Differential effect of caffeine intake in subjects with genetic susceptibility to Parkinson's Disease

We examined if caffeine intake has a differential effect in subjects with high and low genetic susceptibility to Parkinson's disease (PD), a common neurodegenerative disorder. A case control study involving 812 subjects consisting of PD and healthy controls were conducted. Caffeine intake assessed by a validated questionnaire and genotyping of PD gene risk variant (LRRK2 R1628P) was carried out. Compared to caffeine takers with the wild-type genotype (low genetic susceptibility), non-caffeine takers with R1628P variant (high genetic susceptibility) had a 15 times increased risk of developing PD (OR = 15.4, 95% CI = (1.94, 122), P = 0.01), whereas caffeine takers with R1628P (intermediate susceptibility) had a 3 times risk (OR = 3.07, 95% CI = (2.02, 4.66), P < 0.001). Caffeine intake would significantly reduce the risk of PD much more in those with high genetic susceptibility compared to those with low genetic susceptibility.

Complementary therapies in hemifacial spasm and comparison with other movement disorders

OBJECTIVES

We determined the prevalence, range and factors influencing the use of complementary therapy among hemifacial spasm patients and compared the patterns of use of complementary therapies across different movement disorders in a systematic pooled analysis of published literature.

METHODS

A structured questionnaire was administered to 96 hemifacial spasm patients evaluating frequency of complementary therapy use, and factors influencing patients' decision to seek these therapies. We also performed a PubMed search of epidemiology studies on use of complementary therapies in movement disorders.

RESULTS

Fifty-one per cent of patients had tried complementary therapies, of which 47% reported some perceived benefit and 4.1% informed their doctor. Acupuncture (71.4%) and facial massage (17.6%) were most commonly used. Complementary therapy use was associated with greater HFS severity. The mean cost of treatment was about $78 per month. We identified eight articles on use of complementary therapies in movement disorders; Parkinson's disease (5), Tourette syndrome (2) and dystonia (1). Twenty-five to 88% of patient had tried complementary therapies, of which 32-70% reported some benefit. Trials of acupuncture (2-63%) and massage (7-38%) were reported across the spectrum of movement disorders studied. Mean cost of complementary therapies varied from 43 to 102 USD per month.

CONCLUSION

Complementary therapies are used by over 50% of HFS patients, and the use is correlated with severity of disease. Despite differences in race, culture and population demographics, acupuncture and massage are used by patients across the spectrum of movement disorders.

Analysis of GWAS-linked loci in Parkinson disease reaffirms PARK16 as a susceptibility locus

OBJECTIVE

A genome-wide association study (GWAS) in the Japanese population identified 2 new Parkinson disease (PD) susceptibility loci on 1q32 (PARK16) (OMIM 613164) and BST1. We analyzed single nucleotide polymorphism (SNPs) located at the GWAS-linked loci (PARK16, PARK8, PARK1, and BST1) in a Chinese population and also conducted a meta-analysis in Asians by pooling 2 independent replication studies from Japan.

METHODS

We conducted an analysis of 13 SNPs associated with PD GWAS-linked loci in 2 case-control cohorts comprised of 1,349 ethnic Chinese subjects.

RESULTS

PARK16, PARK8, and PARK1 loci but not BST1 were found to be associated with PD. PARK16 SNPs were associated with a decreased risk while PARK1 and PARK8 SNPs were associated with an increased risk of PD. A pooled analysis of our Chinese cohorts and 2 Japanese replication cohorts involving 1,366 subjects with PD and 16,669 controls revealed robust association with these 3 loci and also BST1. There was a trend toward a stronger protective effect of SNPs at the PARK16 locus in sporadic PD compared to familial cases and in older compared to younger subjects.

CONCLUSIONS

Our study reaffirms the role of GWAS-linked loci in PD in Asian subjects and the strength of association is similar between Chinese and Japanese subjects. Efforts to elucidate the associated gene within PARK16 locus are warranted.

