GABA and glutamate moderate beta-amyloid related functional connectivity in cognitively unimpaired old-aged adults

Background

Effects of beta-amyloid accumulation on neuronal function precede the clinical manifestation of Alzheimer's disease (AD) by years and affect distinct cognitive brain networks. As previous studies suggest a link between beta-amyloid and dysregulation of excitatory and inhibitory neurotransmitters, we aimed to investigate the impact of GABA and glutamate on beta-amyloid related functional connectivity.

Methods

29 cognitively unimpaired old-aged adults (age = 70.03 ± 5.77 years) were administered 11C-Pittsburgh Compound B (PiB) positron-emission tomography (PET), and MRI at 7 Tesla (7T) including blood oxygen level dependent (BOLD) functional MRI (fMRI) at rest for measuring static and dynamic functional connectivity. An advanced 7T MR spectroscopic imaging (MRSI) sequence based on the free induction decay acquisition localized by outer volume suppression’ (FIDLOVS) technology was used for gray matter specific measures of GABA and glutamate in the posterior cingulate and precuneus (PCP) region.

Results

GABA and glutamate MR-spectra indicated significantly higher levels in gray matter than in white matter. A global effect of beta-amyloid on functional connectivity in the frontal, occipital and inferior temporal lobes was observable. Interactive effects of beta-amyloid with gray matter GABA displayed positive PCP connectivity to the frontomedial regions, and the interaction of beta-amyloid with gray matter glutamate indicated positive PCP connectivity to frontal and cerebellar regions. Furthermore, decreased whole-brain but increased fronto-occipital and temporo-parietal dynamic connectivity was found, when GABA interacted with regional beta-amyloid deposits in the amygdala, frontal lobe, hippocampus, insula and striatum.

Conclusions

GABA, and less so glutamate, may moderate beta-amyloid related functional connectivity. Additional research is needed to better characterize their interaction and potential impact on AD.

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Combined ultra-high fieldstrength FIDLOVS MRSI at 7 Tesla with 11C-PIB PET.

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Assessment of gray matter specific levels of GABA and glutamate.

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Identification of interactive effects of GABA, glutamate and beta-Amyloid.

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GABA may moderate dysfunctional beta-Amyloid effects on pre-clinical brain pathology.

Size Matters! Differences in Nutritional Care between Small, Medium and Large Nursing Homes in Germany

OBJECTIVES

The aim of this study is to comprehensively describe nutritional care in German nursing homes (NHs) and to examine if nutritional care differs between small, medium and large NHs.

DESIGN

Nationwide cross-sectional postal survey.

SETTING

Nursing homes.

PARTICIPANTS

541 NHs across Germany.

MEASUREMENTS

Information on structural NH characteristics and nutritional care (food provision and menu planning, nursing care, and management and quality assurance) was collected by means of a questionnaire addressed to the management of a random sample of German NHs. NHs were grouped by size as small (≤ 50 beds), medium (50 - 100 beds) or large (> 100 beds) institutions. Frequencies were used to describe nutritional care, and Chi2-test to identify differences in nutritional care by NH size.

RESULTS

Aspects in the domain of food provision and menu planning regarding food variety and choice were widely implemented in German NHs (77 - 100 %). Best results were achieved in the domain of nursing care, where all aspects were implemented in at least 68 % of the NHs. Aspects regarding management and quality assurance, especially those concerning staffing, i.e. the availability of an interface manager (14 %), an interdisciplinary nutrition team (12 %) and a dietician (42 %), were only rarely implemented. Differences by NH size were found between small and medium or large NHs. On the one hand, small NHs stated more often to consider individual capabilities of the residents with texture-modified food (81 % vs. 60 %, p<0.05) and produce more often hot meals at ward level on a regular base (46 % vs. 32 %, p<0.05) than large NHs. On the other hand, several aspects regarding food provision and menu planning, and management and quality assurance were significantly more often implemented in larger than smaller NHs.

CONCLUSION

Whereas kitchen and nursing-related aspects of nutritional care seem to be widely implemented in German NHs, management and quality assurance demands are often not met. The differences found by NH size support the hypothesis that the number of residents living in a NH has an impact on how nutritional care is performed.

Association of anger-related traits with SNPs in the TPH gene

Since both aggression-related traits and serotonergic activity are partially heritable and correlate inversely, variations in genes of the serotonergic system might then, to some extent, account for variations in aggression-related behavior. Tryptophan hydroxylase (TPH) is the rate limiting biosynthetic enzyme in the serotonin pathway and regulates levels of serotonin. Recently, a genetic variation in TPH has been associated with aggression and anger-related traits in volunteers. We investigated a sample of community-based healthy volunteers (n = 154) and suicide attempters (n = 86), a clinical population with a high risk for elevated impulsive aggression and related traits. The subjects were genotyped for a A218C and a A779C single nucleotide polymorphism (SNP) located in the TPH gene. All subjects were administered standard psychiatric interviews as well as self-report questionnaires for aggression, irritability and anger-related traits. For anger-related traits, a multivariate effect of the tryptophan hydroxylase genotype and an interaction effect for genotype and diagnosis was observed in healthy volunteers and suicide attempters after controlling for age and educational level. U-carriers in both groups showed higher scores for State Anger, Trait Anger and Angry Temperament. These findings support the hypothesis that the A218C and the A779C SNP in the TPH gene may be associated with anger-related traits in German samples.

Association study of suicidal behavior and affective disorders with a genetic polymorphism in ABCG1, a positional candidate on chromosome 21q22.3

The gene that codes for the ABC transporter ABCG1 is located in a chromosomal susceptibility region (21q22.3) for affective disorders. Genetic variations in ABCG1 have been associated with affective disorders in Japanese males. In this study, we investigated the distribution of a G2457A polymorphism in patients with affective disorders, suicide attempters with various psychiatric diagnoses and healthy subjects. We initially found a trend towards a modest association with affective disorders in males (p = 0.046 for allele frequencies and p = 0.046 for AA versus GG). We conducted a replication study with independent patients and controls. There was no association with affective disorders, either in the replication or in the combined group. Furthermore, we found no association with suicidal behavior. These findings do not support the hypothesis that ABCG1 is a susceptibility gene for affective disorders or suicidal behavior.