Comparing the gut microbiome of obese, African American, older adults with and without mild cognitive impairment

Cerebrovascular Pathology and Cognitive Outcomes in Older Black Decedents

BACKGROUND

Few neuropathologic studies focus on the associations of cerebrovascular pathologies with cognition in older Black adults.

METHODS

We conducted a nested substudy of participants who were enrolled in 1 of 4 harmonized longitudinal cohort studies-the Minority Aging Research Study, African American Clinical Core, Rush Memory and Aging Project, and Religious Order Study before coming to autopsy. Neuropathologic evaluation included assessment of cerebrovascular and neurodegenerative pathologies. We first documented single and mixed cerebrovascular profiles and neurodegenerative pathologies in 112 Black decedents and examined the pathological burden with cognitive function proximate to death. In secondary analyses, we matched 2:1 the 112 Black decedents to 214 White decedents from the same cohorts using Mahalanobis distance matching and conducted linear regression models to examine racial differences in the burden of each vascular pathology and their associations with cognition.

RESULTS

In older Black decedents, macroscopic infarcts were present in 37%, microinfarcts in 30%, basal ganglia arteriolosclerosis in 20%, cerebral amyloid angiopathy in 32%, and atherosclerosis in 14%. Single cerebrovascular profiles were present in 29% and mixed cerebrovascular profiles in 40%. Microinfarcts (estimate=-0.51, SE=0.23, P=0.03) and arteriolosclerosis in the basal ganglia (estimate =-0.29, SE=0.13, P=0.03) were associated with lower global cognition independent of neurodegenerative pathologies. Further, microinfarcts were associated with lower episodic and semantic memory, and perceptual speed, whereas arteriolosclerosis was associated with only semantic memory. Mixed vascular profiles were also associated with lower episodic memory and perceptual speed. In secondary analyses, the burden of cerebrovascular pathologies and cognitive associations were similar across races.

CONCLUSIONS

Cerebrovascular pathologies are common in older Black decedents, most often as a mixed cerebrovascular pathology profile. Arteriosclerosis and microinfarcts were associated with lower cognition above and beyond the presence of neurodegenerative pathologies. Burden and cognitive associations with cerebrovascular pathologies were similar across races.

Discovery of the microbiota-gut-brain axis mechanisms of acupuncture for amnestic mild cognitive impairment based on multi-omics analyses: A pilot study

OBJECTIVES

Acupuncture is a promising therapy for amnestic mild cognitive impairment (aMCI). Growing evidence suggest that alterations in the microbiota-gut-brain (MGB) axis contribute to the development and progression of aMCI. However, little is known about whether and how acupuncture change the MGB axis of aMCI individuals.

METHODS

This was a randomized, controlled, clinical trial. Forty patients with aMCI were randomly allocated to either the acupuncture group or the waitlist group. The primary outcome was the change in the Alzheimer's Disease Assessment Scale-Cognitive Scale (ADAS-Cog) score. In addition, multi-omics was performed to detect changes in brain function, gut microbiota, and serum metabolites. Generalized estimating equations were used to estimate the outcomes, and correlational analyses were performed to explore the relationships between the clinical and multi-omics data.

RESULTS

Compared to a mean baseline to week 12 change of -3.94 in the acupuncture group, the mean change in the waitlist group was 1.72 (net difference, -5.66 [95 % CI, -6.98 to -4.35]). Compared to the waitlist group, acupuncture's MGB axis modulatory effect exhibited altered the regional homogeneity values of Frontal_Med_Orb_L, Cingulum_Mid_L, and Frontal_Sup_Medial_L, relative abundance of gut Ruminococcus_sp_AF43_11 and s_Eubacterium_coprostanoligenes, and levels of serum (11E,15Z)-9,10,13-trihydroxyoctadeca-11,15-dienoic acid, dipropylene glycol dimethyl ether, N6-Me-dA, and DPK, which correlated with changes in ADAS-Cog scores.

CONCLUSIONS

Our data imply that acupuncture ameliorates overall cognitive function, along with changes in brain activity, gut microbiota, and serum metabolites, providing preliminary evidence of the mechanisms acting through the MGB axis underlying the effects of acupuncture on aMCI.

