Harmane Concentrations Research Articles

Essential tremor: A three-dimensional neurosphere in vitro model to assess the neurotoxicity of harmane

Considering that the 3 Rs of regulation (replacing, reducing, and refining) are meant to reduce the number and suffering of research animals and that current two-dimension (2D) in vitro and animals models do not completely mimic the human presentation of the disease, there is a growing demand to develop alternative models. Therefore, we propose here the use of a novel in vitro model of three-dimensional (3D) neurosphere cultures to assess neurotoxic or neuroprotective effects with harmane as a model compound. A reproducible model of 3D spheroids was developed from embryonic mouse cortical neurons, using molded agarose micro-wells; this method seems particularly practical as it is customizable and widely available and does not require specific cell treatments or assay components different from 2D cultures, allowing for the easy transposition of routine protocols. To assess the neurotoxic effects of harmane, a resazurin assay was performed to measure cell viability, and a highly sensitive fluorometric method, based on the oxidation of dichlorodihydrofluorescein, was applied to measure eventually induced reactive oxygen species (ROS) after exposure to harmane at increasing concentrations of 50 100, and 250 μM. Hydrogel microwells facilitated the assembly of spheroids containing neurons and glial cells into a complex 3D structure and prevented the agglomeration of spheroids. Exposure to harmane induced cytotoxicity in 3D neural spheroids, which was correlated with harmane concentrations, with a 27% reduction in viability at 250 μM. Harmane that did not induce significant levels of oxidative stress was detected for all tested concentrations. This 3D neurosphere model mimics a neuronal microenvironment, allowing a fine study of neurodegenerative disorders and the effects of chemicals on the brain. This model opens novel opportunities, not only from a pathogenetic point of view but also from a therapeutic perspective.

Meat Consumption and Meat Cooking Practices in Essential Tremor: A Population-Based Study in the Faroe Islands.

Background:Elevated tissue levels of the tremor-producing neurotoxin, harmane, have been detected in patients with essential tremor (ET) in the USA and Spain. Recently, a study in the Faroe Islands similarly noted an elevation in blood harmane concentrations in probable and definite ET cases. The underlying mechanism is not understood. Possible mechanisms include increased dietary consumption (esp. through cooked meats), impaired metabolism, or increased endogenous production of harmane. To investigate this issue further, we conducted a population-based study in the Faroe Islands to examine meat consumption and meat cooking practices in ET cases and controls.Methods:1,328 Faroese adults were screened for tremor and 27 ET cases were identified. Meat consumption and meat cooking practices were compared to 200 controls. Detailed data were collected via questionnaires regarding current meat consumption for 14 meat types and meat cooking doneness for 8 meat types. Data were also available on blood harmane concentrations.Results:Current meat consumption was similar in ET cases and controls in 12 out of 14 meat types, with no differences observed after a Bonferroni correction in any meat type; no difference was observed when stratified by gender. No difference was observed in meat doneness between ET cases and controls. Blood harmane concentrations were not correlated with dietary data.Discussion:This is the first population-based study of harmane-linked dietary factors in ET. The study suggests the observed difference in blood harmane in ET is not driven by dietary differences and is likely due to other mechanisms (e.g., impaired metabolism).

Blood Harmane (1-Methyl-9H-Pyrido[3,4-b]indole) and Mercury in Essential Tremor: A Population-Based, Environmental Epidemiology Study in the Faroe Islands

Background: Essential tremor (ET) is among the most prevalent neurological diseases. Its environmental determinants are poorly understood. Harmane (1-methyl-9H-pyrido[3, 4-b]indole), a dietary tremor-producing neurotoxin, has been linked to ET in a few studies in New York and Madrid. Mercury, also a tremor-producing neurotoxin, has not been studied in ET. The Faroe Islands have been the focus of epidemiological investigations of numerous neurological disorders. Objective: In this population-based, case-control study, we directly measured blood harmane concentrations (HA) and blood mercury concentrations (Hg) in ET cases and controls. Methods: In total, 1,328 Faroese adults were screened; 26 ET cases were identified whose (HA) and (Hg) were compared to 197 controls. Results: Although there were no statistically significant differences between diagnostic groups, median (HA) was 2.7× higher in definite ET (4.13 g^–10/mL) and 1.5× higher in probable ET (2.28 g^–10/mL) than controls (1.53 g^–10/mL). Small sample size was a limitation. For definite ET versus controls, p = 0.126. (Hg) were similar between groups. Conclusions: We demonstrated marginally elevated (HA) in definite and probable ET. These data are similar to those previously published and possibly extend etiological links between this neurotoxin and ET to a third locale. The study did not support a link between mercury and ET.

