An efficient method for fractionated whole rodent brain radiation.

OBJECTIVE: In order to test for mechanisms of whole brain radio therapy side effects and possible neuroprotective measures, a rodent model is desirable. In many models, a high single dose of 8-20 Gray (Gy) of whole brain irradiation is used. These experimental radiation protocols do not closely reflect the clinical situation, where the cumulative dosage is applied in smaller fractions. We describe an efficient method to perform repetitive, fractionated whole brain radio therapy to the rat brain. METHODS: Fifteen-week-old rats were irradiated with a dose of 5 or 10 Gy on four consecutive days, resulting in a cumulative dose in opposing fields of 20 Gy (n = 15) and 40 Gy (n = 17), respectively. Sham-irradiated rats (n = 14) received the same procedure but without application of cranial irradiation. Four collimators with a diameter of 3 cm each were used to place four rats and an ionization chamber simultaneously in the dose field for monitoring. RESULTS: Fourteen days after the procedure, irradiated animals showed decreased open-field activity (two-tailed t-test, sham versus 20 Gy, P<0.001; sham versus 40 Gy, P = 0.002), but no cognitive deficit as indicated by latencies in the Morris water maze test. Six weeks after the irradiation, no group showed alterations of histopathology such as vascular changes, demyelination, or white matter necrosis. DISCUSSION: The proposed model represents an efficient and safe method to perform fractioned high-dose irradiation of the rodent brain. Speculatively, it is possible to increase the cumulative dosage and dose per fraction used in this model to achieve a higher degree of radiation-induced toxicity.

Prolonged atrial fibrillation following generalized tonic-clonic seizures.

We describe two male patients with focal epilepsy in whom transitory episodes of atrial fibrillation (AF) lasting for up to 25h were detected in the context of generalized tonic-clonic seizures (GTCSs). In five of seven previously published cases of transitory AF associated with epileptic seizures, AF was also associated with GTCS, suggesting a pathophysiological link via GTCS-related increase in sympathetic tone and release of catecholamines. Importantly, AF increases the risk of thromboembolic cerebral ischemia, prompting the question of whether antithrombotic preventive treatment should be initiated in people with pharmacoresistant epilepsy and prolonged peri-ictal AF. Furthermore, AF can considerably impair cardiac output and may, via this mechanism, contribute to the risk of sudden unexpected death in epilepsy following GTCS.

Antiepileptic drugs and vitamin B6 plasma levels in adult patients.

Treatment with several antiepileptic drugs (AED) is associated with lower serum concentrations of folate or vitamin B12. This prospective monocenter study analyzed vitamin B6 blood levels in 400 serial patients with epilepsy, AED-treated (n=385), untreated (n=15) and healthy controls (n=233). The mean plasma vitamin B6 levels of the AED-treated (12.1±10.1; p=0.093) and the untreated patients (15.6±12.4; p=0.664) were not significantly different from the controls (13.9±15.2). These observations do not support the hypothesis that vitamin B6 blood levels are influenced by AED treatment.

A possible genetic link between MTHFR genotype and smoking behavior.

BACKGROUND: Hyperhomocysteinemia is an independent risk factor for stroke and other vascular events. The variant methylenetetrahydrofolate reductase (MTHFR) C677T is associated with elevated homocysteine levels, cardiovascular disease and stroke, which supports a causal relationship between hyperhomocysteinemia and vascular disease. However, MTHFR variants have also been reported to be associated with smoking behavior, which could be an important confounder. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed the MTHFR variants C677T and A1298C in two independent samples of 525 and 535 individuals, respectively. 21% of the non-smokers, but only 12% of the smokers were homozygous carriers of both MTHFR wildtype alleles, i.e. 677CC and 1298AA (Chi²â€Š= 15.8; p<0.001; binary regression). Plasma homocysteine levels were higher in smokers (13.9±4.1 µmol/L) than in non-smokers (12.6±4.0 µmol/L; F = 11.4; p = 0.001; ANOVA). Smoking MTHFR 677TT individuals had the highest plasma homocysteine levels (16.2±5.2 µmol/L), non-smoking 677CC individuals had the lowest (12.2±13.6 µmol/L). CONCLUSIONS/SIGNIFICANCE: In our study samples, MTHFR variants and smoking behaviour were associated with homocysteine plasma levels. In addition, the MTHFR variants were associated with smoking behaviour. Such an association may be a relevant confounder between MTHFR variants, homocysteine plasma levels and vascular diseases.

