Das Darmmikrobiom bei der Parkinson-Krankheit

Gastrointestinal involvement in Parkinson's disease: pathophysiology, diagnosis, and management

Growing evidence suggests an increasing significance for the extent of gastrointestinal tract (GIT) dysfunction in Parkinson's disease (PD). Most patients suffer from GIT symptoms, including dysphagia, sialorrhea, bloating, nausea, vomiting, gastroparesis, and constipation during the disease course. The underlying pathomechanisms of this α-synucleinopathy play an important role in disease development and progression, i.e., early accumulation of Lewy pathology in the enteric and central nervous systems is implicated in pharyngeal discoordination, esophageal and gastric motility/peristalsis impairment, chronic pain, altered intestinal permeability and autonomic dysfunction of the colon, with subsequent constipation. Severe complications, including malnutrition, dehydration, insufficient drug effects, aspiration pneumonia, intestinal obstruction, and megacolon, frequently result in hospitalization. Sophisticated diagnostic tools are now available that permit more detailed examination of specific GIT impairment patterns. Furthermore, novel treatment approaches have been evaluated, although high-level evidence trials are often missing. Finally, the burgeoning literature devoted to the GIT microbiome reveals its importance for neurologists. We review current knowledge about GIT pathoanatomy, pathophysiology, diagnosis, and treatment in PD and provide recommendations for management in daily practice.

'GutFeel': an in silico method for predicting gut health status based on the metabolic functional capabilities of the resident microbiome

Dysbiosis or imbalance in the gut microbiome has been correlated with the etiology of a number of diseases/disorders. Thus, gut microbial communities can potentially be utilized for assessing the health of the human gut. Although the taxonomic composition of the microbiomes is dependent on factors such as diet, lifestyle, and geography, these microbes perform a specific set of common functions in the gut. In this study, metabolic pathway-based markers (agnostic to above-mentioned factors) specific to commensals and those specific to pathogens are utilized as indicators of gut health. Furthermore, this gut health assessment requires only a small set of features rather than complete sequencing of metagenomes. The proposed scheme can also be used to design personalized biotherapeutics, depending on functional aspects observed in an individual.

Fucoxanthin has potential for therapeutic efficacy in neurodegenerative disorders by acting on multiple targets

Fucoxanthin, one of the most abundant carotenoids from edible brown seaweeds, for years has been used as a bioactive dietary supplement and functional food ingredient. Recently, fucoxanthin was reported to penetrate the blood-brain barrier, and was superior to other carotenoids to exert anti-neurodegenerative disorder effects via acting on multiple targets, including amyloid protein aggregation, oxidative stress, neuroinflammation, neuronal loss, neurotransmission dysregulation and gut microbiota disorder. However, the concentration of fucoxanthin required for in vivo neuroprotective effects is somewhat high, and the poor bioavailability of this molecule might prevent its clinical use. As such, new strategies have been introduced to overcome these obstacles, and may help to develop fucoxanthin as a novel lead for neurodegenerative disorders. Moreover, it has been shown that some metabolites of fucoxanthin may produce potent in vivo neuroprotective effects. Altogether, these studies suggest the possibility for future development of fucoxanthin as a one-compound-multiple-target or pro-drug type pharmaceutical or nutraceutical treatment for neurodegenerative disorders.Trial registration: ClinicalTrials.gov identifier: NCT03625284.Trial registration: ClinicalTrials.gov identifier: NCT02875392.Trial registration: ClinicalTrials.gov identifier: NCT03613740.Trial registration: ClinicalTrials.gov identifier: NCT04761406.

Much ado about nothing? Off-target amplification can lead to false-positive bacterial brain microbiome detection in healthy and Parkinson's disease individuals

BACKGROUND

Recent studies suggested the existence of (poly-)microbial infections in human brains. These have been described either as putative pathogens linked to the neuro-inflammatory changes seen in Parkinson's disease (PD) and Alzheimer's disease (AD) or as a "brain microbiome" in the context of healthy patients' brain samples.

METHODS

Using 16S rRNA gene sequencing, we tested the hypothesis that there is a bacterial brain microbiome. We evaluated brain samples from healthy human subjects and individuals suffering from PD (olfactory bulb and pre-frontal cortex), as well as murine brains. In line with state-of-the-art recommendations, we included several negative and positive controls in our analysis and estimated total bacterial biomass by 16S rRNA gene qPCR.

