Blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentrations in essential tremor: repeat observation in cases and controls in New York

Genomic Markers for Essential Tremor

There are many reports suggesting an important role of genetic factors in the etiopathogenesis of essential tremor (ET), encouraging continuing the research for possible genetic markers. Linkage studies in families with ET have identified 4 genes/loci for familial ET, although the responsible gene(s) have not been identified. Genome-wide association studies (GWAS) described several variants in LINGO1, SLC1A2, STK32B, PPARGC1A, and CTNNA3, related with ET, but none of them have been confirmed in replication studies. In addition, the case-control association studies performed for candidate variants have not convincingly linked any gene with the risk for ET. Exome studies described the association of several genes with familial ET (FUS, HTRA2, TENM4, SORT1, SCN11A, NOTCH2NLC, NOS3, KCNS2, HAPLN4, USP46, CACNA1G, SLIT3, CCDC183, MMP10, and GPR151), but they were found only in singular families and, again, not found in other families or other populations, suggesting that some can be private polymorphisms. The search for responsible genes for ET is still ongoing.

Discovery of Gut Bacteria Specific to Alzheimer's Associated Diseases is a Clue to Understanding Disease Etiology: Meta-Analysis of Population-Based Data on Human Gut Metagenomics and Metabolomics

Alzheimer's disease (AD)-associated sequence (ADAS) of cultured fecal bacteria was discovered in human gut targeted screening. This study provides important information to expand our current understanding of the structure/activity relationship of ADAS and putative inhibitors/activators that are potentially involved in ADAS appearance/disappearance. The NCBI database analysis revealed that ADAS presents at a large proportion in American Indian Oklahoman (C&A) with a high prevalence of obesity/diabetes and in colorectal cancer (CRC) patients from the US and China. An Oklahoman non-native group (NNI) showed no ADAS. Comparison of two large US populations reveals that ADAS is more frequent in individuals aged ≥66 and in females. Prevalence and levels of fecal metabolites are altered in the C&A and CRC groups versus controls. Biogenic amines (histamine, tryptamine, tyramine, phenylethylamine, cadaverine, putrescine, agmatine, spermidine) that present in food and are produced by gut microbiota are significantly higher in C&A (e.g., histamine/histidine 95-fold) versus NNI (histamine/histidine 16-fold). The majority of these bio-amines are cytotoxic at concentrations found in food. Inositol phosphate signaling implicated in AD is altered in C&A and CRC. Tryptamine stimulated accumulation of inositol phosphate. The seizure-eliciting tryptamine induced cytoplasmic vacuolization and vesiculation with cell fragmentation. Present additions of ADAS-carriers at different ages including infants led to an ADAS-comprising human sample size of 2,830 from 27 studies from four continents (North America, Australia, Asia, Europe). Levels of food-derived monoamine oxidase inhibitors and anti-bacterial compounds, the potential modulators of ADAS-bacteria growth and biogenic amine production, were altered in C&A versus NNI. ADAS is attributable to potentially modifiable risk factors of AD associated diseases.

Delta-amino-levulinic acid dehydratase gene and essential tremor

BACKGROUND

Several reports found a relationship between increased serum lead levels and the risk for essential tremor (ET), especially in carriers of the minor allele of the single nucleotide polymorphism (SNP) rs1800435 in the aminolevulinate dehydratase (ALAD) gene, which is involved in the synthesis of haem groups. Our group reported decreased risk for ET in carriers of the minor alleles of the rs2071746 and rs1051308 SNPs in the haem-oxygenases 1 and 2 (HMOX1 and HMOX2), respectively, involved in haem metabolism. We analysed whether ALAD rs1800435 alone and their interactions with the four common SNPs in the HMOX1 and HMOX2 genes are associated with the risk for ET.

MATERIALS AND METHODS

We analysed the genotype and allele variants frequencies of ALAD rs1800435 in 202 patients with familial ET and 218 healthy controls using a TaqMan method. We also analysed the role of the interaction between ALAD rs1800435 and the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363 and HMOX2 rs1051308 with the risk of developing ET.

RESULTS

The frequencies of genotype and allelic variants of ALAD rs1800435 did not differ significantly between patients with ET and controls, and were not influenced by gender. Subjects carrying the ALAD rs1800435CC genotype (wild-type) and the HMOX2 rs1051308GG genotype or the HMOX2 rs1051308G allele had significantly decreased risk for ET.

CONCLUSIONS

These results suggest that the ALAD rs1800435 SNP is not related with the risk for ET, but its interaction with the HMOX2 rs1051308 SNP could be weakly associated with the risk for this disease.

Agnosia for head tremor in essential tremor: prevalence and clinical correlates

BACKGROUND

Lack of awareness of involuntary movements is a curious phenomenon in patients with certain movement disorders. An interesting anecdotal observation is that patients with essential tremor (ET) often seem unaware of their own head tremor. In the current study, we asked ET patients whether they were aware of head tremor while it was occurring on examination, thereby allowing us to gauge real-time awareness of their involuntary movement.

METHODS

ET cases enrolled in an ongoing clinical research study at the Columbia University Medical Center (2009-2014). During a videotaped tremor examination, they were questioned about the presence of head tremor. True positives were cases who exhibited head tremor on examination and were aware of it; false negatives were cases who exhibited head tremor but were unaware of it.

