Abstract
Coffee or caffeine has recently been suggested as prophylaxis for dementia. Although memory problems are hallmarks of Alzheimer’s disease, this dementia is also characterized by neuropsychiatric symptoms called Behavioral and Psychological Symptoms of Dementia (BPSD). The impact of preventive/therapeutic strategies on both cognitive and non-cognitive symptoms can be addressed in the 3xTg-AD mice, since they exhibit cognitive but also BPSD-like profiles. Here, we studied the long-term effects of a low dose of caffeine in male 3xTg-AD mice and as compared to age-matched non-transgenic (NTg) counterparts with normal aging. Animals were treated (water or caffeine in drinking water) from adulthood (6 months of age) until middle-aged (13 months of age), that in 3xTg-AD mice correspond to onset of cognitive impairment and advanced stages, respectively. The low caffeine dosing used (0.3 mg/ml) was previously found to give a plasma concentration profile in mice roughly equivalent to that of a human coffee drinker. There were significant effects of caffeine on most behavioral variables, especially those related to neophobia and other anxiety-like behaviors, emotionality, and cognitive flexibility. The 3xTg-AD and NTg mice were differently influenced by caffeine. Overall, the increase of neophobia and other anxiety-related behaviors resulted in an exacerbation of BPSD-like profile in 3xTg-AD mice. Learning and memory, strongly influenced by anxiety in 3xTg-AD mice, got little benefit from caffeine, only shown after a detailed analysis of navigation strategies. The worsened pattern in NTg mice and the use of search strategies in 3xTg-AD mice make both groups more similar. Circadian motor activity showed genotype differences, which were found to be enhanced by caffeine. Selective effects of caffeine on NTg were found in the modulation of behaviors related to emotional profile and risk assessment. Caffeine normalized splenomegaly of 3xTg-AD mice, a physical indicator of their impaired peripheral immune system, and trended to increase their corticosterone levels. Our observations of adverse caffeine effects in an Alzheimer’s disease model together with previous clinical observations suggest that an exacerbation of BPSD-like symptoms may partly interfere with the beneficial cognitive effects of caffeine. These results are relevant when coffee-derived new potential treatments for dementia are to be devised and tested.
Highlights
Caffeine, a non-selective A1 and A2A receptor antagonist, is one of the most consumed drugs all over the world
Vertical activity was influenced by caffeine, with treated animals showing higher latencies to perform a first rearing [T, F(1,30) = 4.676; p < 0.05] and a reduction in the total number of rearings [T, F(1,30) = 4.571; p < 0.05]
Once the animals arrived to the periphery, self-grooming behavior was delayed in time in NTg+caff mice as compared to their control group [T, F(1,30) = 7.158; p < 0.05 and GxT, F(1,30) = 8.194; p < 0.01] the total duration of self-grooming (NTg-Veh: 2.25 s ± 0.48; NTg-Caff: 1.00 s ± 0.50; Tg-Veh: 1.50 s ± 0.50; Tg-Caff: 1.75 s ± 0.52) was not modified
Summary
A non-selective A1 and A2A receptor antagonist, is one of the most consumed drugs all over the world. Low doses of caffeine (20–200 mg/day) have been associated with positive effects on subjective mood: wellbeing, confidence, motivation, alert, security, efficiency, concentration, and desire for socialization (see Griffiths et al, 1990; Silverman et al, 1994). In this low range, caffeine (up to 300–400 mg) has a stimulating action with biphasic motor effects (Fredholm et al, 1999). Restraint from moderate or high intake of coffee (more than four cups a day) is recommended due to negative effects of caffeine on pregnancy, risk of osteoporosis, cardiovascular problems, anxiety, sleep disturbances, and alterations in physiological functions such as locomotion (Fredholm et al, 1999; Johansson et al, 2001; Giménez-Llort et al, 2005; Fredholm, 2007; Hermansen et al, 2012)
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