Abstract
BackgroundAlzheimer's disease (AD) is the most frequently diagnosed form of dementia resulting in cognitive impairment. Many AD mouse studies, using the methyl donor S-adenosylmethionine (SAM), report improved cognitive ability, but conflicting results between and within studies currently exist. To address this, we conducted a meta-analysis to evaluate the effect of SAM on cognitive ability as measured by Y maze performance. As supporting evidence, we include further discussion of improvements in cognitive ability, by SAM, as measured by the Morris water maze (MWM).MethodsWe conducted a comprehensive literature review up to April 2014 based on searches querying MEDLINE, EMBASE, Web of Science, the Cochrane Library and Proquest Theses and Dissertation databases. We identified three studies containing a total of 12 experiments that met our inclusion criteria and one study for qualitative review. The data from these studies were used to evaluate the effect of SAM on cognitive performance according to two scenarios: 1. SAM supplemented folate deficient (SFD) diet compared to a folate deficient (FD) diet and 2. SFD diet compared to a nutrient complete (NC) diet. Hedge's g was used to calculate effect sizes and mixed effects model meta-regression was used to evaluate moderating factors.ResultsOur findings showed that the SFD diet was associated with improvements in cognitive performance. SFD diet mice also had superior cognitive performance compared to mice on an NC diet. Further to this, meta-regression analyses indicated a significant positive effect of study quality score and treatment duration on the effect size estimate for both the FD vs SFD analysis and the SFD vs NC analysis.ConclusionThe findings of this meta-analysis demonstrate efficacy of SAM in acting as a cognitive performance-enhancing agent. As a corollary, SAM may be useful in improving spatial memory in patients suffering from many dementia forms including AD.
Highlights
As of 2013, approximately 44.4 million people suffer from dementia [1]
MEDLINE, EMBASE, Web of Science, the Cochrane Library and Proquest Theses and Dissertations database were used to search for articles containing a combination of the following words: s-adenosylmethionine, adomet, cognitive, cognition, dementia and Alzheimer’s
14 articles were eliminated because there was no cognitive performance outcome included in the study design or because the study did not incorporate a SAM intervention
Summary
Alzheimer’s disease is the most widely recognized and diagnosed form of dementia [2]. It is a neurodegenerative disease characterized by severe cognitive impairment, with learning, memory, and visuospatial abilities being three of the most prominent behavioral processes to deteriorate [3]. SAM plays an integral role as methyl donor in the metabolism of Methionine (Met) to homocysteine (Hcy). In this conversion, SAM regulates epigenetic processes via DNA methylation [10] that have been implicated in its efficacy for the treatment of depression, osteoarthritis and liver support in humans [7,11,12]. We include further discussion of improvements in cognitive ability, by SAM, as measured by the Morris water maze (MWM)
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