RESULTS

The 126 ET cases had a mean age of 72.6 ± 12.4 years. Nineteen (48.7 %) of 39 cases with head tremor on examination did not report having head tremor at that moment. Even among cases with moderate or severe head tremor on examination, unawareness of head tremor was 45.5 %. We assessed the clinical correlates of unawareness of head tremor, comparing true positives to false negatives, and unawareness was correlated with older age, lower mental status test scores and several other clinical variables.

CONCLUSIONS

Nearly one-half of ET cases with head tremor on examination were acutely unaware of their tremor. Whether such agnosia for tremor may be leveraged as a diagnostic feature of ET is a question for future clinical studies.

Heme Oxygenase 1 and 2 Common Genetic Variants and Risk for Essential Tremor

Several reports suggested a role of heme oxygenase genes 1 and 2 (HMOX1 and HMOX2) in modifying the risk to develop Parkinson disease (PD). Because essential tremor (ET) and PD share phenotypical and, probably, etiologic factors of the similarities, we analyzed whether such genes are related with the risk to develop ET. We analyzed the distribution of allelic and genotype frequencies of the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363, and HMOX2 rs1051308 single nucleotide polymorphisms, as well as the presence of copy number variations of these genes in 202 subjects with familial ET and 747 healthy controls. Allelic frequencies of rs2071746T and rs1051308G were significantly lower in ET patients than in controls. None of the studied polymorphisms influenced the disease onset. The present study suggests a weak association between HMOX1 rs2071746 and HMOX2 rs1051308 polymorphisms and the risk to develop ET in the Spanish population.

Tandem gait performance in essential tremor patients correlates with cognitive function

Background

Emerging yet separate literatures have highlighted gait/balance impairments (i.e., mild ataxia) and cognitive problems in patients with essential tremor (ET). However, the relationship between the two has not been studied. The goal of these analyses was to study the relationship between gait/balance impairments and cognitive problems in ET. One-hundred-twenty ET cases were enrolled in an epidemiological study at Columbia University Medical Center. A Telephone Interview for Cognitive Status (TICS, range = 0–41 [no deficits]) was administered and a videotaped assessment of tandem gait was performed, during which the number of missteps during 10-steps was counted.

Results

The mean TICS score was 35.7 (range 25–39), and mean number of tandem mis-steps was 2.9 (range 0–10). The number of tandem mis-steps was correlated with the TICS score (Spearman’s r = −0.245, p = 0.011, i.e., individuals who had more tandem gait difficulty also had more cognitive difficulty). In a multivariate analysis, tandem mis-steps were associated with TICS score (p = 0.04) independent of age and other factors.

Conclusions

More cognitive difficulty was associated with more tandem gait difficulty in ET. Ambulation often requires the concurrent use of both cognitive and motor neural systems; hence it is possible that the cognitive and gait problems in ET reflect an underlying pervasive disorder affecting both cognitive and motor circuits.

Non-steroidal anti-inflammatory drug use and essential tremor

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to be inversely related to Parkinson's disease and Alzheimer's disease, both of which may share common mechanisms with essential tremor (ET). Use of these medications has not been studied in ET cases vs. controls.

OBJECTIVE

To investigate the relationships between NSAID (esp. ibuprofen) and aspirin use and ET.

METHODS

Subjects were enrolled in a case-control study of the environmental epidemiology of ET at the Columbia University Medical Center (CUMC; 2009-2014). We compared 92 ET cases to 107 controls (∼1:1 matching) in terms of self-reported NSAID (esp. ibuprofen) and aspirin use.

RESULTS

The proportion of NSAID or aspirin users (current or past) was similar in ET cases and controls (for current user, p = 0.66; for past user, p = 0.90). Among users, however, the total dosage of ibuprofen (frequency in past year × number of tablets taken at a time × typical average strength of tablets) was higher in controls than ET cases (p = 0.04). ET cases and controls did not differ with respect to aspirin use in the past year.

CONCLUSION

The proportion of NSAID or aspirin users did not differ in ET cases or controls; yet interestingly, ibuprofen use was less in ET cases than in controls. The latter raises the possibility that ibuprofen use could have a potential protective role in ET.

Elevated brain harmane (1-methyl-9H-pyrido[3,4-b]indole) in essential tremor cases vs. controls

BACKGROUND

Harmane (1-methyl-9H-pyrido[3,4-β]indole), a potent neurotoxin that has tremor-producing properties in animal models, is present in many foods; although we have demonstrated a difference in tissue harmane concentrations in ET cases vs. controls, all work to date has involved blood samples.

OBJECTIVES

We quantified harmane concentrations in human cerebellum, a brain region of particular pathogenic interest in essential tremor (ET), comparing ET to control brains.

METHODS

Cerebellar cortex was snap frozen and stored at -80°C in aliquots for biochemical analyses. Harmane concentration was assessed using high performance liquid chromatography.

RESULTS

Geometric mean brain harmane concentrations (adjusted for postmortem interval [PMI] and freezer time) were higher in ET cases than controls: 1.0824 (95% confidence interval=0.9405-1.2457) vs. 0.8037 (0.6967-0.9272), p=0.004. Geometric mean of brain harmane concentrations (adjusting for PMI and freezer time) was highest in ET cases who reported other relatives with tremor (1.2005 [0.8712-1.6541]), intermediate in ET cases without family history (1.0312 ([0.8879-1.1976]), and both were significantly higher than controls (p=0.02).

CONCLUSIONS

This study provides additional evidence of a possible etiological importance of this toxin in some cases of the human disease ET.