Tau is a protein present in all nerve cells, where it plays a key role in keeping them functioning properly.
But a rogue form of the protein can trigger the formation of protein clumps within nerve cells known as neurofibrillary tangles. It is thought that these tangles are likely to be a major cause of Alzheimer's disease.
In the latest study researchers, led by a team from University Hospital, Basel, extracted sections of brain from mice expressing a mutant form of human tau protein.
Analysis showed that this induced normal human tau proteins in the healthy mice to clump together to form neurofibrillary tangles. These newly-formed tangles were also able to spread to nearby regions in the brain.
Another type of rogue protein - the prions - which cause diseases such as vCJD, are thought to be able to twist themselves into a shape which gives them the ability to "infect" nearby healthy tissue.
"This opens new avenues in dementia research that will aim to understand how abnormal tau can spread. We can also investigate how diseases caused by tau aggregates and prions are similar."
-Dr. Michel Goedert of the MRC Laboratory of Molecular Biology in Cambridge
2. Chemical Clue to Dementia Decline
The latest study was based on 49 people who had been diagnosed with very mild Alzheimer's disease.
A sample of spinal fluid was taken from each, and analysed for levels of several chemicals - or biomarkers - associated with Alzheimer's. The patients were then followed up an average of three-and-a-half years later.
The researchers linked accelerated progress of Alzheimer's to several low levels of a protein called amyloid, and high levels of two other proteins, called tau and phosphorylated tau 181.
The disease also progressed more rapidly in people whose tau level was relatively high in comparison to their amyloid level.
"This interesting research could lead to a new way of detecting people with dementia early, before they develop devastating symptoms. This is absolutely vital if we are to find drugs that help people at an early stage."-Dr Susanne Sorensen, head of research at the Alzheimer's Society
3.Controlling Fatty Acid Levels in the Brain Could Help
Scientists from Gladstone Institute of Neurological Disease and the University of California looked at fatty acids in the brains of normal mice and compared them with those in mice genetically engineered to have an Alzheimer's-like condition.
They identified raised levels of a fatty acid called arachidonic acid in the brains of the Alzheimer's mice.
Its release is controlled by the PLA2 enzyme.The scientists again used genetic engineering to lower PLA2 levels in the animals, and found that even a partial reduction halted memory deterioration and other impairments.
Dr. Rene Sanchez-Mejia, who worked on the study, said: "The most striking change we discovered in the Alzheimer's mice was an increase in arachidonic acid and related metabolites [products] in the hippocampus, a memory centre that is affected early and severely by Alzheimer's disease."
He suggested too much arachidonic acid might over-stimulate brain cells, and that lowering levels allowed them to function normally.
Dr. Lennart Mucke, who led the research, added: "In general, fatty acid levels can be regulated by diet or drugs. Our results have important therapeutic implications because they suggest that inhibition of PLA2 activity might help prevent neurological impairments in Alzheimer's disease.
"But a lot more work needs to be done before this novel therapeutic strategy can be tested on humans."
"This is a novel and potentially exciting area of research, but it is still at a very early stage. Much more research is needed to see if fatty acids could lead to a treatment for those living with the devastating effects of Alzheimer's disease."-Professor Clive Ballard, director of Research at the Alzheimer's Society
4. Nicotinamide May Be 'Alzheimer's Aid'
A vitamin found in meat, fish and potatoes may help protect the brain from Alzheimer's disease - and even boost memory in healthy people.
US researchers found vitamin B3 lowered levels of a protein linked to Alzheimer's damage in mice.
The Journal of Neuroscience study also showed the animals performed better at memory tests.
UK Alzheimer's charities said people should not start taking the vitamin before results from human studies. The vitamin, also called nicotinamide by scientists, is sold in UK pharmacies and health food shops.
It has already been shown to help people suffering from diabetes complications and has some anti-inflammatory qualities.
The researchers, from the University of California at Irvine, added the vitamin to drinking water given to mice bred to develop a version of Alzheimer's disease, then tested the levels of certain chemicals associated with the condition.
They found that levels of one, called phosphorylated tau, were significantly lower in the animals. This protein is involved in abnormal 'deposits' in brain cells, called 'tangles', which contribute to the brain damage which progressively affects people with Alzheimer's.
"Nicotinamide has a very robust effect on neurons. It prevents loss of cognition in mice with Alzheimer's disease, and the beauty of it is we already are moving forward with a clinical trial."
-Dr. Kim Green, head of the study at University of California at Irvine