Intestinal microbiome in normal ageing, frailty and cognition decline

Influence of human gut microbiome on the healthy and the neurodegenerative aging

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

Underlying Mechanisms of the Protective Effects of Lifestyle Factors in the Prevention of Age-Related Diseases

The rise in life expectancy has significantly increased the occurrence of age-related chronic diseases, leading to escalating expenses for both society and individuals. Among the main factors influencing health and lifespan, lifestyle takes a forefront position. Specifically, nutrition, mental activity, and physical exercise influence the molecular and functional mechanisms that contribute to the prevention of major age-related diseases. Gaining deeper insights into the mechanisms that drive the positive effects of healthy lifestyles is valuable for creating interventions to prevent or postpone the development of chronic degenerative diseases. This review summarizes the main mechanisms that underlie the positive effect of lifestyle factors in counteracting the major age-related diseases involving brain health, musculoskeletal function, cancer, frailty, and cardiovascular diseases, among others. This knowledge will help to identify high-risk populations for targeted intervention trials and discover new biomarkers associated with healthy aging.

Vegetable Gardening and Health Outcomes in Older Cancer Survivors: A Randomized Clinical Trial

Importance

Cancer survivors experience accelerated functional decline that threatens independence and quality of life. Previous studies have suggested that vegetable gardening may improve diet, physical activity, and physical function in this vulnerable population, which comprises more than 5% of the US population.

Objective

To assess whether diet, physical activity and functioning, and other outcomes improved in older cancer survivors assigned to a vegetable gardening intervention compared with a waitlist.

Design, Setting, and Participants

From May 11, 2016, to May 2, 2022, a 2-arm, assessor-blinded, crossover-designed, intent-to-treat, randomized clinical trial was conducted at cancer survivors' homes across Alabama. Medicare-eligible survivors of cancers with 5-year survival of 60% or more were registry ascertained and screened for suboptimal vegetable and fruit consumption (<5 servings per day), physical activity (<150 moderate-to-vigorous minutes per week), and physical function (36-Item Short Form Health Survey [SF-36] subscale score ≤90). Consented participants underwent baseline assessments, were randomly assigned to intervention or waitlisted arms, and were reassessed at 1-year follow-up.

Intervention

One-year, home-based vegetable gardening intervention providing gardening supplies and mentorship by cooperative extension-certified master gardeners to plant and maintain spring, summer, and fall gardens. Waitlisted participants received the identical intervention after 12 months.

Main Outcomes and Measures

The main outcome was a composite index of improvements in self-reported vegetable and fruit consumption, physical activity, and physical function corroborated by plasma α-carotene levels, accelerometry, and physical performance assessments, respectively.

Results

Of 381 enrolled participants (mean [SD] age, 69.8 [6.4] years; range, 50-95 years; 263 [69.0%] female), 194 were assigned to the gardening intervention and 187 were waitlisted (attrition rates, 7.2% and 7.0%, respectively). Intent-to-treat analyses did not detect a significant improvement in the composite index of vegetable and fruit intake, moderate-vigorous physical activity, and physical function (intervention arm vs waitlisted arm, 4.5% vs 3.1%; P = .53) or between-arm differences in vegetable and fruit intake (mean difference, 0.3 [95% CI, -0.1 to 0.7] servings per day; P = .10). The intervention arm experienced a significant improvement in vegetable and fruit intake (mean increase, 0.3 [95% CI, 0.0-0.6] servings per day; P = .04). Significant improvements also were observed in the intervention arm vs waitlisted arm in physical performance (mean difference for 2-minute step test, 6.0 [95% CI, 0.8-11.2] steps; P = .03; for 30-second chair stand, 0.8 [95% CI, 0.1-1.5] repetitions; P = .02), perceived health (8.4 [95% CI, 3.0-13.9] points on a 100-point scale [higher scores indicate better health]; P = .003), and gut microbiome alpha diversity (84.1 [95% CI, 20.5-147.6] more observed species; P = .01). The COVID-19 pandemic significantly moderated effects (eg, odds of improvement in self-reported physical functioning were greater before vs during the pandemic: odds ratio, 2.17; 95% CI, 1.12-4.22; P = .02).

Conclusions and Relevance

In this randomized clinical trial including older cancer survivors, a vegetable gardening intervention did not significantly improve a composite index of diet, physical activity, and physical function; however, survivors assigned to the intervention had significantly increased vegetable and fruit consumption and, compared with waitlisted survivors, experienced significant improvements in perceived health and physical performance. Further study in broader populations and during pandemic-free periods is needed to determine definitive benefits.

Trial Registration

ClinicalTrials.gov Identifier: NCT02985411.

