'Caffeine Can Prevent Memory Loss Linked to Diabetes' Say Researchers

The neurodegeneration that Rodrigo Cunha from the Centre for Neuroscience and Cell Biology of the University of Coimbra in Portugal see caused by diabetes is the same that occurs at the first stages of several neurodegenerative diseases, including Alzheimer’s and Parkinson’s, suggesting that caffeine (or drugs with similar mechanism) could help them too.

7 May 2012 --- A study has discovered how diabetes affects a brain area called hippocampus causing memory loss, and also how caffeine can prevent this.

Type 2 diabetes (which accounts for about 90%of all diabetic cases) is a full blown public health disaster – 285 million people affected worldwide (6.4% of the world population) with numbers expected to almost double by 2030. And this without counting pre-diabetic individuals. The problem is that the disease is triggered by obesity, sedentary lifestyle and bad eating habits (although there is also a genetic predisposition), all of which are increasingly widespread.

Diabetes is caused by high levels of sugar in the blood, and in type 2 this occurs because the body becomes increasingly resistant to insulin –the hormone that allows the cells to take the sugar from the blood to use it as “fuel” – resulting in toxic high levels of sugar in the blood that damage nerves and blood vessels and, with time, cause severe complications.

In the study out now in the journal PLoS, João Duarte, Rodrigo Cunha and colleagues take advantage of a new mouse model of diabetes type 2, which, like humans, develops the disease in adults as result of a high-fat diet, to look at one of the least understood complications of diabetes – the disease effect on the brain, more specifically, on memory. They also investigate a possible protective effect by caffeine as this psychostimulant has been suggested to prevent memory loss in a series of neurodegenerative diseases, maybe even in diabetes, although how this happens is not known. And when we consider that coffee is the world leading beverage right after water, with about 500 billion cups consumed annually, this, if true, needs to be better understood.

With that aim the Portuguese researchers compared four groups of mice - diabetic or normal animals without or with caffeine (equivalent to 8 cups of coffee a day) in their water – to find that long-term consumption of caffeine not only diminished the weight gain and the high levels of blood sugar typical of diabetes, but also prevented the mice's memory loss (diabetic animals had significantly poorer memory than normal ones). This confirmed that caffeine could, in fact, protect against diabetes as well as prevent memory impairment, probably by interfering with the neurodegeneration caused by toxic sugar levels.

To investigate this, next, the researchers looked at a brain region linked to memory and learning, which is often atrophied in diabetics, called hippocampus. And in fact, diabetic mice had abnormalities in this area showing synaptic degeneration (synapses are the structures at the end of each neuron used to communicate between neurons) and astrogliosis (an abnormal increase of the cells that surround neurons normally as result of the deathof nearby neurons). Both phenomena are known to affect memory and caffeine consumption prevented the abnormalities.

But to be able to develop drugs based on caffeine’s protective effect, it was necessary to understand its molecular mechanisms. So next the researchers looked at the only brain molecules known to respond to caffeine – the adenosine receptors A1R and A2AR - in the hippocampus. And here, A2AR seemed to be the key for caffeine’s memory rescue since its density - which increases with noxious insults - was high in diabetic animals but normal in those treated with caffeine. This agrees with the previous studies that showed that A2AR inhibition protected against synaptic degeneration and memory dysfunction.

In conclusion, Duarte and Cunha’s work – using an animal model of diabetes type 2 that closely mimics the human form of the disease – suggests that diabetes affects memory by causing synaptic degeneration, astrogliosis and increased levels of A2AR. The study indicates as well that chronic consumption of caffeine can prevent the neurodegeneration and the memory impairment. And this not only in diabetes, since synaptic degeneration and astrogliosis are both part of a cascade of events common to several neurodegenerative diseases, suggesting that caffeine (or similar drugs) could help them too through the same mechanisms.

Source: PloS, Public Library of Science