A 3D neurons model to evaluate the neurotoxicity of harmane, a β carboline alkaloid incriminated in Essential Tremor

Event Abstract Back to Event A 3D neurons model to evaluate the neurotoxicity of harmane, a β carboline alkaloid incriminated in Essential Tremor Rania Aro1*, Alpha Diallo2, 3, Marvyn Pichueque2, 3, Mathilde Wauters4, Amandine Nachtergael1, Laurence Ris4, Pierre Duez1 and Mario Manto2, 3 1 University of Mons, Belgium 2 Free University of Brussels, Belgium 3 Service de Neurologie, Centre Hospitalier Universitaire de Charleroi, Belgium 4 Research Institute for Biosciences, University of Mons, Belgium Introduction: β-Carbolines alkaloids (βCAs) are indole alkaloids, such as harmane, that naturally occur in plants and food and are also endogenously produced in mammals and humans. Some βCAs are potent tremor inductors and exhibit neurotoxicological activities. They have been incriminated in the pathogenesis of Essential tremor (ET) as blood Harmane levels have been found to be abnormally increased in ET patients. Harmane has also been detected in post-mortem brain samples. Essential tremor (ET) is one of the most prevalent neurological diseases but, despite a high prevalence, its physiopathology remains poorly understood. There is converging evidence that both genetic and environmental factors play a role in ET pathogenesis and so the identification of involved environmental factors is a critical step towards risk reduction through the implementation of prevention strategies or interventional studies. 2D cell cultures do not represent the real cell environment where cells spatially and chemically interact; their lack in predictivity increases the cost and failure rate of clinical trials, especially in neurosciences. Recently, 3D cell cultures have received much attention, as these are closer to tissues models, although their main challenges reside in end-point measurements. Methods: We propose the use of a 3D neural spheroid cultures ("mini-brains") in vitro model to assess the neurotoxic effects of harmane. We have generated a model of 3D spheroids from embryonic mouse cortical neurons using micro-molded agarose wells. After exposure to harmane at increasing concentrations of 50, 100, 250 µM, a resazurin assay was performed to measure cell viability and a highly sensitive fluorometric method, based on the oxidation of di-chlorodihydrofluorescein DCFH, was used to measure eventually induced reactive oxygen species (ROS). Results: Hydrogel microwells facilitated the assembly of spheroids containing neurons and glia into a complex 3D structures and prevented the agglomeration of spheroids. Exposure to harmane induced a cytotoxicity in 3D neural spheroids that was correlated with harmane concentrations, with a viability down to 24 % at 250 µM. On the other hand, lower levels of oxidative stress were detected as the harmane concentration increased, although the effect was limited in time. Conclusions: We demonstrated our ability to produce a 3D culture using simple materials and routine laboratory equipment. Despite high challenges related to 3D cultures and data acquisition, this 3D neural spheroid model mimics a neuronal microenvironment, allowing a fine study of neurodegenerative disorder pathologies and the effect of chemicals on the brain. The viability and oxidative stress data support so far a dual role of harmane, as both neurotoxic and neuroprotective agent. Further studies are required to elucidate its biological activities and their eventual relationship with the ET disorder. Acknowledgements This research is in part funded through a FMRH grant and a Kangaroo grant from the UMONS Health Institute .

Blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentration in dystonia cases vs. controls

BackgroundHarmane (1-methyl-9H-pyrido[3,4-b]indole) (HA) is a potent neurotoxin that has been linked to two neurological diseases, essential tremor and Parkinson's disease. Blood harmane concentrations [HA] are elevated in patients with both diseases. An important question is whether HA is specifically linked with these diseases or alternatively, is a non-specific marker of neurological illness. ObjectivesWe assessed whether blood [HA] was elevated in patients with a third neurological disease, dystonia, comparing them to controls. MethodsBlood [HA] was quantified by high performance liquid chromatography. Subjects comprised 104 dystonia cases and 107 controls. ResultsMean log blood [HA] in dystonia cases was similar to that of controls (0.41±0.51g−10/ml vs. 0.38±0.61g−10/ml, t=0.42, p=0.68). In unadjusted and adjusted logistic regression analyses, log blood [HA] was not associated with the outcome (diagnosis of dystonia vs. control): odds ratio (OR)unadjusted=1.11, 95% confidence interval (CI)=0.69–1.79, p=0.68; ORadjusted=1.07, 95% CI=0.58–1.97, p=0.84. ConclusionsIn contrast to the elevated blood [HA] that has been reported in patients with essential tremor and Parkinson's disease, our data demonstrate that blood [HA] was similar in patients with dystonia and controls. These findings provide the first support for the notion that an elevated blood [HA] is not a broad feature of neurological disease, and may be a specific feature of certain tremor disorders.

