Prevention of gut leakiness by a probiotic treatment leads to attenuated HPA response to an acute psychological stress in rats

Target Dysbiosis of Gut Microbes as a Future Therapeutic Manipulation in Alzheimer's Disease

Alzheimer’s disease (AD) is commonly an age-associated dementia with neurodegeneration. The pathogenesis of AD is complex and still remains unclear. The inflammation, amyloid β (Aβ), and neurofibrillary tangles as well misfolded tau protein in the brain may contribute to the occurrence and development of AD. Compared with tau protein, Aβ is less toxic. So far, all efforts made in the treatments of AD with targeting these pathogenic factors were unsuccessful over the past decades. Recently, many studies demonstrated that changes of the intestinal environment and gut microbiota via gut–brain axis pathway can cause neurological disorders, such as AD, which may be involved in the pathogenesis of AD. Thus, remodeling the gut microbiota by various ways to maintain their balance might be a novel therapeutic strategy for AD. In the review article, we analyzed the characteristics of gut microbiota and its dysbiosis in AD and its animal models and investigated the possibility of targeting the gut microbiota in the treatment of the patients with AD in the future.

Supplementation with Combined Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 Across Development Reveals Sex Differences in Physiological and Behavioural Effects of Western Diet in Long-Evans Rats

The gut microbiome affects various physiological and psychological processes in animals and humans, and environmental influences profoundly impact its composition. Disorders such as anxiety, obesity, and inflammation have been associated with certain microbiome compositions, which may be modulated in early life. In 62 Long–Evans rats, we characterised the effects of lifelong Bifidobacterium longum R0175 and Lactobacillus helveticus R0052 administration—along with Western diet exposure—on later anxiety, metabolic consequences, and inflammation. We found that the probiotic formulation altered specific anxiety-like behaviours in adulthood. We further show distinct sex differences in metabolic measures. In females, probiotic treatment increased calorie intake and leptin levels without affecting body weight. In males, the probiotic seemed to mitigate the effects of Western diet on adult weight gain and calorie intake, without altering leptin levels. The greatest inflammatory response was seen in male, Western-diet-exposed, and probiotic-treated rats, which may be related to levels of specific steroid hormones in these groups. These results suggest that early-life probiotic supplementation and diet exposure can have particular implications on adult health in a sex-dependent manner, and highlight the need for further studies to examine the health outcomes of probiotic treatment in both sexes.

Identification of a Signaling Mechanism by Which the Microbiome Regulates Th17 Cell-Mediated Depressive-Like Behaviors in Mice

OBJECTIVE

Microbiota dysbiosis has been linked to major depressive disorder, but the mechanisms whereby the microbiota modulates mood remain poorly understood. The authors tested whether specific changes in the microbiome modulate depressive-like behaviors.

METHODS

Stools from learned helpless, non-learned helpless, and non-shocked mice were analyzed by V4 16S RNA sequencing to identify gut bacteria associated with learned helplessness and to quantify the level of the quorum-sensing molecule autoinducer-2 (AI-2). T cells were analyzed by flow cytometry, and serum amyloid proteins (SAA) were analyzed by quantitative real-time polymerase chain reaction. Fecal transfer approach and administration of oleic acid and AI-2 were used to determine the effects of the microbiome and quorum-sensing molecules on depressive-like behaviors.

RESULTS

Mice deficient in segmented filamentous bacteria (SFB) were resilient to the induction of depressive-like behavior, and were resensitized when SFB was reintroduced in the gut. SFB produces the quorum-sensing AI-2 and promotes the production of SAA1 and SAA2 by the host, which increases T helper 17 (Th17) cell production. Th17 cells were required to promote depressive-like behaviors by AI-2, as AI-2 administration did not promote susceptibility to depressive-like behaviors or SAA1 and SAA2 production in Th17-deficient mice after stress. Oleic acid, an AI-2 inhibitor, exhibited antidepressant properties, reducing depressive-like behavior, intestinal SAA1 and SAA2 production, and hippocampal Th17 cell accumulation. Stool samples from 10 people with current depressive symptoms and 10 matched healthy control subjects were analyzed as well. Patients with current major depressive disorder exhibited increased fecal interleukin 17A, SAA, and SFB levels.

CONCLUSIONS

The study results reveal a novel mechanism by which bacteria alter mood.

"Gut-brain axis": Review of the role of the probiotics in anxiety and depressive disorders

BACKGROUND

Depressive disorders are the leading cause of disability worldwide and together with anxiety contribute to a very high burden of disease. Therefore, improving their treatment is a significant medical research target: The role of probiotics is a topic of great interest for the current research in this field.

OBJECTIVES

To explore the current literature about the impact of probiotics on anxious and depressive symptoms.

METHODS

Scoping review following the PRISMA guidelines.

RESULTS

The selection process yielded 23 studies. Probiotics positively affected depressive symptomatology and anxiety symptoms according to 53.83% and 43.75% of the selected studies, respectively. Among the studies assessing inflammatory biomarkers, 58.31% found they were decreased after administration of probiotics.

CONCLUSION

The results emerging from the existing literature about probiotic supplementation for depression treatment are encouraging, but further research is needed considering the shortage of clinical trials on this topic and the heterogeneity of the samples analyzed.

Fecal Microbiota Changes in Patients With Postpartum Depressive Disorder

Postpartum depressive disorder (PPD) is a unique subtype of major depressive disorder and a substantial contributor to maternal morbidity and mortality. However, the pathogenesis of PPD has still remained elusive, and it may associate with genetic and environmental factors. Gut microbiota has already been proved to be associated with depression; however, a limited number of studies have concentrated on PPD. The present study aimed to explore the potential correlations between gut microbiota and PPD. In this study, 57 participants were enrolled, in which fecal samples of 28 patients with PPD and 16 healthy controls (HCs) were collected and then analyzed by high-throughput sequencing of the 16S ribosomal RNA (rRNA) gene. The results showed that diversity and composition of gut microbial communities were partly different between PPD patients and HCs. The relative abundance of Firmicutes phyla was lower in PPD patients. The levels of several predominant genera were significantly different between PPD patients and HCs. More importantly, the PPD patients experienced reduced levels of Faecalibacterium, Phascolarctobacterium, Butyricicoccus, and Lachnospiraceae, as well as increased levels of Enterobacteriaceae family. In addition, a correlation was observed between levels of Phascolarctobacterium, Lachnospiraceae, Faecalibacterium, and Tyzzerella.3 and the severity of depressive symptoms. Various kinds of bacteria, such as Lachnospiraceae and Faecalibacterium, were found to be associated with levels of sex hormones. This study indicated the correlation between gut microbiota and PPD, and gut microbiota-based biomarkers may be helpful for the diagnosis and treatment of PPD patients. However, further studies need to be conducted to clarify the cause–effect relationship between PPD patients and gut microbiota and to highlight the suitability of gut microbiome as a biomarker.

The Brain-Gut-Microbiome Axis in Psychiatry

Beginning with the concept of the brain-gut axis, the importance of the interaction between the brain and the gastrointestinal tract has been extended to the microbiome with increasing clinical applications. With the recent development of various techniques for microbiome analysis, the number of relevant preclinical and clinical studies on animals and human subjects has rapidly increased. Various psychotic symptoms affect the intestinal microbiome through the hypothalamus-pituitary-adrenal gland axis. Conversely, the intestinal microbiome regulates the gastrointestinal tract environment and affects psychological factors by means of the microorganisms or their metabolites, either acting directly on the brain or through the synthesis of various neurotransmitters. This review discusses the clinical applicability of the brain-gut-microbiome axis and directions for improving psychological symptoms based on the studies published to date.

