Preliminary Studies Of Magnetic Resonance Spectroscopy And SNCA Gene In Patients With Parkinson's Disease With Cognitive Impairment

Parkinson's disease (PD) as a degenerative disease of the central nervous system is common in the elderly population and the incidence is second to Alzheimer's disease. The PD pathology is characterized by the progressive loss of substantia nigra dopaminergic neurons and the presence of cytoplasmic inclusions named Lewy bodies. The typical clinical symptoms of PD are resting tremor, muscle rigidity, bradykinesia and postural balance.In addition, PD is often accompanied by a series of non-motor symptoms. Cognitive impairment and dementia are more common than other non-motor symptoms. PD can significantly increase the risk of cognitive impairment and dementia. Cognitive impairment and dementia will reduce the patients' quality of life, increase the burdens of families and society, and are also important risk factors associated with long-term death of PD patients.The neuropathological and biochemical basis of cognitive decline in PD is still not clear, and early diagnosis is relied on clinical manifestations lacking of objective evidence. Pathological study is a useful method for revealing the nature of diseases, but considerable difficulties still exist for pathological study on the central nervous system diseases, especially in the early stage. Therefore, a technology that can solve the problem of "pathology" research in vivo will be very helpful for pathogenesis studies and early diagnosis of diseases. Magnetic Resonance Spectroscopy (MRS) technique is an effective method of analyzing the biochemical and metabolic changes in vivo and can also detect the compounds quantitatively. MRS technique achieves the great change from traditional structural imaging studies to biochemical studies in vivo, so called "non-invasive biopsy". MRS also provides a new technique for the study of pathophysiology and diagnosis in disease.Parkinson's disease dementia (PDD) patients have significant structural and metabolic changes in the cerebral cortex, suggestting that pathophysiological changes of cerebral cortex may affect cognitive function in PD. So far, there have only two studies published (Bowen 1995; Summerfield 2002) about occipital lobe using MRS analysis in PDD, and found the increase of Lac/NAA ratio or decrease of NAA value. However, the sample sizes of the two studies were too small, with only 4 cases and 14 cases included, and Bowen's results did not reach statistical significance.PD cognitive impairment refers to the transitional stage of PDD. The above two studies suggest that PD Patients with early cognitive impairment may have pathophysiological changes in occipital lobe.Cingulate cortex may play important roles in memory and cognitive function. Currently, only Camiciol investigated the cingulate cortex of PD patients with cognitive impairment using MRS technique. The results showed that non-demented PD patients but with mild to moderate cognitive impairment had obvious metabolic changes in posterior cingulate, and the NAA/Cr ratio change was significantly correlated with memory decline. The sample size of Camiciol's study was also small, and only 12 cases and.10 controls were included. The study did not set a cognitively normal PD group for comparison.The main pathology of PD is the degeneration of substantia nigra-striatal pathway, and these changes may be associated with cognitive decline. Sawamoto's study suggested that executive deficits in early patients with PD were associated with impaired nigrostriatal dopaminergic function resulting in abnormal processing in the cortico-basal ganglia circuit. Nieoullon's study supportted the view that the striatum was part of the neuronal network that was mediating prefrontal cognitive functions with a single photon emission computed tomography (SPECT) of [123I]β-CIT. Summarily, Biochemical metabolic changes of occipital lobe, cingulate gyrus and substantia nigra-striatum pathway may be assionated with cognitive impairment in PD. The sample size of Bowen, Summerfield and Camiciol studies was small and a 1.5T MR scanner was used for MRS analysis. In our previous studies on non-motor symptoms and MRS analysis, we found that cognitive impairment and emotional disorders were common in PD. In our previous study, we carried out a multi-voxel MRS analysis of substantia nigra and striatum in PD, and found that, compared with the control group, NAA/Cr ratio of the substantia nigra in the symptoms contralateral of PD was reduced significantly and Cho/Cr ratio significantly rised. The NAA/Cr and Cho/Cr ratios were significantly different in the bilateral substantia nigra in PD patients. Compared with the control group, the NAA/Cr ratio of the striatum in the symptoms contralateral of PD was reduced significantly and Cho/Cr ratio significantly rised. The NAA/Cr and Cho/Cr ratios were significantly different in the bilateral striatum in PD patients.We intend to do some further research based on previous studies, and carry out a MRS analysis of occipital lobe, cingulate regions and substantia nigra-striatum system using advanced 3.0-T MR scanner. No studies have been reported on occipital lobe MRS analysis in PD patients with cognitive impairment.We will carry out another single voxel MRS analysis of occipital lobe, posterior cingulate, nigra and striatum, using advanced 3.0T MR scanner and investigate the value of MRS in PD with cognitive impairment.The pathogenesis of PD is not yet clear. Most researchers support that PD is a product of gene-environment interactions. In recent years, genes associated with familial PD have been discovered successively and these findings played important roles in the progress of PD pathogenesis studies. Genetic factors in PD are receiving more and more attention.