Effects of prebiotic galacto-oligosaccharide on postoperative cognitive dysfunction and neuroinflammation through targeting of the gut-brain axis

Targeting gut dysbiosis as a means to enhance recovery from surgical brain injury

Background

Surgical brain injury (SBI) impacts roughly 800,000 people who undergo neurosurgical procedures each year. SBI is the result of unavoidable parenchymal damage, vessel disruption, and thermal injury that is an inherent part of all neurosurgical procedures. Clinically, SBI has been associated with postoperative seizures and long-term neurobehavioral deficits. Current therapies are aimed at providing symptom relief by reducing swelling and preventing seizures. However, there are no therapies aimed at reducing the extent of SBI preoperatively. The microbiome-gut-brain axis may serve as a potential target for the development of new preventative therapies due to its extensive involvement in central nervous system function.

Methods

An extensive literature review was conducted to determine whether there is a potential role for dysbiosis treatment in reducing the extent of SBI.

Results

Treatment of gut dysbiosis deserves further exploration as a potential means of reducing the extent of unavoidable SBI. Dysbiosis has been correlated with increased neuroinflammation through impaired immune regulation, increased blood-brain barrier permeability, and increased production of reactive metabolites. Recently, dysbiosis has also been linked to acute neurological dysfunction in the postoperative state. Importantly, treatment of dysbiosis has been correlated with better patient outcomes and decreased length of stay in surgical patients.

Conclusion

Current literature supports the role of dysbiosis treatment in the preoperative setting as a means of optimizing neurological recovery following unavoidable SBI that results from all neurosurgical procedures.

Effects of Transcutaneous Electrical Acupoint Stimulation on Postoperative Cognitive Decline in Elderly Patients: A Pilot Study

Background

Postoperative cognitive decline (POCD) in the old ages seriously delays the rapid recovery. Here, we aimed to investigate the effects of transcutaneous electrical acupoint stimulation (TEAS) against POCD in elderly patients undergoing laparoscopic radical colon cancer surgery, as well as the potential mechanism.

Methods

A prospective, single-center, parallel-group, randomized trial was designed. A total of 100 patients (age ≥65 years) undergoing laparoscopic radical resection of colon cancer were involved and randomly divided into TEAS (Group T) and control (Group C) groups. The patients in Group T were performed with percutaneous acupoint electrical stimulation in bilateral Hegu, Neiguan and Zusanli points from 30 minutes before anesthesia induction to the end of surgery. A Z-score based on Mini-Mental State Exam (MMSE) was used to assess the incidence of POCD. The levels of serum IL-6, hs-CRP, CGRP at 0 min before TEAS (T0), 1 h after beginning of surgery (T1) and the end of surgery (T2) were evaluated.

Results

Our data showed that the cumulative duration of POCD on postoperative day 2 and 3 in Group T was significantly decreased compared to Group C (P < 0.05). Compared with T0, the levels of serum IL-6, hs-CRP, and CGRP in both Group T and C were statistically elevated at T1 and T2 (P < 0.05). Moreover, the levels of serum IL-6 and hs-CRP were decreased, but the level of CGRP was increased in Group T compared to Group C at T1 and T2 (P < 0.05).

Conclusion

TEAS is associated with a lower cumulative duration of POCD in elderly patients undergoing laparoscopic radical colon cancer surgery, which may be related to the regulation of inflammatory factors and neuropeptides interacted with gut–brain axis.

Going with the grain: Fiber, cognition, and the microbiota-gut-brain-axis

Healthy dietary intake has been acknowledged for decades as one of the main contributors to health. More recently, the field of nutritional psychiatry has progressed our understanding regarding the importance of nutrition in supporting mental health and cognitive function. Thereby, individual nutrients, including omega-3 fatty acids and polyphenols, have been recognized to be key drivers in this relationship. With the progress in appreciating the influence of dietary fiber on health, increasingly research is focusing on deciphering its role in brain processes. However, while the importance of dietary fiber in gastrointestinal and metabolic health is well established, leading to the development of associated health claims, the evidence is not conclusive enough to support similar claims regarding cognitive function. Albeit the increasing knowledge of the impact of dietary fiber on mental health, only a few human studies have begun to shed light onto the underexplored connection between dietary fiber and cognition. Moreover, the microbiota-gut-brain axis has emerged as a key conduit for the effects of nutrition on the brain, especially fibers, that are acted on by specific bacteria to produce a variety of health-promoting metabolites. These metabolites (including short chain fatty acids) as well as the vagus nerve, the immune system, gut hormones, or the kynurenine pathway have been proposed as underlying mechanisms of the microbiota-brain crosstalk. In this minireview, we summarize the evidence available from human studies on the association between dietary fiber intake and cognitive function. We provide an overview of potential underlying mechanisms and discuss remaining questions that need to be answered in future studies. While this field is moving at a fast pace and holds promise for future important discoveries, especially data from human cohorts are required to further our understanding and drive the development of public health recommendations regarding dietary fiber in brain health.