Clinical Evidence of Antidepressant Effects of Insulin and Anti-Hyperglycemic Agents and Implications for the Pathophysiology of Depression-A Literature Review

Close connections between depression and type 2 diabetes (T2DM) have been suggested by many epidemiological and experimental studies. Disturbances in insulin sensitivity due to the disruption of various molecular pathways cause insulin resistance, which underpins many metabolic disorders, including diabetes, as well as depression. Several anti-hyperglycemic agents have demonstrated antidepressant properties in clinical trials, probably due to their action on brain targets based on the shared pathophysiology of depression and T2DM. In this article, we review reports of clinical trials examining the antidepressant effect of these medications, including insulin, metformin, glucagon like peptide-1 receptor agonists (GLP-1RA), and peroxisome proliferator-activated receptor (PPAR)-γ agonists, and briefly consider possible molecular mechanisms underlying the associations between amelioration of insulin resistance and improvement of depressive symptoms. In doing so, we intend to suggest an integrative perspective for understanding the pathophysiology of depression.

Probiotics: A Dietary Factor to Modulate the Gut Microbiome, Host Immune System, and Gut-Brain Interaction

Various benefits of probiotics to the host have been shown in numerous human clinical trials. These organisms have been proposed to act by improving the balance of the gut microbiota and enhancing the production of short-chain fatty acids, as well as by interacting with host cells in the gastrointestinal tract, including immune cells, nerve cells, and endocrine cells. Although the stimulation of host cells by probiotics and subsequent signaling have been explained by in vitro experiments and animal studies, there has been some skepticism as to whether probiotics can actually interact with host cells in the human gastrointestinal tract, where miscellaneous indigenous bacteria coexist. Most recently, it has been shown that the ileal microbiota in humans after consumption of a fermented milk is occupied by probiotics for several hours, indicating that there is adequate opportunity for the ingested strain to stimulate the host cells continuously over a period of time. As the dynamics of ingested probiotics in the human gastrointestinal tract become clearer, further progress in this research area is expected to elucidate their behavior within the tract, as well as the mechanism of their physiological effects on the host.

The HPA axis dysregulation in severe mental illness: Can we shift the blame to gut microbiota?

Accumulating evidence indicates that patients with severe mental disorders, including major depression, bipolar disorder and schizophrenia present with various alterations of the gut microbiota and increased intestinal permeability. In addition, the hypothalamic-pituitary-adrenal (HPA) axis dysregulation and subclinical inflammation have been reported in this group of patients. Although it has been found that the HPA axis dysregulation appears as a consequence of psychosocial stress, especially traumatic life events, the exact mechanisms of this observation remain unclear. Animal model studies have unraveled several mechanisms linking the gut microbiota with the HPA axis dysfunction. Indeed, the gut microbiota can activate the HPA axis through several mediators that cross the blood-brain barrier and include microbial antigens, cytokines and prostaglandins. There is also evidence that various microbial species can affect ileal corticosterone production that may impact the activity of the HPA axis. However, some metabolites released by various microbes, e.g., short-chain fatty acids, can attenuate the HPA axis response. Moreover, several bacteria release neurotransmitters that can directly interact with vagal afferents. It has been postulated that the HPA axis activation can impact the gut microbiota and intestinal permeability. In this article, we discuss various mechanisms linking the gut microbiota with the HPA axis activity and summarize current evidence for a cross-talk between the gut-brain axis and the HPA axis from studies of patients with mood and psychotic disorders. Finally, we show potential clinical implications that can arise from future studies investigating the HPA axis activity with respect to the gut microbiota in severe mental disorders.

The Microbiome-Metabolome Response in the Colon of Piglets Under the Status of Weaning Stress

Weaning is stressful for piglets involving nutritional, physiological, and psychological challenges, leading to an increase in the secretion of cortisol, changes in gut microbiome and metabolites, whereas the underlying relationships remain unclear. To elucidate this, 14 Meishan female piglets were divided into the weaning group and the suckling group at the age of 21 days paired by litter and body weight. After 48 h of experiment, weaned piglets had lower body weight, but higher salivary cortisol level than that of their suckling litter mates (P < 0.05). The composition of the colonic bacterial community and metabolites were different between the two groups, and the first predominant genus of the suckling and weaned piglets colonic microbiome were Bacteroides and Prevotellaceae-NK3B31 group respectively. The suckling piglets had higher proportions of phylum Bacteroidetes and Lentisphaerae, and genus Bacteroides and Lactobacillus in the colonic microbial community, but lower abundance of genus Prevotellaceae-NK3B31 group than that of the weaned piglets (P < 0.05). Accordingly, there were 15 colonic metabolites differed between the two groups, in which 2 metabolites (phenylacetic acid and phenol) negatively related to the abundant of Lactobacillus genus (P < 0.05), while 9 metabolites (acetic acid, arabitol, benzoic acid, caprylic acid, cholesterol, dihydrocholesterol, galactinol, glucose phenol, phenylacetic acid, and oxamic acid, glycerol, propionic acid) positively associated with the proportion of Prevotellaceae-NK3B31 group genus (P < 0.05). Furthermore, the salivary cortisol level negatively associated with the abundance of phylum Lentisphaerae, but positively associated with the phylum Bacteroidetes and the genus Prevotellaceae-NK3B31 group (P < 0.05) respectively. These results provide us with new insights into the cause of the gut microbiome and stress, and the contributions of gut microbiome in metabolic and physiological regulation in response to weaning stress.

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.

Complex Feed-Forward and Feedback Mechanisms Underlie the Relationship Between Traumatic Brain Injury and the Gut-Microbiota-Brain Axis

Traumatic brain injury (TBI) contributes to nearly 1 in 3 injury-related deaths in the United States and accounts for a substantial public health burden and cost. The current literature reports that physiologic responses in the gastrointestinal system after TBI include, but are not limited to, epithelial barrier dysfunction, microbiota changes, and immunologic transformations. Recent evidence suggests gut alterations after TBI modify the homeostasis of the bidirectional gut-microbiota-brain axis, resulting in altered immune responses in the periphery and the brain. This cascade possibly contributes to impaired central nervous system (CNS) healing. Although attention to the gut-brain-microbiota axis has been increasing in the literature, the precise mechanisms underlying the changes observed after TBI remain unclear. The purpose of this review are to describe our current understanding regarding alterations to the gut-microbiota-brain axis after TBI, highlight the pathophysiologic changes involved, and evaluate how these variations modify healing in the CNS or even contribute to secondary injury. We also discuss current investigations into potential medical therapies directed at the gut-microbiota-brain axis, which might offer improved outcomes after TBI.

