Intestinal dysbacteriosis mediates the reference memory deficit induced by anaesthesia/surgery in aged mice

Exploring the gut microbiome-Postoperative Cognitive Dysfunction connection: Mechanisms, clinical implications, and future directions

Postoperative Cognitive Dysfunction (POCD) is a common yet poorly understood complication of surgery that can lead to long-term cognitive decline. The gut-brain axis, a bidirectional communication system between the central nervous system and the gut microbiota, plays a significant role in maintaining cognitive health. The potential for anesthetic agents and perioperative medications to modulate the gut microbiota and influence the trajectory of POCD suggests the need for a more integrated approach in perioperative care. Perioperative medications, including opioids and antibiotics, further compound these disruptions, leading to dysbiosis and consequent systemic and neuroinflammation implicated in cognitive impairment. Understanding how surgical interventions and associated treatments affect this relationship is crucial for developing strategies to reduce the incidence of POCD. Strategies to preserve and promote a healthy gut microbiome may mitigate the risk and severity of POCD. Future research should aim to clarify the mechanisms linking gut flora alterations to cognitive outcomes and explore targeted interventions, such as probiotic supplementation and microbiota-friendly prescription practices, to safeguard cognitive function postoperatively.

Emerging Insights into Postoperative Neurocognitive Disorders: The Role of Signaling Across the Gut-Brain Axis

The pathophysiological regulatory mechanisms in postoperative neurocognitive disorders (PNCDs) are intricately complex. Currently, the pathogenesis of PNCDs has not been fully elucidated. The mechanism involved may include a variety of factors, such as neuroinflammation, oxidative stress, and neuroendocrine dysregulation. Research into the gut microbiota-induced regulations on brain functions is increasingly becoming a focal point of exploration. Emerging evidence has shown that intestinal bacteria may play an essential role in maintaining the homeostasis of various physiological systems and regulating disease occurrence. Recent studies have confirmed the association of the gut-brain axis with central nervous system diseases. However, the regulatory effects of this axis in the pathogenesis of PNCDs remain unclear. Therefore, this paper intends to review the bidirectional signaling and mechanism of the gut-brain axis in PNCDs, summarize the latest research progress, and discuss the possible mechanism of intestinal bacteria affecting nervous system diseases. This review is aimed at providing a scientific reference for predicting the clinical risk of PNCD patients and identifying early diagnostic markers and prevention targets.

Deciphering the dual role of N-methyl-D-Aspartate receptor in postoperative cognitive dysfunction: A comprehensive review

Postoperative cognitive dysfunction (POCD) is a common complication following surgery, adversely impacting patients' recovery, increasing the risk of negative outcomes, prolonged hospitalization, and higher mortality rates. The N-methyl-D-aspartate (NMDA) receptor, crucial for learning, memory, and synaptic plasticity, plays a significant role in the development of POCD. Various perioperative factors, including age and anesthetic use, can reduce NMDA receptor function, while surgical stress, inflammation, and pain may lead to its excessive activation. This review consolidates preclinical and clinical research to explore the intricate relationship between perioperative factors affecting NMDA receptor functionality and the onset of POCD. It discusses the influence of aging, anesthetic administration, perioperative injury, pain, and inflammation on the NMDA receptor-related pathophysiology of POCD. The comprehensive analysis presented aims to identify effective treatment targets for POCD, contributing to the improvement of patient outcomes post-surgery.

The relationship between the gut microbiota and oxidative stress in the cognitive function of schizophrenia: A pilot study in China

Cognitive impairment is a core symptom of schizophrenia. The gut microbiota (GM) and oxidative stress may play important roles in the pathophysiological mechanisms of cognitive impairment. This study aimed to explore the relationship between GM and oxidative stress in the cognitive function of schizophrenia. GM obtained by 16S RNA sequencing and serum superoxide dismutase (SOD) levels from schizophrenia patients (N = 68) and healthy controls (HCs, N = 72) were analyzed. All psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Cognitive function was assessed using the MATRICS Consensus Cognitive Battery (MCCB). Correlation analysis was used to explore the relationship between GM, SOD, and cognitive function. Machine learning models were used to identify potential biomarkers. Compared to HCs, the relative abundances of Collinsella, undefined Ruminococcus, Lactobacillus, Eubacterium, Mogibacterium, Desulfovibrio, Bulleidia, Succinivibrio, Corynebacterium, and Atopobium were higher in patients with schizophrenia, but Faecalibacterium, Anaerostipes, Turicibacter, and Ruminococcus were lower. In patients with schizophrenia, the positive factor, general factor, and total score of MCCB positively correlated with Lactobacillus, Collinsella, and Lactobacillus, respectively; SOD negatively correlated with Eubacterium, Collinsella, Lactobacillus, Corynebacterium, Bulleidia, Mogibacterium, and Succinivibrio, but positively correlated with Faecalibacterium, Ruminococcus, and MCCB verbal learning index scores; Faecalibacterium and Turicibacter were positively correlated with MCCB visual learning index scores and speed of processing index scores, respectively. Our findings revealed a correlation between SOD and GM and confirmed that cognitive dysfunction in patients with schizophrenia involves abnormal SOD levels and GM changes.

Propionic acid ameliorates cognitive function through immunomodulatory effects on Th17 cells in perioperative neurocognitive disorders

Background

Elderly patients undergoing surgery are prone to cognitive decline known as perioperative neurocognitive disorders (PND). Several studies have shown that the microglial activation and the decrease of short-chain fatty acids (SCFAs) in gut induced by surgery may be related to the pathogenesis of PND. The purpose of this study was to determine whether microglia and short-chain fatty acids were involved in cognitive dysfunction in aged rats.

Methods

Male wild-type Wistar rats aged 11-12 months were randomly divided into control group (Ctrl: Veh group), propionic acid group (Ctrl: PA group), exploratory laparotomy group (LP: Veh group) and propionic acid + exploratory laparotomy group (LP: PA group) according to whether exploratory laparotomy (LP) or PA pretreatment for 21 days was performed. The motor ability of the rats was evaluated by open field test on postoperative day 3 (POD3), and then the cognitive function was evaluated by Y-maze test and fear conditioning test. The expression of IL-1β, IL-6, RORγt and IL-17A mRNA in hippocampus was detected by RT-qPCR, the expression of IL-17A and IL-17RA in hippocampus was detected by Western blot, and the activation of microglia was detected by immunofluorescence.

Results

The PND rat model was successfully established by laparotomy. Compared with Ctrl: Veh group, the body weight of LP: Veh group decreased, the percentage of spontaneous alternations in Y maze decreased (P < 0.001), and the percentage of freezing time in contextual fear test decreased (P < 0.001). Surgery triggers neuroinflammation, manifested as the elevated levels of the inflammatory cytokines IL-1β (P < 0.001) and IL-6 (P < 0.001), the increased expression of the transcription factor RORγt (P = 0.0181, POD1; P = 0.0073, POD5)and major inflammatory cytokines IL-17A (P = 0.0215, POD1; P = 0.0071, POD5), and the increased average fluorescence intensity of Iba1 (P < 0.001, POD1; P < 0.001, POD5). After PA preconditioning, the recovery of rats in LP: PA group was faster than that in LP: Veh group as the body weight lost on POD1 (P = 0.0148) was close to the baseline level on POD5 (P = 0.1846), and they performed better in behavioral tests. The levels of IL-1β (P < 0.001) and IL-6 (P = 0.0035) inflammatory factors in hippocampus decreased on POD1 and the average fluorescence intensity of Iba1 decreased (P = 0.0024, POD1; P < 0.001, POD5), representing the neuroinflammation was significantly improved. Besides, the levels of RORγt mRNA (P = 0.0231, POD1; P = 0.0251, POD5) and IL-17A mRNA (P = 0.0208, POD1; P = 0.0071, POD5) in hippocampus as well as the expression of IL-17A (P = 0.0057, POD1; P < 0.001, POD5) and IL-17RA (P = 0.0388) decreased.

Conclusion

PA pretreatment results in reduced postoperative neuroinflammation and improved cognitive function, potentially attributed to the regulatory effects of PA on Th17-mediated immune responses.

Research progress on intestinal microbiota regulating cognitive function through the gut-brain axis

The intestinal microbiota community is a fundamental component of the human body and plays a significant regulatory role in maintaining overall health and in the management disease states.The intestinal microbiota-gut-brain axis represents a vital connection in the cognitive regulation of the central nervous system by the intestinal microbiota.The impact of intestinal microbiota on cognitive function is hypothesized to manifest through both the nervous system and circulatory system. Imbalances in intestinal microbiota during the perioperative period could potentially contribute to perioperative neurocognitive dysfunction. This article concentrates on a review of existing literature to explore the potential influence of intestinal microbiota on brain and cognitive functions via the nervous and circulatory systems.Additionally, it summarizes recent findings on the impact of perioperative intestinal dysbacteriosis on perioperative neurocognitive dysfunction and suggests novel approaches for prevention and treatment of this condition.