Atractylon treatment prevents sleep-disordered breathing-induced cognitive dysfunction by suppression of chronic intermittent hypoxia-induced M1 microglial activation

Chronic intermittent hypoxia (CIH) induced by sleep-disordered breathing (SDB) is a key factor involved in cognitive dysfunction (CD). Increasing evidence has shown that atractylon (ATR) has anti-inflammatory effects. However, it remains unclear if ATR has a protective effect against SDB-induced nerve cell injury and CD. So, in the present study, CIH-exposed mice and CIH-induced BV2 cells were used to mimic SDB. The results showed that ATR treatment decreased CIH-induced CD and the expression of inflammatory factors in the hippocampal region by suppression of M1 microglial activation and promotion of M2 microglial activation. Also, ATR treatment promoted sirtuin 3 (SIRT3) expression. Down-regulation of SIRT3 decreased the protective effect of ATR against CIH-induced microglial cell injury. Furthermore, in vitro detection found that SIRT3 silencing suppressed ATR-induced M2 microglial activation after exposure to CIH conditions. Taken together, these results indicate that ATR treatment prevents SDB-induced CD by inhibiting CIH-induced M1 microglial activation, which is mediated by SIRT3 activation.

Gut microbial dysbiosis after traumatic brain injury modulates the immune response and impairs neurogenesis

The influence of the gut microbiota on traumatic brain injury (TBI) is presently unknown. This knowledge gap is of paramount clinical significance as TBI patients are highly susceptible to alterations in the gut microbiota by antibiotic exposure. Antibiotic-induced gut microbial dysbiosis established prior to TBI significantly worsened neuronal loss and reduced microglia activation in the injured hippocampus with concomitant changes in fear memory response. Importantly, antibiotic exposure for 1 week after TBI reduced cortical infiltration of Ly6Chigh monocytes, increased microglial pro-inflammatory markers, and decreased T lymphocyte infiltration, which persisted through 1 month post-injury. Moreover, microbial dysbiosis was associated with reduced neurogenesis in the dentate gyrus 1 week after TBI. By 3 months after injury (11 weeks after discontinuation of the antibiotics), we observed increased microglial proliferation, increased hippocampal neuronal loss, and modulation of fear memory response. These data demonstrate that antibiotic-induced gut microbial dysbiosis after TBI impacts neuroinflammation, neurogenesis, and fear memory and implicate gut microbial modulation as a potential therapeutic intervention for TBI.

Gut microbiota: a new player in the pathogenesis of perioperative neurocognitive disorder?

Perioperative neurocognitive disorder (PND), including postoperative delirium and postoperative cognitive dysfunction (POCD), is a common postoperative complication in elderly patients, who represent an expanding segment of our population. PND is a multifactorial disease resulting in higher morbidity and mortality. The precise mechanism of PND is yet to be fully delineated. Identifying the modifiable risk factors and mechanisms for PND would be an important step forward in preventing such adverse events and thus improving patients' outcomes. It is increasingly recognized that gut microbiota also manifest effects in the central nervous system via the microbiota-gut-brain axis, which has emerged as an important player in shaping aspects of behavior and cognitive function. Recent studies have found that patients with cognitive dysfunction after surgery and anesthesia have obvious gut microbiome disorders. These findings are paralleled by a growing body of preclinical investigations aimed at better understanding how surgery and anesthesia affect the central nervous system and possibly contribute to cognitive decline. Here, we present a broad topical review of the literature supporting the role of gut microbiota in PND. We provide an overview of the mechanisms underlying the pathogenesis of PND from pre-clinical and human studies. Therefore, gut microbiota could be a putative therapeutic target for PND in the future.

Unravelling the role of gut microbiota in Parkinson's disease progression: Pathogenic and therapeutic implications

In recent years, researchers have shown interest in bi-directional interaction between the brain and gut, called "gut-brain axis". Emerging pieces of evidence indicate that disturbances in this axis is found to be associated with the Parkinson's disease (PD). Several clinical investigations revealed the crucial role of gut microbiota in the pathogenesis of PD. It has been suggested that aggregation of misfolded protein α-syn, the neuropathological hallmark of PD, might begin in gut and propagates to the CNS via vagus nerve and olfactory bulb. Emerging evidences also suggest that initiation and progression of PD may be due to inflammation originating from gut. It has been shown that microbial gut dysbiosis causes the production of various pathogenic microbial metabolites which elevates pro-inflammatory environment in the gut that promotes neuroinflammation in the CNS. These observations raise the intriguing question - how gut microbial dysbiosis could contribute to PD progression. In this context, various microbiota-targeted therapies are under consideration that can re-establish the intestinal homeostasis which may have greater promise in the prevention and treatment of PD. This review focuses on the role of the gut microbiota in the initiation, progression of PD and current therapeutic intervention to deplete the severity of the disease.

