To evaluate the comprehensive metabolic profile of serum in patients with PD.NMR spectroscopy of bio-fluids provides a wealth of information about the metabolic processes of living organism¹. Parkinson’s disease (PD) is a neurodegenerative disorder caused by selective loss of dopaminergic neurons in the substantia nigrapars compacta which leads to dysfunction of cerebral pathways critical for the control of movements. The diagnosis of PD is based on motor symptoms, such as bradykinesia, akinesia, muscular rigidity, postural instability, and resting tremor, which are evidently after the degeneration of a significant number of dopaminergic neurons². We investigated the metabolic profile differences in serum samples using ¹H NMR technique to differentiate between patients with PD and healthy controls, and if possible, identify biomarkers for early diagnosis of PD.

Blood samples were collected from 6 PD patients (4M/ 2F, mean age: 57 ± 7.0 years) and 6 age and gender matched healthy controls (3M/3F, mean age: 49 ± 2.22 years) after 12 hours fasting, centrifuged at 2000g for 10 min at 4 ^ͦC and stored at -80^o C until NMR experiments were performed. The diagnosis of PD was made according to the UKPDS (United Kingdom Parkinson Disease Society) brain bank criteria³. For NMR experiments 200µl serum and 30µl TSP (0.5mM) were added in D₂O making total volume to 600µl sample and NMR experiments were carried out using 700 MHz NMR spectrometer (M/s. Agilent Technologies, USA). The chemical shifts of resonances referenced to TSP. Proton NMR spectra of serum samples were acquired using 1D CPMG with presaturation using 90˚ pulse sequence, with 64 number of scans; relaxation delay=70s; spectral width= 9000Hz; data points=32k; echo time=15ms. 2D NMR Spectroscopy was carried out for assignment of resonances of 1D spectra. The data is processed and integrated values were obtained using the Vnmrj2.3A software.

Statistical Analysis: PLS-DA multivariate analysis was performed to explore biochemical dissimilarities between PD patients and HC using MetaboAnalyst (3.0), a web-based metabolomics data processing software.

From the obtained spectrum from blood sera (Figure 1), 15 metabolites were assigned unambiguously using 1D and 2D NMR and the integration of those metabolites were evaluated. For comparison between PD and HC and estimation of significant difference, t- test (non-parametric tests - Wilcoxon rank-sum test) was used. Significant increase in the integral values of Lactate, Glutamine and Methyl Guanidine were observed in PD patients as compared to healthy controls (Table 1). PLS-DA analysis depicts clear separation between PD and HC (Figure 2).The elevated Methyl Guanidine concentration in PD as compared to healthy controls may be attributed to oxidative stress and protein metabolism impairment⁴. Increased levels of glutamate may be ascribed to impaired mitochondrial function, due to increased vulnerability of affected neurons⁵. The above results suggest that NMR based metabolomics study may be useful for understanding the pathogenesis of PD and further help in identification and establishment of biomarker(s) for the diagnosis of PD.