Metabolic and immune risk factors for dementia and their modification by flavonoids: New targets for the prevention of cognitive impairment?

Abstract

A number of contributory factors have been implicated in the pathogenesis of Alzheimer's disease. One of these factors is chronic inflammation, with the over expression of pro-inflammatory cytokines and acute phase reactants consistently observed in the post mortem brain and plasma of AD patients. Furthermore, cardiovascular risk factors, such as hypertension, impaired vascular function and elevated LDL cholesterol, also appear to be predictive of increased dementia risk. Although classically associated with cardiovascular disease risk, both vascular and immune mediators may have direct deleterious effects on the brain, which contribute to the development of vascular dementia and Alzheimer's disease, as well as impairments in memory and neuro-cognitive function. Dietary agents previously noted for their ability to modulate these cardiovascular risk factors leading to reductions in chronic, low-grade inflammation and/or vascular dysfunction, may also possess an ability to moderate the progression of dementia. Flavonoid-rich foods such as tea, berries and cocoa have been reported to attenuate age-related deficits in memory and cognition, although the precise mechanisms of their action are unclear. As these flavonoid rich-foods/beverages also appear to mediate inflammatory processes, attenuate endothelial dysfunction and reduce hypertension, such actions may contribute to their efficacy in the brain. This review will explore these concepts with the view to further unravelling the actions of flavonoids and flavonoid-rich foods against brain disease and to highlight the importance measuring such factors in future clinical studies.