Perinatal transmission of a probiotic Bifidobacterium strain protects against early life stress-induced mood and gastrointestinal motility disorders

A systematic review of preclinical studies targeted toward the management of co-existing functional gastrointestinal disorders, stress, and gut dysbiosis

Modern dietary habits and stressed lifestyle have escalated the tendency to develop functional gastrointestinal disorders (FGIDs) through alteration in the gut-brain-microbiome axis. Clinical practices use symptomatic treatments, neglect root causes, and prolong distress in patients. The past decade has seen the evolution of various interventions to attenuate FGIDs. But clinical translation of such studies is very rare mostly due to lack of awareness. The aim of this review is to meticulously integrate different studies and bridge this knowledge gap. Literature between 2013 and 2023 was retrieved from PubMed, ProQuest, and Web of Science. The data was extracted based on the PRISMA guidelines and using the SYRCLE's risk of bias and the Cochrane Risk of Bias tools, quality assessment was performed. The review has highlighted molecular insights into the coexistence of FGIDs, stress, and gut dysbiosis. Furthermore, novel interventions focusing on diet, probiotics, herbal formulations, and phytoconstituents were explored which mostly had a multitargeted approach for the management of the diseases. Scientific literature implied positive interactions between the interventions and the gut microbiome by increasing the relative abundance of beneficial bacteria and reducing stress-related hormones. Moreover, the interventions reduced intestinal inflammation and regulated the expression of epithelial tight junction proteins in different in vivo models. This systematic review delves deep into the preclinical interventions to manage coexisting FGIDs, stress, and gut dysbiosis. However, in most of the discussed studies, long-term risks and toxicity profile of the interventions are lacking. So, it is necessary to highlight them for improved clinical outcomes.

The mind, brain, and body study: A protocol for examining the effects of the gut-brain-immune axis on internalizing symptoms in youth exposed to caregiving-related early adversity

Experiences of caregiving-related adversity are common and one of the strongest predictors of internalizing psychopathology (i.e., anxiety and depression). Specifically, individuals who have been exposed to such early adversities have altered affective neurodevelopment, impaired memory systems, increased risk of developing internalizing disorders, greater inflammation, and differences in gastrointestinal (gut) microbiome composition. Crucially, the gut microbiome undergoes a sensitive period of development that precedes neural and immune sensitive periods, thus making it a potentially fruitful target for intervention. Though previous work has assessed neural, immune, and gut microbiome systems in individuals exposed to early adversity, studies have primarily looked at these biological systems independently. The Mind, Brain, and Body study (MBB) implements multimodal and longitudinal design to assess how changes in the gut microbiome following caregiving-related adversity may underlie altered affective neurodevelopment, memory, and immune functioning in youth and contribute to internalizing symptoms. Across three waves, spread approximately 12-18 months apart, youth with and without previous experiences of caregiving-related adversity completed self-report measures of mental and physical health, provided stool, saliva, hair, and blood samples, and completed an MRI scan. Results of this study will expand our knowledge on how the gut microbiome shapes several biological and cognitive systems and motivate future work investigating the gut microbiome as potential target for intervention.

A new target for treating intervertebral disk degeneration: gut microbes

Intervertebral disk degeneration (IDD) is a common clinical spinal disease and one of the main causes of low back pain (LBP). Generally speaking, IDD is considered a natural degenerative process with age. However, with the deepening of research, people have discovered that IDD is not only related to age, but also has many factors that can induce and accelerate its progression. In addition, the pathogenesis of IDD remains unclear, resulting in limited traditional treatment methods that cannot effectively prevent and treat IDD. Conservative treatment may lead to patients' dependence on drugs, and the pain relief effect is not obvious. Similarly, surgical treatment is highly invasive, with a longer recovery time and a higher recurrence rate. With the deepening of exploration, people have discovered that intestinal microorganisms are an important symbiotic microbial community in the human body and are closely related to the occurrence and development of various diseases. Changes in intestinal microorganisms and their metabolites may affect the body's inflammatory response, immune regulation, and metabolic processes, thereby affecting the health of the intervertebral disk. In this context, the gut microbiota has received considerable attention as a potential target for delaying or treating IDD. This article first introduces the impact of gut microbes on common distal organs, and then focuses on three potential mechanisms by which gut microbes and their metabolites influence IDD. Finally, we also summarized the methods of delaying or treating IDD by interfering with intestinal microorganisms and their metabolites. Further understanding of the potential mechanisms between intestinal microorganisms and IDD will help to formulate reasonable IDD treatment strategies to achieve ideal therapeutic effects.

