S-adenosylmethionine is decreased in the cerebrospinal fluid of patients with Alzheimer's disease.

BACKGROUND: Increased plasma homocysteine levels have been described as an independent risk factor for Alzheimer's disease (AD), but the underlying pathophysiology is unclear. OBJECTIVE: This single-center, cross-sectional, correlational study analyzed homocysteine metabolism in 60 AD patients and 60 control subjects. METHODS: Fasting plasma levels of vitamin B12, folate and homocysteine as well as cerebrospinal fluid (CSF) levels of folate derivates, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and homocysteine were measured. In addition, the apolipoprotein E (APOE) genotype was determined. RESULTS: As expected, the APOE4 allele was significantly overrepresented in AD patients compared with controls (p < 0.001). Homocysteine plasma levels in the highest quartile were more frequent in the AD patients than in the controls (p = 0.008). In addition, AD patients had significantly lower CSF levels of the methyl group donor SAM (193 ± 31 vs. 207 ± 37 nmol/l; p = 0.032). Accordingly, the SAM/SAH ratio, which represents the methylation capacity, was significantly lower in the CSF of the AD patients (7.6 ± 2.4 vs. 9.1 ± 2.8; p = 0.003). Further, explorative analysis of all subjects showed that CSF SAM levels were lower in carriers of the APOE4 allele compared with noncarriers (189 ± 30 vs. 207 ± 36 nmol/l; p = 0.010). Of the individuals with CSF SAM levels in the lowest quartile, 63% carried the APOE4 allele compared with 17% of the individuals with CSF SAM levels in the highest quartile (Pearson: χ² = 9.9; p = 0.002; odds ratio 0.126, 95% confidence interval 0.32-0.49). CONCLUSION: These data suggest that AD is associated with lower CSF SAM levels and that this is at least partly due to an association of the APOE4 allele with reduced SAM levels in the CSF.

Influence of 5-HT3 receptor subunit genes HTR3A, HTR3B, HTR3C, HTR3D and HTR3E on treatment response to antipsychotics in schizophrenia.

OBJECTIVES: Among serotonin (5-HT) receptors, the 5-HT3 receptor is the only ligand-gated ion channel. 5-HT3 antagonists such as ondansetron and tropisetron may improve auditory gating and neurocognitive deficits in schizophrenic patients. Moreover, many antipsychotic drugs are antagonists at 5-HT3 receptors. However, the role of 5-HT3 receptor variants on response to antipsychotic drugs in schizophrenic patients is still unclear. METHODS: In a prospective, randomized, double-blind study, we have assessed six functional and coding variants of the subunit genes HTR3A, HTR3B as well as the novel HTR3C, HTR3D, and HTR3E subunits in the response to haloperidol or risperidone. Seventy patients were treated for 4 weeks and positive symptoms, negative symptoms, and general psychopathology were measured by the Positive and Negative Syndrome Scale (PANSS). RESULTS: HTR3E had an effect on the speed of response to antipsychotics. GG-allele carriers responded more quickly to treatment on the PANSS negative symptom subscale (P = 0.03) and on the total PANSS score (P = 0.04) irrespective of medication. In a second independent study of 144 schizophrenia patients treated with atypical antipsychotics, this effect could not be confirmed. CONCLUSION: Our findings argue against a major effect of HTR3 variants in response to antipsychotics. Solely, the HTR3E and also the HTR3A variant could exert a weak effect on the speed of response to antipsychotics.

Homocysteine metabolism and cerebrospinal fluid markers for Alzheimer's disease.