Considering the Microbiome in Stress-Related and Neurodevelopmental Trajectories to Schizophrenia

Early life adversity and prenatal stress are consistently associated with an increased risk for schizophrenia, although the exact pathogenic mechanisms linking the exposures with the disease remain elusive. Our previous view of the HPA stress axis as an elegant but simple negative feedback loop, orchestrating adaptation to stressors among the hypothalamus, pituitary, and adrenal glands, needs to be updated. Research in the last two decades shows that important bidirectional signaling between the HPA axis and intestinal mucosa modulates brain function and neurochemistry, including effects on glucocorticoid hormones and brain-derived neurotrophic factor (BDNF). The intestinal microbiome in earliest life, which is seeded by the vaginal microbiome during delivery, programs the development of the HPA axis in a critical developmental window, determining stress sensitivity and HPA function as well as immune system development. The crosstalk between the HPA and the Microbiome Gut Brain Axis (MGBA) is particularly high in the hippocampus, the most consistently disrupted neural region in persons with schizophrenia. Animal models suggest that the MGBA remains influential on behavior and physiology across developmental stages, including the perinatal window, early childhood, adolescence, and young adulthood. Understanding the role of the microbiome on critical risk related stressors may enhance or transform of understanding of the origins of schizophrenia and offer new approaches to increase resilience against stress effects for preventing and treating schizophrenia.

The Role of the Gut Microbiota in Dietary Interventions for Depression and Anxiety

There is emerging evidence that an unhealthy dietary pattern may increase the risk of developing depression or anxiety, whereas a healthy dietary pattern may decrease it. This nascent research suggests that dietary interventions could help prevent, or be an alternative or adjunct therapy for, depression and anxiety. The relation, however, is complex, affected by many confounding variables, and is also likely to be bidirectional, with dietary choices being affected by stress and depression. This complexity is reflected in the data, with sometimes conflicting results among studies. As the research evolves, all characteristics of the relation need to be considered to ensure that we obtain a full understanding, which can potentially be translated into clinical practice. A parallel and fast-growing body of research shows that the gut microbiota is linked with the brain in a bidirectional relation, commonly termed the microbiome-gut-brain axis. Preclinical evidence suggests that this axis plays a key role in the regulation of brain function and behavior. In this review we discuss possible reasons for the conflicting results in diet-mood research, and present examples of areas of the diet-mood relation in which the gut microbiota is likely to be involved, potentially explaining some of the conflicting results from diet and depression studies. We argue that because diet is one of the most significant factors that affects human gut microbiota structure and function, nutritional intervention studies need to consider the gut microbiota as an essential piece of the puzzle.

Gut Microbiota and Neurologic Diseases and Injuries

The brain-gut axis is a bidirectional communication pathway connecting the central nervous system (CNS) and the gastrointestinal tract via nerve transmission, hormone, immune system, and other molecular signals. The bacterial flora of the human gut contributes direct and indirect signals to the CNS along the brain-gut axis. Alterations in gut flora, a state known as dysbiosis, has been tied to systemic inflammation, increased bacterial translocation, and increased absorbance of microbial by-products. An increase in recent literature has highlighted the role of the gut-brain axis in CNS pathology. This chapter reviews the association between gut flora dysbiosis and disorders of the central nervous system including autoimmune disease, developmental disorders, physiologic response to traumatic injury, and neurodegenerative disease.

Peripheral and Central Nervous System Immune Response Crosstalk in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by muscle weakness due to the degeneration of the upper and lower motor neurons. Neuroinflammation is known as a prominent pathological feature of ALS. Although neuroinflammation cannot trigger ALS, activated central nervous system (CNS) microglia and astrocytes, proinflammatory periphery monocytes/macrophages and T lymphocytes, and infiltrated monocytes/macrophages and T lymphocytes, as well as the immunoreactive molecules they release, are closely related to disease progression. The crosstalk between the peripheral and CNS immune components mentioned above significantly correlates with survival in patients with ALS. This review provides an update on the role of this crosstalk between the CNS and peripheral immune responses in ALS. Additionally, we discuss changes in the composition of gut microbiota because these can directly or indirectly influence this crosstalk. These recent advances may well provide innovative ways for targeting the molecules associated with this crosstalk and breaking the current treatment impasse in ALS.

Gut microbiota modulates stress-induced hypertension through the HPA axis

Stress is associated with an increased risk of hypertension, and the incidence of stress-related hypertension has risen rapidly in recent years; however, the underlying mechanisms remain elusive. Gut dysbiosis has been demonstrated to contribute to hypertension and hyperactivation of the hypothalamus-pituitary-adrenal (HPA) axis. Based on our previous findings showing the altered gut microbiota in the rats of stress-induced hypertension (SIH), the present study aims to investigate whether the stress-induced alteration in gut microbiota can lead to the dysfunction of the HPA axis which contributes to the development of SIH. SIH was developed in rats subjected to electric foot-shock combined with buzzer noise stressors. The gut microbiota of rats were deleted by administering an antibiotic cocktail containing ampicillin (1 g/L), vancomycin (500 mg/L), neomycin (1 g/L), and metronidazole (1 g/L) in drinking water. The serum levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were tested using enzyme-linked immunosorbent assay (ELISA). The mRNA expression of glucocorticoid receptor (GR) and corticotropin-releasing factor (CRF), CRFR1 and CRFR2 was detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The cellular protein expressions of corticotropin-releasing hormone (CRH), c-fos, and GR were examined by immunohistochemical staining. In the present study, SIH rats showed a hyperactive HPA axis as indicated by the increased CRH expression in the paraventricular nucleus (PVN) of the hypothalamus, the elevated serum ACTH or CORT concentrations, and increased adrenal gland index. The decreased GR expression and increased CRFR1 in the hypothalamus might underlie the hyperactivation of the HPA axis. The microbial deletion by antibiotics mitigated the hyperactivation of the HPA axis and attenuated the stress-induced elevation of blood pressure, indicating that the causal link of gut microbiota to SIH is mediated, at least in part, by the HPA axis activity. Our findings shed new light on the mechanisms underlying SIH.

Crosstalk between the microbiota-gut-brain axis and depression

Nutritional and microbiological psychiatry, especially the contribution of the gut microbiota to depression, has become a promising research field over the past several decades. An imbalance in the "microbiota-gut-brain axis", which reflects the constant bidirectional communication between the central nervous system and the gastrointestinal tract, has been used as a hypothesis to interpret the pathogenesis of depression. Alterations in gut microbiota composition could increase the permeability of the gut barrier, activate systemic inflammation and immune responses, regulate the release and efficacy of monoamine neurotransmitters, alter the activity and function of the hypothalamic-pituitary-adrenal (HPA) axis, and modify the abundance of brain-derived neurotrophic factor (BDNF), eventually leading to depression. In this article, we review changes in gut microbiota in depressive states, the association between these changes and depression-like behavior, the potential mechanism linking gut microbiota disruptions and depression, and preliminary attempts at using gut microbiota intervention for the treatment of depression. In summary, although the link between gut microbiota and depression and the potential mechanism have been discussed, a more detailed mechanistic understanding is needed to fully realize the importance of the microbiota-gut-brain axis in depression. Future efforts should aim to determine the potential causative mechanisms, which will require further animal and clinical research as well as the development of analytical approaches.

