Throughout the last decade, scientists have investigated the relationship between gut microbiota and the brain, as well as how it affects neurologic symptoms. Several research has found that the gut microbiota has an impact on neurogenesis, behavior, emotions, cognitive development, and the advancement of neuropsychiatric illnesses. A new study published in Frontiers in Medicine examined recent literature on the relationship between gut microbiota, the brain, and neurological illnesses.
The gut microbiota is a complex ecology of bacteria that evolves in the human host. About 100 trillion microorganisms live in the human gut and influence host fitness, phenotype, and health. Many ailments are caused by microbial dysbiosis or imbalance at various physiological levels.
The Interaction between Gastrointestinal Microbiota and Brain Manifestations
Gut microbiota can affect immune system function, brain activity, metabolic and nutritional homeostasis, and intestinal barrier integrity. As a result, the host’s physiological systems are impacted. Microbes have been found to be important signaling components in the bidirectional communication of the gut-brain axis.
Gastrointestinal symptoms such as functional biliary pain, gastroesophageal reflux disease (GRD), cyclic vomiting syndrome (CVS), gastroparesis, and chronic abdominal pain are caused by disruptions in the brain-gut axis. The previous study demonstrated that these illnesses have an impact on the neurenteric system.
Researchers have concentrated on the prevalence of neuropsychiatric consequences of gut microbiota. Many studies have found that gut dysbiosis has an impact on neurological illnesses such as anxiety, depression, Alzheimer’s disease, multiple sclerosis, schizophrenia, Parkinson’s disease, bipolar disorders, epilepsy, and dementia.
Food has an impact on the bacteria community in the gut. An animal-based diet, for example, increases the abundance of Alistipes, Bilophila, and Bacteroides while decreasing the abundance of Firmicutes. These abnormalities have an impact on digestion as well as other physiological systems. Firmicutes are related to the successful metabolization of dietary plant polysaccharides; thus, reducing their abundance is likely to have a negative impact on digestion.
The gut microbiota biosynthesizes neurotransmitters, interacts with the Brain, and influences neurological health. As a result, gut dysbiosis contributes to the occurrence of neurodegenerative diseases.
Antidepressants with antibacterial effects against specific microbes of the human gut, such as Akkermansia muciniphila, Bifidobacterium animalis, and Bacteroides fragilis, may aggravate pre-existing neurological disorders. A previous study found that a tiny level of Faecalibacterium in the gut is associated with depression.
Numerous investigations have found that the level of Bacteroides is much lower in people suffering from serious depression. Negative thoughts, impatience, sleep issues, and muscle tension are all symptoms of a generalized anxiety disorder (GAD). Furthermore, gastrointestinal tract inflammation is associated with gut dysbiosis, which promotes the release of pro-inflammatory cytokines and increases tumor necrosis factor-alpha (TNF-), which is directly related to anxiety symptoms.
Increased abundance of intestinal Bacteroides has been linked to anxiety-like conditions. In addition, patients with GAD have low amounts of Faecalibacterium, Lachnospira, Eubacterium, and Sutterella.
Bipolar disorder (BD) is another neuropsychiatric condition that is common throughout the world. Patients with bipolar disorder (BD) have episodes of acute low mood, great dissatisfaction, feelings of despair or high mood, excessively positive thinking, and a low sleep demand.
An imbalance in the gut microbiome has been associated with the occurrence of BD. Numerous investigations have found that patients with BD had higher levels of bacterial translocation indicators from the intestinal lumen. Furthermore, BD is associated with obesity and metabolic abnormalities, which increases the chance of a poor disease prognosis.
A low Faecalibacterium level has also been linked to BD. Moreover, Clostridiaceae and Collinsella, which enhance carbohydrate fermentation and produce short-chain fatty acids, were revealed to be significant in gut barrier integrity. Importantly, decreased Bifidobacterium levels impacted stress response due to cortisol generation. Schizophrenia has been connected to gut dysbiosis caused by gastrointestinal inflammation.
Many studies have found that neurological illnesses, such as autism and schizophrenia, have a deleterious impact on gut bacteria. Dementia is a psychiatric condition that involves poor memory, personality and thinking changes, and impaired reasoning. It was discovered that changes in Bacteroides levels had a direct impact on the stimulating variables connected to cognitive decline in dementia. Importantly, Lactobacillus and Bifidobacterium were discovered to increase the activity and release of neurotransmitters (acetylcholine), which influence learning and memory processes.
Probiotic Treatment for Neurological and Psychiatric Diseases
According to recent research, new psychotropic medications for treating mental diseases such as depression must target the host microbiota. To treat mental problems, several prebiotic and probiotic formulations have been produced.
“Psychobiotics” are formulations that directly influence gut microorganisms and brain interactions. They have anxiolytic and antidepressant properties, and they alter emotional, systemic, cognitive, and neurological characteristics.
Probiotic strains, such as Lactobacillus rhamnosus, have been shown in animal tests to effectively reduce stress-related behavior and corticosterone production. Another probiotic strain used to treat psychiatric and gastrointestinal problems in patients with major depressive disorder is Bifidobacterium breve. Another study found Lactobacillus fermentum PS150 to be effective in treating stressed rats. This strain not only reduced stress symptoms but also reduced cognitive deficiencies.