Darm, Muskeln, Gedächtnis: Was die neuen Studien zur Darm-Hirn-Achse wirklich zeigen

Obesity in older adults is a known risk factor for Alzheimer's disease and related dementias, potentially driven by metabolic dysfunction, inflammation and gut dysbiosis. The gut-brain axis, influenced by diet and the gut microbiome, is increasingly recognized as a contributor to neurodegeneration. In this sub-analysis of a 10-week randomized dietary education intervention (NCT06121986), we examined how obesity modulates gut microbiome, metabolome, and cognitive responses in 31 adults aged 55-85, with or without mild cognitive impairment. Participants received education on either a Mediterranean Diet or a Modified Mediterranean-Ketogenic Diet. Analyses were stratified by baseline obesity (BMI ≥30 kg/m²). Individuals with obesity exhibited lower microbial alpha-diversity, higher <i>Bacteroides</i>, and lower <i>Akkermansia</i> and <i>Christensenellaceae_R-7_group</i>, along with poorer memory and executive function. Only in the obese group did fat loss correlate with improvements in episodic memory and cognitive flexibility. In contrast, increased fat mass was associated with improved memory in non-obese participants. Gains in skeletal muscle mass predicted cognitive improvement in adults aged ≥73. Changes in gut (acetate, propionate, lactate) and plasma (acetate, pyruvate, citric acid) metabolites were linked to cognitive and body composition outcomes. These exploratory findings highlight the gut-muscle-brain axis as a modifiable target to enhance cognitive health in aging po

<b>Background</b>: The human gut microbiota plays a pivotal role in maintaining health throughout the lifespan, and age-related alterations in its composition and diversity have been implicated in numerous chronic and neurodegenerative conditions. However, the combined effects of aging, dementia, and shared living environments on gut microbial communities remain incompletely understood. <b>Methods</b>: This study included 56 older adults residing in a nursing home, of whom 29 had been diagnosed with dementia. Gut microbiota composition was characterized by 16S ribosomal RNA (rRNA) gene sequencing. Microbial diversity was assessed using alpha- and beta-diversity metrics, and differences in amplicon sequence variants (ASVs)/features were determined. Analyses adopted some covariates as potential confounders variables including age, sex, frailty status, drug use, and time spent in the nursing home. <b>Results</b>: Alpha diversity was significantly higher in older adults compared with younger, while beta-diversity analyses revealed distinct microbial community structures between age groups. In older individuals, <i>Bacteroidota</i> and <i>Proteobacteria</i> were the most abundant phyla, whereas <i>Firmicutes</i> and <i>Actinobacteriota</i> declined with advancing age. Notably, older adults exhibited an increased relative abundance of <i>Euryarchaeota</i>, a phylum encompassing <i>Archaea</i>, predominantly methanogens involved in anaerobic carbon dioxide reduction to methane. In s

The human gut microbiome and its relationship with both physiological and pathological functions have long intrigued researchers. One of the most fascinating and important areas within this domain is cognitive function. Given that a substantial number of studies, especially interventional ones, have been conducted on animal models, the findings of which are not fully generalizable to humans and may therefore be misinterpreted, the purpose of this study is to synthesize evidence from the most recent human research. Current evidence indicates that the gut microbiota is linked to cognitive function in both healthy and diseased states, with numerous studies suggesting a potential causal relationship between the two. Although the majority of these studies associate changes in cognitive function with differences in the composition of the gut microbiota, some findings also indicate an inverse relationship.

With rising life expectancy and global population aging, cognitive decline has become a major and growing public health challenge. Advances in nutritional neuroscience highlight the gut microbiota-immune-brain axis as a key biological pathway through which diet may influence cognitive function during aging. The gut microbiota, a metabolically active ecosystem, responds dynamically to habitual dietary patterns and produces bioactive metabolites capable of modulating immune signaling, neuroinflammation, and neuronal function. Diets rich in microbiota-modulating foods (e.g., dietary fiber, polyphenols, prebiotics, and probiotics) promote beneficial microbial communities. These communities support short-chain fatty acid production, maintain intestinal barrier integrity, and regulate systemic immune responses, processes increasingly associated with cognitive resilience in aging populations. In contrast, Western-style dietary patterns characterized by high intakes of saturated fats and refined sugars are linked to microbial dysbiosis, impaired gut barrier function, metabolic endotoxemia, and chronic low-grade inflammation, which may contribute to neuroinflammatory pathways involved in cognitive decline. This narrative review synthesizes evidence from observational studies, dietary intervention trials, and mechanistic animal models to examine how diet-driven alterations in gut microbiota composition and microbial metabolites interact with and modulate immune pathways to influence br

The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet has emerged as a promising dietary pattern associated with reduced Alzheimer's disease (AD) risk, supported by growing evidence that both diet and the gut microbiota are modifiable contributors to disease development and progression. Observational studies have linked higher MIND diet adherence to lower AD incidence and slower cognitive decline, with certain comparative analyses reporting stronger associations with cognitive outcomes than those observed for the parent Mediterranean or DASH diets. Developed specifically to support cognitive health, the MIND diet emphasizes leafy green vegetables, berries, and olive oil while restricting butter, cheese, fried foods, sweets, and red meat. While these features suggest a biologically plausible basis for neuroprotection, the underlying mechanisms remain incompletely defined. The microbiota-gut-brain axis offers a potential mechanistic framework, as diet is a major determinant of gut microbiota composition and microbiota-derived metabolites that may influence brain function and AD-related pathways. However, direct evidence characterizing MIND diet-specific effects on the gut microbiota remains limited, with most mechanistic insights derived from related dietary patterns or individual dietary components. Accordingly, this review synthesizes evidence from these related dietary patterns and key MIND components to propose a conceptual framework linking the MIND d