A human-origin probiotic cocktail ameliorates aging-related leaky gut and inflammation via modulating the microbiota/taurine/tight junction axis

Inflammation is a major risk factor of morbidity and mortality in older adults. Although its precise etiology is unknown, low-grade inflammation in older adults is commonly associated with increased intestinal epithelial permeability (leaky gut) and abnormal (dysbiotic) gut microbiota. The increasing older population and lack of treatments to reduce aging-related microbiota dysbiosis, leaky gut, and inflammation culminates in a rise in aging-related comorbidities, constituting a significant public health concern. Here, we demonstrate that a human-origin probiotic cocktail containing 5 Lactobacillus and 5 Enterococcus strains isolated from healthy infant gut prevented high-fat diet-induced (HFD-induced) microbiota dysbiosis, leaky gut, inflammation, metabolic dysfunctions, and physical function decline in older mice. Probiotic-modulated gut microbiota primarily reduced leaky gut by increasing tight junctions, which in turn reduced inflammation. Mechanistically, probiotics modulated microbiota in a way to increase bile salt hydrolase activity, which in turn increased taurine abundance in the gut that stimulated tight junctions and suppressed gut leakiness. Furthermore, in Caenorhabditis elegans, taurine increased life span, reduced adiposity and leaky gut, and enhanced physical function. The results suggest that such probiotic therapies could prevent or treat aging-related leaky gut and inflammation in the elderly.

The multicomponent medication Spascupreel attenuates stress-induced gut dysfunction in rats

BACKGROUND

Irritable bowel syndrome (IBS) is a common disorder worldwide. It is characterized by abdominal pain/discomfort and changes in bowel habits. Due to the multifactorial pathophysiology and the heterogeneity of IBS patients, appropriate treatment of IBS is still a challenge. Spascupreel (SP-11), as a multicomponent medication, has the potential to modulate multiple pathophysiological pathways simultaneously. Therefore, the objective of the current study was to investigate the effects of oral SP-11 treatment on stress-induced changes of peripheral and central functions in a rat model mimicking human IBS.

METHODS

Naïve Wistar rats were treated with SP-11 (0.9 tab/kg) or NaCl 0.9% by oral gavage for 4 days before 2-hour partial restraint stress (PRS) procedure. Twenty minutes after PRS, central and peripheral stress-induced changes affecting IBS were assessed. These include the hypothalamic-pituitary-adrenal (HPA) axis response through plasma ACTH and corticosterone measurements, visceral pain in response to colorectal distension, gut permeability, colonic mast cell number, and sensitization as well as gut transit time.

RESULTS

Treatment with SP-11 reduced the HPA axis activation in response to PRS. At the gut level, a reduction in colonic hypersensitivity to colorectal distension, a normalization of gut transit time acceleration, a reduced mast cell sensitization, and a trend toward reduced gut hyperpermeability were observed.

CONCLUSIONS

These data suggest that stress-induced IBS signs can be reduced using SP-11 in rats. The observed effects and the good tolerability of the drug make SP-11 an innovative candidate in the management of IBS.

Traditional Chinese Medicine in Emergency Treatment Mechanism and Application

Traditional Chinese medicine has usually been recognized to be efficacious to treat chronic diseases from the western point-of-view. However, there is a long history in China of applying traditional Chinese medicine in many acute and urgent medical conditions. In this review, selected methods documented in traditional Chinese medicine including blowing air to ear, nose insufflating therapy, acupuncture and moxibustion were presented as the common practices to promote consciousness recovery from coma. We aimed to explore the mechanism of these four methods with current scientific evidence, further discuss the potential of traditional Chinese medicine to be applied in emergency medicine and provide a path forward to more rigorously validate these procedures. The development of the integrated traditional Chinese medicine and western medicines provides a new therapeutic direction for the new first-aid treatment.

Chronic unpredictable stress-induced reproductive deficits were prevented by probiotics

Stress can induce reproductive deficits by activating the HPA and causing oxidative stress. Some studies have indicated that the neurologic diseases or disorders induced by stress could be relieved by probiotics. Whether chronic unpredictable stress (CUS)-induced reproductive deficits could be prevented by probiotics is unclear. The present experiment was designed to evaluate the effects of L. rhamnosus Gorbach-Goldin (LGG) on CUS-induced reproductive deficits. Kunming mice were divided into control, stress, and LGG groups randomly. The mice in stress and LGG groups were exposed to CUS for 40days, in the meantime, the mice in LGG group were orally administered with LGG suspension at a dose of 0.3 mL/mouse (1×10¹⁰ cells/mL), and the mice in control and stress groups were orally administered with volume-equivalent sterile saline once a day. The results showed that the CUS-induced the sperm deficits including the count, motility, morphology, ultrastructure, DNA integrity, and chromatin condensation were protected by oral administration of LGG. In addition, the change of testosterone level induced by CUS was prevented by up-regulating the expressions of StAR and P450scc in the testes. Moreover, LGG could increase the activities of catalase, glutathione peroxidase, and superoxide dismutase significantly, and decrease the levels of oxidative products malondialdehyde and protein carbonyls significantly, as well as the levels of cyclooxygenase 2, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α, to block the CUS-induced inflammatory response and the oxidative stress. The results indicated that the CUS-induced male reproductive deficits could be prevented by oral administration of LGG.

The role of the gut microbiome in opioid use

Although the gut and brain are separate organs, they communicate with each other via trillions of intestinal bacteria that collectively make up one's gut microbiome. Findings from both humans and animals support a critical role of gut microbes in regulating brain function, mood, and behavior. Gut bacteria influence neural circuits that are notably affected in addiction-related behaviors. These include circuits involved in stress, reward, and motivation, with substance use influencing gut microbial abnormalities, suggesting significant gut-brain interactions in drug addiction. Given the overwhelming rates of opioid overdose deaths driven by abuse and addiction, it is essential to characterize mechanisms mediating the abuse potential of opioids. We discuss in this review the role of gut microbiota in factors that influence opioid addiction, including incentive salience, reward, tolerance, withdrawal, stress, and compromised executive function. We present clinical and preclinical evidence supporting a bidirectional relationship between gut microbiota and opioid-related behaviors by highlighting the effects of opioid use on gut bacteria, and the effects of gut bacteria on behavioral responses to opioids. Further, we discuss possible mechanisms of this gut-brain communication influencing opioid use. By clarifying the relationship between the gut microbiome and opioid-related behaviors, we improve understanding on mechanisms mediating reward-, motivation-, and stress-related behaviors and disorders, which may contribute to the development of effective, targeted therapeutic interventions in opioid dependence and addiction.

Fructo-oligosaccharides from Morinda officinalis remodeled gut microbiota and alleviated depression features in a stress rat model

BACKGROUND

Inulin-type fructo-oligosaccharides (FOSs) purified from Morinda officinalis How., an effective oral antidepressant for mild to moderate depression, have a largely unknown efficacy and poor bioavailability.

PURPOSE

Therefore, the microbiota-gut-brain axis was used to investigate the antidepressive properties of FOSs at the interface of the gut microbiota (GM).

STUDY DESIGN AND METHODS

FOSs was introduced via intragastric gavage to rats exposed to chronic unpredictable mild stress (CUMS), and the antidepressive effects were investigated through behavioral tests, intestinal morphology and corticosterone levels. Bacterial genomic DNA was extracted from feces, and the GM was profiled for using enterobacterial repetitive intergenic consensus (ERIC)-PCR analysis, partial least squares-discriminant analysis (PLS-DA) and 16S rRNA gene pyrosequencing.

