Research, published today in the journal Neurology, describes how mutations in a specific gene that codes for a neural growth factor appear to predict how quickly memory loss will progress in people with Alzheimer's disease.
Today, an estimated 5 million people in the United States are living with the disease.
The hallmark of Alzheimer's disease is a buildup of two types of protein: beta-amyloid plaques outside of nerve cells, and tau tangles within neurons.
Although these proteins appear to be involved in the pathology of Alzheimer's, little is known about why the condition begins and how it progresses. Early detection is still difficult, and treatment options are poor.
Because of the aging population in Western societies, the number of people with Alzheimer's is steadily rising. As a result of this, and together with the lack of successful pharmacological interventions, research focused on understanding the condition is vital.
Looking for Alzheimer's markers
Researchers from University of Wisconsin School of Medicine in Madison recently set out to investigate whether they could identify an early marker for Alzheimer's disease. They focused on brain-derived neurotrophic factor (BDNF), a protein coded by a gene of the same name.
BDNF is known to support nerve cells, helping them to grow, specialize, and survive. This makes it a good target for Alzheimer's research. Earlier research has not always found solid links between levels of BDNF and Alzheimer's, so this time, the team looked specifically at a gene mutation called the BDNF Val66Met allele, or simply Met allele.
In total, 1,023 participants - aged 55 on average - were included, and all were healthy but at risk of developing Alzheimer's. They were followed for a maximum of 13 years. At the start of the study, blood samples were taken to test for the Met allele mutation, and it was found to be present in 32 percent of the individuals.
All participants carried out cognitive and memory tests at the beginning of the trial and up to five more times throughout the study's duration. Also, 140 of them underwent neuroimaging to look for beta-amyloid plaques.
The data showed that those with the Met allele mutation lost cognitive and memory skills "more rapidly" when compared with those who did not have the mutation. Furthermore, individuals who carried both the mutation and plaques experienced an even quicker decline.
In verbal learning and memory tests, individuals without the gene mutation improved by 0.002 units per year, whereas those with the mutation worsened by 0.021 units each year.
"When there is no mutation, it is possible the BDNF gene, and the protein it produces are better able to be protective, thereby preserving memory and thinking skills. This is especially interesting because previous studies have shown that exercise can increase levels of BDNF.
It is critical for future studies to further investigate the role that the BDNF gene and protein have in beta-amyloid accumulation in the brain."
Study author Ozioma Okonkwo, Ph.D.
Because current treatment is most successful if given earlier in the disease's progression, this could be a vital part of the jigsaw. As Okonkwo says, "Because this gene can be detected before the symptoms of Alzheimer's start, and because this presymptomatic phase is thought to be a critical period for treatments that could delay or prevent the disease, it could be a great target for early treatments."
There are some shortfalls in the research. These include the fact that all participants were white, whereas various ethnicities are affected differently by the disease. For instance, African Americans appear to be more susceptible. Another shortfall of the study is that the beta-amyloid data were limited.
However, the study carries some weight because it involved a large number of participants, and the findings are sure to spark more research.