The LRRK2 Gly2385Arg variant is associated with Parkinson’s disease: genetic and functional evidence

Evidence of LRRK2 haplotypes associated with Parkinson's disease (PD) risk was recently found in the Chinese population from Singapore, and a common LRRK2 missense variant, Gly2385Arg, was independently detected as a putative risk factor for PD in the Chinese population from Taiwan. To test the association between the Gly2385Arg variant in a large case-control sample of Chinese ethnicity from Singapore, and to perform functional studies of the wild type and Gly2385Arg LRRK2 protein in human cell lines. In a case-control study involving 989 Chinese subjects, the frequency of the heterozygous Gly2385Arg genotype was higher in PD compared to controls (7.3 vs. 3.6%, odds ratio = 2.1, 95% CI: 1.1-3.9, P = 0.014); these values yield an estimated population attributable risk (PAR) of approximately 4%. In a multivariate logistic regression analysis with the disease group (PD vs. controls) as the dependent variable and the genotype as an independent factor with adjustments made for the effect of age and gender, the heterozygous Gly2385Arg genotype remained associated with an increased risk of PD compared to wild type genotype (odds ratio = 2.67, 95% CI: 1.43-4.99, P = 0.002). The glycine at position 2385 is a candidate site for N-myristoylation, and the Gly2385Arg variant replaces the hydrophobic glycine with the hydrophilic arginine, and increases the net positive charge of the LRRK2 WD40 domain. In transfection studies, we demonstrated that both the wild type and Gly2385Arg variant LRRK2 protein localize to the cytoplasm and form aggregates. However, under condition of oxidative stress, the Gly2385Arg variant was more toxic and associated with a higher rate of apoptosis. Our study lends support to the contention that the Gly2385Arg is a common risk factor for PD in the Chinese population. Our bioinformatics and in-vitro studies also suggest that the Gly2385Arg variant is biologically relevant and it might act through pro-apoptotic mechanisms.

Genetic analysis of SCA2, 3 and 17 in idiopathic Parkinson's disease

Recent reports of SCA2 and SCA3 patients who presented with levodopa responsive parkinsonism have generated considerable interest as they have implications for genetic testing. It is unclear whether ethnic race alone or founder effects within certain geographical region explain such an association. In this study, we conducted genetic analysis of SCA2, 3, 17 in an ethnic Chinese cohort with early onset and familial Parkinson's disease (PD) and healthy controls. A total of 191 subjects comprising of 91 PD and 100 healthy controls were examined. We identified one positive case of SCA2 in an early-onset sporadic PD patient who had CAG 36 repeats, yielding a prevalence of 2.2% in early-onset sporadic PD patients and less than 1.0% in our study PD population. The size of the repeats was lower than the expanded repeats (38-57) in SCA2 patients with ataxia in our population. All the children of the patient were physically normal even though some of them carried the repeat expansion of similar size. No cases and controls were positive for SCA3 and SCA17. We do not think routine screening of SCA2, SCA3 and SCA17 for all idiopathic PD patients is cost-effective in our ethnic Chinese population. However, SCA2 should be a differential diagnosis in young onset sporadic PD when genetic mutations of other known PD genes have been excluded.

Analysis of LRRK2 functional domains in nondominant Parkinson disease

A comprehensive sequence analysis of 29 exons that code for the functional domains of LRRK2 in 160 nondominant Parkinson disease (PD) patients was performed. Novel variant screening in a further 470 sporadic PD patients and 630 controls revealed two novel variants (R1067Q and IVS33 + 6 T>A), which are likely to be pathogenic in five patients. One patient presented initially with a typical essential tremor phenotype, expanding the phenotypic spectrum of LRRK2 mutations.

Impaired transcriptional upregulation of Parkin promoter variant under oxidative stress and proteasomal inhibition: clinical association

We provided data to show that the transcriptional activity of wildtype -258T in the parkin promoter region was significantly higher than the -258G variant in human cell lines. The transcriptional activity of wildtype -258T was significantly increased under oxidative stress by hydrogen peroxide, but this was not observed for the -258G variant. The transcriptional upregulation was significantly higher for wildtype -258T compared to -258G variant at 0.1, 0.2 and 0.4 mM of hydrogen peroxide. Similar results were obtained when the cells were treated with a proteasome inhibitor, MG132.Furthermore, in a case control study involving 753 subjects, we demonstrated that the parkin promoter -258G variant was associated with an increased risk of sporadic Parkinson's disease (PD) in the elderly ethnic Chinese population. Our clinical and laboratory data provide corroborative evidence that some older individuals who have the -258G variant may have a higher risk of developing PD.

The G2019S LRRK2 mutation is uncommon in an Asian cohort of Parkinson's disease patients

A common heterozygous leucine-rich repeat kinase 2 (LRRK2) mutation 6055G > A transition (G2019S) accounts for about 3-7% of familial Parkinson's disease (PD) and 1-1.6% sporadic PD in a number of European populations. To determine the prevalence of the G1019S mutation in our Asian population, we conducted genetic analysis of this mutation in 1000 PD and healthy controls. The G2019S mutation was not detected in any of our study subjects. The prevalence of G2019S mutation is rare (< 0.1%) in our population, suggesting that occurrence of this mutation may vary amongst different ethnic races. This has important clinical implication when implementing guidelines for genetic testing.

