A mouse study just revealed a new molecular link between hunger and exercise


It is certain that regular exercise benefits our bodies, not least in protecting against obesity, but scientists are continuing to investigate why this happens at the molecular level.

In a new study, scientists put mice on intense treadmill workouts and analyzed how the chemicals in the animals’ cells began to change over time. They found the appearance of a metabolite called Lac-Phe (N-lactoyl-phenylalanine), synthesized from lactate and phenylalanine.

Phenylalanine is an amino acid that together form proteins, and you may know lactate: it is produced by the body after strenuous exercise.

The study authors believe they have identified an important biological pathway opened by exercise, which then has an impact on the rest of the body — particularly in appetite levels and the amount of food ingested.

Further tests confirmed these results. Researchers gave high doses of Lac-Phe to mice on a high-fat diet, causing the mice to eat about half as much over the next 12 hours as compared to a group of control mice. Meanwhile, the animals’ movement and energy expenditure remained unchanged.

Over a 10-day period, the Lac-Phe doses resulted in a decrease in food intake, a resulting decrease in body weight and improved glucose tolerance in the mice. Those are positive results when thinking about ways to fight obesity and obesity-related diseases.

There were some caveats though. The differences in appetite suppression caused by Lac-Phe were only noticeable after exercise and in mice on a high-fat diet. The same effects were not seen in more sedentary mice fed normally.

The scientists also looked at the effects of exercise in humans and racehorses and found increased levels of Lac-Phe, particularly after sprinting in humans. However, the knock-on effects have not been looked at and more research will be needed to see if these results can be fully translated in humans.

By shedding more light on the molecular responses to physical activity, the study’s findings will help a number of areas of research, including treatments.

There is probably much more to discover. The researchers note that since Lac-Phe is produced in multiple cell types in mice, it’s likely that it’s not just the muscles in the body that know when we’re exercising.

“Future work to uncover the downstream molecular and cellular mediators of Lac-Phe action in the brain may provide novel therapeutic avenues to capture the cardiometabolic benefits of physical activity for human health,” write to the researchers†

The research was published in Nature

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