RESULTS

It was observed that FOSs alleviated depression-like behaviors and repaired intestinal epithelia damages. FOSs treatment lowered corticosterone levels in the plasma and urine of the model rats. Moreover, the GM compositions of normal and model rats were distantly clustered and were mainly related to the disappearance of beneficial bacteria (e.g., Acinetobacter, Barnesiella, Coprococcus, Dialister, Lactobacillus, and Paenibacillus) and appearance of depression-associated bacteria (e.g., Anaerostipes, Oscillibacter, Proteobacteria, and Streptococcus) in depressive rats. Interestingly, the dysbiosis in depressive rats' gut was reinstated with FOSs treatments. Notably, FOSs promoted the abundance of the bacterial phylum Cyanobacteria, a group of bacteria known for the secretion of pharmacologically important metabolites, such as H₂S, that exhibit antidepressant-like properties. Apparently, FOSs-induced modulation of GM was more antidepressive compared to a component of FOSs, degrees of polymerization (DP) 5, and fluoxetine, the standard antidepressant drug.

CONCLUSION

In conclusion, this study implied that antidepressant efficacy of FOSs was inseparable from and strongly associated with the modulation of the host' s GM.

Finding intestinal fortitude: Integrating the microbiome into a holistic view of depression mechanisms, treatment, and resilience

Depression affects at least 322 million people globally, or approximately 4.4% of the world's population. While the earnestness of researchers and clinicians to understand and treat depression is not waning, the number of individuals suffering from depression continues to increase over and above the rate of global population growth. There is a sincere need for a paradigm shift. Research in the past decade is beginning to take a more holistic approach to understanding depression etiology and treatment, integrating multiple body systems into whole-body conceptualizations of this mental health affliction. Evidence supports the hypothesis that the gut microbiome, or the collective trillions of microbes inhabiting the gastrointestinal tract, is an important factor determining both the risk of development of depression and persistence of depressive symptoms. This review discusses recent advances in both rodent and human research that explore bidirectional communication between the gut microbiome and the immune, endocrine, and central nervous systems implicated in the etiology and pathophysiology of depression. Through interactions with circulating inflammatory markers and hormones, afferent and efferent neural systems, and other, more niche, pathways, the gut microbiome can affect behavior to facilitate the development of depression, exacerbate current symptoms, or contribute to treatment and resilience. While the challenge of depression may be the direst mental health crisis of our age, new discoveries in the gut microbiome, when integrated into a holistic perspective, hold great promise for the future of positive mental health.

Effect of probiotic administration on gut microbiota and depressive behaviors in mice

BACKGROUND

The gut microbiota is closely associated with the bidirectional gut-brain axis that modulates neuropsychological functions of the central nervous system, thereby affecting mental disorders such as depression. Although it is known that probiotics affect brain functions, the impact of probiotics on the regulation of the prevalence and composition of gut microbiota, leading to anti-depressive effects has not been well understood.

METHODS

Mice were randomly divided into four different groups (n = 10 for each group) as follows: Group G1 (normal group) as control and group G2 (stress group) were given sterile saline via oral route daily for 8 weeks without and with stress condition, respectively. Under the stress condition, group G3 (fluoxetine group) was administered with fluoxetine hydrochloride and group G4 (probiotic group) was orally given multi-strains of probiotics daily for 8 weeks. After treatment, all mice underwent behavioral testing. Furthermore, fecal samples were collected from randomly selected 5 mice of each group on day 60 and taxonomical analysis of intestinal microbial distribution was performed.

RESULTS

Mice subjected to restraint stress showed depressive-like behaviors along with high corticosterone levels in serum. However, probiotic administration alleviated depressive-like behaviors and decreased corticosterone level. Moreover, fecal microbiota was distinctly altered in probiotic-treated mice of the stress group. The relative abundance of phylum and genus levels was significantly decreased in the stress group, but probiotic administration restored the composition of microbes restored.

CONCLUSION

Ingested probiotics alter the composition of gut microbiota, likely improving the symptoms of depression. Graphical abstract Probiotic administration alters gut microbiota and reduces depressive-like behaviors.

Microbiota and Alcohol Use Disorder: Are Psychobiotics a Novel Therapeutic Strategy?

In recent years, there has been an exciting focus of research attempting to understand neuropsychiatric disorders from a holistic perspective in order to determine the role of gut microbiota in the aetiology and pathogenesis of such disorders. Thus, the possible therapeutic benefits of targeting gut microbiota are being explored for conditions such as stress, depression or schizophrenia. Growing evidence indicates that there is bidirectional communication between gut microbiota and the brain that has an effect on normal CNS functioning and behavioural responses. Alcohol abuse damages the gastrointestinal tract, alters gut microbiota and induces neuroinflammation and cognitive decline. The relationship between alcohol abuse and hypothalamic-pituitary-adrenal axis activation, inflammation and immune regulation has been well documented. In this review, we explore the connection between microbiota, brain function and behaviour, as well as the mechanisms through which alcohol induces microbiota dysbiosis and intestinal barrier dysfunction. Finally, we propose the study of psychobiotics as a novel pharmaceutical strategy to treat alcohol use disorders.

Stress and the gut microbiota-brain axis

Stress is a nonspecific response of the body to any demand imposed upon it, disrupting the body homoeostasis and manifested with symptoms such as anxiety, depression or even headache. These responses are quite frequent in the present competitive world. The aim of this review is to explore the effect of stress on gut microbiota. First, we summarize evidence of where the microbiota composition has changed as a response to a stressful situation, and thereby the effect of the stress response. Likewise, we review different interventions that can modulate microbiota and could modulate the stress according to the underlying mechanisms whereby the gut-brain axis influences stress. Finally, we review both preclinical and clinical studies that provide evidence of the effect of gut modulation on stress. In conclusion, the influence of stress on gut microbiota and gut microbiota on stress modulation is clear for different stressors, but although the preclinical evidence is so extensive, the clinical evidence is more limited. A better understanding of the mechanism underlying stress modulation through the microbiota may open new avenues for the design of therapeutics that could boost the pursued clinical benefits. These new designs should not only focus on stress but also on stress-related disorders such as anxiety and depression, in both healthy individuals and different populations.

Acute intake of B. longum probiotic does not reduce stress, anxiety, or depression in young adults: A pilot study

Background

The gut microbiome communicates bidirectionally with the brain, linking the gut to psychological phenomena such as stress, depression, and anxiety. Probiotics, or ingestible supplements containing billions of mutualistic bacteria, have demonstrated the mechanistic potential to influence mood; however, few studies have experimentally examined the acute effects of these compounds on individuals not recruited for psychopathology or gut dysfunction. The present study hypothesized reductions in stress, anxiety and depression symptoms following an acute, one week dosing period of B. longum intake.

Methods

The efficacy of a one-week period of orally administered B. longum was tested utilizing a double-blind experimental design. Participants were randomly assigned to either placebo or probiotic capsules under double blinded conditions and completed the Perceived Stress Scale (PSS), the Center for Epidemiological Studies Depression scale (CES-D), and the State-Trait Anxiety Inventory (STAI Y2 form) to assess for differences before and after one-week intervention.

Results

No significant reduction in symptoms between groups over the one-week period was found.

Conclusions

These findings suggest that 7-days of B. longum does not reduce stress, depressive symptoms, or anxiety in generally healthy young adults.

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Microbiota can act via the gut-brain axis (GBA) to influence psychological variables such as stress, depression and anxiety.

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B. longum specifically has been found to reduce stress in humans.

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Probiotics, which contain various microbiota strain(s), are used to improve overall health.

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One week of B. longum did not significantly reduce stress, depression or anxiety in young adults.

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There is a great need for future research to continue to search for time and dose effects on probiotics.

