The causes of Parkinson’s disease (PD) in most South African patients differ from those found in European, American and Asian populations, suggesting that drug treatments developed overseas may not be applicable here.
Novel genetic defects
“More research is urgently needed on South African patients to understand the unique aspects of the disease affecting local populations,” says Prof Soraya Bardien, a senior scientist with the Parkinson’s Disease Research Group at the Faculty of Medicine and Health Sciences (FMHS), Stellenbosch University.
This is the only group in South Africa investigating the genetic causes and mechanisms that lead to PD and their research over the past eight years have revealed novel genetic defects in South African patients.
It has also identified the potential therapeutic benefits of curcumin (the active ingredient in turmeric, a common household spice) in a laboratory (cellular) model of PD.
“PD is a debilitating and incurable disorder that results from the loss of brain cells (neurons) in a specific part of the brain known as the ‘substantia nigra’,” explains FMHS neurologist Prof Jonathan Carr. “Once lost, these cells never grow back.
Depression, psychosis, sleep disturbances and dementia
"This loss results in a number of symptoms which include stiff muscles, extremely slow movements and reflexes, involuntary trembling of the body and limbs, and difficulty in maintaining balance.”
In addition to these symptoms, PD patients also experience a number of psychological issues such as depression, psychosis, sleep disturbances and dementia. These symptoms can appear up to 10 years before the symptoms related to movement.
The symptoms of Parkinson's Disease can be treated to a certain extent with various drugs and with surgery, but these do not halt the disease progression and currently there is no cure.
The prevalence of PD in South Africa is unknown, but internationally it affects between one and two individuals in every 100 people over the age of 60 years, and four in every 100 people over the age of 80 years.
In about 15% of patients, the disorder appears before the age of 50 years and this is referred to as "early-onset PD". The American actor Michael J Fox has this form of the disorder. PD is found in all ethnic groups.
'Needle in a haystack'
In order to discover novel PD-causing genes, the PD Research Group are using a technique called whole exome sequencing which involves the simultaneous screening of approximately 20,000 human genes.
“The challenge is to sift through the masses of data that this technique generates to find the proverbial ‘needle-in-a haystack’ causative gene, and this research is on-going,” Bardien explains.
“Also, we have used specialised protein techniques to study the biological pathways that the known PD-causing genes e.g. parkin are involved in and have identified interesting processes that may be implicated in the development of PD.
These findings are important as it may ultimately contribute to the design of more effective drug therapies for PD.
The group have also found a novel genetic defect in one South African patient and compared its effect to another genetic defect in the same gene which is a common cause of the disease in some populations overseas.
“Interestingly, our results show that the novel defect we found has more severe effects on the cell,” says Bardien. “It is important to raise awareness about this disorder as it may be misdiagnosed and therefore not treated appropriately.
Patients with PD may also be stigmatised and other factors such as witchcraft may be blamed for the symptoms. Therefore, it needs to be highlighted that this is a disorder like hypertension and schizophrenia, and that treatment exists that can alleviate many of the devastating symptoms,” says Bardien.