Scientific highlights

27.05.2020

You are what you eat

While you will not literally become a broccoli if you eat one, this saying has a deeper meaning. We all require energy to grow, to reproduce and to just live! Because unlike plants we cannot produce energy ourselves, we need to eat. Our metabolism makes sure that energy is extracted from food. However, the metabolic activity needs to be adjusted to the energy sources, because sometimes we eat pizza and not broccoli. Prof. Robert Schneider, Director of the Institute of Functional Epigenetics (IFE) at the Helmholtz Zentrum München, and Dr. Till Bartke, the Deputy Director, have put together a special issue of Molecular Metabolism encompassing a collection of review articles illuminating the “epigenetic” processes that modulate metabolic responses from different angles and that highlight how these processes link metabolism, nutrition, and metabolic disorders such as diabetes. In their editorial to this special issue they explain some of the key concepts behind such a rich collection of articles.

@Bartke and Schneider, 2020, Molecular Metabolism

It does not matter how organized we are – our day is automatically structured by the times when we eat: breakfast in the morning, lunch at noon, and dinner in the evening. We eat when we are hungry or simply because we like food. We know that it is not good if we do not have anything to eat and we also are painfully aware when we overeat. Every cell in our body requires energy to function, and this is not only true for humans. Every cell in every living organism, from bacteria to plants to animals, needs energy and a metabolism that takes care of extracting energy from the surroundings and putting it to proper use. Autotrophic organisms, such as plants, can produce energy by themselves. Because they usually cannot move, their metabolism had to adapt to environmental fluctuations such as changes in temperature, light or water supply. In contrast, heterotrophic organisms, including us humans, are dependent on external sources for energy production, and environmental fluctuations do not affect us as much as plants. We can go grocery shopping if we need food or stay inside if it is cold. However, the metabolism of heterotrophic organisms has to cope with changing energy sources, because we do not eat the same things all the time or sometimes food is in short supply, for example.

The “hard drive” of each cell is the organism’s genome, which refers to the DNA sequence that encodes the hereditary information. The output of the genome, which can be proteins including metabolic enzymes, is tightly controlled – but at the same time it must be adjustable to the organism’s needs. For example, different enzymes are required to exploit energy from meat than from carrots. In general, regulating the processes that control the expression of genes is fundamental for all living beings in order to adapt and to respond to changing environments. However, not only the DNA sequence of a gene determines its output but also whether it is accessible for the machineries driving gene expression. Eukaryotes, such as plants, animals and us humans, package their genomes into a structure called chromatin to fit the DNA into the tiny nucleus and this packaging adds another layer of control to regulate the output of a genome. It is simply not possible that all genes can be accessible for the expression machineries at all times. “Epigenetic” mechanisms can change the chromatin structure at a specific location. They can “open up” the chromatin and enable expression of a specific gene, encoding a metabolic enzyme that might be needed, for example. But they can also shut down its expression again, if the enzyme is no longer required, by compacting the chromatin structure of the gene. However if these mechanism go wrong it can results in for example metabolic disorders or cancer.

Over the past years, it has become clear that metabolism and epigenetic regulation of gene expression are profoundly inter-connected. “There are still some open questions and the impact of diet and nutrition on epigenetic regulation and how that may affect human health is not yet well understood”, said Dr. Bartke. “Does the metabolism play a role in environmental diseases such as diabetes? Are epigenetic mechanisms or even inheritance the trigger for such diseases? Such questions need to be answered.” Prof. Schneider adds: “It might be that a change in nutrition can alter epigenetic “programming” and maybe this can be used to find new treatment approaches for metabolic disorders or foreven certain cancers.”

The review articles in the special issue ‘Epigenetics and Metabolism’ of Molecular Metabolism address these and other open questions with respect to the current knowledge of how the two processes are linked. The editorial by Robert Schneider and Till Bartke provides an additional perspective of the key concepts highlighting the fact that epigenetic mechanisms and metabolism depend on each other and illustrates how this holds true for many aspects of life.

To read the full editorial, please go here.