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Idiopathic Parkinson's disease is determined by a combination of genetic and environmental factors. Recently, the first genome-wide association study on short-tandem repeats in Parkinson's disease reported on eight suggestive short-tandem repeat-based risk loci (α = 5.3 × 10-6), of which four were novel, i.e. they had not been implicated in Parkinson's disease risk by genome-wide association analyses of single-nucleotide polymorphisms before. Here, we tested these eight candidate short-tandem repeats in a large, independent Parkinson's disease case-control dataset (n = 4757). Furthermore, we combined the results from both studies by meta-analysis resulting in the largest Parkinson's disease genome-wide association study of short-tandem repeats to date (n = 43 844). Lastly, we investigated whether leading short-tandem repeat risk variants exert functional effects on gene expression regulation based on methylation quantitative trait locus data in human 'post-mortem' brain (n = 142). None of the eight previously reported short-tandem repeats were significantly associated with Parkinson's disease in our independent dataset after multiple testing correction (α = 6.25 × 10-3). However, we observed modest support for short-tandem repeats near CCAR2 and NCOR1 in the updated meta-analyses of all available data. While the genome-wide meta-analysis did not reveal additional study-wide significant (α = 6.3 × 10-7) short-tandem repeat signals, we identified seven novel suggestive Parkinson's disease short-tandem repeat risk loci (α = 5.3 × 10-6). Of these, especially a short-tandem repeat near MEIOSIN showed consistent evidence for association across datasets. CCAR2, NCOR1 and one novel suggestive locus identified here (LINC01012) emerged from colocalization analyses showing evidence for a shared causal short-tandem repeat variant affecting both Parkinson's disease risk and cis DNA methylation in brain. Larger studies, ideally using short-tandem repeats called from whole-sequencing data, are needed to more fully investigate their role in Parkinson's disease.

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Gaucher disease (GD) is an autosomal recessive lysosomal disorder caused by pathogenic variants in GBA1 which result in the deficient activity of glucocerebrosidase (GCase). There are few data on the genetic characterization of Brazilian GD patients. This study aimed at characterizing the genotype of 72 unrelated Brazilian GD patients (type I = 63, type II = 4, type III = 5; male = 31). Forty patients were from South Brazil (SB), and 32 were from other regions of Brazil (Others). The exons and exon/intron junctions of GBA1 were analyzed by Sanger sequencing in 8 patients, or by massive parallel sequencing followed by Sanger of exons 9 and 10 in 64 patients. In total, 31 pathogenic variants were identified. The most frequent allele found was N370S (p.(Asn409Ser)) (41.0%), and the most frequent genotype was N370S/RecNciI p.[Asn409Ser];[Leu483Pro;Ala495Pro;Val499=](23.6%). Three variants (N370S - in exon 9, and RecNciI and L444P (p.(Leu483Pro), in exon 10) correspond to 76.3% of total alleles in SB and 59.4% in Others. Two novel variants were described: c.326del(p.(Gln109Argfs*9)) and c.690G>A (p.(?)). Although sequencing all the exons of GBA1 is the gold-standard method for the genetic analysis of GD patients, a step analysis can be proposed for Brazilian patients, starting with analysis of exons 9 and 10. The N370S allele is the most frequently associated with GD in Brazil.

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Introduction: Coffee has been inversely associated with Parkinson's disease (PD) in many studies, and caffeine is the leading candidate to mediate this effect. Mate (Ilex paraguariensis, IP), a caffeinated beverage rich in antioxidants consumed in South America, was also inversely associated with PD in one study from Argentina. Other varieties of IP infusion, such as chimarrão, were never studied in PD. Chimarrão is a common caffeinated beverage consumed in Brazil made with the leaves and stems of IP. Methods: A case-control study was conducted to evaluate the relationship between chimarrão ingestion and PD in southern Brazil. All subjects answered a questionnaire about the frequency of chimarrão and coffee intake. A multiple regression analysis adjusted for age and sex was performed to assess the association between PD and chimarrão consumption. Results: We included 200 PD patients and 200 healthy controls. High consumption of chimarrão was inversely associated with PD (OR = 0.44, 95% CI = 0.24-0.81, P = 0.008). High consumption of coffee was also inversely associated with PD, as expected. Chimarrão remained associated when adjusted for coffee consumption, smoking history, and age (OR 0.46, 95% CI = 0.25-0.86, P = 0.014). These two exposures showed an additive effect. Conclusion: Chimarrão consumption was inversely associated with PD, even after adjusting for coffee intake, suggesting a possible protective role. IP's effect can be mediated by caffeine and through its antioxidant components. Chimarrão has a lower concentration of caffeine compared with coffee and has numerous substances with antioxidative effects that may be important to PD protection. Further studies are needed to test this hypothesis.

