Cerebral cortical thinning in Parkinson's disease depends on the age of onset

Identification of Novel Genetic Loci Affecting Age at Onset of Parkinson's Disease: A Genome-wide Association Study

BACKGROUND

The age at onset (AAO) of Parkinson's disease (PD) varies widely among individuals and significantly influences disease progression and prognosis. However, few genome-wide association studies (GWASs) have investigated genetic variants determining AAO, particularly in East Asian populations.

OBJECTIVES

To identify single-nucleotide polymorphisms (SNPs) affecting AAO of PD in Korean patients.

METHODS

We conducted a GWAS on AAO of PD in 1048 Korean patients using sex-adjusted linear regression models. Additionally, we conducted downstream analyses of our primary GWAS results.

RESULTS

rs2134545 demonstrated genome-wide significance (β = -2.459; standard error [SE] = 0.851; P = 1.898 × 10-8) and is an intergenic SNP near the ALCAM gene associated with an average AAO reduction of 3.47 years. Additionally, rs4366309 (LYST; MIR1537) demonstrated suggestive significance (β = 2.949; SE = 1.072; P = 8.68 × 10-8) and was associated with an average delay of 3.05 years. The polygenic risk score based on known PD risk loci also affected the AAO for European and Korean PD risk loci, respectively (β = -0.149; P < 0.001 and β = -0.096; P = 0.002). However, the proportion of variance was small (r2 = 0.022 and 0.009, respectively).

CONCLUSION

We identified a novel SNP associated with the AAO of PD near the ALCAM gene, distinct from previously reported PD risk loci. These findings need further functional validation; however, they suggest unique genetic pathways influencing the AAO of PD and highlight the need for further research in diverse populations. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association of Striatal Dopamine Depletion and Brain Metabolism Changes With Motor and Cognitive Deficits in Patients With Parkinson Disease

BACKGROUND AND OBJECTIVES

Parkinson disease (PD) shows degeneration of dopaminergic neurons in the substantia nigra and characteristic changes in brain metabolism. However, how they correlated and affect motor and cognitive dysfunction in PD has not yet been well elucidated.

METHODS

In this single-site cross-sectional study, we enrolled patients with PD who underwent N-(3-[18F]fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (18F-FP-CIT) PET, 18F-fluorodeoxyglucose (18F-FDG) PET, the Movement Disorder Society-sponsored Unified PD Rating Scale examination, and detailed neuropsychological testing. General linear models and mediation analyses were implemented to investigate the association between striatal dopamine transporter availability, brain metabolism, and parkinsonian motor subscores or domain-specific cognitive scores. Healthy controls (HCs) who underwent 18F-FP-CIT and 18F-FDG PET were also enrolled.

RESULTS

Compared with HCs (n = 38, mean age 67.3 ± 5.9 years; 19 women), patients with PD (n = 143, mean age 69.0 ± 9.0 years; 69 women) characteristically showed relative brain hypermetabolism and hypometabolism that correlated with striatal dopamine transporter availability. As the loss of putaminal dopamine transporter availability increased, brain metabolism relatively increased from the paracentral lobule, pons, and limbic system to the cerebellum and anterior cingulate cortex, whereas brain metabolism relatively decreased from the lateral temporal and frontal cortices to the occipital and inferior parietal cortices. Reduced putaminal dopamine was associated with a higher rigidity subscore by the mediation of relative hypermetabolism in the paracentral lobule (standardized indirect effect, β = -0.070, p = 0.025) and directly associated with a higher bradykinesia subscore (β = -0.274, p = 0.011). Reduced caudate dopamine was associated with a higher axial subscore (β = -0.125, p = 0.004) and lower executive (β = 0.229, p = 0.004), visuospatial (β = 0.139, p = 0.006), and memory (β = 0.140, p = 0.004) domain scores by the mediation of relative brain hypometabolism. The tremor subscore and language and attention scores were not associated with striatal dopamine availability or brain metabolism.

DISCUSSION

Our findings suggest that in PD, striatal dopamine depletion and altered brain metabolism are closely linked, that changes in brain metabolism occur in specific spatial patterns depending on the degree of dopamine depletion, and that both differentially affect motor and cognitive dysfunction depending on each symptom.