Maternal gut microbiota in the health of mothers and offspring: from the perspective of immunology

Due to the physiological alteration during pregnancy, maternal gut microbiota changes following the metabolic processes. Recent studies have revealed that maternal gut microbiota is closely associated with the immune microenvironment in utero during pregnancy and plays a vital role in specific pregnancy complications, including preeclampsia, gestational diabetes, preterm birth and recurrent miscarriages. Some other evidence has also shown that aberrant maternal gut microbiota increases the risk of various diseases in the offspring, such as allergic and neurodevelopmental disorders, through the immune alignment between mother and fetus and the possible intrauterine microbiota. Probiotics and the high-fiber diet are effective inventions to prevent mothers and fetuses from diseases. In this review, we summarize the role of maternal gut microbiota in the development of pregnancy complications and the health condition of future generations from the perspective of immunology, which may provide new therapeutic strategies for the health management of mothers and offspring.

Determining the emotional regulation function of Bifidobacterium breve: the role of gut metabolite regulation over colonization capability

Psychobiotics that modulate the gut-brain axis have emerged as promising interventions for clinical mental disorders. Bifidobacterium breve CCFM1025 has demonstrated antidepressant effects in both mice and patients with major depression. Nevertheless, the precise mechanism of action of CCFM1025 in emotional regulation remains ambiguous. This study aimed to explore the colonization capacity of CCFM1025 and its dose-dependent effect on emotional regulation in mice exposed to chronic unpredictable mild stress (CUMS). Additionally, we examined its regulatory effects on intestinal and serum metabolites in mice. The results revealed that CCFM1025 did not exhibit a heightened gut retention capability compared to the conspecific control strain. Nevertheless, CCFM1025 exhibited dose-dependent mitigation of anxiety-like behavior and memory impairment induced by CUMS, while also restoring gut microbiota homeostasis. Notably, CCFM1025 demonstrated a robust ability to exert potent gut metabolite regulation, resulting in significant elevation of bile acid and tryptophan metabolites in the gut contents and serum of mice. These findings indicate that the impact of CCFM1025 on emotional regulation may be attributed to its regulation of gut metabolites rather than its gut retention capability. The potential of Bifidobacterium to modulate bile acid metabolism may serve as a valuable avenue for regulating the gut microbiota and successfully exert emotion regulation.

Bifidobacteria in disease: from head to toe

Bifidobacteria as a strictly anaerobic gram-positive bacteria, is widely distributed in the intestine, vagina and oral cavity, and is one of the first gut flora to colonize the early stages of life. Intestinal flora is closely related to health, and dysbiosis of intestinal flora, especially Bifidobacteria, has been found in a variety of diseases. Numerous studies have shown that in addition to maintaining intestinal homeostasis, Bifidobacteria may be involved in diseases covering all parts of the body, including the nervous system, respiratory system, genitourinary system and so on. This review collects evidence for the variation of Bifidobacteria in typical diseases among various systems, provides mild and effective therapeutic options for those diseases that are difficult to cure, and moves Bifidobacteria from basic research to further clinical applications.

Decoding the role of the gut microbiome in gut-brain axis, stress-resilience, or stress-susceptibility: A review