Haplotype analysis of the 5,10-methylenetetrahydrofolate reductase (MTHFR) c.1298A>C (E429A) polymorphism.

BACKGROUND: The polymorphism 5,10-methylenetetrahydrofolate reductase (MTHFR) c.1298A>C is associated with various diseases. 45 DNA samples homozygous for the A allele and 40 DNA probes homozygous for the C allele were taken from healthy German subjects of white Caucasian origin to analyze the haplotype of the two MTHFR c.1298A>C alleles. Samples were genotyped for the polymorphism MTHFR c.677C>T and for the silent polymorphisms MTHFR c.129C>T, IVS2 533 G>A, c.1068C>T and IVS10 262C>G. FINDINGS: Haplotype construction revealed that the C-allele of MTHFR c.1298A>C was more frequently observed in cis with c.129T, IVS2 533A, c.677C, c.1068T, and IVS10 262 G than expected from normal distribution. Estimation of the most recent common ancestor with the DMLE + 2.3 program resulted in an estimated age of approximately 36,660 years of the MTHFR c.1298C allele. CONCLUSION: Given that the era from 30,000 to 40,000 years ago is characterised by the spread of modern humans in Europe and that the prevalence of the MTHFR c.1298C allele is significantly higher in Central Europe in comparison to African populations, a selective advantage of MTHFR c.1298C could be assumed, e. g. by adaption to changes in the nutritional environment. The known founder ancestry of the T allele of MTHFR c.677C>T allele, together with the present data suggests that the MTHFR mutant alleles c.677T and 1298C arose from two independent ancestral alleles, that both confer a selective advantage.

Antiepileptic drugs interact with folate and vitamin B12 serum levels.

OBJECTIVE: Antiepileptic drugs (AEDs) are important for the treatment of epilepsy, psychiatric diseases, and pain syndromes. Small studies have suggested that AED treatment reduces serum levels of folate and vitamin B12. METHODS: This prospective monocenter study aimed at testing the hypothesis that AED treatment is associated with folate and vitamin B12 serum levels in a large population. A total of 2730 AED-treated and 170 untreated patients with epilepsy and 200 healthy individuals were enrolled. RESULTS: Treatment with carbamazepine, gabapentin, oxcarbazepine, phenytoin, primidone, or valproate was associated with lower mean serum folate levels or with a higher frequency of folate levels below the reference range in comparison with the entire group of patients, untreated patients, or controls. Treatment with phenobarbital, pregabalin, primidone, or topiramate was associated with lower vitamin B12 levels compared with the entire group of patients. Vitamin B12 serum levels were higher in patients treated with valproate compared with the entire group of patients, untreated patients, and healthy controls. Folate or vitamin B12 levels below the reference range were associated with higher mean corpuscular volume (MCV) and higher homocysteine plasma levels. Vitamin substitution for 3 months in 141 patients with folate or vitamin B12 levels below the reference range yielded normal vitamin levels in 95% of the supplemented patients and reduced MCV and homocysteine plasma levels. INTERPRETATION: Treatment with most of the commonly used AEDs is associated with reduced folate or vitamin B12 serum levels and is a risk factor for hyperhomocysteinemia. Oral substitution is effective to restore vitamin, MCV, and homocysteine levels.

The G allele of transcobalamin 2 c.776C→G is associated with an unfavorable lipoprotein profile.