Black raspberry supplementation on overweight and Helicobacter pylori infected mild dementia patients a pilot study

Alzheimer's disease (AD) is the most common form of dementia. H. pylori infection and overweight have been implicated in AD via the gut-brain axis (GBA). This study aimed to determine whether supplementation of BRBs has a meaningful effect on H. pylori infection, overweight, and AD development in a clinical trial setting. We conducted a randomized placebo-controlled clinical trial in patients with mild clinical dementia who also had H. pylori infection and were overweight. The study was conducted over 10 weeks, consisting of an 8-week intervention period (25 g powder of black raspberries, BRBs, or placebo twice daily, morning and evening) and a 2-week follow-up. The primary outcomes were changes in Clinical Dementia Rating (CDR), Urea Breath Test (UBT), and Body Mass Index (BMI). Consumption of BRBs improved cognitive functions (p < 0.00001), compared to the placebo group (p > 0.05). Besides, BRBs ingestion decreased H. pylori infection and BMI (p < 0.00001 and p < 0.05 respectively) while the placebo group stayed statistically the same (p = 0.98 and p = 0.25 respectively). BRBs significantly decreased inflammatory markers, improved oxidative index, and adiponectin (p < 0.05) compared to the placebo group, while adenosine monophosphate-activated protein kinase (AMPK) and leptin did not significantly change. BRBs modulated the abundance of several fecal probiotics, particularly, Akkermansia muciniphila. Our results provided that BRBs suppressed H. pylori infection, decreased BMI, and rebalanced the gut microbiome, which could improve cognitive functions in mild dementia patients. Longer and larger randomized clinical trials of BRB interventions targeting H. pylori infection, overweight, or mild dementia are warranted to confirm the results from this pilot trial. Trial Registration: ClinicalTrials.gov identifier: NCT05680532.

The Role of the Intestinal Flora and Its Derivatives in Neurocognitive Disorders: A Narrative Review from Surgical Perspective

Perioperative neurocognitive dysfunction is a significant concern for population health, impacting postoperative recovery and increasing the financial burden on patients. With an increasing number of surgical procedures being performed, the prevention and management of perioperative neurocognitive dysfunction have garnered significant attention. While factors such as age, lifestyle, genetics, and education are known to influence the development of cognitive dysfunction, recent research has highlighted the role of the gut microbiota in neurological health. An increased abundance of pro-inflammatory gut microbiota can trigger and worsen neuroinflammation, neuronal cell damage, and impaired cellular autophagy. Moreover, the inflammation-promoting gut microbiota can disrupt immune function, impair neuroautophagy, and affect the production and circulation of extracellular vesicles and neurotransmitters. These factors collectively play a role in the onset and advancement of cognitive impairment. This narrative review delves into the molecular mechanisms through which gut microbiota and their derivatives contribute to cognitive impairment, focusing on the impact of anesthesia surgery, changes in gut microbial populations, and perioperative cognitive impairment associations. The study suggests that alterations in the abundance of various bacterial species and their metabolites pre- and post-surgery may be linked to postoperative cognitive impairment. Furthermore, the potential of probiotics or prebiotics in addressing cognitive impairment is discussed, offering a promising avenue for investigating the treatment of perioperative neurocognitive disorders.

Maternal Gut Microbiome-Mediated Epigenetic Modifications in Cognitive Development and Impairments: A New Frontier for Therapeutic Innovation

Cognitive impairment in various mental illnesses, particularly neuropsychiatric disorders, has adverse functional and clinical consequences. While genetic mutations and epigenetic dysregulations of several genes during embryonic and adult periods are linked to cognitive impairment in mental disorders, the composition and diversity of resident bacteria in the gastrointestinal tract-shaped by environmental factors-also influence the brain epigenome, affecting behavior and cognitive functions. Accordingly, many recent studies have provided evidence that human gut microbiota may offer a potential avenue for improving cognitive deficits. In this review, we provide an overview of the relationship between cognitive impairment, alterations in the gut microbiome, and epigenetic alterations during embryonic and adult periods. We examine how various factors beyond genetics-such as lifestyle, age, and maternal diet-impact the composition, diversity, and epigenetic functionality of the gut microbiome, consequently influencing cognitive performance. Additionally, we explore the potential of maternal gut microbiome signatures and epigenetic biomarkers for predicting cognitive impairment risk in older adults. This article also explores the potential roles of nutritional deficiencies in programming cognitive disorders during the perinatal period in offspring, as well as the promise of gut microbiome-targeted therapeutics with epigenetic effects to prevent or alleviate cognitive dysfunctions in infants, middle-aged adults, and older adults. Unsolved challenges of gut microbiome-targeted therapeutics in mitigating cognitive dysfunctions for translation into clinical practice are discussed, lastly.

