Impaired age-dependent increases in phosphoglycerate kinase activity in red blood cells of Parkinson's disease patients.

Background: Impaired bioenergetics are partially involved in the pathogenesis of Parkinson's disease (PD). Phosphoglycerate kinase (PGK), an essential enzyme for glycolysis, has recently attracted attention due to its pathogenic role in PD and as a target for disease-modifying therapies. This study is aimed to evaluate the profiles of PGK activity in red blood cells (RBCs) of PD patients and controls.

Methods: Sixty-eight PD patients and thirty-four age-matched unrelated controls were enrolled. PGK activities of RBCs were measured by the established colorimetric assay and standardized by the same RBC samples.

Results: PGK activity of the PD group was significantly higher than that of the control group in participants aged sixty-five years or younger, whereas it was not significantly different between the two groups at any age. PGK activity was positively correlated with aging in the control group, but this was not noted in the PD group. On multivariable analysis by partial correlation in the PD group, PGK activity was negatively correlated with the specific binding ratio of dopamine transporter scintigraphy in the striatum. The levodopa-equivalent daily dose was not significantly correlated with the enzyme activity.

Conclusion: The results support the following: 1) elevation of PGK activities in RBCs can be detected in relatively young PD patients and with normal aging; 2) the degree of striatonigral degeneration is associated with elevated PGK activities. These are important considerations when the PGK assay is applied as a diagnostic biomarker of PD and to therapeutically monitor PGK-enhancing treatments.