Mom's diet matters: Maternal prebiotic intake in mice reduces anxiety and alters brain gene expression and the fecal microbiome in offspring

Compelling evidence links enteric microbes to brain function and behavior. Galacto-oligosaccharide prebiotics have been shown to modulate the composition of gut flora and induce metabolic, neurochemical, and behavioral changes in adult rodents. Despite the brain being most susceptible to environmental factors, such as nutrients and toxins, during the earliest stages of development, it is unknown whether maternal prebiotic supplementation during gestation and lactation influences the offspring gut microbiome, brain, or behavior. The aim of this study was to test whether maternal galacto-oligosaccharide intake during pregnancy and lactation alters the brain and behavior in naïve and endotoxin-challenged offspring. CD1 female mice received either normal drinking water or water supplemented with Bimuno® galacto-oligosaccharides (B-GOS) during gestation and suckling. Offspring behavior was tested at weaning age or adulthood, and a cross-foster design was employed in a separate cohort to differentiate between effects of prenatal and postnatal maternal B-GOS intake. Lipopolysaccharide was also administered to pups at postnatal day 9 to determine whether maternal B-GOS influences the neurobiological and behavioral effects of a neonatal pro-inflammatory challenge in adulthood. Fecal microbiome composition and metabolites were analyzed to explore potential relationships between the maternal microbiome, the offspring gut microbiome, and the offspring brain and behavior. Maternal B-GOS supplementation increased exploratory behavior and reduced expression of hippocampal glutamate receptor genes in young, weaning-age offspring. In addition, postnatal, but not prenatal, B-GOS supplementation increased fecal butyrate and propionate levels. Finally, in adult offspring, perinatal B-GOS intake increased cortical glutamate receptor subunits in females, increased social preference, and reduced anxiety. We provide novel and comprehensive evidence for the influence of maternal prebiotic intake on offspring behavior, brain gene expression, and gut microbiome composition in mice.

Curcumin Reduces Neuroinflammation and Improves the Impairments of Anesthetics on Learning and Memory by Regulating the Expression of miR-181a-5p

OBJECTIVE

The purpose of this study was to explore the role of curcumin (Cur) in isoflurane (ISO)-induced learning and memory dysfunction in Sprague-Dawley rats and further elucidate the mechanism of the protective effect produced by Cur.

METHODS

Rat models of cognitive impairment were established by inhaling 3% ISO. The Morris water maze test was used to assess the cognitive function of rats. ELISA and qRT-PCR were used to analyze the protein levels of pro-inflammatory cytokines and expression levels of miR-181a-5p, respectively.

RESULTS

Cur significantly improved the ISO-induced cognitive dysfunction in rats and alleviated the ISO-induced neuroinflammation. miR-181a-5p was overexpressed in ISO-induced rats, while Cur treatment significantly reduced the expression of miR-181a-5p. Overexpression of miR-181a-5p promoted the cognitive impairment and the release of inflammatory cytokines and reversed the neuroprotective effect of Cur.

CONCLUSION

Cur has a protective effect on ISO-induced cognitive dysfunction, which may be achieved by regulating the expression of miR-181a-5p.

SIRT1 mediates improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway

OBJECTIVES

Clinically, there is no effective therapy for postoperative cognitive dysfunction (POCD). Inflammation after surgery is closely associated with POCD.

METHODS

In this study, we explored the role of sirtuin 1 (SIRT1) in POCD. POCD in mice was induced by cardiac surgery. The mRNA and protein levels of related genes were determined by real-time polymerase chain reaction and western blot, respectively. Plasma concentrations of inflammatory factors were measured using an ELISA kit. Novel object and novel location recognition tests were carried out to measure recognition ability. The Morris water maze (MWM) test was performed to measure learning and memory ability.

RESULTS

There was a clear decrease in SIRT1 expression after POCD. The SIRT1 activator SRT1720 promoted recognition, learning, and memory ability of mice with POCD. Moreover, SRT1720 treatment greatly inhibited plasma inflammatory cytokine levels and TLR4 and P65 protein expression in the hippocampus of POCD mice. The effect of SRT1720 on POCD was in a TLR4-dependent manner.

CONCLUSIONS

SIRT1 mediates the improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway.

