Fig. 3
From: The interaction between ageing and Alzheimer's disease: insights from the hallmarks of ageing
Changes in systemic ageing markers between normal and ageing (in AD) brains. Microbiota homeostasis maintains normal nutrient metabolism, immune defense and signaling transduction to the brain and other organs [229]. Dysbiosis, including decreased diversity of microbiota, decreased abundance of beneficial microbes, increased abundance of harmful microbes and decreased levels of bile acids and SCFAs, can cause a persistent inflammatory reaction [230]. Moreover, disruption of the BBB allows macrophages to enter the brain and aggravate neuroinflammation [231]. AD Alzheimer’s disease, SCFAs short-chain fatty acids