α-synuclein gene (SNCA) was first found among the PD related genes, and the aggregate ofα-synuclein in the formation of Lewy bodies is the characteristic pathological change of PD. The SNCA point-mutations and multiplications can cause familial PD. Most PD cases are sporadic, and sporadic PD is also closely associated with SNCA gene. SNCA gene may affect the onset of sporadic PD by increasing the gene expression. Present studies also confirmed that SNCA gene expression levels were increased at mRNA and protein in brain tissues or peripheral blood in sporadic PD. Polymorphisms may be important factors for regulating SNCA gene expression.SNCA protein is associated with PD and PD cognitive impairment. A post-mortem study of 22 casess (13 PDD,9 non-demented PD) by Apaydin indicated that the number of Lewy bodies in cerebral cortex and limbic system in PDD was nearly 10 times higher than the non-dementia PD. In another study of 88 pathologically confirmed PD cases, Braak found that 79 cases developed mild to moderate cognitive impairment and there existed a correlation between the MMSE scores and Lewy bodies. In the PD families with SNCA point mutations (E46K,A30P,A53T), the patients were prone to develop dementia.The post-mortem study of PD cases with E46K showed that a large number of Lewy bodies lied in cortical and subcortical structures. Ross made a genomic investigation of a-synuclein multiplication, and found that SNCA dosage was responsible for parkinsonism, autonomic dysfunction, and dementia observed within each family.Several studies have confirmed a series of SNCA polymorphisms associated with PD.Studies abroad have reported several single nucleotide polymorphisms(SNPs) (rs1372525, rs356200, rs356165, rs3822086,and rs356203) in the different regions of SNCA gene (promoter, intron 4 and 3'UTR) may be associated with PD susceptibility,but the results were inconsistency.Geographical and ethnic differences influence the polymorphisms greatly. As yet, there is no report about the studies of SNCA gene polymorphism in Chinese Han population. We intend to investigate the relationship between the SNCA gene polymorphisms and PD cognitive impairment.This paper includes two parts:Ⅰ. the magnetic resonance spectroscopy of Parkinson's disease and Parkinson's disease with cognitive impairment.Ⅱ. the polymorphisms analysis of SNCA gene in Parkinson's disease. PartⅠThe Magnetic Resonance Spectroscopy Analysis in Patients with PD with Cognitive ImpairmentObjective:To investigate the application value of'H-MRS for the research of pathophysiology and diagnosis in PD with cognitive impairment.Method:72 PD patients and 24 controls were included.To assess the PD patients using the Unified Parkinson disease rating scale (UPDRS-Ⅲ), Hoehn-Yahr(H-Y), Mini-mental state examination (MMSE), Montreal Cognitive Assessment (MoCA), Hamilton anxiety Scale(HAMA) and Hamilton depression Scale (HAMD). PD patients will be divided into PD with cognitive impairment group (PD-CI) and cognitively normal PD group(PD-CN) in accordance with the MoCA scores.To scan the brain occipital, cingulate gyrus, striatum and substantia nigra using the single voxel 1H-MRS in both PD and control subjects. To make comparisons of NAA/Cr and Cho/Cr ratios among groups, and analyze the clinical factors that could affect the 1H-MRS results. Use the Independent samples t-test, One-way ANOVA,Stepwise Logistic Regression and Partial correlation analysis for statistics. A value of P<0.05 (2-sided) was considered statistically significant.Results:1.72 PD patients were enrolled,41 males and 31 females, average age (61.2±12.6)years, range (24 to 86) years. According to the results of MoCA assessment, PD patients were divided into PD-CI and PD-CN group.42 patients were in the PD-CI group,21 males,21 females; average age (64.5±10.6) years, years of education (10.4±2.5) years; 30 patients were in the PD-CN group,20 males,10 females; average age (59.4±13.2) years; years of education (8.8±3.5) years. The number of control subjects was 24,12 males,12 females; average age (57.7±14.1) years; range(34～80)years. There were no significant differences in age and gender between PD and control group (P> 0.05). There were no significant differences in age,gender and education years among the PD-CI,PD-CN and control group (P>0.05).2. The comparisons of MRS results between