International Society of Sports Nutrition Position Stand: Probiotics

Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the mechanisms and use of probiotic supplementation to optimize the health, performance, and recovery of athletes. Based on the current available literature, the conclusions of the ISSN are as follows: 1)Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO).2)Probiotic administration has been linked to a multitude of health benefits, with gut and immune health being the most researched applications.3)Despite the existence of shared, core mechanisms for probiotic function, health benefits of probiotics are strain- and dose-dependent.4)Athletes have varying gut microbiota compositions that appear to reflect the activity level of the host in comparison to sedentary people, with the differences linked primarily to the volume of exercise and amount of protein consumption. Whether differences in gut microbiota composition affect probiotic efficacy is unknown.5)The main function of the gut is to digest food and absorb nutrients. In athletic populations, certain probiotics strains can increase absorption of key nutrients such as amino acids from protein, and affect the pharmacology and physiological properties of multiple food components.6)Immune depression in athletes worsens with excessive training load, psychological stress, disturbed sleep, and environmental extremes, all of which can contribute to an increased risk of respiratory tract infections. In certain situations, including exposure to crowds, foreign travel and poor hygiene at home, and training or competition venues, athletes' exposure to pathogens may be elevated leading to increased rates of infections. Approximately 70% of the immune system is located in the gut and probiotic supplementation has been shown to promote a healthy immune response. In an athletic population, specific probiotic strains can reduce the number of episodes, severity and duration of upper respiratory tract infections.7)Intense, prolonged exercise, especially in the heat, has been shown to increase gut permeability which potentially can result in systemic toxemia. Specific probiotic strains can improve the integrity of the gut-barrier function in athletes.8)Administration of selected anti-inflammatory probiotic strains have been linked to improved recovery from muscle-damaging exercise.9)The minimal effective dose and method of administration (potency per serving, single vs. split dose, delivery form) of a specific probiotic strain depends on validation studies for this particular strain. Products that contain probiotics must include the genus, species, and strain of each live microorganism on its label as well as the total estimated quantity of each probiotic strain at the end of the product's shelf life, as measured by colony forming units (CFU) or live cells.10)Preclinical and early human research has shown potential probiotic benefits relevant to an athletic population that include improved body composition and lean body mass, normalizing age-related declines in testosterone levels, reductions in cortisol levels indicating improved responses to a physical or mental stressor, reduction of exercise-induced lactate, and increased neurotransmitter synthesis, cognition and mood. However, these potential benefits require validation in more rigorous human studies and in an athletic population.

Interactions Between Gut Microbiota and Acute Restraint Stress in Peripheral Structures of the Hypothalamic-Pituitary-Adrenal Axis and the Intestine of Male Mice

The gut microbiota play an important role in shaping brain functions and behavior, including the activity of the hypothalamus-pituitary-adrenocortical (HPA) axis. However, little is known about the effect of the microbiota on the distinct structures (hypothalamus, pituitary, and adrenals) of the HPA axis. In the present study, we analyzed the influence of the microbiota on acute restraint stress (ARS) response in the pituitary, adrenal gland, and intestine, an organ of extra-adrenal glucocorticoid synthesis. Using specific pathogen-free (SPF) and germ-free (GF) male BALB/c mice, we showed that the plasma corticosterone response to ARS was higher in GF than in SPF mice. In the pituitary, stress downregulated the expression of the gene encoding CRH receptor type 1 (Crhr1), upregulated the expression of the Fkbp5 gene regulating glucocorticoid receptor sensitivity and did not affect the expression of the proopiomelanocortin (Pomc) and glucocorticoid receptor (Gr) genes. In contrast, the microbiota downregulated the expression of pituitary Pomc and Crhr1 but had no effect on Fkbp5 and Gr. In the adrenals, the steroidogenic pathway was strongly stimulated by ARS at the level of the steroidogenic transcriptional regulator Sf-1, cholesterol transporter Star and Cyp11a1, the first enzyme of steroidogenic pathway. In contrast, the effect of the microbiota was significantly detected at the level of genes encoding steroidogenic enzymes but not at the level of Sf-1 and Star. Unlike adrenal Sf-1, the expression of the gene Lrh-1, which encodes the crucial transcriptional regulator of intestinal steroidogenesis, was modulated by the microbiota and ARS and this effect differed between the ileum and colon. The findings demonstrate that gut microbiota have an impact on the response of the pituitary, adrenals and intestine to ARS and that the interaction between stress and the microbiota during activation of glucocorticoid steroidogenesis differs between organs. The results suggest that downregulated expression of pituitary Pomc and Crhr1 in SPF animals might be an important factor in the exaggerated HPA response of GF mice to stress.

Psychobiotics

Psychobiotics are live bacteria that directly and indirectly produce positive effects on neuronal functions by colonizing into the intestinal flora. Preliminary studies, although in limited numbers, have found that these bacteria have anxiolytic and antidepressant activities. No research has yet been published on the antipsychotic efficacy of psychobiotics. However, these preliminary studies have opened up new horizons and raised the idea that a new class is emerging in psychopharmacology. About 70 years have passed since the discovery of chlorpromazine, and while the synaptic transmission is understood in almost all details, there seems to be a paradigm shift in psychopharmacology. In recent years, the perspective has shifted from synapse to intestinal microbiota. In this respect, germ-free and conventional animal experiments and few human studies were examined in a comprehensive manner. In this article, after a brief look at the history of contemporary psychopharmacology, the mechanisms of the gut-brain relationship and the evidence of metabolic, systemic, and neuropsychiatric activities of psychobiotics were discussed in detail. In conclusion, psychobiotics seem to have the potential for treatment of neuropsychiatric disorders in the future. However, there are many questions and we do not know the answers yet. We anticipate that the answer to these questions will be given in the near future.

Exercise, diet and stress as modulators of gut microbiota: Implications for neurodegenerative diseases

The last decade has witnessed an exponentially growing interest in gut microbiota and the gut-brain axis in health and disease. Accumulating evidence from preclinical and clinical research indicate that gut microbiota, and their associated microbiomes, may influence pathogenic processes and thus the onset and progression of various diseases, including neurological and psychiatric disorders. In fact, gut dysbiosis (microbiota dysregulation) has been associated with a range of neurodegenerative diseases, including Alzheimer's, Parkinson's, Huntington's and motor neuron disease, as well as multiple sclerosis. The gut microbiota constitutes a dynamic microbial system constantly challenged by many biological variables, including environmental factors. Since the gut microbiota constitute a changeable and experience-dependent ecosystem, they provide potential therapeutic targets that can be modulated as new interventions for dysbiosis-related disorders, including neurodegenerative diseases. This article reviews the evidence for environmental modulation of gut microbiota and its relevance to brain disorders, exploring in particular the implications for neurodegenerative diseases. We will focus on three major environmental factors that are known to influence the onset and progression of those diseases, namely exercise, diet and stress. Further exploration of environmental modulation, acting via both peripheral (e.g. gut microbiota and associated metabolic dysfunction or 'metabolopathy') and central (e.g. direct effects on CNS neurons and glia) mechanisms, may lead to the development of novel therapeutic approaches, such as enviromimetics, for a wide range of neurological and psychiatric disorders.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

Depression's Unholy Trinity: Dysregulated Stress, Immunity, and the Microbiome

Depression remains one of the most prevalent psychiatric disorders, with many patients not responding adequately to available treatments. Chronic or early-life stress is one of the key risk factors for depression. In addition, a growing body of data implicates chronic inflammation as a major player in depression pathogenesis. More recently, the gut microbiota has emerged as an important regulator of brain and behavior and also has been linked to depression. However, how this holy trinity of risk factors interact to maintain physiological homeostasis in the brain and body is not fully understood. In this review, we integrate the available data from animal and human studies on these three factors in the etiology and progression of depression. We also focus on the processes by which this microbiota-immune-stress matrix may influence centrally mediated events and on possible therapeutic interventions to correct imbalances in this triune.

