Impact of gut microbiota on brain and behavior

Abstract Text:

The concept of the gut influencing brain and behaviour has existed for almost two centuries. However, a new player has emerged in the past decade: the gut microbiota, which is now seen as a key regulator of the gut-brain axis. The gut is home to a diverse array of trillions of microbes which significantly to outnumber human cells. Advances in sequencing technologies show that the microbiota influences almost all aspects of human biology. Bacterial colonisation of the gut plays a major role in postnatal development and maturation of key systems that have the capacity to influence central nervous system (CNS) programming and signaling, including the immune and endocrine systems. Individually, these systems have been implicated in the neuropathology of many CNS disorders and collectively they form an important bidirectional pathway of communication between the microbiota and the brain in health and disease.  Evidence of a crucial role for the microbiota in regulating stress-related changes in physiology, behaviour, and brain function has emerged mostly from animal studies. Mice that grow up devoid of a microbiome (in a germ-free environment) have an exaggerated hypothalamic-pituitary axis response to stress and altered anxiety-related behaviours. Converse findings have shown that stress (either early in life or in adulthood) changes microbiota composition. Moreover, the concept that bacteria were required for normal brain development has emerged and that the microbiota is regulates many key processes in the adult brain, such as neurogenesis, blood brain barrier function and microglia activation.  Thus, the ability to target the brain via the microbiome is viewed as a paradigm shift in neuroscience and psychiatry and has led to the concept of psychobiotics (bacteria with positive effects on mental health) being put forward. Moreover, microbiota is essential for both social cognition and visceral pain. Finally, there are critical time-windows early in life when the effects of microbiota on brain and behaviour appear to be more potent. Our data also demonstrates that these effects may be mediated via the vagus nerve, spinal cord, or neuroendocrine systems. Such data offer the enticing proposition that specific modulation of the enteric microbiota by dietary means may be a useful "psychobiotic"-based strategy for brain disorders.

Keywords: Stress, Neurodevelopment, probiotic