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The IL22RA2 locus is associated with risk for multiple sclerosis (MS) but causative variants are yet to be determined. In a single nucleotide polymorphism (SNP) screen of this locus in a Basque population, rs28385692, a rare coding variant substituting Leu for Pro at position 16 emerged significantly (p = 0.02). This variant is located in the signal peptide (SP) shared by the three secreted protein isoforms produced by IL22RA2 (IL-22 binding protein-1(IL-22BPi1), IL-22BPi2 and IL-22BPi3). Genotyping was extended to a Europe-wide case-control dataset and yielded high significance in the full dataset (p = 3.17 × 10-4). Importantly, logistic regression analyses conditioning on the main known MS-associated SNP at this locus, rs17066096, revealed that this association was independent from the primary association signal in the full case-control dataset. In silico analysis predicted both disruption of the alpha helix of the H-region of the SP and decreased hydrophobicity of this region, ultimately affecting the SP cleavage site. We tested the effect of the p.Leu16Pro variant on the secretion of IL-22BPi1, IL-22BPi2 and IL-22BPi3 and observed that the Pro16 risk allele significantly lowers secretion levels of each of the isoforms to around 50%-60% in comparison to the Leu16 reference allele. Thus, our study suggests that genetically coded decreased levels of IL-22BP isoforms are associated with augmented risk for MS.

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Parkinson's disease (PD) is a progressive and multifactorial neurodegenerative disease. It has been suggested that a dysregulation of the hypothalamic-pituitary-adrenal axis (HPA) occurs in PD. Furthermore, this dysregulation may be involved in triggering, exacerbation or progression of disease. The objective of this study was to systematically review the literature regarding cortisol levels and their relation with motor, cognitive and behavioral symptoms in patients with PD. A systematic search was performed in PubMed and Embase databases, according to PRISMA norms. Twenty-one studies were included, which evaluated baseline levels of cortisol and motor, cognitive, behavioral symptoms, drugs administration or deep brain stimulation to PD treatment. Sample size ranged from 7 to 249 individuals. In 14 studies that assessed cortisol levels in PD patients, seven showed elevation of cortisol levels. In relation to symptomatology, high levels of cortisol were associated with worst functional scores evaluated by UPDRS, depression and behavior in risk preference. Medication interactions showed an influence on the regulation of cortisol release, mainly, conventional drugs used in the PD's treatment, such as levodopa. The results found in this review point to a possible relationship between cortisol levels and symptoms in PD, indicating that an HPA axis dysfunction related to cortisol level occurs in PD.

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The role of neuroinflammation in Parkinson's disease (PD) has been demonstrated through several different approaches. It was suggested an inflammation-derived oxidative stress and cytokine-dependent toxicity role in the nigrostriatal pathway degeneration and hasten progression of disease. Tumor necrosis factor alpha (TNFA) gene promoter polymorphisms might alter the expression of this cytokine contributing to the pro- and anti-inflammatory polarization. An increased TNFA expression might lead to inflammatory profile predominance. The aim of study was to determine if TNFA haplotypes are associated with PD age at onset. Five polymorphisms in TNFA gene were investigated in 226 patients with idiopathic PD in relation to age at onset. Haplotype grouping was based on allele expression. Logistic binary regression analysis showed that the genetic background leading to higher TNF-α expression confers a higher risk to develop PD earlier. Gender and ancestry did not differ between groups. High TNFA expression may contribute for faster dopaminergic neuron degeneration. In this context, a higher genetic pro-inflammatory profile confers a higher risk to develop PD earlier.