BACKGROUND/AIM: Recent studies have suggested a relation of homocysteine with lipid metabolism. The aim of this study was to analyze a possible genetic basis for such a relation in 504 individuals including 135 consecutive Caucasian patients diagnosed with cerebrovascular disease as well as the patients' healthy spouses (n = 100) and offspring (n = 269). METHODS: We analyzed the association of plasma levels of lipoprotein(a), total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides with plasma homocysteine levels and with the following 7 variants of homocysteine metabolism: dihydrofolate reductase c.594 + 59del19bp, cystathionine ß-synthase c.844_855ins68, methionine synthase c.2756A→G, methylenetetrahydrofolate reductase c.677C→T and c.1298A→C, reduced folate carrier 1 c.80G→A, and transcobalamin 2 (Tc2) c.776C→G. RESULTS: Linear regression analysis showed an association of Tc2 c.776C→G with LDL (p = 0.010), HDL (p = 0.009), and TG (p = 0.007), with the G allele of Tc2 c.776C→G associated with an unfavorable blood lipid profile. Moreover, the G allele of Tc2 c.776C→G was associated with higher homocysteine plasma levels in the subgroup of patients (p = 0.013, 1-way ANOVA). CONCLUSION: These data support the hypothesis that alterations in homocysteine metabolism and an unfavorable blood lipoprotein profile may have a common genetic basis. Such conditions may be relevant for studies investigating independent risk factors for vascular disease.

Plasma folate levels are associated with the lipoprotein profile: a retrospective database analysis.

BACKGROUND: Several studies demonstrated an association of homocysteine plasma levels and the plasma lipoprotein profile. This cross-sectional pilot study aimed at analyzing whether blood levels of the two important cofactors of homocysteine metabolism, folate and vitamin B12, coincide with the lipoprotein profile. METHODS: In a retrospective single center approach, we analyzed the laboratory database (2003-2006) of the University Hospital Bonn, Germany, including 1743 individuals, in whom vitamin B12, folate and at least one lipoprotein parameter had been determined by linear multilogistic regression. RESULTS: Higher folate serum levels were associated with lower serum levels of low density lipoprotein cholesterol (LDL-C; Beta = -0.164; p < 0.001), higher levels of high density lipoprotein cholesterol (HDL-C; Beta = 0.094; p = 0.021 for trend) and a lower LDL-C-C/HDL-C-ratio (Beta = -0.210; p < 0.001). Using ANOVA, we additionally compared the individuals of the highest with those of the lowest quartile of folate. Individuals of the highest folate quartile had higher levels of HDL-C (1.42 +/- 0.44 mmol/l vs. 1.26 +/- 0.47 mmol/l; p = 0.005), lower levels of LDL-C (3.21 +/- 1.04 mmol/l vs. 3.67 +/- 1.10 mmol/l; p = 0.001) and a lower LDL-C/HDL-C- ratio (2.47 +/- 1.18 vs. 3.77 +/- 5.29; p = 0.002). Vitamin B12 was not associated with the lipoprotein profile. CONCLUSION: In our study sample, high folate levels were associated with a favorable lipoprotein profile. A reconfirmation of these results in a different study population with a well defined status of health, diet and medication is warranted.

Common genetic coagulation variants are not associated with ischemic stroke in a case-control study.

OBJECTIVE: Abnormalities in the coagulation pathway are often included in the diagnostic work-up of stroke patients, especially in young adults with cryptogenic stroke. METHODS: Three common genetic variants within the coagulation cascade were investigated in 500 control subjects and in 167 patients with ischemic stroke defined by TOAST subclassification. Analysed variants were factor V Leiden, prothrombin 20210G-->A and factor XIII Val34Leu. RESULTS: The factor V Leiden mutation was over-represented in patients with cardioembolic stroke for trend, whereas the prothrombin 20210G-->A variant and the factor XIII polymorphism Val34Leu were not associated with stroke of any subtype. The three polymorphisms showed no association with stroke in subgroups of patients defined by age (<40, 40-49, 50-59, > or =60 years). DISCUSSION: This study suggests that the analysis of prothrombin 20210G-->A and factor XIII Val34Leu is not a useful diagnostic procedure in the work-up of ischemic stroke.

The effect of MTHFR c.677C>T on plasma homocysteine levels depends on health, age and smoking.

