Could flies show how to personalise diet?

Fruit flies and humans don’t just share a love of fruit in the warm summer months. We also share key genetic features, which scientists have been able to take advantage of in new research to better understand how diet affects health.

The latest study, which is led by the University of Glasgow and published in PLOS Biology, suggests that small genetic changes can make bad diets good and good diets bad, emphasising the importance of understanding how human genetics might shape our response to food.

The research found that genetic differences in tiny compartments inside fly cells can shape how different foods affect the insects’ health. Human cells have the same compartments with similar genetics, and the researchers expect the same mechanisms may shape whether a diet is good or bad for human health too.

Food not only fuels our bodies, it also affects all aspects of health. However, because individuals can respond quite differently to the same foods, a good diet for one individual may be less good for another. Keen to understand why, researchers from the University of Glasgow, Monash University, Australia, and Dresden University of Technology, Germany, studied the impact two different diets had on fruit fly health.

The researchers found that, for some aspects of health, genetics shaped the impact of diet so strongly that there may be no such thing as a good diet for everyone. Instead, the findings suggest that it might be more beneficial to find the right individual diet.

Variation between individuals is encoded genetically, in our DNA. While most DNA is found in the nucleus of the cell, a small amount is also found in the energy-producing “powerhouse of the cell” – the mitochondria – which play a key role in processing nutrients. Both mitochondrial DNA and nuclear DNA can vary between individuals, and researchers are coming to realise that we can’t understand the impact of variation in one without the other. The interplay between them creates an effect called mito-nuclear variation, which may hold the key to why individuals respond differently to the same foods.

Although flies and humans are outwardly quite different, at the level of cells, genetics and metabolism they are very similar, and researchers can understand these processes more quickly in flies than in humans. In this case, studying mito-nuclear variation and responses to different foods in flies has important implications for the health impacts of human diets.

The team generated mito-nuclear variation in flies and fed the flies high-protein or high-fat foods, to model common dietary choices in people. They then measured reproduction – one of the best measures of overall fly health – and found that the different combinations of mitochondrial DNA and nuclear DNA dramatically altered the health impacts of the different foods. In some cases, this was a matter of life and death, with small mito-nuclear genetic changes meaning that a dietary change was beneficial for some, but lethal for others.

The team even found that the variation in responses to the different foods could be transmitted from parents to offspring, even when the offspring themselves did not eat different foods.

Dr Adam Dobson, who led the study from the University of Glasgow, said: “To understand how to personalise nutrition, we need first to understand the biology of why individual responses vary. In fruit flies we found that a three-way interaction of diet, mitochondrial DNA and nuclear DNA had a big effect on health.

“The biggest surprise was how dramatic some of these effects were. The genetic differences in the flies that we studied were able to completely change the effect of changing diet, from beneficial to toxic or even lethal. This suggests that we might need to understand how mitochondria and other parts of the cell work together if we want to improve human health by personalising diet.”

The study, ‘Mitonuclear interactions define both direct and parental effects of diet on fitness, and involve a SNP in mitoribosomal 16s rRNA’ is published in PLOS Biology. The study was funded by UK Research and Innovation (UKRI) and the German Research Council (DFG). A link to the full study can be found here