cell memory

You’ve probably heard someone complain about putting on the pounds they worked so hard to gain by using a low-calorie diet to lose weight, or maybe it’s even happened to you. This is known as “bounce effect” or “yo-yo effect” and it’s annoying, but now a group of scientists from Federal Institute of Technology Zurich (ETH Zurich) found a possible explanation for this phenomenon that could help prevent it.

These Swiss researchers showed that the problem is rooted in epigeneticsa branch of genetics that relies on small chemical signals. Although the genetic sequence evolves over time and we inherit it from our parents, epigenetic marks are more dynamic, and environmental factors and our lifestyle (such as eating habits) or our physical condition (such as overweight or obesity) can change them throughout life.

While these marks are variable, they can also remain stable for years or even decades, determining which genes are active or inactive in our cells. “Epigenetics tells the cell what type of cell it is and what it should do,” he explained. Laura Hintgraduate student in a group led by Ferdinand von Meyenne, professor of nutrition and metabolic epigenetics, in a paper published by ETH Zurich.

Cells that remember obesity and promote the rebound effect

von Meyenne’s team along with Daniel Castellano Castilloformer postdoctoral fellow in his group, studied molecular causes of the yo-yo effect in mice. They analyzed fat cells from overweight mice and those who had lost weight through dieting and found that obesity caused characteristic epigenetic changes in the nucleus of fat cells and that these changes persist even after weight loss.

“Fat cells remember being overweight and can return to that state more easily,” von Meyenne says. The researchers were able to show that mice with these epigenetic markers gained weight faster when they were given access to a high-fat diet again. “This means we have found the molecular basis for the yo-yo effect,” he adds.

They also found evidence for this mechanism in humans. They analyzed adipose tissue biopsies from obese people who had undergone Gastric reduction or gastric bypass surgery. These samples were obtained from studies carried out at the Karolinska Institutet in Stockholm and hospitals in Leipzig, Dresden and Karlsruhe, and revealed patterns of gene expression consistent with the results in mice. The results were published in the journal Nature.

“Fat cells remember the overweight state and can more easily return to that state, meaning we have found the molecular basis of the yo-yo effect.”

One mystery that researchers have not yet solved is how how long can they remember obesity fat cellsbecause, according to Hinte, “fat cells have a long lifespan, on average ten years, before our body replaces them with new cells.”

It is currently not possible to modify these epigenetic marks in the cell nucleus using drugs that erase epigenetic memory. “Maybe in the future we will be able to do this,” says Hinte, “but for now we will have to live with this memory effect.” Von Meyenne adds that “it is because of this memory effect that it is so important to avoid excess weight, as it is the easiest way to combat the yo-yo phenomenon,” a message she addresses especially to children and young people.

Research by ETH experts has shown for the first time that fat cells have epigenetic memory of obesitybut they suspect they are not the only cells with this ability. “Other cells in the body may also play a role in the yo-yo effect,” says von Meyenne. It’s likely that cells in the brain, blood vessels and other organs also remember obesity and contribute to the yo-yo effect, von Meyenne concludes. Future studies will seek to confirm this hypothesis.