PURPOSE: The role of homocysteine in the pathogenesis of arteriosclerosis and stroke is under debate. It is important to determine the interplay of factors that influence homocysteine plasma levels, such as age, gender, smoking and the genetic background. The T-allele of the common variant methylenetetrahydrofolate reductase (MTHFR) c.677C > T is the most prevalent known genetic cause of elevated plasma homocysteine levels, but the association of this allele with vascular disease has been controversial. The aim of the present study was to examine whether the influence of MTHFR c.677C > T on homocysteine levels depends on individual factors. METHODS: From an ongoing study on atherosclerosis, we analyzed 523 Caucasian individuals, including patients with cerebrovascular disease (n=141), their healthy spouses (n=106) and the offspring (n=276). ANOVA and regression analyses were employed to separately analyze the effect of MTHFR c.677C > T on homocysteine levels in patients, spouses and offspring as well as in subgroups defined by age, gender and smoking. RESULTS: MTHFR c.677C > T was associated with homocysteine plasma levels in the study sample (P < 0.001), but not in the patients with cerebrovascular disease, if analyzed separately. Analyses of subgroups divided by the age of 55 years revealed that the MTHFR c.677 C > T genotype was associated with homocysteine plasma levels in the younger (P < 0.001), but not in the older individuals. In addition, if individuals with at least less than ten cigarette package years were analyzed separately, MTHFR c.677C > T was associated with plasma homocysteine levels only in the group with the lower cigarette consumption (P=0.002). CONCLUSION: In our study, the association of the MTHFR c.677C > T genotype with plasma homocysteine levels was weakened by other factors that impact homocysteine levels. The effect of MTHFR c.677C > T on plasma homocysteine levels may, thus, be of major importance for healthy, young, non-smoking persons. Such specifications may explain the controversial results of epidemiological studies on the relevance of MTHFR c.677C > T.

fMRI of global visual perception in simultanagnosia.

The integration of visual elements into global perception seems to be implemented separately to single object perception. This assumption is supported by the existence of patients with simultanagnosia who can identify single objects but are incapable of integrating multiple visual items. We investigated a case of simultanagnosia due to posterior cortical atrophy without structural brain damage who demonstrated an incomplete simultanagnosia. The patient successfully recognized a global stimulus in one trial but failed to do so just a few seconds later. Using event-related fMRI, we contrasted post hoc selected trials of successful global perception with trials of global recognition failure. We found circumscribed clusters of activity at the right and left primary intermediate sulci and a bilateral cluster at the ventral precuneus. The integration of multiple visual elements resulting in a conscious perception of their gestalt seems to rely on these bilateral structures in the human lateral and medial inferior parietal cortex.

Association of genetic variants of methionine metabolism with methotrexate-induced CNS white matter changes in patients with primary CNS lymphoma.

Methotrexate (MTX) is an important anticancer drug and the most efficient chemotherapy component in primary CNS lymphoma (PCNSL). A typical side effect of intravenous high-dose MTX is the occurrence of confluent CNS white matter changes (WMC). Because MTX directly interferes with methionine metabolism, we analyzed the impact of genetic variants of methionine metabolism on the occurrence of WMC as a model of MTX toxicity. In a retrospective analysis of 68 PCNSL patients treated with MTX-based polychemotherapy with (n = 42) or without (n = 26) intraventricular treatment, 10 genetic variants influencing methionine metabolism were analyzed. Pearson's chi(2) test and multinominal regression analysis were used to define the relevance of these genetic variants for the occurrence of WMC. In this patient sample, the occurrence of WMC was significantly predicted by the TT genotype of methylenetetrahydrofolate reductase c.677C>T (chi(2) = 8.67; p = 0.013; df = 2), the AA genotype of methylenetetrahydrofolate reductase c.1298A>C (chi(2) = 13.5; p = 0.001; df = 2), and the GG genotype of transcobalamin 2 c.776C>G (chi(2) = 19.73; p < 0.001), in addition to male gender (chi(2) = 11.95; p = 0.001). These data strengthen the hypothesis that MTX effects are influenced by methionine metabolism, which may offer new strategies to improve MTX-based therapies.

Methionine metabolism in an animal model of sepsis.