Exerkine irisin mitigates cognitive impairment by suppressing gut-brain axis-mediated inflammation

INTRODUCTION

Exercise has been recognized to improve cognitive performance by optimizing gut flora and up-regulating exerkine irisin.

OBJECTIVE

Although exercise-induced irisin is beneficial to cognitive improvement, whether this benefit is achieved by optimizing gut microbiota and metabolites is not fully explored.

METHODS

After aerobic exercise and exogenous irisin interventions for 12 weeks, the 16S rRNA and metabolites in feces of 21-month-old mice were analyzed. Meanwhile, the differential miRNAs and mRNAs in hippocampal tissues were screened by high-throughput sequencing. Relevant mRNAs and proteins were evaluated by RT-PCR, Western blot, and immunofluorescence.

RESULTS

Compared with the young control mice, irisin levels and cognitive capacity of aged mice revealed a significant reduction, while aerobic exercise and intraperitoneal injection of exogenous irisin reversed aging-induced cognitive impairment. Similarly, 147 up-regulated and 173 down-regulated metabolites were detected in aged mice, while 64 and 45 up-regulated and 225 and 187 down-regulated metabolites were detected in aged mice with exercise and irisin interventions, respectively. Moreover, during hippocampal miRNA and mRNA sequencing analysis, 9 differential gut flora and 35 differential genes were identified to be correlated with the inflammatory signaling mediated by the TLR4/MyD88 signal pathway.

CONCLUSION

Aging-induced cognitive impairment is due to insulin resistance induced by TLR4/MyD88 signaling activation in hippocampal tissues mediated by gut microbiota and metabolite changes. Myokine irisin may be an important mediator in optimizing gut microbiota and metabolism for an improved understanding of mitigated aging process upon exercise interventions.

Environmental, Metabolic, and Nutritional Factors Concerning Dementia in African American and Hispanic American Populations

African Americans and Hispanic Americans experience a higher incidence and prevalence of dementia than white Americans while also experiencing more environmental, metabolic, and nutritional factors potentially promoting such disparities. Greater exposure to air, water, and soil pollutants, including toxic metals associated with neurodegeneration, accrues in both minorities, as does worse dental care than Whites exposing them to periodontitis, raising dementia risk. Hispanic Americans experience greater occupational exposure to herbicides and pesticides, and have a higher rate of developing non-alcoholic fatty liver disease (NAFLD), predisposing to dementia. African Americans have a greater likelihood of both vitamin D deficiency and magnesium deficiency, increasing neuroinflammation and dementia risk. Both have greater air pollution exposure, a known dementia risk. Nutritional changes, including greater nut consumption and reduced sugar drink consumption, improved dental care, and reduced toxicant exposure, may help reduce this higher risk of dementia among African Americans and Hispanic Americans.

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.

Mild cognitive impairment and microbiota: what is known and future perspectives

Mild cognitive impairment (MCI) is a heterogeneous condition definable as the intermediate clinical state between normal aging and dementia. As a pre-dementia condition, there is a recent growing interest in the identification of non-invasive markers able to predict the progression from MCI to a more advanced stage of the disease. Previous evidence showed the close link between gut microbiota and neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's disease (PD). Conversely, the actual relationship between gut microbiota and MCI is yet to be clarified. In this work, we provide an overview about the current knowledge regarding the role of gut microbiota in the context of MCI, also assessing the potential for microbiota-targeted therapies. Through the review of the most recent studies focusing on this topic, we found evidence of an increase of Bacteroidetes at phylum level and Bacteroides at genus level in MCI subjects with respect to healthy controls and patients with AD. Despite such initial evidence, the definitive identification of a typical microbiota profile associated with MCI is still far from being achieved. These preliminary results, however, are growingly encouraging research on the role of gut microbiota modulation in improving the cognitive status of pre-dementia subjects. To date, few studies evaluated the role of probiotics in MCI subjects, and they showed favorable results, although still biased by small sample size, heterogeneity of study design and short follow-up.