Exercise attenuates the perioperative neurocognitive disorder induced by hyperhomocysteinemia in mice

The perioperative neurocognitive disorder (PND) is a severe complication that affects millions of surgical patients each year. Homocysteine (Hcy) is known to increase the risk of developing PND in both young and elderly mice. However, whether Hcy alone can induce cognitive deficits in middle-aged mice (12-month-old), whether exercise can attenuate Hcy-induced hippocampus-related cognitive deficits after surgery through suppressing neuroinflammation, synaptic elimination, and the level of Hcy remains unknown. The present study aimed to answer these questions through testing the possibility of establishing a PND model using 12-month-old mice which received homocysteine injections before exploratory laparotomy and the therapeutic mechanism of exercise. In the present study, it was found that levels of serum homocysteine were age-dependently increased in mice with a significant difference between that of 18-month-old mice and 6-week, 6-month, and 12-month-old mice. PND occurred in 18-month but not in 12-month-old mice after exploratory laparotomy under isoflurane anesthesia. Intraperitoneal injection of Hcy for 3 consecutive days before surgery rendered 12-month-old mice to develop PND after abdominal laparotomy under isoflurane anesthesia at a minimal dosage of 20 mg/kg. Neuroinflammation and synaptic elimination was present in 12-month-old preoperative Hcy-injected mice. Preoperative voluntary wheel exercise could prevent PND in 12-month-old mice that have received Hcy injection before surgery, which might be related to the decreased level of serum Hcy. Activation of glial cells, proinflammatory phenotype markers and synaptic elimination were attenuated in the hippocampus of 12-month-old preoperative Hcy-injected mice by this exercise. These results provide direct evidence that hyperhomocysteinemia can induce postoperative cognitive deficits in middle-aged mice. Pre-surgery exercise can effectively prevent Hcy-precipitated postoperative cognitive dysfunction.

The involvement of the gut microbiota in postoperative cognitive dysfunction based on integrated metagenomic and metabolomics analysis

IMPORTANCE

As the population ages and medical technology advances, anesthesia procedures for elderly patients are becoming more common, leading to an increased prevalence of postoperative cognitive dysfunction. However, the etiology and correlation between the gut microbiota and cognitive dysfunction are poorly understood, and research in this area is limited. In this study, mice with postoperative cognitive dysfunction were found to have reduced levels of fatty acid production and anti-inflammatory flora in the gut, and Bacteroides was associated with increased depression, leading to cognitive dysfunction and depression. Furthermore, more specific microbial species were identified in the disease model, suggesting that modulation of host metabolism through gut microbes may be a potential avenue for preventing postoperative cognitive dysfunction.

Electroacupuncture modulates gut microbiota in mice: A potential target in postoperative cognitive dysfunction

The detailed mechanism of inflammation in postoperative cognitive dysfunction (POCD) is unclear. This study aimed to determine whether electroacupuncture (EA) ameliorates POCD by modulating gut microbial dysbiosis. Compared to the control group, mice in the EA group were treated at the acupoints Zusanli (ST36), Quchi (L111), Baihui (GV20), and Dazhui (GV14) 1 week before appendectomy. Novel object recognition and the Morris water maze tests were used to assess learning and spatial reference memory deficits, whereas hippocampus samples and stool samples were collected for central inflammatory tests and 16S-rRNA sequencing of intestinal flora, respectively. In amyloid precursor protein/presenilin 1 (APP/PS1) mice, EA enhanced spatial memory and learning deficits. The fecal microbial community was altered in APP/PS1 mice in the absence of EA following surgery. Among them, Coprococcus and Bacteroidetes were more abundant in the EA groups than in the control groups; however, Actinobacteriota, Helicobacteraceae, and Escherichia/shigella constitute the minor bacterial colonization in the EA groups. Furthermore, we found a significant negative correlation between Firmicutes and escape latency (Pearson correlation coefficient - 0.551, p < 0.01) and positive correlation between Proteobacteria and escape latency (Pearson correlation coefficient 0.462, p < 0.05). Electron microscopy revealed signs of blood-brain barrier (BBB) impairments and immunofluorescence images showed glial cells activated in the hippocampus of APP/PS mice without EA, and serum diamine oxidase levels were increased in these mice; whereas EA treatment significantly relieved the above pathological changes. Our findings implied that EA decreases hippocampal inflammation of APP/PS1 by upregulating benificial  gut microbiota, reducing BBB and intestinal barrier dysfunction, thus alleviates postoperative cognitive dysfunction. This may provide a novel target in POCD management.

Intermittent Fasting on Neurologic Diseases: Potential Role of Gut Microbiota

As the global population ages, the prevalence of neurodegenerative diseases is surging. These disorders have a multifaceted pathogenesis, entwined with genetic and environmental factors. Emerging research underscores the profound influence of diet on the development and progression of health conditions. Intermittent fasting (IF), a dietary pattern that is increasingly embraced and recommended, has demonstrated potential in improving neurophysiological functions and mitigating pathological injuries with few adverse effects. Although the precise mechanisms of IF's beneficial impact are not yet completely understood, gut microbiota and their metabolites are believed to be pivotal in mediating these effects. This review endeavors to thoroughly examine current studies on the shifts in gut microbiota and metabolite profiles prompted by IF, and their possible consequences for neural health. It also highlights the significance of dietary strategies as a clinical consideration for those with neurological conditions.

Surgery-induced gut microbial dysbiosis promotes cognitive impairment via regulation of intestinal function and the metabolite palmitic amide

BACKGROUND

Perioperative neurocognitive disorders (PND) are the most common postoperative complications with few therapeutic options. Gut microbial dysbiosis is associated with neurological diseases; however, the mechanisms by which the microbiota regulates postoperative gastrointestinal and cognitive function are incompletely understood.

METHODS

Behavioral testing, MiSeq 16S rRNA gene sequencing, non-target metabolism, intestinal permeability detection, protein assays, and immunofluorescence staining were employed to discern the impacts of surgery on microbial profiles, intestinal barriers, serum metabolism, and the brain. Interventions in mice included fecal microbiota transplantation, the anti-inflammatory agent dexamethasone, Lactobacillus supplementation, indole propionic acid supplementation, and palmitic amide administration.

RESULTS

Surgery-induced cognitive impairment occurs predominantly in aged mice, and surgery-induced alterations in the microbiota composition profile exacerbate intestinal barrier disruption in aged mice. These adverse effects can be mitigated by transferring microbiota from young donors or by bolstering the intestinal barrier function using dexamethasone, Lactobacillus, or indole propionic acid. Moreover, microbiota composition profiles can be restored by transplanting feces from young mice to aged surgical mice, improving neuropathology and cognitive function, and these effects coincide with increased intestinal permeability. Metabolomic screening identified alterations in metabolites in mouse serum after surgery, especially the increase in palmitic amide. Palmitic amide levels in serum and brain can be decreased by transplanting feces from young mice to aged surgical mice. Oral palmitic amide exacerbates cognitive impairment and neuropathological changes in mice.

CONCLUSIONS

Gut microbial dysbiosis in mice after surgery is a key mechanism leading to cognition dysfunction, which disrupts the intestinal barrier and metabolic abnormalities, resulting in neuroinflammation and dendritic spine loss. Intestinal barrier damage and high level of palmitic amide in old mice may be the cause of high incidence of PND in the elderly. Preoperative microbiota regulation and intestinal barrier restoration may be of therapeutic benefit in preventing PND. Video Abstract.

General anesthesia alters the diversity and composition of the lung microbiota in rat

BACKGROUND

The lung microbiome plays a crucial role in human health and disease. Extensive studies have demonstrated that the disturbance of the lung microbiome influences immune response, cognition, and behavior. The goal of this study was to investigate the effect of general anesthetics on lung microbiome.

METHODS

Eight-week-old male SD rats received a continuous intravenous infusion of propofol or inhalation of isoflurane for 4 h. 16S rRNA gene amplification from BALF samples was used to investigate the changes in the lung microbiome after interventions. We further performed neurobehavioral assessments to find the differential strains' association with behavior disorder after isoflurane anesthesia.

RESULTS

The absolute and relative quantitation of 16S rRNA sequencing data showed that isoflurane altered the diversity and abundance of the lung microbiome in rats more than propofol. Elusimicrobia increased significantly in the isoflurane group. Both EPM and OFT results showed that rats exhibited depression-like behaviors after inhalation of isoflurane. In addition, significant differences were found in the COG/KO/MetaCyc/KEGG pathway enrichment analyses among the groups.

CONCLUSION

Continuous inhalation of isoflurane changed the diversity and composition of the lung microbiota in rats, resulting in post-anesthesia depression.

Preoperative Pain Facilitates Postoperative Cognitive Dysfunction via Periaqueductal Gray Matter-Dorsal Raphe Circuit

Postoperative cognitive dysfunction (POCD) is a medically induced, rapidly occurring postoperative disease, which is hard to recover and seriously threatens the quality of life, especially for elderly patients, so it is important to identify the risk factors for POCD and apply early intervention to prevent POCD. As we have known, pain can impair cognition, and many surgery patients experience different preoperative pain, but it is still unknown whether these patients are vulnerable for POCD. Here we found that chronic pain (7 days, but not 1 day acute pain) induced by Complete Freund's Adjuvant (CFA) injected in the hind paw of rats could easily induce spatial cognition and memory impairment after being exposed to sevoflurane anesthesia. Next, for the mechanisms, we focused on the Periaqueductal Gray Matter (PAG), a well-known pivotal nucleus in pain process. It was detected the existence of neural projection from ventrolateral PAG (vlPAG) to adjacent nucleus Dorsal Raphe (DR), the origin of serotonergic projection for the whole cerebrum, through virus tracing and patch clamp recordings. The Immunofluorescence staining and western blot results showed that Tryptophan Hydroxylase 2 (TPH2) for serotonin synthesis in the DR was increased significantly in the rats treated with CFA for 7 days and sevoflurane for 3 hours, while chemo-genetic inhibition of the vlPAG-DR projection induced obvious spatial learning and memory impairment. Our study suggests that preoperative chronic pain may facilitate cognitive function impairment after receiving anesthesia through the PAG-DR neural circuit, and preventative analgesia should be a considerable measure to reduce the incidence of POCD.

