Study Rationale: Increasing evidence suggests that the disorder we refer to as Parkinson’s disease (PD) might represent several diseases, each driven by different biological mechanisms. The heterogeneous nature of PD is a major obstacle hindering the development of treatments that can slow disease progression. Thus, efforts are being made to divide PD into smaller groups, termed subtypes, based on their biological mechanisms. We find that dysfunction in mitochondria, the cells’ microscopic powerhouses, occurs in the neurons of a specific group of people with PD. We call this subgroup, which accounts for approximately 25 to 30% of all cases, “mitoPD.”
Hypothesis: We propose to develop blood tests for identifying individuals who fall in the mitoPD subtype, allowing them to be selected for tailored treatment trials that specifically target mitochondrial dysfunction.
Study Design: Because brain samples cannot be safely obtained from living people, we will attempt to identify individuals with the mitoPD form of PD using blood tests. Working with several hundred people with PD and healthy individuals, we will obtain two types of blood cells (white blood cells and platelets) and examine them for evidence of mitochondrial dysfunction. Among other things, we will measure the mitochondria’s energy conversion machinery, as well as the mitochondria’s genetic material, called mitochondrial DNA. We will then group our study population according to our mitochondrial readouts to identify the group of mitoPD.
Impact on Diagnosis/Treatment of Parkinson’s disease: The ability to identify people who have the mitoPD variant of PD will make it possible to steer those persons toward experimental treatments designed specifically to improve mitochondrial function. Such stratification will increase the chances of success in studies aimed at discovering new treatments for PD.
Next Steps for Development: The next step will be to confirm our results in larger and more diverse populations and to establish a simpler test method that can be routinely applied at most health institutions.