Dietary polyamine supplement prevents aging-related memory impairments in Drosophila
It is well known that aging results in cognitive decline, including memory impairments, even in the absence of any dementing neurodegenerative disorders per se such as Alzheimer’s disease. Given the rapidly aging populations in many countries, the causes of the aging-related memory impairments have been a focus of intensive research. One central challenge for research on aging-related memory impairments has been posed by the relatively long lifespan of most animal models. Conditioning paradigms that can be used in Drosophila (aka "fruit flies") provide a model where aging-related memory impairments are seen over the course of days and weeks instead of years, thus offering a model that can be effectively used to study the underlying molecular mechanisms.
In their recent study, Dr. Varun K Gupta et al. (2013) conducted a series of experiments where they first observed that polyamine spermidine and putrescine levels decreased in the heads of aging Drosophila. In the following experiment they observed that dietary sperminide supplement reduced aging-related memory impairment in the Drosophila, as assessed with a maze-learning task involving olfactory cues and electric shocks. Investigating the possible underlying molecular mechanisms, the authors observed that dietary spermidine, in addition to reducing aging-related memory impairment, prevented aging-related decrease of autophagy. Furthermore, when the autophagic mechanisms were genetically impaired, the spermidine-induced reduction of aging-related memory impairment was blocked.
This impressive set of findings demonstrates how the Drosophila model can be highly effectively used to study molecular mechanisms that underlie aging-related memory impairments. The authors point out that prior to their observations, few substances (and all of them exogenous) have been observed to protect against aging-related memory impairments. Spermidine, being an endogenous substance, thus holds a lot of potential for further studies and might ultimately provide a candidate substance for prevention of aging-related memory deficits in humans.
Reference: Gupta VK, Scheunemann L, Eisenberg T, Mertel S, Bhukel A, Koemans TS, Kramer JM, Liu KSY, Schroeder S, Stunnenberg HG, Sinner F, Magnes C, Pieber TR, Dipt S, Fiala A, Schenck A, Schwaerzel M, Madeo F, Sigrist SJ. Restoring polyamines protects from age-induced memory impairment in an autophagy-dependent manner. Nature Neuroscience (2013) e-publication ahead of print. http://dx.doi.org/10.1038/nn.3512