Role of Huangqin Decoction in Intestinal Homeostasis and Colon Carcinogenesis Based on "SREBP1 Cholesterol Metabolism Treg Cell Differentiation"

Objective

To explore the role of Huangqin Decoction in intestinal homeostasis maintenance and colon carcinogenesis based on "sterol regulatory element binding protein-1c (SREBP-1)-cholesterol metabolism regulatory T cell (Treg) differentiation."

Methods

It was decided to utilize a total of 50 healthy Wistar rats for the study, 20 of which were chosen at random to serve as controls, and 30 of which were used to create an intestinal homeostasis imbalance model. It was determined whether or not the modeling was successful by killing 10 rats from each of the two groups. The remaining 10 rats in the normal group were then employed as the control group for the experiment. The random number table method was used to split the rats into two groups: the Huangqin Decoction (n = 10) and the Natural Recovery (n = 10) groups. For seven days, participants in the Huangqin Decoction group received the herb, whereas those in the natural healing group received normal saline. The relative density of SREBP1, the levels of cholesterol ester (CE), free cholesterol (FC), total cholesterol (TC), and Treg cells were detected and compared.

Results

When compared to the control group, the relative density of SREBP1 increased significantly before administration in the Huangqin Decoction group and the natural recovery group, but decreased significantly after administration, with statistical significance (P < 0.05) in the Huangqin Decoction group and the natural recovery group; the Huangqin Decoction group and natural recovery group had significantly higher levels of CE, FC, and TC than the control group before to administration, and these levels increased significantly after administration. CE, FC, and TC levels in Huangqin Decoction and natural recovery groups were much lower than those in natural recovery groups, and the difference was statistically significant (P < 0.05), according to the results; Prior to administration, Treg cell levels in Huangqin Decoction group and the natural recovery group were significantly higher, and Treg cell levels in the Huangqin Decoction group and natural recovery group were significantly lower after administration; the decrease in the Huangqin Decoction group was significantly greater than that in natural recovery group. P < 0.05 indicated that the difference was significant.

Conclusion

Using Huangqin Decoction, one may efficiently regulate SREBP1, cholesterol metabolism, and Treg cell development, all of which play an important role in maintaining intestinal stability and minimizing the incidence of colon cancer.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

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.

The association between gut microbiota and postoperative delirium in patients

Postoperative delirium is a common postoperative complication in older patients, and its pathogenesis and biomarkers remain largely undetermined. The gut microbiota has been shown to regulate brain function, and therefore, it is vital to explore the association between gut microbiota and postoperative delirium. Of 220 patients (65 years old or older) who had a knee replacement, hip replacement, or laminectomy under general or spinal anesthesia, 86 participants were included in the data analysis. The incidence (primary outcome) and severity of postoperative delirium were assessed for two days. Fecal swabs were collected from participants immediately after surgery. The 16S rRNA gene sequencing was used to assess gut microbiota. Principal component analyses along with a literature review were used to identify plausible gut microbiota, and three gut bacteria were further studied for their associations with postoperative delirium. Of the 86 participants [age 71.0 (69.0-76.0, 25-75% percentile of quartile), 53% female], 10 (12%) developed postoperative delirium. Postoperative gut bacteria Parabacteroides distasonis was associated with postoperative delirium after adjusting for age and sex (Odds Ratio [OR] 2.13, 95% Confidence Interval (CI): 1.09-4.17, P = 0.026). The association between delirium and both Prevotella (OR: 0.59, 95% CI: 0.33-1.04, P = 0.067) and Collinsella (OR: 0.57, 95% CI: 0.27-1.24, P = 0.158) did not meet statistical significance. These findings suggest that there may be an association between postoperative gut microbiota, specifically Parabacteroides distasonis, and postoperative delirium. However, further research is needed to confirm these findings and better understand the gut-brain axis's role in postoperative outcomes.

Gut microbiota in perioperative neurocognitive disorders: current evidence and future directions

Perioperative neurocognitive disorders (PND) is a common surgical anesthesia complication characterized by impairment of memory, attention, language understanding and social ability, which can lead to a decline in the quality of life of patients, prolong the hospitalization period and increase the mortality rate. PND has a high incidence rate, which has a great impact on postoperative recovery and quality of life of patients, and has caused a heavy economic burden to society and families. In recent years, PND has become an important public health problem. The high risk population of PND is more prone to gut microbiota imbalance, and gut microbiota may also affect the inflammatory response of the central nervous system through the microbiota-gut-brain axis. Meanwhile, Neuroinflammation and immune activation are important mechanisms of PND. Regulating gut microbiota through probiotics or fecal bacteria transplantation can significantly reduce neuroinflammation, reduce the abnormal activation of immune system and prevent the occurrence of PND. This review summarizes the research progress of gut microbiota and PND, providing basis for the prevention and treatment of PND.

The contribution of probiotics for the double-edge effect of cefazolin on postoperative neurocognitive disorders by rebalancing the gut microbiota

Introduction

Emerging data suggest that perioperative gut dysbiosis is prevalent and may be associated with postoperative neurocognitive disorders (PND). Antibiotics and probiotics are key factors influencing the microbiota. Many antibiotics have anti-microorganisms and direct anti-inflammatory properties, which may have cognitive repercussions. NLRP3 inflammasome activation has been reported to be involved with cognitive deficits. This study aimed to determine the effect and mechanism of probiotics on neurocognitive problems associated with perioperative gut dysbiosis by the NLRP3 pathway.

Methods

In a randomized, controlled trial, adult male Kunming mice undergoing surgery were administered cefazolin, FOS + probiotics, CY-09, or a placebo in four distinct experimental cohorts. Fear conditioning (FC) tests evaluate learning and memory. Following FC tests to evaluate inflammatory response (IR) and the permeability of barrier systems, the hippocampus and colon were extracted, and feces were collected for 16 s rRNA.

Results

One week after surgery, surgery/anesthesia decreased the frozen behavior. Cefazolin attenuated this declination but aggravated postoperative freezing behavior 3 weeks after surgery. Probiotics ameliorated surgery/anesthesia-induced memory deficits and perioperative cefazolin-induced postoperative memory deficits 3 weeks after surgery. NLRP3, caspase-1, Interleukin-1β (IL-1β), and Interleukin-18 (IL-18) levels were increased 1 week after the hippocampus and colon surgery, which were attenuated by CY-09 and probiotics, respectively.

Discussion

Probiotics could correct dysbacteria and IR caused by surgery/anesthesia stress and cefazolin alone. These findings imply that probiotics are an efficient and effective way of maintaining the balance of gut microbiota, which may reduce NLRP3-related inflammation and alleviate PND.

Dexmedetomidine alleviates host ADHD-like behaviors by reshaping the gut microbiota and reducing gut-brain inflammation

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders that affects children and even continues into adulthood. Dexmedetomidine (DEX), a short-term sedative, can selectively activate the α2-adrenoceptor. Treatment with α2-adrenergic agonists in patients with ADHD is becoming increasingly common. However, the therapeutic potential of DEX for the treatment of ADHD is unknown. Here, we evaluated the effect of DEX on ADHD-like behavior in spontaneously hypertensive rats (SHRs), a widely used animal model of ADHD. DEX treatment ameliorated hyperactivity and spatial working memory deficits and normalized θ electroencephalogram (EEG) rhythms in SHRs. We also found that DEX treatment altered the gut microbiota composition and promoted the enrichment of beneficial gut bacterial genera associated with anti-inflammatory effects in SHRs. The gut pathological scores and permeability and the level of inflammation observed in the gut and brain were remarkably improved after DEX administration. Moreover, transplantation of fecal microbiota from DEX-treated SHRs produced effects that mimicked the therapeutic effects of DEX administration. Therefore, DEX is a promising treatment for ADHD that functions by reshaping the composition of the gut microbiota and reducing inflammation in the gut and brain.

Efficiency of probiotics in elderly patients undergoing orthopedic surgery for postoperative cognitive dysfunction: a study protocol for a multicenter, randomized controlled trial

BACKGROUND

Postoperative cognitive dysfunction (POCD) refers to a neurological dysfunction after a major surgery and anesthesia. It is common in elderly patients and is characterized by impairment in consciousness, orientation, thinking, memory, and executive function after surgical anesthesia. However, at present, there is no definite preventive or treatable strategy for it. Previous animal experiments showed that giving probiotics to mice before operation can prevent POCD, but there is a lack of clinical evidence. This study aims to intervene with the intestinal flora imbalance using probiotics during the perioperative period to reduce the incidence of POCD in elderly patients after orthopedic surgery and to provide new ideas and methods for the clinical prevention and treatment of POCD.