Gut-Brain Axis: Role of Gut Microbiota on Neurological Disorders and How Probiotics/Prebiotics Beneficially Modulate Microbial and Immune Pathways to Improve Brain Functions

The gut microbiome acts as an integral part of the gastrointestinal tract (GIT) that has the largest and vulnerable surface with desirable features to observe foods, nutrients, and environmental factors, as well as to differentiate commensals, invading pathogens, and others. It is well-known that the gut has a strong connection with the central nervous system (CNS) in the context of health and disease. A healthy gut with diverse microbes is vital for normal brain functions and emotional behaviors. In addition, the CNS controls most aspects of the GI physiology. The molecular interaction between the gut/microbiome and CNS is complex and bidirectional, ensuring the maintenance of gut homeostasis and proper digestion. Besides this, several mechanisms have been proposed, including endocrine, neuronal, toll-like receptor, and metabolites-dependent pathways. Changes in the bidirectional relationship between the GIT and CNS are linked with the pathogenesis of gastrointestinal and neurological disorders; therefore, the microbiota/gut-and-brain axis is an emerging and widely accepted concept. In this review, we summarize the recent findings supporting the role of the gut microbiota and immune system on the maintenance of brain functions and the development of neurological disorders. In addition, we highlight the recent advances in improving of neurological diseases by probiotics/prebiotics/synbiotics and fecal microbiota transplantation via the concept of the gut-brain axis.

The Potential Mediation of the Effects of Physical Activity on Cognitive Function by the Gut Microbiome

The population of older adults is growing dramatically worldwide. As older adults are at greater risk of developing disorders associated with cognitive dysfunction (i.e., dementia), healthcare costs are expected to double by 2040. Evidence suggests dementia may be slowed or prevented by lifestyle interventions, including physical activity (PA). PA is associated with improved cognitive function and may reduce risk for dementia by mitigating known risk factors (i.e., cardiovascular diseases) and/or by enhancing neurochemical processes. An emerging area of research suggests the gut microbiome may have similar neuroprotective effects. Altering the gut microbiome has been found to target physiological processes associated with dementia risk, and it influences gut-brain-microbiome axis signaling, impacting cognitive functioning. The gut microbiome can be altered by several means (i.e., disease, diet, prebiotics, probiotics), including PA. As PA and the gut microbiome independently influence cognitive function and PA changes the composition of the gut microbiome, cognitive improvement due to PA may be partially mediated by the gut microbiome. The present article provides an overview of the literature regarding the complex associations among PA, cognitive function, and the gut microbiome, as well as their underlying biological mechanisms. A comprehensive, theoretical model integrating evidence for the potential mediation is proposed.

Prebiotic administration modulates gut microbiota and faecal short-chain fatty acid concentrations but does not prevent chronic intermittent hypoxia-induced apnoea and hypertension in adult rats

BACKGROUND

Evidence is accruing to suggest that microbiota-gut-brain signalling plays a regulatory role in cardiorespiratory physiology. Chronic intermittent hypoxia (CIH), modelling human sleep apnoea, affects gut microbiota composition and elicits cardiorespiratory morbidity. We investigated if treatment with prebiotics ameliorates cardiorespiratory dysfunction in CIH-exposed rats.

METHODS

Adult male rats were exposed to CIH (96 cycles/day, 6.0% O2 at nadir) for 14 consecutive days with and without prebiotic supplementation (fructo- and galacto-oligosaccharides) beginning two weeks prior to gas exposures.

FINDINGS

CIH increased apnoea index and caused hypertension. CIH exposure had modest effects on the gut microbiota, decreasing the relative abundance of Lactobacilli species, but had no effect on microbial functional characteristics. Faecal short-chain fatty acid (SCFA) concentrations, plasma and brainstem pro-inflammatory cytokine concentrations and brainstem neurochemistry were unaffected by exposure to CIH. Prebiotic administration modulated gut microbiota composition and diversity, altering gut-metabolic (GMMs) and gut-brain (GBMs) modules and increased faecal acetic and propionic acid concentrations, but did not prevent adverse CIH-induced cardiorespiratory phenotypes.

INTERPRETATION

CIH-induced cardiorespiratory dysfunction is not dependant upon changes in microbial functional characteristics and decreased faecal SCFA concentrations. Prebiotic-related modulation of microbial function and resultant increases in faecal SCFAs were not sufficient to prevent CIH-induced apnoea and hypertension in our model. Our results do not exclude the potential for microbiota-gut-brain axis involvement in OSA-related cardiorespiratory morbidity, but they demonstrate that in a relatively mild model of CIH, sufficient to evoke classic cardiorespiratory dysfunction, such changes are not obligatory for the development of morbidity, but may become relevant in the elaboration and maintenance of cardiorespiratory morbidity with progressive disease.