Elevated blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentrations in Parkinson's disease

BackgroundParkinson's disease (PD) is a late-life neurodegenerative disease. Genetic and environmental factors play an etiological role. Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent tremor-producing neurotoxin that shows structural resemblance to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). ObjectivesIn 2002 and 2007, we demonstrated elevated blood harmane concentrations [HA] in essential tremor (ET) cases. We now assessed whether blood [HA] were elevated in Parkinson's disease (PD) as well. MethodsBlood [HA] were quantified by high performance liquid chromatography. Subjects comprised 113 PD cases and 101 controls. ResultsMean log blood [HA] in PD cases was double that of controls (0.59±0.63g−10/ml vs. 0.27±0.63g−10/ml, p<0.001). A non-parametric test on non-transformed data (median blood [HA]=3.31g−10/ml in cases and 1.44g−10/ml in controls) also showed this difference (p<0.001). In unadjusted and then adjusted logistic regression analyses, log blood [HA] was associated with PD (odds ratio [OR]unadjusted 2.31, 95% confidence interval [CI] 1.46–3.67, p<0.001; ORadjusted 2.54, 95% CI 1.55–4.16, p<0.001). In PD, log blood [HA] co-varied with family history, being lowest in PD cases with no family history (0.54±0.60g−10/ml) and highest in PD cases with a family history of both ET and PD (0.84±0.68g−10/ml) (p=0.06). ConclusionsBlood harmane appears to be elevated in PD. The finding needs to be reproduced in additional cohorts to assess its generalizability. The higher concentration in familial PD suggests that the mechanism may involve genetic factors.

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

BackgroundHarmane (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. ObjectivesWe quantified harmane concentrations in human cerebellum, a brain region of particular pathogenic interest in essential tremor (ET), comparing ET to control brains. MethodsCerebellar cortex was snap frozen and stored at −80°C in aliquots for biochemical analyses. Harmane concentration was assessed using high performance liquid chromatography. ResultsGeometric 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). ConclusionsThis study provides additional evidence of a possible etiological importance of this toxin in some cases of the human disease ET.

Blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentration in essential tremor cases in Spain

BackgroundEnvironmental correlates for essential tremor (ET) are largely unexplored. The search for such environmental factors has involved the study of a number of neurotoxins. Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent tremor-producing toxin. In two prior case–control studies in New York, we demonstrated that blood harmane concentration was elevated in ET patients vs. controls, and especially in familial ET cases. These findings, however, have been derived from a study of cases ascertained through a single tertiary referral center in New York. ObjectiveOur objective was to determine whether blood harmane concentrations are elevated in familial and sporadic ET cases, ascertained from central Spain, compared to controls without ET. MethodsBlood harmane concentrations were quantified by a well-established high performance liquid chromatography method. ResultsThe median harmane concentrations were: 2.09g−10/ml (138 controls), 2.41g−10/ml (68 sporadic ET), and 2.90g−10/ml (62 familial ET). In an unadjusted logistic regression analysis, log blood harmane concentration was not significantly associated with diagnosis (familial ET vs. control): odds ratio=1.56, p=0.26. In a logistic regression analysis that adjusted for evaluation start time, which was an important confounding variable, the odds ratio increased to 2.35, p=0.049. ConclusionsBlood harmane levels were slightly elevated in a group of familial ET cases compared to a group of controls in Spain. These data seem to further extend our observations from New York to a second cohort of ET cases in Spain. This neurotoxin continues to be a source of interest for future confirmatory research.