Relationship between the gut microbiome and brain function

It has become increasingly evident in recent years that the gut microbiome and the brain communicate in a bidirectional manner, with each possibly affecting the other's functions. Substantial research has aimed to understand the mechanisms of this interaction and to outline strategies for preventing or treating nervous system-related disturbances. This review explores the evidence demonstrating how the gut microbiome may affect brain function in adults, thereby having an impact on stress, anxiety, depression, and cognition. In vitro, in vivo, and human studies reporting an association between a change in the gut microbiome and functional changes in the brain are highlighted, as are studies outlining the mechanisms by which the brain affects the microbiome and the gastrointestinal tract. Possible modes of action to explain how the gut microbiome and the brain functionally affect each other are proposed. Supplemental probiotics to combat brain-related dysfunction offer a promising approach, provided future research elucidates their mode of action and possible side effects. Further studies are warranted to establish how pre- and probiotic interventions may help to balance brain function in healthy and diseased individuals.

Approach to stress endocrine response: somatization in the context of gastroenterological symptoms: a systematic review

Background

Stress can be defined as an acute threat to the homeostasis of an organism, and in order to manage stress, and maintain stability, the allostatic systems activate an adaptive response. Stress has been shown to have both short - and long-term effects on the function of the gastrointestinal tract, but long-term exposure to stress is more likely to cause endocrine disorders.

Objective

The aim of this study was to investigate the endocrine response to stress, and evaluate the relationship between somatization and gastrointestinal symptoms.

Methods

A systematic literature search was conducted on several academic databases, which included, Pubmed, EBSCO and Science Direct. The search was performed using the keywords, “endocrine response to stress”, “somatization” and “gastrointestinal symptoms”.

Results

The hypothalamic-pituitary-adrenal (HPA) axis is essential in controlling physiological stress responses. Dysfunction is related to several mental disorders, including anxiety and depression, or somatization. Symptoms associated with genetic, or other traumatic experiences of individuals under stress, can lead to a maladaptive response to stress. These stressful life events were found to be associated with digestive system-related chronic diseases. Gastrointestinal disorders significantly affect millions of people worldwide.

Conclusion

This study examined how the endocrine system responds to stress, and the effect this has in causing stress-related gastrointestinal distresses. Our findings indicate that stress-related psychological disorders are strongly associated with the severity of gastrointestinal symptoms.

Probiotics for Parkinson's Disease

Parkinson's disease (PD) is a complex neurological disorder classically characterized by impairments in motor system function associated with loss of dopaminergic neurons in the substantia nigra. After almost 200 years since the first description of PD by James Parkinson, unraveling the complexity of PD continues to evolve. It is now recognized that an interplay between genetic and environmental factors influences a diverse range of cellular processes, reflecting on other clinical features including non-motor symptoms. This has consequently highlighted the extensive value of early clinical diagnosis to reduce difficulties of later stage management of PD. Advancement in understanding of PD has made remarkable progress in introducing new tools and strategies such as stem cell therapy and deep brain stimulation. A link between alterations in gut microbiota and PD has also opened a new line. Evidence exists of a bidirectional pathway between the gastrointestinal tract and the central nervous system. Probiotics, prebiotics and synbiotics are being examined that might influence gut-brain axis by altering gut microbiota composition, enteric nervous system, and CNS. This review provides status on use of probiotics for PD. Limitations and future directions will also be addressed to promote further research considering use of probiotics for PD.

Gut microbes, ageing & organ function: a chameleon in modern biology?

All species, including humans, are cohabited by a myriad of microbial species, which massively influences body function in a diet‐, exercise‐ and age‐dependent manner. The microbiome composition differs between individuals, partly due to the polymorphic immune system, as well as the environment, making the microbe–host interplay unique in each one of us. Ageing is a gradual loss of function in part due to reduced repair mechanisms and accumulation of tissue damage through mechanisms largely unknown. Accumulating evidence suggests that our indigenous microbes, a known major regulator of human physiology, are also connected to regulate the ageing process through signalling pathways and metabolites though the biological mechanisms are unknown. At an ageing meeting in Singapore in 2018, investigators discussed the current understanding of microbe regulation and its impact on healthy ageing. This review summarizes the highlights from the meeting and conveys some of the new ideas that emerged around gut microbes and the biology of ageing. While highly speculative, an idea emerged in which gut microbes constantly respond and evolve to environmental cues, as part of an ageing process, thus serving as a second messenger to support and attenuate organ decline in a diet‐, gender‐ and age‐dependent manner.

Targeting Microbiota: What Do We Know about It at Present?

The human microbiota is a variety of different microorganisms. The composition of microbiota varies from host to host, and it changes during the lifetime. It is known that microbiome may be changed because of a diet, bacteriophages and different processes for example, such as inflammation. Like all other areas of medicine, there is a continuous growth in the area of microbiology. Different microbes can reside in all sites of a human body, even in locations that were previously considered as sterile; for example, liver, pancreas, brain and adipose tissue. Presently one of the etiological factors for liver disease is considered to be pro-inflammatory changes in a host’s organism. There are lot of supporting data about intestinal dysbiosis and increased intestinal permeability and its effect on development of liver disease pointing to the gut–liver axis. The gut–liver axis affects pathogenesis of many liver diseases, such as chronic hepatitis B, chronic hepatitis C, alcoholic liver disease, non-alcoholic liver disease, non-alcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma. Gut microbiota has been implicated in the regulation of brain health, emphasizing the gut–brain axis. Also, experiments with mice showed that microorganisms have significant effects on the blood–brain barrier integrity. Microbiota can modulate a variety of mechanisms through the gut–liver axis and gut–brain axis. Normal intestinal flora impacts the health of a host in many positive ways, but there is now significant evidence that intestinal microbiota, especially altered, have the ability to impact the pathologies of many diseases through different inflammatory mechanisms. At this point, many of the pathophysiological reactions in case of microbial disbyosis are still unclear.

Different duck products protein on rat physiology and gut microbiota

We report the effects of protein from different duck products on the intestinal flora and physiology of rats. After 30 days of feeding, rats fed water-boiled salted duck protein had the lowest gut microbial diversity and richness. Allobaculum, Lactobacillus, Coprococcus and Eubacterium increased in rats fed wine-cured duck protein, while rats fed water-boiled salted and wine-cured duck protein showed increased serum urea (UREA) concentrations and serum cholesterol (CHOL) to HDL-cholesterol (HDLC) ratios, but decreased retroperitoneal white adipose tissue (rWAT) and perirenal white adipose tissue (pWAT) to body weight ratios. The changes in gut bacteria were mainly associated with the fat-mass index (weight of rWAT or pWAT to body weight ratio), accompanied by the opposite correlation with UREA content. SIGNIFICANCE: It showed that protein from different duck products impacted the intestinal flora and caused physiological changes in rats. Different sources of processed protein vary in their digestibility and digestive kinetics, all of which can affect the intestinal microbiota and physiology. We report the effects is an effort to map the complex interactions of "host physiology-nutrition-microbiota" in order to provide some insights into that food processing can be improved to promote beneficial gut microbes and enhance human health.