FUNDING

Department of Physiology and APC Microbiome Ireland, University College Cork, Ireland. APC Microbiome Ireland is funded by Science Foundation Ireland, through the Government's National Development Plan.

Perioperative neurocognitive dysfunction: thinking from the gut?

With the aging of the world population, and improvements in medical and health technologies, there are increasing numbers of elderly patients undergoing anaesthesia and surgery. Perioperative neurocognitive dysfunction has gradually attracted increasing attention from academics. Very recently, 6 well-known journals jointly recommended that the term perioperative neurocognitive dysfunction (defined according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition) should be adopted to improve the quality and consistency of academic communications. Perioperative neurocognitive dysfunction currently includes preoperatively diagnosed cognitive decline, postoperative delirium, delayed neurocognitive recovery, and postoperative cognitive dysfunction. Increasing evidence shows that the gut microbiota plays a pivotal role in neuropsychiatric diseases, and in central nervous system functions via the microbiota-gut-brain axis. We recently reported that abnormalities in the composition of the gut microbiota might underlie the mechanisms of postoperative cognitive dysfunction and postoperative delirium, suggesting a critical role for the gut microbiota in perioperative neurocognitive dysfunction. This article therefore reviewed recent findings on the linkage between the gut microbiota and the underlying mechanisms of perioperative neurocognitive dysfunction.

The Gut Microbiome as a Component of the Gut-Brain Axis in Cognitive Health

INTRODUCTION

The human microbiome, the microorganisms living in and on the body, plays a vital role in brain physiology and pathophysiology. The gut microbiome (GMB) has been identified as a link in the gut-brain axis moderating cognitive development and health.

OBJECTIVES

The objectives of this scoping review are to discuss mechanisms of the microbiome-gut-brain axis in cognition, review the existing literature on the GMB and cognition, and discuss implications for nursing research.

METHODS

We searched Pubmed using the terms "gut microbiome," "brain," and "cognition" and the terms "gut brain axis," "microbiome," and "cognition"; removed duplicates, studies not published in English, and unrelated publications; and added additional articles identified through references. We retained the 85 most relevant publications for this review.

RESULTS

Common themes in the current literature include GMB components; interactions on cognitive development; effects of GMB-gut-brain interactions on cognition, mild cognitive impairment and Alzheimer's disease; effects of GMB interactions with physiologic stress on cognition in critical care; and GMB modification for improved cognition. Review of the literature on each of these topics reveals multiple theoretical mechanisms of action for GMB-gut-brain interaction that modify cognitive development and function across the lifespan.

DISCUSSION

GMB components and dysbiosis have been implicated in many cognitive states, and specific microbiota constituents contribute to cognitive development, stability, and impairment. The study of these interactions is relevant to nursing research as it addresses the holistic human experience and microbiome constituents are modifiable, facilitating translation into the clinical setting.

Bioavailability Based on the Gut Microbiota: a New Perspective

The substantial discrepancy between the strong effects of functional foods and various drugs, especially traditional Chinese medicines (TCMs), and the poor bioavailability of these substances remains a perplexing problem. Understanding the gut microbiota, which acts as an effective bioreactor in the human intestinal tract, provides an opportunity for the redefinition of bioavailability. Here, we discuss four different pathways associated with the role of the gut microbiota in the transformation of parent compounds to beneficial or detrimental small molecules, which can enter the body's circulatory system and be available to target cells, tissues, and organs. We further describe and propose effective strategies for improving bioavailability and alleviating side effects with the help of the gut microbiota. This review also broadens our perspectives for the discovery of new medicinal components.

Anesthesia and surgery induce cognitive dysfunction in elderly male mice: the role of gut microbiota

It is well known that the incidence of postoperative cognitive dysfunction (POCD) is high in elderly patients. The pathogenesis and therapeutic mechanisms of POCD, however, have not yet been completely elucidated. The effects of gut microbiota, particularly in terms of regulating brain function, have gradually attracted increasing attention. In this study, we investigated the potential role of gut microbiota in POCD in aged male mice and attempted to determine whether alterations in gut microbiota would be helpful in the diagnosis of POCD. POCD and non-POCD mice were classified by hierarchical cluster analysis of behavioral results. Additionally, α- and β-diversity of gut microbiota showed a differential profile between the groups. In total, 24 gut bacteria were significantly altered in POCD mice compared with those in non-POCD mice, in which 13 gut bacteria were significantly correlated with escape latency in the Morris water maze test (MWMT). Remarkably, receiver operating characteristic curves revealed that the Dehalobacteriaceae family and Dehalobacterium genus are potentially important bacteria for the diagnosis of POCD. These findings indicate that alterations in the composition of gut microbiota are probably involved in the pathogenesis of POCD in aged mice. Novel therapeutic strategies regulating specific gut bacteria may be helpful for the prevention and treatment of POCD.

