Microbiota-Gut & Brain Axis

Microbiota-Gut & Brain Axis

• The gut microbiota plays a significant role in various health conditions and is studied extensively in relation to the brain
• Studies show the gut microbiota influences brain function and behavior
• Dysbiosis (imbalance in gut microbiota) can lead to various diseases, including those related to the brain
• Some diseases are linked to gut dysbiosis, including obesity, metabolic syndrome, certain cancers, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and chronic fatigue syndrome
• The gut microbiota can affect the immune system, which may impact neurological function
• The brain influences the gut, and the gut influences the brain in a bidirectional manner (gut-brain axis)
• The gut microbiota impacts cognitive function, mood, and nociception (pain processing)
• The gut-brain axis involves bidirectional communication between the gut microbiome, central nervous system, and other systems.
• Alterations in gut microbiota, inflammatory response, and immune system function can affect the brain and behavior.
• Probiotics and changes to the gut microbiome can affect mood, anxiety, and cognition.
• The gut microbiome can impact the production and metabolism of neurotransmitters like serotonin, GABA, and others
• The gut microbiota is implicated in the development of neurological diseases, including autism spectrum disorder (ASD), Parkinson's disease, Alzheimer's disease, and multiple sclerosis (MS).
• There is a bidirectional relationship, where the gut and the brain are connected and influence each other through various mechanisms.

Gut Microbiota Locations

• Bacteria and yeasts are present in various locations in the human body, often as the 'indigenous microbiome' or normal microbiota.
• These locations include the ears, eyes, mouth, upper respiratory tract, skin, mouth, nose, nasopharynx, oropharynx, gastrointestinal tract (GI tract) and genitourinary tract (GU tract).
• Some areas are colonized by specific types of bacteria/yeasts

Major Bacteria Phyla and Genera

• Firmicutes is the most abundant phylum in the human gut, comprising 60-80% of the flora.
• Bacteroidetes accounts for 20-30%
• Actinobacteria and Proteobacteria represent smaller proportions
• Representative genera within these phyla are highly variable and numerous

Microbiota Characteristics in Different Parts of the GI Tract

• Stomach: High pH, sparse bacterial load, low diversity, Firmicutes and Actinobacteria dominate
• Duodenum: Neutral pH, low oxygen, bile, mucus, low diversity, Firmicutes and Proteobacteria
• Colon: Neutral pH, low oxygen, mucus, host-indigestible polysaccharides, high bacterial load, high diversity, Firmicutes and Bacteroidetes predominate

Gut-Brain Axis Mechanisms

• The gut microbiota can affect the brain via the vagus nerve, immune system, and production of metabolites.
• These metabolites may influence neurotransmission and immune response,
• Interactions between gut microbiota and the central nervous system (CNS) are implicated in a variety of conditions and diseases.
• The gut microbiota-CNS axis can be influenced by factors such as diet, stress, and immune response.

Diseases Associated with Gut Dysbiosis

• Several types of diseases are associated with gut dysbiosis, with particular attention to mental health.
• Several types of diseases are associated with gut dysbiosis.

Probiotics and Gut Microbiota

• Probiotic interventions may modulate gut microbiota, and could potentially have therapeutic applications to those with certain diseases.
• Probiotics are live microorganisms which when consumed in adequate amounts confer a health benefit to the host.
• Research has explored the impact of probiotics, which are good bacteria, and their roles in modulating the gut microbiome, influencing brain function, and promoting conditions associated with the gut-brain axis.

Other Neurological Diseases and Microbiota

• Other neurological diseases, including multiple sclerosis(MS), Parkinson's disease, and Alzheimer's disease, have been linked to gut microbiome dysbiosis