Increased exposure to stress is associated with stress-related disorders, including depression, anxiety, and neurodegenerative conditions. However, susceptibility to stress is not seen in every individual exposed to stress, and many of them exhibit resilience. Thus, developing resilience to stress could be a big breakthrough in stress-related disorders, with the potential to replace or act as an alternative to the available therapies. In this article, we have focused on the recent advancements in gut microbiome research and the potential role of the gut-brain axis (GBA) in developing resilience or susceptibility to stress. There might be a complex interaction between the autonomic nervous system (ANS), immune system, endocrine system, microbial metabolites, and bioactive lipids like short-chain fatty acids (SCFAs), neurotransmitters, and their metabolites that regulates the communication between the gut microbiota and the brain. High fiber intake, prebiotics, probiotics, plant supplements, and fecal microbiome transplant (FMT) could be beneficial against gut dysbiosis-associated brain disorders. These could promote the growth of SCFA-producing bacteria, thereby enhancing the gut barrier and reducing the gut inflammatory response, increase the expression of the claudin-2 protein associated with the gut barrier, and maintain the blood-brain barrier integrity by promoting the expression of tight junction proteins such as claudin-5. Their neuroprotective effects might also be related to enhancing the expression of brain-derived neurotrophic factor (BDNF) and glucagon-like peptide (GLP-1). Further investigations are needed in the field of the gut microbiome for the elucidation of the mechanisms by which gut dysbiosis contributes to the pathophysiology of neuropsychiatric disorders.

Microglia are necessary for probiotics supplementation to improve impaired fear extinction caused by pregnancy stress in adult offspring of rats

The prevention and treatment of fear-related disorders in offspring affected by pregnancy stress remains challenging at clinic. Here, we examined the effects of gut microbiota of stressed pregnant rats on the fear extinction of their offsprings, and the potential mechanisms. We found that gut microbiota transplantation from rats with pregnancy stress to normal pregnant rats impaired fear extinction, induced microglial activation and synaptic phagocytosis, increased synapse loss in offsprings. Probiotics supplement during pregnancy stress partly normalized pregnancy stress-induced gut microbiota dysbiosis of pregnant rats, and promoted fear memory extinction, inhibited fear memory reappearance, and limited microglial activation and synaptic phagocytosis in offsprings. These data revealed that gut microbiota of stressed pregnant mother improved the development of fear-related disorders of offspring, which may be associated with microglial synaptic pruning.

The Survival of Psychobiotics in Fermented Food and the Gastrointestinal Tract: A Review

In recent years, scientists have been particularly interested in the gut-brain axis, as well as the impact of probiotics on the nervous system. This has led to the creation of the concept of psychobiotics. The present review describes the mechanisms of action of psychobiotics, their use in food products, and their viability and survival during gastrointestinal passage. Fermented foods have a high potential of delivering probiotic strains, including psychobiotic ones. However, it is important that the micro-organisms remain viable in concentrations ranging from about 10⁶ to 10⁹ CFU/mL during processing, storage, and digestion. Reports indicate that a wide variety of dairy and plant-based products can be effective carriers for psychobiotics. Nonetheless, bacterial viability is closely related to the type of food matrix and the micro-organism strain. Studies conducted in laboratory conditions have shown promising results in terms of the therapeutic properties and viability of probiotics. Because human research in this field is still limited, it is necessary to broaden our understanding of the survival of probiotic strains in the human digestive tract, their resistance to gastric and pancreatic enzymes, and their ability to colonize the microbiota.

Recognizing the role of the vagus nerve in depression from microbiota-gut brain axis

Depression is a worldwide disease causing severe disability, morbidity, and mortality. Despite abundant studies, the precise mechanisms underlying the pathophysiology of depression remain elusive. Recently, cumulate research suggests that a disturbance of microbiota-gut-brain axis may play a vital role in the etiology of depression while correcting this disturbance could alleviate depression symptoms. The vagus nerve, linking brain and gut through its afferent and efferent branches, is a critical route in the bidirectional communication of this axis. Directly or indirectly, the vagus afferent fibers can sense and relay gut microbiota signals to the brain and induce brain disorders including depression. Also, brain changes in response to stress may result in gut hyperpermeability and inflammation mediating by the vagal efferents, which may be detrimental to depression. Notably, vagus nerve stimulation owns an anti-inflammatory effect and was proved for depression treatment. Nevertheless, depression was accompanied by a low vagal tone, which may derive from response to stress and contribute to pathogenesis of depression. In this review, we aim to explore the role of the vagus nerve in depression from the perspective of the microbiota-gut-brain axis, highlighting the relationship among the vagal tone, the gut hyperpermeability, inflammation, and depression.