The role of prebiotics in cognition, anxiety, and depression

The disruption of the gut microbial composition, defined as dysbiosis, has been associated with many neurological disorders with inflammatory components. The alteration of the gut microbiota leads to an increase in pro-inflammatory cytokines that are associated with metabolic diseases (such as obesity and type 2 diabetes), autoimmune arthritis, and neuropsychiatric diseases. Prebiotics are defined as non-digestible carbohydrates and promote the growth of beneficial bacteria such as bifidobacteria and lactobacillus, exert beneficial effects on improving dysbiosis and its associated inflammatory state. Preclinical and clinical data indicated that some prebiotics also have positive impacts on the central nervous system (CNS) due to the modulation of neuroinflammation and thus may have a key role in the modulation of cognitive impairment, anxiety, and depression. The present manuscript reviews the state-of-art of the effects of prebiotics in cognitive impairment, anxiety, and depressive disorders. Data from clinical studies are still scarce, and further clinical trials are needed to corroborate the potential therapeutic cognitive, antidepressant, and anxiolytic of prebiotics. Prebiotics may provide patients suffering from cognitive deficits, depression, and anxiety with a new tool to minimize disease symptoms and increase the quality of life.

Dietary natural products as epigenetic modifiers in aging-associated inflammation and disease

Covering: up to 2020Chronic, low-grade inflammation is linked to aging and has been termed "inflammaging". Inflammaging is considered a key contributor to the development of metabolic dysfunction and a broad spectrum of diseases or disorders including declines in brain and heart function. Genome-wide association studies (GWAS) coupled with epigenome-wide association studies (EWAS) have shown the importance of diet in the development of chronic and age-related diseases. Moreover, dietary interventions e.g. caloric restriction can attenuate inflammation to delay and/or prevent these diseases. Common themes in these studies entail the use of phytochemicals (plant-derived compounds) or the production of short chain fatty acids (SCFAs) as epigenetic modifiers of DNA and histone proteins. Epigenetic modifications are dynamically regulated and as such, serve as potential therapeutic targets for the treatment or prevention of age-related disease. In this review, we will focus on the role for natural products that include phytochemicals and short chain fatty acids (SCFAs) as regulators of these epigenetic adaptations. Specifically, we discuss regulators of methylation, acetylation and acylation, in the protection from chronic inflammation driven metabolic dysfunction and deterioration of neurocognitive and cardiac function.

Reply to Comment on Watanabe, A.; Kadota, Y.; Yokoyama, H.; Tsuruda, S.; Kamio, R.; Tochio, T.; Shimomura, Y.; Kitaura, Y. Experimental Determination of the Threshold Dose for Bifidogenic Activity of Dietary 1-Kestose in Rats. Foods 2020, 9, 4

The manuscript entitled "Comment on Experimental Determination of the Threshold Dose for Bifidogenic Activity of Dietary 1-Kestose in Rats" by Shen et al [...].

Fucose Ameliorates Tryptophan Metabolism and Behavioral Abnormalities in a Mouse Model of Chronic Colitis

Growing evidence suggests that intestinal mucosa homeostasis impacts immunity, metabolism, the Central Nervous System (CNS), and behavior. Here, we investigated the effect of the monosaccharide fucose on inflammation, metabolism, intestinal microbiota, and social behavior in the Dextran Sulfate Sodium (DSS)-induced chronic colitis mouse model. Our data show that chronic colitis is accompanied by the decrease of the serum tryptophan level and the depletion of the intestinal microbiota, specifically tryptophan-producing E. coli and Bifidobacterium. These changes are associated with defects in the male mouse social behavior such as a lack of preference towards female bedding in an odor preference test. The addition of fucose to the test animals' diet altered the bacterial community, increased the abundance of tryptophan-producing E. coli, normalized blood tryptophan levels, and ameliorated social behavior deficits. At the same time, we observed no ameliorating effect of fucose on colon morphology and colitis. Our results suggest a possible mechanism by which intestinal inflammation affects social behavior in male mice. We propose fucose as a promising prebiotic, since it creates a favorable environment for the beneficial bacteria that promote normalization of serum tryptophan level and amelioration of the behavioral abnormalities in the odor preference test.

