Bidirectional Brain-gut-microbiota Axis in increased intestinal permeability induced by central nervous system injury.

Central nervous system injuries may lead to the disorders of the hypothalamic-pituitary-adrenal axis, autonomic nervous system, and enteric nervous system. These effects then cause the changes in the intestinal microenvironment, such as a disordered intestinal immune system as well as alterations of intestinal bacteria. Ultimately, this leads to an increase in intestinal permeability. Inflammatory factors produced by the interactions between intestinal neurons and immune cells as well as the secretions and metabolites of intestinal flora can then migrate through the intestinal barrier, which will aggravate any peripheral inflammation and the central nervous system injury. The brain-gut-microbiota axis is a complex system that plays a crucial role in the occurrence and development of central nervous system diseases. It may also increase the consequences of preventative treatment. In this context, here we have summarized the factors that can lead to the increased intestinal permeability and some of the possible outcomes.

Li XJ ，You XY ，Wang CY ，Li XL ，Sheng YY ，Zhuang PW ，Zhang YJ ... -  《-》

Gut Microbiota-brain Axis.

Wang HX ，Wang YP 《-》

Gut-Microbiota-Brain Axis and Its Effect on Neuropsychiatric Disorders With Suspected Immune Dysregulation.

Gut microbiota regulate intestinal function and health. However, mounting evidence indicates that they can also influence the immune and nervous systems and vice versa. This article reviews the bidirectional relationship between the gut microbiota and the brain, termed the microbiota-gut-brain (MGB) axis, and discusses how it contributes to the pathogenesis of certain disorders that may involve brain inflammation. Articles were identified with a search of Medline (starting in 1980) by using the key words anxiety, attention-deficit hypersensitivity disorder (ADHD), autism, cytokines, depression, gut, hypothalamic-pituitary-adrenal (HPA) axis, inflammation, immune system, microbiota, nervous system, neurologic, neurotransmitters, neuroimmune conditions, psychiatric, and stress. Various afferent or efferent pathways are involved in the MGB axis. Antibiotics, environmental and infectious agents, intestinal neurotransmitters/neuromodulators, sensory vagal fibers, cytokines, and essential metabolites all convey information to the central nervous system about the intestinal state. Conversely, the hypothalamic-pituitary-adrenal axis, the central nervous system regulatory areas of satiety, and neuropeptides released from sensory nerve fibers affect the gut microbiota composition directly or through nutrient availability. Such interactions seem to influence the pathogenesis of a number of disorders in which inflammation is implicated, such as mood disorder, autism-spectrum disorders, attention-deficit hypersensitivity disorder, multiple sclerosis, and obesity. Recognition of the relationship between the MGB axis and the neuroimmune systems provides a novel approach for better understanding and management of these disorders. Appropriate preventive measures early in life or corrective measures such as use of psychobiotics, fecal microbiota transplantation, and flavonoids are discussed.

Petra AI ，Panagiotidou S ，Hatziagelaki E ，Stewart JM ，Conti P ，Theoharides TC ... -  《-》

Microbiome and substances of abuse.

There is a growing amount of evidence showing a reciprocal relation between the gut microbiota and the brain. Substance use disorders (SUD), which are a major cause of preventable morbidity and mortality worldwide, have an influence on the gut microbiota and on the gut-brain axis. The communication between the microbiota and the brain exists through different pathways: (1) the immune response elicited by bacterial products, coupled with alterations of the intestinal barrier allowing these products to enter the bloodstream, (2) the direct and indirect effects of bacterial metabolites such as short chain fatty acids (SCFAs) or tryptophan on the brain, (3) and the hypothalamic-pituitary-adrenal (HPA) axis, whose peripheral afferents can be influenced by the microbiota, and can in turn activate microglia. Among substances of abuse, alcohol has been the subject of the greatest number of studies in this field. In some but not all patients suffering from alcohol-use-disorder (AUD), alcohol alters the composition of the gut microbiota and the permeability of the intestinal barrier, directly and through dysbiosis. It has also been well demonstrated that alcohol induces a peripheral inflammation; it is still unclear whether it induces a central inflammation, as there are contradictory results in human studies. In animal studies, it has been shown that neuroinflammation increases during alcohol withdrawal. Literature on opioids and stimulants is less numerous. Chronic morphine intake induces dysbiosis, increased intestinal permeability and a probable neuroinflammation, which could explain symptoms such as tolerance, hyperalgesia and deficit in reward behavior. Cocaine induces a dysbiosis and conversely the microbiome can modulate the behavioral response to stimulant drugs. Tobacco cessation is associated with an increase in microbiota diversity. Taken together, the findings of our narrative literature review suggest a bidirectional influence in the pathogenesis of substance use disorders.

Salavrakos M ，Leclercq S ，De Timary P ，Dom G ... -  《-》

Can the gut be the missing piece in uncovering PD pathogenesis?

It is now well established that Parkinson's disease (PD) is not only a movement disorder of the CNS but also a gastrointestinal disorder affecting the enteric nervous system (ENS). The gut-brain axis is a bidirectional communication between the brain and the gastrointestinal tract, which comprises besides the CNS and the ENS, the intestinal epithelial barrier, the intestinal microbiota and the enteroendocrine systems. In this review, we present the clinical and pathological evidence suggesting that the gut-brain axis is dysfunctional in PD by discussing the possible role of gut microbiota, inflammation and permeability in the development of the disease.

Chapelet G ，Leclair-Visonneau L ，Clairembault T ，Neunlist M ，Derkinderen P ... -  《-》