Differential expression of splice variant and wild-type parkin in sporadic Parkinson's disease

BACKGROUND

Altered splicing of parkin under cellular stress could lead to changes in gene expression and altered protein activity. The causative role of parkin in sporadic Parkinson's disease (PD) is unknown.

OBJECTIVES

We described a parkin splice variant (SV) in the substantia nigra and leukocytes of sporadic PD patients. Using a case control methodology, we investigated the exon 4 SV (E4SV) and wild-type parkin expression in the leukocytes of sporadic PD patients and healthy individuals.

METHODS/RESULTS

We identified a parkin E4SV in the substantia nigra and leukocytes of sporadic PD patients and controls by reverse transcriptase-polymerase chain reaction (PCR). The exon 4 (122 bp) deletion resulted in a reading frame shift over the junction of exons 3-5 and a stop codon (tga) 17 bp downstream from exon 3. The translated truncated protein was associated with a total loss of the two-RING finger functional domain. Utilizing TaqMan real-time PCR with probes located across the junction of exons 3-4 or 3-5, we demonstrated an over-expression of E4SV/wild-type parkin ratio in the leukocytes of sporadic PD patients compared to age-, gender-, and race-matched controls (p<0.0005). A multivariate regression analysis demonstrated that the ratio of E4SV/wild-type parkin expression increased with age in PD patients, but this was not observed in the controls (p<0.0005).

CONCLUSION

The relative expression of E4SV/wild type parkin was increased in sporadic PD compared to healthy controls. Based on our observations, further functional studies to determine the pathophysiologic role of E4SV in sporadic PD patients will be of importance.

Prescribing pattern in Parkinson's disease: are cost and efficacy overriding factors?

Information on prescribing pattern of antiparkinsonian medications and factors influencing neurologists' choice of such drugs are important considerations in evaluating healthcare cost of Parkinson's disease (PD). We surveyed neurologists' perceived factors influencing their choice of drugs and actual prescribing pattern in PD. Three hundred and six patients at a tertiary hospital, diagnosed with idiopathic PD and who were dispensed antiparkinsonian drugs during a 6-month period were randomly selected. Patient demographics, type and dose of medications were analysed. A questionnaire survey evaluating the factors influencing choice of medications was administered to neurologists who practiced at the institution. The study population had a mean age of 64.4 years (SD +/- 9.9 years), and more than 80% were at Hoehn & Yahr stage 2-3. 92.3% of the study population were receiving levodopa and monotherapy, with levodopa being the most common treatment regimen. Patients who were prescribed levodopa were significantly older and at a later stage of disease compared to those without levodopa (p < 0.05). Only 26.8% of patients were prescribed dopamine agonists. In the survey, the neurologists cited severity of symptoms, and patients' intolerance of side effects, and efficacy as the most important factors influencing their choice of drugs. However, the actual prescribing pattern revealed a strong positive correlation of drug usage with cost subsidy by the institution. While factors affecting drug usage in PD are well recognised, cost and efficacy of a drug appear to be overriding practical factors in influencing usage pattern in clinical practice.

Fragile X premutation alleles in SCA, ET, and parkinsonism in an Asian cohort

Among 367 subjects, the authors analyzed 167 patients with essential tremor, sporadic progressive cerebellar ataxia, multiple-system atrophy, and atypical parkinsonism and 200 healthy control subjects for FMR1 premutation alleles. None of the subjects carried alleles within the premutation range. These findings suggest that in the absence of other supportive clinical or imaging features, the cost-effectiveness of routine fragile X tremor/ataxia syndrome screening in this Asian cohort with movement disorders was low.

Alpha-synuclein haplotypes implicated in risk of Parkinson's disease

The authors examined four- and six-loci haplotype constructs (from five single nucleotide polymorphisms and three microsatellite regions) of the alpha-synuclein gene in patients with Parkinson's disease (PD) and controls in an ethnic Chinese population. Logistic regression analysis demonstrated an association of NACP-Rep1 (p = 0.002) and L478 (p < 0.0001) with risk of PD after correction for the effects of age, sex, and the other polymorphic loci. Specific four-loci and six-loci haplotypes were significantly associated with an increased or decreased risk of PD.

Dose-dependent protective effect of coffee, tea, and smoking in Parkinson's disease: a study in ethnic Chinese

INTRODUCTION

Few studies have examined the relationship of coffee and tea in Parkinson's disease (PD). The potential protective effect of coffee intake and risk of PD has not been studied in a Chinese population. There is a high prevalence of caffeine takers among Chinese in our population.