Blood Harmane (1-Methyl-9H-pyrido[3,4-b]indole) Concentrations in Essential Tremor: Repeat Observation in Cases and Controls in New York

Essential tremor (ET) is a widespread late-life neurological disease. Genetic and environmental factors are likely to play important etiological roles. Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent tremor-producing neurotoxin. Previously, elevated blood harmane concentrations were demonstrated in ET cases compared to controls, but these observations have all been cross-sectional, assessing each subject at only one time point. Thus, no one has ever repeat-assayed blood harmane in the same subjects twice. Whether the observed case-control difference persists at a second time point, years later, is unknown. The current goal was to reassess a sample of our ET cases and controls to determine whether blood harmane concentration remained elevated in ET at a second time point. Blood harmane concentrations were quantified by a well-established high-performance liquid chromatography method in 63 ET cases and 70 controls. A mean of approximately 6 yr elapsed between the initial and this subsequent blood harmane determination. The mean log blood harmane concentration was significantly higher in cases than controls (0.30 ± 0.61 g−10/ml versus 0.08 ± 0.55 g−10/ml), and the median value in cases was double that of controls: 0.22 g−10/ml versus 0.11 g−10/ml. The log blood harmane concentration was highest in cases with a family history of ET. Blood harmane concentration was elevated in ET cases compared to controls when reassessed at a second time point several years later, indicating what seems to be a stable association between this environmental toxin and ET.

Blood Harmane Concentrations in 497 Individuals Relative to Coffee, Cigarettes, and Food Consumption on the Morning of Testing

Harmane, a potent neurotoxin linked with several neurological disorders, is present in many foods, coffee, and cigarettes. We assessed whether morning food/coffee consumption and smoking were reflected in blood harmane concentrations (BHCs) we obtained in an epidemiologic sample (n = 497). Participants who smoked on the morning of phlebotomy had similar logBHCs to those who had not smoked (P = .57); there was no correlation between logBHCs and number of cigarettes (P = .59). Among the coffee drinkers, there was no correlation between number of cups and logBHCs (P = .98). Participants who had eaten on the morning of phlebotomy had similar logBHCs to those who had not (P = .49); logBHCs did not correlate with the time latency between last food consumption and phlebotomy (P = .74). BHCs in this sample of ~500 individuals did not covary with recent smoking, coffee, or food consumption, suggesting that our inability to withhold these exposures on the morning of phlebotomy was not reflected in the BHCs we measured.

Blood harmane, blood lead, and severity of hand tremor: Evidence of additive effects

Background Tremor is a widespread phenomenon in human populations. Environmental factors are likely to play an etiological role. Harmane (1-methyl-9H-pyrido[3,4-β]indole) is a potent tremor-producing β-carboline alkaloid. Lead is another tremor-producing neurotoxicant. The effects of harmane and lead with respect to tremor have been studied in isolation. Objectives We tested the hypothesis that tremor would be particularly severe among individuals who had high blood concentrations of both of these toxicants. Methods Blood concentrations of harmane and lead were each quantified in 257 individuals (106 essential tremor cases and 151 controls) enrolled in an environmental epidemiological study. Total tremor score (range = 0–36) was a clinical measure of tremor severity. Results The total tremor score ranged from 0 to 36, indicating that a full spectrum of tremor severities was captured in our sample. Blood harmane concentration correlated with total tremor score ( p = 0.007), as did blood lead concentration ( p = 0.045). The total tremor score was lowest in participants with both low blood harmane and lead concentrations (8.4 ± 8.2), intermediate in participants with high concentrations of either toxicant (10.5 ± 9.8), and highest in participants with high concentrations of both toxicants (13.7 ± 10.4) ( p = 0.01). Conclusions Blood harmane and lead concentrations separately correlated with total tremor scores. Participants with high blood concentrations of both toxicants had the highest tremor scores, suggesting an additive effect of these toxicants on tremor severity. Given the very high population prevalence of tremor disorders, identifying environmental determinants is important for primary disease prevention.

