Abstract
The gut-microbiota–brain axis plays an important role in stress-related disorders, and dysfunction of this complex bidirectional system is associated with Alzheimer’s disease. This study aimed to assess the idea that whether gut microbiota depletion from early adolescence can alter anxiety- and depression-related behaviours in adult mice with or without Alzheimer-like disease. Male C57BL/6 mice were treated with an antibiotic cocktail from weaning to adulthood. Adult mice received an intracerebroventricular injection of amyloid-beta (Aβ)1–42, and were subjected to anxiety and depression tests. We measured, brain malondialdehyde and glutathione following anxiety tests, and assessed brain oxytocin and the hypothalamic–pituitary–adrenal (HPA) axis function by measuring adrenocorticotrophic hormone (ACTH) and corticosterone following depression tests. Healthy antibiotic-treated mice displayed significant decreases in anxiety-like behaviours, whereas they did not show any alterations in depression-like behaviours and HPA axis function. Antibiotic treatment from early adolescence prevented the development of anxiety- and depression-related behaviours, oxidative stress and HPA axis dysregulation in Alzheimer-induced mice. Antibiotic treatment increased oxytocin in the brain of healthy but not Alzheimer-induced mice. Taken together, these findings suggest that gut microbiota depletion following antibiotic treatment from early adolescence might profoundly affect anxiety- and depression-related behaviours, and HPA axis function in adult mice with Alzheimer-like disease.
Highlights
The gut-microbiota–brain axis plays an important role in stress-related disorders, and dysfunction of this complex bidirectional system is associated with Alzheimer’s disease
Clinical studies suggest considerable comorbidity between Alzheimer’s disease (AD) and anxiety or depression[22,23]. These findings are broadly supported by the animal studies linking brain Aβ administration to anxiety- and depression-like b ehaviours[24,25,26] there is a high prevalence of anxiety and depression in AD patients, no previous study has investigated the effects of gut microbiota depletion from early adolescence on anxiety- and depression-related symptoms in adult mice with Alzheimer-like disease
The antibiotic treatment prevented the development of anxiety-related behaviour in male C57BL/6 mice with Alzheimer-like disease
Summary
The gut-microbiota–brain axis plays an important role in stress-related disorders, and dysfunction of this complex bidirectional system is associated with Alzheimer’s disease. Antibiotic treatment increased oxytocin in the brain of healthy but not Alzheimer-induced mice Taken together, these findings suggest that gut microbiota depletion following antibiotic treatment from early adolescence might profoundly affect anxiety- and depression-related behaviours, and HPA axis function in adult mice with Alzheimer-like disease. Clinical studies suggest considerable comorbidity between AD and anxiety or depression[22,23] These findings are broadly supported by the animal studies linking brain Aβ administration to anxiety- and depression-like b ehaviours[24,25,26] there is a high prevalence of anxiety and depression in AD patients, no previous study has investigated the effects of gut microbiota depletion from early adolescence on anxiety- and depression-related symptoms in adult mice with Alzheimer-like disease. The relationship between antibiotic-induced gut microbiota depletion and these hormonal systems might be involved in the pathogenies of depression-related behaviours in AD-induced mice
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