METHODS

A multicenter, double-blind, placebo-controlled clinical trial will be performed to evaluate the efficacy of probiotics in elderly patients undergoing orthopedic surgery. Participants (n = 220) will receive probiotics (Peifeikang, Live Combined Bifidobacterium, 210 mg per capsule, twice a day, four capsules each time, which contains Bifidobacterium longum, Lactobacillus acidophilus and Streptococcus faecalis no less than 1.0 × 10⁷ CFU viable bacteria respectively) or placebo from 1 day before surgery to 6 days after surgery. Neuropsychological tests will be performed 1 day before surgery and 1 week and 1 month after surgery. The main outcome of this study is the incidence of POCD 7 days after surgery. Our secondary objective is to assess the incidence of POCD 1 month after surgery; the cognitive status will be determined based on a telephone interview and will be evaluated via TICS-m; postoperative delirium will be assessed 7 days after surgery using the Confusion Assessment Method (CAM).

DISCUSSION

Discovering the correlation between the intestinal microbiota and POCD is an important breakthrough. Based on the key role of the intestinal microbiota in other cognitive disorders, we hope that probiotics can reduce its incidence in elderly orthopedic patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04017403. Registered on August 15, 2019.

The effects of microbiome-targeted therapy on cognitive impairment and postoperative cognitive dysfunction-A systematic review

BACKGROUND

The gut-brain axis involves bidirectional communication between the gut-microbiota and central nervous system. This study aimed to investigate whether probiotics and/or prebiotics, known as Microbiome-targeted Therapies (MTTs), improve cognition and prevent postoperative cognitive dysfunction (POCD).

METHODS

Relevant animal and human studies were identified using a systematic database search (PubMed, EMBASE, Cochrane Library, and Web of Science), focusing on the effects of MTTs on inflammation, perioperative and non-perioperative cognitive impairment. Screening and data extraction were conducted by two independent reviewers. The Risk of bias was assessed using the SYRCLE's risk of bias tool for animal studies. The revised Cochrane risk of bias tool (RoB 2) was used for human studies.

RESULTS

A total of 24 articles were selected; 16 of these involved animal studies, and 8 described studies in humans. In these papers, the use of MTTs consistently resulted in decreased inflammation in perioperative and non-perioperative settings. Out of 16 animal studies, 5 studies (2 associated with delirium and 3 studies related to POCD) were conducted in a perioperative setting. MTTs improved perioperative cognitive behavior and reduced inflammation in all 5 animal studies. Eleven animal studies were conducted in a non-perioperative setting. In all of these studies, MTTs showed improvement in learning and memory function. MTTs showed a positive effect on levels of pro-inflammatory cytokines and biomarkers related to cognitive function. Among the 8 human studies, only one study examined the effects of perioperative MTTs on cognitive function. This study showed a reduced incidence of POCD along with improved cognitive function. Of the remaining 7 studies, 6 suggested that MTTs improved behavioral test results and cognition in non-perioperative environments. One study failed to show any significant differences in memory, biomarkers of inflammation, or oxidative factors.

CONCLUSION

In the studies we examined, most showed that MTTs decrease inflammation by down-regulating inflammatory cytokines and oxidative stress in both perioperative and non-perioperative settings. In general, MTTs also seem to have a positive effect on cognition through neural, immune, endocrine, and metabolic pathways. However, these effects have not yet resulted in a consensus regarding preventative strategies or treatments. Based on these current research results, MTTs could be a potential new preventative strategy for cognitive impairment after surgery.

The association between gut microbiota and postoperative delirium in patients

Postoperative delirium is one of the most common postoperative complications in older patients. Its pathogenesis and biomarkers, however, remain largely undetermined. Majority of human microbiota is gut microbiota and gut microbiota has been shown to regulate brain function. Therefore, this study aimed to determine the association between gut microbiota and postoperative delirium in patients. Of 220 patients (65 years old or older) who had a knee replacement, hip replacement, or laminectomy under general or spinal anesthesia, 86 participants were included in the data analysis. The incidence (primary outcome) and severity of postoperative delirium was assessed for two days. Fecal swabs were collected from participants immediately after surgery. The 16S rRNA gene sequencing was used to assess gut microbiota. Using principal component analyses along with a literature review to identify biologically plausible mechanisms, and three bacterials were studied for their associations with postoperative delirium. Of the 86 participants [age 71.0 (69.0-76.0, 25%-75% percentile of quartile), 53% female], ten (12%) developed postoperative delirium. Postoperative gut bacteria Parabacteroides distasonis (Odds Ratio [OR] 2.13, 95% Confidence Interval (CI): 1.09-4.17, P = 0.026) was associated with postoperative delirium after adjusting for age and sex. The association between delirium and both Prevotella (OR: 0.59, 95% CI: 0.33-1.04, P = 0.067) and Collinsella (OR: 0.57, 95% CI: 0.27-1.24, P = 0.158) did not meet statistical significance. These findings suggest that postoperative gut microbiota (e.g., Parabacteroides distasonis ) may serve as biomarkers in the pathogenesis of postoperative delirium, pending confirmative studies.

Perioperative probiotics attenuates postoperative cognitive dysfunction in elderly patients undergoing hip or knee arthroplasty: A randomized, double-blind, and placebo-controlled trial

Background

Postoperative cognitive dysfunction (POCD) is a common complication in elderly patients following surgery. The preventive and/or treatment strategies for the incidence remain limited.

Objective

This study aimed to investigate the preventive effect of perioperative probiotic treatment on POCD in elderly patients undergoing hip or knee arthroplasty.

Methods

After obtaining ethical approval and written informed consent, 106 patients (age ≥60 years) were recruited, who scheduled elective hip or knee arthroplasty, from 16 March 2021 to 25 February 2022 for this randomized, double-blind, and placebo-controlled trial. They were randomly assigned with a 1:1 ratio to receive either probiotics or placebo treatment (four capsules, twice/day) from hospital admission until discharge. Cognitive function was assessed with a battery of 11 neuropsychological tests on the admission day and the seventh day after surgery, respectively.

Results

A total of 96 of 106 patients completed the study, and their data were finally analyzed. POCD occurred in 12 (26.7%) of 45 patients in the probiotic group and 29 (56.9%) of 51 patients in the placebo group (relative risk [RR], 0.47 [95% confidence interval [CI], 0.27 to 0.81]; P = 0.003). Among them, mild POCD occurred in 11 (24.4%) in the probiotic group and 24 (47.1%) in the placebo group (RR, 0.52 [95% CI, 0.29 to 0.94]; P = 0.022). No significant difference in severe POCD incidence was found between the two groups (P = 0.209). Compared with the placebo group, the verbal memory domain cognitive function was mainly improved in the probiotic group.

Conclusion

Probiotics may be used perioperatively to prevent POCD development and improve verbal memory performance in elderly patients receiving hip or knee arthroplasty.

Clinical trial registration

www.chictr.org.cn, identifier: ChiCTR2100045620.

Heterogeneous nuclear ribonucleoprotein A2/B1 as a novel biomarker in elderly patients for the prediction of postoperative neurocognitive dysfunction: A prospective nested case-control study

Background and objective

Postoperative neurocognitive dysfunction (PND) occurs in up to 54% of older patients, giving rise to the heavy psychological and economic burdens to patients and society. To date, the development of PND biomarkers remains a challenge. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1) is an RNA-binding protein whose prion-like structure is prone to mutation and hence leads to neurodegenerative diseases, but its expression changes in PND remains unclear. Here, we detect the preoperative hnRNPA2/B1 level in patients with PND, and to explore its value in the prediction and diagnosis of PND.

Methods

The study included 161 elderly patients undergoing lumbar decompression and fusion in Nankai University Affinity the Third Central Hospital from September 2021 to July 2022. Neuropsychological and psychometric evaluations were performed before surgery, 1 week and 3 months after surgery to diagnose the occurrence of PND, then the peripheral blood was collected from patients before induction of anesthesia. The concentration in plasma of hnRNPA2/B1 and amyloid-β 42 were determined by enzyme-linked immunosorbent assay. The median fluorescence intensity and mRNA levels of hnRNPA2/B1 in peripheral blood mononuclear cells was detected by indirect intracellular staining flow cytometry and quantitative real-time PCR, respectively.

Results

The preoperative hnRNPA2/B1 level in patients with PND was higher both in short-time and long-time follow-up. We found significantly higher concentrations of hnRNPA2/B1 in PND at 7 days after surgery (median, 72.26 pg/mL vs. 54.95 pg/mL, p = 0.022) compared with patients without PND, and so as 3 months after surgery (median, 102.93 pg/mL vs. 56.38 pg/mL, p = 0.012). The area under the curve (AUC) was predicted to be 0.686 at 7 days after surgery and 0.735 at 3 months. In addition, when combining several clinical information, the diagnostic efficiency of hnRNPA2/B1 for PND could further increase (AUC, 0.707 at 7 days, 0.808 at 3 months).

Conclusion

Based on the findings reported here, hnRNPA2/B1 may serve as a new and powerful predictive biomarker to identify elderly patients with PND.

Effects of different types of non-cardiac surgical trauma on hippocampus-dependent memory and neuroinflammation

Background

Older individuals have been reported to suffer from cognitive disorders after surgery. Various types of surgical trauma have been used to establish postoperative cognitive dysfunction (POCD) animal models in preclinical studies. However, few comparative analyses of these animal models were conducted.

Methods

Tibial surgery, abdominal surgery, and extended abdominal surgery were performed on aged ICR mice to establish POCD models. Behavioral tests included open field, novel object recognition, fear conditioning, and Morris water maze tests. The Z-score methodology was adopted to obtain a comprehensive and integrated memory performance profile. The changes in hippocampal neuroinflammation were analyzed by ELISA, PCR, and immunofluorescence.

