Adolescence and aging: impact of adolescence inflammatory stress and microbiota alterations on brain development, aging and neurodegeneration.

Puberty/adolescence is a critical phase during neurodevelopment with numerous structural, neurochemical, and molecular changes occurring in response to genetic and environmental signals. A consequence of this major neuronal reorganizing and remodelling, is a heightened level of vulnerability to stressors and immune challenge. The gut microbiota is a fundamental modulator of stress and immune responses and has been found to play a role in mental health conditions and neurodegenerative disorders. Environmental insults (stress, infection, neuroinflammation, use of antibiotics) during adolescence can result in dysbiosis subsidizing the development of brain disorders later in life. Also, pubertal neuroinflammatory insults can alter neurodevelopment, impact brain functioning in an enduring manner, and contribute to neurological disorders related to brain aging such as Alzheimer's disease, Parkinson's disease and depression. Exposure to probiotics during puberty can mitigate inflammation, reverse dysbiosis and decrease vulnerabilities to brain disorders later in life. The goal of this review is to reveal the consequences of pubertal exposure to stress and immune challenges on the gut microbiota, immune reactivity within the brain and the risk or resilience to stress-induced mental illnesses and neurodegenerative disorders. We propose that consumption of probiotics during adolescence contribute to the prevention of brain pathologies in adulthood.