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AIM: Levodopa is first-line treatment of Parkinson's disease motor symptoms but, dose response is highly variable. Therefore, the aim of this study was to determine how much levodopa dose could be explained by biological, pharmacological and genetic factors. PATIENTS & METHODS: A total of 224 Parkinson's disease patients were genotyped for SV2C and SLC6A3 polymorphisms by allelic discrimination assays. Comedication, demographic and clinical data were also assessed. RESULTS: All variables with p < 0.20 were included in a multiple regression analysis for dose prediction. The final model explained 23% of dose variation (F = 11.54; p < 0.000001). CONCLUSION: Although a good prediction model was obtained, it still needs to be tested in an independent sample to be validated.

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Parkinson's disease (PD) is one of the most common neurodegenerative diseases worldwide. Besides characteristic PD motor features, the disease has important non-motor characteristics such as cognitive impairment. The role of genetic factors in cognitive impairment associated with PD is still unclear. In this study, we examined whether BDNF Val66Met was associated with impaired cognition in Parkinson's disease. One hundred and seventy five patients with a clinical diagnosis of Parkinson's disease were included. Global cognitive abilities of the patients were measured by the Mini-Mental State Examination (MMSE). Poisson Regression models were used to test for association between 66Met carriers and cognitive impairment controlling for covariates. Carriers of at least one BDNF 66Met allele presented a higher prevalence of cognitive impairment (p=0.005 RR=1.45 IC=95% [1.1-1.8]). These results suggest a role for BDNF Val66Met polymorphism on cognitive impairment in PD.

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AIM: Levodopa is first line treatment of Parkinson's disease (PD). However, its use is associated with the presence of motor fluctuations and dyskinesias. In recent years, adenosine A2A receptor (A2AR) is rising as a therapeutic target for PD. The aim of the present study was to investigate whether ADORA2A is associated with levodopa adverse effects. PATIENTS & METHODS: Two hundred and eight PD patients on levodopa therapy were investigated. rs2298383 and rs3761422 at the ADORA2A gene were genotyped by allelic discrimination assays. RESULTS: A trend for association was observed for both polymorphism and diplotypes with dyskinesia. CONCLUSION: The present results should be considered as positive preliminary evidence. Further studies are needed to determine the association between ADORA2A and dyskinesia. Original submitted 3 December 2014; Revision submitted 13 February 2015.

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The requirement for dopaminergic drugs in Parkinson's disease (PD) is highly variable. Visual hallucinations are a frequent and serious complication of chronic levodopa therapy. Polymorphisms in the DAT1 gene might affect the reuptake of dopamine in the synaptic cleft, but the influence of this variability on adverse effects or levodopa equivalent dose on PD patients is still poorly investigated. Therefore, the aim of the present study was to investigate DAT1 gene polymorphisms on levodopa equivalent dose and visual hallucination occurrence in PD patients. Altogether, 196 PD patients in treatment with at least 200 mg levodopa equivalent dose for at least 1 yr were included. These patients were genotyped for the -839 C > T and 3' VNTR DAT1 polymorphisms by PCR-based methodologies. Visual hallucinations occurred in 25.5% of the sample. After controlling for confounders, the dopamine transporter (DAT) -839 C allele was associated with visual hallucinations (prevalence ratio 2.5, 95% confidence intervals 1.13-5.5, p = 0.02). Levodopa equivalent dose was lower in carriers of the nine repeat allele of the DAT 3'UTR VNTR (741.2 ± 355.0 vs. 843.4 ± 445.7), explaining 21% of dose variability (p = 0.01). Our results support an effect of DAT1 polymorphisms in adverse effects of anti-Parkinsonian drugs and in levodopa equivalent dose usage.

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AIM: Dyskinesia and motor fluctuation are frequent and serious complications of chronic levodopa therapy in patients with Parkinson's disease. Since genetic factors could play a role in determining the occurrence of these problems, the aim of the present study was to investigate whether possible functional polymorphisms among DRD2 and ANKK1 genes are associated with the risk of developing dyskinesia and motor fluctuations in Parkinson's disease patients. PATIENTS & METHODS: One hundred and ninety nine patients in treatment with levodopa were genotyped for the -141CIns/Del, rs2283265, rs1076560, C957T, TaqIA and rs2734849 polymorphisms at the DRD2/ANKK1 gene region. RESULTS: Carriers of the TTCTA haplotype showed an increased risk for the presence of dyskinesia (p = 0.007; 1.538 [95% CI: 1.126-2.101]). CONCLUSION: Our data suggest an influence of the DRD2/ANKK1 gene region on levodopa-induced dyskinesia.

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