Results

In this study, we found that each type of non-cardiac surgical trauma has a different effects on locomotor activity. Tibial and extended abdominal surgeries led to more significant cognitive impairment than abdominal surgery. Inflammatory cytokines peaked on postoperative day 1 and decreased to control levels on days 3 and 7. Hippocampal neuroinflammation indicators between the three surgery types on postoperative day 1 had no statistical differences.

Conclusion

Overall, the type and intensity of non-cardiac surgical trauma can affect cognitive behavioral outcomes and central inflammation. The shortcomings and emerging issues of POCD animal research methods need to be further studied and solved.

Preoperative Intestinal Microbiome and Metabolome in Elderly Patients with Delayed Neurocognitive Recovery

BACKGROUND

Delayed neurocognitive recovery (dNCR) is a common complication of the central nervous system in elderly patients. Currently, it is not clear whether the occurrence of dNCR is associated with the intestinal microbiota and its related metabolites. This study investigated the preoperative intestinal microflora and faecal metabolites of dNCR patients.

METHODS

Twenty-two elderly urological patients were divided into a dNCR group (D group) and a non-dNCR group (ND group) according to the postoperative Mini-Mental State Examination (MMSE) score on the first and third day after surgery. A postoperative MMSE score ≤ 2 points compared with the preoperative score was considered evidence of dNCR. We used a comprehensive method that combined 16S rRNA gene sequencing and untargeted metabolomics to study the preoperative intestinal microflora and faecal metabolites of the two groups, and conducted correlation analysis between them.

RESULTS

Compared with the D group, the microbial community in the ND group was more abundant. At the family level, the ND group was significantly enriched in Lachnospiraceae, Peptostreptococcaceae and Muribaculaceae. At the genus level, the faecal microbiota of the ND group was differentially enriched in Agathobacter, Dorea, Fusicatenibacter, Coprococcus_2 and Romboutsia while that of the D group was differentially enriched in Anaerofilum. Untargeted metabolomics revealed significant differences in eight different metabolites between the two groups, including ribose, ethanol, leucine, maltose, pentadecanoic acid, malonic acid 1,3,4-dihydroxybenzoic acid and 3-hydroxypalmitic acid. In addition, differential metabolites were associated with the abundance of specific bacteria.

CONCLUSIONS

The occurrence of dNCR may be associated with the intestinal flora and its related metabolite composition of patients before surgery.

Intestinal dysbacteriosis-propelled T helper 17 cells activation mediate the perioperative neurocognitive disorder induced by anesthesia/surgery in aged rats

BACKGROUND

Perioperative neurocognitive disorders (PND) is a common postoperative disease in elderly patients, but its pathogenesis remains unclear.

METHODS

Exploratory laparotomy was performed to establish PND model under sevoflurane anesthesia. 16S rRNA high-throughput sequencing was used to detect the changes of intestinal flora. Antibiotics were used to relatively eliminate intestinal flora before anesthesia/surgery, and behavior tests, such as open field, Y maze, and fear conditioning tests were applied to detect the changes of memory ability. The number of Th17 cells and Foxp3 cells was detected by flow cytometry in the Peyer's patches (PP), mesenteric lymph nodes (MLN), blood and brain. Western blot was used to detect the expression of IL17, IL17RA, IL6 and IL10 in the hippocampus. Immunofluorescence was used to detect the expression of IL17, IL17R and IBA1 (ionized calcium binding adaptor molecule1) in the hippocampus.

RESULTS

Anesthesia/surgery caused intestinal flora imbalance and induced neurocognitive impairment, increased the number of Th17 cells in the PP, MLN, blood and brain, increased the level of IL17, IL17R and inflammatory factors production in the hippocampus. Antibiotics administration before anesthesia/surgery significantly decreased the number of Th17 cells and the level of IL17, IL17R and inflammatory factors production, and improved the memory function. In addition, we found that IL17R was co-labeled with IBA1 in a large amount in the hippocampus through immunofluorescence double-staining.

CONCLUSION

Our study suggested that intestinal dysbacteriosis-propelled T helper 17 cells activation and IL17 secretion might play an important role in the pathogenesis of PND induced by anesthesia/surgery in aged rats.

Progress in the correlation of postoperative cognitive dysfunction and Alzheimer's disease and the potential therapeutic drug exploration

Postoperative cognitive dysfunction (POCD) is a decrease in mental capacity that can occur days to weeks after a medical procedure and may become permanent and rarely lasts for a longer period of time. With the continuous development of research, various viewpoints in academic circles have undergone subtle changes, and the role of anesthesia depth and anesthesia type seems to be gradually weakened; Alzheimer's disease (AD) is a latent and progressive neurodegenerative disease in the elderly. The protein hypothesis and the synaptic hypothesis are well-known reasons. These changes will also lead to the occurrence of an inflammatory cascade. The exact etiology and pathogenesis need to be studied. The reasonable biological mechanism affecting brain protein deposition, neuroinflammation, and acetylcholine-like effect has a certain relationship between AD and POCD. Whereas there is still further uncertainty about the mechanism and treatment, and it is elusive whether POCD is a link in the continuous progress of AD or a separate entity, which has doubts about the diagnosis and treatment of the disease. Therefore, this review is based on the current common clinical characteristics of AD and POCD, and pathophysiological research, to search for their common points and explore the direction and new strategies for future treatment.

Gut Microbiome in Anesthesiology and Pain Medicine

The gut microbiome plays critical roles in human health and disease. Recent studies suggest it may also be associated with chronic pain and postoperative pain outcomes. In animal models, the composition of the gut microbiome changes after general anesthesia and affects the host response to medications, including anesthetics and opioids. In humans, the gut microbiome is associated with the development of postoperative pain and neurocognitive disorders. Additionally, the composition of the gut microbiome has been associated with pain conditions including visceral pain, nociplastic pain, complex regional pain syndrome, and headaches, partly through altered concentration of circulating bacterial-derived metabolites. Furthermore, animal studies demonstrate the critical role of the gut microbiome in neuropathic pain via immunomodulatory mechanisms. This article reviews basic concepts of the human gut microbiome and its interactions with the host and provide a comprehensive overview of the evidence linking the gut microbiome to anesthesiology, critical care, and pain medicine.

Mechanical Bowel Preparation Is a Risk Factor for Postoperative Delirium as It Alters the Gut Microbiota Composition: A Prospective Randomized Single-Center Study

Background and Objective

Postoperative delirium (POD) is a frequent complication in patients undergoing gastrectomy. Increasing evidence suggests that abnormal gut microbiota composition may contribute to its morbidity. However, it is unclear whether mechanical bowel preparation would cause postoperative delirium by altering the gut microbiota of patients. This study aimed to investigate the association between mechanical bowel preparation and postoperative delirium in patients undergoing gastrectomy.

Methods

A prospective randomized single-center study was performed. A total of 81 patients with gastric cancer were enrolled and randomly assigned to two groups: preparation group and non-preparation group according to whether the patient received MBP before surgery. To diagnose postoperative delirium, we used the 3-Min Diagnostic Interview for Confusion Assessment Method-defined delirium for five successive days after surgery. 16s rRNA gene sequencing was used to investigate changes in the intestinal bacteria. The linear discriminant analysis and effect size (LefSe) analysis were also used to identify the different taxa of fecal microbiota between the postoperative delirium and non-postoperative delirium groups.

Results

We found that there was a significant difference in β-diversity of the gut microbiota between the preparation group and non-preparation group (P = 0.048). Furthermore, patients in the preparation group had a much higher rate of postoperative delirium (13/40, 32.5%) compared with that in non-preparation groups (4/41, 9.8%). Multivariate regression analysis adjusted by other risk factors indicated that mechanical bowel preparation was associated with the occurrence of delirium (odds ratio = 4.792; 95% confidence interval: 1.274–18.028; P = 0.020). When comparing the gut microbiota of patients with and without POD, Bacteroides and Veillonella (genus), which were higher in the preparation group, were also higher in delirium patients (P < 0.05). Genus Olsenella was both relatively higher in the non-preparation group and non-POD group (P < 0.05).

Conclusion

Mechanical bowel preparation not only altered the gut microbiota composition of patients with gastric cancer but also increased the incidence of postoperative delirium. Among all the gut microbiota altered by mechanical bowel preparation, Bacteroides and Veillonella genus might be a risk factor of POD. Genus Olsenella might be a beneficial bacteria to reduce the incidence of POD.

Progress in Research on the Effect of Melatonin on Postoperative Cognitive Dysfunction in Older Patients

Postoperative cognitive dysfunction (POCD) is a common complication of the central nervous system in elderly patients after operation. It will prolong the length of stay, reduce the independence and quality of daily life, and increase the risk of death. However, at present, there is a lack of safe and effective ideal drugs for the prevention and treatment of POCD. Melatonin is one of the hormones secreted by the pineal gland of the brain, which has the functions of regulating circadian rhythm, anti-inflammation, anti-oxidation, anti-apoptosis, and so on. Some recent studies have shown that MT can prevent and treat POCD by adjusting circadian rhythm, restoring cholinergic system function, neuroprotection, and so on. This article will introduce POCD, melatonin and the mechanism of melatonin on POCD, respectively, to provide a basis for clinical prevention and treatment of POCD in the elderly.

