Abstract
Retrospective and prospective epidemiologic studies suggest that enhanced coffee/caffeine intake during aging reduces risk of Alzheimer's disease (AD). Underscoring this premise, our studies in AD transgenic mice show that long-term caffeine administration protects against cognitive impairment and reduces brain amyloid-β levels/deposition through suppression of both β- and γ-secretase. Because coffee contains many constituents in addition to caffeine that may provide cognitive benefits against AD, we examined effects of caffeinated and decaffeinated coffee on plasma cytokines, comparing their effects to caffeine alone. In both AβPPsw+PS1 transgenic mice and non-transgenic littermates, acute i.p. treatment with caffeinated coffee greatly and specifically increased plasma levels of granulocyte-colony stimulating factor (GCSF), IL-10, and IL-6. Neither caffeine solution alone (which provided high plasma caffeine levels) or decaffeinated coffee provided this effect, indicating that caffeine synergized with some as yet unidentified component of coffee to selectively elevate these three plasma cytokines. The increase in GCSF is particularly important because long-term treatment with coffee (but not decaffeinated coffee) enhanced working memory in a fashion that was associated only with increased plasma GCSF levels among all cytokines. Since we have previously reported that long-term GCSF treatment enhances cognitive performance in AD mice through three possible mechanisms (e.g., recruitment of microglia from bone marrow, synaptogenesis, and neurogenesis), the same mechanisms could be complimentary to caffeine's established ability to suppress Aβ production. We conclude that coffee may be the best source of caffeine to protect against AD because of a component in coffee that synergizes with caffeine to enhance plasma GCSF levels, resulting in multiple therapeutic actions against AD.
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