Anesthesia and surgery induce age-dependent changes in behaviors and microbiota

The neuropathogenesis of postoperative delirium remains mostly unknown. The gut microbiota is implicated in the pathogenesis of neurological disorders. We, therefore, set out to determine whether anesthesia/surgery causes age-dependent gut microbiota dysbiosis, changes in brain IL-6 level and mitochondrial function, leading to postoperative delirium-like behavior in mice. Female 9 or 18 months old mice received abdominal surgery under 1.4% isoflurane for two hours. The postoperative delirium-like behavior, gut microbiota, levels of brain IL-6, PSD-95 and synaptophysin, and mitochondrial function were determined by a battery of behavioral tests, 16s rRNA sequencing, ELISA, Western blot and Seahorse XFp Extracellular Flux Analyzer. Intragastric administration of Lactobacillus (10 days) and probiotic (20 days) were used to mitigate the anesthesia/surgery-induced changes. Anesthesia/surgery caused different alterations in gut microbiota, including change rate of reduction in the levels of gut lactobacillus, between the 18 and 9 months old mice. The anesthesia/surgery induced greater postoperative delirium-like behavior, increased brain IL-6 levels, decreased PSD-95 and synaptophysin levels, and mitochondrial dysfunction in 18 than 9 months old mice. Treatments with Lactobacillus and probiotic mitigated the anesthesia/surgery-induced changes. These data suggest that microbiota dysbiosis may contribute to neuropathogenesis of postoperative delirium and treatment with Lactobacillus or a probiotic could mitigate postoperative delirium.

The potential mechanism of postoperative cognitive dysfunction in older people

Postoperative cognitive dysfunction (POCD) is a common disorder following surgery, which seriously threatens the quality of patients' life, especially the older people. Accumulating attention has been paid to POCD worldwide in pace with the popularization of anesthesia/surgery. The development of medical humanities and rehabilitation medicine sets higher demands on accurate diagnosis and safe treatment system of POCD. Although the research on POCD is in full swing, underlying pathogenesis is still inconclusive due to these conflicting results and controversial evidence. Generally, POCD is closely related to neuropsychiatric diseases such as dementia, depression and Alzheimer's disease in molecular pathways. Researchers have come up with various hypotheses to reveal the mechanisms of POCD, including neuroinflammation, oxidative stress, autophagy disorder, impaired synaptic function, lacking neurotrophic support, etc. Recent work focused on molecular mechanism of POCD in older people has been thoroughly reviewed and summed up here, concerning the changes of peripheral circulation, pathological pathways of central nervous system (CNS), the microbiota-gut-brain axis and the related brain regions. Accordingly, this article provides a better perspective to understand the development situation of POCD in older people, which is conductive to uncover the pathological mechanism and exploit reasonable treatment strategy of POCD.

The microbiome: implications for perioperative and critical care

PURPOSE OF REVIEW

The host-microbiota relationship is integral in human health and can be rapidly disrupted in ways that may contribute to poor recovery from surgery or acute illness. We review key studies by organ system to understand the effect of perioperative and critical illness stress on the microbiota. Throughout the review, our focus is on potential interventions that may be mediated by the microbiome.

RECENT FINDINGS

Although any perioperative intervention can have a profound impact on the gut microbiota, it is less clear how such changes translate into altered health outcomes. Preoperative stress (anxiety, lack of sleep, fasting), intraoperative stress (surgery itself, volatile anesthetics, perioperative antibiotics, blood transfusions), and postoperative stress (sepsis, surgical site infections, acute respiratory distress syndrome, catecholamines, antibiotics, opioids, proton pump inhibitors) have all been associated with alterations of the commensal microflora. These factors (e.g. administration of antibiotics or opioids) can create a favorable environment for emergence of pathogen virulence and development of serious infections and multiorgan failure. Data to recommend therapies aimed at restoring a disrupted microbiota, such as probiotics/prebiotics and fecal microbiota transplants is currently scarce.

SUMMARY

The microbiome is likely to play an important role in the perioperative and ICU setting but existing data is largely descriptive. There is an expanding number of mechanistic studies that attempt to disentangle the complicated bi-directional relationship between the host and the resident microbiota. When these results are combined with ongoing clinical studies, we should be able to offer better therapies aimed at restoring the microbiota in the future.

The presence of elevated circulating trimethylamine N-oxide exaggerates postoperative cognitive dysfunction in aged rats

