New research using animal models suggests a test of the ability to smell may be an important tool to screen people who are likely to develop Parkinson’s disease (PD).
According to German scientists, the fast, simple and noninvasive test may help in the development of treatments for the early stages of the disease before motor symptoms become evident.
Dr. Silke Nuber and colleagues from Germany, Switzerland, and the UK decided to study transgenic mice with high levels of human alpha-synuclein, a protein known to be crucial in the development of PD.
Alpha-synuclein can be turned off in these animals by administration of an antibiotic, allowing scientists to look at the reversibility of neuropathological alterations.
“The mice expressed alpha-synuclein primarily in neurons of the olfactory bulb,” said Dr. Nuber, “and we therefore expected to find alterations in smell-related behavior in these animals. Since one of the earliest symptoms in Parkinson’s disease patients is a reduction in the sense of smell, we felt that these mice could mimic the early stages of the disease.”
Parkinson’s disease is a degenerative disorder of the central nervous system that affects the control of motor skills, speech, mood and behavioral problems, and cognitive functions. It is characterized by muscle rigidity, tremor, and slowing or loss of physical movement. It is a chronic, progressive condition and there is currently no cure.
The researchers say that it would be worthwhile to develop some standardized tests for testing smell function.
“We don’t know whether the existing drugs used at a later stage in PD would be effective in the earlier phases of the disease, but having an early biomarker would enable us to try to develop different treatment strategies,” said Dr. Nuber.
“Based on what we know now, the clinical definition for the diagnosis of PD should not rely solely on the diagnosis of motor symptoms. It would be helpful to test the ability of olfactory detection and learning.”
“Even if we cannot preserve olfactory structures and functioning, it will enable us to diagnose the disease earlier on and also help with the development of treatment strategies to halt or even reverse the underlying disease process in Parkinson’s disease. We believe that detailed functional imaging analyses paralleled by behavioral studies in the mouse model could lead to the development of an efficient preclinical therapy that can be used to halt the massive dopaminergic neurodegeneration that takes place in human PD patients,” she concluded.