Brain-Periphery Interactions in Huntington's Disease: Mediators and Lifestyle Interventions

Prominent pathological features of Huntington's disease (HD) are aggregations of mutated Huntingtin protein (mHtt) in the brain and neurodegeneration, which causes characteristic motor (such as chorea and dystonia) and non-motor symptoms. However, the numerous systemic and peripheral deficits in HD have gained increasing attention recently, since those factors likely modulate disease progression, including brain pathology. While whole-body metabolic abnormalities and organ-specific pathologies in HD have been relatively well described, the potential mediators of compromised inter-organ communication in HD have been insufficiently characterized. Therefore, we applied an exploratory literature search to identify such mediators. Unsurprisingly, dysregulation of inflammatory factors, circulating mHtt, and many other messenger molecules (hormones, lipids, RNAs) were found that suggest impaired inter-organ communication, including of the gut-brain and muscle-brain axis. Based on these findings, we aimed to assess the risks and potentials of lifestyle interventions that are thought to improve communication across these axes: dietary strategies and exercise. We conclude that appropriate lifestyle interventions have great potential to reduce symptoms and potentially modify disease progression (possibly via improving inter-organ signaling) in HD. However, impaired systemic metabolism and peripheral symptoms warrant particular care in the design of dietary and exercise programs for people with HD.

The interaction between Mediterranean diet and intestinal microbiome: relevance for preventive strategies against frailty in older individuals

Age-related changes in intestinal microbiome composition and function are increasingly recognized as pivotal in the pathophysiology of aging and are associated with the aging phenotype. Diet is a major determinant of gut-microbiota composition throughout the entire lifespan, and several of the benefits of a healthy diet in aging could be mediated by the microbiome. Mediterranean diet (MD) is a traditional dietary pattern regarded as the healthy diet paradigm, and a large number of studies have demonstrated its benefits in promoting healthy aging. MD has also a positive modulatory effect on intestinal microbiome, favoring bacterial taxa involved in the synthesis of several bioactive compounds, such as short-chain fatty acids (SCFAs), that counteract inflammation, anabolic resistance, and tissue degeneration. Intervention studies conducted in older populations have suggested that the individual response of older subjects to MD, in terms of reduction of frailty scores and amelioration of cognitive function, is significantly mediated by the gut-microbiota composition and functionality. In this context, the pathophysiology of intestinal microbiome in aging should be considered when designing MD-based interventions tailored to the needs of geriatric patients.

A mediation analysis of the role of total free fatty acids on pertinence of gut microbiota composition and cognitive function in late life depression

BACKGROUND

Extensive evidence demonstrates correlations among gut microbiota, lipid metabolism and cognitive function. However, there is still a lack of researches in the field of late-life depression (LLD). This research targeted at investigating the relationship among gut microbiota, lipid metabolism indexes, such as total free fatty acids (FFAs), and cognitive functions in LLD.

METHODS

Twenty-nine LLD patients from the Cognitive Outcome Cohort Study of Depression in Elderly were included. Cognitive functions were estimated through the Chinese version of Montreal Cognitive Assessment (MoCA). Blood samples were collected to evaluate serum lipid metabolism parameters. Fecal samples were evaluated for gut microbiota determination via 16S rRNA sequencing. Spearman correlation, linear regression and mediation analysis were utilized to explore relationship among gut microbiota, lipid metabolism and cognitive function in LLD patients.

RESULTS

Spearman correlation analysis revealed significant correlations among Akkermansia abundance, total Free Fatty Acids (FFAs) and MoCA scores (P < 0.05). Multiple regression indicated Akkermansia and total FFAs significantly predicted MoCA scores (P < 0.05). Mediation analysis demonstrated that the correlation between decreased Akkermansia relative abundance and cognitive decline in LLD patients was partially mediated by total FFAs (Bootstrap 95%CI: 0.023-0.557), accounting for 43.0% of the relative effect.

CONCLUSION

These findings suggested a significant relationship between cognitive functions in LLD and Akkermansia, as well as total FFAs. Total FFAs partially mediated the relationship between Akkermansia and cognitive functions. These results contributed to understanding the gut microbial-host lipid metabolism axis in the cognitive function of LLD.

Melatonin, BAG-1 and cortisol circadian interactions in tumor pathogenesis and patterned immune responses