Influence of gut microbiota on the development of most prevalent neurodegenerative dementias and the potential effect of probiotics in elderly: A scoping review

Dementia is one of today's greatest public health challenges. Its high socio-economic impact and difficulties in diagnosis and treatment are of increasing concern to an aging world population. In recent years, the study of the relationship between gut microbiota and different neurocognitive disorders has gained a considerable interest. Several studies have reported associations between gut microbiota dysbiosis and some types of dementia. Probiotics have been suggested to restore dysbiosis and to improve neurocognitive symptomatology in these dementias. Based on these previous findings, the available scientific evidence on the gut microbiota in humans affected by the most prevalent dementias, as well as the probiotic trials conducted in these patients in recent years, have been here reviewed. Decreased concentrations of short-chain fatty acids (SCFA) and other bacterial metabolites appear to play a major role in the onset of neurocognitive symptoms in Alzheimer disease (AD) and Parkinson disease dementia (PDD). Increased abundance of proinflammatory taxa could be closely related to the more severe clinical symptoms in both, as well as in Lewy Bodies dementia. Important lack of information was noted in Frontotemporal dementia behavioral variant. Moreover, geographical differences in the composition of the gut microbiota have been reported in AD. Some potential beneficial effects of probiotics in AD and PDD have been reported. However, due to the controversial results further investigations are clearly necessary.

The gut microbiome modulates the susceptibility to traumatic stress in a sex-dependent manner

Post-traumatic stress disorder (PTSD), a psychological condition triggered by exposure to extreme or chronic stressful events, exhibits a sex bias in incidence and clinical manifestations. Emerging research implicates the gut microbiome in the pathogenesis of PTSD and its roles in stress susceptibility. However, it is unclear whether differential gut microbiota contribute to PTSD susceptibility in male and female rats. Here, we utilized the single prolonged stress animal model and employed unsupervised machine learning to classify stressed animals into stress-susceptible subgroups and stress-resilient subgroups. Subsequently, using 16S V3-V4 rDNA sequencing, we investigated the differential gut microbiota alterations between susceptible and resilient individuals in male and female rats. Our findings revealed distinct changes in gut microbiota composition between the sexes at different taxonomic levels. Furthermore, the abundance of Parabacteroides was lower in rats that underwent SPS modeling compared to the control group. In addition, the abundance of Tenericutes in the stress-susceptible subgroup was higher than that in the control group and stress-resilient subgroup, suggesting that Tenericutes may be able to characterize stress susceptibility. What is particularly interesting here is that Cyanobacteria may be particularly associated with anti-anxiety effects in male rats. This study underscores sex-specific variations in gut microbiota composition in response to stress and sex differences should be taken into account when using macrobiotics for neuropsychiatric treatment, highlighting potential targets for PTSD therapeutic interventions.

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.

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

Exploring the Effects of a Mediterranean Diet and Weight Loss on the Gut Microbiome and Cognitive Performance in Older, African American Obese Adults: A Post Hoc Analysis

African American adults have a higher prevalence of Alzheimer's dementia (AD) than non-Hispanic Whites. The impact of a Mediterranean Diet (Med Diet) and intentional weight loss (IWL) on the gut microbiome may alter AD risk. A post hoc analysis of the Building Research in Diet and Cognition (BRIDGE) trial was performed to determine whether participation in an 8-month Med Diet lifestyle intervention with (n = 35) or without IWL (n = 31) was associated with changes in gut microbiota structure, abundance, and function and whether these changes were related to changes in cognitive performance. The results showed that family and genus alpha diversity increased significantly in both groups combined (p = 0.0075 and p = 0.024, respectively). However, there were no other significant microbially related within- or between-group changes over time. Also, an increase in Med Diet adherence was significantly associated with a decrease in alpha diversity at the phylum level only (p = 0.049). Increasing alpha diversity was associated with decreasing cognitive performance, but this association was attenuated after controlling for Med Diet adherence. In sum, an 8-month Med Diet lifestyle intervention with or without IWL did not appreciably alter the gut microbiome.