General anesthesia bullies the gut: a toxic relationship with dysbiosis and cognitive dysfunction

Perioperative neurocognitive disorder (PND) is a common surgery outcome affecting up to a third of the elderly patients, and it is associated with high morbidity and increased risk for Alzheimer's disease development. PND is characterized by cognitive impairment that can manifest acutely in the form of postoperative delirium (POD) or after hospital discharge as postoperative cognitive dysfunction (POCD). Although POD and POCD are clinically distinct, their development seems to be mediated by a systemic inflammatory reaction triggered by surgical trauma that leads to dysfunction of the blood-brain barrier and facilitates the occurrence of neuroinflammation. Recent studies have suggested that the gut microbiota composition may play a pivotal role in the PND development by modulating the risk of neuroinflammation establishment. In fact, modulation of gut microbiome composition with pre- and probiotics seems to be effective for the prevention and treatment of PND in animals. Interestingly, general anesthetics seem to have major responsibility on the gut microbiota composition changes following surgery and, consequently, can be an important element in the process of PND initiation. This concept represents an important milestone for the understanding of PND pathogenesis and may unveil new opportunities for the development of preventive or mitigatory strategies against the development of these conditions. The aim of this review is to discuss how anesthetics used in general anesthesia can interact and alter the gut microbiome composition and contribute to PND development by favoring the emergence of neuroinflammation.

Probiotics attenuate alcohol-induced muscle mechanical hyperalgesia: Preliminary observations

Alcohol use disorder (AUD) is a major health problem that causes millions of deaths annually world-wide. AUD is considered to be a chronic pain disorder, that is exacerbated by alcohol withdrawal, contributing to a high (∼80%) relapse rate. Chronic alcohol consumption has a marked impact on the gut microbiome, recognized to have a significant effect on chronic pain. We tested the hypothesis that modulating gut microbiota through feeding rats with probiotics can attenuate alcohol-induced muscle mechanical hyperalgesia. To test this hypothesis, rats were fed alcohol (6.5%, 4 days on 3 days off) for 3 weeks, which induced skeletal muscle mechanical hyperalgesia. Following alcohol feeding, at which time nociceptive thresholds were ∼37% below pre-alcohol levels, rats received probiotics in their drinking water, either Lactobacillus Rhamnosus GG (Culturelle) or De Simone Formulation (a mixture of 8 bacterial species) for 8 days; control rats received plain water to drink. When muscle mechanical nociceptive threshold was evaluated 1 day after beginning probiotic feeding, nociceptive thresholds were significantly higher than rats not receiving probiotics. Mechanical nociceptive thresholds continued to increase during probiotic feeding, with thresholds approaching pre-alcohol levels 5 days after starting probiotics; nociceptive threshold in rats not receiving probiotics remained low. After probiotics were removed from the drinking water, nociceptive thresholds gradually decreased in these two groups, although they remained higher than the group not treated with probiotic (21 days after ending alcohol feeding). These observations suggest that modification of gut microbiota through probiotic feeding has a marked effect on chronic alcohol-induced muscle mechanical hyperalgesia. Our results suggest that administration of probiotics to individuals with AUD may reduce pain associated with alcohol consumption and withdrawal, and may be a novel therapeutic intervention to reduce the high rate of relapse seen in individuals with AUD attempting to abstain from alcohol.

Human Umbilical Cord Mesenchymal Stem Cells Improve Locomotor Function in Parkinson’s Disease Mouse Model Through Regulating Intestinal Microorganisms

Parkinson’s disease (PD) is a progressive neurological disorder characterized by loss of neurons that synthesize dopamine, and subsequent impaired movement. Umbilical cord mesenchymal stem cells (UC-MSCs) exerted neuroprotection effects in a rodent model of PD. However, the mechanism underlying UC-MSC-generated neuroprotection was not fully elucidated. In the present study, we found that intranasal administration of UC-MSCs significantly alleviated locomotor deficits and rescued dopaminergic neurons by inhibiting neuroinflammation in a PD mouse model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, a toxic agent which selectively destroys nigrostriatal neurons but does not affect dopaminergic neurons elsewhere). Furthermore, UC-MSC treatment altered gut microbiota composition characterized by decreased phylum Proteobacteria, class Gammaproteobacteria, family Enterobacteriaceae, and genus Escherichia-Shigella. In addition, the neurotransmitter dopamine in the striatum and 5-hydroxytryptamine in the colon were also modulated by UC-MSCs. Meanwhile, UC-MSCs significantly maintained intestinal goblet cells, which secrete mucus as a mechanical barrier against pathogens. Furthermore, UC-MSCs alleviate the level of TNF-α and IL-6 as well as the conversion of NF-κB expression in the colon, indicating that inflammatory responses were blocked by UC-MSCs. PICRUSt showed that some pathways including bacterial invasion of epithelial cells, fluorobenzoate degradation, and pathogenic Escherichia coli infection were significantly reversed by UC-MSCs. These data suggest that the beneficial effects were detected following UC-MSC intranasal transplantation in MPTP-treated mice. There is a possible neuroprotective role of UC-MSCs in MPTP-induced PD mice by cross talk between the brain and gut.

Gut-Brain Axis: Possible Role of Gut Microbiota in Perioperative Neurocognitive Disorders

Aging is becoming a severe social phenomenon globally, and the improvements in health care and increased health awareness among the elderly have led to a dramatic increase in the number of surgical procedures. Because of the degenerative changes in the brain structure and function in the elderly, the incidence of perioperative neurocognitive disorders (PND) is much higher in elderly patients than in young people following anesthesia/surgery. PND is attracting more and more attention, though the exact mechanisms remain unknown. A growing body of evidence has shown that the gut microbiota is likely involved. Recent studies have indicated that the gut microbiota may affect postoperative cognitive function via the gut-brain axis. Nonetheless, understanding of the mechanistic associations between the gut microbiota and the brain during PND progression remains very limited. In this review, we begin by providing an overview of the latest progress concerning the gut-brain axis and PND, and then we summarize the influence of perioperative factors on the gut microbiota. Next, we review the literature on the relationship between gut microbiota and PND and discuss how gut microbiota affects cognitive function during the perioperative period. Finally, we explore effective early interventions for PND to provide new ideas for related clinical research.

Isoorientin Affects Markers of Alzheimer's Disease via Effects on the Oral and Gut Microbiota in APP/PS1 Mice

BACKGROUND

There is growing evidence of strong associations between the pathogenesis of Alzheimer's disease (AD) and dysbiotic oral and gut microbiota. Recent studies demonstrated that isoorientin (ISO) is anti-inflammatory and alleviates markers of AD, which were hypothesized to be mediated by the oral and gut microbiota.

OBJECTIVES

We studied the effects of oral administration of ISO on AD-related markers and the oral and gut microbiota in mice.

METHODS

Eight-month-old amyloid precursor protein/presenilin-1 (AP) transgenic male mice were randomly allocated to 3 groups of 15 mice each: vehicle (AP) alone or with a low dose of ISO (AP + ISO-L; 25 mg/kg) or a high dose of ISO (AP + ISO-H; 50 mg/kg). Age-matched wild-type (WT) C57BL/6 male littermates were used as controls. The 4 groups were treated intragastrically with ISO or sterilized ultrapure water for 2 months. AD-related markers in the brain, serum, colon, and liver were analyzed with immunohistochemical and histochemical staining, Western blotting, and ELISA. Oral and gut microbiotas were analyzed using 16S ribosomal RNA gene sequencing.

RESULTS

The high-dose ISO treatment significantly decreased amyloid beta 42-positive deposition by 38.1% and 45.2% in the cortex and hippocampus, respectively, of AP mice (P < 0.05). Compared with the AP group, both ISO treatments reduced brain phospho-Tau, phosphor-p65, phosphor-inhibitor of NF-κB, and brain and serum LPS and TNF-α by 17.9%-72.5% and increased brain and serum IL-4 and IL-10 by 130%-210% in the AP + ISO-L and AP + ISO-H groups (P < 0.05). Abundances of 26, 25, and 23 microbial taxa in oral, fecal and cecal samples, respectively, were increased in both the AP + ISO-L and AP + ISO-H groups relative to the AP group [linear discriminant analysis (LDA) >3.0; P < 0.05]. Gram-negative bacteria, Alteromonas, Campylobacterales, and uncultured Bacteroidales bacterium were positively correlated (rho = 0.28-0.59; P < 0.05) with the LPS levels and responses of inflammatory cytokines.

CONCLUSIONS

The microbiota-gut-brain axis is a potential mechanism by which ISO reduces AD-related markers in AP mice.