Umbilical cord blood-derived exosomes attenuate dopaminergic neuron damage of Parkinson's disease mouse model

BACKGROUND

Umbilical cord blood (UCB) is a rich source of multifunctional stem cells characterized by low immunogenicity. Recent research in the fields of aging and regenerative medicine has revealed the potential of human umbilical cord blood-derived exosomes (UCB-Exos) in promoting wound healing, anti-aging, and regeneration. However, their role in neurodegenerative diseases, specifically Parkinson's disease (PD), remains unexplored. This study investigates the potential therapeutic effects and underlying mechanisms of UCB-Exos on PD.

METHODS

Large extracellular vesicles (LEv), Exos, and soluble fractions (SF) of human UCB plasma were extracted to investigate their effects on motor dysfunction of the MPTP-induced PD mouse model and identify the key components that improve PD symptoms. UCB-Exos were administered by the caudal vein to prevent or treat the PD mouse model. The motor function and pathological markers were detected. Differentially expressed gene and KEGG enrichment pathways were screened by transcriptome sequence. MN9D and SH-SY5Y cells were cultured and evaluated for cell viability, oxidative stress, cell cycle, and aging-related indexes by qRT-PCR, western blot, immunofluorescence, and flow cytometry. The protein expression level of the MAPK p38 and ERK1/2 signaling pathway was detected by western blot.

RESULTS

We observed that LEv, Exos, and SF all exhibited potential in ameliorating motor dysfunction in MPTP-induced PD model mice, with UCB-Exos demonstrating the most significant effect. UCB-Exos showed comparable efficacy in preventing and treating motor dysfunction, cognitive decline, and substantia nigra pathological damage in PD mice. Further investigations revealed that UCB-Exos could potentially alleviate oxidative damage, aging and degeneration, and energy metabolism disorders in neurons. Transcriptome sequencing results corroborated that genes differentially expressed due to UCB-Exos were primarily enriched in the neuroactive ligand-receptor interaction, Dopaminergic synapse, and MAPK signaling pathway. We also observed that UCB-Exos significantly inhibited the hyperphosphorylation of the MAPK p38 and ERK1/2 signaling pathways both in vitro and in vivo.

CONCLUSIONS

Our study provides a comprehensive evaluation of UCB-Exos on the neuroprotective effects and suggests that inhibition of hyperphosphorylation of MAPK p38 and ERK 1/2 signaling pathways by regulating transcription levels of HspB1 and Ppef2 may be the key mechanism for UCB-Exos to improve PD-related pathological features.

A multi-site study on sex differences in cortical thickness in non-demented Parkinson's disease

Clinical, cognitive, and atrophy characteristics depending on sex have been previously reported in Parkinson's disease (PD). However, though sex differences in cortical gray matter measures in early drug naïve patients have been described, little is known about differences in cortical thickness (CTh) as the disease advances. Our multi-site sample comprised 211 non-demented PD patients (64.45% males; mean age 65.58 ± 8.44 years old; mean disease duration 6.42 ± 5.11 years) and 86 healthy controls (50% males; mean age 65.49 ± 9.33 years old) with available T1-weighted 3 T MRI data from four international research centers. Sex differences in regional mean CTh estimations were analyzed using generalized linear models. The relation of CTh in regions showing sex differences with age, disease duration, and age of onset was examined through multiple linear regression. PD males showed thinner cortex than PD females in six frontal (bilateral caudal middle frontal, bilateral superior frontal, left precentral and right pars orbitalis), three parietal (bilateral inferior parietal and left supramarginal), and one limbic region (right posterior cingulate). In PD males, lower CTh values in nine out of ten regions were associated with longer disease duration and older age, whereas in PD females, lower CTh was associated with older age but with longer disease duration only in one region. Overall, male patients show a more widespread pattern of reduced CTh compared with female patients. Disease duration seems more relevant to explain reduced CTh in male patients, suggesting worse prognostic over time. Further studies should explore sex-specific cortical atrophy trajectories using large longitudinal multi-site data.