Relationship between blood harmane and harmine concentrations in familial essential tremor, sporadic essential tremor and controls

Introduction Harmane, a potent tremor-producing β-carboline alkaloid, may play a role in the etiology of essential tremor (ET). Blood harmane concentrations are elevated in ET cases compared with controls yet the basis for this elevation remains unknown. Decreased metabolic conversion (harmane to harmine) is one possible explanation. Using a sample of >500 individuals, we hypothesized that defective metabolic conversion of harmane to harmine might underlie the observed elevated harmane concentration in ET, and therefore expected to find a higher harmane to harmine ratio in familial ET than in sporadic ET or controls. Methods Blood harmane and harmine concentrations were quantified by high performance liquid chromatography. Results There were 78 familial ET cases, 187 sporadic ET cases, and 276 controls. Blood harmane and harmine concentrations were correlated with one another (Spearman's r = 0.24, p < 0.001). The mean (±SD) harmane/harmine ratio = 23.4 ± 90.9 (range = 0.1–987.5). The harmane/harmine ratio was highest in familial ET (46.7 ± 140.4), intermediate in sporadic ET (28.3 ± 108.1), and lowest in controls (13.5 ± 50.3) ( p = 0.03). In familial ET cases, there was no association between this ratio and tremor severity (Spearman's r = 0.08, p = 0.48) or tremor duration (Spearman's r = 0.14, p = 0.24). Conclusion The basis for the elevated blood harmane concentration, particularly in familial ET, is not known, although the current findings (highest harmane/harmine ratio in familial ET cases) lends support to the possibility that it could be the result of a genetically-driven reduction in harmane metabolism.

Cancer and blood concentrations of the comutagen harmane in essential tremor

Blood concentrations of harmane, a tremor-producing neurotoxin, are elevated in essential tremor (ET). Harmane is also a comutagen. Using a case-control design, we compared the prevalence of cancer in ET cases vs. controls, and determined whether blood harmane concentrations are elevated among ET cases with cancer. 66/267 (24.7%) ET cases vs. 55/331 (16.6%) controls had cancer (adjusted OR 1.52, 95% CI 1.01-2.30, P = 0.04). Among specific cancer types, colon cancer was more prevalent in ET cases than controls (2.6% vs. 0.6%, P = 0.04). Log blood harmane concentration was higher in ET cases vs. controls (P = 0.02) and in participants with vs. without cancer (P = 0.02). Log blood harmane concentration was highest in ET cases with cancer when compared with other groups (P = 0.009). These links between cancer and ET and between high blood harmane and cancer in ET deserve further study.

Dietary Epidemiology of Essential Tremor: Meat Consumption and Meat Cooking Practices

Background/Aim: Harmane [1-methyl-9H-pyrido(3,4-b)indole] is a tremor-producing neurotoxin. Blood harmane concentrations are elevated in essential tremor (ET) patients for unclear reasons. Potential mechanisms include increased dietary harmane intake (especially through well-cooked meat) or genetic-metabolic factors. We tested the hypothesis that meat consumption and level of meat doneness are higher in ET cases than in controls. Methods: Detailed data were collected using the Lawrence Livermore National Laboratory Meat Questionnaire. Results: Total current meat consumption was greater in men with than without ET (135.3 ± 71.1 vs. 110.6 ± 80.4 g/day, p = 0.03) but not in women with versus without ET (80.6 ± 50.0 vs. 79.3 ± 51.0 g/day, p = 0.76). In an adjusted logistic regression analysis in males, higher total current meat consumption was associated with ET (OR = 1.006, p = 0.04, i.e., with 10 additional g/day of meat, odds of ET increased by 6%). Male cases had higher odds of being in the highest than lowest quartile of total current meat consumption (adjusted OR = 21.36, p = 0.001). Meat doneness level was similar in cases and controls. Conclusion: This study provides evidence of a dietary difference between male ET cases and male controls. The etiological ramifications of these results warrant additional investigation.

Higher blood harmane (1-methyl-9 H-pyrido[3,4- b]indole) concentrations correlate with lower olfactory scores in essential tremor

Background Harmane (1-methyl-9 H-pyrido[3,4- b]indole), a neurotoxin, may be an environmental risk factor for essential tremor (ET). Harmane and related chemicals are toxic to the cerebellum. Whether it is through this mechanism (cerebellar toxicity) that harmane leads to ET is unknown. Impaired olfaction may be a feature of cerebellar disease. Objective To determine whether blood harmane concentrations correlate with olfactory test scores in patients with ET. Methods Blood harmane concentrations were quantified using high performance liquid chromatography. Odor identification testing was performed with the University of Pennsylvania Smell Identification Test (UPSIT). Results In 83 ET cases, higher log blood harmane concentration was correlated with lower UPSIT score ( ρ = −0.46, p < 0.001). 25/40 (62.5%) cases with high log blood harmane concentration (based on a median split) had low UPSIT scores (based on a median split) vs. 12/43 (27.9%) ET cases with low log blood harmane concentration (adjusted odd ratios (OR) 4.04, 95% confidence intervals (CI) 1.42–11.50, p = 0.009). When compared with the low log blood harmane tertile, the odds of olfactory dysfunction were 2.64 times higher in cases in the middle tertile and 10.95 times higher in cases in the high tertile. In 69 control subjects, higher log blood harmane concentration was not correlated with lower UPSIT score ( ρ = 0.12, p = 0.32). Conclusions Blood harmane concentrations were correlated with UPSIT scores in ET cases but not controls. These analyses set the stage for postmortem studies to further explore the role of harmane as a cerebellar toxin in ET.