Cefazolin Improves Anesthesia and Surgery-Induced Cognitive Impairments by Modulating Blood-Brain Barrier Function, Gut Bacteria and Short Chain Fatty Acids

Emerging evidence suggests that anesthesia and surgery may induce gut dysbiosis. Gut dysbiosis leads to imbalance in circulating contents of microbiota-derived metabolites and disrupts the integrity of the blood-brain barrier (BBB), contributing to postoperative cognitive dysfunction (POCD). The composition of gut microbiota may be influenced by various antibiotics. However, how perioperative use of antibiotics affects POCD needs more explorations. In the present study, we explored the effect of cefazolin, a common antibiotic used in perioperative period, on cognitive function, BBB integrity, gut bacteria and short chain fatty acids (SCFAs), a group of widely studied metabolites in aged mice, using 18-month-old male mice. Significant BBB disruptions and decreased levels of tight junction proteins, zonula occludens-1 (ZO-1) and Occludin (OCLN) were seen in the mice of POCD model. Cefazolin treatment attenuated these changes induced by anesthesia and surgery. Furthermore, cefazolin reversed the changes in several fecal bacteria (β-, γ/δ-, ε-Proteobacteria, and Bacteroidetes) as determined by qPCR tests. Analysis of plasma SCFAs showed that almost all types of SCFAs were reduced in POCD and cefazolin administration reversed the changes in expression of the two most abundant SCFAs (acetic and propionic acids). In conclusion, this study demonstrated that cefazolin improved POCD. Mechanistically, cefazolin suppressed the disruption of BBB, gut microbiota or SCFAs, thereby ameliorating POCD.

MD2 contributes to the pathogenesis of perioperative neurocognitive disorder via the regulation of α5GABAA receptors in aged mice

BACKGROUND

Perioperative neurocognitive disorder (PND) is a long-term postoperative complication in elderly surgical patients. The underlying mechanism of PND is unclear, and no effective therapies are currently available. It is believed that neuroinflammation plays an important role in triggering PND. The secreted glycoprotein myeloid differentiation factor 2 (MD2) functions as an activator of the Toll-like receptor 4 (TLR4) inflammatory pathway, and α5GABA_A receptors (α5GABA_ARs) are known to play a key role in regulating inflammation-induced cognitive deficits. Thus, in this study, we aimed to investigate the role of MD2 in PND and determine whether α5GABA_ARs are involved in the function of MD2.

METHODS

Eighteen-month-old C57BL/6J mice were subjected to laparotomy under isoflurane anesthesia to induce PND. The Barnes maze was used to assess spatial reference learning and memory, and the expression of hippocampal MD2 was assayed by western blotting. MD2 expression was downregulated by bilateral injection of AAV-shMD2 into the hippocampus or tail vein injection of the synthetic MD2 degrading peptide Tat-CIRP-CMA (TCM) to evaluate the effect of MD2. Primary cultured neurons from brain tissue block containing cortices and hippocampus were treated with Tat-CIRP-CMA to investigate whether downregulating MD2 expression affected the expression of α5GABA_ARs. Electrophysiology was employed to measure tonic currents. For α5GABA_ARs intervention experiments, L-655,708 and L-838,417 were used to inhibit or activate α5GABA_ARs, respectively.

RESULTS

Surgery under inhaled isoflurane anesthesia induced cognitive impairments and elevated the expression of MD2 in the hippocampus. Downregulation of MD2 expression by AAV-shMD2 or Tat-CIRP-CMA improved the spatial reference learning and memory in animals subjected to anesthesia and surgery. Furthermore, Tat-CIRP-CMA treatment decreased the expression of membrane α5GABA_ARs and tonic currents in CA1 pyramidal neurons in the hippocampus. Inhibition of α5GABA_ARs by L-655,708 alleviated cognitive impairments after anesthesia and surgery. More importantly, activation of α5GABA_ARs by L-838,417 abrogated the protective effects of Tat-CIRP-CMA against anesthesia and surgery-induced spatial reference learning and memory deficits.

CONCLUSIONS

MD2 contributes to the occurrence of PND by regulating α5GABA_ARs in aged mice, and Tat-CIRP-CMA is a promising neuroprotectant against PND.

Clemastine Ameliorates Perioperative Neurocognitive Disorder in Aged Mice Caused by Anesthesia and Surgery

Perioperative neurocognitive disorder (PND) leads to progressive deterioration of cognitive function, especially in aged patients. Demyelination is closely associated with cognitive dysfunction. However, the relationship between PND and demyelination remains unclear. Here we showed that demyelination was related to the pathogenesis of PND. Clemastine, an antihistamine with potency in remyelination, was predicted to have a potential therapeutic effect on PND by next-generation sequencing and bioinformatics in our previous study. In the present study, it was given at 10 mg/kg per day for 2 weeks to evaluate the effects on PND in aged mice. We found that clemastine ameliorated PND and reduced the expression levels of inflammatory factors such as tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β). Further investigation suggested clemastine increased the expression of oligodendrocyte transcription factor 2 (OLIG2) and myelin basic protein (MBP) to enhance remyelination by inhibiting the overactivation of the WNT/β-catenin pathway. At the same time, the expression of post-synaptic density protein 95 (PSD95, or DLG4), brain-derived neurotrophic factor (BDNF), synaptosomal-associated protein 25 (SNAP25) and neuronal nuclei (NEUN) were also improved. Our results suggested that clemastine might be a therapy for PND caused by anesthetic and surgical factors in aged patients.

Effect of Anesthesia/Surgery on Gut Microbiota and Fecal Metabolites and Their Relationship With Cognitive Dysfunction

Aims: Post-operative cognitive dysfunction (POCD) is the decline in cognitive function of the central nervous system (CNS) after anesthesia/surgery. The present study explored whether anesthesia/surgery altered gut microbiota and fecal metabolites, examining their associations with risk factors of cognitive dysfunction in aged mice.

Methods: Sixteen-month-old C57BL/6 mice underwent abdominal surgery under isoflurane anesthesia to establish an animal model of POCD. The Morris water maze test (MWMT) was used as an indicator of memory after surgery. The effects of anesthesia/surgical interventions on gut microbiota, fecal metabolites, hippocampus, and serum levels of inflammatory factors were examined.

Results: The anesthesia/surgery induced more serious POCD behavior, increasing brain interleukin (IL)-6, and IL-1β levels than sham control mice. The relative abundance of bacterial genera Bacteroidales_unclassified, Mucispirillum, and Clostridiales_unclassified declined, whereas that of Escherichia–Shigella, actinomyces, Ruminococcus_gnavus_group, and Lachnospiraceae_FCS020_group were enriched after anesthesia/surgery compared to the baseline controls. Liquid chromatography–mass spectrometry (LC–MS) showed that the metabolites differed between post-anesthesia+surgery (post_A + S) and baseline samples and were associated with the fecal metabolism of tryptophan, kynurenic acid, N-oleoyl γ-aminobutyric acid (GABA), 2-indolecarboxylic acid, and glutamic acid. Furthermore, the differential metabolites were associated with alterations in the abundance of specific bacteria. These results indicate that the POCD intervention may be achieved by targeting specific bacteria associated with neurotransmitter metabolism.

Conclusions: A transient cognitive disturbance induced by anesthesia/surgery may be associated with unfavorable alterations in gut microbiota and fecal metabolites, thereby contributing to the POCD development.

Postoperative pain and the gut microbiome

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Poorly controlled postoperative pain remains a major unresolved challenge globally.

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The gut microbiome impacts on inflammatory pain and neuropathic pain.

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Microbiota metabolites can regulate peripheral and central sensitisation.

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Stress is linked to both postoperative pain and an altered gut microbiome.

In excess of 300 million surgical procedures are undertaken worldwide each year. Despite recognition of the prevalence of postoperative pain, and improvements in pain management techniques, poorly controlled postoperative pain remains a major unresolved challenge globally. An estimated 71% and 51% of patients experience moderate to severe pain after surgery in in-patient and outpatient settings, respectively. Inadequately controlled pain after surgery is associated with significant perioperative morbidity including myocardial infarction and pulmonary complications.

As many as 20–56% of patients develop chronic pain after commonly performed procedures such as hernia repair, hysterectomy, and thoracotomy. Traditional analgesics and interventions are often ineffective or partially effective in the treatment of postoperative pain, resulting in a chronic pain condition with related socio-economic impacts and reduced quality of life for the patient. Such chronic pain which occurs after surgery is referred to as Persistent Post-Surgical Pain (PPSP). The complex ecosystem that is the gastrointestinal microbiota (including bacteria, fungi, viruses, phage) plays essential roles in the maintenance of the healthy state of the host. A disruption to the balance of this microbiome has been implicated not only in gastrointestinal disease but also neurological disorders including chronic pain. The influence of the gut microbiome is well documented in the context of visceral pain from the gastrointestinal tract while a greater understanding is emerging of the impact on inflammatory pain and neuropathic pain (both of which can occur during the perioperative period). The gut microbiome is an essential source for driving immune maturation and maintaining appropriate immune response. Given that inflammatory processes have been implicated in postoperative pain, aberrant microbiome profiles may play a role in the development of this type of pain. Furthermore, the microorganisms in our gut produce metabolites, neurotransmitters, and neuromodulators which interact with their receptors to regulate peripheral and central sensitisation associated with chronic pain. Microbiota-derived mediators can also regulate neuroinflammation, which is associated with activation of microglia as well as infiltration by immune cells, known to modulate the development and maintenance of central sensitisation. Moreover, risk factors for developing postoperative pain include anxiety, depression, and increased stress response. These central nervous system-related disorders have been associated with an altered gut microbiome and microbiome targeted intervention studies indicate improvements. Females are more likely to suffer from postoperative pain. As gonadal hormones are associated with a differential microbiome and pre-clinical studies show that male microbiome confers protection from inflammatory pain, it is possible that the composition of the microbiome and its by-products contribute to the increased risk for the development of postoperative pain. Very little evidence exists relating the microbiome to somatic pain. Here we discuss the potential role of the gut microbiome in the aetiology and pathophysiology of postoperative pain in the context of other somatic pain syndromes and what is known about microbe-neuron interactions. Investigations are needed to determine the specific role of the gut microbiome in this type of pain which may help inform the development of preventative interventions as well as management strategies to improve patient outcome.