A dysregulated circadian rhythm is significantly associated with cancer risk, as is aging. Both aging and circadian dysregulation show suppressed pineal melatonin, which is indicated in many studies to be linked to cancer risk and progression. Another independently investigated aspect of the circadian rhythm is the cortisol awakening response (CAR), which is linked to stress-associated hypothalamus-pituitary-adrenal (HPA) axis activation. CAR and HPA axis activity are primarily mediated via activation of the glucocorticoid receptor (GR), which drives patterned gene expression via binding to the promotors of glucocorticoid response element (GRE)-expressing genes. Recent data shows that the GR can be prevented from nuclear translocation by the B cell lymphoma-2 (Bcl-2)-associated athanogene 1 (BAG-1), which translocates the GR to mitochondria, where it can have diverse effects. Melatonin also suppresses GR nuclear translocation by maintaining the GR in a complex with heat shock protein 90 (Hsp90). Melatonin, directly and/or epigenetically, can upregulate BAG-1, suggesting that the dramatic 10-fold decrease in pineal melatonin from adolescence to the ninth decade of life will attenuate the capacity of night-time melatonin to modulate the effects of the early morning CAR. The interactions of pineal melatonin/BAG-1/Hsp90 with the CAR are proposed to underpin how aging and circadian dysregulation are associated with cancer risk. This may be mediated via differential effects of melatonin/BAG-1/Hsp90/GR in different cells of microenvironments across the body, from which tumors emerge. This provides a model of cancer pathogenesis that better integrates previously disparate bodies of data, including how immune cells are regulated by cancer cells in the tumor microenvironment, at least partly via the cancer cell regulation of the tryptophan-melatonin pathway. This has a number of future research and treatment implications.

Bioactive compounds for human and planetary health

Bioactive compounds found in edible plants and foods are vital for human and planetary health, yet their significance remains underappreciated. These natural bioactives, as part of whole diets, ingredients, or supplements, can modulate multiple aspects of human health and wellness. Recent advancements in omic sciences and computational biology, combined with the development of Precision Nutrition, have contributed to the convergence of nutrition and medicine, as well as more efficient and affordable healthcare solutions that harness the power of food for prevention and therapy. Innovation in this field is crucial to feed a growing global population sustainably and healthily. This requires significant changes in our food system, spanning agriculture, production, distribution and consumption. As we are facing pressing planetary health challenges, investing in bioactive-based solutions is an opportunity to protect biodiversity and the health of our soils, waters, and the atmosphere, while also creating value for consumers, patients, communities, and stakeholders. Such research and innovation targets include alternative proteins, such as cellular agriculture and plant-derived protein; natural extracts that improve shelf-life as natural preservatives; upcycling of agricultural by-products to reduce food waste; and the development of natural alternatives to synthetic fertilizers and pesticides. Translational research and innovation in the field of natural bioactives are currently being developed at two levels, using a systems-oriented approach. First, at the biological level, the interplay between these compounds and the human host and microbiome is being elucidated through omics research, big data and artificial intelligence, to accelerate both discovery and validation. Second, at the ecosystem level, efforts are focused on producing diverse nutrient-rich, flavorful, and resilient, yet high-yield agricultural crops, and educating consumers to make informed choices that benefit both their health and the planet. Adopting a system-oriented perspective helps: unravel the intricate and dynamic relationships between bioactives, nutrition, and sustainability outcomes, harnessing the power of nature to promote human health and wellbeing; foster sustainable agriculture and protect the ecosystem. Interdisciplinary collaboration in this field is needed for a new era of research and development of practical food-based solutions for some of the most pressing challenges humanity and our planet are facing today.

Evaluation of Gut Microbiota in Healthy Persons and Type 1 Diabetes Mellitus Patients in North-Western Russia

Bacterial microbiota in stool may vary over a wide range, depending on age, nutrition, etc. The purpose of our work was to discriminate phyla and genera of intestinal bacteria and their biodiversity within a healthy population (North-Western Russia) compared to the patients with type 1 diabetes mellitus (T1DM). The study group included 183 healthy persons 2 to 53 years old (a mean of 26.5±1.0 years old), and 41 T1DM patients (mean age 18.2±1.8 years old). The disease onset was at 11±1.5 years, with a T1DM experience of 7±1.5 years. Total DNA was isolated from the stool samples, and sequencing libraries were prepared by amplifying the V3-V4 region of the 16S rRNA gene sequenced by Illumina MiSeq. Bioinformatic processing of NGS databases was adapted for microbiota evalutaion. Despite the broad scatter, the biological diversity for bacterial microbiota expressed as the Shannon index was significantly increased from younger to older ages in the comparison group, higher in adult healthy persons, with a trend for decrease in the Actinomycetota phylum which includes Bifidobacterium longum species. Similar but non-significant age trends were noted in the T1DM group. Concordant with the Bacillota prevalence in stool samples of diabetic patients, some anaerobic bacteria (Faecalibacteria, Lachnospira and Ruminococcae, Roseburia) were enriched in the T1DM microbiome against controls. Hence, correction of microbiota for Ruminococcus and Lachnospiraceae requires future search for new probiotics. Lower abundance of Actinomycetota and Bifidobacter in T1DM suggests potential usage of Bifidobacter-based probiotics in this cohort.

