The impact of ageing and diet on cognitive performance
Researchers on the project NUVASCOG (Nutrition and microvascular dynamics in cognitive health) worked to generate new knowledge on microvascular mechanisms of cognitive decline. The central hypothesis was that impairment of brain microvascular plasticity as a result of ageing, diet or disease is a pivotal mechanism of cognitive decline. The project's first aim was to test this hypothesis. The second was to identify folate-responsive pathways that regulate microvascular plasticity in brain in young and old rats. Building on prior research, the team implemented a series of studies, combining major experimental systems for assessing animal behaviour, cerebrovascular physiology and neurovascular anatomy. They predicted that folate deficiency and ageing can limit brain circulation and oxygen delivery by diminishing microvascular plasticity, leading to impaired cognition. Using a putative animal model of vascular cognitive impairment, researchers placed young and old rats on either regular or folate-deficient diets. In young rats, folate deficiency caused a reduction of brain blood volume, which was partially mitigated by dietary supplementation with methionine. Repletion with normal dietary folate resulted in a reversal of the reduction of brain blood volume. This finding is relevant to the project's first aim. Experimental work revealed that the effects of ageing were greater than the effects of diet – ageing appears to diminish the density of the brain microvascular bed irrespective of diet. Relevant to the project's second aim, NUVASCOG identified folate- and methionine-responsive signalling pathways, including vascular signalling, metabolic and inflammatory genes in brain tissue. Young rats did not show any cognitive deficits as a result of diet, while ageing resulted in a significant decrement, compared to younger rats, in cognitive performance. As with the young rats, no cognitive deficits were identified in the old rats as a result of diet. Project findings point to diminished brain circulation with age as a potential cause of cognitive decline. This is consistent with cross-sectional findings in young and old adult humans. NUVASCOG has provided actionable insight into the dietary (life-style) factors that confer risk of cognitive impairment and dementia in older adults. As such, work can progress on interventions that prevent or mitigate the heavy burden these conditions place on individuals and society at large.