RESULTS

Amplicon sequencing did detect bacterial signals in both human and murine samples, but estimated bacterial biomass was extremely low in all samples. Stringent reanalyses implied bacterial signals being explained by a combination of exogenous DNA contamination (54.8%) and false positive amplification of host DNA (34.2%, off-target amplicons). Several seemingly brain-enriched microbes in our dataset turned out to be false-positive signals upon closer examination. We identified off-target amplification as a major confounding factor in low-bacterial/high-host-DNA scenarios. These amplified human or mouse DNA sequences were clustered and falsely assigned to bacterial taxa in the majority of tested amplicon sequencing pipelines. Off-target amplicons seemed to be related to the tissue's sterility and could also be found in independent brain 16S rRNA gene sequences.

CONCLUSIONS

Taxonomic signals obtained from (extremely) low biomass samples by 16S rRNA gene sequencing must be scrutinized closely to exclude the possibility of off-target amplifications, amplicons that can only appear enriched in biological samples, but are sometimes assigned to bacterial taxa. Sequences must be explicitly matched against any possible background genomes present in large quantities (i.e., the host genome). Using close scrutiny in our approach, we find no evidence supporting the hypothetical presence of either a brain microbiome or a bacterial infection in PD brains. Video abstract.

Self-reported sleep quality is associated with gut microbiome composition in young, healthy individuals: a pilot study

OBJECTIVES

The microbiota-gut-brain axis is an intricate communication network that is emerging as a key modulator of psychological and physiological wellbeing. Recent pioneering work in the field has suggested a possible link between gut microbiome composition with sleep, an evolutionarily conserved behavior demonstrated to play a critical role in health. This study is the first to address relationships between self-reported sleep habits and gut microbiome composition in young, healthy individuals.

METHODS

A total of 28 young, healthy subjects (17 males/11 females; 29.8 ± 10.4 years) that were free of metabolic or cardiovascular disease, and that did not take sleep medication or antibiotics within the past six months were included in the study. Relationships between self-reported sleep quality, obtained using the Pittsburgh Sleep Quality Index (PSQI), with microbial diversity (Shannon Index), the Firmicutes/Bacteroidetes (F/B) ratio, and select bacterial taxa were assessed.

RESULTS

Alpha diversity (r = -0.50) and F/B ratio (r = -0.47) were inversely associated (P < 0.05) with the PSQI score. Ten bacterial taxa were associated (P < 0.05) with the PSQI score, including genus-level Blautia (r = -0.57), Ruminococcus (r = -0.39), and Prevotella (r = 0.39).

CONCLUSIONS

In young healthy individuals, self-reported sleep quality was positively associated with microbial diversity. We also observed a positive association between sleep quality with F/B ratio, seemingly due to a greater relative abundance of Blautia and Ruminococcus (Firmicutes) and lower proportions of Prevotella (Bacteroidetes) in individuals reporting superior sleep quality. Future studies are encouraged to evaluate mechanistic links between the gut microbiome with sleep, as well as the health implications of this relationship.

Tryptophan Metabolism by Gut Microbiome and Gut-Brain-Axis: An in silico Analysis

The link between gut microbiome and brain is being slowly acknowledged due to the speculated role of resident gut microbial community in altering the functions of gut-brain axis (GBA). Recently, a number of microbial metabolites (referred to as neuro-active metabolites) produced through tryptophan metabolism have been suggested to influence the GBA. In view of this, the current study focuses on microbial tryptophan metabolism pathways which produce neuro-active metabolites. An in silico analysis was performed on bacterial genomes as well as publicly available gut microbiome data. The results provide a comprehensive catalog of the analyzed pathways across bacteria. The analysis indicates an enrichment of tryptophan metabolism pathways in five gut-associated phyla, namely, Actinobacteria, Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria. Further, five genera, namely, Clostridium, Burkholderia, Streptomyces, Pseudomonas, and Bacillus have been predicted to be enriched in terms of number of the analyzed tryptophan metabolism pathways, suggesting a higher potential of these bacterial groups to metabolize tryptophan in gut. Analysis of available microbiome data corresponding to gut samples from patients of neurological diseases and healthy individuals suggests probable association of different sets of tryptophan metabolizing bacterial pathways with the etiology of different diseases. The insights obtained from the present study are expected to provide directions toward designing of microbiome based diagnostic and therapeutic approaches for neurological diseases/disorders.