Eating fat damages the brain

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A bratwurst at the Christkindlmarkt, the Christmas goose for the festival and constant butter biscuits, stollen and rum balls - especially in the Advent season, many expect their bodies to have a lot of fat. But this not only increases the risk of cardiovascular disease or diabetes, it can also damage our thinking cells.

To investigate this connection, Alex M. Stranahan and his colleagues from the Department of Neuroscience and Regenerative Medicine at Georgia Regents University conducted an experiment with male mice.

The researchers randomly divided the animals into two groups. Group one received a low-fat diet with a low fat content of ten percent. Group two were fed a very high fat diet that contained 60 percent fat. "The composition was roughly equivalent to a healthy diet compared to a fast-food diet in humans," explains Stranahan.

More fat, fewer synapses

After four, eight and twelve weeks, Stranahan and colleagues checked the animals' weight, blood sugar and the amount of insulin in the blood. They also measured synaptic markers in the hippocampus - the part of the brain that is responsible for learning and remembering. These proteins provide information about the number of synapses in the brain and thus allow conclusions to be drawn about the number of connections between the individual nerve cells. In addition, the amount of cytokines in the brain that are typical for inflammatory processes was determined.

The result: While the researchers found no difference between the synaptic markers in both groups of mice after four and eight weeks, although group two had gained significantly in weight, that changed after twelve weeks. Fewer synapse proteins were found in the fat mice, and the researchers also measured increased levels of inflammation. This suggests that the rodents' brains were damaged by the unhealthy diet, the researchers said.

Immune defense eats up nerve endings

But what could that be related to? Stranahan and colleagues suspect that this has something to do with the so-called glial cells. They form a kind of support structure for the nerve cells in the brain and have other important tasks. Among other things, they protect the nerve cells from intruders - in other words, they form the brain's immune system. Too much fat, however, fuels chronic inflammatory processes, which probably lead to an autoimmune reaction of the glial cells. These then destroy their own synapses. “Usually the microglia move in the brain,” explains Stranahan. "But if they are overweight they stop doing it and start eating up the synapses."

Nerve cells can recover

The good news: this process can be reversed. After the scientists put half of the fat mice on a healthy diet, the brain returned to its original state after two months.

Further studies have yet to show whether the results of Stranahan's study can be transferred to humans. Then you can also answer the question of whether it makes sense to recommend drugs to obese people as a precautionary measure that block the inflammatory cytokines in the brain. But what can't do any harm: Consciously eating less fat again after the holiday feast.

Source: Stranahan A. M. et al .: Dietary obesity reversibly induces synaptic stripping by microglia and impairs hippocampal plasticity. Brain, Behavior and Immunity. 2015. doi: 10.1016 / j.bbi.2015.08.023.

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