Dementia gene found in a third of teenagers

by Anna Hodgekiss for The Daily Mail:A form of Alzheimer's disease has been found in some teenagers - more than 20 years before symptoms even develop, according to a new study.Research on a group of young adults found about 30 per cent have a mutation of a gene called presenilin 1 (PSEN1), which makes them more likely to develop Alzheimer's at an unusually young age.Although the inherited form of the disease is rare, the researchers say it offers them a critical opportunity to look for early signs of the disease before clinical symptoms appear. Disappointing results in recent drug trials of prospective Alzheimer's treatments is thought to be down to timing - once the symptoms of the disease are apparent, damage to the nervous system may already be too extensive for drug treatments to have their greatest impact.As a result, if scientists could identify signs that an individual is likely to get Alzheimer's before symptoms appear, this could lead to more effective clinical trials, and result in advances in prevention of the disease. In the new study, published in the journal Lancet Neurology,  the researchers performed brain imaging, blood tests and analysis of cerebrospinal fluid (CSF) on 44 adults aged 18 to 26.Results showed 20 of the participants had the PSEN1 mutation, and were therefore certain to develop Alzheimer's; 24 did not carry the mutation.Researchers at The Banner Alzheimer's Institute in Arizona, Boston University and the University of Antioquia also found none of the participants showed any evidence of cognitive impairment at the time of the study.They discovered notable differences in brain structure and function between the two groups, with the PSEN1 mutation carriers experiencing greater activity in regions of the brain called the hippocampus - involved in memory - and the parahippocampus, as well as having less grey matter in certain brain areas. Results also showed CSF of those with the mutation had higher levels of a protein called amyloid beta, which appears to be over-produced. Amyloid beta is involved in the deposition of amyloid plaques in the brain, identified as a key biomarker of Alzheimer's - usually being present around 10 to 15 years before clinical onset.As 45 is the average age people with the PSEN1 mutation start showing cognitive impairment, the results show the biomarkers for Alzheimer's are evident at least 20 years before symptoms start.Dr Eric Reiman, of the Banner Alzheimer's Institute, said: 'These findings suggest that brain changes begin many years before the clinical onset of Alzheimer's disease, and even before the onset of amyloid plaque deposition. 'They raise new questions about the earliest brain changes involved in the predisposition to Alzheimer's and the extent to which they could be targeted by future prevention therapies."Another study using a technique called florbetapir PET to track amyloid plaque in people with the mutation found the plaques began accumulating when the individuals are in their late 20s.Dr Adam Fleisher, of the Banner Alzheimer's Institute, said the study will 'help set the stage for the evaluation of treatments to prevent familial Alzheimer's disease, and hopefully aid our understanding of the early stages of late-onset Alzheimer's disease, which is more widespread.'Professor Nick Fox, of University College London, said: 'These findings question our models of Alzheimer's disease on several fronts. 'They suggest that neurodegenerative changes occur over 20 years before symptom onset and somewhat earlier than was suggested by previous brain imaging studies of individuals at risk of inherited Alzheimer's disease. 'Further research is needed, but one interpretation of these results might be that they add to the accumulating evidence that Alzheimer's disease is characterised by a long pre-symptomatic period of slowly progressive changes that can potentially be tracked, thereby opening up a therapeutic window for early intervention.'Source: http://www.dailymail.co.uk/health/article-2228527/Dementia-gene-teenagers.html?ito=feeds-newsxmlPicture: Corbis