Elevated blood harmane (1-methyl-9H-pyrido[3,4- b]indole) concentrations in essential tremor

Essential tremor (ET) is a widespread late-life neurological disease. Genetic and environmental factors likely play an etiological role. Harmane (1-methyl-9H-pyrido[3,4- b]indole) is a potent tremor-producing neurotoxin. In 2002, we demonstrated elevated blood harmane concentrations in an initial sample of 100 ET cases compared to 100 controls. Between 2002 and 2007, we assembled a new and larger sample of ET cases and controls. We now attempt to replicate our previous findings. Cases and controls were frequency-matched on age, gender, and race. Blood harmane concentrations were quantified by high-performance liquid chromatography. Subjects comprised 150 ET cases and 135 controls (mean age 65.3 ± 15.5 vs. 65.5 ± 14.2 years, p = 0.94). Mean log blood harmane concentration was ∼50% higher in cases than controls (0.50 ± 0.54 g −10/ml vs. 0.35 ± 0.62 g −10/ml, p = 0.038). In a logistic regression analysis, log blood harmane concentration was associated with ET (OR adjusted 1.56, 95% CI 1.01–2.42, p = 0.04), and odds of ET was 1.90 (95% CI 1.07–3.39, p = 0.029) in the highest versus lowest log blood harmane tertile. Log blood harmane was highest in ET cases with familial ET (0.53 ± 0.57 g −10/ml), intermediate in cases with sporadic ET (0.43 ± 0.45 g −10/ml) and lowest in controls (0.35 ± 0.62 g −10/ml) (test for trend, p = 0.026). Blood harmane appears to be elevated in ET. The higher concentrations in familial ET suggests that the mechanism may involve genetic factors.

Mediterranean Diet and Essential Tremor

Background: Higher adherence to the Mediterranean diet (MeDi) has been related to lower Alzheimer’s disease risk. Some dietary factors have been studied in patients with essential tremor (ET), but the MeDi’s effect has not been investigated. Methods: Adherence to the MeDi was calculated from a food frequency questionnaire administered in a case-control study of environmental epidemiology of ET in the New York Tri-State area. Logistic regression models were used to examine whether adherence to the MeDi predicted ET (vs. control) outcome. The models adjusted for age, gender, ethnicity, education, caloric intake, body mass index, smoking, ethanol consumption, coffee intake and blood harmane concentrations. Results: 148 ET cases adhered less to MeDi (0–9 scale with higher scores indicating higher adherence) than 250 controls (mean 4.3 ± 1.7 vs. 4.7 ± 1.7; p = 0.03). Higher adherence to MeDi was associated with lower odds for ET [0.78 (0.61–0.99); p = 0.042]. As compared to subjects at the lowest MeDi adherence tertile, those at the middle tertile had lower ET odds [0.41 (0.16–1.05)], while subjects at the highest tertile had an even lower ET odds [0.29 (0.10–0.82); p for trend 0.021]. Conclusions: Compared to controls, ET cases adhered less to MeDi. The gradual reduction in ET odds with higher MeDi adherence tertiles suggests a possible dose-response effect. The mechanisms that underlie this association merit further study.