From isoniazid to psychobiotics: the gut microbiome as a new antidepressant target

An awareness of the importance of the gut-brain axis in psychiatric disorders such as depression is increasing. The gut microbiome is a key component of this axis. Gut bacteria can communicate with the brain through a variety of pathways including the hypothalamic-pituitary-adrenal axis, immune modulation, tryptophan metabolism and the production of various neuroactive compounds. Patients with depression, and other mood and anxiety disorders, show distinct compositional changes in their gut bacteria profile, raising the question about a possible aetiological role for the microbiome in these disorders. Evidence is emerging that the gut microbiome may represent a new potential antidepressant target and the term 'psychobiotic' has been coined to describe bacteria which confer mental health benefits. Gut bacteria are easily accessible and can be altered in a variety of ways including through the use of probiotics, prebiotics and dietary change. Psychobiotics containing various Lactobacillus and Bifidobacterium species have demonstrated the ability to improve mood, reduce anxiety and enhance cognitive function in both healthy populations and patient groups. This article provides an overview of the identification and development of antidepressant psychobiotics, from the preclinical evidence in the laboratory to the more recent encouraging results from human trials.

SCI and depression: Does inflammation commandeer the brain?

The incidence of depression is almost twice as high in the spinally injured population compared to the general population. While this incidence has long been attributed to the psychological, economic, and social burdens that accompany spinal cord injury (SCI), data from animal studies indicate that the biology of SCI may play an important role in the development of depression. Inflammation has been shown to impact stress response in rodents and humans, and inflammatory cytokines have been associated with depression for decades. The inflammation inherent to SCI may disrupt necessary mechanisms of mental homeostasis, such as serotonin production, dopamine production, and the hypothalamic pituitary adrenal axis. Additionally, gut dysbiosis that occurs after SCI can exacerbate inflammation and may cause further mood and behavior changes. These mediators combined may significantly contribute to the rise in depression seen after SCI. Currently, there are no therapies specific to depression after SCI. Elucidation of the molecular pathways that contribute to SCI-specific depression is crucial for the understanding of this disease and its potential treatments.

Crude fiber modulates the fecal microbiome and steroid hormones in pregnant Meishan sows

The beneficial effects of dietary fiber on the reproductive performance and welfare of sows have been discussed broadly, but few researches examined the causal changes and the association of gut microbiota and the steroid hormones, the main regulators of reproductive function. To shed light on this, thirty-six Meishan sows were allocated into 2.5% crude fiber (CF) group and 7.5% CF group respectively for an entire farrowing interval. On the 90th day of gestation, the saliva and fresh stool of sows were individually collected in the morning (06:00-07:00) for steroid hormones, short-chain fatty acids (SCFAs) and microbiome analysis. In addition, the parameter of pregnant behavioral and farrowing performance was recorded and evaluated. We observed that, as compared with the 2.5% CF treatment, 7.5% CF significantly increased the litter size (p = 0.01), reduced the stereotypic behaviors including sham chewing, rolling tongue and licking ground (p = 0.02, 0.04, 0.01) at later gestation stage, but increased lying time (p = 0.00). In coincide with this, 7.5% CF diet increased the salivary progesterone (p = 0.00), fecal estradiol and progesterone (p = 0.01, 0.02) level, fecal water and SCFAs content (p = 0.02, 0.03), decreased the salivary and fecal cortisol (p = 0.01, 0.00) level. Further, 7.5% CF diet increased the fecal microbiota richness (ACE, p = 0.04; Chao, p = 0.07) and diversity (Shannon, p = 0.01; Simpson, p = 0.04), the proportion of genus Ruminococcus, Butyrivibrio, Lactobacillus and Fibrobacter (p = 0.02, 0.05, 0.04, 0.00), whereas reduced the proportion of genus Clostridium, Streptococcus, Bacteroides and Escherichia-Shigella (p = 0.00, 0.00, 0.04, 0.04). These results indicate that, fibrous diet can regulate the steroid hormones secretion and modulate the gut with more cellulose-degrading and probiotic bacterium, but less opportunistic pathogens, and this may contribute to the improvement of reproductive performance and welfare in sows.

A Mechanistic Model of Gut-Brain Axis Perturbation and High-Fat Diet Pathways to Gut Microbiome Homeostatic Disruption, Systemic Inflammation, and Type 2 Diabetes

Type 2 diabetes (T2D) is a highly prevalent metabolic disease, affecting nearly 10% of the American population. Although the etiopathogenesis of T2D remains poorly understood, advances in DNA sequencing technologies have allowed for sophisticated interrogation of the human microbiome, providing insight into the role of the gut microbiome in the development and progression of T2D. An emerging body of research reveals that gut-brain axis (GBA) perturbations and a high-fat diet (HFD), along with other modifiable and nonmodifiable risk factors, contribute to gut microbiome homeostatic imbalance. Homeostatic imbalance or disruption increases gut wall permeability and facilitates translocation of endotoxins (lipopolysaccharides) into the circulation with resultant systemic inflammation. Chronic, low-grade systemic inflammation ensues with pro-inflammatory pathways activated, contributing to obesity, insulin resistance (IR), pancreatic β-cell decline, and, thereby, T2D. While GBA perturbations and HFD are implicated in provoking these conditions, prior mechanistic models have tended to examine HFD and GBA pathways exclusively without considering their shared pathways to T2D. Addressing this gap, this article proposes a mechanistic model informed by animal and human studies to advance scientific understanding of (1) modifiable and nonmodifiable risk factors for gut microbiome homeostatic disruption, (2) HFD and GBA pathways contributing to homeostatic disruption, and (3) shared GBA and HFD pro-inflammatory pathways to obesity, IR, β-cell decline, and T2D. The proposed mechanistic model, based on the extant literature, proposes a framework for studying the complex relationships of the gut microbiome to T2D to advance study in this promising area of research.

Pharmacological restoration of gut barrier function in stressed neonates partially reverses long-term alterations associated with maternal separation

RATIONALE

Intestinal permeability plays an important role in gut-brain axis communication. Recent studies indicate that intestinal permeability increases in neonate pups during maternal separation (MS).

OBJECTIVES

The present study aims to determine whether pharmacological inhibition of myosin light chain kinase (MLCK), which regulates tight junction contraction and controls intestinal permeability, in stressed neonates, protects against the long-term effects of MS.

METHODS

Male Wistar rats were exposed to MS (3 h per day from post-natal day (PND)2 to PND14) or left undisturbed and received daily intraperitoneal injection of a MLCK inhibitor (ML-7, 5 mg/kg) or vehicle during the same period. At adulthood, emotional behaviors, corticosterone response to stress, and gut microbiota composition were analyzed.

RESULTS

ML-7 restored gut barrier function in MS rats specifically during the neonatal period. Remarkably, ML-7 prevented MS-induced sexual reward-seeking impairment and reversed the alteration of corticosterone response to stress at adulthood. The effects of ML-7 were accompanied by the normalization of the abundance of members of Lachnospiraceae, Clostridiales, Desulfovibrio, Bacteroidales, Enterorhabdus, and Bifidobacterium in the feces of MS rats at adulthood.

CONCLUSIONS

Altogether, our work suggests that improvement of intestinal barrier defects during development may alleviate some of the long-term effects of early-life stress and provides new insight on brain-gut axis communication in a context of stress.