BACKGROUND: Sepsis is a disease with high incidence and lethality and is accompanied by profound metabolic disturbances. In mammalian methionine metabolism, S-adenosylmethionine (SAM) is produced, which is important in the synthesis of neurotransmitters and glutathione and as an anti-inflammatory agent. The degradation product and antagonist of SAM is S-adenosylhomocysteine (SAH). In this study, we investigated changes in methionine metabolism in a rodent model of sepsis. METHODS: Sepsis was induced in male Wistar rats (n=21) by intraperitoneal injection of bacterial lipopolysaccharide (10 mg/kg). Controls (n=18) received vehicle only. Blood was collected by cardiac puncture 24 h later. Puncture of the suboccipital fossa was performed to collect cerebrospinal fluid (CSF). Methionine metabolites were measured using stable isotope dilution tandem mass spectrometry. Plasma total homocysteine and cysteine were measured by HPLC using fluorescence detection. Glutathione was assayed using a modified enzymatic microtiter plate assay. RESULTS: We observed significantly higher plasma levels of SAM (p<0.001) and SAM/SAH ratio (p=0.004) in septic animals. In CSF, there was also a trend for higher levels of SAM in septic animals (p=0.067). Oxidative stress was reflected by an increase in the ratio of oxidized/reduced glutathione in septic animals (p=0.001). CONCLUSIONS: Sepsis is associated with an increase in SAM/SAH ratio in plasma and CSF in rodents. This indicates an altered methylation potential during sepsis, which may be relevant for sepsis-associated impairment of transmethylation reactions, circulation and defense against oxidative stress. If verified in humans, such findings could lead to novel strategies for supportive treatment of sepsis, as methionine metabolism can easily be manipulated by dietary strategies.

Polymorphisms of homocysteine metabolism are associated with intracranial aneurysms.

BACKGROUND: Impaired homocysteine metabolism is associated with a number of vasculopathies including extracranial aneurysms. We analyzed the possible association of nine genetic variants of homocysteine metabolism with the occurrence of intracranial aneurysms. METHODS: Caucasian patients (n = 255) treated at two German hospitals for intracranial aneurysms and local controls (n = 348) were genotyped for the following polymorphisms: methionine synthase (MTR) c.2756A-->G, methylenetetrahydrofolate reductase (MTHFR) c.677C-->T, MTHFR c.1298A-->C, cystathionine beta-synthase (CBS) c.844_855ins68, CBS c.833T-->C, dihydrofolate reductase (DHFR) c.594 + 59del19bp, glutathione S-transferase Omega-1 (GSTO1) c.428C-->A, reduced folate carrier 1 (RFC1) c.80G-->A and transcobalamin 2 (Tc2) c.776C-->G. RESULTS: The G-allele of the missense polymorphism Tc2 c.777C-->G was found to be underrepresented in patients, suggesting that this variant may protect from the formation of cerebral aneurysms [odds ratio per two risk alleles (OR) 0.48; 95% confidence interval (CI) 0.30-0.77; p = 0.002]. We obtained borderline results for the G-allele of RFC1 c.80G-->A (OR 1.64; 95% CI 1.01-2.65; p = 0.051) and the insertion allele of DHFR c.594 + 59del19bp (OR 1.61; 95% CI 1.00-2.60; p = 0.059), which were found to be overrepresented in patients. CONCLUSION: Polymorphisms of homocysteine metabolism are possible risk factors for the formation of intracranial aneurysms.

The methylenetetrahydrofolate reductase (MTHFR) variant c.677C>T (A222V) influences overall survival of patients with glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults. Prognosis is poor. Using a series of 214 GBM patients, we observed an effect of the variant 5,10-methylenetetrahydrofolate reductase (MTHFR) c.677C>T on overall survival. This effect was strongest in patients younger than 60 years at diagnosis (overall survival, median +/- SE: genotype CC, 13 +/- 1 months; CT, 11 +/- 2 months; TT, 7 +/- 3 months; multivariate Cox regression analysis, Wald = 8.58, p = 0.007). In addition, the MTHFR genotype significantly influenced the overall survival of patients with a postoperative Karnofsky score >70 (CC, 12 +/- 2 months; CT, 11 +/- 1 months; TT, 10 +/- 4 months; Wald = 5.89, p = 0.015). These data suggest the MTHFR c.677C>T variant is a risk factor for survival in GBM patients.

Polymorphisms of methionine metabolism and susceptibility to meningioma formation: laboratory investigation.