the PD and control group There were no significant differences in substantia-nigra and cingulate NAA/Cr ratios between PD and control group (P>0.05). Compared with the control group, the NAA/Cr ratios of occipital lobe and striatum significantly decreased in PD group (P<0.05).There were no significant differences in Cho/Cr ratios in occipital lobe, cingulate gyrus, striatum and substantia nigra between PD and control group(P> 0.05).3. The comparisons of MRS results among the PD-CI, PD-CN and control group3.1 There were significant differences in the occipital lobe, cingulate gyrus and striatum NAA /Cr ratios among the three groups with a global comparison, and a further comparison was needed.The results showed that:(1) There were no significant differences in occipital lobe, cingulate gyrus and striatum NAA/Cr ratios between the PD-CI and PD-CN group, but a NAA/Cr ratio decline trend was found in cingulate gyrus in PD-CI (P=0.054) suggestting that cingulate metabolism changes may be associated with PD cognitive impairment.(2) Compared with the control group, there was a significant NAA/Cr ratios decline in the occipital lobe, cingulate gyrus and striatum in the PD-CI (P<0.05)(3) Compared with the control group, there was a significant NAA/Cr ratios decline in striatum in PD-CN group (P<0.05),but with no significant decline in occipital lobe and cingulate gyrus (P>0.05)3.2 There were no significant differences of NAA/Cr ratios among the three groups in substantia nigra with a global comparison (P>0.05)3.3 There were no significant differences of Cho/Cr ratios among the three groups in occipital lobe, cingulate gyrus, striatum and substantia nigra with a global comparison (P>0.05)3.4 Logistic-regression analysis results showed that PD cognitive impairment was associated with age and H-Y. PD patients with more severe symptoms and advanced age are more prone to cognitive dysfunction.The partial correlation analysis between clinical data and MRS results in PD showed that there was a significant correlation between the striatal NAA/Cr ratio and H-Y (P<0.05).Conclusions:1. The significant decrease of NAA/Cr ratio in striatum in PD suggests a serious neurons loss. The pathophysiological changes in striatum in PD are significantly correlated with disease severity, and may be associated with PD cognitive impairment.2. The NAA/Cr ratio of posterior cingulate shows a declining trend when the PD patients are prone to cognitive impairment, although not significant in the early stage of cognitive impairment. The metabolic changes in the occipital lobe and cingulate gyrus regions may affect cognitive functions in PD.3. Single voxel MRS technique may lead to a false-negative result in analyzing the substantia nigra because of larger sample volume than multi-voxel MRS. PartsⅡ:The polymorphisms analysis of SNCA gene in PDObjective:To analyze the SNCA gene polymorphisms in Chinese Han population and to investigate the relationship between the SNCA gene polymorphisms and PD susceptibility.Methods:90 PD cases and 96 normal controls were included for research. The PD patients will be divided into PD-CI and PD-CN groups in accordance with MoCA socres. To analyze the genotypes of the five SNPs (rs1372525, rs356203, rs356200, rs3822086 and rs356165) using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) combined with DNA sequencing, and a statistical analysis of the data was made. Genotype and allele frequencies were tested for significance using a 95% two-sidedχ2 test between the groups.Results:The genotype frequencies were consistent with Hardy-Weinberg equilibrium distribution in PD and control groups. PD compared with control group:1. There were significant differences in the genotypes(A/A,A/G,G/G) and alleles (A. G)frequencies of rs356200 between PD and control group (P<0.05)2. There were significant differences in the genotypes(C/C,C/T,T/T) and alleles (A,G)frequencies of rs3822086 between PD and control group (P<0.05)3. We found a significant difference in the genotype(A/A,A/G,G/G) frequencies of rs356203 (P<0.05), but no significant difference in the allele(A,G) frequencies between the two groups (P>0.05)4. We found a significant difference in the genotype (A/A,A/G,G/G)frequencies of rs356165 (P<0.05), but no significant difference in the allele (A,G)frequencies between the two groups (P>0.05)5. No significant differences were found in the genotype(A/A,A/G,G/G) and allele(A,G) frequencies of rs1372525 between the two groups (P>0.05)6. Make comparisons of alleles frequencies among the PD-CI, PD-CN and control groups, the results show that there was a significant difference in the allele frequencies of rs3822086 (χ2=7.454,P=0.024), sugestting that rs3822086 polymorphisms may be associated with PD cognitive impairment.Conclusions:1.The polymorphisms of rs356200,rs3822086 and rs3656203 within intron 4 of SNCA gene may be associated with PD in Chinese Han population;2.The rs3822086 polymorphisms may be associated with PD cognitive impairment.3.The rs356165 polymorphisms in 3'UTR of SNCA may be associated with PD in Chinese Han population.