The findings of a study by scientists at the Buck Institute for Age Research have indicated that it is possible to test humans to find out if they are at a risk of developing Parkinson's disease (PD). The study, led by Buck faculty member Julie Andersen, PhD, has suggested that preventive treatment may be useful for those who have high levels of MAO-B, an enzyme that regulates nerve activity in the brain and leads to Parkinson's-like symptoms in mice genetically engineered to overexpress the protein.
Also, the drugs in use these days as and additional therapy for PD in humans prevented the development of its symptoms in these same animals. Also, drugs currently used as an adjunct therapy for Parkinson's in humans.
It is well known that measurable levels of MAO-B vary 50-fold in humans and tend to increase with age. It has also been suggested through many studies that increases in MAO-B leads to neurodegeneration associated with PD, but direct proof of a causative role for the enzyme has not yet been found.
Since a long time, a drug called deprenyl, which inhibits MAO-B, has been used as a therapy for Parkinson's in combination with other drugs that boost the level of dopamine, an important neurotransmitter that is preferentially reduced in the disease.
According to clinical studies, the fact that deprenyl treatment solely does not have any impact on mortality associated with Parkinson's, has raised doubts on the role of MAO-B in the disease itself. However, Andersen claimed that this might not be true.
'Those studies were targeted to patients who already had symptoms of Parkinson's -- by the time Parkinson's is symptomatically detectable, dopamine loss is usually at least 60%. Therefore the lack of effectiveness of MAO-B inhibition in these patients does not negate a role for MAO-B increase in disease development.' Andersen added, 'We have demonstrated that elevations in MAO-B result in selective loss of neurons associated with Parkinson's in a mouse model and that the severity of this loss is age-dependent,' said Andersen.
Though, specific tests for measuring levels of MAO-B are not currently available to the general public, it is possible to track enzyme levels in clinical trials.
Andersen said that MAO-B testing could be similar to current practices involving cholesterol, which is measured and monitored as a risk factor for cardiovascular disease.
'However, it is important to note that Parkinson's is a multi-factor disease. The fact that someone has high levels of MAO-B does not necessarily mean they are fated to develop Parkinson's,' said Andersen.
She also said that the results of the study point to the need for an early diagnostic test for Parkinson's.
'Currently, by the time people are diagnosed with the disease they have already lost 60% of the neurotransmitter levels implicated in Parkinson's; treatment with a drug like deprenyl would likely be most effective if taken before symptoms appear in order to halt disease progression,' she said.
The study appears in the latest issue of the open-access, online Journal, PLoS One.