Vagus nerve stimulation in brain diseases: Therapeutic applications and biological mechanisms

Brain diseases, including neurodegenerative, cerebrovascular and neuropsychiatric diseases, have posed a deleterious threat to human health and brought a great burden to society and the healthcare system. With the development of medical technology, vagus nerve stimulation (VNS) has been approved by the Food and Drug Administration (FDA) as an alternative treatment for refractory epilepsy, refractory depression, cluster headaches, and migraines. Furthermore, current evidence showed promising results towards the treatment of more brain diseases, such as Parkinson's disease (PD), autistic spectrum disorder (ASD), traumatic brain injury (TBI), and stroke. Nonetheless, the biological mechanisms underlying the beneficial effects of VNS in brain diseases remain only partially elucidated. This review aims to delve into the relevant preclinical and clinical studies and update the progress of VNS applications and its potential mechanisms underlying the biological effects in brain diseases.

Effects of Sevoflurane Inhalation Anesthesia on the Intestinal Microbiome in Mice

In recent years, more and more attention has been paid to intestinal microbiome. Almost all operations will go through the anesthesia process, but it is not clear whether the intervention of anesthesia alone will affect the change in the intestinal microbiome. The purpose of this study was to verify the effect of sevoflurane inhalation anesthesia on the intestinal microbiome. The animal in the experimental group was used to provide sevoflurane inhalation anesthesia for 4 hours. The control group was not intervened. The feces of the experimental group and the control group were collected on the 1st, 3rd, 7th and 14th days after anesthesia. Sevoflurane inhalation anesthesia will cause changes in the intestinal microbiome of mice. It appears on the 1st day after anesthesia and is most obvious on the 7th day. The specific manifestation is that the abundance of microbiome and the diversity of the microbiome is reduced. At the same time, Untargeted metabonomics showed that compared with the control group, the experimental group had more increased metabolites related to the different microbiome, among which 5-methylthioadenosine was related to the central nervous system. Subsequently, the intestinal microbiome diversity of mice showed a trend of recovery on the 14th day. At the genus level, the fecal samples obtained on the 14th day after anesthesia exhibited significantly increased abundances of Bacteroides, Alloprevotella, and Akkermansia and significantly decreased abundances of Lactobacillus compared with the samples obtained on the 1st day after anesthesia. However, the abundance of differential bacteria did not recover with the changing trend of diversity. Therefore, we believe that sevoflurane inhalation anesthesia is associated with changes in the internal microbiome and metabolites, and this change may be completed through the brain-gut axis, while sevoflurane inhalation anesthesia may change the intestinal microbiome for as long as 14 days or longer.

Elevation of miR-146a Inhibits BTG2/BAX Expression to Ameliorate Postoperative Cognitive Dysfunction Following Probiotics (VSL#3) Treatment

It has been reported that the gut microbiome modulates postoperative cognitive dysfunction (POCD), and that administration of probiotics (VSL#3) may effectively relieve POCD. In this study, we aimed to identify the underlying mechanism of VSL#3 in POCD. A mouse model of POCD was constructed in adult male C57BL/6 mice, which were then treated with VSL#3. VSL#3 exerted a protective role against POCD and resultant neuronal apoptosis. The expression of miR-146a was found to be downregulated in hippocampal tissues of POCD mice, while VSL#3 could restore its expression. Loss- and gain-function approaches were conducted to determine the roles of microRNA (miR)-146a, B-cell translocation gene 2 (BTG2), and Bcl-2-associated X protein (Bax) in post-operative effects on cognitive function and neuronal apoptosis. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were measured to determine oxidative stress in brain tissue. The dual-luciferase reporter gene assay identified that miR-146a could target BTG2 and negatively regulate its expression. BTG2 knockdown suppressed neuronal apoptosis and contributed to shortened time of latency, prolonged time of mice spent in the target quadrant, and reduced oxidative stress through downregulating Bax expression. Finally, VSL#3 treatment upregulated the expression of miR-146a to block BTG2/Bax axis and consequently inhibited neuronal apoptosis and reduced oxidative stress in POCD mice. Taken together, the study suggested that miR-146a-mediated suppression of BTG2/Bax contributed to the protective role of probiotics treatment against POCD.

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.

Electroacupuncture Pretreatment Ameliorates Anesthesia and Surgery-Induced Cognitive Dysfunction via Activation of an α7-nAChR Signal in Aged Rats

OBJECTIVE

Postoperative cognitive dysfunction (POCD) after anesthesia and surgery (AS) is a common complication in the elderly population. A cholinergic-dependent signal, the alpha7-nicotinic acetylcholine receptor (α7-nAChR), has been suggested to regulate cognitive processes in a variety of neurologic diseases. In the current study, we determined whether electroacupuncture (EA) pretreatment ameliorates AS-induced POCD in aged rats, as well as the underlying mechanism.

METHODS

Male Sprague-Dawley rats (20 months old) were randomly assigned to the following 5 groups (n=12): vehicle; POCD (tibial fracture surgery); EA plus POCD; EA plus POCD and alpha-bungarotoxin (α-BGT); and POCD plus α-BGT groups. Alpha-bungarotoxin (1 μg/kg), a selective antagonist of α7-nAChR, was administrated via intraperitoneal injection before EA. Thirty days post-AS, the Morris water maze and a novel objective recognition test were used to evaluate cognitive function. Neuronal amount, apoptosis, microglial activation, percentage of high mobility group box 1 (HMGB1)- and nuclear factor-κB (NF-κB)-positive microglia, and levels of HMGB-1 downstream factors, including NF-κB, interleukin-6 (IL-6), and IL-1β, were detected by Nissl staining, immunofluorescence, and Western blot assays.

RESULTS

EA pretreatment significantly increased crossing platform times and elevated the time with a novel object, restored the quantity of neurons, decreased TUNEL-positive neurons, alleviated activation of microglia, downregulated expression of HMGB1 and NF-κB in the microglia, and reduced levels of phosphor-NF-κB, IL-6, and IL-1β 35 days after AS, while α-BGT partially reversed these changes.

CONCLUSION

EA pretreatment improved AS-induced POCD in aged rats, and the underlying mechanism may be associated with inhibition of HMGB1-NF-κB via an α7-nAChR signal in the microglia.

Appropriate exercise level attenuates gut dysbiosis and valeric acid increase to improve neuroplasticity and cognitive function after surgery in mice

Postoperative cognitive dysfunction (POCD) affects the outcome of millions of patients each year. Aging is a risk factor for POCD. Here, we showed that surgery induced learning and memory dysfunction in adult mice. Transplantation of feces from surgery mice but not from control mice led to learning and memory impairment in non-surgery mice. Low intensity exercise improved learning and memory in surgery mice. Exercise attenuated surgery-induced neuroinflammation and decrease of gut microbiota diversity. These exercise effects were present in non-exercise mice receiving feces from exercise mice. Exercise reduced valeric acid, a gut microbiota product, in the blood. Valeric acid worsened neuroinflammation, learning and memory in exercise mice with surgery. The downstream effects of exercise included attenuating growth factor decrease, maintaining astrocytes in the A2 phenotypical form possibly via decreasing C3 signaling and improving neuroplasticity. Similar to these results from adult mice, exercise attenuated learning and memory impairment in old mice with surgery. Old mice receiving feces from old exercise mice had better learning and memory than those receiving control old mouse feces. Surgery increased blood valeric acid. Valeric acid blocked exercise effects on learning and memory in old surgery mice. Exercise stabilized gut microbiota, reduced neuroinflammation, attenuated growth factor decrease and preserved neuroplasticity in old mice with surgery. These results provide direct evidence that gut microbiota alteration contributes to POCD development. Valeric acid is a mediator for this effect and a potential target for brain health. Low intensity exercise stabilizes gut microbiota in the presence of insult, such as surgery.

Effects of continuous intravenous infusion of propofol on intestinal flora in rats

Under normal circumstances, the gut microbiota, host, and external environment establish a dynamic ecological balance and maintain human health. Once this balance is broken, the intestinal flora dysregulation will form, manifested by changes in the diversity, richness, proportion, location and biological characteristics of the gut microbiota. The hypothesis that propofol alters gut microbes was tested in a rat model with continuous intravenous infusion of propofol. Eight male wistar rats underwent tail vein puncture and catheterization respectively, and were continuously pumped with propofol for 3 h. Feces were collected from each rat before and on the 1 st, 3rd, 7th and 14th days after intervention. Finally, the effect of continuous intravenous infusion of propofol on the intestinal flora of rats was analyzed by high-throughput 16S rRNA gene amplification sequencing. Through high-throughput 16S rRNA gene amplicon sequencing analysis, we found that continuous intravenous infusion of propofol had little effect on intestinal flora in rats. Analysis of Alpha (shannon diversity index) showed that group A-7 was different from group P and group A-1 (P = 0.034), and recovered on the 14th day. Although the species diversity analysis showed a significant difference among the five groups (P = 0.049), the distribution of most fecal samples in the PCoA showed a clustered distribution, indicating similarity. In addition, no significant difference was found in the statistical KEGG difference pathway through LEfSe analysis.