by the year 2050.

Genetic variation is recognised as a key contributor to the risk of AD with three genes being identified through research in the 1990s, as accounting for “autosomal dominant inheritance”[2] and another being associated with inheritance. Significant efforts have been made in the past decade to effectively evaluate the genetic studies associated with AD. Promising results have been confirmed from the “genome-wide association studies (GWAS)”[1] conducted recently. Four reports were made available of GWAS for AD through January in 2009. These reports analysed independent genotypes, while an additional study utilised a “pooling strategy”[2] to examine the latent functionality of “single nucleotide polymorphisms (SNPs)”[3]. Studies were made by different groups through 2007, 2008 and 2009. Each study used varied sample sizes, most of which were deemed to be of modest size for a GWAS. No sign of overlap has been seen between the studies other than Apolipoprotein E (APOE), for identified loci. Despite theses studies and the results obtained, not enough data has been collected from GWAS to draw concrete conclusions for AD. With more replications and further analysis it is expected that more genes will be identified to be associated with AD as a result of these studies.

At the current point in time, more than fifteen years after the uncovering of the first genes to be associated with AD, a huge amount has been learnt about this condition, even though many are still on a quest to discover additional genes. It has been shown through studies conducted recently, that a potential approach of treatment of AD is the regulation of APOE. Despite there still being no cure or even a prevention strategy, knowledge of AD and the risks it poses as well as prenatal diagnosis is now available to a far greater degree than was once possible.

Frustration has often plagued scientists and investigators that are associated with AD, and even followed the initial successes with the genetics of this debilitating disease. No additional genes have been identified since the 1990s, however an influx of new data has been gained from “genetic linkage and association studies”[2]. It is expected that as new genes are identified and the biological pathways of AD are researched, the prevention and even treatment of the disease may be plausible.

References:

Reece, J. B. et al., 2011. Campbell Biology. 9th (Australian Version) ed. Pearson Australia Group Pty Ltd.

[1] Moraes CF, Lins TC, Carmargos EF, Naves JO, Pereira RW, Nóbrega OT. (2011) Lessons from genome-wide association studies findings in Alzheimer's disease. DOI: 10.1111/j.1479-8301.2011.00378.x. Epub 2011 Oct 27.

[2] Dimitrios Avramopoulos. (2009) Genetics of Alzheimer’s disease: recent advances. DOI:10.1186/gm34. Published: 27 March 2009

[3] Reitz C, Conrad C, Roszkowski K, Rogers RS, Mayeux R. (2012) Effect of Genetic Variation in LRRTM3 on Risk of Alzheimer Disease. PMID:22393166. 2012 Mar 5. [Epub ahead of print]

Briones N, Dinu V. (2012) Data mining of high density genomic variant data for prediction of Alzheimer's disease risk. PMID:22273362. 2012 Jan 25;13(1):7. [Epub ahead of print]

David M. Holtzman, Joachim Herz, and Guojun Bu. (2012) Apolipoprotein E and Apolipoprotein E Receptors: Normal Biology and Roles in Alzheimer Disease. Cold Spring Harb Perspect Med. 2012 March; 2(3): a006312.



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