Cognitive impairment associated with Alzheimer’s disease is a leading cause of disability worldwide. Prolonged exposure to lifestyle factors such as stress, an unhealthy diet, sedentary behaviour negatively affects brain plasticity and cognitive function, while positive factors such as a healthy diet and exercise may mitigate the progression of cognitive decline. A brain structure that is particularly receptive to lifestyle influence is the hippocampus. The hippocampus is responsible for learning, memory and regulation of emotion and it is also one of the first and primary brain regions to be affected in Alzheimer’s. Much evidence now shows that gut microbiota are extremely responsive to lifestyle factors. Alzheimer’s patients display a decrease in diversity of microbiota, which is recognised as a potential hallmark of healthy ageing. Thus, determining associations or causal roles between gut microbiota, hippocampal function and Alzheimer’s disease is a promising area of research. To determine if a gut microbiota signature in Alzheimer’s played a role in cognitive symptoms and neuroplasticity, we transplanted faecal microbiota from Alzheimer’s patients into young adult rats. We found impairments in behaviours reliant on adult hippocampal neurogenesis, an essential cellular process for certain memory functions and mood, after Alzheimer's patient transplants. The severity of impairments correlated with clinical cognitive scores in donor patients. Results suggest that symptoms of Alzheimer’s can be transferred to a healthy young organism via the gut microbiota and thus that symptoms of the disease may, in part, be caused by alterations in gut microbiota.
Yvonne Nolan is Professor in Neuroscience, a Science Foundation Ireland Investigator and an Investigator in APC Microbiome Ireland, University College Cork (UCC). She leads a research team investigating the impact of lifestyle influences such as exercise, stress and diet on gut health, brain plasticity and memory, especially during middle and older age and in Alzheimer’s disease. She is a cell, animal model and translational neuroscientist. She has secured funding from Science Foundation Ireland, Reta Lila Weston Trust, Marigot Ltd, Irish Research Council, Health Research Board and led a European Centres of Excellence in Neurodegeneration (COEN) project on Gut microbes, Neuroinflammation and Alzheimer’s disease. She is currently a partner on a European ERA4Health project: Modulation of brain ageing through nutrition and healthy lifestyle – “NutriBrain”. Yvonne is Vice Head of Graduate Studies in Medicine and Health at UCC, where she has strategic oversight of education for doctoral degrees in the health sciences. Yvonne graduated from NUI, Galway with a BSc in Biochemistry and a PhD in Neuropharmacology. She was a visiting fellow at McGill University Montreal, Canada and held postdoctoral positions in Trinity College, Dublin before joining UCC as academic staff.