OBJECT: Functionally relevant polymorphisms of methionine and folate metabolism have been shown to be associated with various human cancer entities including cerebral lymphoma and glioblastoma multiforme. The authors investigated the association of 7 functional polymorphisms of methionine metabolism with meningioma formation. METHODS: This case-controlled, monocenter association study included 290 patients of Caucasian origin undergoing surgical resection for intracranial meningioma (World Health Organization [WHO] Grade I, 190 cases; WHO Grade II, 82 cases; WHO Grade III, 18 cases) and 287 age- and sex-matched local controls. The authors analyzed the following genetic variants: dihydrofolate reductase c.594+59del19, 5,10-methylenetetrahydrofolate reductase c.677C > T and c.1298A > C, 5-methyltetrahydrofolate-homocysteine S-methyltransferase (MTR) c.2756A > G, reduced folate carrier 1 c.80G > A, cystathionine beta-synthase (CBS) c.844_855ins68 and transcobalamin 2 c.776C > G. RESULTS: The variant CBS c.844_855ins68 -- that is, the allele carrying the insertion ("ins" or "i") as opposed to the wild-type allele designated as deletion ("del" or "d") -- was significantly overrepresented in meningioma patients (dd/ id/ii: 0.81/0.18/0.01) in comparison with the controls (dd/id/ii: 0.88/0.12/0; 2 df, chi-square 8.97, p = 0.011; multiple nominal regression with age and sex as covariables). In addition, explorative analyses revealed an association of the MTR c.2756A > G variant with meningioma WHO Grade III (AA/AG/GG: patients, 1.0/0/0; controls, 0.64/0.32/0.04; 2 df, chi-square 14.44, p = 0.001). CONCLUSIONS: The results of this study suggest that genetic variants of methionine metabolism are associated with meningioma formation.

Global DNA methylation is influenced by smoking behaviour.

The level of epigenetic DNA methylation is an important factor in the pathogenesis of various human diseases. As smoking may influence DNA methylation, we investigated the effect of smoking habits on global DNA methylation in 298 genomic DNA samples (73 fathers, 69 mothers and 156 offspring). We did not find a direct effect of smoking on global DNA methylation. However, there was an association of the offspring's DNA methylation with paternal DNA methylation that was strongest if both had never smoked (R2corr=0.41, Beta=0.68, p=0.02) and completely vanished if the offspring smoked or had ever smoked. These findings suggest an association between smoking behaviour and global DNA methylation, which may be of importance for a wide range of diseases.

The methionine synthase polymorphism c.2756A>G alters susceptibility to glioblastoma multiforme.

Genetic polymorphisms of methionine metabolism, in particular methionine synthase (MTR) c.2756A>G (D919G) and methylenetetrahydrofolate reductase (MTHFR) c.677C>T (A222V), have been associated with various human cancers. We investigated MTR c.2756A>G, MTHFR c.677C>T, and a third polymorphism, transcobalamin 2 c.776C>G (P259R), for a potential association with the formation of glioblastoma multiforme. The MTR c.2756G allele was significantly underrepresented among 328 glioblastoma multiforme patients of Caucasian origin when compared with 400 population controls [patients AA/AG/GG: 0.72/0.26/0.02 and controls AA/AG/GG: 0.57/0.38/0.05, degrees of freedom = 2; chi(2) = 17.86 (Pearson); P < 0.001]. No association between glioblastoma multiforme and the two other polymorphisms was observed.

Homocysteine and carotid intima-media thickness in a german population: lack of clinical relevance.

BACKGROUND AND PURPOSE: Common carotid artery intima-media thickness (CCA IMT) is a predictor of stroke. This study aimed to analyze whether homocysteine (Hcys) metabolism influences CCA IMT. METHODS: We analyzed the association of personal, clinical, and biochemical data (multivariate analysis) and of 9 polymorphisms involved in Hcys metabolism (ANOVA) with CCA IMT in 714 individuals of 187 families. RESULTS: CCA IMT was significantly predicted by age, sex, creatinine levels, lipoprotein(a) levels, pack-years of smoking, the presence of hypertension, and the presence of diabetes mellitus but not by Hcys levels. Homozygosity for the T allele of the polymorphism methylenetetrahydrofolate reductase c.677C>T was significantly associated with higher Hcys levels but not with a higher CCA IMT. CONCLUSIONS: These data do not support the thesis that elevated Hcys levels are causally involved in cerebrovascular disease.