Potential neuroprotective effects of fermented foods and beverages in old age: a systematic review

Purpose

Numerous articles have recently studied the involvement of the gut microbiota in neurological diseases. Aging is associated with changes in the microbiome, which implies a reduction in microbial biodiversity among other changes. Considering that the consumption of a fermented-food diet improves intestinal permeability and barrier function, it seems of interest to study its participation in the prevention of neurodegenerative diseases. This article reviews existing studies to establish whether the consumption of fermented foods and fermented beverages prevents or ameliorates neurodegenerative decline in old age.

Methods

The protocol used was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Details of the protocol for this systematic review are registered on PROSPERO (CRD42021250921).

Results

Out of 465 articles identified in the Pubmed, Scopus, and Cochrane Library databases, a total of 29 that examined the relationship of the consumption of fermented products with cognitive impairment in old people were selected (22 cohort, 4 case-control, and 3 cross-sectional studies). The results suggest that low-to-moderate alcohol consumption and daily intake of coffee, soy products, and fermented-food diets in general are associated with a lower risk of dementia and Alzheimer's disease.

Conclusion

Daily consumption of fermented foods and beverages, either alone or as part of a diet, has neuroprotective effects and slows cognitive decline in old people.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=250921, identifier: CRD42021250921.

The possible role of gut microbiota dysbiosis in the pathophysiology of delirium in older persons

Delirium is a clinical syndrome characterized by an acute change in attention, awareness and cognition with fluctuating course, frequently observed in older patients during hospitalization for acute medical illness or after surgery. Its pathogenesis is multifactorial and still not completely understood, but there is general consensus on the fact that it results from the interaction between an underlying predisposition, such as neurodegenerative diseases, and an acute stressor acting as a trigger, such as infection or anesthesia. Alterations in brain insulin sensitivity and metabolic function, increased blood-brain barrier permeability, neurotransmitter imbalances, abnormal microglial activation and neuroinflammation have all been involved in the pathophysiology of delirium. Interestingly, all these mechanisms can be regulated by the gut microbiota, as demonstrated in experimental studies investigating the microbiota-gut-brain axis in dementia. Aging is also associated with profound changes in gut microbiota composition and functions, which can influence several aspects of disease pathophysiology in the host. This review provides an overview of the emerging evidence linking age-related gut microbiota dysbiosis with delirium, opening new perspectives for the microbiota as a possible target of interventions aimed at delirium prevention and treatment.

Dementia, infections and vaccines: 30 years of controversy

This paper reports the proceedings of a virtual meeting convened by the European Interdisciplinary Council on Ageing (EICA), to discuss the involvement of infectious disorders in the pathogenesis of dementia and neurological disorders leading to dementia. We recap how our view of the infectious etiology of dementia has changed over the last 30 years in light of emerging evidence, and we present evidence in support of the implication of infection in dementia, notably Alzheimer's disease (AD). The bacteria and viruses thought to be responsible for neuroinflammation and neurological damage are reviewed. We then review the genetic basis for neuroinflammation and dementia, highlighting the genes that are currently the focus of investigation as potential targets for therapy. Next, we describe the antimicrobial hypothesis of dementia, notably the intriguing possibility that amyloid beta may itself possess antimicrobial properties. We further describe the clinical relevance of the gut-brain axis in dementia, the mechanisms by which infection can move from the intestine to the brain, and recent findings regarding dysbiosis patterns in patients with AD. We review the involvement of specific pathogens in neurological disorders, i.e. SARS-CoV-2, human immunodeficiency virus (HIV), herpes simplex virus type 1 (HSV1), and influenza. Finally, we look at the role of vaccination to prevent dementia. In conclusion, there is a large body of evidence supporting the involvement of various infectious pathogens in the pathogenesis of dementia, but large-scale studies with long-term follow-up are needed to elucidate the role that infection may play, especially before subclinical or clinical disease is present.

Gut microbiota in relation to frailty and clinical outcomes

PURPOSE OF REVIEW

The gut microbiota is involved in several aspects of host health and disease, but its role is far from fully understood. This review aims to unveil the role of our microbial community in relation to frailty and clinical outcomes.

RECENT FINDINGS

Ageing, that is the continuous process of physiological changes that begin in early adulthood, is mainly driven by interactions between biotic and environmental factors, also involving the gut microbiota. Indeed, our gut microbial counterpart undergoes considerable compositional and functional changes across the lifespan, and ageing-related processes may be responsible for - and due to - its alterations during elderhood. In particular, a dysbiotic gut microbiota in the elderly population has been associated with the development and progression of several age-related disorders.

SUMMARY

Here, we first provide an overview of the lifespan trajectory of the gut microbiota in both health and disease. Then, we specifically focus on the relationship between gut microbiota and frailty syndrome, that is one of the major age-related burdens. Finally, examples of microbiome-based precision interventions, mainly dietary, prebiotic and probiotic ones, are discussed as tools to ameliorate the symptoms of frailty and its overlapping conditions (e.g. sarcopenia), with the ultimate goal of actually contributing to healthy ageing and hopefully promoting longevity.