But after all: What are psychobiotics?
The population is increasingly susceptible to physical and mental illnessdue to the fast pace, stressed and anxious of current life. Therefore, considering that through two-way communication between the intestine and the brain, emotional well-being directly impacts physical well-being and vice versa, and vice versa, and this mediation is done mainly by the intestinal microbiota, which studies have shown to play a vital role in neurodevelopment and etiopathogenesis from the simplest to the most complex neuropsychiatric disorder.
The role of the intestinal microbiota is also evident by the fact that important disorders related to the brain are accompanied by intestinal dysbiosis, which allows us to assume that early probiotic interventions seem promising to reduce the risk of development or minimize their symptoms. In this context, Probiotics are living microorganisms that, when ingested in adequate amounts, help maintain a healthy intestinal environment, however, their role is not only limited to digestive health, but also affects neural, immune, hypothalamic, adrenal and pituitary development.
Meanwhile, psychobiotics are a special class of probiotics that provide mental health benefits to individuals. They differ from conventional probiotics in their ability to produce or stimulate the production of neurotransmitters, short-chain fatty acids, enteroendocrine hormones and anti-inflammatory cytokines. Due to this potential, psychobiotics have a wide spectrum of applications, from mood and stress relief to adjuvant in the therapeutic treatment of various neurodevelopmental and neurodegenerative disorders.
What are psychobiotics?
The pathways through which the intestine and brain, more precisely the central nervous system, communicate with each other include the neuroendocrine, neuroimmune, autonomic nervous system, enteric and intestinal microbiota. Since the Enteric nervous system (CNS) and central nervous system (CNS) communicate bidirectionally due to positive and negative feedback scans through the vagus nerve.
More precisely, the brain sends signals through neurons to the vagus nerve, which regulates and relays such a signal to intestinal interneurons, thus regulating gut activity or vice versa. This, in turn, was established as a possible way for the intestinal microbiota to affect the activity of the brain and intestine.
In addition, this hypothesis is consolidated by several studies that identify altered behavior patterns in germ free mice when compared to normal mice in stress-related circumstances that, when administering probiotics for microbiome restoration, have its normalized behavioral responses, reinforcing the notion that intestinal microbiota and brain functioning are intertwined as well as the therapeutic potential of psychobiotics.
Psychobiotics x Enteric Microbiota-Nervous System Interaction
Hormones produced in the gut or neurotransmitters produced by their resident bacteria when in contact with the vagus nerve transmit signals to the CNS. This, in turn, between psychobiotics and their psychophysiological effects that is responsible for psychological benefits. Since this mechanism is proven by the literature from studies that when performing vagotomy, a surgical section in the vagus nerve, does not observe any physiological response to the administration of psychobiotics.
As, for example, an experiment in which mice not vagotomized when treated with probiotic administration (L. rhamnosus), a decrease in the intensity of anxiety, depression and lasting changes in gamma-aminobutyric acid (GABA) receptor expression in the CNS is observed, however, there is no same response when the same experiment is done in vagotomized mice.
Psychobiotics and vagus nerve
Therefore, psychobiotics act through the vagus nerve and through the action of metabolites such as short-chain fatty acids (GCAs), enteroendocrine hormones, cytokines and neurotransmitters. For GcAcs it is possible to observe the production of acetate, butyrate, lactate and propionate that, when interacting with the endocrine cells of the mucosa induce the production of the hormones colecistocinin (CCK), intestinal peptide hormone (PYY) and glucagon-like peptide-1 (GLP-1). However, compared to probiotics, prebiotics may have more significant effects in this regard, causing such prebiotics are also considered as psychobiotic, since the physiological response induced by them also confers benefits to mental health.
In addition, psychobiotic bacteria also stimulate an increased production of a variety of neurotransmitters through the metabolism of indigestible fibers. These include dopamine and norepinephrine stimulated by the family Bacillus, GABA by family Bifdobacteria, serotonin by families Enterococci and Streptococci, norepinephrine and serotonin by the family Escherichia promotes as well as GABA and Acetylcholine by the family Lactobacilli, this precision elucidates the specificity of the strains.
Psychobiotics have been shown to be effective not only against simple mood disorders such as anxiety and depression, but also in complex neuropsychiatric disorders. However, the professional who wishes to use this with his patients needs to be aware that all psychobiotics are probiotics, but not all probiotics are psychobiotic, this is because the benefits derived from psychobiotics are directly associated with strains. But beforehand, the bacteria with the most consumed psychobiotic potential are
Lactobacillus plantarum, L. helveticus
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Sharma R, Gupta D, Mehrotra R, Mage P. Psychobiotics: The Next-Generation Probiotics for the Brain. Curr Microbiol. 2021 Feb;78(2):449-463. Doi: 10.1007/s00284-020-02289-5. Epub 2021 Jan 4. PMID: 33394083.