Disturbed homocysteine metabolism is a risk factor for Alzheimer's disease (AD) and may contribute to the disease pathophysiology by increasing both amyloid-beta (Abeta) production and phosphorylated tau (P-tau) accumulation. Here, we evaluated the relationship between the cerebrospinal fluid (CSF) concentrations of homocysteine (Hcys), S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and 5-methyltetrahydrofolate (5-MTHF), and the markers for AD pathology, Abeta(1-42) and P-tau181, in 98 cognitively healthy subjects aged 16-81 years and 54 AD patients. In multivariate regression tests including age, gender, creatinine, and presence of the apolipoprotein E epsilon4 allele, P-tau181 was associated with SAH (beta = 0.490; p < 0.001), 5-MTHF (beta = -0.273; p = 0.010) levels, and SAM/SAH ratio (beta = -0.319; p = 0.013) in controls, and with SAH (beta = 0.529; p = 0.001) in AD patients. The levels of Abeta(1-42) were not associated with the CSF concentrations of Hcys, SAM, SAH, or 5-MTHF neither in the AD nor in the control group. The results suggest that alteration of the homocysteine metabolism is related to increased accumulation of phosphorylated tau and may contribute to the neurofibrillary pathology in normal aging and in AD.

Functional serotonin 1A receptor variant influences treatment response to atypical antipsychotics in schizophrenia.

The serotonin (5-HT) 1A receptor has been found to be dysregulated in prefrontal cortex and other brain regions in schizophrenia, and 5-HT1A receptor levels in the amygdala have been related to negative schizophrenia symptoms. We have assessed the impact of the functional C-1019G variant of the 5-HT1A receptor on the response to risperidone or haloperidol in a prospective, randomized, double-blind study. Patients were treated for 4 weeks and negative symptoms assessed weekly. The variant influenced the response to risperidone: improvement of negative symptoms by 4.38 points for carriers of the C allele, compared with the GG genotype (1.22 points, P=0.046). In a second independent study of 130 schizophrenia patients treated with atypical antipsychotics, this effect was confirmed (P=0.003). The functional variant of the 5-HT1A receptor thus influences the response of schizophrenia patients to atypical antipsychotics and may be useful in the future to predict the pharmacogenetics of negative symptoms.

CSF cortisol in Alzheimer's disease and mild cognitive impairment.

Hypercortisolaemia occurs in Alzheimer's disease (AD) and may be involved in the AD related neurodegenerative process. In order to determine whether brain structures are exposed to high cortisol concentrations early in AD, we measured cerebrospinal fluid (CSF) cortisol in 66 subjects with AD, 33 subjects with mild cognitive impairment (MCI) and 34 control subjects. CSF cortisol concentrations were higher in AD subjects compared to controls (p<0.001) and to MCI subjects (p=0.002). There was no significant increase of cortisol in MCI subjects compared with controls suggesting that the increase of CSF cortisol is not an early event in the course of AD.

Patterns of subjective memory impairment in the elderly: association with memory performance.

BACKGROUND: The association of subjective memory impairment (SMI) with cognitive performance in healthy elderly subjects is poor because of confounds such as depression. However, SMI is also a predictor for future dementia. Thus, there is a need to identify subtypes of SMI that are particularly related to inferior memory performance and may represent at-risk stages for cognitive decline. METHOD: A total of 2389 unimpaired subjects were recruited from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), as part of the German Competence Network on Dementia. Clusters of SMI according to patterns of response to SMI questions were identified. Gender, age, depressive symptoms, apolipoprotein E (apoE) genotype, delayed recall and verbal fluency were included in a Classification and Regression Tree (CART) analysis to identify discriminators between the clusters. RESULTS: We identified three clusters. Cluster 1 contained subjects without memory complaints. Cluster 2 contained subjects with general memory complaints, but mainly without memory complaints on individual tasks of daily living. Cluster 3 contained subjects with general memory complaints and complaints on individual tasks of daily living. Depressive symptoms, as the first-level discriminator, distinguished between clusters 1 and 2 versus cluster 3. In subjects with only a few depressive symptoms, delayed recall discriminated between cluster 1 versus clusters 2 and 3. CONCLUSIONS: In SMI subjects with only a minor number of depressive symptoms, memory complaints are associated with delayed recall. As delayed recall is a sensitive predictor for future cognitive decline, SMI may be the first manifestation of future dementia in elderly subjects without depression.