Surgical trauma can cause brain oxidative stress and neuroinflammation, leading to postoperative cognitive dysfunction (POCD), especially in the elderly. Additionally, the pre-existing risk factors may enhance POCD. Gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) has recently been shown to contribute to the pathogenesis of many diseases by increasing oxidative stress and inflammation in the peripheral tissues. Here we examined whether the presence of elevated circulating TMAO would influence surgery-induced cognitive decline. Aged rats were treated with vehicle or TMAO for 3 weeks. After two weeks of treatment, these rats underwent sham-operation or laparotomy. One week after surgery, rats underwent laparotomy exhibited hippocampal-dependent cognitive dysfunction as evidenced by reduced contextual freezing time, which was associated with elevated plasma proinflammatory cytokine levels, increased microglia-mediated neuroinflammation and reactive oxygen species (ROS) production in the hippocampus. Treatment with TMAO, which elevated plasma TMAO before and 1 week after surgery, further increased microglia-mediated neuroinflammation and ROS production in the hippocampus, resulting in exaggerated cognitive dysfunction in laparotomy group but not in sham-operation group. Moreover, TMAO treatment decreased expression of antioxidant enzyme methionine sulfoxide reductase (Msr) A in both groups. The results suggest that the presence of elevated circulating TMAO downregulates antioxidant enzyme MsrA in the hippocampus, which may increase the susceptibility to surgery-induced oxidative stress, contributing to exaggerations of neuroinflammation and cognitive decline in aged rats following surgery. Interventions to reduce circulating TMAO in the perioperative period may be a novel strategy to prevent the exaggeration of cognitive decline in elderly patients with high circulating TMAO.

BIS-guided deep anesthesia decreases short-term postoperative cognitive dysfunction and peripheral inflammation in elderly patients undergoing abdominal surgery

OBJECTIVES

Postoperative cognitive dysfunction (POCD) is a common clinical complication, with an underlying pathophysiology linked to heightened levels of neuroinflammation. However, it requires clarification as to whether the depth of anesthesia modulates postoperative cognitive dysfunction. This study investigated the association between depth of anesthesia and POCD in elderly patients undergoing abdominal surgery.

METHODS

A total of 120 patients aged 60 years or older who were planned for abdominal surgery under total intravenous anesthesia were included in this study. The depth of anesthesia was guided by monitoring Bispectral Index (BIS) data. All study participants completed a battery of nine neuropsychological tests before surgery and at 7 days and 3 months after surgery. POCD was calculated by using the reliable change index. Plasma concentration of C-reactive protein (CRP), interleukin (IL)-1β, IL-10, S-100β, and norepinephrine (NE) were measured.

RESULTS

The incidence of POCD at 7 days after surgery in the deep anesthesia group was 19.2% (10/52), which was significantly lower (p = 0.032) than the light anesthesia group 39.6% (21/53). The depth of anesthesia had no effect on POCD at 3 months after surgery (10.3% vs 14.6%, respectively, p = 0.558). Similarly, plasma levels of CRP and IL-1β in deep anesthesia group were lower than that in light anesthesia group at 7 days after surgery (p < 0.05), but not at 3 months after surgery (p > 0.05). There were no significant differences in the plasma concentration of IL-10, S-100β, and NE between the groups (p > 0.05).

CONCLUSIONS

Deep anesthesia under total intravenous anesthesia could decrease the occurrence of short-term POCD and inhibit postoperative peripheral inflammation in elderly patients undergoing abdominal surgery, compared with light anesthesia.

MicroRNA-155 Promotes Heat Stress-Induced Inflammation via Targeting Liver X Receptor α in Microglia

Background: The neuroinflammatory responses of microglial cells play an important role in the process of brain dysfunction caused by heat stroke. MicroRNAs are reportedly involved in a complex signaling network and have been identified as neuroinflammatory regulators. In this study, we determined the biological roles of microRNA-155 in the inflammatory responses in heat-stressed microglia and explored the underlying mechanisms.

Methods: MicroRNA-155 mimic and inhibitor were used to separately upregulate or downregulate microRNA-155 expression. The activation state of BV-2 microglial cells (BV-2 cells) was assessed via immunoreactions using the microglial marker CD11b and CD68. Levels of induced interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured using real-time reverse transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assays (ELISAs). The activation of nuclear factor kappa B (NF-κB) signaling proteins was evaluated by Western blotting for inhibitory kappa B alpha (IκBα) and NF-κB p65 phosphorylation and indirect immunofluorescence analysis using a p65 phosphorylation antibody. A luciferase reporter assay was used to verify liver X receptor α (LXRα) as a target gene of microRNA-155.

Results: Heat stress significantly induced IL-1β, IL-6, and TNF-α release and increased the expression of CD11b and CD68. In addition, IκBα and NF-κB p65 phosphorylation were dramatically increased by heat stress, and microRNA-155 expression was also elevated. High expression of microRNA-155 in heat-stressed microglial cells was inversely correlated with LXRα expression. We then determined the role of microRNA-155 in the heat stress-induced inflammatory responses. The results revealed that by targeting LXRα, microRNA-155 enhanced NF-κB signaling activation and facilitated immune inflammation in heat stress-treated BV-2 cells.

Conclusion: MicroRNA-155 promotes heat stress-induced inflammatory responses in microglia. The underlying mechanisms may include facilitating inflammatory factors expression by increasing NF-κB pathway activation via targeting LXRα.