Need a snack?
Cravings for food after alcohol were explained at the cellular level
Kristina Ulasovich, N+1
Scientists have explained why drinking alcoholic beverages encourages us to eat, even when we are not really hungry. An experiment on mice showed that alcohol activates neurons in the brain that are responsible for appetite. The study was published in the journal Nature Communications (Cains et al., Agrp neuron activity is required for alcohol-induced overeating).
The main role in the occurrence of hunger is played by AgRP neurons, which are located in the hypothalamus. Studies have shown that when they are activated, mice immediately start eating or looking for food, even if their stomach is full, and when deactivated, on the contrary, they refuse food, even if they need it. AgRP neurons play a similar role in the human body. In natural conditions, they are activated when our body needs energy, and give a signal that it's time to look for food. However, in the case of alcohol, a paradox arises: despite the fact that strong alcoholic beverages are very high in calories, after consuming them, on the contrary, a person begins to want to eat. The authors of the new work suggested that this may be due to the effect of alcohol on "appetite neurons".
To test their hypothesis, the researchers conducted an experiment. For three days, they injected an average dose of ethanol into the stomachs of mice once a day (at the rate of 2 grams per kilogram of weight) – for a human, it would be equivalent to two bottles of wine or six pints of beer. As expected, after receiving alcohol, the mice ate more than when sober, which confirmed the link between alcohol consumption and increased appetite.
The researchers then studied how ethanol affects the activity of AgRP neurons. They introduced genetic reporter constructs into the arcuate nucleus of the hypothalamus, where the "appetite neurons" are located, which force cells to synthesize fluorescent proteins sensitive to calcium (that is, to the excitation of nerve cells). After that, neuroscientists placed brain samples in solutions with different concentrations of ethanol (from 10 to 100 millimoles per liter) and monitored the activity of AgRP neurons.
It turned out that alcohol leads AgRP neurons to an excited state. Scientists also registered a surge in the electrical activity of "appetite neurons" after placing them in a solution with ethanol. After the alcohol was washed out of the brain samples, the activity of AgRP neurons became normal again, which indicates the temporary nature of the exposure. In addition, in genetically modified mice with selectively disabled AgRP neurons, alcohol consumption did not cause a jump in appetite. This suggests that alcohol causes hunger precisely through its effect on the "appetite neurons", and not on other mechanisms.
The results of the study show that alcohol directly activates AgRP neurons that control hunger in mice. This forces animals to eat, even when they don't need it at all. According to scientists, something similar happens in the human brain, although it cannot be said with certainty only on the basis of this work.
The researchers emphasize that the discovery and study of the relationship between alcohol consumption and increased appetite can help in the fight against obesity. In the future, scientists plan to investigate how alcohol affects food choice.
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12.01.2017