OBJECTIVE

We undertook a case control study to examine the relationship between coffee and tea drinking, cigarette smoking, and other enviromental factors and risk of PD among ethnic Chinese in our population.

METHODS AND RESULTS

300 PD and 500 population controls were initially screened. Two hundred case control pairs matched for age, gender, and race were finally included in the analysis. Univariate analysis revealed significant association of PD with coffee drinking (p<0.0005), tea drinking (p=0.019), alcohol drinking (p=0.001), cigarette smoking (p<0.0005), and exposure to heavy metals (p=0.006). Conditional logistic regression analysis demonstrated that amount of coffee drunk (OR 0.787, 95%CI 0.664-0.932, p=0.006), amount of tea drunk (OR 0.724, 95%CI 0.559-0.937, p=0.014), number of cigarettes smoked (OR 0.384, 95%CI 0.204-0.722, p=0.003), history of heavy metal and toxin exposure (OR 11.837, 95%CI 1.075-130.366, p=0.044), and heart disease (OR 5.518, 95%CI 1.377-22.116, p=0.016) to be significant factors associated with PD. One unit of coffee and tea (3 cups/day for 10 years) would lead to a 22% and 28% risk reduction of PD. One unit of cigarette smoke (3 packs/day for 10 years) reduced the risk of PD by 62%.

CONCLUSIONS

We demonstrated a dose-dependent protective effect of PD in coffee and tea drinkers and smokers in an ethnic Chinese population. A history of exposure to heavy metals increased the risk of PD, supporting the multifactorial etiologies of the disease.

Electrophysiological features in the management of meralgia paraesthetica

Meralgia paraesthetica is a condition which presents with pain and paresthesia over the anterolateral thigh, due to entrapment of the lateral femoral cutaneous nerve. Our local experience of 12 cases highlights the usefulness of antidromic sensory nerve conductions in the diagnostic and prognostic aspects of this condition. Follow-up studies suggest that patients with initial reduction rather than absent sensory amplitudes on the affected side more likely to experience symptomatic improvement over an 8 to 24 month period.

Vascular assessment in the neuropathic diabetic foot

Diabetic foot infections, a common source of morbidity and mortality, often have been related to vasculopathy and neuropathy in its etiopathogenesis, especially in the elderly person with diabetes. However, blood flow in the neuropathic diabetic foot has not been evaluated extensively, and there is evidence of abnormal blood flow patterns in the neuropathic diabetic foot unrelated to ischemia. The authors studied young persons with diabetes, with varying degrees of neuropathy, to assess the extent of vasculopathy in their lower limbs. Twelve young persons with insulin-dependent (Type I) diabetes (mean age, 36.1 +/- 1.975 years) and peripheral neuropathy, all of whom had previous surgery for diabetic foot infections, were identified. Confirmatory evidence of neuropathy was made using electromyographic studies and clinical tests that showed severe peripheral neuropathy. The results of vascular assessment of both lower limbs did not reveal any change in the pulse wave velocities from the popliteal to the digital vessels of the big toe as compared with correspondingly matched controls. There also was no significant stenosis in any of the vessels studied as far as the level of the dorsalis pedis and posterior tibial vessels. The normal triphasic pattern of arterial blood flow was lost. A monophasic pattern was present in all patients with prolonged diastolic flow at the level of the dorsalis pedis and posterior tibial arteries and distally. The pulsatility index was 3.14 +/- 0.81 as compared with 9.85 +/- 4.2. Mean toe pressures in the patient with diabetes was 64.17 +/- 20.87 mm Hg as compared with 98.23 +/- 10.12 mm Hg in controls. A linear correlation of decreasing toe pressures with increasing severity of neuropathy was seen (R = 0.7). The data suggest that changes exist in the blood flow patterns in young patients with diabetes and neuropathy, even in the absence of lower limb ischemia.

Clinical study of magnetic stimulation of peripheral nerves

Magnetic stimulation of the peripheral nerves is a recently developed technique and has exciting prospects in clinical neurophysiology. An experiment was performed comparing the conventional electric stimulation with magnetic stimulation of the median nerve of a normal population. Magnetic stimulation produced comparable results as far as latency, amplitudes and configuration of action potentials in most patients. The technique of magnetic stimulation is discussed. Its shortcomings are in locating the magnetic coil's point of stimulation on the nerve and difficulty in achieving supramaximal stimulation. Its great advantage is that it is painless and that deep nerves can be reached.