Promising uses of probiotic bacteria as depression and neurodegenerative diseases therapy support - recent studies review

Abstract

The intestinal microbiota – the living organisms that populate the gastrointestinal tract – plays a key role in proper body functioning. Disturbances to its homeostasis negatively affect the function of many organs, contributing to the development of diseases – for instance they negatively affect the functioning of the gastrointestinal tract and the intestinal barrier, which can lead to the development of metabolic disorders, autoimmune and psychiatric diseases. Intestinal dysbiosis has been found in patients with functional gastrointestinal disorders, irritable bowel syndrome, atopic dermatitis and psychiatric disorders including depression, Alzheimer's disease and schizophrenia. The aim of this study is to review current scientific publications regarding recent studies conducted in animal models and clinical trials assessing the impact and role of probiotics in the treatment of depression, neurodegenerative diseases and to clarify the concept of the brain-gut axis. Probiotics and prebiotics that play a role in the functioning of the gut-brain axis, populating the gastrointestinal tract seal the intestinal barrier, support the function of the nervous system (through the synthesis of serotonin, norepinephrine, acetylcholine, gamma-aminobutyric acid, among others), the endocrine system (reduce cortisol levels) and the immune system (stimulate the synthesis of anti-inflammatory cells). In the case of neurodegenerative diseases, i.e. Parkinson's or Alzheimer's disease, probiotic bacteria alleviate accompanying symptoms, improve intestinal and brain function, increase patients' quality of life and, in addition, contribute to inhibiting the development of these conditions. Current data confirm changes in the gut microflora in the aforementioned diseases, and suggest positive effects on health and brain activity. The microbiota has been proven to be involved in the production of neurotransmitters, affecting the hypothalamic-pituitary-adrenal axis, which is important in the course of depression and some psychiatric disorders. Despite numerous studies confirming the efficacy of supplementing the gut microbiota with defined bacterial strains, this promising often practiced method requires further clinical studies and a deeper understanding of the underlying mechanisms.

Keywords

• depression
• neurodegenerative diseases
• probiotic bacteria
• gut–brain axis