Role of the Intestinal Microbiome, Intestinal Barrier and Psychobiotics in Depression

Abstract

The intestinal microbiota plays an important role in the pathophysiology of depression. As determined, the microbiota influences the shaping and modulation of the functioning of the gut–brain axis. The intestinal microbiota has a significant impact on processes related to neurotransmitter synthesis, the myelination of neurons in the prefrontal cortex, and is also involved in the development of the amygdala and hippocampus. Intestinal bacteria are also a source of vitamins, the deficiency of which is believed to be related to the response to antidepressant therapy and may lead to exacerbation of depressive symptoms. Additionally, it is known that, in periods of excessive activation of stress reactions, the immune system also plays an important role, negatively affecting the tightness of the intestinal barrier and intestinal microflora. In this review, we have summarized the role of the gut microbiota, its metabolites, and diet in susceptibility to depression. We also describe abnormalities in the functioning of the intestinal barrier caused by increased activity of the immune system in response to stressors. Moreover, the presented study discusses the role of psychobiotics in the prevention and treatment of depression through their influence on the intestinal barrier, immune processes, and functioning of the nervous system.

HPA Axis in the Pathomechanism of Depression and Schizophrenia: New Therapeutic Strategies Based on Its Participation

“…Furthermore, systemic administration of butyric acid (which belongs to SCFAs) has been shown to exert antidepressant and neuromodulatory effects [81,82]. The microbiota not only affects the release of various intestinal peptides (peptide YY, glucagon-like peptide 1) but is also involved in their production (Bifidobacterium dentium are able to produce γ-aminobutyric acid (GABA)) [83,84]. In order to investigate the role of the microbiota on HPA axis function, the researchers conducted a study using isolation-cultured mice (GF) [85].…”

Chronic Stress and Oxidative Stress as Common Factors of the Pathogenesis of Depression and Alzheimer’s Disease: The Role of Antioxidants in Prevention and Treatment

“…Elevated levels of IL-1 may be associated with the development of depression, as confirmed by preclinical studies. Impaired social inhibition and reduced sexual activity were observed in test animals [ 70 ]. BDNF affects the formation of new dopaminergic, serotonergic, noradrenergic, and cholinergic connections.…”

“…Due to BDNF’s ability to cross the blood–brain barrier (BBB), its blood concentration is thought to correlate with its concentration in the cerebral cortex. In a study performed on rats, significantly reduced plasma BDNF concentrations were observed in a group of depressed patients compared to a control sample [ 70 , 71 ]. It is possible that the use of antidepressants is associated with the elevated levels of BDNF in serum in patients suffering from depression.…”

Maintaining the Balance of Intestinal Flora through the Diet: Effective Prevention of Illness

“…However, in some cases, the reciprocal relationship becomes skewed, with changes in diet and long-term exposure to antibiotics and other drugs [63]. The contribution of the host's gut-balanced diet to microbial dysfunction and its vital role in coordinating host-microbiome interactions have been demonstrated [64].…”