Blood harmane is correlated with cerebellar metabolism in essential tremor

On proton magnetic resonance spectroscopic imaging ((1)H MRSI), there is a decrease in cerebellar N-acetylaspartate/total creatine (NAA/tCr) in essential tremor (ET), signifying cerebellar neuronal dysfunction or degeneration. Harmane, which is present in the human diet, is a potent tremor-producing neurotoxin. Blood harmane concentrations seem to be elevated in ET. To assess in patients with ET whether blood harmane concentration is correlated with cerebellar NAA/tCR, a neuroimaging measure of neuronal dysfunction or degeneration. Twelve patients with ET underwent (1)H MRSI. The major neuroanatomic structure of interest was the cerebellar cortex. Secondary regions were the central cerebellar white matter, cerebellar vermis, thalamus, and basal ganglia. Blood concentrations of harmane and another neurotoxin, lead, were also assessed. Mean +/- SD cerebellar NAA/tCR was 1.52 +/- 0.41. In a linear regression model that adjusted for age and gender, log blood harmane concentration was a predictor of cerebellar NAA/tCR (beta = -0.41, p = 0.009); every 1 g(-10)/mL unit increase in log blood harmane concentration was associated with a 0.41 unit decrease in cerebellar NAA/tCR. The association between blood harmane concentration and brain NAA/tCR only occurred in the cerebellar cortex; it was not observed in secondary brain regions of interest. Furthermore, the association was specific to harmane and not another neurotoxin, lead. This study provides additional support for the emerging link between harmane, a neurotoxin, and ET. Further studies are warranted to address whether cerebellar harmane concentrations are associated with cerebellar pathology in postmortem studies of the ET brain.

Quantification of the Neurotoxic β-Carboline Harmane in Barbecued/Grilled Meat Samples and Correlation with Level of Doneness

Harmane, one of the heterocyclic amines (HCAs), is a potent neurotoxin linked to human diseases. Dietary exposure, especially in cooked meats, is the major source of exogenous exposure for humans. However, knowledge of harmane concentrations in cooked meat samples is limited. Our goals were to (1) quantify the concentration of harmane in different types of cooked meat samples, (2) compare its concentration to that of other more well-understood HCAs, and (3) examine the relationship between harmane concentration and level of doneness. Thirty barbecued/grilled meat samples (8 beef steak, 12 hamburger, 10 chicken) were analyzed for harmane and four other HCAs (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine [PhIP], amino-3,8-dimethylimidazo[4,5-f]quinoxaline [MeIQx], 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline [DiMeIQx], and 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine [IFP]). Mean (± SD) harmane concentration was 5.63 (± 6.63) ng/g; harmane concentration was highest in chicken (8.48 ± 9.86 ng/g) and lowest in beef steak (3.80 ± 3.6 ng/g). Harmane concentration was higher than that of the other HCAs and significantly correlated with PhIP concentration. Harmane concentration was associated with meat doneness in samples of cooked beef steak and hamburger, although the correlation between meat doneness and concentration was greater for PhIP than for harmane. Evidence indicates that harmane was detectable in nanograms per gram quantities in cooked meat (especially chicken) and, moreover, was more abundant than other HCAs. There was some correlation between meat doneness and harmane concentration, although this correlation was less robust than that observed for PhIP. Data such as these may be used to improve estimation of human dietary exposure to this neurotoxin.

Blood harmane concentrations and dietary protein consumption in essential tremor

Beta-carboline alkaloids (e.g., harmane) are highly tremorogenic chemicals. Animal protein (meat) is the major dietary source of these alkaloids. The authors previously demonstrated that blood harmane concentrations were elevated in patients with essential tremor (ET) vs controls. Whether this difference is due to greater animal protein consumption by patients or their failure to metabolize harmane is unknown. The aim of this study was to determine whether patients with ET and controls differ with regard to 1) daily animal protein consumption and 2) the correlation between animal protein consumption and blood harmane concentration. Data on current diet were collected with a semiquantitative food frequency questionnaire and daily calories and consumption of animal protein and other food types was calculated. Blood harmane concentrations were log-transformed (logHA). The mean logHA was higher in 106 patients than 161 controls (0.61 +/- 0.67 vs 0.43 +/- 0.72 g(-10)/mL, p = 0.035). Patients and controls consumed similar amounts of animal protein (50.2 +/- 19.6 vs 49.4 +/- 19.1 g/day, p = 0.74) and other food types (animal fat, carbohydrates, vegetable fat) and had similar caloric intakes. In controls, logHA was correlated with daily consumption of animal protein (r = 0.24, p = 0.003); in patients, there was no such correlation (r = -0.003, p = 0.98). The similarity between patients and controls in daily animal protein consumption and the absence of the normal correlation between daily animal protein consumption and logHA in patients suggests that another factor (e.g., a metabolic defect) may be increasing blood harmane concentration in patients.